2019 is set to be the year of 5G when the next-generation network technology finally arrives and changes the face of the mobile world. But for operators to make a success of 5G deployments, they need to prepare their transport and synchronization architectures for a host of new challenges.
Unprecedented levels of accuracy
From a timing perspective, a major part of the evolution to 5G is meeting the stringent phase and time demands of networks based on time division duplex (TDD) and cooperative radio techniques. Previous generations of mobile technology mainly required frequency synchronization. Now operators are looking to design networks capable of delivering phase synchronization to base stations and small cells with an accuracy in the range of a few hundred nanoseconds to 1.5 microseconds.
There are different ways to achieve this, with some opting for a full on-path support model with the entire network designed to be PTP capable. Others can’t do this due to cost and limitations on existing network elements and so are distributing grandmaster clock technology close to small cells and end applications. Both methods can work and Oscilloquartz’s comprehensive portfolio of timing products supports either approach.
With this in mind, ITU-T is developing a set of clocks that use Precision Time Protocol (PTP) and Sync-E with improved specification to deliver timing across packet-switched networks with accuracy in the order of a few hundred nanoseconds.
Also important here are the new set of enhanced clocks defined by ITU-T and designed for greater timing accuracy at the network core. Enhanced primary reference clocks (ePRCs) and enhanced primary reference time clocks (ePRTCs) combined can deliver phase synchronization better than 30 nanoseconds.
Another aspect of the 5G timing challenge involves networks relying on the Global Navigation Satellite System (GNSS) to deliver Coordinated Universal Time (UTC). Most of today’s network elements use GNSS L1 band signals with standard GNSS receivers. The new generation of GNSS receivers, however, utilizes other GNSS bands through multi-band receivers to better cope with delay variation between satellite and receiver. Compensating for this will be vital for technologies like autonomous driving, as it enables high-precision positioning with centimetre-level accuracy. Such multiband receivers can also deliver improved timing accuracy, which can be leveraged to significantly reduce the time error of the primary timing source of cellular network synchronization.
Of course, the other challenge of 5G timing is ensuring backup in the case of GNSS outages. Removing this vulnerability with ePRTC technology will be vital. That’s why we created our OSA ePRTC solution comprising two OSA devices: an OSA ePRC cesium clock compliant to G.811.1 ePRC, which is connected to either an OSA 5430 or OSA 5440 clock combiner and grandmaster clock compliant to G.8272.1 ePRTC. This provides phenomenal holdover accurate to UTC within +/-100nsec for up to two weeks, ensuring resilience and optimized performance.
Another part of the picture involves improved accuracy in boundary clocks which allow accurate distribution of timing in the network . These timing functionalities are incorporated into transport equipment, enabling timing distribution across the sync trail. Until recently, ITU-T had two types of boundary clocks, A and B specified. These boundary clocks added a constant time error of 50 and 20 nanoseconds respectively. Now the ITU-T has set a new bar and the latest breed of boundary clock named class C and D will distribute time with constant time error up to 5 or 10 nanoseconds.
New ITU-T standards for Synchronous Ethernet (Sync-E) are also part of this model. As well as phase, synchronizing frequency is still important and, used in combination with PTP, enhanced Sync-E will enable much better frequency distribution over the frequency layer.
As well as meeting these challenges head on, we at Oscilloquartz have made sure our products also provide new levels of redundancy and resilience, deployment agility and unbeatable scale. With our most comprehensive portfolio, we’re sure we have 5G timing solutions for all network scenarios.