EM-based acquisition of DS-CDMA waveforms for radiolocation

A handshaking protocol for radiolocation is considered using DS-CDMA packet transmission. The expectation-maximization (EM) algorithm is employed for code delay acquisition. It is shown that the systematic application of EM on the flat-fading channel yields a parallel interference cancellation (PIC)-based technique for acquisition. On the frequency-selective channel, it is necessary to jointly estimate both the code delays and multipath coefficients. The EM approach in this latter case yields an algorithm that combines PIC with an eigendecomposition/eigenvalue maximization step for channel identification.