基于OMAP3530的无线双模视频监控系统设计与实现

针对无线视频传输系统的难点,提出了双模视频传输系统。该系统在硬件上采用OMAP3530芯片,编码上使用H.264编码,充分利用了H.264标准在数据压缩率和网络友好性等方面无可比拟的优势。无线传输利用TD-SCDMA和CDMA20001x两种3G无线传输信道,采用双模调度和管理算法提高了网络可利用带宽,增加了视频传输的稳定性。     

无线视频通信中信道特性的研究

在无线视频通信中，无线信道环境的好坏将直接影响到通信质量，信号传输中的带宽．波动、高误码率和接收的异种性为视频通信系统的设计带来了极大的困难。讨论了无线信道电波传播的特性，给出了无线时变衰落信道的模型并分析了视频传输的信道失真，为复杂无线环境下的视频通信系统的设计提供了理论依据。     

基于CDMA1x的H.264无线远程视频监控押运系统

在分析当前无线远程视频监控系统的发展趋势的基础上,给出了一种基于CDMA1x无线网络,采用DSP实现H.264编码协议的无线远程视频传输系统的设计方案.结合嵌入式Linux构成一个数据采集编码处理终端,将采集到的图像数据按照H.264标准进行编码,得到的码流可以通过CDMA1x无线信道传输.接收端的解码显示图像格式为CIF或QOF视频,采用帧频的方式显示,在有限的带宽内满足应用需求.     

基于CDMA1x的H．264无线远程视频监控押运系统

在分析当前无线远程视频监控系统的发展趋势的基础上,给出了一种基于CDMA1x无线网络,采用DSP实现H.264编码协议的无线远程视频传输系统的设计方案。结合嵌入式Linux构成一个数据采集编码处理终端,将采集到的图像数据按照H.264标准进行编码,得到的码流可以通过CDMA1x无线信道传输。接收端的解码显示图像格式为CIF或QCIF视频,采用帧频的方式显示,在有限的带宽内满足应用需求。     

Ad Hoc上的新协议——流实时传输协议

在Ad Hoc网络中传输多媒体数据会受到网络拓扑变化和无线信道干扰的限制.多流实时传输协议MRTP(multi-flow real-time transport protocol)是一种可以分配和传输多个视频数据流的新协议.它结合多描述编码和多径传输,能提高无线对等网络上视频传输的效率和质量.     

Ad Hoc上的新协议——多流实时传输协议

在Ad Hoc网络中传输多媒体数据会受到网络拓扑变化和无线信道干扰的限制。多流实时传输协议MRTP（multi—flow real—time transport protocol）是一种可以分配和传输多个视频数据流的新协议。它结合多描述编码和多径传输。能提高无线对等网络上视频传输的效率和质量。     

无线双模视频传输设备的硬件设计与实现

针对高速无线视频传输的需求,设计了一种基于双核(ARM+DSP)CPU OMAP3530,融合TD-SCDMA和CDMA2000无线网络技术的手持双模远程视频传输设备.论述了无线双模视频传输设备硬件设计中的关键技术,包括主要器件选型、电路设计和PCB制作以及软件设计.实验结果表明,本系统经过在DSP内实现的H.264视频压缩和ARM中实现的负载均衡算法后,能有效提高编码效率,减少发送数据量,并能充分利用无线网络带宽资源.在TD-SCDMA和CDMA2000双模的环境下,能够为远程监控提供清晰流畅的视频效果,可有效解决第二代无线通信在视频传输时带宽不足的问题.     

RTP/UDP协议在无线视频传输中的应用研究

设计了RTP/UDP/IP框架下的传输协议,并应用于CDMA IX的无线视频传输系统中.结合无线信道特点和UDP协议的固有缺陷,提出了利用RTP协议的序列号域进行差错控制的方法,在克服网络丢包和传输乱序方面获得了良好的效果.     

