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Showing papers in "IEEE Communications Surveys and Tutorials in 2007"


Journal ArticleDOI
TL;DR: Techniques are described for efficiently estimating and compensating for the effects of a communication channel in a multi-carrier wireless communication system using the fact that the transmitted symbols are drawn from a finite-alphabet to efficiently estimate the propagation channel.
Abstract: Techniques are described for efficiently estimating and compensating for the effects of a communication channel in a multi-carrier wireless communication system. The techniques exploit the fact that the transmitted symbols are drawn from a finite-alphabet to efficiently estimate the propagation channel for multi-carrier communication systems, such systems using OFDM modulation. A transmitter transmits data through a communication channel according to the modulation format. A receiver includes a demodulator to demodulate the data and an estimator to estimate the channel based on the demodulated data. The channel estimator applies a power-law operation to the demodulated data to identify the channel. The techniques can be used in both blind and semi-blind modes of channel estimation.

604 citations


Journal ArticleDOI
TL;DR: A survey of the existing techniques for creating covert channels in widely deployed network and application protocols and an overview of common methods for their detection, elimination, and capacity limitation, required to improve security in future computer networks are given.
Abstract: Covert channels are used for the secret transfer of information. Encryption only protects communication from being decoded by unauthorised parties, whereas covert channels aim to hide the very existence of the communication. Initially, covert channels were identified as a security threat on monolithic systems i.e. mainframes. More recently focus has shifted towards covert channels in computer network protocols. The huge amount of data and vast number of different protocols in the Internet seems ideal as a high-bandwidth vehicle for covert communication. This article is a survey of the existing techniques for creating covert channels in widely deployed network and application protocols. We also give an overview of common methods for their detection, elimination, and capacity limitation, required to improve security in future computer networks.

543 citations


Journal ArticleDOI
TL;DR: This document offers an up-to-date survey of most major contributions to the pool of QoS routing solutions for MANETs published in the period 1997¿2006, including a thorough overview ofQoS routing metrics, resources, and factors affecting performance and classify the protocols found in the literature.
Abstract: In mobile ad hoc networks (MANETs), the provision of quality of service (QoS) guarantees is much more challenging than in wireline networks, mainly due to node mobility, multihop communications, contention for channel access, and a lack of central coordination. QoS guarantees are required by most multimedia and other time- or error-sensitive applications. The difficulties in the provision of such guarantees have limited the usefulness of MANETs. However, in the last decade, much research attention has focused on providing QoS assurances in MANET protocols. The QoS routing protocol is an integral part of any QoS solution since its function is to ascertain which nodes, if any, are able to serve applications? requirements. Consequently, it also plays a crucial role in data session admission control. This document offers an up-to-date survey of most major contributions to the pool of QoS routing solutions for MANETs published in the period 1997?2006. We include a thorough overview of QoS routing metrics, resources, and factors affecting performance and classify the protocols found in the literature. We also summarize their operation and describe their interactions with the medium access control (MAC) protocol, where applicable. This provides the reader with insight into their differences and allows us to highlight trends in protocol design and identify areas for future research.

308 citations


Journal ArticleDOI
TL;DR: This article aims to provide researchers in the field with an understanding of ALM protocols by identifying significant characteristics, from both application requirements and networking points of view, and by using those characteristics as a basis for organizing the protocols into an integrated and well-structured format.
Abstract: In light of the slow deployment of IP Multicast technology on the global Internet and the explosive popularity of peer-to-peer (P2P) file-sharing applications, there has been a flurry of research activities investigating the feasibility of implementing multicasting capability at the application layer, referred to as Application Layer Multicasting (ALM), and numerous algorithms and protocols have been proposed. This article aims to provide researchers in the field with an understanding of ALM protocols by identifying significant characteristics, from both application requirements and networking points of view, and by using those characteristics as a basis for organizing the protocols into an integrated and well-structured format. Current trends and directions for further research are also presented. This article surveys the literature over the period 1995?2005 on different application layer multicasting approaches.

