Showing papers on "Broadband networks published in 2004"

Relay-based deployment concepts for wireless and mobile broadband radio

Abstract: In recent years, there has been an upsurge of interest in multihop-augmented infrastructure-based networks in both the industry and academia, such as the seed concept in 3GPP, mesh networks in IEEE 802.16, and converge extension of HiperLAN/2 through relays or user-cooperative diversity mesh networks. This article, a synopsis of numerous contributions to the working group 4 of the wireless world research forum and other research work, presents an overview of important topics and applications in the context of relaying. It covers different approaches to exploiting the benefits of multihop communications via relays, such as solutions for radio range extension in mobile and wireless broadband cellular networks (trading range for capacity), and solutions to combat shadowing at high radio frequencies. Furthermore, relaying is presented as a means to reduce infrastructure deployment costs. It is also shown that through the exploitation of spatial diversity, multihop relaying can enhance capacity in cellular networks. We wish to emphasize that while this article focuses on fixed relays, many of the concepts presented can also be applied to systems with moving relays.

DakNet: rethinking connectivity in developing nations

Abstract: DakNet provides extraordinarily low-cost digital communication, letting remote villages leapfrog past the expense of traditional connectivity solutions and begin development of a full-coverage broadband wireless infrastructure. What is the basis for a progressive, market-driven migration from e-governance to universal broadband connectivity that local users will pay for? DakNet, an ad hoc network that uses wireless technology to provide asynchronous digital connectivity, is evidence that the marriage of wireless and asynchronous service may indeed be the beginning of a road to universal broadband connectivity. DakNet has been successfully deployed in remote parts of both India and Cambodia at a cost two orders of magnitude less than that of traditional landline solutions.

In-building wideband partition loss measurements at 2.5 and 60 GHz

Abstract: This paper contains measured data and empirical models for 2.5 and 60 GHz in-building propagation path loss and multipath delay spread. Path loss measurements were recorded using a broadband sliding correlator channel sounder which recorded over 39000 power delay profiles (PDPs) in 22 separate locations in a modern office building. Transmitters and receivers were separated by distances ranging from 3.5 to 27.4 m and were separated by a variety of obstructions, in order to create realistic environments for future single-cell-per-room wireless networks. Path loss data is coupled with site-specific information to provide insight into channel characteristics. These measurements and models may aid in the development of future in-building wireless networks in the unlicensed 2.4 and 60 GHz bands.

Modeling of transfer Characteristics for the broadband power line communication channel

Abstract: This paper presents a novel approach to model the transfer function of electrical power lines for broadband power line communication. In this approach, the power line is approximated as a transmission line and the two intrinsic parameters, the characteristic impedance and the propagation constants, are derived based on the lumped-element circuit model. Using these intrinsic parameters, the transfer characteristics for a N-branch power distribution network are derived based on the scattering matrix method. Detail derivation of this line model is given in this paper. The model has been verified with practical measurements conducted on actual power networks. It is demonstrated that the model accurately determine the line characteristics under different network configuration and when different household appliances are connected.

Ethernet PONs: a survey of dynamic bandwidth allocation (DBA) algorithms

Abstract: Optical networks are poised to dominate the access network space in coming years. Ethernet passive optical networks, which leverage the ubiquity of Ethernet at subscriber locations, seem destined for success in the optical access network. In this article we first provide a brief introduction to Ethernet passive optical networks, followed by a discussion of the problem of dynamic bandwidth allocation. We then introduce a framework for classifying dynamic bandwidth allocation schemes and provide a comprehensive survey of the dynamic bandwidth allocation methods proposed to date. We conclude with a side by side comparison of the schemes based on their most prominent characteristics, and outline future developments of dynamic bandwidth allocation schemes.

Bandwidth estimation in broadband access networks

Abstract: There has been much work on developing techniques for estimating the capacity and the available bandwidth of network paths based on end-point measurements. The focus has primarily been on settings where the constrained link can be modeled as a point-to-point link with a well-defined bandwidth, serving packets in FIFO order. In this paper, we point out that broadband access networks, such as cable modem and 802.11-based wireless networks, break this model in various ways. The constrained link could (a) employ mechanisms such as token bucket rate regulation, (b) schedule packets in a non-FIFO manner, and (c) support multiple distinct rates. We study how these characteristics impede the operation of the various existing methods and tools for capacity and available bandwidth estimation, and present a new available bandwidth estimation technique, Probe- Gap, that overcomes some of these difficulties. Our evaluation is based on experiments with actual 802.11a and cable modem links.

