LTE RESOURCE Scheduling (HUAWEI) .pptx

LTE RESOURCE Scheduling (HUAWEI) .pptx

1. Page Revision Record Don’t Print This Page Course Code Product Product Version C ourse V ersion ISSUE OEO107040 LTE eRAN6.0 1.00 Developer/Modifier Time Approver New/ Update Yuan Shuai 2013-3 Zhu Dianrong Update from eRAN3.0

2. LTE eRAN6.0 Scheduling Feature

3. Objectives Upon completion of this course, you will be able to: Describe scheduling mechanism in eNodeB Describe the details for DL and UL scheduling Describe the scheduling enhancement in eRAN6.0 Monitor scheduling statistic in M2000 Page 2

4. Contents Scheduling Overview Downlink Scheduling Feature Uplink Scheduling Feature Relevant Monitoring Page 3

5. Scheduling Functionality Scheduling Function: Ensure high spectrum high spectral efficiency while providing the required. Page 4

6. Scheduling Scheme Page 5

7. Scheduler Introduction The scheduler is located at the MAC layer of LTE system Function: Guarantee system signaling sending Ensure QoS requirements Take user differentiation and fairness into account Maximize the system throughput Page 6

8. Scheduling Execution DCI/UCI info for scheduling Resource allocation header: indicate allocation type Resource assignment block MCS (Modulation Coding Scheme) MIMO scheme NDI( New Data Indication) HARQ process number Page 7 DCI info

9. Contents Scheduling Overview Downlink Scheduling Feature Uplink Scheduling Feature Relevant Monitoring Page 8

10. Contents Downlink Scheduling 2.1 Scheduling Priority Processing 2.2 MCS Selection & Resource Allocation Page 9

11. DL Scheduler Page 10 DL Scheduler Channel Quality HARQ feedback QoS parameters UE Capability Selected UE RB number MCS/MIMO Every scheduling period Priority calculation MCS selection Resource allocation

12. DL Scheduling Priority Page 11

13. Control Information Scheduling Common control information: Include SIBs, paging and RA response message Dedicated control information: Include SRB0, SRB1, SRB2. Generally, control information has higher priority than user plane data, it uses fixed lower phase MCS to ensure the quality. IMS signaling is a special user plane data which has the same priority and mechanism as SRB1 and SRB2 Page 12

14. DL Retransmission Scheduling DL retransmission adopts synchronized HARQ process, the minimal delay is 8 ms and maximum delay is 8+DrxReTxtimer ms Priority handling: Based on the waiting time, eNdoeB determine the priority for retransmission. MCS selection & resource allocation: the same mechanism as initial transmission. eNodeB stop scheduling when retransmissions for all UEs are complete or all resources are allocated. Page 13

15. Constraint of HARQ Retransmission HARQ retransmissions cannot be performed for a UE in any of the following scenarios: The UE is in a measurement gap or enters a measurement gap The UE enters sleep time in DRX The UE is not synchronized with the eNodeB or a radio link failure (RLF) occurs Page 14

16. DL Initial Transmission Scheduling Page 15 Schedule users according to prio until until all RBs used up Frequency Selective Scheduling - Sub band CQI Non-Frequency Diversity Scheduling - Wide band CQI MCS Selection Resource Allocation Remove users which are In measurement gap In DRX mode Out of synch R emove the beares which are: Experience HARQ scheduling Fulfills GBR Fulfills AMBR Of the remaining (EPF) GBR - CQI, PDB, GBR (QCI) Non-GBR - CQI, AMBR, Min_GBR, QCI By AMC mechanism, eNodeB selects appropriate MCS to maximum system throughput. Screen users/ bearers Priority Calculation

