and make a comparison study. Finally we end withthe discussion and few useful references.
2. Unique VANET characteristics andcomparison with MANET
2.1 Unique VANET characteristics
Though Vehicular network share commoncharacteristics with conventional ad-hoc sensornetwork such as self organized and lack of centralcontrol. VANET have unique challenges thatimpact the design of communication system and itsprotocol security. These challenges include-
1. Potentially high number of nodes.
RegardingVANETs as the technical basis for envisionedIntelligent Transportation System (ITS) we expectthat a large portion of vehicles will be equippedwith communication capabilities for vehicularcommunication. Taking additionally potential road-side units into account, VANET needs to bescalable with a very high number of nodes.
2. High mobility and frequent topologychanges
. Nodes potentially move with high speed.Hence in certain scenarios such as when vehiclepass each other, the duration of time that remainsfor exchange of data packets is rather small. Also,intermediate nodes in a wireless multi-hop chain offorwarding nodes can move quickly.
3. High application requirement on datadelivery.
Important VANET applications are fortraffic safety to avoid road accidents; potentiallyincluding safety-of-life. These applications havehigh requirements with respect to real time andreliability. An end-to-end delay of seconds canrender a safety information meaningless.
4. No confidentiality of safety information.
Forsafety application the information contained in amessage is of interest for all road users and hencenot confidential.
Communication capabilities in vehiclesmight reveal information about the driver/user,such as identifier, speed, position and mobilitypattern. Despite the need of messageauthentication and non-repudiation of safetymessages, privacy of users and drivers should berespected in particular location privacy andanonymity.
2.2 Comparison of MANET and VANET
Mobile Ad-hoc networks and Vehicular Ad-hocnetworks are very much similar on varioustechnical grounds but following are someparameters on the basis of which we can contrastboth environments.Sr.No. Parameters MANET VANET1. Cost ofproductionCheap Expensive2. Change inn/wtopologySlow Frequent and very fast3. Mobility Low High4. NodedensitySparse Dense and frequently variable5. Bandwidth HundredkpsThousand kps6. Range Upto100mUpto 500m7. NodeLifetimeDependson powerresourceDepend on lifetime of vehicle