Performance of mMIMO FD Relay Networks With Limited Relay State Knowledge

Massive MIMO (mMIMO) is a key technology forimproving propagation conditions and extending geographicalcoverage of wireless communications. We here address a mMIMOfull-duplex relay network for machine-type-communicationswhere channel state information availability at the transmitter isimpractical. In this scenario, we argue that high end-to-end datarates can be achieved even if no precoding is performed at thetransmitting nodes. We first formulate an optimization problemaiming at maximizing the achievable rate, considering the sourcetransmit power to depend on the transmit power distribution atthe relay node. We then solve this problem by letting the number of antennas grow large, and derive closed-form expressionsfor the transmit power at the source and relay, as well as forthe system data rate. Our results, show that the rate obtainedwhen no precoding is implemented at the relay, or at any of thetransmitters, closely matches that of SVD precoding under theoptimum receiver, and still achieves very high values in the caseof the ZF and the MMSE receiver.