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PSK [Phase Shift Keying] varies the carrier (power level) signal. Like with multiple shifts (changes) in frequency, there are many changes in phases. BPSK [Binary PSK] shifts 180 degrees. With DPSK [Differential PSK], the phase is not shifted by some known factor but by the phase of the last symbol sent. PAM [Pulse Amplitude Modulation] uses a single carrier frequency which is determined. UWB does not have a center frequency it broadcasts over the entire frequency range. With 7,500 MHz of unlicensed frequency available, UWB is emerging as a high-speed system for extremely short range data transmission.
UWB, or 802.15.3, is a study group under the IEEE and operates within the presence of other 802.11 Wi-Fi systems. That is, UWB will co-exist with Wi-Fi systems. In other words, if a UWB system detects an 802.11 signal, it will change frequency. The technical requirements for UWB so far are: (subject to change)
- Bit rate – 110 and 200 megabits and up to 480
- Range – 30 feet and 12 feet
- Power consumption – 100 and 250 milliwatts
- Frequency range – 3.1 to 7.1 GHz – giga Hertz
- Channel bandwidth – 500 MHz – mega Hertz
UWB signals are designed for short-range, low-power applications such as motion-detection (auto collision detectors), monitoring large numbers of sensors like weather, hazardous materials, inventory tracking, home automation and many others including range-finding (determining distances) for military (bomb-finding) and penetrating capabilities such as stud-finding (nails in walls). Here is a graphic of UWB versus Spread Spectrum signal bursts. As you can see, UWB is sending short bursts or signal pulses over a wide or large number of frequencies. Whereas, Spread Spectrum is larger bursts over a smaller number of different frequencies. In other words, short versus long bursts and wide versus narrow frequency bands.
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