AV’s Wireless Future Getting Sold Off

By Josh Srago & George Tucker

Are wireless microphones moving from the endangered species list to near extinct at the hands of the FCC? How many more times will we be forced to purchase new hardware, or manage more limitations implemented by this oversight organization?

DTV Took my White Space Away

In 1999** the official move to digital off-air transmissions began, providing High Definition on  TV channels. The result was ending the separate analog broadcast of the color, picture and sound signals to one single signal. Many wireless microphones and intercom communications devices had been living in the valleys and ‘white spaces’ between signals and channels. Without the analog signals the broadcasts were able to be consolidated and reorganized, opening up great expanses of RF spectrum for use.

On the eve of the transition from analog to digital television broadcasts, the FCC detailed plans for the resulting free frequencies. It was announced that the portions of the frequency spectrum RF microphones utilized would now be auctioned off  for commercial use. Great swaths of the spectrum were snatched up by telecoms and companies like Google.

What was once a relied upon placement for pro wireless became non-existent. Continued reallocation of ‘open’ spectrum continues. Soon we are to find out just how much more squeeze the FCC is to put on the wireless mic systems.

Re-Location, Re-Location, Re-Location

As recent as 2010 Wireless microphones were forced to relocate themselves from the 700MHz spectrum and move to the 500 or 600 MHz spectrum.  At the end of this month we are going to find ourselves facing another spectrum frequency auction. This time the 600 MHz frequency spectrum wireless audio units were pushed into as a result of the digital television transition is in question.

In anticipation of losing more frequencies to auction, several wireless microphone manufacturers went to the FCC in August of 2015. The purpose was to discuss the concerns of the industry, fight for a larger presence in the FCC’s considerations and look for other opportunities where our devices might find operable frequencies.

The key thing that you need to know if you’re trying to understand where we are at this point, is that we have a little time before things will change in the 600 MHz space. Once the auction has happened it will take the FCC several months to determine the results and reallocate which frequencies are going to remain available for the wireless microphone manufacturers.  All we can do is sit and wait.

After the official determinations are made, the FCC will issue the Channel Reassignment Public Notice, detailing the changes and licence assignments. This is where things get a bit tense. From the release of that public notice the industry will have 39 months to relocate out of the conflicting 600 MHz spectrum we currently inhabit. During this time there will not be a restriction on using the 600 MHz microphones so long as they do not interfere with any other transmission devices, new or old.

The question that remains, though, is what frequencies are going to be opened up for wireless microphones after the March auction and resulting reallocation take place?  As it stands, the chart below shows the current available spectrum for wireless microphones and related audio devices.

 

Frequency Band Licensed/unlicensed Rule Part
26.1-26.48 MHz (VHF) Licensed Part 74
161.625-161.775 MHz (VHF) Licensed Part 74
Portions of 169-172 MHz band (VHF) Licensed Part 90
88-108 MHz (FM) Unlicensed Part 15
450-451, 455-456 MHz (UHF) Licensed Part 74
54-72, 76-88, 174-216, 470-608, 614-698 MHz (VHF and UHF) Licensed and

unlicensed

Part 74 and

Part 15 (waiver)

944-952 MHz (UHF) Licensed Part 74
902-928 MHz, 2.4 GHz, 5 GHz (ISM bands) Unlicensed  Part 15
1920-1930 MHz (unlicensed PCS) Unlicensed Part 15
Ultra-wideband (3.1-10.6 GHz) Unlicensed Part 15

 

The FCC, after soliciting information from wireless microphone manufacturers, used this public discussion to look at new opportunities in the 169-172 MHz band and the 944-952 MHz band. They also opened up portions of three other sets of spectrum bands – 941-944 MHz and 952-960 MHz, the 1435-1525 MHz band, and the 6876-7125 MHz band – all for sharing with licensed wireless microphone operations under specific conditions.

Yes, but will it Blend?

Radio_mic_racks1In addition to specifying new frequencies, the declaration also makes the assumption that manufacturers will continue to advance the technology.  The assertion is that new technology will make  more efficient use of the spectrum made available, particularly in that 1 GHz space. There are no provisions or call outs to what technology would provide this efficiency but it can be presumed we are looking at compression schemes and other bandwidth reducing overhead functions like collision avoidance.

There is something more about the frequency options that the FCC opened up, something that could truly curtail wireless mic usage. The potential could result in greater restrictions on who will be able to use them. Throughout the discussion, a perpetual reiteration and emphasis of one word holds the key.  The word? “Licensed.”

As we all know, currently there are likely, at minimum, tens of thousands of unlicensed wireless microphone units in use throughout the United States. Currently it is blatantly obvious when there’s a transmission issue with a microphone – i.e. noise. How will we be able to pair with other low-power devices operating nearby that we know nothing about? Who will manage the allocations and approvals?  

