一种移动无线网络分组公平调度算法

提出了一种支持时延限制的无线多媒体流公平调度算法。算法根据无线信道的服务质量,动态调整该信道连接的业务速率,并根据各个业务请求当时的时延因子的大小来公平地补偿和再分配带宽。仿真验证了算法的可行性和科学性。支持对时延敏感的流和对差错敏感的流,能做到区别补偿调度,满足各自的QoS需求。     

结合机会链的联合频谱分配算法

基于机会链模型和遗传算法,提出一种优化信道使用的联合分配算法。该算法利用遗传算法进行初次分配,然后构建满足链和需求链两种机会链模型,在避免弱势用户问题的同时,优化初次分配方案,增大系统总带宽,降低系统带宽需求缺口,从而提高频谱利用率。通过仿真验证了该算法的有效性。     

结合机会链模型的联合频谱分配算法

基于机会链模型和遗传算法,提出一种优化信道使用的联合分配算法。该算法利用遗传算法进行初次分配,然后构建满足链和需求链两种机会链模型,在避免弱势用户问题的同时,优化初次分配方案,增大系统总带宽,降低系统带宽需求缺口,从而提高频谱利用率。通过仿真验证了该算法的有效性。     

混合TDM/WDM EPON中动态带宽分配算法

针对TDM EPON向WDM EPON升级过程中各个光网络单元(ONU)支持波长数不尽相同的特点,提出一种基于波长间负载均衡的动态带宽分配算法(LB-DBA).该算法在分配带宽时考虑波长信道的带宽约束,同时分两步确定授权给ONU的发送波长和发送时间,有利于波长信道间的负载均衡.仿真结果表明,LB-DBA可以避免已有算法在混合TDM/WDM EPON中可能出现的授权周期长度增加和资源利用率低等问题,有效改善网络性能.     

一种多信道ATM交换机的实现

本文研究了一种多信道ATM交换网络,使用一种多路径交换结构网络作为多信道交换的路由网络代替Banyan网络。给出了信道分配网络的设计原理。阐明了多信道ATM交换的带宽分配方案,重点说明了传输阶段的带宽分配方法。     

一种信道自适应的无线视频流差错控制机制

提出了一种自适应的无线视频流差错保护方法。该方法充分考虑MPEG-4FGS码流细粒度可扩展的特性,根据码流的重要性程度采用不等的保护措施,同时能够自适应地根据无线信道的具体状况,将信道带宽在MPEG-4FGS信源编码速率和信道编码速率之间进行最优化分配,使得接收端能获得最佳的重建视频质量。实验结果表明,在各种不同信道状况下,与均等错误保护和固定的不等错误保护方法相比,该方法均可获得更好的性能。     

基于星上多波束天线的卫星功率带宽联合优化新算法

目前已有的卫星功率优化分配策略未考虑功率与带宽的耦合关系。为了进一步提高星上资源的利用率,在考虑各点波束业务需求差异及共信道干扰的基础上,通过构建卫星系统模型,提出一种将卫星功率和带宽联合优化分配的算法。该算法基于系统公平性建立优化目标函数,并采用迭代方法求解资源优化的最优解。与传统固定分配方式相比,这种耦合的资源分配方式可根据当前业务需求和信道条件对星上功率和带宽资源进行实时再分配,提高了系统容量,系统业务匹配率提高10%,具有较高的星上资源利用率。     

卫星信道按需分配解决方案

本文介绍了卫星通信地面应用系统中，网管中心按全按需分配方式分配卫星信道时需要考虑的若干问题、卫星通信系统简单工作原理、信道全按需分配常用的解决方案，详细阐述了由于不同的通信带宽需求，网管中心按全按需分配方式分配卫星信道的解决方案。     

基于差值分配的信道分配算法研究

资源的高效利用与服务质量保证是多频时分多址(MF-TDMA)卫星通信系统正常运行的关键技术。通过对典型的周期轮询信道分配算法进行分析,针对该算法实时业务掉线率较高的缺点,提出了差值分配算法。新算法是在周期轮询信道分配算法的基础上,结合业务带宽需求动态变化的特点,将业务带宽申请分为固定部分与差值部分并分别采取不同的分配策略。仿真结果表明,新算法可以有效地降低实时业务的掉线率。     

