Relay-Aided Multi-User OFDM Relying on Joint Wireless Power Transfer and Self-Interference Recycling

Relay-aided multi-user OFDM is investigated under which multiple sources transmit their signals to a multi-antenna relay during the first relaying stage and then the relay amplifies and forwards the composite signal to all destinations during the second stage. The signal transmission of both stages experience frequency selectivity. The relay is powered both by an energy source through the wireless power transfer as well as by the energy recycled from its own self-interference during the second stage. Accordingly, we jointly design the power allocations both at the multiple source nodes and at a common relay node for maximizing the network's sum-throughput, which poses a large-scale nonconvex problem, regardless whether proper Gaussian signaling (PGS) or improper Gaussian signaling (IGS) is used for signal transmission to the relay. We develop new alternating descent procedures for solving our joint optimization problems, which are based on closed-forms and thus are of very low computational complexity even for large numbers of subcarriers. The results show the superiority of IGS over PGS in terms of both its sum-rate and individual user-rate. Another benefit of IGS over PGS is that the former promises fairer rate distribution across the subcarriers. Moreover, the recycled self-interference also provides a beneficial complementary energy source.

Automated summary

This study investigates relay-aided multi-user OFDM systems, where multiple sources transmit signals to a multi-antenna relay in the first stage and the relay amplifies and forwards the composite signal to all destinations in the second stage. The relay is powered by wireless power transfer and recycled self-interference. The power allocations at the source nodes and the relay are jointly designed to maximize the network's sum-throughput. The results show that improper Gaussian signaling (IGS) outperforms proper Gaussian signaling (PGS) in terms of both sum-rate and individual user-rate, and the recycled self-interference provides a beneficial complementary energy source.