Quality of Service Scheduling for 802.16 Broadband Wireless Access Systems

1. Quality of Service Schedulingfor 802.16Broadband Wireless Access Systems Sih-Han Chen Department of Computer Science and Information Engineering National Taipei University of Technology 2006.11.21

2. Outline • Overview IEEE 802.16 • IEEE 802.16 MAC and QoS • Proposed QoS strategy • Simulation result • Summary and Reference

3. Wireless Technologies Bandwidth IEEE 802.15 IEEE 802.11 IEEE 802.16 3GPP 1 Gbps 802.15.3 High Speed Wireless PAN 100 Mbps Wi-Fi 802.11a/g Wi-Fi 802.11b Wi-MAX 802.16 (802.16-2004 & 802.16e) 10 Mbps 4G 3G 2.5G 1 Mbps 802.15.1 Bluetooth <1m 10m 100m Up to 50Km Up to 80Km PAN LAN MAN WAN PAN: Personal area networks MAN: Metropolitan area networks LAN: Local area networks Wide area networks

4. IEEE 802.16 Operation Mode

5. IEEE 802.16 TDD frame structure

6. DL-MAP and UL-MAP

7. Downlink Subframe Broadcast

8. Uplink Subframe

9. Outline • Overview IEEE 802.16 • IEEE 802.16 MAC and QoS • Proposed QoS strategy • Simulation result • Summary and Reference

10. IEEE Std 802.16 MAC Protocol Layering

11. Service Specific Convergence Sublayer

12. MAC Convergence Sublayer • Functions: • Classification processing of higher-layer PDUs • Delivery to proper MAC SAP • Receives CS PDUs from peer • Two sublayers specified: • ATM convergence sublayer • Packet convergence sublayer Service Specific Convergence Sublayer (CS)

13. ATM Convergence Sublayer • ATM cells mapped to MAC frames • Differentiates Virtual Path switched / Virtual Channel switched ATM connections • Assigns channel ID (CID) • Can perform Payload Header Suppression (PHS)

14. Packet Convergence Sublayer • Used for all packet-based protocols, such as IPv4, IPv6, Ethernet, and VLAN • Similar functions as ATM convergence sublayer, including PHS

15. Defines multiple-access mechanism Functions ： connection establishment connection maintenance Call admission control bandwidth request bandwidth allocation MAC Common Part Sublayer MAC Common Part Sublayer (MPC)

16. Security Sublayer • Two component protocols • Encapsulation protocol for data encryption • Privacy key management (PKM) • describes how the BS distributes keys to client SS Security Sublayer

17. Media Acces Control (MAC) • Connection orienteded • Service Flow(SF) • Connection ID (CID) • Channel access: • UL-MAP • Defines uplink channel access • Defines uplink data burst profiles • DL-MAP • Defines downlink data burst profiles • UL-MAP and DL-MAP are both transmitted in the beginning of each downlink subframe (FDD and TDD).

18. Bandwidth Request • SSs may request bandwidth in 3 ways: • Use the ”contention request opportunities” interval upon being polled by the BS (unicast, multicast or broadcast poll) • Send a standalone MAC message called ”BW request” in an already granted slot • Piggyback a BW request message on a data packet

19. BS grants/allocates bandwidth in one of two modes Grant Per Subscriber Station (GPSS) Grant Per Connection (GPC) Decision based on requestedBW, QoS parameters and available resources Grants are realized through the UL-MAP Bandwidth Allocation

20. Service Classes • Unsolicited Grant Services (UGS): • Constant Bit Rate (CBR) services, • T1/E1 emulation, and Voice Over IP (VoIP) • Real-Time Polling Services (rtPS): • real-time services variable size data packets • MPEG video or VoIP with silence suppression. • Non-Real-Time Polling Services (nrtPS): • Used for delay tolerant traffic requiring some minimum data rate • FTP • Best Effort Services (BE) : • Used for streams with no rate guarantees. • WEB , HTTP

21. QoS mechanisms • Classification • Mapping from MAC SDU fields (e.g destination IP address or TOS field to CID and SFID • Call admission Control • Scheduling • Downlink scheduling module • Uplink scheduling module • No algorithms defined in standard

