Blind multiuser detection over highly-dispersive CDMA channels in presence of diversity reception

This paper addresses blind multiuser detection in a direct-sequence code-division multiple-access (DS/CDMA) network in presence of both multiple-access interference (MAI) and intersymbol interference (ISI). In particular, it considers a DS/CDMA system where K out of N users are transmitting: the N admissible spreading codes are known and so is the code of the user to be demodulated. The number of interferers, the corresponding signatures, and the channel impulse response of each active user are unknown. The spreading codes of the K - 1 interferers are determined via a procedure exploiting the knowledge of the set of the N admissible transmitted codes and of the code of the user of interest. The procedure can be applied to both synchronous and asynchronous systems which employ diversity reception techniques. The performance assessment of a blind decorrelating detector, implemented by resorting to the above-proposed identification procedure, shows that it outperforms a plain subspace-based blind decorrelator for small sizes of the estimation sample.