Downlink Transmission of Multicell Distributed Massive MIMO With Pilot Contamination Under Rician Fading

Abstract

In this paper, we investigate the spectral efficiency (SE) of a multicell downlink (DL) distributed massive MIMO (DM-MIMO) system with pilot contamination operating over Rician fading channels in which each remote access unit (RAU) is equipped with a large number of distributed massive antenna arrays, while each user has a single antenna. In contrast to many previous works about DM-MIMO systems, the channel between users and the RAUs antennas in the same cell is modeled to be Rician fading, which is general for the 5G scenarios like Internet of Things. We explore maximum-ratio transmission (MRT) and line-of-sight (LOS) component-based equal-gain transmission (EGT) under imperfect channel state information. The tractable, but accurate closed-form expressions for the lower bounds of the achievable rate are derived for the MRT and the LOS component-based EGT over Rician fading channels in the DM-MIMO systems. Based on the obtained closed-form expressions, various power scaling laws concerning DL data transmit power and pilot transmit power are analyzed in detail. Numerical results are used to corroborate that these approximations are asymptotically tight, but accurate for systems. They also show that employing the LOS component-based EGT processing is more preferable than the MRT processing for DM-MIMO systems in conditions having a large number of RAU antennas and stronger LOS scenarios. Finally, the simulation results further show that when the number of all antennas for RAUs is fixed, the better SE performance can be obtained with more RAUs. INDEX TERMS Distributed Massive MIMO (DM-MIMO), Rician fading, Line-of-sight (LOS) component, power scaling law.

C-RAN Zero-Forcing With Imperfect CSI: Analysis and Precode & Quantize Feedback

“…Developments in several fields play an essential role in realizing large-scale JT; also known as cell-free massive-MIMO. These include advanced pilot allocation [4][5][6] and robust design [7], alleviating pilot contamination, fronthaul data compression [8] and allocation [9], energy-efficient algorithms [10][11][12], and retransmission protocols at the network edge [8]. Other key factors are the emergence of software-defined networks (SDN) and fog-based RAN [13], which decouple the control plane and data plane, and its incorporation into C-RAN [3], providing a suitable environment for non-centralized JT [14][15][16][17].…”

“…bounds for the broadcast channel and D-MIMO with imperfect CSI appear in [21,22] and [5,6,28,29,32], respectively, all of which consider C-CSIT. The proposed bound here differs from the latter bounds due to the JPM quantization, which does not exist in the C-CSIT.…”

“…This sub-block quantization induces an entirely different CSI error distribution leading to a distinct bound. Moreover, [5,6,28,29,32] consider the large system regime, whereas the analysis here does not. 4 Finally, [5,6] deal with channel impairment due to pilot contamination, whereas in this paper, the error is due to CSI quantization.…”

“…Moreover, [5,6,28,29,32] consider the large system regime, whereas the analysis here does not. 4 Finally, [5,6] deal with channel impairment due to pilot contamination, whereas in this paper, the error is due to CSI quantization. Another relevant rate-loss bound is [19], which, unlike here, considers the D-CSIT setup, which is different as discussed above.…”

Massive MIMO relaying with imperfect RF chains and coarse ADC/DAC in beyond 5G networks

“…3 The main reason is that massive MIMO can effectively mitigate interference while simultaneously serving a huge amount of users on the same time-frequency channel. [4][5][6] Also, with massive MIMO, the transmit power is significantly cut down and the main computation is performed at the base station (BS), 4 which is especially helpful to meet the low-power and low-cost requirements of battery-powered IoT devices. Considering the massive connectivity requirement and energy limitation of IoT networks, the application of massive MIMO to IoT networks has gained considerable attention in recent years.…”