## 2 Related Work  
### Routing in WMSNs  
In this subsection, we briefly survey the major and recent related works in multipath and cluster-based routing protocols for WMSNs. In [6], an extensive survey has been conducted on the routing techniques with QoS assurance, and also a classification for the methodologies used for the proposed routing protocols can be found in [1]. An energy and QoS-aware hierarchical routing protocol, PEMuR [7], is proposed to handle multimedia data over WMSNs. PEMuR uses video packet scheduling algorithm based on an analytical distortion prediction model to reduce the video transmission rate (dropping less significant packets) while keeping minimum accepted distortion. The adopted routing protocol enables the selection of the energy efficient routing paths, manages the network load according to the energy residues of the nodes and prevents useless data transmissions through the proposed use of an energy threshold. PEMuR assumes that the network is deployed with homogeneous nodes where the number of cluster heads is predefined and they are elected by a powerful base station that can transmit to all network nodes. A multipath routing protocol for WMSNs is presented in [8] called MPDT. This Multipath Data Transfer protocol provides simultaneous multiple paths for communication between sources and destination. The routing discovery process starts from the sources toward the sink using discovery messages. MPDT aims to prolong the lifetime of the network by providing load balancing and to be immune to some specific attacks by splitting the data into parts and encoding them using Reed Solomon (RS) algorithm. Another multipath and QoS routing protocol is proposed for WMSNs in [9] called REAR. In this protocol metadata is used instead of the real data to establish multi-path routing in order to reduce the energy consumption and delay. Route establishment starts from the sources when they have data to be sent by sending control messages to their neighbors containing the metadata. Intermediate nodes that are interested in those metadata forward the control messages toward the sink. Found routes are then optimized using modified version of Dijkstra algorithm to meet the QoS requirements for the real data. Multimedia-aware Multipath Multi-Speed (Multimedia-aware MMSPEED) routing protocol is proposed in [10]. Multimedia-aware MMSPEED is an extension over MMSPEED routing protocol to take into account the embedded information in the received packets in which near optimum path is reserved for I-packets and marginal paths are used for P-frames. MMSPEED protocol [11], which is also an extension for SPEED protocol [12] that was designed for WSN, can differentiate between flows with different delay and reliability requirements and has significant potential in video transmission applications. However, experimental results in [10] show that MMSPEED is not compatible with some special features of Multimedia traffic such as high video frame rate and packets information dependency. A non-interfering disjoint multipath routing for WMSN is proposed in [13]. It addressed the problem of interference between multiple paths using one channel in WMSN and suggested an incremental on-demand approach in which only one path is built for a given source and additional paths are built when required in case of path congestion or lack of bandwidth. In order to solve the problem of interference between close paths, the proposed solution forces the multipath routing to build paths that are not interfering with each other from the beginning by putting all the interfering nodes of a given path in a passive state. Passive nodes do not further participate in building any other path in future and consequently will not interfere with previously built paths. The process starts at the sink when it floods the network with requests until they reach the source nodes.