Symmetry-Embedded Spreading Sequences for Multicarrier CDMA

It was shown by Slimane that the bit error rate (BER) performance of the downlink of multicarrier code-division multiple-access (MC-CDMA) systems can be improved significantly by employing quadrature spreading sequences instead of binary Walsh-Hadamard sequences. Inspired by Slimane's work, we propose a class of complex-valued spreading sequences, which are mathematically derivable from the Kronecker product of some basic matrices. The good algebraic structure in the proposed spreading sequences, when applied in a BPSK based MC-CDMA system, can be exploited for multiple access interference (MAI) suppression, for order-2 diversity combining, and for the reduction of peak-to-average power ratio. The new spreading sequences outperform the Slimane's quadrature sequences, as evidenced by various numerical results.