At the end of last week, it was announced that both LA City Fire and LA County Health Department had joined FirstNet. LA County Fire, which is part of the Los Angeles Regional Interoperable Communications System (LA-RICS), already uses FirstNet. It seems a new agency joins FirstNet every week and the network continues to grow.
Spectrum Demand
Spectrum that can be used for wireless communications is a finite resource. In only the last few years, there has been an ever-increasing demand for this spectrum from many including broadband network operators, companies and organizations that want to deploy private networks, and those who want additional unlicensed spectrum. As a result, spectrum allocation has become increasingly difficult. The National Telecommunications and Information Administration (NTIA) and the Federal Communications Commission (FCC) are being called upon to make some difficult decisions. This situation is further complicated by the advent of 5G, which can be deployed in the low bands (600 MHz up to 1 GHz), mid-band (1 GHz to 6 GHz), and Millimeter Wave band (20 GHz and above) (mmWave).
The NTIA and FCC have been working together to free up additional spectrum and to identify federal spectrum regulated by the NTIA that could be shared with commercial users. Only a few years ago, some of the “new spectrum” in the millimeter-wave band was not deemed usable for broadband commercial deployment. However, it was allocated to others for other purposes and now they will have to either share the spectrum or relocate (if there is some satisfactory spectrum available).
The most significant issue is that, for years, spectrum below about 6 GHz has been licensed to many different types of users. As noted last week, mid-band spectrum (between 1 GHz and 6 GHz), has become a sweet-spot for 5G system deployment. When the specified use for a portion of spectrum is changed, those already using that spectrum cannot simply be disregarded. They must either be relocated or some form of spectrum sharing must be established with the understanding that interference to and from existing users and new users will be minimized.
Today there are many different ways to share spectrum, and there is ongoing research and testing being focused on spectrum sharing in the 5G mmWave bands. And a number of groups and organizations are working on Open Radio Access Network (Open RAN) technology as well as cloud-based hosting and infrastructure testing and experimentation.
The issue facing spectrum regulators is how to satisfy the need for commercial broadband network expansions while also protecting critical-communications systems, including public-safety, so they can continue to operate with only a minimum of interference. As these new spectrum-sharing ideas are being implemented or tested, it is vitally important to minimize interference to those already using the spectrum.
Spectrum Interference
In last week’s Advocate, I wrote about NTIA’s request for a stay of last year’s FCC approval authorizing Legado to use its L-band spectrum for a terrestrial 5G network.
The NTIA filed this stay request on behalf of fifteen federal agencies that are concerned about the Legado network interfering with the existing Global Positioning System (GPS) satellite location service. These federal agencies are not alone in their concern as a number of private companies and organizations have also expressed doubts about the Legado network and the potential for interference to location services we all use every day.
6-GHz Potential Interference
As many of you are aware, last year, the FCC approved adding unlicensed Wi-Fi 6 underneath existing point-to-point and point-to-multipoint microwave systems that already occupy the band. Many of these systems provide backhaul for public safety, critical communications, utilities, and broadcast stations.
Now that this band has begun to be used, there are already reports of interference. The issue when mixing licensed and unlicensed users is if licensed users experience interference caused by unlicensed users, it is far more difficult to determine which device(s) at which locations are causing the problem. When the FCC granted access to unlicensed use of 6 GHz, it claimed its automatic system would identify both the location and spectrum that could be used for Wi-Fi 6 without causing interference.
Some of the problems being encountered indicate there is interference even with the automatic system. I will be participating on a panel at IWCE that will discuss the 6-GHz band and other potential interference.
12 GHz
Activity surrounding the 12-MHz band is coming from terrestrial and satellite companies. Many terrestrial companies are pushing to have a portion of the 12-GHz band reallocated for 5G broadband. However, a number of allocations for satellite service have already been made in this band and there are questions about how this spectrum could provide both types of service.
