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

This paper provides detailed analysis and simulation for exploring the impact of out-of-band emissions (OOBE) from adjacent wireless cellular services to receive-only digital mobile radio services. Based on an extensive analysis of interference from vehicles with mobile cellular users in realistic roadway conditions, we propose proper methods for determining out-of-band emission spectral masks that should be used in interference coordination in mobile to mobile interference conditions. Analysis for roadway and propagation conditions in various US cities resulted in the suggested interference protection masks. This work offers approaches that can be used to determine spectral masks to allow harmonious co-existence of mobile digital receivers with new cellular and fixed broadband mobile services that operate in adjacent spectrum bands.

Analysis and Simulation of Adjacent Service Interference to Vehicle-Equipped Digital Wireless Receivers from Cellular Mobile Terminals

160 meter transmission line antenna

A new approximation for the diffraction coefficient for dielectric wedges is presented using curve-fits based on the inverse problem theory It is shown that significant improvement over existing heuristic formulations can be obtained by polynomial curve-fitting of the multiplying factors in the UTD diffraction coefficients Although this solution is based on a parametric analysis for a right-angle dielectric wedge, it is conjectured to be extensible to geometries with arbitrary angles The construction of a UTD-like form for the diffraction coefficient is essentially a reasonable simplification of the exact solution in the sense that the most important terms in series expansions of the multiplying factors constitute the primary components of the diffraction coefficient Therefore, the proposed method potentially allows faster and more accurate propagation modeling Further work is required to see if this is a viable generic approach

http://www.faculty.poly.edu/~tsr/wp-content/uploads/CV/ICP/2004-06-A%20Parametric%20Formulation%20of%20the%20UTD%20Diffraction%20Coefficients%20for%20a%20Dielectric%20Wedge.pdf

A parametric formulation of the UTD diffraction coefficients for a dielectric wedge

Faculty from Virginia Tech and the University of Missouri-Rolla, with support from the NSF/CRCD program, are developing a three-course sequence in wireless communications. The third course in the sequence is devoted to the simulation of communication systems. The simulation course not only provides students with the knowledge required to effectively use simulation in the design and analysis process but also, through the use of projects, gives students needed experience in proposal preparation and in research management. A number of MATLAB-based examples, demonstrations and analysis programs are being developed as a part of this effort.

http://faculty.poly.edu/~tsr/wp-content/uploads/CV/ICP/1996-11-The%20Role%20of%20Simulation%20in%20the%20Teaching%20of%20Communications.pdf

Theodore S. Rappaport

Papers

Analysis and Simulation of Adjacent Service Interference to Vehicle-Equipped Digital Wireless Receivers from Cellular Mobile Terminals

160 meter transmission line antenna

A parametric formulation of the UTD diffraction coefficients for a dielectric wedge

The role of simulation in the teaching of communications

It's a wireless world