Users Capacity Upper Bound of Multi-Pair Massive MIMO AF Relay System under Pilot Contamination

Massive MIMO relay system promises large spectral and energy efficiencies. It also allows admitting more users in the network with controlled quality of service. In this paper, we seek the answer of the following question: what is the maximum number of users that can be admitted in a two-way relay network with massive number of antennas at the relay side and subject to a minimum quality of service at the user side? In order to answer this question, we develop lower bound on the achievable user rate which we then use to bound the maximum number of the admissible users.We also study the effect of the non orthogonality of the pilot sequences on the user capacity in a small cell (dense) network and propose an interference mitigation scheme which improves the spectral efficiency. It is shown that large number of users can coexist using the proposed scheme.