Rayleigh Fading Channel

In mobile communication systems, multiuser detection is also known under the names of cochannel interference sup- pression, multiuser demodulation, or interference cancella- tion, and requires rather complicated high-precision power control. The design of multiuser detectors has been mo- tivated by the channel environment encountered in many CDMA applications, for channels with fading, multipath, or noncoherent modulation have been considered [1, 2]. In par- ticular, recent focus has been on the blind (or non-data- aided) multiuser detectors such as SIC [3], PIC [4], and DFD [5], these require no training data sequence, but only knowledge of the desired user signature sequence and its tim- ing [6]. The main motivation of employing a blind mul- tiuser detector in CDMA is to recover the original sequence from the received signal that is corrupted by noise and MAI, without the help of training sequences and a priori knowl- edge of the channel. Prior work by Ristaniemi and Jout- sensalo [7] leads to the proposal of two types of receivers, RAKE-ICA and MMSE-ICA, in a Rayleigh fading channel using the modified FastICA algorithm [8]. However, the es- timation of eigenvectors and eigenvalues becomes an addi- tional burden for the proposed RAKE-ICA. Also, the MMSE- ICA which required training sequences causes an increase in

Orthogonal Frequency Division Multiplexing (OFDM) using Quadrature Amplitude system keying is a very common approach in multi carrier communication. In this paper, we have shown a comparative analysis between the GRAY and NAÏVE QPSK scheme with OFDM in both AWGN and Rayleigh fading channel. We have chosen the parameters BER vs SNR for Gray and naïve and Rayleigh for the performance analysis as these two are the most important parameter for any wireless communications.

Abstract – The goal for the third generation of mobile communications system is to integrate a wide variety of communication services such as high speed data, video and multimedia traffic as well as voice signals. Under the Universal Mobile Telecommunication System (UMTS) environment the Third Generation (3G) has many advantages such as highly efficient spectrum utilisation and variable user data rates. In this paper, we present the bit error rate (BER) performance analysis of Rake Receiver under UMTS environment with BPSK modulation technique and the convolutional coding at the transmitter and viterbi decoding at the receiver side. The Standard Gaussian Approximation (SGA) is used to evaluate the performance of Rake Receiver over a frequency selective Rayleigh fading channel. The data is modulated, encoded, spread and transmitted through a frequency selective Rayleigh fading channel. The transmitted signal is corrupted by multiple access interference, and is further corrupted by AWGN at the receiver. In the receiver, dispreading, decoded and demodulated. Rake Receiver, directive antenna are employed to improve the system performance. We examined the BER performance of Rake Receiver with, varying the number of users, spreading factor, Rake fingers, Interfering Cells, and the value of directivity of antenna at base Station. From the results we have seen that the BER performance of Rake Receiver is affected by varying these parameters and gives useful results.

ABSTRACT: Fading is the most important issue for Wireless Communication .To remove adverse effect of fading in wireless channels a well-known scheme used is diversity combining technique. Transmitted signal is received through multiple numbers of independent fading paths in diversity receiver. These signals are combined to improve the signal- to-noise ratio (SNR) of the received signal. A new hybrid diversity scheme MRC/EGC for Rayleigh fading channel in which M number of branches carry out maximal ratio combining and L number of branches carry out equal gain combining is proposed in this paper. The effectiveness of this hybrid diversity scheme is evaluated by analysing the performance of the system in terms of Outage Probability and Average Bit Error Rate (ABER).

Abstract—This paper investigates the channel characterization of Rayleigh fading channel using K- band frequency-modulated continuous wave (FMCW) radar system. An IF (intermediate frequency) signal of K-band FMCW radar can be treated as time and frequency domain signals due to a unique property of linear frequency modulation (LFM). First, channel sounder FMCW radar stability has been confirmed by measuring power flatness of transmitted radio frequency signal and estimated range in anechoic chamber before conducting the experiment for channel characterization of Rayleigh fading channel. Next, the measurement setup has been conducted in reverberation chamber which emulates multipath fading phenomena. In reverberation chamber, four different cases have been examined by changing the boundary conditions inside it with and without flat microwave absorbers. This investigation leads to obtained scattered plots, normalized propagation delay profiles (PDPs), mean excess delay, root-mean-square (RMS) delay spread and envelope distribution of Rayleigh fading channel at about 24.591 GHz.

In this paper, we present a two-user cooperative automatic repeat request (C-ARQ) protocol which combines cooperative diversity at the physical layer and ARQ at the link layer. In this scheme, distributed Alamouti space-time block coding (DASTBC) is applied to achieve cooperative diversity, and ARQ is used to improve the data link layer reliability. To analyze the performance of the proposed protocol, we derive the average frame error rate (FER) and throughput with multiple phase shift keying (MPSK) over a Rayleigh fading channel. Numerical simulation results show that the performance gain of average FER with ARQ retransmission is about 2 dB more than the case without ARQ retransmission in the same conditions. Moreover, the combined DASTBC and quadrature phase shift keying (QPSK) with ARQ retransmission will lead to an approximate 3 Mbits/s increase in transmission rate.

