# Energy Efficient Routing in Wireless Sensor Networks: A Comprehensive Survey
## 5 Reliable Routing
### QoS Based
Multimedia Geographic Routing (MGR) [138] is a protocol for multimedia applications introduced to exploit Mobile Multimedia Nodes (MMN) in an architecture called Mobile Multimedia Sensor Network (MMSN). MGR tries to guarantee the delay with high priority and, after that, it continuously minimizes energy consumption to magnify network lifetime. In order to select the best next hop location of a selected node, it divides the distance of the selected node to the base station, with ideal hop counts from selected node to the base station and calculates the desired hop distance to pick the next hop. MGR saves up to 30% more energy compared to classical geographic routing. In addition, in most cases, there is guaranteed small delay. However, the delay guaranteeing is the top priority goal. Energy Aware QoS routing [139] is a protocol where real-time traffic is generated from imaging nodes. A minimum cost energy efficient path meeting a certain end to end delay during the connection is found. The function of link cost captures various communication parameters as energy reservoir, transmission energy, and error rate. To support simultaneously best effort and real-time traffic, the protocol employs a class based queuing model, which allows for sharing services for real-time and non-real-time traffic. Initially defined by the gateway, a starting value of bandwidth ratio \(r\) represents the limit of dedicated bandwidth to the real-time and non-real-time traffic on a specific link in case of congestion. Adjusting \(r\) value does not reduce normal data throughput. This protocol finds a list of minimum cost paths using an extended version of [PERSON]'s algorithm and picks the path from the list that meets the required end to end delay. Energy Aware QoS routing is good in terms of both QoS and energy. Its disadvantage is that \(r\) value is initially defined to be the same for all nodes, thus not providing flexibility for different links. The _Maximum lifetime energy routing_[140] algorithm suggests a solution which is based on a network flow approach, which maximizes network operation time by defining the link cost as a function of remaining energy and required transmission energy of a node using that link. The routing problem of sensor networks can be also solved by calculating traffic distribution that maximizes feasible operating network time. To find the best link metric for the maximization problem, two algorithms have been proposed that are different in the definition of link cost and the nodes' residual energy. Using the shortest path Belmann-Ford algorithm for the link costs, the minimum cost routes to the destination are found. The residual energy in a minimum cost link path is largest among all the other paths. These algorithms are compared to Minimum Transmitted Energy (MTE) algorithm, which uses \(e_{ij}\) for the link cost. Specifically, on average, greater operation time than in MTE is achieved. However, computational overhead is considerable. In [141], the so-called Maximum Lifetime Data Gathering problem is studied. It is the problem of finding how to both collect the data from all of the network nodes and transmit them to the base station, in order to have the network lifetime maximized. In order to solve this problem, the authors in [141] propose the _Maximum Lifetime Data Aggregation_ (MLDA) algorithm, which takes into account data aggregation while it sets up maximum lifetime routes. A variation of the algorithm has been proposed for the applications for which data aggregation cannot be applied as video node broadcasts. This algorithm is called _Maximum Lifetime Data Routing_ (MLDR) and is modeled as a network flow problem that takes into account node energy constraints. Both MLDA and MLDR are compared with hierarchical-PEGASIS in terms of system operating time. They are both significantly better than Hierarchical-PEGASIS in terms of performance. In terms of network lifetime, the performance of MLDA is better than that of other protocols.