Non-Packet Time-of-Day Distribution

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1 Non-Packet Time-of-Day Distribution Presented to: WSTS 2011 Session 2 Telcordia Contact: Tom Bowmaster Principal Analyst Advanced Technology Solutions tbowmast@telcordia.com May 10,

2 What Do You Mean By Non-Packet? ToD distribution methods other than NTP or PTP Possibilities include IRIG DTI ASCII-based time code Includes proprietary and NMEA 0183 With or without a separate 1-pps signal PTTI Others? 2

3 Applications Likely to be used for intra-location ToD distribution GPS unit to equipment that needs ToD GPS-based PRS to ToD-capable BITS TSG GPS unit to (stratum 1) NTP server ToD-capable BITS TSG to collocated NEs requiring ToD 3

4 IRIG Defined in Range Commanders Council (RCC) IRIG Standard , IRIG Serial Time Code Formats Family of serial time code formats that differ in Pulse rates Form designations (physical coding) Carrier frequencies Particular information that is communicated Formats are designated by a letter and a string of three numbers (e.g., IRIG B122) 4

5 IRIG Pulses Pulse rates 1 pulse per minute ( D ) 1 pps ( H ) 10 pps ( E ) 100 pps ( B ) 1,000 pps ( A ) 10,000 pps ( G ) Each pulse corresponds to a time code bit Pulse width determines whether that bit is a 0 (0.2 1/pulse rate) 1 (0.5 1/pulse rate) Reference or Position Identifier (0.8 1/pulse rate) 5

6 IRIG Form Designations DC Level Shift (DCLS, designated 0) Amplitude modulated sine wave carrier (1) Amplitude of a pulse is equal to 3 to 6 times the amplitude of the inter-pulse signal Modified Manchester modulated (2) Ten Manchester coded sub-bits per pulse period The width of the pulse indicated by setting the first two, five or eight of those sub-bits to ones Modification has to do with which edge is on time Rising (1) or falling (0) edge at the start of the sub-bit time period instead of in the middle Not applicable for the three slowest pulse rates (D, H, E) 6

7 IRIG Physical Coding Examples (Figure 4-2 in IRIG Standard ) 7

8 IRIG Carrier Frequencies None (0) Exclusively associated with DCLS (and vice versa) 100 Hz (1) 1 khz (2) 10 khz (3) 100 khz (4) 1 MHz (5) Some pulse rate/frequency pairs are not allowed Higher frequencies and pulse rates are used together Lower (non-dc) frequencies and pulse rates are used together 8

9 IRIG Time Codes Eight valid combinations (0 through 7) of four types of information Information transmitted in 60-bit frames for IRIG D and H 100-bit frames for IRIG A, B, E and G Some pulse rate/time code information pairs are not allowed Any of the eight valid combinations can be used with A and B pulse rates Combinations 1 and 2 can be used with any pulse rate Combinations 5 and 6 can also be used with E and G pulse rates 9

10 IRIG Time Code Information (1) Certain bit positions are used as Reference, Position Identifier or Index Marker (unused) bits The Reference bit is the time code s on-time marker Index Marker bits are set to 0 Binary Coded Decimal Time Of Year (BCD TOY ) at the start of the current frame Represented as the day of year (001 to 366) and hour (00 to 23), and possibly (depending on the frame rate) the minute (00 to 59), second (00 to 59), tenth of second (0 to 9) and/or hundredth of second (0 to 9) Requires 2, 3 or 4 bits per decimal digit Included in all eight of the defined combinations Time information follows its Reference bit 10

11 IRIG Time Code Information (2) BCD Year, Can have a value from 00 to 99 Requires 4 bits per decimal digit Currently corresponds to 2000 to 2099 Included in defined combinations 4, 5, 6 and 7 Straight Binary Second (SBS) of the day Can have a value from 0 to 86,400 Requires 17 bits ( = 131,071) Included in defined combinations 1, 3, 4 and 7 Control function information Included in defined combinations 1, 2, 4 and 5 11

