Performance Evaluation and Improvement of an Ad Hoc Wireless Network

1. Performance Evaluation and Improvementof an Ad Hoc Wireless Network Takayuki YamamotoGraduate School of Engineering Science,Osaka University, Japantak-ymmt@ics.es.osaka-u.ac.jp

2. Contents • Introduction of Target System - the Flexible Radio Network - • Basic Network Performance forSome Different System Parameter Values • Suggestions for Performance Improvement • Conclusion ICOIN-16

3. Flexible Radio Network • Wireless Ad Hoc Network Systemdeveloped by Fuji Electric Co. Ltd. • Multi-hop Network organized byStationary Terminals • Application Examples • Power Consumption Collectionin Manufacturing Plants • Sales Account Collectionfrom Vending Machines • Usage Data Collection from Ski Lift Gates http://www.fujielectric.co.jp/eng/index.html ICOIN-16

4. Destination Node ID B E ‥ Route entries 1 (B,1) (C,2) ‥ E D 2 (C,4) (B,3) ‥ B ： ： ： Network Configuration Table at node A C A System Description • Network Configuration Table • updated by Periodic Table Exchange • Each Node maintains Multiple Routesto All Nodes in the Same Network • Route Entry = (Neighbor ID, Hop Count) ICOIN-16

5. Slot 0 1 2 3 4 5 Node A Node A eavesdrops node B’sforward transmission.When node A’s first transmissionsuccesses, node A can hear therelay echo and delete the packetin its buffer. relay echo send Node B forward(relay) Protocol Description • Time Division, Slot-based Transmission • Packet Maximum Lifetime set in a Source Node • decreased by one per slot even when it stays in a buffer • Hop-by-Hop Receipt Acknowledgementbased on Relay Echo Mechanism ICOIN-16

6. Slot 0 1 2 3 4 Node A × retransmission to node B or another node transmissionfailure Node B If no relay echo can be received,node A retransmits the packet. Protocol Description • Retransmission Control ICOIN-16

7. Slot 0 1 2 3 4 to B Node A Node B Destination Node returns an ACKpacket by way of relay echo Protocol Description • ACK from Destination ACK ICOIN-16

8. Simulation Description for Original System Evaluation • Network Simulator - ns-2with our implementation of FRN • Maximum Lifetime = 12, 64 and 128 (slots) • Data Collection Network Model ICOIN-16

9. Original System Evaluation Packet Loss Rate Throughput Short Lifetime Packetcauses High Loss Ratefor Low Load Environment Long Lifetime Packetcauses Congestion Throughput = Number of Packets received by the Destination per slotPacket Loss Rate = Ratio of unreached Packets to the DestinationLoad = Average Number of Packets produced per slotL(h) = Maximum Lifetime ( h is described later) ICOIN-16

10. Performance Improvement • Adaptive Maximum Lifetime • Source Node calculates the Maximum Lifetime for Each Packet according to the shortest Hop Count to its Destination • Methods to Prevent Packet Collision leads to Packet Duplication • Random Wait for Retransmission • Packet Rejection earlier than its Lifetime expires ICOIN-16

11. L(h)=24 L(h)=18 L(h)=30 Adaptive Maximum Lifetime Example Function: L(h) = 6h+12 ( h is Hop Count of the shortest route) E D B F C A G ICOIN-16

12. Long-living Packet can berejected effectively Low Loss Rate forLow Network Load Adaptive Maximum Lifetime ICOIN-16

13. Packet TransmissionFailure Relay Echo ReceiptFailure Packet Retransmission Unique Packetin the Network PacketDuplication Additional Network Loadand Performance Degradation Packet Duplication Problem ICOIN-16

14. Packet Collision repeatsdue to Fixed Wait Duration Slot 0 1 2 3 4 5 Node X send resend × × resend × × Node A echo loss echo loss send Node B echo echo forward forward Random Wait for Retransmission • Reduction of Packet Duplication Repeat Case 1: Fixed Wait Duration (3 slots) collision collision ICOIN-16

15. Probability of repeatedecho loss can be reducedby random delay time Slot 0 1 2 3 4 5 Node X send × resend collision Node A × echo loss send resend echo Node B echo echo forward forward Random Wait for Retransmission • Reduction of Packet Duplication Repeat Case 2: Random Wait Duration ICOIN-16

16. This Method is effective underLarge Maximum Lifetime Setting Random Wait for Retransmission ICOIN-16

17. (X, D, 1) (X, D, 0) Packet： (source, destination, lifetime) Early Packet Rejection • Packet Rejection earlier than its Lifetime reaches Zero • Unreachable Packets cause Useless Collisions Detect and Reject the unreachable Packet whose Lifetime is shorter than the Shortest Hop Count to its Destination (X, D, 2) D ICOIN-16

18. This Method is effective underSmall Maximum Lifetime Setting Early Packet Rejection ICOIN-16

19. PLR for All Methods Together ICOIN-16

20. Conclusion and Future Work • Flexible Radio Network (FRN) system • Relay Echo Mechanism, Multiple Route Maintenance for Reliability • Maximum Lifetime Calculation with Route Lengthis capable of increasing Network Reliability • Packet Duplication caused by Relay Echo and Retransmission Mechanism • Relationship between Maximum Lifetime Setting and Effect of Random Wait Duration, Early Packet Rejection • Much Better Performance is achieved by applying All Methods Together • Future Works • Evaluation for End-to-End Protocol on FRN • Implementation into actual FRN Terminals ICOIN-16