are much more affordable. Provided they are
engineered with user outcomes in mind, they can
provide levels of performance not easily provided on
Cellular systems seem to fail during natural disasters.
Quite apart from the extreme load on public systems
during events, natural disasters frequently destroy
infrastructure. LMR survives these events better
than cellular. For example, a disaster usually affects
quite a small region in the context of an LMR system.
Statistically, the few LMR towers will end up surviving
better than the larger number of cellular towers. This
also gives LMR an advantage when power is disrupted,
since refuelling a smaller number of LMR backup
systems is often easier and faster.
LMR systems are effectively circuit switched so you get
exclusive access to some resource for a short period.
This precious resource can also be consumed fully in
an emergency so LMR can be overloaded too.
On balance then, LMR seems a better bet for critical
communications in a disaster. But this does not mean
that a cellular system is unreliable – it comes down to
what service it is designed to deliver. Private cellular
systems like LTE can be engineered to deliver whatever
WHICH BEARER IS BEST? COMPARING LMR AND CELLULAR FOR MISSION-CRITICAL COMMUNICATIONS
RELIABILITY AND EVENT OVERLOAD
We have all experienced cellular systems apparently
failing. Usually this is call drops at the edge of coverage
but during times of extraordinary high use such as
natural disasters, they also seem to fail. Or do they?
Technically, cellular systems are designed to 5x9s or
6x9s reliability, which exceeds normal LMR standards
by some margin. So the issue is not that cellular
systems are less reliable technically. It’s all about
perceived reliability. What a user experiences is a
combination of effects:
• The cellular system is a commercial operation that
delivers service on that basis. LMR is designed for
mission critical use, with short bursts of guaranteed
connectivity. Comparing their reliability is not
straightforward because of the different purpose.
• When we lose a cellular call, often it’s a result of a
3G cell ‘breathing’ its coverage due to loading and
failing to hand off your call to an adjacent cell. With
LMR there is no concept of a ‘cell’, you either get
access or you don’t.
4G LTE systems behave differently again, and so
comparing LMR with 3G and using that to imply
expected behaviour on future 4G LTE systems is risky
– like comparing apples with oranges, then assuming
what is true for apples is also true for pears.
For example, it’s difficult and expensive to create
private 3G systems, but private 4G LTE systems