Impact of multi-cell pilot reuse on the achievable uplink rate for massive MIMO systems

In massive multiple-input multiple-output (MIMO) systems, multi-cell pilot reuse is an important factor affecting the achievable system uplink rate. A generalized channel model with adaptable power control was used to derive the lower bound on the achievable uplink rate for both least square (LS) and minimum mean square error (MMSE) channel estimations. Then, the impact of pilot reuse as the number of base station (BS) antennas tends to infinity is analyzed based on these bounds. For uncorrelated channels, the ultimate achievable uplink rate of a user is mainly limited by pilot contamination and partially by the large-scale fading coefficients from a pilot interfering with users communicating to their base stations of their own cells due to power control. For correlated channels, pilot contamination is not the only factor that constrains the ultimate achievable system uplink rate, but always exists when LS channel estimation is used, but may vanish when MMSE is used.