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 authors have evaluated the performance of the mobile-to-base link of a cellular code-division multiple access (CDMA) system. The analysis incorporates the effects of flat Rayleigh fading, and it is found, for example, that using a rate 1/2 block code and a processing gain of 511 allows somewhere between 80 and 150 simultaneously active users at a decoded bit error rate (BER) of 10/sup -3/. The lower number arises from a propagation exponent of two, and the higher number results when the exponent is four. These numbers, of course, will roughly double when voice activity effects are included. >

Analysis of the mobile-to-base link in cellular CDMA

Cellular Digital Packet Data (CDPD) is a new wireless packet data communication system which was developed by a consortium of US cellular service providers to augment cellular voice communications. CDPD provides wireless packet data connectivity to mobile data communications customers. This paper presents an introduction to CDPD networks, various hardware interface challenges, and a software approach to implementing the (83,47) Reed-Solomon error correction code.

http://faculty.poly.edu/~tsr/wp-content/uploads/CV/ICP/1996-10-Cellular%20Digital%20Packet%20Data%20(CDPD)%20Equipment-%20%20Some%20Practical%20Design%20Issues.pdf

Cellular Digital Packet Data (CDPD) equipment: some practical design issues

Sixth generation (6G) cellular systems are expected to extend the operational range to sub-Terahertz (THz) frequencies between 100 and 300 GHz due to the broad unexploited spectrum therein. A proper channel model is needed to accurately describe spatial and temporal channel characteristics and faithfully create channel impulse responses at sub-THz frequencies. This paper studies the channel spatial statistics such as the number of spatial clusters and cluster power distribution based on recent radio propagation measurements conducted at 142 GHz in an urban microcell (UMi) scenario. For the 28 measured locations, we observe one to four spatial clusters at most locations. A detailed spatial statistical multiple input multiple output (MIMO) channel generation procedure is introduced based on the derived empirical channel statistics. We find that beamforming provides better spectral efficiency than spatial multiplexing in the LOS scenario due to the boresight path, and two spatial streams usually offer the highest spectral efficiency at most NLOS locations due to the limited number of spatial clusters.

Sub-Terahertz Spatial Statistical MIMO Channel Model for Urban Microcells at 142 GHz.

This paper provides detailed analysis and simulation for explol'ing the impact of out-of-band emissions (OOBE) of adjacent wireless services to the Sirius XM digital satellite radio service. 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 by new WCS cellular subscriber transmitters. in the 2.3 GHz band. Analysis for roadway and propagation conditions in various US cities resulted in the suggested masks. This work presents the first simulation of its ldnd and offers approaches that federal regulators may use to determine spectral masks that allow harmonious co-existence of existing mobile radio listeners with new cellular and fixed broadband mobile services in adjacent spectrum bands.

http://faculty.poly.edu/~tsr/wp-content/uploads/CV/ICP/2010-09-Analysis%20and%20Simulation%20of%20Adjacent%20Service%20Interference%20to%20Vehicle-Equipped%20Satellite%20Digital%20Radio%20Receivers%20From%20Cellular%20Mobile%20Terminals.pdf

Theodore S. Rappaport

Papers

Analysis of the mobile-to-base link in cellular CDMA

Cellular Digital Packet Data (CDPD) equipment: some practical design issues

Sub-Terahertz Spatial Statistical MIMO Channel Model for Urban Microcells at 142 GHz.

Analysis and Simulation of Adjacent Service Interference to Vehicle-Equipped Satellite Digital Radio Receivers From Cellular Mobile Terminals

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