On the throughput region of single and two-way multi-hop fading networks with relay piggybacking

One and two-way communication strategies are studied in a two-hop model in which the intermediate node (relay) piggybacks data packets intended for the end-users. Assuming quasi-static fading channels, memoryless processing at all the nodes and no latency constraints, the region of simultaneously achievable throughputs for the two end-users and the relay, measured in reliably transmitted bits per second per Hz, is investigated. For both one-way and two-way transmission, outer and inner bounds to the throughput region are derived. The considered achievable strategies involve type-I HARQ, decode-and-forward and joint or superposition encoding at the relay. The trade-off between the user and relay throughputs is analyzed and studied via numerical simulations, yielding insight into optimal design choices.