Verification: Constructive and Destructive Full Duplex Relays

Abstract

With recent advances in in-band full duplex techniques, full duplex capable relays have been shown feasible in many recent works. Instead of generating data itself to transmit, a full duplex relay can forward the received signal while receiving it. It also has the opportunity to properly modify the signal before forwarding it, which has been explored to enable constructive and destructive full duplex relaying recently. With these designs, the signal through the full duplex relay could constructively or destructively add up with the signal from the direct link at the receiver side. As a result, the received signal power may be boosted or greatly reduced, compared with direct forwarding. In this paper, we do detailed analysis on whether such constructive and destructive full duplex relays are possible. We find that for OFDM signals, such relays can not be achieved if the additional latency of the relayed path is more than one sample time than the direct link. Our analysis and results challenge the assumptions on the relay latency requirements of previous works to realize such systems.