Uplink acquisition of a new user accessing a fixed wireless DS-CDMA system

In this paper, we consider synchronization and detection in a space-time bit-interleaved coded modulation (BICM) scheme for an asynchronous direct-sequence code division multiple access (DS-CDMA) uplink transmission over static frequency selective channels for fixed wireless transmission. We propose a strategy to synchronize and detect a new user accessing the system by exploiting the knowledge of the synchronization parameters of previously synchronized users. In this way, we can synchronize one user at a time and hereby avoid complex multi-dimensional optimization problems. To limit the number of pilot symbols required for this problem, we exploit all available information, i.e., pilot symbols and the unknown coded symbols of all users. We resort to the iterative space alternating generalized expectation maximization (SAGE) algorithm to tackle this problem in a systematic manner.