293 citations


Journal ArticleDOI
TL;DR: This survey attempts to provide an overview of the issues as well as the solutions proposed in recent literature at overcoming the deficiencies of energy consumption of the sensor nodes, guaranteeing the sensor network's existence and increasing the sensors network's lifetime in such energy-constrained environments through more power control schemes regarding resource allocation, routing and low-energy consumption.
Abstract: ith the proliferation in sensor nodes and the development in wireless communication technologies, Wireless Sensor Networks (WSNs) have gained worldwide attention in recent years. They facilitate monitoring and controlling of physical environments from remote locations with great accuracy and represent a significant improvement over wired sensor networks. WSNs are employed in a vast variety of fields, such as: environmental monitoring (e.g., temperature, humidity), monitoring disaster areas providing relief, file exchange, conferencing, home, health (monitoring patients and assisting disabled patients), commercial applications including managing inventory and monitoring product quality and military purposes. Their function is to collect and disseminate critical data, while their position does need to be engineered or predetermined, in contrast to the wired ones. This allows random deployment in inaccessible terrains or disaster relief operations. On the other hand, this also means that WSN protocols and algorithms must possess self-organizing capabilities [1]. Realization of the wireless sensor network applications requires wireless ad-hoc networking techniques. Although a great number of protocols and algorithms have been proposed for wireless ad-hoc networks, they are not well-suited to the unique features and application requirements of WSNs for the following reasons: • The topology of a WSN changes very frequently. • The number of sensor nodes in a WSN can be several orders of magnitude higher than the number of sensor nodes in a wireless ad-hoc network. • Sensor nodes are densely deployed in a sensor field • Sensor nodes mainly use a broadcast communication paradigm, whereas most wireless ad-hoc networks are based on point-to-point communications. • Sensor nodes may not have global identification due to their large amount of overhead and large number of sensors in the WSN. • Sensor nodes are limited in power, computational capacity and memory. This last requirement is the primary limitation of the WSNs. Their survivability, as it has already been mentioned, depends on power control and power management of the consumed energy, as well as on network connectivity. Considerable research has been focused at overcoming the deficiencies of energy consumption of the sensor nodes, guaranteeing the sensor network's existence and increasing the sensor network's lifetime in such energy-constrained environments through more power control schemes regarding resource allocation, routing and low-energy consumption. This survey attempts to provide an overview of these issues as well as the solutions proposed in recent literature. ABSTRACT A Wireless Sensor Network (WSN) is actually composed of a large number of very small …

292 citations


Journal ArticleDOI
TL;DR: An overview of the void problem is presented and the currently available void-handling techniques (as of July 2006) for geographic routing are surveyed, each designed with a different approach.
Abstract: Communications voids, where geographic greedy forwarding fails to move a packet further towards its destination, are an important issue for geographic routing in wireless networks. This article presents an overview of the void problem and surveys the currently available void-handling techniques (as of July 2006) for geographic routing. In the survey, we classify these void-handling techniques into six categories, each designed with a different approach, that is, planar-graph-based, geometric, flooding-based, costbased, heuristic, and hybrid. For each category, we present its basic principle and illustrate some classic techniques as well as the latest advances. We also provide a qualitative comparison of these techniques and discuss some possible directions of future research.

233 citations


Journal ArticleDOI
TL;DR: In this survey, past and current mechanisms for discovering the internet topology at various levels are discussed: the IP interface, the router, the AS, and the PoP level, and insights are provided into some of the wellknown properties of the internetTopology.
Abstract: Since the beginning of the nineties, the internet has undergone impressive growth. This growth can be appreciated in terms of the equipment, such as routers and links, that has been added, as well as in the numbers of users and the value of commerce that it supports. In parallel to this expansion, over the past decade the networking research community has shown a growing interest in discovering and analyzing the internet topology. Some researchers have developed tools for gathering network topology data while others have tried to understand and model the internet?s properties. These efforts have brought us to a crucial juncture for toplogy measurement infrastructures: while, previously, these were both small (in terms of number of measurement points) and monolithic, we are starting to see the deployment of large-scale distributed systems composed of hundreds or thousands of monitors. As we look forward to this next generation of systems, we take stock of what has been achieved so far. In this survey, we discuss past and current mechanisms for discovering the internet topology at various levels: the IP interface, the router, the AS, and the PoP level. In addition to discovery techniques, we provide insights into some of the wellknown properties of the internet topology.