12 IRIG Transmission Typical transmission methods include Balanced signals over twisted pairs for DCLS formats Unbalanced signals over 50 Ω coaxial cable for amplitude modulated formats Optical signals over fiber Accuracy can range from nanoseconds to milliseconds depending on the format and equipment One-way protocol, so no automatic compensation for cable length 12

13 DOCSIS Timing Interface (DTI) Defined in ITU-T Recommendation J.211, Timing interface for cable modem termination systems Provides frequency and ToD information from a DTI server s MHz master clock to DTI clients Utilizes two-way messaging across a single twisted pair of wires via time division duplexing Same delay in each direction of transmission, allowing very accurate compensation for that delay Messages are sent at a rate of 5.12 Mb/s in 512-bit (100 μs) frames First 256 bits constitute a server timeslot Next (last) 256 bits constitute a client timeslot 13

14 DTI Server Timeslot Server message is sent in the first 234 bits 68-bit preamble (repeating 1001 ) 82 payload bits 68 reserved bits (set to 1 ) 16 CRC bits 10-kHz DTI frame clock is aligned with the leading edge of the first bit of the preamble 14

15 DTI Server Payload Information (1) Server type information (8 bits) Root server external timing source (none, GPS, network) Server hop count (root server, connected to root server) Root server clock type (ITU Type I, II or III, ST3) Server status flags (8 bits) Server considers the client s performance stable/not stable Cable delay has/has not been calculated and inserted into the cable advance field Server s current mode of operation is normal, holdover, fast, free-run or warm-up 15

16 DTI Server Payload Information (2) 22 most significant bits of the 32-bit DOCSIS timestamp The 10 least significant bits of the timestamp are the number of MHz clock ticks since the beginning of the DTI frame 10-bit ToD message field that includes A pps flag that is set to indicate that the start of the next frame will be coincident with the start of a second on the server s ToD clock A data-valid flag that indicates if the remaining 8 bits are a byte of the ToD message or a stuff byte (i.e., all ones) A byte of the ToD message or a stuff byte 16

17 DTI ToD Message 6 (short mode) or 41 (verbose mode) bytes of ToD information are sent each second, including Status information A gpssec timestamp Indicates what the ToD will be at the next on-time marker Cumulative leap second information Difference between GPS and UTC Possibly ASCII-based date, time, leap second and time zone information Entire message is required to be sent in a 100-ms (1000-frame) window Byte 1 is apparently sent in the on-time frame 17

18 DTI Server Payload Information (3) Cable advance information (24 bits) Calculated by the DTI server based on its measurement of when the client frames are arriving, or set manually Used by client to adjust its clock and thus the time at which it transmits its portion of the frame Can be adjusted in increments of 1/256 th of a MHz clock cycle (about 26.1-ps), once per second A path traceability field that contains, for example, the IP address of the root DTI server (10 bits) 2 flag bits and a data byte Data bytes carry information in TLV format Server and root server IP addresses, port numbers (0 to 255), and DTI version numbers 18

19 DTI Client Timeslot Client message is also 234 bits 68-bit preamble ( ) 82 payload bits (32 of which are reserved) 68 reserved bits (set to 1 ) 16 CRC bits Goal is that it is received at the server such that the leading edge of the first bit of the preamble is aligned with the 257 th bit of the 512-bit frame 19

20 DTI Client Payload Information Client type information (8 bits) Client clock type (ITU Type I, II or III, ST3, DTI Minimum Clock) Client status flags (8 bits) Client s current mode of operation is normal, bridging, holdover, fast, free-run or warm-up 32 reserved bits Client clock integer phase error or integrated phase (24 bits, with the last 8 set to all zeros) In increments of MHz clock cycles (about 6.7 ns) Reported as a signed 2 s complement number Client DTI version number 20

21 DTI Server Performance Specifications J.211 contains various performance specifications, including Free-run accuracy better than 1 ppm Clock-type-dependent holdover performance A maximum phase slew rate of 5 ns over a ten-second period during normal operation Jitter < 50 ps RMS Ranging wander < 250 ps RMS 21

22 DTI Client Performance Specifications J.211 contains various performance specifications, including Master clock output frequency of or MHz Needed for generating client messages at Mb/s Does not prohibit additional output frequencies 22

