This document analyzes the performance of OFDM systems in the presence of Doppler effect. It derives a new expression for total carrier frequency offset that includes both static offset from local oscillator imperfections and dynamic offset from Doppler effect. It then examines inter-carrier interference and carrier-to-interference ratio (CIR) as a function of speed and angle, showing that CIR decreases with increasing speed and for certain angle ranges, with maximum CIR when the Doppler effect is canceled at 90 degrees. Bit error rate performance is evaluated through Monte Carlo simulation.
Analog Communications Jntu Model Paper{Www.Studentyogi.Com}guest3f9c6b
The document is a set of exam questions for an Analog Communications course. It contains 8 questions related to topics like:
1. Explanation of AM modulation and calculation of power in sidebands when modulation depth is reduced.
2. Circuit diagram and operation of a balanced ring modulator, and generation and spectrum of an AM-SC signal.
3. Time domain representation of SSB and percentage power saved compared to AM.
4. Operation of a balanced slope detector and its advantages over a slope detector. Calculation of bandwidth for an FM signal.
5. Role of signal-to-noise ratio in communication channel performance.
6. Block diagram and operation of an SSB-
This document discusses channel estimation techniques in OFDM systems. It compares LS and MMSE estimation methods. It also describes simulating an OFDM transmission in Matlab to analyze how the bit error ratio is affected by changing the signal-to-noise ratio and multipath effects. The key steps of the simulation are outlined, including OFDM transmission, channel estimation using LS and MMSE, and calculating the bit error ratio to compare performance of the estimation techniques.
Evidence Of Bimodal Crystallite Size Distribution In Microcrystalline Silico...Sanjay Ram
It is known that there is a bimodal size distribution in microcrystalline silicon. How can the deconvolution of the Raman spectra be done with incorporation of a bimodal CSD to obtain more accurate and physical picture of the microstructure in this material?
COMMUNICATION ENGINEERING ASSIGNMENT(INSTITUTE ELECTIVE-1) SEM-4 SVMITVishal Soni
The document provides instructions for several experiments involving amplitude modulation transmitter and receiver circuits, including circuits for DSB-AM, SSB-AM, and DSB-AM with AGC. Diagrams of the circuits are included, along with procedures to observe waveforms, adjust frequencies and gains, and measure modulation index. Students are to record their observations and conclusions from completing the experiments.
Analyse Performance of Fractional Fourier Transform on Timing and Carrier Fr...ijwmn
This paper deals with the performance of the use of fractional Fourier transform (FRFT) instead of
conventional Fourier transform (FFT) in either symbol timing offset (STO) and carrier frequency offset
(CFO) estimation. Orthogonal frequency division multiplexing is widely used in many systems due to
advantages of theses technique compared with mono-carrier systems. In spite of his advantages, OFDM
presents drawbacks such as sensitivity to timing and frequency offsets. Many techniques are used in the
literature to estimate these two parameters in order to compensate them (synchronization task). These
techniques used conventional Fourier transform. In this paper, we are interested in estimating STO and
CFO using fractional Fourier transform. Monte Carlo simulation demonstrates the performance of the use
of FRFT instead of FFT.
Analysis and Simulation of Pseudo Ranging Noise codes for Geo-Stationary Sate...IDES Editor
This document analyzes and simulates pseudo ranging noise codes for geo-stationary satellites, including their Doppler effect. It examines the auto-correlation function and cross-correlation function properties of Gold codes, Kasami codes, and their truncation effects. The simulations were performed using MATLAB and System View. The results show that truncating the codes degrades their correlation properties. Doppler frequency shift on carrier frequencies and codes for geo-stationary satellites was also analyzed and found to be negligible.
Analog Communications Jntu Model Paper{Www.Studentyogi.Com}guest3f9c6b
The document is a set of exam questions for an Analog Communications course. It contains 8 questions related to topics like:
1. Explanation of AM modulation and calculation of power in sidebands when modulation depth is reduced.
2. Circuit diagram and operation of a balanced ring modulator, and generation and spectrum of an AM-SC signal.
3. Time domain representation of SSB and percentage power saved compared to AM.
4. Operation of a balanced slope detector and its advantages over a slope detector. Calculation of bandwidth for an FM signal.
5. Role of signal-to-noise ratio in communication channel performance.
6. Block diagram and operation of an SSB-
This document discusses channel estimation techniques in OFDM systems. It compares LS and MMSE estimation methods. It also describes simulating an OFDM transmission in Matlab to analyze how the bit error ratio is affected by changing the signal-to-noise ratio and multipath effects. The key steps of the simulation are outlined, including OFDM transmission, channel estimation using LS and MMSE, and calculating the bit error ratio to compare performance of the estimation techniques.
Evidence Of Bimodal Crystallite Size Distribution In Microcrystalline Silico...Sanjay Ram
It is known that there is a bimodal size distribution in microcrystalline silicon. How can the deconvolution of the Raman spectra be done with incorporation of a bimodal CSD to obtain more accurate and physical picture of the microstructure in this material?
COMMUNICATION ENGINEERING ASSIGNMENT(INSTITUTE ELECTIVE-1) SEM-4 SVMITVishal Soni
The document provides instructions for several experiments involving amplitude modulation transmitter and receiver circuits, including circuits for DSB-AM, SSB-AM, and DSB-AM with AGC. Diagrams of the circuits are included, along with procedures to observe waveforms, adjust frequencies and gains, and measure modulation index. Students are to record their observations and conclusions from completing the experiments.
Analyse Performance of Fractional Fourier Transform on Timing and Carrier Fr...ijwmn
This paper deals with the performance of the use of fractional Fourier transform (FRFT) instead of
conventional Fourier transform (FFT) in either symbol timing offset (STO) and carrier frequency offset
(CFO) estimation. Orthogonal frequency division multiplexing is widely used in many systems due to
advantages of theses technique compared with mono-carrier systems. In spite of his advantages, OFDM
presents drawbacks such as sensitivity to timing and frequency offsets. Many techniques are used in the
literature to estimate these two parameters in order to compensate them (synchronization task). These
techniques used conventional Fourier transform. In this paper, we are interested in estimating STO and
CFO using fractional Fourier transform. Monte Carlo simulation demonstrates the performance of the use
of FRFT instead of FFT.
Analysis and Simulation of Pseudo Ranging Noise codes for Geo-Stationary Sate...IDES Editor
This document analyzes and simulates pseudo ranging noise codes for geo-stationary satellites, including their Doppler effect. It examines the auto-correlation function and cross-correlation function properties of Gold codes, Kasami codes, and their truncation effects. The simulations were performed using MATLAB and System View. The results show that truncating the codes degrades their correlation properties. Doppler frequency shift on carrier frequencies and codes for geo-stationary satellites was also analyzed and found to be negligible.
The document summarizes research on using Run Length Encoding (RLE) to reduce Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) systems. Simulation results showed that RLE reduced PAPR by about 3 dB at a probability of 10-2 while maintaining a compression ratio of 1.7. The symbol error rate performance in additive white Gaussian noise and Rayleigh fading channels was unchanged with RLE. Thus, RLE is an effective PAPR reduction technique that does not degrade system performance.
Variation of Electrical Transport Parameters with Large Grain Fraction in Hig...Sanjay Ram
The electrical transport and its correlation with the microstructural properties in single phase microcrystalline silicon may be very different from the transport in microcrystalline silicon with a mixed phase of amorphous silicon. We have shown that the transport in single phase microcrystalline silicon may be predicted by the large grain fraction.
