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

Curriculum innovation for simulation and design of wireless communications systems

This paper provides novel analysis methods and detailed simulations for determining the impact of out-of-band emissions (OOBE) of adjacent band wireless services on mobile receive-only wireless services. Using the interference from the adjacent cellular bands on an operational digital wireless receive-only system as an example, we demonstrate the impact of the interference from adjacent cellular band transmitters and determine the performance impact such as outage on satellite receivers in realistic roadway conditions. This paper presents new methods for determining appropriate OOBE spectral masks for use by new cellular subscriber transmitters. This paper considers realistic propagation and traffic conditions in five cities throughout the United States and offers approaches that the engineering community may use to determine interference conditions between new cellular and fixed broadband mobile services in adjacent spectrum bands to existing receive-only mobile receiver systems, such as satellite radio.

Analysis and Simulation of Interference to Vehicle-Equipped Digital Receivers From Cellular Mobile Terminals Operating in Adjacent Frequencies

Spatial division multiple access (SDMA) is recognized as a promising technique for improving capacity in future cellular systems, by exploiting the spatial filtering capability of adaptive antennas. In SDMA systems, in-cell users can share the same channel, making the channel allocation strategy play an important role in the system performance. In this paper, we analyze by simulation different strategies for channel allocation in cellular systems employing adaptive antennas and SDMA technique. Results show that high performance in SDMA systems is achieved by balancing channel reuse among cells with channel reuse within cells. Attempts to maximize channel reuse within cells may increase excessively cochannel interference, limiting capacity. Results also show that, while carried traffic is not severely affected by high level of user mobility, other performance parameters, such as the number of channel reassignment requests, are strongly affected by user mobility.

http://www.faculty.poly.edu/~tsr/wp-content/uploads/CV/ICP/2001-10-Channel%20Allocation%20In%20SDMA%20Cellular%20Systems.pdf

Channel allocation in SDMA cellular systems

This paper presents the performance of space-time block coding based transmit diversity (STTD) in WCDMA on correlated fading channels and on unbalanced transmitted power. Then, based on the performance, transmitter location optimization in indoor environments is considered. Results indicate that the effective diversity order is retained even when high cross correlation exists and power imbalance exists between signals from different antennas. Also, a global optimization algorithm with the help of a ray tracer can find transmitter locations which are optimal (global optimum) in the sense of power coverage or overall BER in the area of interest.

/pdf/wcdma-sttd-performance-analysis-with-transmitter-location-453pg758hy.pdf

WCDMA STTD performance analysis with transmitter location optimization in indoor systems using ray-tracing technique

This paper presents a 3-dimensional millimeterwave statistical channel impulse response model from 28 GHz and 73 GHz ultrawideband propagation measurements [1], [2] . An accurate 3GPP-like channel model that supports arbitrary carrier frequency, RF bandwidth, and antenna beamwidth (for both omnidirectional and arbitrary directional antennas), is provided. Time cluster and spatial lobe model parameters ar e extracted from empirical distributions from field measurements. A step-by-step modeling procedure for generating channel coefficients is shown to agree with statistics from the field measurements, thus confirming that the statistical channel model faithfully recreates spatial and temporal channel impulse responses for use in millimeter-wave 5G air interface desig ns.

Theodore S. Rappaport

Papers

Curriculum innovation for simulation and design of wireless communications systems

Analysis and Simulation of Interference to Vehicle-Equipped Digital Receivers From Cellular Mobile Terminals Operating in Adjacent Frequencies

Channel allocation in SDMA cellular systems

WCDMA STTD performance analysis with transmitter location optimization in indoor systems using ray-tracing technique

3-D Statistical Channel Model for Millimeter-Wave Outdoor Communications.