  A common approach to obtain channel state information for massive MIMO
networks is to use the same orthogonal training sequences in each cell. We call
this the full-pilot reuse (FPR) scheme. In this paper, we study an alternative
approach where each cell uses different sets of orthogonal pilot (DOP)
sequences. Considering uplink communications with matched filter (MF)
receivers, we first derive the SINR in the large system regime where the number
of antennas at the base station, the number of users in each cell, and training
duration grow large with fixed ratios. For tractability in the analysis, the
orthogonal pilots are drawn from Haar distributed random unitary matrices. The
resulting expression is simple and easy to compute. As shown by the numerical
simulations, the asymptotic SINR approximates the finite-size systems
accurately. Secondly, we derive the user capacity of the DOP scheme under a
simple power control and show that it is generally better than that of the FPR
scheme.
