Distributed space-time coding for two-way wireless relay networks

We consider distributed space-time coding for two-way wireless relay networks, where communication between two terminals is assisted by relay nodes. We compare existing and new protocols that operate over 2, 3 or 4 times slots. Particularly, a new class of relaying protocols, termed as partial decode-and-forward (PDF), is proposed for the 2 time slots transmission. We show that the proposed amplify and forward (AF) protocols achieve the diversity order of min{N,T} (1 - log log P/log P) where N is the number of relays, P is the total pow r f the etwork, and T is the number of symbols transmitted during each time slot. When linear dispersion (LD) codes with random unitary matrices are used, the proposed PDF protocols resemble random linear network coding, where the former operates on unitary group and the latter works on finite field.