1 Routing and Admission Control in IEEE Distributed Mesh Networks Tzu-Chieh Tsai Dept. of Computer Science National Chengchi University Taipei, Taiwan

2 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Simulations Conclusion

3 Outline Introduction Wireless Mesh Networks IEEE Mesh Mode Problems Related Work Our Routing and CAC Algorithm Simulations Conclusion

4 Introduction— Wireless Mesh Networks

5 Ad-hoc network basis Self organization Fault tolerance Scalability Lower infrastructure cost Wider coverage Standard activities s (in progress) (in progress, mainly in PHY) Mesh mode is already included in standards.

6 IEEE mesh mode

7 Terminology Mesh Base Station (MBS or BS) Mesh Subscriber Station (MSS or SS) Extended neighborhood (2-hop neighbors) Defers from PMP mode (Point to Multi-Point) Traffic can occur directly between SSs Only TDD is supported in Mesh Frame format Not compatible A frame is composed with Control subframe Network control subframe Schedule control subframe Data subframe

8 IEEE Mesh Mode Frame Formats

9 IEEE Mesh Mode Scheduling mechanism: Centralized Using MSH-CSCH, MSH-CSCF msgs. Distributed Coordinated Uncoordinated –Both using MSH-DSCH msgs. –Mesh Distributed Scheduling messages

10 IEEE Mesh Mode In distributed coordinated mesh mode, each node periodically broadcasts : MSH-NCFG Mesh-Network Config Exchanges the basic parameters between SSs –ID of BS, hop count to BS, number of neighbors, … MSH-DSCH msgs. Mesh-Distributed Scheduling Both using Mesh election algorithm to determined next transmission time.

11 IEEE Mesh Mode The information elements (IEs) of MSH-DSCH msgs. Scheduling IE: Determines the next transmission time of MSH-DSCH msgs. To avoid collision of MSH-DSCH msgs. Request IE: Convey the resources over a link Availability IE: Carry the information of the available resources Grant IE: Convey the confirm information of the resources

12 IEEE Mesh Mode— 3-way Handshake MSH-DSCH: Request Src. sends to dest. along with MSH-DSCH: Availibilities Indicate the empty timeslots of src. Node MSH-DSCH: Grant Dest. Chooses a range of empty timeslots according to MSH-DSCH:request, and, Dest. replies with this msg. MSH-DSCH: Grant Src. Copies the received grant and sends it back to destination node

13 IEEE QoS Classes Four QoS classes Unsolicited Grant Service (UGS) Real-time Polling Service (rtPS) Non-real-time Polling Service (nrtPS) Best Effort (BE)

14 IEEE Mesh Mode – QoS Mesh mode uses CID (Connection ID) to define the service parameters Reliability To re-transmit or not Priority The priority of the connection Drop Precedence When congestion occurs, the likelihood of dropping the packets

15 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Simulations Conclusion

16 Problems QoS provisioning for each class, we need: A Routing Method suitable in distributed mesh mode A way to do admission control The above 2 things are not specified in the standard Our solutions: SWEB (Shortest-Widest Efficient Bandwidth) metrics for routing TAC (Token-bucket based Admission Control)

17 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Simulations Conclusion

18 Related Work In [3], a token-based call admission control and a math model is proposed under IEEE PMP mode The bandwidth of a flow is estimated as

19 Related Work - Token Bucket Mechanism Token bucket parameters Token rate r Bucket size b In time duration t, the output volume of data would be:, at most.

20 Related Work In [7], routing metrics “ETX” is proposed Expected Transmission Count Under ad-hoc networks Forwarding delivery ratio:,reverse delivery ratio: Determined by sending probe packets ETX is calculated as:

21 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Routing Modified 3-way handshake TAC algorithm Simulations Conclusion

22 Routing and CAC algorithms Static Routing is suitable in IEEE mesh networks: Stations do not move or have the minimum mobility Topology and channel conditions do not change severely IEEE d standard does not support mobility Providing QoS of one flow over multiple routes can be in-efficient and difficult

23 Routing To minimize delay and achieve good throughput P i,j : packet error rate of link (i,j) C i,j : Capacity of link (i,j) A bandwidth of a link is Node 1Node 2Node 3Node 4

24 Routing Capacity of all links = C Effective bandwidth Path1 =C*min((1-0.1),(1-0.2),(1-0.1))/2 =0.4*C Path2=0.25C Path3=0.4C Path 3 is preferable. divided by hopCount Path1=0.4C/3 Path3=0.4C/2 S D Path1 Path2 Path3

25 SWEB Routing Routing is done off-line. Path metric= h: hop count SWEB (Shortest-Widest Efficient Bandwidth) Metrics Node 1Node 2Node 3Node 4

26 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Routing Modified 3-way handshake TAC algorithm Simulations Conclusion

27 Modified 3-way handshake To shorten the call setup time, we modified the 3- way handshake Original 3-way handshake:

28 Modified 3-way handshake Original 3-way handshake in a multi-hop environment

29 Modified 3-way handshake

30 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Routing Modified 3-way handshake TAC algorithm Simulations Conclusion

31 Bandwidth Estimation Assume that each flow is controlled by the token bucket mechanism. Each flow reports the parameters when it is initiated: r: token rate b: bucket size d :Delay requirement (for real-time traffics) Using token bucket, the required bandwidth is: Over-estimated.

