HARRISON
Timing and synchronisation

The initial application of precise time came from the telecommunication industry. The basic concept was a hierarchical architecture with a central point a centralised Master Clock that distributed the time reference to other nodes arranged according to priority level or layers. This architecture imposed a dedicated infrastructure and intrinsic synchronisation degradation performances from the upper to lower layers and with distance from the Master Clock. The availability of GNSS changed this approach: the signal in space (SIS) is available to all network nodes with the same level of accuracy and without any additional distribution infrastructure.

The availability of an inexpensive timing receiver able to extract the time reference from the SIS makes this approach cheaper than any other previous time distribution system. GNSS is therefore of interest for high performance synchronisation to any application domain that can be described in terms of nodes distributed over a geographical area.

Two different aspects are related to time services: the need for high accuracy in time determination and event synchronisation, and the need for using an authenticated and certified time. The first aspect is quite clear to understand: the better the synchronisation the better the accuracy and resolution in case of localisation of events propagating on a transmission network; while the second aspect answers to the need of demonstrating to a third party that a certain event has happened (i.e. time stamped) at a certain time. The two aspects described above are not mutually exclusive nor present with the same level of required performances in the various application domain. The users are all those applications that need a precise time reference for event synchronisation and time event recording.

The project deals with time and synchronisation applications and aims to study the advantages offered by Galileo for these.

Description

The project is basically arranged in three major phases: User community analysis The user community analysis includes a market analysis performed by a specialised company to identify business opportunities in timing applications for the forthcoming Galileo constellation. The purpose of this project phase is to analyse the time and synchronisation applications for each domain and study the advantages offered by the availability of a common precise time reference recovered by the Galileo SIS. Moreover this activity is also stimuli for the development of new ideas. During this analysis phase, consolidation of user requirements and service provision schemes and interfaces will also be performed.

Development of an ACTS demonstrator The proposed demonstrator is called Authenticated and Certified Time Solution (ACTS) and is aimed at studying the feasibility of using the time distributed by the Galileo system, which would be authenticated and certified through the Galileo System. Field trials of the ACTS The demonstrators are in the following application domains: - astronomy and quantum cryptography by performing synchronised observation in Ljubljana and in Asiago (PD); - power and energy by performing synchronised measurement of voltage and current grid to detect failure, failure propagation and transient waveform propagation; - cryptography.

Objectives

Applications are mainly driving these requirements into two main categories: high accuracy and resolution for demanding users in science, power distribution and telecommunications.

The main objectives of the project are:

• to demonstrate the benefit of using GNSS services in time distribution and event synchronisation over wide geographical areas and to define the requirements for added value services;
• to demonstrate that the basic GNSS services can be improved to offer custom added-value solutions to the time and synchronisation user community; this objective is achieved by putting the Galileo satellite system developers in contact with the user community to identify a set of user requirements;
• to define and develop a hardware/software solution that is able to offer authenticated and certified time for event synchronisation purposes over wide geographical networks with the implementation of a service centre and remote terminals;
• to implement pilot projects that use the authenticated and certified time solution (ACTS) for field demonstrations;
• to disseminate information on the project to reach the greatest number of potential users.

The ACTS concept is linked to the definition of legal time and to the possible application of this concept. A Work Package deals with the laws and acts on the subject in the EU and other major countries. Particular attention has been paid to the integrity information provided by the Galileo system SIS that is one of the major key features of Galileo concerning the possibility of using the Galileo time reference as certified time. The project proposes the Concept of the ACTS, which is a system that uses the Galileo distributed signal and integrity to build a certified and authenticated time reference with an additional crosscheck made with a GNSS independent time reference source.