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Wireless USB + UWB Demotion Goes Ahead For Linux 5.4

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  • #11
    Originally posted by mlau View Post

    I was told at university 20 years ago by an Infineon engineer that the basic idea of UWB is to spread the signal power over a very wide band (few hundred MHz to GHz),
    with a special spreading code. So instead of having a power peak around the center frequency it was basically "hiding" the signal in the background noise. The same spreading code
    applied in the receiver would then filter out the signal from the noise. I always thought it was a brilliant technology for clandestine transmissions: When you casually look at
    a signal plot you wouldn't notice anything because it's indistinguishable from the noise floor.
    That is actually a common misconception.
    UWB does indeed spread the signal over a very large bandwidth - but it does not use spreading codes for it.
    Spreading-code modulation also exists in various forms and has been quite popular. Among the most widely used technologies using spreading-codes are the US Verizon 2G system (Qualcomms cdmaOne) as well as the internationally successfull 3G-System UMTS (WCDMA).
    Both use spreading codes, but those spreading code systems are based on a constant carrier wave.
    It is also common for those systems, that the reception of handsets is achieved below the noise floor.

    UWB however is no spread spectrum technology, as it is a carrier-less system and doesn't use spreading codes.
    The spreading is achieved by merely using very short pulses in the digital domain, which - after the fourier transform - translates to very wide bandwidths in the analog domain.
    It does however look somewhat similar to spread-spectrum and has some of the same properties.


    • #12
      I guess some folks enjoy spreading their spectrum. Whatever floats your boat, I hear it's common practice in American prisons.