Showing papers on "Wireless published in 2002"

An application-specific protocol architecture for wireless microsensor networks

Abstract: 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.

An energy-efficient MAC protocol for wireless sensor networks

Abstract: This paper proposes S-MAC, a medium-access control (MAC) protocol designed for wireless sensor networks Wireless sensor networks use battery-operated computing and sensing devices A network of these devices will collaborate for a common application such as environmental monitoring We expect sensor networks to be deployed in an ad hoc fashion, with individual nodes remaining largely inactive for long periods of time, but then becoming suddenly active when something is detected These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 80211 in almost every way: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important S-MAC uses three novel techniques to reduce energy consumption and support self-configuration To reduce energy consumption in listening to an idle channel, nodes periodically sleep Neighboring nodes form virtual clusters to auto-synchronize on sleep schedules Inspired by PAMAS, S-MAC also sets the radio to sleep during transmissions of other nodes Unlike PAMAS, it only uses in-channel signaling Finally, S-MAC applies message passing to reduce contention latency for sensor-network applications that require store-and-forward processing as data move through the network We evaluate our implementation of S-MAC over a sample sensor node, the Mote, developed at University of California, Berkeley The experiment results show that, on a source node, an 80211-like MAC consumes 2-6 times more energy than S-MAC for traffic load with messages sent every 1-10 s

Fine-grained network time synchronization using reference broadcasts

Abstract: Recent advances in miniaturization and low-cost, low-power design have led to active research in large-scale networks of small, wireless, low-power sensors and actuators. Time synchronization is critical in sensor networks for diverse purposes including sensor data fusion, coordinated actuation, and power-efficient duty cycling. Though the clock accuracy and precision requirements are often stricter than in traditional distributed systems, strict energy constraints limit the resources available to meet these goals.We present Reference-Broadcast Synchronization, a scheme in which nodes send reference beacons to their neighbors using physical-layer broadcasts. A reference broadcast does not contain an explicit timestamp; instead, receivers use its arrival time as a point of reference for comparing their clocks. In this paper, we use measurements from two wireless implementations to show that removing the sender's nondeterminism from the critical path in this way produces high-precision clock agreement (1.85 ± 1.28μsec, using off-the-shelf 802.11 wireless Ethernet), while using minimal energy. We also describe a novel algorithm that uses this same broadcast property to federate clocks across broadcast domains with a slow decay in precision (3.68 ± 2.57μsec after 4 hops). RBS can be used without external references, forming a precise relative timescale, or can maintain microsecond-level synchronization to an external timescale such as UTC. We show a significant improvement over the Network Time Protocol (NTP) under similar conditions.

Space-Time Codes for High Data Rate Wireless Communications

Abstract: Space-time codes (STC) are a class of signaling techniques, offering coding and diversity gains along with improved spectral efficiency. These codes exploit both the spatial and the temporal diversity of the wireless link by combining the design of the error correction code, modulation scheme and array processing. STC are well suited for improving the downlink performance, which is the bottleneck in asymmetric applications such as downstream Internet. Three original contributions to the area of STC are presented in this dissertation. First, the development of analytic tools that determine the fundamental limits on the performance of STC in a variety of channel conditions. For trellis-type STC, transfer function based techniques are applied to derive performance bounds over Rayleigh, Rician and correlated fading environments. For block-type STC, an analytic framework that supports various complex orthogonal designs with arbitrary signal cardinalities and array configurations is developed. In the second part of the dissertation, the Virginia Tech Space-Time Advanced Radio (VT-STAR) is designed, introducing a multi-antenna hardware laboratory test bed, which facilitates characterization of the multiple-input multiple-output (MIMO) channel and validation of various space-time approaches. In the third part of the dissertation, two novel space-time architectures paired with iterative processing principles are proposed. The first scheme extends the suitability of STC to outdoor wireless communications by employing iterative equalization/decoding for time dispersive channels and the second scheme employs iterative interference cancellation/decoding to solve the error propagation problem of Bell-Labs Layered Space-Time Architecture (BLAST). Results show that remarkable energy and spectral efficiencies are achievable by combining concepts drawn from space-time coding, multiuser detection, array processing and iterative decoding.