24 GHz
As I was writing this section, another interference issue came to my attention, this time in the 24-GHz band. You may recall that the FCC recently auctioned this spectrum for 5G millimeter wave deployments. mmWave is also used for weather satellites, and when interference was first reported, the response was that the two groups should try getting along with each other (as if that would solve the problem).
Most know there are many types of interference. Some forms become apparent fairly quickly when they interfere with existing transmissions. When every user in a specific portion of spectrum is licensed, it is relatively easy to identify the source of the interfering signal. However, when interference is caused by intermodulation (the mixing of two or more transmit frequencies), it could originate from a variety of sources including rusted bolts, fencing, or barbed wire at a site.
Interference studies are usually run at a site before cellular or other systems and antennas are installed on towers. Without these studies, there is no way to evaluate the potential for interference before the new system is turned on.
Other types of interference, especially from systems that raise the noise floor in a specific segment of spectrum, can cause loss of the receiver’s range. I like to cite the example in which people who have installed Wi-Fi in their homes or businesses over the past ten years find their coverage has deteriorated over time. The first indication will probably be a noticeable reduction in data speeds. The typical response is to add more Wi-Fi access points in an effort to restore the desired coverage and data speeds.
With inbuilding Wi-Fi, the noise floor has risen primarily because more Wi-Fi devices have been added in neighboring houses, offices, or even different floors in the same building. There are several things that can be done to reduce the noise floor and other interference issues. The first is to change the channel your Wi-Fi system is programmed to use. Cable companies that provide modems and routers to distribute broadband to many homes and offices via Wi-Fi often use the default channel for every installation in an area.
As more spectrum sharing is permitted and more users share spectrum, the chances that the spectrum’s incumbent users will experience interference increase. I am sure the FCC, in its deliberations, tries to determine whether there will be interference, but there are countless causes to consider.
When all users in a portion of spectrum are licensed, it is usually understood that the newest license holder will be responsible for any new interference that occurs and that the newest license holder is obligated to work with existing license holders to mitigate the interference.
Solving interference problems becomes much more difficult when some users are licensed for the spectrum and others are allowed to use the same spectrum without licenses. As the demand for spectrum increases, the FCC will have to find suitable ways for users to share spectrum. Even something as simple as testing before authorizing secondary or additional users on spectrum that is in use could help avoid potential interference. However, there is no way to be absolutely certain new users will not introduce interference over time.
FCC LTE Coverage Maps
Last week, the FCC announced availability of an LTE coverage map. According to the FCC, this map is based on information provided by the four largest carriers: AT&T, T-Mobile, Verizon, and US Cellular. It should be interesting to compare the FCC’s coverage map with coverage maps the carriers show their customers.
I am also curious to see signal-level parameters reported for each carrier. Remember, LTE data rates vary based on how close the user is to the center of the cell site, how much traffic is in the cell sector during the tests, and many other factors.
I have to wonder how the current FCC will make the maximum amount of spectrum that will cause the least amount of interference available to existing licensed users. The push to allocate more and more spectrum for 5G and for 6G, which is already being developed and uses even higher frequencies. How much 5G spectrum is enough, and how much is too much? The previous FCC seemed to believe broadband networks and unlicensed spectrum should rule the day. I am hopeful the new Commission will take a more balanced approach and give consideration to those who need spectrum for critical communications and other wireless communications that is on a par with the consideration that has been given to broadband network operators who want more spectrum. Some seem to believe the solution is to convert all available spectrum to 5G broadband and for a mix of users to share systems for all their communications requirements. This is shortsighted, but I have faith that the current FCC will weigh the needs of all communications groups.
Rural Broadband Updates
The U.S. Senate has approved the bipartisan infrastructure bill and it has moved on to the House (which is on vacation). As we wait for final approval, a number of states, counties, and federal agencies are moving forward with plans to deliver broadband to their citizens who do not have broadband access or cannot afford it.
