Achievable Rate Region for Energy Harvesting Asynchronous Two-Way Relay Networks

In this paper, we consider an asynchronous two-way relay network where two single-antenna transceivers are using a single carrier communication scheme to exchange information and incur different delays. It is assumed that the relay nodes can harvest energy from their surrounding environment and utilize this harvested energy to forward their received messages using harvest-then-forward protocol. Since the transceiver-relay paths are subject to different propagation delays, the end-to-end channel can be viewed as a multi-path channel, which can cause inter-block-interference (IBI) in the signal blocks received by the two transceivers. In order to avoid such an IBI, we deploy a relay selection scheme where only those relay nodes are selected that contribute to a single tap end-to-end channel. Our goal is to maximize the sum rate of such a network subject to individual and total power constraints as well as energy harvesting profiles of the relays in order to obtain the maximum achievable rate region. Numerical results show that for a relay selection scheme and considering specific energy harvesting profiles for the relay nodes and under the condition that the total transmit budget of the transceivers are limited, the so obtained achievable rate region is the union of the rate region for each individual tap of the end-to-end channel.