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Wireless Communications, IEEE

Issue 4 • Date August 2007

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Displaying Results 1 - 16 of 16
  • Front cover - IEEE Wireless Communications

    Page(s): c1
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    Freely Available from IEEE
  • Table of contents

    Page(s): 1
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    Freely Available from IEEE
  • Smart Radios [Message from the Editor-in-Chief]

    Page(s): 2 - 3
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    Freely Available from IEEE
  • Cognitive Wireless Networks {Guest Editorial}

    Page(s): 4 - 5
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    Freely Available from IEEE
  • Utilization of Location Information in Cognitive Wireless Networks

    Page(s): 6 - 13
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (353 KB) |  | HTML iconHTML  

    Location awareness is an essential characteristic of cognitive radios as well as networks. In this article a location awareness engine architecture is proposed for the realization of location awareness in cognitive radios and networks. The proposed architecture consists of location estimation and/or sensing, seamless positioning and interoperability, statistical learning and tracking, security and privacy, mobility management, and location-based applications. However, the focus of this article is on location-based applications where we demonstrate the utilization of location information in cognitive wireless networks by presenting some representative location-assisted network optimization applications such as location-assisted spectrum management, network planning and expansion, and handover. Our study unveils that location information can be used in cognitive wireless networks to optimize network performance. Possible solutions to the implementation issues are proposed, and the remaining open issues are also addressed. View full abstract»

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  • A Decision-Theoretic Framework for Opportunistic Spectrum Access

    Page(s): 14 - 20
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (178 KB) |  | HTML iconHTML  

    Built on a hierarchical access structure with primary and secondary users, opportunistic spectrum access improves spectrum efficiency while maintaining compatibility with legacy wireless systems. The basic idea is to allow secondary users to exploit instantaneous spectrum availability while limiting the interference to primary users. In this article, we identify basic components, fundamental trade-offs, and practical constraints in opportunistic spectrum access. We introduce a decision-theoretic framework based on the theory of partially observable Markov decision processes. This framework allows us to systematically tackle the optimal integrated design and quantitatively characterize the interaction between signal processing for opportunity identification and networking for opportunity exploitation. A discussion of open problems, potential applications, and recent developments is also provided. View full abstract»

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  • Teamwork and Collaboration in Cognitive Wireless Networks

    Page(s): 22 - 27
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (579 KB) |  | HTML iconHTML  

    This article looks at the principles and significant potential of teamwork in cognitive networks. These concepts represent a new evolutionary stage in the development of cognitive radio and cognitive networks, where wireless communication progresses from an individual, device-centric approach toward group and team behavior. This creates the potential for more effective and more robust communication solutions when deemed necessary. The key elements of effective cognitive network teamwork are introduced in this article. These include group formation, distributed co-ordination, goal and role identification, accountability, and reward mechanisms for the outcomes of team behavior. The value of the group as a whole can be increased rather than individual gain for only a single device. Focusing on an early experimental cognitive network teamwork testbed designed by CTVR, this article outlines the potential of developing cognitive networks that can work as a team. Potential applications and market opportunities for this technology also are described. View full abstract»

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  • Cognitive Radio: A Communications Engineering View

    Page(s): 28 - 33
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (142 KB) |  | HTML iconHTML  

    Cognitive radio is an emerging technology that enables the flexible development, construction, production, shipping, and deployment of highly adaptive radios that are built upon software defined radio technology. This contribution starts with a brief section that underlines the paramount importance of the mobile radio communications channel. Then, spectrum issues are discussed to emphasize the reasons for spectrum scarcity as well as the importance of dynamic spectrum allocation. Some remarks about the development of software defined radio from digital radio lead to a discussion of the most important engineering aspects of CR, for example, location and spectrum awareness, transmission power control, and signal analysis. Because usually papers about CR are somewhat visionary, we first describe practical steps to an implementation of helpful CR properties into a mobile communication base station, as well as user terminal equipment. The article concludes with a short summary. View full abstract»

