Initial code acquisition in spread spectrum systems involves two steps: coarse acquisition and fine code tracking.
Coarse acquisition searches for the correct timing by testing different phase hypotheses using techniques like serial search, parallel search, or multi-dwell detection to minimize acquisition time.
Fine code tracking then uses a tracking loop like a delay lock loop (DLL) with early, late, and punctual correlators to maintain precise synchronization.
I am Norman H. I am a Computer Networking Assignment Expert at computernetworkassignmenthelp.com. I hold a Master's in Computer Science from, McMaster University, Canada. I have been helping students with their assignments for the past 15 years. I solve assignments related to Computer Networking.
Visit computernetworkassignmenthelp.com or email support@computernetworkassignmenthelp.com.
You can also call on +1 678 648 4277 for any assistance with Computer Networking Assignment.
The document discusses using ping tests to test connectivity between points using an 860 DSPi meter. It provides guidance on setting packet size and delay for different types of tests. Ping can test connectivity, routing, delay, packet loss and throughput. The document recommends pinging a location near the CMTS or a server provided by Trilithic to test from the 860 DSPi through the HFC network. It also provides tips for configuring ping in MS DOS.
This document provides an overview of TCP congestion control algorithms. It describes the basic additive increase/multiplicative decrease approach and key mechanisms like slow start, fast retransmit, and fast recovery. It also discusses algorithms for setting the retransmission timeout value and adaptations made in protocols like New Reno and Cubic.
The document provides an overview of phase-locked loops (PLLs), including their history, applications, components, and design requirements. It discusses how PLLs work, beginning with an early use in 1932 for radio signal reception. Key applications include frequency multiplication, modulation/demodulation, data synchronization, and use in devices like cell phones and hard disk drives. Diagrams and equations are provided to illustrate the relationships between phase and frequency in a PLL system and its voltage-controlled oscillator, phase detector, and charge pump components.
This document discusses the design and operation of an all-digital phase locked loop (ADPLL). It covers topics such as the digitally controlled oscillator (DCO) core design, noise modeling in the ADPLL, tuning the ADPLL for GSM, impairments like capacitor mismatch and compensation techniques.
The document provides an overview of phase-locked loops (PLLs) including their history, applications, components, and design considerations. It discusses how PLLs work, beginning with the basic block diagram and signals. Key topics covered include loop stability, classifications, transfer functions, and synthesizing component values. Diagrams and equations illustrate PLL principles such as the relationship between phase and frequency in voltage-controlled oscillators and phase detectors. Examples show PLL behavior in both locked and acquisition states.
A PLL consists of a phase detector, filter, voltage controlled oscillator (VCO), and optional divider. The phase detector compares the phase of the input signal to the VCO output signal and generates an error voltage. The filter smooths the error voltage which is fed to the VCO. The VCO then adjusts its output frequency according to the error voltage to minimize the phase difference between its output and the input signal. An optional divider may be included to scale the VCO output frequency before feeding it back to the phase detector for comparison to the input signal. In this way, the PLL is able to lock its output phase to the input phase or some multiple of the input phase.
I am Norman H. I am a Computer Networking Assignment Expert at computernetworkassignmenthelp.com. I hold a Master's in Computer Science from, McMaster University, Canada. I have been helping students with their assignments for the past 15 years. I solve assignments related to Computer Networking.
Visit computernetworkassignmenthelp.com or email support@computernetworkassignmenthelp.com.
You can also call on +1 678 648 4277 for any assistance with Computer Networking Assignment.
The document discusses using ping tests to test connectivity between points using an 860 DSPi meter. It provides guidance on setting packet size and delay for different types of tests. Ping can test connectivity, routing, delay, packet loss and throughput. The document recommends pinging a location near the CMTS or a server provided by Trilithic to test from the 860 DSPi through the HFC network. It also provides tips for configuring ping in MS DOS.
This document provides an overview of TCP congestion control algorithms. It describes the basic additive increase/multiplicative decrease approach and key mechanisms like slow start, fast retransmit, and fast recovery. It also discusses algorithms for setting the retransmission timeout value and adaptations made in protocols like New Reno and Cubic.
The document provides an overview of phase-locked loops (PLLs), including their history, applications, components, and design requirements. It discusses how PLLs work, beginning with an early use in 1932 for radio signal reception. Key applications include frequency multiplication, modulation/demodulation, data synchronization, and use in devices like cell phones and hard disk drives. Diagrams and equations are provided to illustrate the relationships between phase and frequency in a PLL system and its voltage-controlled oscillator, phase detector, and charge pump components.
This document discusses the design and operation of an all-digital phase locked loop (ADPLL). It covers topics such as the digitally controlled oscillator (DCO) core design, noise modeling in the ADPLL, tuning the ADPLL for GSM, impairments like capacitor mismatch and compensation techniques.
The document provides an overview of phase-locked loops (PLLs) including their history, applications, components, and design considerations. It discusses how PLLs work, beginning with the basic block diagram and signals. Key topics covered include loop stability, classifications, transfer functions, and synthesizing component values. Diagrams and equations illustrate PLL principles such as the relationship between phase and frequency in voltage-controlled oscillators and phase detectors. Examples show PLL behavior in both locked and acquisition states.
A PLL consists of a phase detector, filter, voltage controlled oscillator (VCO), and optional divider. The phase detector compares the phase of the input signal to the VCO output signal and generates an error voltage. The filter smooths the error voltage which is fed to the VCO. The VCO then adjusts its output frequency according to the error voltage to minimize the phase difference between its output and the input signal. An optional divider may be included to scale the VCO output frequency before feeding it back to the phase detector for comparison to the input signal. In this way, the PLL is able to lock its output phase to the input phase or some multiple of the input phase.
The document provides an overview of phase locked loops (PLLs). It discusses:
- The basic components of a PLL including a phase detector, low pass filter, and voltage controlled oscillator (VCO). The phase detector compares the phase difference between an input signal and VCO output.
- Applications of PLLs such as frequency modulation decoding, frequency synthesis, and clock generation.
- Key parameters like lock range, which is the range of input frequencies a PLL can lock onto, and capture range, which is the range a PLL can lock onto when starting unlocked.
- Operation of a basic PLL, including free running, capture, and phase lock stages where the VCO frequency adjusts until matching the
This document provides an overview of phase locked loops (PLL) including:
1. The basic components of a PLL including a phase detector, low pass filter, and voltage controlled oscillator that work together in a closed loop to lock the output frequency and phase to the input signal.
2. Examples of PLL applications such as frequency multiplication, FM demodulation, and motor speed control.
3. A more detailed description of the 565 PLL IC including its pin configuration and characteristics such as operating frequency range and drift with temperature/voltage.
The document discusses phase-locked loops (PLLs), including what they are, how they are modeled and operate, properties of PLLs, and applications. A PLL is a negative feedback system that automatically adjusts the frequency and phase of a control signal to match a reference signal. It consists of a phase detector, loop filter, and voltage-controlled oscillator. The document provides examples of modeling and simulating a PLL using Simulink. It also summarizes tests of a PLL design under different conditions and discusses other applications of PLLs beyond frequency demodulation.
This document discusses the components used to generate accurate and variable frequencies for a local oscillator super heterodyne receiver and signal generator. A crystal oscillator provides a reference frequency which is then multiplied using a voltage controlled oscillator and divider to generate the output frequency. A phase detector compares the feedback and voltage controlled oscillator frequencies and a loop filter integrates any voltage difference to control the voltage controlled oscillator frequency.