195 citations


Journal ArticleDOI
TL;DR: The thesis addresses dependability differentiation in connection-oriented backbone communication networks with a proposal of using adaptive management to increase compliance with interval availability guarantees and a classification scheme for how to approach differentiation is proposed.
Abstract: Unintentional failures affect links and nodes in communication networks. Recovery mechanisms are the key tool for achieving the dependability required by the services using the network. However, high dependability in communication networks comes at a high cost in terms of the capacity needed by these mechanisms.The traffic from all services and users is carried by the same backbone network. Since the users and services have different requirements, and users have different willingness to pay for a high quality of service, it is desirable to have methods that enable provision of different levels of dependability in the same network, i.e. dependability differentiation. The thesis addresses dependability differentiation in connection-oriented backbone communication networks. Two methods to provide connections meeting differentiated guarantees on the asymptotic availability are proposed.The first of these uses a novel flexible arrangement for dedicated protection denoted a protection pattern. The protection pattern is used in a proposed distributed connection management system. The system is compared with alternative proposals based on centralized management and shows good performance. The second proposal uses shared protection, which may potentially use less resources in terms of bandwidth, but has higher complexity than dedicated protection. The proposed system is based on rules to control the sharing to enable provision of guarantees. Simulation results show that the proposed method performs significantly better than an alternative strategy based on dedicated protection.A different approach to availability-guaranteed services is to offer guarantees on the interval availability which is a measure commonly used Service Level Agreements (SLAs). The thesis contains a proposal of using adaptive management to increase compliance with interval availability guarantees. Different adaptive management policies are proposed and compared to alternative static provisioning policies in a case study. The thesis also addresses the problem of measuring dependability by simulation. To reduce the simulation effort needed to obtain precise estimates of dependability attributes, a rare-event simulation technique has been applied to the well-known Network Simulator 2 (NS2). The results show that the technique is applicable to this types of simulation scenario, but the gain is modest. The thesis also contains a broad literature survey of dependability differentiation research. This is the first survey of the topic. Hence, it is in itself a significant contribution. A classification scheme for how to approach differentiation is proposed and a critical evaluation of the state of art is given.This thesis contributes to fill in some of the ``gaps'' identified, but there are still significant challenges ahead before differentiation may be deployed in operational networks.

156 citations


Journal ArticleDOI
TL;DR: A fast-handoff framework is introduced which adaptively meets different application requirements via a cross-layer approach and important design considerations for mobility support in future IEEE 802.11 networks are suggested.
Abstract: With the advance of wireless local area network (WLAN) technology, handoff support has become one of the most important issues in IEEE 802.11 WLANs. However, the current IEEE 802.11 specification does not provide the fast handoff required for real-time multimedia applications. To support fast handoff in IEEE 802.11 networks, a number of fast-handoff schemes have been proposed in the literature. In this article we review these fast-handoff schemes and analyze their advantages and disadvantages qualitatively. After that, important design considerations for mobility support in future IEEE 802.11 networks are suggested. Also, we introduce a fast-handoff framework which adaptively meets different application requirements via a cross-layer approach.

149 citations




Journal ArticleDOI
TL;DR: A survey of solutions for integrating MANETs with the Internet, with the intent of serving as a quick reference to current research proposals for Internet connectivity for mobile ad hoc networks based on IP mobility protocols.
Abstract: A mobile ad hoc network (MANET) is an infrastructureless, autonomous, and standalone network. A MANET can be flexibly and simply deployed in almost any environment, but it has limited wireless coverage and its connectivity is limited to the MANET boundary. The growth of the Internet and its services and applications ? and the trend in the fourth generation (4G) wireless networks toward All-IP networks ? have led to an increasing demand for enabling MANET nodes to connect to the Internet and use its services and applications. Mobile IP and IP micromobility protocols enable a mobile node to access the Internet and change its access point without losing the connection. The mobile node should be in the coverage range of the access point and should have a direct connection to it. So, with the cooperation between MANET routing protocols and the IP mobility protocol, Internet connectivity to MANET nodes can be achieved. Many solutions have been proposed to enable MANETs to connect to the Internet using IP mobility protocols. This article presents a survey of solutions for integrating MANETs with the Internet, with the intent of serving as a quick reference to current research proposals for Internet connectivity for mobile ad hoc networks based on IP mobility protocols. A qualitative comparison of the routing solutions for integration is presented. The limitations of these integration solutions are also investigated. A framework for integrating the Cellular IP access network and MANETs is introduced. This survey concludes with further points for investigation.

Journal ArticleDOI
TL;DR: A comparison is conducted based on a set of well-defined criteria, leading to a selection of few approaches that can serve as the guide in designing a global service discovery system for large-scale and multi-technology networks.
Abstract: With the increasing need for networked applications and distributed resource sharing, there is a strong incentive for an open large-scale service infrastructure operating over multidomain and multi-technology networks. Service discovery, as an essential support function of such an infrastructure, is a crucial current research challenge. Although a few survey papers have been published on this subject, our contribution focuses on comparing and analyzing key discovery approaches in the context of large-scale and multidomain networks. The comparison is conducted based on a set of well-defined criteria, leading to a selection of few approaches that can serve as the guide in designing a global service discovery system for large-scale and multi-technology networks.