Energy-efficient computing for wildlife tracking: design tradeoffs and early experiences with ZebraNet

Abstract: Over the past decade, mobile computing and wireless communication have become increasingly important drivers of many new computing applications. The field of wireless sensor networks particularly focuses on applications involving autonomous use of compute, sensing, and wireless communication devices for both scientific and commercial purposes. This paper examines the research decisions and design tradeoffs that arise when applying wireless peer-to-peer networking techniques in a mobile sensor network designed to support wildlife tracking for biology research.The ZebraNet system includes custom tracking collars (nodes) carried by animals under study across a large, wild area; the collars operate as a peer-to-peer network to deliver logged data back to researchers. The collars include global positioning system (GPS), Flash memory, wireless transceivers, and a small CPU; essentially each node is a small, wireless computing device. Since there is no cellular service or broadcast communication covering the region where animals are studied, ad hoc, peer-to-peer routing is needed. Although numerous ad hoc protocols exist, additional challenges arise because the researchers themselves are mobile and thus there is no fixed base station towards which to aim data. Overall, our goal is to use the least energy, storage, and other resources necessary to maintain a reliable system with a very high `data homing' success rate. We plan to deploy a 30-node ZebraNet system at the Mpala Research Centre in central Kenya. More broadly, we believe that the domain-centric protocols and energy tradeoffs presented here for ZebraNet will have general applicability in other wireless and sensor applications.

Efficient power control via pricing in wireless data networks

Abstract: A major challenge in the operation of wireless communications systems is the efficient use of radio resources. One important component of radio resource management is power control, which has been studied extensively in the context of voice communications. With the increasing demand for wireless data services, it is necessary to establish power control algorithms for information sources other than voice. We present a power control solution for wireless data in the analytical setting of a game theoretic framework. In this context, the quality of service (QoS) a wireless terminal receives is referred to as the utility and distributed power control is a noncooperative power control game where users maximize their utility. The outcome of the game results in a Nash (1951) equilibrium that is inefficient. We introduce pricing of transmit powers in order to obtain Pareto improvement of the noncooperative power control game, i.e., to obtain improvements in user utilities relative to the case with no pricing. Specifically, we consider a pricing function that is a linear function of the transmit power. The simplicity of the pricing function allows a distributed implementation where the price can be broadcast by the base station to all the terminals. We see that pricing is especially helpful in a heavily loaded system.

Exploiting the 60 GHz band for local wireless multimedia access: prospects and future directions

Abstract: This article addresses basic issues regarding the design and development of wireless access and wireless LAN systems that will operate in the 60 GHz band as part of the fourth-generation (4G) system. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space (5 GHz) has been allocated worldwide for dense wireless local communications. The article gives an overview of 60 GHz channel characteristics and puts them in their true perspective. In addition, we discuss how to achieve the exploitation of the abundant bandwidth resource for all kinds of short-range communications. The main tenor is that an overall system architecture should be worked out that provides industry with plenty of scope for product differentiation. This architecture should feature affordability, scalability, modularity, extendibility, and interoperability. In addition, user convenience and easy and efficient network deployment are important prerequisites for market success. This article discusses these features and indicates a number of key research topics.

On the minimum node degree and connectivity of a wireless multihop network

Abstract: This paper investigates two fundamental characteristics of a wireless multi -hop network: its minimum node degree and its k--connectivity Both topology attributes depend on the spatial distribution of the nodes and their transmission range Using typical modeling assumptions :--- :a random uniform distribution of the nodes and a simple link model :--- :we derive an analytical expression that enables the determination of the required range r0 that creates, for a given node density ρ, an almost surely k--connected network Equivalently, if the maximum r0 of the nodes is given, we can find out how many nodes are needed to cover a certain area with a k--connected network We also investigate these questions by various simulations and thereby verify our analytical expressions Finally, the impact of mobility is discussedThe results of this paper are of practical value for researchers in this area, eg, if they set the parameters in a network--level simulation of a mobile ad hoc network or if they design a wireless sensor network

The bits and flops of the n-hop multilateration primitive for node localization problems

Abstract: The recent advances in MEMS, embedded systems and wireless communication technologies are making the realization and deployment of networked wireless microsensors a tangible task. Vital to the success of wireless microsensor networks is the ability of microsensors to ``collectively perform sensing and computation''. In this paper, we study one of the fundamental challenges in sensor networks, node localization. The collaborative multilateration presented here, enables ad-hoc deployed sensor nodes to accurately estimate their locations by using known beacon locations that are several hops away and distance measurements to neighboring nodes. To prevent error accumulation in the network, node locations are computed by setting up and solving a global non-linear optimization problem. The solution is presented in two computation models, centralized and a fully distributed approximation of the centralized model. Our simulation results show that using the fully distributed model, resource constrained sensor nodes can collectively solve a large non-linear optimization problem that none of the nodes can solve individually. This approach results in significant savings in computation and communication, that allows fine-grained localization to run on a low cost sensor node we have developed.

