Performance of quasisynchronous scale time code division multiple access for AWGN channel
Computers and Electrical Engineering
Further performance analysis of the generalized MC DS-CDMA system in Nakagami-m fading channels
Computers and Electrical Engineering
Performance of multi-processing gain QS-CDMA over AWGN and Rayleigh fading channels
Digital Signal Processing
A ZCZ-CDMA system with BFSK modulation
International Journal of Communication Systems
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Proposes a multicarrier orthogonal CDMA signaling scheme for a multiple-access communication system, such as the reverse channel of a cellular network, as an alternative to the multi-user interference cancellation approach. The average variance of cross-correlations between sequences is used as a measure for sequence design. The authors search for sets of sequences that minimize the probability of symbol detection error, given that there is imperfect synchronization among the signals, that is, the signals are quasi-synchronous. Orthogonal sequences based on the Sylvester-type Hadamard matrices (Walsh functions) are shown to provide a significant improvement over the case where a Hadamard (orthogonal) matrix is chosen at random. Computer searches suggest that this set of codes is optimal with respect to the above measure. The issue of chip pulse shaping is investigated. Optimal pulses designed to minimize multiple-access interference in quasi-synchronous systems are obtained for various bandwidths and are shown to provide a large improvement over the raised cosine pulses. A multicarrier signaling scheme is introduced in order to reduce chip level synchronization offsets between the users