A multiple access scheme for the uplink of broadband wireless systems

Abstract: We present a multiple access scheme for the uplink of broadband wireless systems. We consider SC (single carrier) based block transmission, with all users transmitting continuously, regardless of their data-rate. The transmitted signals can have very low envelope fluctuations. Moreover, the different users remain orthogonal, even for severe time-dispersive channels. By employing IB-DFE (iterative block decision feedback equalization) techniques we can have detection performances close to the matched filter bound, and even for fully loaded systems and severe time-dispersive channels.

Broadband data services over vehicle power lines

Abstract: A method of providing broadband data services over power lines for moving vehicles is provided herein. Using broadband over power line (BPL) networking, a data signal is connected to a vehicle that is connected to a transport power line. The signal is communicated from the transport power line to the vehicle. The signal is then demodulated for use aboard the vehicle. The data signal connection allows for access to wide area networks such as the Internet. Access points can wirelessly broadcast wide area network signals from stationary locations to define meshed wireless networks in metropolitan areas.

Achieving Wireless Broadband with WiMax

Abstract: When users want broadband Internet service, they're generally restricted to a T1, DSL, or cable-modem-based connection. However, these wireline infrastructures can be considerably more expensive and time consuming to deploy than a wireless one. In addition, rural areas and developing countries frequently lack optical fiber or copper-wire infrastructures for broadband services, and providers are unwilling to install the necessary equipment for regions with little profit potential. Many residents thus must do without broadband service. Wireless approaches could address this problem. Therefore, proponents are advocating WiMax (worldwide interoperability for microwave access), a technology based on an evolving standard for point-to-multipoint wireless networking. Carriers can use WiMax to provide wireless Internet service via transceivers to users' antennas. In addition to IEEE 802.16, WiMax addresses the European Telecommunications Standards Institute's (ETSI) similar high-performance radio metropolitan area network (HiperMAN) broadband standard.

Proxy caching for media streaming over the Internet

Abstract: Streaming media has contributed to a significant amount of today's Internet traffic. Like conventional Web objects (e.g., HTML pages and images), media objects can benefit from proxy caching; but their unique features such as huge size and high bandwidth demand imply that conventional proxy caching strategies have to be substantially revised. This article discusses the critical issues and challenges of cache management for proxy-assisted media streaming. We survey, classify, and compare the state-of-the-art solutions. We also investigate advanced issues of combining multicast with caching, cooperating among proxies, and leveraging proxy caching in overlay networks.

Waiting for Broadband: Local Competition and the Spatial Distribution of Advanced Telecommunication Services in the United States

Abstract: With the passage of the Telecommunications Act of 1996, Congress directed the Federal Communications Commission and all fifty U.S. states to encourage the deployment of advanced telecommunication capability in a reasonable and timely manner. Today, with the rollout of advanced data services such as digital subscriber lines (xDSL), cable modems, and fixed wire- less technologies, broadband has become an important component of telecommunication service and competition. Unfortunately, the deployment of last-mile infrastructure enabling high-speed access has proceeded more slowly than anticipated and competition in many areas is relatively sparse. More importantly, there are significant differences in the availability of broadband services between urban and rural areas. This paper explores aspects of broadband access as a function of market demand and provider competition. Data collected from the Federal Commu- nications Commission is analyzed using a geographic information system and spatial statistical techniques. Results suggest significant spatial variation in broadband Internet access as a func- tion of provider competition in the United States.

Link error prediction methods for multicarrier systems

Abstract: Multicarrier modulations such as OFDM with adaptive modulation and coding (AMC) are well suited for high data rate broadband systems that operate in multipath environments and are considered as promising candidates for future generation cellular systems (e.g., 4G). Cellular system performance is normally investigated with system level simulations that are computationally complex. For broadband multicarrier systems, incorporating a detailed physical layer emulator into the system simulator becomes impractical, so there is a need for simplified link performance predictors. However, due to the large variability of the channel in the frequency domain, two links with the same average SNR can experience drastically different performance, thus making it difficult to accurately predict the instantaneous link performance such as the frame error rate. In this paper, the accuracy of two FER prediction methods is studied: Packet error rate indicator (PER-indicator) and exponential effective SIR mapping (Exp-ESM). Both methods are shown to have accuracy within a few tenths of a dB under a wide range of modulation schemes, coding rates and channel types. These methods are then extended to handle more advanced link enhancements such as hybrid ARQ and Alamouti encoding. The Exp-ESM method has slightly better accuracy than the PER-indicator, and is the preferred link error predictor for a system simulator.

