This document discusses feedback methods for multiple-input multiple-output (MIMO) wireless systems. It introduces MIMO technology and outlines its benefits for improving spectral efficiency and signal quality. The document then discusses channel adaptive or closed-loop MIMO systems that use feedback to allow the transmitter to adapt to channel conditions. It proposes a limited feedback framework where a codebook known to both transmitter and receiver is used to convey channel state through a low-rate feedback path. The document explores applications of this framework for beamforming, precoded orthogonal space-time block codes, and precoded spatial multiplexing. It addresses challenges in codeword selection and codebook design for each application.
This document provides an overview of a course on multi-antenna techniques and their applications. It discusses the use of multiple antennas to combat fading through diversity combining and spatial multiplexing to achieve higher data rates. It notes that while more antennas can improve performance, there are diminishing returns due to factors like mutual coupling between closely spaced antennas. The document also compares spatial multiplexing and diversity, noting that multiplexing transmits multiple streams for higher throughput while diversity transmits one stream redundantly for better reliability.
This document provides an overview of wireless communications and mobile WiMax systems. It discusses key topics like the wireless environment, link budgets, MIMO and OFDM techniques, and hardware/software partitioning in wireless systems. It also introduces FPGAs and their role in building DSP subsystems for digital baseband processing in wireless applications. Mobile WiMax is presented as an example wireless communication system that utilizes many of these technologies.
11.performance evaluation of maximal ratio receiver combining diversity with ...Alexander Decker
The document evaluates the performance of Maximal Ratio Receiver Combining (MRRC) diversity technique for an Interleave-Division Multiple Access (IDMA) receiver with single transmit and two receive antennas. Simulation results show that MRRC diversity provides significant improvement to the bit error rate (BER) performance of IDMA. The BER performance of an IDMA system using a prime interleaver is found to be similar to one using a random interleaver, but with reduced bandwidth and memory requirements.
Performance evaluation of maximal ratio receiver combining diversity with pri...Alexander Decker
This document summarizes a research paper that evaluates the performance of Maximal Ratio Receiver Combining (MRRC) diversity with different interleavers for an Iterative Interleave-Division Multiple Access (IDMA) receiver. The paper finds that using MRRC diversity with one transmit and two receive antennas significantly improves the bit error rate performance of IDMA. It also finds that using a prime interleaver achieves similar performance to a random interleaver but with reduced bandwidth and memory requirements. The document introduces IDMA and describes the system model, interleaving techniques, and MRRC diversity approach that are evaluated through simulation to analyze the bit error rate performance of the IDMA system under different conditions.
Hybrid Beamforming in Massive-MIMO mmWave- Fatimah Azeez 30-1-2021.pptxFatima Azeez
This document summarizes a paper on hybrid beamforming in massive MIMO mmWave systems using LU decomposition. It first provides background on massive MIMO, beamforming, and hybrid beamforming systems. It then describes a system model for hybrid beamforming that uses digital baseband and analog RF precoding/combining. The document formulates the problem of maximizing spectral efficiency given hardware constraints. Simulation results show the proposed LU decomposition approach achieves higher spectral efficiency than other methods for single-user and multi-user scenarios. The conclusions discuss developing an efficient hybrid beamforming method using LU factorization and future work investigating other environments and factorization techniques.
For MIMO system, (a) Please talk about the advantage and disadvantag.pdfarihantstoneart
For MIMO system, (a) Please talk about the advantage and disadvantage of MIMO technique.
(b) Please explain why we need Cooperative Diversity to replace MIMO in cellular network.
Solution
A)MIMO advantages
• Capacity scales linearly with number of antennas
Channel knowledge/estimation at Rx needed
• MIMO offers potential for
larger data rate
larger spectral efficiency
larger number of users
improved range/coverage
better interference suppression
better quality of service (QoS), lower bit-error rate (BER)
lower Tx power
MIMO disavantages
• Hardware complexity:
Each antenna needs a radio-frequency (RF) unit
Powerful digital signal processing (DSP) unit required
• Software complexity:
Most signal processing algorithms are computationally intensive
Power consumption:
Battery lifetime of mobile devices
Thermal problems
Antennas:
Antenna spacing (electromagnetic mutual coupling-e.g. mobile handsets)
RF interference and antenna correlation
B)
Most of the present researches on cooperative
network in which the user nodes are equipped with a single
antenna or multiple, there have been some new results which
exploit the benefits of multiple antenna deployment.
Cooperative MIMO technology allows a wireless network
system to attain better performance gains than provided by
either usual MIMO or cooperative systems. It promised
significant improvement in spectral efficiency and network
coverage phenomena for different next generation wireless
communication systems. In wireless communication, the path
towards the various techniques that gives high service quality
and data rate has been through the use of the cooperative
network provided by the rich scattering wireless channels.
Due to their great aspects, MIMO and cooperative systems
have found their way into several standards for future
wireless communication systems, especially in cellular
networks and wireless local area networks (LAN) in this
review article we are presenting the comparative analysis..
This document provides an overview of a course on multi-antenna techniques and their applications. It discusses the use of multiple antennas to combat fading through diversity combining and spatial multiplexing to achieve higher data rates. It notes that while more antennas can improve performance, there are diminishing returns due to factors like mutual coupling between closely spaced antennas. The document also compares spatial multiplexing and diversity, noting that multiplexing transmits multiple streams for higher throughput while diversity transmits one stream redundantly for better reliability.
This document provides an overview of wireless communications and mobile WiMax systems. It discusses key topics like the wireless environment, link budgets, MIMO and OFDM techniques, and hardware/software partitioning in wireless systems. It also introduces FPGAs and their role in building DSP subsystems for digital baseband processing in wireless applications. Mobile WiMax is presented as an example wireless communication system that utilizes many of these technologies.
11.performance evaluation of maximal ratio receiver combining diversity with ...Alexander Decker
The document evaluates the performance of Maximal Ratio Receiver Combining (MRRC) diversity technique for an Interleave-Division Multiple Access (IDMA) receiver with single transmit and two receive antennas. Simulation results show that MRRC diversity provides significant improvement to the bit error rate (BER) performance of IDMA. The BER performance of an IDMA system using a prime interleaver is found to be similar to one using a random interleaver, but with reduced bandwidth and memory requirements.
Performance evaluation of maximal ratio receiver combining diversity with pri...Alexander Decker
This document summarizes a research paper that evaluates the performance of Maximal Ratio Receiver Combining (MRRC) diversity with different interleavers for an Iterative Interleave-Division Multiple Access (IDMA) receiver. The paper finds that using MRRC diversity with one transmit and two receive antennas significantly improves the bit error rate performance of IDMA. It also finds that using a prime interleaver achieves similar performance to a random interleaver but with reduced bandwidth and memory requirements. The document introduces IDMA and describes the system model, interleaving techniques, and MRRC diversity approach that are evaluated through simulation to analyze the bit error rate performance of the IDMA system under different conditions.
