Du Push to Talk over Cellular au MCPTT

The main objective of critical communications radio systems is to minimize the response times of the various organizations in emergency situations. A push-to-talk button dedicated provides an efficient mechanism to simplify communications between the caller and the called party. This functionality is essential for the coordination of urgent and complex activities because it allows voice exchanges in a fast, efficient and reliable manner.

Push-To-Talk over Cellular (PTToC) technology has come a long way since its inception. Technological improvements have reduced latency and increased data capacity. Equally important, mobile network operators have dramatically expanded 3G 4G LTE coverage in all geographies, delivering nearly full coverage. This combination of high performance and total coverage provides a high-performance solution suited to the demands of mission-critical communications users.

The demand from emergency services (police, rescue, firefighters, etc.) for bandwidth-rich critical applications is pushing governments to use LTE mobile data networks to meet these needs.

Currently, the PTToC market is composed of non-standardized solutions based on over-the-top (OTT) protocols. There is now an emerging range of PTToC applications based on 3GPP standards that can be integrated into the architecture of LTE networks to enable priority optimization with respect to other services. These 3GPP standard-based applications, known as Mission Critical PTT (MCPTT), have caught the attention of public safety actors due to their superior level of reliability and guaranteed performance.

To achieve the required performance, MCPTT servers are hosted within the architecture of the mobile network operator or the private LTE network core. Data traffic on the network is marked with standardized QoS values ​​that allow preferential access during congestion on the mobile network. The combination of MCPTT solutions integrated with mobile networks providing this standardized quality of service now forms the basis of most deployments of government PTToC solutions. Indeed, following in the footsteps of FirstNet in the United States and Safe-Net in South Korea and their MCPTT solutions, several new government programs aimed at establishing public safety broadband networks are progressing in Europe, Canada, Australia and in New Zealand.

While MCPTT standard deployments have focused on government public safety projects, MCPTT solutions for commercial networks are also available to enable mission-critical communications across certain verticals (e.g., industrial, mining, utilities, transport, etc.). Nevertheless, the integration of an MCPTT network remains complex and must be compared to the advantages that can provide a non-standardized PTToC solution installed on a private LTE network or coupled with a multi-operator offer.

MCPTT standard and interoperability

These new MCPTT systems will not operate as isolated solutions but will need to integrate into heterogeneous hybrid environments. Users must be able to communicate reliably regardless of the technology or type of solution: public safety organizations must be able to combine MCPTT with traditional private radio systems if only for migration scenarios between these technologies.

Therefore, one of the most important factors facing any MCPTT deployment is interoperability. The interoperability of technologies is fundamental to guarantee the effectiveness of an MCPTT solution. The interconnection between the existing classic radios and the MCPTT devices as well as their combined treatment on the command room applications, are essential points that the MCPTT ecosystem must solve through interoperability functions (IWF).

Moreover, one of the major growth drivers of the MCPTT market is attributable to 3GPP standardization efforts. Governments derive many benefits from having a standardized PTToC solution. Indeed, standards-based approaches facilitate roaming and interoperability and allow more economies of scale.
This interoperability feature also offers open protocols that help avoid vendor silo and lock-in issues. Although more work is needed in the MCPTT ecosystem, a number of vendors already offer a carrier-grade interoperability feature today that can host group calls on smartphones and conventional radios.

Benefits of 3GPP standardization

In conclusion, the advantages of 3GPP standardization are:

  • Quality of service and compatibility between providers.
  • Economy of scale.
  • Equipment operating on standardized systems.
  • Integration by the operators of a standardized solution rather than functionalities using particular mechanisms.
  • Integration into command room applications facilitated by the standardized approach offering well-defined and open protocols.
  • Interoperability Feature (IWF) introduced by 16GPP Release 3 to enable communications between conventional private radio systems and MCPTT.

The evolution of PTToC solutions will be shaped by technology, competition and customer preferences. It is undeniable that mission-critical communication users must benefit from mission-critical services beyond simple voice functionalities. The model introduced for the MCPTT standard provides a foundation for other critical services, including data transport and video. Indeed, "push-to-video" is now specified in the 3GPP specifications (MCVIDEO), and critical service architectures have begun to refer to push-to-X functionality instead of push-to-talk more limit.