一种多信道ATM交换机的实现

本文研究了一种多信道ＡＴＭ交换网络,使用一种多路径交换结构网络作为多信道交换的路由网络代替Ｂａｎｙａｎ网络,给出了信道分配网络的设计原理,阐明是了多信道ＡＴＭ交换的带宽分配方案,重点说明了传输阶段的带宽分配方法。     

Dynamic Bandwidth Management in Single-Hop Ad Hoc Wireless Networks

Distributed weighted fair scheduling schemes for Quality of Service (QoS) support in wireless local area networks have not yet become standard. Therefore, we propose an Admission Control and Dynamic Bandwidth Management scheme that provides fairness and a soft rate guarantee in the absence of distributed MAC-layer weighted fair scheduling. This scheme is especially suitable for smart-rooms where peer-to-peer multimedia transmissions need to adapt their transmission rates co-operatively. We present a mapping scheme to translate the bandwidth requirements of an application into its channel time requirements. The center piece of our scheme is a Bandwidth Manager, which allots each flow a share of the channel, depending on the flow's requirements relative to the requirements of other flows in the network. Admitted flows control their transmission rates so they only occupy the channel for the fraction of time allotted to them. Thus co-operation between flows is achieved and the channel time is fair shared. As the available channel capacity changes and the traffic characteristics of various flows change, the Bandwidth Manager dynamically re-allocates the channel access time to the individual flows. Our simulation experiments show that, at a very low cost and with high probability, every admitted flow in the network will receive at least its minimum requested share of the network bandwidth. We also present extensive testbed experiments with our scheme using a real-time audio streaming application running between Linux laptops equipped with standard IEEE 802.11 network cards.     

Doubling the capacity of a communications satellite system

Two one-way channels are normally used in digital two-way voice communication. Each channel is in effect-used only one half the time. A recent discovery of ours recognized that any one-way channel within a satellite spot-beam can be accessed by anyone in the footprint of the beam. In a two-way voice call, the two parties alternate (in principle) in their transmissions-when one speaks the other is silent. Therefore, the two can share a single one-way channel and provide continuous use of the channel, their respective transmissions interleaved with one another. This condition is unique to intrabeam communication via satellite (or balloon). In a satellite system, capacity is a valued commodity, where capacity is limited by allocated bandwidth and power available. Under those two constraints of bandwidth and power limitation, the discovery described generates a doubling of capacity. This article addresses this concept and some of the engineering challenges and opportunities arising therefrom     

Tradeoffs of Source Coding, Channel Coding and Spreading in Frequency Selective Rayleigh Fading Channels

This paper investigates the tradeoffs of source coding, channel coding and spreading in CDMA systems. We consider a system consisting of an image source coder, a convolutional channel coder, an interleaver, and a direct sequence spreading module. With different allocations of bandwidth to source coding, channel coding and spreading, the system is analyzed over a frequency selective Rayleigh fading channel. The performance of the system is evaluated using the cumulative distribution function of peak signal-to-noise ratio. Tradeoffs of different components of the system are determined through simulations. We show that, for a given bandwidth, an optimal allocation of that bandwidth can be found. Tradeoffs among the parameters allow us to tune the system performance to specific requirements.     

用RSVP-TE实现的ASON信令

描述怎样运用信令协议RSVP-TE实现自动交换光网络中动态地建立、删除连接的要求。仿真实现了前向资源预留(FRP)和后向资源预留(BRP)两种不同的信令方案,并收集了阻塞率(BR)、控制信道带宽(CCB: control channel bandwidth)及连接建立时间(CST: connection setup time)等相关统计量,比较了这两种方案的性能,发现在相同的仿真环境以及相同网络负载的情况下,后向资源预留的阻塞率性能优于前向资源预留,同时后向资源预留的连接建立时间以及使用的控制信道带宽都大于前向资源预留。     

Joint Bandwidth Allocation for User-Required Picture Quality Ratio Among Multiple Video Sources

When the multiple video sources are transmitted together through the channel of fixed bandwidth, an efficient joint bandwidth allocation is necessary. This paper presents a joint bandwidth allocation method to satisfy the user requirements that the bandwidths for each sources are assigned to allow differentially the certain picture quality levels according to their priorities. We first find a model of distortion and bitrate for the multiplexing system of multiple sources. Then we obtain the bitrate for each source to keep the required distortion level among the sources by using approximate model parameters for simple implementation. It is shown by simulation that the proposed bandwidth allocation method can keep almost the user-required picture quality level among the sources in comparison to an independent bandwidth allocation method.     

