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We consider a distributed reception scenario where the transmitter transmits a signal and multiple geographically separated receive nodes forward the processed version (using only a small number of bits) of their received signal to the fusion center. The fusion center tries to decode the transmitted signal only based on the forwarded bits from the distributed nodes. We show that there is a strong...
In this paper, channel estimation for massive multiple-input multiple-output (MIMO) systems with a large number of transmit antennas at the base station is considered, and a new algorithm for pilot beam pattern design for optimal channel estimation under the assumption of Gauss-Markov channel processes is proposed. The proposed algorithm designs the optimal pilot beam pattern sequentially by exploiting...
Auctions have been proposed as a way to provide economic incentives to dynamically allocate unused spectrum to users in need of it. Previously proposed auction schemes do not take into account the fact that users' power and bandwidth constraints might prevent them from transmitting their bid prices to the auctioneer with high precision, and that these transmitted bid prices must travel through a noisy...
A major challenge in OFDMA cellular networks is to efficiently allocate scarce channel resources and optimize global system performance. Specifically, the allocation problem across cells/base-stations is known to incur extremely high computational/communication complexity. Recently, Gibbs sampling has been used to solve the downlink inter-cell allocation problem with distributed algorithms that incur...
Wireless technology is now a ubiquitous part of life worldwide. A continuing and evolving concern is the possibility of adverse health effects from long term exposure to electromagnetic radiation. In most countries, regulatory agencies set an exposure threshold in terms of the specific absorption rate (SAR). Surprisingly, portable wireless communication devices, such as mobile phones, are often designed...
Accurate channel state information at the transmitter can significantly enhance the performance of multiple antenna systems, but efficient channel quantization techniques must be developed in order to scale such informed transmitter strategies to frequency division duplexed (FDD) massive MIMO systems. Recent results show that noncoherent trellis-coded quantization (NTCQ) is an effective approach for...
There has been a growing interest in wireless systems that employ a very large number of transmit antennas. Some theoretical results have shown that substantial improvements in network capacity are possible. Despite this work, a major challenge is how these large transmit arrays should perform training to allow receiver channel estimation. Without new techniques, the heavy burden of training could...
Massive multiple-input multiple-output (MIMO) techniques are regarded as a potential breakthrough in cellular network design, with transmit precoding to multiple downlink users playing a central role in the projected capacity gains. Most prior work assumes that the channel estimates required for precoder design are obtained by exploiting reciprocity in time division duplexed (TDD) systems. However,...
SAR codes are designed for transmission by a portable wireless device to provide high reliability and data rates on a wireless channel, while maintaining low human exposure to electromagnetic radiation. We provide design criteria and examples of SAR codes and show that a 3 dB reduction in exposure is within reach on some devices versus standard single-antenna methods or spacetime codes. This reduction...
Relay channels aid in increasing the rate of communication possible from the source to the destination. However, in general, the capacity of a relay channel is still an open problem. In this work, we provide a lower bound for the capacity of the three-terminal relay channel with destination-source feedback in the presence of correlated noise using the recent results in [1] and employing linear processing...
The ultimate objective of additive manufacturing is the implementation of techniques that can be used throughout the full manufacturing cycle. However, since its introduction, the additive manufacturing process has been used for little more than pre-production prototyping. The goal of some current work at ORNL is to change that reality. ORNL recently completed the first step towards optimizing the...
In the past decade, additive manufacturing and printed electronics technologies have expanded rapidly on a global scale. As the additive manufacturing techniques have become more capable and affordable, and able to work with a broader range of materials, the machines are increasingly being used to make advanced products at significantly lower costs and risks. The additive manufacturing industry is...
This work studies the capacity of the 2-receiver multiple-input/multiple-output (MIMO) broadcast packet erasure channels (PECs) with channel output feedback, which is in contrast with the single-input/single-output setting of the existing works. Motivated by the immense success of linear network coding (LNC) in theory and in practice, this work focuses exclusively on LNC schemes and characterizes...
Thermal oxidation of copper is a simple and scalable method to produce copper oxide nanowires. We report for the first time the formation of nanowires on copper powder during thermal oxidation and the resulting nanowire coverage that is dependent on initial particle size. Systematic thermogravimetric analysis (TGA) and in-situ x-ray diffraction (XRD) studies of thermal oxidation of particles of different...
Portable devices sold around the world number in the billions, and they are used daily because of their ability to provide connectivity by integrating processing power, touch screens, cameras, and motion sensors with multiple radios. Many of the radios can run simultaneously, and each radio exposes the user to some level of electromagnetic radiation. The exposure levels are potentially cumulative...
The topic of waveform design is investigated for a multistatic radar scenario where it is assumed that one radar sensor is transmitting while the remaining sensors receive. This is accomplished by using an information-theoretic measure (i.e., mutual information between the image and the radar return) as an objective function for waveform optimization. Simulations are given to illustrate performance...
Due to the projected increased demand for high data rate mobile services, interest has grown in new cellular network architectures such as a tiered networks. This paper proposes a beam searching algorithm and a codebook design for multilevel beamforming in outdoor millimeter wave communication systems. In an outdoor millimeter wave scenario, the received signal suffers from severe path loss and various...
We consider a homogeneous multiple cellular scenario with multiple users per cell, i.e., K??Y1 where K denotes the number of users in a cell. In this scenario, a degrees of freedom outer bound as well as an achievable scheme that attains the degrees of freedom outer bound of the multicell multiple access channel (MAC) with constant channel coefficients are investigated. The users have M antennas,...
We tackle the problem of multistatic radar image formation by simultaneously exploiting the sparsity and covariance structure of radar images measured by a local GSM distribution of wavelet coefficients. Our aim is to gauge the extent to which such local statistical information can be leveraged in addition to the commonly used l1 sparsity constraint. Though we assume knowledge of the covariance structure...
Independent channel fading across different users in a wireless network enables the system to exploit multiuser diversity. In this paper, we investigate the impact of user scheduling on the instantaneous degrees of freedom of multiple interfering cellular networks. Particularly, we consider a homogeneous multiple cellular downlink scenario with multiple users per cell. We show that if the number of...
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