Ultra wideband DS-CDMA via innovations in chip shaping

One important requirement for next generation wireless communication systems is the ability to support a wide range of high rate data services. Despite advances in efficient modulation and multiple access technologies, very high data rate transfer will still require ultra-wide frequency bands. Traditional DS-CDMA systems operate over one single continuous bandwidth, and with the limited spectrum available from the FCC auctioned off in small blocks, it will not be possible for DS-CDMA to operate over a contiguous ultra-wide frequency band. This paper demonstrates how a novel chip shaping scheme, designed specifically for DS-CDMA systems, enables DS-CDMA to operate over non-adjacent frequency bands in a way that is identical to its operation if all these bands are made contiguous. The chip shape corresponds to an interferometry pattern created by the superposition of N carriers (adjacent or non-adjacent in the frequency domain). Besides the ability to operate over non-adjacent bands, this novel chip shaping enables DS-CDMA to achieve very high performance by exploiting frequency diversity (instead of path diversity) over the combined bands. With the exception of chip shape and receiver design for operation over non-contiguous bands, this new system retains all the features of a traditional DS-CDMA system.