Showing papers in "IEEE Communications Surveys and Tutorials in 2009"
TL;DR: In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented and the cooperative sensing concept and its various forms are explained.
Abstract: The spectrum sensing problem has gained new aspects with cognitive radio and opportunistic spectrum access concepts. It is one of the most challenging issues in cognitive radio systems. In this paper, a survey of spectrum sensing methodologies for cognitive radio is presented. Various aspects of spectrum sensing problem are studied from a cognitive radio perspective and multi-dimensional spectrum sensing concept is introduced. Challenges associated with spectrum sensing are given and enabling spectrum sensing methods are reviewed. The paper explains the cooperative sensing concept and its various forms. External sensing algorithms and other alternative sensing methods are discussed. Furthermore, statistical modeling of network traffic and utilization of these models for prediction of primary user behavior is studied. Finally, sensing features of some current wireless standards are given.
4,812 citations
TL;DR: A comprehensive survey of numerous IPSs, which include both commercial products and research-oriented solutions are given, and the trade-offs among these systems are outlined from the viewpoint of a user in a PN.
Abstract: Recently, indoor positioning systems (IPSs) have been designed to provide location information of persons and devices. The position information enables location-based protocols for user applications. Personal networks (PNs) are designed to meet the users' needs and interconnect users' devices equipped with different communications technologies in various places to form one network. Location-aware services need to be developed in PNs to offer flexible and adaptive personal services and improve the quality of lives. This paper gives a comprehensive survey of numerous IPSs, which include both commercial products and research-oriented solutions. Evaluation criteria are proposed for assessing these systems, namely security and privacy, cost, performance, robustness, complexity, user preferences, commercial availability, and limitations.We compare the existing IPSs and outline the trade-offs among these systems from the viewpoint of a user in a PN.
1,538 citations
TL;DR: This paper aims to give a comprehensive review of different TOA-based localization algorithms and their technical challenges, and to point out possible future research directions.
Abstract: Localization of a wireless device using the time-of-arrivals (TOAs) from different base stations has been studied extensively in the literature. Numerous localization algorithms with different accuracies, computational complexities, a-priori knowledge requirements, and different levels of robustness against non-line-of-sight (NLOS) bias effects also have been reported. However, to our best knowledge, a detailed unified survey of different localization and NLOS mitigation algorithms is not available in the literature. This paper aims to give a comprehensive review of these different TOA-based localization algorithms and their technical challenges, and to point out possible future research directions. Firstly, fundamental lower bounds and some practical estimators that achieve close to these bounds are summarized for line-of-sight (LOS) scenarios. Then, after giving the fundamental lower bounds for NLOS systems, different NLOS mitigation techniques are classified and summarized. Simulation results are also provided in order to compare the performance of various techniques. Finally, a table that summarizes the key characteristics of the investigated techniques is provided to conclude the paper.
989 citations
TL;DR: An overview and taxonomy of a large range of mobility models available for vehicular ad hoc networks is proposed to provide readers with a guideline to easily understand and objectively compare the different models, and eventually identify the one required for their needs.
Abstract: Vehicular Ad-hoc Networks (VANETs) have been recently attracting an increasing attention from both research and industry communities. One of the challenges posed by the study of VANETs is the definition of a vehicular mobility model providing an accurate and realistic vehicular mobility description at both macroscopic and microscopic levels. Another challenge is to be able to dynamically alter this vehicular mobility as a consequence of the vehicular communication protocols. Many mobility models have been developed by the community in order to solve these two issues. However, due to the large number of available models claiming to be adapted to vehicular traffic, and also due to their different and somehow incomparable features, understanding their true characteristics, their degree of realism with respect to vehicular mobility, and real capabilities is a hard task. In this survey, we first introduce a framework that proposes a guideline for the generation of vehicular mobility models. Then, we illustrate the different approaches chosen by the community for the development of vehicular mobility models and their interactions with network simulators. Finally, we propose an overview and taxonomy of a large range of mobility models available for vehicular ad hoc networks. The objective is to provide readers with a guideline to easily understand and objectively compare the different models, and eventually identify the one required for their needs.
759 citations
TL;DR: This paper identifies the threats and vulnerabilities to WSNs and summarize the defense methods based on the networking protocol layer analysis first, and gives a holistic overview of security issues.
