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Synchronisation for Packet Networks

Synchronisation for Packet Networks
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Synchronisation for Packet Networks Introduction Networks are transitioning from circuit switched systems to packet switched systems to increase efficiency, flexibility and cost effectiveness. Data for time critical services such as audio and real time video is transported through inherently asynchronous Packet Networks. These networks require timing over packet technologies such as IEEE 1588 to be implemented, in order to support network synchronisation. Packet based synchronisation designs are posing challenges to the methods previously used. Rakon has characterised various types of oscillators under changing environmental conditions that meet the technical requirements of IEEE 1588. Rakon offers a wide range of oscillators that meet a variety of IEEE 1588 application requirements. Choosing the Right Oscillator for Each Application At Rakon we have the expertise to help determine the best oscillator solution for a customer’s system requirements. Choosing the right oscillator solution requires knowledge of the differential in frequency versus the differential in temperature (ΔF/ΔT). Complete characterisation of the oscillator is defined by the operating temperature range, the temperature ramp rates and time domain analysis of measured data. ITU – T has published requirements for clocks based on unaware packet networks – G.8263 based clocks. These clocks support frequency only operation but need to meet very stringent MTIE and TDEV requirements. The G.8273.2 clocks support frequency, phase and time, but are primarily targeted at aware networks. Even though every node in the network supports the packet clocks, the dynamic time error requirement on these clocks demands high stability oscillators. The MTIE requirements of 40 ns over 1000 s and over temperature necessitate ovenised crystal oscillators of a few ppb/°C temperature sensitivity. Rakon’s IC-based, highly reliable Mercury™/Mercury+™ OCXOs are cost-effective solutions for boundary and slave clocks. There are a number of application scenarios which require partially supported networks with no synchronous ethernet synchronisation to support the PTP architecture; these implementations still require higher stability clocks. Rakon has OCXO solutions that can support stability levels of 0.05 ppb pk-pk to ±20 ppb, depending on the needs of the application. Rakon Solutions for Packet Network Synchronisation Oscillators Time to Reach Phase Error Limit (Δt) 1.5 µs Supported Bandwidth Discrete OCXO New Zealand (HQ) Auckland | China Beijing, Shanghai & Shenzhen | France Argenteuil, Mougins & Pont Sainte Marie | Germany Bad Rappenau | Singapore Singapore City | South Korea Seongnam City | Taiwan Taipei City | United Kingdom Harlow | United St

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Synchronisation for Packet Networks Medium Term Stability Challenges for Oscillators used in IEEE 1588 In packet-based synchronisation implementations, the local synchronised oscillator is moving from a physical layer-based phase or frequency locked loop, to a time locked system via secondary layer protocols. 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. Effectively the oscillator’s stability performance is now...

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Synchronisation for Packet Networks 2Pages

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Synchronisation for Packet Networks
2Pages