## 5 Routing Layer in WMSN
### Routing Methodologies in WMSN
However, this routing protocol does not consider the bandwidth as QoS metric for routing decision or prioritizes the incoming packets to schedule them but it does consider the playout deadline in a sense that the data arrives after the deadline will be discarded. Results, show that the presented protocol for multipath video streaming over WSNs obtains higher throughput (even the double in some conditions) than its single path counterpart (EDGE) through the use of multiple disjoint paths. A design of QoS aware routing protocol is presented in [38] to support high data rate for WMSNs by ensuring bandwidth and end-to-end delay requirements of real time data and maximized throughput of non-real time data. The routing protocol uses multiple paths, multiple channels, and QoS packet scheduling technique based on the dynamic bandwidth adjustment and path-length-based proportional delay differentiation (PPDD) techniques to meet the bandwidth and delay requirements respectively. These requirements (bandwidth and delay) are adjusted locally at each node based on the path-length and incoming traffic in static flat wireless network where all the nodes are homogeneous multimedia sensor nodes capable of performing all possible application tasks (video, audio, scalar data) and equippedwith single radio interface and multi-channels. QoS-aware packet scheduling policy considers different priorities for real time packets and non-real time packets by using at each node a classifier that checks the type of the incoming packets and sends to appropriate queues, and a scheduler that schedules the packets according to the delay and bandwidth requirements. The proposed protocol -as shown through simulation- clearly improves average delay per real-time packet, average lifetime of a node, and throughput of non-real-time data when compared with single-r and multi-r mechanisms [39]. An extension for a routing protocol, multimedia enabled Improved Adaptive Routing (M-IAR), is done in [40] to enable handling multimedia content by taking into account two extra QoS parameters, end-to-end delay and jitter. M-IAR is a flat multi-hop routing protocol that exploits the geographical location of the sensor nodes, by assuming that all the nodes know their positions and the positions of their neighbors and the sink node, in order to find the shortest route containing the least number of nodes between the source and the sink. M-IAR uses two types of ants: forward ant and backward ant. Forward ant is used by the source node to explore the path toward the sink and selects the next-hop neighbor with the highest probability according to the mentioned metrics. The backward ant is used by the sink node and uses the global information from the forward ant to update the probability values and reinforce the visited nodes. Unfortunately, the authors of the paper do not compare the results obtained from the proposed protocol with any other protocol. The work in [41] uses the game theory and ant colony algorithm to solve the problem of QoS routing in WMSN. The idea of using game theory together with the ant colony algorithm is to overcome the shortcoming of the current ant-based routing protocols for WMSNs such as: the long time needed by forward ants to find the destination and the overhead occurred from using plenty of backward ants to update the routing probability distribution. Therefore, game theory is used depending on the assumption that the sensor nodes are rational and have selfish action (_i.e._, they try maximize their payoffs with minimum cost). Unfortunately, the paper does not obtain any kind of performance nor does compare the proposed protocol with any other protocol. Multimedia-aware Multipath Multi-Speed (Multimedia-aware MMSPEED) routing protocol is proposed in [42]. 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.