Performance of code acquisition for DS-CDMA overlay

This paper evaluates and compares the performance of two code acquisition schemes for direct-sequence (DS) code-division multiple-access (CDMA). The first techniques is a subspace based estimation technique which uses the well-known MUSIC algorithm. The second method obtains its timing estimation from an adaptive near-far resistant receiver known as the minimum mean-squared error (MMSE) receiver. Both of these techniques have been shown in previous work to be able to obtain reliable code acquisition in a severe near-far environment. It is shown that both of these techniques are also simultaneously robust to narrowband interference and near-far cochannel interference and thus useful in a CDMA overlay scenario. Simulation results are provided which evaluate the performance of these acquisition schemes as it depends on the bandwidth of the narrowband interference and the presence or absence of CDMA power control. The interference is modelled as narrowband Gaussian noise. It is found that the MUSIC estimation strategy provides a consistently better estimate than the MMSE estimator but at the cost of significantly higher complexity