The document discusses a Phase Locked Loop (PLL). It describes PLL as a circuit that synchronizes an output signal generated by an oscillator to match the frequency and phase of a reference input signal. The key functional blocks of a PLL are a phase detector, low pass filter, and voltage controlled oscillator (VCO). The phase detector compares the input and feedback frequencies and provides an error signal. The low pass filter removes noise and the VCO generates the output frequency controlled by the error signal voltage. A PLL goes through free running, capture, and phase locked stages of operation. Applications of PLL include frequency modulation/demodulation and signal synchronization.
1. The document introduces phase locked loops (PLLs), which are electronic circuits that lock the phase of the output signal to the phase of the input signal.
2. A basic PLL system consists of a phase detector that detects the phase difference between the input and output signals, a low pass filter, and a voltage controlled oscillator whose frequency is adjusted based on the output of the filter to reduce the phase difference.
3. Modern PLLs often use a phase/frequency detector and a charge pump instead of just a phase detector, which allows the loop to lock faster and be more stable. Charge pump PLLs work by using the phase/frequency detector to control switches that charge or discharge a capacitor, producing the control voltage
A phase-locked loop (PLL) is an electronic circuit that compares the phase of an input reference signal with the phase of a signal derived from its output oscillator. It adjusts the oscillator frequency to keep the input and output phases matched. A PLL consists of a phase detector, low-pass filter, and voltage-controlled oscillator (VCO). It is used for synchronization, frequency synthesis, and demodulation in applications like wireless communications, radio transmitters, and signal recovery in noise.
This presentation summarizes the key aspects of a Phase Locked Loop (PLL) circuit. It was presented by Aman Jain, Gourav Gupta, Mohit Swarnkar, Narendra Singh Rajput, and Piyush Pal to Ravitesh Mishra. The presentation outlines what a PLL is, the main components of a PLL including the phase detector, filter, and voltage controlled oscillator. It also discusses the locked condition of a PLL, the dynamics and transient response of PLL circuits, and applications of PLLs such as frequency multiplication, jitter reduction, and clock recovery.
The document discusses phase locked loops (PLLs). It provides an outline that covers synchronization, PLL basics, analog PLLs, digital PLLs, and FPGA implementation. It describes how PLLs work, tracking the average phase and frequency of an input reference signal. The key components of an analog PLL are identified as a voltage controlled oscillator (VCO), phase detector (PD), and loop filter. A brief history of PLL development is also presented.
This document describes an experiment involving amplitude shift keying (ASK) and frequency shift keying (FSK) modulation and demodulation. It involves generating ASK and FSK signals, demodulating them using envelope detection and filtering, and restoring the original digital signal using comparators. The objectives are to examine ASK and FSK digital modulation techniques and investigate their generation and reception.
Signal classification of second order cyclostationarity signals using bt scld...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
DYNAMIC CONGESTION CONTROL IN WDM OPTICAL NETWORKcscpconf
This paper is based on Wavelength Division Multiplexing (WDM) optical networking. In this optical networking, prior to data transfer, lightpath establishment between source and
destination nodes is usually carried out through a wavelength reservation protocol. This wavelength is reserved corresponding to a route between the source and destination and the
route is chosen following any standard routing protocol based on shortest path. The backward reservation protocol is implemented initially. A fixed connected and weighted network is
considered. The inputs of this implementation are the fixed network itself and its corresponding shortest path matrix. After this initial level of implementation, the average node usage over a time period is calculated and various thresholds for node usage are considered. Above threshold value, request arriving at that path selects its next shortest path. This concept is
implemented on various wavelengths. The output represents the performance issues of dynamic congestion control.
Spectrum Sensing using Cooperative Energy Detection Method for Cognitive RadioSaroj Dhakal
This document summarizes cooperative spectrum sensing using energy detection in cognitive radio networks. It discusses how cooperative sensing can improve detection performance by exploiting spatial diversity among cognitive radio users. The key points are:
1. Cooperative sensing allows cognitive radio users to share sensing information to make a combined decision that is more accurate than individual decisions. This mitigates issues like multipath fading and shadowing.
2. Energy detection is commonly used for cooperative sensing due to its simplicity. However, its performance depends on noise power uncertainty. Cooperative sensing addresses this by fusing observations from multiple spatially distributed users.
3. The document also discusses challenges in spectrum sensing like hardware requirements, hidden primary users, and detecting spread spectrum
Spectrum Sensing using Cooperative Energy Detection Method for Cognitive RadioSaroj Dhakal
This document summarizes cooperative spectrum sensing using energy detection in cognitive radio networks. It discusses how cooperative sensing can improve detection performance by exploiting spatial diversity among cognitive radio users. The key points are:
1. Cooperative sensing allows cognitive radio users to share sensing information to make a combined decision that is more accurate than individual decisions. This mitigates issues like multipath fading and shadowing.
2. Energy detection is commonly used for cooperative spectrum sensing due to its simplicity. However, its performance depends on noise power uncertainty.
3. Cooperative sensing involves local sensing by each cognitive radio, reporting results to a fusion center, and data fusion to make a combined decision. Centralized, distributed, and relay-
This document describes algorithms for detecting single radio pulses in real-time using graphics processing units (GPUs). It presents two new algorithms that use incomplete sets of boxcar filters to detect pulses at accelerated speeds with minimal signal loss. The algorithms were tested on simulated data and were found to process data 266-500 times faster than real-time on GPUs, detecting pulses with a mean 7% reduction in signal power.
The document proposes a test bench to conduct R&D for an Event Plane and Centrality Detector. Specifically, it will test different detector technologies including scintillator tiles with various pad geometries coupled to silicon photomultipliers. Cosmic ray and electron beam measurements are planned to characterize signal efficiency and timing resolution for different detector configurations. The goals are to optimize pad geometry, understand signal discrimination capabilities, and achieve the best timing resolution.
Challenges, Issues and Research directions in Optical Burst SwitchingEditor IJCATR
This document discusses challenges and research directions in optical burst switching (OBS) networks. It provides background on OBS architecture, including burst assembly, routing, traffic distribution, scheduling, and signaling protocols. Contention resolution strategies in OBS like optical buffering, wavelength conversion, burst deflection routing, and burst segmentation are also covered. Key challenges discussed include implementing burst segmentation in practical systems, such as dealing with switching time and segment boundary detection. Other challenges are the limited buffering capabilities of optical networks and noise introduced by wavelength conversion. The document also notes issues like shadow contention that can occur with certain contention resolution strategies.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document discusses and compares the performance of four blind adaptive multiuser detection algorithms: LMS, RLS, Kalman filter, and subspace-based Kalman filter. It provides background on blind multiuser detection and describes each algorithm's approach. The subspace-based Kalman filter algorithm models the detector as a vector in the signal subspace and employs a Kalman filter to adaptively estimate the coefficients. Simulation results showed that the subspace-based Kalman filter algorithm outperformed the other three algorithms in terms of faster convergence speed and capability to increase the capacity of CDMA systems.
Comparison of signal smoothing techniques for use in embedded system for moni...Dalton Valadares
Paper about the comparison between some signal smoothing techniques for use in an embedded system responsible for monitoring the biofuels quality, specificaly the oxidative stability.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
The document provides an overview of phase locked loops (PLLs). It discusses:
- The basic components of a PLL including a phase detector, low pass filter, and voltage controlled oscillator (VCO). The phase detector compares the phase difference between an input signal and VCO output.
- Applications of PLLs such as frequency modulation decoding, frequency synthesis, and clock generation.
- Key parameters like lock range, which is the range of input frequencies a PLL can lock onto, and capture range, which is the range a PLL can lock onto when starting unlocked.
