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LTE: Schedulers. Содержание  Место планировщика в архитектуре  Функции планировщика  Виды планировщиков 2.

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Presentation on theme: "LTE: Schedulers. Содержание  Место планировщика в архитектуре  Функции планировщика  Виды планировщиков 2."— Presentation transcript:

1 LTE: Schedulers

2 Содержание  Место планировщика в архитектуре  Функции планировщика  Виды планировщиков 2

3 LTE protocol architecture 3

4 Packet scheduling model 4  Channel-Quality Indicator  Inner Loop Link Adaptation (fast) chooses MCS (СКК)  Outer Loop Link Adaptation (slow)  Automatic Repeat-reQuest

5 Time-frequency scheduling 5  Physical Downlink Control Channel  Physical Resource Blocks  Discontinuous Reception (DRX)

6 Frame (bandwidth 1.4 MHz, 6 PRBs, 72 subcarriers) 6 ―cell-specific Reference Signal ― Primary Synchronization Signal ―Secondary Synchronization Signal ―Physical Broadcast Channel ―Physical Hybrid ARQ Indicator Channel ―Physical Control Format Indicator Channel ―Physical Downlink Control Channel ―Unused by selected antenna port

7 Quality Metrics 7  Throughput  Fairness  Packet Loss Rate, %  Scheduling cost (memory, time, etc.) X i - is the throughput for the i-th connection

8 Schedulers  Proportional Fair (PF)  Maximum Rate (Maximum Throughput)  Round Robin (RR)  Joint Time and Frequency domain schedulers  Throughput to Average (TTA)  Buffer-aware schedulers  Modified Largest Weighted Delay First (MLWDF)  Exponential Proportional Fair (EXP-PF)  EXP-LOG Rule  Frame Level Scheduler (FLS) 8

9 RR, PF, Maximum rate 9

10 TTA 10  Throughput To Average

11 Simulation scenario 11

12 MT, PF, PF-PF, TTA - Throughput 12

13 MT, PF, PF-PF, TTA - Fairness 13

14 Scheduler with buffer estimation  Следующие планировщики учитывают задержку пакетов, переполнение буфера 14

15 MLWDF 15  Modified Largest Weighted Delay First D hol is the head-of-line (HOL) delay of user i a time t δ Acceptable packet loss rate for i-th user τ i threshold delay of the i-th user MLDWF prioritizes the user with higher HOL packet delay and better channel conditions relative to its average levels.

16 EXP-PF 16  Exponential Proportional Fair N tr is the number of active real time flows

17 LOG-RULE 17  Log Rule a i, b i, c are tunable parameters

18 EXP-RULE 18  Exponential Rule

19 FLS  Frame Level Scheduler 19  Выбираем простым алгоритмом пользователей для 1 кадра (10мс). Используем PF  Производим распределение по блокам уже внутри кадра. Используем MT

20 PF, MLWDF, EXP-PF, EXP-LOG Rule - Throughput 20 + each user receives three downlink flows (one video, one VoIP, and data).

21 PF, MLWDF, EXP-PF, EXP-LOG Rule - PRL 21 Packet Loss Rate

22 Литература 1.4G LTE and LTE-Advanced for Mobile Broadband 2.LTE for UMTS - OFDMA and SC-FDMA Based Radio Access (2009) 3.Downlink Packet Scheduling in LTE Cellular Networks: Key Design Issues and a Survey 4.3GPP LTE Downlink Scheduling Strategies in Vehicle-to-Infrastructure Communications for Traffic Safety Applications 5.Comparative Performance Study of LTE UplinkSchedulers 6.B. Sadiq, R. Madan, and A. Sampath, “Downlink scheduling for multiclass traffic in lte,” EURASIP J. Wirel. Commun. Netw., vol. 2009, pp. 9–9,

23 QoS в LTE 23

24 Downlink Scheduling in LTE [8]. Part II  New schedulers: 24 Multi-QoS aware Fair [1] Game Theory and Token Mechanism [2] Delay-Prioritized (DPS) [3] Best Effort and VoIP [4] VoIP [5] Priority Set Scheduling [6]

25 Multi-QoS aware Fair. TDPS [1] 25 Flows GBR Non-GBR QoS1class QoS2class priority -Accumulated data rate -Instantaneous bearer data rate at n-th TTI -Smoothing factor

26 Multi-QoS aware Fair. FDPS [1] 26 1)GBR QoS1class: Max SINR Check: Ue buffer full or GBR achieved 2)Non-GBR metric: Max SINR yes next Ue Each iteration everyone get one RB

27 Game Theory and Token Mechanism [2] 27 Sharply value – every flow get resources based on its contribution. TD (Proportional Fair) -Token queue length -Arrival rate of tokens (depends on flow) FD

28 Delay-Prioritized (DPS) [3] 28 For real time traffic Select max SINR for k-th Ue, update PRBs remain? Yes -Delay threshold -HOL delay

29 Best Effort and VoIP. TDPS [4] 29 -Required activity (depending on the traffic) -Incremented every TTI and reset to 0 every time, Ue n is scheduled -Delay sensitivity, determines traffic priorities -Number of Ue after TDPS (parameter)

30 Best Effort and VoIP. FDPS [4] 30 Proportional fair scheduled (PFsch)

31 VoIP [5] 31 The limit of VoIP priority mode is adaptively changed between min and max according VoIP packet drop ratio.

