In-Network Puncturing for Delay-Efficient Rate Control of Distributed Video Coding in Wireless Video Sensor Networks

Wyner-Ziv Video Coding (WZVC) is considered as a promising video coding scheme for Wireless Video Sensor Networks (WVSNs) due to its high comp ression efficiency and error resilience functionalities, as well as its low encoding comp lexity. To achieve a good Rate-Distortion (R-D) performance, the current WZVC paradigms usually adopt an end-to-end rate control scheme in which the decoder rep eatedly requests the additional decoding data from the encoder for decoding Wyner-Ziv frames. Therefore, the waiting time of the additional decoding data is esp ecially long in multihop WVSNs. In this paper, we propose a novel progressive in-network rate control scheme for WZVC. The proposed in-network puncturing-based rate control scheme transfers the partial channel codes puncturing task from the encoder to the relay nodes. Then, the decoder can request the additional decoding data from the relay nodes instead of the encoder, and the total waiting time for decoding Wyner-Ziv frames is reduced consequently. Simulation results validate the proposed rate control scheme.

Predictive Block-Matching Algorithm for Wireless Video Sensor Network Using Neural Network

This paper proposed a back propagation neural network model for predictive block-matching. Predictive block-matching is a way to significantly decrease the computational complexity of motion estimation, but the traditional prediction model was proposed 26 years ago. It is straight forward but not accurate enough. The proposed back propagation neural network has 5 inputs, 5 neutrons and 1 output. Because of its simplicity, it requires very little calculation power which is negligible compared with existing computation complexity. The test results show 10% - 30% higher prediction accuracy and PSNR improvement up to 0.3 dB. The above advantages make it a feasible replacement of the current model.

Error resilient concurrent video streaming over wireless mesh networks

In this paper, we propose a multi-source multi-path video streaming system for supporting high quality concurrent video-on-demand (VoD) services over wireless mesh networks (WMNs), and leverage forward error correction to enhance the error resilience of the system. By taking wireless interference into consideration, we present a more realistic networking model to capture the characteristics of WMNs and then design a route selection scheme using a joint rate/interference-distortion optimiza- tion framework to help the system optimally select concurrent streaming paths. We mathematically formulate such a route selec- tion problem, and solve it heuristically using genetic algorithm. Simulation results demonstrate the effectiveness of our proposed scheme.

Delay-Based Cross-Layer QoS Scheme for Video Streaming in Wireless Ad Hoc Networks

With correlating with human perception, quality of experience(Qo E) is also an important measurement in evaluation of video quality in addition to quality of service(Qo S). A cross-layer scheme based on Lyapunov optimization framework for H.264/AVC video streaming over wireless Ad hoc networks is proposed, with increasing both Qo E and Qo S performances. Different from existing works, this scheme routes and schedules video packets according to the statuses of the frame buffers at the destination nodes to reduce buffer underflows and to increase video playout continuity. The waiting time of head-ofline packets of data queues are considered in routing and scheduling to reduce the average end-to-end delay of video sessions. Different types of packets are allocated with different priorities according to their generated rates under H.264/AVC. To reduce the computational complexity, a distributed media access control policy and a power control algorithm cooperating with the media access policy are proposed. Simulation results show that, compared with existing schemes, this scheme can improve both the Qo S and Qo E performances. The average peak signal-to-noise ratio(PSNR) of the received video streams is also increased.

ESSENTIAL INFORMATION AGGREGATION OF INTRA CODED VIDEO FRAME FOR WIRELESS TRANSMISSON

A novel error resilient method based on Essential Information Aggregation (EIA) technique is proposed for robust wireless transmission of intra coded video frames. This method modifies the original video stream structure so as to mitigate the effect of decoding loss of synchronization within a video frame, for which Macro Block Aligned (MBA) error detection method is accompanied to be developed. Experiments on an Additive White Gaussian Noise (AWGN) wireless simulation platform and H.263+ baseline video codec show that it can obtain better subjective and objective image quality than existing error resilience approaches.

