42dBm ERP

Whilst catching up on my reading I came across this
"The WS410 uses six radio transceivers and six 7.5 dBi omni-directional
antennas. It employs advanced digital beamforming to optimally focus
radio energy to and from network clients on a per-packet basis. While
conventional access points are limited to 36 dBm of effective radiated
power, Wavion’s system is allowed to deliver up to 42 dBm (since it’s
classified as point-to-point service)."
http://www.dailywireless.org/

The FCC rules appear to be in the process of being amended.
"2) In addition to the provisions in paragraphs (b)(1), (b)(3),
(b)(4) and (c)(1)(i) of this section, transmitters operating in the
2400-2483.5 MHz band that emit multiple directional beams,
simultaneously or sequentially, for the purpose of directing signals to
individual receivers or to groups of receivers provided the emissions
comply with the following:......" see pages 105/106
http://www.fcc.gov/oet/info/rules/pa...t15-5-4-07.pdf

On Wed, 27 Jun 2007 19:58:59 +0100, kev <invalid@invalid.invalid>
wrote:

>Whilst catching up on my reading I came across this
>"The WS410 uses six radio transceivers and six 7.5 dBi omni-directional
>antennas. It employs advanced digital beamforming to optimally focus
>radio energy to and from network clients on a per-packet basis. While
>conventional access points are limited to 36 dBm of effective radiated
>power, Wavion’s system is allowed to deliver up to 42 dBm (since it’s
>classified as point-to-point service)."
>http://www.dailywireless.org/

<http://www.wavionnetworks.com/product/index.html>
<http://www.wavionnetworks.com/product/WS410_datasheet.pdf>
Well, at least it's sea gull and possibly pigeon proof.

My baloney filter lit bright red when I saw the data sheet. The
receiver sensitivity specs on the data sheet has this at the bottom:
"Note: Utilizing Coherent Combination of signals"
I don't have a clue what that means or how they measured sensitivity,
but the numbers look way too good to be for real. (Yes, I skimmed the
web pile and Googled for clues).

Also, it can legally deliver even more. For point to point, every 3dB
increase in antenna gain over the maximum +36dBm radiated, the tx
power need only be reduced by 1dB. Handy table:
xmit antenna EIRP EIRP
power gain
+dbm +dbi +dbm watts
30 6 36 4
29 9 38 6.3
28 12 40 10
27 15 42 16
26 18 44 25
25 21 46 40
24 24 48 63
So, with a 24dBi barbeque grill antenna, you can crank out +48dBm
legally.

From the data sheet:
Total Directed Power 42.5 dBm
Calculated from:
EIRP 34.5 dBm
Beam Forming Gain 8 dB
EIRP Calculations:
Radio Power 19 dBm
Antenna Gain 7.5 dBi
Antenna Array 8 dB
Total EIRP 34.5 dBm

Getting that much gain from a circular 6 antenna array using phasing
is really impressive. There's 7.5dBi for a single antenna. 8dB more
gain for the array and 8dB more on top of that for beam forming.
Unless I missed something, the array gain and beamforming are one and
the same and shouldn't be added twice.

It would be interesting to see the FCC reports. I would look it up
except that the FCC ID server is dead (again), and it's not even a
weekend or holiday this time. Maybe tomorrow:
<https://gullfoss2.fcc.gov/oetcf/eas/reports/GenericSearch.cfm>
Search grantees for Wavion.

The rule has been around for quite a long time. I forgot the name of
the company that convinced the former commissioners and staff into
swallowing the idea that beam switching was the same as point to
point. It's not, but that's FCC politics. The original system was
beam switching, where each beam had its own antenna. The logic was
that if you didn't switch antennas too fast, it was like having
multiple independent access points, each with their own antennas. That
kinda makes sense as there are pleny of such system running using
sector antennas with seperate transmitters. Beam switching is just a
"better" sector antenna. Yeah sure, great logic.

Unfortunately, many years later, someone forgot about the slow
switching requirement. Now, it can be on a per packet basis. With
MIMO, it can even be done simultaneously on multiple antennas.
Somehow, the FCC still considers this to be point to point, when it
obviously is not. My never so humble requirement for point to point
would require a directional antenna (with some minimum gain) at BOTH
ends the link. The would eliminate such abominations leaving only
real point to point links.

<http://www.wavion.net/tech/regulatoryRule.html>


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

On Wed, 27 Jun 2007 23:50:51 GMT, Jeff Liebermann
<jeffl@comix.santa-cruz.ca.us> wrote:

>The rule has been around for quite a long time. I forgot the name of
>the company that convinced the former commissioners and staff into
>swallowing the idea that beam switching was the same as point to
>point.

