Page 393 - From GMS to LTE

VoLTE, VoWifi and Mission Critical Communication 379

typically change their devices every 18 months and move from one application to the
next, a PMR system is static and a time frame of 20 years without major network or
device‐type change was the minimum considered in the past. It is unlikely this will
significantly change in the future.

Network Infrastructure Replacement Cycles
Public networks including radio base stations are typically refreshed every four to five
years for reasons such as new generation hardware being more efficient, requiring less
power, being smaller, having new functionalities and offering higher datarates. In PMR
networks, time frames are much more conservative because additional capacity is not
required for the core voice services and there is no competition from other networks,
which in turn does not stimulate operators to make their networks more efficient or to
add capacity. Also, new hardware requires a significant amount of integration and vali-
dation effort, and the resulting costs can only be justified if there is a benefit to the end
user. In PMR systems this is a difficult proposition because PMR organizations typically
do not like change. As a result the only reason for PMR network operators to upgrade
their network infrastructure is because equipment is no longer supported by manufac-
turers and spare parts are no longer available. The effort of upgrading at that point is
even higher than for continuous upgrades as after a certain point technology has
advanced so far that there will be many problems in going from very old hardware to
current generation hardware.

Hardware and Software Requirements
Quality and reliability requirements are significantly different in the commercial and
private radio networks. In public networks the balance between upgrade frequency and
stability often tends toward the former while in PMR networks, reliability is paramount
and hence testing is significantly more rigorous.

Dedicated Spectrum
Using a dedicated frequency band for an LTE‐based PMR network that is otherwise not
used for public services means that devices need a specialized receiver and antenna
configuration. This means that devices might not be mass produced in the same quan-
tity as commercial devices, which can be a significant cost driver. Production runs of
commercial mobile device manufacturers are usually measured in millions rather than
tens of thousands, as is the case for PMR. Perhaps this is less of an issue today as current
production methods allow the design and production run of 10,000 devices or even less
while still keeping costs in check.

Specialized Mobile Hardware
While for many PMR applications off‐the‐shelf devices and device designs can be used,
there are many PMR devices today that were designed to be more sturdy and that have
extra physical functionalities. These include big push‐to‐talk buttons, emergency but-
tons, etc. that can be pressed even with gloves. Many PMR users will also have different
requirements compared to consumers in relation to the screen of the devices, such as
the necessity for the screen to be more rugged than is normal for consumer devices and
to be usable in conditions of extreme heat, cold or humidity, when chemicals are in the
air, etc. This significantly drives cost.