Performance of closed-loop power control in DS-CDMA cellular systems

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Abstract
In situations where the round-trip delay between the mobile and the base stations is smaller than the correlation time of the channel, power-control schemes using feedback from the base station can effectively compensate for the fast fading due to multipath. In this paper, we study several closed-loop power- control (CLPC) algorithms by analysis and detailed simulation. We introduce a new loglinear model for analyzing the received power correlation statistics of a CLPC scheme. The model pro- vides analytical expressions for the temporal correlation of the power-controlled channel parameterized by the update rate, loop delay, and vehicle speed. The received power correlation statistics quantify the ability of closed-loop power control to compensate for the time-varying channel. To study more complex update strategies, detailed simulations that estimate the channel bit-error performance are carried out. Simulation results are combined with coding bounds to obtain quasi-analytic estimates of the reverse link capacity in a direct-sequence code-division multiple- access (DS-CDMA) cellular system. The quasi-analytic approach quantifies the performance improvements due to effective power control in both single-cell and multicell DS-CDMA systems op- erating over both frequency-nonselective and frequency-selective fading channels. The effect of nonstationary base stations on the system performance is also presented.

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