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

GSM quickly is emerging as the leading cellular radio standard throughout the world. With the advent of new personal communications frequencies irt the 1.8 2 GHz band, GSM and its PCS offshoot, DCS, may be implemented in North America within the next 12 months to 18 months. This tutorial is part of an independent learning program prepared by the authors for the IEEE. This material is taught as part of an introductory course on wireless communications at Virginia Tech and will be included in the textbook Wireless Communications: Principles a.;,d Practice published by Prentice-Hall. Global System for Mobile Communications Global system for mobile communications (GSM) is a second-generation cellular system standard that was developed to solve the fragm~ntation problems of the first cellular systems in Europe [Mou92]. Unlike the U.S. cellular carriers which implemented the firstgeneration analog mobile phone system (AMPS) throughout the country, the first-genera. tion cellular service providers in Europe took a provincial view of cellular. Before GSM, European countries used different cellular standards throughout the continent, and it was not possible for a customer to use a single mobile phone' throughout Europe. After five years and hundreds of person-years of engineering, the European community developed an amazingly·robust and complex cellular standard that was first to specify digital modulation and network level architectures and service. GSM originally was developed to serve just the pan-European cellular market and promised a wide range of network services through the use of integrated services digital network (ISDN). However, during the past two years, GSM's success has exceeded the expectations of virtually everyone, and it is now the world's most popular standard for new cellular radio and personal communications equipment throughout the world. It is predicted that by the year 2000, there will be between 20 million and 50 million GSM subscribers worldwide ·[Mou92], [Dec93]. The task of specifying a common mobile communication system for Europe in the 900 MHz band was taken up by the GSM (Groupe special mobile) committee, which was a working gl-oup of the Conference of Europe6ene Pastes des et Te6le6communication (CEPT). The setting of standards for GSM is currently under the aegis of the European Technical Standards Institute (ETSI). GSM first was introduced into the European market in 1991. By the end of 1993, several non-European countries in South America, Asia and Australia had adopted GSM and the technically equivalent offshoot, DCS 1800, which supports personal communication services (PCS) in the 1.8-2.0 GHz radio bands recently created by governments throughout the world. GSM Services, Features GSM services follow ISDN guidelines and are classified as either teleservices or data services. Teleservices include standard mobile telephony and mobileaoriginated or baseoriginated traffic. Data services include computer-to-computer communication and packet-

A tutorial on global system for mobile communications (GSM)

An automated method for quickly generating a complete bill of materials and total cost information in real time. Components for a desired system are specified and/or replaced by substitute components, while continuously predicting the wireless system performance. A design engineer builds a model of the desired wireless communications system and specifies each component necessary to provide sufficient or optimal system performance. A parts list is maintained, in real time, that contains a definition of each system component and its associated performance and cost parameters. As the user changes wireless system designs through a series of "what-if" scenarios, components are replaced with substitute components, cable lengths are modified, antenna systems and base station parameters are re-designed and moved to alternate locations, etc. The bill of materials is automatically updated and component costs and total system costs are immediately available to the design engineer. The designer may choose to swap components for less expensive components or may investigate several alternate radio frequency distribution and antenna schemes, etc. The performance characteristics of the system are automatically updated as is the system cost as the designer to assesses the trade-offs between performance and cost at the same time.

Method and system for site specific communication network design and analysis

Textliche und graphische abgrenzung des orts und interpretation von messungen

Verfahren und system zur automatisierten auswahl des optimalen kommunikationsnetzgerätemodells, der position und konfiguration in 3d

Communications at mm-wave frequencies and above rely heavily on beamforming antenna arrays. Typically, hundreds, if not thousands, of independent antenna channels are used to achieve high SNR for throughput and increased capacity. Using a dedicated ADC per antenna receiver is preferable but it’s not practical for very large arrays due to unreasonable cost and complexity. Frequency division multiplexing (FDM) is a well-known technique for combining multiple signals into a single wideband channel. In a first of its kind measurements, this paper explores FDM for combining multiple antenna outputs at IF into a single wideband signal that can be sampled and digitized using a high-speed wideband ADC. The sampled signals are sub-band filtered and digitally down-converted to obtain individual antenna channels. A prototype receiver was realized with a uniform linear array consisting of 4 elements with 250 MHz bandwidth per channel at 28 GHz carrier frequency. Each of the receiver chains were frequency-multiplexed at an intermediate frequency of 1 GHz to avoid the requirement for multiple, precise local oscillators (LOs). Combined narrowband receiver outputs were sampled using a single ADC with digital front-end operating on a Xilinx ZCU-1285 RF SoC FPGA to synthesize 4 digital beams. The approach allows $M$ -fold increase in spatial degrees of freedom per ADC, for temporal oversampling by a factor of $M$ .

Theodore S. Rappaport

Papers

A tutorial on global system for mobile communications (GSM)

Method and system for site specific communication network design and analysis

Textliche und graphische abgrenzung des orts und interpretation von messungen

Verfahren und system zur automatisierten auswahl des optimalen kommunikationsnetzgerätemodells, der position und konfiguration in 3d

Frequency-Multiplexed Array Digitization for MIMO Receivers: 4-Antennas/ADC at 28 GHz on Xilinx ZCU-1285 RF SoC