DEVELOPMENT OF A PILOT ALLOCATION PROTOCOL TO MITIGATE THE EFFECT OF PILOT CONTAMINATION IN MASSIVE MULTIPLE INPUT MULTIPLE OUTPUT SYSTEM

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Department of Engineering

ABSTRACT
Pilot Contamination (PC) has been considered as a majorlimiting factor of Time Division Duplexing (TDD) Massive Multiple-Input Multiple-Output (M-MIMO) systems, as itsaturates the signal to interference plus noise ratio (SINR) saturated. Similarly, several mitigation techniques such as Eigenvalue decomposition, cooperative Bayesian channel estimation, blind equalization technique, time staggering pilot, smart pilot assignment, etc. proposed in literature to address PC issue have limitations. These proposed methods are either based on initializing all pilot sequences allocated for training as requested by users or require coordination among neighboring cells. Either process is found to be difficult as synchronizing different levels of the network (micro, nano, and pico-cells) and possibly many cells is not only difficult but a huge task of highly computational complexity that requires coordination among neighboring cells. Therefore, this research work developed a Pilot Allocation Protocol (PAP) decontamination technique. The developed scheme was based on sectional pilot sequence initialization and sharing which allocate more than one user to share the same orthogonal pilot sequence within a cell. As a result of the sharing, intra cell interference was created, which in turn suppresses inter cell interference between users sharing the same pilot sequence and mitigate the effect of PC. Simulation was carried out using MATLAB 2016Rb and the performance of the developed PAP technique was then compared with conventional; and; Soft Pilot Reuse and Multi-Cell Block Diagonalization (SPR and MBD) schemes utilizing average Uplink (UL) and Downlink (DL) cell throughputs, and Bit Error Rate (BER) as performance metrics. Results obtained showed that, PAP technique had a better average UL and DL cell throughputs over the conventional; and; SPR and MBD schemes with an improvement of 2 b/s/Hz and 3b/s/Hz when the number of BS antennas considered was set at 64, 20.5 b/s/Hz for uplink and 20.3 b/s/Hz for ix