Designing a mobile broadband wireless access network

Abstract: In this paper, a new OFDM-based air interface technology for a mobile broadband wireless system is described. The technology leverages the standard Internet protocol (IP) network elements to build the system and deploys a new air interface technology based on OFDMA. Cross-layer optimization played a major role in the design where the choices made in the physical, MAC, and link layers are also driven by the goal of extending the Internet to the wireless space. A major physical layer benefit of this air interface comes from the orthogonality property that the results in the elimination of in-cell interference are averaged and a worst-case interferer does not limit the system performance. The physical layer features not only result in high capacity but also provide very fine granularity of allocating air link resources, which improves the MAC and link-layer efficiency. The MAC and link layer provide contention-free, fast control channels between the RAR and the WTs. These channels are used to ferry a variety of signaling such as assignments of traffic channel, acknowledgements, channel quality, and traffic request reports. This holistic approach allows for a scheduler that could not only achieve high spectral efficiency but also allow for a fine control over QoS attributes such as latency, reliability, and service differentiation.

Wireless optical communications: a survey

Abstract: The demand for wireless broadband communications has been growing steadily for last several years. The congestion and the limitations on bandwidths of the radio spectrum have inhibited unrestricted growth of radio wireless systems. Wireless optical, however, holds the promise of delivering data rates that can meet the broadband requirements. As a result, wireless optical is believed to be a viable long term option for many applications of wireless communications. Nevertheless, the advantages of optical wireless have not yet been fully exploited. Basic and applied research is needed at the laboratory and commercial levels to bring the performance of real-life wireless optical systems into higher levels. The Gb/s level data rate has been validated in laboratory, however, available indoor systems only realize a data rate of 155Mb/s. Current research in wireless optical concentrates on increasing the communication capacity and improving the performance. In this paper, we survey the wireless optical discipline emphasizing major design, performance, and safety issues. Research directions that have the potential to close the gap between theory and practice, in wireless optical communications, are also presented.

Fiber to the home: the next big broadband thing

Abstract: This article is a progress report on the use of optical fiber as a successor to copper twisted pair of coax for "last mile" broadband access. We point out that the pressures for more per-user bandwidth are growing; that effective architectures have been designed, standardized, and placed in service; that fiber economies have become at least competitive with copper; and that promising early deployments have succeeded, particularly outside North America. As for North America, which lags the rest of the world in per-capita fiber access deployment, we note that there is already a modest "first wave" of deployments, but the full promise of fiber to the premises awaits a change of heart by the major carriers, probably driven by loss of copper-based broadband customers to the cable companies, user bandwidth growth (including HDTV), and issues of international competitiveness.

A dynamic bandwidth allocation scheme for differentiated services in EPONs

Abstract: Passive optical networks bring high-speed broadband access via fiber to the business, curb and home. Among various types of PONs, Ethernet PONs are gaining more and more attention since they are built on widely used Ethernet technology and can offer high bandwidth, low cost and broad services. EPONs use a point-to-multipoint topology, in which multiple optical network units share one uplink channel to transmit multimedia traffic to a control element, the optical line terminal. To avoid data collision on the shared uplink channel, a key issue in EPONs is a contention-free MAC protocol for the OLT to schedule the transmission order of different ONUs. In this article we first review some DBA schemes available in the literature, then propose a two-layer bandwidth allocation scheme that implements weight based priority for this need. To maximally satisfy the requests of all ONUs and provide differentiated services, an ONU is allowed to request bandwidth for all its available traffic, and all traffic classes proportionally share the bandwidth based on their instantaneous demands. The weight set for each class not only prevents high-priority traffic from monopolizing the bandwidth under heavy load but also ensures a minimum bandwidth allocated to each traffic class.

On the scalability of fixed broadband wireless access network deployment

Abstract: Fixed broadband wireless access systems, such as the local multipoint distribution service, use an open system architecture that supports a scalable solution for the Internet services over IEEE 802.16 wireless networks. This article presents an overview of various features of BWA systems toward realizing a high level of scalability to support a potentially fast expanding network. This is achieved by optimizing various network resources, which include utilizing the available bandwidth efficiency, making a minor enhancement to an existing system that minimizes the disruption to network services during the network expansion process, and combining the benefits of different features to increase network capacity.

