Abstract:
Massive multiple input multiple output (MIMO) systems are essential to meet the growing
need for enhanced capacity and faster data rates in modern wireless communication networks, particularly in the fifth generation (5G). These systems serve many users at once on
the same frequency band by using a lot of antennas at the base station (BS). The computational complexity of many antenna numbers and pilot contamination are the main obstacles
to estimating the channel of the massive MIMO system. To overcome pilot contamination
challenges, this thesis aims to investigate pilot-based channel estimate methods with pilot decontamination in Rician fading. In this thesis, soft pilot reuse is combined with the weighted
graph coloring pilot decontamination mechanism to overcome the impact of pilot contamination in Rician fading scenarios, which is the main weakness in massive MIMO systems.
In both Rayleigh and Rician fading, the accuracy of the channel estimate is increased by
mitigating the effects of pilot contamination. MATLAB simulations are used to examine
how well the minimum mean squared error (MMSE), element-wise minimum mean squared
error (EW-MMSE), and least squares (LS) techniques work with the Rayleigh and Rician
fading channels model. The simulation result shows that the better method for channel estimation in both uplink and downlink situations is MMSE with Rician fading. In the uplink
system, spectral efficiency (SE) of the channel estimate is increased from 20.9 b/s/Hz/cell
to 24.7 b/s/Hz/cell with pilot decontamination at BS antenna M = 90. For downlink, it increased from 21.8 b/s/Hz/cell to 27.5 b/s/Hz/cell. In Rayleigh fading, for the uplink system,
SE increased from 14.0 b/s/Hz/cell to 16.5 b/s/Hz/cell at M = 90 with pilot decontamination,whereas in the downlink it improved from 14.2 b/s/Hz/cell to 17.5 b/s/Hz/cell. The results
show that the addition of decontamination techniques increases the accuracy of channel estimates, hence improving system performance for massive MIMO networks. So, MMSE
are useful for utilizing channel characteristics, while the proposed method (soft pilot reuse
combined with weighted graph coloring) is a reliable way to reduce the impact of pilot contamination on Rayleigh and Rician fading.
