一种基于流星突发通信的分组无线网

流星余迹信道短时突发的特点使得流星突发通信呈现间歇性,在等待一颗适合的流星出现前往往需要等待很长的时间,同时由于流星突发通信的"足迹"和"热点"特性,使其通信距离受到限制。为解决上述问题,提出一种基于流星余迹通信的无线分组网,首先针对流星余迹信道特点给出了适合该网络的路由选择策略,其次介绍了工作流程,最后对分组长度进行了分析,并给出了仿真结果。     

A Three-Node Packet Radio Network

A two-hop packet radio network consisting of three nodes is considered. The three nodes have infinite buffers and share a common radio channel for transmitting their packets. Two of the nodes forward their packets to a third node that acts as a source of data as well as a relay that forwards all the packets entering the network to a main station. We assume that two of the nodes are granted full rights in accessing the channel while the third node uses a random access scheme. For this network we derive the condition for steady state and the generating function of the joint queue length distribution at the nodes in steady state. We also give several numerical examples and compare the performance of the network with and without a relay node.     

多跳结构分组无线网络的性能分析

本文提出了一种应用IEEE 802.11 MAC中RTS/CTS协议的多跳分组无线网络,分析了它的吞吐量,并与时隙ALOHA、CSMA多址接入协议下的网络性能作了比较.最小ID号的分群算法可以通过较少的控制信息快速得到顽健的分群网络结构,选用合适的MAC协议能充分有效地利用多信道.不过,两跳的分群结构使得在群内使用CSMA仍无法避免隐藏终端问题,IEEE 802.11 MAC协议中的RTS/CTS接入方式大大减小了隐藏间的分组碰撞时间,从而提高了网络性能.     

分组无线网的拥塞控制技术

网络拥塞在分组无线网（ＰＲＮＥＴ）中是一个潜在的问题，为减轻或避免拥塞的摧毁效应，在ＰＲＮＥＴ中，有必要对拥塞进行控制。本文首先分析了往的拥控制中存在的问题，然后介绍了两种新的相互合作的拥塞控制技术－建立长期最大－最小端到流率的端到拥塞控制算法以及链路层拥塞避免算法，最一对这种机制的性能进行了相应的分析与评价。     

PERFORMANCE ANALYSIS OF FREQUENCY HOPPING PACKET RADIO NETWORK WITH ACKNOLEDGEMENT TRAFFIC

Performance analysis of an asynchronous frequency hopping packet radio network and numerical results are given. The network has mixed traffic, one type of packet needs an Acknowledgement(Ack), the other type does not need, the background of such a network is tactical missile systems. A reasonable network model is given, based on which the effect of various parameters under multiaccess interference is investigated. The performance curves of throughput and average packet delay is given in this paper.     

分层式分组无线网络结构

介绍了一种分层式一无线网络的结构，这种网络结构使得战术武器指挥，控制，通信与情报系统，在强干扰和大量移动用户的环境下，具有较强的抗干扰性和灵活性。     

一种新的有效支持智能天线应用的多址接入协议

本文研究将智能天线应用于分组无线网络中,提出了支持智能天线应用的自适应时隙分配多址接入协议(ASAMA).该协议采用时分双工(TDD)方式,每一帧开始时用户节点依次发送训练序列,基站的智能天线据此计算出各用户节点的空间特征(Spatial Signature).基于波束形成的信干噪比最大化准则,设计了逐点优化与全局优化两种不同复杂度的时隙分配算法.由基站对上下行业务的时隙进行动态分配,在保证通信质量的前提下,使每个时隙容纳多个数据分组,以充分实现信道的空分复用(SDMA).对该协议的信道利用率进行了近似分析,并利用仿真方法考察其性能.结果表明,ASAMA协议能有效支持智能天线应用并具有很高的信道利用率与良好的时延性能.     

分组无线网的路由选择算法研究

探讨了分组无线网的分布式路由远择算法，分析了以往ＤＡＲＰＡ网中的ＤＡＲ算法存在的缺陷，提出了一种新的ＬＮＲ分布式路由选择算法，并在性能上与ＤＡＲ算法进行了比较。结果表明，由于ＬＮＲ算法克服了环路及无限计数问题，因而ＬＮＲ算法无论在选择最佳路由上，还是在总体开销上，都优于以往以ＤＡＲ为代表的分布式路由选择算法。     

分组无线通信控制器的设计

文章介绍了一种新型的用于组成无线计算机通信网的通信控制器的设计,这种通信控制器具有高速的特点,它可以利用一般的ＵＨＦ,ＶＨＦ通信机通信,组成计算机分组无线网。     

一种改进的多跳分组无线网路由协议

对于多跳分组无线网来说,路由协议非常重要.而传统的主动式路由、按需路由和混合路由由于自身的缺陷,都不能保证多跳分组无线网传输的可靠性.为了适应网络拓扑不断变化的客观环境,提高数据通信的可靠性,提出了一种相邻矩阵路由协议,它克服了传统路由协议的缺点,大大提高了多跳分组无线网的链路性能.     

