As engineers have discovered how to make spectrum in the higher reaches of our radio spectrum useful for purposes no one had thought possible, public safety, along with others who needed it, were assigned some of the spectrum, but by no means enough to satisfy the needs of everyone. Now it seems decisions to re-allocate spectrum are being made more and more by attorneys and other officials with no understanding or regard for the implications of their actions.
When FirstNet was established by Congress in early 2012, the public safety community was forced to accept a give-back of the television spectrum then being used by both public safety and business radio users in eleven major cities and their suburbs. Congress explained that in order to have spectrum for broadband, the public safety community would be required to give back some of its spectrum. However, as I a wrote in an earlier Advocate, this requirement will place a burden on the public safety and business communities now using that TV spectrum. It appeared as though Congress honestly believed what one vendor reportedly was telling it, and that is that push-to-talk over LTE is only a few years away, therefore it won’t be a problem to relocate these agencies to FirstNet by 2022.
Next on the list of spectrum issues for public safety is the continued use of the 4.9-GHz band for public safety-only type Wi-Fi services. The FCC seems to think this band is not being used very heavily and it can be shared. What the FCC is missing is the fact that where the 4.9-GHz spectrum is in use it is providing valuable backhaul for cameras and point-to-point links for simulcast and other systems. Further, once FirstNet is being rolled out, the 4.9-GHz spectrum will be an ideal adjunct to provide more capacity during incidents and to provide connectivity between users and vehicles equipped with FirstNet data services as well as LMR capabilities. Yet it does not appear the FCC has considered that there will be increased demand for this spectrum.
The latest challenge to public safety spectrum in the United States is the move by satellite companies that have introduced a docket to be considered at the 2019 World Administrative Radio Conference (WARC) that would classify the 460–470-MHz band for satellite downlink use and raise the satellite license holders to primary status on that spectrum. This means all public safety systems currently in use in the United States including police, fire, and primary paramedic to hospital channels could be subject to interference. Since satellite users would have primary status on the band, public safety would have no recourse if there was interference.
Some say that because this spectrum would be used for satellite downlinks the chance of interference to terrestrial systems would be small. However, those making these statements are not radio engineers and they do not seem to understand that any new radio radiation in a given portion of the spectrum will raise what is called the “noise floor” of the band. The noise floor is measured as the amount of noise in a band when there are no radio signals using it. This is an important number because the more noise that is present across a portion of the spectrum, the less effective receivers trying to hear radio signals are.
The noise floor increase over the past decade in the Wi-Fi bands is the reason Wi-Fi access points seem to have lost some of their coverage and speed capability. The more Wi-Fi access points there are in a given area, the higher the noise floor and the more difficult it is for an access point to hear a Wi-Fi device and vice versa. There appear to be several trends emerging when it comes to spectrum allocations, re-allocation, and sharing.
The first is that many of those making decisions about spectrum are no longer listening to technical people. This means interference between systems and reduced performance on systems due to noise floor increases will only worsen. Then there is a perception that broadband is the future of all communications so we can start to rid the spectrum of all narrowband users and convert them to broadband so their spectrum can become available for broadband as well.
Public Safety Spectrum
The above spectrum issues affect much more than the public safety systems in use. However, the urgency to stop the erosion of the public safety spectrum needs to be addressed quickly. Unfortunately, some of what is driving the spectrum issues is that the non-technical folks (again) have become believers that the new public safety broadband network known as FirstNet will be able to handle all public safety communications requirements going forward. After all, commercial operators are able to handle 50 million or more users on their broadband networks and by some counts there are less than 5 million public safety people and vehicles in the entire United States (not counting federal agencies). If commercial systems can handle 50 to 100 million users, certainly FirstNet can handle 5 million public safety users so all of the other public safety spectrum will become surplus.
In other countries, public safety networks are built and run by commercial networks and now FirstNet will be built and run by AT&T, and AT&T is making all its spectrum available for public safety use on a pre-emptive basis. So the sooner we move all of the public safety community onto FirstNet and off its land mobile radio systems, the better off public safety will be, correct? NO! Today broadband falls far short of the needs of the public safety community in areas that could cost lives. The FirstNet and AT&T network will be a boon to public safety for sure, but for many years to come the broadband side of public safety, and the Mission Critical Push-to-Talk (MCPTT) voice side will be as important if not more so.
It is difficult to explain the differences between public safety communications and a commercial broadband network to non-technical people. It is also difficult for these people to understand that when they suffer from a dropped call, slow data speeds, or the inability to access the network, it is an inconvenience to them, but to first responders it could mean their life. FirstNet will have pre-emptive priority but I hear people ask about communications deep into a building where fire fighters are searching for people and trying to reach the heart of a fire. What about communications between users when there is no network coverage? What about the ability to take incident communications off the main radio channels and confine them to local communications for those directly involved with the incident? Today none of this is possible with FirstNet or AT&T, perhaps it will be at some point in time but not today.
AT&T will be the first to tell you its FirstNet system needs to co-exist with today’s land mobile radio systems into the future. When will that change? When FirstNet is ready to provide each and every communications service and mode that is available today with a mix of land mobile radio and broadband. Both the public safety community and the public it serves could be put in harm’s way if spectrum is taken away from the public safety community before the new network is proven to be able to support every aspect of the needed communications on a network that has been hardened and meets mission-critical status.
To help solve these spectrum issues, which will only worsen, I believe we need to take a step back in time and hire experts who understand spectrum and noise floor issues, narrowband, and wideband systems, and have them take part in discussions leading up to decisions about what to do in a given situation. LightSquared, which is behind this latest satellite spectrum grab, almost destroyed our ability to use our GPS systems. If you remember, the FCC approved a waiver for it to use the spectrum adjacent to the GPS band for terrestrial instead of satellite services.
The FCC did not spend much time looking at the technical feasibility but seemed to believe the LightSquared folks when they said there would be no interference. It took the industry, the FAA, all branches of the military, and others to make the FCC understand that the GPS systems could not, in fact, withstand broadband cell sites in spectrum so close to the GPS receiver band.
Public safety does not have the clout to bring forces such as these to bear on an issue. The National Public Safety Telecommunications Council (NPSTC) is doing the best it can and has been carefully watching spectrum activities. It has actively sought to change the T-Band ruling, and is now sounding the alarm on the 460–470-MHz spectrum, but it needs more assistance and we need to find a way to make organizations such as the FCC understand that in addition to the attorneys on their staff they really need to find more qualified technical expertise to assist them.
Spectrum is a finite resource and it is being gobbled up for broadband at an alarming rate. Just a few years ago, TV channels 53-69 were in service where today Verizon, AT&T, and others are deploying broadband systems where the first block of public safety spectrum is and where the 700-MHz public safety LMR spectrum is. Some TV stations in the 42-52 range are going away or relocating downward in the TV band for even more broadband spectrum. In the near future TV channels 32 to 42 could also be relocated to enable even more broadband services to be deployed. 5G will start using spectrum much higher in the band for small cell deployment. What is not needed in all this is for public safety to lose its spectrum for the wrong reasons. Giving up spectrum when is it no longer needed, if that ever happens, is one thing. Being forced to give it up or share it before that time should not even be a consideration.
Public safety has had to fight for every kilohertz of spectrum is has, channel by channel, over the years. It cannot afford to lose entire swaths of spectrum because those making the decisions do not understand the ramifications of taking it back or reallocating it to others. Let’s bring some spectrum expertise back into the spectrum allocation process, and soon.
Andrew M. Seybold
©Andrew Seybold, Inc.
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