The document describes the design of a 10-bit, 50MS/s pipelined analog-to-digital converter (ADC) implemented in a 180nm CMOS process. Key aspects of the design include a flip-around track-and-hold amplifier, 1.5-bit per stage pipeline stages with gain of 2, and operational transconductance amplifiers optimized for power efficiency. Simulation results show the ADC achieves 9.64 effective bits, consumes 24.5mW of power, and has a figure of merit better than prior published pipelined ADCs of similar resolution and speed.
The document compares various waveforms that have been proposed for 5G mobile networks, including OFDM, FBMC, GFDM, UFMC, SCFDMA, and SCFDE. It provides a system model and modulation matrix for each waveform, and discusses performance metrics that will be used for comparison such as out-of-band leakage power, peak-to-average power ratio, bit error rate over wireless channels, effects of carrier frequency offset, and spectral efficiency. The analysis aims to help select the most appropriate waveform for 5G systems.
The document discusses routing and wavelength assignment (RWA) in wavelength-division multiplexing (WDM) networks. It covers both static and dynamic RWA problems. For routing, it discusses integer linear programming formulations for static routing and online algorithms for dynamic routing. For wavelength assignment, it discusses graph coloring approaches for static assignment and heuristics like first-fit for dynamic assignment. Several heuristics for RWA are presented, along with their computational complexities and performance. Future research directions like survivable RWA and managing multicast connections are also outlined.
This lab report demonstrates coherent detection of a message signal from a modulated signal using MATLAB. It shows how to generate a message signal, carrier signal, and their modulation to create a DSB-SC signal. Coherent detection is performed by multiplying the DSB-SC signal with a synchronized local oscillator. The effects of oscillator synchronization errors in frequency and phase are examined. Finally, filtering is applied to recover the original message signal. Simulink is also used to model the coherent detection process for sinusoidal and square wave inputs.
This document discusses modeling wireless communication systems using MATLAB. It covers:
- Characterizing the wireless channel from physics of propagation to multi-path fading channels.
- Statistical characterization of channels including Doppler spectrum, delay spread, coherence time and bandwidth.
- Simulating multi-path fading channels in MATLAB and modeling path loss.
- Explaining how multi-path propagation leads to signal distortion and is equivalent to undesired filtering.
What is the main difference between single carrier and ofdm yahoo! answersen_maruf78
Single carrier (SC) transmission has a lower peak-to-average power ratio than orthogonal frequency-division multiplexing (OFDM). SC frequency-division multiple access (SC-FDMA) divides the frequency band into subsets, assigning each user a different subset, whereas OFDM divides data into multiple parallel streams and assigns each stream a unique subcarrier. Both SC-FDMA and OFDM use guard intervals and fast Fourier transforms to combat interference, but SC-FDMA applies these on the transmitter side while OFDM applies them on the receiver side. SC-FDMA has a lower peak-to-average power ratio than OFDM, making it more suitable for applications with power constraints like uplink mobile communications.
Design Ofdm System And Remove Nonlinear Distortion In OFDM Signal At Transmit...Rupesh Sharma
although OFDM seems to be a solution to keep up with
the demand of increasing data rates, it has some drawbacks.
Sensitivity to high PAPR is the most significant of these
drawbacks. The main objective of this paper was to investigate
and document the effects of PAPR on the performance of OFDM
based digital communications under different channel conditions.
A step-by-step approach was adopted in order to achieve the
objective of this paper. The first step is to provide a basic
background on the principles of OFDM. The reasons for the
PAPR and a theoretical analysis of these effects on OFDM
systems are documented. The OFDM system has a high peak-toaverage
power ratio (PAPR) that can cause unwanted saturation
in the power amplifiers, leading to in-band distortion and out-ofband
radiation. To be able to observe the system behavior, the
simulation results for different channel models are presented in
graphical form. Next, the simulation results obtained in this work
are compared to the simulation results reported in related studies
This presentation provides an introduction to Common Reflection Surface (CRS) processing. It outlines the methodology of CRS, including its use of three parameters (RNIP, RN, and R) to model subsurface reflectors rather than a single NMO velocity. Case studies are presented showing how CRS can improve data quality in both time and depth processing through techniques like CRS tomography. Current developments with CRS gathers and its applications in reservoir description are also mentioned.
CRS (constant reflection surface) processing provides several advantages over standard processing methods. [1] CRS uses three parameters (dip, curvature, location) rather than one parameter (velocity) to model subsurface reflectors, allowing for improved imaging of complex geology. [2] Case studies demonstrate how CRS can improve signal-to-noise ratio and lateral resolution for difficult datasets with irregular acquisition patterns. [3] CRS tomography creates smooth velocity models from CRS attributes that are well-suited for depth imaging techniques like pre-stack depth migration (PreSDM).
1. The document proposes an availability-aware routing algorithm for hybrid wireless-optical broadband access networks to improve network availability and throughput.
2. The algorithm calculates the availability of each link and path by considering the mean time to failure and mean time to repair of network components.
3. It finds the most available path between any source-destination pair using a modified Dijkstra's shortest path algorithm that assigns link weights based on availability. This helps route traffic along more reliable paths.
Dynamic Spectrum Derived Mfcc and Hfcc Parameters and Human Robot Speech Inte...IDES Editor
Using the Mel-frequency cepstral coefficients
(MFCC), Human Factor cepstral coefficients (HFCC) and
their new parameters derived from log dynamic spectrum and
dynamic log spectrum, these features are widely used for
speech recognition in various applications. But, speech
recognition systems based on these features do not perform
efficiently in the noisy conditions, mobile environment and
for speech variation between users of different genders and
ages. To maximize the recognition rate of speaker independent
isolated word recognition system, we combine both of the above
features and proposed a hybrid feature set of them. We tested
the system for this hybrid feature vector and we gained results
with accuracy of 86.17% in clean condition (closed window),
82.33% in class room open window environment, and 73.67%
in outdoor with noisy environment.
This document summarizes design issues in OFDM systems. It discusses the OFDM modem block diagram and signal description. It then focuses on key receiver design issues like time and frequency synchronization through techniques like frequency offset correction, carrier phase tracking, and channel equalization. It also addresses signal dynamic range issues and how they are handled in standards like IEEE 802.11a/g. The document provides illustrations of effects of different impairments and solutions used in practical OFDM systems.
This document discusses Orthogonal Frequency Division Multiple Access (OFDMA) and related topics. It provides information on:
- The structure and principles of OFDM symbols, including how they are constructed from orthogonal subcarriers modulated by parallel data streams.
- Challenges caused by carrier frequency offsets and sampling time offsets at the receiver, and how symbol synchronization is needed.
- Channel estimation techniques in OFDMA systems, including least squares estimation, block-type and comb-type pilot structures, and linear/second-order interpolation methods.
- How OFDMA exploits multiuser diversity by adaptively allocating subcarriers to users experiencing favorable channel conditions.
Performances des turbo codes parallèles pour un canal satellite non linéaireRachidz
1) The document analyzes the performance of parallel concatenated codes (turbo codes) with iterative decoding for error correction on nonlinear satellite channels.
2) It simulates a digital satellite transmission system using parallel turbo codes with QPSK modulation.
3) The simulation evaluates how varying parameters like constraint length, interleaver size, and number of iterations affects the bit error rate performance of turbo codes compared to Viterbi decoding.
This document provides an introduction and overview of orthogonal frequency division multiplexing (OFDM). It discusses the limitations of single-carrier transmission at high data rates due to inter-symbol interference (ISI) and the complexity of equalizers. OFDM is presented as a solution that divides the available bandwidth into multiple orthogonal subcarriers. The key concepts of OFDM covered include cyclic prefix, orthogonality of subcarriers, modulation and demodulation, and how the cyclic prefix mitigates ISI between symbols. Bit error rate simulation of an OFDM system is also demonstrated.
