Analysis on the optimal system parameters in massive MIMO systems

Massive MIMO has been identified as one promising green communication technology in 5G to further enhance both EE and SE performance of wireless communication systems. Although there is great potential to get high system performance in theory, it is constrained by many factors in practice, for example, the overhead for acquisition of the channel state information. Under this premise, the optimal antenna configuration and multi-user number are investigated for massive MIMO systems in this paper, where the system performance is limited by the overhead of pilot and channel information feedback. When the number of transmit antenna is fixed, there exists a unique optimal number of multi-user. When the number of multi-user is fixed, the existence of optimal antennas relies on the property of the function of overhead. In addition, considering differences of each user propagation environment, an upper bound of optimal multi-user number is deduced which can be used to reduce the calculation complexity of the multi-user grouping. Numerical simulations are also provided to support the analysis.