An improved Gaussian approximation for probability of bit-erroranalysis of asynchronous bandlimited DS-CDMA systems with BPSK spreading

摘要

This paper analyzes probability of bit-error (Pe)nperformance of asynchronous bandlimited direct-sequence code-divisionnmultiple-access systems with binary phase-shift keying spreading. Thentwo present methods of Pe analysis under bandwidth-efficientnpulse shaping: the often-cited standard Gaussian approximation and thencharacteristic function (CF) method suffer from either a low accuracy innregions of low Pe (< 10-3) or a prohibitivelynlarge computational complexity. The paper presents an alternate methodnof Pe analysis with moderate computational complexity andnhigh accuracy based on a key observation. A sequence of chip decisionnstatistics (whose sum yields a bit statistic) forms a stationary,nm-dependent sequence when conditioned on the chip delay and phase offsetnof each interfering signal. This observation permits the generalizationnof the improved Gaussian approximation previously derived for thenrectangular pulse and the derivation of a numerically efficientnapproximation based on the CF method. Numerical examples of systemsnusing the square-root raised-cosine and IS-95 pulses illustrate THE Pne performance, user capacity and the accuracy of the proposednmethod