应用于无线传感器网络的语音传输系统的设计与实现

随着宽带网络和信息技术的日益普及、企业信息化需求的进一步提高,回话网络、Internet以及移动网络三网分离的局面已不能满足企业办公需要,因此需要一种整合多种通信方式,对统一消息数据进行综合管理的企业融合通信技术。另一方面,随着短距离无线通信技术的成熟与发展,短距离无线通信技术同样需要融入固话网络、Internet以及移动网络。本文在分析无线传感器网络技术的基础上,提出了一种新型的VoIP接入网关的设计方案,给出了一种使用IP网络电话的方式;对VoIP接入网关的硬件设计及系统结构做了详细的分析;对VoIP接入网关的整体硬件进行了详细的设计并给出PCB设计实物。     

OFDM系统符号同步的FPGA设计与实现

分析了符号定时偏差对OFDM系统中数据传输的影响,参考IEEE802.11a标准给出了基于训练序列的符号同步算法在FPGA中的硬件实现方案,并在ISE平台中进行验证.仿真结果表明,该实现方案有效减少了硬件资源的使用,提高了运行效率,能够实现有效的符号同步,并且易于进行工程实现.     

无线宽带IEEE802.16d物理层仿真

针对WiMAX物理层研究的重要性以及根据WiMAX标准所规定的有限测试向量来测试系统带来的不便,利用动态系统仿真工具Simulink按照IEEE802.16d物理层标准构建了一完整的端对端的系统模型,将指标文档变成了一个动态的可执行模型,大大方便了对系统的测试和分析。同时为IEEE802.16d/e两种标准下的信道、均衡、同步算法的研究与应用提供了一个有效的研究平台,对WiMAX标准的研究与开发很有意义。     

基于IEEE1149.7的新一代测试接口实现与应用

随着芯片集成度的不断增加和对低功耗设计的重视,原初开发的JTAG（IEEE STD1149.1）面对新的挑战,不能满足当今设计的需要。CJTAG基于IEEE STD1149.7标准和传统的JTAG的边界扫描原理来提供一个更加强大的测试和调试的标准,来达到现在系统的要求。CJTAG用更少的管脚来提供更多的功能,而同时保证了对IEEE1149.1的软件和硬件的兼容性。     

Deployment of a reliable 802.11e experimental setup for throughput measurements

This paper describes an experimental setup for measuring the throughput of an 802.11 network that supports Quality of Service (QoS) mechanisms, addressing some issues concerning the comparison between experimental and theoretical results. The setup is an ad hoc network in which the nodes implement the Multiband Atheros Driver for Wireless Fidelity (MADWiFi). There are three main contributions of this study. The first one describes the adjustments to the MADWiFi source code that guarantee the control of the QoS parameters in ad hoc mode. The second contribution aims to provide a practical method for verifying if the backoff generated by a given wireless card is uniformly distributed, as dictated by the 802.11 standard. This represents a key point when theoretical and experimental results must be compared, since many vendors adopt nonuniform backoff distributions in their commercial cards. As a third contribution, this paper presents a theoretical nonsaturated analysis that provides the throughput and the successful packet delay of an 802.11 network supporting QoS in presence of nonuniform backoff. The throughput derived from this analysis using a uniform backoff, which is included in the proposed model as a particular case, is compared to the measurements provided by the deployed setup. Copyright © 2010 John Wiley & Sons, Ltd.     

Group scanning scheme for fast target channel decision in seamless handover of wireless networks

In wireless networks, when a mobile roaming station decides to initiate a handover, it should scan multiple channels operated by neighboring base stations (BSs) (or access points (APs)) in order to find an appropriate target base station before the actual handover. In some wireless networks, the active base station is able to provide a list of channels operated by neighboring base stations. However, some of these candidate channels may not be accessible to the mobile station (MS); nonetheless, the MS scans the candidate channels consecutively. For this reason, it may take a relatively long time for the MS to select an adequate target base station channel. This process can degrade the quality of service (QoS) during handovers. To shorten the scanning latency efficiently, in this paper we propose a cooperative channel scanning method whereby groups of MSs scan candidate channels using a dispersive schedule. They then share the scanning results amongst themselves, which results in a fast handover channel decision. To apply the proposed method to a real network environment, we present a group scanning architecture and detailed application scenarios appropriate for IEEE 802.16e worldwide interoperability for microwave access (WiMAX) networks. Numerical analyses and simulation results show that our proposed method achieves a shorter target channel scanning latency. Our method is thus more efficient in terms of scanning time and channel selection accuracy. Copyright © 2010 John Wiley & Sons, Ltd.     

A slot‐based BS scheduling with maximum latency guarantee and capacity first in 802.16e networks

The IEEE 802.16e standard specifies the QoS support at the MAC level for wireless broadband access network. To meet the QoS requirements, an efficient scheduling algorithm at base station (BS), which is not defined in the standard, is necessary for slots allocation. In this paper, a Slot‐based BS scheduling algorithm with Maximum Latency Guarantee and Capacity First (SMLG‐CF) is proposed. With SMLG‐CF, the connection request is satisfied with highest slot capacity first. Together with the use of dynamic sub‐frame adjustment, the overall system transmission can be efficiently improved. Through the finer slots calculation and accurate transmission time scheduling, the maximum latency guarantee can be better achieved for urgent requests. In the simulation, we compare the proposed mechanism with the deficit fair priority queue scheduling algorithm and the Highest Urgency First scheduling algorithm. The simulation results reveal that SMLG‐CF outperforms both algorithms from the aspect of maximum latency violation rate and average transmission rate. Copyright © 2011 John Wiley & Sons, Ltd.     

100 Gbit/s CFP光收发模块的研究

随着网络流量的持续增长,100 Gbit/s以太网已开始商用,100 Gbit/s以太网的客户侧光模块为100 Gbit/s CFP(小型可插拔式)光收发模块。文章介绍了100 Gbit/s CFP光收发模块的相关标准,并给出了一种模块的设计方案。该模块由速率转换单元、发射单元、接收单元及控制单元组成。依照IEEE 802.3ba标准对模块进行了测试,结果显示该模块单通道发射平均光功率达到了1.47dBm,接收灵敏度达到了-9.5dBm,各项性能完全符合相关标准,能够应用于100 Gbit/s以太网中。     

IEEE 802．16中基于信道状态的改进分组调度算法

为适应IEEE802．16无线网路的特点,降低数据的分组超时率,提高数据的平滑性,在基于信道状态的分组调度算法（CSDPS算法）的基础上,提出了一种基于信道状态的改进分组调度算法。该算法把业务区分与信道状态结合起来,既考虑了不同业务的QoS需求,也考虑了无线网络的信道特点。在降低发送速率上,给出降低速率的具体计算公式。通过理论分析,用改进算法与原有CSDPS算法进行了对比。可以发现,改进算法在分组超时率和数据平滑性上都有较大改善。     

基于802.11i 的WLAN动态密钥管理机制分析及改进

介绍了新一代WLAN安全标准802.11i,研究了802.11i协议的动态密钥管理机制,从四步握手角度对其安全性进行了深入分析,指出了可能受到的DoS攻击.提出了两种改进设计方案,有效避免了这些攻击,进一步完善了无线局域网的安全性能.