Talk Outline

1. Ad Hoc Networks and the Associativity-Based Routing ProtocolShafinaz BuruhanudeenInformatics WorkshopSupervisors:John Mellor, Prof Demetres Kouvatsos

2. Talk Outline • What are Ad Hoc networks • Issues with routing in Ad Hoc Networks • Existing Ad Hoc Routing Protocols • Associativity Based Routing -ABR • Simulation and results

3. Ad Hoc? • A collection of two or more devices equipped with wireless communications and networking capability. • Devices communicate with one another within/outside the radio range to forward information packets from source to destination.

4. Formed and deformed on the fly, thus making it self organised, adaptive and does not require system administrator. • Infrastructureless-does not need fixed radio based stations, wires or fixed routers • Can take different forms (mobile, stand-alone, networked) • Routing information changes to reflect changes in link connectivity (since nodes change on the fly) • Power consumption important (wireless networks rely highly on forwarding packets sent by other nodes)

5. Why is routing difficult in Ad Hoc Networks ? • Dynamic nature of the network • No specific devices to do routing • Limitations of Ad Hoc Networks like • high power consumption • low bandwidth • high error rates

6. Spectrum allocation and purchase ad hoc networks must operate under same form allowed/ specifieed spectrum range and use of radio spectrum in under control. Spectrum frequency needs to be purchased - not sure who should pay Media access TDMA and FDMA schemes not suitable since they do not deal with host mobility results in scheduling frames for timely transmission to support QoS difficult sharing of media by mobile ad hoc nodes - access to common channel must be made in distributed fashion through media access control protocol Challenges in ad hoc mobile networks

7. Routing nodes dynamically changes - links made and break in indeterministic fashion and changing topology of network existing distance-state vector and link state based routing protocol not capable to adapt frequent link changes results: low communication throughput and low route convergence NEW ROUTING PROTOCOL NEEDED Energy efficiency most mobile devices are operated by batteries most network protocols do not consider power cunsumption an issue battery technology is still lagging behind microprocessor technology forwarding packets consume power

8. TCP performance enhancements needed to ensure transport protocol performs without affecting end-to-end communication throughput current transport protocols are not designed for wireless ad hoc nwtworks e.g:TCP is an end-to-end protocol that cannot distinguish presence of mobility from congestion Security and privacy ad hoc networks are intranets unless connected to the Internet multiple nodes involve in ad hoc networks, relaying packets has to be authenticated by recognising originator of the packet

9. Existing Ad Hoc Routing Protocols Ad Hoc Routing Protocols Source-initiated on-demand Table driven DSDV WRP Destination sequenced distance vector The Wireless Routing Protocol Ad Hoc On-Demand Distance Vector Routing CGSR Temporally Ordered Routing Algorithm AODV DSR TORA ABR Clusterhead Gateway Switch Routing Dynamic Source Routing Signal Stability Routing SSR

10. Routing Algorithm • Routing algorithm is important to compute a path from one node to another within a finite time • when multiple path exist, selection method needed- common way: shortest path criteria • shortest path=min number of hops or least num of links used in the route

11. Associativity Based Long-Lived Routing (ABR) • Associativity is related to the spatial, temporal and connectivity of a mobile host • Specifically, associativity is measured by one node’s connectivity relationship with its neighbouring nodes • nodes association with its neighbours changes as it is migrating and its transition period identified by associativity ticks/ counts

12. Associativity of a mobile host Associativity Ticks • Migration: after unstable period, exist a period of stability (i.e., a node is constantly associated with certain neighbours over time without loosing connectivity with these neighbours) • mobile host will spend some dormant time (mobile host might/might not move) within a wireless cell before it starts to break connectivity with surrounding neighbours and move outside boundary of existing wireless cell. Dormant time threshold Time

13. Consists of route discovery phase route reconstruction phase route deletion phase when source node desires a route, the route discovery phase is invoked: consists of a) broadcast query (BQ) and b) await reply cycle (REPLY) when links of established route change due to source/ destination/ intermediate node migration, route reconstruction phase evoked when source node no longer desires the route, it initiates the deletion phase ABR Protocol Description

