1. November 4, 2003Applied Research Laboratory, Washington University in St. Louis APOC 2003 Wuhan, China Cost Efficient Routing in Ad Hoc Mobile Wireless Networks Ruibiao Qiu ruibiao@arl.wustl.edu

2. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 2/10 Outline Background and motivation Cost model in ad hoc networks Cost-based routing scheme Adaptation to existing routing protocols Experimental results Conclusions

3. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 3/10 Introduction Wireless networks become increasingly popular and affordable Ad hoc mobile wireless networks –Dynamic and easy deployment –No fixed infrastructure required –Applications Emergency disaster relief, battlefields, information gathering, group interaction Routing is crucial to the success of ad hoc mobile wireless networks

4. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 4/10 Routing in Ad Hoc Networks Select a suitable path between two nodes Routing challenges in ad hoc networks –Dynamics, limited resources, environment complexity Table-driven proactive protocols –Maintain consistent up-to-date route information of the network with constant updates –Examples: DSDV, CGSR, WRP Source-initiated on-demand reactive protocols –Invoked only when there is a data delivery request but no existing paths –Examples: AODV, DSR, TORA, ABR Location-based protocols –Use information about destination location to forward data packets –Examples: LAR, GPSR, SPEED

5. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 5/10 Ad Hoc Networks Cost Model Traditional protocols use hop count only as routing metrics –Unbalanced link bandwidth –Hops  distance –Data forwarding is more costly than wired networks Observation: traffic variation diminishes as flows aggregate More precise cost-based model is desirable –Consolidate all factors –Take advantages of traffic aggregation Higher degree of traffic variation in wireless networks

6. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 6/10 Cost Model Connection cost depends on the individual flows Individual flows exhibit statistically similar behavior Aggregated flow variation is smaller than the sum of all individual flow variation C u,v (f) = l u,v ( f + k  f ½ ) C p (f) =  {(u,v)  p} C u,v (f) =  {(u,v)  p} l u,v ( f + k  f ½ ) –C u,v (f): cost of transmitting flow volume f between nodes u and v –C p (f): cost of transmitting flow volume f on path p –l u,v : length between nodes u and v –f: total traffic flow load –  : individual traffic variation parameter –k: constant factor

7. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 7/10 Cost-based Routing Scheme Use the ad hoc network cost model to replace the hop count as the routing metrics Basic operations –Cost computation By the cost model –Cost update Per-link incremental cost  C u,v incurred by flow increment   C u,v = l u,v [  + k  (f +  ) ½ - k   ½ )] Whole path incremental cost  C u,v is computed similarly  C p =  {(u,v)  p}  C u,v =  {(u,v)  p} l u,v [  + k  (f +  ) ½ - k   ½ )]

8. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 8/10 Adaptation to Existing Routing Protocols Proactive Routing Protocols –Use new routing tables with C u,v (link state protocols) or C p (distance vector protocol) on nodes Reactive Routing Protocols –Route discovery Use  C u,v to determine the optimal among all outgoing links Forward requests with piggybacked increment cost information along all paths, and the destination makes the final decision –Route maintenance Changes trigger updates to neighbors Location-based Routing Protocols –No need to record distance information

9. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 9/10 Experimental Results ns-2 simulator with wireless extension –Varied number of nodes (50 –200) –IEEE 802.11 radio –Modified vs original AODV Total cost comparison AODV-cmod AODV-orig

10. APOC 2003 Wuhan, China Applied Research Laboratory, Washington University in St. Louis 10/10 Conclusions Ad hoc mobile wireless networks present great challenges to traditional routing algorithms A cost model for ad hoc mobile wireless network proposed Cost-based routing scheme is described –Cost efficient routing –Adaptive to existing routing protocols