An Improved Round Robin Packet Scheduler for Wireless Networks

Scheduling algorithms are important components for providing quality-of-service (QoS) guarantees in wireless networks. The design of such algorithms need to take into account bursty errors and location-dependent channel capacity that are characteristics of wireless networks. In this paper, a new scheduling algorithm for packet cellular networks, wireless deficit round robin (WDRR), is proposed. WDRR is a round robin scheduler that has low implementation complexity and offers a low delay bound, tight fairness index, and good isolation property. In error-prone channels, the algorithm provides short-term fairness among sessions that perceive a clean channel, long-term fairness among all sessions, ability to meet specified throughput objectives for all sessions, and graceful service degradation among sessions that received excess service. Both analysis and simulation are used to verify the WDRR properties.     

An Efficient Scheduling Discipline for Packet Switching Networks Using Earliest Deadline First Round Robin

This paper addresses a frame-oriented scheduling discipline, EDF-RR (earliest deadline first round robin), for OQ (output-queued) switch architecture and data traffic consisting of fixed-length cells. Bandwidth reservation for an active session is performed by holding a number of cell slots for the session in a repeatedly-transferred frame. Each cell that is going to be transferred in the frame is assigned a virtual release time and a virtual deadline according to the bandwidth reservation scheme. The transmitting order of the cells in the frame is determined by non-preemptive non-idling EDF algorithm so that cells of a backlogged session in the frame are distributed as uniformly as possible. Through the analysis applying real-time scheduling theory and network calculus as well as network simulation, EDF-RR takes the advantage of O(1) computational complexity, and possesses tight delay bounds and lenient buffer requirements. The proposed scheduling discipline is appropriate for distributed real-time systems as we show that sessions can be configured based on message traffic models and deadline requirements. Also, a modified version of EDF-RR, called EDF-DRR, can be applied as traffic regulator when jitter requirements exist among active sessions. This work was sponsored in part by the Federal Aviation Administration (FAA) via grant DTFA03-01-C-00042. Findings contained herein are not necessarily those of the FAA.     

Power Control for Packet Voice Service with Application to EDGE Wireless System

Using the enhanced data rates for GSM evolution (EDGE) system with cyclic frequency hopping as an example, we apply a Kalman-filter power control method based on interference tracking to packet voice service in wireless networks. Our results show that the power-control method significantly improves the spectral efficiency by enabling the 1/3 frequency reuse while maintaining a stringent requirement of 2% packet loss probability for voice service. Specifically, for allocated spectrum of 1.8, 3.6 and 5.4 MHz, the 1/3 reuse with the Kalman power control can yield 102.5%, 49.5% and 32.5% improvement in spectral efficiency, respectively, over the 3/9 reuse (regardless of whether or not power control is used). We also compare the performance of the Kalman method with a traditional Signal-to-interference-ratio method and a control method that is based on the last interference measurement. We find that appropriate selection of power for the first packet of each talk spurt and the filtering function for noisy measurements are crucial in providing high system capacity for packet voice service. For the EDGE system, we also identify a need for shortening the power update period, which is 480 ms in the specifications.     

基于MINI2440平台的无线局域网语音通信的实现

基于MINI2440 ARM平台实现了无线局域网语音通信,主要完成了语音数据的采集、编码、压缩及实时传输.采用Qt/Embedded跨平台应用程序和UI开发框架实现了嵌入式通信软件的界面、网络及多线程编程.采用G.729B编解码算法实现语音数据的编码及压缩,并对该算法进行了优化来减少其复杂度.     

基于分组的端到端存储转发式语音短信业务的实现

在介绍我国短信业务发展过程的基础上,从语音短信服务器功能、对移动手机终端的要求、其他核心网网元支持、语音短信的优势分析等方面全面阐述了基于分组的端到端存储转发式语音短信业务的实现。     

分组交换网上的增值业务

本文介绍了公用和专用分组交换数据网的现状后，说明了开展标准的增值业务系统的重要性。论述了典型的增值业务系统－电子邮件和传真存储转发系统。     

欧盟的网络语音服务管制框架

从管制框架对VoIP的适用、基于VoIP提供的公共电子通信服务、基于VoIP提供的公共电话服务、对VoIP服务使用者及公共安全的保护以及互联、互用与号码的使用等方面论述了政盟的网络语音服务管制框架．从中可以看出欧盟对于新技术的态度和管制思路。欧盟对于VoIP服务的规定在一定程度上体现了其“技术中立”的管制思路，使于管制政策之间的一贯性和衔接。     

本地传输网分组化演进策略

在对本地传输网分组化演进的需求和分组传输技术进行分析的基础上,提出了本地传输网的演进应以简单、稳定、可靠、可维护性强、经济为原则,分析比较了MSTP和PTN传输分组业务的特点,提出了本地传输网分组化演进的方案。     

