How high-precision timing changes the game for 5G infrastructure

As an important basic technology that has been written into the Chinese government's work report for four consecutive years and leads the "new infrastructure", the importance of 5G in expanding connectivity, driving economic growth, improving people's quality of life, and accelerating the digital transformation and upgrading of related industries is self-evident.

According to the 2020 updated version of the "5G Economy" report independently researched by IHS Markit, 5G is expected to create US$13.1 trillion in global economic output by 2035, and global 5G capital expenditure and R&D investment will increase by 10.8%, with an average annual investment of up to US$265 billion.

The latest data from the Ministry of Industry and Information Technology shows that as of the end of 2020, China has added 580,000 new 5G base stations and promoted the joint construction and sharing of 330,000 5G base stations. The goal of "achieving 5G coverage in all cities and counties" set at the beginning of the year has been achieved.

The number of global 5G connections will exceed 1 billion in 2023, two years earlier than the time it took for 4G to achieve 1 billion connections. It can be seen that although the global economy has been affected by the epidemic, the growth trend of economic output enabled by 5G remains almost unchanged.

Create the most accurate heartbeat of electronic systems

There are many angles to interpret 5G, but today we want to start with the clock known as the "heartbeat of the electronic system."

"Clock IC" is a broad term used to describe integrated circuits that can generate, modulate, manipulate, distribute or control timing signals in electronic systems. When used in today's most advanced electronic and communication systems, clock ICs must also be able to generate precise clock pulses and continuously and reliably distribute the signal for use by various timing devices in the system to meet the needs of "high-precision timing" for many types of applications.

In fact, the 4G/5G communication system we are familiar with is one of the important application scenarios of "high-precision timing". Since the 4G/5G network adopts the TDD time division multiplexing mode, the time synchronization accuracy is extremely high during the high-speed data transmission process. For example, the time synchronization of the TDD time division system represented by TD-LTE requires ±1.5 μs. If the time between communication devices is not synchronized, it will affect the normal operation of communication services such as base station switching and roaming.

How did networks before 5G use timing?

The primary source of precise time for wireless communication networks has been the Global Positioning System (GPS) and the regional satellite constellations that make up the Global Navigation Satellite System (GNSS). GPS is the first satellite constellation deployed worldwide for positioning, navigation and timing (PNT). With the help of carefully designed GPS timing receiver technology, GPS users can recover extremely precise timing from the synchronized atomic clocks on board GPS satellites.

At present, in addition to GPS, a number of GNSS technologies for timing have been deployed around the world, including Galileo (EU) and BeiDou (China). Taking BeiDou as an example, the time of the BeiDou satellite navigation system is called BDT, which is atomic time and can be traced back to the Coordinated Universal Time (UTC) of the China National Time Service Center. The time difference control accuracy with UTC is less than 100 ns.

Even the most powerful GNSS has its shortcomings

Although GNSS satellite timing has higher accuracy and stronger coverage, it also faces huge risks. If GPS/GNSS cannot be used due to interference, deception, failure or other events, the resulting service interruption will have a catastrophic impact on system performance. Just as the power grid is disconnected due to fire/snowstorm, 5G networks are also vulnerable to interruptions in precise time distribution, which may even cause the entire system to be interrupted.

In addition, from high-bandwidth video transmission on smartphones to the Internet of Things (IoT) for self-driving cars, smart cities, and smart factories, the huge capacity and bandwidth growth brought by 5G mobile networks is previously unimaginable. These new services not only rely on the synchronization of a large number of sensors, base stations, and other devices, but also need to transmit very precise time over long distances, resulting in increasingly high endpoint density in 5G networks and the cost of relying on GPS/GNSS for timing.

New time allocation architecture

Operators are in urgent need of solutions that can further reduce or even eliminate their reliance on GPS/GNSS. So, is there a new time distribution architecture that can allow operators to protect their mobile networks from GNSS outages and distribute precise time over long distances to provide nationwide coverage, while also providing the necessary performance to meet the end-to-end budgets required by 5G?

The answer is yes.

The enhanced PRTC (ePRTC) standard is an ideal choice for meeting the challenges of new timing architectures. It is one of several versions of the primary reference clock (PRTC) defined by the ITU-T (ITU Telecommunication Standardization Sector) to improve time accuracy. PRTC Class A can meet the 100 ns (nanosecond) accuracy requirement relative to Coordinated Universal Time (UTC); PRTC Class B is more precise, with an accuracy of 40 ns; and enhanced PRTC has a maximum accuracy of 30 ns in accordance with the ITU-T G.8272.1 definition.

The unique design of ePRTC makes it maximally resilient, able to use cesium as a reference clock for 14 days or more, while maintaining a maximum deviation from UTC of 100 ns throughout the long outage period, which will become a key advantage for 5G mobile operators to deploy ePRTC. If GPS is turned off, service delivery will remain seamless across the entire network, ensuring the required time to repair GPS outages or maintain operations during extended periods of GPS unavailability.

TimeProvider 4100

A typical example of an ePRTC 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, such products can be configured according to application-specific requirements to achieve end-to-end timing and have nanosecond-level accurate time transfer capabilities over long distances.

TimeProvider 4100 is a master clock that uses the IEEE1588 protocol, including the latest ITU-T G.8275.1 and G.8275.2 1588 phase specifications, and also complies with the Chinese communications industry YD /T 2375-2019 high-precision time synchronization technology standard requirements. TimeProvider 4100 supports extensive port expansion for PTP, Network Time Protocol (NTP), Synchronous Ethernet (SyncE), and E1/T1. The 2.1 software version adds key software enhancements to earlier versions, providing a virtual primary reference clock (vPRTC). Virtual PRTC enables the design of redundant precise time distribution architectures for phase protection on fiber optic networks.

TimeProvider 4100 1GE/10GE Expansion Module

Microchip's vPRTC multi-domain architecture is a cost-effective solution that uses existing fiber networks and dedicated lambdas to accurately and securely transmit time, avoiding the use of high-cost dark fiber fees, and providing high-performance, redundant, sub-5 nanosecond precise time distribution on regional and national networks. In addition, version 2.1 complies with the PRTC-B performance standard (according to ITU-T G.8272), supports 1G, 10G, Network Time Protocol (NTP) and Precision Time Protocol (PTP) in a single form factor system, and introduces the Network Time Protocol Daemon (NTPd) with a message digest (MD5) security algorithm.

The TimeProvider 4100 master clock product version 2.2 released by Microchip at the beginning of this year introduced an innovative redundant architecture based on version 2.1 to provide a new level of resilience, thereby meeting the basic needs of 5G networks for redundant, resilient and secure precise timing and synchronization solutions.

Microchip TimeProvider 4100 Grandmaster Clock Product Version 2.2

Conclusion:

Timing is perhaps the largest potential point of failure in 5G systems and can impact performance, reliability, and revenue.

Considering how to minimize the use of GPS sites while retaining a highly resilient and precise time architecture to ensure the continuity of customer service during GNSS outages? When using 5G networks, how are the network nodes from source to endpoint composed, how is the time allocated, and what synchronization functions can these network nodes support? These issues are becoming the biggest concern of operators. As a company that can provide overall system solutions including high-performance clock synchronization, clock management and multiple types of oscillators, Microchip is working with ecosystem partners to create "the most accurate heartbeat of electronic systems."