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Communications Magazine, IEEE

Issue 12 • Date Dec. 1998

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Displaying Results 1 - 16 of 16
  • Multi-Wavelength Fiber Optic Communication

    Publication Year: 1998 , Page(s): 26
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  • Optical Wireless Systems and Networks

    Publication Year: 1998 , Page(s): 70 - 71
    Cited by:  Patents (5)
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  • A robust wireless infrared system with channel reciprocity

    Publication Year: 1998 , Page(s): 100 - 106
    Cited by:  Papers (4)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2580 KB)  

    Mobile computing devices require reliable wireless communication links, whereby data rates, transmission range, and power consumption fit the particular needs of the various types of devices. Proper designs of physical layer functions and medium access control mechanisms are crucial for efficient connectivity and coexistence among all participants in a communication cell. We describe a solution for reliable wireless infrared connectivity based on infrared channel reciprocity. Robust header signalling, and variable data rate coding View full abstract»

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  • Performance modeling of the IrDA protocol for infrared wireless communications

    Publication Year: 1998 , Page(s): 113 - 117
    Cited by:  Papers (5)  |  Patents (3)
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    This article presents a performance analysis of the IrDA protocol used for short-range IR data communication using an analytical mathematical model. The IrDA protocol specifies a protocol stack for reliable short-range infrared wireless data communication between devices with the data link layer (IrLAP) being an HDLC derivative. The mathematical model is based on unidirectional data transfer and uses the concept of the virtual transmission time, which provides the average end-to-end transmission time of a packet, incorporating the time for retransmissions if packet errors occur or other enforced delays. Analytical results are produced for throughput against packet size, BER and minimum turnaround time. They indicate certain limitations of the protocol for efficient throughput at high data speeds, and indicate that the maximum frame size and window size should be increased and the minimum turnaround time minimized for improved results View full abstract»

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  • Optical wireless: the story so far

    Publication Year: 1998 , Page(s): 72 - 74, 79-82
    Cited by:  Papers (54)
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    We present a broad review of the optical wireless field, from early experiments through to today's high-performance systems. Emphasis is placed on understanding the benefits and limitations of optical wireless, all of which ultimately define the applications. A variety of systems are examined, each incorporating a different technological solution to suit the particular application View full abstract»

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  • The infrared physical layer of the IEEE 802.11 standard for wireless local area networks

    Publication Year: 1998 , Page(s): 107 - 112
    Cited by:  Papers (12)
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    The new IEEE 802.11 standard for wireless local area networks defines a specification for an infrared physical layer. This article gives an overview of infrared technology and describes the IEEE 802.11 specification in detail, presenting a historical perspective of its development. The infrared physical layer was designed for diffuse systems supporting two data rates (1 and 2 Mb/s) and includes provisions for a smooth migration to higher data rates. The specification is suitable for low-cost transceivers but allows interoperability with higher-performance systems. The main application envisaged for IEEE 802.11 infrared wireless local area networks is ad hoc networks View full abstract»

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  • Developments in wavelength division multiple access networking

    Publication Year: 1998 , Page(s): 28 - 36
    Cited by:  Papers (13)  |  Patents (1)
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    The last few years have seen a growing interest in WDM for optical networks in order to increase the capacity and overcome the electronic bottleneck. Alongside the improvement in the WDM components there has been continuing development of WDMA networks. A large number of different WDMA strategies have been investigated in terms of both network architecture and the associated protocol requirements. This article identifies major themes and provides examples of experimental and theoretical developments which are anticipated to facilitate WDMA networking View full abstract»

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  • Performance of optical wireless OOK and PPM systems under the constraints of ambient noise and multipath dispersion

    Publication Year: 1998 , Page(s): 83 - 87
    Cited by:  Papers (11)
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    An investigation into the sensitivity performance of both a PPM and an OOK optical wireless communication system has been carried out in the presence of both ambient noise and multipath dispersion. It is shown that the sensitivity of a PPM scheme is more affected by multipath dispersion than a similar OOK format. Under the constraint of ambient noise, the findings were opposite. Both systems operate at 10 Mb/s and a wavelength of 850 nm. In a line-of-sight configuration, PPM offers an 8.77 dB sensitivity improvement over a comparable OOK system. In a semi-diffuse system impaired by multipath dispersion, the sensitivity improvement is reduced to 7.13 dB. When corrupted by ambient noise, the improvement was found to be 8.8 dB, which is slightly more View full abstract»

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  • All-optical wavelength conversion using SOA nonlinearities

    Publication Year: 1998 , Page(s): 56 - 61
    Cited by:  Papers (18)  |  Patents (7)
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    In this article the increasing use of WDM systems in telecommunications networks is highlighted, and the potential role for wavelength conversion in future upgrades of such systems is reviewed. Techniques for achieving wavelength conversion by all-optical means using nonlinearities in semiconductor optical amplifiers are explained, and experimental results obtained at BT Laboratories are used to illustrate the state of the art View full abstract»

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  • Arrayed waveguide gratings for wavelength routing

