Converged TSN/5G Networks

A current trend in the industry and academia is the endeavour for an unification of communication technologies in order to develop a single technology that is capable to serve diverse real-time and non-real-time applications. A solution discussed by industry and standardization groups to address the novel requirements is Time-Sensitive Networking (TSN). TSN is a set of IEEE 802.1 standards which adopts  Ethernet to enable real-time capabilities. In line with the targets of Industry 4.0, wireless technologies will also become an indispensable aspect of future industrial communication at a large scale. The fifth generation cellular network technology (5G) is a promising technology to approach the lack of mobility and scalability in wired networks. 3GPP groups pursue the interest to enable 5G real-time features to make it suitable for industrial applications.  Therein, a key aspect is the seamless integration with TSN to establish converged TSN/5G networks.

A prerequisite for industrial applications and real-time communication is a tight synchronization in the time domain. The synchronization in TSN networks is established through the generalized precision time protocol (gPTP) according to IEEE802.1AS. A major challenge of converged TSN/5G networks, with respect to traditional TSN networks, is to achieve and maintain tight synchronization between end-devices. This is because the convergence of TSN and 5G yields the engagement of heterogeneous synchronization mechanisms (gPTP for TSN networks, PTP telecommunication profile for the 5G core, and 5G built-in reference time indication for the radio access network) and because the deployment of radio links introduce uncertainty. A typical requirement for industrial applications is a synchronization accuracy of < 1us.

The integration of TSN and 5G is heavily discussed by both 3GPP and IEEE yielding the integration of 5G with TSN as virtual TSN bridge (VTB) . The VTB enables a seamless integration of 5G with TSN by concealing the 5G complexity using dedicated TSN translators (TTs). These provide a TSN compliant interface towards the TSN network. A key feature naturally is the support of synchronization through the gPTP. From an architectural perspective, the TSN/5G integration as VTB is thoroughly defined. The VTB user plane architecture and the different synchronization mechanisms are shown in the Figure below.