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Routing and Admission Control in IEEE 802.16 Distributed Mesh Networks

Routing and Admission Control in IEEE 802.16 Distributed Mesh Networks. Tzu-Chieh Tsai Dept. of Computer Science National Chengchi University Taipei, Taiwan. Outline. Introduction Problems Related Work Our Routing and CAC Algorithm Simulations Conclusion. Outline. Introduction

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Routing and Admission Control in IEEE 802.16 Distributed Mesh Networks

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  1. Routing and Admission Control in IEEE 802.16 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 802.16 Mesh Mode • Problems • Related Work • Our Routing and CAC Algorithm • Simulations • Conclusion

  4. Introduction—Wireless Mesh Networks

  5. Introduction—Wireless Mesh Networks • Ad-hoc network basis • Self organization • Fault tolerance • Scalability • Lower infrastructure cost • Wider coverage • Standard activities • 802.11s (in progress) • 802.15.5 (in progress, mainly in PHY) • 802.16 • Mesh mode is already included in standards.

  6. IEEE 802.16 mesh mode

  7. IEEE 802.16 mesh mode • 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 802.16 Mesh Mode Frame Formats

  9. IEEE 802.16 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 802.16 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 802.16 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 802.16 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 802.16 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 802.16 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 802.16 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 802.16 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 802.11 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 802.16 mesh networks: • Stations do not move or have the minimum mobility • Topology and channel conditions do not change severely • IEEE 802.16d standard does not support mobility • Providing QoS of one flow over multiple routes can be in-efficient and difficult

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

  24. 0.2 0.1 Path1 0.1 0.5 0.5 S D Path2 0.2 0.2 Path3 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

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

  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. t+4f t+4f t t t+7f t+7f r r *f *f r r *f *f r r *f *f i i i i i i S D Bandwidth Estimation

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

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

  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

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

  40. SimulationsParameters • 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. SimulationsRouting • Topology • 16 nodes • 4 km * 4km • Radio range = 1.5 km • Node 16 is the MBS.

  42. SimulationsRouting Packet error rate over links: ( in 1/100 )

  43. SimulationsRouting • ETX

  44. SimulationsRouting • Shortest Path

  45. Proposed Routing metrics SimulationsRouting

  46. SimulationsRouting • 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. SimulationsRouting

  48. SimulationsRouting

  49. SimulationsRouting

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

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