EECS 600 Zhihua Wen Feb,14,2005

GPSR: Greedy Perimeter Stateless Routing for Wireless Networks

Dynamic source routing

who gives the path: source

how to obtain a path: route discovery, broadcasting, flooding

what is the routing metric: kind of delay time ( plus random delay)

what information matained: routing path, partial routing path

Geographical Routing:

  Assumption: every node's X & Y are known, when a node A want to route to B, it already knowns B's physical
  location as well as its identifier (e.g. IP address)
  
  How to enforce random beacon interval, then? (If we want to piggyback the position of nodes on all data packets)
  Maybe we can set a time interval, if there is data packet to be sent during this interval, we can piggyback the
  position info, otherwise we can send the position info alone.
  
Greedy forwarding:
  forward the data packet to the next neighbor which has the minmium distnace to the destnation node D.
  
Perimeter forwarding:
  The current node has the local minmium distance to the destnation node D, greedy forwarding fails
  
  counterclock fashion to route around the void area
  
  why need no-crossing heuristics? ( example? Maybe right hand rule will sometimes fails in a graph will crossing edges )
  
  RNG graph and GG graph: The graph is still connected after cutting edges
  
Packet headers include a field indicate greedy forwarding mode or perimeter forwarding mode

Only the packet's source sets the destination field

Perimeter forwarding is only intended to recover from local maximum

It's possbile a packet will travel a loop although it eventually will reach the destnation node D. (e.g.,
a packet follows the greddy forwarding route to a node x with local minmium distance to D, then uses perimeter forwarding
back to a already passed node, but it can continue uses perimeter forwarding until the distance is less than d(xD). 
Eventually it will reaches the destnation if the graph is connected.