H.264/AVC error resilience tools suitable for 3G mobile video services

The emergence of third generation mobile system （3G） makes video transmission in wireless environment possible, and the latest 3GPP/3GPP2 standards require 3G terminals support H.264/AVC. Due to high packet loss rate in wireless environment, error resilience for 3G terminals is necessary. Moreover, because of the hardware restrictions, 3G mobile terminals support only part of H.264/AVC error resilience tool. This paper analyzes various error resilience tools and their functions, and presents 2 error resilience strategies for 3G mobile streaming video services and mobile conversational services. Performances of the proposed error resilience strategies were tested using off-line common test conditions. Experiments showed that the proposed error resilience strategies can yield reasonably satisfactory results.     

基于无线通信的消防管道压力监测系统设计

针对传统压力检测记录方法存在的问题,提出一种低功耗消防管道无线压力监测系统的方法。该方法根据低功耗设计理念,对压力采集系统的硬件电路、软件流程进行设计。硬件电路以PIC18F87K90单片机为核心,具有液晶显示、按键开关、无线传输等功能。软件设计实现了温度补偿功能,并简化了外围电路,降低了系统功耗,提高了数据采集精度。最后给出了传感器在测量范围为0～40MPa的测试结果：最大误差为0.04Mpa,可满足系统的精度要求。     

移动通信中电磁波传播模型及其修正方法

对移动通信信道的复杂性进行了分析，介绍了无线通信中电磁波传播损耗相关的因素及其对信道参数的影响；给出了传播模型的一些基本特性并对主要的预测模型进行了综述，针对模型参数的不确定性，介绍了本地均值的测试方法和对预测模型的一些实用性改进技术。     

2008全球无线通信亮点预测

当前,从全球来看,公众移动通信呈现持续增长的态势,业务应用日趋丰富,3G网络演进稳步推进。与此同时,WiMAX等宽带无线技术和短距离无线技术日益走向成熟,＂泛在网络＂正扬帆起航。2008年,在无线通信领域,有许多热点和亮点值得我们共同关注。     

探讨网络IPSec 和移动IP存在的问题

移动IP和IPSec作为一种适应无线通信需要的网络层解决方案，它主要用于非实时的业务，为了满足未来移动通信系统的要求，对网络层安全的研究开发也出现了很多新的方向。     

无线通信网络输电线路监测平台的研究

随着无线通信网络技术的不断发展和应用,智能电网的研究和建设具有了强有力的通信网络平台的支持,特别是由于输电线路分布范围广泛,其许多电气参数受不同地域、不同污染、不同气候的影响而具有不同的特征,仅靠人工巡视观察已远远不能适应智能电网的发展要求,因此提出了分布式输电线路监测平台,对于监测点分散的输电线路,设计了利用3G无线通信平台能较好地解决其监测数据的传输问题,而对于监测点较集中的输电线路,则设计了利用无线自组网的通信平台来实现监测输电线路的实时运行状态,以便管理人员能及时获得监测信息而快速决策,从而利用无线通信及组网技术实现了输电线路的实时监测来满足智能电网建设需要。     

软硬协同无线通信视频传输实验系统设计

基于QCA9558芯片、嵌入式系统服务、无线组网技术、QT技术,设计了无线视频传输系统,该系统由视频采集节点、Wi-Fi无线多跳网络、上位机客户端软件组成。在MIPS平台上移植嵌入式OpenWrt操作系统;组建Wi-Fi无线多跳网络,完成网关节点和路由节点的设置,制定了数据通信协议;使用QT技术设计PC客户端程序。通过测试,系统性能良好,满足视频传输的需求,系统可以用于实验教学及科研研究。     

Performance of beacon safety message dissemination in Vehicular Ad hoc NETworks （VANETs）

Currently, there is a growing belief that putting an IEEE 802.11-like radio into road vehicles can help the drivers to travel more safely. Message dissemination protocols are primordial for safety vehicular applications. There are two types of safety messages which may be exchanged between vehicles: alarm and beacon. In this paper we investigate the feasibility of deploying safety applications based on beacon message dissemination through extensive simulation study and pay special attention to the safety requirements. Vehicles are supposed to issue these messages periodically to announce to other vehicles their current situation and use received messages for preventing possible unsafe situations. We evaluate the performance of a single-hop dissemination protocol while taking into account the quality of service (QoS) metrics like delivery rate and delay. We realize that reliability is the main concern in beacon message dissemination. Thus, a new metric named effective range is defined which gives us more accurate facility for evaluating QoS in safety applications specifically. Then, in order to improve the performance, the effects of three parameters including vehicle's transmission range, message transmission's interval time and message payload size are studied. Due to special characteristics of the safety applications, we model the relationship between communication-level QoS and application-level QoS and evaluate them for different classes of safety applications. As a conclusion, the current technology of IEEE 802.11 MAC layer has still some challenges for automatic safety applications but it can provide acceptable QoS to driver assistance safety applications.     

无线组网技术及其在船舶上的应用

根据无线网络本身的特点和海上独特的环境条件，利用基于IEEE 802．11标准的无线局域网组网技术实现了舰艇内部无线网络的组建，以及舰艇之间的无线局域网互联，使海外作业的船只间的信息交换和数据传输成为可能，从而提高作业效率。还对无线网络组网技术的特点、安全性、稳定性进行了分析，论述了无线网络组网技术在特殊环境中的应用的可行性和优越性。     

A novel constant modulus array for multiuser detection

This paper proposes a new multitarget constant modulus array structure for code division multiple access (CDMA) systems. The new algorithm for the structure is called pre-despreading and wavelet denoising constant modulus algorithm (D-WD-CMA). In the new algorithm, the pre-despreading is applied to multitarget arrays to remove some multiple access inter- ferences. After that the received signal is subjected to wavelet de-noising to reduce some noise, and used in CMA adaptive iteration …