Hybrid Beamforming in Massive-MIMO mmWave- Fatimah Azeez 30-1-2021.pptxFatima Azeez
This document summarizes a paper on hybrid beamforming in massive MIMO mmWave systems using LU decomposition. It first provides background on massive MIMO, beamforming, and hybrid beamforming systems. It then describes a system model for hybrid beamforming that uses digital baseband and analog RF precoding/combining. The document formulates the problem of maximizing spectral efficiency given hardware constraints. Simulation results show the proposed LU decomposition approach achieves higher spectral efficiency than other methods for single-user and multi-user scenarios. The conclusions discuss developing an efficient hybrid beamforming method using LU factorization and future work investigating other environments and factorization techniques.
For MIMO system, (a) Please talk about the advantage and disadvantag.pdfarihantstoneart
For MIMO system, (a) Please talk about the advantage and disadvantage of MIMO technique.
(b) Please explain why we need Cooperative Diversity to replace MIMO in cellular network.
Solution
A)MIMO advantages
• Capacity scales linearly with number of antennas
Channel knowledge/estimation at Rx needed
• MIMO offers potential for
larger data rate
larger spectral efficiency
larger number of users
improved range/coverage
better interference suppression
better quality of service (QoS), lower bit-error rate (BER)
lower Tx power
MIMO disavantages
• Hardware complexity:
Each antenna needs a radio-frequency (RF) unit
Powerful digital signal processing (DSP) unit required
• Software complexity:
Most signal processing algorithms are computationally intensive
Power consumption:
Battery lifetime of mobile devices
Thermal problems
Antennas:
Antenna spacing (electromagnetic mutual coupling-e.g. mobile handsets)
RF interference and antenna correlation
B)
Most of the present researches on cooperative
network in which the user nodes are equipped with a single
antenna or multiple, there have been some new results which
exploit the benefits of multiple antenna deployment.
Cooperative MIMO technology allows a wireless network
system to attain better performance gains than provided by
either usual MIMO or cooperative systems. It promised
significant improvement in spectral efficiency and network
coverage phenomena for different next generation wireless
communication systems. In wireless communication, the path
towards the various techniques that gives high service quality
and data rate has been through the use of the cooperative
network provided by the rich scattering wireless channels.
Due to their great aspects, MIMO and cooperative systems
have found their way into several standards for future
wireless communication systems, especially in cellular
networks and wireless local area networks (LAN) in this
review article we are presenting the comparative analysis..
Achieving repeatable wireless throughput measurements under realistic conditions has been a monumental challenge for the wireless industry. The reason? Throughput of wireless links is a function of many variables, all of which must be controlled to get repeatable measurements. For benchmark testing, throughput has to be maximized in a manner that is repeatable and reproducible at multiple labs around the world. The challenges and methods of achieving maximum possible throughput and repeatable measurements are the subject of this talk.
The document discusses modeling a 4G LTE system in MATLAB. It provides an overview of 4G LTE standards and features, and presents a case study of modeling the downlink physical layer of an LTE system in MATLAB. Key aspects covered include channel coding, OFDM, MIMO, link adaptation, and options for simulation acceleration and connecting system design to implementation through code generation.
This document summarizes an OFDM channel estimation project. It discusses the objective to maximize OFDM system capacity through channel estimation and adaptive transmission. It outlines the system architecture, including the transmitter, channel, receiver, and channel estimation. It also lists the work completed, such as programs for channel impulse response, Rayleigh fading, and adding noise.
Performance enhancement of maximum ratio transmission in 5G system with multi...IJECEIAES
This document summarizes a research paper that proposes improving the performance of 5G systems using maximum ratio transmission (MRT) with multi-user multiple-input multiple-output (MU-MIMO) by incorporating weighted overlap-add (WOLA) precoding. It compares the proposed WOLA-MRT system to a standard MRT system with orthogonal frequency-division multiplexing (OFDM). Simulation results show the proposed system achieves approximately 60% higher throughput and a 2% lower bit error rate than the standard system, demonstrating significant performance enhancements for 5G massive MIMO networks.
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.
Performance Analysis of MIMO-LTE for MQAM over Fading ChannelsIOSRJECE
LTE (Long Term Evolution) is a 3GPP (Third Generation Partnership Project) wireless standards which uses the standard OFDMA (Orthogonal Frequency Division Multiple Access) modulation, MU-MIMO (Multiuser Multiple Input Multiple Output) technology and different multipath fading models. LTE uses the spectrum more efficiently to deliver high speed data. This paper characterizes the downlink performance of LTE. The MIMO technology which provides high data rate applications to the users made a breakthrough in wireless communication and is defined in the LTE standard. The performance is characterized in terms of BER (Bit Error Rate). In this paper the LTE system is modelled and simulated using MATLAB and the BER for 2×2 and 4×4 MIMO-LTE using 16QAM and 64QAM modulation schemes for Rayleigh fading environment are obtained against different SNR values.
This document discusses the design of point-to-point optical fiber communication links. It covers key considerations like link power and rise time budgets, selecting optical sources and detectors, and noise sources. Factors like transmission distance, data rate, fiber type, wavelength, and power levels must be chosen to satisfy the budgets. Link noise sources include modal, mode partition, and interferometric noise. The document provides examples of link calculations and graphs showing dispersion and noise effects.
Error Rate Analysis of MIMO System Using V Blast Detection Technique in Fadin...IJERA Editor
Wireless communication system with multi- antenna arrays has been a field of intensive analysis on the last years. The appliance of multiple sending antennas and Receiving Antennas either side will considerably enhance the data rate and rate. The review of the performance limitations of MIMO system becomes vital since it will provide lot ideas in understanding and planning the important life MIMO systems. Vertical Bell Laboratories layered space Time (V-BLAST). The thought behind Multiple Input and Multiple Output system is that the signals on the transmitter antennas at one finish and also the receiver antennas at the opposite finish are correlative in such how that the performance (Bit Error Rate or BER) or the info rate (bits/sec) of the wireless communication system for every MIMO subscriber are improved. During this paper we tend to are proposing a technique that evaluates the performance of V-BLAST MIMO system in several thought of Rayleigh attenuation surroundings to urge higher performance of the system. In V- BLAST MIMO system a number of linear detection techniques will be used for interference cancellation. At this point we are using MMSE-IC for the same. Our expected system provide higher error rate performance with the used of matched filter at receiver aspect .The projected system compared within the presence of AWGN. Now matched filter applied on V- BLAST MIMO with MMSE-IC system in fading diversity surroundings.
Cordless systems and wireless local loop (WLL) technologies provide wireless connectivity for voice and data services. Cordless systems operate in residential and office environments using base stations to connect to wired networks. WLL uses point-to-multipoint architectures with stationary antennas to deliver broadband connectivity over longer ranges than cordless systems. Standards like 802.16 specify the protocol architecture and frame formats for WLL, including physical layer modulation and medium access control. Considerations for WLL deployment include propagation effects at high frequencies and mitigating rain attenuation through frequency selection.
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.
