Showing papers in "IEEE Communications Magazine in 2002"

A survey on sensor networks

Abstract: The advancement in wireless communications and electronics has enabled the development of low-cost sensor networks. The sensor networks can be used for various application areas (e.g., health, military, home). For different application areas, there are different technical issues that researchers are currently resolving. The current state of the art of sensor networks is captured in this article, where solutions are discussed under their related protocol stack layer sections. This article also points out the open research issues and intends to spark new interests and developments in this field.

Frequency domain equalization for single-carrier broadband wireless systems

Abstract: Broadband wireless access systems deployed in residential and business environments are likely to face hostile radio propagation environments, with multipath delay spread extending over tens or hundreds of bit intervals. Orthogonal frequency-division multiplex (OFDM) is a recognized multicarrier solution to combat the effects of such multipath conditions. This article surveys frequency domain equalization (FDE) applied to single-carrier (SC) modulation solutions. SC radio modems with frequency domain equalization have similar performance, efficiency, and low signal processing complexity advantages as OFDM, and in addition are less sensitive than OFDM to RF impairments such as power amplifier nonlinearities. We discuss similarities and differences of SC and OFDM systems and coexistence possibilities, and present examples of SC-FDE performance capabilities.

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.

IEEE standard 802.16: a technical overview of the WirelessMAN/sup TM/ air interface for broadband wireless access

Abstract: The broadband wireless access industry, which provides high-rate network connections to stationary sites, has matured to the point at which it now has a standard for second-generation wireless metropolitan area networks. The IEEE standard 802.16, with its WirelessMAN/sup TM/ air interface, sets the stage for widespread and effective deployments worldwide. This article overviews the technical medium access control and physical layer features of this new standard.

Indoor geolocation science and technology

Abstract: This article presents an overview of the technical aspects of the existing technologies for wireless indoor location systems. The two major challenges for accurate location finding in indoor areas are the complexity of radio propagation and the ad hoc nature of the deployed infrastructure in these areas. Because of these difficulties a variety of signaling techniques, overall system architectures, and location finding algorithms are emerging for this application. This article provides a fundamental understanding of the issues related to indoor geolocation science that are needed for design and performance evaluation of emerging indoor geolocation systems.

Routing security in wireless ad hoc networks

Abstract: A mobile ad hoc network consists of a collection of wireless mobile nodes that are capable of communicating with each other without the use of a network infrastructure or any centralized administration. MANET is an emerging research area with practical applications. However, wireless MANET is particularly vulnerable due to its fundamental characteristics, such as open medium, dynamic topology, distributed cooperation, and constrained capability. Routing plays an important role in the security of the entire network. In general, routing security in wireless MANETs appears to be a problem that is not trivial to solve. In this article we study the routing security issues of MANETs, and analyze in detail one type of attack-the "black hole" problem-that can easily be employed against the MANETs. We also propose a solution for the black hole problem for ad hoc on-demand distance vector routing protocol.

RSVP: a new resource reservation protocol

Abstract: A resource reservation protocol (RSVP), a flexible and scalable receiver-oriented simplex protocol, is described. RSVP provides receiver-initiated reservations to accommodate heterogeneity among receivers as well as dynamic membership changes; separates the filters from the reservation, thus allowing channel changing behavior; supports a dynamic and robust multipoint-to-multipoint communication model by taking a soft-state approach in maintaining resource reservations; and decouples the reservation and routing functions. A simple network configuration with five hosts connected by seven point-to-point links and three switches is presented to illustrate how RSVP works. Related work and unresolved issues are discussed. >

IPACT a dynamic protocol for an Ethernet PON (EPON)

Abstract: We investigate design issues for access networks based on passive optical network technology. A PON based on polling, with data encapsulated in Ethernet frames, possesses many desirable qualities, such as dynamic bandwidth distribution, use of a single downstream and a single upstream wavelength, ability to provision a fractional wavelength capacity to each user, and ease of adding a new user. To support dynamic bandwidth distribution, we propose an interleaved polling algorithm called IPACT. We also suggest a scheme for in-band signaling that allows using a single wavelength for both downstream data and control message transmission. To obtain realistic simulation results, we generated synthetic traffic that exhibits the properties of self-similarity and long-range dependence. We then analyzed the network performance under varying offered loads.