- The document discusses wireless channel propagation and fading. It covers topics like large-scale fading (path loss and shadowing), small-scale fading (time-selective and frequency-selective fading), and statistical characterization of fading channels.
- Small-scale fading is caused by multipath propagation and results in rapid fluctuations in the strength of the received signal over short periods of time or travel distances. It can be time-selective or frequency-selective depending on delay spread and Doppler spread.
- Common distributions for modeling fading amplitudes are Rayleigh for non-line-of-sight environments and Rician when there is a dominant line-of-sight path. The document presents models for generating both Rayleigh and Rician fading
Vhdl implementation of ofdm transmitterrajeshr0009
This document discusses multiple access techniques for wireless communications including CDMA, TDMA, and FDMA. It then describes orthogonal frequency-division multiplexing (OFDM), how it works, and its advantages over other techniques. OFDM divides the available bandwidth into multiple orthogonal subcarriers. This eliminates interference between subcarriers and improves spectral efficiency. The document also discusses fast Fourier transforms and their use in implementing OFDM modulation and demodulation.
Low Frequency Oscillations Damping by UPFC with GAPOD and GADC-voltage regulatorIOSR Journals
This document describes a new controller for a Unified Power Flow Controller (UPFC) to damp low frequency oscillations in power systems. The proposed controller is a Multi-Stage Fuzzy (MSF) PID controller with a genetic algorithm-based DC voltage regulator. The MSF controller uses multiple fuzzy logic controllers and a fuzzy switch to better handle system uncertainties. Membership functions for the fuzzy controllers are optimized using a genetic algorithm. Testing on a single machine infinite bus power system model shows the proposed controller more effectively damps low frequency oscillations under different operating conditions compared to other UPFC controllers. The design and implementation of the proposed controller is described to be simpler than other advanced control methods while still providing robust damping performance.
Performance comparison of SVC and SSSC with POD controller for Power System S...IOSR Journals
This document compares the performance of a static synchronous series compensator (SSSC) and static VAR compensator (SVC), both with a power oscillation damping (POD) controller, for improving power system stability. It simulates a test power system in MATLAB/Simulink with each device. The SSSC is able to inject a controllable voltage in series with a transmission line to emulate inductive or capacitive reactance. The SVC injects reactive power to regulate voltage. Simulation results show the SVC with POD controller more effectively enhances voltage stability and increases transmission capacity during faults compared to the SSSC.
The document summarizes research on using Run Length Encoding (RLE) to reduce Peak-to-Average Power Ratio (PAPR) in Orthogonal Frequency Division Multiplexing (OFDM) systems. Simulation results showed that RLE reduced PAPR by about 3 dB at a probability of 10-2 while maintaining a compression ratio of 1.7. The symbol error rate performance in additive white Gaussian noise and Rayleigh fading channels was unchanged with RLE. Thus, RLE is an effective PAPR reduction technique that does not degrade system performance.
Variation of Electrical Transport Parameters with Large Grain Fraction in Hig...Sanjay Ram
The electrical transport and its correlation with the microstructural properties in single phase microcrystalline silicon may be very different from the transport in microcrystalline silicon with a mixed phase of amorphous silicon. We have shown that the transport in single phase microcrystalline silicon may be predicted by the large grain fraction.
The document describes the design of a 10-bit, 50MS/s pipelined analog-to-digital converter (ADC) implemented in a 180nm CMOS process. Key aspects of the design include a flip-around track-and-hold amplifier, 1.5-bit per stage pipeline stages with gain of 2, and operational transconductance amplifiers optimized for power efficiency. Simulation results show the ADC achieves 9.64 effective bits, consumes 24.5mW of power, and has a figure of merit better than prior published pipelined ADCs of similar resolution and speed.
The document compares various waveforms that have been proposed for 5G mobile networks, including OFDM, FBMC, GFDM, UFMC, SCFDMA, and SCFDE. It provides a system model and modulation matrix for each waveform, and discusses performance metrics that will be used for comparison such as out-of-band leakage power, peak-to-average power ratio, bit error rate over wireless channels, effects of carrier frequency offset, and spectral efficiency. The analysis aims to help select the most appropriate waveform for 5G systems.
The document discusses routing and wavelength assignment (RWA) in wavelength-division multiplexing (WDM) networks. It covers both static and dynamic RWA problems. For routing, it discusses integer linear programming formulations for static routing and online algorithms for dynamic routing. For wavelength assignment, it discusses graph coloring approaches for static assignment and heuristics like first-fit for dynamic assignment. Several heuristics for RWA are presented, along with their computational complexities and performance. Future research directions like survivable RWA and managing multicast connections are also outlined.
This lab report demonstrates coherent detection of a message signal from a modulated signal using MATLAB. It shows how to generate a message signal, carrier signal, and their modulation to create a DSB-SC signal. Coherent detection is performed by multiplying the DSB-SC signal with a synchronized local oscillator. The effects of oscillator synchronization errors in frequency and phase are examined. Finally, filtering is applied to recover the original message signal. Simulink is also used to model the coherent detection process for sinusoidal and square wave inputs.
This document discusses modeling wireless communication systems using MATLAB. It covers:
- Characterizing the wireless channel from physics of propagation to multi-path fading channels.
- Statistical characterization of channels including Doppler spectrum, delay spread, coherence time and bandwidth.
- Simulating multi-path fading channels in MATLAB and modeling path loss.
- Explaining how multi-path propagation leads to signal distortion and is equivalent to undesired filtering.
What is the main difference between single carrier and ofdm yahoo! answersen_maruf78
Single carrier (SC) transmission has a lower peak-to-average power ratio than orthogonal frequency-division multiplexing (OFDM). SC frequency-division multiple access (SC-FDMA) divides the frequency band into subsets, assigning each user a different subset, whereas OFDM divides data into multiple parallel streams and assigns each stream a unique subcarrier. Both SC-FDMA and OFDM use guard intervals and fast Fourier transforms to combat interference, but SC-FDMA applies these on the transmitter side while OFDM applies them on the receiver side. SC-FDMA has a lower peak-to-average power ratio than OFDM, making it more suitable for applications with power constraints like uplink mobile communications.
Design Ofdm System And Remove Nonlinear Distortion In OFDM Signal At Transmit...Rupesh Sharma
although OFDM seems to be a solution to keep up with
the demand of increasing data rates, it has some drawbacks.
Sensitivity to high PAPR is the most significant of these
drawbacks. The main objective of this paper was to investigate
and document the effects of PAPR on the performance of OFDM
based digital communications under different channel conditions.
A step-by-step approach was adopted in order to achieve the
objective of this paper. The first step is to provide a basic
background on the principles of OFDM. The reasons for the
PAPR and a theoretical analysis of these effects on OFDM
systems are documented. The OFDM system has a high peak-toaverage
power ratio (PAPR) that can cause unwanted saturation
in the power amplifiers, leading to in-band distortion and out-ofband
radiation. To be able to observe the system behavior, the
simulation results for different channel models are presented in
graphical form. Next, the simulation results obtained in this work
are compared to the simulation results reported in related studies
This presentation provides an introduction to Common Reflection Surface (CRS) processing. It outlines the methodology of CRS, including its use of three parameters (RNIP, RN, and R) to model subsurface reflectors rather than a single NMO velocity. Case studies are presented showing how CRS can improve data quality in both time and depth processing through techniques like CRS tomography. Current developments with CRS gathers and its applications in reservoir description are also mentioned.