- Operation of a basic PLL, including free running, capture, and phase lock stages where the VCO frequency adjusts until matching the
This document provides an overview of phase locked loops (PLL) including:
1. The basic components of a PLL including a phase detector, low pass filter, and voltage controlled oscillator that work together in a closed loop to lock the output frequency and phase to the input signal.
2. Examples of PLL applications such as frequency multiplication, FM demodulation, and motor speed control.
3. A more detailed description of the 565 PLL IC including its pin configuration and characteristics such as operating frequency range and drift with temperature/voltage.
The document discusses phase-locked loops (PLLs), including what they are, how they are modeled and operate, properties of PLLs, and applications. A PLL is a negative feedback system that automatically adjusts the frequency and phase of a control signal to match a reference signal. It consists of a phase detector, loop filter, and voltage-controlled oscillator. The document provides examples of modeling and simulating a PLL using Simulink. It also summarizes tests of a PLL design under different conditions and discusses other applications of PLLs beyond frequency demodulation.
This document discusses the components used to generate accurate and variable frequencies for a local oscillator super heterodyne receiver and signal generator. A crystal oscillator provides a reference frequency which is then multiplied using a voltage controlled oscillator and divider to generate the output frequency. A phase detector compares the feedback and voltage controlled oscillator frequencies and a loop filter integrates any voltage difference to control the voltage controlled oscillator frequency.
The document discusses a Phase Locked Loop (PLL). It describes PLL as a circuit that synchronizes an output signal generated by an oscillator to match the frequency and phase of a reference input signal. The key functional blocks of a PLL are a phase detector, low pass filter, and voltage controlled oscillator (VCO). The phase detector compares the input and feedback frequencies and provides an error signal. The low pass filter removes noise and the VCO generates the output frequency controlled by the error signal voltage. A PLL goes through free running, capture, and phase locked stages of operation. Applications of PLL include frequency modulation/demodulation and signal synchronization.
1. The document introduces phase locked loops (PLLs), which are electronic circuits that lock the phase of the output signal to the phase of the input signal.
2. A basic PLL system consists of a phase detector that detects the phase difference between the input and output signals, a low pass filter, and a voltage controlled oscillator whose frequency is adjusted based on the output of the filter to reduce the phase difference.
3. Modern PLLs often use a phase/frequency detector and a charge pump instead of just a phase detector, which allows the loop to lock faster and be more stable. Charge pump PLLs work by using the phase/frequency detector to control switches that charge or discharge a capacitor, producing the control voltage
A phase-locked loop (PLL) is an electronic circuit that compares the phase of an input reference signal with the phase of a signal derived from its output oscillator. It adjusts the oscillator frequency to keep the input and output phases matched. A PLL consists of a phase detector, low-pass filter, and voltage-controlled oscillator (VCO). It is used for synchronization, frequency synthesis, and demodulation in applications like wireless communications, radio transmitters, and signal recovery in noise.
This presentation summarizes the key aspects of a Phase Locked Loop (PLL) circuit. It was presented by Aman Jain, Gourav Gupta, Mohit Swarnkar, Narendra Singh Rajput, and Piyush Pal to Ravitesh Mishra. The presentation outlines what a PLL is, the main components of a PLL including the phase detector, filter, and voltage controlled oscillator. It also discusses the locked condition of a PLL, the dynamics and transient response of PLL circuits, and applications of PLLs such as frequency multiplication, jitter reduction, and clock recovery.
The document discusses phase locked loops (PLLs). It provides an outline that covers synchronization, PLL basics, analog PLLs, digital PLLs, and FPGA implementation. It describes how PLLs work, tracking the average phase and frequency of an input reference signal. The key components of an analog PLL are identified as a voltage controlled oscillator (VCO), phase detector (PD), and loop filter. A brief history of PLL development is also presented.
This document describes an experiment involving amplitude shift keying (ASK) and frequency shift keying (FSK) modulation and demodulation. It involves generating ASK and FSK signals, demodulating them using envelope detection and filtering, and restoring the original digital signal using comparators. The objectives are to examine ASK and FSK digital modulation techniques and investigate their generation and reception.
Signal classification of second order cyclostationarity signals using bt scld...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
DYNAMIC CONGESTION CONTROL IN WDM OPTICAL NETWORKcscpconf
This paper is based on Wavelength Division Multiplexing (WDM) optical networking. In this optical networking, prior to data transfer, lightpath establishment between source and
destination nodes is usually carried out through a wavelength reservation protocol. This wavelength is reserved corresponding to a route between the source and destination and the
route is chosen following any standard routing protocol based on shortest path. The backward reservation protocol is implemented initially. A fixed connected and weighted network is
considered. The inputs of this implementation are the fixed network itself and its corresponding shortest path matrix. After this initial level of implementation, the average node usage over a time period is calculated and various thresholds for node usage are considered. Above threshold value, request arriving at that path selects its next shortest path. This concept is
implemented on various wavelengths. The output represents the performance issues of dynamic congestion control.
Spectrum Sensing using Cooperative Energy Detection Method for Cognitive RadioSaroj Dhakal
This document summarizes cooperative spectrum sensing using energy detection in cognitive radio networks. It discusses how cooperative sensing can improve detection performance by exploiting spatial diversity among cognitive radio users. The key points are:
1. Cooperative sensing allows cognitive radio users to share sensing information to make a combined decision that is more accurate than individual decisions. This mitigates issues like multipath fading and shadowing.
2. Energy detection is commonly used for cooperative sensing due to its simplicity. However, its performance depends on noise power uncertainty. Cooperative sensing addresses this by fusing observations from multiple spatially distributed users.
3. The document also discusses challenges in spectrum sensing like hardware requirements, hidden primary users, and detecting spread spectrum
Spectrum Sensing using Cooperative Energy Detection Method for Cognitive RadioSaroj Dhakal
This document summarizes cooperative spectrum sensing using energy detection in cognitive radio networks. It discusses how cooperative sensing can improve detection performance by exploiting spatial diversity among cognitive radio users. The key points are:
1. Cooperative sensing allows cognitive radio users to share sensing information to make a combined decision that is more accurate than individual decisions. This mitigates issues like multipath fading and shadowing.
2. Energy detection is commonly used for cooperative spectrum sensing due to its simplicity. However, its performance depends on noise power uncertainty.
3. Cooperative sensing involves local sensing by each cognitive radio, reporting results to a fusion center, and data fusion to make a combined decision. Centralized, distributed, and relay-
This document describes algorithms for detecting single radio pulses in real-time using graphics processing units (GPUs). It presents two new algorithms that use incomplete sets of boxcar filters to detect pulses at accelerated speeds with minimal signal loss. The algorithms were tested on simulated data and were found to process data 266-500 times faster than real-time on GPUs, detecting pulses with a mean 7% reduction in signal power.
The document proposes a test bench to conduct R&D for an Event Plane and Centrality Detector. Specifically, it will test different detector technologies including scintillator tiles with various pad geometries coupled to silicon photomultipliers. Cosmic ray and electron beam measurements are planned to characterize signal efficiency and timing resolution for different detector configurations. The goals are to optimize pad geometry, understand signal discrimination capabilities, and achieve the best timing resolution.
