Complex block codes with low cross-correlation spectrum for synchronous CDMA systems

Since the identification of block codes (sequences) that maximize the sum capacity (SC) of the symbol-synchronous CDMA (S-CDMA) channel with energy constraints, there has been significant research interest in designing such codes. On the other hand, current CDMA systems that focus on low error probability for each user deploy codes with low cross-correlation spectrum, which is not guaranteed by the codes maximizing sum capacity. In this paper we study the design of complex codes that maximize the sum capacity but also exhibit low cross-correlation spectrum. The newly designed codes over N-PSK symbols compare favorably with lower bounds on the maximum cross-correlation.