基于跨层码率适配和差错控制的3D视频无线传输方法

针对纹理视频加深度序列的3D视频无线传输,本文提出一种基于跨层优化的码率适配和差错控制方法.通过最小化端到端3D视频失真,均衡调整和配置应用层3D视频编码的码率和帧内编码更新比例,以及物理层的调制和编码模式,达到信源码率适配信道带宽以及应用层差错控制和物理层信道保护强度相互平衡的目的,进而提高接收端的3D虚拟视点视频质量.实验结果表明,提出的方法能有效的提高3D视频无线传输的性能.     

无线网络中实现ATM的关键技术

无线ＡＴＭ是异步转移模式（ＡＴＭ）技术和移动通信技术发展产物。ＡＴＭ传输和交换以宽带、低误码率和高传输速率的传输介质为前提，可以提供多媒体服务和广泛的信息接入。而无线停产的传输特点是带宽受限、信道传输质量差和传输误码率高。文中首先介绍无线ＡＴＭ的一般概念，其次说明在无线网络中实现ＡＴＭ技术的关键问题及其解决方法，最后介绍无线ＡＴＭ的网络协议。     

QoS guarantee and provisioning for realtime digital video over mobile ad hoc cdma networks with cross-layer design

In this article we investigate the trade-offs and the constraints for multimedia over mobile ad hoc CDMA networks, and propose a cross-layer distributed power control and scheduling protocol to resolve those trade-offs and constraints in order to provide high-quality video over wireless ad hoc CDMA networks. In particular, a distributed power control and scheduling protocol is proposed to control the incurred delay of video streaming over multihop wireless ad hoc networks, as well as the multiple access interference (MAI). We also investigate the impacts of Doppler spread and noisy channel estimates upon the end-to-end video quality, and provide a relatively robust system which employs a combination of power control and coding/interleaving to combat the effects of Doppler spread by exploiting the increased time diversity when the Doppler spread becomes large. Thus, more robust end-to-end video quality can be achieved over a wide range of channel conditions     

Adaptive rate controlled,robust video communication over packet wireless networks

Video transmission over wireless packet networks is gaining importance due to the concept of universal personal communication. Further, it is considered an important step towards wireless multimedia. The challenge however is to achieve good video quality over mobile channels, where typically the channel conditions vary due to signal fading. Hence this paper investigates adaptive rate controlled video transmission for robust video communication under packet wireless environment. A combination of mobile and an ATM backbone network is assumed in this work. An error resilient design for the video coder, as proposed in Rajugopal et al. (1996) is employed here. This video coder comprises wavelet transform (WT), multi-resolution motion estimation (MRME) and a robust design for zero tree quantization. Two configurations, one employing MRME and the other using 1D-WT for temporal analysis, are considered for the video coder. Adaptive dynamic rate control is required to adapt the video communication to the channel conditions. It provides more channel protection when the channel is severe and improves the source rate and hence the performance when the conditions are favorable. An algorithm for dynamic rate control under varying channel conditions is proposed in this paper. It is evaluated under narrowband and broadband channel conditions. From the results, it is concluded that the dynamic rate control is very effective in optimizing the quality under varying mobile channel conditions. It was observed that the dynamic rate control provides at least an acceptable video quality under severe channel conditions and a good video quality when the channel conditions are favorable. This revised version was published online in July 2006 with corrections to the Cover Date.     

Capacity Analysis for Connection Admission Control in Indoor Multimedia CDMA Wireless Communications

In this paper, the capacity analysis for connection admission control is presented for the reverse-link transmission of a packetized indoor multimedia wireless communication system using direct sequence code division multiple access (DS/CDMA). Since CDMA is interference limited, the signal-to-interference-plus-noise ratio criterion is used to check if there is enough system resources (i.e., the CDMA channels and received signal power) for each new connection request. Taking into account the stochastical nature of multimedia traffic, the effective bit rate is used to characterize the resources required by each mobile user and a linear approximation is then used to find the total resources required by all the mobile users already admitted to the system and the new connection request. Transmission errors due to both base station buffer overflow and wireless channel impairments are considered. The capacity of multimedia traffic is determined in such a way that the utilization of the system resources is maximized and, at the same time, the required transmission bit error rate and transmission delay of all users admitted to the system are guaranteed. Computer simulation results are given to demonstrate the performance of the proposed method for capacity analysis.     

