Performance enhancements for DS-CDMA receivers using space-path diversity

This paper presents the performance enhancements which can be obtained using space-path diversity and interference cancellation schemes with a 4-antenna DS-CDMA receiver. The antennas used are 3 circular printed antennas and a monopole antenna placed on a pyramidal structure. The chip rate is equal to 125 Mchip/s and the spreading factor varying between 31 and 127. This corresponds to a bit rate between 403.225 Kbits/s and 98.425 Kbits/s for BPSK modulation. We first characterize the delay profile of the channels and the envelope correlation between sensors from measured data. Then the performance obtained with two interference cancellation schemes are characterized The first is based on eigenfiltering and the second is a classical single sensor least squares (LS) adaptive filter. The results shows that by using space-time processing, the performance is considerably increased in situations where the near-far problem is significant, and further that we can achieve high data rate transmission in a small population of users scenario.