1. DARPAN DEKIVADIYA(09BCE008)

2. Introduction In computer networking, an ad hoc network refers to anetwork connection established for a single sessionand does not require a router or a wireless base station. It is defined as the category of wireless network thatutilize multi-hop radio relaying and capable ofoperating without the support of any fixedinfrastructure . hence, is also called infrastructure -lessnetwork. Routing and Resource management are done in adistributed manner. 3. Types of wireless networks Wireless mesh Cellularnetwork Hybrid wirelesswireless network networkWirelesssensornetworkSingle hop wireless network Multi hop wireless networkorAd hoc network 4. Types of Ad hoc network1. Wireless mesh network formed to provide an alternate communication infrastructurefor mobile or fixed nodes/users, without the spectrum reuseconstraints and the requirements of network planning ofcellular networks.2. Wireless sensor network used to provide a wireless communication infrastructureamong the sensors deployed in a specific application domain. 5. 3. Hybrid wireless network when two nodes in the same cell want tocommunicate with each other, the connection isrouted through multiple wireless hops over theintermediate nodes. the base station maintains theinformation about the topology of the network forefficient routing. 6. Cellular network Base stationA BE CD Mobile node 7. Ad hoc wireless networkWireless linkA BE CDMobile node 8. DifferenceCellular networkAd hoc network Fixed infrastructure No infrastructure Single hop wireless Multi hop wirelesslinklink Centralized routing Distributed routing High cost Low cost Seamless connectivity Frequent path breaksdue to mobility 9. Characteristics Operating without a central coordinator Multi-hop radio relaying Frequent link breakage due to mobile nodes Constraint resources (bandwidth, computingpower, battery lifetime). Instant deployment 10. Applications Military applications Collaborative computing Emergency rescue Mesh networks Wireless sensor networks Multi-hop cellular networks Wireless Community Network 11. General Issue for Ad hoc network Medium access scheme Distributed operation Synchronization Hidden terminal Access delay Fairness Resource reservation Capability of power control 12. General Issue for Ad hoc network Routing Mobility Bandwidth constraint Error prone Minimum rout acquisition Quick rout reconfiguration Loop free routing Security and privacy 13. General Issue for Ad hoc network Multicasting Robustness Efficiency Quality of services Efficient group management Scalability Security 14. General Issue for Ad hoc network Transport layer protocol UDP TCP TORA SMR Pricing Scheme Self organization 15. General Issue for Ad hoc network Security Denial of services Resource consumption Energy depletion Buffer overflow Interference Addressing and Service Discovery 16. SECURITY REQUIREMENTAvailabilityConfidentialityIntegrityauthentication 17. Infrastructure based versus Ad Hoc Networks Infrastructure Networks contain special nodes called accesspoints(APs), which are connected via existing networks.APs are special in the sense that they can interact withwireless nodes as well as with the existing wired network.The other wireless nodes , also known as mobile stations ,communicate via APs. The APs also act as bridges withother networks. Ad hoc LANs do not need any fixed infrastructure. Thesenetworks can be set up on the fly at any place. Nodescommunicate directly with each other or forward messagesthrough other nodes that are directly accessible. 18. The design of infrastructure based networks is simplerbecause most of the network functionality lies withinthe access point ,whereas the client can remain quitesimple. In Ad hoc networks, the complexity of each node ishigher because every node has to implement mediumaccess mechanisms to provide certain quality ofservice. Infrastructure based networks lose some of theflexibility which wireless networks can offer.e.g. They cannot be used for disaster relief in caseswhere no infrastructure is left, where ad hoc networkscan be used. 19. Architecture of Ad Hoc Network IEEE 802.11 Specifies the most famous familyWLAN in which many products are available 802.11 is a set of IEEE standards that governwireless networking transmission methods. Under 802.11 standards mobile terminals canoperate in two modes1. Infrastructure Mode2. Ad Hoc Mode 20. Ad Hoc Mode IEEE 802.11 only covers PHY layer and MAC layer PHY layer is subdivided into 1. Physical Layer Convergence Protocol (PLCP) 2. Physical Medium Dependent sub layer (PMD) PHY management include channel tuning andresponsible for higher layer functions(e.g. control of bridging) MAC management controls authenticationmechanism and power management to save batterypower. 