Comparison of channel Estimation and Performance of MRC and ZF Receivers in Multicell Multiuser Uplink with Very Large Antenna Arrays

A multi cell multiuser MIMO system with a very large number of antennas at the base station (BS) is considered. Assumption is that the channel is estimated by using uplink training. In general, we consider a MIMO model Further a physical channel model in which the angular domain is separated into a finite number of distinct directions is considered. We analyze the so-called pilot contamination effect and show that this effect persists under the finite-dimensional channel model that we consider. In particular, a uniform array at the BS is considered. To understand this it is shown that when the number of BS antennas goes to infinity, the system performance under a finite-dimensional channel model with P angular bins is the same as the performance under an uncorrelated channel model with P antennas. This paper investigates if, for a large number of users, simpler schemes can achieve the same performance. Specifically, we show that a zero-forcing beam forming (ZFBF) strategy Further a lower bound on the achievable rate of uplink data transmission with a linear detector at the BS is derived. Then this lower bound to the cases of maximum-ratio combining (MRC) and zero-forcing (ZF) receivers, for a finite and an infinite number of BS antennas is specialized. Also, we compare the characteristics of the cell channel model and their channel estimates for different Scenario’s.