By Topic

Communications Magazine, IEEE

Issue 3 • Date March 2003

Filter Results

Displaying Results 1 - 21 of 21
  • A tribute to our friend and colleague Salah Aidarous

    Page(s): 12
    Save to Project icon | Request Permissions | PDF file iconPDF (114 KB)  
    Freely Available from IEEE
  • Internet for a mobile generation [Book Review]

    Page(s): 14
    Save to Project icon | Request Permissions | PDF file iconPDF (118 KB)  
    Freely Available from IEEE
  • QoS in integrated 3G networks

    Page(s): 14 - 16
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB) |  | HTML iconHTML  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reasons for optimism

    Page(s): 18 - 36
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB) |  | HTML iconHTML  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Roster of reviewers - 2002

    Page(s): 38 - 42
    Save to Project icon | Request Permissions | PDF file iconPDF (232 KB)  
    Freely Available from IEEE
  • Optical wireless communications

    Page(s): 48
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (87 KB) |  | HTML iconHTML  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 4G mobile research in Asia

    Page(s): 104 - 106
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (278 KB)  

    First Page of the Article
    View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • High-speed integrated transceivers for optical wireless

    Page(s): 58 - 62
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (424 KB) |  | HTML iconHTML  

    Optical wireless LANs have the potential to provide bandwidths far in excess of those available with current or planned RF networks. There are several approaches to implementing optical wireless systems, but these usually involve the integration of optical, optoelectronic, and electrical components in order to create transceivers. Such systems are necessarily complex, and the widespread use of optical wireless is likely to be dependent on the ability to fabricate the required transceiver components at low cost. A number of UK universities are currently involved in a project to demonstrate integrated optical wireless subsystems that can provide line-of-sight in-building communications at 155 Mb/s and above. The system uses two-dimensional arrays of novel microcavity LED emitters and arrays of detectors integrated with custom CMOS integrated circuits to implement tracking transceiver components. In this article we set out the basic approaches that can be used for in-building optical wireless communication and argue the need for an integrated and scalable approach to the fabrication of transceivers. Our work aimed at implementing these components, including experimental results and potential future directions, is then discussed. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wireless network resource management for Web-based multimedia document services

    Page(s): 138 - 145
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (578 KB) |  | HTML iconHTML  

    Advances in wireless technology and availability of portable devices with networking capabilities have enabled ubiquitous Web accessibility. This has created the need to provide advance Internet services to mobile users without causing service failures due to connection migration or handoffs. However, scarcity of wireless resources restricts the provision of multimedia services in wireless networks. We address the issue of managing wireless resources to support Web-based multimedia document services including MPEG-4-based applications, in wireless networks with a high degree of user mobility. In particular, we formulate the resource management problem in wireless networks as an optimization problem with an objective function comprising different quality of presentation parameters. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multiple-subcarrier modulation in optical wireless communications

    Page(s): 74 - 79
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (445 KB) |  | HTML iconHTML  

    This article overviews multiple-subcarrier modulation techniques in optical wireless communications. The basic principles and characteristics of MSM techniques in optical wireless communications are presented. MSM optical wireless systems are explained where some block codes that convert information bits to be transmitted to the symbol amplitudes of subcarriers are used to increase the minimum value of the MS electrical waveform. MSM optical communications systems using subcarrier signal point sequences (SSPS) that can improve the power efficiency of MSM systems are also explained. The performance of MSM optical communications systems is presented in the intensity modulation with direct detection (IM/DD) channel without dispersion and in atmospheric optical communications where the effects of scintillation exist. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Beyond 3G: vision, requirements, and enabling technologies

    Page(s): 120 - 124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (432 KB) |  | HTML iconHTML  

    This article introduces the vision and requirements for future development of mobile communications systems, and discusses several key enabling technologies such as modulation and multiple access schemes, multiple antenna techniques, and an IP-based network, considered important to realize this vision in real-world systems. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 1D MEMS-based wavelength switching subsystem

    Page(s): 88 - 94
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB) |  | HTML iconHTML  

    Over the past few years, micro-electromechanical systems (MEMS) have emerged as a leading technology for realizing transparent optical switching subsystems. MEMS technology allows high-precision micromechanical components such as micromirrors to be mass produced at low cost. These components can be precisely controlled to provide reliable high-speed switching of optical beams in free space. Additionally, MEMS offers solutions that are scalable in both port (fiber) count and the ability to switch large numbers of wavelengths (> 100) per fiber. To date, most of this interest has focused on two-dimensional and three-dimensional MEMS optical crossconnect architectures. We introduce a wavelength-selective switch based on one-dimensional MEMS technology and discuss its performance, reliability, and superior scaling properties. We also review several important applications for this technology in all-optical networks. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • An agile server for cross-provider service peering and aggregation

    Page(s): 126 - 136
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (766 KB) |  | HTML iconHTML  

    Telecommunications and next-generation network IP-based services can be increasingly delivered at network edges and in peered third-party networks. As a result, subscribers bypass operators' services in favor of alternative novel services; accordingly, potential revenue is lost. By bundling existing viable network-based services across providers, however, service providers can create new revenues and avoid further erosion of their market share. Business announcements attest to this growing trend, but thus far cross-provider solutions take the form of point-to-point customized integrations. In the emerging service delivery paradigm, providers must be able to interwork fluidly with partners already operating profitable services, and do so without going through the risky and costly service development cycle, and without the need for extensive customized software development. We outline an intelligent-agent-based service peering and aggregation server whose deployment on service provider networks enables such interworking. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Angle diversity and rate-adaptive transmission for indoor wireless optical communications

