4G Multicell Systems with In-Band Full Duplex Relays: Using Beamforming to Lower Self-Interference and/or Transmitted Powers

In-band full-duplex operation has recently attracted a lot of attention as a possible solution for increasing the spectral efficiency of wireless communication systems. This paper considers a 4G multicell system where base-stations and relays employ beamforming, while relays also operate in in-band full duplex mode. In the context of LTE, the excess SIR gain that is achieved with the help of typical or large scale antenna array beamforming can be used either for reducing the full duplex self-interference cancellation requirement, or for reducing the backhaul and access link transmitted powers. Results indicate that using 'small' antenna arrays with 16 elements can either lower the requirement of full duplex self-interference cancellation by almost 20dB, or lower both the backhaul and access transmitted powers by ~5dB, while keeping the maximum LTE nominal capacity. On the other hand, the results for large scale antenna arrays with 1024 elements show (55/30/24)dB lower values, respectively.