SMIQ
Digital Modulation
1125.5555.03
E-9
2.87
2.10.1
Digital Modulation Methods and Coding
The input sequence of modulation symbols d
n
can be subject to different types of coding. I and Q values
are assigned to the coded modulation symbols dc
n
in the functional block MAPPING.
I,
∆∆∆∆
F
Q
MAPPING
CODING
modulation
symbols
d
n-2
, d
n-1
, d
n
...
dc
n-2
, dc
n-1
, dc
n
...
Fig. 2-49
Functional blocks Coding and Mapping
2.10.1.1 PSK and QAM Modulation
PSK and QAM modulations can be explained on the basis of a rule of assignment (mapping) according
to which each modulation symbol is represented by I and Q values as shown in the following IQ
constellation diagrams. The constellation diagrams apply if
no
coding is switched on.
I
Q
0
1
I
Q
00
01
10
11
I
Q
0000
0001
0011
0010
1010
1000
1001
1011
0101
0111
0110
0100
1111
1110
1100
1101
I
Q
11
01
00
10
I
Q
00
10
11
01
I
Q
001
011
101
111
010
100
110
000
BPSK
QPSK; OQPSK
8PSK, DQPSK
QPSK ISAT
Π/4
ϕ
QPSKIS95
OQPSK IS95
Fig. 2-50
Constellation diagrams of BPSK, QPSK, 8PSK and 16QAM