Francesco Licandro

Wireless mesh networks to support video surveillance: architecture, protocol, and implementation issues

Current video-surveillance systems typically consist of many video sources distributed over a wide area, transmitting live video streams to a central location for processing and monitoring. The target of this paper is to present an experience of implementation of a large-scale video-surveillance system based on a wireless mesh network infrastructure, discussing architecture, protocol, and implementation issues. More specifically, the paper proposes an architecture for a video-surveillance system, and mainly centers its focus on the routing protocol to be used in the wireless mesh network, evaluating its impact on performance at the receiver side. A wireless mesh network was chosen to support a video-surveillance application in order to reduce the overall system costs and increase scalability and performance. The paper analyzes the performance of the network in order to choose design parameters that will achieve the best trade-off between video encoding quality and the network traffic generated.

An analytical framework for the design of intelligent algorithms for adaptive-rate MPEG video encoding in next-generation time-varying wireless networks

Adaptive rate video encoding is required to maximize efficiency when wireless links are involved in the communication. In fact, wireless channels are characterized by high, time-varying bit error rates. To cope efficiently with this problem adaptive forward error correction schemes have been proposed. These schemes introduce an amount of redundancy dependent on the channel conditions. Accordingly, the bandwidth available at the application layer changes: it increases when channel conditions improve, and decreases when channel conditions worsen. Obviously, the encoding parameters must be tuned to adapt the video source transmission rate to the available bandwidth. This adaptation is achieved by means of appropriate feedback laws, which are relationships between the encoding parameters to be used and other variables representing the state of the system. An analytical framework is introduced which can be used for the design of the feedback laws. To this purpose both the channel and the video source are modeled by means of Markov models. The resulting model of the whole system is denoted as SBBP/SBBP/1/K. Analysis is derived which allows to evaluate the most significant performance measures and, therefore, to design optimal feedback laws.

Multipath routing and rate-controlled video encoding in wireless video surveillance networks

Video surveillance systems typically consist of many video sources distributed over a wide area, transmitting live video streams to a central location for processing and monitoring. The target of this paper—to bring down the overall system cost and increase feasibility, scalability, and performance—is to propose a new architecture for a wireless video surveillance network, whose telecommunication infrastructure is based on a wireless mesh network, and where video sources are able to estimate network bandwidth and consequently control their output rate. Multipath routing is applied in such a way that at least part of the information arrives at its destination even if a wireless link is shielded (maliciously or not). A case study is considered to discuss the performance of the proposed architecture, analyzing a comparison between single-path and multipath approaches.

Applying multipath routing to a video surveillance system deployed over a wireless mesh network

Large-scale distributed video surveillance systems typically consists of many video sources distributed over a wide area, transmitting live video streams to a central location for processing and monitoring. The target of this paper to bring down the overall system cost, increasing deployability, scalability, and performance is to propose a new architecture for a WVSN, which is based on a wireless mesh network, and to analyze its performance in order to choose some project parameters to achieve the best trade-off between video encoding quality and the generated network traffic

DARED: a double-feedback AQM technique for routers supporting real-time multimedia traffic in a best-effort scenario

The transmission of real-time multimedia traffic on the Internet is becoming a challenging problem for current research in telecommunications networks. The idea at the basis of this paper consists of using an active queue management (AQM) technique in the router buffers and a rate-control algorithm at the source site which collaborate with each other, in order to meet source QoS requirements, depending on the available resources, simultaneously achieving pro-active control of network congestion. The proposed AQM technique, called dynamically adaptive random early detection (DARED), works on a network architecture characterized by a double feedback: from network to sources, and from sources to network. The paper shows via simulation, how the architecture simultaneously meets different target QoS levels, specified by sources belonging to different classes.

Low-cost SBC cards to provide multipoint to multimedia communications sessions

Multipoint distribution of real-time video constitutes a challenge for the research in the current Internet, mainly due to the poor dissemination of IP Multicast. The target of this paper is to define a low-cost flexible multipoint communication platform for the users of video sessions, which scales for a large number of communication groups with a small number of members. This paper proposes a software-based platform to provide multipoint communications in a heterogeneous unicast/multicast environment. It is constituted by a number of S-MCUs (software MCUs). Each S-MCU runs on a low-cost single board computer (SBC) and is implemented like a software router by using Click. Design, implementation and performance issues are discussed by a comparative numerical analysis at both packet level and application level.

A Multimedia Adaptive-Quality Platform For Real-Time E-Learning Over IP

The interest in creating multimedia support for remote learning is increasing explosively, thanks to the development of a variety of multimedia software packages for slide presentation, on the one hand, and the spread of the Internet in schools, Universities, research laboratories and the majority of student houses, on the other hand. However, most of the e-learning platforms used today are merely off-line. In other words, they consist of a multimedia site where teachers and students can exchange information and didactic material through file transfer and e-mail, or where the teacher can propose evaluation tests to the students. At the same time many videoconference hardware and software platforms have been deployed to support audio/video communications between two or more users. However, their main target is videoconference applications, and they are not suitable for teaching environments. The target of this paper is to provide an overview of the main aspects related to the development of multimedia e-learning tools which allow on-line remote learning, the main characteristic of which is close real-time interaction between teachers and students, and between students themselves. The authors conclude the paper by describing a relevant experience, the VIP-Teach tool, developed according to the principles illustrated in the paper.

A fluid-flow analytical model of networked multimedia TFRC traffic sources

With the advent of multimedia traffic over the Internet several TCP-friendly protocols have been developed to improve UDP with congestion control mechanisms. The most promising TCP-friendly protocol is the TFRC. This paper addresses a novel analytical model for TFRC traffic sources. The model is able to capture TFRC behavior and its dependence on the network congestion state. Moreover, the model includes the TFRC loss probability estimation algorithm performed by the receiver. In order to keep the model manageable, whatever the number of sources and network routers, a fluid-flow approach is used.

Derivation of the Transmission Power Optimizing the Lifetime of a Sensor Network: an Analytical Approach

In this work we define an analytical model to evaluate transient behavior of wireless sensor network. The model includes sleep/active dynamics and battery evolution. We analyze a case study to observe as the sensor lifetime changes according to the sensor transmission radius