Challenges, Issues and Research directions in Optical Burst SwitchingEditor IJCATR
This document discusses challenges and research directions in optical burst switching (OBS) networks. It provides background on OBS architecture, including burst assembly, routing, traffic distribution, scheduling, and signaling protocols. Contention resolution strategies in OBS like optical buffering, wavelength conversion, burst deflection routing, and burst segmentation are also covered. Key challenges discussed include implementing burst segmentation in practical systems, such as dealing with switching time and segment boundary detection. Other challenges are the limited buffering capabilities of optical networks and noise introduced by wavelength conversion. The document also notes issues like shadow contention that can occur with certain contention resolution strategies.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
This document discusses and compares the performance of four blind adaptive multiuser detection algorithms: LMS, RLS, Kalman filter, and subspace-based Kalman filter. It provides background on blind multiuser detection and describes each algorithm's approach. The subspace-based Kalman filter algorithm models the detector as a vector in the signal subspace and employs a Kalman filter to adaptively estimate the coefficients. Simulation results showed that the subspace-based Kalman filter algorithm outperformed the other three algorithms in terms of faster convergence speed and capability to increase the capacity of CDMA systems.
Comparison of signal smoothing techniques for use in embedded system for moni...Dalton Valadares
Paper about the comparison between some signal smoothing techniques for use in an embedded system responsible for monitoring the biofuels quality, specificaly the oxidative stability.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
ENERGY EFFICIENT COOPERATIVE SPECTRUM SENSING IN COGNITIVE RADIOIJCNCJournal
Sensing in cognitive radio (CR) protects the primary user (PU) from bad interference. Therefore, it is
assumed to be a requirement. However, sensing has two main challenges; first the CR is required to sense
the PU under very low signal to noise ratios which will take longer sensing time, and second, some CR
nodes may suffer from deep fading and shadowing effects. Cooperative spectrum sensing (CSS) is supposed
to solve these challenges. However, CSS adds extra energy consumption due to CRs send the sensing result
to the fusion center and receive the final decision from the fusion center. This is in addition to the sensing
energy itself. Therefore, CSS may consume considerable energy out of the battery of the CR node.
Therefore in this paper, we try to find jointly the sensing time required from each CR node and the number
of CR nodes who should perform sensing such that the energy and energy efficiency (i.e., ratio of
throughput to energy consumed) are optimized. Simulation results show that the joint optimization achieves
better in terms of energy efficiency than other approaches that perform separate optimization.
Fast Data Collection with Interference and Life Time in Tree Based Wireless S...IJMER
This document discusses techniques for fast data collection in wireless sensor networks using a tree-based topology. It specifically focuses on minimizing the schedule length for aggregated convergecast (where data is aggregated at each hop) and raw-data convergecast (where packets are individually relayed to the sink).
It first considers time scheduling on a single channel, and then combines scheduling with transmission power control and multiple frequencies to further reduce interference and schedule length. It provides lower bounds on schedule length when interference is eliminated, and proposes algorithms that achieve these bounds.
Evaluation of different channel assignment methods, routing tree topologies, interference models, and their impact on schedule length is also presented. The key findings are that combining scheduling, power control,
Performance analysis of gated ring oscillator designed for audio frequency ra...VLSICS Design
This paper presents performance analysis of Gated Ring Oscillator (GRO). Proposed GRO is designed to
employ in implementation of Time to Digital Converter (TDC) block of Asynchronous ADC. For an audio
frequency range ADC, minimum GRO stages are designed using asynchronous technique. So leads to
reduced area and power. Compared to conventional Ring Oscillator (RO), we avoided to employ the gated
clock; to evade clock design related problems like jitter, additional area and power. Instead we preferred
gating of ring oscillator itself. Consequently during sleep mode, GRO disables automatically which saves
the dynamic power. Furthermore it also provides first order noise shaping of the quantization and
mismatch noise. Proposed GRO is implemented with 0.18μm CMOS Digital Technology in Cadence
Virtuso environment. GRO performance analysis shows oscillation frequency as 286 KHz with 327ps jitter
and average power consumption of 1.08μW
PERFORMANCE ANALYSIS OF GATED RING OSCILLATOR DESIGNED FOR AUDIO FREQUENCY RA...VLSICS Design
This paper presents performance analysis of Gated Ring Oscillator (GRO). Proposed GRO is designed to employ in implementation of Time to Digital Converter (TDC) block of Asynchronous ADC. For an audio frequency range ADC, minimum GRO stages are designed using asynchronous technique. So leads to reduced area and power. Compared to conventional Ring Oscillator (RO), we avoided to employ the gated clock; to evade clock design related problems like jitter, additional area and power. Instead we preferred gating of ring oscillator itself. Consequently during sleep mode, GRO disables automatically which saves the dynamic power. Furthermore it also provides first order noise shaping of the quantization and mismatch noise. Proposed GRO is implemented with 0.18µm CMOS Digital Technology in Cadence Virtuso environment. GRO performance analysis shows oscillation frequency as 286 KHz with 327ps jitter and average power consumption of 1.08µW.
New Proposed Contention Avoidance Scheme for Distributed Real-Time Systemspaperpublications3
Abstract: One method to handle collisions in a contention based distributed system is to optimize collision detection and subsequent recovery. An alternative method to handle collisions in a contention based system is to attempt to avoid them. Some systems may utilize a strict scheduling guideline to identify who may use which resources when. Other systems may have the senders listen to the channel immediately prior to transmitting and determine suitable times to transmit. A primary challenge in Distributed Real-Time Systems applications is how to carry out data given source-to-sink, end-to-end deadlines when the communication resources are scarce. A new scheme resolves collisions and tries to reduce the number of potential collision events. In this paper, we develop New Avoiding Contention Scheme that delays data packet transmission nonlinearly during forwarding for a duration that correlates with their remaining deadline and distance to the destination, and avoiding the contention in bursty traffic by using multi-path routing.
Zigbee based differential pilot protection of transmission lineeSAT Journals
Abstract
This paper describes the limitations of the existing relays in the detection of fault. It also describes the benefits of using the differential pilot protection of the transmission line. Among other advantages one of its main advantages is its speed, which is required in a.c. systems to remain in synchronism (as angle δ is to be kept small). In the end of this paper a model has been created in the laboratory by using two incandescent bulbs in parallel to create the difference in the two parts of the model, this difference is detected and appropriate action is finally taken to trip the circuit.
Keywords: Zig-bee, pilot protection, differential protection, transmission line, Hall Effect sensors.
Zigbee based differential pilot protection of transmission lineeSAT Publishing House
This document describes a study on using Zigbee wireless communication technology for differential pilot protection of transmission lines. It discusses limitations of existing relay-based protection methods, such as inability to differentiate between fault and inrush currents. The paper then presents differential pilot protection as an alternative, enabled by replacing wired pilot communication with wireless technology. A laboratory model is created using hall effect sensors, microcontroller, and Zigbee modules to demonstrate this approach and its ability to precisely define boundaries, detect faults based on both magnitude and direction, and achieve fast tripping times.
This document discusses radio link control options for frequency hopping networks. It examines frequency hopping, power control, and discontinuous transmission and how they can increase capacity by reducing interference. It analyzes their performance in both idealized homogeneous networks and more realistic inhomogeneous networks through system-level simulations. The simulations show that maximum capacity is achieved either through a reuse of 4 with random frequency hopping for good carrier-to-interference ratio and interference diversity, or reuse of 1x1 with management of the mobile allocation index offset for maximum interference diversity, depending on the available spectrum.