Joint routing and rate allocation for multiple video streams in ad-hoc wireless networks

The support for multiple video streams in an ad-hoc wireless network requires appropriate routing and rate allocation measures ascertaining the set of links for transmitting each stream and the encoding rate of the video to be delivered over the chosen links. The routing and rate allocation procedures impact the sustained quality of each video stream measured as the mean squared error (MSE) distortion at the receiver, and the overall network congestion in terms of queuing delay per link. We study the trade-off between these two competing objectives in a convex optimization formulation, and discuss both centralized and dis- tributed solutions for joint routing and rate allocation for multiple streams. For each stream, the optimal allocated rate strikes a balance between the selfish motive of minimizing video distortion and the global good of minimizing network congestions, while the routes are chosen over the least-congested links in the network. In addition to detailed analysis, network simulation results using ns-2 are presented for studying the optimal choice of parameters and to confirm the effectiveness of the proposed measures.

Equation based rate control scheme for video streaming over wireless channels with link level ARQ

Equation based TCP-friendly rate control (TFRC) protocol has been proposed to support video streaming applications. In order to improve TFRC performance in wireless channels, the link level automatic repeat request (ARQ) scheme is usually deployed. However, ARQ cannot ensure strict delay guarantees, especially over multihop links. This paper introduces a theoretical model to deduce an equation for packet size adjustment in transport layer to minimize retransmission delay by taking into con- sideration the causative reasons inducing retransmission in link layer. An enhanced TFRC (ETFRC) scheme is proposed inte- grating TFRC with variable packet size policy. Simulation results demonstrate that higher goodput, lower packet loss rate (PLR), lower frame transmission delay and jitter with good fairness can be achieved by our proposed mechanism.

A network condition classification scheme for supporting video delivery over wireless Internet*

Real-time video transport over wireless Internet faces many challenges due to the heterogeneous environment including wireline and wireless networks. A robust network condition classification algorithm using multiple end-to-end metrics and Support Vector Machine (SVM) is proposed to classify different network events and model the transition pattern of network conditions. End-to-end Quality-of-Service (QoS) mechanisms like congestion control, error control, and power control can benefit from the network condition information and react to different network situations appropriately. The proposed network condition classifica- tion algorithm uses SVM as a classifier to cluster different end-to-end metrics such as end-to-end delay, delay jitter, throughput and packet loss-rate for the UDP traffic with TCP-friendly Rate Control (TFRC), which is used for video transport. The algorithm is also flexible for classifying different numbers of states representing different levels of network events such as wireline congestion and wireless channel loss. Simulation results using network simulator 2 (ns2) showed the effectiveness of the proposed scheme.

基于GNURadio与USRP的OFDM无线通信系统实验

针对目前无线通信课程内容侧重讲述基本理论推导,相关实验多关注模块功能仿真,缺乏系统性和真实场景的问题,提出了以GNURadio软件和通用软件无线电外设(USRP)硬件平台为基础的正交频分复用(OFDM)无线通信系统实验。该实验内容包括掌握OFDM的基本原理、搭建OFDM收发系统、分析相关通信性能和完成硬件系统,最后在实际无线通信场景中完成测试,实现实时视频传输。通过软件系统和硬件平台的协同,学生能充分了解无线通信的基本原理、各通信模块的使用、无线通信系统的架构以及相关的性能分析方法,完成从理论基础到工程应用、从模块验证到系统实现、从理想环境仿真到实际场景测试的跨越,从而全面提升工程素养。

低光照下基于FPGA+ARM的无线视频监控系统设计

视频监控系统视频处理实时性不高,有线视频监控系统迁移扩展性差、布线繁琐,低光照下视频图像获取质量和处理效果较差,针对以上问题,设计了一种低光照环境下基于FPGA+ARM的无线视频监控系统。首先在FPGA端初始化OV5640摄像头,使其输出RGB888格式的图像数据,图像数据经过格式转换缓存到DDR3中。然后提出基于边缘增强模块的改进RetinexNet图像增强算法,在HSV格式中利用高层次综合(High-level Synthesis,HLS)工具对亮度分量V进行硬件加速,在ARM端对亮度分量S进行线性拉伸,并完成低光照图像增强任务。在此基础上,通过5G WiFi模块发送图像数据,上位机显示器通过5G网络接收图像数据并实现HDMI接口输出。实验结果表明,系统针对昏暗图像改善图像细节,具有良好的显示效果,而且处理一帧图像耗时为136.08 ms,相比ARM和PC机,具有处理速度快、便携性高等优点。