Enhancement of VolP over IEEE 802.11 WLAN via dual queue strategy

Abstract: Today's IEEE 802.11 Wireless LAN (WLAN) is an excellent solution for the broadband wireless networking. However, it lacks of the capability to support real-time services such as voice-over-IP (VoIP) properly. In this paper, we present a simple and viable approach to enhance the VoIP performance over the 802.11 WLAN by implementing two queues along with a strict priority queuing on top of the 802.11 medium access control (MAC) controller, e.g., in the device driver of the 802.11 cards. We find via extensive simulations that the proposed scheme is remarkably effective for the VoIP service in the infrastructure-based WLAN in the coexistence with the nonreal-time traffic thanks to the flow control mechanism of the TCP protocol, which is typically used for the nonreal-time traffic today. Due to its simplicity, the proposed scheme should be readily deployable in the existing WLANs via simple software upgrades for the enhanced VoIP services.

An efficient uplink scheduling algorithm for VoIP services in IEEE 802.16 BWA systems

Abstract: An efficient uplink scheduling algorithm for VoIP services is very important for supporting a large number of users with various levels of quality of service (QoS). However, conventional uplink scheduling algorithms for VoIP services in IEEE 802.16 broadband wireless access (BWA) systems cause some problems, such as waste of uplink resources, MAC overhead and unnecessary access delay. We propose an efficient uplink scheduling algorithm for VoIP services in these systems. The base station (BS) assigns uplink resources to the subscriber stations (SS) by considering voice state transitions of the SS. These voice state transitions can be informed to the BS by utilizing one reserved bit in the generic MAC header of IEEE 802.16 BWA systems. We analyze the system throughputs and the access delays of conventional algorithms and of our proposed algorithm, and show, via OPNET simulation, that, in terms of throughput, our proposed algorithm is superior to conventional algorithms in these systems.

On the capacity of broadband relay networks

Abstract: This paper studies a broadband relay network model with multiple source nodes, multiple relay nodes and a single destination node. The capacities using different multiple access schemes (joint coding/decoding and OFDMA) under two relay schemes are derived, respectively. Numerical results are evaluated to compare the two multiple access schemes.

Service configuration and traffic distribution in composite radio environments

Abstract: This paper adopts the assumption that cellular, broadband fixed wireless access (BFWA), wireless local area networks (WLAN), and digital video broadcasting (DVB) systems can be co-operating components of a composite-radio infrastructure. It is believed that through the composite radio concept, operators will be enabled to offer efficient, in terms of cost and QoS, wireless access to broadband IP-based services. The exploitation of this infrastructure calls for the application of computational intelligence (CI) technologies for the development of appropriate, sophisticated service and network resource management functionality. In this context, this paper identifies and addresses the important problem of service configuration and distribution in a composite radio environment (SCD-CRE). The problem's objective is to determine the best way to accommodate a demand volume, with which the composite radio infrastructure is faced. The pro finds the QoS levels that can be offered, and the networks that can support the demand at the selected QoS levels. The paper includes a first approach to the definition, mathematical formulation, and solution of a version of the SCD-CRE problem. Results indicating some of the capabilities of the SCD-CRE are also presented. Further application fields for CI technologies are indicated, in the area of the necessary reconfiguration of the managed, radio and fixed, network segments.

Crossing the digital divide: cost-effective broadband wireless access for rural and remote areas

Abstract: The use of wireless, DSL, and cable for broadband access has become increasingly prevalent in metropolitan areas. While these technologies are being successfully utilized in terms of both service quality and economics in densely populated areas, there are still vast geographic regions where broadband services are either prohibitively expensive or simply unavailable at any price. The article examines several alternatives for using 2.4 GHz 802.11b (WiFi) technology to provide fixed broadband access in rural areas consisting of towns, smaller remote communities, clusters of subscribers separated by large intercluster distances, as well as widely scattered users. Our approach is to model a network based on realistic demographics, equipment and operations costs, service revenues, and customer demand and usage, and calculate the lifecycle economics in terms of capital investment and profitability. We consider the cost benefits of several emerging technologies and architectures, including high gain antennas, dynamically steerable beamforming antennas, and multihop routing. Our results show that cost-effective affordable high-speed wireless Internet access can be provided in rural and remote areas using nontraditional and innovative approaches, bridging the so-called digital divide.

Convergence of residential gateway technology

Abstract: A new OSI-based model is described that can be used for the classification of residential gateways. It is applied to analyze current gateway solutions and draw evolutionary paths for the medium to long term. From this it is concluded that particularly set-top boxes and broadband modems, as opposed to game consoles and PCs, have a strong potential to evolve toward gateways that deliver network services to the home on all OSI layers, although they probably will not converge. In our model, we have not found any compelling reasons for the residential gateway industry to support concurrent multiple broadband access network connections on a single residential gateway in the near future.

