MC LTE in USA
overall coverage issue also comes into
play with ProSe/Sidelink, because
there are large areas of the country
with inadequate coverage. We’re a
bit concerned about ProSe, and we’ll
have to see how it plays out.”
Rehbehn goes further, saying:
“The lack of a viable direct mode/
ProSe solution for MC LTE stands
as the biggest barrier to wholesale
fleet migration to MCPTT.” While
the current 3GPP ProSe might be
adequate for outdoor direct mode,
Rehbehn is doubtful it will be
powerful enough to provide indoorto
outdoor connectivity. In addition,
ProSe has had little support from
silicon vendors, with only Samsung
saying it will implement it.
Alternatives involve either pairing
LTE devices with some form of
other device to provide direct mode
services, or integrating two radios
into a single device. Rehbehn says:
“L3 Harris has made some interesting
developments here, combining LMR
and LTE in cost-effective general
purpose radios for both vehicles and
handheld devices.”
Poltermann says this makes carrier
support for interworking between
LMR and LTE extremely important.
3GPP has completed its work on
the interworking function (IWF)
in Release 16, but ATIS/TIA in
the US are still working on how to
implement it in P25 systems. “We’ll
have to see just how many vendors
implement it,” says Poltermann. “The
ripple-down requirements means that
it will take some time to appear.”
Public safety agency
engagement
One disadvantage AT&T faces is
that it is subject to oversight and
public scrutiny in a way that Verizon,
T-Mobile and Sprint are not. It also
has the weight of the public safety
community’s expectations to contend
with, and it seems this might need
some attention.
Poltermann observes: “FirstNet’s
strategy is not particularly clear.
While a roadmap has been published,
the roadmaps don’t provide timelines
or even solid goals. To be a little
harsh, FirstNet communication
throughout the whole process has
been rather terrible.”
Rehbehn points out that FirstNet is
locked into a very long-term contract
with AT&T with confidential terms
and conditions. “Unfortunately, the
FirstNet: Progress so far
AT&T began work on building the Nationwide Public Safety Broadband
Network (NPSBN) in 2018. This involved building a separate secure network
core for FirstNet, which provides priority and pre-emption services to
FirstNet subscribers. It continues to build out its Band 14 700MHz coverage
sites across the country. The roll-out is ahead of schedule and was about 75
per cent complete in January 2020.
AT&T has not revealed the number of vehicular connections versus people
or what proportion of them are primary or secondary responders, but it
reports that “more than 10,000 public safety agencies and organisations
across the country have subscribed. And over one million FirstNet
connections are in service. Current users span federal, state, local and tribal
public safety agencies of all sizes, as well as an extended community of
users that can be called on to help support first-responders.”
Public safety agencies using FirstNet have access to a nationwide,
dedicated fleet of 76 land-based and airborne portable cell sites. Stationed
across the country, these assets are available 24/7 at no additional charge
to FirstNet subscribers to provide additional connectivity in support of
public safety’s mission. During 2019, the FirstNet Response Operations
Group fielded more than 450 requests for additional planned and
emergency support.
An AT&T spokesperson says: “FirstNet is spurring innovation with
more than 100 FirstNet Ready devices and a catalogue of over 100 apps
specifically certified for public safety that can help cost-effectively increase
first-responders’ capabilities and situational awareness.”
Mission-critical networks need to be ‘hardened’ to withstand power
failure and environmental damage. The AT&T spokesperson says: “We’re
rebuilding with network-hardening materials – when possible, we’re
deploying hardened antennas that can withstand hurricane winds, fibre with
reinforced cores, and steel hurricane poles versus wood for attaching fibre;
during Hurricane Maria, we tallied the much higher rate of steel poles
withstanding winds versus wood poles that snapped.
“We carefully assess each disaster rebuild – whenever possible, we
move networks to updated facilities or to a newer technical solution, such
as copper to fibre. We trench and bury new facilities where possible. Unless
a like-for-like solution is better for the customer for faster restoration,
we look to upgrade. For example, in the recent 2019 Dallas tornadoes,
areas where we had already built fibre to impacted neighbourhoods, we
moved customers on copper over to the new, more reliable fibre service
whenever possible.”
In terms of indoor coverage, the AT&T spokesperson says: “FirstNet
gives public safety access to more than 6,000 existing AT&T in-building
assets. This includes in-building solutions in place at stadiums and
transportation facilities.
“Plus, Band 14 provides good propagation in urban and rural areas,
penetrating buildings and walls easily and covering larger geographic areas
with less infrastructure. Only FirstNet subscribers can obtain always-on
priority access to and, for primary users, pre-emption on, Band 14 – no
other wireless provider can do this.”
AT&T has an advantage over its rivals as it can operate high-power user
equipment (HPUE) on its Band 14 spectrum to extend coverage range.
March 2020 @CritCommsToday 25