Orthogonal Frequency Division Multiplexing (OFDM) is a popular method for high data rate wireless transmission. OFDM may be combined with antenna arrays at the transmitter and receiver to increase the diversity gain and/or to enhance the system capacity on time-variant and frequency- selective channels, resulting in a Multiple-Input Multiple- Output (MIMO) configuration. To investigate the performance of MIMO-OFDM system, its physical layer is simulated using MATLAB and Bit Error Rate (BER) performance is observed. Further performance improvement is achieved using Forward Error Correction (FEC) codes. The goal of this paper is to compare different FEC codes in Additive White Gaussian Noise (AWGN) and Rayleigh fading channel and propose a suitable code for MIMO-OFDM system. Three codes, Reed Solomon-Convolution Code (RS- CC), Convolutional Turbo Code (CTC) and Low Density Parity Check code (LDPC) are considered for this purpose. It is found that CTC gave a coding gain of 0.2dB and 0.25dB than its rival LDPC in AWGN and Rayleigh fading channel respectively.

Abstract -This paper presents an analytical framework for DS-CDMA network with two-branch diversity schemes for a Rayleigh fading channel. An analytical expression for the probability density function of the signal to noise ratio (SNR) at the output of a two-branch maximal ratio system is developed by considering both branches perfectly correlated as well as uncorrelated. Analysis were done incorporating GMSK modulation technique which clearly shows an improvement over QPSK modulation scheme used in [1].

In this paper we evaluate the outage probability of dual hop opportunistic DF relay system in the presence of interference at both relay and the destination node. We derived an outage probability for Rayleigh fading channel expression with low complexity having N relay which use DF protocol. Weanalysed the outage probability of wireless cooperative relay network over twohop that is source to relay and relay to destination, to this end we derived a valid expression of PDF andCDF. In this section we have derived exact expression for the outage probability of various DF protocol. We have verified all these result using MATLAB simulation. The plot of outage probability in figure 1 shows that as the number of relay increase the outage probability decreases.

In this paper proposed MIMO-MMSE transmission scheme is presented by using multiple active antennas to improve the spectral efficiency. In the scheme combine SM with spatial multiplexing. This SM scheme uses several antennas to transmit different symbols at the same time slot, where the active antennas are subset of a larger set of transmitting antennas. By computer simulation, BER Performance for the proposed scheme is evaluated for uncorrelated Rayleigh fading channel and compared with the existing algorithm that is zero-forcing .The results show that the proposed MMSE detection algorithm performs the best result than existing. Furthermore, the performance improvement of the proposed Algorithm Over existing, increases as the transmission rate increases, which makes it is good choice for high data rate transmission systems Example WiMAX and LTE-Advanced..

Three wavelet packets from three different families are used for this simulation namely Daubechies wavelet packets with order 6, db6, Symmlets wavelet packets with order 6 (sym6), and Coiflets wavelet packets with order 2, (coif2). These families are chosen because they are orthogonal and have compact support (i.e., fast de- caying time, which results in good localization in both time and frequency). The filter length is taken to be L = 12. Figure 11 shows BER versus SNR for these three wavelet families for CWPM system for N = 128 over selective Rayleigh fading channel with Doppler spread factor f d T s = 0.015. From this figure, it’s shown that

In order to visually illustrate the resulting, we transmitted Interview sequence over Rayleigh fading channel. Fig.4 illustrate the original color image with its associated depth map for Interview sequence. Fig.5 shows (a):the transmitted color and depth sequences over Rayleigh fading channel at SNR=12 dB and number of relays equal to 1 relay and (b):the same sequences at SNR=12 dB and number of relays equal to 3 relays. It can be seen from the Figure that UEP combined with unequal dual AF-DF cooperative diversity performs better in terms of subjective quality.

In this paper, an improved STBC technique is proposed and implemented on MIMO system Rayleigh Fading Channel .In this work QAM AND BPSK modulation technique is used. MIMO system using Alamouti STBC coding is done over different QAM modulation (8,16,32,64) and compare the results of STBC coding with BPSK modulation with different number of receiving and single transmitting antennas. The performance analysis for BER is done taking proposed approach QAM modulation technique with other existing PSK modulation technique. The simulation results show that the BER is decreases with increase the number of bits in QAM modulation. It is also observed that with increase in the number of antennas, the bit error rate decrease with approximately two times increase in the number of antennas.

Abstract. In this paper, we study the timing and integer carrier frequency offset (ICFO) estimation problem for dynamic lattice multicarrier transmission (DLMT) system over time-varying Rayleigh fading channel. Firstly, a novel preamble structure based on two constant amplitude zero auto-correlation (CAZAC) sequences is designed for DLMT system. Then, by using the designed dual-CAZAC preamble, a discrete cross ambiguity function (DCAF) based timing and ICFO estimation algorithm is proposed. Simulation results show that the proposed DCAF based timing and ICFO estimation algorithm can mitigate the impact of time-varying multipath Rayleigh fading channel and outperforms traditional estimators on the correct estimation probability performance.

