CDMA with Partitioned Spreading

An enhancement to code-division multiple access (CDMA) is proposed whereby the signature sequences are partitioned into sections, which are interleaved before transmission. A multistage receiver successively forms soft-bit estimates based on the received sections, which are used to reduce the interference in subsequent stages via signal cancellation. This significantly increases the user loads which can be supported as the system effectively suppresses interference, with a marked threshold effect below which practically single user performance is achieved. The number of stages required is typically small and independent of the system size, that is the number of users. Furthermore, it is shown that the proposed multistage demodulation is insensitive to variations in the received powers.