Efficient flooding with Passive clustering (PC) in Ad Hoc Networks Taek Jin Kwon, Mario Geria University of California at Los Angeles ACM SIGCOMM 2002

outline Introduction Limitations of existing clustering schemes Passive clustering Simulation Conclusion

introduction CONCEPT Flood search is the capstone of all on-demand routing protocols. Although some mechanism like “duplicates are detected” can reduce some overhead. Flooding generates replicated packet arrivals to each node. Cluster is a good idea to reduce flooding overhead.

Limitations of existing clustering schemes Node locations and neighborhood information are key for clustering; unfortunately, they do vary in time. In the period of neighbor learning and initial clustering, it is essential that there is no mobility for proper convergence. The cluster structure is useful only after the cluster have been created.

Passive clustering On-demand cluster. Create by route request. Utilize the advantages of cluster on the fly. Create a sub-layer under MAC layer for passing the packet for this node.

Cluster sub layer (CSL) MAC Cluster sub layer (CSL) IP Passive clustering Add 2-bits filed in MAC header for 4 states. INITIAL CLUSTERHEAD ORDINARY_NODE GATEWAY embedding/stripping the 4 states in CSL. And another internal state “CLUSERHEAD-READY”

Passive clustering Timing of states Initial: At cold start The number of this non-clusterhead node’s neighbor head is zero。 Clusterhead: At cold start, if the first received MAC packet is not send by header then set itself “CLUSERHEAD-READY” and then set itself “CLUSTERHEAD” when forwarding. ORDINARY_NODE: Anytime when received a message which send by header. Gateway: When a non-clusterhead node hears a packet from a clusterhead, the node becomes a gateway if α*NC + β > NG. NC = the number of cluster-head. NG = the number of neighboring gateway. β, α = user define parameter

Passive clustering An example to show “on the fly”: Source send the RREQ. When the neighbor of source receive the RREQ, change it’s state to ”Clusterhead-Ready.” When any of above node want to forward RREQ, set it’s state to ”CLUSTERHEAD” and broadcast it. The header selection schema is “first declaration wins.”

Passive clustering At this time, all nodes received the clusterhead announcement can changed to gateway (α*NC + β > NG). α set to 1 and β set to 0. Now NC=1 and NG =0. RREQ+gateway state RREQ+head state RREQ+gateway state Find D silence RREQ D S RREQ+head state silence CLUSTERHEAD Gateway CLUSTERHEAD Clusterhead-Ready Clusterhead-Ready

Simulation Simulation environment: Implement in GloMoSim. 100 nodes in 600x600 meters square space. 150m of transmission range. Traffic source are CBR. One packet per sec. Date packet: 512bytes. Control packet: 32 bytes. Each simulation duration is ten min. Use Random way point model. Pause time = 10 sec.

Simulation Test the path-finding (1): Environment: Result: 2400 random source and destination pairs. Ran from cold start one-by-one. Only one data packet is sent from each source to each destination. There is only one source and destination in a given period (which is much larger than cluster time out (=2 seconds)) to ensure that no residual clustering structure remains after the single transmission. Result: 100% packet delivery was observed with the experiment.

Simulation Test the path-finding (2): Environment: Result: Varying nodes speeds of 0,2,4,6,8 meters per sec. Send a packet every 15 sec for 100 min. (1/15 packet/sec) Slow rate to ensure that the previous cluster structure dissolves after timeout(2 sec). Result: The delivery of speeds of 0,2,4 meters/sec is 100%. Speed of 6 meters/sec is 99.25% and 8 meters/sec is 98.25%.

Simulation Throughput(kbits/sec) Throughput(kbits/sec)

Avg hop distance Avg hop distance Offered load(Kbps)

Simulation Number of flooding relay Offered load(Kbps)

Conclusion Passive cluster can reduce more flooding overhead than the active flooding schemas. Passive cluster can solve the limitations of active cluster schema. Obviously, total flooding will work best in sparse and very dynamic networks

END Reference: [1] “On Demand Routing in large AD Hoc wireless Networks with Passive Clustering” (WCNC 2002) [2] ”Energy Balanced Broadcasting Through Delayed Intelligence” (ITCC 2005) [3] ”Scalable AODV with Efficient Flooding based on On-Demand Cluster”( Mobile Computing and Communication Review, Volume 6, Number 3)