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In order to reduce the effect of pilot contamination and maximize the system sum rate while guaranteeing the fairness among users, an efficient and fair pilot allocation scheme is proposed for multi-cell massive MIMO systems in this work. The pilot allocation optimization problem is formulated to maximize the sum rate of the system while guaranteeing the fairness among users. A heuristic algorithm,...
In this work, we investigate the system model, key enabling technique, and the associated performance for an Nr × Nt dual polarized MIMO (DP-MIMO) based communication system, wherein only imperfect channel state information is available at the transmitter. The DP-MIMO channel involves the imperfect spatial fading and perfect polarization fading. At the transmitter, the precoding scheme based on oblique...
A problem that arises with pilot assignment in multicellular massive multiple-input-multiple-output (MIMO) systems is due to inter-cell interference, also known as pilot contamination. This paper focuses on minimizing the inter-cell interference that results from spatial correlation based on signal arrival parameters, assuming the use of a cylindrical antenna array. The signal parameters are used...
This paper investigates user selection and power allocation algorithms in multi-cell massive Multiple-Input Multiple-Output (MIMO) systems. The focus is on designing an algorithm that maximizes a particular cell of interest's sum rate taking into consideration the interference from other cells. This research extends previous work and proposes suboptimal per cell resource allocation models that are...
This paper considers a multi-way massive multiple-input multiple-output amplify-and-forward relaying system, where single-antenna users exchange their information-bearing signals with the assistance of one relay station equipped with unconventionally many antennas. The relay first estimates the channels to all users through the pilot signals transmitted from them. Then, the relay uses maximum-ratio...
In this paper, we analyze uplink sum rate of multiple-input multiple-output (MIMO) systems with maximum-ratio combining (MRC) receivers. To be practical, receive correlation and different powers of users are assumed. Two novel approximate results on sum rate are derived in closed form. Based on the results, we also obtain the asymptotic results on sum rate when the number of base station antenna (M)...
In this paper, we investigate the energy efficiency (EE) of massive multiple-input multiple-output (MIMO) systems with linear maximum ratio combining (MRC) and zero-forcing (ZF) receivers. To be practical, the baseband power consumption with algorithm computational complexity (ACC) is taken into account. Utilizing this model, we maximize the global optimal number of receiver antenna and sum rate with...
The pilot contamination problem is one of the major obstacles that limit the performance of time-division duplex (TDD) multi-cell massive multiple-input multiple-output (MIMO) systems. Pilot contamination results from the re-use of the same set of pilot sequences in the different cells of the system. In this paper, we compare between two different scenarios of pilot signals allocation with respect...
This paper studies the broadcast channel with M antennas at the base-station and M single antenna users. Most of the works in the literature assume perfect channel state information at both ends of each link. In this work, we assume that these links are spatially correlated and only the long-term statistical information corresponding to the covariance matrices of the links are available at both ends...
This paper investigates the downlink of an energy efficient distributed large-scale MIMO system. The studied system is assumed to be made up of a set of remote radio heads (RRHs), each of which is powered by both an independent energy harvesting source and the grid. The grid energy allows to compensate for the randomness and intermittency of the harvested energy. Hence, the problem of grid power consumption...
This paper reports a measurement study of generating Rayleigh fading channels in a reverberation chamber. The latter has a dimension of 1.8 m × 2.4 m × 1.6 m and its operation frequency range is 650 MHz to 6 GHz, suitable for testing mobile handset devices. The fading channel inside the chamber is observed by altering stirring conditions and its difference to the ideal Rayleigh is examined by the...
In this paper, we have proposed an iterative space alternating generalized expectation maximization (SAGE) based semi-blind channel estimation technique for massive multiple-input multiple-output (MIMO) system in multi-cell pilot contamination prone scenario. The benefits of massive MIMO depend largely on the accuracy of channel state information (CSI) available at the base station (Transmitter)....
The maximal ratio combining (MRC) receiver has excellent performance in the uplink of massive multiple-input-multiple-output (MIMO) systems under favorable propagation, but the performance degrades very much in a harsh channel because of interference. Theoretical analysis showing this phenomenon is given for a particular class of fading channel. A novel receiver, exploiting preemphasis/deemphasis...
Massive multiple-input multiple-output (MIMO) is one of the promising technologies to be used in the future fifth generation (5G) wireless networks for its capability to increase the system throughput, improve spectral efficiency and energy efficiency. To achieve these benefits of the massive MIMO, there are many challenges that need to be handled. One of these challenges is the pilot contamination...
In this paper, we have addressed the problem of channel estimation in massive MIMO systems, because the large scale benefits of massive MIMO relies on the accuracy of channel state information (CSI) available with the system. We have proposed an iterative space-alternating generalized expectation maximization (SAGE) based semi-blind channel estimation technique. The proposed method iteratively updates...
This paper introduces a simple and practical channel estimator for multipath multi-cell massive MIMO TDD systems with pilot contamination. Least squares (LS) channel estimators present low performance under moderate to strong pilot contamination, while minimum mean square error (MMSE) estimators perform much better than LS estimators in such conditions. However, MMSE estimators present an issue that...
Pilot contamination caused by non-orthogonal pilot sequences reuse in adjacent cells has become one of the main impairments for massive multiple-input multiple-output (MIMO) systems. A scheme named flexible pilot reuse is proposed in this paper to reduce the effect. The main idea is that users suffered from mild pilot contamination (PC) are allocated the same set of orthogonal pilots, while the users...
In this paper, a multi-pair amplify-and-forward (AF) massive MIMO system is investigated, where multiple source users communicate with multiple destination users via a single relay. The achievable rate of the system and its analytical expression are studied for power-scaling laws when ZFT/ZFR algorithm is adopted at the relay. The imperfect channel state information (CSI) is considered and the MMSE...
This paper studies the downlink sum-rate and energy efficiency (EE) of massive multiple-input multiple-output (MIMO) systems under the effect of channel aging caused by the movements of users. First, a closed-form expression of the downlink sum-rate where zero-forcing (ZF) precoder is adopted at the base station (BS) is derived. Based on the expression, the power-scaling law that when the number of...
Owing to the forever growing demand for faster data transmission speed in the recent or future telecommunication systems, the multiple antenna systems have been actively investigated and successfully deployed for the emerging broadband wireless access networks (e.g., Mobile WiMAX). Even when a wireless channel with high channel capacity is known, we still require to find superior techniques to achieve...
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