Originally posted by mlau
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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.
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