2017-02-20 | Ming Ho


I recently visited some customers who have interest in public safety over LTE (PS-LTE). They told me that IP-PTT service was launched in the market for long time. However, it did not succeed so why will MCPTT be any different?

The IP-PTT service mentioned by the customers is service based on OMA PoC (Push-to-talk over cellular). It was a standard for immediate two-way communications over mobile network for business and consumer users. Yes, the customers are right as PoC service was not so successful.

I discussed with the Product Manager of my company, Haim Raz. He explained the following to me.

The OMA PoC V1.04 was the first standard, approved in 2009, which established Push-to-talk over Cellular (PoC) as a form of immediate two-way communications for business and consumer customers of mobile networks. Then V2.0 was approved in 2011 and expanded on the voice communication that was enabled in V1.04, making it possible to instantaneously share video, still images, text and files with a single recipient or between groups of recipients. In the V2.0 standard, OMA PoC also enabled interoperability among network entities, including an interworking functionality that allowed other external push-to-talk networks to interwork with a PoC service infrastructure. In 2011, OMA’s PoC V2.1 was approved. It took push-to-talk communications beyond business and consumer users, defining new functionalities for critical communication, such as multicast PoC, ad-hoc or pre-defined PoC group communications, prioritization and pre-emption, and dispatcher functions.

OMA developed PCPS V1.0 (Push to Talk over Cellular for Public Safety), which covered all OMA PoC V1.0, V2.0 and V2.1 requirements, including those for critical communication. On March 30, 2015, OMA license was granted to 3GPP, meaning 3GPP will take the work that was done by OMA PoC and later PCPS standards and will use it as the base for MCPTT that standardized as part of Release 12, 13 and further releases.



Haim further explained to me the reasons why PoC was not so successful:

  • The PoC standardization defined how to implement Push-to-talk capabilities, similar to those provided by IDEN in GSM. The intention was to use the mobile network data channel as a pipe, targeting 2G, 3G and LTE networks however GSM, CDMA and UMTS data capabilities lacked the robustness and capabilities of the 4G LTE hence the solution was confined.
  • The PoC was quickly adopted as over-the-top, something the MNOs did not like and would not promote because they failed to recognize revenues from this. Nonetheless, there was some cooperation of PTT applications which enabled the offering but it didn’t have what was considered to meet stringent availability, security, resiliency and robustness mission critical segment (Army, First Responders, Facilities and Utilities communications, ports and airports, Security etc.)
  • Only recently new technologies were introduced to improve the connectivity over Mobile LTE, features like MBMS (Multimedia Broadcast and Multicast Service) which allows improved group communication and rich communication features standardization across mobile operators etc.


On the other hand, MCPTT gains much more momentum:

  • The inclusion of Governments allows funding of the development and much-needed resources, such as dedicated mobile spectrum which is expensive building block and enabler.
  • Legislation and standardization force the progress of the solution as it has to meet the time frames of governmental implementation roadmap.
  • Standardization bodies (3GPP, GSMA, IETF, ITU-T) are more motivated to work with National Safety organizations (NPSTC, NTIA, PSAC) to define the standards.
  • LTE is an enabler for an enriched ecosystem of applications and implementations that requires low-delay and high-speed, broadband data supported by LTE, which was harder to achieve in 2G and 3G (CDMA and UMTS) networks.
  • LTE became widely deployed and its coverage keeps growing every day.


I am not a technical guy but Haim's explanation made me think about the similarity of VoIP vs VoLTE.

VoIP has been in the market for long time. There are many communication applications based on VoIP technology. Everyday, many people are using it even though they may not be aware of it. Before VoLTE, the voice calls in mobile world were based on legacy circuit-switch technology. Even though there were some free VoIP mobile apps, many people still relied on the regular voice call service provided by MNO. Until the massive launch of VoLTE, MNO changed the used technology seamlessly and quietly. Nowadays, when you make a voice call over LTE network, you may find that the voice quality is better and connection time is faster. It is because of VoLTE. Users are not aware as it is seamlessly integrated in your everyday life.

For most people, they do not know what VoLTE or circuit-switch call is. They simply make a voice call via the regular dialer of the mobile phone. If they call another 4G phone that supports VoLTE, the MNO will make the connection based on VoLTE technology. If the receiving side is a 2G phone or 3G phone or 4G phone not supporting VoLTE, then the MNO will fall back the connection to legacy circuit-switch technology. It is just a matter of time, when 2G and 3G phased out, then all voice calls will be unified to use VoLTE technology.