Beamforming Design for IRS-Aided Decode-and-Forward Relay Wireless Network

As a low-cost and low-power-consumption passive reflector, intelligent reflecting surface (IRS) can make significant rate improvement by building programmable wireless environment. To improve the performance coverage range of networks, an IRS-aided decode-and-forward (DF) relay network is proposed with multiple antennas at station (RS). achieve high rate, alternately iterative structure (AIS) maximizing receive power (Max-RP) RS to jointly optimize beamforming vectors phase shifts IRS. Considering its high-complexity, two low-complexity Max-RP schemes null-space projection (NSP) plus maximum ratio combining (MRC) IRS element selection (IRSES) MRC are presented reduce this complexity, respectively. For former, NSP used separate reflected signal from direct transmitted source adopted combine signals RS. latter, basic concept IRSES as follows: partitioned into ${M}$ subsets elements adjusting phases all per subset alignment (PA) corresponding antenna relay. Simulation results show that three methods perform much better than existing single-antenna in terms performance. In particular, 85% gain over scheme achieved signal-to-noise region. Moreover, it verified positions have substantial impact on performance, there exists optimal