CRS (constant reflection surface) processing provides several advantages over standard processing methods. [1] CRS uses three parameters (dip, curvature, location) rather than one parameter (velocity) to model subsurface reflectors, allowing for improved imaging of complex geology. [2] Case studies demonstrate how CRS can improve signal-to-noise ratio and lateral resolution for difficult datasets with irregular acquisition patterns. [3] CRS tomography creates smooth velocity models from CRS attributes that are well-suited for depth imaging techniques like pre-stack depth migration (PreSDM).
1. The document proposes an availability-aware routing algorithm for hybrid wireless-optical broadband access networks to improve network availability and throughput.
2. The algorithm calculates the availability of each link and path by considering the mean time to failure and mean time to repair of network components.
3. It finds the most available path between any source-destination pair using a modified Dijkstra's shortest path algorithm that assigns link weights based on availability. This helps route traffic along more reliable paths.
Dynamic Spectrum Derived Mfcc and Hfcc Parameters and Human Robot Speech Inte...IDES Editor
Using the Mel-frequency cepstral coefficients
(MFCC), Human Factor cepstral coefficients (HFCC) and
their new parameters derived from log dynamic spectrum and
dynamic log spectrum, these features are widely used for
speech recognition in various applications. But, speech
recognition systems based on these features do not perform
efficiently in the noisy conditions, mobile environment and
for speech variation between users of different genders and
ages. To maximize the recognition rate of speaker independent
isolated word recognition system, we combine both of the above
features and proposed a hybrid feature set of them. We tested
the system for this hybrid feature vector and we gained results
with accuracy of 86.17% in clean condition (closed window),
82.33% in class room open window environment, and 73.67%
in outdoor with noisy environment.
This document summarizes design issues in OFDM systems. It discusses the OFDM modem block diagram and signal description. It then focuses on key receiver design issues like time and frequency synchronization through techniques like frequency offset correction, carrier phase tracking, and channel equalization. It also addresses signal dynamic range issues and how they are handled in standards like IEEE 802.11a/g. The document provides illustrations of effects of different impairments and solutions used in practical OFDM systems.
This document discusses Orthogonal Frequency Division Multiple Access (OFDMA) and related topics. It provides information on:
- The structure and principles of OFDM symbols, including how they are constructed from orthogonal subcarriers modulated by parallel data streams.
- Challenges caused by carrier frequency offsets and sampling time offsets at the receiver, and how symbol synchronization is needed.
- Channel estimation techniques in OFDMA systems, including least squares estimation, block-type and comb-type pilot structures, and linear/second-order interpolation methods.
- How OFDMA exploits multiuser diversity by adaptively allocating subcarriers to users experiencing favorable channel conditions.
Performances des turbo codes parallèles pour un canal satellite non linéaireRachidz
1) The document analyzes the performance of parallel concatenated codes (turbo codes) with iterative decoding for error correction on nonlinear satellite channels.
2) It simulates a digital satellite transmission system using parallel turbo codes with QPSK modulation.
3) The simulation evaluates how varying parameters like constraint length, interleaver size, and number of iterations affects the bit error rate performance of turbo codes compared to Viterbi decoding.
This document provides an introduction and overview of orthogonal frequency division multiplexing (OFDM). It discusses the limitations of single-carrier transmission at high data rates due to inter-symbol interference (ISI) and the complexity of equalizers. OFDM is presented as a solution that divides the available bandwidth into multiple orthogonal subcarriers. The key concepts of OFDM covered include cyclic prefix, orthogonality of subcarriers, modulation and demodulation, and how the cyclic prefix mitigates ISI between symbols. Bit error rate simulation of an OFDM system is also demonstrated.
- The document discusses wireless channel propagation and fading. It covers topics like large-scale fading (path loss and shadowing), small-scale fading (time-selective and frequency-selective fading), and statistical characterization of fading channels.
- Small-scale fading is caused by multipath propagation and results in rapid fluctuations in the strength of the received signal over short periods of time or travel distances. It can be time-selective or frequency-selective depending on delay spread and Doppler spread.
- Common distributions for modeling fading amplitudes are Rayleigh for non-line-of-sight environments and Rician when there is a dominant line-of-sight path. The document presents models for generating both Rayleigh and Rician fading
Vhdl implementation of ofdm transmitterrajeshr0009
This document discusses multiple access techniques for wireless communications including CDMA, TDMA, and FDMA. It then describes orthogonal frequency-division multiplexing (OFDM), how it works, and its advantages over other techniques. OFDM divides the available bandwidth into multiple orthogonal subcarriers. This eliminates interference between subcarriers and improves spectral efficiency. The document also discusses fast Fourier transforms and their use in implementing OFDM modulation and demodulation.
Low Frequency Oscillations Damping by UPFC with GAPOD and GADC-voltage regulatorIOSR Journals
This document describes a new controller for a Unified Power Flow Controller (UPFC) to damp low frequency oscillations in power systems. The proposed controller is a Multi-Stage Fuzzy (MSF) PID controller with a genetic algorithm-based DC voltage regulator. The MSF controller uses multiple fuzzy logic controllers and a fuzzy switch to better handle system uncertainties. Membership functions for the fuzzy controllers are optimized using a genetic algorithm. Testing on a single machine infinite bus power system model shows the proposed controller more effectively damps low frequency oscillations under different operating conditions compared to other UPFC controllers. The design and implementation of the proposed controller is described to be simpler than other advanced control methods while still providing robust damping performance.
Performance comparison of SVC and SSSC with POD controller for Power System S...IOSR Journals
This document compares the performance of a static synchronous series compensator (SSSC) and static VAR compensator (SVC), both with a power oscillation damping (POD) controller, for improving power system stability. It simulates a test power system in MATLAB/Simulink with each device. The SSSC is able to inject a controllable voltage in series with a transmission line to emulate inductive or capacitive reactance. The SVC injects reactive power to regulate voltage. Simulation results show the SVC with POD controller more effectively enhances voltage stability and increases transmission capacity during faults compared to the SSSC.
APPLICATION OF STATCOM to IMPROVED DYNAMIC PERFORMANCE OF POWER SYSTEMijsrd.com
Application of FACTS controller called Static Synchronous Compensator STATCOM to improve the performance of power grid with Wind Farms is investigated .The essential feature of the STATCOM is that it has the ability to absorb or inject fastly the reactive power with power grid . Therefore the voltage regulation of the power grid with STATCOM FACTS device is achieved. Moreover restoring the stability of the power system having wind farm after occurring severe disturbance such as faults or wind farm mechanical power variation is obtained with STATCOM controller . The dynamic model of the power system having wind farm controlled by proposed STATCOM is developed . To validate the powerful of the STATCOM FACTS controller, the studied power system is simulated and subjected to different severe disturbances. The results prove the effectiveness of the proposed STATCOM controller in terms of fast damping the power system oscillations and restoring the power system stability.
Static Synchronous Series Compensator (SSSC) with Superconducting Magnetic En...IDES Editor
Static Synchronous Series Compensator (SSSC) has
been designed with Superconducting Magnetic Energy Storage
(SMES) system. A closed loop control scheme has been
proposed with PI controller and real and reactive powers are
taken as references. A 48 pulse voltage source inverter is
designed for the SSSC. Control scheme for the chopper circuit
of SMES coil is also designed. A three area system is taken as
the test system and the operation of SSSC with SMES is
analysed for various transient disturbances. Test results under
different disturbances and operating conditions show the
proposed SSSC with SMES is effective in damping out the
power system oscillations.