Ethernet passive optical network (EPON): building a next-generation optical access network

Abstract: This article describes Ethernet passive optical networks, an emerging local subscriber access architecture that combines low-cost point-to-multipoint fiber infrastructure with Ethernet. EPONs are designed to carry Ethernet frames at standard Ethernet rates. An EPON uses a single trunk fiber that extends from a central office to a passive optical splitter, which then fans out to multiple optical drop fibers connected to subscriber nodes. Other than the end terminating equipment, no component in the network requires electrical power, hence the term passive. Local carriers have long been interested in passive optical networks for the benefits they offer: minimal fiber infrastructure and no powering requirement in the outside plant. With Ethernet now emerging as the protocol of choice for carrying IP traffic in metro and access networks, EPON has emerged as a potential optimized architecture for fiber to the building and fiber to the home.

A fourth-generation MIMO-OFDM broadband wireless system: design, performance, and field trial results

Abstract: Increasing demand for high-performance 4G broadband wireless is enabled by the use of multiple antennas at both base station and subscriber ends. Multiple antenna technologies enable high capacities suited for Internet and multimedia services, and also dramatically increase range and reliability. In this article we describe a multiple-input multiple-output OFDM wireless communication system, lab test results, and field test results obtained in San Jose, California. These are the first MIMO system field tests to establish the performance of MIMO communication systems. Increased capacity, coverage, and reliability are clearly evident from the test results presented in this article.

Position-based routing in ad hoc networks

Abstract: The availability of small, inexpensive low-power GPS receivers and techniques for finding relative coordinates based on signal strengths, and the need for the design of power-efficient and scalable networks provided justification for applying position-based routing methods in ad hoc networks. A number of such algorithms were developed previously. This tutorial will concentrate on schemes that are loop-free, localized, and follow a single-path strategy, which are desirable characteristics for scalable routing protocols. Routing protocols have two modes: greedy mode (when the forwarding node is able to advance the message toward the destination) and recovery mode (applied until return to greedy mode is possible). We discuss them separately. Methods also differ in metrics used (hop count, power, cost, congestion, etc.), and in past traffic memorization at nodes (memoryless or memorizing past traffic). Salient properties to be emphasized in this review are guaranteed delivery, scalability, and robustness.

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.

A brief overview of ad hoc networks: challenges and directions

Abstract: One of the most vibrant and active \" new \" fields today is that of ad hoc networks. Within the past few years the field has seen o rapid expansion of visibility and work due to the proliferation of inexpensive, widely available wireless devices and the network community's interest in mobile computing. ne of the most vibrant and active \" new \" fields today is that of ad hoc networks. Significant research in this area has been ongoing for nearly 30 years, also under the names packet radio or multi-hop networks. Within the past few years, though, the field 0 has seen a rapid expansion of visibility and work due to the proliferation of inexpensive, widely available wireless devices and the network community's interest in mobile computing. An ad hoc network is a (possibly mobile) collection of communications devices (nodes) that wish to communicate, but have no fixed infrastructure available, and have no predetermined organization of available links. Individual nodes are responsible for dynamically discovering which other nodes they can directly communicate with. A key assumption is that not all nodes can directly communicate with each other, so nodes are required t o relay packets on behalf of other nodes in order to deliver data across the network. A significant feature of ad hoc networks is that rapid changes in connectivity and link characteristics are introduced due to node mobility and power control practices. Ad hoc networks can be built around any wireless technology, including infrared and radio frequency (RF). Ad hoc networking is a multi-layer problem. The physical layer must adapt to rapid changes in link characteristics. The multiple access control (MAC) layer needs to minimize collisions, allow fair access, and semi-reliably transport data over the shared wireless links in the presence of rapid changes and hidden or exposed terminals. The network layer needs to determine and distribute information used to calculate paths in a way that maintains efficiency when links change often and bandwidth is at a premium. It'also needs to integrate smoothly with traditional , non ad hoc-aware internetworks and perform functions such as auto-configuration in this changing environment. The transport layer must be able to handle delay and packet loss statistics that are very different than wired networks. Finally, applications need to be designed to handle frequent disconnection and reconnec-tion with peer applications as well as widely varying delay and packet loss characteristics. Ad hoc networks …

