This whitepaper discusses differences between adaptive antennas and transmissio-based beamforming applied in Wi-Fi. Additional value of usingthem together is discovered.
The document describes a simulation project for a communication link using AM and PSK modulation. Students are asked to design and simulate a communication link using AM modulation to transmit an audio signal, investigating the effects of different message signal frequencies and modulation indices. They also simulate communication links using BPSK and QPSK modulation schemes, comparing the performance of each in terms of bandwidth efficiency and required signal power. The project uses Matlab and Simulink to generate signals, design modulators and demodulators, and simulate the overall communication links.
This document summarizes different waveform coding techniques used for analog to digital conversion in communications systems. It describes the basic principles and processes of Pulse Code Modulation (PCM), Differential Pulse Code Modulation (DPCM), Delta Modulation (DM), and Adaptive Delta Modulation (ADM). Key steps like sampling, quantization, encoding, and decoding are discussed for each technique. The techniques are then compared in terms of their advantages, disadvantages, and applications in signal transmission.
This document summarizes modeling and simulation of power distribution noise in semicustom CMOS chips. It presents an approach using transmission line modeling (TLM) to address switching noise caused by simultaneous activation of output buffers. Simulations show:
1) Power and ground noise varies spatially across the chip due to signal propagation in the ring structures and is affected by the number and location of power/ground pads.
2) Output signals exhibit overshoot/undershoot due to ground bouncing, which decreases with additional pads.
3) An internal clock signal shows 500ps of skew and jitter between receivers due to simultaneous switching noise.
OFDM is a digital modulation technique that splits a data stream into several narrowband channels at different frequencies. This reduces interference and crosstalk compared to traditional single-carrier modulation. Fading effects are also reduced since the loss of a subset of bits can be recovered with coding. Windowing and cyclic prefixes are used to reduce interference between channels and intersymbol interference. The cyclic prefix provides a guard interval and allows transforming the linear convolution of the channel to circular convolution in the frequency domain, simplifying processing. While the cyclic prefix reduces data capacity, it provides robustness against multipath effects.
1) The document discusses hybrid beamforming (HB) for downlink multiuser massive MIMO systems with frequency selective channels. It aims to quantify the number of RF chains and phase shifters needed for HB to achieve the same performance as digital beamforming (DB), which uses N RF chains.
2) The paper shows that HB can achieve the same performance as DB using rt RF chains and 2rt(N − rt + 1) phase shifters, where rt is the rank of the combined digital precoder matrices across subcarriers. Additionally, it provides a method to reduce the number of phase shifters with negligible performance loss.
3) For the scenario where the number of deployed RF chains (Na)
Delta modulation is a type of pulse code modulation where the signal is encoded with 1-bit samples. It provides a staircase approximation of an oversampled input signal by increasing or decreasing the approximation by a fixed step size based on whether the input is above or below the approximation. Adaptive delta modulation improves performance by making the step size variable and adapting it based on the input signal, using a larger step size for steep signal segments and a smaller step size when the signal is changing slowly. Delta modulation is suitable for low bit rate applications like audio and speech processing due to its use of only 1 bit per sample, but can result in slope overload distortion or granular noise depending on the step size.
The document describes a simulation project for a communication link using AM and PSK modulation. Students are asked to design and simulate a communication link using AM modulation to transmit an audio signal, investigating the effects of different message signal frequencies and modulation indices. They also simulate communication links using BPSK and QPSK modulation schemes, comparing the performance of each in terms of bandwidth efficiency and required signal power. The project uses Matlab and Simulink to generate signals, design modulators and demodulators, and simulate the overall communication links.
This document summarizes different waveform coding techniques used for analog to digital conversion in communications systems. It describes the basic principles and processes of Pulse Code Modulation (PCM), Differential Pulse Code Modulation (DPCM), Delta Modulation (DM), and Adaptive Delta Modulation (ADM). Key steps like sampling, quantization, encoding, and decoding are discussed for each technique. The techniques are then compared in terms of their advantages, disadvantages, and applications in signal transmission.
This document summarizes modeling and simulation of power distribution noise in semicustom CMOS chips. It presents an approach using transmission line modeling (TLM) to address switching noise caused by simultaneous activation of output buffers. Simulations show:
1) Power and ground noise varies spatially across the chip due to signal propagation in the ring structures and is affected by the number and location of power/ground pads.
2) Output signals exhibit overshoot/undershoot due to ground bouncing, which decreases with additional pads.
3) An internal clock signal shows 500ps of skew and jitter between receivers due to simultaneous switching noise.
OFDM is a digital modulation technique that splits a data stream into several narrowband channels at different frequencies. This reduces interference and crosstalk compared to traditional single-carrier modulation. Fading effects are also reduced since the loss of a subset of bits can be recovered with coding. Windowing and cyclic prefixes are used to reduce interference between channels and intersymbol interference. The cyclic prefix provides a guard interval and allows transforming the linear convolution of the channel to circular convolution in the frequency domain, simplifying processing. While the cyclic prefix reduces data capacity, it provides robustness against multipath effects.
1) The document discusses hybrid beamforming (HB) for downlink multiuser massive MIMO systems with frequency selective channels. It aims to quantify the number of RF chains and phase shifters needed for HB to achieve the same performance as digital beamforming (DB), which uses N RF chains.
2) The paper shows that HB can achieve the same performance as DB using rt RF chains and 2rt(N − rt + 1) phase shifters, where rt is the rank of the combined digital precoder matrices across subcarriers. Additionally, it provides a method to reduce the number of phase shifters with negligible performance loss.
3) For the scenario where the number of deployed RF chains (Na)
Delta modulation is a type of pulse code modulation where the signal is encoded with 1-bit samples. It provides a staircase approximation of an oversampled input signal by increasing or decreasing the approximation by a fixed step size based on whether the input is above or below the approximation. Adaptive delta modulation improves performance by making the step size variable and adapting it based on the input signal, using a larger step size for steep signal segments and a smaller step size when the signal is changing slowly. Delta modulation is suitable for low bit rate applications like audio and speech processing due to its use of only 1 bit per sample, but can result in slope overload distortion or granular noise depending on the step size.
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Enhancement Of Diversity Gain In Mimo Systemmscs12
The document discusses enhancing diversity gain in MIMO systems using maximum ratio combining (MRC). MRC optimally combines signals from multiple receive antennas by weighting each signal based on its signal to noise ratio. Simulations show that as the number of receive antennas increases from 1 to 10 and 30, the signal to noise ratio improves dramatically, though the rate of improvement decreases with more antennas due to complexity. The effective bit energy to noise ratio is also shown to increase approximately linearly with the number of antennas without significantly impacting bit error rate. In conclusion, MRC spatial diversity can significantly improve MIMO system performance by proportionally increasing channel capacity with additional receive antennas.
A New Ultra Low-Power and Noise Tolerant Circuit Technique for CMOS Domino LogicIDES Editor
Dynamic logic style is used in high performance
circuit design because of its fast speed and less transistors
requirement as compared to CMOS logic style. But it is not
widely accepted for all types of circuit implementations due
to its less noise tolerance and charge sharing problems. A
small noise at the input of the dynamic logic can change the
desired output. Domino logic uses one static CMOS inverter
at the output of dynamic node which is more noise immune
and consuming very less power as compared to other proposed
circuit. In this paper we have proposed a novel circuit for
domino logic which has less noise at the output node and has
very less power-delay product (PDP) as compared to previous
reported articles. Low PDP is achieved by using semi-dynamic
logic buffer and also reducing leakage current when PDN is
not conducting. This paper also analyses the PDP of the circuit
at very low voltage and different W/L ratio of the transistors.
This document discusses OFDM (Orthogonal Frequency Division Multiplexing), including its basic idea of using multiple narrowband subcarriers instead of a single wideband carrier. OFDM has advantages like being robust to multipath interference and narrowband interference. It is sensitive to issues like frequency offset and phase noise. OFDM uses orthogonal subcarriers to maximize spectral efficiency and allows overlapping bands. Guard intervals and cyclic prefixes help mitigate inter-symbol interference. OFDM is used in standards like DSL, 802.11a, DAB and DVB. Simulation results show the theoretical and simulated bit error rates for OFDM with BPSK modulation.
1) There are different types of waveform coding including orthogonal, biorthogonal, and transorthogonal coding.
2) Orthogonal coding uses codewords that are mutually perpendicular to each other. Biorthogonal coding uses two sets of orthogonal codes where each codeword in one set has its antipodal codeword in the other set.
3) Transorthogonal coding generates codes from an orthogonal set by deleting the first digit of each codeword. It represents minimum energy equivalence and requires minimum energy per bit for a given symbol error rate.
The document compares coding techniques used to mitigate interference in MU-MIMO systems. It discusses Zero Forcing, Block Diagonalization, Minimum Mean Square Error, and Signal to Leakage Noise Ratio algorithms. A MATLAB simulation was created to analyze the bit error rate performance of each algorithm with varying user numbers. Hardware testing using USRPs and LabVIEW validated the conclusions from the software simulation. It was found that MMSE and SLNR algorithms best addressed noise in the channel and had the lowest error rates, especially with increasing user numbers, due to their use of diversity techniques.
Noise and Bandwidth Consideration in Designing Op-Amp Based Transimpedance Am...journalBEEI
In a visible light communication (VLC) system, there are many modules involved. One of the important modules is Transimpedance Amplifier (TIA) that resides in the analog front-end receiver (Rx-AFE). TIA is responsible for performing signal conversion from current signal, which is provided from the photodiode (PD) to voltage signal. It is the reason why the TIA should be operating in low noise condition and wide bandwidth of frequency. These will enable a flexible coverage of the VLC system in performing its signal processing. Hence, in this research, we provide considerations of the noise and frequency bandwidth analysis in designing TIA to cope with the required design specification of a VLC system.
This document discusses multi-carrier transmission over mobile radio channels. It introduces OFDM and MC-CDMA techniques for combating multipath interference in mobile channels. It describes various receiver designs for OFDM and MC-CDMA, including matrix inversion and decision feedback equalization approaches to estimate channel amplitudes and derivatives in order to reduce intercarrier interference caused by Doppler spread. Simulation results show performance improvements of these techniques over conventional OFDM.
This document discusses peak-to-average power ratio (PAPR) reduction techniques for orthogonal frequency-division multiplexing (OFDM) signals. It begins with an introduction to PAPR and its causes for OFDM signals. It then outlines various PAPR reduction techniques including clipping, coding, probabilistic/scrambling, predistortion, and DFT-spreading. Each technique has benefits but also cons such as distortion, reduced efficiency, or increased complexity. The document provides analysis of PAPR characteristics for different OFDM parameters and modulation schemes.
This document describes an AM receiver project implemented by students. It begins with an abstract stating that the project studies and implements an AM receiver using the superheterodyne principle. It then acknowledges those who provided guidance and support for the project. Finally, it provides the table of contents which outlines the various sections covering modulation, AM demodulation techniques, the superheterodyne receiver design, its implementation in MATLAB, results, and conclusions.
Orthogonal frequency-division multiplexing (OFDM) is a digital multi-carrier modulation technique that partitions the available bandwidth into multiple orthogonal subcarriers. Each subcarrier is modulated with a conventional modulation scheme at a low symbol rate, maintaining high data rates over the entire bandwidth. OFDM has advantages over single-carrier schemes in coping with severe channel conditions without complex equalization filters. It is used widely in digital television and audio broadcasting, wireless networks including WiFi, and mobile phone networks including 4G LTE.
A significant problem in Multicarrier Code Division Multiple Access (MC-
CDMA) system is the possibility of high Peak to Average Power Ratio (PAPR). This is due
to the cumulative sum of N subcarrier peaks in the transmitted signals which reduces Power
efficiency, resolution and battery life. In this paper a technique is proposed to make use of
Inverse Discrete Cosine Transform (IDCT) and Inverse Discrete Wavelet Transform
(IDWT) based Multicarrier Code Division Multiple Access (MC-CDMA) system. This
system is in combination with Modified Exponential Companding with Clipping Transform
(MECCT) technique which reduces PAPR and that is analyzed over Additive White
Gaussian Noise (AWGN) channel, Rayleigh and Stanford University Interim (SUI)
multipath fading channel.
1) The document discusses digital modulation techniques for transmitting digital information over an additive white Gaussian noise (AWGN) channel. It describes geometric representations of signal waveforms and orthogonalization procedures.
2) Binary and M-ary modulation schemes are covered, including binary antipodal signaling, orthogonal signaling, pulse position modulation, and frequency-shift keying. Optimal receivers for the AWGN channel using correlation and matched filtering are also described.
3) Probabilities of error are derived for various digital modulation techniques, including M-ary pulse amplitude modulation, phase-shift keying, and quadrature amplitude modulation. Differential phase-shift keying is also introduced.
This document summarizes various pulse modulation techniques including:
- Pulse-amplitude modulation (PAM) where the carrier amplitude changes with the message signal amplitude.
- Pulse-duration modulation (PDM) where the carrier width changes with the message signal amplitude.
- Pulse-position modulation (PPM) where the carrier position changes with the message signal amplitude.
- Digital pulse modulation techniques like pulse code modulation (PCM) and differential PCM (DPCM) are also discussed. Advantages and disadvantages of each technique are provided.