车载式无线双模音视频传输监控系统设计与实现

基于CDMA2000和WCDMA的无线网络,设计并实现了车载式音视频监控系统,包括运行于后台的监控中心子系统和运行于终端的调用子系统.重点阐述了该监控系统中监控终端以及监控中心的软件设计和关键技术.系统在工程环境下进行了调用测试,测试结果表明,基于该设计的车载终端充分利用了CDMA2000和WCDMA网络的传输带宽,相对于单模的音视频传输,在传输效果上有较大的提高.     

MISO CDMA transmission with simplified receiver for wirelesscommunication handsets

The next-generation wireless personal and mobile communication systems are expected to accommodate not only high-quality voice services, but also a broad range of other multirate services. Of the various multiaccess techniques, wide-band code-division multiple access (CDMA) has been regarded as an important part of the third-generation wireless communication systems because of its high frequency utilization efficiency and suitability for handling multimedia and multirate services. In this paper, we consider a system with a simplified receiver structure for direct-sequence CDMA (DS/CDMA) wireless communication handsets, in which improved performance is demonstrated when compared to a conventional DS/CDMA system with a RAKE receiver at the mobile station. We arrive at this system by finding the optimal solution to a general multiple-input single-output (MISO) DS/CDMA smart antenna system. We find that this solution reduces to a pre-RAKE with space transmit diversity system under the assumption that a simple one-finger matched filter is used at the receiver. This system combines the advantages of pre-RAKE diversity and transmit antenna diversity. It is shown that significant system performance and capacity improvements are possible. The numerical results also reveal that this system is not too sensitive to channel estimation errors     

Design of spread spectrum multicode CDMA transport architecture formultimedia services

We investigate a new application of the well-known spread spectrum code division multiple access (SS-CDMA) techniques to multimedia services related to the development of the next-generation wireless mobile networks interconnecting with a wireline ATM-based broadband network. Such services allow users to share novel multimedia applications without any geographical restrictions. However, since the mobile radio channel has a fixed limited bandwidth, the traditional SS-CDMA system may not be sufficient to accommodate the variable bit rate (VBR) multimedia services requested by multiple mobile users simultaneously. Moreover, the traffic load at the base station can change dynamically due to the time-varying throughput requirement of these requested multimedia services. To tackle this difficulty, a multicode CDMA (MC-CDMA) technique is proposed to provide multirate multimedia services by varying the number of spreading codes assigned to each user in order to meet its throughput requirement. In MC-CDMA, a spreading code can be used to transmit information at a basic bit rate. Users (video or data) who need higher transmission rates can use multiple codes in parallel. Meanwhile, the maximum available number of codes in the MC-CDMA system is still limited. Hence, a cost-effective dynamic code allocation scheme has then been proposed to dynamically assign an appropriate number of codes to each user for achieving the maximum resource utilization for multiuser multimedia services via the mobile radio channel. Finally, a number of real multimedia titles generated from the well-known MacroMind Director are conducted to evaluate performance     

Energy-efficient wireless video coding and delivery

Transmitting video over wireless channels from mobile devices has gained increased popularity in a wide range of applications. A major obstacle in these types of applications is the limited energy supply in mobile device batteries. For this reason, efficiently utilizing energy is a critical issue in designing wireless video communication systems. This article highlights recent advances in joint source coding and optimal energy allocation. We present a general framework that takes into account multiple factors, including source coding, channel resource allocation, and error concealment, for the design of energy-efficient wireless video communication systems. This framework can take various forms and be applied to achieve the optimal trade-off between energy consumption and video delivery quality during wireless video transmission.     