The higher frequency band operations are likely to be much more heavily regulated, requiring local oversight for allocating the frequencies throughout the spectrum. You read that right – local oversight – as in an organization which will be the final arbiter in deciding which theaters get to expand and which cannot.

Take, for example, the 944-952 MHz band. Licensed users are “subject to the frequency selection requirements contained in Section 74.803 of the Rules”. The Society of Broadcast Engineers, or  SBE,  would run local coordination program for the band and its coordination would have to be mandatory. Accordingly, the FCC will also require those looking to use this spectrum to coordinate their proposed use with the local SBE coordinator. While this has the potential for a bureaucratic nightmare, the upside is that with this oversight,  the FCC elected to open 941.4-944 MHz, 952.85-956.25 MHz and 956.45-959.85 for use by wireless microphones.

New Heights at Lower Lows

Moving up the spectrum, the FCC has also elected that the 1.4 GHz be opened up, but only for fixed locations. Facilities, such as sport venues, where the need is to deploy large systems (100+ wireless microphones) are eligible, but with exceptions. While the increased spectrum is welcome, it does come with the caveat that usage would be limited to specific times only. But wait, there’s more. Further restrictions require that devices must be frequency agile from 1435 to 1525 MHz.  Not only does one have to comply with the cornucopia of rules and regulations above, they devices must be able to move frequencies on demand. And (yes, there is yet another ‘and’) the microphones cannot access  more than 30 Mhz bandwidth of the spectrum.

As one moves to higher and higher frequency bands it is a fact that there is a continually considerable  reduced performance ratio. The smaller wavelengths just do not accommodate the modulation needed to provide proper overhead, agility and broadcast quality audio. Having more frequencies to choose from is good but when it comes at the cost of restricting the potential use cases and applications, it may be of no use at all.

Take for example, the 3.5 Ghz band. The manufacturers have been quite clear on this. Sennhesier pointed out that due to the lower performance issues there would likely be a limited appeal for the spectrum. In their opinion, the frequency would most likely to be suited for intercom. Shure added to the commentary stating that this would be a “good place for alternative uses with relaxed performance requirements.”

One can safely make the supposition that neither company sees this allocation as fit for high performance. It’s easy to see this being a place where many of the microphones we use in corporate environments likely find a home.

Despite these exasperating limitations, the FCC raised the discussion of potential use of the 7 Ghz band. Again, higher frequencies and shorter wavelengths create challenges for form-factor and power-limited use, as Shure pointed out above. Additionally, the poor propagation characteristics of the band make its application uses limited to low performance, high latency devices.  Just how bad are the limitations? Consider the fact that simply placing your hand between a wireless boundary microphone and its antenna in this band would effectively mute transmission.

The FCC has proposed that it would permit use of this band on a licensed, secondary basis between 6875-6900 MHz and 7100-7125 MHz, but restrict the remainder of the spectrum. In addition, use of the frequencies would require coordination and interference avoidance to be resolved by the applicant.

The FCC is also considering  the use of  Ultra-wideband (UWB) spectrum – 3.1-10.6 GHz. UWB is used to transmit low power bursts of data over relatively short distances. Spread spectrum jumps from frequency to frequency over time making a collision unlikely.  UWB broadcasts on a number of channels at the same time with a mechanism to keep the transmitter and receiver in sync. The difference is in power use and Ultra-Wideband’s ability to circumvent obstacles that would hinder other methods.

Currently UWB is available for indoor use only and must consist of hand-held devices that may be employed for such activities as peer-to-peer operation, in our work this would qualify as intercom or IFB.  Again, there are severe performance limitations that must be considered when deploying devices in this spectrum.

Mick Jagger Knows Better

2000px-FCC_New_Logo.svgWireless microphones are still an everyday device when it comes to audiovisual systems. The FCC is clearly making an effort to provide us with opportunities in new spaces to allow us to continue to operate and deploy more system solutions.

Our industry will continue to be the technology sector that loses out on the frequencies that allow for the optimum performance. Our relative size is what hinders us.  While the industry may make billions, it is still  small compared to others. We find ourselves competing for space with television channels, with wireless providers (cell phones), and with other developing technologies.

Thanks to manufacturers like Shure, Sennheiser, and Lectrosonics, though, we have a voice that is helping to make sure that our industry is not ignored and we are left with somewhere to go when all is auctioned off.

As the Rolling Stones song states – ‘… You find sometimes, you get what need.”

You have a part in this too. Let your representatives in Washington know how problematic the transition will be. Let your local congressman know that the more money you spend on inventory is one that takes away from hiring local talent.  Remind them that no industry can survive well when the very ground beneath their feet changes every few years.
If you wish to read the full FCC rules as they were adopted by the FCC in August, 2015, you can find them here.

 

**Correction – original date was shown at 2009, but as noted in the comments below, that transition started in 1999.

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