The saga continues (part II) …

Well, I should have known that trying to keep my comments on the 9/2006 xMax patent brief, will only generate more questions. I really do not have the time (or desire) to go through and discuss all the statements in the patent which are wrong – there are simply too many of them. Let me give you just one example, which is related to questions asked by several readers. The patent has the following statements:

“[0109] Thus noise can be overcome by a brief pulse of high amplitude while another signal of much longer duration and more total power can be well below the noise floor, making it virtually un-detectable.”

“[0110] Thus we understand that it is possible to create a high-amplitude/short-duration signal that can rise above the noise floor, yet due to its short duration and low repetition rate the signal contains an average power that is much lower than the instantaneous peak power.”

This is sheer nonsense. A brief pulse of high amplitude and a long pulse of low amplitude which have the same energy (i.e. the same product of power times duration) are detectable to exactly the same degree. The detectability of the pulse has to do with its energy (power times duration), not power. This is because a long duration pulse which is well below the noise floor will be integrated to yield the same signal to noise ratio as the short pulse of high amplitude. The fact that when you look on an oscilloscope one pulse is visible (sticks up above the noise) and the other is invisible (obscured by the noise) is not relevant. The key point is that integrating over the pulse duration builds up the signal and reduces the noise! This is one of the many errors in this patent which reveal a surprising ignorance of basic concepts such as matched filtering and coherent integration.

The inventor is apparently just not getting this. In a 2005 article he is quoted as saying: “If that doesn’t help, think of the zenon strobe lamp. It’s very bright, but only flashes for a very short time. The average power consumed is quite low, yet the flash can be seen for miles.” This is a very nice story, but it completely misses the key point that long duration low power signals can be integrated to become as detectable as short duration high power signals!

The patent has many examples of wrong statements based on fundamental misconceptions by the inventor. If readers have specific questions related to this patent I will try to answer them. However, to try and do a complete line by line sorting of fact from nonsense is more work than I am willing to do. Sorry …

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3 responses to “The saga continues (part II) …

  1. Diedrik Bosmans

    Hello,
    I like your posts on Xmax, I am a wireless communication professional myself and I agree with you 100%, those claims are simply false! Like the WLAN that could run for years on a watch battery, ridiculous!

    What puzzles me though it that such a company gets endorsed by Frost & Sullivan with a technology innovation award, you would expect such companies to do a minimum of due diligence no? And the fact that are valued at +1B is also intriguing.. Some of the misconcepts are so fundamental that I just cannot understand how so many people got fooled? He sure must be a convincing salesman.. It really puzzles me, what the hell is going on here?

    Good idea for a site btw, nice one!
    Diedrik

  2. JimDeGries@gmail.com

    Diedrik

    Thank you for the kind words. It is good to see that someone understands and appreciates what I am trying to do here.

    I am as baffled as you are as to how the xMax people were able to sell a story which any competent communication engineer should immediately recognize as technically false and incompetent. One possibility is that the level of “wireless illiteracy” which I have been talking about is even more widespread than I feared. There are other possibilities which I prefer not to discuss in a public forum. In any case, the main reason for my writing this blog is to try and inform people about some of the false or misleading claims made in the wireless industry. This is not unique to xMax, although they have taken it to a whole new level.

    As to Frost & Sullivan – please look at my post on “Wild Wireless” and the Gaiacomm award also given by Frost & Sullivan. I did communicate with an analyst at Frost & Sullivan about what kind of checking they did before giving the xMax award. Let me just say that I was not impressed.

  3. Diedrik Bosmans

    That’s funny, I have made the same inquiry with Frost & Sullivan, I am waiting for an answer.. I am aware of the Gaiacomm award, but I would expect that such foolishness from the past would make them extra carful now.. Afterall, their reputation is at stake here.

    Here’s a quote from their own xMax vision document: ““It is easier to perceive error than to find truth, for the former lies on the surface and is easily seen, while the latter lies in the depth, where few are willing to search for it.” – Goethe

    🙂 Those investors cannot say they have not been warned !

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