Factors influencing the adoption of residential broadband connections to the Internet

Abstract: Broadband adoption has been slower than anticipated in the United States resulting in a number of proposed policy interventions ranging from nonintervention to extreme measures. Digital divide advocates are concerned that demographics of broadband users reveal the same digital divide gaps that are observed in computer ownership and home Internet access. This study analyzes the factors influencing the adoption of residential broadband services using the current population survey data from September 2001. Three statistical models on computer ownership, home Internet access, and broadband access are analyzed to illustrate the differences in demographics between the dependent variables. Using a logit regression model, the results show that the digital divide is the widest for computer ownership and the narrowest for broadband access. The implications of this study are that public policy interventions to bridge the digital divide should focus more on computer ownership, and less on broadband specific policies.

Performance evaluation of a fixed relay concept for next generation wireless systems

Abstract: This work presents a concept and the related performance evaluation for a wireless broadband system based on fixed relay stations acting as wireless bridges. The system is intended for dense populated areas as an overlay to cellular radio systems. A short introduction is given to the general topic of fixed relaying, the proposed extension to a MAC-frame based access protocol like IEEE 802.11e, 802.15.3, 802.16a and HIPERLAN2 is outlined. A possible deployment scenario is introduced and the simulative traffic performance in a Manhattan-like dense urban environment is presented. It is established that the fixed relaying concept is well suited to substantially contribute to provide high capacity cellular broadband radio coverage in future (NG) cellular wireless broadband systems.

Design and development of a 5.25 GHz software defined wireless OFDM communication platform

Abstract: With growing interest in broadband wireless communication systems, a research platform for evaluating various communication schemes becomes essential. Such a system can be used to validate the assumptions and results of various theoretical and simulation-based studies. This article discusses the design and development of a multicarrier multi-antenna software defined radio, operating at 5.25 GHz in a 25 MHz bandwidth. The calibration process is described in detail along with a discussion of all the issues such as I/Q mismatch and phase noise that degrade and limit the performance of the system. Hardware and software solutions to these problems are described. Results of the calibration process and wireless experiments on the system are presented as well.

Cost drivers and deployment scenarios for future broadband wireless networks - key research problems and directions for research

Abstract: The most prominent problem in providing anywhere, anytime wideband mobile access is the towering infrastructure cost as it is basically proportional to the bandwidth provided. We provide a simple, initial, analysis of the various infrastructure cost factors. This analysis shows that, contrary to what one may expect, the infrastructure cost is not dominated by electronic equipment, but rather by other deployment related costs (towers, wiring, building, network connections) and maintenance costs. In the paper some novel architectural approaches for future wideband mobile access focusing on these dominant cost factors are described and the related key research issues are discussed.

Multiple-length multiple-wavelength optical orthogonal codes for optical CDMA systems supporting multirate multimedia services

Abstract: Multiple-wavelength optical orthogonal codes (MWOOCs) with autocorrelation sidelobes and cross-correlation values of both at most one were recently proposed for wavelength-time optical code-division multiple-access (O-CDMA) systems. The codes have cardinality as a quadratic function of the number of wavelengths and find applications in high bit-rate O-CDMA systems with broadband supercontinuum lasers, in which the number of available wavelengths is larger than the number of time slots. To support multimedia services with different bit-rate and quality-of-service requirements, a new class of multiple-length constant-weight MWOOCs with autocorrelation sidelobes of zero and cross correlations of at most one is constructed algebraically in this paper. The performance of these new codes in an O-CDMA system with double-media services is analyzed. In contrary to conventional single-length codes, our study shows that the performance of these multiple-length codes improves as the code length decreases. This unique property supports "prioritization" in O-CDMA.

Hop-by-hop toward future mobile broadband IP

Abstract: We try to give some perspectives on likely trends in future wireless broadband networking. The treatment is an exploration of some technologies; due to the requirement to cover the topic from a broad perspective, it is not possible to go into technical details. We review current developments toward future mobile broadband networks, and then present the 4G paradigm of trying to combine heterogeneous networks, both cellular wireless hotspots and sensor networks, together with Internet protocols. We show how different networks play their own roles in the emerging infrastructure so that we can hop by hop wave the broadband network from mobile devices toward the fiber optic core network.