Performance Evaluation of Analog Beamforming with Hardware Impairments for mmW Massive MIMO Communication in an Urban Scenario

Abstract

The use of massive multiple-input multiple-output (MIMO) techniques for communication at millimeter-Wave (mmW) frequency bands has become a key enabler to meet the data rate demands of the upcoming fifth generation (5G) cellular systems. In particular, analog and hybrid beamforming solutions are receiving increasing attention as less expensive and more power efficient alternatives to fully digital precoding schemes. Despite their proven good performance in simple setups, their suitability for realistic cellular systems with many interfering base stations and users is still unclear. Furthermore, the performance of massive MIMO beamforming and precoding methods are in practice also affected by practical limitations and hardware constraints. In this sense, this paper assesses the performance of digital precoding and analog beamforming in an urban cellular system with an accurate mmW channel model under both ideal and realistic assumptions. The results show that analog beamforming can reach the performance of fully digital maximum ratio transmission under line of sight conditions and with a sufficient number of parallel radio-frequency (RF) chains, especially when the practical limitations of outdated channel information and per antenna power constraints are considered. This work also shows the impact of the phase shifter errors and combiner losses introduced by real phase shifter and combiner implementations over analog beamforming, where the former ones have minor impact on the performance, while the latter ones determine the optimum number of RF chains to be used in practice.

Joint Transmit Antennas for Energy Efficiency in Downlink Massive MIMO Systems

“…The performance EE gradually increases with equal power allocation, while a decreased number of antennas decreases the performance gain as shown in [6] and [7]. Moreover, increasing the number of users inside the cell requires increasing the total transmit power, which does not satisfy the quality of service (QoS) because the data rate for every user is achieved in parallel and the EE will decrease due to the high transmit power.…”

Distributed Hybrid Precoding for Indoor Deployments Using Millimeter Wave Band

“…Motivated by this, hybrid transmission architectures are being investigated by the research community, where the precoding process is divided between the analog (RF) and digital (baseband) domains, alleviating the number of required RF chains of the system [12]. Several works analyze the performance of this hybrid architecture in different scenarios [13,14]. However, the topic of DAS hybrid precoding in mmWave has not previously been addressed in the literature, to the best of the authors' knowledge.…”

“…Real combiners introduce a power loss in their outputs [25], which is shown to be of great importance in the system design, since losses escalate with the number of branches to be combined [14]. Let us denote by the power loss of a basic combiner with two input branches and assume that a combiner for a generic number of RF chains is implemented by means of a cascade of log 2 two-branch combiners, leading to a total loss, expressed in logarithmic units of…”

Design of an Energy Efficient Future Base Station with Large-Scale Antenna System

“…Due to the limited spectrum resources, it is also inevitable for the number of transmitter (TX) antennas in the BS to continuously increase [11]. Thus, we assume that a future BS has a large number of TX antennas, that is a large-scale (LS) antenna system or LS multiple-input multiple-output (MIMO) [16][17][18]. Actually, in the case of a BS with LS-MIMO, the resource allocation problems are easier to solve if the channel properties provided by LS-MIMO systems are exploited smartly [19,20].…”