Phase Synchronisation the standards and beyond

Transcription

1 Phase Synchronisation the standards and beyond Supporting Your Phase Network Chris Farrow Technical Services Manager 3rd June 2015 Chronos Technology: COMPANY PROPRIETARY

2 Contents Intro Stds overview G focused on greenfield G more pragmatic approach Testing, measuring TE cte dte Summary 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 2

3 Pre-G /06/2015 Chronos Technology: COMPANY PROPRIETARY 3

4 Pre-G /06/2015 Chronos Technology: COMPANY PROPRIETARY 4

5 Pre-G /06/2015 Chronos Technology: COMPANY PROPRIETARY 5

6 G finally 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 6

7 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 7

8 G.811 & G.703 The most widely recognised Telecom sync stds? G.811 sync quality G.703 physical interfaces the ubiquitous 2.048MHz & 2.048MBit/s G.703 has been revised to add phase/time sync interfaces (sect. 17) 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 8

9 Frequency Synchronisation (actually syntonisation) Spinning at the same rate Frequency of clock signals, oscillators (phase relationship is unimportant, although fixed (or at least bounded)) 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 9

10 Frequency Synchronisation (actually syntonisation) In frequency distribution (e.g. SDH) absolute phase is unimportant 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 10

11 Phase Synchronisation (actually synchronisation) Spinning at the same rate, and aligned in phase Frequency & phase of clock signals, oscillators 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 11

12 Phase Synchronisation (actually synchronisation) In frequency & phase distribution (e.g. CDMA-2000) absolute phase is important 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 12

13 Time Synchronisation Spinning at the same rate, and aligned in phase Frequency & phase of clock signals, oscillators and aware of the same time i.e. information is associated with the passing of each cycle or tick 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 13

14 Freq, Phase & Time - Summary Syntonisation: Clocks tick at the same rate Phase Synchronisation: Clocks tick at the same moment ToD Synchronisation: Clocks tick at the same moment & are aware of the same time & date. 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 14

15 ITU G.826x & G.827x series 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 15

16 Time Accuracy requirements Level of Accuracy Range of requirements Typical Applications 1 1 ms 500 ms Billing, Alarms 2 5 µs 100 µs IP Delay monitoring µs - 5 µs 4 1 µs µs 5 6 x ns - 1 µs (x ffs) < x ns (x ffs) LTE TDD (large cell) Wimax-TDD (some configurations) UTRA-TDD, LTE-TDD (small cell) Wimax-TDD (some configurations) Some LTE-A features (ffs 3GPP) 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 16

17 Phase, Time Interval Error (TIE) - ns The Relationship Between Phase & Time ns Freq Offset 1x Freq Offset 1x ns 10ns Elapsed Time - Seconds Freq Offset 1x /06/2015 Chronos Technology: COMPANY PROPRIETARY 17

18 Requirements for phase TDD modulation Frames/Subframes/Timeslots 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 18

19 Cs & Rb in holdover Caesium Stability How long to slip a µs? At 1 x (worst case PRC) it takes 10 5 seconds ~27.78 hours Over 12 years (Cs lifetime) total slip is ~379 x 10 6 seconds x 1 x = 3787µS Rubidium ~1 order of magnitude worse ~2.78 hours [ At would take 10 6 seconds ~11.6 days ] 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 19

20 You can t escape UTC UTC is the global timescale Ensembled from the world s primary National Labs NPL, PTB, NIST etc. Primary freq. stds TAI UTC Referred to as a paper clock Circular-T The easiest, cheapest way to get UTC (k) is probably NTP The most accurate, cost-effective is GPS Somewhere, some backhaul provider/core network will be using GPS 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 20

21 Phase Performance Requirements LTE-A eicic embms CoMP ITU-T G PTP Profile for Phase & Time Delivery full on-path support G PTP Profile for Phase & Time Delivery partial on-path support (assisted 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 24

22 eicic enhanced inter-cell interference co-ordination Macro cell avoids scheduling in or reduces power in protected subframes (ABS vs RPS) Reduced interference from macro cell in protected subframes Advanced Rx in Ue required for range expansion Cell size: Dense urban environment Time alignment: +/-5us required between macro and small cell Latency: No special demands Bandwidth: Low 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 25

23 embms LTE Evolved Multimedia Broadcast Multicast Service embms requires SFN (a la DVB-T) therefore requires ~1μS phase alignment (figures quoted from 1 to 32 μs dependent on implementation ) 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 26

24 CoMP CoMP = Coordinated Multi-Point Transmission and Reception, with two categories: (1) Coherent Joint Processing (JP), aka Network MIMO and (2) Coordinated Scheduling (CS). CoMP - Joint Processing Transmission and/or reception from/to geographically separated antennas. Traffic and control data transfer between enb via X2 interface (logical interface). CoMP - Coordinated Scheduling (CS) Dynamic allocation of air interface resources in overlapping cells. Control data exchange between enb (incl. Pico-eNB) via X2 interface (X2 for control data only). 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 27