Abstract: Wireless sensor networks (WSNs) use small nodes with constrained capabilities to sense, collect, and disseminate information in many types of applications. As sensor networks become wide-spread, security issues become a central concern, especially in mission-critical tasks. In this paper, we identify the threats and vulnerabilities to WSNs and summarize the defense methods based on the networking protocol layer analysis first. Then we give a holistic overview of security issues. These issues are divided into seven categories: cryptography, key management, attack detections and preventions, secure routing, secure location security, secure data fusion, and other security issues. Along the way we analyze the advantages and disadvantages of current secure schemes in each category. In addition, we also summarize the techniques and methods used in these categories, and point out the open research issues and directions in each area.
611 citations
TL;DR: In this paper, the authors provide nonspecialists working in the general area of digital communications with a comprehensive overview of this exciting research field, with focus on spatial multiplexing and spatial diversity techniques.
Abstract: The use of multiple antennas for wireless communication systems has gained overwhelming interest during the last decade - both in academia and industry. Multiple antennas can be utilized in order to accomplish a multiplexing gain, a diversity gain, or an antenna gain, thus enhancing the bit rate, the error performance, or the signal-to-noise-plus-interference ratio of wireless systems, respectively. With an enormous amount of yearly publications, the field of multiple-antenna systems, often called multiple-input multiple-output (MIMO) systems, has evolved rapidly. To date, there are numerous papers on the performance limits of MIMO systems, and an abundance of transmitter and receiver concepts has been proposed. The objective of this literature survey is to provide non-specialists working in the general area of digital communications with a comprehensive overview of this exciting research field. To this end, the last ten years of research efforts are recapitulated, with focus on spatial multiplexing and spatial diversity techniques. In particular, topics such as transmitter and receiver structures, channel coding, MIMO techniques for frequency-selective fading channels, diversity reception and space-time coding techniques, differential and non-coherent schemes, beamforming techniques and closed-loop MIMO techniques, cooperative diversity schemes, as well as practical aspects influencing the performance of multiple-antenna systems are addressed. Although the list of references is certainly not intended to be exhaustive, the publications cited will serve as a good starting point for further reading.
582 citations
TL;DR: The objective of this article is to provide a general overview of the critical issue of jamming in WSNs and cover all the relevant work, providing the interested researcher pointers for open research issues in this field.
Abstract: Jamming represents the most serious security threat in the field of wireless sensor networks (WSNs), as it can easily put out of order even WSNs that utilize strong highlayer security mechanisms, simply because it is often ignored in the initial WSN design. The objective of this article is to provide a general overview of the critical issue of jamming in WSNs and cover all the relevant work, providing the interested researcher pointers for open research issues in this field. We provide a brief overview of the communication protocols typically used in WSN deployments and highlight the characteristics of contemporary WSNs, that make them susceptible to jamming attacks, along with the various types of jamming which can be exercised against WSNs. Common jamming techniques and an overview of various types of jammers are reviewed and typical countermeasures against jamming are also analyzed. The key ideas of existing security mechanisms against jamming attacks in WSNs are presented and open research issues, with respect to the defense against jamming attacks are highlighted.
481 citations
TL;DR: This work applies a classification technique to IVC applications to provide a taxonomy for detailed study of their communication requirements, and divides them into type classes which share common communication organization and performance requirements.
Abstract: Inter-vehicle communication (IVC) protocols have the potential to increase the safety, efficiency, and convenience of transportation systems involving planes, trains, automobiles, and robots. The applications targeted include peer-to-peer networks for web surfing, coordinated braking, runway incursion prevention, adaptive traffic control, vehicle formations, and many others. The diversity of the applications and their potential communication protocols has challenged a systematic literature survey. We apply a classification technique to IVC applications to provide a taxonomy for detailed study of their communication requirements. The applications are divided into type classes which share common communication organization and performance requirements. IVC protocols are surveyed separately and their fundamental characteristics are revealed. The protocol characteristics are then used to determine the relevance of specific protocols to specific types of IVC applications.
475 citations
TL;DR: This survey explains the main techniques and problems known in the field of IP traffic analysis and focuses on application detection, separating traffic analysis into packet-based and flow-based categories and details the advantages and problems for each approach.
