Synchronous DS-SSMA system with improved decorrelating decision-feedback multiuser detection

An improved decorrelating decision-feedback multiuser detector (IDDFD) is proposed, whose complexity is linear in the number of users, but performs closely to the maximum likelihood detector (MLD), whose complexity grows exponentially with the number of users. The IDDFD also relaxes the requirement of correct power ordering which is essential to successfully cancel multiuser interference (MUI) for the standard decorrelating decision-feedback detector (DDFD). Simulation results show that in a direct-sequence spread-spectrum multiple-access (DS-SSMA) system using Gold codes of length 31 an IDDFD with only twice the complexity of the DDFD can simultaneously service 31 users with an error rate of each user close to the interference-free case. The IDDFD is then extended and studied to user numbers larger than the processing gain, complex signature waveforms, and MPSK signaling