25 CoMP Coordinated MulitPoint e.g. UL Joint reception (U1 L1 CoMP) Baseband schedules UEs Radio units receive transmitted data Radios share received data and jointly process it Cell size: Dense urban environment Time alignment: +/-1.5us required between cells Latency: <0.5ms one way Bandwidth: 1Gbps per antenna, internal RBS interface 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 28

26 Supporting the requirements: ITU-T PRTC, T-GM, T-BC & T-TSC specifications ITU-T PTP Profiles for time/phase delivery GNSS/GPS Future PHY enhancements 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 29

27 G.8272 & the PRTC PRC defines frequency source in SONET/SDH PRTC defines Time Source: Timing characteristics of primary reference time clocks 04/06/2015 PRTC= Primary reference Chronos time Technology: clock COMPANY PROPRIETARY 30

28 Telecom Profiles for time & phase G.8275.n 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 31

29 Telecom Profile G Time/Phase distribution Full on-path support (+SyncE) Implies EVERY node is PTP aware, BC initially, could include TC in the future Implies T-GM (master clock only), T-BC and T-TSC (Slave-Only Ordinary Clock). Uses Alternate BMCA. Two-way only, both 1-step & 2-step, 16/s SY & DR Multicast - both non-forwardable & forwardable address C E and 01-1B L ETH 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 32

30 Telecom Profile G (draft 03/15) Time/Phase distribution Partial on-path support Implies only some nodes are PTP aware, e.g. some BCs L3, UDP, Unicast OC only (BC & SyncE allowed options, but outside the scope) Still under discussion, focus has been PRTC time reference, T in f ref (physical layer frequency reference for protection) two-way packet timing signals Packet Master Clock Boundary Clock Packet Slave Clock T out + f ref 04/06/2015 Chronos Technology: COMPANY PROPRIETARY f ref 33

31 Other significant standards G.8260 (definitions) FPP, mintdev, MAFE TE cte & dte Maximum/Minimum/Peak-to-peak average time error (maxate, minate, ppate) Asymmetry 1000/100M at opposing ends BMCA G min reqs for partial timing support assisting GNSS clocks 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 34

32 ITU Time Error Budget: Core to Edge model ±200 ns (network asymmetry compensation) ±200 ns (dynamic time error - PDV) ±200 ns (holdover budget) ±150 ns (enodeb) Standards G.8271 ±50ns Slave clock ±500 ns constant time error ±50 ns per node, 10 BC ±100 ns (PRTC) ±1.5 us end-to-end Time Error Budget PRTC to e.g. ENB 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 35

33 Sync Flow & Network Limits Sync Flow Time error budget calculation Packet Network PTP Slave T-GM T-SC EEC PRTC T-BC EEC T-BC EEC T-BC EEC End Equipment Packet Timing System Possible on geographically small network with few hops and good transport More problematic on geographically large networks with potentially noisy transport, many hops, and complex asymmetry models 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 36

34 Reference Points for Packet Timing Standards G Reference Point A: Network limits as for physical PEC- layer sync chain (EEC, SEC, PEC- SSU or PRC limits) M S-F Reference Point B: Physical Layer Synchronization PTP Packet Network PTP Slave Packet Network timing interface Grandmaster (not currently defined) Reference Point C: Packet timing interface, defined in terms Packet of Timing Floor System Packet Percentage (FPP) Reference Point D: Network limits based on traffic interface (for timing to end application), or physical layer sync chain (for timing to the network) PRC Reference Point A Reference Point B Reference Point C Reference Point D End Equipment 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 37

35 Time Error maxte, cte & dte Standards G For applications that require time/phase alignment, Time Error (TE) is defined Split into 2 components: A fixed component e.g due to link asymmetries in PTP Constant Time Error - cte A varying component e.g. due to PDV in PTP Dynamic Time Error dte 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 38

36 Reference Network Common clock/timescale is GPS GPS TE A TE B TE C TE D UTC PRTC Packet Master (T-GM) Packet Network Packet Slave Clock (T-TSC) End Application Time Clock R1 R2 Simulation Reference Model: Chain of T-GM, 10 x T-BC, T-TSC Time Error TE measured reference points R1 R5 (note R3=R4 if T-TSC is embedded) Typical target requirement TE D < 1.5µS R4 R3 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 39 R5

37 G (draft) Assisted partial timing support slave clock functional model 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 40

38 PHY enhancements xdsl NTR 8kHz reference from ATU-C to ATU-R xpon Modem ranging Standards groups looking at adding phase support to the PHY SG15/Q13 asked Q2 & Q9 for assistance Changed when? Greenfield use? 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 41

39 Summary Standards are changing To provide guidelines for Network Engineering To support service delivery, e.g. LTE-A Phase/Time delivery to meet those requirements provides challenges In the delivery itself In the monitoring/measuring 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 42

40 Thank you for listening Chris Farrow Technical Services Manager Website: 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 43

41 Reference Material Chris Farrow Technical Services Manager Website: 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 44

42 Hybrid techniques & Ensembling, timescales A new philosophy? SyncE for OPS /.2 SyncE as assistance to GPS 04/06/2015 Chronos Technology: COMPANY PROPRIETARY 45