While RFS is focused on the commercial market and
doesn’t off er vertically polarised cable in the 380-430MHz
band typically used by TETRA, Kuklo added that it’s still
possible to use MIMO in this band through the use of
two radiating cables. We briefl y touched on the subject of
passive intermodulation (PIM), which has to be kept to
a minimum in passive infrastructure. André Doll, RFS’s
CTO, highlighted the need for copper cables to be as
clean as possible, while Kuklo said the PIM issue is why
RFS educates engineers and installers on how to properly
connecterise cables. Kuklo also explained that RFS sells
cable for use in US public safety DAS in red, just so
building owners can turn round to their contractors and say
‘whatever you do, don’t cut the red cable’.
One of the most challenging aspects of in-train coverage,
according to Alastair Williamson, CEO of Ranplan Wireless
Network Design, is the way carriages act as Faraday
cages, and the impact this has on RF signal levels must be
considered when designing in-tunnel public safety networks,
so fi rst-responders have the two-way radio service they
require when inside a (typically) stationary train during
an incident. Ranplan’s tools for in-tunnel network design
can model “the physical train”. At MWC, the company
launched a new set of planning tools, one of which is
“focused directly at public safety in-building requirements”.
It can generate the reports that regulatory bodies would need
to see for them to sign off on a network design, designate
areas within a building as mission-critical zones that have to
meet specifi c KPIs and allows the user to understand what
the quality of service will be for a given service (eg, video
streaming or MCPTT) at any point in the building.
When it comes to in-building coverage, public safety’s
requirements diff er from those of commercial network
operators, as the former require coverage in unpopulated
areas, stairwells, basements and elevators. Ingo Flomer,
business development director at Cobham Wireless,
notes that the same holds true for Internet of Th ings
(IoT) devices.
Similarly, it was interesting to hear Commscope’s Buttarelli
say that industrial companies, such as vehicle manufacturers,
are starting to use in-building systems that use commercial
frequencies but are designed from an availability/resilience
perspective with some of the same criteria that are used
for TETRA systems; for example, the use of redundant
equipment to reduce the impact of failures on quality of
service or data throughput.
We have seen that approaches to in-building LTE can vary
widely, and as time progresses it will be interesting to see
which become the most widespread, together with the
degree to which fi rst-responders may become reliant on (and
expect) the data services that will be enabled by in-building
LTE coverage.
Both fi rstresponders
and
IoT sensors need
connectivity
in areas of
buildings that
are not typically
considered by
commercial
mobile network
operators
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