This document discusses modern power transmission techniques and FACTS devices. It explains that transmission losses can be reduced by increasing voltage levels and maintaining a power factor near 1. FACTS devices like STATCOM and SVC use power electronics to dynamically regulate voltage by supplying or absorbing reactive power from the grid. This improves power quality and stability. The document outlines different series and shunt compensation strategies used in FACTS controllers to address issues like improper load distribution, voltage drops, and low currents in transmission lines.
This document discusses the need for transmission interconnections and opportunities provided by FACTS (Flexible AC Transmission Systems) technology. It notes that India has generation surpluses in some grids but deficits in others, and interconnections allow sharing of power to reduce costs. FACTS devices can control power flows and enhance line capacity, enabling more economic energy transfers. They offer advantages over mechanical switching like reduced wear and ability to damp oscillations. FACTS technology opens opportunities to better utilize transmission assets by overcoming thermal, dielectric and stability limitations on line loadings.
The document discusses Thyristor Controlled Series Compensation (TCSC), a FACTS device that uses thyristors to control the capacitive reactance of transmission lines. TCSC can enhance power flow, limit fault current, improve stability and transients. It introduces benefits like mitigating subsynchronous resonance risks, damping power oscillations, and improving post-contingency stability. TCSC operates in modes like blocking, bypass, capacitive boost and inductive boost to accurately regulate power flow and damp oscillations while increasing transmission capacity and stability.
This document compares the effectiveness of STATCOM, SSSC, and UPFC FACTS devices in improving power system stability. It presents a single machine infinite bus system model with each device and analyzes the response to a 3-phase fault. All FACTS devices reduce oscillations and stabilize the system after the fault, while the uncompensated system becomes unstable. STATCOM and SSSC effectively suppress oscillations and stabilize the rotor angle, velocity, and generator output power. UPFC combines features of STATCOM and SSSC to regulate real and reactive power flow and make the system stable.
During Damping of Low Frequency Oscillations in Power Systems with Fuzzy UPFC...IJMER
This document summarizes a research paper about using an adaptive neuro-fuzzy controller for a unified power flow controller (UPFC) to damp low frequency oscillations (LFO) in a power system.
The key points are:
1. LFO can occur in power systems due to a lack of damping torque. Traditionally, power system stabilizers were used but FACTS devices like UPFC can also control power flow and provide damping.
2. An adaptive neuro-fuzzy controller is designed for the UPFC to damp LFO. The controller has 2 inputs of deviation in rotor angle and deviation in frequency. Simulation results show it provides good damping performance.
3. The performance of the neuro-fuzzy
Enhancement of Power System Dynamics Using a Novel Series Compensation SchemeIJMER
Phase imbalanced capacitive compensation is a “hybrid” series compensation scheme, where the
series capacitive compensation in one phase is created using a single-phase TCSC in series with a fixed capacitor
(Cc), and the other two phases are compensated by fixed series capacitors (C). The TCSC control is initially set
such that its equivalent compensations at the power frequency combined with the fixed capacitor yield a
resultant compensation equal to the other two phases. Thus, the phase balance is maintained at the power
frequency while at any other frequency, a phase imbalance is created. The effectiveness of the scheme in damping
power system oscillations for various network conditions, namely different system faults and tie-line power flows is
evaluated using the MATLAB/SIMULINK Software
STATCOM for Improved Dynamic Performance of Wind Farms in Power Grid IJMER
Application of FACTS controller called Static Synchronous Compensator STATCOM to
improve the performance of power grid with Wind Farms is investigated .The essential feature of the
STATCOM is that it has the ability to absorb or inject the reactive power with power grid. Therefore,
the voltage regulation of the power grid with STATCOM FACTS device is achieved. Moreover restoring
the stability of the power system having wind farm after occurring severe disturbance such as faults or
wind farm mechanical power variation is obtained with STATCOM controller. The dynamic model of
the power system having wind farm controlled by proposed STATCOM is developed. To validate the
powerful of the STATCOM FACTS controller, the studied power system is simulated and subjected to
different severe disturbances. The results prove the effectiveness of the proposed STATCOM controller
in terms of fast damping the power system oscillations and restoring the power system stability.
The Crosley CR1205A tablet jukebox allows users to listen to music and watch videos from a docked tablet. It features programmable LED lighting, a backlit song chart, AM/FM radio, CD player with MP3 capability, and external speaker outputs. The retro-inspired wooden cabinet has a hand-rubbed paprika finish and fits tablets up to 9.5" wide and 7.25" tall.
Legislative Council FTU HCMC received the Best Finance Award for Term 13-14. They conducted legislative and auditing meetings to improve financial policies, procedures, and internal processes. Nearly 50% of monthly budget reports were submitted to an online Dropbox and key financial metrics like DSO, asset turnover, debt ratio, and returns indicated strong financial sustainability. Initiatives were also taken to implement online accounting and contribute to national pricing projects.
IOSR Journal of Applied Physics (IOSR-JAP) is an open access international journal that provides rapid publication (within a month) of articles in all areas of physics and its applications. The journal welcomes publications of high quality papers on theoretical developments and practical applications in applied physics. Original research papers, state-of-the-art reviews, and high quality technical notes are invited for publications.
This document summarizes the design and study of a compact and wideband microstrip U-slot patch antenna for Wi-Max applications. The antenna was designed to operate in the 5.25GHz Wi-Max band with very low return loss. Design formulas are provided to calculate the dimensions of the rectangular microstrip patch antenna. Simulation results show the return loss is below -30dB from 5.15GHz to 5.85GHz, meeting the bandwidth requirements. The proposed antenna design achieves wideband operation using a 3-layer substrate with total thickness of 1.6mm.
OFDM allows tightly packed carriers to convey information orthogonally and with high bandwidth efficiency
Objectives Description:
Concepts
Basic idea
Introduction to OFDM
Implementation
Advantages and Drawbacks.
FDMA
Join us for a LIVE WEBINAR on this topic! Wednesday, November 14, 2:00pm ET
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Wide bandwidth modulation is becoming more common in communications. The emergence of the 802.11ac wireless Ethernet standard has extended the modulation bandwidth to 160 MHz which requires very wide band measurement equipment to measure. This presentation illustrates the details of a measurement method that uses a real time digital down converter and post processing software that measures the performance of this signal.
The document discusses small-scale fading or multipath fading in wireless channels. It defines key terms like delay spread and Doppler spread caused by multipath propagation. It describes the time-varying channel impulse response and how multipath components combine constructively or destructively. It also introduces parameters used to characterize mobile multipath channels, such as coherence bandwidth, Doppler spread, and coherence time.
The document discusses different types of filters and their frequency responses. It describes that filters can be either analog and process continuous signals, or digital and process discrete signals. There are four main types of filters: lowpass, highpass, bandstop, and bandpass. The frequency response of these filters can be modeled using concepts like poles, zeros, break/corner frequencies, and Bode plots. Bode plots use logarithmic scales to show how the magnitude and phase of a filter's transfer function change over frequency.
This document summarizes a research paper that investigates the effect of different orthogonal frequency division multiplexing (OFDM) transmission modes on the performance of carrier frequency offset (CFO) estimation using a cyclic prefix-based synchronization technique. Five transmission modes are tested (0.25K, 0.5K, 1K, 2K, 4K) by developing an OFDM system simulation in MATLAB. The results show that synchronization performance, as measured by mean squared error of CFO estimation, improves with increasing transmission mode/IFFT size but requires more estimation time. Larger transmission modes provide better frequency synchronization.
