Gaussian minimum-shift keying
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| Modulation techniques |
|---|
| Analog modulation |
| AM · SSB · FM · PM · QAM · SM |
| Digital modulation |
| OOK · FSK · ASK · PSK · QAM MSK · CPM · PPM · TCM · OFDM |
| Spread spectrum |
| FHSS · DSSS |
In digital communication, Gaussian minimum shift keying or GMSK is a continuous-phase frequency-shift keying modulation scheme. It is similar to standard minimum-shift keying (MSK); however the digital data stream is first shaped with a Gaussian filter before being applied to a frequency modulator. This has the advantage of reducing sideband power, which in turn reduces out-of-band interference between signal carriers in adjacent frequency channels. However, the Gaussian filter increases the modulation memory in the system and causes intersymbol interference, making it more difficult to discriminate between different transmitted data values and requiring more complex channel equalization algorithms such as an adaptive equalizer at the receiver.
GMSK is most notably used in the Global System for Mobile Communications (GSM).
[edit] Spectral efficiency
GMSK has high spectral efficiency, but it needs a higher power level than QPSK, for instance, in order to transmit the same amount of data reliably.
[edit] See also
[edit] External links
- Document from the University of Hull giving a thorough description of GMSK.
- Another good discussion (University of Toronto)
- PSK/GMSK comparison & illustrations (Aerospace)
