Abstract
The deployment of large-scale antenna arrays for cellular base stations (BSs), termed as `Massive MIMO', has been a key enabler for meeting the ever-increasing capacity requirement for 5G communication systems and beyond. Despite their promising performance, fully-digital massive MIMO systems require a vast amount of hardware components including radio frequency chains, power amplifiers, digital-to-analog converters (DACs), etc., resulting in a huge increase in terms of the total power consumption and hardware costs for cellular BSs. Towards both spectrally-efficient and energy-efficient massive MIMO deployment, a number of hardware limited architectures have been proposed, including hybrid analog-digital structures, constant-envelope transmission, and use of low-resolution DACs. In this paper, we overview the recent interest in improving the error-rate performance of massive MIMO systems deployed with 1-bit DACs through precoding at the symbol level. This line of research goes beyond traditional interference suppression or cancellation techniques by managing interference on a symbol-by-symbol basis. This provides unique opportunities for interference-aware precoding tailored for practical massive MIMO systems. Firstly, we characterize constructive interference (CI) and elaborate on how CI can benefit the 1-bit signal design by exploiting the traditionally undesired multi-user interference as well as the interference from imperfect hardware components. Subsequently, we overview several solutions for 1-bit signal design to illustrate the gains achievable by exploiting CI. Finally, we identify some challenges and future research directions for 1-bit massive MIMO systems that are yet to be explored.
Highlights
Massive multiple-input multiple-output (MIMO) has been an attractive technology to support the desired 1000-fold system throughput improvements for fifth-generation (5G) cellular communication systems
B. 1-Bit digital-to-analog converters (DACs) Transmission: The Scope for Interference Exploitation. While both the linear and nonlinear 1-bit precoding techniques mentioned above have their distinct benefits and drawbacks, we note an important feature that has been neglected in these 1-bit precoding designs: When we shift the precoding design from the traditional block level to the symbol level, the mean-squared error (MSE)-based approach shown in Figure 2 that aims to suppress all interference is no longer optimal
This paper provides an overview of constructive interference (CI)-based symbol-level precoding designs tailored for 1bit massive MIMO systems
Summary
Massive multiple-input multiple-output (MIMO) has been an attractive technology to support the desired 1000-fold system throughput improvements for fifth-generation (5G) cellular communication systems. The above potential benefits are premised for ideal fully-digital massive MIMO BSs with infinite-precision digital-to-analog converters (DACs), where losses or signal distortions are not present. This would require a radio frequency (RF) chain, a. Compared to the HAD architecture and CE transmission which reduce the hardware complexity by reducing the total number of RF chains, implementing low-resolution DACs retains the benefits in degrees of freedom for massive MIMO by reducing the hardware cost, complexity and the resulting power consumption on each RF chain [2]. On the mean-squared error (MSE) metric, and further highlight the opportunities and benefits of interference exploitation
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