Performance Analysis of Multi-QoS Model of OCDMA System by Adopting OPPM Sign...IJERA Editor
In this paper, optical CDMA which combines the large bandwidth of the fibre medium with the flexibility of the
CDMA technique to achieve high speed connectivity has been used. For achieving this purpose, OPPM
signalling and switching techniques have been employed. This helps in the achievement of high tolerance to
Multiple Access Interference, further resulting in improvement of both the Bit Error Rate and optical channel
capacity without the need to decrease the light pulse width. An OPPM scheme to support multimedia services
with different transmission rates and Quality of Service requirements is proposed. Packet Switching technique
has been employed to help in the transfer of data in the form of packets from the source to the destination via a
specified route. The results are calculated by using PPM signalling and switching technology.But switching
technology has been found to be far better than the OOK-OCDMA if the average power has been considered as
the restraining factor.
Beamforming for Multiuser Massive MIMO Systems: Digital versus Hybrid Analog-...T. E. BOGALE
The document compares digital and hybrid analog-digital beamforming for multiuser massive MIMO systems. It describes the system model and problem formulation. Digital beamforming requires many RF chains and ADCs which is expensive for massive MIMO. Hybrid beamforming uses limited RF chains by employing analog beamforming at the transmitter with phase shifters. The document proposes a hybrid beamforming algorithm that minimizes the mean square error between the estimated signals of digital and hybrid beamforming. Simulation results show the proposed hybrid approach achieves similar performance as digital beamforming using fewer RF chains and phase shifters. It concludes hybrid beamforming provides significant savings in hardware complexity over digital beamforming for multiuser massive MIMO systems.
An introduction of 3 gpp long term evolution (lte)mojtaba_gh
This document provides an introduction to 3GPP Long Term Evolution (LTE) technology. It discusses the history and basic concepts of LTE, including the use of OFDMA for downlink and SC-FDMA for uplink transmission. It also compares LTE to LTE-Advanced, which supports larger bandwidths up to 100MHz and peak data rates of 1Gbps through techniques like carrier aggregation. The document outlines the evolution of radio access technologies and key aspects of the LTE protocol.
MIMO systems use multiple antennas at both the transmitter and receiver to improve wireless communication performance. By utilizing spatial diversity and spatial multiplexing, MIMO can increase data rates and spectral efficiency without additional bandwidth or power. It also provides diversity gain to combat fading and improve quality of service. Key techniques of MIMO include spatial multiplexing to increase capacity through multiple parallel data streams, and spatial diversity to improve signal quality through redundant transmission paths. MIMO systems show promise to achieve high data rates over wireless channels and help meet the growing demand for wireless network performance.
This document describes a space-time block coding (STBC) orthogonal frequency-division multiplexing (OFDM) system for text message transmission over fading channels using multiple transmit antennas. It evaluates the bit error rate (BER) performance of the system using different digital modulation schemes (BPSK, QPSK, QAM-8) over additive white Gaussian noise (AWGN) channels and fading channels. Low-density parity-check (LDPC) coding is concatenated with convolutional coding in the system to improve error performance. Simulation results show that the system is effective in retrieving the transmitted text message under noise and fading conditions, and that BER performance degrades with increasing noise power as expected.
This document summarizes a research paper that proposes a space-time block coded (STBC) orthogonal frequency-division multiplexing (OFDM) system for text message transmission over fading channels using multiple transmit antennas. The system utilizes low-density parity-check channel coding concatenated with convolutional coding. Simulation results show that the proposed system achieves good error rate performance, especially when using BPSK modulation with 2x4 transmit antennas in AWGN, Rayleigh, and Rician fading channels. The system is effective in properly identifying and retrieving transmitted text messages in noisy and fading environments.
The mobile operators in Libya, as many other operators, use some propagation models to predict the receiver signal strength, but without studying what is the best model for the Tripoli area.
The work proposed in the current research involves the comparison of four radio propagation models based on LTE technology to be applied in the Tripoli environment. Then the tuning of the best model depending on real data from the local environment will be carried out.
Multicarrier modulation can be implemented by using Orthogonal Frequency Division Multiplexing (OFDM) to achieve utmost bandwidth exploitation and soaring alleviation attributes profile besides multipath fading. To support delay sensitive and band bandwidth demanding multimedia applications and internet services, MIMO in addition with other techniques can be used to achieve high capacity and reliability. To obtain high spatial rate by transmitting data on several antennas by using MIMO with OFDM results in reducing error recovery features and the equalization complexities arise by sending data on varying frequency levels. Three parameters frequency OFDM, Spatial (MIMO) and time (STC) can be used to achieve diversity in MIMO-OFDM. This technique is dynamic and well-known for services of wireless broadband access. MIMO if used with OFDM is highly beneficial for each scheme and provides high throughput. There are several space time block codes to exploit MIMO OFDM; one of the techniques is called Alamouti Codes. The paper investigates adaptive Alamouti Codes and their application in IEEE 802.11n.
Introducing Milvus Lite: Easy-to-Install, Easy-to-Use vector database for you...Zilliz
Join us to introduce Milvus Lite, a vector database that can run on notebooks and laptops, share the same API with Milvus, and integrate with every popular GenAI framework. This webinar is perfect for developers seeking easy-to-use, well-integrated vector databases for their GenAI apps.
Achieving repeatable wireless throughput measurements under realistic conditions has been a monumental challenge for the wireless industry. The reason? Throughput of wireless links is a function of many variables, all of which must be controlled to get repeatable measurements. For benchmark testing, throughput has to be maximized in a manner that is repeatable and reproducible at multiple labs around the world. The challenges and methods of achieving maximum possible throughput and repeatable measurements are the subject of this talk.
The document discusses modeling a 4G LTE system in MATLAB. It provides an overview of 4G LTE standards and features, and presents a case study of modeling the downlink physical layer of an LTE system in MATLAB. Key aspects covered include channel coding, OFDM, MIMO, link adaptation, and options for simulation acceleration and connecting system design to implementation through code generation.
This document summarizes an OFDM channel estimation project. It discusses the objective to maximize OFDM system capacity through channel estimation and adaptive transmission. It outlines the system architecture, including the transmitter, channel, receiver, and channel estimation. It also lists the work completed, such as programs for channel impulse response, Rayleigh fading, and adding noise.
Performance enhancement of maximum ratio transmission in 5G system with multi...IJECEIAES
This document summarizes a research paper that proposes improving the performance of 5G systems using maximum ratio transmission (MRT) with multi-user multiple-input multiple-output (MU-MIMO) by incorporating weighted overlap-add (WOLA) precoding. It compares the proposed WOLA-MRT system to a standard MRT system with orthogonal frequency-division multiplexing (OFDM). Simulation results show the proposed system achieves approximately 60% higher throughput and a 2% lower bit error rate than the standard system, demonstrating significant performance enhancements for 5G massive MIMO networks.
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.