Comparative Analysis of Distortive and Non-Distortive Techniques for PAPR Red...IDES Editor
OFDM is a popular and widely accepted modulation
and multiplexing technique in the area of wireless
communication. IEEE 802.15, a wireless specification defined
for WPAN is an emerging wireless technology for short range
multimedia applications. Two general categories of 802.15
are the low rate 802.15.4 (ZigBee) and high rate 802.15.3
(UWB). In their physical (PHY) layer design, OFDM is a
competing technique due to the various advantages it renders
in the practical wireless media. OFDM has been a popular
technique for many years and adopted as the core technique
in a number of wireless standards. It makes the system more
immune to interference like InterSymbol Interference (ISI)
and InterCarrier Interference (ICI) and dispersive effects of
the channel. It is also a spectrally efficient scheme since the
spectra of the signal are overlapping in nature. Despite these
advantages OFDM suffers from a serious problem of high
Peak to Average Power. This limits the system’s capabilities
and increases the complexity. This paper compares the signal
distortion technique of Amplitude Clipping and the
distortionless technique of SLM for Peak to Average Power
reduction
Design of Simulink Model for Constant Envelop OFDM & Analysis of Bit Error RateIJSRD
This paper describes a transformation technique aimed at solving the peak-to-average power ratio (PAPR) problem associated with OFDM (Orthogonal Frequency Division Multiplexing). The Constant Envelop-OFDM solves the problem of high peak-to-average power ratio (PAPR) in OFDM, reducing PAPR to 0 dB. The constant envelope signal can be efficiently amplified with nonlinear power amplifiers thus achieving greater power efficiency. It is shown that CE-OFDM’s performance is better than conventional OFDM when taking into account the effects of the power amplifier. The performance of CE-OFDM is analyzed in additive white Gaussian noise (AWGN) channel. CE-OFDM is shown to achieve good performance with the use of cyclic prefix transmission. By way of computer simulation, CE-OFDM is shown to compare favorably to conventional OFDM. OFDM and CE-OFDM is analyzed on grounds of BER with additive white Gaussian noise (AWGN). The BER is calculated and the performance of OFDM and CE OFDM is compared.
Multi user-MIMO Broadcast Channel techniquesIRJET Journal
This document provides an overview of techniques for multi-user MIMO broadcast channels, including block diagonalization, dirty paper coding, and zero forcing channel inversion. Block diagonalization uses precoding to suppress interference between users by making each user's channel orthogonal. Dirty paper coding codes signals to cancel out interference that is known at the transmitter. Zero forcing channel inversion inverts the channel and applies precoding to eliminate multi-user interference. These techniques aim to reconstruct signals and remove interference to maintain reliable data transmission in multi-user MIMO systems.
Multiplexing generally refers to independent signals, those produced by different sources. SO it is a question of how to share the spectrum with these users. In OFDM the question of multiplexing is applied to independent signals but these independent signals are a sub-set of the one main signal.
In OFDM the signal itself is first split into independent channels, modulated by data and then re-multiplexed to create the OFDM carrier.
OFDM is a combination of modulation and multiplexing.
The PowerLogic Power Meter Series PM9 is a power monitoring unit that offers basic measurement capabilities for monitoring electrical installations. It monitors voltages and currents on 1-phase, 3-phase, and 3-phase + neutral systems. Three models are available for different supply voltages and output options: the PM9 for basic measurements, PM9P with a pulse output, and PM9C with Modbus RS485 communication. The PM9 has a compact design that fits in a standard cutout, a large backlit display, and measures active and reactive power, energy, demand and other electrical parameters.
Building the perfect Wi-Fi network with xirrusXirrus
Did you know that the average university has about the same broadband access speed as a large business, yet hundreds of times as many users?
The demands of 3+ devices per student and government mandates for connectivity are swiftly necessitating high-performance Wi-Fi networks as the new norm on campus. This is easier said than done as mobile usage is exploding, education and personal applications are competing for bandwidth, 802.11ac is a must-have, and IT budgets are still constrained. But settling for networks that are “good enough” is no longer an option, careful planning of the next Wi-Fi design and upgrade is paramount as it must be capable of supporting the dramatic increases in device density and data usage, plus have the longevity to last into the next decade. i.e. “the Perfect Wi-Fi Network’
IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com
Enhancement Of Diversity Gain In Mimo Systemmscs12
The document discusses enhancing diversity gain in MIMO systems using maximum ratio combining (MRC). MRC optimally combines signals from multiple receive antennas by weighting each signal based on its signal to noise ratio. Simulations show that as the number of receive antennas increases from 1 to 10 and 30, the signal to noise ratio improves dramatically, though the rate of improvement decreases with more antennas due to complexity. The effective bit energy to noise ratio is also shown to increase approximately linearly with the number of antennas without significantly impacting bit error rate. In conclusion, MRC spatial diversity can significantly improve MIMO system performance by proportionally increasing channel capacity with additional receive antennas.
A New Ultra Low-Power and Noise Tolerant Circuit Technique for CMOS Domino LogicIDES Editor
Dynamic logic style is used in high performance
circuit design because of its fast speed and less transistors
requirement as compared to CMOS logic style. But it is not
widely accepted for all types of circuit implementations due
to its less noise tolerance and charge sharing problems. A
small noise at the input of the dynamic logic can change the
desired output. Domino logic uses one static CMOS inverter
at the output of dynamic node which is more noise immune
and consuming very less power as compared to other proposed
circuit. In this paper we have proposed a novel circuit for
domino logic which has less noise at the output node and has
very less power-delay product (PDP) as compared to previous
reported articles. Low PDP is achieved by using semi-dynamic
logic buffer and also reducing leakage current when PDN is
not conducting. This paper also analyses the PDP of the circuit
at very low voltage and different W/L ratio of the transistors.
This document discusses OFDM (Orthogonal Frequency Division Multiplexing), including its basic idea of using multiple narrowband subcarriers instead of a single wideband carrier. OFDM has advantages like being robust to multipath interference and narrowband interference. It is sensitive to issues like frequency offset and phase noise. OFDM uses orthogonal subcarriers to maximize spectral efficiency and allows overlapping bands. Guard intervals and cyclic prefixes help mitigate inter-symbol interference. OFDM is used in standards like DSL, 802.11a, DAB and DVB. Simulation results show the theoretical and simulated bit error rates for OFDM with BPSK modulation.
1) There are different types of waveform coding including orthogonal, biorthogonal, and transorthogonal coding.
2) Orthogonal coding uses codewords that are mutually perpendicular to each other. Biorthogonal coding uses two sets of orthogonal codes where each codeword in one set has its antipodal codeword in the other set.
3) Transorthogonal coding generates codes from an orthogonal set by deleting the first digit of each codeword. It represents minimum energy equivalence and requires minimum energy per bit for a given symbol error rate.
The document compares coding techniques used to mitigate interference in MU-MIMO systems. It discusses Zero Forcing, Block Diagonalization, Minimum Mean Square Error, and Signal to Leakage Noise Ratio algorithms. A MATLAB simulation was created to analyze the bit error rate performance of each algorithm with varying user numbers. Hardware testing using USRPs and LabVIEW validated the conclusions from the software simulation. It was found that MMSE and SLNR algorithms best addressed noise in the channel and had the lowest error rates, especially with increasing user numbers, due to their use of diversity techniques.
Noise and Bandwidth Consideration in Designing Op-Amp Based Transimpedance Am...journalBEEI
In a visible light communication (VLC) system, there are many modules involved. One of the important modules is Transimpedance Amplifier (TIA) that resides in the analog front-end receiver (Rx-AFE). TIA is responsible for performing signal conversion from current signal, which is provided from the photodiode (PD) to voltage signal. It is the reason why the TIA should be operating in low noise condition and wide bandwidth of frequency. These will enable a flexible coverage of the VLC system in performing its signal processing. Hence, in this research, we provide considerations of the noise and frequency bandwidth analysis in designing TIA to cope with the required design specification of a VLC system.
This document discusses multi-carrier transmission over mobile radio channels. It introduces OFDM and MC-CDMA techniques for combating multipath interference in mobile channels. It describes various receiver designs for OFDM and MC-CDMA, including matrix inversion and decision feedback equalization approaches to estimate channel amplitudes and derivatives in order to reduce intercarrier interference caused by Doppler spread. Simulation results show performance improvements of these techniques over conventional OFDM.
This document discusses peak-to-average power ratio (PAPR) reduction techniques for orthogonal frequency-division multiplexing (OFDM) signals. It begins with an introduction to PAPR and its causes for OFDM signals. It then outlines various PAPR reduction techniques including clipping, coding, probabilistic/scrambling, predistortion, and DFT-spreading. Each technique has benefits but also cons such as distortion, reduced efficiency, or increased complexity. The document provides analysis of PAPR characteristics for different OFDM parameters and modulation schemes.
This document describes an AM receiver project implemented by students. It begins with an abstract stating that the project studies and implements an AM receiver using the superheterodyne principle. It then acknowledges those who provided guidance and support for the project. Finally, it provides the table of contents which outlines the various sections covering modulation, AM demodulation techniques, the superheterodyne receiver design, its implementation in MATLAB, results, and conclusions.
Orthogonal frequency-division multiplexing (OFDM) is a digital multi-carrier modulation technique that partitions the available bandwidth into multiple orthogonal subcarriers. Each subcarrier is modulated with a conventional modulation scheme at a low symbol rate, maintaining high data rates over the entire bandwidth. OFDM has advantages over single-carrier schemes in coping with severe channel conditions without complex equalization filters. It is used widely in digital television and audio broadcasting, wireless networks including WiFi, and mobile phone networks including 4G LTE.
A significant problem in Multicarrier Code Division Multiple Access (MC-
CDMA) system is the possibility of high Peak to Average Power Ratio (PAPR). This is due
to the cumulative sum of N subcarrier peaks in the transmitted signals which reduces Power
efficiency, resolution and battery life. In this paper a technique is proposed to make use of
Inverse Discrete Cosine Transform (IDCT) and Inverse Discrete Wavelet Transform
(IDWT) based Multicarrier Code Division Multiple Access (MC-CDMA) system. This
system is in combination with Modified Exponential Companding with Clipping Transform
(MECCT) technique which reduces PAPR and that is analyzed over Additive White
Gaussian Noise (AWGN) channel, Rayleigh and Stanford University Interim (SUI)
multipath fading channel.
1) The document discusses digital modulation techniques for transmitting digital information over an additive white Gaussian noise (AWGN) channel. It describes geometric representations of signal waveforms and orthogonalization procedures.
2) Binary and M-ary modulation schemes are covered, including binary antipodal signaling, orthogonal signaling, pulse position modulation, and frequency-shift keying. Optimal receivers for the AWGN channel using correlation and matched filtering are also described.
3) Probabilities of error are derived for various digital modulation techniques, including M-ary pulse amplitude modulation, phase-shift keying, and quadrature amplitude modulation. Differential phase-shift keying is also introduced.
This document summarizes various pulse modulation techniques including:
- Pulse-amplitude modulation (PAM) where the carrier amplitude changes with the message signal amplitude.
- Pulse-duration modulation (PDM) where the carrier width changes with the message signal amplitude.
- Pulse-position modulation (PPM) where the carrier position changes with the message signal amplitude.
- Digital pulse modulation techniques like pulse code modulation (PCM) and differential PCM (DPCM) are also discussed. Advantages and disadvantages of each technique are provided.
Comparative Analysis of Distortive and Non-Distortive Techniques for PAPR Red...IDES Editor
OFDM is a popular and widely accepted modulation
and multiplexing technique in the area of wireless
communication. IEEE 802.15, a wireless specification defined
for WPAN is an emerging wireless technology for short range
multimedia applications. Two general categories of 802.15
are the low rate 802.15.4 (ZigBee) and high rate 802.15.3
(UWB). In their physical (PHY) layer design, OFDM is a
competing technique due to the various advantages it renders
in the practical wireless media. OFDM has been a popular
technique for many years and adopted as the core technique
in a number of wireless standards. It makes the system more
immune to interference like InterSymbol Interference (ISI)
and InterCarrier Interference (ICI) and dispersive effects of
the channel. It is also a spectrally efficient scheme since the
spectra of the signal are overlapping in nature. Despite these
advantages OFDM suffers from a serious problem of high
Peak to Average Power. This limits the system’s capabilities
and increases the complexity. This paper compares the signal
distortion technique of Amplitude Clipping and the
distortionless technique of SLM for Peak to Average Power
reduction
Design of Simulink Model for Constant Envelop OFDM & Analysis of Bit Error RateIJSRD
This paper describes a transformation technique aimed at solving the peak-to-average power ratio (PAPR) problem associated with OFDM (Orthogonal Frequency Division Multiplexing). The Constant Envelop-OFDM solves the problem of high peak-to-average power ratio (PAPR) in OFDM, reducing PAPR to 0 dB. The constant envelope signal can be efficiently amplified with nonlinear power amplifiers thus achieving greater power efficiency. It is shown that CE-OFDM’s performance is better than conventional OFDM when taking into account the effects of the power amplifier. The performance of CE-OFDM is analyzed in additive white Gaussian noise (AWGN) channel. CE-OFDM is shown to achieve good performance with the use of cyclic prefix transmission. By way of computer simulation, CE-OFDM is shown to compare favorably to conventional OFDM. OFDM and CE-OFDM is analyzed on grounds of BER with additive white Gaussian noise (AWGN). The BER is calculated and the performance of OFDM and CE OFDM is compared.
