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Performance Evaluation and Improvement of an Ad Hoc Wireless Network

Performance Evaluation and Improvement of an Ad Hoc Wireless Network. Takayuki Yamamoto Graduate School of Engineering Science, Osaka University, Japan tak-ymmt@ics.es.osaka-u.ac.jp. Contents. Introduction of Target System - the Flexible Radio Network -

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Performance Evaluation and Improvement of an Ad Hoc Wireless Network

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  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

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