21. MAC Layer Provides Asynchronous Data Service and TimeBounded Service 802.11 only offers the Asynchronous Data Service inAd-hoc Mode , but both services can be offered byInfrastructure Mode. Basic access mechanism defined for IEEE 802.11 are1. Distributed Coordination Function (DCF)2. Point Coordination Function (PCF) DCF only offers asynchronous service , while PCFoffers both asynchronous and time bounded service MAC mechanism also called distributed foundationwireless medium access control (DFWMAC) 22. Basic DFWMAC using CSMA/CA Mandatory access mechanism for IEE 802.11 is basedon CSMA/CA CSMA/CA mechanism shown in figure. 23. If medium is busy , nodes have to wait for the duration ofDIFS , entering a contention phase. Each node now choose a random back off time within acontention window and delays medium access for thisrandom amount of time. As soon as a node senses the channel is busy , it has lost thiscycle and has to wait for the next chance. The basic CSMA/CA mechanism is not fair To provide fairness , IEEE 802.11 adds back off timer Each node selects random amount of waiting time If certain station does not get access to the medium in firstcycle it stops its back off timer , waits for the channel to beidle again for DIFS and starts the counter again. 24. DFWMAC with RTS/CTS Hidden terminal problem may occur in 802.11 ,if onestation can receive two others, but those cannotreceive each other. To deal with this problem, mechanism using twocontrol packets , RTS and CTS . After waiting for DIFS , the sender can issue a requestto send (RTS) control packet. Every node receiving this RTS now has to set its netallocation vector (NAV) in accordance with theduration field The NAV than specifies earliest point at which thestation can try to access the medium. 25. If the receiver receives the RTS , it answers with theclear to send (CTS) waiting for SIFS This CTS packet contains duration field and receivershave to adjust their NAV. Now all nodes within receiving distance around senderand receiver are informed that they have to wait moretime before accessing the medium. This mechanism reserves the medium for one senderexclusively. It is also called a Virtual Reservation Scheme. 26. ROUTING ALGORITHM TABLE DRIVEN Maintain the route table The Wireless Routing Protocol localizes the updates toimmediate neighbors. The Cluster Gateway Switch Routingprotocol reduces the size of the tables and amount ofinformation propagation by having each cluster ofnodes select a cluster head. 27. Source initiated on demand On-demand routing protocols are characterized by a path discovery mechanism which is initiated when a source needs to communicate with a destination that it does not know how to reach. 28. Classification of protocols Based on the routing information updatemechanism Proactive or table-driven routing protocols Reactive or on demand routing protocols Hybrid routing protocols Based on the use of Temporal information forRouting Routing protocols using past temporal information Routing protocols that use future temporal information 29. Based on Topology Information Organization Flat topology routing protocols Hierarchical topology routing protocols Based on the Utilization of specific Resources Power aware routing Geographical information assisted routing 30. Table Driven Routing Protocol Destination sequenced distance-vector protocol (DSDV)According to this protocol every node maintains a table that contains the shortest distance and the first node on the shortest path to every other node in the network.It incorporate table update with increasing sequence number tag to prevent loops, to counter to the count-to-infinity problem, and for faster convergences. 31. DSDV (continue ..) Destination Next Hop Distance Sequence Number As routing table : A A0S205_A B B1S334_B C C1S198_C D D1S567_D E D2S767_E F D2S45_F 32. Advantage of DSDV The availability of the routers to all destination at alltimes implies that much less delay is involved in theroute setup process. The mechanism of incremental updates with sequencenumber tags makes the existing wired networkprotocol adaptable to ad hoc networks. Hence wired network protocol can be applied to the adhoc network by less modification. 