A new channel allocation scheme for hierarchical wireless networks

A channel allocation scheme for hierarchical wireless networks was proposed in terms of the connection-level quality of service. The channel allocation scheme was analyzed using both horizontal channel borrowing and vertical traffic overflowing. Pre-emptive priority strategies are used to classify real-time services and non-real-time services, real-time service is given higher priority for it is allowed to pre-empt channels used by non-real-time service. Some channel borrowing thresholds and acceptance ratios are used to avoid channel locking or dynamic power control, which can also be dynamically adjusted according to network load. Simula-tion results show that the proposed schemes can improve the system performance.     

A New Traffic Model for Mobile Wireless Networks

A new traffic model for mobile wireless networks was given and analysed. In the model, it is considered of traffic characteristic for two special periods of time. A pre-emptive priority scheme combined with channel borrowing strategy according to the speciality was proposed. All the channels can be used by non-real-time services, and real-time services are given higher priority for they are allowed to pre-empt channels used by non-real-time services. Either real-time handoff requests or non-real-time handoff requests can be queued in queues when there is no channel can be used. Some channels are reserved for real-time handoff requests, which can also be used by non-real-time service when they are idle. Simulation results are also given. It is seen that our scheme performs better than other schemes when the arrival rate of real-time services is much higher than non-real-time services.     

基于分组的宽带CDMA网络呼叫接纳控制方案

以宽带CDMA网络为研究对象，结合3种主要业务类型（话音、视频、数据）的精确建模，提出了用户连接接纳控制与用户分组接纳控制协作的CAC机制，以及基于优先级的改进CAC方案．该方案根据无线分组网络中以分组为最小资源管理单位的特点，结合系统剩余容量以及不同类型业务的特点，为不同业务设置不同的接入准则．优先接纳对实时性要求高的用户连接和分组，同时尽可能地保证实时性要求较低业务的服务质量．仿真结果表明，所提出的策略有效降低了业务接人的阻塞率和平均接纳延时，同时提高了系统资源利用率．     

Dynamic Channel Allocation in Sectored Cellular Systems

It is known that dynamic channel assignment(DCA) strategy outperforms the fixed channel assignment(FCA) strategy in omni-directional antenna cellular systems. One of the most important methods used in DCA was channel borrowing. But with the emergence of cell sectorization and spatial division multiple access(SDMA) which are used to increase the capacity of cellular systems, the channel assignment faces a series of new problems. In this paper, a dynamic channel allocation scheme based on sectored cellular systems is proposed. By introducing intra-cell channel borrowing (borrowing channels from neighboring sectors) and inter-cell channel borrowing (borrowing channels from neighboring cells) methods, previous DCA strategies, including compact pattern based channel borrowing(CPCB) and greedy based dynamic channel assignment(GDCA) schemes proposed by the author, are improved significantly. The computer simulation shows that either intra-cell borrowing scheme or inter-cell borrowing scheme is efficient enough to uniform and non-uniform traffic service distributions.     

典型Ad hoc网络协议传输多媒体数据的性能分析

针对多媒体数据的特点论述了在Ad hoc网络环境中各性能参数的要求,利用NS2仿真软件模拟了在Ad hoc网络环境中利用AODV,DSR及DSDV路由协议进行多媒体数据传输,并将网络吞吐量、延时抖动等4种多媒体数据敏感参数进行了比较.实验表明,由于多媒体数据类型的不同,AODV,DSR及DSDV协议的性能也各有差异,通过比较发现,DSDV的表路由机制不能满足Adhoc网络的多媒体业务要求,DSR可用于QoS要求不高的视频传输,AODV可用于传输视频及音频,但对延时要求较高的数据则不能满足.     

