Performance Analysis and Design of Scalable Cell-Free Massive MIMO Systems

Abstract

To achieve a high data rates in the fifth generation (5G), the adaptation of Massive Multiple Input Multiple Output (m-MIMO) systems with Small Cells is required to improve the performance for Spectral Efficiency. An m-MIMO provides high spectral efficiency through the deployment of a large number of antenna elements say ten to hundred at the base station compared to a number of User Terminals (UTs) served in the same time-frequency resource with no severe inter-user-interference. The small-cell concept has emerged to obtain the lower latency, reduced energy and high achievable data rate, which are the key requirements for 5G technologies. In this paper, the m-MIMO system is developed with small-cells (SCs) considering the imperfect channel state information by achieving data rates (DRs) in the lower bound by reusing the pilot sequences in time division duplex (TDD). The energy efficiency of cellular networks can be improved by employing massive MIMO at the Base stations or overlaying current infrastructure by a layer of SCAs. The present work provides the far better results with the level of satisfaction shows that the total power consumption is greatly reduced by combining Massive MIMO and Small cells. Most of the benefits are also achievable by low-complexity Beam-forming, such as the proposed Multi-flow RZF beam-forming. Besides it, simulation results show that the Spectral Efficiency and Optimal Energy Efficiency are achievable depending on a fixed number of users and number of antennas utilized by small-cells.