The effect of channel estimation, interleaving and channel coding on RAKE receivers for mobile DS-CDMA systems (original) (raw)
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Error Performance of DS-CDMA over Multipath Channel Using Selective Rake Receiver
IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, 2005
Error performance of DS-CDMA is discussed over independent Rayleigh faded multipath channel employing selective Rake (SRake) receiver. Simple-to-evaluate and accurate error probabilities are given following Holtzman's simplified improved Gaussian approximation (SIGA). Comparing with SIGA, the validity of standard Gaussian approximation (SGA) is then verified. It is shown that SGA is accurate for SRake until some number of combined paths beyond which it becomes optimistic. It is also shown that as compared to single user performance, the SRake performance is relatively less degraded by multiple access interference (MAI) while the number of combined paths is small.
Evaluation of downlink performance of a multiple-cell, rake receiver assisted CDMA mobile system
Journal of Wireless …, 2009
In wireless Code Division Multiple Access (CDMA) system, the use of power control is indispensable to combat near-far and fading problems. Signals transmitted over a multipath propagation channel which exhibits inter-path interference and fading. The receiver has to employ measures to mitigate these effects or it will incur severe performance degradation. A classic approach in CDMA communications is the rake receiver. In this paper, the downlink performance is estimated for a CDMA mobile system at the vertex of multiple adjacent cells. At the base station the received signal is coherently dispread and demodulated using a rake receiver. The effects of power control, error correction and rake receiver were also investigated on the assumption that the received signals undergo Rayleigh fading, lognormal shadowing, and frequency selective fading. The evaluation of performance measures of base to mobile link (downlink) of a multiple-cell CDMA mobile system is presented. This study demonstrates that significant performance improvements are achievable with combined use of power control, rake receiver and error correction scheme.
2009
In wireless Code Division Multiple Access (CDMA) system, the use of power control is indispensable to combat near-far and fading problems. Signals transmitted over a multipath propagation channel which exhib-its inter-path interference and fading. The receiver has to employ measures to mitigate these effects or it will incur severe performance degradation. A classic approach in CDMA communications is the rake receiver. In this paper, the downlink performance is estimated for a CDMA mobile system at the vertex of multiple ad-jacent cells. At the base station the received signal is coherently dispread and demodulated using a rake re-ceiver. The effects of power control, error correction and rake receiver were also investigated on the as-sumption that the received signals undergo Rayleigh fading, lognormal shadowing, and frequency selective fading. The evaluation of performance measures of base to mobile link (downlink) of a multiple-cell CDMA mobile system is presented. This study dem...
Practical RAKE receiver architecture for the downlink communications in a DS-CDMA mobile system
IEE Proceedings - Communications, 1998
The authors deal with a practical architecture for a RAKE receiver suitable for the downlink communication in a direct-sequence code division multiple access (DS-CDMA) mobile system. The proposed RAKE receiver makes use of a pilot signal broadcast by the base station to obtain channel parameter estimation and synchronisation. Computer simulations have been carried out in deriving the performance in terms of bit-error probability under typical multipath fading propagation conditions of GSM applications. Comparisons with an ideal RAKE receiver and with a multipath rejection receiver recently proposed in the literature, for the same type of downlink channel, are shown to highlight the good behaviour of the proposed receiver.
IEEE Transactions on Vehicular Technology, 1999
In this paper, closed-form solutions for the average bit error rate (BER) performance of a direct-sequence codedivision multiple-access system with imperfect power control are derived for both coherent and noncoherent receptions operating over a multipath Rayleigh fading channel. The RAKE structure receivers under consideration employ despreading sequences weighted by adjustable exponential chip waveforms optimized for multiple-access interference rejection. The chip-weighting waveforms employed are determined only by one parameter which leads to easy tuning of the waveforms in practice to achieve the best performance. The results indicate that the number of active users supported at a given BER for the case of tuned to maximize the average signal to interference plus noise ratiô H H H is much larger than the case of = = = 0 (fixed or rectangular despreading sequence). It is shown that imperfect power control affects the irreducible BER for the case of = = = 0. On the other hand, the effect of imperfect power control on BER performance for the case of tuned to maximizeĤ H H is equivalent to a reduction in the average signal-to-noise ratio, and, hence, system performance can be compensated by increasing the transmitter power. It is further shown that the effect due to imperfect power control on BER performance is significant while that on the maximum value ofĤ H H obtained by tuning is rather insignificant. Index Terms-Code-division multiple access, RAKE receivers, spread-spectrum communication. I. INTRODUCTION W ITH THE rapid growth of personal wireless communications, direct-sequence code-division multiple-access (DS-CDMA) technology has attracted considerable attention over the last few years because of its many attractive properties for the wireless medium [1]-[3]. However, as is well known, the major factors which limit the performance, and, hence, the capacity of DS-CDMA systems are multipath fading, multiple-access interference (MAI) and imperfect power control. In many performance analyses of CDMA systems, the assumptions are made that the transmitted power of each user is perfectly controlled and the waveform of despreading sequence in a receiver is the same as the spreading sequence assigned to a reference user [4]-[12].