一种改进的GSM/GPRS网络信道分配策略

在对GSM／GPRS(global system for mobile communications／general packet radio service)蜂窝系统现有典型信道分配策略FRA(fixed resource allocation)和DRA(dynamical resource allocation)及其排队策略进行分析的基础上，提出了基于DRA的改进策略DMC—DRA(dynamical minimum channels of packets for DRA)．新策略能动态改变GPRS包下限信道数，在FRA和DRA之间折衷，提高信道利用率、包传输时间、呼叫阻塞率等综合性能．     

MERGING AND SPLITTING SECOND-ORDER SELF-SIMILAR PROCESSES (TRAFFICS)

Recent traffic measurements in corporate LANs, Variable-Bit-Rate (VBR) video sources, ISDN control channels, and other communication systems, have indicated traffic behavior of self-similar nature, which has implications for design, control and analysis of high-speed networks. Merging and splitting are two basic networking operations. This paper gave the necessary and sufficient conditions for that merging of second-order self-similar traffic streams also results in a second-order self-similar stream. It shows that splitting traffic streams of the second-order self-similar stream are still self-similar streams by the independent splitting operation.     

A simulation study of service differentiation for the bandwidth request scheme in fixed IEEE 802.16 network

Various flexible mechanisms related to quality of service (QoS) provisioning have been specified for uplink traffic at the medium access control (MAC) layer in the IEEE 802.16 standards. Among the mechanisms, contention based bandwidth request scheme can be used to indicate bandwidth demands to the base station for the non-real-time polling and best-effort services. These two services are used for most applications with unknown traffic characteristics. Due to the diverse QoS requirements of those applications, service differentiation (SD) is anticipated over the contention based bandwidth request scheme. In this paper we investigate the SD with the bandwidth request scheme by means of assigning different channel access parameters and bandwidth allocation priorities at different packets arrival probability. The effectiveness of the differentiation schemes is evaluated by simulations. It is observed that the initial backoff window can be efficient in SD, and if combined with the bandwidth allocation priority, the SD performances will be better. Foundation item: the National Basic Research Program (973) of China (No. 2005C13321804)     

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ETC技术的广泛使用有效提高了人工收费效率,缓解了收费站车流拥堵状况,本文对ETC系统优化配置方案进行了研究.根据收费站设计规范和实地调研成果,对高速公路收费站系统构件进行了形式化描述,结合系统各个构件中车辆的行为特征、车辆及收费通道的分类特征,建立了一种适用于高速公路ETC收费站系统的元胞自动机交通流模型.考虑到ETC收费站车流拥堵特性,提出了ETC收费站服务水平的概念及相关计算方法,设计以ETC使用率、ETC车道数量及交通流量为参数的仿真方案,选取封闭式4车道收费站进行仿真分析,基于仿真结果提出了ETC使用率分别为30%、60%和90%时ETC车道数的配置建议,为收费站管理人员合理利用ETC系统提供了理论依据.     

Dynamic wavelength and bandwidth allocation using adaptive linear prediction in WDM/TDM ethernet passive optical networks

Hybrid wavelength-division-multiplexing (WDM)/time-division-multiplexing (TDM) ethernet passive optical networks (EPONs) can achieve low per-subscriber cost and scalability to increase the number of subscribers. This paper discusses dynamic wavelength and bandwidth allocation (DWBA) algorithm in hybrid WDM/TDM EPONs. Based on the correlation structure of the variable bit rate (VBR) video traffic, we propose a quality-of-service (QoS) supported DWBA using adaptive linear traffic prediction. Wavelength and timeslot are allocated dynamically by optical line terminal (OLT) to all optical network units (ONUs) based on the bandwidth requests and the guaranteed service level agreements (SLA) of all ONUs. Mean square error of the predicted average arriv-ing rate of compound video traffic during waiting period is minimized through Wiener-Hopf equation. Simulation results show that the DWBA-adaptive-linear-prediction (DWBA-ALP) algorithm can significantly improve the QoS performances in terms of low delay and high bandwidth utilization.     