One of the most encouraging aspects of this new activity is that several states have formed organizations that will review, plan, and approve how and where funds are spent. As far as I know, local and state organizations still have not approached AT&T about the continued effort to build out FirstNet in rural areas. I find this surprising.
FirstNet (Built with AT&T) is perhaps the largest and most successful public/private partnership in the United States today. As more counties and states prepare to deliver broadband coverage to rural areas and other gaps where there is a lack of access today, it seems logical that they would sit down with either the FirstNet Authority or FirstNet (Built with AT&T) and discuss how they might work together.
The law that created FirstNet requires build-out of rural areas for public-safety broadband services. When new FirstNet sites are developed in outlying areas, they usually include additional AT&T-licensed spectrum. I don’t think local and even state officials understand that it might be possible and economically advantageous to work with AT&T to increase broadband coverage by extending the FirstNet public/private joint venture.
Being able to use public-safety Band 14, which is available to commercial users on a secondary basis as capacity allows, is quite an advantage. It is unlikely that the public-safety community will be using the full capacity of Band 14 in rural areas. Band 14, where available, permits use of high-power devices to extend coverage and greatly increase uplink data speeds.
Next-Generation 9-1-1 (NG911)
In its latest iteration, it appears the first infrastructure bill will not include funding for NG911 Public Safety Answering Point (PSAP) upgrades. The second, much larger bill addresses other items that are important to people but that some do not consider to be part of our infrastructure. The public-safety community remains hopeful that the second bill will include funding for nationwide upgrades to all Emergency Communications Centers (ECCs).
These upgrades, when implemented on a nationwide basis, are vital to being able to provide public- safety personnel with more timely and accurate incoming information from citizens needing assistance or reporting an incident. Many states and local agencies have already upgraded their systems to support text-based access. The important next step is to implement nationwide NG911, which supports broadband services such as images and video in addition to text, voice, and perhaps other forms of data as they become available.
With NG911, first responders can receive more and better data including images and video even before they arrive at the scene of an incident. This alone will better prepare first responders for what they are heading into, and they will be able to call for additional assistance before and as they arrive. In the case of medical emergencies, paramedics and EMTs will know more about what they will need to do when they arrive at their destination.
Winding Down
has been making cradles for handheld and tablet devices for public-safety broadband for a number of years. A few years ago, I wrote about the GPSLockbox cradle, remote speaker, and microphone for the Sonim XP8. Its newest product provides both heating and cooling of the device while it is in the cradle, and a number of other attributes including:
- Purpose-built magnetic charging and locking systems that stay connected in high-vibration environments
- Customizable for Department Of Transportation (DOT) hands-free compliance push-to-talk with speaker, corded hand mic, and amplifier
- Future-proof mounting that evolves with a user’s tablet upgrade
- Smart wiring harness that ensures the health of the device and vehicle battery
I have always found GPSLockbox products to be well designed, rugged, and easy to install.
Last week in my list of upcoming conferences, I neglected to include the Competitive Carriers Association (CCA). The CCA will hold an in-person conference September 20-22 of this year in Phoenix.
It is difficult to watch news reports of fires in the West with the high temperatures and drought conditions. Firefighters are stretched thin and are doing their best to contain and control the fires. I think there were 90 major fires in the western states at last count.
These fires along with weather issues in other parts of the United States are taxing our public-safety resources. The bright spot in all this is that many of those fighting the fires and working to ensure our safety are, for the most part, able to communicate with each other using FirstNet. It was not that many years ago when interoperable communications were impossible because the only way they could communicate was via land mobile radio systems. LMR is still vitally important today and these systems are being augmented with FirstNet.
As more agencies join FirstNet, everyone will benefit from the ability to communicate with other agencies and personnel. Wider communications will enhance coordination and, therefore, first responders will be more effective in how they handle major incidents.
Until next week…
Andrew M. Seybold
©2021, Andrew Seybold, Inc.
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