MIMO无线通信系统研究现状及其技术路线

多输入多输出(MIMO)技术能在不增加带宽的情况下成倍地提高通信系统的容量和频谱利用率,是下一代移动通信系统中最富有竞争力的技术之一.本文分析了MIMO无线通信系统的空域相关性、信道建模以及信道估计研究现状,并提出了相应的技术路线,这些为更加深入地研究MIMO通信技术奠定了坚实的理论基础.     

Expressnet: A High-Performance Integrated-Services Local Area Network

Expressnet is a local area communication network comprising an inbound channel and an outbound channel to which the stations are connected. Stations transmit on the outbound channel and receive on the inbound channel. The inbound channel is connected to the outbound channel so that all signals transmitted on the outbound channel are duplicated on the inbound channel, thus achieving broadcast communication among the stations. In order to transmit on the bus, the stations utilize a distributed access protocol which achieves a conflict-free round-robin scheduling. This protocol is more efficient than existing round-robin Schemes as the time required to switch control from one active user to the next in a round is minimized (on the order of a carrier detection time), and is independent of the end-to-end network propagation delay. This improvement is particularly significant when the channel data rate is so high, or the end-to-end propagation delay is so large, Or the packet size is so small as to render the end-to-end propagation delay a significant fraction of, or larger than, the transmission time of a packet. Moreover, some features of Expressnet make it particularly suitable for voice applications. In view of integrating voice and data, a simple access protocol is described which meets the bandwidth requirement and maximum packet delay constraint for voice communication at all times, while guaranteeing a minimum bandwidth requirement for data traffic. Finally, it is noted that the voice/data access protocol constitutes a highly adaptive allocation scheme of channel bandwidth, which allows data users to recover the bandwidth unused by the voice application. It can be easily extended to accommodate any number of applications, each with its specific requirements.     

Collaborative transmit diversity with adaptive radio resource and power allocation

We consider optimized collaborative transmit diversity schemes for the situation when the source and the relay know the magnitudes of all channel gains in the system. We demonstrate how one can optimally allocate not only transmit power but also the time and bandwidth used by the different nodes. Numerical examples illustrate the possible performance gain over nonadaptive collaboration.     

Joint power and bandwidth allocation in downlink transmission

We formulate and analyze the problem of optimal downlink scheduling with instantaneous channel and queue size information when both power and bandwidth may be adaptively split among multiple users. We derive optimal solutions of low computational complexity, as well as faster and simpler approximations, to various versions of this problem when the power, rate, and bandwidth allocations to the users can all take continuous values. For this case, we show that the optimal scheme requires transmission to no more than two users during each time slot when users can receive at arbitrary rates, even when the user rate per unit of bandwidth is upper bounded by the best available modulation scheme. Our methods also extend easily to incorporate other intuitive constraints such as upper limits on user rates to improve frame fill efficiency. Simulation results suggest that the simple approximations work nearly as well as the throughput optimal schemes when continuous bandwidth and power partitions are allowed. In practice, the rate and bandwidth assignments to users take discrete values, and we present heuristic methods motivated by the continuous optimum to this discrete case.     

A Viterbi-like algorithm with adaptive clustering for channelassignment in cellular radio networks

A new channel assignment algorithm, called the Viterbi (1967) -like algorithm (VLA), is proposed to solve the channel assignment problem in cellular radio networks. The basic idea of the proposed algorithm is step-by-step (sequential) channel assignment with the objectives of minimum bandwidth required at every step, subject to adjacent channel and cochannel separation constraints. The VLA provides the benefits of minimum required bandwidth, stability of solution, and fast execution time. The performance of the VLA is evaluated by computer simulation, applied first to 19 benchmark problems on channel assignment and then applied to study cellular radio network performance. Results from computer simulation studies show that bandwidth requirements by VLA closely match or are sometimes better than those of the existing channel assignment algorithms. Furthermore, it is found that execution of VLA is approximately two times faster than the local search algorithm-the existing channel assignment algorithm with the least bandwidth requirements. The combined advantages of minimum required bandwidth, stability of solution, and fast execution time make the VLA a useful candidate for cellular radio network planning