Multi user-MIMO Broadcast Channel techniquesIRJET Journal
This document provides an overview of techniques for multi-user MIMO broadcast channels, including block diagonalization, dirty paper coding, and zero forcing channel inversion. Block diagonalization uses precoding to suppress interference between users by making each user's channel orthogonal. Dirty paper coding codes signals to cancel out interference that is known at the transmitter. Zero forcing channel inversion inverts the channel and applies precoding to eliminate multi-user interference. These techniques aim to reconstruct signals and remove interference to maintain reliable data transmission in multi-user MIMO systems.
Multiplexing generally refers to independent signals, those produced by different sources. SO it is a question of how to share the spectrum with these users. In OFDM the question of multiplexing is applied to independent signals but these independent signals are a sub-set of the one main signal.
In OFDM the signal itself is first split into independent channels, modulated by data and then re-multiplexed to create the OFDM carrier.
OFDM is a combination of modulation and multiplexing.
The PowerLogic Power Meter Series PM9 is a power monitoring unit that offers basic measurement capabilities for monitoring electrical installations. It monitors voltages and currents on 1-phase, 3-phase, and 3-phase + neutral systems. Three models are available for different supply voltages and output options: the PM9 for basic measurements, PM9P with a pulse output, and PM9C with Modbus RS485 communication. The PM9 has a compact design that fits in a standard cutout, a large backlit display, and measures active and reactive power, energy, demand and other electrical parameters.
Building the perfect Wi-Fi network with xirrusXirrus
Did you know that the average university has about the same broadband access speed as a large business, yet hundreds of times as many users?
The demands of 3+ devices per student and government mandates for connectivity are swiftly necessitating high-performance Wi-Fi networks as the new norm on campus. This is easier said than done as mobile usage is exploding, education and personal applications are competing for bandwidth, 802.11ac is a must-have, and IT budgets are still constrained. But settling for networks that are “good enough” is no longer an option, careful planning of the next Wi-Fi design and upgrade is paramount as it must be capable of supporting the dramatic increases in device density and data usage, plus have the longevity to last into the next decade. i.e. “the Perfect Wi-Fi Network’
Bit Error Rate Performance of MIMO Spatial Multiplexing with MPSK Modulation ...ijsrd.com
Wireless communication is one of the most effective areas of technology development of our time. Wireless communications today covers a very wide array of applications. In this, we study the performance of general MIMO system, the general V-BLAST architecture with MPSK Modulation in Rayleigh fading channels. Based on bit error rate, we show the performance of the 2x2 schemes with MPSK Modulation in noisy environment. We also show the bit error rate performance of 2x2, 3x3, 4x4 systems with BPSK modulation. We see that the bit error rate performance of 2x2 systems with QPSK modulation gives us the best performance among other schemes analysed here.
This document provides an introduction to MIMO (Multiple Input Multiple Output) technology. MIMO uses multiple antennas at the transmitter and receiver to improve wireless communication performance. It allows for spatial diversity, spatial multiplexing, and beamforming. Many modern wireless standards have adopted MIMO, including 3GPP UMTS, WiMAX, WLAN, and LTE to provide higher data rates and better coverage. Rohde & Schwarz offers signal generators, analyzers, testers and systems to test devices implementing these MIMO standards.
The document discusses best practices for wireless LAN deployment and security. It covers wireless concepts and standards, security issues with wireless networks like weak encryption and rogue access points, and common attacks. It also provides countermeasures like using encryption, limiting the broadcast range of access points, implementing authentication, and monitoring for unauthorized devices on the network.
The document discusses interconnection facilities and trends in the interconnection business. It finds that network-dense interconnection facilities charge higher prices due to their value, but competition is increasing as competitors work to build similar facilities. Demand for interconnection is driven by growth in internet traffic and services that require improved network performance and pushing of content to network edges. This is increasing demand for interconnection options in both large and small markets.
HIAST-Ayman Alsawah Lecture on Multiple-Antenna Techniques in Advanced Mobile...Ayman Alsawah
This document discusses multiple-antenna techniques. It begins by explaining why multiple antennas can be used to enhance signal-to-noise ratio through spatial diversity or beamforming gain, and to enhance bit rate through spatial multiplexing. It then covers various multiple-antenna configurations and techniques including single-user and multi-user MIMO, transmit diversity methods like space-time block coding, and receive diversity methods like selection combining, equal gain combining and maximum ratio combining. Beamforming using antenna arrays to synthesize radiation patterns is also discussed.
Security+ Guide to Network Security Fundamentals, 3rd Edition, by Mark Ciampa
Knowledge and skills required for Network Administrators and Information Technology professionals to be aware of security vulnerabilities, to implement security measures, to analyze an existing network environment in consideration of known security threats or risks, to defend against attacks or viruses, and to ensure data privacy and integrity. Terminology and procedures for implementation and configuration of security, including access control, authorization, encryption, packet filters, firewalls, and Virtual Private Networks (VPNs).
CNIT 120: Network Security
http://samsclass.info/120/120_S09.shtml#lecture
Policy: http://samsclass.info/policy_use.htm
Many thanks to Sam Bowne for allowing to publish these presentations.
Interconnection Network
in this presentation there are some explain to Interconnection Network , and espically in computer architecture and parallel processing.
This document discusses various types of antennas and antenna arrays. It begins by describing common antenna types including helical antennas, horn antennas, and parabolic reflector antennas. It then discusses how antenna arrays work, noting that they are composed of multiple similar radiating elements whose spacing and excitation determine the array's properties. Examples of linear and 2D arrays are provided. The document also summarizes different array configurations and beamforming techniques as well as applications such as smart antennas and adaptive arrays. Key benefits of arrays like controlling radiation patterns electronically are highlighted.
Overview of the upcoming 802.11ac standard and what to expect from wave 1 and wave 2 products.
Customer expectations vs. the real features which are going to be available in "wave 1" and "wave 2" products. To avoid the unnecessary frustration...
Multiple Input Multiple Output (MIMO) technology uses multiple antennas at both the transmitter and receiver to improve channel robustness and throughput. By utilizing reflected signals, MIMO can provide gains in channel robustness and throughput. MIMO was initially developed in the 1990s after additional processing power made it possible to utilize both spatial diversity and spatial multiplexing. MIMO systems provide either spatial multiplexing gain to maximize transmission rate or diversity gain to minimize errors and prioritize reliability. MIMO is now used in many wireless communication standards and ongoing research aims to develop more advanced MIMO techniques.
The document discusses routing and routing protocols. It defines routing as the process routers use to forward packets toward their destination network based on the destination IP address. It describes static routing, where network administrators manually configure routes, as well as dynamic routing protocols, where routers automatically share information to build and update routing tables. It outlines common routing protocols including RIP, IGRP, EIGRP, OSPF, and BGP and their key characteristics such as the metrics and timers they use.
This document discusses multiple-input multiple-output (MIMO) systems. It begins by outlining the motivations and aspirations for developing MIMO systems, including achieving high data rates near 1 gigabit/second while maintaining quality of service. It then provides an overview of MIMO system modeling and capacity studies. Key topics covered include diversity versus spatial multiplexing design criteria, example architectures, MIMO with orthogonal frequency-division multiplexing, and networking applications involving MAC protocols.
This document provides an overview of MIMO (Multiple Input Multiple Output) technology and its use in 802.11n wireless networks. MIMO works by using multiple antennas at both the transmitter and receiver to improve communication in three ways: by providing signal diversity to increase range and resilience, by enabling spatial multiplexing to increase data rates, and by allowing beamforming to focus signals in certain directions. The 802.11n standard will incorporate MIMO to achieve data rates up to 600Mbps using techniques like multi-path mitigation, modulation schemes, channel coding, and frame formatting adapted for MIMO transmissions. MIMO thus allows 802.11n to continue advancing wireless LAN speeds and performance.
Link-state routing protocols use Dijkstra's algorithm to calculate the shortest path to all destinations based on a link-state database containing the full network topology. Each router runs the same algorithm locally to determine the optimal path. Key aspects include link-state advertisements to share connectivity information, the topological database to store network maps, and shortest path first calculations to derive routes. Common link-state protocols are OSPF and IS-IS. They provide fast convergence and scalability but require more resources than distance-vector protocols.
The document outlines a presentation by two speakers on hacking and information security. It introduces the speakers and their backgrounds in cybersecurity. The presentation topics include basics of WiFi networks, wireless standards, encryption algorithms, wireless hacking methodology and common attacks. It also covers how to stay secure and defensive tools. Interactive portions engage the audience on their WiFi security concerns and ask for feedback to improve future sessions.
This document provides an introduction to routing and packet forwarding. It describes routers as computers that specialize in sending packets between networks by selecting the best path using routing tables. The document outlines router components, the boot-up process, interface types, and how routers examine packet headers to determine the best path and switch packets between incoming and outgoing interfaces. It also discusses topics like routing table structure, static and dynamic routing, path determination, and how packets are forwarded hop-by-hop between routers while headers are updated.
The document discusses human resource planning, including what it is, why it is important, and how it is done. It describes human resource planning as involving forecasting an organization's human resource needs and developing plans to meet those needs. The key aspects of human resource planning discussed are analyzing supply and demand, developing action plans to address surpluses or shortages, and linking it to the organization's strategic planning process.
PLNOG 6: Scott Reeves - Marketing v, Reality in Multi-Antenna Wi-FiPROIDEA
This document summarizes the differences between chip-based beamforming marketed by Wi-Fi vendors and Ruckus BeamFlex beamforming. It notes that chip-based beamforming has limitations like generating interference and an inability to adapt to interference, while BeamFlex can position antenna nulls to mitigate interference. It also explains that chip-based beamforming and spatial multiplexing are mutually exclusive, whereas BeamFlex supports both techniques to provide better performance and range. The document uses examples and diagrams to illustrate these concepts in an accessible way.
This summary provides the key details from the document in 3 sentences:
The document discusses troubleshooting methods for improving microwave links used by TATA DOCOMO in India. It proposes a system to control the power of indoor units using water sensors and control diesel generators using auxiliary ports. The document also describes the various acknowledgment alarms generated in NEC microwave systems and their associated troubleshooting methods to reduce call drops.
PNAPlus Product Brochure: Nonlinear Starter Kit For Agilent VNANMDG NV
The NM310S Nonlinear Starter Kit allows users to make their first steps in nonlinear measurement techniques using their Agilent vector network analyzer. The kit includes hardware and software to measure the fundamental and harmonic frequencies of devices under test up to 3 GHz. It provides new insights into how diodes, transistors, and other devices behave under nonlinear RF conditions. The included ICE software guides users through system configuration, calibration, and nonlinear measurements in both frequency and time domains.
NM310S Product Brochure: Nonlinear Starter Kit For Agilent VNANMDG NV
The document describes the NM310S Nonlinear Starter Kit for extending a vector network analyzer's capabilities to characterize nonlinear components. The starter kit includes hardware and software to measure fundamental and harmonic frequencies up to 3 GHz of devices under test. It allows visualization of measurements in frequency domain plots, Smith charts, time domain waveforms, and 3D trajectories. The software provides easy setup and calibration for nonlinear measurements.
ZVxPlus Product Brochure: Nonlinear Starter Kit For R&S VNANMDG NV
The document describes the NM310S Nonlinear Starter Kit for characterizing the nonlinear behavior of RF components using a vector network analyzer (VNA). The starter kit includes hardware and software to measure the fundamental and harmonic frequencies of devices under test up to 3 GHz. It allows users to gain experience with large-signal network analyzer techniques through visualizing spectral data, impedances on Smith charts, and time-domain waveforms. The kit is a cost-effective first step for engineers to explore nonlinear RF measurement capabilities.
NM310S Product Brochure: Nonlinear Starter Kit For R&S VNANMDG NV
The document describes the NM310S Nonlinear Starter Kit which allows users to perform introductory nonlinear measurements using their vector network analyzer (VNA). The kit includes a comb generator and software to measure the fundamental and harmonic response of devices up to 3 GHz. It allows visualization of time domain waveforms, spectral data, and derived metrics like gain to characterize the nonlinear behavior of diodes, transistors, and other RF components under real operating conditions with minimal additional equipment. The starter kit is designed to provide a low-cost entry point for engineers to gain experience with nonlinear measurement techniques.
Low Power LC-Quadrature VCO with Superior Phase Noise Performance in 0.13 μmR...VIT-AP University
The presented work intends to encounter the challenge of optimizing frequency tracking
in the C-band WLAN spectrum, with a tuning range and phase noise (PN)
performance. A Quadrature Voltage Controlled Oscillator (QVCO) design in 130 nm
CMOS technology has been presented to cover the most sought WLAN/WiFi spectrum
of modern wireless systems, employing the current reuse technique and an
on-chip inductor implementation. To provide better compensation of LC losses at
reduced power dissipation, a cross-coupled structure combining NMOS and PMOS
has been used.We have run an extensive simulation using the industry-standard ADS
(Keysight technology) platform. The simulation study attributed to the superior phase
noise performance of − 160 dBc/Hz at 1 MHz (near f max) at a power dissipation
of 6.52 mW from 1.2 V supply. With the moderate voltage tuning range, the entire
desired frequency span of 5.400–5.495 GHz was obtained with a fairly high resolution
of 2.375 MHz/1 mV, which allows serving a larger crowd for this spectrum. A
fairly moderate VCO gain along with the obtained phase noise and power dissipation
provides a well-established Figure of Merit (FOM) of − 187 dB. Finally, a comparison
study in terms of power dissipation, phase noise, tuning range, voltage tuning,
and Kvco is performed to demonstrate that the provided work is considerably more
significant than traditional efforts.