LTE Physical Layer Transmission Mode Selection Over MIMO Scattering ChannelsIllaKolani1
Although LTE networks systems profits from recent advanced transmission techniques as MIMO systems, it encounters particularly two mains challenges:
MIMO channel Modeling or MIMO channel estimation .
An Optimal Dynamic MIMO transmission modes switching following the variation of MIMO Channel.
This Thesis proposes a channel model taking into account the motion of the UE first and after use this model to design an optimal transmission mode selection for 4G networks
4g LTE and LTE-A for mobile broadband-notePei-Che Chang
This document discusses the basic principles of OFDM (Orthogonal Frequency Division Multiplexing) transmission. It covers several key topics:
1) OFDM uses multiple subcarriers to transmit data in parallel. The subcarriers are spaced closely together with minimal spacing between them.
2) OFDM modulation and demodulation can be implemented efficiently using IDFT/DFT (IFFT/FFT) processing.
3) Cyclic prefixes are added to combat inter-symbol interference from multipath channels. This preserves subcarrier orthogonality.
4) With a cyclic prefix, the channel appears flat on each subcarrier, allowing one-tap frequency domain equalization. Channel estimation is done using reference symbols.
This document discusses an algorithm for estimating the velocity of multiple reflecting objects using standard OFDM communication signals without any specific coding of the transmitted data. The algorithm processes the symbols that compose the OFDM symbols directly rather than the baseband signals. Range and Doppler information can be extracted from the received OFDM signal and used to implement radar sensing functions in a joint radar and communication system, such as for vehicular applications. Simulation and measurement results demonstrating the algorithm's effectiveness are presented.
A New Underwater Acoustic Navigation Method Based on the Doppler PrincipleNooria Sukmaningtyas
In this paper, a new underwater acoustic navigation method is proposed, which is named from
Doppler Acoustic Omnirange Beacon (DAOB). It is borrowed from the idea of Doppler VHF Omnirange
(DVOR) and based on the Doppler principle. The cause of Doppler effect in the received signal is the
motion or position change of one or two sources. The effect of multipath is analyzed, and an improved
signal form is presented to solve the rigorous multipath environment underwater. Some simulation is
presented to verify the performance.
Multiplexing generally refers to independent signals, those produced by different sources. SO it is a question of how to share the spectrum with these users. In OFDM the question of multiplexing is applied to independent signals but these independent signals are a sub-set of the one main signal.
In OFDM the signal itself is first split into independent channels, modulated by data and then re-multiplexed to create the OFDM carrier.
OFDM is a combination of modulation and multiplexing.
This document discusses multi-carrier transmission over mobile radio channels. It introduces OFDM and MC-CDMA techniques for combating multipath interference in mobile channels. It describes various receiver designs for OFDM and MC-CDMA, including matrix inversion and decision feedback equalization approaches to estimate channel amplitudes and derivatives in order to reduce intercarrier interference caused by Doppler spread. Simulation results show performance improvements of these techniques over conventional OFDM.
This document summarizes a research paper that analyzes the performance of different pilot-based channel estimation schemes for OFDM systems using QPSK and 16-QAM modulation over Rayleigh fading channels with Doppler frequency shifts. It compares block-type pilot arrangement, which inserts pilots into all subcarriers periodically, to comb-type arrangement, which inserts pilots into each symbol and requires interpolation. It evaluates channel estimation algorithms like LS, LMMSE, SVD for block pilots and linear, quadratic, and cubic spline interpolation for comb pilots. The goal is to analyze how bit error rate is affected by Doppler shifts. Simulations are conducted in MATLAB to compare the schemes.
Blind Estimation of Carrier Frequency Offset in Multicarrier Communication Sy...IDES Editor
Orthogonal Frequency Division Multiplexing
(OFDM) systems are very sensitive to carrier frequency offset
(CFO), caused by either frequency differences between
transmitter and receiver local oscillators or by frequency
selective channels. The CFO disturbs the orthogonality among
subcarriers of OFDM system and results intercarrier
interference (ICI), which degrades the bit error rate (BER)
performance of the system. This paper presents a new blind
CFO estimation scheme for single-input single-output (SISO)
OFDM systems. The presented scheme is based on the
assumption that the channel frequency response changes
slowly in frequency domain. In this scheme an excellent tradeoff
between complexity and performance, as compared to
existing estimation schemes, is obtained. The improved
performance of the present scheme is confirmed through
extensive simulations.
1. The document discusses various methods of FM demodulation including balanced slope detector, Foster-Seeley discriminator, phase locked loop demodulator, and ratio detector.
2. It provides details on the basic principles and circuit operations of each method. The balanced slope detector uses three tuned circuits which makes it difficult to tune. The Foster-Seeley discriminator and ratio detector have better linearity due to their use of phase relationships.
3. The phase locked loop demodulator tracks the instantaneous frequency of the input signal using a voltage controlled oscillator and error signal in a feedback loop. It has good performance even at low signal-to-noise ratios.
Coherent Optical Orthogonal Frequency Division Multiplexing (CO-OFDM )BhaSkar Nath
Principle of orthogonal frequency-division multiplexing (OFDM)
Optical transmitter for CO-OFDM
Optical spectral efficiency for CO-OFDM
Channel model for CO-OFDM
The channel model describes the behavior of communications systems, thus fundamentally determining the performance of the systems
Analysis Of Ofdm Parameters Using Cyclostationary Spectrum SensingOmer Ali
Defining Software Defined Radios, Cognitive Radios, the need for spectrum sensing and an insight on the Cyclostationary parameters that better help in feature detection in Cognitive Radios
Concept of Flip OFDM and its applicationsDarshan Bhatt
OFDM is the advanced FDM technique used for wireless communication. But for Uni-polar communication and Optical Wireless communication (OWC) its modified version called Flip OFDM is quiet efficient technique.
Naveen Kumar's document discusses small-scale fading in mobile wireless channels. It describes the effects of multipath propagation, Doppler shifts from mobility, and how these cause rapid fluctuations in signal strength over small distances and time periods. It also defines several key parameters that characterize mobile multipath channels, including coherence bandwidth, Doppler spread, coherence time, delay spread, and excess delay spread. These parameters quantify the time-dispersive and time-varying nature of wireless channels.
IJCER (www.ijceronline.com) International Journal of computational Engineerin...ijceronline
This document proposes an acceptance sampling plan developed through maximum allowable percent defective (MAPD) having a single sampling plan as an attribute plan. It obtains test termination ratios by fixing MAPD and assuming lifetime follows different distributions like Burr XII, Weibull, log-logistic, and Rayleigh. It constructs operating characteristic functions and provides tables showing minimum sample sizes, acceptance probabilities, and test termination ratios for different distributions at fixed MAPD values. The plan aims to reduce test termination ratios and increase product mean life by introducing MAPD.
This document evaluates GNSS code and phase solutions. It summarizes the key differences between code-only and code+phase differential GPS (DGPS) processing techniques. Code measurements are affected by biases while phase measurements also contain integer ambiguities. The document tests DGPS code and code+phase solutions using a dual-frequency GPS receiver to collect data at points within 10km of a reference station. Results show coordinate discrepancies between the two solutions are generally below 1m.
This document provides a technical review of secure banking using RSA and AES encryption methodologies. It discusses how RSA and AES are commonly used encryption standards for secure data transmission between ATMs and bank servers. The document first provides background on ATM security measures and risks of attacks. It then reviews related work analyzing encryption techniques. The document proposes using a one-time password in addition to a PIN for ATM authentication. It concludes that implementing encryption standards like RSA and AES can make transactions more secure and build trust in online banking.