17. Scheduling Strategy for Initial Transmission Page 16 Scheduling Strategy Effect Factor Scheduling Priority Application Scenario Max C/I Channel quality The UE with better channel quality has a higher priority in scheduling. To verify the maximum system throughput RR None Each UE has equal opportunity to be scheduled. To verify the upper limit of scheduling fairness PF Service rate and channel quality The UE with a small ratio between the service rate and channel quality has a higher priority in scheduling. To verify the system throughput and fairness EPF Service rate, channel quality, UE capability, and QoS requirement Intergraded priority with service rate, UE category, QoS and CQI. In operating networks

18. Priority of GBR Service Scheduling The priority of GBR service is determined by the following formula: f(CQI): indicates the channel quality. f(delay): indicate packet delay budget which is specified in 3GPP Page 17

19. Priority of Non-GBR Service Scheduling The priority of non-GBR service is determined by the following formula: eff : Indicates the channel quality Alpha: indicates the capacity adjustment factor for EPF (eRAN6.0 enhancement) r: indicates the historical number of transmitted bits for the UE per unit of time : indicates scheduling priorities corresponding to different QCIs f(delay): indicates the delay for the service to wait for scheduling on the eNodeB side. Using a delay factor, the eNodeB converges multiple DL data packets before sending them, which helps shorten the transmission delay of the non-GBR service packets. (eRAN6.0 enhancement) Page 18

20. Capacity Factor (eRAN6.0 Enhancement) Introduce a capacity factor to adjust the cell throughput and edge throughput. Factor > 1: More RBs tend to be allocated to the higher SINR UE. The larger factor is, the higher cell total throughputs. Factor =1: Default setting. RBs tends to be allocated fair. Factor <1: More RBs tend to be allocated to the lower SINR UE to increase cell edge performance. Page 19

21. DL Non-GBR Packet Bundling (e RAN6.0 Enhancement) Background: Many small packet traffic occupy more control channel resources and decrease cell capacity Page 20 CCE CCE CCE Packet1 Packet2 Packet3 PDCCH Converge CCE CCE CCE saved Packet1 + Packet2 + Packet3 RB assigned once Based on delay control

22. QoS Guarantee GBR services take precedence over non-GBR services if both services are running simultaneously, because non-GBR services have a lower priority than GBR services. Scheduler can ensure the PELR and PDB as well as the service rate for GBR services. Scheduler can ensure only the PELR for non-GBR services and uses a best-effort policy in terms of the non-GBR service rates Page 21

23. Enhanced Proportion for Non-GBR When the Uu resources of a cell are congested, there is a possibility that non-GBR services cannot be allocated resources if there is a larger proportion of GBR services in the cell. Huawei allows operators to set the following parameters to address this issue: NonGbrResourceRatio : This parameter specifies the preset proportion of time-domain resources reserved for non-GBR services. (eRAN6.0 enhancement) DLminGbr : This parameter specifies the minimum service rate for non-GBR services. Page 22

24. Enhanced Proportion for Non-GBR ( Cont .) In congestion scene, Non-GBR service will be starving The priority of Non-GBR service is lower than GBR service. Page 23 0K time 100K Throughput (bps) Non- GBR GBR Normal Congestion Non-GBR is starving GBR Non- GBR 0K time 100K Throughput (bps) Non- GBR GBR Normal Congestion Non-GBR avoid starvation GBR Non- GBR Non-GBR service should be protected when cell congestion. Resource reservation for non-GBR services

25. Relevant Configuration Page 24

26. Relevant Configuration ( Cont .) Page 25

27. Contents Downlink Scheduling 2.1 Scheduling Priority Processing 2.2 MCS Selection & Resource Allocation Page 26

28. MCS Selection The eNodeB obtains the I TBS according to the adjusted CQI.( eNodeB internal mapping ) If frequency diversity scheduling is used, UE will adopt full band CQI report If frequency selective scheduling is used, UE will adopt sub_band CQI report If CQI adjustment is enabled, the eNodeB adjusts the CQI reported by the UE and selects an MCS based on the adjusted CQI, otherwise eNodeB use the original UE CQI report The eNodeB selects I MCS according to the mapping from I TBS to I MCS. ( Specified in 3GPP) For the handover in UE, eNodeB use fixed MCS to ensure the quality until eNodeB receives the valid CQI report Page 27