33. Disadvantage of DSDV A small network with high mobility or a large networkwith low mobility can completely choke the availablebandwidth. Hence this protocol suffers from excessivecontrol overhead that is proportional to the number ofnodes in the network. In order to obtain information about a particulardestination node, a node has to wait for a table updatemessage initiated by the same destination node. 34. Wireless Routing protocol It is also known as WRP protocols. It is same as DSDV protocol ,but contain some additional flag in table like status of the path which is simple path(correct) or a loop(error), or the destination node not marked(null). 35. Advantage of WRP It is the faster convergence and involves fewer tableupdates. 36. Disadvantage of WRP Complexity of maintenance of multiple tablesdemands a larger memory and greater processingpower from the nodes. At the high mobility, the control overhead involved inupdating table entries is almost the same as DSDV. Soit is not suitable for highly dynamic and also for verylarge ad hoc networks. 37. Cluster head Gateway Switch Routing protocol It is also called CGSR protocols CGSR organizes nodes into clusters, with coordinationamong the member of each cluster instructed nodesnamed cluster head. CGSR protocol creates a fixed region in the network.Each node in the cluster region is known as clustermember and they all are connected with pivot nodewhich is called cluster-head .Two cluster region areconnected via node which are place in intersectionregion of two cluster region and called cluster-gateway. 38. Advantage CGSR is a hierarchical routing scheme which enablespartial coordination between nodes by electingcluster-heads. Hence , better bandwidth utilization ispossible. It is easy to implement priority scheduling schemewith token scheduling and gateway code scheduling. 39. Disadvantage It increases in path length and instability in the systemat high mobility when the rate of change of cluster-heads is high. To avoid gateway conflicts, more resources arerequired. The power consumption at the cluster-head node isalso a matter of concern because the battery-drainingrate at the cluster-head is higher than that at a normalnode. 40. On-Demand routing protocols Dynamic Source Routing Protocol (DSR) In this routing protocol does not require periodichello packet transmission, which are used by a nodeto inform its neighbors of its presence. The basicapproach of this protocol during the routingconstruction phase is to establish a route by floodingRoute-Request packets in the network. Thedestination node, On receiving a Route-Request packet, respond bysending Route-Reply packets back to the resource. 41. Advantage Do not exchange routing update periodically, sooverhead transmission is greatly reduced Can refer to cache for the new route when link fails. 42. Disadvantages Scalability problem: High route discovery latency for large network. High mobility problem: although the packet dropped may not be substantional, the overhead traffic will increase a lot. 43. Ad Hoc On-Demand DistanceVector In AODV, a field of the number of hops is used in theroute record, instead of a list of intermediate routeraddresses. Each intermediate router sets up a temporary reverselink in the process of a route discovery. This link points to the router that forwarded therequest. 44. Advantage AODV is loop-free due to the destination sequence numbers associated with routes. Therefore, it offers quick convergence when the ad hoc network topology changes which, typically, occurs when a node moves in the network Disadvantage Poor scalability is a disadvantage of AODV. 45. Hybrid routing protocols Zone Routing Protocol (ZRP) ZRP is formed by two sub-protocols, the Intrazone Routing Protocol (IARP) and the Interzone Routing Protocol (IERP). 46. IARP is a limited scope proactive routing protocolused to improve the performance of existing globallyreactive routing protocols. It relies on the service of acertain neighbor discovery protocol (NDP) to provideneighbor information. IARP may use a scheme basedon the time-to-live (TTL) field in IP packets tocontrol the zone range. IERP is the reactive routing component of ZRP. Thisscheme is responsible for finding a global path. Itavoids global queries for destinations that would besent to surrounding hop neighbors. When globalqueries are required, the routing zone basedbroadcast service can be used to efficiently guideroute queries outward, rather than blindly relayingqueries from neighbor to neighbor . 47. References Mobile Communications- Jochen H. Schiller Ad Hoc Wireless Networks- C. Siva Ram Murthy- B. S. Manoj 48. THANKYOU?