# Energy Efficient Routing in Wireless Sensor Networks: A Comprehensive Survey
## 5 Reliable Routing
### Multipath Based
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Protocol** & **Advantages** & **Disadvantages** & **Scalability** & **Mobility** & **Routing** & **Robustness** \\ \hline \multirow{4}{*}{CCWM [150]} & The energy & \multirow{4}{*}{\begin{tabular}{c} Requirements for \\ cluster head election \\ limits the cluster size. \\ \end{tabular} } & Cluster head election & Limited & None & \
\begin{tabular}{c} Nodes send data to \\ the BS via the \\ cluster heads. \\ \end{tabular} & Low \\  & It improves network & It doesn’t take into & & & Nodes send data to \\  & lifetime and has stable & account the distance & Good & Limited & the BS via the \\  & performance. & between nodes. & & cluster heads. \\  & It reduces energy & & & & Nodes send data to \\  & consumption and & It suffers from the & & & the BS via the \\  & provides energy & energy holes problem. & Good & None & the BS via the \\  & balance. & Energy efficiency is & When the number of & & & The route with \\  & good. Each packet’s & & nodes increases, & & minimum average \\  & priority is considered. & Maintenance cost of & Limited & None & weighed QoS is \\  & Multiple routes from & tables is high. & & used. & \\  & nodes are set. & & & Maximum PDR and & \\  & & & & minimum & \\  & & & & minimum & \\  & end-to-end delay and & Path selection creates & Limited & None &
\begin{tabular}{c} end-to-end delay & Good \\  & energy consumption. & & & consumption routes & \\  & & & & are used. & \\ \hline \hline \end{tabular}
\end{table} 
Table 13: Cont. of all the labels it has seen along with the associated neighbors the labels coming from. By using LMR, energy consumption is decreased. Overhead of routing and delay to setup a backup route with label information are reduced too. However, overhead is caused due to various types of messages. _GRAdient Broadcast_ (GRAB) [157] protocol uses advertisement packets (ADV) that include link cost, in order to send reliable packets to the destination. ADV packets contain broadcast costs of sender node, saved in a cost field for later use. The receiving node adds a link cost between sender node and itself, to the cost in the received ADV message and compares calculated and sender costs. The receiving node's cost will be set as the smaller of these two costs and then it will send an ADV packet containing it. In addition, a sender node can adjust data delivery's robustness by controlling bandwidth depending of the credits contained in the data message. GRAB is both energy efficient and robust. In addition, it does not depend on individual nodes to deliver data. However, overhead due to redundant data may be caused. _Hierarchy based Multipath Routing Protocol_ (HMRP) [158] uses two characteristics within the operation of each node, a layer construction packet that is broadcasted initially one time and a table with Candidates Information called CIT. During packet transmission, sender nodes need to know only the parent sensor node that will receive the packet. HMRP supports mechanisms as data aggregation in every node except leaf nodes, multiple candidate paths to forward data through them and can be used with multiple base stations. By using HMRP, extension of network lifetime using data aggregation and energy balanced routing is achieved. In addition, great scalability with low overhead among nodes is attained. Moreover, simplicity is attained with a small number of operations and maintained states in every node. However, only one broadcast of the layer construction packet is used. _Cluster based Multi-Path Routing_ (CBMPR) [159] protocol combines cluster based and multi-path routing to route data efficiently. To reduce routing control overhead and improve network scalability, it uses a cluster network to find multiple paths that provides independent paths. CBMPR sets cluster heads and cluster nodes that send regular HELLO messages.