Joint Optimization of Beamforming and Subarray Assignment for Full-Duplex Arrays in Next Generation Broadcast Systems

The full-duplex (FD) technique provides spectrum-efficient transmission service by supporting uplink and downlink transmission at the same time over the same frequency band. Combined FD with multi-input multi-output (MIMO) antenna systems can improve the capability and efficiency of next-generation broadcasting to provide various services for multiple users. However, the strong self-interference (SI) coupled between the transmit and receive arrays is a significant challenge for simultaneous transmission and reception. This study considers multi-user oriented broadcast systems where the transmit array with subarray division allows simultaneous multi-beam transmission. Our objective is to mitigate SI from two aspects: 1) subarray assignment; 2) adaptive transmit beamforming (TxBF). We propose a min-SI TxBF design jointly with subarray assignment, which determines the best subarray assignment pattern and provides a closed-form solution of the optimal TxBF weight. Theoretical analysis and simulations show our design has a low algorithm complexity. Based on the measured SI channel data collected from a hardware prototype testbed, simulation results verify that the min-SI TxBF design with subarray assignment can effectively enhance SI cancelation.