1. 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　

2. 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

3. 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

4. Wireless Mesh Networks

5. 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

6. N-node chain topology

7. Unfairness in 802.11 MAC Layer Throughput

8. End-to-End Fairness Study [1]

9. End-to-End Fairness Study (cont)

10. More Simulations with
3 nodes
4 nodes

11. 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

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

13. 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

14. Separated Queues for Per Flow
Single Queue
Per Flow Fair Queue

15. End-to-End Flows Comparison – TDS-4

16. End-to-End Flows Comparison –TDS3

17. 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

18. 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

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