32 Bandwidth Estimation tt+7f r i *fr i r i t+4f tt+7f r i *fr i r i t+4f S D

33 Bandwidth Estimation t+6f r i *fr i r i r i t+12f t+5f b i r i *fr i r i r i r i t+9ft+6f r i *fr i r i r i t+12f t+5f b i r i *fr i r i r i r i t+9f S D

34 Bandwidth Estimation t+6f r i *fr i r i r i t+12f t+5f r i *fr i r i r i r i t+9f b i/ m i -1 b m i -1 t+6f r i *fr i r i r i t+12f t+5f r i *fr i r i r i r i t+9f S D

35 Bandwidth Estimation We estimate the Max. volume transmitted by a real- time flow in a frame as:,where

36 TAC (Token-bucket Based Admission Control) algorithm Goal: Guarantee delay requirements for real-time flows Avoid starvation To guarantee delay Use the above-mentioned bandwidth estimation. To avoid starvations Set minimum usage of each class: CBR_min, VBR_min, and BE_min.

37 TAC algorithm Concept:

38 TAC algorithm Fields in CID (connection ID) are used to identify QoS levels Priority (3 bits) Reliability (1 bit) Drop Precedence (2 bits) CBR700 CBR_DG401 VBR600 VBR_DG302 BE510 BE_DG213

39 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Simulations Routing TAC Conclusion

40 Simulations Parameters Parameters Frame length = 8 ms Slot capacity = 144 bytes Data timeslots =165 QPSK coding rate =3/4 676 OFDM symbols per frame For CTRL subframe=16 For DATA subframe=660 4 OFDM symbols per slot

41 Simulations Routing Topology 16 nodes 4 km * 4km Radio range = 1.5 km Node 16 is the MBS.

42 Simulations Routing Packet error rate over links: ( in 1/100 )

43 Simulations Routing ETX

44 Simulations Routing Shortest Path

45 Simulations Routing Proposed Routing metrics

46 Simulations Routing Since we primarily focus on VBR traffics, VBR traffics are compared across 3 routing trees. Throughput Delay Jitter The number of each class traffic flow is ranging from 5 to 25.

47 Simulations Routing

48 Simulations Routing

49 Simulations Routing

50 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Simulations Routing TAC Conclusion

51 Simulations parameters Minimum usage: CBR 10 timeslots VBR 40 timeslots BE 75 timeslots Token rate (bps) Bucket size (bits) Delay requirement CBR ms VBR2000k ms BE750k2000--

52 Simulations CAC

53 Simulations CAC WiMaxTAC is added

54 Simulations CAC WiMax TAC is added

55 Outline Introduction Problems Related Work Our Routing and CAC Algorithm Simulations Conclusion

56 Conclusion We proposes a CAC (called TAC) mechanism that guarantee the delay requirements of real-time traffic flows, and Avoid starvations A simple routing metric SWEB that is suitable for IEEE mesh networks A modified 3-way handshake that Reduces call setup time

57 Reference [1]IEEE, “IEEE Standard for Local and metropolitan area networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems”, IEEE standard, October [2] Harish Shetiya and Vinod Sharma, "Algorithms for routing and centralized scheduling to provide QoS in IEEE mesh networks", Proceedings of the 1st ACM workshop on Wireless multimedia networking and performance modeling,WMuNeP '05. Pages: [3] Tzu-Chieh Tsai, Chi-Hong Jiang, and Chuang-Yin Wang, "CAC and Packet Scheduling Using Token Bucket for IEEE Networks", in Journal of Communications (JCM, ISSN ), Volume : 1 Issue : 2, Page(s): Academy Publisher.

58 Reference [4] Fuqiang LIU, Zhihui ZENG, Jian TAO, Qing LI, and Zhangxi LIN, "Achieving QoS for IEEE in Mesh Mode",8th International Conference on Computer Science and Informatics, Salt Lake City, USA [5] Hung-Yu Wei, Samrat Ganguly, Rauf Izmailov, and Zygmunt J. Haas, "Interference-Aware IEEE WiMax Mesh Networks", in Proceedings of 61st IEEE Vehicular Technology Conference (VTC 2005 Spring). [6] Min Cao, Qian Zhang, Xiaodong Wang, and Wenwu Zhu, "Modelling and Performance Analysis of the Distributed Scheduler in IEEE Mesh Mode", Proceedings of the 6th ACM international symposium on Mobile ad hoc networking and computing

59 Reference [7] Douglas S. J. De Couto, Daniel Aguayo, John Bicket, and Robert Morris, “A High-Throughput Path Metric for Multi-Hop Wireless Routing”, ACM MobiCom ’03.