Analysis Of Massive MIMO Multi-pair Two-Way Relay Systems

The 4th mobile communication system has already been large-scale commercial.Countries around the world are studying 5th communication system.As one of the key technologies for 5G to improve system capacity,massive MIMO has been extensively researched to meet the 5G high performance index.Massive MIMO system employs hundreds of antennas to transmit information at the same frequency resource and the same time.Massive MIMO can utilize scarce and precious frequency resource effectively to improve system capacity.Moreover,Internet of Things(IoT)as one of important application scenarios of 5G,not only does it need enormous system capacity,but also need to support numerous devices to communication simultaneously.Therefore,massive MIMO multi-pair two-way relay system supports multi-pair devices to communication and has high system capacity,which meet the huge amounts of connection and communication requirements of 5G IoT and has been one of the most hot topics recently.In this paper,first of all,when it comes to the huge cost of massive MIMO,we put forward a massive MIMO half-duplex multi-pair two-way relay system based on low-cost radio frequency chains.For the hardware impairments induced by low-cost radio frequency chains,we analyze the spectrum and energy efficiency of the system.We derive the approximated closed-form expression of the spectrum and energy efficiency based on the large number law in case of the number of antennas approaches infinity.We also obtain the optimal numbers of antennas or device pairs to achieve the maximum energy efficiency.Then we propose the hardware scaling law,which proves that relay can employ more low-cost antennas to reduce the hardware cost without loss of significant system performance.Furthermore,due to the fact that it is hard to get perfect channel state information in the practical scenes,we propose a massive MIMO half-duplex multi-pair two-way relay channel estimation error models suffered from hardware impairments.The research shows that the spectrum and energy efficiency decrease with the increasing of the channel estimation error.The hardware scaling law for this scenario proves that the channel estimation error would improve the cost of hardware deployments.Therefore,the relay should employ more antennas to ensure that the loss of system performance is negligible.Finally,to further satisfy the requirements of system capacity of 5G IoT,we investigate a massive MIMO full-duplex multi-pair two-way relay system suffered from hardware impairments.The research denotes that full-duplex system can significantly improve the spectrum and energy efficiency.However,when the loop interference brought by the full-duplex system is large,it would lose the advantage of time efficiency and the system performance would be inferior to the half-duplex system.Furthermore,we prove that the hardware scaling law in this case is same as the case of the half-duplex system.In conclusion,this paper analyzes the influence of the parameters such as the number of antennas and device pairs,channel fading,the degree of hardware impairments,channel estimation error and loop interference on the massive MIMO multi-pair two-way relay system,which provides theoretical guidance to the design of the practical 5G system.We prove that such system can provide the high-speed data onto transmission of the large numbers of connection and communication requirements of 5G IoT.