Dual iterative algorithm for hybrid beamforming in mmWave downlink massive multi-user MIMO systems

Signal loss is a basic issue in any communication system. Multiple Input Multiple Output (MIMO) also faces a similar challenge. In Millimeter-Wave (mm-Wave) or massive MIMO systems, beamforming gain is a feature to manage such challenges. The advanced MIMO systems need an intelligent beamforming controller for better signal reception. Therefore, Hybrid Beamforming, a combination of both beamforming techniques, analog and digital, can overcome this problem. An mm-Wave downlink massive multi-user MIMO system has been considered based on a fully-connected structure for implementing the proposed algorithm. For this, focus on the overall system's performance which is maximized in terms of sum-rate and power efficiency. To improve the system's performance and reduce computational complexity, a successive approximation method is used to design the Digital Beamforming. Based on the criterion to minimize the path loss, the Analog Beamforming with the proposed dual iterative algorithm has been used to optimize the results which consist of outer and inner iterations for maximizing the sum-rate and improving power efficiency. The results showed that the proposed dual iterative algorithm achieves a better sum-rate and power efficiency than other state-of-the-art methods for both large and small base station antenna numbers.