Joint scheduling and power control for wireless ad-hoc networks

Abstract: In this paper we introduce power control as a solution to the multiple access problem in contention-based wireless ad-hoc networks. The motivation for this study is two fold, limiting multi-user interference to increase single-hop throughput, and reducing power consumption to increase battery life. We focus on next neighbor transmissions where nodes are required to send information packets to their respective receivers subject to a constraint on the signal-to-interference-and-noise ratio. The multiple access problem is solved via two alternating phases, namely scheduling and power control. The scheduling algorithm is essential to coordinate the transmissions of independent users in order to eliminate strong interference (e.g. self-interference) that can not be overcome by power control. On the other hand, power control is executed in a distributed fashion to determine the admissible power vector, if one exists, that can be used by the scheduled users to satisfy their single-hop transmission requirements. This is done for two types of networks, namely TDMA and TDMA/CDMA wireless ad-hoc networks.

Multifunctional world wide walkie talkie, a tri-frequency cellular-satellite wireless instant messenger computer and network for establishing global wireless volp quality of service (qos) communications, unified messaging, and video conferencing via the internet

Abstract: World-Wide-Walkie-Talkie, a high speed multifunction interstellar wireless computer/instant messenger communicator, Personal Digital Assistant (PDA), coupled with a resilient, robust, VoIP data network and internet server method, deploying multiple wireless networks and protocols such as Voice Over IP, GPRS, WAP, Bluetooth, PCS, I-Mode, comprising a high speed Intel Pentium 4 Mobile™ or compatible Processor, to formulate a internet gateway system ( 99 ) and network bridge ( 150 ) for establishing instant low cost, real time global communications to the Public Switched Telephone Network via the internet ( 54 ). A PUSH-TO-TALK-WORLDWIDE button ( 21 ) instantly initiates global bisynchronous communications, or videoconferencing sessions. Fax, VideoMail, and unified messaging services are immediately available. GPS and mass memory provides global navigational tracking and data storage. Internet users, telephones, and cellular/satellite phone users can intercommunicate with the invention via VoIP/IM services. The invention provides uniformed global wireless communications, eliminates traditional long distance costs, and operates anywhere on earth.

Introduction to Wireless and Mobile Systems

Abstract: Learn how wireless systems work, how mobility is supported, what the underlying infrastructure is and what interactions are needed among different functional components with INTRODUCTION TO WIRELESS AND MOBILE SYSTEMS, 4e. Focusing on qualitative descriptions and the realistic explanations of relationships between wireless systems and performance parameters, this user-friendly book helps you learn this exciting technology through relevant examples, such as understanding how a cell phone starts working as soon as they get out of an airplane.

GloMoSim: A Scalable Network Simulation Environment

Abstract: Large-scale hybrid networks that include wireless, wired, and satellite based communications are becoming common in both military and commercial situations. This paper describes a scalable simulation environment called GloMoSim (for Global Mobile Information System Simulator) that effectively utilizes parallel execution to reduce the simulation time of detailed high-fidelity models of large communication networks. The paper also presents a set of case studies that evaluate the performance of large wireless networks with thousands of nodes and compares the impact of different lower layer protocols on the performance of typical applications.

Goodput analysis and link adaptation for IEEE 802.11a wireless LANs

Abstract: Link adaptation to dynamically select the data transmission rate at a given time has been recognized as an effective way to improve the goodput performance of the IEEE 802.11 wireless local-area networks (WLANs). Recently, with the introduction of the new high-speed 802.11a physical layer (PHY), it is even more important to have a well-designed link adaptation scheme work with the 802.11a PHY such that its multiple transmission rates can be exploited. In this paper, we first present a generic method to analyze the goodput performance of an 802.11a system under the distributed coordination function (DCF) and express the expected effective goodput as a closed-form function of the data payload length, the frame retry count, the wireless channel condition, and the selected data transmission rate. Then, based on the theoretical analysis, we propose a novel MPDU (MAC protocol data unit)-based link adaptation scheme for the 802.11a systems. It is a simple table-driven approach and the basic idea is to preestablish a best PHY mode table by applying the dynamic programming technique. The best PHY mode table is indexed by the system status triplet that consists of the data payload length, the wireless channel condition, and the frame retry count. At runtime, a wireless station determines the most appropriate PHY mode for the next transmission attempt by a simple table lookup, using the most up-to-date system status as the index. Our in-depth simulation shows that the proposed MPDU-based link adaptation scheme outperforms the single-mode schemes and the autorate fallback (ARF) scheme-which is used in Lucent Technologies' WaveLAN-II networking devices-significantly in terms of the average goodput, the frame drop rate, and the average number of transmission attempts per data frame delivery.