Design of Real-time Self Establish Wireless Sensor For Dynamic NetworkIJTET Journal
Abstract— Wireless sensor network in the recent trend engaged with high speed responsive real time system. This type of real time system requires reliable and compatible sensor to work in an environment where the sensor is dynamic in nature. Sensor network is to design to perform a set of high level information processing tasks such as detection, tracking or classification. Application of sensor networks is wide ranging and can vary significantly in application requirements, modes of deployment, sensing modality, power supply. Dynamic configuring of wireless sensor involves timing constraints to configure the sensor or to switch an adaptive sensor when working node failure due to energy, data rate, packet loss and range of the sensor. So the network, with such dynamic nature needs a background sensor which is able to be switched when the active sensor has a problem and improper functioning due to the network deploy environment. The background sensor lies inactive inside the range of the active sensor; ensure that the sensor is about to die and make sure the last data transfer successful find delay time to switch. Fault tolerance is achieved by switching the background sensor with the active sensor, where the background sensor self establish themselves in the network and perform similar routing metrics and configure them self with the network as soon they are switched. Once, the actual sensor retained back to the active condition then the background sensor will go to inactive state during this switching process the sensor will not loss data packet.
Basic Telecom concepts
Various Wireless Technologies
Cellular concepts & Principal of cellular Comm.
GSM Network Architecture
GSM channel Architecture
Call Flows in GSM
GSM Planning steps (Nominal Plan & RF surveys)
Alternative means of wireless communication
Walkie - Talkie
Pagers
Trunked private radios
Mobile Phone - the magic technology that enables everyone to communicate anywhere with anybody.
Till 1982 Cellular Systems were exclusively Analog Radio Technology.
Advanced Mobile Phone Service (AMPS)
U.S. standard on the 800 MHz Band
Total Access Communication System (TACS)
U.K. standard on 900 MHz band
Nordic Mobile Telephone System (NMT)
Scandinavian standard on the 450 & 900 MHz band
The GSM standard was developed by the Groupe SpecialMobile, which was an initiative of the Conference of European Post and Telecommunications (CEPT) administrations.
The responsibility for GSM standardization now resides with the
Special Mobile Group (SMG) under the European Telecommunication Standard Institute (ETSI).
Fully digital system utilizing the 900MHz frequency band.
TDMA over radiocarriers(200 kHz carrier spacing)
8 full rate or 16 half rate TDMA channels per carrier
User/terminal authentication for fraud control
Encryption of speech and data transmissions over the radio path
Full international roaming capability
Low speed data services (upto 9.6kb/s)
Compatibility with ISDN for supplementary services
Support of short message services(SMS)
GSM supports a range of basic and supplementary services, and these services are defined analogous to those for ISDN(i.e.,bearer services, teleservices, and supplementary services).
The most important service supported by GSM is Telephony.
Other services derived from telephony included in the GSM specification are emergency calling and voice messaging.
Bearer services supported in GSM include various asynchronous and synchronous data services for information transfer.
Teleservices based on these bearer services include group 3 fax and short message service(SMS)
The data capabilities of GSM have now been enhanced to include high speed circiut-switched data(HSCSD) and general packet radio service (GPRS).
Call offering services call forwarding
Call resrtiction services call barring
Call waiting service
Call hold service
Multi party service tele conferencing
Calling line presentation restriction services
Advice of charge service
Closed user group service
The GSM System comprises of Base Transceiver Station (BTS), Base Station Controllers (BSC), Mobile Switching Centers (MSC), and set of registers (databases) to assist in mobility management and security functions.
All signaling between the MSC and the various registers (databases) as well as between the MSCs takes place using the Signaling System 7(SS7) network, with the application level messages using the Mobile Application Protocol (MAP) designed specifically for GSM.
The MAP protocol utilizes the lower layer functions from the SS7 protocol stack.
This chapter provides an overview of basic wireless communication concepts such as frequency, bandwidth, channels, transmission rate and modulation methods. It describes Time Division Multiple Access (TDMA) used in digital cellular systems and discusses advantages of digital transmission over analog. Transmission problems like path loss, shadowing, multipath fading and solutions like channel coding, interleaving, antenna diversity and adaptive equalization are also covered. The chapter then explains the GSM transmission process from analog to digital conversion to burst formatting and modulation.
Full rate => Used for speech at 13 Kbits/s
or sending data at 9.6 Kbits/s
Half rate => Used for speech at 6.5 Kbits/s
or sending data at 4.8 Kbits/s
Enhanced Full rate => Used for speech at 13 Kbits/s
or sending data at 9.6 Kbits/s but
with almost Land line quality
FCCH = FREQUENCY CORRECTION CHANNEL
=> To tell the Mobile that this is the BCCH carrier
=> To able the Mobile to synchronize to the frequency
(Downlink only)
SCH = SYNCHRONISATION CHANNEL
=> Used for sending BSIC (Base station Identity Code)
=> Give TDMA frame number to the Mobile.
(Downlink only)
BCCH = BROADCAST CONTROL CHANNEL
=> Used for sending information to the mobile like
CGI (Cell Global identity), LAI (Location Area Identity),
BCCH carriers of the neighboring cells,
maximum output power allowed in the cell and other
broadcast messages like barred cell. (Downlink only)
PCH = PAGING CHANNEL
=> Used for paging the Mobile. (Downlink only)
Reason could be an incoming call or an incoming Short Message.
RACH = RANDOM ACCESS CHANNEL
=> Used for responding to the paging (terminating), Location updating
or to make call access (originating) by asking for a signaling channel.
(Uplink only)
AGCH = ACCESS GRANT CHANNEL
=> Used to allocate SDCCH to the mobile.
(Downlink only)
ell Allocation (CA) is the subset of the total frequency band that is available for one BTS. It can be viewed as the total transport resource available for traffic between the BTS and its attached MSs. One Radio Frequency CHannel (RFCH) of the CA is used to carry synchronization information and the Broadcast Control CHannel (BCCH). This can be any of the carriers in the cell and it is known as the BCCH carrier or the c
carrier. Strong efficiency and quality requirements have resulted in a
0
rather complex way of utilizing the frequency resource. This chapter describes the basic principles of how to use this resource from the physical resource itself to the information transport service offered by the BTS.
Carrier separation is 200 kHz, which provides: • 124 pairs of carriers in the GSM 900 band • 374 pairs of carriers in the GSM 1800 band • 299 pairs of carriers in the GSM 1900 band
Using Time Division Multiple Access (TDMA) each of these carriers is divided into eight Time Slots (TS). One TS on a TDMA frame is called a physical channel, i.e. on each duplex pair of carriers there are eight physical channels.
A variety of information is transmitted between the BTS and thMS. The information is grouped into different logical channelsEach logical channel is used for a specific purpose such as paging, call set-up and speech. For example, speech is sent on the logical channel Traffic CHannel (TCH). The logical channels are mapped onto the physical channels.
The information in this chapter does not include channels specific for GPRS (General Packet Radio Service). For basic information on GPRS see chapter 14 of this documentation.
Common core mechanics in Nokia UltraSite EDGE BTS Outdoor and Nokia UltraSite EDGE BTS Indoor
Common plug-in units
1940 x 770 x 750 mm (H x W x D)
Identical footprint to CityTalk BTS
Weight
Max weight (12 TRX) 340 kg
Heaviest single part 58 kg (core mechanics)
Heaviest plug-in unit 18 kg (RTC)
Acoustic noise (max): 68 dB(A)
Climatic conditions:
w/o heater -10°C ... +50°C
with optional heater -33°C ... +50°C
Ingress Protection Class: IP 55
Two level environmental protection:
BTS core and cabinet door provides EMC shielding
Outdoor kit provides additional weather proofing
The GENEX Assistant is excellent software tool for
Post-Processing 2G & 3G Drive Test Data.
