A Distance Routing Effect Algorithm for Mobility (DREAM)* Stefano Basagni Irnrich Chlamtac Violet R. Syrotiuk Barry A. Woodward Outline • Introduction • DREAM -Dissemination of Location Information -A model of DREAM -DREAM procedure • Simulations and Results • Conclusion Introduction • Old problem for Ad hoc network routing: -Proactive: it corresponds to a next hop table lookup, sequence is not explicit; -Reactive: the movement of any node in the sequence renders the path invalid. • A new definition of routing table entry is needed Dissemination of Location Information (DREAM) • Each node transmits control messages bearing its current location to all the others. (e.g. geographic coordinates; obtained by the use of GPS ) • The frequency with which these control messages is determined by: -distance effect -mobility rate Dissemination of Location Information (control message) • We assign each control packet a life time • A majority of the packets have a “short” life time: short lived packets are sent at high frequency, and “die” after they have traveled. • Long lived packets, sent less frequently, travel farther through the network. A Model for DREAM • S sends a message to node R, it refers to its LT (Location Table) in order to retrieve location information about R. • S selects from among its neighbors those nodes that are in the direction of R • It is guaranteed that R can be found with a given probability p, 0< p <1, following result in that direction. A Model for DREAM • The time interval from t0 to tl, tl > t0 • x = (tl – t0)v • Node R, whose speed is v, cannot be anywhere outside the circle C • one hop neighbors those nodes A, direction A. lies within the range [θ- α, θ+ α] • Angle α must be chosen in a way that the probability of finding R in the sector S is at least p. • we want to find a minimum value for α A Model for DREAM (method of finding α)-1 A Model for DREAM (method of finding α)-2 Distance Routing Effect Algorithm for Mobility (DREAM procedure) Distance Routing Effect Algorithm for Mobility (DREAM procedure) Distance Routing Effect Algorithm for Mobility (DREAM procedure: Recovery) • Its actual implementation may vary, depending on the characteristic of the network. • For instance, flooding Simulations Results • Simulated our DREAM protocol using MAISIE  • Placing n = 30 nodes randomly on a grid of size 100 x 100. • we assume that each node has the same speed V • given in grid units per 100 ticks of the simulation clock • average end-to-end delay Conclusions • Simulation results showed that with over 80% probability this method can find a route to a given node. (if any exists) • The average end-to-end delays with respect to the DSR reactive protocol are lower. • DREAM protocol provides loopfree routes, and is robust in providing multiple routes.
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