Multipath Rician Fading Channels Research Articles

Cyclostationary Algorithm for Signal Analysis in Cognitive 4G Networks with Spectral Sensing and Resource Allocation

Cognitive Radio (CR) effectively involved in the management of spectrum to perform improved data transmission. CR system actively engaged in the data sensing, learning and dynamic adjustment of radio spectrum parameters with management of unused spectrum in the signal. The spectrum sensing is indispensable in the CR for the management of Primary Users (PUs) and Secondary users (SUs) without any interference. Spectrum sensing is considered as the effective adaptive signal processing model to evaluate the computational complexity model for the signal transmission through Matched filtering, Waveform and Cyclostationary based Energy sensing model. Cyclostationary based model is effective for the energy based sensing model based on unique characteristics with estimation of available channel in the spectrum to extract the received signal in the PU signal. Cyclostationary based model uses the spectrum availability without any periodic property to extract the noise features. This paper developed a Adaptive Cross Score Cyclostationary (ACSCS) to evaluate the spectrum sensing in the CR network. The developed ACSCS model uses the computational complexity with estimation of Signal-to-Interference-and-Noise Ratio (SINR) elimination of cost function. ACSCS model uses the Adaptive Least square Spectral Self-Coherence Restoral (SCORE) with the Adaptive Cross Score (ACS) to overcome the issues in CR. With the derived ACSCS algorithm minimizes the computational complexity based on cost function compared with the ACS algorithm. To minimize the computational complexity pipeline triangular array based Gram-Schmidt Orthogonalization (GSO) structure for the optimization of network. The simulation performance analysis with the ACSCS scheme uses the Rician Multipath Fading channel to estimate detection probability to sense the Receiver Operating Characteristics, detection probability and probability of false alarm using Maximum Likelihood (ML) detector. The ACSC model uses the Square-law combining (SLC) with the moment generation function in the multipath fading channel for the channel sensing with reduced computational complexity. The simulation analysis expressed that ACSC scheme achieves the maximal detection probability value of 1. The analysis expressed that proposed ACSC scheme achieves the improved channel estimation in the 4G communication environment.

Characterization of Orthogonal Frequency Division Multiplexing (OFDM) Communication Links

The demand for high data rate transmission is rapidly increasing in the area of wireless communications and Orthogonal Frequency Division Multiplexing (OFDM) is known to be a promising technique for high-rate transmission that can overcome the inter symbol interference (ISI) which results from the time dispersive nature of wireless channels. The idea is to utilize a number of carriers, spread regularly over a frequency band, in such a way so that the available bandwidth is utilized to maximal efficiency. This study presents the comparison of the performance of different modulation schemes: M-ary phase shift keying (M-PSK) and M-ary quadrature amplitude modulation (M-QAM) over Additive White Gaussian Noise (AWGN), Rayleigh and Rician multipath fading channels in OFDM system. Bit error rate (BER) was used to evaluate the performance of the system; the number of fast Fourier transform (FFT) points used during the transmission was also examined. The results showed that for all the channels, lower order modulation schemes perform better than the higher order schemes. This comes at the detriment of the data rate, as lower order schemes have lower data rates compared with their higher order counterparts. In addition, it was observed that the system performed better in AWGN channel than Rayleigh and Rician fading channels for all the modulation schemes used. It was observed that the number of FFT points used during the transmission do not have much effects on the performance of the system.

On the Bit Error Probability of OFDM and FBMC-OQAM Systems in Rayleigh and Rician Multipath Fading Channels

On the Bit Error Probability of OFDM and FBMC-OQAM Systems in Rayleigh and Rician Multipath Fading Channels

Improving the BER Performance of M-FSK in a Noisy Multipath Rayleigh, and Rician Fading Channels Using Reed-Solomon Forward Error Correction Method

This paper focuses on the application of Reed-Solomon Error Correction Code evaluation technique on the Bit-Error-Rate performance of M-ary Frequency Shift Keying (M-FSK) in noisy multipath Rayleigh and Rician fading channel. The detection and correction of the received information errors from the multipath fading channel was done using the Forward Error Correction (FEC) technique. The message is encoded and decoded using the error-correcting Reed-Solomon Codes were employed to encode and decode the message. The entire model based design, modelling and simulation was done using MATLAB/SIMULINK. It was observed that the BER performance of M-FSK with RS codes improved greatly compared to M-FSK system without error correction. Decrease of BER performance was observed as the length of codeword symbols (n) increase at constant code rate and error correcting capability. The redundancy increases as code rate decreases leading to an improved Bit-Error-Rate performance. The improvement of the BER of M-FSK by using Reed-Solomon error correction code was achieved.

Moments of Macrodiversity SC Receiver with Two Microdiversity EGC Receivers over Gamma Shadowed Rician Multipath Fading Channel

SC macrodiversity system with dual EGC microdiversity receivers operating over shadowed multipath fading environment is considered. Received signal experiences correlated Gamma long term fading and Rician short term fading. SC macrodiversity receiver reduces Gamma large scale fading effects, while EGC microdiversity receivers mitigate short term fading effects on system performance. Closed form expressions for arbitrary order output moments of macrodiversity structure output signal is evaluated. Numerical results, obtained for arbitrary order output moments are presented graphically to show Gamma long term fading severity effect, correlation coefficient effects and Rician factor effect.