跳频分组无线网的路由算法分析

跳频分组无线网抗干扰性好,保密性强,广泛应用于战术通信系统。讨论了几种跳频分组无线网的路由选择算法,着重分析了针对传输多类型分组跳频网的ALR路由算法,并将此路由算法的性能与DAR算法的性能进行了比较,证实了该算法在吞吐量、端-端正确传输率等方面都优于传统的方法。     

Adaptive Spatial Filtering for an FH/SSMA Packet Radio Network with Packet Combining

In this paper, packet throughput is analyzed and simulated for a show FH/SSMA packet radio network with adaptive antenna array and packet combining in a Rayleigh fading channel with shadowing. The packet throughput is defined as the average number of captured packets per slot. To enhance the throughput performance, an adaptive spatial filtering through adaptive antenna array and a packet combining scheme are employed. As a random access protocol, slotted ALOHA is considered, and synchronous memoryless hopping patterns are assumed. A packet consists of codewords from an (n, k) RS (Reed-Solomon) code. The tap weights of an adaptive processor is updated by RLS (recursive-least-square) algorithm. From the simulation results, it is shown that a pre-processing by adaptive antenna array and a post-processing by packet combining are very effective to improve reception performance of an FH/SSMA network.     

短波网络的拓扑性能分析

对短波网络的拓扑结构方面作了定性和定量的分析,给出了能够符合短波通信组网要求的网络结构。     

Analytical Model for Initialization of Single Hop Packet Radio Networks

Recent studies have shown that packet radio networks (PRNET) can easily be saturated and become unstable unless efficient routing and flow control algorithms are used. To enable point-to-point packet transportation, network stations assign a code (label) to each repeater; the process of assigning such labels is referred to as "network initialization." The initialization procedure assumes that the network topology is not known a priori and is changing with time. Thus, the initialization procedure involves mapping of network topology, determining network structure (labels for repeaters), and transmitting labels to the repeaters. Although many authors have developed analytical models to study channel access schemes, no one has yet addressed directly the initialization issue. In this paper we present two models which enable one to estimate the optimal rates at which repeaters and stations must transmit connectivity information to minimize the network initialization time in a one-hop network. The first model assumes complete interference (all repeaters can communicate directly with each other), while the second (but more complex) model can provide initialization time under partial interference pattern. With these models we illustrate the effects of varying repeater and station transmission rates for small networks. Our most important results are that the network initialization time is relatively insensitive to the station transmission rate, but the repeater transmission rate must be carefully chosen to achieve rapid initialization.     

分组交换网传送语音信息

本文先简单说明传统公用电话网的电路交换和数据通信网的分组交换原理。然后介绍语音压缩和分组语音技术在互联网和内部网上的应用 ,以实现互联网电话的新趋向。     

IP网络分组传送性能讲座第4讲:IP网络性能的测试与评估

1 IP业务的可用性 IP业务可用性用于描述IP网络能否可靠支持IP业务信息传送,有效支持各类IP业务应用的程度,换句话说,IP业务可用性描述了IP网络性能的劣化程度.一般来说,网络会定义一组相关的性能指标门限值,当网络性能劣化到低于这组门限值时,就说网络业务处于不可用状态,反之,网络业务处于可用状态.     

IP网络分组传送性能讲座第3讲:IP分组传送时延

1 IP分组传送时延(IPTD,IP Packet Transfer Delay) IP分组传送时延被定义为所有成功或差错IP分组结果通过一个基本段或NSE所用的时间.即IPTD是发生两个相关IP分组传送参考事件的时间差(t2-t1),其中输入事件发生在t1,输出事件发生在t2,这里t2＞t1,并且t2-t1≤Tmax.     

IP网络分组传送性能讲座第2讲:IP网络性能参数与网络服务质量

1 IP网络性能测试的环境与条件 为了在IP网络中对IP业务的性能进行测试,要规定一些环境条件,并且定义网络性能的测试点(MP,Measurement Point).如图1所示.     

A Simple and Comprehensive Saturation Packet Delay Model for Wireless Industrial Networks

With the emerging popularity of the wireless local area network technology, many analytical models for its main medium access control mechanism, Distributed Coordination Function (DCF), have been reported. However, most of them are based on some oversimplifying assumptions, or need very complicated mathematical manipulations. In this paper, a simple and accurate packet delay model has been proposed for the IEEE 802.11 DCF mechanism in saturated traffic and error-prone industrial applications which is based on a modified discrete-time Markov chain model of the DCF mechanism which accounts for the backoff freezing. It estimates various delay parameters including the average, jitter, Cumulative Distribution Function, and the effect of Retry Limit. The simulation results confirm the accuracy of the proposed delay model compared with other similar models in the literature.     

Packet Radio Performance Over Slow Rayleigh Fading Channels

Expressions for the throughput and average packet delay for a Pure-ALOHA single-hop packet radio system operating in slow Rayleigh fading are derived. For noncoherent frequency-shift-keying (NCFSK), an exact closed form expression is presented. For coherent phase-shift-keying (CPSK) an excellent approximation for large packet sizes is derived. This approximation technique is valid in general for other modulation schemes and for other fading channel statistical characterizations. The packet length which maximizes the useful data throughput in slow Rayleigh fading is found. The results of this investigation indicate that a packet radio system can be designed with a modest link margin for fading and achieve identical throughput performance over a nonfading channel and a fading channel with only a small increase in average packet delay for the fading channel.