Recently, researchers [1] opened a new dimension on optimizing binary convolutional codes for communication systems by applying NTCs to enhance Viterbi Algorithm decoders without necessarily increasing code constraint length or using SDD at the decoding part. This technique was first assessed in another work by the same researchers [7] where it achieved 83.7 percent improvement in reducing residual errors when 6NTCs were applied to Viterbi Algorithm decoder. However, the assessment relied on the classical Additive White Gaussian Noise (AWGN) model only. AWGN channel model does not account for interference, frequency selectivity, fading, nonlinearity or dispersion [8], [9] which are significant factors in wireless communication systems. This fact motivated the researchers to extend their study using a flat and slow Rayleigh fading channel model. To the best of our knowledge there are no other work reported on the performance of locked convolutional encoders with Non-transmittable codewords.

Full-rate is very important in any data transmission coding. For transmitting data at low bit rate than full-rate code, higher modulation scheme is required. But it is impossible to design full rate orthogonal designs with complex constellation for more than two transmit antennas. Only Ala- mouti code provides full-rate for two transmit antennas. In this paper, Bit Error Rate (BER) is cal- culated for Quasi-Orthogonal Space-time Block Coding (QOSTBC). Here we work with Rayleigh fading channel. We consider the codes which decodes pairs of symbols instead of simple separate decoding like Orthogonal Space-Time Block Coding. In Quasi-Orthogonal Space-time Block Code full-rate is achieved but full-diversity is sacrificed. Diversity is the most important techniques for providing reliable communication over fading channels. One of the diversity techniques that uses multiple transmit and/or receive antennas is space diversity. Multiple antenna technique pro- vides a space diversity to struggle with the fading without necessarily sacrificing bandwidth re- sources, so the excellent solutions of removing the fading of the channel for broadband wireless communications is using space diversity. Then, with the constellation rotation of the symbol, ro- tated version of Quasi-Orthogonal Space-Time Block Code is generated. It provides full diversity. We simulate BER for QOSTBC, rotated QOSTBC, orthogonal STBC and for uncoded system. The si- mulation result shows that QOSTBC and rotated QOSTBC perform better than other systems. It shows that QOSTBC provides a full transmission rate but that rotated QOSTBC provides the full rate with the full diversity.

In this paper Bit Error Rate performance of OFDM - BPSK System over Rayleigh fading channel is analyzed. OFDM is an orthogonal frequency division multiplexing to reduce inter-symbol interference problem. Two of the most equalization al gorit hms are minimum mean square error (MMSE) equalizer and maximum likelihood sequence estimation (MLSE) equalizer. Finally simulations of OFDM signals are carried with Rayleigh faded signals to understand the effect of channel fading and to obtain optimum value of Bit Error Rate (BER) and Signal to noise ratio (SNR)

In this paper an improved prediction-based power control is proposed for code division multiple access (CDMA) systems in Rayleigh fading channel environments. One of the most serious problems which degrades the performance of power control algorithm is the effect of feedback delay. To overcome the effect of feedback delay, power control needs to employ prediction algorithm which utilises the correlation property of the past channel samples measurements to predict the future sample values. In CDMA power control, however, the correlation property of channel measurements is destroyed because the transmit power is continuously updated for each power control interval. The prediction algorithm in this paper uses the recursive least square (RLS) technique and an improved predictor algorithm is proposed to compensate for the channel correlation. The result shows that the performance of improved predictive power control proposed in this paper evaluated in terms of bit error rate (BER) as a function of bit energy-to- interference power density ratio E b /I o improved significantly from that of the conventional predictor.

Abstract-- This paper presents the performance of adaptive modulation with multiple input multiple output orthogonal space time block coding MIMO-OS TBC over frequency selective Rayleigh fading channel using Bit Error Rate (BER) and spectral efficiency (S E) as performance measures. The increase in demand for communication networks has turned the spectrum into a precious resource, which leads to channel impairment that increases the BER and reduces the S E of the M-ary Quadrature Amplitude Modulation (M-QAM) transmitted signal. The channel model for OS TBC for 2x2, 3x3 and 4x4 transmit antenna is developed. The system model is formulated using the constellation sizes of 4-QAM, 16-QAM, 32-QAM and 64-QAM at different signal-to-noise ratio (S NR). S imulation approach using randomly generated data is carried out to determine the performance of the system with MATLAB application package. The results show that S E and BER improve significantly as the S NR increases for all the antenna configurations.

The fading channel can be expressed by two models, Rayleigh fading channel which contains multiple reflective paths, and there is no line-of-sight signal component, and Rician fading channel that contains a dominant non-fading line-of-sight propagation path [9]. Also, the fading channel can be classified, according to the characteristics of the signal as frequency nonselective (flat) versus frequency selective. A flat fading, if the signal bandwidth is small compared with coherence bandwidth, and in this case, all frequency components of the signal will be affected by the channel in the same manner., so it does not introduce ISI distortion, but the performance degrade due to the loss is SNR whenever the signal is fading. On the other hand, if the signal bandwidth is large compared with coherence bandwidth, the channel is then classified as frequency selective, and different frequency components of the signal will be affected by the channel differently so it has different degrees of fading. So it will introduce ISI distortion [2].