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AN INTEGRATED ROUTING AND DISTRIBUTED SCHEDULING APPROACH FOR HYBRID IEEE 802.16E MESH NETWORKS FOR VEHICULAR BROADBAND COMMUNICATIONS Rahul Amin Electrical and Computer Engineering Clemson University M.S Thesis Defense, 11/25/2008 Advisor – Dr. Kuang-Ching Wang. Outline.

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  1. AN INTEGRATED ROUTING AND DISTRIBUTED SCHEDULING APPROACH FOR HYBRID IEEE 802.16E MESH NETWORKS FOR VEHICULAR BROADBAND COMMUNICATIONS Rahul Amin Electrical and Computer Engineering Clemson University M.S Thesis Defense, 11/25/2008 Advisor – Dr. Kuang-Ching Wang

  2. Outline • Background and Relevant Work • Objective • Network Model • Routing and Scheduling Solution • Analytical Model and Simulation studies • Conclusions and Future Work

  3. Background – WiMAX Operation Modes • WiMAX – Worldwide Interoperability for Microwave Access • IEEE 802.16-2004 • IEEE 802.16e-2005 (Mobile WiMAX) extends mobility (handover) support • Point-to-Multipoint (PMP) • Subscriber Stations (SS) connect via Base Station (BS) • BS in charge of coming up with a transmission schedule • Five Classes of Service defined to support QoS • Mesh • SSs and BSs can communicate directly to other SSs and BSs • Scheduling solution can be centralized or distributed • QoS differentiation is on packet-by-packet basis

  4. Background – PMP Mode Frame Structure • Each frame divided into uplink and downlink sub-frame • Uplink-to-downlink ratio adjusted according to traffic demand • Sub-frame further divided into mini-slots to send data bursts

  5. Background – Mesh Mode Frame Structure • Each frame divided into control and data sub-frame • No uplink or downlink sub-frame distinction • Control sub-frame length depends on length of the mesh

  6. Background – WiMAX Handover Support • Standard Handover • Defined only for PMP mode in IEEE 802.16e-2005 • Each Mobile Station (MS) maintains an up-to-date CINR for target BSs • Either BS or MS can initiate the handover procedure • MS decides the target BS • Two optional fast handover methods • Macro-Diversity Handover (Soft Handover) • Fast Base Station Switching (Hard Handover)

  7. Background – Relevant Work • WiMAX network architecture • Coverage: IEEE 802.16j workgroup (Relay Station Infrastructure) • Link-level performance: [Hartzog 2006] • Last mile Connectivity: [Bennett 2006], [Wongthavarawat 2003] • Mobile Ad Hoc Networks (MANET): [Sherman 2006], [Lebrun 2006] • Scheduling schemes • PMP Mode: [Zhe 2007], [Jayaparvathy 2005], [Lera 2007], [Lin 2008] • Mesh Mode • Centralized: [Wei 2005], [Chen 2006], [Qing 2006] • Distributed: [Cao 2007]

  8. Objective • Challenge – WiMAX requires routing and scheduling packets for rapidly changing network topology due to fast moving vehicles • Goals: • Develop Network Architecture • Routing and Scheduling solution • Throughput performance analysis

  9. Network Model

  10. Network Model Components • Routing • Mobility-Aware Intra-Gateway Routing (MAIGR) • Ad Hoc Routing Protocols and Mobile IP • Scheduling • PMP mode: between MS and MBS/MSS • Mesh mode: among MSS and MBS • Handover • Scheduling options migrate from current BS to target BS

  11. Mesh BS Mobile IP Home/foreign agents IP MAIGR PMP LINK + PHY Mesh LINK + PHY Mesh SS BS Protocol Architecture • Base stations (MBS and MSS) support: – Dual radios (PMP mode, Mesh mode)– Routing: MAIGR • MBS also supports:– Routing: IP and Mobile IP MAIGR PMP LINK + PHY Mesh LINK + PHY

  12. MS Application Transport (TCP, UDP) IP PMP LINK + PHY MS Protocol Architecture • Mobile Station (MS) supports:– Single radio (PMP mode)– Routing: IP – Transport layer protocols– Application specific protocols