Abstract: The area of Internet traffic measurement has advanced enormously over the last couple of years. This was mostly due to the increase in network access speeds, due to the appearance of bandwidth-hungry applications, due to the ISPs' increased interest in precise user traffic profile information and also a response to the enormous growth in the number of connected users. These changes greatly affected the work of Internet service providers and network administrators, which have to deal with increasing resource demands and abrupt traffic changes brought by new applications. This survey explains the main techniques and problems known in the field of IP traffic analysis and focuses on application detection. First, it separates traffic analysis into packet-based and flow-based categories and details the advantages and problems for each approach. Second, this work cites the techniques for traffic analysis accessible in the literature, along with the analysis performed by the authors. Relevant techniques include signature-matching, sampling and inference. Third, this work shows the trends in application classification analysis and presents important and recent references in the subject. Lastly, this survey draws the readers' interest to open research topics in the area of traffic analysis and application detection and makes some final remarks.
385 citations
TL;DR: A survey of the multicast routing protocols designed for MANETs shows that all these protocols could be placed under one of two broad routing selection categories: multicasts routing based on application independence and multicast routed based onApplication dependence.
Abstract: A Mobile Ad-hoc NETwork (MANET) is composed of Mobile Nodes (MNs) without any infrastructure. MNs selforganize to form a network over radio links. In this environment, multicast routing protocols are faced with the challenge of producing multi-hop routing under host mobility and bandwidth constraint. Multicast routing plays a significant role in MANETs. In recent years, various multicast routing protocols with distinguishing feature have been newly proposed. In order to provide a comprehensive understanding of these multicast routing protocols designed for MANETs and pave the way for the further research, a survey of the multicast routing protocols is discussed in detail in this paper. Qualitatively, based on their primary multicast routing selection principle, we show that all these protocols could be placed under one of two broad routing selection categories: multicast routing based on application independence and multicast routing based on application dependence.
302 citations
TL;DR: No matter which optimization method is used, in both classes, the overall performance is improved with the increase in the number of users, due to multiuser diversity.
Abstract: This article surveys different resource allocation algorithms developed for the downlink of multiuser OFDM wireless communication systems. Dynamic resource allocation algorithms are categorized into two major classes: margin adaptive (MA) and rate adaptive (RA). The objective of the first class is to minimize the total transmit power with the constraint on users' data rates whereas in the second class, the objective is to maximize the total throughput with the constraints on the total transmit power as well as users' data rates. The overall performance of the algorithms are evaluated in terms of spectral efficiency and fairness. Considering the trade-off between these two features of the system, some algorithms attempt to reach the highest possible spectral efficiency while maintaining acceptable fairness in the system. Furthermore, a large number of RA algorithms considers rate proportionality among the users and hence, are categorized as RA with constrained-fairness. Following the problem formulation in each category, the discussed algorithms are described along with their simplifying assumptions that attempt to keep the performance close to optimum but significantly reduce the complexity of the problem. It is noted that no matter which optimization method is used, in both classes, the overall performance is improved with the increase in the number of users, due to multiuser diversity. Some on-going research areas are briefly discussed throughout the article.
TL;DR: The purpose of this article is to provide a comprehensive survey of various PLIs, their effects, and the available modeling and mitigation techniques and identify several important research issues that need to be addressed to realize dynamically reconfigurable next-generation optical networks.
Abstract: In WDM optical networks, the physical layer impairments (PLIs) and their significance depend on network type-opaque, translucent, or transparent; the reach-access, metro, or core/long-haul; the number and type of network elements-fiber, wavelengths, amplifiers, switching elements, etc.; and the type of applications-real-time, non-real time, missioncritical, etc. In transparent optical networks, PLIs incurred by non-ideal optical transmission media accumulate along an optical path, and the overall effect determines the feasibility of the lightpaths. If the received signal quality is not within the receiver sensitivity threshold, the receiver may not be able to correctly detect the optical signal and this may result in high bit-error rates. Hence, it is important to understand various PLIs and their effect on optical feasibility, analytical models, and monitoring and mitigation techniques. Introducing optical transparency in the physical layer on one hand leads to a dynamic, flexible optical layer with the possibility of adding intelligence such as optical performance monitoring, fault management, etc. On the other hand, transparency reduces the possibility of client layer interaction with the optical layer at intermediate nodes along the path. This has an impact on network design, planning, control, and management. Hence, it is important to understand the techniques that provide PLI information to the control plane protocols and that use this information efficiently to compute feasible routes and wavelengths. The purpose of this article is to provide a comprehensive survey of various PLIs, their effects, and the available modeling and mitigation techniques. We then present a comprehensive survey of various PLI-aware network design techniques, regenerator placement algorithms, routing and wavelength assignment algorithms, and PLI-aware failure recovery algorithms. Furthermore, we identify several important research issues that need to be addressed to realize dynamically reconfigurable next-generation optical networks. We also argue the need for PLI-aware control plane protocol extensions and present several interesting issues that need to be considered in order for these extensions to be deployed in real-world networks.
