A coded modulation technique for cooperative diversity in wireless networks

We propose a novel coded modulation (CM) protocol for user cooperation diversity in wireless networks. Unlike most existing protocols, the proposed scheme does not involve repetition. This translates to significant gains in terms of achievable rates. Hence, it is suitable for higher spectral efficiencies too. Each user transmits its own bits, along with bits of cooperating users, in every allotted symbol at appropriate positions on a specially labelled signal constellation. The scheme achieves full diversity order in the number of cooperating relays and obtains additional coding gains compared to repetition protocols. We show gains ranging from 2 dB to 3 dB over repetition protocols for cases involving two and three cooperating users. In its simplest form, the proposed scheme has a complexity at the relay equal to that of repetition protocols. Complexity at the base station, however, is increased.