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  • A Statistical Method for Reconfiguration of Cognitive Radios

    Page(s): 34 - 40
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (101 KB) |  | HTML iconHTML  

    Recent developments in computer technology have enabled radio developers to accomplish in software what traditionally was performed with application-specific integrated circuits. A radio that has the core of its functionality implemented in software is called a software-defined radio. When an SDR has the capability to sense, reason, and dynamically adapt to requirements and environmental change, we call this more capable device a cognitive radio. Many private and public agencies are investing in the promise of CR to improve the utilization of radio frequency spectrum. They envision devices that can sense frequency vacancies and dynamically reconfigure to utilize idle channels. The promise of CR depends on the capability of a radio to change operating frequencies, power, and/or modulation schemes (physical layer flexibility). In addition to this physical layer flexibility, there are a large number of opportunities to capitalize on the interplay of the CR physical layer configuration and other parameters in the radio network protocol stack. At the core of CR functionality is the ability to select from thousands of potential configurations to maximize performance-be it in terms of spectrum use, throughput, or reliability. In this article, we describe a method for selecting from a number of potential configurations to fulfill the communication requirements of a CR network. By using accepted statistical methods, we show how parameters at the physical, data link, network, and application layers interact to affect performance. We build upon this parametric insight with our presentation of a technique for predicting radio performance. View full abstract»

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  • Policy-Based Cognitive Radios

    Page(s): 41 - 46
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (92 KB) |  | HTML iconHTML  

    We present a new language for expressing policies that allow opportunistic spectrum access while not causing interference. CoRaL has expressive constructs for numerical constraints, supports efficient reasoning, and will be verifiable. The language is extensible so that unanticipated policy types can be encoded. We also describe a policy reasoner that reasons about CoRaL policies, and show how this reasoner can be used with various cognitive radios (in this case, an XG radio) to guarantee policy-specified behaviors while allowing spectrum sharing. View full abstract»

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  • Applications of Machine Learning to Cognitive Radio Networks

    Page(s): 47 - 52
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (207 KB) |  | HTML iconHTML  

    Cognitive radio offers the promise of intelligent radios that can learn from and adapt to their environment. To date, most cognitive radio research has focused on policy-based radios that are hard-coded with a list of rules on how the radio should behave in certain scenarios. Some work has been done on radios with learning engines tailored for very specific applications. This article describes a concrete model for a generic cognitive radio to utilize a learning engine. The goal is to incorporate the results of the learning engine into a predicate calculus-based reasoning engine so that radios can remember lessons learned in the past and act quickly in the future. We also investigate the differences between reasoning and learning, and the fundamentals of when a particular application requires learning, and when simple reasoning is sufficient. The basic architecture is consistent with cognitive engines seen in AI research. The focus of this article is not to propose new machine learning algorithms, but rather to formalize their application to cognitive radio and develop a framework from within which they can be useful. We describe how our generic cognitive engine can tackle problems such as capacity maximization and dynamic spectrum access. View full abstract»

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  • Mobile Host-Based intrusion Detection and Attack Identification

    Page(s): 53 - 60
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    Although much attention has focused on optimizing power in batteries for mobile devices, little attention to date has focused on battery constraints to determine if an attack is present. This research proposes that resident monitoring of the demands placed on a battery's current (mA) and other system processes can be used as an early-warning, trip-wire-like sensor for mobile hosts as a means to block attacks as well as to identify them. View full abstract»

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  • Adaptive Coding and Modulation for the DVB-S2 Standard Interactive Applications: Capacity Assessment and Key System Issues

    Page(s): 61 - 69
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (739 KB) |  | HTML iconHTML  

