# On the Feasibility of Wireless Multimedia Sensor Networks over IEEE 802.15.5 Mesh Topologies
## 2 Related Work
One of them considers cross-layer approaches to improve QoS, [PERSON] _et al._[12] used application-level QoS parameters to tune the MAC and physical layers of the popular IEEE 802.15.4 standard. An important increase in the maximum throughput for one-hop multimedia transmissions was achieved by means of a series of optimizations which maximized the amount of data transmitted and avoided collisions due to imperfect synchronization and other issues. In addition, the proposed solution remained compliant with the original standard. [PERSON] _et al._[13] proposed another cross-layer architecture for multi-hop clustered networks where, upon congestion,nodes are requested to reduce the data transmission rate to avoid congestion. The authors used a differentiated services approach that classifies data traffic according to six different classes and where nodes producing less data and low priority data are penalized more than those producing high volumes of data and high priority data. [PERSON] _et al._[14] evaluated other QoS routing protocols for real-time WMSN applications, among which the Pheromone Termite (PT) protocol [15] offered better performance. The protocol, though, relies on both ad-hoc MAC and, more importantly, physical layers, which makes its implementation on real devices very difficult. In video transmission, the importance of each video frame can be used to select different QoS profiles. [PERSON] _et al._[16] developed a video distortion model that made it possible to predict the effect on video quality of dropping each packet. In case of congestion, typically found when transmitting multimedia flows, this model is used to selectively drop less significant packets prior to transmission, therefore improving performance at the expense of additional computing load. The authors also used a hierarchical routing protocol with asymmetrical communications, where the sink is able to transmit directly to all nodes, with no intermediary hops. [PERSON] _et al._[17] developed a multipath protocol that obtained three different paths toward a sink node and, based on Bit Error Rate and delay, selected the best of them for the transmission of the most important video frames (the I frames, explained in Section 3). In general, multipath communication has traditionally been used to increase robustness or reliability in WMSNs. For example, the MMSPEED protocol [18] uses probabilistic multipath forwarding to control the number of paths based on the required delivery probability. In this way, depending on the packet loss rate and QoS requirements, it can send multiple copies of a same packet to ensure the delivery of data. In WMSNs, multipath can also be used to increase the throughput in data-intensive flows. [PERSON] _et al._[19] proposed a routing protocol, I2 MR, that transmits simultaneously through two paths. In order to avoid interference between them, the protocol uses the shortest path between source and destination as the primary path and marks one- and two-hop neighbors of nodes in the primary path as the interference zone. A secondary path as well as a backup path are then constructed using nodes outside the interference zone. This protocol is intended for less energy-constrained 802.11 networks, but there are similar proposals using more energy-constrained standards. [PERSON] [20] developed the MR2 protocol. This protocol, which is better suited for dense WSN deployments, is also interference-aware, and constructs paths incrementally. After obtaining a new path, all of the nodes neighboring to the path, which potentially may cause interference, are notified and put in a passive mode and cannot be used for new paths. Therefore, avoiding interference and saving energy. [PERSON] _et al._[21] proposed GEAM, a Geographic Energy-Aware Multipath routing scheme that divides the network into what the authors named \"districts\". The distance between them is sufficiently large to avoid transmission interference. To send a packet, GEAM assigns the packet to a district and forwards it to the sink using the greedy algorithm.