User mobility profile prediction: An adaptive fuzzy inference approach

Predicting the probabilities that a mobile user will be active in other cells at future moments poses a significant technical challenge to network resource management in multimedia wireless communications. The probability information can be used to assist base stations to maintain a balance between guaranteeing quality of service (QoS) to mobile users and achieving maximum resource utilization. This paper proposes a novel adaptive fuzzy logic inference system to estimate and predict the probability information for direct sequence code division multiple access (DS/CDMA) wireless communications networks. The estimation is based on measured pilot signal strengths at the mobile user from a number of nearby base stations, and the prediction is obtained using the recursive least square (RLS) algorithm. Numerical results are presented to demonstrate the performance of the proposed technique under various path loss and channel shadowing conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Cross-layer architecture for scalable video transmission in wireless network

Multimedia applications such as video conference, digital video broadcasting (DVB), and streaming video and audio have been gaining popularity during last years and the trend has been to allocate these services more and more also on mobile users. The demand of quality of service (QoS) for multimedia raises huge challenges on the network design, not only concerning the physical bandwidth but also the protocol design and services. One of the goals for system design is to provide efficient solutions for adaptive multimedia transmission over different access networks in all-IP environment. The joint source and channel coding (JSCC/D) approach has already given promising results in optimizing multimedia transmission. However, in practice, arranging the required control mechanism and delivering the required side information through network and protocol stack have caused problems and quite often the impact of network has been neglected in studies. In this paper we propose efficient cross-layer communication methods and protocol architecture in order to transmit the control information and to optimize the multimedia transmission over wireless and wired IP networks. We also apply this architecture to the more specific case of streaming of scalable video streams. Scalable video coding has been an active research topic recently and it offers simple and flexible solutions for video transmission over heterogeneous networks to heterogeneous terminals. In addition it provides easy adaptation to varying transmission conditions. In this paper we illustrate how scalable video transmission can be improved with efficient use of the proposed cross-layer design, adaptation mechanisms and control information.     

Video transmission in mobile ad hoc networks using multiple interfaces and multiple channels

Mobile Ad hoc NETworks (MANETs) are an important part of wireless communications and the increasing use of mobile devices is confirming that. MANETs can be of great value in Emergency Response situations where communication between mobile deployed units is critical and wired or wireless infrastructures may not be present or functional. In emergency scenarios, multimedia communication is very important for decision making and situation assessment. This requires up‐to‐date (on‐line) information feed on the situation, including voice and video from the affected zone. However, MANETs do not seem to efficiently support multimedia applications, and this is quite evident in video transmission. One way to remedy this is to use more (wireless) interfaces per mobile node and consequently more communication channels. In this work, we perform an analytical study on the use of multiple interfaces and multiple channels (MIMC) in video transmission with respect to the requirements of Emergency Response Ad hoc Networks. More specifically, we examine and present the impact of using MIMC on MANETs during video transmission applications, we evaluate the performance of three basic routing protocols in MANETs, and we propose a channel selection mechanism in MANET nodes with MIMC for enhanced video transmission. In addition, we evaluate video transmission streams with rate adaptation and present comparative results. The proposed mechanism is evaluated using the ns‐2 network simulator and the simulations are performed for a variety of topologies. Simulation results show that the different routing protocols respond differently when MIMC is introduced. The Ad hoc On‐Demand Multipath Distance Vector and (especially) the Ad hoc On‐Demand Distance Vector routing protocols benefit significantly, while the Destination Sequenced Distance Vector shows fewer improvements. The proposed mechanism is shown to be beneficial for transmitting video streams and enhances the network's ability to accommodate more streams and reduce packet delay. Copyright © 2016 John Wiley & Sons, Ltd.