    Publication Year: 1998 , Page(s): 62 - 68
    Cited by:  Papers (21)  |  Patents (2)
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    Wavelength routing can be performed in the optical domain for both long-haul and passive optical networks. Arrayed waveguide gratings (AWGs) can perform wavelength routing for a large number of optical channels and provide a high level of functionality on an integrated chip. The AWG guides light on a planar lightwave circuit into an array of waveguides that provide dispersion to separate the different wavelengths of light. Routing functions can be performed on individual wavelengths. With this technology, optical cross-connects, optical add/drop multiplexers, and passive optical routers have been demonstrated. Performance issues-such as insertion loss, polarization dependence, passband shape, passband position, crosstalk, and temperature dependence-are being addressed so that AWGs will be practical for deployment into systems View full abstract»

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  • Imaging diversity receivers for high-speed infrared wireless communication

    Publication Year: 1998 , Page(s): 88 - 94
    Cited by:  Papers (39)  |  Patents (22)
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    We discuss two modifications to the design of wireless infrared links that can yield significant performance improvements, albeit at the price of increased complexity. In line-of-sight and non-line-of-sight links, replacement of a single-element receiver by one employing an imaging light concentrator and a segmented photodetector can reduce received ambient light noise and multipath distortion. For a fixed receiver entrance area, such an imaging receiver can reduce transmit power requirements by as much as about 14 dB, depending on the link design and the number of photodetector segments. Imaging receivers also reduce co-channel interference, and may therefore enable infrared wireless networks to employ space-division multiplexing, wherein several transmitters located in close proximity can transmit simultaneously at the same wavelength. In nondirected non-line-of-sight links, replacement of the diffuse transmitter by one that projects multiple narrow beams can reduce the path loss, further reducing the transmit power requirement by several decibels. We describe the design of an experimental 100 Mb/s infrared wireless link employing a multibeam transmitter and a 37-pixel imaging receiver View full abstract»

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  • Tunable optical filters for dense WDM networks

    Publication Year: 1998 , Page(s): 50 - 55
    Cited by:  Papers (45)  |  Patents (31)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1188 KB)  

    WDM is currently taking over as the leading technology in point-to-point transmission links. For optical implementation of WDM networks, logical functionalities such as wavelength (channel) selection should be carried out in the wavelength domain; thus, the development of dynamic optical devices is required. One key device is a tunable optical filter. Important features of such a filter include low insertion loss, narrow bandwidth, high sidelobe suppression, large dynamic range, fast tuning speed, a simple control mechanism, small size, and cost effectiveness. Here, an extensive overview of the different technologies used to produce tunable optical filters is presented. Among them, fiber filters such as fiber Bragg gratings and fiber Fabry Perot are the most commercialized, yet inherently limited in their dynamic speeds. For high demanding dynamics, micro-machined and acousto-optic filters can offer a good solution for microsecond tuning speeds. Faster tunable devices, in nanosecond tuning speeds, might emerge out of microresonators, electrooptic filters, and active DBR filters View full abstract»

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  • Multiwavelength receivers for WDM systems

    Publication Year: 1998 , Page(s): 42 - 49
    Cited by:  Papers (3)  |  Patents (8)
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    Multiwavelength array receivers and tunable receivers are some of the key devices much needed in future WDM links and networks. This article offers a description of this rapidly developing field. Both hybrid and monolithic integrated versions of WDM receivers are described. Related packaging issues are also discussed View full abstract»

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  • ATM infrared wireless LANs: a proposed architecture

    Publication Year: 1998 , Page(s): 118 - 123
    Cited by:  Papers (1)
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    As infrared wireless LANs for in-building applications become more popular because of their many advantages, it is of interest to design such LANs to support the ATM protocol and therefore provide wireless access to fixed ATM networks. The architecture of such a LAN is presented in this article. Emphasis is placed on the protocol stacks of the model to provide seamless operation with the wired network, on the cellular topology, and on the MAC protocol. Under the proposed topology the system performance is revealed in terms of packet dropping probability, average access delay, channel throughput, and statistical multiplexing gain for a range of system parameters View full abstract»

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  • Multifrequency lasers and applications in WDM networks

    Publication Year: 1998 , Page(s): 39 - 41
    Cited by:  Papers (7)  |  Patents (4)
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    The current status and applications of multifrequency lasers (MFL) are reviewed. An MFL consists of an array of N optical amplifiers monolithically integrated with a 1×N optical multiplexer. The laser provides the functionality of N independent lasers whose optical wavelengths are precisely locked together by the common intracavity optical multiplexer. The design of an MFL together with its fundamental characteristics are discussed, and state-of-the-art results are shown. The functionality of an MFL is compared to that of an integrated DFB array. Finally, we show some applications of single-wavelength tunable transmitters and multiwavelength transmitters View full abstract»

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  • Digital pulse interval modulation for optical communications

    Publication Year: 1998 , Page(s): 95 - 99
    Cited by:  Papers (26)
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    This article presents a study of digital pulse interval modulation (DPIM) for optical wireless communications using intensity modulation with direct detection. The DPIM code properties are discussed, and expressions for the transmission capacity, power spectrum, and error probability are presented. We show that for a given number of bits per symbol, DPIM has a higher transmission capacity, a similar spectral profile, and only a marginally inferior error probability performance compared with pulse position modulation, and is rather less complex to implement. Finally, problems associated with the nonuniform symbol length characteristics of DPIM together with possible solutions are discussed View full abstract»

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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.

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Editor-in-Chief
Osman Gebizlioglu
Huawei Technologies