The document discusses the design and implementation of a P-band RF low noise amplifier (LNA). It begins with an introduction to LNAs, explaining that their main function is to amplify weak signals while introducing minimal noise. It then discusses the use of pseudomorphic high electron mobility transistors (pHEMTs) for LNA design due to their ability to provide high gain and low noise figure. The document outlines the objectives and methodology for the project, which is to design an LNA with specifications including a frequency range of 50MHz-1GHz, gain of at least 22dB, noise figure below 4dB and input/output impedance of 50 ohms. It provides background on relevant LNA design concepts and
Wr@p the last meter technology for energy aware networked smart appliancesValerio Aisa
This paper presents a detailed analysis of Wr@p technology (Web Ready Appliances Protocol, also known as Power Modulation), an ultra-low-cost powerline communication solution devoted to the electrical appliance market. Wr@p technology is aimed at adding communication capability to a household appliance without affecting its industrial cost, thus speeding up the diffusion of “smart” appliances interacting with the power distribution grid and contributing to the smart grid paradigm.
A Wr@p transceiver establishes a narrow-band powerline communication exploiting the “last meter”, i.e. the power supply cord between the appliance and the outlet, where a proxy device, the smart adapter (SA), flexibly deals with standard home networking solutions. At the appliance side, such an approach allows for (i) connectivity at negligible cost and, (ii) keeps hardware and software virtually independent from the actual home networking protocol (since different configurations of the smart adapter take care of it). In this work, after recalling the basics of Wr@p point-to-point communication, an extension to the multipoint-to-point scenario is introduced. Design of silicon implementations integrated into commercial microcontroller architectures are presented and the results of extensive test of fabricated devices under actual operating conditions are detailed. Moreover, we present a complete Wr@p development solution, featuring wireless networks integration.
Low Noise Amplifier using Darlington Pair At 90nm Technology IJECEIAES
The demand of low noise amplifier (LNA) has been rising in today’s communication system. LNA is the basic building circuit of the receiver section satellite. The design concept demonstrates the design trade off with NF, gain, power consumption. This paper reports on with analysis of wideband LNA. This paper shows the schematic of LNA by using Darlington pair amplifier. This LNA has been fabricated on 90nm CMOS process. This paper is focused on to make comparison of three stage and single stage LNA. Here, the phase mismatch between these patameters is quantitavely analyzed to study the effect on gain and noise figure (NF). In this paper, single stage LNA has shown the 23 dB measured gain, while the three stages LNA has demonstrated 29 dB measured gain. Here, LNA designed using darlington pair shows low NF of 3.3-4.8 dB, which comparable to other reported single stage LNA designs and appreciably low compared to the three stages LNA. Hence, findings from this paper suggest the use of single stage LNA designed using Darlington pair in transceiver satellite applications.
Smart Antennas offer significant benefits for wireless networks including increased network capacity and improved transmission quality. They work by directing antenna beams towards desired users to increase their signal strength while placing nulls towards interfering signals. This allows serving more users per base station. Smart Antennas adapt their antenna weights based on algorithms that estimate signal directions and qualities. Their introduction impacts radio network planning by requiring consideration of directional channel characteristics and spatially dependent interference.
Open Source SDR Frontend and Measurements for 60-GHz Wireless ExperimentationAndreaDriutti
Summary of Open Source SDR Frontend and Measurements for 60-GHz Wireless Experimentation
Tesi fast track, laurea triennale Ingegneria Elettronica e Informatica.
Research Inventy : International Journal of Engineering and Science is publis...researchinventy
This document summarizes the design and development of a switchable fractal patch antenna for GPS applications. The antenna uses a stacked fractal patch design to reduce size and mitigate interference. Two fractal patch antennas with different radiation patterns are stacked and selected using diode switching. Simulation results show the stacked fractal patch antenna achieves a return loss of -29.01 dB, VSWR of 1.30, and size reduction of up to 62.4% compared to a basic patch antenna design through the use of fractal iterations. The stacked fractal patch design provides a compact antenna that can directly replace existing antennas for GPS applications.
Design and Development of Linearly Polarized Patch Antenna of Circular Shape ...IRJET Journal
This document describes the design and simulation of a circular patch antenna for lower ultra-wideband (UWB) applications ranging from 3.1 GHz to 5.1 GHz. The antenna is designed on an FR-4 substrate with a copper patch and fed using a tapered transmission line for impedance matching. Simulations show the antenna achieves a 10 dB return loss bandwidth of 2 GHz and gain variation of less than 0.8 dBi across the frequency band. The antenna also maintains stable radiation patterns between 3.1 GHz and 5.1 GHz, making it suitable for lower UWB applications such as wireless personal area networks.
This document describes a winning design for a low-power RF identification transponder that can be mounted on rail cars to allow their identification as they pass reader transceivers along the track. The design uses a single microwave diode and inexpensive FR-4 printed circuit board to rectify energy from an interrogating RF field and power a microcontroller unit, which returns data via amplitude modulation. The simple, passive design eliminates batteries and has a low profile, rugged construction, and low manufacturing cost. It was shown to operate reliably from up to 20 feet away using less than 2 mW of transmitted power.
IOSR Journal of Electronics and Communication Engineering(IOSR-JECE) is an open access international journal that provides rapid publication (within a month) of articles in all areas of electronics and communication engineering and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in electronics and communication engineering. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
Designing an Antenna System That Can Perform Conditional RF to DC Harnessing ...IOSRJECE
Electromagnetic energy or RF energy will play a pivotal role in wireless technology and wireless communication in the impending future. The paper proposes a concept for a patch antenna based system that can harness RF energy upon triggering and can convert the harnessed RF to DC from the radio frequency of 1 GHz to 3 GHz, the design frequency is 2.4GHz. The patch antenna system contains a high gain patch antenna along with a wireless communicating module and a conversion circuit. The return loss of the antenna is approximately 27.1dB. The power gain is 30.1 dBm .The converter circuit is designed in), Multi-Sim to get an output voltage of around 5V that can be used to power a mobile-device or maybe stored in a battery. The triggering part is done with the help of a T-mote which is simulated in a network simulator, Cooja. The patch antenna is simulated in High Frequency Structural Simulator
A novel autonomous wireless sensor node for IoT applicationsTELKOMNIKA JOURNAL
A novel wireless sensor network node (WSNN) is presented in this paper where the solar energy
harvester system is used as an autonomous power solution for endless battery lifetime. In this sensor
node, the meander-line Inverted-F-Antenna (MIFA) is proposed and integrated in a single-CC2650 chip of
Texas Instrument. The simple structure, low cost, compact size, high efficiency and low power
consumption are advantages of this single-chip WSNN. The experimental results show that MIFA antenna
is promising solution to enhance communication performance in WSN. In addition, the investigated
single-chip WSNN with multi-wireless technologies including Bluetooth Low Energy and Zigbee as well as
6LowPAN is an attractive device for internet of thing (IoT) applications.
A Review on Wide Bandwidth Low Noise Amplifier for Modern Wireless CommunicationIRJET Journal
This document reviews techniques for designing wide bandwidth low noise amplifiers for modern wireless communication. It discusses several techniques used in recent decades to improve the performance and linearity of low noise amplifiers, including wide range derivative superposition technique, direct-coupled amplifier topology, resistive shunt feedback topology, forward combining technique, and gate-inductive gain-peaking technique. The document also reviews the applications of low noise amplifiers in areas like low noise amplifier, distributed amplifier, broadband mixer, power amplifier and active balunes.
Active optical networks have advantages over passive optical networks in terms of bandwidth. With AONs, bandwidth allocation is flexible and each subscriber can be allocated from 100 Mbps to 1 Gbps. In contrast, PON bandwidth is determined by the splitting factor, with each subscriber receiving less bandwidth depending on the number of subscribers on the network. Upgrading bandwidth is also simpler with AONs, as subscribers can be upgraded by changing fiber optic leads or boards. However, PONs allow for higher subscriber counts due to their point-to-multipoint topology.
The document summarizes the results of independent Wi-Fi performance testing conducted by Croatian Academic and Research Network (CARNet) on 19 access points from 8 vendors. The APs were tested in a classroom environment under increasing loads of 12, 23, 36, and 60 clients. Ruckus APs consistently outperformed other APs, taking top marks in almost every test scenario. Specifically, in the test with 60 clients, the Ruckus R700 achieved an aggregate throughput of 107Mbps, significantly higher than the next best performers.
The document discusses the shift from online to offline engagement as the new frontier for business innovation. With increasing mobile internet usage, organizations now have to pay attention to both online and offline user experiences through location-based marketing and services. New location technologies like Wi-Fi can provide indoor location data to help businesses better understand customer behavior and create engaging mobile experiences. However, challenges remain in achieving accurate positioning and network control to enable more sophisticated location-based applications and services.
How do the 802.11u and HotSpot 2.0 work?Michal Jarski
This document provides a detailed overview of the 802.11u and Hotspot 2.0 protocols which enhance Wi-Fi capabilities for network discovery, selection, and roaming. It describes how new information elements are used to advertise network properties and capabilities. Key elements include the Interworking element which provides details on access network type and security, and the Roaming Consortium element which identifies supported credential providers. The Advertisement Protocol element allows clients to query the access point for additional details using the Access Network Query Protocol. The specifications aim to improve the Wi-Fi user experience when connecting to unfamiliar networks.
The document summarizes a stress test performed on several Wi-Fi access points from different vendors. The test aimed to determine each AP's breaking point under high client load and use of applications like video streaming. Ruckus' ZoneFlex 7982 AP had the highest average TCP throughput and lowest number of video transmission errors, performing best overall. The document attributes Ruckus' superior performance to its BeamFlex statistical optimization technology, which constantly selects the highest data rates for clients through antenna pattern selection and sampling of the environment.
802.11ac is the next generation Wi-Fi standard that significantly increases network speeds by utilizing wider channel bandwidths up to 160MHz, more spatial streams up to 8, and more efficient modulation up to 256-QAM. While maximum theoretical speeds can reach nearly 7Gbps, real-world performance will depend on factors like number of antennas, radio environment, and device capabilities. Wide channels and high-order modulation will primarily benefit small home networks, while enterprise networks may find 80MHz channels and additional spatial streams more useful.
Ruckus provides a solution for BYOD implementations using Dynamic Pre-Shared Keys (DPSK) and Zero-IT Activation that simplifies setup while maintaining security. DPSK assigns unique credentials to each user/device instead of using a shared passphrase. Zero-IT Activation automates configuration of client devices upon first connection by generating and deploying DPSKs without IT intervention. A provisioning network can also be created to securely configure mobile devices on an open wireless network and then connect them to the corporate network.
1) Bring Your Own Design (BYOD) allows employees and students to use personal devices on corporate or educational networks.
2) Ruckus Wireless proposes simplifying BYOD through role-based access using technologies like Zero IT, dynamic pre-shared keys (D-PSK), and client fingerprinting.
3) These technologies allow devices to automatically authenticate, receive network permissions based on the user's role, and be securely onboarded and managed on the network.
The document discusses two network protocols, GTP and PMIP, that help mobile operators support IP mobility across heterogeneous radio access networks to maintain session continuity. GTP was originally developed for GPRS networks while PMIP is a more recent IETF standard. The document focuses on the technical and economic attributes of GTP and PMIP-based mobility solutions for optimizing interworking between Wi-Fi and other mobile networks in 3G and EPC environments. Operators must choose between these protocols based on their goals and the standards supported by clients.
ZoneFlex 7982 - the best access point everMichal Jarski
Ruckus introduced new Wi-Fi innovations to bolster their portfolio, addressing top problems of capacity, performance, and reliability. This included the ZoneFlex 7982, the first 3-stream 802.11n access point with adaptive antennas, delivering the highest performance and capacity. Ruckus' solutions utilize adaptive signal control, interference mitigation, and other techniques to provide pervasive Wi-Fi performance anywhere and everywhere.
Introduction to Ruckus Carrier SolutionsMichal Jarski
Ruckus provides carrier-grade Wi-Fi solutions including access points and wireless gateways. It has over 12,000 customers worldwide, has shipped over 3 million access points, and has experienced strong revenue growth rates. Ruckus touts its radio performance innovations including BeamFlex adaptive antenna technology which can provide better range, capacity and reliability compared to competitors. It also claims its solutions can reduce capital and operating costs. Ruckus discusses key requirements for carrier Wi-Fi including great connectivity in challenging environments and seamless integration with mobile networks.
HCL Notes and Domino License Cost Reduction in the World of DLAUpanagenda
Webinar Recording: https://www.panagenda.com/webinars/hcl-notes-and-domino-license-cost-reduction-in-the-world-of-dlau/
The introduction of DLAU and the CCB & CCX licensing model caused quite a stir in the HCL community. As a Notes and Domino customer, you may have faced challenges with unexpected user counts and license costs. You probably have questions on how this new licensing approach works and how to benefit from it. Most importantly, you likely have budget constraints and want to save money where possible. Don’t worry, we can help with all of this!
We’ll show you how to fix common misconfigurations that cause higher-than-expected user counts, and how to identify accounts which you can deactivate to save money. There are also frequent patterns that can cause unnecessary cost, like using a person document instead of a mail-in for shared mailboxes. We’ll provide examples and solutions for those as well. And naturally we’ll explain the new licensing model.