32 VoIP experiment [5] 32

33 Priority Set Scheduling. TDPS [6] 33 Flows Below-GBR Other priority -Past average throughput of Ue n. -Instantaneous bearer data rate at n-th TTI (BET) (PF) T- time window (99 lena) Take N Ue

34 Priority Set Scheduling. FDPS [6] 34 -Is an estimate of the user throughput if user was scheduled every sub frame

35 Scheduling input parameters 35 NameRequested bitrate Average datarate Queue sizeMax delay HOL 1XX 2XX 3XX 4XXX 5X 6XX

36 Scheduler in LENA 36 Allocation bitmap which identifies RBs SCHEDULER Data Control Indication (DCI) Modulation and Coding Scheme (MCS) MAC Transport Block (TB) size

37 Transmit operations in downlink 37

38 Usage  If you want to use PSS scheduler in project: Ptr lteHelper = CreateObject (); lteHelper->SetSchedulerType ("ns3::PssFfMacScheduler"); lteHelper->SetSchedulerAttribute("nMux", UIntegerValue(yourvalue)); the max num of UE selected by TD scheduler  Guarantee Bit Rate (GBR) or Maximum Bit Rate (MBR) can be configured in epc bearer respectively enum EpsBearer::Qci q = EpsBearer::yourvalue; // define Qci type GbrQosInformation qos; qos.gbrDl = yourvalue; // Downlink GBR qos.gbrUl = yourvalue; // Uplink GBR qos.mbrDl = yourvalue; // Downlink MBR qos.mbrUl = yourvalue; // Uplink MBR EpsBearer bearer (q, qos); lteHelper->ActivateEpsBearer (ueDevs, bearer, EpcTft::Default ()); 38

39 Ns-3 experiment 39  1 eNB  50 Ues  Radius 5000 m  Pathloss Model – FriisSpectrumPropagationLossModel  Time 10 sec  Traffic GBR_VOICE  Bandwidth 25 PRB System throughput Mbit/s PF - 12 PSS PSS

40 New Directions  Carrier Aggregation A broader spectrum utilization  Multi-User MIMO Same RB to different users  Coordinated Multi-Point Transmission Coordinating and synchronization among different eNBs  Scheduling in Heterogeneous Networks Inter-cell interference management by means of dynamic spectrum access 40

41 References  [1]Y. Zaki, T. Weerawardane, C. Gorg, and A. Timm-Giel, “Multi-QoS-Aware FairScheduling for LTE”, in Proc. IEEE Veh. Tech. Conf., VTC-Spring, May  [2]M. Iturralde, A. Wei, and A.Beylot, “Resource Allocation for Real Time Services Using Cooperative Game Theory and a Virtual TokenMechanism in LTE Networks,” in Proc. IEEE Personal IndoorMobile Radio Commun., PIMRC, Sydney, Australia, Jan  [3]K. Sandrasegaran, H. A. Mohd Ramli, and R. Basukala, “Delay-Prioritized Scheduling (DPS) for Real Time Traffic in 3GPP LTE System,” in Proc. IEEE Wireless Commun. And Net. Conf., WCNC, Apr  [4]G. Monghal, D. Laselva, P. Michaelsen, and J. Wigard, “Dynamic Packet Scheduling for Traffic Mixes of Best Effort and VoIP Users in E-UTRAN Downlink,” in Proc. IEEE Veh. Tech. Conf., VTC-Spring,Marina Bay, Singapore, May  [5]S. Choi, K. Jun, Y. Shin, S. Kang, and V. Lau, “MAC Scheduling Scheme for VoIP Traffic Service in 3G LTE,” in Proc. IEEE Veh. Tech. Conf., VTC-Fall, Baltimore, MD, USA, Oct  [6] G.Mongha, K.I. Pedersen, I.Z. Kovacs, P.E. Mogensen, " QoS Oriented Time and Frequency Domain Packet Schedulers for The UTRAN Long Term Evolution", In Proc. IEEE VTC, 2008  [7]http://lena.cttc.es/manual/index.htmlhttp://lena.cttc.es/manual/index.html  [8]F. Capozzi, G. Piro, L.A. Grieco, G. Boggia, P. Camarda, “Downlink Packet Scheduling in LTE Cellular Networks: Key Design Issues and Survey.” 41


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