A low-cost non-coherent transmission for uncoded two-way relay channels

In this paper, we investigate a two-phase two-way relay protocol for a scenario without channel coding or channel estimation. The considered configuration represents practical sensor networks, where the nodes wish to exchange some low rate messages (e.g. 1 bit) via a shared relay under a strict complexity or latency constraint (corresponding to our assumptions of no-coding and no-channel estimation). A new scheme which incorporates a single-threshold non-coherent energy detection and a digital network coding process at the relay node is proposed. The energy detection is optimized for both phases of the protocol and a threshold that exhibits no error floors is derived in a closed form. Numerical results validate the efficiency of the proposed scheme and introduce the two-way relay channel as an efficient structure also for non-coherent and uncoded systems.