Foundit. Vivato.
<http://www.vivato.net/prodtech_overview.html>
<http://www.vivato.net/downloads/VP12001210%20Datasheet.pdf>
Note the TX ERP is 44dBm which is 25 watts.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 jeffl@comix.santa-cruz.ca.us
# http://802.11junk.com jeffl@cruzio.com
# http://www.LearnByDestroying.com AE6KS

Jeff Liebermann wrote:
> On Wed, 27 Jun 2007 19:58:59 +0100, kev <invalid@invalid.invalid>
> wrote:
>
>> Whilst catching up on my reading I came across this
>> "The WS410 uses six radio transceivers and six 7.5 dBi omni-directional
>> antennas. It employs advanced digital beamforming to optimally focus
>> radio energy to and from network clients on a per-packet basis. While
>> conventional access points are limited to 36 dBm of effective radiated
>> power, Wavion’s system is allowed to deliver up to 42 dBm (since it’s
>> classified as point-to-point service)."
>> http://www.dailywireless.org/
>
> <http://www.wavionnetworks.com/product/index.html>
> <http://www.wavionnetworks.com/product/WS410_datasheet.pdf>
> Well, at least it's sea gull and possibly pigeon proof.
>
> My baloney filter lit bright red when I saw the data sheet. The
> receiver sensitivity specs on the data sheet has this at the bottom:
> "Note: Utilizing Coherent Combination of signals"
> I don't have a clue what that means or how they measured sensitivity,
> but the numbers look way too good to be for real. (Yes, I skimmed the
> web pile and Googled for clues).
>
<Snip>
From their web site

"Beamforming is done by multiplying the signal at each antenna by a set of
complex (phase and amplitude) weights. This weighing is implemented per bin
in the frequency domain. In transmit, the beamforming weights are set so
that the signals from the different antennas sum up coherently at the
receiving client. In receive, the weights are set so that the signals from
the different antennas sum up coherently at the beamformer output."
http://www.wavion.net/tech/beamforming.html

I presume "coherent" in this case means "In Phase".

I did find this:-(WO/2005/022833) WLAN CAPACITY ENHANCEMENT USING SDM
http://www.wipo.int/pctdb/en/wo.jsp?...3&DISPLAY=DESC

It was interesting to note that last year the initial issue of the AP
was not going to include the SDMA software :-
http://www.wifinetnews.com/archives/006833.html

It appears that they were one of several manufacturers being sued for
patent infringement :-
http://www.theinquirer.net/images/articles/linex.pdf

kev <invalid@invalid.invalid> hath wroth:

>"Beamforming is done by multiplying the signal at each antenna by a set of
>complex (phase and amplitude) weights. This weighing is implemented per bin
>in the frequency domain. In transmit, the beamforming weights are set so
>that the signals from the different antennas sum up coherently at the
>receiving client. In receive, the weights are set so that the signals from
>the different antennas sum up coherently at the beamformer output."
>http://www.wavion.net/tech/beamforming.html

Yeah, I saw that. My question is how they managed to get BOTH 8dB of
processing gain, and 8dB of direction beam forming gain out that that
array. Very roughly, you get a 3dB gain boost every time you double
the size of an antenna array. So, you start with one reference
antenna at 7.4dBi gain.
2 antennas = 10.4dBi
4 antennas = 13.4dBi
6 antennas = 14.8dBi
That's an increase of 7.4dB gain over a single antenna, which is a bit
less than the claimed 8dB gain. There's no compensation for losses
and phasing errors. I don't think 8dB beam forming gain is possible.

>I presume "coherent" in this case means "In Phase".

Agreed. Never use the technically correct term when a suitable
marketing buzzword is available.

>I did find this:-(WO/2005/022833) WLAN CAPACITY ENHANCEMENT USING SDM
>http://www.wipo.int/pctdb/en/wo.jsp?...3&DISPLAY=DESC

Argh. That's messy and difficult to understand. I'll read it when I
have time.

>It was interesting to note that last year the initial issue of the AP
>was not going to include the SDMA software :-
>http://www.wifinetnews.com/archives/006833.html

Let me guess(tm).... it's rather difficult to impliment?

>It appears that they were one of several manufacturers being sued for
>patent infringement :-
>http://www.theinquirer.net/images/articles/linex.pdf

That's actually a good thing. No patent troll would sue an
unsuccessful company. That means that the patent trolls have
confidence in the technology and expect Wavion to make money.

