Packet reservation multiple access for local wirelesscommunications

Simulation work is reported indicating that packet reservation multiple access (PRMA) allows a variety of information sources to share the same wireless access channel. Some of the sources, such as speech terminals, are classified as periodic and others, such as signaling, are classified as random. Packets from all sources contend for access to channel time slots. When a periodic information terminal succeeds in gaining access, it reserves subsequent time slots for uncontested transmission. Both computer simulations and a listening test reveal that PRMA achieves a promising combination of voice quality and bandwidth efficiency     

OEIC WDM transceiver modules for local access networks

The authors report measurements of fibre-optic transceiver modules which use a single optoelectronic integrated circuit (OEIC) subsystem. The optical circuit contains a DFB laser, 3 dB coupler, WDM, monitor photodiode and pin photodetector elements, which are monolithically integrated on a semi-insulating substrate indium phosphide chip. This assembly is designed to provide complete subscriber-termination functionality for bidirectional telephony and unidirectional broadband communication links for access networks. The dual-in-line module provides single fibre network interfacing, is physically compact, is stable for domestic and business environments, requires no cooling, and has the potential to be manufacturable at low cost     

Fiber-based local access network architectures

The attributes of the various architectural alternatives are discussed. Several systems proposed for the delivery of telephone service and/or distributive video services in the local access network are described. The status of the standardization of interfaces for the broadband integrated services digital network (BISDN) based on the synchronous optical network (SONET) and asynchronous transfer mode (ATM) is examined     

Alternative local area network access protocols

The course of recent research is outlined, and state-of-the-art protocols are surveyed. The various classes of access protocols and corresponding performance models are covered. These are fixed assignment access, random-assignment access, demand assignment access, integrated local area networks, and multichannel local area networks     

宽带接入用户驻地网建设浅析

随着高速上网、VOD点播、网络电视、远程教育等宽带业务的推出,宽带接入网的建设已成为各电信运营商的重点建设内容。目前,应用较多的有FTTx LAN、FTTx xDSL、FTTx HFC等接入方式。在宽带接入网的建设中,首先遇到的是用户驻地网（CPN）问题,即通常所说的最后100m的问题。所谓用户驻地网一般是指用户终端至用户网络接口所包含的机线设备（通常在一个楼房内）,由完成通信和控制功能的用户驻地布线系统组成,以使用户终端可以灵活方便地进入接入网。目前属于CPN范畴的有4种方式：①普通铜缆双绞线;②同轴电缆;③5类双绞线（…     

Bandwidth-efficient PON system for broad-band access and local customer Internetworking

We present a new passive optical network (PON) architecture for broad-band access and local customer networking. It provides high bandwidth efficiency for delivering both PON and customer internetworking services. The architecture separates the local optical network from the PON system, thereby enhancing security, flexibility, and allowing the use of any media access control protocol. The local customer internetworking feature is demonstrated with insignificant penalty to the overall PON system performance.     

Energy and bandwidth-efficient channel access for local area machine-to-machine communication

Wireless Networks - Ticket Election Multiple Access (TEMA) is introduced for local machine-to-machine communication that is energy and bandwidth-efficient. TEMA is based on distributed elections...     

Connection-based media access for multichannel local and metropolitan area networks

A multichannel access technique is proposed for local and metropolitan area networks. The method presented achieves load balancing in a single-connection environment by employing a dynamic channel assignment scheme. Analytic and simulation results show that the nonpersistent mode of the protocol performs as well as the best existing multichannel CSMA/CD protocol. This is accomplished with a considerable reduction in hardware per network connection.     

Comparison of sequences for local area networks usingspread-spectrum multiple access

The construction and comparative analysis of sequence sets that are often used as a basis for code-division multiple access (CDMA) systems and spread-spectrum local area networks (SS-LAN) are presented. The results obtained are useful in the definition of the ideal code properties and the selection of sequence sets for particular types of SS-LAN applications     

高功率钛宝石激光放大系统的研究进展

总结了高功率钛宝石激光放大系统的研究成果及研究状况，并展望了今后的发展方向和发展趋势。     

Novel approach for simple fabrication of high-performance InP-switch matrix based on laser-amplifier gates

We report here on an InP-switch matrix based on laser-amplifier gates with gain- and polarization-insensitive (as low as 1 dB) operation. A novel integration scheme is demonstrated that provides over 10 dB net chip gain for both input polarizations. Fiber-to-fiber operation with gain can moreover be obtained. Design and switching characteristics are detailed.     

Frequency-hopped spread-spectrum random access with local adaptation

A decentralised transmission policy that rejects a blocked packet that has been retransmitted a number of times is analysed for the frequency-hopping channel. For stability considerations and for channel throughput increase, the information packet is enclosed by a Reed-Solomon code. The way in which the code rate should be adjusted and the number of transmission attempt pairs that guarantees network stability are investigated.<>     

Media access control for high-speed local area and metropolitanarea communications networks

The features, architectures, and principles of key media access control (MAC) schemes for high-speed LAN and MAN systems are categorized and reviewed. These architectures are related to the hierarchical structure of a telecommunications network. An overview is given of the MAC protocol operation of key local- and metropolitan-area network systems, as defined by standards committees, covering current methods as well as approaches for future broadband integrated services digital networks. Modeling and analysis techniques are then reviewed for key classes of relevant MAC schemes, including fixed-assignment time-division-multiaccess (TDMA) schemes; demand-assignment reservation schemes, involving, in particular, pure packet-switched, pure circuit-switched and hybrid-switched integrated-services demand-assignment TDMA and time-division-multiplexing structures; demand-assigned polling procedures; and random-access policies     

Using generalized capacitated trees for designing the topology of local access networks

