Packet Network Sync v1
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Rakon Limited (Corporate Head Office) Phone: +64 (9) 573 5554 Fax: +64 (9) 573 5559 Email: [email protected] Rakon Europe Limited (Europe, Middle East, Africa) Phone: +44 (1522) 883500 Fax: +44 (1522) 883524 Email: [email protected] Rakon Taiwan Representative Office (Asia) Phone: +886 (2) 2759 0259 Fax: +886 (2) 2759 2668 Email: [email protected] Rakon Limited Shenzhen Representative Office (China) Phone: +86 (755) 8283 5991 Fax: +86 (755) 8283 5990 Email: [email protected] Rakon America LLC (Americas) Phone: +1 (847) 930 5100 Fax: +1 (847) 844 3236 Email: [email protected] www.rakon.com Networks are transioning from circuit switched to packet switched to become more efficient, flexible and cost effecve. With me crical services such as audio and real me video being transported through the inherently asynchronous Packet Networks, Timing over Packet technologies such as IEEE1588 is used to support synchronizaon and is becoming prominent. The requirements of Synchronizaon designs posing challenges to tradional methods. Rakon has characterised various types of oscillators under changing environmental condions for the loop me periods relevant to IEEE 1588v2. Rakon presents a wide range of oscillators that economically fit a wide range of applicaon requirements in the IEEE 1588 space. Introduction and Rakon Solutions The local synchronised oscillator is moving from a physical layer based, phase or frequency locked loop, to a me locked system via secondary layer protocols. The non stochasc nature of the Packet Delay Variaons (PDV) force the loop to have smaller bandwidths and thus longer me constants. Oscillators present themselves as high pass filters in the control loop, thus smaller loop bandwidths can mean that the medium term stability performance of an oscillator is important to the overall system performance. Effecvely the oscillator’s stability performance is now dominated by environmental changes during the extended me periods. The oscillator stability over the medium term (minutes to hours) is either poorly characterised or not been accounted for at all, since the stability under these condions is covered indirectly by other oscillator/system specificaons. Medium Term Stability Challenges for Oscillators Used in IEEE 1588v2 Historically there have been only two “oscillator / lock bandwidth” combinaons, namely Stratum 3 and Stratum 3E. For Stratum 3 oscillators, the effect of variable temperature on TDEV and MTIE was likely to be minimal since the oscillator has a lock bandwidth in the 0.1 to 10 Hz range (me constants of 1.6s to 0.02s) and any slow changes in frequency due to, for example, temperature fluctuaons were filtered out. Conversely, with the Stratum 3E oscillator, because of the very high stability required for the variable temperature stability requirement (±5 ppb), small changes in temperature would not affect the TDEV and MTIE even with a 1 millihertz (mHz) lock bandwidth (me constants of 160s. Packet Network Synchronisation Rakon Devices Stability Slope Aging Δt * = 1µs Δt * = 3µs Δt * = 7µs Band Width ROX5242T2 (10 MHz) ±0.2 ppb -20 to 70°C Positive ≤ ±0.07 ppb/day 3 hours 12 hours 36 hours 0.1 mHz ROX3827T3 (10MHz) ±1 ppb -20 to 70°C Positive ≤ ±0.1 ppb/day 1 hour 6 hours 12 hours 0.3 mHz ROX2522S4 (10MHz) ±5 ppb -20 to 70°C ±0.5 ppb/°C ≤ ±0.5 ppb/day 30 minutes 2 hours 4 hours 1 mHz RMO1490B ±10 ppb -40 to 85°C ±2 ppb/°C ≤ ±1 ppb/day 20 minutes 35 minutes 55 minutes 0.05 mHz RFPO45 G.8263 ±20 ppb -40 to 85°C ±2 ppb/°C ≤ ±1 ppb/day 20 minutes 35 minutes 55 minutes 0.05 ~ 3 mHz * Δt: Time to reach phase error limit with ±20°C temperature variation (ΔT) at 10°C/hour Packet Based Synchronization
description
Packet
Transcript of Packet Network Sync v1
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Rakon Limited(Corporate Head Of ce)
Phone: +64 (9) 573 5554Fax: +64 (9) 573 5559Email: [email protected]
Rakon Europe Limited(Europe, Middle East, Africa)
Phone: +44 (1522) 883500Fax: +44 (1522) 883524Email: [email protected]
Rakon TaiwanRepresentative Of ce (Asia)
Phone: +886 (2) 2759 0259Fax: +886 (2) 2759 2668Email: [email protected]
Rakon Limited ShenzhenRepresentative Of ce (China)
Phone: +86 (755) 8283 5991Fax: +86 (755) 8283 5990Email: [email protected]
Rakon America LLC(Americas)
Phone: +1 (847) 930 5100Fax: +1 (847) 844 3236Email: [email protected]
www.rakon.com
Networks are transiti oning from circuit switched to packet switched to become more e cient, exible and cost e ecti ve. With ti me criti cal services such as audio and real ti me video being transported through the inherently asynchronous Packet Networks, Timing over Packet technologies such as IEEE1588 is used to support synchronizati on and is becoming prominent. The requirements of Synchronizati on designs posing challenges to traditi onal methods.
Rakon has characterised various types of oscillators under changing environmental conditi ons for the loop ti me periods relevant to IEEE 1588v2. Rakon presents a wide range of oscillators that economically t a wide range of applicati on requirements in the IEEE 1588 space.
