Allocate high-precision time to optical networks in the 5G world

Mobile operators are investing heavily in the deployment of LTE-Advanced networks and 5G networks, which will bring major changes to cellular communications and connections. However, they face a huge risk: the high-performance mobile services provided through these networks rely heavily on the precise time provided by GPS and other similar regional constellations called the Global Navigation Satellite System (GNSS) in order to synchronize radios and support New applications and minimize interference. If GPS/GNSS cannot be used due to interference, deception, malfunction or other events, the resulting service interruption will have a catastrophic impact on system performance.

Author: Eric Colard, Head of Emerging Products, Frequency and Time Systems Business Unit, Microchip Technology

Mobile operators are investing heavily in the deployment of LTE-Advanced networks and 5G networks, which will bring major changes to cellular communications and connections. However, they face a huge risk: the high-performance mobile services provided through these networks rely heavily on the precise time provided by GPS and other similar regional constellations called the Global Navigation Satellite System (GNSS) in order to synchronize radios and support New applications and minimize interference. If GPS/GNSS cannot be used due to interference, deception, malfunction or other events, the resulting service interruption will have a catastrophic impact on system performance.

Just as the power grid is highly susceptible to climate, heat, high winds, and dry vegetation that can lead to large-scale fires (such as the recent fire in California), 5G networks are also susceptible to interruptions in precise time allocation and may even lead to the entire system. Interrupted. New technologies enable mobile operators to protect their networks from these threats. These technologies have created a new architecture that allocates ultra-high-precision time over long distances while taking advantage of existing deployments. They not only minimize additional costs, but also provide the necessary performance to meet the high requirements of 5G.

Technology trends

The latest LTE-Advanced and 5G mobile networks have brought huge capacity and bandwidth growth, which can be used to provide new services to consumer, industrial, urban and specific market segments. From the high-bandwidth video transmission of smartphones to the Internet of Things (IoT) for autonomous vehicles, smart cities, and smart factories, these new services all rely on the synchronization of a large number of sensors, base stations, and other devices.

To do this, very precise time needs to be transmitted over long distances. Without it, mobile operators will not be able to take full advantage of deployment investments by minimizing interruptions and risks. In addition, they must also develop a plan that can function in the event of a GPS/GNSS failure. At the same time, they need to make effective use of optical networks and other existing infrastructure so that they do not need to make expensive new investments in dark fiber.

Standards bodies define very strict requirements for precise time and synchronization, such as the primary reference clock (PRTC), which includes 100 nanoseconds (ns) PRTC class A (PRTC-A), 40 ns PRTC class B (PRTC- B) and 30 ns enhanced PRTC (ePRTC) performance specifications. In order to meet these requirements, there must be a high-quality time source, and a very flexible, efficient and high-performance allocation mechanism is needed to transfer time from the source to various time-consuming devices (ie base stations, sensors, vehicles, etc.) ).

The problem with relying on GPS/GNSS to meet these requirements is that, given the increasing density of endpoints, its deployment costs may be very high. In addition, there is a technical loophole in the GNSS receiver located in the cellular base station. Once the GNSS receiver cannot track the satellite correctly for any reason, it must stop using the radio quickly to avoid interference problems caused by the short retention period of the oscillator technology used by the radio. Due to these technical and financial considerations, operators urgently need solutions that can reduce or even eliminate reliance on GNSS in many places.

Other considerations for operators include: time allocation from source to endpoint when using the network; network nodes; and various synchronization functions that these network nodes can support. Generally, the highest-level clock of the Precision Time Protocol (PTP) is located at the beginning of the time service chain and meets the performance specifications of 100 ns PRTC-A or 40 ns PRTC-B, so it can transfer the precise time to within +/-1.5 microseconds. The end of the chain. The network nodes on the path are usually embedded with a time boundary clock (T-BC) function that meets Type A (50 ns) or Type B (25 ns).

A new type of time allocation architecture is needed to meet these requirements and considerations to allow operators to protect their mobile networks from GNSS outages and allocate precise time over long distances to cover the whole country. In addition, this architecture must also provide the necessary performance to meet the end-to-end budget for 5G requirements.

A different time allocation architecture

The high-precision time allocation architecture should have multiple functions to enable operators to eliminate GPS/GNSS vulnerabilities in the most effective way and solve other challenges in their 5G networks. This architecture should:

・ Make full use of the existing optical network (thereby avoiding the high cost of dark fiber)

・ Use a dedicated lambda to transfer time in the fastest way

・ Maximum protection of redundant time source, this time source meets the highest performance of 30 ns ePRTC, and uses a combination of cesium atomic clock and GNSS

・ Two time flows (East and West) are provided so that redundant paths can be used in the event of any problems from the source to the end point

・ Possess a series of high-precision boundary clocks (HP BC), which can meet the requirements of the highest performance level specified by today’s standards (T-BC Class D 5 ns)

This type of multi-domain architecture provides a redundant, sub-microsecond end-to-end timing function, which is suitable for delivering high-performance and precise time allocation of 5 nanoseconds per node at a low cost within a range of hundreds of miles.

An example of such a solution is Microchip’s TimeProvider 4100, which can be configured as an ePRTC with PRTC-A and PRTC-B time transfer functions at the source end of the timing chain, or as an HP BC on an optical network path. In addition, this type of product can also be configured according to application-specific requirements to achieve end-to-end timing, and has a nanosecond-level accurate time transfer capability over long distances.

Ensure precise timing

The success of the next generation of high-performance mobile services will depend on whether operators can successfully resolve today’s critical GPS/GNSS vulnerabilities. Interference, spoofing, malfunctions, or other events can cause the 5G network to synchronize radios, support applications, and interrupt the precise GPS/GNSS timing required to minimize interference. The latest high-precision time allocation architecture reduces these risks with minimal additional cost and provides operators with the performance required to support new and demanding 5G services (from IoT-based applications to receiving high bandwidth on smartphones) video).

The Links:   APT2X61D100J RM500DZ-2H

Author: Fymicohuang

Leave a Reply

Your email address will not be published. Required fields are marked *