Zero-forcing design of precoders and decoders in multiuser CDMA cooperative networks

Consider a multiuser cooperative CDMA networks where multiple sources transmit signals toward their respective destinations with assistance of multiple relays. We propose joint designs of precoders at relays and decoders at the destinations to eliminate MAI and improve system performance. Specifically, two sub-optimal designs of precoders are developed to maximize SNR averaged over all users and to maximize SNR of the worst user respectively. It shows through computer simulations that the precoder maximizing average SNR favors the best user, while the precoder maximizing the minimal SNR balances radio usage of relays such that all users can achieve near-optimal diversity order.