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 [7]) • 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

result in that direction.

be found with a given probability p, 0< p <1, following

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 [1] • 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.