This document analyzes the performance of various modulation schemes for achieving energy efficient communication over fading channels in wireless sensor networks. It finds that for long transmission distances, low-order modulations like BPSK are optimal due to their lower SNR requirements. However, as transmission distance decreases, higher-order modulations like 16-QAM and 64-QAM become more optimal since they can transmit more bits per symbol, outweighing their higher SNR needs. Simulations show lifetime extensions up to 550% are possible in short-range networks by using higher-order modulations instead of just BPSK. The optimal modulation depends on transmission distance and balancing the energy used by electronic components versus power amplifiers.
This document provides a review of mobility management techniques in vehicular ad hoc networks (VANETs). It discusses three modes of communication in VANETs: vehicle-to-infrastructure (V2I), vehicle-to-vehicle (V2V), and hybrid vehicle (HV) communication. For each communication mode, different mobility management schemes are required due to their unique characteristics. The document also discusses mobility management challenges in VANETs and outlines some open research issues in improving mobility management for seamless communication in these dynamic networks.
This document provides a review of different techniques for segmenting brain MRI images to detect tumors. It compares the K-means and Fuzzy C-means clustering algorithms. K-means is an exclusive clustering algorithm that groups data points into distinct clusters, while Fuzzy C-means is an overlapping clustering algorithm that allows data points to belong to multiple clusters. The document finds that Fuzzy C-means requires more time for brain tumor detection compared to other methods like hierarchical clustering or K-means. It also reviews related work applying these clustering algorithms to segment brain MRI images.
1) The document simulates and compares the performance of AODV and DSDV routing protocols in a mobile ad hoc network under three conditions: when users are fixed, when users move towards the base station, and when users move away from the base station.
2) The results show that both protocols have higher packet delivery and lower packet loss when users are either fixed or moving towards the base station, since signal strength is better in those scenarios. Performance degrades when users move away from the base station due to weaker signals.
3) AODV generally has better performance than DSDV, with higher throughput and packet delivery rates observed across the different user mobility conditions.
This document describes the design and implementation of 4-bit QPSK and 256-bit QAM modulation techniques using MATLAB. It compares the two techniques based on SNR, BER, and efficiency. The key steps of implementing each technique in MATLAB are outlined, including generating random bits, modulation, adding noise, and measuring BER. Simulation results show scatter plots and eye diagrams of the modulated signals. A table compares the results, showing that 256-bit QAM provides better performance than 4-bit QPSK. The document concludes that QAM modulation is more effective for digital transmission systems.
The document proposes a hybrid technique using Anisotropic Scale Invariant Feature Transform (A-SIFT) and Robust Ensemble Support Vector Machine (RESVM) to accurately identify faces in images. A-SIFT improves upon traditional SIFT by applying anisotropic scaling to extract richer directional keypoints. Keypoints are processed with RESVM and hypothesis testing to increase accuracy above 95% by repeatedly reprocessing images until the threshold is met. The technique was tested on similar and different facial images and achieved better results than SIFT in retrieval time and reduced keypoints.
This document studies the effects of dielectric superstrate thickness on microstrip patch antenna parameters. Three types of probes-fed patch antennas (rectangular, circular, and square) were designed to operate at 2.4 GHz using Arlondiclad 880 substrate. The antennas were tested with and without an Arlondiclad 880 superstrate of varying thicknesses. It was found that adding a superstrate slightly degraded performance by lowering the resonant frequency and increasing return loss and VSWR, while decreasing bandwidth and gain. Specifically, increasing the superstrate thickness or dielectric constant resulted in greater changes to the antenna parameters.
This document describes a wireless environment monitoring system that utilizes soil energy as a sustainable power source for wireless sensors. The system uses a microbial fuel cell to generate electricity from the microbial activity in soil. Two microbial fuel cells were created using different soil types and various additives to produce different current and voltage outputs. An electronic circuit was designed on a printed circuit board with components like a microcontroller and ZigBee transceiver. Sensors for temperature and humidity were connected to the circuit to monitor the environment wirelessly. The system provides a low-cost way to power remote sensors without needing battery replacement and avoids the high costs of wiring a power source.
1) The document proposes a model for a frequency tunable inverted-F antenna that uses ferrite material.
2) The resonant frequency of the antenna can be significantly shifted from 2.41GHz to 3.15GHz, a 31% shift, by increasing the static magnetic field placed on the ferrite material.
3) Altering the permeability of the ferrite allows tuning of the antenna's resonant frequency without changing the physical dimensions, providing flexibility to operate over a wide frequency range.
This document summarizes a research paper that presents a speech enhancement method using stationary wavelet transform. The method first classifies speech into voiced, unvoiced, and silence regions based on short-time energy. It then applies different thresholding techniques to the wavelet coefficients of each region - modified hard thresholding for voiced speech, semi-soft thresholding for unvoiced speech, and setting coefficients to zero for silence. Experimental results using speech from the TIMIT database corrupted with white Gaussian noise at various SNR levels show improved performance over other popular denoising methods.
This document reviews the design of an energy-optimized wireless sensor node that encrypts data for transmission. It discusses how sensing schemes that group nodes into clusters and transmit aggregated data can reduce energy consumption compared to individual node transmissions. The proposed node design calculates the minimum transmission power needed based on received signal strength and uses a periodic sleep/wake cycle to optimize energy when not sensing or transmitting. It aims to encrypt data at both the node and network level to further optimize energy usage for wireless communication.
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The document summarizes a study of different microstrip patch antenna configurations with slotted ground planes. Three antenna designs were proposed and their performance evaluated through simulation: a conventional square patch, an elliptical patch, and a star-shaped patch. All antennas were mounted on an FR4 substrate. The effects of adding different slot patterns to the ground plane on resonance frequency, bandwidth, gain and efficiency were analyzed parametrically. Key findings were that reshaping the patch and adding slots increased bandwidth and shifted resonance frequency. The elliptical and star patches in particular performed better than the conventional design. Three antenna configurations were selected for fabrication and measurement based on the simulations: a conventional patch with a slot under the patch, an elliptical patch with slots
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2) Drive testing was performed before and after optimization using TEMS software to record network parameters like RxLevel, RxQuality, and events.
3) Analysis found call drops were occurring due to issues like handover failures between sectors, interference from adjacent channels, and overshooting due to antenna tilt.
4) Corrective actions taken included defining neighbors between sectors, adjusting frequencies to reduce interference, and lowering the mechanical tilt of an antenna.
5) Post-optimization drive testing showed improvements in RxLevel, RxQuality, and a reduction in dropped calls.
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This document discusses image deblurring techniques. It begins by introducing image restoration and focusing on image deblurring. It then discusses challenges with image deblurring being an ill-posed problem. It reviews existing approaches to screen image deconvolution including estimating point spread functions and iteratively estimating blur kernels and sharp images. The document also discusses handling spatially variant blur and summarizes the relationship between the proposed method and previous work for different blur types. It proposes using color filters in the aperture to exploit parallax cues for segmentation and blur estimation. Finally, it proposes moving the image sensor circularly during exposure to prevent high frequency attenuation from motion blur.
This document describes modeling an adaptive controller for an aircraft roll control system using PID, fuzzy-PID, and genetic algorithm. It begins by introducing the aircraft roll control system and motivation for developing an adaptive controller to minimize errors from noisy analog sensor signals. It then provides the mathematical model of aircraft roll dynamics and describes modeling the real-time flight control system in MATLAB/Simulink. The document evaluates PID, fuzzy-PID, and PID-GA (genetic algorithm) controllers for aircraft roll control and finds that the PID-GA controller delivers the best performance.
