LAR – Location Aided Routing

The main problems of previous mechanisms

Node location changes rapidly.

No information regarding:

• Current location.

• Speed.

• Direction.

Knowing the location.

• Minimizes the search zone.

• No need to flood the network.

Knowing the speed and/or direction.

• More minimization of the search zone.

• Increases the probability to find the necessary node.

Location-Aided Routing (LAR)

Each node knows its location at every moment.

Using location information for route discovery.

Routing is done using the last known location + an assumption.

Route discovery is initiated when.

• S does not know a route to D.

• The previous route from S to D is broken.

Assumptions.

• Location knowledge.

• No error.

• 2D movement.

• Full cooperation.

Location information

• Alignment of satellites and ground stations.

• Global Positioning System (GPS) - USA.

• Global Navigation Satellite System (GLONASS) - Russia.

• Galileo – EU.

• 3D positioning.

• Accuracy 3-100 meters.

• Can provide further information.

  • Velocity.

  • Time.

• Cutting-edge technology.

• Already in use in many fields.

Definitions

Expected Zone

• S knows the location L of D in t0.

• Current time t1.

• The location of D in t1 is the expected zone.

• Assume Max/Avg speed v.

Request Zone

• Flood with a modification.

• Node S defines a request zone for the route request.

• How to determine the size and shape of the request zone?

• Several considerations.

  • If the destination’s EZ does not include the source node, other regions must be included in the RZ.

  • Not always a route will be found using a certain RZ.

Scheme 1

Algorithm

Node I receives RREQ.

• Location of I – (Xi, Yi).

• If it is within the rectangular, I forwards the RREQ to its neighbors.

• Else I discards the RREQ.

Node D receives the RREQ.

• Replies RREP.

• Adds its current location.

Some issues

The rectangular size is proportional to:

• Average speed (v).

• Time elapsed (t1-t0).

Therefore:

• Low speed -> small v in the same (t1-t0) -> smaller RZ.

• High speed -> large v in the same (t1-t0) -> larger RZ.

Improvements:

• D can add its speed/avg. speed in the RREP, this can help other nodes in future route discoveries.

• D can piggyback its location in other packets.