Decontaminating Pilots in Massive MIMO -5G Systems

Abstract

In this chapter, the proposed centralized Laplacian scattering-spatially correlated Rayleigh fading model performance is compared with both one- ring scattering-correlated Rayleigh fading and uncorrelated Rayleigh fading channel models performances for different pilot reuse factors and for different combining and precoding schemes in mitigating pilot contamination and realizing larger SE using MATLAB simulation. The highest SE of the proposed Laplacian centralized scattering-spatially correlated Rayleigh fading model is achieved when using M-MMSE combining and precoding scheme and the pilot reuse factor equals 4 but at the expense of increased computational complexity. Increasing the pilot reuse factor improves system SE and reduces the effect of interfering signals but leads to an increase of pilot samples and reduction of the number of UL and DL data samples in the coherence block. The TDD Massive MIMO system achieves higher cell throughput than the LTE system for the same channel bandwidth. Spatial channel correlation increases the degree of favorable propagation when the correlation matrices of UTs are sufficiently different. Channel estimation at the BS is key to achieve the full potential of Massive MIMO, which is typically accomplished using UL pilot transmission. The cost of interference rejection and SE enhancement is an increase in the system computational complexity, M-MMSE scheme provides the highest SE and requires the highest computational complexity, while MR scheme has the lowest computational complexity and SE. The RZF scheme provides a good SE-complexity tradeoff.