There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

http://www.eecs.ucf.edu/~dcm/Teaching/COT4810-Spring2011/Literature/SensorNetworksSurvey.pdf

Wireless sensor networks: a survey

We develop and analyze low-complexity cooperative diversity protocols that combat fading induced by multipath propagation in wireless networks. The underlying techniques exploit space diversity available through cooperating terminals' relaying signals for one another. We outline several strategies employed by the cooperating radios, including fixed relaying schemes such as amplify-and-forward and decode-and-forward, selection relaying schemes that adapt based upon channel measurements between the cooperating terminals, and incremental relaying schemes that adapt based upon limited feedback from the destination terminal. We develop performance characterizations in terms of outage events and associated outage probabilities, which measure robustness of the transmissions to fading, focusing on the high signal-to-noise ratio (SNR) regime. Except for fixed decode-and-forward, all of our cooperative diversity protocols are efficient in the sense that they achieve full diversity (i.e., second-order diversity in the case of two terminals), and, moreover, are close to optimum (within 1.5 dB) in certain regimes. Thus, using distributed antennas, we can provide the powerful benefits of space diversity without need for physical arrays, though at a loss of spectral efficiency due to half-duplex operation and possibly at the cost of additional receive hardware. Applicable to any wireless setting, including cellular or ad hoc networks-wherever space constraints preclude the use of physical arrays-the performance characterizations reveal that large power or energy savings result from the use of these protocols.

Cooperative diversity in wireless networks: Efficient protocols and outage behavior

Cognitive radio is viewed as a novel approach for improving the utilization of a precious natural resource: the radio electromagnetic spectrum. The cognitive radio, built on a software-defined radio, is defined as an intelligent wireless communication system that is aware of its environment and uses the methodology of understanding-by-building to learn from the environment and adapt to statistical variations in the input stimuli, with two primary objectives in mind: /spl middot/ highly reliable communication whenever and wherever needed; /spl middot/ efficient utilization of the radio spectrum. Following the discussion of interference temperature as a new metric for the quantification and management of interference, the paper addresses three fundamental cognitive tasks. 1) Radio-scene analysis. 2) Channel-state estimation and predictive modeling. 3) Transmit-power control and dynamic spectrum management. This work also discusses the emergent behavior of cognitive radio.

/pdf/cognitive-radio-brain-empowered-wireless-communications-9m6gu0vz1z.pdf

Cognitive radio: brain-empowered wireless communications

Networking together hundreds or thousands of cheap microsensor nodes allows users to accurately monitor a remote environment by intelligently combining the data from the individual nodes. These networks require robust wireless communication protocols that are energy efficient and provide low latency. We develop and analyze low-energy adaptive clustering hierarchy (LEACH), a protocol architecture for microsensor networks that combines the ideas of energy-efficient cluster-based routing and media access together with application-specific data aggregation to achieve good performance in terms of system lifetime, latency, and application-perceived quality. LEACH includes a new, distributed cluster formation technique that enables self-organization of large numbers of nodes, algorithms for adapting clusters and rotating cluster head positions to evenly distribute the energy load among all the nodes, and techniques to enable distributed signal processing to save communication resources. Our results show that LEACH can improve system lifetime by an order of magnitude compared with general-purpose multihop approaches.

/pdf/an-application-specific-protocol-architecture-for-wireless-1s7y9fiv40.pdf

An application-specific protocol architecture for wireless microsensor networks

A software channel simulator for UHF indoor radio channels in open-plan buildings is introduced. The simulator is based on wideband statistical models of individual multipath component amplitudes and delays. The simulator creates closely spaced channel impulse responses for both line-of-sight (LOS) and obstructed (OBS) topographies. The effects of transmitter-receiver (T-R) distance and the correlation of individual multipath component amplitudes over time and space are incorporated in the simulation. the simulator has been extended to yield narrowband fading over small distances by synthesizing the phases of multipath components. Multipath power delay profiles, RMS delay spread distributions, and narrowband fading distributions produced by the simulator accurately portray typical radio channels in a variety of open-plan building environments. >

