Abstract
A downlink cellular network in which base stations (BSs) are distributed according to a homogeneous Poisson point process is considered. Each BS simultaneously serves multiple single-antenna users for downlink transmission; zero-forcing beamforming (ZFBF) is used for spatial division multiplexing. Each user quantizes and feeds back the channel state information (CSI) to the transmitter to ensure that at least partial CSI is available at the transmitter. The net spectral efficiency is introduced as a main performance metric; it measures the net profit achieved by using limited-feedback-based ZFBF. This paper mainly analyzes the optimal number of feedback bits that maximizes the net spectral efficiency. The optimal number is analyzed with respect to various important system parameters by extending and generalizing previous studies. Specifically, this paper analyzes the asymptotic behaviors of the optimal number with respect to the signal-to-noise ratio (SNR) and the channel coherence time; it does so by providing close approximations to the optimal number that is generally satisfied regardless of the values of the SNR, number of users, path loss exponent, and channel coherence time. It is demonstrated by simulation that the proposed approximations are extremely close to the optimal number on the region of interest of the system parameters.
Highlights
Multiple-input and multiple-output (MIMO) systems have been widely studied as promising technologies for increasing the spectral efficiencies of wireless communications
The optimal number of feedback bits that maximizes the net spectral efficiency of a multi-antenna system in a cellular network was analyzed in this paper
To closely capture both the effect of the inter-cell interference in realistic cellular networks and the effect of intra-cell interference induced from limited CSI at the transmitter (CSIT), this paper adopted the stochastic geometry and limited feedback
Summary
Multiple-input and multiple-output (MIMO) systems have been widely studied as promising technologies for increasing the spectral efficiencies of wireless communications. In terms of limited feedback, the authors in [36] provided a common mathematical framework that considered the effects of both the limited CSIT and multi-cell interference in cellular networks They considered a homogeneous Poisson point process (PPP) for BS topology, and intensive analysis results were provided with respect to various performance metrics including the distribution of signal-to-interference ratio, ergodic rate of the system, and optimal number of feedback bits. The author in [37] analyzed the behavior of the optimal number for small values of Tc by investigating the valid region of the analytical bounds of the optimal number Both [36] and [37] provided important insights into the system-level performance of limited-feedback-based MIMO systems in realistic cellular networks; the results therein omitted the effect of additive noise by assuming the system to be interference limited.
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