A study of error distribution in a direct-sequence CDMA system

The pattern of error distributions in an asynchronous direct-sequence code division multiple-access system (DS CDMA) is examined. The study considers a 2-ray frequency-selective multipath fading channel with up to 2 interfering signals. The DS CDMA employs 127 chip Gold sequences as the spreading codes. The error distributions are characterised as the probability of m errors in N bits, P(m,N), the probability of m bursts of length l bits of less in N bits, P( ml,N), the bit-error rate (BER), the block-error rate, P_b, and the bursts and gaps distributions. It is shown that at channel SNR of -2.0 dB, the errors occur mainly as bursts of length 15 bits or less for about 50-60% of the time. Additional BER performance results obtained from a software simulation of the DS CDMA system for different excess time delays are also featured