Join HCL Ambassador Marc Thomas in this webinar with a special guest appearance from Franz Walder. It will give you the tools and know-how to stay on top of what is going on with Domino licensing. You will be able lower your cost through an optimized configuration and keep it low going forward.
These topics will be covered
- Reducing license cost by finding and fixing misconfigurations and superfluous accounts
- How do CCB and CCX licenses really work?
- Understanding the DLAU tool and how to best utilize it
- Tips for common problem areas, like team mailboxes, functional/test users, etc
- Practical examples and best practices to implement right away
Generating privacy-protected synthetic data using Secludy and MilvusZilliz
During this demo, the founders of Secludy will demonstrate how their system utilizes Milvus to store and manipulate embeddings for generating privacy-protected synthetic data. Their approach not only maintains the confidentiality of the original data but also enhances the utility and scalability of LLMs under privacy constraints. Attendees, including machine learning engineers, data scientists, and data managers, will witness first-hand how Secludy's integration with Milvus empowers organizations to harness the power of LLMs securely and efficiently.
5th LF Energy Power Grid Model Meet-up SlidesDanBrown980551
5th Power Grid Model Meet-up
It is with great pleasure that we extend to you an invitation to the 5th Power Grid Model Meet-up, scheduled for 6th June 2024. This event will adopt a hybrid format, allowing participants to join us either through an online Mircosoft Teams session or in person at TU/e located at Den Dolech 2, Eindhoven, Netherlands. The meet-up will be hosted by Eindhoven University of Technology (TU/e), a research university specializing in engineering science & technology.
Power Grid Model
The global energy transition is placing new and unprecedented demands on Distribution System Operators (DSOs). Alongside upgrades to grid capacity, processes such as digitization, capacity optimization, and congestion management are becoming vital for delivering reliable services.
Power Grid Model is an open source project from Linux Foundation Energy and provides a calculation engine that is increasingly essential for DSOs. It offers a standards-based foundation enabling real-time power systems analysis, simulations of electrical power grids, and sophisticated what-if analysis. In addition, it enables in-depth studies and analysis of the electrical power grid’s behavior and performance. This comprehensive model incorporates essential factors such as power generation capacity, electrical losses, voltage levels, power flows, and system stability.
Power Grid Model is currently being applied in a wide variety of use cases, including grid planning, expansion, reliability, and congestion studies. It can also help in analyzing the impact of renewable energy integration, assessing the effects of disturbances or faults, and developing strategies for grid control and optimization.
What to expect
For the upcoming meetup we are organizing, we have an exciting lineup of activities planned:
-Insightful presentations covering two practical applications of the Power Grid Model.
-An update on the latest advancements in Power Grid -Model technology during the first and second quarters of 2024.
-An interactive brainstorming session to discuss and propose new feature requests.
-An opportunity to connect with fellow Power Grid Model enthusiasts and users.
zkStudyClub - LatticeFold: A Lattice-based Folding Scheme and its Application...Alex Pruden
Folding is a recent technique for building efficient recursive SNARKs. Several elegant folding protocols have been proposed, such as Nova, Supernova, Hypernova, Protostar, and others. However, all of them rely on an additively homomorphic commitment scheme based on discrete log, and are therefore not post-quantum secure. In this work we present LatticeFold, the first lattice-based folding protocol based on the Module SIS problem. This folding protocol naturally leads to an efficient recursive lattice-based SNARK and an efficient PCD scheme. LatticeFold supports folding low-degree relations, such as R1CS, as well as high-degree relations, such as CCS. The key challenge is to construct a secure folding protocol that works with the Ajtai commitment scheme. The difficulty, is ensuring that extracted witnesses are low norm through many rounds of folding. We present a novel technique using the sumcheck protocol to ensure that extracted witnesses are always low norm no matter how many rounds of folding are used. Our evaluation of the final proof system suggests that it is as performant as Hypernova, while providing post-quantum security.
Paper Link: https://eprint.iacr.org/2024/257
Your One-Stop Shop for Python Success: Top 10 US Python Development Providersakankshawande
Simplify your search for a reliable Python development partner! This list presents the top 10 trusted US providers offering comprehensive Python development services, ensuring your project's success from conception to completion.
Taking AI to the Next Level in Manufacturing.pdfssuserfac0301
Read Taking AI to the Next Level in Manufacturing to gain insights on AI adoption in the manufacturing industry, such as:
1. How quickly AI is being implemented in manufacturing.
2. Which barriers stand in the way of AI adoption.
3. How data quality and governance form the backbone of AI.
4. Organizational processes and structures that may inhibit effective AI adoption.
6. Ideas and approaches to help build your organization's AI strategy.
Essentials of Automations: Exploring Attributes & Automation ParametersSafe Software
Building automations in FME Flow can save time, money, and help businesses scale by eliminating data silos and providing data to stakeholders in real-time. One essential component to orchestrating complex automations is the use of attributes & automation parameters (both formerly known as “keys”). In fact, it’s unlikely you’ll ever build an Automation without using these components, but what exactly are they?
Attributes & automation parameters enable the automation author to pass data values from one automation component to the next. During this webinar, our FME Flow Specialists will cover leveraging the three types of these output attributes & parameters in FME Flow: Event, Custom, and Automation. As a bonus, they’ll also be making use of the Split-Merge Block functionality.
You’ll leave this webinar with a better understanding of how to maximize the potential of automations by making use of attributes & automation parameters, with the ultimate goal of setting your enterprise integration workflows up on autopilot.
AppSec PNW: Android and iOS Application Security with MobSFAjin Abraham
Mobile Security Framework - MobSF is a free and open source automated mobile application security testing environment designed to help security engineers, researchers, developers, and penetration testers to identify security vulnerabilities, malicious behaviours and privacy concerns in mobile applications using static and dynamic analysis. It supports all the popular mobile application binaries and source code formats built for Android and iOS devices. In addition to automated security assessment, it also offers an interactive testing environment to build and execute scenario based test/fuzz cases against the application.
This talk covers:
Using MobSF for static analysis of mobile applications.
Interactive dynamic security assessment of Android and iOS applications.
Solving Mobile app CTF challenges.
Reverse engineering and runtime analysis of Mobile malware.
How to shift left and integrate MobSF/mobsfscan SAST and DAST in your build pipeline.
"Frontline Battles with DDoS: Best practices and Lessons Learned", Igor IvaniukFwdays
At this talk we will discuss DDoS protection tools and best practices, discuss network architectures and what AWS has to offer. Also, we will look into one of the largest DDoS attacks on Ukrainian infrastructure that happened in February 2022. We'll see, what techniques helped to keep the web resources available for Ukrainians and how AWS improved DDoS protection for all customers based on Ukraine experience
Introduction of Cybersecurity with OSS at Code Europe 2024Hiroshi SHIBATA
I develop the Ruby programming language, RubyGems, and Bundler, which are package managers for Ruby. Today, I will introduce how to enhance the security of your application using open-source software (OSS) examples from Ruby and RubyGems.
The first topic is CVE (Common Vulnerabilities and Exposures). I have published CVEs many times. But what exactly is a CVE? I'll provide a basic understanding of CVEs and explain how to detect and handle vulnerabilities in OSS.
Next, let's discuss package managers. Package managers play a critical role in the OSS ecosystem. I'll explain how to manage library dependencies in your application.
I'll share insights into how the Ruby and RubyGems core team works to keep our ecosystem safe. By the end of this talk, you'll have a better understanding of how to safeguard your code.
In the realm of cybersecurity, offensive security practices act as a critical shield. By simulating real-world attacks in a controlled environment, these techniques expose vulnerabilities before malicious actors can exploit them. This proactive approach allows manufacturers to identify and fix weaknesses, significantly enhancing system security.
This presentation delves into the development of a system designed to mimic Galileo's Open Service signal using software-defined radio (SDR) technology. We'll begin with a foundational overview of both Global Navigation Satellite Systems (GNSS) and the intricacies of digital signal processing.
The presentation culminates in a live demonstration. We'll showcase the manipulation of Galileo's Open Service pilot signal, simulating an attack on various software and hardware systems. This practical demonstration serves to highlight the potential consequences of unaddressed vulnerabilities, emphasizing the importance of offensive security practices in safeguarding critical infrastructure.
Monitoring and Managing Anomaly Detection on OpenShift.pdfTosin Akinosho
Monitoring and Managing Anomaly Detection on OpenShift
Overview
Dive into the world of anomaly detection on edge devices with our comprehensive hands-on tutorial. This SlideShare presentation will guide you through the entire process, from data collection and model training to edge deployment and real-time monitoring. Perfect for those looking to implement robust anomaly detection systems on resource-constrained IoT/edge devices.
Key Topics Covered
1. Introduction to Anomaly Detection
- Understand the fundamentals of anomaly detection and its importance in identifying unusual behavior or failures in systems.
2. Understanding Edge (IoT)
- Learn about edge computing and IoT, and how they enable real-time data processing and decision-making at the source.
3. What is ArgoCD?
- Discover ArgoCD, a declarative, GitOps continuous delivery tool for Kubernetes, and its role in deploying applications on edge devices.
4. Deployment Using ArgoCD for Edge Devices
- Step-by-step guide on deploying anomaly detection models on edge devices using ArgoCD.
5. Introduction to Apache Kafka and S3
- Explore Apache Kafka for real-time data streaming and Amazon S3 for scalable storage solutions.
6. Viewing Kafka Messages in the Data Lake
- Learn how to view and analyze Kafka messages stored in a data lake for better insights.
7. What is Prometheus?
- Get to know Prometheus, an open-source monitoring and alerting toolkit, and its application in monitoring edge devices.
8. Monitoring Application Metrics with Prometheus
- Detailed instructions on setting up Prometheus to monitor the performance and health of your anomaly detection system.
9. What is Camel K?
- Introduction to Camel K, a lightweight integration framework built on Apache Camel, designed for Kubernetes.
10. Configuring Camel K Integrations for Data Pipelines
- Learn how to configure Camel K for seamless data pipeline integrations in your anomaly detection workflow.
11. What is a Jupyter Notebook?
- Overview of Jupyter Notebooks, an open-source web application for creating and sharing documents with live code, equations, visualizations, and narrative text.
12. Jupyter Notebooks with Code Examples
- Hands-on examples and code snippets in Jupyter Notebooks to help you implement and test anomaly detection models.
Dandelion Hashtable: beyond billion requests per second on a commodity serverAntonios Katsarakis
This slide deck presents DLHT, a concurrent in-memory hashtable. Despite efforts to optimize hashtables, that go as far as sacrificing core functionality, state-of-the-art designs still incur multiple memory accesses per request and block request processing in three cases. First, most hashtables block while waiting for data to be retrieved from memory. Second, open-addressing designs, which represent the current state-of-the-art, either cannot free index slots on deletes or must block all requests to do so. Third, index resizes block every request until all objects are copied to the new index. Defying folklore wisdom, DLHT forgoes open-addressing and adopts a fully-featured and memory-aware closed-addressing design based on bounded cache-line-chaining. This design offers lock-free index operations and deletes that free slots instantly, (2) completes most requests with a single memory access, (3) utilizes software prefetching to hide memory latencies, and (4) employs a novel non-blocking and parallel resizing. In a commodity server and a memory-resident workload, DLHT surpasses 1.6B requests per second and provides 3.5x (12x) the throughput of the state-of-the-art closed-addressing (open-addressing) resizable hashtable on Gets (Deletes).
1. Using All the
Tools You Can
Ruckus Wireless | White Paper Getting the Best Wi-Fi Performance
Possible through Both Beamforming
and Adaptive Antennas
Introduction
User demands on Wi-Fi networks continue to rise quickly This paper provides a thorough introduction to these smart
across every segment of the industry, and as a direct result, antenna technologies, how they can be used together, and
great radio performance matters more than ever. Achiev- the results their combination makes possible in real-world
ing that high performance is no small challenge in the face WLAN networks.
of high AP density, high client counts, and interference —
requiring the use of every technology tool available to better Understanding the Principles of Beamforming
control and improve radio behavior in the environment. This will take some explanation. One of the causes of vendor
marketing excesses in this area is the simple fact that the con-
The latest generation of Wi-Fi chipsets are bringing a poten-
cepts in multi-antenna technology can get complicated, espe-
tially useful new addition to the toolkit: transmit beamforming
cially for Wi-Fi buyers and users who may have strong techni-
with explicit feedback (commonly referred to as “TxBF”). TxBF
cal backgrounds in other fields but who have little experience
can offer gains under the right circumstances, but it has some
in the arcana of advanced radio-frequency engineering — in
inherent limitations that mean it cannot solve the perfor-
other words, the majority of you. We certainly don’t mean that
mance challenge all by itself, despite some vigorous vendor
observation as a slight to any of you, since it’s just fine with
marketing claims to the contrary.
us that you leave the detailed engineering work in this area
Used in combination with adaptive antennas, though, TxBF to the experts. No one would expect you to design your own
can become an essential tool in a comprehensive approach to compact fluorescent light bulbs or LCD televisions, either. The
achieving maximum radio performance in today’s challenging downside, though, is that it’s easy for vendors to mislead cus-
environments. tomers about RF behaviors while sounding vaguely credible,
often without even realizing themselves that they’re com-
Ruckus is continuing in its long tradition of pioneering work pletely disconnected from the real physics of wireless (since
in the cost-effective application of smart antenna concepts to very few marketing people really understand how this all
Wi-Fi, by enhancing our statistical optimization approach to works, either), and certainly with little chance of savvy custom-
radio performance with this combination of TxBF and adap- ers calling the technical foul.
tive antennas. As a result, APs equipped with our BeamFlex
2.0 technology, such as the recently launched ZoneFlex 7982
3x3:3 dual-band 802.11n AP, are setting new performance
benchmarks for the industry.