    Point-to-point multibeam satellite systems based on the DVB-S standard are currently designed for link closure in the worst-case propagation and location conditions. The DVB-S standard, conceived for broadcasting applications, considers a fixed coding rate and modulation format that are selected according to the assumed coverage and availability requirements. This approach implies the occurrence of high margins in the majority of the cases, when interference and propagation conditions allow for higher signal-to-noise-plus-interference ratio. The adaptive coding and modulation (ACM) introduction in the new DVB-S2 standard for the interactive service profile opens up a number of appealing opportunities for the design and development of satellite broadband networks. In this article we show how the ACM introduction in the satellite downlink enables greatly enhanced system performance but also has a profound impact on the way the system and some of the key system components are designed. View full abstract»

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  • Short-Range Wireless Communications for Next-Generation Networks: UWB, 60 GHz Millimeter-Wave WPAN, And ZigBee

    Page(s): 70 - 78
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB) |  | HTML iconHTML  

    This article presents standardization, regulation, and development issues associated with short-range wireless technologies for next-generation personal area networks (PAN). Ultra-wideband (UWB) and 60 GHz millimeter-wave communication technologies promise unprecedented short-range broadband wireless communication and are the harbingers of multigigabit wireless networks. Despite the huge potential for PAN, standardization and global spectrum regulations challenge the success of UWB. On the other hand, ZigBeetrade is expected to be a crucial short-range technology for low throughput and ultra low-power consumption networks. The current status and direction of future development of UWB, emerging 60 GHz millimeter-wave PAN, and low data rate ZigBee are described. This article also addresses wireless MAC protocol issues of 60 GHz multigigabit PAN. View full abstract»

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  • Wireless Mesh Networks: Current Challenges and Future Directions of Web-In-The-Sky

    Page(s): 79 - 89
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (201 KB) |  | HTML iconHTML  

    Within the short span of a decade, Wi-Fi hotspots have revolutionized Internet service provisioning. With the increasing popularity and rising demand for more public Wi-Fi hotspots, network service providers are facing a daunting task. Wi-Fi hotspots typically require extensive wired infrastructure to access the backhaul network, which is often expensive and time consuming to provide in such situations. wireless mesh networks (WMNs) offer an easy and economical alternative for providing broadband wireless Internet connectivity and could be called the web-in-the-sky. In place of an underlying wired backbone, a WMN forms a wireless backhaul network, thus obviating the need for extensive cabling. They are based on multihop communication paradigms that dynamically form a connected network. However, multihop wireless communication is severely plagued by many limitations such as low throughput and limited capacity. In this article we point out key challenges that are impeding the rapid progress of this upcoming technology. We systematically examine each layer of the network and discuss the feasibility of some state-of-the-art technologies/protocols for adequately addressing these challenges. We also provide broader and deeper insight to many other issues that are of paramount importance for the successful deployment and wider acceptance of WMNs. View full abstract»

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  • Wireless sensor networks with energy harvesting technologies: a game-theoretic approach to optimal energy management

    Page(s): 90 - 96
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (134 KB) |  | HTML iconHTML  

    Energy harvesting technologies are required for autonomous sensor networks for which using a power source from a fixed utility or manual battery recharging is infeasible. An energy harvesting device (e.g., a solar cell) converts different forms of environmental energy into electricity to be supplied to a sensor node. However, since it can produce energy only at a limited rate, energy saving mechanisms play an important role to reduce energy consumption in a sensor node. In this article we present an overview of the different energy harvesting technologies and the energy saving mechanisms for wireless sensor networks. The related research issues on energy efficiency for sensor networks using energy harvesting technology are then discussed. To this end, we present an optimal energy management policy for a solar-powered sensor node that uses a sleep and wakeup strategy for energy conservation. The problem of determining the sleep and wakeup probabilities is formulated as a bargaining game. The Nash equilibrium is used as the solution of this game. View full abstract»

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Aims & Scope

IEEE Wireless Communications Magazine deals with all technical and policy issues related to personalization, location-independent communications in all media.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Hsiao-Hwa Chen
Cheng Kung University, Taiwan