TL;DR: This paper presents a systematic approach for determining common and complementary characteristics of five widely-used concepts, dependability, fault-tolerance, reliability, security, and survivability.
Abstract: A number of qualitative and quantitative terms are used to describe the performance of what has come to be known as information systems, networks or infrastructures. However, some of these terms either have overlapping meanings or contain ambiguities in their definitions presenting problems to those who attempt a rigorous evaluation of the performance of such systems. The phenomenon arises because the wide range of disciplines covered by the term information technology have developed their own distinct terminologies. This paper presents a systematic approach for determining common and complementary characteristics of five widely-used concepts, dependability, fault-tolerance, reliability, security, and survivability. The approach consists of comparing definitions, attributes, and evaluation measures for each of the five concepts and developing corresponding relations. Removing redundancies and clarifying ambiguities will help the mapping of broad user-specified requirements into objective performance parameters for analyzing and designing information infrastructures.
TL;DR: In this survey, undergroundMine communication is investigated and major issues which underground mine communication systems must take into account are discussed.
Abstract: After a recent series of unfortunate underground mining disasters, the vital importance of communications for underground mining is underlined one more time. Establishing reliable communication is a very difficult task for underground mining due to the extreme environmental conditions. Until now, no single communication system exists which can solve all of the problems and difficulties encountered in underground mine communications. However, combining research with previous experiences might help existing systems improve, if not completely solve all of the problems. In this survey, underground mine communication is investigated. Major issues which underground mine communication systems must take into account are discussed. Communication types, methods, and their significance are presented.
TL;DR: A comprehensive survey of the basic elements, the different types and phases of the handoff procedure and particular interest has been given in the horizontal handoff execution phase by discussing and classifying the most recent handoff prioritization schemes into categories based on the concepts that these schemes adopt.
Abstract: Handoff is a key element in wireless cellular networks in order to provide quality of service (QoS) to the users and to support users' mobility. Handoff failure will result in the forced termination of an ongoing call. From the user's point of view, the service of a handoff request is more important, as the forced termination of an ongoing call is more annoying than the blocking of new calls. Therefore, in order to support QoS to the users and to provide ubiquitous coverage, the handoff procedure ought to be further investigated. This paper provides a comprehensive survey of the basic elements, the different types and phases of the handoff procedure. Moreover, particular interest has been given in the horizontal handoff execution phase by discussing and classifying the most recent handoff prioritization schemes into categories based on the concepts that these schemes adopt, e.g. channel reservation, handoff queueing, channel transferred, subrating, genetic and hybrid schemes and in the vertical handoff decision phase by presenting different decision algorithms.
TL;DR: This article introduces the most relevant survivable MANET initiatives where either preventive or reactive defenses are combined with tolerant ones and classify the defense lines taking into account intrusion tolerance mechanisms and also identifies properties and requirements of survivability.
Abstract: Many efforts have been done towards secure MANETs, but the conventional lines of defense are still inefficient to put all attacks off. This article examines survivable approaches whose goal is to enable networks to fulfill correctly their critical functions even in the presence of attacks or intrusions. We introduce the most relevant survivable MANET initiatives where either preventive or reactive defenses are combined with tolerant ones. We classify the defense lines taking into account intrusion tolerance mechanisms and also identify properties and requirements of survivability. The initiatives are categorized in three groups: routing discovery, data transmission and key management. For each one, they are correlated in terms of requirements and properties. The survey shows that security solutions do not yet explore relevant survivability properties and have only focused on one network layer or one type of attack.
TL;DR: The requirements and the main contributions for the building blocks of any autonomic network management system (ANMS) are analyzed and a coherent classification methodology is described to compare existing ANMS architectures.
