The harmful influence of employing a large number of pilot-resources on the performance of massive MIMO systems

Abstract

One of the severe constraints that limit the implementation of massive multi-input multi-output (M-MIMO) systems is called pilot contamination (PC). To overcome this problem, soft pilot reuse (SPR) strategy was proposed, which aims to properly allocate the Pilot Sequences (PS) to the users based on their properties e.g., Quality-of-Service. Despite its flaws, which can damage the spectral efficiency, the SPR strategy has been, heavily, employed as a decontaminating strategy. To reveal the weakness of this approach, this paper adopts a SPR based-strategy that separates the users within cells based on their large scale fading coefficients, therefore, because the edge-users (EUs) are mostly affected by the PC compared to the centre-users (CUs), a set of orthogonal pilots is allocated to the EUs of the overall cells, while the CUs of each cell are obliged to reuse the same set of orthogonal pilots as the CUs of adjacent cells.