23 ASCII-Based Time Codes Various ASCII-based time codes are apparently used for transmitting ToD info These generally provide The ToD associated with an on-time marker Some combination of additional information, such as The time zone in which the reported ToD applies Whether the indicated time is standard or daylight savings time Quality information Typically transmitted over a serial interface (e.g., RS-232, RS-422) 23

24 ASCII-Based Time Code On-Time Markers On-time markers may be Particular characters in the code itself Pulses in a separate (typically 1-pps) signal Generally expected to provide much higher precision 24

25 ASCII-Based Time Code Examples NTP Type 4 Also referred to as Format 7 in the Spectracom SecureSync Instruction Manual Does not appear to be in any way associated with the packet-based ToD distribution protocol, NTP Cisco Serial ToD Also referred to as the telecom-solutions option in the Cisco IOS ntp command National Marine Electronics Association (NMEA)

26 NTP Type 4 ASCII-Based Time Code Information is provided in six fields Most fields are separated by spaces Each set of fields is preceded and followed by ASCII <cr> and <lf> characters <cr><lf>1^2^3^45^6<cr><lf> Leading <cr> character is the on-time marker to which the ToD information applies 26

27 NTP Type 4 Time Code Fields (1) 1. Alarm field Space to indicate the receiver has satellite availability? for no satellite available 2. Year of century Two digits, such as 11 for the year Day of year Three digits, such as 001 for January 1 4. ToD HH:MM:SS.XXX 27

28 NTP Type 4 Time Code Fields (2) 5. Leap second Blank space for no leap second pending L for leap second pending 6. Daylight savings time indicator S for standard time D for daylight savings time 28

29 Cisco Serial ToD Time Code (1) Information is provided in 14 fields Most fields are separated by commas A few are separated by spaces 1,2,3,4,5,67,8,9,10,11,12^13^14 A 1-pps signal may be provided via either The same interface as the time code, on either of two RS-232 leads Clear-To-Send (CTS) Ring Indicator (RI) A separate interface 29

30 Cisco Serial ToD Time Code (2) The start bit for the asterisk in the first field is supposed to be transmitted 19 (±1) bit times after each 1-pps pulse The ToD information indicates the time at which the next pulse will occur 30

31 Cisco Serial ToD Time Code Fields (1) 1. Satellite availability * for valid! for not valid 2. Revision or format (e.g., A) 3. Modified Julian date Number of days past midnight on November 17, 1858 (e.g., for January 1, 2011) 4. Year/month/day, with two digits for the year (e.g., 11/01/01 for January 1, 2011) 5. ToD HH:MM:SS 31

32 Cisco Serial ToD Time Code Fields (2) 6. Sign of time zone offset +,, or 0, where all but one of the US time zones are 7. Time zone offset (e.g., 05, 0005 or 05.0 for EST) 8. Leap second indicator 0 for no leap second pending 1 for leap second pending (at the end of the day) 9. Latitude (e.g., 40N for the Telcordia location in Piscataway, NJ) 10.Longitude (e.g., 074W for the Telcordia location) 32

33 Cisco Serial ToD Time Code Fields (3) 11.Altitude above mean sea level in meters (e.g., for the Telcordia location) 12.Alarm severity (e.g., MN [minor], MJ [major]) 13. Alarm source (e.g., GPS) 14.Alarm cause (e.g., LOS, holdover, warm-up, hardware fault) 33

34 NMEA 0183 ASCII-Based Time Code NMEA 0183 is a proprietary standard that Defines two types of devices Talkers Listeners Defines multiple standard talker and query sentences Allows for definition of proprietary sentences Includes physical interface recommendations RS-422 or RS-232 Shielded twisted pair 4800 baud/s 8 data bits 1 stop bit No parity or handshake 34

35 NMEA 0183 Talker Sentences Consist of up to 83 characters (total) Start with $ttsss, where tt is a two letter talker identifier (e.g., GP for a GPS unit, ZA or ZQ for an atomic or quartz timekeeper) sss is a sentence identifier (e.g., GGA for GPS System Fix Data, ZDA for Time & Date) Contain information fields separated by commas If no information is available for a field, it can be null Number of decimal places may be variable May include a 2-hex character checksum (hh) Separated from the information fields by an asterisk End with ASCII <cr> and <lf> characters 35