可视化遥控高压绝缘电动高枝剪设计

输配电线路走廊内植被生长侵犯线路空间是线路维护中存在的普遍问题,是造成线路故障的主要原因之一,常用高枝剪(锯)存在工具笨重、操作费力、工作强度大、有触电隐患等缺陷。因此设计并制作一款新型电动高枝剪,该高枝剪延长杆采用高等级绝缘杆制作,绝缘等级可达10 kV,长度可达6 m,以STM32单片机为主控芯片,采用蓝牙无线模式遥控高枝剪动作,通过WiFi进行视频传输。经实验测试,该高枝剪具有实时查看工作面状况(必要时可全程录像)、全绝缘、质量轻、操作方便省力且安全可靠等优点。能有效帮助工作人员精准定位修剪树枝,减轻了工作强度,提高了工作效率及安全性,能有效地保护作业人员人身安全及电力作业的顺利进行,具有很好的推广价值。

基于机器视觉的变电站一体化安防管控系统设计

为解决变电站安防设备简单、智能化程度低的问题,设计出基于机器视觉的一体化安防管控系统;安装现场视觉控制器作为系统硬件前端信息采集中心,利用以太网实现各设备通信连接一体化,门电路和变电站周界环境终端电子相连接,检测激光电子围栏危险入侵检测,序列巡检围栏编号,确定危险入侵围栏位置;通过线性二次型调节器算法对机器人期望位姿和实际位姿之间的耦合关系实行解耦处理,将处理结果作为神经网络的输入;输出机器人移动轨迹跟踪控制结果,完成视觉识别定位,实现动态物体监测、火苗、温度等多种危险因素的自动识别和预警;经过实验分析证明:系统通过机器视觉准确监测到了高温设备的位置和温度,并且响应性能良好,安防信号传输环境稳定,危险情况预判能力及预警能力较强,鲁棒性好。

基于数字签名的无线通信网络视频数据安全传输方法

常规的无线通信网络视频数据传输方法丢包率较高,因此,该文基于数字签名,设计一种全新的无线通信网络视频数据安全传输方法。构建视频数据安全传输模型,利用数字签名生成通信网络视频数据安全传输框架,实现无线通信网络视频数据的安全传输。实验结果表明,无线通信网络视频数据安全传输方法的传输丢包率较低,传输效果较好,可靠性较高,有一定的应用价值。

视频图像在无线传输中运用微波技术的研究

视频图像的无线传输在现代通信技术中具有重要意义。随着互联网的普及和多媒体应用的飞速发展,人们对于高质量、实时的视频传输需求越来越迫切。而微波技术作为一种广泛应用于通信领域的技术,其在视频图像无线传输中扮演着关键的角色。文章研究视频图像在无线传输中运用微波技术的相关问题,并探讨其优势、挑战,最后提出具体应用要点,为相关人员提供参考。

煤矿井下人员定位视频监控系统设计与实施

以无线网络技术为依托,开发了一种煤矿井下人员定位视频监控系统方案。该系统包括系统管理、人员定位、视频监控、报警等功能模块,通过这些功能的协同作用,能有效管理井下人员,准确显示其位置信息,有助于提升煤矿井下人员的管理水平,加强对井下人员生命安全的保护。结果表明,该系统具有一定的应用价值。

面向高速移动场景的高速公路视频采集和自动化传输系统设计

针对高速移动带来的多普勒频移以及子载波干扰,设计了面向高速移动场景下的高速公路视频采集和自动化传输系统。通过数据采集层获取高速公路开关量信号以及视频信息,由数据处理层对其作降噪及增强,采用数据传输层的无线数字传输网络调用基于BEM-wiener的信道估计算法确定高速公路视频传输信道,完成视频信息的上传后,通过应用层分析,实现高速公路路况及突发异常事件的监测。通过试验,得出该系统可采集高速公路视频图像,视频图像清晰、视野宽阔、路况信息丰富;高速移动场景下高速公路视频数据包接收成功率达到0.9左右,BER指标值最小,数据传输效率高,传输时间最多不超过2.5 s,且丢包率小,最大丢包率为1.25%,具有较强的应用性。

Improving Low Bitrate Video Coding via Computation Incorporating A Priori Information

The growing number of mobile users, as well as the diversification in types of services have resulted in increasing demands for wireless network bandwidth in recent years. Although evolving transmission techniques are able to enlarge the network capacity to some degree, they still cannot satisfy the requirements of mobile users. Meanwhile, following Moore's Law, the data processing capabilities of mobile user terminals are continuously improving. In this paper, we explore possible methods of trading strong computational power at wireless terminals for transmission efficiency of communications. Taking the specific scenario of wireless video conversation, we propose a model-based video coding scheme by learning the structures in multimedia contents. Benefiting from both strong computing capability and pre-learned model priors, only low-dimensional parameters need to be transmitted; and the intact multimedia contents can also be reconstructed at the receivers in real-time. Experiment results indicate that, compared to conventional video codecs, the proposed scheme significantly reduces the data rate with the aid of computational capability at wireless terminals.