The design of the topology of a local access network is a complex process which builds on many different combinatorial optimization problems such as the concentrator quantity problem, the concentrator location problem, the terminal clustering problem and the terminal layout problem. Usually, these four subproblems are solved separably and sequentially and the solution of one subproblem is used as data for the next subproblem. There are two main drawbacks associated to this four‐phase approach: i) without knowing the optimal solution to the global problem it is difficult to set the parameters for some of the subproblems which appear in the earlier phases and ii) in many cases, wrong decisions taken at one of the earlier phases are “passed” to the subsequent phases. Our aim in this paper is to formulate the two last subproblems, clustering and layout, as one single generalized capacitated tree problem. We formulate the clustering/layout problem as a capacitated single‐commodity network flow problem with adequate capacities on the arcs. We adapt a reformulation presented in (Gouveia, 1995) of a single‐commodity flow model presented in (Gavish, 1983). We present several inequalities which can be used to tighten the LP relaxation of the original formulation. We present two heuristics for obtaining feasible solutions for the clustering/layout problem. Computational results taken from tests with 50, 100 and 200 nodes indicate that in most of the cases the best heuristic produces topologies with lower cost than the ones obtained by solving separately and sequentially the two individual subproblems. This revised version was published online in June 2006 with corrections to the Cover Date.     

Cellular access control and charging for mobile operator wireless local area networks

This article presents a system architecture, design considerations, and rationale for a mobile operator wireless LAN. The article also discusses the system implementation and performance issues. The system presented reuses GSM and GPRS mechanisms for user authentication, access control, subscriber management, operator roaming, and billing, while still being compatible with wireless Internet service provider networks and IETF and IEEE protocols such as RADIUS, EAP, and IEEE 802.1x. The architecture is a result of research carried out by Nokia between 1999 and 2002. The designed architecture has also been verified in a complete system implementation.     

单端口管脚驱动双LED的方法

大多数现代微控制器都提供I/O端口,可以在程序执行期间改变这些端口的功能。当用作输出时,这些电路可以吸收或流出相当大的电流。本设计实例示出了用一个I/ O管脚驱动双管脚、双色LED的三种方法。图1是一个可能的方案,它使用外接反相器IC_1来驱动一只红/     

Materials for magneto-optic modulators

A review of the current status of magneto-optic modulator materials is presented with emphasis on operation at the Nd³⁺:YAG wavelength of 1.064 μm. Because the iron garnets are “cubic”, exhibit small values of linear magnetic birefringence, and offer great flexibility in ion substitutions and some flexibility in optical absorption values, these materials provide clear advantages over any other known class of magnetic compounds. Recent work has also shown that Faraday rotati ons in the iron garnets can be remarkably enhanced by Bi³⁺ and/or Pr³⁺ substitutions. The physical origin of this enhancement is briefly outlined in terms of the iron garnet energy level structure. An important problem that has not as yet been completely resolved is the question of intrinsic optical absorption at 1.064 μm. Evidence is presented showing that optical losses in the 1–4 cm⁻¹ (0.43–1.7 db/mm) range should be achievable in praseodymium-substituted gadolinium iron garnet, but thus far the lowest observed absorption coefficient is 5.9 cm⁻¹ = 2.6 db/mm. In the case of bismuth-substituted garnets the lowest observed absorption at 1.064 μm is 13 cm⁻¹ = 5.6 db/mm. The importance of impurities, nonstoichiometry, and Pb incorporation from the flux is emphasized. Finally, we point out that other material properties such as magnetocrystalline anisotropy, ferromagnetic resonance frequency and linewidth, and values of 4πM_S should be included in any complete materials evaluation.     

Wideband local access: wireless LAN and wireless ATM

An overview of the status of wideband wireless local access technologies is provided. Service scenarios and availability of the market and products for wireless LAN and wireless ATM technologies are discussed. Similarities among IEEE 802.11 and HIPERLAN standards for wireless LANs and the developing prototypes for wireless ATM are evaluated. An update on the status of the available unlicensed bands in the United States as well as the status of the wideband wireless projects in the European Community and Japan are presented     

Subpicosecond pulse compression and Raman generation using amode-locked erbium-doped fiber laser-amplifier

Pulses of 20 ps duration from a 1536-nm erbium-doped fiber laser mode-locked at 10 MHz were soliton-compressed in a 1-km fiber to 1.5 ps. The pulses were then amplified in an erbium-doped fiber amplifier and compressed in a second fiber to less than 300 fs. Pulses give rise to stimulated Raman scattering in fibers; the direct output from the erbium fiber laser-amplifier has sufficient peak power to pump fiber Raman lasers. The sources can be made very compact and, with laser diode pumping, an all-fiber design can be realized. Such sources will find use in high-speed optical and electrooptical sampling instrumentation. Peak powers are high enough to study the nonlinear fiber effects that usually require a high-power Nd:YAG or color center laser     

A nonpreemptive priority-based access control scheme for broadbandad hoc wireless ATM local area networks

The DQRUMA (distributed-queueing request update multiple access) protocol has been considered as an access protocol for the BAHAMA (broadband ad hoc wireless ATM local area network). However, it cannot support the service discipline of integrated multimedia traffic since it does not include any priority and access control policy. In this paper, we propose a nonpreemptive priority-based access control scheme for the DQRUMA protocol. Under such a scheme, modifying the CSMA/CA protocol in the contention period supports many levels of priorities such that user mobility (handoff) can be supported in BAHAMA. Besides, the proposed transmit-permission policy and adaptive bandwidth allocation scheme provide various QoS (quality-of-service) guarantees while maintaining high bandwidth utilization. Simulations show that it provides a good performance in ad hoc wireless ATM LAN environments