基于RFCS的城轨列车无线视频监控统切换机制

针对城轨列车跨越多个无线接入点AP高速运行时存在切换延迟的问题,在对城轨列车无线视频监控系统研究的基础上,提出一种RFCS（RF channel switched）机制,在这种机制下,无线接入点AP按照预定的顺序周期性的改变RF信道来防止相邻AP信道的重叠,从而减小了切换延迟,增大了网络吞吐量,最终实现无缝切换.并用NS2仿真软件对该方案进行仿真,与传统的切换过程相比,该方案明显减小了切换时延,保证了城轨列车无线视频监控系统的实时性.     

非均匀多业务分层网络的资源分配策略分析

研究一种支持多种业务(包括语音对话业务和数据流业务)的分层蜂窝网,在信道共享和信道分割 2 种资源分配策略下的网络性能.网络中的数据流业务根据当前的业务负载情况动态分配带宽,并通过双阈值带宽预留(DTBR)来保证不同业务的不同业务质量(QoS).实验数据显示了在不同业务量情况下2种资源分配方法的性能比较.     

一种无线通信网中的跨层分组调度方案

提出了基于未来无线多媒体通信标准下的一种跨层分组调度方案,在调度时,首先对多媒体混合业务进行了合理分类,即实时性业务和非实时性业务;在调度优先级的确定过程中,利用跨层优化的思想估算优先级公式中的相关参数,由此给出了跨层分组调度方案的具体算法流程.仿真结果表明,与传统经典的比例公平调度算法（PFS）相比,该方案在实时性、数据吞吐量、信道利用率等方面具有更好的性能.     

无线多媒体传感器网络的QoS路由算法

作为一种全新的信息获取和处理技术,无线多媒体传感器网络较之传统传感器网络更多地关注于音频、视频、图像等大数据量、大信息量媒体的采集与处理,在军事、民用及商业领域中具有广阔的应用前景.文中针对具有Mesh结构的无线多媒体传感器网络,给出了其带宽、时延和时延抖动等多约束的QoS路由问题模型的描述.基于基本遗传算法提出了一种多约束的QoS路由算法,给出了算法的具体实现流程,并对算法的收敛性和路由成功率等进行了实验仿真.     

In-home power line communication media access control protocol based on collision resolution

Most existing media access control (MAC) protocols in power line communication (PLC) networks just discard the colliding data packets when collision occurs. The collision deteriorates throughput and delay performance of system under high traffic conditions. This article presents a novel media access scheme with fast collision resolution for in-home power line networks. It works by first recognizing the colliding stations through detecting the inserted unique ID sequence ahead of data packets, then the source nodes retransmitting their packets immediately after the collision slot. The proposed protocol maintains the benefits of ALOHA systems. It needs no scheduling overhead and is suitable for bursty sources, such as multimedia data packets. Computer simulations have demonstrated that this approach can achieve high throughput due to its ability of resolving collisions.     

Switching between antenna subset selection and quasi-orthogonal space-time block code in presence of correlation

We address the problem of adaptive modulation and coding scheme (AMCS) for a multi-input multioutput (MIMO) system in presence of time-varying transmitting correlation. Antenna subset selection and quasiorthogonal space-time block code (QOSTBC) have different error performances with different signal-to-noise ratios (SNRs) and in different spatial correlation scenarios. The error performance can be improved by selecting an appropriate transmission scheme to adapt to various channel conditions. The maximum distance criterion is the simplest and very effective algorithm for the antenna subset selection without needs of complex calculation and channel state information at transmitter (CSIT). The minimum error performance criteria and the simplified linear decision strategy are developed for constant transmission rate traffic to select the optimal transmission scheme. It can dramatically decrease algorithm complexity for obtaining error probability according to the known quantities comparing with using instant CSIT. Simulation results show that, remarkable performances including low SNR and weak spatial correlation at the expense of simple calculation and almost no bandwidth loss by adopting AMCS can be achieved. The proposed AMCS improves robustness of slowly varying spatial correlated channels.     