Abstract: Autonomic network management is an innovative vision promising new horizons of efficient networking systems free from human control. This promise has, thus far, ushered in enormous yet dispersed research contributions in both industry and academia. The work presented in this article aims at putting these efforts into perspective deriving a more holistic view of the literature in this area. We analyze the requirements and the main contributions for the building blocks of any autonomic network management system (ANMS). We then describe a coherent classification methodology to compare existing ANMS architectures. Based on this analysis, we suggest a reference framework and highlight some open challenges and describe new research opportunities.
TL;DR: This paper aims to provide a comprehensive survey of the salient unicast AC schemes designed for IEEE 802.11- based multi-hop MANETs, which were published in the peer-reviewed open literature during the period 2000-2007.
Abstract: Mobile ad hoc networks (MANETs) promise unique communication opportunities. The IEEE 802.11 standard has allowed affordable MANETs to be realised. However, providing quality of service (QoS) assurances to MANET applications is difficult due to the unreliable wireless channel, the lack of centralised control, contention for channel access and node mobility. One of the most crucial components of a system for providing QoS assurances is admission control (AC). It is the job of the AC mechanism to estimate the state of the network's resources and thereby to decide which application data sessions can be admitted without promising more resources than are available and thus violating previously made guarantees. Unfortunately, due to the aforementioned difficulties, estimating the network resources and maintaining QoS guarantees are non-trivial tasks. Accordingly, a large body of work has been published on AC protocols for addressing these issues. However, as far as it is possible to tell, no wide-ranging survey of these approaches exists at the time of writing. This paper thus aims to provide a comprehensive survey of the salient unicast AC schemes designed for IEEE 802.11- based multi-hop MANETs, which were published in the peer-reviewed open literature during the period 2000-2007. The relevant considerations for the design of such protocols are discussed and several methods of classifying the schemes found in the literature are proposed. A brief outline of the operation, reaction to route failures, as well as the strengths and weaknesses of each protocol is given. This enables patterns in the design and trends in the development of AC protocols to be identified. Finally, directions for possible future work are provided.
TL;DR: Various methods that have been proposed in order to enhance the channel utilization by improving the spatial reuse of the medium access control protocol are surveyed.
Abstract: In multihop wireless ad-hoc networks, the medium access control (MAC) protocol plays a key role in coordinating the access to the shared medium among wireless nodes. Currently, the distributed coordination function (DCF) of the IEEE 802.11 is the dominant MAC protocol for both wireless LANs and wireless multihop ad hoc environment due to its simple implementation and distributed nature. The current access method of the IEEE 802.11 does not make efficient use of the shared channel due to its conservative approach in assessing the level of interference; this in turn affects the spatial reuse of the limited radio resources and highly affect the achieved throughput of a multihop wireless network. This paper surveys various methods that have been proposed in order to enhance the channel utilization by improving the spatial reuse.
TL;DR: This paper provides a tutorial on current security standards for XML and Web services and discusses standards including XML Signature, XML Encryption, the XML Key Management Specification (XKMS), WS-Security, WS-Trust,WS-SecureConversation, Web Services Policy, and the Security Assertion Markup Language (SAML).
Abstract: XML and Web services are widely used in current distributed systems. The security of the XML based communication, and the Web services themselves, is of great importance to the overall security of these systems. Furthermore, in order to facilitate interoperability, the security mechanisms should preferably be based on established standards. In this paper we provide a tutorial on current security standards for XML and Web services. The discussed standards include XML Signature, XML Encryption, the XML Key Management Specification (XKMS), WS-Security, WS-Trust, WS-SecureConversation, Web Services Policy, WS-SecurityPolicy, the eXtensible Access Control Markup Language (XACML), and the Security Assertion Markup Language (SAML).
TL;DR: This paper surveys the existing data replication protocols in mobile ad-hoc networks and proposes a classification scheme that categorizes the protocols into various classes, with respect to the issues they address, and provides a comparison of the protocols.
Abstract: In mobile ad-hoc networks, frequent network partitioning and the failure of mobile nodes due to exhaustion of their battery power can considerably decrease data availability. In addition, the increase in network size and node mobility cause the performance of data access to degrade. To deal with these issues, a number of data replication protocols have been proposed in the recent years. This paper surveys the existing data replication protocols in mobile ad-hoc networks and proposes a classification scheme that categorizes the protocols into various classes, with respect to the issues they address. Network partitioning, energy consumption, and scalability are the three issues that are identified in this paper, and which have not been previously considered in the fixed networks. The paper also provides a comparison of the protocols and investigates opportunities for future research.
