FCC Frees Up Vacant TV Airwaves For "Super Wi-Fi" Technologies and Other Technologies.

9/23/2010 2:58 PM EDT

Here is a link to the FCC announcement:
http://hraunfoss.fcc.gov/edocs_public/attachmatch/DOC-301650A1.pdf

9/23/2010 3:42 PM EDT

The TV broadcast spectrum is grossly under-utilized and the NAB's argument against allowing white space devices is weak -- especially after the FCC set aside dedicated channels for wireless MICs.

After all the studies, analysis and debate of the last few years, the FCC rightfully decided that the public benefits of new unlicensed spectrum far outweigh the risks of inconveniencing performers and other wireless MIC users who might now have to use a different channel that the one they've been using all these years.

9/23/2010 3:57 PM EDT

@Feory

That might satisfy the case for wireless microphones, not withstanding the requirements for new capital expenditures. Now let's address the implications on TV over-the-air and CATV headends.

Anyone out there have the numbers for adjacent channel rejection in a modern TV receiver?

9/23/2010 4:32 PM EDT

Modern ATSC DTV receivers must tolerate -33 dB D/U (desired to undesired) for upper or lower channel DTV into DTV adjacent channel interference. Even the cheap converter boxes with the $40 NTIA coupons had to meet that spec.

9/23/2010 4:52 PM EDT

I was guessing -32 to -36 dBc, so that sounds like a good number. Doesn't leave much margin for my TV and my neighbors new "white spaces" WiFi system!

9/23/2010 10:20 PM EDT

The cold reality of the OTA television band is that it is tremendously underutilized. Very large numbers of channels in rural areas are completely unused but were nonetheless verboten until this decision. It was commonly accepted that nothing useful could be done without these Draconian protections until WiFi succeeded in bandwidth that was so bad that no one else wanted it. Personally, I think that this decision is long overdue and a very rare case of government acting in the best interests of its citizens.
Larry M.

9/23/2010 10:50 PM EDT

@LarryM

I'm not going to say you are wrong, but if the need was so great why haven't we seen greater adoption of the 900 MHz unlicensed band? The band is currently available, has similar co-channel issues as 2450 MHz, but very desirable propagational characteristics similar to those of the UHF TV channels.

9/24/2010 1:20 AM EDT

I'd have to agree with Feory and Larry M. There are lots of ways to split up the spectrum these days; time division multiplexing, CDMA, etc. The days of "walled gardens" and simple frequency channels hogged by single users are over. Is it easy or simple to make sure the users don't interfere with each other - no, of course not. Think of it as job security for those of us who have to design the systems to do so.

9/24/2010 1:51 AM EDT

Speaking of job security, I think it will be interesting to see how the database of protected channels will be handled. How often? If the update fails is the device disabled? How about the device location? The Report and Order should be public soon, now that it's been signed. We should see answers soon.

Remember TDMA systems requires stations in the network to keep time and CDMA, codes. That's easy when stations are in the same network, not so much when they are not.

Gee, I wonder if over-the-air TV viewers can declare themselves as quiet zones?

So, is this decision the "death nail in the coffin" of over the air TV broadcasting?

"Simple frequency channels hogged by single users" is the basis for FCC frequency auctions, but that's another topic.

9/24/2010 1:35 PM EDT

Here is the link to the "SECOND MEMORANDUM OPINION AND ORDER" signed yesterday:

http://www.fcc.gov/Daily_Releases/Daily_Business/2010/db0924/FCC-10-174A1.pdf

9/24/2010 7:28 PM EDT

Like most death nails this one is probably just helping it along. The final one will be when convergence on seeing video on all computer devices happens. The technology could in place now, but when greed, lawsuits, and politics get involved don't hold your breath for that last nail.

9/24/2010 8:23 PM EDT

I reviewed the new regulations today and it looks like the power levels will not exceed +26dBm EIRP, and limits on PFD are set in the new regulations, which I believe, is a good bit lower than that permitted in the 900 MHz band. Remember that each of the TV Channels is only 6 MHz wide as compared to wider channel(s) in 900 MHz.

I got some satisfaction in seeing limits on power on adjacent channels, both in absolute power and relative power based on incumbents. That comforts me a bit related to OTA broadcasts. I haven't done a C/I calculation yet. I hope it beats the number Feory's provided, at minimal distances.

My work is related to wireless broadband, but this potential to harm OTA has really concerned me, maybe just on principal.

I did a quick link budget calculation and it looks like 2 miles will be about it.

9/27/2010 4:29 PM EDT

Frank, et al,

I just did a calculation for the -38 dBm contour for a full power DTV broadcast station. -38 dBm - 33 dB = -71 dBm, it sure looks to me like a 40 mW TVBD inside 1500 feet could be a problem. Anyone care to comment?

9/27/2010 7:59 PM EDT

Very interesting article. Thanks for the link