Acquisition of synchronism in direct sequence CDMA mobile networks

Code division multiple access (CDMA) is being proposed as a powerful spectrum sharing technique. Rejection of multiple access interference (MAI) is achieved by the cross-correlation properties of the selected code family. However, before the receiver has acquired synchronism to the desired sequence, the presence of interference is a major impairment. It has been argued that the performance of the acquisition sub-system in CDMA systems may limit the multiple access capacity more than error probability specifications. Therefore, analysis of the acquisition of synchronism process in CDMA systems must take into account the effect of MAI. In this work the performance of a non-coherent straight serial search acquisition sub-system has been evaluated in the presence of interference from other users, data modulation and noise. For this purpose, an analytical approach has been used, which allows the characterization of the effects of the interfering sequences on the acquisition process without the adoption of a Gaussian approximation. Several configurations have been analysed, and their performance obtained in terms of mean time to acquisition and overall probability of detection.<>