Low complexity high resolution subspace-based delay estimation for DS-CDMA

We consider the problem of estimating the propagation delays of a synchronous direct-sequence code division multiple access (DS-CDMA) system operating over a multipath fading channel. In a mobile receiver, the task of delay estimation can be divided into an acquisition of all multipath delays and subsequent tracking of the individual delays e.g. with a RAKE structure. Both tasks are especially challenging in indoor scenarios which commonly exhibit low delay-spread and thus require a high resolution of the estimation algorithms. A novel delay acquisition algorithm is presented, which is able to resolve multipaths whose delay difference is below one chip duration with high probability of acquisition and low computational complexity. It is based on a decomposition of the time-averaged correlation matrix of the output of a sliding correlator into signal and noise subspaces, with subsequent MUSIC spectrum computation and maximum search. The performance of the algorithm is assessed by means of computer simulations.