Home networking with IEEE 802.15.4: a developing standard for low-rate wireless personal area networks

Abstract: This article presents the IEEE 802.15.4 draft standard and its home networking applications. The main features of the standard are network flexibility, low cost, and low power consumption; the standard is suitable for many applications in the home requiring low-data-rate communications in an ad hoc self-organizing network.

RAP: a real-time communication architecture for large-scale wireless sensor networks

Abstract: Large-scale wireless sensor networks represent a new generation of real-time embedded systems with significantly different communication constraints from traditional networked systems. This paper presents RAP, a new real-time communication architecture for large-scale sensor networks. RAP provides convenient, high-level query and event services for distributed micro-sensing applications. Novel location-addressed communication models are supported by a scalable and light-weight network stack. We present and evaluate a new packet scheduling policy called velocity monotonic scheduling that inherently accounts for both time and distance constraints. We show that this policy is particularly suitable for communication scheduling in sensor networks in which a large number of wireless devices are seamlessly integrated into a physical space to perform real-time monitoring and control. Detailed simulations of representative sensor network environments demonstrate that RAP significantly reduces the end-to-end deadline miss ratio in the sensor network.

Characterizing user behavior and network performance in a public wireless LAN

Abstract: This paper presents and analyzes user behavior and network performance in a public-area wireless network using a workload captured at a well-attended ACM conference. The goals of our study are: (1) to extend our understanding of wireless user behavior and wireless network performance; (2) to characterize wireless users in terms of a parameterized model for use with analytic and simulation studies involving wireless LAN traffic; and (3) to apply our workload analysis results to issues in wireless network deployment, such as capacity planning, and potential network optimizations, such as algorithms for load balancing across multiple access points (APs) in a wireless network.

Communication and proximity authorization systems

Abstract: A proximity service unit for providing at least one predetermined service for use with multiple types of wireless devices. The proximity service unit includes a multiple channel wireless transceiver, a proximity unit validation assembly, and a legacy activation unit. The multiple channel wireless transceiver receives at least two signal types, such as infrared region signals, 900 MHz region signals, 1.8 GHz region signals, and 2.4 GHz region signals. The multiple channel wireless transceiver receives a request authorization code from each of a plurality of respective wireless devices such that the plurality of wireless devices communicate simultaneously with the multiple channel wireless transceiver without air time. The proximity unit validation assembly communicates with the multiple channel wireless transceiver and receives and validates the plurality of request authorization codes received by the multiple channel wireless transceiver. The legacy activation unit receives a service authorization code and provides at least one predetermined service for each wireless device providing the request authorization code resulting in a service authorization code.

Adaptive modulation and MIMO coding for broadband wireless data networks

Abstract: Link adaptation techniques, where the modulation, coding rate, and/or other signal transmission parameters are dynamically adapted to the changing channel conditions, have emerged as powerful tools for increasing the data rate and spectral efficiency of wireless data-centric networks. While there has been significant progress on understanding the theoretical aspects of time adaptation in LA protocols, new challenges surface when dynamic transmission techniques are employed in broadband wireless networks with multiple signaling dimensions. Those additional dimensions are mainly frequency, especially in multicarrier systems, and space in multiple-antenna systems, particularly multiarray multiple-input multiple-output communication systems. We give an overview of the challenges and promises of link adaptation in future broadband wireless networks. We suggest guidelines to help in the design of robust, complexity/cost-effective algorithms for these future wireless networks.