Broadband wireless access solutions based on OFDM access in IEEE 802.16

Abstract: Broadband wireless access is the most challenging segment of the wireless revolution since it has to demonstrate a viable alternative to the cable modem and DSL technologies that are strongly entrenched in the last mile access environment. The Analysis, Research, and Consultancy (ARC) Group forecasts that the fixed wireless deployments in both homes and businesses will reach almost 28 million by 2005, with North America and Western Europe accounting for 24 percent and 27 percent of these, respectively. Whether the promise of BWA will materialize depends on its appeal to telecom operators from the perspective of deployment economics, where the critical factor is the ease of installation of broadband wireless subscriber units. This ultimately leads to nonprofessional installation of integrated all-indoor BWSUs. Consequently the physical layer (PHY) has to mitigate the very tough impairments that characterize these non-line-of-sight environments. In this context we overview the work of the one of the IEEE 802.16 standard subcommittee projects that deals with a BWA solution based on OFDM access (OFDMA) aiming at the most challenging NLOS scenarios.

Standardization of mobile phone positioning for 3G systems

Abstract: Finding the location of the mobile phone is one of the important features of the 3G mobile communication system. Many valuable location-based services can be enabled by this new feature. Telecommunication managers and engineers are often puzzled by location terminologies and techniques as well as how to implement them, since location systems are not natural evolution from past generations of telecommunication systems. In this paper, we discuss briefly why locating mobile phone becomes a hot topic and what technologies are being studied. We then describe and clarify the latest standards issues surrounding the positioning methods specified for 3G systems. These include cell-ID-based, assisted GPS, and TDOA-based methods, such as OTDOA, E-OTD, and A-FLT.

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.

Defending against flooding-based distributed denial-of-service attacks: a tutorial

Abstract: Flooding-based distributed denial-of-service (DDoS) attack presents a very serious threat to the stability of the Internet. In a typical DDoS attack, a large number of compromised hosts are amassed to send useless packets to jam a victim, or its Internet connection, or both. In the last two years, it was discovered that DDoS attack methods and tools are becoming more sophisticated, effective, and also more difficult to trace to the real attackers. On the defense side, current technologies are still unable to withstand large-scale attacks. The main purpose of this article is therefore twofold. The first one is to describe various DDoS attack methods, and to present a systematic review and evaluation of the existing defense mechanisms. The second is to discuss a longer-term solution, dubbed the Internet-firewall approach, that attempts to intercept attack packets in the Internet core, well before reaching the victim.

Traffic engineering with traditional IP routing protocols

Abstract: Traffic engineering involves adapting the routing of traffic to network conditions, with the joint goals of good user performance and efficient use of network resources. We describe an approach to intradomain traffic engineering that works within the existing deployed base of interior gateway protocols, such as Open Shortest Path First and Intermediate System-Intermediate System. We explain how to adapt the configuration of link weights, based on a networkwide view of the traffic and topology within a domain. In addition, we summarize the results of several studies of techniques for optimizing OSPF/IS-IS weights to the prevailing traffic. The article argues that traditional shortest path routing protocols are surprisingly effective for engineering the flow of traffic in large IP networks.

A comparison of the HIPERLAN/2 and IEEE 802.11a wireless LAN standards

Abstract: At present, WLANs supporting broadband multimedia communication are being developed and standardized around the world. Standards include HIPERLAN/2, defined by ETSI BRAN, 802.11a, defined by the IEEE, and HiSWANa defined by MMAC. These systems provide channel adaptive data rates up to 54 Mb/s (in a 20 MHz channel spacing) in the 5 GHz radio band. An overview of the HIPERLAN/2 and 802.11a standards is presented together with software simulated physical layer performance results for each of the defined transmission modes. Furthermore, the differences between these two standards are highlighted (packet size, upper protocol layers etc.), and the effects of these differences on throughput are analyzed and discussed.

