Coverage Analysis for Cell-Free Massive MIMO High-Speed Railway Communication Systems

In traditional cellular framework, the frequent handoff is one of the main factors that affect the performance of high-speed railway (HSR) communication systems. The cell-free massive multiple input multiple output (MIMO) is proposed as a promising technique for the antenna point (AP) deployment of HSR communication systems. This paper investigates the coverage performance of the cell-free massive MIMO HSR communication systems with multiple APs and multiple users. Initially, the system and channel models are proposed. Based on the established models, the uplink training, uplink data transmission and downlink data transmission are analyzed, respectively. By using the deterministic equivalent analysis, we derive a deterministic signal-to-interference-plus-noise ratio expression for downlink transmission. Then, a tight upper bound on the coverage probability is derived. In the high power regime, the asymptotic coverage performance is also analyzed. Numerical results verify the correctness of the derived theoretical expressions. Moreover, the effects of the downlink transmit power, AP’s antenna number, AP’s density, user number, and channel fading parameter on coverage performance are also discussed.