Abstract
We analyze the performance for reverse-link synchronous DS-CDMA system in a frequency-selective Rayleigh fading channel with an imperfect power control scheme. The performance degradation due to power control error (PCE), which is approximated by a log-normally distributed random variable, is estimated as a function of the standard deviation of the PCE. In addition, we investigate the impacts of the multipath intensity profile (MIP) shape and the number of resolvable paths on the performance. Finally, the coded bit error performance is evaluated in order to estimate the system capacity. Comparing with the conventional CDMA system, we show an achievable gain of from 59% to 23% for reverse-link synchronous transmission technique (RLSTT) in the presence of imperfect power control over asynchronous transmission for . As well, the effect of tradeoff between orthogonality and diversity can be seen according to the number of multipaths, and the tendency is kept even in the presence of PCE. We conclude that the capacity can be further improved via the RLSTT, because the DS-CDMA system is very sensitive to power control imperfections.
Highlights
Direct-sequence code-division multiple-access (DS-CDMA) has been considered as the most promising multiple-access scheme for the generation mobile communications, because of its high flexibility in offering various services with variety of rates and its possibility of achieving greater capacity [1, 2]
We consider the capacity of a reverselink synchronous DS-CDMA system over frequency selective Rayleigh fading channels in the presence of imperfect power control scheme
We investigate the effects of the selection of system parameters on the performance of a coherent binary phase shift keying (BPSK) Rake receiver with reverse-link synchronous transmission technique (RLSTT) in terms of the average bit error rate (BER) and the supportable number of users for exponential multipath intensity profile (MIP)
Summary
Direct-sequence code-division multiple-access (DS-CDMA) has been considered as the most promising multiple-access scheme for the generation mobile communications, because of its high flexibility in offering various services with variety of rates and its possibility of achieving greater capacity [1, 2]. In a practical mobile radio environment, an adaptive power control (APC) scheme is always essential to compensate for the distance losses, shadowing, and fading effects. Such a scheme attempts to maintain a constant average performance among the users, and reduce the MAI effect. This results in a randomly varying power control error (PCE), which may be caused by the dynamic range of the APC, the spatial user distributions, and the propagation statistics [8, 9, 10, 11].
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