Massive Mimo Relaying Assisted D2d With Opportunistic Energy Harvesting

In this paper, massive MIMO amplify-and-forward multi-pair relaying is considered to assist device-to-device (D2D) communications. The direct D2D communication is underlaid with the source-to-relay transmission in the first hop, hence the D2D signals are also received at the relay, which are then forwarded in the second hop, overlapping with the relay-to-destination transmission. Moreover, D2D users are assumed to be able to harvest energy from the relay signal. Therefore, the D2D receivers, who failed in the direct D2D, can perform information detection (ID) with an opportunistic energy harvesting (EH) in the second hop. Closed-form deterministic equivalents of the associated signal to interference-plus-noise ratio in the ID and the harvested energy in the EH are derived, for both the maximum ratio combining/transmission and zero-forcing based relaying. A particular result of the asymptotic analysis indicates that the transmit power of source users can be made inversely proportional to the number of relay antennas, such that non-vanishing relay assisted D2D rate and harvested energy of D2D users exist. Simulations validate the analytical results, and illustrate the capability of massive MIMO relaying in assisting D2D via the so-called rate-energy region.