Wireless Multimedia Sensor Networks (WMSN)


The availability of inexpensive hardware such as CMOS cameras and microphones has fostered the development of Wireless Multimedia Sensor Networks (WMSNs), i.e., networks of wirelessly interconnected devices that are able to ubiquitously retrieve multimedia content such as video and audio streams, still images, and scalar sensor data from the environment. In this project, we shall first survey the state of the art in algorithms, protocols, and hardware for wireless multimedia sensor networks and identify open research issues. In the course of this process, we shall evaluate existing solutions and open research issues at the application, transport, network, link, and physical layers of the communication stack, along with possible cross-layer synergies and optimizations. This ultimately forms the groundwork for our interest in developing an optimally efficient suite of multimedia communication protocols. We envisage a cross-layered approach that may combine, under one umbrella, recent advances in coding, multi-channel MAC protocols, emerging technologies like UWB, amongst others.

The first step in creating a WMSN is equipping a single sensor device with audio and visual information collection modules. As an example, the Cyclops image capturing and inference module, is designed for extremely light-weight imaging and can be interfaced with a host mote such as Crossbow's MICA2 or MICAz. In addition to the ability to retrieve multimedia data, WMSNs will also be able to store, process in real time, correlate and fuse multimedia data originated from heterogeneous sources. Wireless multimedia sensor networks will not only enhance existing sensor network applications such as tracking, home automation, and environmental monitoring, but they will also enable several new applications such as:

  • Multimedia Surveillance Sensor Networks. Video and audio sensors will be used to enhance and complement existing surveillance systems against crime and terrorist attacks. Large scale networks of video sensors can extend the ability of law enforcement agencies to monitor areas, public events, private properties and borders.

  • Traffic Congestion Avoidance Systems. It will be possible to monitor car traffic in big cities or highways and deploy services that offer traffic routing advice to avoid congestion. Automated parking assistance is another possible related application. 

  • Advanced Health Care Delivery. Telemedicine sensor networks can be integrated with 3G multimedia networks to provide ubiquitous health care services. Patients will carry medical sensors to monitor parameters such as body temperature, blood pressure, pulse oximetry, ECG, breathing activity. Similarly, elderly and family monitors will help in providing timely and essential support to the less able sections of society. 

  • Industrial Process Control. Multimedia content such as imaging, temperature, or pressure amongst others, may be used for time-critical industrial process control. The integration of machine vision systems with WMSNs can simplify and add flexibility to systems for visual inspections and automated actions that require high-speed, high-magnification, and continuous operation.

Many of the above applications require the sensor network paradigm to be re-thought in view of the need for mechanisms to deliver multimedia content with a certain level of quality of service (QoS). Since the need to minimize the energy consumption has driven most of the research in sensor networks so far, mechanisms to efficiently deliver application-level QoS, and to map these requirements to network-layer metrics such as latency and jitter, have not been primary concerns in mainstream research on sensor networks.

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