With the GENEXAssistant, you can:
Have a panorama view of network performance
Locate network troubles
Improve network quality
Verify network planning and optimization
ANALYSIS OF LOGFILE
FOR POST PROCESSING OF LOGFILE IN
GENEX ASSISTANCE WE NEED TO
OPEN A NEW PROJECT
. Overview
2. Handover Causes & Priorities
3. Threshold Comparison Process
4. Target Cell Evaluation Process
5. Handover Algorithms
Power Budget (PBGT)
Level & Quality (RXLEV & RXQUAL)
Umbrella (& Combined Umbrella/PBGT)
MS Speed (FMMS & MS_SPEED_DETECTION)
6. Imperative Handovers
Distance
Rapid Field Drop (RFD) & Enhanced Rapid Field Drop (ERFD)
7. Handover Timers
Call continuity - to ensure a call can be maintained as a MS moves geographical location from the coverage area of one cell to another
Call quality - to ensure that if an MS moves into a poor quality/coverage area the call can be moved from the serving cell to a neighbouring cell (with better quality) without dropping the call
Traffic Reasons - to ensure that the traffic within the network is optimally
distributed between the different layers/bands of a network
If 2 or more handover (PC) criteria are satisfied simultaneously the following priority list
is used in determining which process is performed;
. Uplink and downlink Interference
2. Uplink quality
3. Downlink quality
4. Uplink level
5. Downlink level
6. Distance
7. Enhanced (RFD)
8. Rapid Field Drop (RFD)
9. Slow moving MS
10. Better cell i.e. Periodic check (Power Budget HO or Umbrella HO)
11. PC: Lower quality/level thresholds (UL/DL)
12. PC: Upper quality/level thresholds (UL/DL)
Introduction
Channel Configuration
Idle Mode Operation
Protocols
Radio resources
Measurements
Power Control
HO process
Intelligent Underlay Overlay
Handover Support for Coverage Enhanchements
The extended cell
Dynamic Hotspot
Dual band GSM/DCS Network Operation
Half Rate
HSCSD
Transmission management in BSS is a feature used in managing the Base Station Subsystem transmission system functions such as supervision, alarms, statistics
and settings. The network element mainly responsible for transmission management in BSS is the Base Station Controller (BSC).
Transmission management functionalities make it possible for the operators to manage the transmission equipment remotely from the BSC or from Nokia
NetAct integrated network management system, which simplifies network maintenance and operation. Supervision functions help minimise the time spent in maintenance, and statistics collection helps the operators analyse and optimise
the use of their transmission equipment. Moreover, new software can be downloaded in a way that does not interfere with the traffic.
Hardware and software requirements BSS transmission network elements
BSS transmission management functionalities Transmission parameters Transmission alarms
Transmission measurements
2.Hardware and software requirements
There are no specific hardware or software requirements for the transmission management functionalities. However, the type of the BTS poses certain
limitations.
The BTS type specific functionalities are listed in the table below.
More details about the functionalities can be found in BSS transmission management functionalities .
Polling list sending with priority is a functionality used in positioning. To ensure accurate positioning calculations, the LMU unit must supply Radio Interface Timing System (RIT) information to the network faster than the normal Q1 polling is able to do. Faster LMU polling is achieved by defining a Q1 polling
priority for each Q1 device, with the LMU having the highest priority. For more information see Location Services .
3.BSS transmission network elements
The base Station Subsystem (BSS) consists of at least one Base Station Controller (BSC) and its Base Transceiver Stations (BTS). The Transcoder Submultiplexer
(TCSM) is also part of the BSS although it is actually located in the MSC site. The three basic configurations (topologies) for transmission between the BSC and
the BTSs are: point-to-point connection
multidrop chain multidrop loop
In point-to-point configuration each BTS is connected directly to the BSC. In the multidrop chain, BTSs form a chain and the first BTS in the network is connected directly to the BSC. In the loop connection, the BTSs form a loop where the first and the last BTS in the loop are connected directly to the BSC via a crossconnecting node. The topology used depends on a number of factors such as the distance between the BSC and the BTS, the number of transceivers (TRXs) used at a particular BTS site and the signalling channel rate between the BSC and the\ BTS. Usually the topology used is a mixture of the three basic topologies. Formore information on the topologies, refer to Nokia BSS Transmission\Configuration .
This document discusses selecting the appropriate capacity for a Base Station Controller (BSC) in a mobile telecommunications network. It provides the following guidelines:
1. Allow a 20% margin for additional TRXs and space for future upgrading. Minimize handovers between BSCs.
2. Calculate required capacity based on offered traffic plus a 10% margin, not installed capacity.
3. Use Erlang B calculations to determine the number of channels needed to support the traffic load at a 0.1% blocking rate.
4. Divide the number of required channels by the number supported per Ater link or interface to determine the number of links needed between the BSC and core network.
– There are others : IS95 HDR, EDGE, etc.
» Direct Spread CDMA TDD
» Direct Spread CDMA FDD
» Multi-carrier CDMA FDD
Global 3G comprises of 3 modes :
– Marketed as Global 3G CDMA implying a single unified standard. In reality,
– Mostly dominated by Direct Sequence CDMA.
– Market is expected to be fragmented amongst several competing
IMT2000 guidelines defined by the ITU.
– Analog was 1G. GSM/IS95 were 2G. Next is 3G.
What is 3G ?
standards.
across the world.
Envisioned as a single Global standard allowing seamless roaming
Used interchangeably with IMT2000 although there are some specific
A loosely defined term referring to next generation wireless systems.
4
encompasses three optional modes of operation.”
Telecommunications Union (ITU) of a single CDMA third generation standard that
“Qualcomm and Ericsson ... jointly support approval by the International
Jun 1999 found compromise at the OHG.
“Qualcomm … is not prepared to grant licences according to the … ETSI IPR Policy.”
fair, reasonable and non-discriminatory basis in accordance with the ... ETSI IPR Policy.”
“Ericsson … is prepared to grant licences to these [W-CDMA & TD-CDMA] patents on
Dec 1998 saw a stand-off in standards.
WCDMA, WTDMA, OFDMA, Global CDMA 1 & 2.
Asia Pacific (ARIB & TTA):
WCDMA N/A, UWC-136, cdma2000, WIMS WCDMA, WP-CDMA.
North America(T1P1, TR45.3, TR45.5, TR46.1):
WCDMA, WTDMA,TDMA/CDMA, OFDMA, ODMA.
Europe (ETSI):
In
n
scrambling achieve?
scrambling achieve?
6
Secure link: a linear sequence of length 2
doesn’t
Benefits of wideband signals: multipath provides temporal diversity instead of ISI.
Spectral re-use factor of 1: all cells can use the same frequency spectrum.
does
What
What
Low cross-correlation (at any time offset).
High auto-correlation (at any time offset).
What are their important properties?
in to a low amplitude, wide bandwidth signal.
Converts a high amplitude, narrow bandwidth signal
How do they work?
Pseudo-random sequences: Gold codes, Kasami codes (M-sequences).
‘W’ of WCDMA.
W
This document provides an overview of MapInfo software and how to use its various functions. It discusses MapInfo basics like tables, workspaces and layers. It also covers how to register raster images, create vector maps, perform network analysis using drive test data, and output maps. The goal of the tutorial is to introduce common MapInfo operations and help users get familiar with the software for tasks like network planning and map maintenance.
Third generation mobile networks will provide significantly higher data rates and allow for convergence of various communication services. 3G networks will transition to an all-IP infrastructure and support multiple access technologies and standards to provide connectivity anywhere in the world. This will enable always-on high-speed access to multimedia applications and the internet from mobile devices.