On credibility of simulation studies of telecommunication networks

Abstract: In telecommunication networks, as in many other areas of science and engineering, the proliferation of computers as research tools has resulted in the adoption of computer simulation as the most commonly used paradigm of scientific investigations. This, together with a plethora of existing simulation languages and packages, has created a popular opinion that simulation is mainly an exercise in computer programming. In new computing environments, programming can be minimized, or even fully replaced, by the manipulation of icons (representing prebuilt programming objects containing basic functional blocks of simulated systems) on a computer monitor. One can say that we have witnessed another success of modern science and technology: the emergence of wonderful and powerful tools for exploring and predicting the behavior of such complex stochastic dynamic systems as telecommunication networks. But this enthusiasm is not shared by all researchers in this area. An opinion is spreading that one cannot rely on the majority of the published results on performance evaluation studies of telecommunication networks based on stochastic simulation, since they lack credibility. Indeed, the spread of this phenomenon is so wide that one can speak about a deep crisis of credibility. In this article this claim is supported by the results of a survey of over 2200 publications on telecommunication networks in proceedings of IEEE INFOCOM and such journals as IEEE Transactions on Communications, IEEE/ACM Transactions on Networking, and Performance Evaluation Journal. The discussion focuses on two important necessary conditions of a credible simulation study: use of appropriate pseudo-random generators of independent uniformly distributed numbers, and appropriate analysis of simulation output data. Having considered their perils and pitfalls, we formulate guidelines that, if observed, could help to ensure a basic level of credibility of simulation studies of telecommunication networks.

An overview of constraint-based path selection algorithms for QoS routing

Abstract: Constraint-based path selection aims at identifying a path that satisfies a set of quality of service (QoS) constraints. In general, this problem is known to be NP-complete, leading to the proposal of many heuristic algorithms. We provide an overview of these algorithms, focusing on restricted shortest path and multi-constrained path algorithms.

Wireless communications: past events and a future perspective

Abstract: the 21 st century. ireless communications has emerged as one of the largest sectors of the telecommunications ,industry, evolving from a niche business in the last decade to one of the most promising areas for growth in the 21st cenW tury. This article explores some of the key technological advances and approaches that are now emerging as core components for wireless solutions of the future.

Next-generation wireless communications concepts and technologies

Abstract: Next-generation wireless (NextG) involves the concept that the next generation of wireless communications will be a major move toward ubiquitous wireless communications systems and seamless high-quality wireless services. This article presents the concepts and technologies involved, including possible innovations in architectures, spectrum allocation, and utilization, in radio communications, networks, and services and applications. These include dynamic and adaptive systems and technologies that provide a new paradigm for spectrum assignment and management, smart resource management, dynamic and fast adaptive multilayer approaches, smart radio, and adaptive networking. Technologies involving adaptive and highly efficient modulation, coding, multiple access, media access, network organization, and networking that can provide ultraconnectivity at high data rates with effective QoS for Next Gare are also described.

JumpStart: a just-in-time signaling architecture for WDM burst-switched networks

Abstract: We present an architecture for a core dWDM network which utilizes the concept of optical burst switching coupled with a just-in-time signaling scheme. It is a reservation-based architecture whose distinguishing characteristics are its relative simplicity, its amenability to hardware implementation, and the ability to support multicast natively. Another important feature is data transparency-the network infrastructure is independent of the format of the data being transmitted on individual wavelengths. We present the signaling protocol designed for this architecture, as well as an unified signaling message structure to be used in conjunction with the protocol. We also present the future directions of this research.

Transmit diversity in 3G CDMA systems

Abstract: Transmit diversity (TD) is one of the key contributing technologies to defining the ITU endorsed 3G systems W-CDMA and cdma2000. Spatial diversity is introduced into the signal by transmitting through multiple antennas. The antennas are spaced far enough apart that the signals emanating from them can be assumed to undergo independent fading. In addition to diversity gain, antenna gain can also be incorporated through channel state feedback. This leads to the categorization of TD methods into open loop and closed loop methods. Several methods of transmit diversity in the forward link have been either under consideration or adopted for the various 3G standards. This article describes the concept of transmit diversity and explains the features of selected TD techniques.

