Adaptive Load-Aware Congestion Control Protocol for Wireless Sensor Networks

Congestion control in wireless sensor networks (WSNs) is crucial. In this article, we discuss congestion control and the adaptive load-aware problem for sensor nodes in WSNs. When the traffic load of a specific node exceeds its the available capacity of the node, a congestion problem occurs because of buffer memory overflow. Congestion may cause serious problems such as packet loss, the consumption of power, and low network throughput for sensor nodes. To address these problems, we propose a distributed congestion control protocol called adaptive load-aware congestion control protocol (ALACCP). The protocol can adaptively allocate the appropriate forwarding rate for jammed sensor nodes to mitigate the congestion load. Through the buffer management mechanism, the congestion index of neighboring sensor nodes, and an adjustment of the adaptive forwarding rate, the degree of congestion is alleviated markedly. The performance in allocating the forwarding rate effectively to neighboring sensor nodes also improves. The ALACCP can avoid packet loss because of traffic congestion, reduce the power consumption of nodes, and improve the network throughput. Simulation results revealed that the proposed ALACCP can effectively improve network performance and maintain the fairness of networks.     

Adaptive Congestion Control of mSCTP for Vertical Handover Based on Bandwidth Estimation in Heterogeneous Wireless Networks

This paper proposes a new congestion control scheme of mobile Stream Control Transmission Protocol (mSCTP) for vertical handover across heterogeneous wireless/mobile networks. The proposed scheme is based on the estimation of available bandwidths in the underlying network as a cross-layer optimization approach. For congestion control of mSCTP, the initial congestion window size of the new primary path is adaptively configured, depending on the available bandwidth of the new link that a mobile node moves into. By ns-2 simulation, the proposed scheme is compared with the existing congestion control schemes in the throughput perspective. From the numerical results, we can see that the proposed mSCTP congestion control scheme could give better performance than the existing schemes in the wireless networks with an amount of background traffic.     

Adaptive Rate System for Wireless Packet Networks

The severe channel and interference condition can limit the throughput of the wireless packet networks. We thus propose an adaptive rate system to increase the throughput of the wireless packet networks. In this system, the data rate is adapted to the channel and interference condition. By optimizing the data rate for a given channel and interference condition, we establish the optimal adaptive rate system. It can be shown that the optimal adaptive rate system provides higher throughput than the fixed rate system.     

异构无线网络的自适应垂直切换判决算法

在未来的异构环境中,网络间的垂直切换将对QoS保证产生重要影响。针对移动终端在异构网络间切换不理想的问题,提出了一种自适应的垂直切换判决算法。采用基于用户多应用的代价函数对接入网络进行评估与选择,综合考虑移动终端当前的电池电量,判断当前业务是否需要进行网络切换,使移动终端能自适应地进行切换判决。仿真结果表明,该算法可以有效地延长移动终端的工作时间,减少乒乓效应,提高系统的切换性能,改善业务的QoS。     

无线Mesh网络中的自适应队列调度算法研究

针对无线mesh网络的网络特性,分析了无线网络中的队列调度算法,提出了一种自适应的队列调度算法AQSM,详细讨论了该算法的具体实现过程及参数变化规则,通过仿真验证了该算法在提高网络性能的同时还可以实现对不同业务流的业务区分。     

CASHeW: Cluster-based Adaptive Scheme for Multimedia Delivery in Heterogeneous Wireless Networks

Multimedia streaming over heterogeneous wireless networks has attracted significant interest in recent years from both telecom network operators and end users. However, the heterogeneity of the wireless network makes it very difficult to synchronize real-time multimedia streaming to different types of end-user devices across different wireless networks. In addition, with different delay and packet loss across different networks, multimedia delivery over the heterogeneous wireless networks cannot provide good quality streaming video. This paper proposes CASHeW—a novel cluster-based design with an in-built feedback-based adaptive mechanism that results in a higher video perceived quality in two-hop heterogeneous wireless network environments. CASHeW employs a proxy-client-server mechanism between the base station (BS) and the end-user; and importantly uses a quality-oriented adaptive scheme for efficient multimedia delivery. Simulation-based tests indicate that the performance of CASHeW not only outperforms transport layer adaptive delivery protocols like the TCP-Friendly Rate Control Protocol (TFRCP) and Loss Delay Adaptation (LDA+), but also is better than that of medium access control (MAC) layer protocols such as the Receiver Based Auto Rate (RBAR) and Enhanced Distributed Channel Access (EDCA) in terms of average perceived quality, average bit rate and loss rate.     

