PN code acquisition for asynchronous CDMA communications based on interference cancellation

A novel PN (pseudonoise) code acquisition technique based on interference cancellation is developed for asynchronous CDMA (code division multiple access) communication systems. The acquisition scheme is robust because the near-far problem is alleviated by the cancellation process. Two schemes are proposed. One is based on a one-by-one cancellation, in which the estimated strongest signal is removed from the current composite signal at one stage and never reestimated at the following stages. The signals are removed one by one until the weakest signal is detected. The other scheme is based on a simultaneous estimation and cancellation technique, in which all the signals so far detected are estimated together and removed from the original composite signal at each stage. The latter scheme has a better acquisition performance; however, the former one requires fewer computations