TL;DR: This survey analyzes various multi-domain routing models for emerging Layer 2 and WDM switched networks which have been proposed till date, and highlights some open issues and future challenges pertaining to scalability, reliability, multi- domain QoS, control plane interworking and dynamic peering.
Abstract: The emergence of carrier grade transport technologies has led to a paradigm shift in inter-domain routing which became an important feature of the transport layer based on optical transmission and switching. While the new technologies have capabilities to provide end-to-end guaranteed quality of service (QoS), the lack of inter-operability between different technologies, administrative areas and control planes makes interdomain peering and provisioning below the conventional Internet Protocol (IP) layer a challenge. In this survey, we analyze various multi-domain routing models for emerging Layer 2 and WDM switched networks which have been proposed till date, and based on that survey, we highlight some open issues and future challenges pertaining to scalability, reliability, multi-domain QoS, control plane interworking and dynamic peering.
TL;DR: This survey provides a description of key projected features of the physical (PHY) and medium access control (MAC) layers of 802.16m, as a major candidate for providing aggregate rates at the range of Gbps to high-speed mobile users.
Abstract: In order to meet the requirements of 4G mobile networks targeted by the cellular layer of IMT-advanced, next generation mobile WiMAX devices based on IEEE 802.16m will incorporate sophisticated signal processing, seamless handover functionalities between heterogeneous technologies and advanced mobility mechanisms. This survey provides a description of key projected features of the physical (PHY) and medium access control (MAC) layers of 802.16m, as a major candidate for providing aggregate rates at the range of Gbps to high-speed mobile users. Moreover, a new unified method for simulation modeling, namely the evaluation methodology (EVM), introduced in 802.16m, is also presented.
TL;DR: A survey on the protocols proposed for reliable data transport in space Internet, with a focus on the latest developments, is presented, classification of these protocols into different approaches.
Abstract: A variety of protocols have been proposed for reliable data transport in space Internet and similar network environments. It is necessary to conduct a survey on these protocols to investigate and compare among them. In this article, we present a survey on the protocols proposed for reliable data transport in space Internet, with a focus on the latest developments. The survey includes the following contents: (1) classification of these protocols into different approaches; (2) discussions and comments on the design and operation methods of the protocols; and (3) comparisons and comments on the main techniques and performance of the protocols.
TL;DR: This survey paper is the first attempt to present a rapid overview of this interesting subject and provide and agile reference of the broad p-cycle topic.
Abstract: This paper presents a comprehensive survey for the pre-configured cycle (p-cycle) protection method which is a relatively new scheme for network survivability with many interesting properties, and has been attracting quite a lot of attention. We review different aspects of p-cycles and survey the studies on this and other related survivability schemes. This survey paper is the first attempt to present a rapid overview of this interesting subject and provide and agile reference of the broad p-cycle topic. In addition to addressing the concepts and preliminaries, this survey covers advanced topics related to p-cycles such as path protecting p-cycles, availability-aware design with p-cycles, p-cycle reconfiguration, column generation approach for p-cycle network design and p-cycles in multicast networks.
TL;DR: This work reviews recent techniques to secure BGP and provides a basis for evaluation of the techniques to understand coverage of published works as well as to determine the best avenues for future research.
Abstract: Web surfing is an example (and popular) Internet application where users desire services provided by servers that exist somewhere in the Internet. To provide the service, data must be routed between the user's system and the server. Local network routing (relative to the user) can not provide a complete route for the data. In the core Internet, a portion of the network controlled by a single administrative authority, called an autonomous system (AS), provides local network support and also exchanges routing information with other ASes using the border gateway protocol (BGP). Through the BGP route exchange, a complete route for the data is created. Security at this level in the Internet is challenging due to the lack of a single administration point and because there are numerous ASes which interact with one another using complex peering policies. This work reviews recent techniques to secure BGP. These security techniques are categorized as follows: 1) cryptographic/attestation, 2) database, 3) overlay/group protocols, 4) penalty, and 5) data-plane testing. The techniques are reviewed at a high level in a tutorial format, and shortcomings of the techniques are summarized as well. The depth of coverage for particular published works is intentionally kept minimal, so that the reader can quickly grasp the techniques. This survey provides a basis for evaluation of the techniques to understand coverage of published works as well as to determine the best avenues for future research.
