Rohde & Schwarz SMIQ02B - PN Generators as Internal Data Source; Table 2-32 PRBS Generators for DECT

Digital Standard DECT SMIQ
1125.5555.03 E-92.320
2.19.2 PN Generators as Internal Data Source
Independent PN generators (Pseudo Noise) can be selected for each slot as data sources for the data
fields A-FIELD, B-FIELD and DATA. These PN generators provide pseudo-random bit sequences of
different length or period. That is why they are also called PRBS generators (Pseudo R
andom Binary
Sequence).
Data sequences are sequences of maximum length which are generated by means of feedback shift
registers.
The following figure gives an example of a 9-bit generator with feedbacks after register 4 and 0 (output).
8
765 4 3
2
10
DATA
EXOR
The pseudo-random sequence of a PRBS generator is clearly defined by the number of registers and
the feedback. The following table describes all PRBS generators available:
Table 2-32 PRBS generators for DECT
PRBS generator Length in bits Feedback after
9 bit 2
9
-1 = 511 Register 4, 0
11 bit 2
11
-1 =2047 Register 2, 0
15 bit 2
15
-1 = 32767 Register 1, 0
16 bit 2
16
-1 = 65535 Register 5, 3, 2, 0
20 bit 2
20
-1 = 1048575 Register 3, 0
21 bit 2
21
-1 = 2097151 Register 2, 0
23 bit 2
23
-1 = 8388607 Register 5, 0
PN generators PN9,11,15,20 and PN23 are configured according to CCITT Rec. 0.151/152/153. The
output sequence is inverted for generators PN15 and PN23.
The start value of the PN generators is different in the slots and equals
start value hex slotnumber=+ ×114
Example: PN9 generator in slot 1 with start value 15hex = 10101 binary.
10
DATA
EXOR
1100 0 0 0
The resulting output sequence is 1010100000010100101011110010 etc.