29. Classification CQI Report Regarding the delivery channel: Periodic CQI report: Delivered by PUCCH, the period is configured by RRC Aperiodic CQI report: Delivered by PUSCH Regarding report bandwidth: Wide bandwidth CQI report: Reflect DL quality for whole band Sub_band CQI report: Reflect DL quality for some sub_bands , For 1.4 MHz bandwidth, it only supports wide band CQI report Page 28

30. CQI Adjustment The UE-reported CQI cannot always reflect the actual channel quality. Consider the following situations: The CQI reporting period is far greater than the scheduling period, which leads to a difference between the CQI at the reporting time and the CQI at the scheduling time CQI report will be delayed due to the transmission delay and eNodeB process capability, If the CQI reporting delay is longer than the channel coherence time, the CQI reported by the UE is inconsistent with the channel quality at the time of scheduling. Page 29

31. CQI Adjustment ( Cont .) If CqiAdjAlgoSwitch is set to Off, the DL CQI adjustment algorithm is not used. The scheduler selects an MCS based on the reported CQI. If CqiAdjAlgoSwitch is set to ON, eNodeB adjusts the reported CQI, make the IBLER convergent with the target. Page 30

32. IBLER Target The IBLER target could be adjusted by eNodeB If DlVarIBLERtargetSwitch is set to OFF, eNodeB adopts 10% as IBLER target If DlVarIBLERtargetSwitch is set to ON, eNodeB adopts 30% as IBLER target Page 31

33. RB Calculation & Allocation RB calculation: The scheduler obtains the amount of data to be scheduled and the I TBS and estimates the number of RBs to be scheduled based on the 3GPP specification Based on estimate RB number and remaining power, eNodeB finally decide the RB number RB allocation: If frequency diversity scheduling is used, eNodeB allocate all the RB from lower end to the higher end of a frequency band based on full band CQI report If frequency selective scheduling is used, eNodeB schedules the UEs to frequency bands with the optimum channel quality. This brings frequency selective gains. Page 32

34. Frequency Selective Scheduling Scheme Required aperiod sub_band aperiod CQI report Calculate user’s priority in each sub-band with user queue Allocate the resource in each sub-band based on user queue Page 33 UEn UEn UEn UE1 UEn UE2 … 1 RBG or 1 subband UE2 UE1 UE1 10 9 8 13 6 5 … 6 12 12 8 6 6 5 8 … 10 11 13 10 11 10 7 5 … 9 10 … … UE2 UEn

35. FSS VS FDS Page 34 FSS FDS

36. Contents Scheduling Overview Downlink Scheduling Feature Uplink Scheduling Feature Relevant Monitoring Page 35

37. Contents Uplink Scheduling 3.1 Scheduling Priority Processing 3.2 MCS Selection & Resource Allocation Page 36

38. UL Scheduling Overview Scheduling on the uplink is more difficult than on the downlink Limited visibility of quantity of queued data per radio bearer Scheduler is unable to offer per-radio bearer grants Page 37 UL data UL grant (On PUCCH) Scheduling Request BSR & PHR ( OnPUSCH ) Periodic or Event triggered UE eNodeB Scheduling among UEs Logical Channel Prioritization & Multiplexing

39. UL Scheduler in eNodeB Page 38

40. UL Scheduling Flow Page 39

41. UL Scheduling Resource Acquisition The PUSCH occupies the available UL resources in addition to PUCCH and PRACH resources in the UL bandwidth The PUCCH occupies RBs at two ends of a cell bandwidth, and the number of RBs depends on the resources used to carry information on the PUCCH. The PRACH periodically occupies 6 RBs at an interval specified by a related parameter. Continuous UL resources are allocated and the number of allocated RBs is, where,, andare not minus integers. Page 40