  13. Network Operation Base Station Setup All MBSs use existing ad-hoc solutions to reach core network All MSSs find closest path to MBS using MAIGR’s mesh topology discovery phase All BSs (MSS and MBS) come up with initial mesh schedule using centralized mesh scheduler All BSs maintain Mesh Link Capacity for PMP scheduler using the initially derived mesh schedule All BSs use PMP scheduler to communicate with MS Mobile Station Setup MS sets up routes to transmit/receive traffic to/from MBS using MAIGR MS uses PMP scheduler to communicate with MSS/MBS Operational Phase Depending on PMP traffic load at each BS, Mesh scheduler at each BS adapts its schedule PMP scheduling options for a MS migrate to the target BS during the handover procedure Mobile IP used by MBSs to assign care-of address to MS that switches routing zones

  14. Base Station Route Setup Base Station Setup All MBSs use existing ad-hoc solutions to reach core network All MSSs find closest path to MBS using MAIGR’s mesh topology discovery phase All BSs (MSS and MBS) come up with initial mesh schedule using centralized mesh scheduler All BSs maintain Mesh Link Capacity for PMP scheduler using the initially derived mesh schedule All BSs use PMP scheduler to communicate with MS Mobile Station Setup MS sets up routes to transmit/receive traffic to/from MBS using MAIGR MS uses PMP scheduler to communicate with MSS/MBS Operational Phase Depending on PMP traffic load at each BS, Mesh scheduler at each BS adapts its schedule PMP scheduling options for a MS migrate to the target BS during the handover procedure Mobile IP used by MBSs to assign care-of address to MS that switches routing zones

  15. Base Station Route Setup Core Network MSS: Mesh SS MBS: Mesh BS MS: Mobile Station Traditional Ad Hoc Routing Solutions MS S MSS MBS MSS MSS MSS MSS MBS MSS MSS MSH_NCFG: Entry MSH_NCFG: Entry Zone 1 Zone 2

  16. Base Station Scheduler Setup Base Station Setup All MBSs use existing ad-hoc solutions to reach core network All MSSs find closest path to MBS using MAIGR’s mesh topology discovery phase All BSs (MSS and MBS) come up with initial mesh schedule using centralized mesh scheduler All BSs maintain Mesh Link Capacity for PMP scheduler using the initially derived mesh schedule All BSs use PMP scheduler to communicate with MS Mobile Station Setup MS sets up routes to transmit/receive traffic to/from MBS using MAIGR MS uses PMP scheduler to communicate with MSS/MBS Operational Phase Depending on PMP traffic load at each BS, Mesh scheduler at each BS adapts its schedule PMP scheduling options for a MS migrate to the target BS during the handover procedure Mobile IP used by MBSs to assign care-of address to MS that switches routing zones

  17. Base Station Scheduler Setup Core Network MSS: Mesh SS MBS: Mesh BS MS: Mobile Station x 2x 3x 3x 2x x MS S MS S MSS MBS MSS MSS MSS x x x x x x MSH_CSCH: Request MSH_CSCH: Request MSH_CSCH: Grant

  18. Centralized Mesh Scheduling Solution • Interference-aware solution achieving near-optimal throughput [Wei 2005, VTC] • Procedure: • Transmission occurs in order of highest transmission demand • Non-interfering links transmit simultaneously • Proposed changes: • QoS considered • Constraints: • Unidirectional traffic considered x 2x 3x 3x 2x x MS S MS S MSS MBS MSS MSS MSS Carrier Sense Range: 1       Tx Rx Tx Rx

  19. Mobile Station Setup Base Station Setup All MBSs use existing ad-hoc solutions to reach core network All MSSs find closest path to MBS using MAIGR’s mesh topology discovery phase All BSs (MSS and MBS) come up with initial mesh schedule using centralized mesh scheduler All BSs maintain Mesh Link Capacity for PMP scheduler using the initially derived mesh schedule All BSs use PMP scheduler to communicate with MS Mobile Station Setup MS sets up routes to transmit/receive traffic to/from MBS using MAIGR MS uses PMP scheduler to communicate with MSS/MBS Operational Phase Depending on PMP traffic load at each BS, Mesh scheduler at each BS adapts its schedule PMP scheduling options for a MS migrate to the target BS during the handover procedure Mobile IP used by MBSs to assign care-of address to MS that switches routing zones

  20. Mobile Station Setup Core Network MSS: Mesh SS MBS: Mesh BS MS: Mobile Station x 2x 3x 3x 2x x MS S MS S MSS MBS MSS MSS MSS x x x x x x DHCP REQ DHCP REP Service Flow: REQ Service Flow: REP MS