PERFORMANCE EVALUATION OF MC - CDMA UNDER THE EFFECT OF MULTIPATH FADING CHANNEL USING RAKE RECEIVER
In this paper we have shown the performa nce evaluation of multi - carrier CDMA (MC - CDMA) wireless communication system with orthogonal frequency division multiplexing (OFDM) in the presence of Rayleigh fading environment. Due to the effect of multipath propagation the quality of signal received i s degrade. For minimizing the effect of multipath fading (MC - CDMA) RAKE receiver is used. Equal Gain Combining (EGC), Maximal Ratio Combining (MRC) and Minimum Mean Square Error (MMSE) Equ alization techniques are used .
2012 7th International Conference on Electrical and Computer Engineering, 2012
An analytical approach is developed to derive the expression of the Multiple Access Interference (MAI) and Bit Error Rate (BER) of a MC-DS-CDMA system using multiple receiving antennas with Maximal Ratio Combining (MRC), considering Rayleigh fading channel. The analysis is extended to RAKE receiver with Equal Gain Combining (EGC). The results are presented in terms of BER and improvement of receiver sensitivity due to diversity and multicarrier orthogonal modulation. It is noticed that there are significant improvement due to diversity as well as the number of subcarriers in MC-DS-CDMA system.
Study and Simulation of DS-CDMA over Communication Channels
2014
Performance of synchronous DS-CDMA systems over multipath fading channel and AWGN Channel is evaluated. The synchronous DS-CDMA system is well known for eliminating the effects of multiple access interference which limits the capacity and degrades the BER performance of the system. This paper investigated the bit error rate (BER) performance of a synchronous DS-CDMA system over AWGN and Rayleigh channel, which is affected by the different number of users, as well as different types spreading codes. The promising simulation results explore the comparative study of different DS-CDMA system parameter and showed the possibility of applying this system to the wideband channel. In this paper, Rayleigh channel and AWGN Channel are introduced and investigated the bit error rate (BER) performance of a synchronous DS-CDMA system over these channels. In the DS-CDMA system, the narrowband message signal is multiplied by a large bandwidth signal, which is called the spreading of a signal. The spreading signal is generated by convolving a GOLD sequence code with a chip waveform whose duration is much smaller than the symbol duration.
IJERT-Performance Analysis of Multiuser DS-CDMA System
International Journal of Engineering Research and Technology (IJERT), 2021
https://www.ijert.org/performance-analysis-of-multiuser-ds-cdma-system https://www.ijert.org/research/performance-analysis-of-multiuser-ds-cdma-system-IJERTCONV9IS05052.pdf This paper examines the Bit Error Rate (BER) performance of Multiuser Direct Sequence Code Division Multiple Access (DS-CDMA) using spreading codes in fading channels. Code Division Multiple Access (CDMA) system operating over frequency selective, slowly fading channels is considered and its performance is studied analytically and by computer simulations. We consider the downlink of a cellular radio system where for each user a BPSK modulation is used. The spreading codes are arranged in a way that reduces the effect of the multipath fading channel and restores some of the orthogonality losses between users. The obtained results show considerable performance improvement compared to conventional OFDM and to CDMA that uses single spreading codes. Moreover, the spreading codes chosen by the method are in a consistent sequence. Using this code selection method, the system capacity of MU-CDMA can be effectively increased without increasing too much system complexity. Simulation results show that the presented method can work well for fading channels.