Page 391 - From GMS to LTE

VoLTE, VoWifi and Mission Critical Communication 377

5.7.2 Advantages of LTE for Mission Critical Communication
In the 1990s basing a PMR network on hardware and software designed for commercial
wireless networks such as GSM was not possible as network and services were tightly
integrated. As technology advanced, however, it became possible to separate the radio
network from the services running over it. LTE was thus designed with a clear split into
a network that transports IP packets and services that send data, including voice pack-
ets, transparently over the network. This allows the use of LTE technology not only for
commercial customers but also for PMR services. Before looking at the technical details
the following sections give an overview of the benefits of separating the network from
the PMR services running over it.

Voice and Data on the Same Network
A major feature that 2G PMR networks lack today is broadband data‐transfer capabilities.
LTE’s broadband data capabilities can easily overcome this shortcoming. Video back-
hauling is perhaps the most demanding broadband feature but there are countless other
applications for PMR users that will benefit from a fast IP‐based data channel, such as
for example number plate validation and identity checks, and access to police databases,
maps, confidential building layouts, etc.

Clear Split into Network and Services
For the most part, PMR functionality is independent of the underlying core network
and radio infrastructure in LTE. For example, the group call and push‐to‐talk (MCPTT)
functionality is implemented as an Application Server (AS) in the IP Multimedia
Subsystem (IMS), which is mostly independent from the radio and core transport
networks.

Separation of Services for Commercial Customers and PMR Users
One option for deployment of a public safety network is to share resources with an
already‐existing commercial LTE network and to extend the software in the access and
core network for public safety use. In addition, the IP Multimedia Subsystem (IMS)
infrastructure for commercial customers and their VoLTE voice service can be com-
pletely independent from the IMS infrastructure used for PMR users. This way, the two
parts can evolve independently from each other, which is important as public safety
networks typically evolve much more slowly and in fewer steps compared to commer-
cial services, as there is no competitive pressure to evolve the network.

Apps vs. Deep Integration on Mobile Devices
On mobile devices, PMR functionality could be delivered as applications (apps) rather
than being tightly built into the operating system of devices as is the case with 2G PMR
systems. This allows updating of the operating system and applications independently
and easier movement from one device generation to the next.

Separation of Mobile Hardware and Software Manufacturers
Use of ‘over‐the‐top’ PMR apps allows separation between the mobile device hardware
and operating system manufacturers and companies developing PMR functionality,
except for a few necessary interfaces, such as the interface for setting up Quality of