Throughput Enhancement in WiMax Mesh Network Using Concurrent Transmission

1. Throughput Enhancement in WiMax Mesh Network Using Concurrent Transmission Advisor: Dr. Kai-Wei Ke Speaker: Jaw-Woei Ma Date:03/28/2006

2. Outline • Introduction 1.WiMAX 2.Mesh Network • Scheduling • Concurrent Transmission • Simulation and Analysis • Conclusions • References

3. WiMAX • Worldwide Interoperability for Microwave Access(全球微波存取互通性) • A wireless broadband network connection technique. • the last mile. • Cost saving. • Easy to employ

4. WiMAX versus WiFi • WiFi Bandwidth:11Mbps (802.11b) , 54Mbps (802.11g) Range:100m • WiMAX Bandwidth:134Mbps, 300kbps~2Mbps (末端用戶) Range:48km WiMAX,WiFi和有線網路屬於”互補關係”

5. Mesh Network • PMP ( point to multipoint ) The downlink, from the BS to the user,operates on a PMP basis • Mesh Traffic can be routed through other SSs and can be occur directly between SSs Subscriber station share uplink to the BS on a demand basis all above

6. Mesh Network (cont.) • Distributed Scheduling • Superiority of the Mesh BS, which effectively result in Centralized Scheduling • On a combination of both

7. Scheduling in Mesh Mode • Distributed Scheduling No clearly defined BS a distributed manner like an ad-hoc network

8. Centralized Scheduling BS determines slot allocation for all SSs a centralize manner like PMP mode traffics can be relayed by other SSs through a multi-hop route which is defferent from PMP mode

9. Combination a hybrid of both can be adopted in Mesh mode

10. Two Control Message • MSH-CSCF (Mesh Centralized Scheduling Configuration) deliver the information of channel configuration and routing tree

11. MSH-CSCH (Mesh Centralized Scheduling) deliver the information of bandwidth request and grant and updating of routing tree Grant/Request Flag: 0 = Grant (downlink ) 1 = Request ( uplink )

12. Each entry of Scheduling Tree • NodeID • NumberOfChildren • ChildIndex (table) • Uplink/Downlink Burst Profile

13. Scheduling • The BS generates MSH-CSCF and broadcasts it to all its neighbors BS -> SS (MSH-CSCF) • According to the routing tree in MSH-CSCF message, all the SSs maintain a routing tree whose root is BS and children are SSs SS -> BS ( MSH-CSCH: Request ) • BS can gather bandwidth requests from all the SSs, and assign spatial resource for SSs (put in MSH-CSCH: Grant message) rebroadcast until all the SSs receive MSH-CSCH:Grant

14. Scheduling (cont.) • After receiving a MSH-CSCH:Grant message, the SSs determine its actual uplink and downlink transmission time from MSH-CSCH:Grant by a common algorithm which divides the frame proportionally

15. TDMA

16. Concurrent Transmission

17. Link Interference • solid lines : directional links in the routing tree • dashed lines : connect the neighboring nodes in one-hop • the curves : the interference by an active link

18. L(x,y) represent the link from x to y • the interfered links by L(4,6) are L(6,4), L(2,4), L(5,2), L(4,2),L(BS,2),L(BS,1),L(3,1) • i.e. when node 4 is transmitting data to node 6,The number of interfered links by L(x,y) is given by I(x,y), so I(4,6)=7

19. Constructing Routing Tree • Py(x) = I(x,y) + I(y,x) + Pz(y). • for example, P4(6) = I(4,6) + I(6,4) + P2(4).

20. network begins with only one BS • all the SSs enter the network one by one • all its neighbor nodes are eligible to be the father node of the entering SS • entering SS should select a father node with minimal interference

21. Father node is where Neighbor(x) is a set of x’s neighbor nodes.

23. After SS5 entered the network • P2(4)=46,P5(4)=30 • so the father node of SS4 is adjusted from SS2 to SS5

24. Concurrent Transmission Algorithm • The order of transmission time determination in uplink is the same as transmission order of MSH-CSCH: Request

25. The idea • The transmission time should be as early as possible on condition that no collision would happen • The transmission time of an SS should not be earlier than any of its children’s

26. Algorithm (Uplink)

27. Algorithm (Downlink) • the algorithm in downlink is similar to that in uplink

28. Simulation • Simulation Scenario: Random topology is generated in an L*L square. ( L = d √(n / 2) ) n is the number of SSs d is the maximal transmission range between two nodes.

29. single channel network with no bit errors • all the SSs are immobile and working in half duplex • highest available rate (set to 50Mbps here) regardless of the channel state • Every SS request 0.5Mbps bandwidth for both uplink and downlink

30. Result • show the overall end-to-end throughput with different routing trees • The number of SSs increases from 20 to 120 with a step of 10 • The throughput values are the average of simulations in 500 times

31. Results (Uplink)

32. Results (Downlink)

33. Analysis • Throughput: (1). interference-based routing tree > random routing tree (2). adjusted interference based routing tree > non-adjusted interference-based routing tree

34. Analysis (cont.) • This concurrency algorithm performs best when using an adjusted and interference-base routing tree.

35. Conclusions • promote spatial resource reuse, which increases the overall end-to-end throughput • Simulation results indicate that different constructions of routing tree impact the performance of the concurrent algorithm

36. Future Work • With rapid demands of mobility wireless access we need • Consider the scenario that SSs are mobile to improve our algorithm

37. Reference [1] Jian Tao, Fuqiang Liu, Zhihui Zeng, and Zhangxi Lin, “Throughput enhancement in WiMax mesh networks using concurrent transmission,” Proceedings of 2005 International Conference on Wireless Communications, Networking and Mobile Computing. • [2] Hung-yu Wei, Samrat Ganguly, Rauf Izmailov, and Zygmunt Haas,"Interference-Aware IEEE 802.16 WiMax Mesh Networks," The 61st IEEE Vehicular Technology Conference (VTC Spring'05), May 2005. [3] IEEE 802.16 standard