ADInstruments S7200 Operation Manual page 174

AD INSTRUMENTS S7200 TV Signal Analyzer Operation Manual
a manner that the two components in the imaginary plane, in-phase I and
quadrature Q, carry all the binary information. Then, the real and imaginary parts
of each symbol are cyclically delayed and end up being transmitted in different
subcarriers. This increases the reception robustness in the presence of deep fades
but requires a high demodulation complexity.
S
K
Figure 6-48 Discrete mapping of constellation points on the I and Q axis with a
rotated constellation diagram.
In reality, however, the whole process is slightly more complex. With a rotated
diagram, the Q component is not transmitted on the same carrier, or more
precisely in the same "cell", but with delay on another carrier (Figure 6-49 and
Figure 6-50) or better in another cell. From one QAM, virtually two ASKs
(Amplitude Shift Keying modulations) in the I and Q direction are then produced
which are then transmitted on independent carriers – "cell" which are disturbed
differently in practice and are thus intended to contribute to the reliability of
demodulation.
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