The role of optical CDMA in access networks

Abstract: We investigate the possible role of optical CDMA (O-CDMA) in future access networks. We begin with a short review of the O-CDMA technique for those unfamiliar with the technology. Next, we investigate in detail those characteristics of O-CDMA that make it an attractive technology for application in metro access networks: fairness, flexibility, simplified network control and management, service differentiation, and increased security. Although O-CDMA has many favorable attributes, it also has several actual or perceived drawbacks. We discuss the technical, economic, and perception barriers that may have limited the widescale deployment of O-CDMA access networks. We try to determine which of these drawbacks may be surmountable in the near future and which may be true "showstoppers".

Understanding Internet traffic streams: dragonflies and tortoises

Abstract: We present the concept of network traffic streams and the ways they aggregate into flows through Internet links. We describe a method of measuring the size and lifetime of Internet streams, and use this method to characterize traffic distributions at two different sites. We find that although most streams (about 45 percent of them) are dragonflies, lasting less than 2 seconds, a significant number of streams have lifetimes of hours to days, and can carry a high proportion (50-60 percent) of the total bytes on a given link. We define tortoises as streams that last longer than 15 minutes. We point out that streams can be classified not only by lifetime (dragonflies and tortoises) but also by size (mice and elephants), and note that stream size and lifetime are independent dimensions. We submit that ISPs need to be aware of the distribution of Internet stream sizes, and the impact of the difference in behavior between short and long streams. In particular, any forwarding cache mechanisms in Internet routers must be able to cope with a high volume of short streams. In addition ISPs should realize that long-running streams can contribute a significant fraction of their packet and byte volumes-something they may not have allowed for when using traditional "flat rate user bandwidth consumption" approaches to provisioning and engineering.

Antenna systems for broadband wireless access

Abstract: Broadband wireless access along with evolving mobile Internet and multimedia services are driving the surge of research and development activities for future wireless communication systems. We provide an overview of antenna systems for broadband wireless communications and introduce some of the important issues surrounding them. The approach we use is to first provide a general framework of how antenna systems may be utilized in wireless communication systems and then describe the antenna systems themselves. In particular, we consider antenna systems for the base station, mobile station, and then finally multiple-input multiple-output antenna systems where antenna systems are utilized at both the base and mobile stations.

Network intrusion and fault detection: a statistical anomaly approach

Abstract: With the advent and explosive growth of the global Internet and electronic commerce environments, adaptive/automatic network/service intrusion and anomaly detection in wide area data networks and e-commerce infrastructures is fast gaining critical research and practical importance. We present and demonstrate the use of a general-purpose hierarchical multitier multiwindow statistical anomaly detection technology and system that operates automatically, adaptively, and proactively, and can be applied to various networking technologies, including both wired and wireless ad hoc networks. Our method uses statistical models and multivariate classifiers to detect anomalous network conditions. Some numerical results are also presented that demonstrate that our proposed methodology can reliably detect attacks with traffic anomaly intensity as low as 3-5 percent of the typical background traffic intensity, thus promising to generate an effective early warning.

Handover management for mobile nodes in IPv6 networks

Abstract: We analyze IPv6 handover over wireless LAN. Mobile IPv6 is designed to manage mobile nodes' movements between wireless IPv6 networks. Nevertheless, the active communications of a mobile node are interrupted until the handover completes. Therefore, several extensions to Mobile IPv6 have been proposed to reduce the handover latency and the number of lost packets. We describe two of them, hierarchical Mobile IPv6, which manages local movements into a domain, and fast handover protocol, which allows the use of layer 2 triggers to anticipate the handover. We expose the specific handover algorithms proposed by all these methods. We also evaluate the handover latency over IEEE 802.11b wireless LAN. We compare the layer 2 and layer 3 handover latency in the Mobile IPv6 case in order to show the saving of time expected by using anticipation. We conclude by showing how to adapt the IEEE 802.11b control frames to set up such anticipation.