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

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 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 Scheduling

14 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 Scheduling (cont.)

15 TDMA

16 Concurrent Transmission

17 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 Link Interference

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

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.

22

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 WiMax Mesh Networks," The 61st IEEE Vehicular Technology Conference (VTC Spring'05), May [3] IEEE standard