Introduction and Rakon Solutions
The local synchronised oscillator is moving from a physical layer based, phase or frequency locked loop, to a ti me locked system via secondary layer protocols. The non stochasti c nature of the Packet Delay Variati ons (PDV) force the loop to have smaller bandwidths and thus longer ti me constants.
Oscillators present themselves as high pass lters in the control loop, thus smaller loop bandwidths can mean that the medium term stability performance of an oscillator is important to the overall system performance. E ecti vely the oscillators stability performance is now dominated by environmental changes during the extended ti me periods.
The oscillator stability over the medium term (minutes to hours) is either poorly characterised or not been accounted for at all, since the stability under these conditi ons is covered indirectly by other oscillator/system speci cati ons.
Medium Term Stability Challenges for Oscillators Used in IEEE 1588v2
Historically there have been only two oscillator / lock bandwidth combinati ons, namely Stratum 3 and Stratum 3E.
For Stratum 3 oscillators, the e ect of variable temperature on TDEV and MTIE was likely to be minimal since the oscillator has a lock bandwidth in the 0.1 to 10 Hz range (ti me constants of 1.6s to 0.02s) and any slow changes in frequency due to, for example, temperature uctuati ons were ltered out.
Conversely, with the Stratum 3E oscillator, because of the very high stability required for the variable temperature stability requirement (5 ppb), small changes in temperature would not a ect the TDEV and MTIE even with a 1 millihertz (mHz) lock bandwidth (ti me constants of 160s.
Packet Network Synchronisation
Rakon Devices Stability Slope Aging t * = 1s t * = 3s t * = 7s Band Width
ROX5242T2 (10 MHz)
0.2 ppb-20 to 70C
Positive 0.07ppb/day
3 hours 12 hours 36 hours 0.1 mHz
ROX3827T3(10MHz)
1 ppb-20 to 70C
Positive 0.1ppb/day
1 hour 6 hours 12 hours 0.3 mHz
ROX2522S4(10MHz)
5 ppb-20 to 70C
0.5 ppb/C
0.5ppb/day
30 minutes 2 hours 4 hours 1 mHz
RMO1490B10 ppb-40 to 85C
2 ppb/C
1ppb/day
20 minutes 35 minutes 55 minutes 0.05 mHz
RFPO45 G.826320 ppb-40 to 85C
2 ppb/C
1ppb/day
20 minutes 35 minutes 55 minutes 0.05 ~ 3 mHz
* t: Time to reach phase error limit with 20C temperature variation (T) at 10C/hour
Packet Based Synchronization
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Packet Network Synchronisati on
Rakon Limited(Corporate Head Of ce)
Phone: +64 (9) 573 5554Fax: +64 (9) 573 5559Email: [email protected]
Rakon Europe Limited(Europe, Middle East, Africa)
Phone: +44 (1522) 883500Fax: +44 (1522) 883524Email: [email protected]
Rakon TaiwanRepresentative Of ce (Asia)
Phone: +886 (2) 2759 0259Fax: +886 (2) 2759 2668Email: [email protected]
Rakon Limited ShenzhenRepresentative Of ce (China)
Phone: +86 (755) 8283 5991Fax: +86 (755) 8283 5990Email: [email protected]
Rakon America LLC(Americas)
Phone: +1 (847) 930 5100Fax: +1 (847) 844 3236Email: [email protected]
www.rakon.com
The non - stati onary nature of the PDVs impose new requirements for the local oscillator. Loops operate with lock bandwidths in the 10 mHz to 0.1 mHz (ti me constant 1600s) region to lter the wander introduced by PDV. System speci cati ons of frequency stability, holdover requirements for frequency and if required phase will determine the requirements for Oscillators.
At Rakon we have the experti se to help determine the best oscillator soluti on for our customers systems requirements. Oscillator soluti ons require knowledge of the di erenti al in frequency versus the di erenti al in temperature. Full characterisati on is determined by de ning the temperature ramp and measurement rate and a detailed analysis over the characterisati on ti me period.
Right oscillator for right application
ROX2522S4 - 40/85oC (10oC/hour) 1 mHz loop lterRFPO45 - 40/85oC (10oC/hour) 3 mHz loop lter
Rakons RFPO45 G.8263, RMO1490B and ROX2522S4 OCXO are designed for bandwidths of 3 ~ 1 mHz and below and for very ti ght holdover performance, these products are designed for the most stringent system requirements.
For systems that does not require holdover, oscillators that are compliant to G.8263 speci cati ons may sti ll provide the wander ltering necessary to meet the TDEV / MTIE requirements. The challenge for the system designer is to assess which oscillator will work at which lock bandwidth and sti ll meet the implied TDEV/MTIE requirements in locked conditi ons and assess what oscillators may be required to provide adequate holdover for speci ed durati on of ti me required by the applicati on. This is where Rakon can help.
G.8263 OP1 MTIEG.8263 OP2 MTIE
G.8263 OP1 MTIE
MercuryTM and Conventi onal OCXO
High-end Telecom OCXO
Rakons ROX5242T2 and ROX3627T3 have the best stability performance. They are designed for bandwidths of 0.3 ~ 0.1 mHz and below and for very ti ght holdover performance, these products are designed for systems that require frequency and ti me holdover will require Stratum 3E or higher temperature stability performance.
Rakon proposed a Thermal Pro le to represent a more realisti c usage environment and most chipset vendors and OEMs suppported thie contributi on.
E.g.: The limit is 20C movement at (0.5C/min or t 1C/min as required) be taken to cover both the external environmental e ects.
Rkon Contribution to ITU-T
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