Cdma2000 network problem analysis with mobile station 20030212-a-v1.0Tempus Telcosys
This document describes how to use a mobile station (MS) to locate network problems in CDMA2000 networks. It explains how to view debugging screens on different MSs to check indices like pilot strength, receive level, and transmit level, which can indicate issues with forward or reverse coverage. It also discusses using reverse frame error rate tests on the network side to evaluate connection quality and voice quality. The document provides guidance on interpreting these metrics and diagnosing potential problems based on the results, like interference issues affecting transmit levels or poor coverage in certain areas.
It is required that after the course study
you should:
Have a general concept about DT
Master Panorama DT operation
Master Panorama data analysis
Chapter 1 DT Introduction
Chapter 2 Panorama DT Introduction
Chapter 3 Panorama DT Data Analysis
Collect System Air interface data
Analyze Air interface data
Assist Export Analysis report
Qualcom CAIT
CDMA Air Interface Tester
WILL TECH DM2K/Pecker
Pecker Navigator, Pecker Analyzer
Panorama
Qualcom CAIT
CDMA Air Interface Tester
WILL TECH DM2K/Pecker
Pecker Navigator, Pecker Analyzer
Panorama
QCTest™ CDMA Air Interface Tester (CAIT™) 3.1 User’s GuideTempus Telcosys
QUALCOMM Proprietary
Export of this technology or software is regulated by the U.S. Government. Diversion contrary to Ulaw prohibited.
All data and information contained in or disclosed by this document are confidential and proprietinformation of QUALCOMM Incorporated, and all rights therein are expressly reserved. By acceptthis material, the recipient agrees that this material and the information contained therein are heldconfidence and in trust and will not be used, copied, reproduced in whole or in part, nor its contentsrevealed in any manner to others without the express written permission of QUALCOMM Incorporated.
Mobile communications is one of the communications fields that develop rapidly and energetically. The antenna builds the bridge between user terminals and base control devices. It is widely used in the mobile communications and the wireless access communication system. The rapid development of the antenna greatly promotes its technology innovation.
It is important to deeply grasp the knowledge of the antenna, which is useful to:
Install and maintain products.
Promote the network planning.
Chapter 1 Working Principle
Chapter 2 Classification
Chapter 3 Electrical Index
Chapter 4 Mechanical Index
When the conducting cable carries the alternating current, the electromagnetic wave radiation can be formed.
If two conducting cables are close, the directions of their current are opposite, and the electromotive force is counteracted. Thus the radiation becomes week.
If two conducting cables are open, the directions of their current are the same. Thus the radiation becomes strong.
When the length of the conducting cable is like the wavelength, the current on the cable will be enhanced. Thus the radiation becomes strong.
The straight conducting cable which can generate the strong radiation is called the dipole.
The pole whose two arms are of the same length (1/4 Wavelength) is called as dipole or half-wave-length dipole.
C cf radio propagation theory and propagation modelsTempus Telcosys
The radio propagation theory is an important lesson in the radio communication curriculum. This lesson answers the following questions:
How are radio waves transmitted from one antenna to the other antenna?
What features does the radio wave have during the propagation? Which factors affect the propagation distance?
What fruits are achieved by predecessors in the radio wave propagation theory? How to apply the theory to practice?
Chapter 1 Radio Propagation Theory
Chapter 2 Radio Propagation Environment
Chapter 3 Radio Propagation Models
2. Direct Sequence and Frequency hopped spread spectrum.
Spreading sequence and their correlation function.
Acquisition and tracking of spread spectrum signals.
Thursday, May 30, 2013www.tempustelcosys.com
3. No matter which form of spread spectrum technique we employ, we
need to have the timing information of the transmitted signal in order
to despread the received signal and demodulate the despread
signal.
If we are off even by a single chip duration, we will be unable to
despread the received spread spectrum signal, since the spread
sequence is designed to have a small out-of-phase autocorrelation
magnitude.
Therefore, the process of acquiring the timing information of the
transmitted spread spectrum signal is essential to the
implementation of any form of spread spectrum technique.
Thursday, May 30, 2013www.tempustelcosys.com
4. Usually the problem of timing acquisition is solved via a two-step
approach:
Initial code acquisition (coarse acquisition or coarse synchronization)
which synchronizes the transmitter and receiver to within an uncertainty of
Tc
Code tracking which performs and maintains fine synchronization
between the transmitter and receiver.
Thursday, May 30, 2013www.tempustelcosys.com
5. Given the initial acquisition, code tracking is a relatively easy task and is
usually accomplished by a delay lock loop (DLL). The tracking loop keeps
on operating during the whole communication period. If the channel
changes abruptly, the delay lock loop will lose track of the correct timing
and initial acquisition will be re-performed. Sometimes, we perform initial
code acquisition periodically no matter whether the tracking loop loses
track or not.
Compared to code tracking, initial code acquisition in a spread spectrum
system is usually very difficult.
First, the timing uncertainty, which is basically determined by the
transmission time of the transmitter and the propagation delay, can be
much longer than a chip duration.
Thursday, May 30, 2013www.tempustelcosys.com
6. As initial acquisition is usually achieved by a search through all possible
phases (delays) of the sequence, a larger timing uncertainty means a
larger search area. Beside timing uncertainty, we may also encounter
frequency uncertainty which is due to Doppler shift and mismatch
between the transmitter and receiver oscillators.
Thus this necessitates a two-dimensional search in time and frequency.
Moreover, in many cases, initial code acquisition must be accomplished
in low signal-to-noise-ratio environments and in the presence of
jammers. The possibility of channel fading and the existence of multiple
access interference in CDMA environments can make initial acquisition
even harder to accomplish.
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7. Thursday, May 30, 2013www.tempustelcosys.com
As mentioned before, the objective of initial code acquisition is to
achieve a coarse synchronization between the receiver and the
transmitted signal. In a DS-SS system, this is the same as matching
the phase of the reference spreading signal in the despreader to the
spreading sequence in the received signal. We are going to introduce
several acquisition techniques which perform the phase matching just
described. They are all based on the following basic working principle
depicted in Figure.
The receiver hypothesizes a phase of the spreading sequence and
attempts to despread the received signal using the hypothesized
phase. If the hypothesized phase matches the sequence in the
received signal, the wide-band spread spectrum signal will be
despread correctly to give a narrowband data.
9. Then a band pass filter, with a bandwidth similar to that of the
narrowband data signal, can be employed to collect the power of the
despread signal. Since the hypothesized phase matches the received
signal, the BPF will collect all the power of the despread signal. In this
case, the receiver decides a coarse synchronization has been achieved
and activates the tracking loop to perform fine synchronization.
On the other hand, if the hypothesized phase does not match the
received signal, the despreader will give a wideband output and the BPF
will only be able to collect a small portion of the power of the despread
signal. Based on this, the receiver decides this hypothesized phase is
incorrect and other phases should be tried.
Thursday, May 30, 2013www.tempustelcosys.com
10. The type of energy detecting scheme considered in the above
example is called the matched filter energy detector since the
combination of the despreader and the integrator is basically an
implementation of the matched filter for the spreading signal.
There also exists another form of energy detector called the
radiometer which is shown in next Figure .
As before, the receiver hypothesizes a phase of the spreading
process. The despread signal is band pass filtered with a
bandwidth roughly equal to that of the narrowband data signal.
The output of the band pass filter is squared and integrated for a
duration of Td to detect the energy of the despread signal.
Thursday, May 30, 2013www.tempustelcosys.com
12. The time needed to evaluate is usually referred to as the dwell time.
Neglecting the processing time for the other components in the
acquisition circuit, the dwell time for the matched filter energy
detector and the radiometer are determined by the integration times
of the respective integrators in the matched filter energy detector
and the radiometer.
