Intelligent Reflecting Surface-Assisted mmWave Communication With Lens Antenna Array

In millimeter wave (mmWave) communication, lens antenna array has been considered as a potential technique to combat the severe path loss. However, blockage effect still exists. To address this issue, we design an intelligent reflecting surface (IRS) assisted wideband mmWave communication system with lens antenna array with limited radio frequency (RF) chains. This is the first attempt to design a mmWave communication system with the integration of IRS and lens antenna array. The designed system can realize high robust, low-complexity and cost-effective mmWave communication. To achieve desired performance, we first derive the signal-to-interference-plus-noise ratio (SINR) expression with the intersymbol interference, then we formulate a SINR maximization problem, by jointly considering the beamforming vector at base station with limited RF chains and reflection coefficient matrices at IRS with discrete phase levels. This problem is intractable and non-convex. To solve it, we optimize the reflection coefficient matrices by quadratic transformation with low-complexity closed-form expression, and the beamforming vector is handled by sparse beamforming optimization, where the l(0) norm is approximated by the l(1) norm. Finally, simulation results demonstrate the advantages of our proposed algorithm compared with benchmark schemes, e.g., 5 dB SINR gain can be achieved compared with existing algorithm.