Robotics-based location sensing using wireless ethernet

Abstract: A key subproblem in the construction of location-aware systems is the determination of the position of a mobile device. This paper describes the design, implementation and analysis of a system for determining position inside a building from measured RF signal strengths of packets on an IEEE 802.11b wireless Ethernet network. Previous approaches to location awareness with RF signals have been severely hampered by non-linearity, noise and complex correlations due to multi-path effects, interference and absorption. The design of our system begins with the observation that determining position from complex, noisy and non-linear signals is a well-studied problem in the field of robotics. Using only off-the-shelf hardware, we achieve robust position estimation to within a meter in our experimental context and after adequate training of our system. We can also coarsely determine our orientation and can track our position as we move. By applying recent advances in probabilistic inference of position and sensor fusion from noisy signals, we show that the RF emissions from base stations as measured by off-the-shelf wireless Ethernet cards are sufficiently rich in information to permit a mobile device to reliably track its location.

Method and system for distributing content over a wireless communications system

Abstract: A method for providing informational content to a user of a communications device being wirelessly communicatively coupled to a communications network, the method including: identifying information associated with the user and indicative of user attributes; selecting a plurality of candidate messages using the identified information; pseudo-randomly selecting at least one of the plurality of candidate messages as selected content; and, delivering the selected content to the communications device using the wireless communications network.

Radio Over Fiber Technologies for Mobile Communications Networks

Abstract: Basic Microwave Properties of Optical Links - Insertion Loss and Noise Figure Concepts. A Brief Summary. Direct-Modulated Optical Links. Optical Links of External Intensity Modulation. Heterodyning Microwave/Millimeter Wave Optical Links. Low Cost Optical Fiber Links for Remote Antenna Feeding - Introduction. Requirements for Remote Antenna Feeding Links. Comparison Between Coax and Fiber-Optic Remote Antenna Feeding Links. Laser and Photodiode Nonlinearities and Their Influence on Link Performance. Laser Diode Noise and Its Influence on Link Performance. Low Cost Fiber-Optic Links. Fiber and Multicarrier Effects. Linearization of Fiber-Optic Links. Low Cost Laser Diode Driver and Photoreceiver Design for Fiber-Optic Remote Antenna Feeding Links. Extended Low Cost Fiber-Optic Link Concepts and Applications. Sub-Carrier Optical Fiber Transmission Systems: Fiber-Optic Transmission of Microwave Signals - Fiber-Optic Transmission of Microwave 64-QAM Signals. 256-QAM Sub-Carrier Transmission Using Coding. Laser Nonlinearity Compensation for SCM Applications. Radio Over Fiber Systems for Mobile Applications - Introduction. Coverage Problems. Competing Solutions. Advantages of Radio Over Fiber. Current Technologies. Emerging Technologies. Economic Aspects. Evolution to 3G. Conclusions. Fiber-Optic Radio Networking/Radio Highway Networks/Software Radio NW - Introduction. Various Types of Radio Highway. FDMA. TDMA. CDMA. Chirp Multiple Access (CMA). WCDMA Radio Over Fiber For Mobile Microcellular Communication Networks - WCDMA Computer Simulation Model. Evaluation of the Impact of Spreading Bandwidth. Using The Simulation Approach to Investigate Handover Algorithm performance. The Feasibility of Using Similar Macrodiversity-Combining Technique in the Uplink of ROF Microcellular Systems. Theoretical and Simulation Analysis of Power Control Performance for WCDMA ROF Microcellular Systems. Radio Over Fiber: Current Applications and Future Potential Advantages and Challenges for a Powerful Technology - ROF in the World. Market Acceptance and Competitive Analysis. Third Generation Technological Challenge. Industrial Possibility for ROF and Wireless Infrastructure Convergence. Commercial Advantages Associated With ROF. ROF Multiple Services Communication Systems - Road-to-Vehicle Communications. Wireless Local Loop Systems. Potential for Future Communication Systems. Conclusion.

Turbo-BLAST for wireless communications: theory and experiments

Abstract: Turbo-BLAST is a novel multitransmit multireceive (MTMR) antenna scheme for high-throughput wireless communications. It exploits the following ideas: the Bell Labs layered space time (BLAST) architecture; random layered space-time (RLST) coding scheme by using independent block codes and random space-time interleaving; sub-optimal turbo-like receiver that performs iterative decoding of the RLST codes and estimation of the channel matrix in an iterative and, most important, simple fashion. The net result is a new transceiver that is not only computationally efficient compared with the optimal maximum likelihood decoder, but it also yields a probability of error performance that is orders of magnitude smaller than traditional BLAST schemes for the same operating conditions. This paper also presents experimental results using real-life indoor channel measurements demonstrating the high-spectral efficiency of turbo-BLAST.

