On Uplink User Capacity for Massive MIMO Cellular Networks
  Under the conditions where performance in a massive MIMO network is limited by pilot contamination, the reverse link signal-to-interference ratio (SIR) exhibits different distributions when using different pilot allocation schemes. By utilising different sets of orthogonal pilot sequences, as opposed to reused sequences amongst adjacent cells, the resulting SIR distribution is more favourable with respect to maximising the number of users on the network while maintaining a given quality of service (QoS) for all users. This paper provides a simple expression for uplink user capacity on such networks and presents uplink user capacity figures for both pilot allocation schemes for a selection of quality of service targets. 
Anand Sivamalai and Jamie S. Evans
cs.IT math.IT