2. Page 2
Using All the Tools You Can
Since these RF fundamentals matter so much now to the FIGURE 1: Radio signal distribution pattern from an access point
performance of your network, and to the experience of your with one omni-directional antenna.
users, we’re ready to take up the challenge of getting you
enough knowledge to make good Wi-Fi network design
decisions nonetheless. To build the foundation in “how stuff Omni
works” required to accurately assess claims and likely per- Transmit (Tx)
formance benefits for multi-antenna systems, we’re going to Pattern
go back to the basics here, using lots of pictures and defin-
ing carefully the necessary jargon along the way to try to help
make things very clear.
Next we introduce another omni antenna to begin to explore
We start with an old-fashioned single-antenna access point, the options this might provide us for better control of the
shown in Figure 1, with a common omni-directional antenna, radio signal. As shown in Figure 2, the combination of two
or an “omni”. When this device transmits, as the antenna’s copies of the same signal transmitted from two neighbor-
name suggests, it sends the same signal in all directions in the ing omni antennas creates a set of intersecting troughs and
horizontal plane (we’ll worry about what happens in the verti- peaks, much like the wave rings you would get by tossing
cal direction in section 4). While this approach has a certain two separate rocks into a still pond at the same time. In some
satisfying design simplicity, it has substantial performance locations, the peaks of the signal from transmit antenna 1
disadvantages. The vast majority of this radio energy is com- (“Tx 1”, in the jargon) line up in space and time with the peaks
pletely wasted, since an access point can only talk to one client from Tx 2 — this is referred to as constructive combination. In
at a time. Beyond mere waste, this excess energy causes prob- other locations, the peaks of Tx 1’s signal are lined up with the
lems in the form of more self-interference in the WLAN, step- troughs of signal from Tx 2, which yields destructive combina-
ping on neighboring APs and their clients and reducing the tion. If a receive (Rx) antenna is placed in the zone of perfect
possibility of channel reuse nearby. Meanwhile, the tiny frac- constructive combination, it would pick up roughly twice the
tion of transmit energy that actually reaches the client yields a signal strength of a single Tx antenna’s output, without doing
lower throughput rate, as we’ll show shortly, than would be the any intelligent work on its own — its analog receive electron-
case if the energy could be focused more tightly (since client ics simply sum the signals received automatically. In contrast,
throughput is directly related to available signal strength). a zone of complete destructive combination would yield zero
FIGURE 2: Fundamental concepts in multi-antenna processing for increased signal strength (technology often broadly categorized as
“beamforming”)
Signal strength
Tx Antenna 1
2x signal
Time Receive
Antenna (Rx)
Constructive In Phase
Combination
Tx Antenna 2
No signal
Destructive Tx 1
Combination
180º Out Rx
of Phase
Tx 2
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3. Page 3
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FIGURE 3: How signal phase control works in beamforming.
Tx 1
Constructive
Combination
Rx
Destructive
Combination Tx 2
Phase adjustment per antenna to direct
location of constructive combination on client
Client antenna
signal, a phenomenon useful in reducing intra-AP interfer- so that the signals from Tx 1 and Tx 2 arrive at Rx with their
ence at the network level (more on this later). The repeating peaks aligned in time, maximizing signal strength at the cli-
patterns in radio communication signals allow us to use the ent. So far, so simple. Things need to get a little more inter-
concept of phase to describe the peak or trough match-up esting to assess with clarity what’s being used in Wi-Fi today.
relationship between two different signals.
A key underlying requirement in beamforming is that both Tx
One way in which the phenomena of constructive and destruc- 1 and Tx 2 are transmitting the same signal. To understand
tive combinations of multiple transmit sources can be put to why that is important, we need a short word on the nature
productive use is through the addition of active control of of the signals themselves. So far we’ve been using simple
individual transmit signal phases. This is the narrow (and most sinusoidal curves to depict our wireless signals, so they may
technically correct) definition of the term beamforming, and appear to be just generic energy levels, and it might not be
the type of multi-antenna processing that we mentioned at obvious why one segment of the orange curve couldn’t be
the outset is arriving in the current generation of Wi-Fi chip- combined at Rx with any other. The signal-shape reality of
sets. In beamforming systematic manipulation of the phase today’s encoded wireless transmissions is much more com-
of signals transmitted from multiple antennas is used to place plex. In order to achieve high throughput, many bits are trans-
zones of constructive combination that fall ideally at the loca- mitted at the same time on a single signal “wave”, in a format
tion of the client of interest. We illustrate this in Figure 3. The called a constellation, where at a single snapshot in time each
depiction of the transmission pattern has been cleaned up bit holds a particular place in a matrix in the real and imagi-
here in order to show only the areas of strongest constructive nary number space. Fortunately for the many of you we’ve just
combination, which is the common convention for showing lost with that last sentence, this particular batch of complexity
“antenna patterns” — essentially the equivalent of geographic is not important to understand fully in the context of evaluat-
contour maps, where the lines in this case indicate levels of ing multi-antenna processing technology. For sake of keeping
signal strength rather than height. You can see where the term things as simple as possible, we’ll show “real” wireless signals
beamforming arises, since the resulting patterns tend to have through squiggles we borrowed from the audio electronics
lobes of constructive combination areas that look somewhat world, in order to illustrate some key concepts.
like “beams” of energy shining out from the antenna array,
We put this into practice first in Figure 4. Remember that
much like the beam of a flashlight, that are “formed” by the
the receive processing done by the client in a phase-based
system controlling the individual phases of the antennas.
beamforming system is just simple summation of the sig-
“Controlling phase” in this context means essentially “chang-
nals received at any given time. Figure 4 illustrates visually a
ing when you start transmitting.” Outside the lobes of the pat-
point we can also make through a music analogy: if you had
tern as drawn are areas of destructive combination.
two audio speakers side by side blasting two different tunes
Phase is adjusted by the system to compensate for different (say, Bach’s Brandenburg Concerto #1 and Black Sabbath’s
travel times between each antenna and the client of interest,
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4. Page 4
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FIGURE 4: Phase-based beamforming can only be used with copies of the same signal.
Same waveform Different waveforms
2x signal strength Garbage
Tx 1 Tx 1
In Phase Rx In Phase Rx
Tx 2 Tx 2
“Fairies Wear Boots”) at the same time, you’d hear essentially performance assessment that beamforming with implicit feed-
just noise. If they were both playing the same tune at exactly back really just doesn’t work very well, for primarily this reason.
the same time, you’d hear a louder version of the tune. So to
Explicit Feedback: To improve on the poor performance
repeat: TxBF requires multiple copies of the same signal arriv-
of implicit feedback, the alternative accommodated in the
ing in phase at the receiver.
802.11n standard that is just now coming into infrastructure
The other key underlying requirement in beamforming is that products and (eventually, it is hoped) clients in Wi-Fi involves
the system knows where the client is, in an RF-signal-path communication from the client to the AP of what would work
sense of the term “where”, in order to choose phase adjust- best for the client (in terms of the AP’s transmit phases and
ments to point or “steer” one of its beams in the right direc- other settings), given the client’s current vantage point in the
tion. In the Wi-Fi world there are two different approaches radio space. This is the variety of beamforming to which we
being used for educating the AP about client “location”: referred in our introduction, commonly termed TxBF. Wi-Fi
client adoption of this feature will be a gradual process over
Implicit Feedback: In the normal course of communication
the coming years, so this approach faces some commercial
from client to AP, the AP can detect from its multiple anten-
challenges in practice. More technically, while it certainly
nas the different phases of arrival of a signal from the client
improves the quality of the AP’s understanding of the charac-
on each of the AP’s antennas. This is roughly analogous to
teristics of the best radio path to the client, it remains subject
the way human ears process sounds that arrive at each ear at
to the limitations intrinsic to small-antenna-count beamform-
different times and therefore give an indication of the direc-
ing in the context of Wi-Fi networks. We elaborate on the
tion from which the sound came. It’s worth noting that for
nature of these limitations in the following sections.
the same reason our ears can be deceived by sound bounc-
ing off acoustically reflective surfaces, the AP’s impression of One final note on this category: since the manipulation of sig-
the client achieved by measurement of signal arrival phase nal phase must be done at the PHY layer (at the lowest level of
differences is not a terribly reliable indication of actual physi- hardware), both implicit and explicit beamforming functional-
cal location — because of signal reflection off surfaces in ity must be built into the Wi-Fi chipset. For this reason, these
the environment in which the AP and client are operating. In techniques are sometimes referred to as “chip-based beam-
implicit beamforming the phase differences are used as just forming” in the industry.
that — phase differences that should be applied to the AP’s
transmit antennas to achieve maximum constructive combina- The next fundamental building block:
tion on the next transmit to that client. Spatial multiplexing
Phase-based beamforming was actually the simpler story. The
The flaw in using the radio-space characteristics of the uplink
more complex topic that is more essential to the high data
from client to AP as a model for what should be used to manip-
rates defined in the 802.11n Wi-Fi protocol is spatial multi-
ulate signals in the downlink is that signal behavior can differ
plexing, or SM. Note that in the Wi-Fi community the term
substantially between the uplink and downlink paths, largely
MIMO is often used as a synonym for SM, which it’s not, really.
because of the differing antenna geometries of APs and cli-
ents. We’ll show quantitatively in our subsequent section on
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5. Page 5
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FIGURE 5: How spatial multiplexing works.
Different coded
waveforms Matrix decode,
(on same frequency) not simple sum
Data stream
split ...1011 Tx 1 Rx 1 ...1011
...1101001101 and cross-encoded for Tx Data stream recombined ...1101001101
...0010 Tx 2 Air, Rx 2 ...0010
with
spatial
diversity
or
Since we’re trying to sort things out clearly here, it’s worth certainly forgotten by now. For our purposes here we can just
cleaning this one up at the outset with a couple definitions: say that the combination of special pre-encoding and spatial
diversity (signals differing based on where in physical space
MIMO = an acronym for “multiple input, multiple output”.
they are received) are leveraged in receive processing to dis-
Defined from the vantage point of the air between an AP and a
entangle the streams that got combined in the air between
client, the term refers simply to a system design where more than
Tx and Rx. Note that this technology can be used by clients to
one transmit antenna put signals into the air (multiple input), and
send multiple streams to APs as well. Also note that without
where more than one receive antenna extracts these signals from
spatial diversity between the streams, decoding fails. This spa-
the air (multiple output). MIMO systems can be used to do a vari-
tial diversity requirement will become important when we look
ety of different forms of multi-antenna processing, but not neces-
at optimal tool selection for different radio jobs in a moment,
sarily all at the same time, as we’ll discuss below.
as will the nature of the signals involved. As we’ve illustrated
SM = spatial multiplexing. A system in which a single flow of in Figure 5, spatial multiplexing requires that Tx antennas pro-
bits is broken up into two or more streams that are transmit- duce different signal waveforms in order for the system to code
ted into the air from Tx antennas separated in space (with and decode the multiple streams. Phase-based beamforming
one stream per antenna). These multiple streams are then requires the transmission of multiple copies of the same signal
extracted from the air by the same number of Rx antennas, waveform, as we showed previously. With two transmit anten-
also separated in space, and then recombined into the origi- nas (and two receive antennas on the other end of the air link,
nal single bit flow. SM requires a MIMO antenna architecture, to complete the MIMO requirement for SM), it should be obvi-
i.e., multiple antennas on both client and AP. The point of the ous that a system can do spatial multiplexing or phase-based
exercise is to get bits over the air interface faster through beamforming, but not both at the same time.
additional parallel “lanes” for traffic on the same spectrum.
To put the impact of this in context, we repeat for conve-
Figure 5 illustrates how this works from a radio signal perspec- nience in Figure 6 the well-known tabulation of bit rates
tive. It may appear at first glance to break the rules for signal defined for the various modulation and coding schemes in
combination we introduced in section 2, since the blue and the IEEE’s Wi-Fi standards series. The highlighted part of the
orange signals received on each client antenna look like our 802.11n table emphasizes that all the more interesting rates
metaphorical Bach and Black Sabbath arriving at the same ear- require two or more spatial streams. In other words, sensible
drum, just creating noise. The details of exactly how SM signals 802.11 systems will bias their designs toward maximizing the
are coded on transmit and decoded on receive go beyond the use of spatial multiplexing for clients that can support it.
scope of this paper and would require reviving matrix-math
tricks you learned in the undergrad linear algebra class you’ve
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7. Page 7
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In Contrast: Understanding Adaptive Antennas FIGURE 7: High-level view of Ruckus BeamFlex architecture.