14. Although route selected using ABR tends to be long-lived, there are cases where association stability relationship is violated eg:mobility RRC procedured invoked to cope with mobility ABR localise route repair operation intelligently to avoid excessive control overhead and disturbing unconcerned nodes ABR route discovery is fast because it repairs broken route on-the-fly in realtime (partial discovery) ABR route maintenance phase consists of: partial route discovery invalid route erasure valid route update and new route discovery (worst case) Route Reconstruction Phase (RRC)

15. Route Deletion Phase • When a discovered route is no longer desired, a route delete (RD) broadcast will be initiated by the source so that all INs will update their routing table entries

16. Simulation applet

17. Simulation For each node desiring a route to Dest, the SRC will send a BQ. In the simulator, the user will input the SRC node number and the DEST node number and the ‘SEND BQ” button is clicked. Once the BQ expires i.e. timeout period reached the route formation stops for that particular BQ, but for other BQs, the same process continues. Depending on the BQ timeout specified by user, the route will be transformed (if any) at every instant. Any number of BQs can be fired during the simulation period. In the simulation, there is a table (n by n matrix) of AT for each node. The matrix shows the AT between 2 nodes, depending on the number of nodes decided by user. This matrix changes dynamically, updating at every instant.

18. The use of AT will enable us to get a route which is stable, and since in mobile ad hoc networks, mobility is the main issue, we don’t want routes to break off as soon as we get a link to the destination. For comparison study, I have carried out the simulation without the feature of AT. This protocol (XAT), uses the feature of minimum hop to get to destination. For this version of the protocol, I did not include the feature of AT, thus route established may or may not be stable. • Stability here refers to routes which can maintain its link for a minimum of 2 units of time in the simulation. However, in 90% of the cases, routes tend to break at or before 1 unit of time. • The lifetime of a particular route is dependent on the speed and direction of movement of all the nodes involved in the route.

19. Simulation results • Stable routes means routes can maintain or remain long enough for data packets to be transmitted to the destination node. • with increasing number of nodes, the percentage of unstable routes increases with the protocol without the use of AT (XAT). This is because nodes move out of connectivity or because routes are constructed on migrating nodes, thus making the routes break. Depending on the type of message to transmit, both, the protocol with AT and XAT can be useful.

20. with increasing number of nodes, the protocol with the use of AT seem to have more number of hops compared to the protocol without. In mobile ad hoc networks, a route with shortest path alone doesn’t determine that the route will last and be stable. Thus, having more number of hops when the route is surely stable, can be helpful than having to reconstruct the route if it breaks. The process of reconstructing routes may lead to more time and a high cost.

21. The increasing pattern of successful routes tends to increase linearly with all combination of nodes. With more nodes in the network, the probability of establishing routes would be more, and with lesser nodes, to get a high probability of routes, a bigger transmission power would be needed.

22. The result shows that with lesser nodes, it takes more time to reach DEST. It is almost likely to happen that the protocol might not work at all in a sparse environment. With more nodes in the network, the average time it takes to reach DEST is lesser, since there are more intermediate nodes to participate in the network. Also it shows that with more number of nodes, the maximum hops increases, thus showing that more nodes participate to reach DEST.

24. with varying motion speed limit, the number of routes increases. Motion speed 0 indicates that the nodes are not at all in motion. Since the positioning of the nodes in the simulation is random, there are times when the intended source node and destination are directly connected to each other, thus making it possible for a direct link. • when the motion speed limit increases till half the transmission power size, the number of possible routes increases almost linearly. However, when the motion speed increases to 30 and above, the percentage of routes established drops linearly and when the speed reaches 60 pixel/time, with a transmission range of 50, there are no routes constructed, since there will be no value for AT at this speed.

25. Conclusion • In conclusion, if there is no feature to determine a stable road (for my simulation, the use of AT), then the protocol might not be as efficient. Transiting nodes may be chosen to relay data packets thus resulting in link breakage very often. • The use of ABR with its AT promises long lived, stable routes, which is important to carry big data packets in the network such as video or audio files or for web browsing. However, with small data packets, where the duration of the call is just intended for less than 3 units of time, then, we may not need a protocol with the use of AT since that might be a waste in bandwidth and signal strength.

26. Further Work • A constrained environment where mobility models can differ from one area to another will be modelled • Different kinds of mobility models will then be incorporated in the simulation model to evaluate the protocol and obtain results from it. • Queing theory models will be included