1. Author：Zarei.M.；Faez.K. ；Nya.J.M.
Modified Reverse AODV Routing Algorithm using Route Stability in Mobile Ad Hoc Networks
Multitopic Conference,INMIC IEEE International Dec Page(s):
Author：Zarei.M.；Faez.K. ；Nya.J.M.
Speaker: Arak

2. Outline
Introduction
Ad-Hoc On Demand Distance Vector Routing Protocol (AODV)
Reverse AODV algorithm (RAODV)
Modified Reverse Ad Hoc On Demand Distance Vector(MRAODV) routing algorithm
Path Maintenance in MRAODV Routing Algorithm
Simulation environment and results
Conclusions
Reference

3. Introduction (1/2)
Mobile ad hoc networks (MANET) consist of mobile platform which communicate with each other through wireless links, without any predetermined infrastructure.
If the source and destination nodes are not within the transmission range of each other, then intermediate nodes would be served as intermediate routers for the communication between the two nodes.

4. Introduction (2/2)
Moreover, mobile platform moves autonomously and communicates via dynamically changing network.
Self configuration
Frequent change of the network topology is a main challenge for many important topics

5. Ad-Hoc On Demand Distance Vector Routing Protocol (AODV)
The Ad-hoc On-Demand Distance Vector Routing Protocol (AODV), is one of more common routing algorithm in ad hoc networks and is based on the principle of discover routes as needed.
AODV is a reactive algorithm that has some capabilities such as; low processing, memory overhead, low network utilization.

6. Ad-Hoc On Demand Distance Vector Routing Protocol (AODV)
In AODV routing algorithm, the source node distributes a route request packet at the time when a path is needed to the destination node.
The source node initiates path discovery by broadcasting a route request (RREQ) packet to its neighbors.
When the intermediate nodes receive route reply packet (RREP), they update the forward route to the destination.

7. Ad-Hoc On Demand Distance Vector Routing Protocol (AODV)
Route Request (RREQ) Message Format

8. Ad-Hoc On Demand Distance Vector Routing Protocol (AODV)
Route Reply (RREP) Message Format

9. Ad-Hoc On Demand Distance Vector Routing Protocol (AODV)
AODV protocol uses sequence numbers to determine the timeliness of each packet and to prevent creation of loops.
Sequence number indicates the freshness of the received information.
AODV algorithm uses Route Error Message (RERR) route failures and link failures propagated by a RERR from a broken link to the source node of the corresponding route.

10. Ad-Hoc On Demand Distance Vector Routing Protocol (AODV)
When the next hop link breaks, RERR packets are sent by the starting node of the link to a set of neighboring nodes that communicate over the broken link with the destination.

11. Reverse AODV algorithm (RAODV)
AODV routing algorithm builds a single loop-free path to each other node on the network.
One disadvantage of AODV and most on-demand routing protocols is a route reply message loss.
In route discovery phase, a route reply message (RREP) of AODV obtains by the spending cost of flooding the entire network or a partial area.

12. Reverse AODV algorithm (RAODV)
Route request packet in RAODV like AODV contain following fields where, the source and destination addresses, together with the broadcast ID, uniquely identify this RREQ packet.

13. Reverse AODV algorithm (RAODV)
When the destination node receives first route request message, it generates reverse request (R-RREQ) message and broadcasts it to neighbor nodes within transmission range.
If neighbor nodes already received the same message, the message is dropped, otherwise forwards to next nodes and when the source node receives first reverse request message, then it starts packet transmission.

14. Reverse AODV algorithm (RAODV)
RAODV routing algorithm increases performance and when route fails occurs, the source node should select the best route between available routs.
RAODV algorithm solves this problem with selecting the rout with minimum length in available set of routes that have been already found.

15. Modified Reverse Ad Hoc On Demand Distance Vector(MRAODV) routing algorithm
When a source node wants to communicate with a destination node, first it broadcasts a RREQ packet.
When destination receives a RREQ message, it broadcasts R-RREQ message to find source node.
Each intermediate node which receives the R-RREQ message, calculates route stability by equation (2) and the route stability for each router is calculated by equation (1) .

16. Modified Reverse Ad Hoc On Demand Distance Vector(MRAODV) routing algorithm

17. Modified Reverse Ad Hoc On Demand Distance Vector(MRAODV) routing algorithm
When source node receives R-RREQ, it will have multiple routes to destination, so it selects stable route to destination node. This process is illustrated in figure 3.

18. Modified Reverse Ad Hoc On Demand Distance Vector(MRAODV) routing algorithm
According to this figure when one intermediate node moves and causes link breaks then active route fails and a new route must be selected.
In AODV, this process is done by initializing route discovery procedure and in RAODV with selecting one available route with minimum hop count.
In MRAODV, a new route with maximum stability is selected between available routes.

19. Path Maintenance in MRAODV Routing Algorithm
When a route established between source and destination, data transmission stage can be started.
In high mobility environments, link failure is a common phenomenon which can be occurred.

20. Path Maintenance in MRAODV Routing Algorithm
In both reverse RAODV and AODV routing algorithms, source node selects new path based on shortest path method and when mobile node moves quickly, these algorithms can not show good performance.

21. Simulation environment and results(1/2)
We used the ns-2 simulator to implement our routing algorithm for comparison with RAODV and AODV routing algorithms and to check the effectiveness of the proposed method.
For evaluation of MRAODV routing algorithm performance, we used two metrics:
Packet Delivery Ratio
Control Packet Overhead

22. Fig.4

23. Fig.5

24. Fig.6

25. Conclusions(1/2)
This paper presented a new protocol for mobile ad hoc networks based on link stability and reverse packet transmission. We changed RAODV routing algorithm and made an optimized version of AODV.

26. Conclusions(2/2)
According to the simulation results, this algorithm is better than other version of AODV algorithm.
We compared our method with AODV and RAODV routing algorithm in average to end delay and packet delivery ratio.
We found that the presented protocol is suitable for high mobility rate environment and it shows a good performance when the number of nodes increases.

27. Reference
Zarei, M., Faez, K. and Nya, J.M., “Modified Reverse AODV Routing Algorithm using Route Stability in Mobile Ad hoc Networks,” Proceedings of 2008 IEEE International Multitopic Conference, Dec. 2008, pp
Chonggun Kim, Elmurod Talipov, and Byoungchul Ahn, "A Reverse AODV Routing Protocol in Ad Hoc Mobile Networks" , LNCS 4097, pp ,2006.
RFC 3561