姓名:劉柏廷 系所:國立中正大學 電機所網路通訊組 Enhancing End-to-End Throughput and Fairness in Wireless Mesh Networks with Error-free Channel 姓名:劉柏廷 系所:國立中正大學 電機所網路通訊組　

Outline Overview of Wireless Mesh Networks Background and Related Work MAC Layer Fairness End-to-End Fairness Token-Based Distributed Scheduling Solution of End-to-end Fairness Results of Simulation Conclusion and Future Work

Overview Advantage of WMN Low cost Scalability Reliability The MAC protocols in WMNs require the following features Be capable of more than one hop communication – Multi-hop Be distributed

Wireless Mesh Networks

Desired Approach We should ensure the fairness of each node in wireless mesh network Throughput tuning to desired proportion Avoiding hidden terminal problem is difficult to achieve Two fairness issues are studied MAC layer fairness End-to-end flow fairness We focus on chain topologies

N-node chain topology

Unfairness in 802.11 MAC Layer Throughput

End-to-End Fairness Study [1]

End-to-End Fairness Study (cont)

More Simulations with 802.11 3 nodes 4 nodes

Token-Based Distributed Scheduling TDMA-like system Token Concept Concept of Cluster Traffic Model CBR traffic flow to neighbor Fixed Packet size 512 bytes 2Mbps bandwidth Assumptions Chain topology Location knowledge No-routing overhead All nodes always have packets to send Fixed Packet size

Token-Based Distributed Scheduling Better !! Problem!! Round-Robin Round-Trip

TDS-3 Because of the direction of traffic in WMN is uni-direction to gateway. Number of members in a Cluster change to 3. RTS (1,1) RTS (5,2) CTS CTS Data Data Ack Ack RTS (2,1) CTS CTS Data Ack Ack RTS (2,1) CTS Data Ack NAV Return,0,1 RTS (1,1) RTS (5,2) CTS CTS Data Data Ack Ack

Separated Queues for Per Flow Single Queue Per Flow Fair Queue

End-to-End Flows Comparison – TDS-4

End-to-End Flows Comparison –TDS3

End-to-End Throughput Comparison H ( # of hops ) TDS-4 (Mbps) TDS-3 (Mbps) Improvement for TDS-4 (%) 4 0.31 0.41 33% 5 6 0.43 39% 7 8

Conclusions and future work MAC layer The hidden terminal problem causes serious unfairness in throughput in multi-hop networks. Propose a token-based distributed scheduling (TDS) that can achieve the fairness result and desired proportion in three hops. Network Layer Analyze and solve the end-to-end unfairness Future work Recovery of RTS/Token in noisy channel

Reference [1] J. Jun and L. Sichitiu, “The Nominal capacity of wireless mesh networks,” IEEE Wireless Communication, pp. 8–14, October 2003.