Top Down Implementation of Joint MODEM and CODEC Transceiver Design for DSRC Coded-FSK Systems Over High Mobility Fading Channels

The joint detection and verification of frequency shift keying (FSK) modulation and demodulation (MODEM), Manchester coding and decoding (CODEC) schemes are proposed for dedicated short range communication (DSRC) systems over high mobility fading channels. The proposed joint coded-FSK detection scheme with low complexity advantage can outperform the conventional separated coded-FSK detection scheme. It is due to the joint scheme with time diversity gain to enhance the detection performance. Moreover, the proposed joint algorithms with floating-point and fixed-point designs are realized in the software-defined-ratio (SDR) platform. Based on the measurement results via SDR equipments, it is confirmed that the implementation of VHDL hardware circuit design of the proposed joint detection scheme can provide robust performance over high mobility Rician multipath fading channel environment.

New results for Shannon capacity over generalized multipath fading channels with MRC diversity

In this article, we investigate the Shannon capacity for L-branch maximal combining ratio (MRC) over generalized multipath fading channel. We derive closed-form expressions of the maximal spectral efficiency over Rayleigh, Rician, Nakagami-m, and Weibull multipath fading channel under flat fading conditions. The results are expressed in terms of Meijer G-functions, which can be evaluated numerically using mathematical tools such as Mathematica and Maple. We show, in particular, that the more the number L increases, the larger the Shannon capacity is. We deduce that four branches are sufficient in several cases to mitigate the fading effect and the channel model will approaches the one of AWGN.

Chip‐interleaving direct sequence spread spectrum system over Rician multipath fading channels

ABSTRACTChip interleaving (CI) is a unique technique to exploit time diversity in direct sequence spread spectrum (DS/SS)‐based systems operating in fading environments. In order to facilitate design of CI systems in various fading situations, we present a performance analysis for CI DS/SS system over Rician multipath time‐varying fading channels. We derive the analytical bit error rate (BER) expression for CI DS/SS to allow fast and accurate evaluation of BER performance based on the interleaving depth selected, spreading codes employed, and the time correlation function of the channel. We then discuss some ideal cases by using the analytical results to reveal some of the insights presented in the performance analysis. For the purpose of comparison, we also obtain the BER expression for conventional DS/SS system as a special case of CI system with an interleaving depth of one. Using numerical examples, we verify the analytical results with computer simulations and illustrate the BER performance behavior of CI DS/SS system with varying interleaving depth for all possible combinations of two sets of spreading codes of different type and two different time correlation functions of the channel. Copyright © 2011 John Wiley & Sons, Ltd.

Non-Coherent Mutual Information of Multipath Rician Fading Channels in the Low SNR Regime

Non-coherent mutual information of general fading channels is an open problem. In this study, based on the proposed in-block flash signal scheme, a closed form expression of the noncoherent mutual information of the general multipath Rician block fading channel is derived in the low SNR regime. This is a general result and can be seen as an extension of previous work on multipath Rayleigh fading channel and memoryless Rician fading channel.

Performance of decorrelating receivers in multipath Rician fading channels

This letter focuses on the performance analysis of the decorrelating receiver in multipath Rician faded CDMA channels. M-ary QAM scheme is employed to improve the spectral efficiency. Approximate expressions are first derived for the two performance indexes: the average symbol error rate (SER) and the average bit error rate (BER) when the decorrelating-first receiver perfectly knows the channel information of the user of interest. To achieve desirable closed-form expressions of the SER and the BER, we exploit results in large system analysis and make assumptions of a high signal-to-interference ratio (SIR) and/or a small Rician K-factor. To measure the receiver performance in the practical scenario, we further derive expressions to approximate the average SER and BER of the decorrelating-first scheme with channel uncertainty. Simulation results demonstrate that the analytical results can also be employed to evaluate the performance of the combining-first receiver.

Impact of the Line-of-Sight Propagation Component on the Orthogonality Factor of the Synchronous DS-CDMA Uplink

This paper investigates a modifying orthogonality factor for synchronous DS-CDMA uplink in dispersive Rician multipath fading channels, which reflects upon the effects of specular path power as well as decaying channel characteristics. Using this investigation, the orthogonal factors in indoor environments are evaluated and compared with the various parameters such as decaying factor, line-of-sight component, and the number of multipaths.

Analysis of a Combined Antenna Arrays and Reverse-Link Synchronous DS-CDMA System over Multipath Rician Fading Channels

We present the BER analysis of antenna array (AA) receiver in reverse-link asynchronous multipath Rician channels and analyze the performance of an improved AA system which applies a reverse-link synchronous transmission technique (RLSTT) in order to effectively make a better estimation of covariance matrices at a beamformer-RAKE receiver. In this work, we provide a comprehensive analysis of user capacity which reflects several important factors such as the ratio of the specular component power to the Rayleigh fading power, the shape of multipath intensity profile, and the number of antennas. Theoretical analysis demonstrates that for the case of a strong specular path's power or for a high decay factor, the employment of RLSTT along with AA has the potential of improving the achievable capacity by an order of magnitude.