From the discussion above, the dwell times for the matched filter
energy detector and the radiometer are T and Td, respectively. In
practice, we would like the dwell time to be as small as possible.
Thursday, May 30, 2013www.tempustelcosys.com
13. Thursday, May 30, 2013www.tempustelcosys.com
The time needed to evaluate is usually referred to as the dwell
time. Neglecting the processing time for the other components in
the acquisition circuit, the dwell time for the matched filter energy
detector and the radiometer are determined by the integration
times of the respective integrators in the matched filter energy
detector and the radiometer.
From the discussion above, the dwell times for the matched filter
energy detector and the radiometer are T and Td, respectively. In
practice, we would like the dwell time to be as small as possible.
14. The presence of noise causes two different kinds of errors in the
acquisition process:
1. A false alarm occurs when the integrator output exceeds the
threshold for an incorrect hypothesized phase.
2. A miss occurs when the integrator output falls below the threshold for
a correct hypothesized phase.
A false alarm will cause an incorrect phase to be passed to the code
tracking loop which, as a result, will not be able to lock on to the DS-
SS signal and will return the control back to the acquisition circuitry
eventually. However, this process will impose severe time penalty to
the overall acquisition time.
Thursday, May 30, 2013www.tempustelcosys.com
15. Thursday, May 30, 2013www.tempustelcosys.com
On the other hand, a miss will cause the acquisition circuitry to
neglect the current correct hypothesized phase. Therefore a correct
acquisition will not be achieved until the next correct hypothesized
phase comes around. The time penalty of a miss depends on
acquisition strategy.
In general, we would like to design the acquisition circuitry to
minimize both the false alarm and miss probabilities by properly
selecting the decision threshold and the integration time. Since the
integrators in both the matched filter energy detector and the
radiometer act to collect signal energy as well as to average out
noise, a longer integration time implies smaller false alarm and miss
probabilities. We note that because of the reason indicated before,
we can only increase the integration time of the matched filter
energy detector in multiples of T. No such restriction is imposed on
the radiometer.
16. Thursday, May 30, 2013www.tempustelcosys.com
Summarizing the discussions so far, we need to design the dwell
time (the integration time) of the acquisition circuitry to achieve a
compromise between a small overall acquisition time and small
false alarm and miss probabilities. Another important practical
consideration is the complexity of the acquisition circuitry.
Obviously, there is no use of designing an acquisition circuit
which is too complex to build.
17. There are usually two major design approaches for initial code
acquisition.
The first approach is to minimize the overall acquisition time given a
predetermined tolerance on the false alarm and miss probabilities.
The second approach is to associate penalty times with false alarms
and misses in the calculation and minimization of the overall
acquisition time.
In applying each of the two approaches, we need to consider any
practical constraint which might impose a limit on the complexity of
the acquisition circuitry.
Thursday, May 30, 2013www.tempustelcosys.com
Design approaches
for initial code
acquisition.
18. With all these considerations in mind, we will discuss several
common acquisition strategies and compare them in terms of
complexity and acquisition time.
Serial search
The first acquisition strategy we consider is serial search. In this
method, the acquisition circuit attempts to cycle through and test all
possible phases one by one (serially) as shown in Figure. The circuit
complexity for serial search is low. However, penalty time associated
with a miss is large. Therefore we need to select a larger integration
(dwell) time to reduce the miss probability. This, together with the
serial searching nature, gives a large overall acquisition time (i.e.,
slow acquisition).
Thursday, May 30, 2013www.tempustelcosys.com
20. Parallel search
Unlike serial search, we test all the possible phases simultaneously
in the parallel search strategy as shown in Figure. Obviously, the
circuit complexity of the parallel search is high. The overall
acquisition time is much smaller than that of the serial search.
Thursday, May 30, 2013www.tempustelcosys.com
22. Since the penalty time associated with a false alarm is large, we
usually set the decision threshold in the serial search circuitry to a
high value to make the false alarm probability small. However, this
requires us to increase integration time Td to reduce the miss
probability since the penalty time associated with a miss is also
large. As a result, the overall acquisition time needed for the serial
search is inherently large. This is the limitation of using a single
detection stage
Thursday, May 30, 2013www.tempustelcosys.com
23. A common approach to reduce the overall acquisition the overall
acquisition time is to employ a two-stage detection scheme as
shown in Figure . Each detection stage in Figure represents a
radiometer with the integration time and decision threshold shown.
The first detection stage is designed to have a low threshold and a
short integration time such that the miss probability is small but the
false alarm probability is high. The second stage is designed to have
small miss and false alarm probabilities. With this configuration, the
first stage can reject incorrect phases rapidly and second stage,
which is entered occasionally, verifies the decisions made by the first
stage to reduce the false alarm probability. By properly choosing the
integration times and decision thresholds in the two detection stage,
the overall acquisition time can be significantly reduced.
Thursday, May 30, 2013www.tempustelcosys.com
24. This idea can be extended easily to include cases where more than
two decision stages are employed to further reduce the overall
acquisition time. This type of acquisition strategy is called multidwell
detection. We note that the multidwell detection strategy can be
interpreted as a serial search with variable integration (dwell) time.
Thursday, May 30, 2013www.tempustelcosys.com
26. The purpose of code tracking is to perform and maintain fine
synchronization.
A code tracking loop starts its operation only after initial acquisition
has been achieved. Hence, we can assume that we are off by small
amounts in both frequency and code phase.
The circuitry required is known as a tracking loop, as it tracks the
transmitter's code clock frequency variations. Without a tracking loop
synchronization will be lost as the transmitter and receiver PN code
clocks will tend to drift apart.
Thursday, May 30, 2013www.tempustelcosys.com
27. The code tracking loops perform either coherently or non coherently.
Coherent loops use carrier phase information whereas non coherent
loops do not require knowledge of carrier phase.
A common fine synchronization strategy is to design a code tracking
circuitry which can track the code phase in the presence of a small
frequency error. After the correct code phase is acquired by the code
tracking circuitry, a standard phase lock loop (PLL) can be employed
to track the carrier frequency and phase.
Thursday, May 30, 2013www.tempustelcosys.com
29. DLL uses two correlators called an early correlator and a late
correlator. An early correlator uses a code reference that is
advanced in time by some fraction of a chip with respect to the
currently estimated code phase whereas late is delayed by same
amount. The difference between two is used to sense small
deviations of incoming spreading codes timing with respect to early
and late code timing.
The result of correlation between an incoming direct sequence
signal and the receiver PN code is a triangular function two chips
(code bits) wide.
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30. Assuming synchronization two correlated signals (each with a
triangular correlation waveform) are produced with their correlation
peaks separated by the delay between the early and late receiver
PN codes. If the two correlation signals are summed in a difference
amplifier and filtered, then a composite correlation function is
produced. This composite correlation function has a linear region
between its maximum and minimum values.
If this composite correlation function is used to control the receiver's
code clock frequency (for example by driving a voltage controlled
oscillator) then the receiver will track the transmitter's code clock at
a point halfway between the maximum and minimum values of the
composite correlation function.
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33. The correlators that uses the reference code is called Punctual
Correlator
This is an optimum solution which provide a third on-time (punctual)
PN sequence correlator channel for signal recovery, with early and
late correlators simply providing tracking to keep the on-time
channel in the middle of the correlation window. Such an approach
provides an optimally correlated (despread) output signal for
subsequent data demodulation.
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35. PLL
DLL
TDL tau dither loop which is time shared Early Late tracking loop
DDL double dither loop
PSD DLL product of sum difference DLL
MCTL Modified code tracking loop.
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