Multi-Dimensional Adaptive SINR Based Vertical Handoff for Heterogeneous Wireless Networks

Vertical handoff in next generation heterogeneous wireless networks is a multi-dimensional issue. In this article we propose a multi-dimensional adaptive SINR based vertical handoff algorithm (MASVH) which uses the combined effects of SINR, user required bandwidth, user traffic cost and utilization from participating access networks to make handoff decisions for multi-attribute QoS consideration. Simulation results confirm that the new MASVH algorithm improves the system performance in terms of higher throughput and lower dropping probability, as well as reduces the user traffic cost for accessing the integrated wireless networks.     

基于负载自适应的无线自组网视频传输队列调度算法

移动终端多媒体业务的发展目前已经成为终端发展的必然趋势.如何在移动终端构成Ad hoc网络时有效地进行视频传输是无线网络研究的热点之一.提出了一种基于负载状况的跨层优化方案,其基本思想是结合应用层视频编码的特点和接入层的网络负载和资源的情况联合进行优化.在特定的资源下通过概率接入的方法对重要性更高的数据包进行更优先的接入.仿真结果显示,在网络处于高负载、多跳传输等场景下,提出的方案视频传输质量PSNR值提升3 dB以上.相对于传统调度算法,系统时延也可以大幅度降低.     

无线多跳网络的自适应容量感知优化与控制技术

In wireless multimedia communications, it is extremely difficult to derive general end-to-end capacity results because of decentralized packet scheduling and the interference between communi-cating nodes. In this paper, we present a state-based channel capacity perception scheme to provide sta-tistical Quality-of-Service (QoS) guarantees under a medium or high traffic load for IEEE 802.11 wire-less multi-hop networks. The proposed scheme first perceives the state of the wireless link from the MAC retransmission information and extends this information to calculate the wireless channel capaci-ty, particularly under a saturated traffic load, on the basis of the interference among flows and the link state in the wireless multi-hop networks. Finally, the adaptive optimal control algorithm allocates a net-work resource and forwards the data packet by tak-ing into consideration the channel capacity deploy-ments in multi-terminal or multi-hop mesh net-works. Extensive computer simulations demonstrate that the proposed scheme can achieve better per-formance in terms of packet delivery ratio and net-work throughput compared to the existing capacity prediction schemes.     

Optimal Rate Allocation Based on Cross-Layer Design and End-to-End Congestion Control in WCDMA Networks

In this paper, a novel idea for rate allocation combining both vertical coupling and horizontal coupling constraints is proposed, and a unified utility function to balance two paradoxical issues: efficiency and fairness, revenue and cost is elaborated in WCDMA networks. Then, the optimal rate allocation problem is formulated as a network utility maximization(NUM) model based on cross-layer design and end-to-end congestion control, aiming at exploring the impacts of wired networks and the characteristics of radio access networks(RANs) on rate allocation. Furthermore, a distributed algorithm is derived, which can effectively match load states between RANs and wired networks, followed by a detailed illustration of the practical implementations. Numerical results demonstrate a signifi cant performance improvement in the end-to-end throughput.     

一种异构网络TCP拥塞控制算法

针对互联网中端对端带宽、时延和丢包率等的差异性日益加剧,导致TCP传输性能严重退化,该文提出一种链路自适应TCP拥塞控制算法(INVS)。INVS在拥塞避免阶段初期采用基于指数函数的凸窗口增长函数,以提高链路利用率;在窗口增长函数中引入了自适应增长因子实现窗口增长速率与链路状态相匹配;采用了自适应队列门限的丢包区分策略以提高无线环境下TCP的性能。性能分析和评估表明,INVS提高了TCP拥塞控制算法的吞吐量、公平性、链路利用率和RTT公平性。     

Jointly Optimal Region-Classified Adaptive Vector Quantization for Very Low Bit Rate Video Coding

In this paper, a video coding algorithm suitable for the very low bit rate video coding system is presented. It takes advantage of the prior knowledge of the image type to segment the image to different regions, then codes each region with different coding criterion and method according to the different importance. An adaptive region-classified vector quantization strategy is exploited in this algorithm also. With segmentation of the frame and high correlation between frames, better codebooks of vector quantization are constructed to improve the quality. According to the simulation results, acceptable quality at about 10 kbits per second can be obtained for the typical test sequences.     

异构无线网络业务接入多目标优化控制算法

提出了一种应用于异构无线网络环境的基于多目标优化的业务接入控制算法.该算法以业务占用总资源最少、业务阻塞率最低和网络间负载最均衡为目标建立了多目标优化控制模型,采用高斯和戒上型组合隶属函数将多目标问题模糊化,利用最大化满意度指标法将多目标问题转化为单目标问题,并通过遗传算法求得最优解.仿真结果表明,所提算法能在兼顾各网络资源高效利用的同时,保证业务接入的可靠性,并相对于参考算法有效降低了业务阻塞率.     

