A digitalized DS/SS receiver structure with adaptive control of soft limiting

The development of digital and integrated communication terminals is specially important for mobile and personal communication. The concept of optimum soft limiting for DS/SS digital matched filtering (DMF) or correlation is proposed. It is found that soft limiting has to be controlled properly not only for making full use of finite quantization, but also for effective interference suppression. A digital DS/SS receiver structure with adaptive control of soft limiting using DSP techniques is developed. A set of formula are derived to calculate the spread spectrum processing gain, asymptotic relative efficiency (ARE) and bit error rate (BER) approximately. An adaptive algorithm with robustness consideration is also presented. Analysis and simulation results show that the proposed scheme is robust to some degree and a nearly optimal performance of the bit error rate can be reached.