Network-adaptive HD MPEG-2 video streaming with cross-layered channel monitoring in WLAN

In this paper, we propose a practical design and implementation of network-adaptive high definition (HD) MPEG-2 video streaming combined with cross-layered channel monitoring (CLM) over the IEEE 802.11a wireless local area network (WLAN). For wireless channel monitoring, we adopt a cross-layered approach, where an access point (AP) periodically measures lower layers such as medium access control (MAC) and physical (PHY) transmission information (e.g., MAC layer loss rate) and then sends the monitored information to the streaming server application. The adaptive streaming server with the CLM scheme reacts more quickly and efficiently to the fluctuating wireless channel than the end-to-end application-layer monitoring (E2EM) scheme. The streaming server dynamically performs priority-based frame dropping to adjust the sending rate according to the measured wireless channel condition. For this purpose, the proposed streaming system nicely provides frame-based prioritized packetization by using a real-time stream parsing module. Various evaluation results over an IEEE 802.11a WLAN testbed are provided to verify the intended Quality of Service (QoS) adaptation capability. Experimental results showed that the proposed system can mitigate the quality degradation of video streaming due to the fluctuations of time-varying channel.

Video quality based link adaptation for low latency video transmission over WLANs

Wireless Local Area Networks (WLANs) such as IEEE 802.11a/g and Hiperlan/2 utilise numerous transmission modes, each providing different throughputs and reliability levels. Many link adaptation algorithms proposed in the literature either maximise the error-free data throughput based on channel conditions or are based on the number of failed transmissions. However, these algo- rithms do not take into account the content of the data stream and strongly rely on the use of Automatic Repeat Requests (ARQs). Low latency video applications such as real-time video transmission may require no retransmission, or only a limited number of retrans- missions. Moreover, completely error-free communication is not essential, especially if robust video compression techniques are applied. In such scenarios, improved decoded video quality can be obtained with a video stream transmitted at a higher bit rate using a higher link speed but with some degree of transmission error, rather than an error-free video stream at a lower bit rate using a lower link speed. In this work, we investigate a link adaptation scheme that improves the Quality of Service (QoS) for video transmission, based on the overall received video quality (Peak Signal to Noise Ratio, PSNR), rather than by maximising the error-free throughput. We also study a practical link adaptation approach that uses PER thresholds at the PHY layer. An empirical study showed that thresholds for switching from one mode to another are much lower (almost error free) than those currently used by throughput based schemes. We show that traditional link adaptation strategies are not appropriate for real-time video transmission with no retransmis- sion. Simulation results using the H.264 video compression standard over IEEE 802.11a are presented.

On the QoS Assessment of Video Sessions in Heterogeneous 3G-WLAN Networks with Seamless and Secure Mobility Support

Real-time video data transmission is currently emerging as a popular application among mobile users but it is very sensitive to QoS degradation due to packet losses in wireless networks.In order to achieve service continuity and integrity upon handoffs among heterogeneous networks,provisioning of seamless and secure mobility is required.However,in order to reduce the delay and packet losses during vertical handovers we need to employ supportive protocols like context transfer.In this paper we evaluate the QoS of video transmission over a heterogeneous 3G-WLAN network.The aggregate video data traffic is represented by a dynamic two-dimensional Markov chain model,which has been evaluated against real video data measurement.Upon the vertical handover, appropriate AAA handshaking and enhanced mobility management using context transfer have been considered.Perceived QoS evaluation of video streams was performed based on peak signal-noise ratio(PSNR) measurements,while we analyticallyestimated the number of packet losses during handovers.The results show that both packet loss within the converged network and loss occurrence affecting the perceived video quality is reduced. Moreover,the proposed context transfer scheme minimizes handover delay and the number of lost packet up to 3 times compared to standard AAA handshaking.