42. Pre-reserved Resource on PUSCH The following resource should be reserved on PUSCH: Msg3 transmission: Msg3 is a special message during the random access, to ensure the receiving performance, eNodeB adopts the fixed MCS for transmission. SRS: Sounding reference signal occupies the last symbol on PUSCH, the period of SRS is configurable. Page 41

43. Synchronized UL Retransmission Page 42

44. Control Plane Data Scheduling Similar as downlink, UL control plane data consists of SRB0,SRB1,SRB2 and IMS signaling Fixed MCS will be adopted to ensure receiving performance Page 43

45. Initial Transmission Scheduling eNodeB scheduler determines the priority of each UE and ensure the QoS for UE level. If multiple QCIs exists in UE, then UE scheduers determine the priority and QoS for each QCI Page 44

46. QoS Guarantee in eNodeB QoS guarantee Guarantee the bit rate requirement for GBR services with specific logic channel group Enforce the Aggregate Maximum Bit Rate for Non-GBR services. Minimum Bit Rate is set for Non-GBR services to avoid starvation Page 45 Adopt token bucket algorithm to guarantee the QoS

47. Priority in eNodeB Scheduler After QoS elimination, eNodeB determines the priority with the following formula: eff : Indicates the channel quality, evaluated by SRS measurement in eNodeB r: indicates the historical number of transmitted bits for the UE per unit of time alpha: indicates the capacity adjustment factor for EPF, same as DL scheduling : indicates the priority weight for each QCI, similar as DL scheduling Page 46

48. Priority in UE Scheduler Page 47 Logical Channel Type PBR Configuration Priority QCI 1 8 kbyte /s Not configurable QCI 2 to QCI 4 Configurable Not configurable QCI 5 8kbyte/s Not configurable QCI 6 to QCI 9 Configurable Configurable

49. UL Preallocation Scheduling Benefit: eNodeB proactively allocate resource to UE so that latency could be reduced. After GBR or min-GBR is guaranteed, if there is still remaining resource, then preallocation could be performed for the UE with unsatisfied AMBR under the following scenarios: The UE is not scheduled within the current TTI. Preallocation weight is more than 0 The UE meets the requirement for the minimum interval between preallocations Page 48

50. Classification of Preallocation There are two preallocation mode in eNodeB Normal preallocation : Not supported for DRX status Smart preallocation : Support UE in DRX status. (eRAN6.0 enhancement) Page 49

51. Relevant Configuration Page 50

52. Relevant Configuration ( Cont .) Page 51

53. Contents Uplink Scheduling 3.1 Scheduling Priority Processing 3.2 MCS Selection & Resource Allocation Page 52

54. MCS Selection The process of determining MCSs for UL scheduling consists of three parts: SINR adjustment, initial MCS selection, and MCS adjustment Page 53 SINR adjustment IBLER measurement SRS measurement IBLER target Adjusted SINR Initial MCS selection Whether message 3 is transmitted on UL MCS adjustment SRS transmission UCI transmission UE capability Final MCS

55. SINR Adjustment The SINR adjustment scheme is adopted to adjust the SINR reported by the physical layer in order to correct the SINR measurement errors. Page 54

56. Resource Allocation The following info are required to determine number of RB Buffer report from UE Power headroom report from UE QoS satisfaction rate UE capability: Maximum data volume in each TTI Page 55

57. Contents Scheduling Overview Downlink Scheduling Feature Uplink Scheduling Feature Relevant Monitoring Page 56

58. Scheduled User Statistic Monitoring Page 57

59. UE MCS/PRB Monitoring Page 58

60. Summary The functionality of scheduling Scheduling flow for DL and UL. Enhanced EPF scheduling in eNodeB . Page 59

61. Abbreviation BSR: Buffer Status Report CQI: Channel Quality Index EPF: Enhanced Proportional Fairness MCS: Modulation Coding Scheme PF: Proportional Fairness PHR: Power Headroom Report RR: Round Robin SINR: Signal Interference Ratio SR: Scheduling Request Page 60