Performance Analysis of MIMO-LTE for MQAM over Fading ChannelsIOSRJECE
LTE (Long Term Evolution) is a 3GPP (Third Generation Partnership Project) wireless standards which uses the standard OFDMA (Orthogonal Frequency Division Multiple Access) modulation, MU-MIMO (Multiuser Multiple Input Multiple Output) technology and different multipath fading models. LTE uses the spectrum more efficiently to deliver high speed data. This paper characterizes the downlink performance of LTE. The MIMO technology which provides high data rate applications to the users made a breakthrough in wireless communication and is defined in the LTE standard. The performance is characterized in terms of BER (Bit Error Rate). In this paper the LTE system is modelled and simulated using MATLAB and the BER for 2×2 and 4×4 MIMO-LTE using 16QAM and 64QAM modulation schemes for Rayleigh fading environment are obtained against different SNR values.
This document discusses the design of point-to-point optical fiber communication links. It covers key considerations like link power and rise time budgets, selecting optical sources and detectors, and noise sources. Factors like transmission distance, data rate, fiber type, wavelength, and power levels must be chosen to satisfy the budgets. Link noise sources include modal, mode partition, and interferometric noise. The document provides examples of link calculations and graphs showing dispersion and noise effects.
Error Rate Analysis of MIMO System Using V Blast Detection Technique in Fadin...IJERA Editor
Wireless communication system with multi- antenna arrays has been a field of intensive analysis on the last years. The appliance of multiple sending antennas and Receiving Antennas either side will considerably enhance the data rate and rate. The review of the performance limitations of MIMO system becomes vital since it will provide lot ideas in understanding and planning the important life MIMO systems. Vertical Bell Laboratories layered space Time (V-BLAST). The thought behind Multiple Input and Multiple Output system is that the signals on the transmitter antennas at one finish and also the receiver antennas at the opposite finish are correlative in such how that the performance (Bit Error Rate or BER) or the info rate (bits/sec) of the wireless communication system for every MIMO subscriber are improved. During this paper we tend to are proposing a technique that evaluates the performance of V-BLAST MIMO system in several thought of Rayleigh attenuation surroundings to urge higher performance of the system. In V- BLAST MIMO system a number of linear detection techniques will be used for interference cancellation. At this point we are using MMSE-IC for the same. Our expected system provide higher error rate performance with the used of matched filter at receiver aspect .The projected system compared within the presence of AWGN. Now matched filter applied on V- BLAST MIMO with MMSE-IC system in fading diversity surroundings.
Cordless systems and wireless local loop (WLL) technologies provide wireless connectivity for voice and data services. Cordless systems operate in residential and office environments using base stations to connect to wired networks. WLL uses point-to-multipoint architectures with stationary antennas to deliver broadband connectivity over longer ranges than cordless systems. Standards like 802.16 specify the protocol architecture and frame formats for WLL, including physical layer modulation and medium access control. Considerations for WLL deployment include propagation effects at high frequencies and mitigating rain attenuation through frequency selection.
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.
Performance Analysis of Multi-QoS Model of OCDMA System by Adopting OPPM Sign...IJERA Editor
In this paper, optical CDMA which combines the large bandwidth of the fibre medium with the flexibility of the
CDMA technique to achieve high speed connectivity has been used. For achieving this purpose, OPPM
signalling and switching techniques have been employed. This helps in the achievement of high tolerance to
Multiple Access Interference, further resulting in improvement of both the Bit Error Rate and optical channel
capacity without the need to decrease the light pulse width. An OPPM scheme to support multimedia services
with different transmission rates and Quality of Service requirements is proposed. Packet Switching technique
has been employed to help in the transfer of data in the form of packets from the source to the destination via a
specified route. The results are calculated by using PPM signalling and switching technology.But switching
technology has been found to be far better than the OOK-OCDMA if the average power has been considered as
the restraining factor.
Beamforming for Multiuser Massive MIMO Systems: Digital versus Hybrid Analog-...T. E. BOGALE
The document compares digital and hybrid analog-digital beamforming for multiuser massive MIMO systems. It describes the system model and problem formulation. Digital beamforming requires many RF chains and ADCs which is expensive for massive MIMO. Hybrid beamforming uses limited RF chains by employing analog beamforming at the transmitter with phase shifters. The document proposes a hybrid beamforming algorithm that minimizes the mean square error between the estimated signals of digital and hybrid beamforming. Simulation results show the proposed hybrid approach achieves similar performance as digital beamforming using fewer RF chains and phase shifters. It concludes hybrid beamforming provides significant savings in hardware complexity over digital beamforming for multiuser massive MIMO systems.
An introduction of 3 gpp long term evolution (lte)mojtaba_gh
This document provides an introduction to 3GPP Long Term Evolution (LTE) technology. It discusses the history and basic concepts of LTE, including the use of OFDMA for downlink and SC-FDMA for uplink transmission. It also compares LTE to LTE-Advanced, which supports larger bandwidths up to 100MHz and peak data rates of 1Gbps through techniques like carrier aggregation. The document outlines the evolution of radio access technologies and key aspects of the LTE protocol.
MIMO systems use multiple antennas at both the transmitter and receiver to improve wireless communication performance. By utilizing spatial diversity and spatial multiplexing, MIMO can increase data rates and spectral efficiency without additional bandwidth or power. It also provides diversity gain to combat fading and improve quality of service. Key techniques of MIMO include spatial multiplexing to increase capacity through multiple parallel data streams, and spatial diversity to improve signal quality through redundant transmission paths. MIMO systems show promise to achieve high data rates over wireless channels and help meet the growing demand for wireless network performance.
This document describes a space-time block coding (STBC) orthogonal frequency-division multiplexing (OFDM) system for text message transmission over fading channels using multiple transmit antennas. It evaluates the bit error rate (BER) performance of the system using different digital modulation schemes (BPSK, QPSK, QAM-8) over additive white Gaussian noise (AWGN) channels and fading channels. Low-density parity-check (LDPC) coding is concatenated with convolutional coding in the system to improve error performance. Simulation results show that the system is effective in retrieving the transmitted text message under noise and fading conditions, and that BER performance degrades with increasing noise power as expected.
This document summarizes a research paper that proposes a space-time block coded (STBC) orthogonal frequency-division multiplexing (OFDM) system for text message transmission over fading channels using multiple transmit antennas. The system utilizes low-density parity-check channel coding concatenated with convolutional coding. Simulation results show that the proposed system achieves good error rate performance, especially when using BPSK modulation with 2x4 transmit antennas in AWGN, Rayleigh, and Rician fading channels. The system is effective in properly identifying and retrieving transmitted text messages in noisy and fading environments.
The mobile operators in Libya, as many other operators, use some propagation models to predict the receiver signal strength, but without studying what is the best model for the Tripoli area.
The work proposed in the current research involves the comparison of four radio propagation models based on LTE technology to be applied in the Tripoli environment. Then the tuning of the best model depending on real data from the local environment will be carried out.