Journal ArticleDOI
TL;DR: A comprehensive survey of the literature in dynamic traffic grooming is presented, indicating some essential further directions of research in this emerging topic.
Abstract: Traffic grooming refers to the techniques used to aggregate subwavelength traffic onto high speed lightpaths, while at the same time minimizing some measure of network cost, usually optoelectronic equipment cost. In the last few years, traffic grooming has come to be recognized as an important research area, and has produced extensive literature. Recently, the dynamic traffic grooming problem, where traffic carried in the network varies with the time, has gained in interest. This is because of the growing applicability of QoS concerns and associated network design methodologies in networks closer to the indivdual users than backbone networks, where the traffic cannot be well modeled as essentially static. A number of studies in this area have recently appeared in the literature, but there is as yet no good resource that introduces a reader to the problem in all its forms, and provides a review of the literature. In this paper, we fill this void by presenting a comprehensive survey of the literature in this emerging topic, and indicating some essential further directions of research in dynamic traffic grooming.

Journal ArticleDOI
TL;DR: This work attempts to clarify the central themes of the area, namely communication system performance at the low SNR regime and the issue the degrees of freedom of a communication channel.
Abstract: This survey presents the information theory of wideband communication systems, a research area that became active in the last decade following technological and regulatory advances. This work attempts to clarify the central themes of the area, namely communication system performance at the low SNR regime and the issue the degrees of freedom of a communication channel.


Journal ArticleDOI
TL;DR: Various types of potential network structure targeted attacks are elaborated, starting from simple passive monitoring, to masquerading and theft of service (ToS), presenting a complete and detailed image of security threats in EPONs.
Abstract: We discuss in detail all major security-related issues inherently present in PON systems. Ethernet PON (EPON) type networks have very specific requirements for data- and system-level security, due to combining - for the first time using Ethernet links ? residential and business customers with different security awareness levels and protection demands. Various types of potential network structure targeted attacks are elaborated, starting from simple passive monitoring, through flavors of denial of service (DoS), towards masquerading and theft of service (ToS), presenting a complete and detailed image of security threats in EPONs. Authentication and security mechanisms, as well as their shortcomings, are also briefly examined.

Journal ArticleDOI
Steven Wright1
TL;DR: This tutorial takes an ontological perspective within which to categorize admission control schemes, and industrystandard architectures are used to illustrate some of the key concepts.
Abstract: Admission Control (AC) has long been considered as a key mechanism to support Quality of Service objectives in networks. There is a significant base of literature in the area of admission control algorithms, but not all of these algorithms are directly comparable in terms of inputs, outputs or objectives. Current theory does not well describe the when, where, and how to best apply AC in designing network and service infrastructure for multi-service IP networks. This tutorial takes an ontological perspective within which to categorize admission control schemes. Industrystandard architectures (both core and access networks) are used to illustrate some of the key concepts. Two tables are provided to summarize the different approaches for categorization of admission control schemes.

Journal ArticleDOI
TL;DR: This article analyses and compares the prominent methods proposed so far that optimize the secure handoff process in terms of delay and are suitable for uninterruptible secure multimedia service delivery.
Abstract: In the very near future, we shall witness the coexistence of networks with heterogeneous link layer technologies. Such networks will naturally overlap each other and mobile users will need to frequently handoff among them for a number of reasons, including the quest for higher speeds and/or lower cost. Handoffs between such hybrid networks should be fast enough to support demanding applications, like multimedia content delivery, but also secure enough since different network providers are involved. This gets even more complicated considering that network providers may not simultaneously be multimedia service providers as it is the case today. In order to support security operations in a large scale the employment of an AAA protocol is mandated; however, this adds more delay to the handoff process. This article analyses and compares the prominent methods proposed so far that optimize the secure handoff process in terms of delay and are suitable for uninterruptible secure multimedia service delivery.

Journal ArticleDOI
TL;DR: A unified pricing scheme is proposed which attempts to encompass the various design issues into a single comprehensive framework that can potentially lead to a scalable, differentiated-services wireless network architecture for the future.
Abstract: Unlike the bandwidth in a wired network, radio spectrum is a significantly scarce resource. This resource needs to be efficiently shared and reused by a number of users who may be simultaneously accessing a variety of mobile services. Thus, careful planning and management of the radio spectrum is required to maximize its value across all users and all accessed services. The evolving need for supporting differentiated services for novel multimedia applications in the wireless network adds a new dimension to this complex problem. Network researchers and architects are investigating the use of pricing to efficiently handle many of the corresponding network design and management issues. In this paper, we make two important contributions on this topic. First, we review the existing body of literature that attempts to utilize pricing in the design of next-generation wireless networks. Specifically, we classify the existing works into three categories: (a) pricing-based resource provisioning; (b) pricing-based static planning; and (c) pricing-based adaptive resource management. Second, we propose a unified pricing scheme which attempts to encompass the various design issues into a single comprehensive framework that can potentially lead to a scalable, differentiated-services wireless network architecture for the future.