22. IEEE 802.16 QoS Architecture

23. Call Admission Control in IEEE 802.16 • Admission control • To ensure required QoS is guaranteed while admit a new connection • Assessment of admission connection • Usually use traffic descriptor and effective bandwidth • But… • Traffic descriptors may not reflect the real traffic • Traffic descriptors is very simple (peak rate, avg. rate, etc…) • Users may overestimate their requirements • QoS is uneasy to guarantee

24. Outline • Overview IEEE 802.16 • IEEE 802.16 MAC and QoS • Proposed QoS strategy • Simulation result • Summary and Reference

25. Hierarchical and Distributed QoS Architecture

26. Scheduling Algorithm at BS • Define two types of queue • Type (I) queue • Type (I I) queue • Admission Control • Scheduling Algorithm

27. At BS Scheduling for Type I queue • Type I queue Use for • UGS • Dedicated request opportunities for rtps and nrtps • Guarantee grants to be scheduled without interrupt • First-in First-out (FIFO)，is employed

28. At BS Scheduling for Type II queue • Type II queue Use for • rtPS，nrtPS，and BE • To Guarantee • Minimum bandwidth for each service flow • Fairness to distributing excess bandwidth • To propose a fair queuing algorithm

29. Type II QueueBandwidth Allocation • Grant Per Connection (GPC) • BiMIN：the minimum reserved bandwidth for connection i • BRi：bandwidth currently demanded by the connection

30. Call Admission Control (CAC) • The sum of minimum reserved bandwidth for all the connection should not exceed the available bandwidth B

31. Fairnessto distributing excess bandwidth

32. A Extended Issue • It also can be wasted when ： • Certain of connections don’t need so much bandwidth • Solution： • It allows the empty connection queue to contribute its unused portion to the next round of excess bandwidth allocation

33. Scheduling Algorithm at SS • WHY ? • Due to the large Round Trip Delay (RTD) • Possible collision occurred in the uplink channel • So…BS has only limited or even outdated information about each uplink connection

34. At SS Priority of scheduling service

35. At SS UGS Queue Scheduling • Properties • Critical delay • Critical delay jitter • Firstly guarantee the bandwidth

36. At SS rpPS Queue Scheduling • Properties • Should meet tight delay bound • Each packet of rtPS should be mark a deline • t：arrival time • tolerated delay：Maximum Latency for each service flow • Schedule base on the deadline stamp

37. At SS nrtPS Queue Scheduling • Properties • Target at maintaining throughput • Each packed with a virtual time stamp • When a new packer arrives in，the virtual time must be calculated at first

38. Virtual Time Stamp

39. At SS BE Queue Scheduling • Properties • There is no QoS guarantee required • A simple FIFO mechanisms is applied

40. Outline • Overview IEEE 802.16 • IEEE 802.16 MAC and QoS • Proposed QoS strategy • Simulation result • Summary and Reference

41. Simulation Environment • Used NS2 • PMP MAC operation • TDD-OFDM • One BS and 20 SSs

42. PHY layer parameters

43. The End-to-End Delay

44. The End-to-End Delay (for UGS_1)

45. Compare Delay of rtPS_1 service

46. For rtPSDifferent number of background SS

47. Throughput of nrtPS

48. Outline • Overview IEEE 802.16 • IEEE 802.16 MAC and QoS • Proposed QoS strategy • Simulation result • Summary and Reference

49. Summary • Introduced a hierarchicaldistributed QoS • At BS • Guarantee the minimum bandwidth • Fairness distributing excess bandwidth • At SS • Flexible QoS support four service flow • Reduce the delay of real-time application • Guarantee the throughput of non-real-time application

50. References [1] Sun, J.; Yanling Yao; Hongfei Zhu,“Quality of Service Scheduling for 802.16 Broadband Wireless Access Systems” Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd Volume 3, 2006 Page(s):1221 - 1225 [2] Jayaparvathy, R.; Sureshkumar, G.; Kanakasabapathy, P., “Performance evaluation of scheduling schemes for fixed broadband wireless access systems”,2005 13th IEEE International Conference on Volume 2, 16-18 Nov. 2005 Page(s):6 pp. [3] IEEE 802.16 Standard (2004), "IEEE Standard For Local and Metropolitan Area Networks - Part 16:Air Interface for Fixed Broadband Wireless Access Systems".