Multicarrier modulation can be implemented by using Orthogonal Frequency Division Multiplexing (OFDM) to achieve utmost bandwidth exploitation and soaring alleviation attributes profile besides multipath fading. To support delay sensitive and band bandwidth demanding multimedia applications and internet services, MIMO in addition with other techniques can be used to achieve high capacity and reliability. To obtain high spatial rate by transmitting data on several antennas by using MIMO with OFDM results in reducing error recovery features and the equalization complexities arise by sending data on varying frequency levels. Three parameters frequency OFDM, Spatial (MIMO) and time (STC) can be used to achieve diversity in MIMO-OFDM. This technique is dynamic and well-known for services of wireless broadband access. MIMO if used with OFDM is highly beneficial for each scheme and provides high throughput. There are several space time block codes to exploit MIMO OFDM; one of the techniques is called Alamouti Codes. The paper investigates adaptive Alamouti Codes and their application in IEEE 802.11n.
Introducing Milvus Lite: Easy-to-Install, Easy-to-Use vector database for you...Zilliz
Join us to introduce Milvus Lite, a vector database that can run on notebooks and laptops, share the same API with Milvus, and integrate with every popular GenAI framework. This webinar is perfect for developers seeking easy-to-use, well-integrated vector databases for their GenAI apps.
Full-RAG: A modern architecture for hyper-personalizationZilliz
Mike Del Balso, CEO & Co-Founder at Tecton, presents "Full RAG," a novel approach to AI recommendation systems, aiming to push beyond the limitations of traditional models through a deep integration of contextual insights and real-time data, leveraging the Retrieval-Augmented Generation architecture. This talk will outline Full RAG's potential to significantly enhance personalization, address engineering challenges such as data management and model training, and introduce data enrichment with reranking as a key solution. Attendees will gain crucial insights into the importance of hyperpersonalization in AI, the capabilities of Full RAG for advanced personalization, and strategies for managing complex data integrations for deploying cutting-edge AI solutions.
TrustArc Webinar - 2024 Global Privacy SurveyTrustArc
How does your privacy program stack up against your peers? What challenges are privacy teams tackling and prioritizing in 2024?
In the fifth annual Global Privacy Benchmarks Survey, we asked over 1,800 global privacy professionals and business executives to share their perspectives on the current state of privacy inside and outside of their organizations. This year’s report focused on emerging areas of importance for privacy and compliance professionals, including considerations and implications of Artificial Intelligence (AI) technologies, building brand trust, and different approaches for achieving higher privacy competence scores.
See how organizational priorities and strategic approaches to data security and privacy are evolving around the globe.
This webinar will review:
- The top 10 privacy insights from the fifth annual Global Privacy Benchmarks Survey
- The top challenges for privacy leaders, practitioners, and organizations in 2024
- Key themes to consider in developing and maintaining your privacy program
Cosa hanno in comune un mattoncino Lego e la backdoor XZ?Speck&Tech
ABSTRACT: A prima vista, un mattoncino Lego e la backdoor XZ potrebbero avere in comune il fatto di essere entrambi blocchi di costruzione, o dipendenze di progetti creativi e software. La realtà è che un mattoncino Lego e il caso della backdoor XZ hanno molto di più di tutto ciò in comune.
Partecipate alla presentazione per immergervi in una storia di interoperabilità, standard e formati aperti, per poi discutere del ruolo importante che i contributori hanno in una comunità open source sostenibile.
BIO: Sostenitrice del software libero e dei formati standard e aperti. È stata un membro attivo dei progetti Fedora e openSUSE e ha co-fondato l'Associazione LibreItalia dove è stata coinvolta in diversi eventi, migrazioni e formazione relativi a LibreOffice. In precedenza ha lavorato a migrazioni e corsi di formazione su LibreOffice per diverse amministrazioni pubbliche e privati. Da gennaio 2020 lavora in SUSE come Software Release Engineer per Uyuni e SUSE Manager e quando non segue la sua passione per i computer e per Geeko coltiva la sua curiosità per l'astronomia (da cui deriva il suo nickname deneb_alpha).
Essentials of Automations: The Art of Triggers and Actions in FMESafe Software
In this second installment of our Essentials of Automations webinar series, we’ll explore the landscape of triggers and actions, guiding you through the nuances of authoring and adapting workspaces for seamless automations. Gain an understanding of the full spectrum of triggers and actions available in FME, empowering you to enhance your workspaces for efficient automation.
We’ll kick things off by showcasing the most commonly used event-based triggers, introducing you to various automation workflows like manual triggers, schedules, directory watchers, and more. Plus, see how these elements play out in real scenarios.
Whether you’re tweaking your current setup or building from the ground up, this session will arm you with the tools and insights needed to transform your FME usage into a powerhouse of productivity. Join us to discover effective strategies that simplify complex processes, enhancing your productivity and transforming your data management practices with FME. Let’s turn complexity into clarity and make your workspaces work wonders!
20 Comprehensive Checklist of Designing and Developing a WebsitePixlogix Infotech
Dive into the world of Website Designing and Developing with Pixlogix! Looking to create a stunning online presence? Look no further! Our comprehensive checklist covers everything you need to know to craft a website that stands out. From user-friendly design to seamless functionality, we've got you covered. Don't miss out on this invaluable resource! Check out our checklist now at Pixlogix and start your journey towards a captivating online presence today.
Let's Integrate MuleSoft RPA, COMPOSER, APM with AWS IDP along with Slackshyamraj55
Discover the seamless integration of RPA (Robotic Process Automation), COMPOSER, and APM with AWS IDP enhanced with Slack notifications. Explore how these technologies converge to streamline workflows, optimize performance, and ensure secure access, all while leveraging the power of AWS IDP and real-time communication via Slack notifications.
Dr. Sean Tan, Head of Data Science, Changi Airport Group
Discover how Changi Airport Group (CAG) leverages graph technologies and generative AI to revolutionize their search capabilities. This session delves into the unique search needs of CAG’s diverse passengers and customers, showcasing how graph data structures enhance the accuracy and relevance of AI-generated search results, mitigating the risk of “hallucinations” and improving the overall customer journey.
Why You Should Replace Windows 11 with Nitrux Linux 3.5.0 for enhanced perfor...SOFTTECHHUB
The choice of an operating system plays a pivotal role in shaping our computing experience. For decades, Microsoft's Windows has dominated the market, offering a familiar and widely adopted platform for personal and professional use. However, as technological advancements continue to push the boundaries of innovation, alternative operating systems have emerged, challenging the status quo and offering users a fresh perspective on computing.
One such alternative that has garnered significant attention and acclaim is Nitrux Linux 3.5.0, a sleek, powerful, and user-friendly Linux distribution that promises to redefine the way we interact with our devices. With its focus on performance, security, and customization, Nitrux Linux presents a compelling case for those seeking to break free from the constraints of proprietary software and embrace the freedom and flexibility of open-source computing.
Sudheer Mechineni, Head of Application Frameworks, Standard Chartered Bank
Discover how Standard Chartered Bank harnessed the power of Neo4j to transform complex data access challenges into a dynamic, scalable graph database solution. This keynote will cover their journey from initial adoption to deploying a fully automated, enterprise-grade causal cluster, highlighting key strategies for modelling organisational changes and ensuring robust disaster recovery. Learn how these innovations have not only enhanced Standard Chartered Bank’s data infrastructure but also positioned them as pioneers in the banking sector’s adoption of graph technology.
