The First Responder Network Authority’s (FirstNet) award of a contract to AT&T to build the authority’s nationwide public safety broadband network was well-received by the public safety communications community.
The network holds the promise of much-needed advanced wireless broadband communications and interoperability among first responders. The national, seamless, IP-based high-speed mobile communications network will give first responders around the country their own dedicated multimedia capabilities over a common and dedicated LTE 700-MHz Band 14 (B14) network. LTE, short for Long Term Evolution, is a global standard developed by the 3rd Generation Partnership Project standards body.
As an early commitment to provide first responders with priority communications, AT&T announced that, for any states opting in to its program, FirstNet will give preemptive priority to first responders already using AT&T’s commercial cellular network. This priority will ensure first responders access to LTE services ahead of FirstNet network availability, and certainly will be a motivation for the states to opt in.
Big challenges loom for AT&T’s efforts to build a separate LTE network on B14 radio-frequency spectrum: achieving coverage objectives, building the network on time and making use of capital expenditures (capex).
As a first pass, AT&T probably will install macro LTE Band 14 Evolved Node Bs (eNBs) in major urban centers to overlay its existing national commercial cellular network that involves some 40,000 cell sites. An eNB is an LTE base station component. This nearterm approach helps AT&T make use of its lease agreements with tower companies in major metro markets around the country and activates a truly segmented LTE B14 network in dense population areas where a separate first responder network is imperative.
Where to Begin?
Questions are being raised, however, as to how much public safety broadband network coverage AT&T can achieve over the next five years. There are five criteria or datasets that determine where the FirstNet network will be built. These are:
- Number of police, fire and emergency medical service (EMS) users in a given jurisdiction
- Public safety high risk/areas of interest
- S. Census block population data
- Developed areas and buildings (what firefighters call the built environment)
- State and interstate roadways
- These datasets help develop suitable coverage maps on a state-wide basis
Even so, coverage maps show many open spaces where the FirstNet network will not reach. This limitation suggests that many small towns and rural areas may not adequately be covered by the network for quite some time, if ever.
Urban, suburban and rural first responders will continue relying on legacy technology such as P25 land mobile radio (LMR) systems whether there is FirstNet public safety broadband network coverage or not. These widely deployed P25 LMR systems, although not interoperable for the most part, do provide individual police, fire and EMS organizations a way to communicate.
These older P25 systems are not going away, even where AT&T will install the FirstNet B14 network. Coverage for first responders is not just outdoors; coverage is needed indoors in underground parking garages and other areas that are challenging for any radio system. As such, it will take time for the FirstNet LTE network to reach these areas and match the coverage the numerous P25 systems deliver today.
Timing and Funding
Timing of the nationwide public safety broadband network build-out is another big issue. AT&T committed to a build-out schedule that achieves 60 percent coverage in two years, 80 percent in three years and a nearly full build-out in five years. Even with a sense of urgency and AT&T’s offer of preemptive first-responder priority on its public LTE network, building a separate and autonomous FirstNet network in that time frame is questionable without a significantly different approach to network design and deployment. Faced with the prospect that critical sites may not be built for some time, the state governors or AT&T itself may elect to accelerate and augment the FirstNet main deployment plan with supplemental coverage.
Finally, there’s the money. Expect the lion’s share of AT&T’s planned $40 billion capital investment to construct the network in major cities and populated areas. How much will go to small town and rural areas still is an open question. Capex for extending the public safety broadband network to small towns and rural areas probably needs be scaled proportionally. In other words, from an equipment perspective, the same large macro cells used in high-traffic areas probably are not the ones needed in applications involving fewer first responders that operate over wide areas. Are the small cells offered by AT&T’s LTE established equipment suppliers suitable for rural FirstNet deployments? They certainly were not designed to serve few users over wide areas as the FirstNet challenge poses.
In these situations, when planned coverage will not be delivered for some time, a better solution is a much smaller, self-contained and all-outdoor eNB. These fit-for-purpose eNBs are well-suited as supplemental eNBs — they are highly functional and easy to deploy, and they come at a much lower price. Supplemental eNBs offer additional coverage, reach and capacity, as do the large eNBs, but for areas with low first-responder density.
It is important to note the supplemental eNBs will not operate in isolation from the nationwide public safety broadband network. Rather, supplemental eNBs enable the state governors, FirstNet and AT&T to deliver communications in a complementary manner, supporting all the same handheld devices (smartphones, radios), laptops and tablets and all FirstNet applications, but at much less expense. In fact, supplemental eNBs will connect directly to the network’s Evolved Packet Core (EPC) via wireless or fiber cable backhaul. Supplemental eNBs will only be used with First- Net and AT&T’s approval, and will enable a faster, less-expensive means to build a truly separate B14 coverage overlay where macro cell density is not needed.
Typical places where supplemental eNBs could be used to advantage include rural towns, cities and villages; rural road coverage; national parks; aboriginal lands; rail lines; long stretches of highways; and industrial sites used in oil and gas, mining and forestry operations.
The point is that supplemental eNBs are part of the FirstNet network architecture and design. They can help First- Net, AT&T, state governors, public safety communications officials and U.S. taxpayers achieve much greater coverage, while meeting FirstNet’s performance requirements faster and for less money than merely extending the same large-scale infrastructure components used in the backbone network.
Several radio manufacturers have proven the viability of supplemental eNBs in recent field trials.
One vendor successfully demonstrated its end-to-end LTE B14 supplemental network solution at the Ohio State University (OSU) football stadium in November 2016. Even in an urban area, there is a clear need for a separate LTE B14 network to give first responders autonomous, dedicated broadband communications capabilities. With support from a supplemental LTE B14 network, OSU first responders ensured security and safety for the more than 100,000 fans in attendance. In today’s super-connected world, most or all of the fans carry smartphones that could easily bog down the commercial cellular network during a game.
The OSU field trial confirmed consistent and reliable operation of programmed handheld devices with push-to-talk (PTT) capability, laptops and tablets over the vendor LTE B14 network. Moreover, purpose-built servers and gateways delivered PTT interoperability between the LTE B14 and several older P25 LMR networks.
In the end, supplemental eNBs will augment coverage in areas where the nationwide public safety broadband network cannot or will not reach, and can be deployed in timely and economic ways that first responders require.
Contribution Thanks to
- John Celentano
- Rod Cronin
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