一种具有低时延的分组公平循环调度

本文提出了一种新的分组循环调度算法LFRR(Large weight First Round Robin)。为了具有良好的时延特性和较低的实现复杂度,LFRR采取了以下方法：(1)在调度表中为流分配时隙时,LFRR以时隙完全均匀分布为参照,确保分配给一个流的时隙不会过早或过晚地出现在调度表中。(2)LFRR算法中采用了等权值流合并的技术,把权值大于1且权值相等的流合并成一个虚流,以虚流为处理对象,使算法需要处理的对象数目大为减小。(3)当一个时隙适合分配给多个虚流时,LFRR采用了简单的权值大的虚流优先占用时隙的原则。本文对LFRR进行了理论分析和计算机仿真,结果表明LFRR算法的时延性能比WRR(Weighted Round Robin)有了很大提高,同时LFRR算法的公平性也有保证。     

Integration of Voice and Data in the Wideband Packet Satellite Network

The Wideband (packet satellite) network is an experimental 3 Mbit/s communications system developed under sponsorship of the Defense Advanced Research Projects Agency and the Defense Communications Agency. This system is being used to evaluate the use of packet transmission for efficient voice communication, voice conferencing, and integration of voice and data over a satellite channel. Each station in the Wideband network consists of an earth terminal (dedicated 5 m antenna plus associated IF/RF equipment), a burst-modem and codec unit, and a station controller. Station controllers provide interfaces to host computers (including packet speech sources) and manage the allocation of the satellite channel on a TDMA demand-assigned basis. TDMA demand-assignment is implemented using a reservation-based packet-oriented protocol capableof handling traffic at multiple priority levels. The channel protocol provides a reservation-per-message mode of service (datagrams) to support transmission from bursty traffic sources and a reservation-per-call mode of service (streams) to support traffic with more regular arrival statisticS (e.g., vioce). A distributed scheduler running in every station controller eliminates the need for a central control station and minimizes network transit delay for datagram transmission as well as stream creation, modification, and deletion. In this paper we describe the protocols and mechanisms upon which the Wideband packet satellite network is based.     

无线局域网简介

介绍了无线局域网的优势、标准和功能等，提出了按802．116标准组网的基本运作模式和典型解决方案，最后介绍了无线局域网的应用前景及存在的问题。     

Experiences with a Layered Approach to Local Area Network Design

The Nestar Plan 4000 network was designed using the ISO Open Systems Interconnection model. The Xerox Network Systems Internet Transport Protocols (XNS) were chosen for the network and transport layers, a token-passing protocol (Arcnet) for the physical and datalink layers, and existing Nestar server software for the highest layers. The physical and datalink layers are supported by a VLSI chip and their implementation was straightforward. In spite of their detailed specification, implementing the network and transport layers presented some unanticipated challenges. This paper discusses details of our experience in implementing the network with emphasis on the problems encountered and how they were solved.     

虚拟局域网

虚拟局域网是网络用户独立于网络物理配置和位置的一个逻辑组合，综结合了网络交换和管理功能，使网络根据用户需要分割成多个逻辑网，管理员对分布于各个网段的用户视作在同一逻辑网中进行管理，在网络性能、保护用户投资及向ＡＴＭ过渡方面具有很好的性能。本文对虚拟局域网技术进行综述。     

无线局域网

1 概述 无线局域网(Wireless LAN,简称WLAN)是90年代计算机网络与无线通信技术相结合的产物。随着信息技术的飞速发展,人们对网络通信的需求不断提高,希望不论在何时、何地、与何人能够进行包括数据、话音、图像等任何内容的通信,并希望能实现主机在网络中漫游。于是计算机网络由有线向无线、由固     

计算机局域网（上）

本文简要地讨论了计算机局网的基本技术、协议和标准，并对几个典型的局域网便子作了概要的介绍。     

34Mbit／sDQDB光纤综合业务局域网

本文介绍了一种３４．３６８Ｍｂｉｔ／ｓＤＱＤＢ光纤综合业务局域网。该网络由双总线环形构成，采用ＤＱＤＢ协议和混合交换方式，可传输数字话音，高／低速计算机数据，高质量静止图像和压缩视频图像等综合业务。     

A Local Area Network as a Telephone Local Subscriber Loop

The technical feasibility, of utilizing a local area network (LAN) as a multidrop local subscriber loop for a PABX is shown. The network capacity is found through simulation both with a contention protocol (CSMA/CD) and a virtual token protocol (GBRAM) used for media access. It is shown that a stable configuration, utilizing distributed call blocking procedures, will result in less than two percent of the voice packets being lost during busy periods. Listener tests with a packet phone and dropped packets confirm that this is acceptable to the user.     

Modeling a Voice Network with Preemption

This paper describes the results of a study to calculate the grade of service (GOS) in a telephone network carrying two classes of traffic. When blocked, the higher class calls may preempt calls of the lower class. Two preemption disciplines are considered in this study. They are the ruthless and friendly search preemption disciplines of channels on interswitch trunk groups. The results of a computer model agree very well with a proven network simulator. The CPU time to determine the network GOS was reduced from hours to minutes.     

GSM话音业务网络负荷监控及处理

本文论述了GSM无线系统网络负荷监控的种类,并根据在监控中的实际维护经验分析了话务业务负荷监控的多手段和现象。讨论了GSM数字移动通信网络负荷监控的问题;总结了一些常见的解决措施及经验。