# Energy Reduction Multipath Routing Protocol for MANET Using Recoil Technique
## 3 Proposed Protocol (AOMDV-ER)
### Computation of Recoil off time
The proposed approach is based on received signal strength (RSS) to carry out the maintenance at the nearest failure link, which requires keeping two additional entries in the routing table in addition to existing entries (as in AODV protocol, Figure 7b,c). These entries are the Receive Signal Strength (RSS) of the last node and the RSS difference at the last hop with next node. These values keep on updating at fixed intervals of time as well as compared with the RSS threshold value (THRS). If it is found below the THRS, then a new link is need to be established. Hence, a RMA (Route Maintenance Algorithm) needs to be called in order to remove such an undesirable problem. In Figure 7a, there is a route S\(\rightarrow\)C\(\rightarrow\)A\(\rightarrow\)D and link AD is broken due to erroneous condition. Now, node A (last node) sets the flag = false for route leading from A to D. Furthermore, Node A carries out repair at a local level instead of sending RERR to source. During local repair mechanism, when node F receives RREQ from A, send back RREP as it has route to node D, now creates a route entry in its routing table with D as its destination node. However, A does not send RREQ to J and wait till recoil time expires. If node F is fails to reply within the recoil time then the same steps are repeated with node J till path is repaired. The REPLY message is sent back to the source (S), which contains the number of hop information. \[y-y_{1}=\frac{b}{a}(x-x_{1})\]1 (**a**) Node mobility; (**b**) Mobility estimation. \[y-y_{1}=\frac{b}{a}(x-x_{1})\]2 _Cont._  
The pseudo code for optimal route discovery is given in Algorithm 3. ```
begin if(S sends data to D) then //finds a route between S and D AODV() end if for(each node between S and D) for(each link between S and D)  manage a table containing parameters RSS of last hop, Address of last hop, Distance variation, difference in RSS. end for endfor Case 1:if(difference in RSS >Th) then  RMA () end if Case 2:if(distance variation >DTh) then  RMA () end if  RMA () begin  it sends a packet LBD (link break down) to the last node AODV() end
```  
**Algorithm 3** Route Maintenance  
Tables 1-3 show the routing field in routing table for AODV, AOMDV and AOMDV-ER respectively. \[y-y_{1}=\frac{b}{a}(x-x_{1})\]3 (**a**) Illustrates the route maintenance between nodes A and D; (**b**) Packet transmission from S to D and table entry with route request in network; (**c**) Illustrates. The principal structure of routing table entry in the three mentioned protocols is shown in \[y-y_{1}=\frac{b}{a}(x-x_{1})\]4 There are few main differences, namely; (i) the hopcount is replaced by advertised hopcount in AOMDV & AOMDV-ER; (ii) the nxthop is replaced by route list, where AOMDV & AOMDV-ER keep the nxthop along with the corresponding number of hops in the route and they utilizes multiple path to the destination; (iii) AOMDV-ER has residual energy, threshold energy in order to select the Max-Min path in the network (Figure 2a,b); (iv) furthermore to estimate the link strength receive signal strength and difference between RSS values are kept; and (v) recoiled off time is necessary to limit the number of transmissions. The function of algorithm has been shown in Figure 6b and the corresponding values are depicted in \[y-y_{1}=\frac{b}{a}(x-x_{1})\]5 The received signal strength (rss_val) is calculated with the help of the signal received by the antenna whereas the recoiled off time (recoil_off_time) is configured just before the execution of the algorithm in the simulator. The threshold energy (thr_eng) of each node (the minimum energy required to transmit a packet to its neighbor) is also set, which helps in the selection of path compared with the residual energy at that instance. \begin{table}
\begin{tabular}{c} \hline \hline
**Routing Table Field** \\ \hline destination Id \\ seq Number \\ hopcount \\ expiration\_timeout \\ nxthop \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Routing Table (AODV).