  21. Operational Phase Scheduler Interaction Base Station Setup All MBSs use existing ad-hoc solutions to reach core network All MSSs find closest path to MBS using MAIGR’s mesh topology discovery phase All BSs (MSS and MBS) come up with initial mesh schedule using centralized mesh scheduler All BSs maintain Mesh Link Capacity for PMP scheduler using the initially derived mesh schedule All BSs use PMP scheduler to communicate with MS Mobile Station Setup MS sets up routes to transmit/receive traffic to/from MBS using MAIGR MS uses PMP scheduler to communicate with MSS/MBS Operational Phase Depending on PMP traffic load at each BS, Mesh scheduler at each BS adapts its schedule PMP scheduling options for a MS migrate to the target BS during the handover procedure Mobile IP used by MBSs to assign care-of address to MS that switches routing zones

  22. New Flow Requests UGS ertPS rtPS nrtPS BE Queue Size > Threshold? Pending Connection Queue Empty? No Pending Connection Queue Yes Yes Yes Mesh link limitation? Enough Free Slots Available? No Yes No Active Connection Queue Reject Flow PMP Mode Scheduler Distributed Adaptation Centralized Scheduling Mesh Scheduler PMP Scheduler

  23. Mesh Scheduler Distributed Adaptation (General Case) MS S MS S MS S MS S MSS MSS MBS MBS MSS MSS MSS MSS MSS MSS x x x x x x 0 2x x x x x 0 x 2x 2x 3x 3x 3x 3x 2x 2x x x • Up to x slots can be borrowed in general

  24. Mesh Scheduler Distributed Adaptation(Upper Bound) • Case I: • Borrowing occurs from MSS away from MBS • 2x slots can be borrowed as an upper bound MS S MS S MS S MS S MSS MSS MBS MBS MSS MSS MSS MSS MSS MSS x x x x x x 0 3x 0 x x x x 0 2x 3x 3x 3x 3x 3x 2x 2x x x

  25. Mesh Scheduler Distributed Adaptation(Upper Bound) • Case II: • Borrowing occurs from MSS closer to MBS • x/2 slots can be borrowed as upper bound MS S MS S MS S MS S MSS MSS MBS MBS MSS MSS MSS MSS MSS MSS x x x x x x x x x 1.5x 0 x 1.5x x 1.5x 2x 3x 3x 3x 3x 2x 2x x x

  26. Operational Phase Handover Scenario Base Station Setup All MBSs use existing ad-hoc solutions to reach core network All MSSs find closest path to MBS using MAIGR’s mesh topology discovery phase All BSs (MSS and MBS) come up with initial mesh schedule using centralized mesh scheduler All BSs maintain Mesh Link Capacity for PMP scheduler using the initially derived mesh schedule All BSs use PMP scheduler to communicate with MS Mobile Station Setup MS sets up routes to transmit/receive traffic to/from MBS using MAIGR MS uses PMP scheduler to communicate with MSS/MBS Operational Phase Depending on PMP traffic load at each BS, Mesh scheduler at each BS adapts its schedule PMP scheduling options for a MS migrate to the target BS during the handover procedure Mobile IP used by MBSs to assign care-of address to MS that switches routing zones

  27. Operation Phase Handover Scenario Tactical Network Gateway MSS: Mesh SS MBS: Mesh BS MS: Mobile Station Mobile IP Msg MS S MSS MBS MSS MSS MSS MSS MBS MSS MSS Care-of Address HO_IND Msg MS Zone 1 Zone 2

  28. Analytical Model • Throughput Comparison • centralized only mesh scheduling algorithm • centralized with distributed adaptation algorithm • Topology considered • Symmetric Chain Topology • Single Intersection Topology • Throughput bounds derived for • Dense Network • Sparse Network

  29. Percentage Increase in Network Throughput per Routing Zone (Dense Network) x – q3’ x – q2’ x – q1’ x – q1 x – q2 x – q3 Link 3’ MSS 3’ MSS 2’ Link 2’ MSS 1’ Link 1’ MBS Link 1 MSS 1 Link 2 MSS 2 Link 3 MSS 3 x 2x 3x 3x 2x x Case I: Case II:

