Rohde & Schwarz SMIQ02B - Page 200

SMIQ Digital Standard IS-95 CDMA
1125.5555.03 E-92.131
To generate a reverse link signal, two different operating modes are available. The following figure
shows the schematic of reverse link signal generation without channel coding.
Delay
1/2 Chip
64 fach
Orthogonal
Modulator
307200 bps
28800 bps
Pattern
PRBS
PN
I
PN
Q
1.2288 Mcps
+
+
I
Q
Baseband
FIR Filter
List
Fig. 2-77 Reverse link signal generation without channel coding
Simple bit patterns, PRBS and freely programmable data sequences in a data list are available as
modulation data. At a chip rate of 1.2288 MHz, the modulation data rate of the reverse link is
28800 bps/s. The modulation type is offset-QPSK. A FIR filter is preset as baseband filter without
equalizer according to IS-95 (FILTER TYPE IS-95).
The second reverse link mode also comprises channel coding. With this reverse link coded mode, both
an access channel (4800 bps) and a traffic channel can be generated with all the data rates between
1200 bps and max. 14400 bps complying with IS-95 (Rate Set 1 and 2). The following figure gives an
example of signal generation for the traffic channel with 9600 bps and shows the associated frame
structure.
Delay
1/2 Chip
64 fach
Orthogonal
Modulator
307200 bps
PN
I
PN
Q
1.2288 Mcps
+
+
I
Q
Baseband
FIR Filter
28800 bps
PRBS
List
Block
Interleaver
Convolutional
Encoder
Add
FQ Indicator,
Encoder Tail
8600 bps
9600 bps
Fig. 2-78 Traffic channel 9600 in "Reverse Link Coded" mode