Symbol synchronization and data detection in DS/CDMA systems affected by multiple narrowband interferers

We consider an asynchronous direct-sequence code division multiple access (DS/CDMA) system operating in a frequency band partially occupied by several narrowband communication signals. The problem of symbol timing recovery and reliable data detection for the CDMA users is considered in this paper. First of all, we show that conventional timing and data detection, based on the matched filter, does incur a severe performance loss in the presence of several narrowband interferers and CDMA users. We thus propose two digital reception algorithm which are resistant to narrowband interferers. The first algorithm performs interference cancellation; it may be used in a centralized receiver wherein the narrowband signals have been acquired and detected. The second algorithm operates on a frequency-domain representation of the data. A new symbol synchronization algorithm is also given; this procedure operates on the samples of the received signal (i.e., synchronization is extracted processing the discrete-time data rather than the continuous-time observables). Results show that the proposed algorithms achieve performance levels much larger than those of the conventional algorithms based on matched filtering.