1. Achieving Throughput Fairness in Wireless Mesh Network Based on IEEE 802.11 Janghwan Lee and Ikjun Yeom Division of Computer Science KAIST jlee@cnlab.kaist.ac.krjlee@cnlab.kaist.ac.kr yeom@cs.kaist.ac.kr yeom@cs.kaist.ac.kr jlee@cnlab.kaist.ac.kryeom@cs.kaist.ac.kr

2. Wireless Mesh Network Multi-hop wireless infrastructure Multi-hop wireless infrastructure Uses IEEE 802.11 Uses IEEE 802.11 Residential user or small business Internet Gateway node Router node Client node

3. Fairness Problem Unfair bandwidth sharing among flows with different hop distance

4. Related Work Centralized scheme [Gamboriza] Every node in the network knows about global topology and offered load. Calculate proper ingress rate at each node. Hard to know offered load. Not scalable.

5. Related Work Queueing Scheme Per flow queueing [Jun] Limit queue share [Nandiraju] Cannot resolve MAC layer contention Wasting bandwidth Cannot apply to the case when queue is not occupied enough

6. Problem Statement Support the same bandwidth to every leaf node with distributed algorithm. uplink Assume multi-radio, multi-channel To make a model simple Separate uplink and downlink channel Eliminate propagation of interference Independent collision domain Common in [Brezezinski], [Raniwala] Find proper weight f (p,i) that satisfies c i =c j for all i,j

7. Proposed Scheme

8. Node Weight Estimation Need to know the number of active nodes Just counting the number of nodes with timeout is too naive Hard to adjust timeout value because of highly dynamic network We can estimate the weight by dividing the aggregate throughput by the average throughput of leaf nodes How to know L i ?

9. Node Number Estimation Leaf nodes piggyback their sending rate on packets Intermediate nodes calculate average value from leaf rate Need to compensate bias

10. Weighted Scheduling Achieving efficient channel utilization and weighted fairness for data communications in IEEE 802.11 WLAN under DCF, In Proc. of IWQOS 2002Achieving efficient channel utilization and weighted fairness for data communications in IEEE 802.11 WLAN under DCF, In Proc. of IWQOS 2002 Differentiate nodes using collision model Has a problem in multi-hop network

11. Weighted Scheduling From the model in [Qiao] and [Bianchi], the probability that node i attempts to transmit on given slot as, The probability that node i successfully transmits on a given slot, To satisfy the weight of node i and j, f i and f j,

12. Weighted Scheduling With exponential backoff, Unfortunately, we cannot get the solution of equations with closed form. Numerical solution

13. Weighted Scheduling Contention window size according to weighted scheduling model when the base contention window is 30

14. Weighted Scheduling Normalized throughput with changing the weight from 2 to 5 using different models

15. Simulation Result Simulation Topology

16. Simulation Result At 20 sec stops at 60 At 40 sec At 60 sec Initial Weight estimation and weighted schduling

17. Simulation Result TCP Throughput of each node (sorted in ascending order) Aggregate throughput of proposed scheme achieves 97% of the IEEE 802.11 throughout simulations

18. Simulation Result UDP throughput of each node at different load (sorted in ascending order)

19. Conclusion We proposed a scheme to realize throughput fairness in wireless mesh network. Our scheme performed well without significant loss of aggregate throughput

20. Issues Are the assumptions about topology and channel environment reasonable? Cannot apply to the single channel or unplanned network

21. References [Gambiroza] V. Gambiroza et al. End-to-end performance and fairness in multihop wireless backhaul networks., in proc. of Mobicom 04 [Nandiraju] N. S. Nandiraju et al., A novel queue management mechanism for improving performance of multihop flows in IEEE 802.11s based mesh networks In Proc. of IPCCC 2006, April 2006. [Jun] J. Jun and M. L. Sichitiu, Fairness and QoS in multihop wireless network. In Proc. of VTC 2003-Fall [Qiao] D. Qiao et al., Achieving efficient channel utilization and weighted fairness for data communications in IEEE 802.11 WLAN under DCF, In Proc. of IWQOS 2002 [Bianchi] G. Bianchi, Performance anlysis of the IEEE 802.11 distributed coordination function., JSAC March, 2000.