While we often use the term “beamforming” loosely, in the
generic sense of “shaping radio energy in space,” to talk about Off-the-Shelf RF
the variety of multi-antenna processing we have employed in 802.11 Silicon
RF
our APs to date, as a matter of convenience when we don’t
Host MAC PHY RF
want to have a long discussion about distinctions between
n antenna elements
different multi-antenna architectures, that’s not an entirely
accurate term for what we have been doing, given the strict
Better antenna patterns
definition we introduced in section 2. As we illustrate in Figure
The baseline for comparison here is the kinds of beam patterns
7, the approach we’ll call for the moment BeamFlex 1.0 involves
that can be created with phase-based beamforming — illus-
digitally switching a selection from a large number of antenna
trated in Figure 8. This approach is limited to using only as many
elements to connect with the individual radio chains in the RF
antennas as it has radio chains. With only two or three anten-
front end of off-the-shelf Wi-Fi silicon. A “radio chain” is the RF
nas at work, the shapes that can be created are fairly limited in
engineering term for the analog radio part between the chip
structure, and they have consistent characteristics that diminish
doing the digital Wi Fi protocol processing and the antennas.
their utility in practice: they are symmetric, and their lobes or
In BeamFlex 1.0 there is no analog adjustment of phase on
beams tend to be relatively narrow. The symmetry means that
each radio chain. Instead, an optimal combination of antennas
from the perspective of a target client, half the energy transmit-
is selected on a packet-by-packet basis to focus patterns of
ted is wasted. From the vantage point of neighboring APs in
radio energy in the right radio-space ‘direction’ based on the
the WLAN, this energy is worse than wasted — it means louder
inherent characteristics of the antenna elements themselves.
co-channel interference. The narrow widths mean they are
The selection for a given client is based on the throughput last
pretty unforgiving about inaccurately pointed beams. If an AP’s
achieved with that client, confirmed through the ACK packet
estimate of the right phase combination to use for its antennas
that is a standard part of the 802.11a, b, g, and n Wi-Fi proto-
is a little off (either because it was using imperfect implicit feed-
cols and that is supported by all clients today. [Note that some
back, or because the higher-quality explicit feedback forthcom-
vendors attempt to compensate for their lack of intellectual
ing in Wi-Fi systems has gotten out of date because of delays in
property contributions in Wi-Fi by de-positioning BeamFlex
its use, high client mobility, or rapid changes in the environment
as “non-standard” — which couldn’t be further from the truth.
like a door closing), the beam formed will fall where the client
Our APs are absolutely 100% compliant with the 802.11 proto-
isn’t, and an area of destructive combination will fall where the
cols, as proven by the Wi-Fi Alliance certification we receive
client is, making the whole exercise worse than useless.
on every model we sell, and require absolutely zero special
behavior on the part of clients.] With AA, in contrast, highly asymmetric patterns can be
achieved that have much more forgiving lobe shapes, and
Of the many terms used in the general area of multi-antenna
with huge variety across physical as well as polarization space
processing techniques (such as smart antennas, beam switch-
(See Figure 9). Because the n elements of a Ruckus antenna
ing, beamforming, and so on), the most accurate classification
matrix can be switched combinatorially to the radio chains of
of BeamFlex 1.0 would probably be in the category of adap-
a Wi-Fi chipset, the number of possible patterns is 2n. Typical
tive antennas (AA). The statistical optimization engine that AP configurations contain thousands of possible patterns.
powers its superior performance is also managing a number
of other variables at the system level, including rate selection The asymmetry of these patterns provides very significant
and power control, so it is about more than just antenna adap- benefits when you look at a WLAN with many access points.
tation itself, an idea to which we will return in a moment in the As Figure 10 shows, a typical Ruckus AA pattern has as much
context of BeamFlex 2.0. as 10 to 15 dB of inherent self-interference suppression over
more than half of the total coverage area. As a result, Ruckus
There are three primary functional advantages in our ability APs tend to be better neighbors of each other in a network
to use a combination of multiple antennas on individual Wi Fi than is the case for conventional approaches, whether they
radio chains in AA: better antenna patterns, compatibility with using TxBF or simple omni antennas alone.
spatial multiplexing, and more effective support for polariza-
tion diversity. We’ll look at each in turn.
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FIGURE 8: Full range of patterns of constructive signal combination that can be achieved through phase-based beamforming, with
two or three transmit antennas in a typical Wi-Fi AP’s configuration (other patterns not shown are simple mirror images of these
across a vertical axis).
Two Antennas
Three Antennas
FIGURE 9: Sample of patterns of constructive signal combination that can be achieved through Ruckus BeamFlex (total variations
available = 2n, where n = the number of elements in the AP’s antenna matrix)
1 2 3 4 5 6 2n
•••
Finally, when combined with TxBF in BeamFlex 2.0, our asym- FIGURE 10: Typical BeamFlex antenna system pattern and
inherent interference reduction.
metric adaptive antenna patterns deliver better client connec-
tions while continuing to reduce self-interference, relative to dBi
10 Client
TxBF operation alone. Figure 11 illustrates how this works. 5
0
Typical
-5
BeamFlex
-10
Pattern
Compatibility with Spatial Multiplexing -15
BeamFlex is the industry’s only multi-antenna approach that -20
-25
can support both spatial multiplexing and constructive signal -30
combination at the same time using only two transmit radio
chains. An example of how this works is shown in Figure 12
10 – 15 db
below. [We’ll note in the interest of full disclosure that it is
interference
technically possible to support the combination of SM and mitigation over more
TxBF on an AP with four radio chains, but that configuration than 180°
is not commercially viable in today’s Wi-Fi market because of
high hardware costs and power requirements beyond the lim-
its of the 802.3af PoE source that is used for the vast majority
of AP installations.]
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FIGURE 11: Advantages of BeamFlex AA and TxBF working in concert.
Problem Best-of-Both-Worlds Solution
Client Direction
AP
+ =
Conventional TxBF Pattern Asymmetric Composite BeamFlex 2.0
BeamFlex AA Pattern AA + TxBF Pattern
Net Result:
Better Client Connection TxBF alone
Composite AA + TxBF
Less Self-Interference than
Symmetric TxBF Pattern
FIGURE 12: Ruckus’ unique ability to enhance spatial multiplexing with adaptive antennas.
1
Two-stream encoding 2
as in Figure 5. 3
4
Rx 1
Tx RF 5
6
7 Decoding
as in Figure 5.
Tx RF
8
9 Rx 2
10
11
BeamFlex engine 12 Better, and balanced, Higher signal strength
assigns streams to coherent combination enables higher modulation
antennas selected of both signals on both class (bit rate) on both
for best signal Rx antennas streams, for higher 802.11n
propagation MCS
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Support for Polarization Diversity Up until a few years ago, Wi-Fi networks were largely verti-
To explain this final difference between AA and TxBF, we cally polarized affairs. The vast majority of connected devices
need to introduce one more fundamental RF concept, the were laptops, and these were used generally in only one ori-
idea of signal polarization — the understanding of which entation, with the keyboard horizontal, and the display (which
requires a little more discussion of how radios and anten- commonly houses the antenna) vertical. APs used vertically-
nas work. Recall our simple “omni” antenna from Section 1. polarized antennas, and all was well.
In very simple terms, signal transmission from this antenna
occurs because a power amplifier in the AP moves electrons The avalanche of smart mobile devices on Wi-Fi networks
in the antenna, and the motion of the electrons causes travel- has changed all this. They are used in any number of angles
ing disturbances in the electromagnetic field that surrounds relative to horizontal, and more important, they are used in
them — an effect commonly known as radio waves. As the both landscape and portrait modes. Figure 14 indicates the
shape and configuration of our simple antenna example problem this causes in simple terms: with vertically-polarized
(repeated in Figure 13) suggests, the electrons’ motion is ori- antennas in both a tablet and the AP with which it is commu-
ented vertically in the figure. This results in a configuration of nicating, rotating the tablet 90º will produce a horizontally-
the electromagnetic (or radio) wave that is known as vertical polarized wave that the AP can’t receive.
polarization — meaning that the energy in the wave oscillates
FIGURE 14: Effect of polarization on connection quality.
in a vertical plane aligned with the direction of travel. Radio
waves can have purely vertical or purely horizontal polariza-
tion, or oscillation around the direction of the travel that is at
an angle somewhere between the two. To receive a signal,
APs and client devices both apply essentially the reverse of H wave vertically
the transmit physics. Instead of the current applied to the
polarized Rx
antenna that is used on transmit, on receive the antenna
“picks up” the incident radio wave in the form of electron
near 0% received
motion in the antenna that is stimulated by the electromag- V wave 100% signal received
netic field disturbance arriving at it. The tiny current in the
receive antenna created by the electrons’ motion is detected
by the sensitive electronics to which the antenna is con-
Fortunately, the situation is not quite as dire as all that, or
nected and then amplified to permit processing of the signal.
there would have been much more mass revolt about the
Antenna elements are usually specified as either vertically or
poor Wi-Fi performance of the whole smart mobile device
horizontally polarized, which indicates which polarization of
class than has so far been the case. Multipath and reflec-
waves they can both transmit and receive.
tions in the radio environment typically cause changes in the
FIGURE 13: Illustration of radio wave polarization. polarization angle of waves as they travel from client to AP
and vice-versa, so a vertically-polarized AP will still be able
to receive some vertical component of the signal. But this
vertically polarized
wave remains a legitimate concern when capacity demands on the
network stipulate squeezing every available bit of productivity
out of the channel being used.
There are a couple of different approaches to addressing
this issue on the AP side — which is where the work must be
Understanding both the transmit and receive physics at this
done, given very tight constraints on antenna count and con-
simple level is required to grasp why the polarization of Tx
figuration on mobile devices. The first is an inelegant kludge,
and Rx must be the same: if the Tx signal polarization is verti-
involving simply tilting omni antennas on a conventional AP,
cal but the Rx antenna is horizontal (or vice-versa), the wave
and the second involves use of our adaptive antenna designs
cannot excite electrons in the right direction on the receive
to deliver much more effective diversity in practice.
side, and essentially no signal is detected.
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Once again, we have to introduce a little more detail in the This means that if you attempt to provide Tx and Rx diversity
behavior of our omni antenna in order to illustrate the differ- by tilting antennas of this design, as we illustrate in Figure 16
ences between the common kludge and our proper AA solu- (using an elevation view of the coverage patterns for clarity),
tion. It turns out that the “omni” antenna example we’ve been you tilt the whole “donut” of coverage along with it — leav-
using isn’t actually omnidirectional in the broadest sense of ing potentially very large coverage holes in many areas for
the term. In the horizontal plane, yes, but not in the vertical. one or even both antennas. The fundamental mismatch in this
As Figure 15 shows, the coverage pattern of an omni stick configuration between the coverage of the multiple anten-
antenna is actually more like a donut in 3D space. nas will defeat the purpose of having more than one antenna
in the first place: essentially any multi-antenna processing on
FIGURE 15: 3D coverage pattern from a single omni antenna. transmit or receive will fail frequently, including TxBF, spa-
tial multiplexing, and maximum ratio combining (MRC), the
receive processing most commonly used in Wi-Fi to extract
the best possible signal from multiple Rx antennas. Further,
fixed polarization diversity of this nature, where it does actu-
ally achieve effective overlap from two antennas, significantly
reduces the effectiveness of TxBF. If two signals with opposite
polarization arrive at a receive antenna of arbitrary orienta-
tion, somewhere between 50 and 100% of the potential gain
from the intended coherent signal combination will be lost
because the Rx antenna can capture only one component
(either vertical or horizontal, but not both) of the signals.
In contrast, Ruckus APs, equipped with a large number of
FIGURE 16: Major coverage-hole downside to the common
adaptive antenna elements, cover a generally hemispheri-
technique of achieving “faux” polarization diversity by changing
the fixed orientation of a small number of omni antennas. cal aggregate pattern (illustrated in Figure 17), using com-
binations of vertical and horizontal polarization throughout,
Significant coverage gaps,
especially for TxBF, MRC, or not, as client orientation and path optimization dictate.
or spatial multiplexing Hence our AA approach can use polarization diversity in con-
cert with spatial multiplexing and MRC, where it can provide
material performance enhancement in today’s multi-orienta-
tion mobile-device world, and choose not to use polarization
diversity to enhance the performance of TxBF where that is
the most productive multi-antenna approach to employ.
FIGURE 17: Ruckus AP aggregate coverage pattern, including A proper multi-antenna processing taxonomy
adaptive polarization diversity throughout. To summarize the multi-antenna technologies we’ve reviewed
here, and to set the stage for our final assessment sections 6
and 7, we present on the next page a thorough taxonomy of
current approaches.
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12. Page 12
Using All the Tools You Can
Implicit Explicit Adaptive Antennas BeamFlex 2.0
Attributes Beamforming Beamforming (TxBF) (AA) AA+TxBF
802.11 protocols supported a, b, g, n n a, b, g, n a, b, g, n
adaptation effectively open loop closed loop closed loop closed loop
must send AP trans-
client behavior requirement none mit characteristics none as with TxBF
‘recommendation’
measurement of standard client ACK
client’s client reco for TxBF +
source of feedback uplink signal from packet on previous
recommendation ACK for AA
client transmission
supports 802.11n spatial multiplexing NO* NO* YES YES
supports polarization diversity NO NO YES YES
typical SINR gain, Tx none 3 dB 4–6 dB 8 dB
typical SINR gain, Rx none none 4 dB 4 dB
network self-interference reduction none none 10–15 dB 10-15 dB
* ould require 2 or more radio chains and antennas per spatial stream, a commercially impractical configuration given high hardware costs and
w
power requirements exceeding 802.3af PoE limits
Performance Gains
As we’ve developed a baseline understanding of how the vari- bination that are both sensitive to phasing inaccuracies and very
ous multi-antenna processing techniques work, we’ve noted a symmetric (generating more concentrated co-channel interfer-
few characteristics that affect their performance. Now we pull ence to neighboring APs).
these observations together, along with external validation, to
As a result, it’s reasonable to expect at best modest perfor-
quantify these technologies’ typical performance gains in real
mance gains. In fact, results we’ve seen from 3rd-party testing
networks. We’ll discuss the key metrics and validation for each
(See Figure 18) suggest that the gains can be closely approxi-
of the four categories in turn.
mated by the number 0. We exclude implicit beamforming
from further analysis here for this reason.