  30. Percentage Increase in Network Throughput per Routing Zone (Sparse Network) 0 x-q2’ 0 0 0 0 Link 3’ MSS 3’ MSS 2’ Link 2’ Link 1’ MBS Link 1 MSS 1 Link 2 MSS 2 Link 3 MSS 3 MSS 1’ x 2x 3x 3x 2x x Case I: Case II:

  31. Simulation Studies • Network Simulator ns-2 used • Based on NIST IEEE 802.16 module (version pre-release2) • Supports PMP mode, standard handover • Scheduler functionality added • Extension made to support: • TDD mesh links between base stations (emulated with wired links) • Dual radios at each base station • Chain topology presented • Carrier sensing range equal to communication range assumed • Analytical Model verified using simulation results

  32. Mesh Mode Simulation Parameters

  33. Simulation Model – Dense Network Internet Sink Tactical Network Gateway MSS 0 28 MSS 1 56 MSS 2 84 MBS 84 MSS 3 56 MSS 4 MSS 5 28 28-4 28-12 28-12 28-12 28-12 28-12 28-12 MS MS MS MS MS MS MS MS MS 2 * 0.64 Mbps UGS Flows per MS (16 Data Slots) . .

  34. Simulation Results – Dense Network (Stationary) Centralized Scheduling Only Distributed Adaptation Scheduling

  35. Simulation Model – Sparse Network Internet Sink Tactical Network Gateway MSS 0 28 MSS 1 56 MSS 2 84 MBS 84 MSS 3 56 MSS 4 MSS 5 28 28-4 0 0 0 0 0 MS MS MS 1 * 0.64 Mbps UGS Flow per MS (8 Data Slots) MS MS

  36. Simulation Model – Sparse Network Internet Sink Tactical Network Gateway MSS 0 28 MSS 1 56 MSS 2 84 MBS 84 MSS 3 56 MSS 4 MSS 5 28 0 28-4 0 0 0 0 MS MS MS 1 * 0.64 Mbps UGS Flow per MS (8 Data Slots) . . .

  37. Simulation Results – Sparse Network (Stationary)

  38. Conclusions • The network architecture simplifies scheduling re-computation by only involving base-stations as opposed to a complete ad-hoc solution • Distributed adaptation does not increase the throughput significantly under dense network conditions (~8.2 %) due to the inability of neighboring BSs to lend slots • Distributed adaptation increases throughput significantly under sparse network conditions (~ 232 %)

  39. Future Work • Different topologies such as grid topology need to be studied • Borrowing from 1-hop neighbor only is not optimal and studies needs to be expanded to determine the performance improvement if borrowing from multi-hop neighbors is allowed

  40. Thank You

  41. Backup - Routing Partitions

  42. Mobility-Aware Intra-Gateway Routing • Mesh Topology discovery • Each Mesh BS sends a flooding message at periodic intervals • Each Mesh SS records the next hop towards the closest Mesh BS • Packet Forwarding from Mesh BS to MS • At serving BS, the next hop is the connection identifier (CID) of MS’s data connection established during network entry or handover • At non-serving BS, the next hop is a mesh link CID which is obtained in one of two ways • When receiving a packet from neighboring BS forwarded by an unknown MS, record the neighboring BS as next hop to the unknown MS • When notified of a handover of currently associated MS, record target BS as next hop to MS • Packet Forwarding from MS to Mesh BS • At MS, the next hop is always the CID of currently serving BS’s data connection • At subsequent Mesh SS’s, the next hop is the mesh link CID towards the closest Mesh BS obtained during Mesh Topology discovery phase

  43. Scheduling Solution • PMP Mode Scheduling • Order determined according to service classes (UGS, ertPS, rtPS, nrtPS, BE) • Same service classes are serviced in FIFO order • Mesh Mode Scheduling • Centralized interference-awaresolution • Transmission occurs in order of highest transmission demand [Wei] • Distributed Adaptation • Need-based borrowing

  44. Mesh Mode Scheduler • Initial schedule using centralized algorithm • Upon network deployment • Every time BS is added to the mesh • Uses average traffic load information if available, else assumes uniform traffic distribution • Distributed adaptation copes with changes in traffic loads • Whenever pending queue length exceeds predefined threshold • Slots borrowed from immediate (1-hop) neighbors • Three-way handshake technique used

  45. Distributed Adaptation

  46. Centralized Algorithm

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