    Page(s): 64 - 73
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (666 KB) |  | HTML iconHTML  

    The main degrading factor in indoor wireless optical communication systems for bit rates up to several megabits per second is the shot noise induced by ambient light (sunlight and artificial light produced by incandescent and fluorescent lamps). Due to the directional nature of both signal and ambient light noise, the spatial distribution of the signal-to-noise ratio in indoor environments can show large variations. This article compares techniques that are able to mitigate the effect of such SNR variations: rate-adaptive transmission and angle diversity. In the first technique, the effective data rate is adjusted to the local SNR conditions by introducing different levels of redundancy. The second technique explicitly explores the directionality of the SNR by combining signals collected from different observation angles. We address the performance of rate-adaptive transmission and angle diversity techniques, and compare them based on experimental results obtained in a typical indoor environment. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Quality of service terminology in IP networks

    Page(s): 153 - 159
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (572 KB) |  | HTML iconHTML  

    This article provides an overview of commonly used terminology related to quality of service assurance in IP networks. Several approaches to QoS definition, including those of IETF, ITU, and ETSI, are presented and compared. Terms associated with QoS like class of service, grade of service, service level agreement, as well as service level specification (SLS), traffic conditioning agreement (TCA), and traffic conditioning specification (TCS) are discussed. Terminology used in two QoS architectures, IntServ and DiffServ, is also introduced. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Microoptical phased arrays for spatial and spectral switching

    Page(s): 96 - 102
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (538 KB) |  | HTML iconHTML  

    This article describes two optical devices based on linear arrays of micromirrors. The first is a phased array of micromirrors that can be rotated as well as translated vertically to maintain coherence across the array. We demonstrate experimentally that such micromirrors are capable of high-diffraction-efficiency phased-array scanning of laser beams. The second device is a Gires-Tournois (1969) interferometer with a micromirror array that provides tunable phase modulation for the multitude of partially reflected beams within the interferometer. We demonstrate experimentally that the MEMS-GT interferometer can operate as a tunable deinterleaver for dense wavelength-division multiplexed fiber optic communication. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Flexible optical wireless links and networks

    Page(s): 51 - 57
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (539 KB) |  | HTML iconHTML  

    The worldwide demand for broadband communications is being met in many places by installed single-mode fiber networks. However, there is still a significant "first-mile" problem, which seriously limits the availability of broadband Internet access. Free-space optical wireless communications has emerged as a viable technology for bridging gaps in existing high-data-rate communications networks, and as a temporary backbone for rapidly deployable mobile wireless communication infrastructure. In this article we describe research designed to improve the performance of such networks along terrestrial paths, including the effects of atmospheric turbulence, obscuration, transmitter and receiver design, and topology control. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Distributed wireless communication system: a new architecture for future public wireless access

    Page(s): 108 - 113
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (464 KB) |  | HTML iconHTML  

    The distributed wireless communication system (DWCS) is a new architecture for a wireless access system with distributed antennas, distributed processors, and distributed control. With distributed antennas, the system capacity can be expanded through dense frequency reuse, and the transmission power can be greatly decreased. With distributed processors control, the system works like a software or network radio, so different standards can coexist, and the system capacity can be increased by coprocessing of signals to and from multiple antennas. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The perspectives of large area synchronous CDMA technology for the fourth-generation mobile radio

    Page(s): 114 - 118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (404 KB) |  | HTML iconHTML  

    Some basic relations among system bandwidth, threshold SIR, maximum number of access users, as well as system spectral efficiency are studied for both traditional CDMA and large area synchronous CDMA (LAS-CDMA). The perspectives of LAS-CDMA for the 4G are also studied. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A novel approach of backup path reservation for survivable high-speed networks

    Page(s): 146 - 152
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (520 KB) |  | HTML iconHTML  

    For high-speed networks, a restoration mechanism based on backup path (BP) provides a means for assuring their survivability. We propose a two-phase BP reservation mechanism for high-speed networks. In the admission phase, a pair of working path (WP) and backup path is selected from the provisioned sets of WPs and BPs. In the adjustment phase, if backup capacity utilization exceeds the preset threshold, BP assignments are rearranged to optimize the usage of backup capacity. A mathematical model is formulated to verify the quality of the optimized solutions. Computational experiments indicate that the proposed mechanism significantly reduces the consumption of backup capacity while still maintaining a high degree of survivability. Moreover, experiments show that the optimized solutions obtained are on average within 3.6 percent of optimal. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance evaluation of a triangular pyramidal fly-eye diversity detector for optical wireless communications

    Page(s): 80 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (536 KB) |  | HTML iconHTML  

    Background noise and multipath propagation are the major impairments in indoor optical wireless links. They can introduce heavy distortion in the received optical signal and can degrade the system performance. An investigation into the optical wireless system performance has been carried out for two configurations: a hybrid system, and a diffuse system with a single detector and a triangular pyramidal fly-eye diversity receiver (PFDR). Original results for both systems that employ a PFDR antenna, under different fields of view (FOVs), are presented. The design goal is to reduce the effect of signal spread and improve the signal-to-noise ratio when the system operates under the constraints of background noise and multipath dispersion. It is demonstrated that through PFDR FOV optimization the directional background interference can be reduced and the received pulse shape improved. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

Aims & Scope

IEEE Communications Magazine covers all areas of communications such as lightwave telecommunications, high-speed data communications, personal communications systems (PCS), ISDN, and more.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Sean Moore
Centripetal Networks