Cross layer based fast handover for IEEE 802.16e networks

To guarantee the QoS in real time applications in wireless networks, handover delay is one of the most important parameters to be considered while mobile users are changing their point of attachment to the access networks. This calls for a fast handover mechanism that will be able to offer uninterrupted services to mobile users. In this paper, a cross layer based fast handover mechanism is proposed to reduce handover delay and signaling load in IEEE 802.16e wireless metropolitan area networks. This is achieved by overlapping the functions of Medium Access Control (MAC) Layer and Internet Protocol (IP) layer. The analytical results show that the proposed mechanism significantly enhances the handover performance in terms of handover delay and signaling load thus resulting into fast handover.     

IEEE802.16e标准下LDPC码译码性能分析

LDPC码是一种逼近香农极限的线性分组码。对IEEE802.16e标准下LDPC码校验矩阵的构造及硬判决算法、BP算法、Log-BP算法和Min-Sum算法原理进行了简单介绍。基于Matlab仿真对不同码长译码性能及不同方法译码性能进行分析比较,结果显示随着码长的增加LDPC译码性能变好,讨论的几种译码算法中硬判决译码性能较差,Min-Sum译码好于硬判决译码,但稍差于BP译码和Log-BP译码,BP译码和Log-BP译码性能较好且基本一致。     

Adaptive packet scheduling for the uplink traffic in IEEE 802.16e networks

IEEE 802.16e is a telecommunication standard technology designed to support a wide variety of multimedia applications. It defines five service classes, each one with its respective QoS requirements, but does not define the scheduling algorithm for these service classes. In this paper, an adaptive packet scheduling algorithm for the uplink traffic in IEEE 802.16e networks is proposed. This algorithm is designed to be completely dynamic, mainly in networks that use various modulation and coding schemes (MCSs). The algorithm is applied directly to the bandwidth request queues in the base station (BS) and aims at supporting the real‐time and non‐real‐time applications. Using a cross‐layer approach and the states of the bandwidth request queues in the BS, a new deadlines based scheme was defined, aiming at limiting the maximum delay to the real‐time applications. Moreover, this algorithm interacts with the polling management mechanisms of the BS and controls the periodicity of sending unicast polling to the real‐time and non‐real‐time service connections, in accordance with the QoS requirements of the applications. The proposed algorithm was evaluated by means of modeling and simulation in environments where various MCSs were used and also in environments where only one type of modulation was used. The simulations showed satisfactory results in both environments. Copyright © 2012 John Wiley & Sons, Ltd.     

Improving IPTV Forwarding Mechanism in IEEE 802.16j MMR Networks Based on Aggregation

Internet protocol television (IPTV) service depends on the network quality of service (QoS) and bandwidth of the broadband service provider. IEEE 802.16j mobile multihop relay Worldwide Interoperability for Microwave Access networks have the opportunity to offer high bandwidth capacity by introducing relay stations. However, to actually satisfy QoS requirements for offering IPTV services (HDTV, SDTV, Web TV, and mobile TV) for heterogeneous users' requests, providers must use a video server for each IPTV service type, which increases the network load, especially bandwidth consumption and forwarding time. In this paper, we present a solution for forwarding IPTV video streaming to diverse subscribers via an 802.16j broadband wireless access network. In particular, we propose a new multicast tree construction and aggregation mechanism based on the unique property of prime numbers. Performance evaluation results show that the proposed scheme reduces both bandwidth consumption and forwarding time.     

Entire network load‐aware cooperative routing algorithm for video streaming over mobile ad hoc networks

In this paper, we present an entire network load‐aware cooperative routing algorithm based on IEEE 802.11 multi‐rate for video streaming over mobile ad hoc networks. The proposed routing algorithm is designed to minimize the consumed time slots while guaranteeing the required time slots at all the pairs of adjacent nodes over the route and the contention neighbors of these nodes to support the route. Furthermore, the proposed routing algorithm can distribute the network loads well over the entire network. This technology is essential because video streaming applications require stringent quality of service and even larger network resources compared with traditional data services, and these demands may dramatically increase the entire network load and/or cause network congestion. Finally, experimental results are provided to show a performance of the proposed routing algorithm. Copyright © 2011 John Wiley & Sons, Ltd.     

支持空间迷你时槽重用的IEEE 802.16Mesh网络多播调度算法

In this paper, we propose a mechanism for multicast data transmission in IEEE 802.16 mesh networks aimed at increasing the throughput by incorporating mini-slot spatial reuse. The proposed mechanism includes two novel algorithms: a source-based multicast tree topology construction algorithm followed by an interference-aware multicast scheduling algorithm. The proposed multicast interfer-ence-aware scheduling algorithm can be ap-plied to both source-based and rendez-vous-based multicast tree topologies. Results of our simulation study show that in compari-son to the mechanism used for the IEEE 802.16’s standard, the proposed multicast tree generation algorithm reduces the number of consumed mini-slots by 64% on average. Moreover, using the proposed interfer-ence-aware scheduling algorithm decreases the number of required mini-slots by a further 22% on average. Therefore, the proposed multicast scheduling mechanism shows a higher throughput than the previous ap-proaches and it is more scalable with respect to increasing the number of multicast groups as well as increasing the number of members inside each multicast group.     

基于确定与随机Petri网的IEEE 1394b总线性能评价(英文)

IEEE 1394b is a high-speed data bus that is widely used in local area networks and consumer electronics. To best utilize this data bus, we need to fully understand its performance. To evaluate its performance for both isochronous and asynchronous data transfers, we model the IEEE 1394b bus using Deterministic and Stochastic Petri Nets (DSPNs), and conduct simulations using TimeNET 4.0. Using the DSPNs model, we simulate both the average waiting times of isochronous and asynchronous packets. From the simulation results, we determine the factors that influence performance, such as throughput, size of packets, arrival rate of packets, number of isochronous channels, and bus configuration.     

改进的不恢复余数的浮点开方算法的研究与FPGA实现

对一种改进的不恢复余数的开方算法(non-restoring square-root algorithm)进行了讨论,并将其应用于基于IEEE 754标准的32位浮点格式的开方运算中,以一款FPGA为载体,实现了进行运算的基本电路。对目前存在的几种开方算法进行了评述,分析了他们的优缺点,提出了改进的不恢复余数开方算法模块化的设计思路与关键电路,并分析了仿真和逻辑综合的结果,证明了该算法运算速度较快且占用资源极少的特点。     

基于IEEE488标准接口的自动测试系统

介绍了一种并行的与仪器相接的标准接口—IEEE488标准接口;论述了如何利用通用的智能仪器构建一个自动测试系统,阐述了仪器软面板的设计规范,分析了传统自动测试系统软件存在的缺点,提出了一个全新的编程思路即测试程序与测试流程数据库相联系的自动测试软件框架。     

IEEE802．11的WEP算法安全性浅析

本文简要介绍了IEEE 80 2 .11无线局域网的安全保证算法———WEP算法 ,指出了该算法的安全性漏洞 ,并针对这些漏洞给出了对其实施攻击的方式。随后介绍了它的改进版本TKIP算法对WEP存在问题的对策。最后提出了一些现有设备使用中提高安全性的解决措施。