Rail
TETRA’s railway role
Back in February, the Finnish Transport Infrastructure Agency (FTIA) deployed
Frequentis’s Unified Railway Communication and Application (URCA) system,
which makes use of the company’s FTS Bearer Independent Communication
(BIC) solution, to allow it to migrate off GSM-R. This was driven by the GSM-R
network’s operational costs and issues around interference that were being
aggravated by greater use of 3G and 4G within the country. Frequentis’s
Myslivec says “we had no major or even minor outages or incidents since we
went live earlier this year and feedback from end-users and in particular from
the management is very good – the URCA system is actually doing what it
was intending to do”. He also sees little difficulty around eventually adapting
the BIC system to work with FRMCS.
More recently, and as we reported in our last issue, Teltronic’s TETRA
solution has been successfully integrated with the ETCS (European Train
Control System) signalling application provided by Bombardier along the
approximately 300km-long Zhetygen-Altynkol railway line in Kazakhstan, and
has been certified by the line’s operator, Kazakhstan Temir Zholy.
sites), while allowing peaceful coexistence with the existing
GSM-R system – the White Space FRMCS concept. This
entails overlaying a 5G carrier over the GSM-R system and
making optimal use of the spectrum available below or in
between GSM-R frequency pairs.
Tane describes it as a “very convenient solution”
compared with using the 1900MHz band, given the
latter’s potential need for more sites. He says this approach
is “gaining traction and that the proposed contents and
schedule of the test campaign for it has been published in
the relevant ETSI standardisation group, with the first step
expected to take place at the end of October, followed by a
second stage in February and a third and final phase at the
end of June 2020.
Going public?
Frequentis’s Myslivec expects that with FRMCS there will
still be a dedicated network handling the mission-critical/
safety-relevant communications, but there will also be an
additional element in the form of non-critical services such
as passenger information and video transmission. When
it comes to the latter, he is convinced that “the railways
may not be able to afford to build their own network with
sufficient capacity – they will not get the spectrum for that
– so they will share with public MNOs or public safety
authorities and use their networks”.
Rothbaum adds that Ericsson and Deutsche Bahn are
carrying out network slicing trials in “the framework of
FRMCS” along a 30km section of track between Nuremberg
and Ingolstadt in Bavaria on a high-speed test train. “We
were trying to show that we were able to isolate the network
into three different slices, one carrying video surveillance
feeds, one carrying IoT traffic, and one carrying passenger
connectivity traffic over one carrier, but isolating it so that
we could guarantee the throughput over any particular
slice.” While he says that in the trial, there was just an IoT
test device onboard, the IoT use-case being considered here
have operating at 900MHz and the fact that the expense
of building a single new site may be as much as €150,000,
with most of the cost arising from civil works, passive
infrastructure, redundant power supplies and backhaul.
Use of the 1.4MHz option would also allow the railways
to be “more in control of their spending because the idea
is not to force railways to overly densify their base station
sites as soon as FRMCS arrives, but rather let them have
a smooth introduction whereby they would reuse their
existing sites to have a basic level of services over FRMCS
in the beginning, and then with new services being brought
into the picture they could either add new 900MHz sites,
but only where they want it, or add the new complementary
band that is foreseen at the European level, which is most
probably going to be the 1900-1910MHz range.”
He adds that there are two main drivers for network
densification in an FRMCS context – the desire to
guarantee more throughput and the need to co-exist with
other systems. “The 900MHz spectrum is located just on
the outskirts of the public 900MHz band and it might on
occasion be required to densify in certain locations to
make sure that we keep interference to the public networks
to a reasonable minimum”, as that could allow the output
power at each site to be reduced.
Rothbaum highlights techniques such as MOCN (Multi-
Operator Core Network), which allow operators to share
spectrum. He says this (in combination with prioritisation
techniques) could allow more efficient use of the 920-
925MHz band through allowing MNOs to use the spectrum
in the geographical areas where it is not being used for
FRMCS, as opposed to the regulator exclusively allocating it
for railway use. Rothbaum adds that this would be a “win-win
solution as it would increase the ecosystem for the chipsets
so there would be more attraction for chipsets to handle that
particular band and the countries would get more revenue
in allowing that spectrum to be used”. It is of course worth
noting here that there are parallels with CBRS (Citizens
Broadband Radio Service) in the US.
Turning to the 1900MHz band, Rothbaum notes that
one of its big advantages is that it is a standard 3GPP band
– Band 39 – which is predominantly used in China and
is supported by today’s consumer smartphones. However,
given its higher frequency than the 900MHz band currently
used for GSM-R, this raises the question as to how many
additional sites it may require and the cost of building
these. Rothbaum says Ericsson is currently performing a
study for ETSI to simulate “the edge throughput at 4km
at 1900MHz”. He adds that a similar study has been
performed by other companies for the extra 1.4MHz in
900MHz option.
There is a third option for FRMCS that is being
promoted by Kontron Transportation to facilitate the
maximal reuse of the 900MHz infrastructure (particularly
The railways may not be able to
afford to build their own network with
sufficient capacity – they will not get
the spectrum for that
October 2019 @CritCommsToday 19