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We consider the problem of maximizing the total wireless signal power delivered by a distributed antenna array to a receiver where the transmitting nodes each have known frequency-selective channel responses to the receiver and are subject to individual total transmit power constraints. This optimization problem is mathematically quite different from the power maximization problems involving single...
We conducted one of the most comprehensive many-antenna MU-MIMO channel measurement campaigns ever reported. Our measurement system supports full mobility with very high time-frequency resolution. We report channel traces in the UHF, 2.4 GHz, and 5 GHz bands, in diverse environments, with up to 104 base-station antennas serving 8 users. We characterize channel stability and capacity across these bands...
We characterize upper bounds on the throughput capacity of a multi-tier millimeter wave (mmWave) network with diverse blockage probability, p(n), scaling scenarios. Communication links in the network are divided into three communication tiers sharing a single mmWave frequency. The bottom tier considers transmissions between n terminals and M (n) access points (APs). The top tier includes links between...
Three prominent features of massive MIMO are studied using channel measurements. Those features are extensively exploited in signal processing methods for massive MIMO and have been only partially, or not at all, validated. First, channel hardening is characterized as a function of the number of antennas. Second, user decorrelation is evaluated as a function of the distance between users. At last,...
While most literature in compressive sensing mostly concentrates on recovering a sparse signal from a reduced number of measurements, parameter estimation problems have recently been studied under this acquisition framework. In this paper, we focus on the problem of direction-of-arrival (DOA) estimation from compressive measurements taken at each antenna in a receiver array. In contrast with the common...
We consider wireless backhauling in mobile networks, employing large-scale full-dimension MIMO antenna arrays on both sides of the link. Our focus is on design strategies for transmit and receive antenna combiners, assuming FDD transmission and limited feedback operation. We investigate the performance of two competing philosophies: 1) An algebraic approach in which antenna combiners are calculated...
Spectrum pooling is not typically used in current cellular networks, because it only provides a slight performance improvement while requiring heavy coordination among different cellular operators. However, these problems can be potentially overcome in millimeter-wave (mmWave) networks, thanks to the use of beamforming both at base stations and at user equipments. In this paper, we develop a joint...
The large number of analog received signals to be processed in massive MIMO systems renders conventional high-precision analog-to-digital conversion (ADC) not feasible in terms of cost- and power-efficiency. In this paper we present a novel ADC architecture inspired by the principles of integer-forcing source coding, which jointly reconstructs the received signals in the digital domain. This scheme...
We consider wireless networks of remote radio heads (RRH) with large antenna-arrays, operated in TDD, with uplink (UL) training and channel-reciprocity based downlink (DL) transmission. To achieve large area spectral efficiencies, we advocate the use of methods that rely on rudimentary scheduling, decentralized operation at each RRH and user-centric DL transmission. A slotted system is assumed, whereby...
Millimeter-wave (mmWave) cellular systems are a promising option for a very high data rate connectivity in near future because of the large bandwidths available at this range of frequencies. Communication at mm Waves, however, is quite challenging due to the large path-loss exponent compared with the traditional sub-6GHz counterpart. Directional beamforming with large antenna gains both at the user...
Massive multi-user (MU) multiple-input multiple-output (MIMO) is widely believed to be a core technology for the upcoming fifth-generation (5G) wireless communication standards. The use of low-precision digital-to-analog converters (DACs) in MU-MIMO base stations is of interest because it reduces the power consumption, system costs, and raw baseband data rates. In this paper, we develop novel algorithms...
Mixed hybrid-low resolution MIMO architectures reduce both the number of ADCs and their resolution to reduce power consumption. In such a system, the received signal suffers from two compression stages. One is due to the analog processing stage and the reduced number of RF chains, while the other is a result of signal quantization by the ADC converters. The compression steps both complicate the estimation...
Conventional centralized data detection algorithms for massive multi-user multiple-input multiple-output (MU-MIMO) systems, such as minimum mean square error (MMSE) equalization, result in excessively high raw baseband data rates and computing complexity at the centralized processing unit. Hence, practical base-station (BS) designs for massive MU-MIMO that rely on state-of-the-art hardware processors...
In this paper, we construct and comprehensively analyze a practical downlink (DL) multiuser (MU) multi-input-multi-output (MIMO) scheduling algorithm over LTE Advanced (LTE-A) massive MIMO cellular networks. We first design an efficient approximation algorithm to maximize the weighted sum rate subject to certain mandatory practical constraints, and prove that our algorithm can yield a meaningful approximation...
In order to realistically model urban micro-cell environments with low base station heights, a measurement campaign has been conducted in the 3.5–3.8 GHz frequency band. The two scenarios of interest are the Urban Micro (UMi) Campus and Open Square scenarios. The findings of this campaign led to a parameter set for the quasi deterministic radio channel generator (QuaDRiGa) channel model and shall...
Massive MIMO and beamforming is commonly considered as one of the key technologies for future cellular communications. It is targeted to solve the capacity requirements in enhanced mobile broadband and enable new services in other communication fields, e.g. machine type communications. In this work, we study M-MIMO technology in a novel approach, combining system simulations and modeling with hardware...
With the standardization of 5G cellular systems now underway, new frequency bands are being considered for 5G deployments, namely, cmWave bands (3–30 GHz) and mmWave bands (30–100 GHz). An early use case for 5G in these non-traditional cellular bands is to provide fixed access wireless services to residential users in suburban neighborhoods. In this paper, we present a massive MIMO system concept...
This paper presents the close-form expression of the spatial security outage probability, which is a novel performance metric that measures the security level of the legitimate transmission from the spatial aspect in the presence of Poisson Point Process distributed eavesdroppers. Beamforming is used to create the exposure region where any randomly located eavesdropper causes secrecy outage, based...
With the persistent densification of cellular networks, especially in urban environments, three-dimensional beam-forming utilizing full dimension MIMO antenna arrays becomes of interest for mobile communications, since it allows to mitigate the inter-cell interference and enables high order spatial multiplexing of a multitude of users. In this paper, we consider beamformer optimization with the goal...
This work explores challenges in silicon integration of scalable high-throughput “Wireless Fiber” links that exploit the increase in spatial and spectral degrees of freedom at higher carrier frequencies due to LOS MIMO spatial multiplexing and higher bandwidths. In order to utilize these increased degrees of freedom, however, hardware must scale in dynamic range, speed and number of antenna elements...
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