On 8/29/2013 7:00 AM, Ray Bellis wrote:
On 25 Aug 2013, at 23:39, Vincent Chen <[email protected]> wrote:
All,
As was brought up before (and at) the F2F, the current encoding for a spectrum
profile
has a "channelized" view:
- List of (startHz, stopHz, power)
- Has no ability to specify power level in "unavailable" ranges
Example:
{
"point": { "startHz": 5.18e8, "stopHz": 5.24e8, "maxPsdDbmPerBw": 30.0 },
"point": { "startHz": 5.24e8, "stopHz": 5.30e8, "maxPsdDbmPerBw": 36.0 },
}
Question: Should we use a more flexible encoding?
There were two proposals made on the list:
- Option 1: List of (startHz, startPower, stopHz, stopPower)
- Option 2: Ordered list of (freqHz, power)
At the F2F, we agreed that Option 2 was the more general form.
Example:
{
"point": { "freqHz": 4.70e8, "maxPsdDbmPerBw": -56.8 },
"point": { "freqHz": 5.18e8, "maxPsdDbmPerBw": -56.8 },
"point": { "freqHz": 5.18e8, "maxPsdDbmPerBw": 30.0 },
"point": { "freqHz": 5.24e8, "maxPsdDbmPerBw": 30.0 },
"point": { "freqHz": 5.24e8, "maxPsdDbmPerBw": 36.0 },
"point": { "freqHz": 5.30e8, "maxPsdDbmPerBw": 36.0 },
"point": { "freqHz": 5.30e8, "maxPsdDbmPerBw": -56.8 },
"point": { "freqHz": 6.98e8, "maxPsdDbmPerBw": -56.8 }
}
This example explicitly specifies the power levels in the unavailable frequency
ranges.
This example also shows that it's possible to encode "square edges" by having
two
points using the same frequency, but does allow for "slanted edges" for more
gentle roll-offs.
I recall discussion of whether interpolated ramps were a good idea, and clarification that having the same
"stop" and "start" power would be effectively the same as having a "startHz" and
"stopHz" with a single power level, and thus could also generalise to represent the channelised model.
However I recall no discussion of the latter encoding - I thought the proposal
was to go with your #1 above.
BTW, what value of "Bw" would be used to calculate the Psd when the interval
between points is not constant? Given the OFCOM and ETSI requirement for both a
channel-wide in-block EIRP *and* a 100 kHz spectral density, how would these be encoded
in either of these variations?
Also, I don't understand the note about specifying power levels in "unavailable" ranges. You appear to be suggesting
that the "magic value" of -56.8 dBm above indicates "unavailable", but I can't find the thread that gives the
rationale for this. It only appears to be necessary because there's no scope within a single array of "points" to omit
a range of frequencies, whereas option #1 allows that by explicitly only listing "available" ranges.
I too was confused by this, and *think* I have figured it out (perhaps
incorrectly):
"Unavailable" means the channel is not indicated as available at the
specific location and time of the query. Thus intentional radiation by
a whitespace device is not allowed. In real RF systems, a device
transmitting in an available channel near the unavailable channel will
have some energy "spill" outside the boundaries of the channel. The
white space issued and proposed regulations I have reviewed have
different definitions of what is allowed to "spill". I assume (dangerous
word alert) that the intention is to allow communication of these
different regulatory requirements.
FCC regulations do not define "unavailable" but do specify limits on
emissions by TVWS devices outside of the TV channel being used, whether
it is indicated as "available" or not. This is specified as a level
relative to transmit signal level, not absolute dBm (" 72.8 dB below the
highest average power in the TV channel in which the device is
operating."). For frequencies beyond the TV channel adjacent to channel
being used, maximum emissions are defined as field strength (15.209).
Representing the later is in dBm requires defining the parameters for
conversion; Note FCC received multiple comments suggesting changing the
adjacent channel requirement to an absolute level and not relative to an
actual level. I don't see how the FCC requirements as issued can be
expressed in this format.
I might be misinterpreting the intention.
Ben
kind regards,
Ray
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