Beamforming with Implicit Feedback
A number of vendors have embraced the chip-based approaches
Beamforming with Explicit Feedback
to beamforming over the past couple of years, largely just to add
At this writing, very few vendors have brought APs to market
“beamforming” to their marketing materials, since we’ve done
based on the new generation of Wi-Fi chipsets that include
so much to popularize the idea. Given that the explicit version
explicit-feedback beamforming that is nominally part of the
requires client functionality that still has not yet reached the mar-
802.11n standard. Since there are still no client devices on the
ket (more on this very important point in Section 8), all but a very
market that support this technology, we have not seen any
limited subset of the entrants in the beamforming race are using
performance testing from third parties.
implicit-feedback beamforming. As we saw in section 2, implicit
beamforming suffers from fundamental flaws: the absence of any We do have close working relationships with the chipset ven-
corrective feedback about whether or not a set of antenna phase dors who are enabling this next step in phase-based beamform-
decisions has been effective at all, the reliance on uplink charac- ing. In conversations far from the limelight of AP vendor market-
teristics to estimate the downlink (an unreliable metric), incom- ing efforts, the engineering teams at the Wi-Fi chipset suppliers
patibility with 802.11n spatial multiplexing rates (without adding
impractical numbers of RF chains), and patterns of coherent com-
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13. Page 13
Using All the Tools You Can
FIGURE 18: Example third-party comparative test results for BeamFlex AA
implicit beamforming. We have a large number of external validation points from cus-
tomers and other third parties that indicate our APs perform
Zap
UDP Mb/sec, 2.4 GHz about twice as well as conventional APs from any of the others
Location 2
in real-world implementations. This can take the form of 2x
Ruckus 7962 107.63
the throughput for a given client distribution, 2x the coverage,
Cisco Aironet LAP1142N w/ BF 72.9
and/or 2x the throughput in the face of interference. This kind
Cisco Aironet LAP1142N w/o BF 69.85 of performance improvement can most easily be summarized
as a 6 dB gain in link budget on the downlink, averaging across
Aruba AP125 43.4
many different situations.
0 20 40 60 80 100 120
Minimum @ 50% (average throughout)
Zap Polarization Diversity
UDP Mb/sec, 2.4 GHz
Location 5 On the uplink, our support for polarization diversity in our AP
Ruckus 7962 35.775 designs has been shown to yield up to 4 dB of effective link bud-
Cisco Aironet LAP1142N w/ BF 23.7
get gain at the 80th percentile, measuring throughput to iPad cli-
ents across a variety of locations and orientations (See Figure 19).
Cisco Aironet LAP1142N w/o BF 25.875
Aruba AP125 0.85
Putting it all together
0 5 10 15 20 25 30 35 40 We summarize these performance perspectives in Figure 20.
Minimum @ 50% (average throughout)
First off, for those of you wondering what happened to the 450
Mbps rate that 3-stream spatial multiplexing is advertised to
(many of whom have long histories in the area of multi-antenna
deliver, please note the conditions assumed for this compari-
processing techniques and therefore credible views on the sub-
son. The peak 3-stream rate of 450 is raw bits in a 40 MHz wide
ject) have provided us the following information:
5 GHz channel at 400 ns guard interval (see our separate white
For
1. the same reasons we’ve outlined above (incompat-
FIGURE 19: Throughput test results for iPads in a variety of orien-
ibility with spatial multiplexing, limited beam-shaping
tations show that polarization diversity adds the equivalent of 4
degrees of freedom when you have at most three anten- dB SINR gain in the 80th percentile range.
nas, and the inaccuracy-sensitivity of the narrow beams
Snoop vs Dal uplink
thus formed), they have low expectations for the techni- 250
snoopvvh
cal value of implementing the explicit beamforming part snoopvvv
of the 802.11n standard. Dal5g
200
2. fact, their own lab testing has shown that the tech-
In
nique is only marginally more effective than implicit
beamforming — yielding gains that range from a fraction
150
of a dB to at most 3 dB.
mbps
3. follows naturally that commercial implementation has
It
always been a low priority for the chip vendors, and its 100
entry into chips now was motivated almost exclusively
by pressure from their larger AP vendor customers who
wanted to add the capability to their sales story. 50
For the purposes of our quantitative comparison in the bal-
ance of this paper, we will give the technology a little benefit
0
10 20 30 40 50 60 70 80 90 100
of the doubt and assume the chipset vendors’ figure of 3 dB in
% of 50ms samples (combined across locations)
performance gain is a reasonable expectation.
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14. Page 14
Using All the Tools You Can
FIGURE 20: Rate and range comparison of various multi-antenna technologies. See text for additional explanatory notes and sources.
RF Technology Comparison
300 DL Throughput, Mbps
[1] 1x1:1 omni
250 [2] 1x1:1 TxBF
[3] 1x1:1 AA+TxBF
[4] 3x3:3 omni
200
[5] 3x3:3+TxBF (for non-SM MCSs)
[6] 3x3:3 AA + TxBF (non-SM)
150
100
50
0
0 10 20 30 40 50 60 70
Range, m
RF Technology Comparison
100 UL Throughput, Mbps
90
[7] 1x1:1 single-polarization MRC
80
70 [8] 1x1:1 polarization-diversity MRC
60
50
40
30
20
10
0
0 10 20 30 40 50 60 70
Range, m
Notes on conditions: 5 GHz, 40 MHz channel, 800 ns guard interval, ETSI EIRP level, UDP traffic,
medium level of Wi-Fi and other interference, near LoS link conditions, indoors.
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15. Page 15
Using All the Tools You Can
paper Caveat Emptor for more details on translation from [4] DL 802.11n 3x3:3 omni. For this and the next two curves,
peak Wi-Fi claims to real-world usable throughput rates). We we depict system performance with a high-end laptop on the
prefer to frame the analysis in a domain relevant to real-world client side, supporting three spatial streams. The baseline
net usable packet throughput (net of 802.11 protocol over- for this use case is a conventional AP with omni antennas and
head and other factors) for real equipment. So our analysis neither TxBF nor AA. Most of this curve is actually coincident
depicts UDP traffic in 5 GHz, which cuts the peak three-stream with the next curve, [5], for reasons that will become clear in a
rate down from the theoretical maximum of 450 to 272 Mbps. moment. Note the descent of the 3x3 system’s performance as
The other dimension of realism is client to AP range — we’ve a function of range. The higher modulation classes (based on
assumed here ETSI requirements for EIRP (100 mW) and a 64 QAM, a very complex constellation) in combination with 3
healthy dose of interference and fading margin for busy indoor spatial streams are only effective, in practice, at shorter ranges
conditions (15 dB). where there is enough diversity in the signal paths to accu-
rately decode the three streams. Note that the performance
Now to explain each of the curves:
of the 3x3:3 system converges toward that of the 1x1:1 system
[1] DL 802.11n 1x1:1 omni. This is the low water mark, depict- at longer range, as the realities of RF propagation reduce the
ing the kind of performance expected from a conventional ability to achieve SM with reliability even for 2 streams.
omni-equipped AP with no multi-antenna processing, com-
[5] DL 802.11n 3x3:3 + TxBF for non-SM MCSs. As we’ve
municating in downlink (DL) with a single-antenna client like a
noted, TxBF cannot be used simultaneously with SM. One can,
smartphone or a tablet.
however, consider its use for the non-SM MCS rates (0 through
[2] DL 802.11n 1x1:1 + Explicit-Feedback Transmit Beam- 7) in 802.11n, to enhance link budget under conditions (such as
forming. As we explained in section 2, the addition of explicit- low diversity or long range) where SM is not possible. We’ve
feedback beamforming on a conventional 2- or 3-stream AP shown this effect in the right-hand side of curve [5], where it
(the only practical model extant today) provides the system diverges from curve [4]. For speeds above 25 Mbps, roughly,
the choice of using TxBF or spatial multiplexing, but not both SM would be employed and scenario [4] and [5] are the same.
at the same time. With only 3 dB of incremental gain to offer,
[6] DL 802.11n 3x3:3 + BeamFlex 2.0. This adds BeamFlex
TxBF does not provide enough of a performance benefit to
AA gains on top of the SM-based rates in a 3-stream 11n chan-
outweigh the data rate gains from SM in any case other than
nel along with TxBF gains for the non-SM MCSs on the right
that for which SM is not an option, the 1x1:1 system. As can
end of the chart. As with curve [3], the advantages in through-
be seen, 3 dB doesn’t buy a lot, in terms of either throughput
put at a given range driven by BeamFlex AA technology
increases or range extension — roughly a 30% increase.
remain quite substantial.
[3] DL 802.11n 1x1:1 with Adaptive Antennas + TxBF
[7] UL 802.11n 1x1:1 Single-Polarization MRC. This depicts
(BeamFlex 2.0). Here we apply both adaptive antennas and
the baseline performance in uplink from a single-antenna
TxBF to a single-stream client, yielding a 2x or better improve-
smart mobile device to a 3-antenna AP performing conven-
ment in range or capacity from the combination.
tional MRC processing, assuming all 3 antennas have the same
This reflects the two spatial streams performance of an AP polarization.
equipped with 2 omni antennas communicating with a 2 Rx
[8] UL 802.11n 1x1:1 Polarization-Diversity MRC. Finally, we
equipped client such as a laptop. Note that the performance
depict the results of introducing BeamFlex adaptive polariza-
of the 2x2:2 system converges to that of the 1x1:1 system at
tion on the multi-antenna AP Rx side, which allows polarization-
longer range, as the realities of RF propagation reduce the
diversity MRC (PD MRC) processing and yields around 4 dB of
ability to achieve spatial multiplexing with reliability. The per-
effective SINR improvement. As the curve shows, this can yield
formance of an AP with implicit or explicit beamforming capa-
substantial (~2x) improvements in client throughput on uplink,
bilities would look exactly the same as this curve, because of
which is commonly the limiting metric for network dimension-
the mutual exclusivity of spatial multiplexing and phase-based
ing in today’s user-generated-content-rich application environ-
beamforming.
ment and therefore an extremely valuable improvement.
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16. Page 16
Using All the Tools You Can
Using the Right Tool for the Job ers of the limited subset of chip vendors who have done so in
As we noted at the start, the introduction of TxBF on the smart response, they have been able to advertise that they support
antenna scene does add a potentially productive new tool to TxBF. With the launch of our ZoneFlex 7982 and 7321 products,
our radio performance kitbag, but as we’ve shown in the bal- we are joining this select group, but with the twist of using it in
ance of this paper, it’s clear one has to be careful to under- combination with our adaptive antenna technology, as we do
stand for which jobs this new tool is well suited in practice. believe TxBF technology used in this way will provide value in
We’ve summarized our findings on the best application of the certain situations, as we’ve shown.
various multi-antenna approaches below.
There are two further steps that must be taken by the Wi-Fi
industry in order for any benefits to be realized out in the real
That’s all fine, but where are the clients? world of enterprise and carrier Wi-Fi networks, however. Client
After all this heavy lifting, it’s unfortunate that we must report (i.e. mobile device) manufacturers and their chipset provid-
there is a show-stopper issue in the way of realizing any ben- ers must implement the optional 802.11n feature on their side
efits from TxBF in the near term. To explain, we need to step of the connection (in order to support the explicit feedback
out of the realm of how the technologies themselves work, required to make transmit beamforming worthwhile at all), and
and into the matter of how the business of Wi-Fi equipment then the Wi-Fi Alliance must add the feature to the multiven-
supply works. dor interop testing done as part of their mandatory product
certification requirements program, after having secured the
We’ve mentioned that Wi-Fi infrastructure vendors have participation of five infrastructure and five client vendors in
been pressuring the chipset providers to put TxBF — an support of the feature. At this writing (April, 2012), neither of
optional feature in the 802.11n standard — into their recent these has happened, and there is currently no expectation
chip releases, largely for the marketing benefit of “checking that they will anytime soon, if ever, for the 802.11n standard.
the beamforming box” on RFP feature lists. For the custom- There is a version of TxBF included in the 802.11ac standard
Conventional
Omni Antennas Adaptive Antennas BeamFlex 2.0
Applications (no smarts) TxBF (AA + PD-MRC) AA+TxBF
Higher SINR improvement than TxBF (and
Useful, given Even better, given
DL to mobile devices lower network self-interference) under all
client support client support
circumstances
Useful at long
No legitimate Higher SINR improvement than TxBF (and Even better where
range (where
DL to laptops technical reason lower network self-interference) under all SM fails, given client
SM fails), given
to continue using circumstances support
client support
these under any
circumstances
Same as AA alone
UL from mobile devices
No help Substantial gain from polarization diversity (no impact from TxBF
or laptops
addition)
Helpful where Even better where
Meshing Higher SINR improvement
SM fails SM fails
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