Pilot-aided multipath delay estimation for downlink DS-CDMA

Decentralized single user multipath channel estimation for the downlink direct-sequence code-division multiple-access (DS-CDMA) is addressed. Sparse channels and bandwidth efficient signaling are considered. Under the assumption of sparse channels, it is more efficient to estimate the continuous path delays, and associated complex coefficients, rather than adopting the typical equally spaced tapped delay line model, for which the number of parameters to be estimated can be much larger. On the other hand, estimation of the continuous delays is rather challenging for bandlimited pulse shapes. A pilot aided scheme for the estimation of the continuous delays is proposed, which reduced the interval over which the delay is searched. Performance improvement can be achieved by exploiting the fact that all users share the same channel: however no knowledge of the interfering users is assumed. Finally, for the single path channel, a closed form solution is obtained. The estimation algorithms for evaluated through simulations