A code tracking technique for direct sequence spread spectrum using adaptive filtering

Synchronizing a direct sequence spread spectrum (DS-SS) system involves determining code timing in a two step procedure, acquisition of symbol timing and tracking the code timing. This paper deals with tracking issues and assumes successful initial acquisition. Tracking is necessary because code timing is not constant, due to varying channel delays and clock imperfections at the transmitter and receiver. Most tracking schemes employ matched filtering based delay-locked-loops (DLLs). However, matched filter based DLLs are susceptible to multiple access interference (MAI). For the specific needs of an adaptive demodulation also know as a linear single-user multiple access (LSUMA) a new tracking scheme is introduced and its performance is demonstrated for handling multiple access interference. The new tracking scheme does not require the use of a pilot channel or training symbols