36 NMEA 0183 GGA Sentence $ttgga,1,2,3,4,5,6,7,8,9,10,11,12,13,14*hh<cr><lf> 1. UTC time in hhmmss.xx format 2. Latitude, apparently in ddmm.xx format 3. N or S 4. Longitude apparently in dddmm.xx format 5. E or W 6. GPS quality indictor Etc. 0 for fix not available 1 for GPS fix 2 for Differential GPS fix 36

37 NMEA 0183 ZDA Sentence $ttzda,1,2,3,4,5,6,*hh<cr><lf> Several definitions of the fields were found, including 1. Local time in hhmmss.xx format 2. Day (01 to 31) 3. Month (01 to 12) 4. Year (apparently 4 digits) 5. Local time zone offset hours part (-13 to +13) 6. Local time zone offset minutes part (0 to 59) 37

38 Precise Time and Time Interval Interface ICD-GPS-060 Revision B, GPS User Equipment (Phase III) Interface Control Document for the Precise Time and Time Interval (PTTI) Interface Defines methods of communicating ToD information from a GPS unit to GPS user equipment, and from GPS user equipment to downstream equipment Uses a combination of three or four signals 1 pps BCD time code Timing fault discrete 1 pulse per minute (output only) 38

39 PTTI 1-pps Signal Pulse width is 16 to 30 μs Amplitude of approximately 10 V Rise time of less than 50 ns Synchronized to the UTC second rollover 39

40 PTTI BCD Time Code Signal 40-bit message plus 10 stuff bits (all ones) Sent once per second at a serial bit rate of 50 b/s Starts within 100 μs after the start of a 1-pps pulse Indicates The UTC ToD at the time of that pulse (i.e., the ToD information follows the pulse at which it applies) HHMMSS (6 4 = 24 bits) Possibly the day of the year (3 4 = 12 bits) Note that the year has to be communicated by other means Possibly the Time Figure of Merit (TFOM, 4 bits) Indicates the estimated time error with respect to UTC, and ranges from 1 ns (1) to > 10 ms (9) 40

41 PTTI Timing Fault Discrete Signal Indicates whether or not the other two signals are valid Valid is denoted by a voltage of +3 to +5.5 V dc Invalid is denoted by a voltage of 0 to +0.5 V dc 41

42 PTTI Physical Interfaces BCD time code interface 2-wire, balanced, 100 Ω 1 denoted by line A having a voltage of 0.8 (transmit) or 0.1 (receive) to 6 V dc greater than line B 0 denoted by line A having a voltage of 0.8 or 0.1 to 6 V dc less than line B Receiver input impedance 5000 Ω 1-pps and timing fault discrete signals are typically carried on 50-Ω coax 42

Summary Method IRIG DTI ASCIIbased time code PTTI Accuracy Information Varies at least from ±500 ms to ±10 µs Better than ±5 ns expected ±10s of ns with a 1-pps signal, or µs or ms accuracy without

43 Summary Method IRIG DTI ASCIIbased time code PTTI Accuracy Information Varies at least from ±500 ms to ±10 µs Better than ±5 ns expected ±10s of ns with a 1-pps signal, or µs or ms accuracy without TFOM codes defined for better than ±1 ns through worse than ±10 ms Automatic Cable Length Compensation Defined in a Standard On-Time Marker No Yes Precedes ToD information Yes Yes Precedes ToD information No Generally no Follows ToD information in at least some cases (not standardized) No Yes Precedes ToD information 43

44 Q & A 44

Power Matters. Time Interfaces. Adam Wertheimer Applications Engineer. 03 November Microsemi Corporation.

Power Matters. Time Interfaces. Adam Wertheimer Applications Engineer. 03 November Microsemi Corporation. Power Matters Time Interfaces Adam Wertheimer Applications Engineer 03 November 2011 2011 Microsemi Corporation. Why do we need time? What time is it? It is 11:53 AM on the third of November 2011. High