Observability Concepts EVERY Developer Should Know -- DeveloperWeek Europe.pdfPaige Cruz
Monitoring and observability aren’t traditionally found in software curriculums and many of us cobble this knowledge together from whatever vendor or ecosystem we were first introduced to and whatever is a part of your current company’s observability stack.
While the dev and ops silo continues to crumble….many organizations still relegate monitoring & observability as the purview of ops, infra and SRE teams. This is a mistake - achieving a highly observable system requires collaboration up and down the stack.
I, a former op, would like to extend an invitation to all application developers to join the observability party will share these foundational concepts to build on:
Removing Uninteresting Bytes in Software FuzzingAftab Hussain
Imagine a world where software fuzzing, the process of mutating bytes in test seeds to uncover hidden and erroneous program behaviors, becomes faster and more effective. A lot depends on the initial seeds, which can significantly dictate the trajectory of a fuzzing campaign, particularly in terms of how long it takes to uncover interesting behaviour in your code. We introduce DIAR, a technique designed to speedup fuzzing campaigns by pinpointing and eliminating those uninteresting bytes in the seeds. Picture this: instead of wasting valuable resources on meaningless mutations in large, bloated seeds, DIAR removes the unnecessary bytes, streamlining the entire process.
In this work, we equipped AFL, a popular fuzzer, with DIAR and examined two critical Linux libraries -- Libxml's xmllint, a tool for parsing xml documents, and Binutil's readelf, an essential debugging and security analysis command-line tool used to display detailed information about ELF (Executable and Linkable Format). Our preliminary results show that AFL+DIAR does not only discover new paths more quickly but also achieves higher coverage overall. This work thus showcases how starting with lean and optimized seeds can lead to faster, more comprehensive fuzzing campaigns -- and DIAR helps you find such seeds.
- These are slides of the talk given at IEEE International Conference on Software Testing Verification and Validation Workshop, ICSTW 2022.
Unlocking Productivity: Leveraging the Potential of Copilot in Microsoft 365, a presentation by Christoforos Vlachos, Senior Solutions Manager – Modern Workplace, Uni Systems
Generative AI Deep Dive: Advancing from Proof of Concept to ProductionAggregage
Join Maher Hanafi, VP of Engineering at Betterworks, in this new session where he'll share a practical framework to transform Gen AI prototypes into impactful products! He'll delve into the complexities of data collection and management, model selection and optimization, and ensuring security, scalability, and responsible use.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024
WSN PPT.ppt
1. Feedback Methods for Multiple-Input
Multiple-Output Wireless Systems
David J. Love
WNCG
The University of Texas at Austin
March 4, 2004
2. Wireless Networking and Communication Group 2
Outline
Introduction
MIMO Background
MIMO Signaling
Channel Adaptive (Closed-Loop) MIMO
Limited Feedback Framework
Limited Feedback Applications
Beamforming
Precoded Orthogonal Space-Time Block Codes
Precoded Spatial Multiplexing
Other Areas of Research
3. Wireless Networking and Communication Group 3
Wireless Challenges
Spectral efficiency
Spectrum very expensive $$$
Maximize data rate per bandwidth bits/sec/Hz
Quality
Wireless links fluctuate
Desire SNR to have large mean and low variance
Limited transmit power
How can we maximize spectral efficiency
and quality?
4. Wireless Networking and Communication Group 4
Solution: MIMO Wireless Systems
Multiple-input multiple-output (MIMO) using multiple antennas at
transmitter and receiver
Antennas spaced independent fading
Allow space-time signaling
Receiver
•
•
•
Transmitter •
•
•
5. Wireless Networking and Communication Group 5
SNR (dB)
MIMO Capacity Benefits [Telatar]
Multiply Data Rate
Multiply throughput $$$
Multiply # users $$$
min(Tx,Rx) antennas
Rate
Slope
1 by 1 antenna
4.3 b/s/Hz
8 by 8
antennas
32.3 b/s/Hz
Capacity
1 by 16
antennas
9 b/s/Hz
6. Wireless Networking and Communication Group 6
Signal Quality Through Diversity
Antennas provide diversity advantage [Brennan]
Large gains for moderate to high SNR
Reduced fading!
Better user experience $$$
Signal
Power
standard
with MIMO
time
1 antenna
4th order
diversity
Diversity = -slope
SNR (dB)
Error
Rate
(log
scale)
7. Wireless Networking and Communication Group 7
MIMO Systems are Relevant
Fixed wireless access
802.16.3 standard (optional)
3G cellular
HSDPA – (optional)
Local area networks
802.11N Study Group (possibly mandatory)
Mobile Broadband Wireless
802.20 Working Group (possibly mandatory --- too early)
4G
Lots of discussion
8. Wireless Networking and Communication Group 8
Space-Time Signaling
Design in space and time
Transmit matrices – transmit one column each
transmission
Sent over a linear channel
time
space
Assumption: is an i.i.d. complex Gaussian matrix
9. Wireless Networking and Communication Group 9
Role of Channel Knowledge
Open-loop MIMO [Tarokh et al]
Signal matrix designed independently of channel
Most popular MIMO architecture
Closed-loop MIMO [Sollenberger],[Telatar],[Raleigh et al]
Signal matrix designed as a function of channel
Performance benefits
10. Wireless Networking and Communication Group 10
Closed-Loop Performance Benefits
Channel capacity fundamentally
larger
Simplified decoding
Reduced error rate
Allows multiuser scheduling
(transmit to group of best users)
SNR (dB)
Capacity
SNR (dB)
Error
Rate
(log
scale)
4b/s/Hz
12 dB
11. Wireless Networking and Communication Group 11
Transmitter Channel Knowledge
Fundamental problem: How does the transmitter find out
the current channel conditions?
Observation: Receiver knows the channel
Solution: Use feedback
Transmitter
...
...
Receiver
Feedback
12. Wireless Networking and Communication Group 12
Solution: Send back feedback [Narula et al],[Heath et al]
Feedback channel rate very limited
Rate 1.5 kb/s (commonly found in standards, 3GPP, etc)
Update 3 to 7 ms (from indoor coherence times)
Limited Feedback Problem
Transmitter Receiver
...
...
Data
Feedback
Feedback amount around 5 to 10 bits
13. Wireless Networking and Communication Group 13
Outline
Introduction
MIMO Background
MIMO Signaling
Channel Adaptive (Closed-Loop) MIMO
Limited Feedback Framework
Limited Feedback Applications
Beamforming
Precoded Orthogonal Space-Time Block Codes
Precoded Spatial Multiplexing
Other Areas of Research
14. Wireless Networking and Communication Group 14
Prior work [Narula et al],[Jongren et al]: Quantize channel
Channel quantization fails for MIMO
8x8 MIMO = More than 128 bits of feedback!
Singular value structure sensitive to quantization
Feedback Design Problem
Transmitter Receiver
...
...