Measurements of a wireless link in an industrial environment using an IEEE 802.11-compliant physical layer

Abstract: The design and simulation of coding schemes, medium access control (MAC), and link-layer protocols for future industrial wireless local area networks can be supported by some understanding of the statistical properties of the bit error patterns delivered by a wireless link (which is an ensemble of transmitter, channel, receiver, modems). The authors present results of bit error measurements taken with an IEEE 802.11-compliant radio modem in an industrial environment. In addition to reporting the most important results, they draw some conclusions for the design of MAC and link-layer protocols. Furthermore, they show that the popular Gilbert/Elliot model and a modified version of it are a useful tool for simulating bit errors on a wireless link, despite their simplicity and failure to match certain measured statistics.

SWAN: service differentiation in stateless wireless ad hoc networks

Abstract: We propose SWAN, a stateless network model which uses distributed control algorithms to deliver service differentiation in mobile wireless ad hoc networks in a simple, scalable and robust manner. We use rate control for UDP and TCP best-effort traffic, and sender-based admission control for UDP real-time traffic. SWAN uses explicit congestion notification (ECN) to dynamically regulate admitted real-time traffic in the face of network dynamics brought on by mobility or traffic overload conditions. We use the term "soft" real-time services to indicate that real-time sessions could be regulated or dropped due to mobility or excessive traffic overloading at mobile wireless routers. SWAN is designed to limit such conditions, however. A novel aspect of SWAN is that it does not require the support of a QOS-capable MAC. Rather, soft real-time services are built using existing best effort wireless MAC technology. Simulation, analysis, and results from an experimental wireless testbed show that real-time applications experience low and stable delays under various multi-hop, traffic and mobility conditions. The wireless testbed and ns-2 simulator source code are available from the Web (comet.columbia.edu/swan).

Space-Time Wireless Channels

Abstract: A practical, "first-principles" approach to space-time wireless channel design. A practical approach to space-time wireless channel design Integrates essential principles from communications, electromagnetics, and random process theory Includes detailed coverage of diversity, multipath applications, and antenna array design Contains extensive examples, illustrations, and problem setsNext-generation broadband radio systems must deliver unprecedented performance and higher data rates, while coping with increased spectral congestion. To achieve these goals, engineers need an in-depth understanding of radio channels that fade in time, frequency, and space. In Space-Time Wireless Channels, leading researcher Gregory D. Durgin presents a pragmatic, first-principles approach that integrates crucial concepts and techniques from communications, electromagnetics, and random process theory.Durgin focuses on comprehension and practicality, offering extensive examples, illustrations, and problem sets, while avoiding gratuitious mathematics and moving most derivations to end-of-chapter appendices. Coverage includes: Fundamentals of space, time, and frequency transmission and random process theory Electromagnetic description of space-time channels and the physics of small-scale fading First- and second-order statistics of fading channels Angle spectrum concepts and applications, including vector/scalar space and multipath shape factors Antenna diversity, temporal diversity, and bit error rates Multipath channels: separation, signaling, block coding, and antenna array design Appendices list special functions, Fourier transform examples, and random process theory concepts, as well as all relevant mathematical symbols, conventions, and acronyms.

Models and solution techniques for frequency assignment problems

Abstract: Wireless communication is used in many different situations such as mobile telephony, radio and TV broadcasting, satellite communication, wireless LANs, and military operations. In each of these situations a frequency assignment problem arises with application specific characteristics. Researchers have developed different modeling ideas for each of the features of the problem, such as the handling of interference among radio signals, the availability of frequencies, and the optimization criterion.

Electrical power metering system

Abstract: A wireless electrical power metering system is provided. A processor having a multichannel power line transceiver, a wireless transceiver, and a power meter attached thereto measures power consumption information on a power line inductively coupled with the power meter. The processor converts the power consumption information into IP-based data, and transmits same over the wireless transceiver. The information can be wirelessly received by a remote monitoring station or transmitted across the Internet for storage, analysis, and billing. The processor generates appliance control signals and generates same across the multichannel power line transceiver to remotely control appliances in response to power consumption trends. The processor provides firewall capabilities, and relays information between a wired or wireless network and a power line network, thereby expanding the size of existing household networks. Further, the processor allows multiple dwellings to be networked using power lines, and households to be connected to the Internet via a power line network.