1. IOSR Journal of Electrical and Electronics Engineering (IOSR-JEEE)
e-ISSN: 2278-1676 Volume 4, Issue 3 (Jan. - Feb. 2013), PP 24-27
www.iosrjournals.org
Performance analysis of OFDM systems in the presence of
Doppler-effect
Mohamed Tayebi1, Merahi Bouziani1
1
(Telecommunications and Digital Signal Processing Laboratory, Djillali LiabesUniversity, Algeria)
Abstract : Carrier Frequency Offset (CFO) in Orthogonal Frequency Division Multiplexing (OFDM) systems
is generated partly by imperfections of the local oscillators (static CFO) and secondly, by the Doppler-effect
(dynamic CFO). The aim of the present study is to investigate the impact of Doppler-effect on OFDM
performances. A new expression of the global CFO is derived and Bit Error Rate performance is obtained by
Monte-Carlo simulation.
Keywords - Orthogonal Frequency Division Multiplexing (OFDM), Carrier Frequency Offset (CFO), Doppler-
effect, Inter Carriers Interferences (ICI), Carrier to Interferences Ratio (CIR).
I. Introduction
OFDM is simply implemented using Fast Fourier Transform (FFT) and presents innumerable
advantages such as high spectral efficiency and robustness against multipath fading. These advantages have
enabled telecommunication systems to make a significant forward step and access gain to new perspectives.
OFDM has found its place in optical communications [1] and in a large variety of broadcast standards such as
Digital Audio Broadcasting (DAB), Digital Video Broadcasting (DVB). However, its main disadvantage is its
sensitivity to Carrier Frequency Offset (CFO). This is mainly due to imperfections in local oscillators and
Doppler-effect present in mobile radio channels [2]. CFO gives rise to inter-carrier interference responsible for
the degradation of system performance[3,4,5]. For a transmitter-receiver pair, the offset due to the imperfections
of the local oscillators is constant, while the shift due to the Doppler- effect is variable and random. We can talk
about static CFO and dynamic CFO. This letter concerns the dynamic CFO where a new expression of the
global CFO is derived and in order to evaluate the OFDM performances, Bit Error Rates are obtained.
II. Doppler-effect and Carrier Frequency Offset analysis
The OFDM symbol is transmitted by the radio frequency circuit. The carrier is noted fp. Assume that
local oscillators of the transmitter and of the receiver do not oscillate at the same frequency, the frequency at the
receiver is:
f r f p f diff (1)
fdiff is the frequency difference between the transmitter and the receiver. This frequency difference caused by the
imperfections of the local oscillators is constant and still exists. The normalized value is equal to:
diff Tfdiff (2)
When a mobile is moving at a speed v, a frequency shift fd occurs. This shift is called the Doppler-effect. Its
mathematical expression is given by:
v
f d f p cos (3)
c
where c is the light speed, fp is the carrier frequency and is the angle between the velocity vector and the
direction of the electromagnetic wave. The normalized value is:
v
d Tf p cos (4)
c
Figure 1 shows that the normalized Doppler frequency increases with velocity v and the angle determines its
sign. For a mobile receiver, the received frequency is given by:
f r f p f diff 1 cos
v
(5)
c
www.iosrjournals.org 24 | Page
2. Performance analysis of OFDM systems in the presence of Doppler-effect
The total carrier frequency offset will be:
v v
fT f p cos f diff 1 cos (6)
c c
Its normalized value is equal to:
v v v
T Tf p cos diff 1 cos Tf p cos diff (7)
c c c
0.5
0
d
-0.5
0 -200
5 0
10 200
(°)
v (m/s)
Fig.1: Normalized Doppler frequency
III. Inter-Carrier Interference and performance analysis
3.1 Inter-Carrier Interference analysis
The orthogonality between the sub-carriers of the OFDM signal is broken, which leads to the rise of
inter-carrier interference. The amplitude of ICI coefficients between the lth and the kth subcarriers is given by [4]:
v
sin l k Tf p cos diff
S (l k ) c (8)
v
N sin l k Tf p cos diff
N c
These coefficients depend on the relative speed of the mobile, the angle and the subcarrier indexes.
3.2 Carrier to Interference Ratio
This section examines the performances in the presence of the Doppler effect in terms of the CIR
which is given by [4]:
2
S (0)
CIR N 1 2 (9)
S (l )
l 1
knowing that [5]:
N 1 2
S (l )
l 0
1 (10)
and:
v
sin Tf p cos diff
c (11)
S (0)
v
N sin Tf p cos diff
N c
www.iosrjournals.org 25 | Page
3. Performance analysis of OFDM systems in the presence of Doppler-effect
We can rewrite Eq(9) in the following form:
2
S (0)
CIR (12)
1 S (0)
2
Figure 2 shows the CIR as a function of speed v and the angle for T = 224.10-6 s and fp = 5 Ghz. The CIR
decreases when the relative velocity v increases and when the angle is in the range: 90 0 and
90 180. The CIR is maximum for = 90 °, meaning that the Doppler-effect is cancelled.
50
40
30
CIR (dB)
20
10
0
10
5 150
100
50
0 0
v (m/s) (°)
Fig.2: Carrier to Interferences Ratio
3.3 Bit Error Rate (BER)
Using the Monte Carlo method, Figure 3 shows the evolution of the BER for different values of
Signal to Noise Ratio (SNR) given an angle of arrival . The simulation was performed with the following
values (relative velocity v = 100m/s and the normalized frequency offset 0.2 ). For 0 , the Doppler
effect is completely absent. For 90 , the shift due to the Doppler effect is positive, whereas for 90 , it
is negative. In this case, the performance is improved since the global offset is reduced.
0
10
= 90°
= 60°
-1 = 120°
10
-2
10
BER
-3
10
-4
10
-5
10
0 5 10 15 20 25 30
SNRo
Fig.3: BER versus Signal to Noise Ratio for different values of .
IV. Conclusion
In this letter, a new expression for the global CFO is derived for OFDM systems. We deduce that the
system performance, in terms of BER, is degraded by the CFO due to imperfections of the local oscillators and
the CFO due to the Doppler effect contributes to an additional degradation if it is in the same direction as the
first. However, performance will be improved if the two CFOs are in opposite directions.
www.iosrjournals.org 26 | Page
4. Performance analysis of OFDM systems in the presence of Doppler-effect
REFERENCES
Journal Papers:
[1] K.Kikuchi, ―Digital coherent optical communication systems: fundamental and future prospects‖, IEIEC Electronics Express, 8(20),
2011, 1642-1662.
[2] Y. Zhao and S.-G. Häggman, ―Sensitivity to Doppler shift and carrier frequency errors in OFDM systems—The consequences and
solutions,‖ Proc. 46th IEEE Vehicular Technology Conference, Atlanta, GA, 1996, 1564–1568.
[3] R. Uma Mahesh and A. K. Chaturvedi, " Closed Form BER Expressions for BPSK OFDM Systems with Frequency Offset" IEEE
Communications Letters, 14(8), 2010, 731-733.
[4] Y. Zhao and S.-G.Haggman, ―Intercarrier interference self-cancellation scheme for OFDM mobile communication systems,‖ IEEE
Transactions on Communications, 49(7), 2001, 1185–1191.
[5] J. Lee, H. Lou, D. Toumpakaris, and J. Cioffi, ―SNR Analysis of OFDM Systems in the Presence of Carrier Frequency Offset for
Fading Channels‖ IEEE Transactions on wireless communications, 5(12), 2006, 3360–3364.
www.iosrjournals.org 27 | Page