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)."

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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
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Reply to
kev
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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:

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.

Reply to
Jeff Liebermann

Foundit. Vivato.

Note the TX ERP is 44dBm which is 25 watts.

Reply to
Jeff Liebermann

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."

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

I did find this:-(WO/2005/022833) WLAN CAPACITY ENHANCEMENT USING SDM

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It was interesting to note that last year the initial issue of the AP was not going to include the SDMA software :-
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It appears that they were one of several manufacturers being sued for patent infringement :-
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Reply to
kev

kev hath wroth:

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.

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

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

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

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.

Reply to
Jeff Liebermann

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.

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Reply to
kev

kev hath wroth:

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.

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, 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.

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

Reply to
Jeff Liebermann

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