Quantizer
15. Wireless Networking and Communication Group 15
Solution: Limited Feedback Precoding
Use open-loop algorithm with linear transformation
(precoder)
Restrict to
Codebook known at transmitter/receiver and fixed
Convey codebook index when channel changes
bits
H
Choose F
from
codebook
Update
precoder
Low-rate feedback path
…
Open-Loop
Space-Time
Encoder
Receiver
…
H
X
F
…
…
FX
16. Wireless Networking and Communication Group 16
Use selection function such that
Selection function depends on
Underlying open-loop algorithm
Performance criterion
Solution: Use perfect channel knowledge selection but
optimize over codebook
Challenge #1: Codeword Selection
Channel
Realization
H
Codebook
matrix
17. Wireless Networking and Communication Group 17
Challenge #2: Codebook Design
Codebook design very important
Given:
Underlying open-loop algorithm
Selection function
Goal: Quantize (in some sense) the perfect channel
knowledge precoder
18. Wireless Networking and Communication Group 18
Communications Vector Quantization
Let
Communications Approach: [Love et al]
System parameter to maximize
Design Objective: Improve system performance
Different than traditional vector quantization
19. Wireless Networking and Communication Group 19
Outline
Introduction
MIMO Background
MIMO Signaling
Channel adaptive (Closed-Loop) MIMO
Limited Feedback Framework
Limited Feedback Applications
Beamforming
Precoded Orthogonal Space-Time Block Codes
Precoded Spatial Multiplexing
Other Areas of Research
20. Wireless Networking and Communication Group 20
Convert MIMO to SISO
Beamforming advantages:
Error probability improvement
Resilience to fading
Limited Feedback Beamforming [Love et al]
Coding &
Modulation
...
H
f
...
fs
Detection
and
Decoding
Feedback
y
s
unit vector
r
Complex
number
21. Wireless Networking and Communication Group 21
Nearest neighbor union bound [Cioffi]
Instantaneous channel capacity [Cover & Thomas]
[Love et al]
Challenge #1: Beamformer Selection
22. Wireless Networking and Communication Group 22
Want to maximize on average
Average distortion
Using sing value decomp & Gaussian random matrix
results [James 1964] ( )
where is a uniformly distributed unit vector
Challenge #2: Beamformer Codebook
channel term codebook term
23. Wireless Networking and Communication Group 23
Codebook as Subspace Code
is a subspace distance – only
depends on subspace not vector
Codebook is a subspace code
Minimum distance [Sloane et al]
set of lines
24. Wireless Networking and Communication Group 24
Bounding of Criterion
Grassmannian Beamforming Criterion [Love et al]:
Design
by maximizing
Grassmann
manifold
metric ball volume [Love et al]
radius2
25. Wireless Networking and Communication Group 25
Feedback vs Diversity Advantage
Question: How does the feedback amount affect diversity
advantage?
Diversity Theorem [Love & Heath]: Full diversity advantage if
and only if bits of feedback
Proof Sketch:
1. Use: Gaussian matrices are isotropically random
2. Bound by selection diversity (known full diversity)
26. Wireless Networking and Communication Group 26
Simulation
3 by 3
QPSK
SNR (dB)
Error
Rate
(log
scale)
0.6 dB
27. Wireless Networking and Communication Group 27
Beamforming Summary
Contribution #1: Framework for beamforming when channel not
known a priori at transmitter
Codebook of beamforming vectors
Relates to codes of Grassmannian lines
Contribution #2: New distance bounds on Grassmannian line codes
Contribution #3: Characterization of feedback-diversity relationship
More info:
D. J. Love, R. W. Heath Jr., and T. Strohmer, “Grassmannian Beamforming for Multiple-Input
Multiple-Output Wireless Systems,” IEEE Trans. Inf. Th., vol. 49, Oct. 2003.
D. J. Love and R. W. Heath Jr., “Necessary and Sufficient Conditions for Full Diversity Order
in Correlated Rayleigh Fading Beamforming and Combining Systems,” accepted to IEEE
Trans. Wireless Comm., Dec. 2003.
28. Wireless Networking and Communication Group 28
Outline
Introduction
MIMO Background
MIMO Signaling
Channel Adaptive (Closed-Loop) MIMO
Limited Feedback Framework
Limited Feedback Applications
Beamforming
Precoded Orthogonal Space-Time Block Codes
Precoded Spatial Multiplexing
Other Areas of Research
29. Wireless Networking and Communication Group 29
Constructed using orthogonal designs [Alamouti, Tarokh et al]
Advantages
Simple linear receiver
Resilience to fading
Do not exist for most antenna combs (complex signals)
Performance loss compared to beamforming
Orthogonal Space-Time Block Codes (OSTBC)
Space-time
Receiver f e d c b a
f e d c b a
*
*
a
b
b
a
Transmission 1
30. Wireless Networking and Communication Group 30
Solution: Limited Feedback Precoded
OSTBC [Love et al]
Require
Use codebook:
Space-Time
Encoder
...
H
F
...
Feedback
C
...
FC
Detection
and
Decoding
31. Wireless Networking and Communication Group 31
Challenge #1: Codeword Selection
Can bound error rate [Tarokh et al]
Choose matrix from from as [Love et al]
Channel
Realization
H
Codebook
matrix
32. Wireless Networking and Communication Group 32
Challenge #2: Codebook Design
Minimize loss in channel power
Grassmannian Precoding Criterion [Love & Heath]: Maximize
minimum chordal distance
Think of codebook as a set (or packing) of subspaces
Grassmannian subspace packing
33. Wireless Networking and Communication Group 33
Feedback vs Diversity Advantage
Question: How does feedback amount affect diversity
advantage?
Theorem [Love & Heath]: Full diversity advantage if and only
if bits of feedback
Proof similar to beamforming proof.
Precoded OSTBC save at least
bits compared to beamforming!
34. Wireless Networking and Communication Group 34
Simulation
8 by 1
Alamouti
16-QAM
9.5dB
Open-Loop
16bit
channel
8bit lfb
precoder
Error
Rate
(log
scale)
SNR (dB)
35. Wireless Networking and Communication Group 35
Precoded OSTBC Summary
Contribution #1: Method for precoded orthogonal space-time block
coding when channel not known a priori at transmitter
Codebook of precoding matrices
Relates to Grassmannian subspace codes with chordal distance
Contribution #2: Characterization of feedback-diversity relationship
More info:
D. J. Love and R. W. Heath Jr., “Limited feedback unitary precoding for orthogonal space
time block codes,” accepted to IEEE Trans. Sig. Proc., Dec. 2003.
D. J. Love and R. W. Heath Jr., “Diversity performance of precoded orthogonal space-time
block codes using limited feedback,” accepted to IEEE Commun. Letters, Dec. 2003.
36. Wireless Networking and Communication Group 36
Outline
Introduction
MIMO Background
MIMO Signaling
Channel Adaptive (Closed-Loop) MIMO
Limited Feedback Framework
Limited Feedback Applications
Beamforming
Precoded Orthogonal Space-Time Block Codes
Precoded Spatial Multiplexing
Other Areas of Research
37. Wireless Networking and Communication Group 37
True “multiple-input” algorithm
Advantage: High-rate signaling technique
Decode
Invert (directly/approx)
Disadvantage: Performance very sensitive to channel singular values
Spatial Multiplexing [Foschini]
{
Multiple
independent
streams
...
