Abstract
In this paper, we study two novel massive multiple-input multiple-output (MIMO) transmitter architectures for millimeter wave (mmWave) communications which comprise few active antennas, each equipped with a dedicated radio frequency (RF) chain, that illuminate a nearby large intelligent reflecting/transmitting surface (IRS/ITS). The IRS (ITS) consists of a large number of low-cost and energy-efficient passive antenna elements which are able to reflect (transmit) a phase-shifted version of the incident electromagnetic field. Similar to lens array (LA) antennas, IRS/ITS-aided antenna architectures are energy efficient due to the almost lossless over-the-air connection between the active antennas and the intelligent surface. However, unlike for LA antennas, for which the number of active antennas has to linearly grow with the number of passive elements (i.e., the lens aperture) due to the non-reconfigurablility (i.e., non-intelligence) of the lens, for IRS/ITS-aided antennas, the reconfigurablility of the IRS/ITS facilitates scaling up the number of radiating passive elements without increasing the number of costly and bulky active antennas. We show that the constraints that the precoders for IRS/ITS-aided antennas have to meet differ from those of conventional MIMO architectures. Taking these constraints into account and exploiting the sparsity of mmWave channels, we design two efficient precoders; one based on maximizing the mutual information and one based on approximating the optimal unconstrained fully digital (FD) precoder via the orthogonal matching pursuit algorithm. Furthermore, we develop a power consumption model for IRS/ITS-aided antennas that takes into account the impacts of the IRS/ITS imperfections, namely the spillover loss, taper loss, aperture loss, and phase shifter loss.
Highlights
M ILLIMETER wave communication systems are promising candidates for realizing the high data rates expected from the generation of wireless communication networks [2], [3]
We show that the power consumption of the conventional fully digital (FD), FC, and PC architectures significantly increases as a function of the number of transmit antennas whereas the power consumption of the lens array (LA) and intelligent reflecting/transmitting surface (IRS/ITS)-aided antennas is almost independent of the number of transmit antennas
We study the impact of the system parameters on the achievable rate via simulations and show that a proper positioning of the active antennas with respect to the intelligent surface in IRS/ITS-aided antennas leads to a considerable performance improvement
Summary
M ILLIMETER wave (mmWave) communication systems are promising candidates for realizing the high data rates expected from the generation of wireless communication networks [2], [3]. In order to improve the scalability and energy efficiency of mmWave massive MIMO systems, in this article, we consider two novel massive MIMO transmitter architectures which comprise few active antennas and a large intelligent reflecting surface (IRS), see Fig. 1 e), or a large intelligent transmitting surface (ITS), Fig. 1 f). Structure and the power consumption of the IRS/ITS-aided antennas are provided Such accurate models are needed for a fair performance comparison of different MIMO architectures and the design of IRS/ITS-aided MIMO structures (e.g., the adjustment of the relative positions and orientations of the active antennas with respect to the intelligent surface) which was not investigated in [37]. SIGNAL, SYSTEM, AND CHANNEL MODELS we present the system, transmit signal, and channel models for the considered IRS/ITS-aided MIMO systems
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