Design of ATM Networks Congestion Controller Based on the Virtual Queue

International Telecommunications Union (ITU) adopts asynchronous transfer mode (ATM) as the typical transfer technology for broad integrated services digital network (BISDN) in the future. ATM networks can support many types of services. According to the ATM Forum specifications, ATM networks currently offer six service categories[1]: constant bit rate (CBR), real-time variable bit rate (rt-vbr), nonreal-time variable bit rate (nrt-vbr), available bit rate (ABR), unspecified bit rat…     

异构无线网络可信接入设计及实现

异构无线网络互连后的安全问题是当前网络安全研究的一个热点问题,为了解决异构网络互连后产生的接入安全问题,提出了一种基于信任模型的可信接入框架,该框架建立了异构无线网络间的信任评价体系,对接入异构无线网络用户除了进行身份验证,还必须进行用户信任度的验证,既拒绝了恶意节点接入,又确保了合法节点的安全接入,从而保证异构无线网络互连接入的安全和可信。     

Data Broadcast with Adaptive Network Coding in Heterogeneous Wireless Networks

In this paper, we propose a new data broadcast mechanism with network coding in heterogeneous wireless networks. Our mechanism adaptively clusters the mobile hosts in fewer cells to minimize the bandwidth consumption. In addition, we adaptively code the data according to the data temporarily stored in each mobile host with a distributed manner. Our mechanism allows each delivered message to be coded from only a subset of data to further reduce the number of required messages. We formulate the cell selection and broadcast coding problem with integer programming and prove that the problem is NP-hard. We design a distributed algorithm based on Lagrangean relaxation. Our algorithm needs no server to record the location, queried, and stored information of receivers. Moreover, our algorithm is adaptive to the dynamic group membership, mobility, queried, and stored data of receivers.     

Congestion Control Framework for Ad-Hoc Wireless Networks

During the last few years, bandwidth and traffic control have immerged as issues of great importance in ad-hoc wireless networks, requiring sophisticated managing techniques. Moreover, due to the increasing variety of applications and consequently respective need for bandwidth control, such issues are expected to become even more critical in the near future. Main characteristics of MANETs such as multi-hop communication and supporting dynamically varying topologies rapidly and unpredictably change or remain static over long periods of time augments the complexity of the problem as well as the need to efficiently handle it. In order to circumvent those problems, many researchers turn their attention to cross-layer design which provides the possibility to create lightweight and flexible substrate for the demanding ad-hoc wireless networks. This design approach provides critical features that suit the characteristics of ad-hoc wireless networks. This paper proposes a novel, lightweight and efficient cross-layer architecture for congestion control at wireless ad-hoc networks. The performance of this framework is evaluated considering characteristic ad-hoc routing protocols, such as AODV and DSR, in static as well as mobile network topologies using the well known network simulator NS2.     

基于无线传感器网络的跨层拥塞控制协议

无线传感器网络(WSN)中由拥塞引起的大量分组重传以及重传多次失败后的分组丢弃会导致较长的时延、较高的分组丢失率和较多的能量消耗.为了准确探测和控制网络拥塞,提出了一种基于跨层设计的拥塞控制协议,即上行拥塞控制(UCC)协议.该协议利用节点在媒质接人控制(MAC)层中未占用的缓冲器区间大小和所预测的通信流量作为该节点的...     

Node-Based Optimal Power Control, Routing, and Congestion Control in Wireless Networks

In wireless networks, important network functionalities such as power control, rate allocation, routing, and congestion control must be optimized in a coherent and integrated manner. In this work, an interference-limited wireless network is considered, whereby power control and routing variables are chosen to minimize the sum of link costs which depend on both link capacities and link flow rates. The necessary conditions for optimality are established. These conditions are sufficient for optimality if link cost functions are jointly convex, and imply Pareto optimality if link costs are strictly quasi-convex. Network algorithms based on the scaled gradient projection method, where power control and routing are performed on a node-by-node basis, are presented. For these algorithms, explicit scaling matrices and stepsizes are found which lead to more distributed implementation, and which guarantee fast convergence to a network configuration satisfying the optimality conditions, starting from any initial configuration with finite cost. Refinements of the algorithms for more accurate link capacity models are presented, and the results are extended to wireless networks where the physical-layer rate region is given by an arbitrary convex set. Finally, it is shown that the power control and routing algorithms can naturally be extended to incorporate congestion control.      

无线移动传感器网络自适应体系结构的设计

随着无线网络技术的日益成熟及其对小型、微型移动设备的支持,无线移动传感器网络已经逐渐成为一个研究的热点。主要讨论了为无线移动传感器网络设计的一个自适应的体系结构。在该体系结构中,使用了一个区域和核心路由节点相结合的多层结构的方法来增加无线移动网络的信息传输能力、可扩充性和可靠性,并降低网络的能耗,这样就可以适应无线移动网络的高度动态性和移动性。