Reverse-link performance of synchronous DS-CDMA systems in dispersive Rician multipath fading channels

The reverse-link performance of synchronous DS-CDMA is investigated in Rician multipath fading environments. The numerical results show that the performance benefits of synchronous transmission depend on the specular path's power as well as on the multipath intensity decay factor of the channel. The achievable bit-error-rate reduction may become as high as an order of magnitude in comparison to the corresponding asynchronous system.

Performance analysis of the RAKE receiver in the presence of multipath delay estimation errors and Rician fading channels

We derive here a novel unified framework for computing the average bit-error-ratio (BER) of a direct-sequence spread spectrum receiver using maximum ratio combiner (MRC), in the presence of code synchronization errors and multipath Rayleigh or Rician fading channels. Traditionally, for single-user systems, the signal-to-noise ratio at the output of MRC is modeled as a quadratic form in complex Gaussian variables. We show that this model does not hold when delay errors are present and we propose an improved generic model incorporating the multipath delay estimation errors. We also discuss the case when the RAKE receiver is employed in the presence of multiple users. Based on our theoretical model, BER can be easily derived in a semi-analytical fashion, for any type of pulse shaping and any spacing between multipaths. Very fast results can be obtained for high spreading factors, when inter-chip (ICI) and inter-symbol interference (ISI) may be neglected. These results also give the lower bounds on BER for low spreading factors. Theoretical BER curves with QPSK modulation are validated by link level simulations for different downlink Rayleigh and Rician fading channels. Moreover, we discuss the impact of the delay error distribution on BER and we emphasize some practical applications of our generic technique. Copyright © 2003 AEI.

Performance analysis of the RAKE receiver in the presence of multipath delay estimation errors and Rician fading channels

Performance analysis of the RAKE receiver in the presence of multipath delay estimation errors and Rician fading channels

Performance of DS/SSMA system using turbo TCM/FPMover multipath Rician fading channel

The synergy between frequency and phase modulation (FPM) using trellis-coded modulation (TCM) leads to greater gains than can be achieved using conventional TCM/MPSK modulation. An iterative structure is introduced into a TCM/FPM scheme to give a new scheme, the turbo TCM/FPM scheme. Simulation results show that the new scheme can achieve a significant performance improvement with respect to the turbo TCM 8PSK and TCM/FPM schemes, respectively, for a DS/SSMA system over a multipath Rician fading channel.

Systematic study of channel non-symmetry fordifferentially coherent detection in general Ricianfading channels

A study is presented into the phenomenon of differing BEPs for different symbols transmitted (termed channel non-symmetry) for binary and quaternary differential phase shift keying (2/4-DPSK) in arbitrarily correlated multipath Rician fading channels. The systematic study is facilitated by the moment generating function (MGF) of the decision statistic of 2/4-DPSK. The work unifies many of the previously published results for channel non-symmetry and gives new insight into the problem.

Estimation and equalization of multipath Rician fading channels with stochastic tap coefficients

This study investigates the estimation and equalization problems of multipath Rician fading channels with stochastic tap coefficients. The time-varying tap coefficients of fading channels under investigation are typically modeled as complex-valued Gaussian processes. First, least squares estimation methods are used to estimate the mean and variance of the stochastic tap coefficients. Then, based on these estimated statistical characteristics, an optimal equalization filter is designed to recover the transmitted sequence. In the proposed design method, a realizable equalization filter is constructed to minimize the mean square error from the perspective of frequency domain. Also, both calculus of variation technique and spectral factorization method are employed in the design procedure. To exhibit the superior performance of the proposed design method, some illustrative simulations are presented.

Predetection diversity for CDMA indoor radio communications

This paper investigates the average bit error rate performance of a direct sequence code division multiple access system operating over a multipath Rician fading channel (which models indoor radio propagation in factories). We consider both phase shift-keying modulation with coherent demodulation and differential phase-shift-keying modulation with non-coherent demodulation. Predetection multipath diversity (maximal-ratio-combining for coherent reception and equal gain combining for non-coherent reception) is considered for improving the BER performance.

Multitone spread spectrum multiple access communications system in a multipath Rician fading channel

The paper proposes a new multiple access communications system based on the combination of multitone transmission and direct sequence spectrum spreading (DS/SS). Multitone transmission is proposed because the associated larger symbol duration is favorable to combat the effects of multipath propagation. The multiple access capability of the system is achieved by means of DS/SS which also helps to combat the presence of several paths. On the other hand, DS/SS is also attractive to decrease the multiple access interference. The performance of this system is investigated for a multipath, slowly Rician fading and frequency selective channel, and a suboptimal receiver based on matched filters. The multiple access interference is also taken into account, A model for the computation of the bit error probability is derived for QPSK modulation of the orthogonal tones by the spread symbols. The system performance is investigated for selection diversity and maximal ratio combining (RAKE reception). Then the influence of the number of tones is investigated for given bandwidth, bit rate and transmission power. The positive effect of a multitone spread spectrum transmission is demonstrated. >