When any rule or regulation — from the highest law of the land on down — lacks unified standards or clearly defined guidelines, confusion and conflict soon follow. Anyone who has played a board game with someone who uses their own rules has no doubt experienced this, hopefully with grace and good cheer. But when the stakes are higher, the resulting turmoil has widespread implications.
That is the situation we have at present with public safety wireless communications. We have no nationwide standards — only a jumble of local standards and frequency bands (VHF, UHF, 800 P25). But over the next decade, that is all going to change.
The first standardized nationwide emergency responder network from the First Responder Network Authority (FirstNet) will use LTE high-speed wireless data communications technology in the 700-MHz frequency band and will eventually supplant the use of existing public safety frequencies. The FirstNet network soon will become available for use. This is a good thing, on the surface, but there are already challenges that will be caused by the network’s deployment.
New Opportunity, New Challenges
Initially, the FirstNet network will be deployed as a macro network. Although signals on FirstNet’s dedicated frequency, 700 MHz penetrate buildings better than signals at some higher frequencies, many midsize and large buildings will not be able to obtain the usable signal strength needed for indoor penetration and coverage.
Although the FirstNet network represents an attempt to unify the national public safety communications infrastructure, it doesn’t initially address specific in-building wireless communications needs. Despite the current use of lower frequencies (150 MHz to 850 MHz) to support public safety radios, many buildings experience insufficient radio coverage. Even at these low frequencies, building construction materials can block outdoor radio signals from penetrating indoors.
Underground areas, such as basements or tunnels, are impossible to cover from the outside, and energy-efficient buildings with Leadership in Energy and Environmental Design (LEED) certification that use low-emission windows that block exterior cell signals make matters worse. LEED-certified buildings already enclose 2.5 billion square feet, and approximately 45 percent of nonresidential building construction this year will be green (environmentally responsible and resource-efficient).
Many local governments mandate the use of in-building wireless communications systems for public safety wireless communications systems in buildings over a certain size, but even existing systems will be in for a revamp as the FirstNet network comes online.
In many instances, it will be necessary to rip out and replace existing public safety (or even commercial, in some cases) in-building wireless systems to facilitate the support of the network — and that means buildings need a system that works not just now, but well into the future.
Solving Challenges with DAS
A DAS network is one option for public safety agencies and building owners to use to ensure that they are ready for the FirstNet network and ready to meet current challenges of indoor coverage.
DAS comprises cabling, small remote units and antennas that are distributed throughout a building and linked to a central distribution hub. This hub in turn connects to the RF source used by the mobile operators. Through a DAS, the wireless signal is distributed to all parts of the building.
Because the signal used to support a DAS is separate from outdoor cellular towers, capacity is dedicated to the building, and because the cellular signal brought into the building is operator-provided and operator-supported, users receive a guaranteed level of service, as opposed to unguaranteed performance of a voice-over-Wi-Fi service, for example. Plus, calls can seamlessly hand off from the inside network to the outside network as users move from the inside to the outside of the building.
Six Qualities of a FirstNet DAS
When buying or upgrading an in-building wireless communications system to a DAS, make sure it has the basic functionality for use with the FirstNet network.
First, it should support 700-MHz FirstNet frequencies while still supporting existing cellular and internet of things (IoT) frequencies. In addition to the current lack of a unified standard, public safety wireless communications systems vary by city and county across the nation. Some systems use 150-MHz and 450-MHz frequencies (which penetrate buildings well), while others use 800-MHz frequencies (which do not).
A building might be using 150 MHz, 450 MHz or 800 MHz today, but when the FirstNet network arrives, the building will have to transition to 700-MHz frequency bands. It is probable that all these frequency bands will be in use until the complete FirstNet transition occurs, which may take several years.
A truly wideband DAS can support any frequency from 150 MHz to 2700 MHz. So it could support many different frequencies with a single layer of equipment, including the 700-MHz FirstNet network, as well as seamlessly supporting future services with no need for additional hardware, such as cabling or remote antenna units. This will simplify both deployment and maintenance while keeping costs down.
Second, it should use fiber infrastructure. Different fire jurisdictions mandate either coaxial cabling or fiber as the transport layer of a public safety wireless communications system. Although most public safety systems today employ coaxial cable, as commercial networks evolve toward fiber, and as FirstNet LTE can be most efficiently deployed on the same layer as commercial LTE, a public safety transition to more fiber is natural. Fiber ensures high signal quality and strength at each remote unit and often can make use of existing spare fiber in a building to connect the public safety wireless system.
Third, it must comply with fire, life and safety standards.DAS components should be certified for use in public safety deployments by the National Fire Protection Association and should comply with various international fire codes. They should be protected bythe appropriate enclosures to shieldremote units from dust, smoke and ash.
Fourth, it should offer a low total cost of ownership. Although a public safety wireless communications system is typically in the budget for new building construction, existing buildings will have to retrofit these systems to support FirstNet frequencies, and they will have to find the money to pay for them. Combined with the previously mentioned synergies with commercial deployments, it can further reduce the costs of deploying the FirstNet network.
Fifth, it must offer symmetrical performance. First responders must have a clear, strong signal wherever they are in a structure, especially in places where signal is not typically critical for commercial users, such as in stairwells and elevator banks. A DAS must provide a uniformly strong signal at every antenna.
Sixth, it must be future-ready.A DAS shouldsupport today’s and tomorrow’s public safety frequencies. Users should not have to install special remote units or modules to support one frequency or another, or upgrade remote units when the FirstNet network comes.
Moving Closer to FirstNet
The FirstNet network represents both a challenge and an opportunity. Many in-building wireless communications systems will have to be upgraded or deployed — some existing systems support other frequencies but not the new 700-MHz FirstNet frequencies, and some buildings lack any kind of indoor coverage.
There is a positive angle, however. As building owners begin looking at the technologies that will allow them to support the FirstNet network and comply with regulations, they have a chance to deploy a single, converged in-building wireless communications system that supports all wireless traffic.
Although the FirstNet network will take several years to roll out, getting ready now with a future-ready, full-spectrum in-building DAS is a must for ensuring clear and consistent radio coverage for both building occupants and first responders, both now and years down the line.
James Martin is vice president of operations at Zinwave.