  We consider the uplink of a multicell multiuser multiple-input
multiple-output system where the channel experiences both small and large-scale
fading. The data detection is done by using the linear zero-forcing technique,
assuming the base station (BS) has perfect channel state information. We derive
new, exact closed-form expressions for the uplink rate, symbol error rate, and
outage probability per user, as well as a lower bound on the achievable rate.
This bound is very tight and becomes exact in the large-number-of-antennas
limit. We further study the asymptotic system performance in the regimes of
high signal-to-noise ratio (SNR), large number of antennas, and large number of
users per cell. We show that at high SNRs, the system is interference-limited
and hence, we cannot improve the system performance by increasing the transmit
power of each user. Instead, by increasing the number of BS antennas, the
effects of interference and noise can be reduced, thereby improving the system
performance. We demonstrate that, with very large antenna arrays at the BS, the
transmit power of each user can be made inversely proportional to the number of
BS antennas while maintaining a desired quality-of-service. Numerical results
are presented to verify our analysis.
