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Do you believe it is technically feasible to protect DSRC systems from harmful interference if unlicensed (Part 15) devices share the 5.9 GHz band?
_______________________________________________________________________________This time with a more accurate subject line...
From: Andy Scott
Sent: Friday, January 30, 2015 10:52 AM
To: STDS-802-11-REG@xxxxxxxxxxxxxxxxx
Subject: RE: [STDS-802-11-REG] Issues with Straw Poll Question 7
All,
In addition to the discussion on Q7, NCTA would like to discuss further Q1.
Q1 as written:
"Do you believe that sharing of the 5.9GHz band by unlicensed (Part 15) devices should be allowed?"
We suggest the following formulation:
"Do you believe that sharing of the 5.9GHz band by unlicensed (Part 15) devices should be allowed if sharing does not cause harmful interference to incumbent operations?"
Rationale: The FCC did not ask for an opinion on whether sharing should or should not be allowed. It asked about the technical feasibility of preventing harmful interference.
Comments welcome.
Regards,
Andy Scott
Vice President of Engineering
National Cable & Telecommunications Association
25 Massachusetts Avenue, N.W.
Suite 100
Washington DC, 20001
From: *** Regulatory and Spectrum Allocation Topics *** [mailto:STDS-802-11-REG@xxxxxxxx] On Behalf Of John Kenney
Sent: Thursday, January 29, 2015 5:54 PM
To: STDS-802-11-REG@xxxxxxxxxxxxxxxxx
Subject: [STDS-802-11-REG] Issues with Straw Poll Question 7
Hi All:
Distinct from the Q5 suggestions I made yesterday, I also want to note prior to tomorrow's TT call that several of us from the DSRC community have some issues with Q7.
Q7 currently reads:
If band sharing is allowed, would you prefer that the upper edge of the U-NII4 band be at 5.925 GHz (all 75 MHz) or 5.895 GHz (only the lower 45 MHz)?
- Only lower 45 MHz
- All 75 MHz
- No opinion
- I do not support band sharing
The question is accompanied by a diagram.
I think it is fair to say that one goal of the Qualcomm proposal is to enable sharing between a U-NII device operating below 5.895 GHz and a DSRC device operating above 5.895 GHz in the same time and place. For example, they would support sharing between an 802.11 device operating in 160-MHz Ch. 163 (5735-5895) and a DSRC device operating in adjacent Ch. 180, or in Ch. 182 or 184. So, I would expect most proponents of that proposal to select "Only lower 45 MHz".
Among those of us who do not support the Qualcomm proposal there are many who do not think sharing should be on a "same time & place" basis. Nevertheless, within that group there may be a reason to prefer the U-NII4 boundary at 5.895.
Speaking only for myself, I believe if sharing is to be permitted, it must be on a DSRC band-wide basis. That means that if DSRC is detected anywhere in the band a U-NII device will cease operation everywhere in the band. Detection is therefore the first line of defense for DSRC activity, including DSRC in Channels 180, 182 and 184. Placing the U-NII4 boundary at 5.895 GHz can then provide a secondary, admittedly weaker, defense for DSRC in those upper channels. That is because Part 15 does not impose an in-band out-of-channel emission limit (like a Tx mask, which does apply to DSRC devices), but it does impose an out-of-band-emission limit. So, if detection somehow fails, this secondary defense could also help avoid harmful interference to those three channels. Placing the U-NII-4 boundary at 5.925 GHz does not provide that secondary protection to Channels 180, 182 and 184.
All other things being equal, I can see supporting the placement of the U-NII4 boundary at 5.895 GHz. But, that view stems from a diametrically opposed concept of sharing than is held by others who will vote the same way. I think this is an indication of a question that needs improvement.
I have two suggestions for consideration:
a) if we cannot reword the question so that there is a straightforward interpretation of the results, perhaps it would be better to delete it
b) Split the "only lower 45 MHz" answer into two answers:
1) "Only lower 45 MHz, and permit U-NII devices to operate at the same time as nearby DSRC devices that use the upper 30 MHz"
2) "Only lower 45 MHz, and do not permit U-NII devices to operate when DSRC activity is detected in the upper 30 MHz"
I welcome comments and suggestions.
Best Regards,John
--
John Kenney
Principal Researcher
Toyota InfoTechnology Center, USA
465 Bernardo Avenue
Mountain View, CA 94043
Tel: 650-694-4160. Mobile: 650-224-6644
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