Digital Modulation and Detection
WS 19/20 Wireless Communications ‐ Modulation 1
Recall from GdRN
Wireless Communications ‐ Modulation 67
image source: William Stallings, „Data and Computer Communications“, Seventh Edition, 2004 WS 19/20
Wireless Communications ‐ Modulation
Some more details about MSK
Bits are divided into two channels, the bit duration is doubled
Based on the bit values of the two channels, the two carrier frequencies are assigned their orientation
Higher carrier frequency performs half an oscillation more during one bit
(Equivalent to offset QPSK)
WS 19/20 74
Example of MSK Modulation
WS 19/20 Wireless Communications ‐ Modulation 75
data even bits odd bits
1 0 1 1 0 1 0
t low
frequency
high frequency
MSK signal
bit
even 0 1 0 1
odd 0 0 1 1
signal h l l h value ‐ ‐ + +
h: high resp.
l: low frequency +: positive resp.
‐: negative direction
not phase offsets!
•High frequency always when even and odd bits are equal
•Invert signal if the odd bit is 0.
