Gaussian MSK (GMSK)[Under Modulation >> Digital modulation]
Popular user of GMSK is GSM systems. In MSK, digital 1 and 0s were replaced by half sinusoidals. In GMSK, instead of sinusoidal shape, "Gaussian pulse shape" is used. This is achieved by using "Gaussian filter".
Diagram below show Gaussian function.
| Gaussian filter
In signal processing, a filter allow only signals with certain characteristics; typically being certain frequencies. Gaussian filers are supposed to reduce rise and fall time, so good for our purpose of abrupt phase changes. |
Gaussian pulse has a factor (property) called "BT" determining how quick is the rise/fall time. BT value is to be chosen optimally, looking at signal power, error rate etc. GSM uses [ref: Document from the University of Hull] BT value of 0.3 with T=48/13 μs.
Just like MSK, GMSK is viewed/implemented as FSK technique.
© Copyright Samir Amberkar 2010
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