Looks like Linex is suing everyone that makes MIMO hardware for
infringing on their patent.
<http://www.google.com/patents?id=skYQAAAAEBAJ&dq=6,757,322>


--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:
> kev <invalid@invalid.invalid> hath wroth:
>
>> "Beamforming is done by multiplying the signal at each antenna by a set of
>> complex (phase and amplitude) weights. This weighing is implemented per bin
>> in the frequency domain. In transmit, the beamforming weights are set so
>> that the signals from the different antennas sum up coherently at the
>> receiving client. In receive, the weights are set so that the signals from
>> the different antennas sum up coherently at the beamformer output."
>> http://www.wavion.net/tech/beamforming.html
>
> Yeah, I saw that. My question is how they managed to get BOTH 8dB of
> processing gain, and 8dB of direction beam forming gain out that that
> array. Very roughly, you get a 3dB gain boost every time you double
> the size of an antenna array. So, you start with one reference
> antenna at 7.4dBi gain.
> 2 antennas = 10.4dBi
> 4 antennas = 13.4dBi
> 6 antennas = 14.8dBi
> That's an increase of 7.4dB gain over a single antenna, which is a bit
> less than the claimed 8dB gain. There's no compensation for losses
> and phasing errors. I don't think 8dB beam forming gain is possible.
They and the FCC are using a different method.
Array gain is the gain provided by coherently combining the beamformer's
N antenna signals.

In receive, this gain is given by 10·logN when the signals at the
different antennas are equal, and slightly lower when the signals are
not equal due to the effect of multipath. However, 10·logN is a good
approximation for all practical purposes. This implies that for a six
element antenna array (N=6), the array gain is about 8dB.

In transmit, the array gain depends on the total power transmitted. If
the power transmitted from the array is equal to the power transmitted
from the reference single-antenna, then the transmit array gain is equal
to the receive array gain, i.e., 10·logN. If, however, each antenna
element in the array transmits the same power as the reference
single-antenna, then the total power transmitted from the array is N
times that of the reference antenna. In this case the array gain is
given by 20·log N. So for a six element array, the array gain is 16dB.

http://www.wavion.net/tech/linkGain.html

kev <invalid@invalid.invalid> hath wroth:

>Jeff Liebermann wrote:
>> kev <invalid@invalid.invalid> hath wroth:
>>
>>> "Beamforming is done by multiplying the signal at each antenna by a set of
>>> complex (phase and amplitude) weights. This weighing is implemented per bin
>>> in the frequency domain. In transmit, the beamforming weights are set so
>>> that the signals from the different antennas sum up coherently at the
>>> receiving client. In receive, the weights are set so that the signals from
>>> the different antennas sum up coherently at the beamformer output."
>>> http://www.wavion.net/tech/beamforming.html
>>
>> Yeah, I saw that. My question is how they managed to get BOTH 8dB of
>> processing gain, and 8dB of direction beam forming gain out that that
>> array. Very roughly, you get a 3dB gain boost every time you double
>> the size of an antenna array. So, you start with one reference
>> antenna at 7.4dBi gain.
>> 2 antennas = 10.4dBi
>> 4 antennas = 13.4dBi
>> 6 antennas = 14.8dBi
>> That's an increase of 7.4dB gain over a single antenna, which is a bit
>> less than the claimed 8dB gain. There's no compensation for losses
>> and phasing errors. I don't think 8dB beam forming gain is possible.

>They and the FCC are using a different method.
>Array gain is the gain provided by coherently combining the beamformer's
>N antenna signals.

Ummm... that's exactly what I did. I wanted to derive the method, so
I combined the output of all the antennas. Comparing results:
10*log(6) = 7.8dB gain.
7.4dBi (single antenna gain) + 7.8dB = 15.2dBi array gain.
Close enough.


>In receive, this gain is given by 10·logN when the signals at the
>different antennas are equal, and slightly lower when the signals are
>not equal due to the effect of multipath. However, 10·logN is a good
>approximation for all practical purposes. This implies that for a six
>element antenna array (N=6), the array gain is about 8dB.

What I'm ranting about is that I don't think it can be done in
practice. Nailing the phase of 6 antennas, through 6 allegedly
identical transmitters, and conglomerating the resultant decoded data
is not easy. It's not just matching the assorted digital and analog
delays, it's also the susceptibility to multipath and moving doppler
sources. I would be really impressed if it could be made to work.

>In transmit, the array gain depends on the total power transmitted. If
>the power transmitted from the array is equal to the power transmitted
>from the reference single-antenna, then the transmit array gain is equal
>to the receive array gain, i.e., 10·logN. If, however, each antenna
>element in the array transmits the same power as the reference
>single-antenna, then the total power transmitted from the array is N
>times that of the reference antenna. In this case the array gain is
>given by 20·log N. So for a six element array, the array gain is 16dB.

In transmit, in order for this to work, the system has to assume that
it knows at which azimuth the receiver is located. If it's off angle
somewhat, the combined arriving signals get smeared with phase
distortion and possibly (not sure) inter symbol trash. In other
words, I wanna see it work under realistic conditions.

>http://www.wavion.net/tech/linkGain.html

Thanks. I see how it works. I'm just suspicious if the numbers are
achievable.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558