关于中国海事卫星数据服务系统的研究

中国海事卫星数据服务系统是具有我国自主知识产权、与移动卫星通信相衔接的卫星数据服务系统。系统在通信平台与上层应用之间采用了松散耦合的结构,易于扩展新的增值应用,可支持未来新的海事卫星业务。系统开发了自有通信协议,并兼容TCP／IP协议,实现了全双工通信、断点续传、在线压缩、信道加密等先进通信手段,优化提升了卫星信道使用效率。     

面向智能内河航运通信的无线信道测量与典型信道特征

为了明确新一代移动通信技术服务智能内河航运的作用机理，基于内河航运无线通信发展现状和通信环境特殊性，搭建了4G和5G临时无线通信网络，分别对以长江武汉段为例的典型内河通信场景开展了实际信道测量活动，以探寻内河航运无线通信特性的影响因素；利用高精度无线信道测量仪采集了信道传输函数、信号接收强度、时延等信道参数；基于无线传播理论和抽头延迟线模型，提取了传输路径损耗、功率时延分布、时延扩展、多普勒扩展等典型无线信道特征；基于信道典型特征参数，预测了4G和5G无线传播信号在内河场景下的有效覆盖范围及信号传输速率，探究了内河航运无线通信的多径来源和时延分布。测量和分析结果表明:内河航运无线通信中，桥梁、岸边建筑、过往大型船舶等均为无线传播信号多径效应的主要来源；桥梁可以造成最大18.0 dB的衍射损耗，岸边建筑和过往船舶遮挡会分别造成25.0、10.6 dB的能量衰减；4G无线通信的最大测量速率为95.32 Mb·s-1，而5G通信测量速率最高可达0.72 Gb·s-1；大型过往船舶还会造成均方根时延扩展增大约754.94 ns。可见，根据内河通信特殊环境构建合适的新一代移动通信专网，可以更好地为智能航运提供通信保障服务。      

基于3D CNN的道路视频交通状态自动识别

为了从视频直接有效地提取交通信息,提出了基于三维卷积神经网络 （3D convolutional neural networks,3D CNN）的交通状态识别方法.首先,以C3D （convolutional 3D）深度卷积网络为3D CNN原型,对卷积层数量与位置、平面卷积尺寸及三维卷积深度进行优化调整,形成了37个备选模型;其次,建立了视频数据集,对备选模型进行系统的训练测试,提出了交通状态识别模型C3D*;然后,对C3D* 和现有三维卷积网络模型进行视频交通状态识别测试分析;最后,对比测试了C3D* 及常用二维卷积网络的交通状态识别效果. 对比结果显示:针对视频交通状态识别,C3D* 的F均值为91.32%,比C3D、R3D （region convolutional 3D network）、R (2+1) D （resnets adopting 2D spatial convolution and a 1D temporal convolution）分别高12.24%、26.72%、28.02%;与LeNet、AlexNet、GoogleNet、VGG16的图像识别结果相比,C3D* 的F均值分别高32.61%、69.91%、50.11%、69.17%.      

A bintree energy approach for colour image segmentation using adaptive channel selection

A new hierarchical approach called bintree energy segmentation was presented for color image segmentation. The image features are extracted by adaptive clustering on multi-channel data at each level and used as the criteria to dynamically select the best chromatic channel, where the segmentation is carried out. In this approach, an extended direct energy computation method based on the Chan-Vese model was proposed to segment the selected channel, and the segmentation outputs are then fused with other channels into new images, from which a new channel with better features is selected for the second round segmentation. This procedure is repeated until the preset condition is met. Finally, a binary segmentation tree is formed, in which each leaf represents a class of objects with a distinctive color. To facilitate the data organization, image background is employed in segmentation and channels fusion. The bintree energy segmentation exploits color information involved in all channels data and tries to optimize the global segmentation result by choosing the ＂best＂ channel for segmentation at each level. The experiments show that the method is effective in speed, accuracy and flexibility.