H
...
s
Detection
and
Decoding
...,s1+Mt,s1
...,s2Mt,sMt
y
38. Wireless Networking and Communication Group 38
Limited Feedback Precoded SM [Love et al]
Assume
Again adopt codebook approach
Coding &
Modulation
..
H
F
...
Fs
Feedback
s
... Detection
and
Decoding
39. Wireless Networking and Communication Group 39
Challenge #1: Codeword Selection
Selection functions proposed when known
Use unquantized selection functions over
MMSE (linear receiver) [Sampath et al], [Scaglione et al]
Minimum singular value (linear receiver) [Heath et al]
Minimum distance (ML receiver) [Berder et al]
Instantaneous capacity [Gore et al]
Channel
Realization
H
Codebook
matrix
40. Wireless Networking and Communication Group 40
Challenge #2: Distortion Function
Min distance, min singular value, MMSE (with trace) [Love
et al]
MMSE (with det) and capacity [Love et al]
41. Wireless Networking and Communication Group 41
Codebook Criterion
Grassmannian Precoding Criterion [Love & Heath]:
Maximize
Min distance, min singular value, MMSE (with trace) –
Projection two-norm distance
MMSE (with det) and capacity – Fubini-Study distance
42. Wireless Networking and Communication Group 42
Simulation
4 by 2
2 substream
16-QAM
16bit channel
Perfect
Channel
6bit lfb
precoder 4.5dB
Error
Rate
(log
scale)
SNR per bit (dB)
43. Wireless Networking and Communication Group 43
Precoded Spatial Multiplexing Summary
Contribution #1: Method for precoding spatial multiplexing
when channel not known a priori at transmitter
Codebook of precoding matrices
Relates to Grassmannian subspace codes with projection two-
norm/Fubini-Study distance
Contribution #2: New bounds on subspace code density
More info:
D. J. Love and R. W. Heath Jr., “Limited feedback unitary precoding for spatial
multiplexing systems,” submitted to IEEE Trans. Inf. Th., July 2003.
44. Wireless Networking and Communication Group 44
Outline
Introduction
MIMO Background
MIMO Signaling
Channel Adaptive (Closed-Loop) MIMO
Limited Feedback Framework
Limited Feedback Applications
Beamforming
Precoded Orthogonal Space-Time Block Codes
Precoded Spatial Multiplexing
Other Areas of Research
45. Wireless Networking and Communication Group 45
Multi-Mode Precoding
Fixed rate
Adaptively vary number of
substreams
Yields
Full diversity order
Rate growth of spatial multiplexing Capacity
Ratio
Spatial
Multiplexer
...
...
H
FM
M: # substreams Adapt precoder
matrix
... H
Mode
selector
Feedback
Detect
&
Decode
>98%
>85%
SNR (dB)
D. J. Love and R. W. Heath Jr., “Multi-Mode Precoding for MIMO Wireless Systems Using
Linear Receivers,” submitted to IEEE Transactions on Signal Processing, Jan. 2004.
46. Wireless Networking and Communication Group 46
Space-Time Chase Decoding
Decode high rate MIMO signals “costly”
Existing decoders difficult to implement
Solution([Love et al] with Texas Instruments): Space-time
version of classic Chase decoder [Chase]
Use linear or successive decoder as “initial bit estimate”
Perform ML decoding over set of perturbed bit estimates
D. J. Love, S. Hosur, A. Batra, and R. W. Heath Jr., “Space-Time Chase Decoding,” submitted
to IEEE Transactions on Wireless Communications, Nov. 2003.
47. Wireless Networking and Communication Group 47
Assorted Areas
MIMO channel modeling
IEEE 802.11N covariance generation
Joint source-channel space-time coding
Diversity 4
Diversity 2
Diversity 1
Visually important
Visually unimportant
…
48. Wireless Networking and Communication Group 48
Future Research Areas
Coding theory
Subspace codes
Binary transcoding
Reduced complexity Reed-Solomon
UWB & cognitive (or self-aware) wireless
Capacity
MIMO (???)
Multi-user UWB
Cross layer optimization (collaborative)
Sensor networks
Broadcast channel capacity schemes
49. Wireless Networking and Communication Group 49
Conclusions
Limited feedback allows closed-loop MIMO
Beamforming
Precoded OSTBC
Precoded spatial multiplexing
Diversity order a function of feedback amount
Large performance gains available with limited feedback
Multi-mode precoding & Efficient decoding for MIMO
signals
50. Wireless Networking and Communication Group 50
Beamforming Criterion
[Love et al]
Differentiation maximize
52. Wireless Networking and Communication Group 52
Precode OSTBC – Cont.
[Barg et al]
Differentiation maximize
53. Wireless Networking and Communication Group 53
Precode Spat Mult Criterion – Min SV
Let
Differentiation maximize
54. Wireless Networking and Communication Group 54
Precode Spat Mult Criterion – Capacity
Let
Differentiation maximize
55. Wireless Networking and Communication Group 55
SM Susceptible to Channel
Decreasing
Fix
Condition number
56. Wireless Networking and Communication Group 56
Vector Quantization Relationship
Observation: Problem appears similar to vector
quantization (VQ)
In VQ,
1. Choose distortion function
2. Minimize distortion function on average
VQ distortion chosen to improve fidelity of quantized
signal
Can we define a distortion function that ties to
communication system performance?
57. Wireless Networking and Communication Group 57
Grassmannian Subspace Packing
Complex Grassmann manifold
set of M-dimensional subspaces in
Packing Problem
Construct set with maximum
minimum distance
Distance between subspaces
Chordal
Projection Two-Norm
Fubini-Study
Column spaces of codebook matrices
represent a set of subspaces in
1
2
58. Wireless Networking and Communication Group 58
Channel Assumptions
Flat-fading (single-tap)
Antennas widely spaced (channels independent)
BW
frequency (Hz)
59. Wireless Networking and Communication Group 59
Solution: Limited Feedback Precoding
Use codebook
Codebook known at transmitter and receiver
Convey codebook index when channel changes
Space-Time
Encoder
...
H
r
F
... H
Low-rate feedback path
S
Update
Precoder
...
Choose F
from
codebook
FS
Detection
and
Decoding
bits
60. Wireless Networking and Communication Group 60
Communications Vector Quantization
Let
VQ Approach:
Design Objective: Approximate optimal solution
Communications Approach: [Love et al]
System parameter to maximize
Design Objective: Improve system performance
61. Wireless Networking and Communication Group 61
True “multiple-input” algorithm
Advantage: High-rate signaling technique
Decode
Invert (directly/approx)
Disadvantage: Performance very sensitive to channel singular values
Spatial Multiplexing [Foschini]
}Multiple
independent
streams
…
62. Wireless Networking and Communication Group 62
Assorted Areas
MIMO channel modeling
IEEE 802.11N covariance generation
Joint source-channel space-time coding
Diversity 4
Diversity 2
Diversity 1
Visually important
Visually insignificant
…