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 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 [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.