1. GPSR: Greedy Perimeter Stateless Routing for Wireless Networks
Eileen Balci

2. About GPSR
GPSR allows nodes to figure out who its closest neighbors are (using beacons) that are also close to the final destination the information is supposed to travel to
To calculate a path, GPSR uses a greedy forwarding algorithm that will send the information to the final destination using the most efficient path possible. If the greedy forwarding fails, perimeter forwarding will be used which routes around the perimeter of the region.

3. About the Greedy Forwarding Algorithm
Assuming the wireless routers [nodes] know their own locations the Greedy forwarding algorithm will try to find the closest router which is also the closest to the final destination

4. Greedy Forwarding Algorithm Benefits
A node just has to remember the location of neighbors with in one-hop
Routing decisions can be dynamically made

5. Greedy Forwarding Algorithm Drawback
If the network is dense enough that each interior node has a neighbor in every 2/3 angular sector, Greedy Forwarding will always succeed. However, the greedy forwarding algorithm can fail:
Greedy Forwarding fails

6. Perimeter Forwarding Algorithm Benefits
When the Greedy Forwarding algorithm fails, the Perimeter Forwarding algorithm will be used
Apply the right-hand rule to traverse the edges of the void and find a path using the topology’s perimeter

7. Perimeter Forwarding Algorithm Drawback
The Perimeter Forwarding Algorithm uses a longer path to the destination so the perimeter forwarding algorithm less efficient and cannot be used alone

8. Greedy Perimeter Stateless Routing - GPSR
Putting Greedy Forwarding and Perimeter Forwarding together makes the final GPSR which will use the necessary algorithm(s) to find the best path in a given topology
greedy fails
Greedy Forwarding
Perimeter Forwarding
have left local maxima
greedy works
greedy fails

9. GPSR
The GPSR is a responsive and efficient routing protocol for mobile, wireless networks. GPSR can be applied to Sensor networks, Rooftop networks, Vehicular networks and ad-hoc networks.

10. Credits www.cs.binghamton.edu/~kang/teaching/cs580s/gpsr.ppt