Promoting Interoperability in the 700 MHz Commercial Spectrum

Interoperability of Mobile User Equipment
Across Paired Commercial Spectrum Blocks in the 700 MHz Band

12-69 06-01-2012 QUALCOMM Incorporated 7021921420

So normally I see things like this come and go and I don’t utter a word, however I would like to point out a few things about Qualcomm’s position that I feel like should be made more clear.

Below is a diagram of the lower 700MHz spectrum. A key problem for everyone today is there are DTV broadcasts in many urban areas with extremely high power transmitters. The current FCC requirements allow DTV stations on Channel 50 and 51 to spew interference into the lower portions of the 700MHz spectrum (See Channel A, B and C.) Furthermore, there are 2 blocks, the D and E block in the lower 700MHz that also allow high power (think 50KW of RF power) to be broadcast. For LTE this could be a huge issue to both devices and base stations. Fundamentally, this is an unfair situation to those that purchased spectrum in the lower 700MHz areas and ultimately a problem for end users due to the limitations this places on what we can or can’t do now.

OK so Qualcomm didn’t create this problem but they are aware of it as they have been working on providing components to handset OEMs that utilize this spectrum. So they are trying to facilitate the use of multiple radio bands into the devices we love so dearly but it’s complicated. See their list of spectrum’s they are interesting in building to:

…blah blah…

In fact, Qualcomm’s innovations and ongoing work with carriers and manufacturers demonstrate that there is no need for any FCC mandate.7 Because of the difficult interference challenges described herein, the fact that existing technology does not offer a solution to these challenges, and Qualcomm’s ongoing innovation and collaboration with all carriers and manufacturers, the Commission should not require mobile equipment to be capable of operating over all paired commercial spectrum blocks in the Lower 700 MHz band. 

In reviewing their document it’s clear that they are protecting their interests, that is they are developing and have been shipping products around Band 17 and Band 13, where their orders have been coming from. I read it as they (QCOM) are not interested in the 700MHz Band 12 spectrum holder issues as much since these smaller interests represent a greater deal of complexity and will have less payback than serving the larger operators. The issue they hold up as the big fish is the fact a large signal from Channel 51 or D/E block causes blocking and IM at the device receivers.

Sooo naturally

 part of the American experience (IMHO) is the fight for the little guy. If Qualcomm is allowed to ignore Band 12 issues and only sell to the big guys then big business wins and the little guy loses. 

It doesn’t have to be this way, there is a way to get what you want but some things will have to change. 

Let me take a moment to crow, and eat crow. I wrote a series of posts deriding Apple for its design choices regarding the Qualcomm transceivers. I only went off of publicly available information to keep everything on the up and up. 

On the other hand, I was right about everything I said in the corrections on the Qualcomm parts. My assertions are backed up in Qualcomm’s document. The reason I say that is because this story is possible to resolve amicably and my assumptions are built on some truths.

Key point is new components such as Qualcomm’s WTR1605L make Band 12 deployment possible, just not supported without changes to the propagation environment of the broadcasters thanks to Qualcomm not wanting to go any further on the solution development.

Recommendations!

1. FCC doesn’t need to mandate the world to use Qualcomm’s products, much less the WTR1605L, the MDM9615/MFM8930 etc… There’s already a huge challenge getting multiple suppliers in the space and layers and layers IPR issues that haven’t even been made public yet….
2. The rules on the side skirts of the Channel 51 and D and E block spectrum holders is causing harm to a greater number of people than changes to these rules would. Make the roll off’s sharp such that interference is minimized. Be more fair and only make it an optional mitigation to be whipped out in case an operator actually wants to deploy in the A, B or C blocks (Band 12) and not just for Band 17.
3. Qualcomm could feel free to improve the Band 12 filter.
4. Baseband interference cancellation would be a good part of a solution too.
5. Utilize a small cell strategy to target users very effectively. It’s one thing dealing with interference from a 1000′ tower to the users served by your 200′ tower and another when the device and base station are within 100 meters of each other. I can help you do this if you don’t know how to make it happen.
6. Lower 700MHz spectrum holders can consider a fixed deployment instead of mobile. It’s less difficult to null out interferers.
7. If all else fails, just contact me directly. I will sell you TX filters to reduce the transmission of the interference and help you work it out with the broadcasters to boot.

  At the end of the day, it’s up to the little guy to fight the power. People need to voice their opinions on this matter. Do you want better LTE data coverage? Do you want more companies to be able to offer LTE? More devices? Are you completely confident that Verizon and ATT will pass any device savings on to you that they could get from locking out variations?

Contact the FCC and let them know what you think.

BTW, Mariam Sorond, VP of Technology Development at DISH networks states that TX filters are sufficient to allow normal operations and no FCC rule changes like reducing TX power of D/E block (DISH broadcast) is required…. See her response.

http://apps.fcc.gov/ecfs/document/view;jsessionid=f796PTRD1w7bWhL1w1BnJdbpT1jT52XDGhMGQzMqsGvb0QMQxlGj!-1221852939!-1969853125?id=7021921464