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Efficient Pilot Decontamination Schemes in 5G Massive MIMO Systems

1
Communication Engineering Department, King Abdullah II School of Engineering, Princess Sumaya University for Technology PSUT, Amman 11941, Jordan
2
Department of Electrical Engineering, University of Engineering & Technology, Peshawar 814, Pakistan
3
School of Intelligent Mechatronics Engineering, Sejong University, Seoul 05006, Korea
*
Author to whom correspondence should be addressed.
Electronics 2019, 8(1), 55; https://doi.org/10.3390/electronics8010055
Received: 26 November 2018 / Revised: 26 December 2018 / Accepted: 27 December 2018 / Published: 3 January 2019
(This article belongs to the Special Issue Massive MIMO Systems)
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Abstract

Massive Multiple-input Multiple-output (MIMO) is an emerging technology for the 5G wireless communication systems which has the potential to provide high spectral efficient and improved link reliability and accommodate large number of users. Aiming at the problem of pilot contamination in massive MIMO systems, this paper proposes two algorithms to mitigate it. The first algorithm is depending on the idea of Path Loss to perform User Grouping (PLUG) which divide the users into the center and edge user groups depending on different levels of pilot contamination. It assigns the same pilot sequences to the center users which slightly suffer from pilot contamination and assign orthogonal pilot sequences to the edge users which severely suffer from pilot contamination. It is assumed that the number of users at the edge of each cell is the same. Therefore, to overcome such limitations of PLUG algorithm, we propose an improved PLUG (IPLUG) algorithm which provides the decision parameters for user grouping and selects the number of central and edge users in each cell in a dynamic manner. Thus, the algorithm prevents the wrong division of users in good channel conditions being considered as an edge user which causes large pilot overhead, and also identifies the users with worst channel conditions and prevents the wrong division of such users from the center user group. The second algorithm for pilot decontamination utilizes the idea of pseudo-random codes in which orthogonal pilot are assigned to different cells. Such codes are deployed to get a transmission pilot by scrambling the user pilot in the cell. Since the pilot contamination is generated because different cells multiplex the same set of orthogonal pilots and the pseudo-random sequences have good cross-correlation characteristics, this paper uses this feature to improve the orthogonality of pilots between different cells. Simulation results show that the proposed algorithms can effectively improve channel estimation performance and achievable rate as compared with other schemes. View Full-Text
Keywords: Massive MIMO; pilot decontamination; MSE; dynamic user scheduling; dynamic pilot allocation Massive MIMO; pilot decontamination; MSE; dynamic user scheduling; dynamic pilot allocation
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Saraereh, O.A.; Khan, I.; Lee, B.M.; Tahat, A. Efficient Pilot Decontamination Schemes in 5G Massive MIMO Systems. Electronics 2019, 8, 55.

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