Mobile operators are investing heavily in the deployment of LTE-Advanced and 5G networks, which will revolutionize cellular communications and connectivity. However, they face a huge risk: the high-performance mobile services delivered over these networks rely heavily on precise time provided by GPS and other similar regional constellations called Global Navigation Satellite Systems (GNSS) in order to synchronize radios, support New apps and minimize distractions. If GPS/GNSS becomes unavailable due to jamming, spoofing, glitches or other events, the resulting service outage can have a catastrophic impact on system performance.
Just as power grids are extremely vulnerable to climate, heat, wind, and dry vegetation that can lead to large-scale fires (like the recent California fires), 5G networks are also vulnerable to disruptions in precise timing distribution that could even cause system-wide disruptions interrupt. New technologies enable mobile operators to protect their networks from these threats. These techniques create new architectures for distributing ultra-precise time over long distances while leveraging existing deployments. Not only do they minimize additional costs, they also provide the necessary performance to meet the high demands of 5G.
The latest LTE-Advanced and 5G mobile networks bring huge capacity and bandwidth increases that can be used to deliver new services to consumer, industrial, urban and specific market segments. From high-bandwidth video transmission from smartphones, to the Internet of Things (IoT) in autonomous vehicles, smart cities, and smart factories, these new services rely on the synchronization of vast numbers of sensors, base stations, and other devices.
To do this requires very precise time delivery over long distances. Without it, mobile operators will not be able to make the most of deployment investments by minimizing disruption and risk. In addition, they must have a plan that can function in the event of a GPS/GNSS failure. At the same time, they need to make efficient use of optical networks and other existing infrastructure so that expensive new investments in dark fiber are not required.
Standards bodies define very strict requirements for precise timing and synchronization, such as the Primary Reference Clock (PRTC), which includes PRTC Class A (PRTC-A) at 100 nanoseconds (ns), PRTC Class B (PRTC-A) at 40 ns B) and 30 ns performance specification of enhanced PRTC (ePRTC). To meet these requirements, a high-quality time source is necessary, and a very resilient, efficient, and high-performance distribution mechanism is required to transfer time from the source to the various time-consuming devices (i.e. base stations, sensors, vehicles, etc. ).
The problem with relying on GPS/GNSS to meet these requirements is that deployment costs can be high given the increasing density of endpoints. In addition, there is a technical vulnerability in the GNSS receiver located at the cellular base station. Once a GNSS receiver fails to track a satellite properly for any reason, the radio must be stopped quickly to avoid interference problems caused by the short hold-up 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 locations.
Other considerations for operators include: time distribution from source to endpoint when using the network; network nodes; and the various synchronization functions that these network nodes can support. Typically, the Precision Time Protocol (PTP) superlative clock is located at the beginning of the timing chain and conforms to the 100 ns PRTC-A or 40 ns PRTC-B performance specification, so it can deliver precise time to +/- 1.5 microseconds end of the chain. Network nodes along the path typically embed a time boundary clock (T-BC) function that satisfies class A (50 ns) or class 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 for nationwide coverage. In addition, this architecture must also provide the necessary performance to meet the end-to-end budget required by 5G.
A Different Time Allocation Architecture
A high-accuracy time allocation architecture should have multiple capabilities that allow operators to eliminate GPS/GNSS vulnerabilities and address other challenges in their 5G networks in the most efficient way. This schema should:
Make the most of your existing optical network (thus avoiding expensive dark fiber charges)
Use a dedicated lambda for the fastest way to transfer time
Maximum protection of redundant time source that meets the highest performance of 30 ns ePRTC and uses a combination of cesium atomic clock and GNSS
Provides two time streams (East and West) so that redundant paths can be utilized in the event of any issues going from source to endpoint
Features a range of High Precision Boundary Clocks (HP BC) to meet the highest performance levels required by today’s standards (T-BC Class D 5 ns)
This type of multi-domain architecture provides redundant, sub-microsecond, end-to-end timing, suitable for delivering high-performance precise time distribution of 5 nanoseconds per node at low cost over hundreds of miles.
An example of such a solution is Microchip’s TimeProvider 4100, which can be configured either as an ePRTC with PRTC-A and PRTC-B time transfer capabilities at the source of the timing chain, or as an HP BC on the optical network path. In addition, these products can be configured according to application-specific requirements for end-to-end timing with nanosecond precision time delivery over long distances.
Ensure accurate timing
The success of next-generation high-performance mobile services will depend on operators’ ability to successfully address today’s critical GPS/GNSS vulnerabilities. Jamming, spoofing, glitches or other events can cause disruptions in the precise GPS/GNSS timing required for 5G networks to synchronize radios, support applications and minimize interference. The latest high-accuracy time allocation architecture reduces these risks with minimal additional cost and provides operators with the performance they need to support demanding new 5G services ranging from IoT-based applications to receiving high bandwidth on smartphones video).