Simulation of UHF indoor radio channels for open-plan building environments

Exemplary embodiments include a communication system comprising a portal between radio-frequency propagation environments; one or more of interface points disposed in the plurality of propagation environment and configured to communicate with each other via the portal; and one or more access points disposed in one of the propagation environments, at least a portion being configured to communicate with a particular interface point. Other embodiments include apparatus for communicating across radio-frequency propagation environments comprising at least one antenna array, a computer arrangement, and a non-transitory, computer-readable medium comprising computer-executable instructions that configure an adaptive antenna array to receive expected signals from a device or system disposed in a first propagation environment and to reject interfering signals originating in the same environment; and transmit the received expected signals to a compatible apparatus in a second propagation environment via a portal that is relatively permeable with respect to a particular frequency.

System, device, and method for high-frequency millimeter-wave wireless communication using interface points

Millimeter-wave (mmWave) and Terahertz (THz) will be used in the sixth-generation (6G) wireless systems, especially for indoor scenarios. This paper presents an indoor three-dimensional (3-D) statistical channel model for mmWave and sub-THz frequencies, which is developed from extensive channel propagation measurements conducted in an office building at 28 GHz and 140 GHz in 2014 and 2019. Over 15,000 power delay profiles (PDPs) were recorded to study channel statistics such as the number of time clusters, cluster delays, and cluster powers. All the parameters required in the channel generation procedure are derived from empirical measurement data for 28 GHz and 140 GHz line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios. The channel model is validated by showing that the simulated root mean square (RMS) delay spread and RMS angular spread yield good agreements with measured values. An indoor channel simulation software is built upon the popular NYUSIM outdoor channel simulator, which can generate realistic channel impulse response, PDP, and power angular spectrum.

3-D Statistical Indoor Channel Model for Millimeter-Wave and Sub-Terahertz Bands

Wireless Personal Communications: Channel Modeling and Systems Engineering presents a broad range of topics in wireless communications, including perspectives from both industry and academia. This book serves as a reflection of emerging technologies in wireless communications and features papers from world-renowned authors on the subject. Wireless Personal Communications: Channel Modeling and Systems Engineering is divided into six sections. The first five of these cover the following topics: Propagation and Channel Modeling (4 papers); Antennas (6 papers); Multiuser Detection (3 papers); Radio Systems and Technology (4 papers); and Wireless Data (3 papers). The last section contains invited papers on areas of significant interest. Wireless Personal Communications: Channel Modeling and Systems Engineering serves as an excellent reference source and may be used as a text for advanced courses on the subject. It is an essential tool for graduate students, postgraduate researchers, academics, and anyone working in the research aspect of the wireless communications industry.

Wireless Personal Communications: Channel Modeling and Systems Engineering

Joint communication and sensing allows the utilization of common spectral resources for communication and localization, reducing the cost of deployment. By using fifth generation (5G) New Radio (NR) (i.e., the 3rd Generation Partnership Project Radio Access Network for 5G) reference signals, conventionally used for communication, this paper shows sub-meter precision localization is possible at millimeter wave frequencies. We derive the geometric dilution of precision of a bistatic radar configuration, a theoretical metric that characterizes how the target location estimation error varies as a function of the bistatic geometry and measurement errors. We develop a 5G NR compliant software test bench to characterize the measurement errors when estimating the time difference of arrival and angle of arrival with 5G NR waveforms. The test bench is further utilized to demonstrate the accuracy of target localization and velocity estimation in several indoor and outdoor bistatic and multistatic configurations and to show that on average, the bistatic configuration can achieve a location accuracy of 10.0 cm over a bistatic range of 25 m, which can be further improved by deploying a multistatic radar configuration.

Theodore S. Rappaport

Papers

Simulation of UHF indoor radio channels for open-plan building environments

System, device, and method for high-frequency millimeter-wave wireless communication using interface points

3-D Statistical Indoor Channel Model for Millimeter-Wave and Sub-Terahertz Bands

Wireless Personal Communications: Channel Modeling and Systems Engineering

Target Localization using Bistatic and Multistatic Radar with 5G NR Waveform