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

The development and operation of a dual-band time-domain radar system used to measure indoor multipath propagation characteristics in several office buildings and factories are described. The system operates at 1.3 GHz and 4.0 GHz and uses 4-ns RMS pulses to provide estimates of indoor radio channel impulse responses. The effects of antenna diversity, frequency scaling, and topography on indoor radio system design are quantified through analyses of measured propagation data. The data are used to develop and refine wideband channel models for multipath propagation in factories and open-plan office buildings and provide insight into the validity of geometric modeling techniques for predicting channel characteristics. >

Indoor wideband radio propagation measurement system at 1.3 GHz and 4.0 GHz

This paper presents a 3-D statistical channel model of the impulse response with small-scale spatially correlated random coefficients for multi-element transmitter and receiver antenna arrays, derived using the physically-based time cluster - spatial lobe (TCSL) clustering scheme. The small-scale properties of multipath amplitudes are modeled based on 28 GHz outdoor millimeter-wave small-scale local area channel measurements. The wideband channel capacity is evaluated by considering measurement-based Rician-distributed voltage amplitudes, and the spatial autocorrelation of multipath amplitudes for each pair of transmitter and receiver antenna elements. Results indicate that Rician channels may exhibit equal or possibly greater capacity compared to Rayleigh channels, depending on the number of antennas.

MIMO Channel Modeling and Capacity Analysis for 5G Millimeter-Wave Wireless Systems

Wireless Personal Communications: Emerging Technologies for Enhanced Communications presents a broad range of topics in wireless communications, including perspectives from both industry and academia. The book serves as a reflection of emerging technologies in wireless communications. Wireless Personal Communications: Emerging Technologies for Enhanced Communications is divided into six sections. The first five are devoted to the following topics: Smart Antennas and Diversity; Propagation; Interference Cancellation; Equalization; and Modulation, Coding and Networking. The contributions reflect current research thrusts as the wireless community strives to enhance the capabilities of wireless communications. The final section includes contributions on a variety of pertinent topics. Wireless Personal Communications: Emerging Technologies for Enhanced Communications serves as an excellent reference source and may be used as a text for advanced courses on the subject.

Wireless personal communications: emerging technologies for enhanced communications

The authors present novel site-specific propagation prediction methods for emerging personal communication system (PCS) services which will offer high capacity in urban settings. The propagation prediction models, composed of 3-D diffraction and ray tracing, are being implemented as software tools on SUN computer workstations. A geographical information system software package is being used to interface building and terrain data with the propagation prediction programs. Early work at Virginia Tech's Mobile and Portable Radio Research Group shows that the predicted signal strengths are within a few decibels of average measured signal strengths for some test cases. >

http://faculty.poly.edu/~tsr/wp-content/uploads/CV/ICP/1992-10-Site%20Specific%20Propagation%20Prediction%20Models%20for%20PCS%20Design%20and%20Installation.pdf

Site specific propagation prediction models for PCS design and installation

Indoor parasitic cellular systems reuse the same frequencies as outdoor cellular (macrocellular) systems to provide wireless communications inside a building or campus. This paper provides a simulation strategy to determine future channel availability that is possible between in-building and outdoor cellular systems that share the same radio spectrum. Capacity that is currently available inside an urban office building is first derived from field-strength measurements of all the channels in the macrocellular system made inside the building. We then create a simulation that determines the effect of a growing outdoor cellular system on in-building frequency reuse. Future in-building frequency reuse is predicted over a 6-yr timeline in 3-mo intervals and includes the effect of height above ground inside the building. Results show that indoor reuse is practical as long as interference levels of about -85 dBm can be tolerated from the outdoor macrocellular system.

http://www.faculty.poly.edu/~tsr/wp-content/uploads/CV/MTJ/1999-01-A%20simulation%20of%20cellular%20system%20growth%20and%20its%20effect%20on%20urban%20in-building%20parasitic%20frequency%20reuse.pdf

Theodore S. Rappaport

Papers

Indoor wideband radio propagation measurement system at 1.3 GHz and 4.0 GHz

MIMO Channel Modeling and Capacity Analysis for 5G Millimeter-Wave Wireless Systems

Wireless personal communications: emerging technologies for enhanced communications

Site specific propagation prediction models for PCS design and installation

A simulation of cellular system growth and its effect on urban in-building parasitic frequency reuse