Survey of QoS routing protocols in Wireless Multimedia Sensor Networks <s> Support for Node <s> In this paper, we propose an efficient Two-Phase geographic Greedy Forwarding (TPGF) routing algorithm for WMSNs. TPGF takes into account both the requirements of real time multimedia transmission and the realistic characteristics of WMSNs. It finds one shortest (near-shortest) path per execution and can be executed repeatedly to find more on-demand shortest (near-shortest) node-disjoint routing paths. TPGF supports three features: (1) hole-bypassing, (2) the shortest path transmission, and (3) multipath transmission, at the same time. TPGF is a pure geographic greedy forwarding routing algorithm, which does not include the face routing, e.g., right/left hand rules, and does not use planarization algorithms, e.g., GG or RNG. This point allows more links to be available for TPGF to explore more routing paths, and enables TPGF to be different from many existing geographic routing algorithms. Both theoretical analysis and simulation comparison in this paper indicate that TPGF is highly suitable for multimedia transmission in WMSNs. <s> BIB001 </s> Survey of QoS routing protocols in Wireless Multimedia Sensor Networks <s> Support for Node <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> BIB002 </s> Survey of QoS routing protocols in Wireless Multimedia Sensor Networks <s> Support for Node <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> Support for Node <s> Abstract Wireless multimedia sensor network (WMSN) applications require strong multimedia communication competence. Therefore, in WMSN applications, it is necessary to use specific mechanisms in order to handle multimedia communication challenges and address desired energy efficiency and reliability goals. Nevertheless, the existing communication protocols are not suitable for the communication challenges and the desired goals. In this respect, specific mechanisms for prioritization, link-quality estimation and multi-path selection can be employed by quality of service (QoS)-aware routing protocols to meet the reliability and delay requirements of WMSN applications. In this study a novel approach is proposed to set different reliability values for image packets for image transmission in WMSNs. Using this prioritization, important parts of an image are assigned high priority and take priority during data transmission. In order to evaluate the proposed approach, the performance of single-path and multi-path QoS-aware routing protocols has been investigated for WMSN-based image transmission applications. Specifically, comparative performance analysis of single-path routing and multi-path routing in image transmission have been conducted in terms of peak signal-to-noise ratio (PSNR), average delay, reachability, and control overhead. As proven by the results of the performance evaluations in this study, multi-path routing is better than single-path routing in terms of reliability. On the other hand, at high traffic loads, multi-path routing may perform worse in terms of delay due to its associated overhead. <s> BIB004 </s> Survey of QoS routing protocols in Wireless Multimedia Sensor Networks <s> Support for Node <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> BIB005
Mobility. In applications like mobile object tracking, border surveillance with Unmanned Aerial Vehicles (UAVs), sensor nodes move to various locations for collecting necessary information. Also, nodes surrounding sink deplete their energy much faster compared to the nodes located far away due to heavy overhead. This shortens network lifetime. Due to the mobility of sensor nodes the network topology becomes highly dynamic, and it generates considerable overhead. In fact, it reduces the number of required nodes with an increase in complexity. Figure 5 shows a simple scenario where source node is mobile and path is explored with TPGF BIB001 . Due to source mobility, network topology and routing paths are changed ( Figures  5(b) and 5(c)). Mobility can be applied to sink, source, and other relay nodes. Node mobility provides greater coverage, helps to mitigate congestion, reduces delay, and increases reliability. However, node mobility poses new challenges with regard to balancing energy efficiency and QoS guarantee. Support for node mobility is relatively unexplored and thus routing with node mobility is an interesting area for future research BIB002 BIB005  BIB003 BIB004 .