Special issue on wireless multimedia sensor networks

With the availability of low-cost, small-scale imaging sensors, CMOS cameras, and microphones – all of which may ubiquitously capture multimedia content from the field – Wireless Multimedia Sensor Networks (WMSN) have been proposed and have received the immediate attention of the research community. WMSN applications, e.g., multimedia surveillance networks, target tracking, environmental monitoring, and traffic management systems, require effective harvesting and communication of event features in the form of multimedia such as audio, image, and video. To this end, additional challenges for energy-efficient multimedia processing and communication in WMSN, i.e., heterogeneous multimedia reliability definitions, tight QoS expectations, and high bandwidth demands, must be addressed as well. For this very exciting and interdisciplinary topic, we have received 32 responses to our call-for-papers. As a result of a thorough review process by experts in the respective areas, this special issue consists of 6 selected papers describing the state-of-the-art, reliable and efficient multimedia processing and delivery solutions which are imperative for the realization of WMSN. The first paper by N. Saxena, A. Roy, and J. Shin presents an adaptive contention, window-based quality of service (QoS) medium access control (MAC) protocol for wireless multimedia sensor networks. The proposed MAC protocol adopts the carrier-sense multiple access – collision avoidance (CSMA-CA) technique and adaptively adjusts the contention window depending on application-specific QoS-requirements for multimedia delivery over sensor networks as well as on the traffic and wireless channel characteristics. It also dynamically adapts its duty cycle based on the major application traffic pattern. Experimental results confirm the technique’s operation and show that the technique preserves energy resources without compromising multimedia QoS requirements. The second paper is authored by C. Na, Y. Yang, and A. Mishra and introduces an optimal guaranteed-time-slot (GTS) scheduling algorithm for time-sensitive multimedia delivery over sensor networks employing the low rate wireless personal area networks (LR-PAN) standard developed by the IEEE, i.e., IEEE 802.15.4. It presents a mathematical formulation to check the schedulability of a set