TL;DR: This work goes over some of the known issues found in common P2P networks, and analyzes the relevance of such issues and the applicability of existing solutions when using P1P architectures for real-time communication.
Abstract: Peer to peer (P2P) networks offer higher robustness against failure, easier configuration and are generally more economical as compared to their client-server counterparts. This has made it reasonable for resource consuming and typically centralized applications like voice over IP (VoIP) and, in general, real-time communication to adapt and exploit the benefits of P2P. Such a migration needs to address a new set of P2P specific security problems. We go over some of the known issues found in common P2P networks. We then analyze the relevance of such issues and the applicability of existing solutions when using P2P architectures for real-time communication.
TL;DR: This survey covers solutions that enhance the Ethernet's path computation, allowing it to scale in larger, more complex environments, as a specific example of Ethernet's application in large scale networks.
Abstract: The higher transmission rates currently supported by Ethernet lead to the possibility of expanding Ethernet beyond the local area network scope, bringing it into the core of large scale networks, of which a metropolitan area network (MAN) is a significant example. However, originally Ethernet was not devised to scale in such environments: its design does not contemplate essential requirements of larger and more complex networks, such as the need for resilience, scalability, or even integrated control features. Furthermore, its spanning-tree based forwarding results in slow convergence and weak resource efficiency. Specifically focusing on Ethernet's forwarding behaviour, this survey covers solutions that enhance the Ethernet's path computation, allowing it to scale in larger, more complex environments. General notions concerning the application of Ethernet in Metro areas are also provided, as a specific example of Ethernet's application in large scale networks.
TL;DR: By focusing on the air interface-centric approach, it is shown that the resource allocation problem can be formulated as an optimization problem with a certain objective function and some particular constraints.
Abstract: Cross-layer scheduling is a promising solution for improving the efficiency of emerging broadband wireless systems. In this tutorial, various cross-layer design approaches are organized into three main categories namely air interface-centric, user-centric and route-centric and the general characteristics of each are discussed. Thereafter, by focusing on the air interface-centric approach, it is shown that the resource allocation problem can be formulated as an optimization problem with a certain objective function and some particular constraints. This is illustrated with the aid of a customer-provider model from the field of economics. Furthermore, the possible future evolution of scheduling techniques is described based on the characteristics of traffic and air interface in emerging broadband wireless systems. Finally, some further challenges are identified.
TL;DR: A comparative analysis of the physical (PHY) layers in the original main proposals for the 11n amendment (the TGn Sync, WWiSE and TGn Joint proposals) is presented, and key architectural differences governing the performance of these proposals are outlined.
Abstract: IEEE 802.11n is a newly emerged WLAN standard capable of providing dramatically increased throughput, as well as improved range, reduced signal fading, over the existing IEEE 802.11a/g WLAN standards. These benefits are achieved through use of MIMO (multiple-input,multiple-output). The latest draft for IEEE 802.11n describes rates up to 600 Mbps, exceeding the maximum rate with the 11a/g standards by more than ten times. In addition, techniques such as space-time block coding and beamforming provide the potential of increasing signal strength at the receiver with optimal efficiency, based on the diversity order used. In this paper, a comparative analysis of the physical (PHY) layers in the original main proposals for the 11n amendment (the TGn Sync, WWiSE and TGn Joint proposals) is presented. The key architectural differences governing the performance of these proposals are outlined. In addition, insights are provided into the choices leading to the TGn Joint proposal, which reflects the PHY architecture described in the 11n standard. The insights and challenges described relate to the choices made in the TGn Joint proposal regarding the areas of channel estimation (considering the use of beamforming, channel smoothing), bit interleaving techniques (for maximizing coding gain under channels with high frequency diversity), space-time block coding (STBC) options (designed in an effort to achieve a good balance between achieving high diversity gain and low receiver design complexity), and pilot tone selection (for a reasonable tradeoff of robustness and link-level performance). Performance curves (based on simulation models developed in MATLAB/SIMULINK) are used to verify the analysis presented. This paper also includes a discussion of some of the future challenges for the 11n amendment.