Rohde & Schwarz R&S SMW200A - Page 292

Configuring the Internal Baseband Source
R&S
®
SMW200A
292User Manual 1175.6632.02 ─ 30
Table 5-14: Common coding algorithms
Coding Coding algorithm Applicable for
K bit/symbol
"None" b
n
= a
n
k = 1...8
"Differential"
b
n
= (a
n
+ b
–1
) modulo 2
k
k = 1...7
"Differential + Gray" Gray coding with additional differential coding k = 1...7
"GSM"
1)
d
n
= NOT (d
n
EXOR d
–1
) k = 1
"Phase Differential"
1)
b
1n
= [NOT (a
1n
EXOR a
0n
) AND (a
1n
EXOR b
1(n-1)
)] OR
[(a
1n
EXOR a
0n
) AND (a
1n
EXOR b
0(n-1)
)]
b
0n
= [NOT (a
1n
EXOR a
0n
) AND (a
0n
EXOR b
0(n-1)
)] OR
[(a
1n
EXOR a
0(n-1)
) AND (a
0n
EXOR b
1(n-1)
)]
-
1)
Requires R&S SMW-B10.
"Coding > Phase Differential/INMARSAT" correspond to system standards Inmarsat-M
and DVB according to ETS 300 429. You can use INMARSAT coding for modulation
types with 2 bits/symbol, such as QPSK.
Examples
The following examples illustrate how some of the different common coding schemes
combined with a modulation method influence the signal.
Example: Differential coding for QPSK modulation with K = 2 bit/symbol
Decimal display; the value range for modulation symbols is a
n
= {0, 1, 2, 3}
According to Table 5-14 and for k = 2, the recursive coding is defined as b
n
= (a
n
+ b
–1
)
modulo 4
Depending on the state of a preceding modulation symbol b
–1
, the coded modulation
symbol b
n
is obtained, for example, from modulation symbol a
n
= 2 as follows:
b
–1
0 1 2 3
b
n
2 3 0 1
With differential coding, the assignment of modulation symbols a
n
(binary indication:
MSB, LSB) to the phase differences shown in the following table is generated:
Table 5-15: Phase difference for QPSK
Modulation symbol a
n
00 01 10 11
Phase difference 0° 90° 180° 270°
Generating Custom Digital Modulated Signals