Survey of QoS routing protocols in Wireless Multimedia Sensor Networks <s> Adapting Green Technology. <s> The recent technological advances in micro electro-mechanical systems have promoted the development of a powerful class of sensor-based distributed intelligent systems capable of ubiquitously retrieving multimedia information, namely Wireless Multimedia Sensor Networks (WMSNs). WMSNs are gaining more popularity day by day as they are envisioned to support a large number of both non-real time and real-time multimedia applications. However, satisfying the stringent quality of service (QoS) requirements of multimedia transmission in a resource-constrained sensor network environment places new challenges to routing. As an outcome, optimal energy and application-specific QoS aware routing for WMSNs has gained considerable research attention recently. In this paper, current state-of-the-art in energy-efficient routing techniques for WMSNs is surveyed together with the highlights of the performance issues of each strategy. We outline the design challenges of routing protocols for WMSNs followed by the limitations of current techniques designed for non-multimedia data transmission. Further, a classification of recent routing protocols for WMSNs and a discussion of possible future research trends are presented. <s> BIB001 </s> Survey of QoS routing protocols in Wireless Multimedia Sensor Networks <s> Adapting Green Technology. <s> Wireless Sensor Networks (WSNs) have enjoyed dramatic developments over the last decade. The availability of CMOS cameras and microphones enlarged the scope of WSNs paving the way to the development of Wireless Multimedia Sensor Networks (WMSN). Among the envisaged WMSN applications, Real-time Multimedia Monitoring constitutes one of the most promising. However, the resource requirements of these applications place difficult challenges in terms of network lifetime and scalability. This paper starts by identifying the main characteristics and requirements of Real-time Multimedia Monitoring applications and then highlights key research directions that may help to overcome those challenges. <s> BIB002 </s> Survey of QoS routing protocols in Wireless Multimedia Sensor Networks <s> Adapting Green Technology. <s> Video represents a form of data that needs large storage space. In addition, and due to the complexity of video coding (encoding/decoding) techniques, they usually involve computationally intensive operations. This imposes heavy burdens upon sending and receiving entities that are required to have high processing power and abundant storage capacity, as well as the network infrastructure transporting video content that is required to have sufficient transmission bandwidth. Therefore, it is important to tailor video coding techniques to resource-constrained wireless sensors. Moreover, the intensive computations needed by video codecs consume substantial power, which is a scarce resource of wireless sensor nodes as they are usually battery powered. Therefore, it is of paramount importance to design power-aware coding, streaming, and routing schemes for the emerging wireless video sensor networks (WVSNs), that also achieve high levels of QoS and QoE. This paper introduces a brief survey of the recently published research on some important topics about WVSNs including video coding and routing and point to possible venues for future research. <s> BIB003 </s> Survey of QoS routing protocols in Wireless Multimedia Sensor Networks <s> Adapting Green Technology. <s> Multimedia applications are gradually becoming an essential--and flourishing--part of our daily lives. The area of wireless sensor networks is not an exception to this trend, as multimedia data have attracted the attention of researchers. Their importance is due to the shift of focus from traditional scalar sensors to sensors equipped with multimedia devices, as well as to the next-generation wireless multimedia sensor networks (WMSNs). The highly sensitive nature of multimedia traffic makes data routing with security even more important in WMSNs. This paper discusses the challenges of secure routing in WMSNs, where most of the proposed works in the literature deal with routing and security as individual issues. A critical and comprehensive review of state-of-the-art routing and security approaches for WMSNs is presented, followed by the discussion of their limitations and features. It is hoped that this extensive review and discussion ultimately identifies the future research directions and the open challenges of secure routing approaches in WMSNs. <s> BIB004
WMSNs are strictly constrained with regard to memory, processing capability, and particularly energy. Although batteries can provide wireless sensors with energy, it is extremely limited. Network lifetime is directly proportional to the amount of energy consumed for routing the data traffic. In addition, there is a tradeoff between energy-efficiency and multimedia QoS guarantee. Hence, it is important to balance energy efficiency and QoS to develop energy-efficient routing techniques in WMSNs BIB001 BIB004  BIB002 BIB003 . Additionally, efficient data compression techniques with low complexity are required to limit energy and bandwidth consumption. Many works providing bandwidth saving and energy preservation in WMSNs have been reported. However, the problem of achieving efficient image compression and transmission in resource-constrained WMSNs is not completely solved. Several research works surveyed in this paper do not consider an energy constraint in routing. All of these schemes can be further explored to reduce energy consumption. The penetration of WMSNs will benefit largely from adaption of green technology.