AP1.3 Channel types and Signal processing
AP1-24
Unique Word
The 252 symbols from the encoder are affixed with an unique word (uw) to be used for
bit synchronization at the recorder. The uw is 64 bits in length on the MES signaling
channel and 64x2 bits on the NCS/CES TDM channel.
Interleaving and
Permuting Encoder
UW symbol
BPSK modulator
or
interleaver
added
Fig. AP1.3.8 UW
Interleaving and Permuting Encoder
The figure below shows the interleave matrix, consisting of 64 rows by 162 columns.
Symbol data comes in column by column. Note that columns 0 and 1 are filled with
unique words.
Fig. AP1.3.9 Interleave Matrix
The first 64 symbols of convolutional encoder output go to column 2, rows 0 to 63.
The next 64 symbols to column 3, rows 0 to 63 and so on.
The interleave block is transmitted on a row by row basis. The symbols in a row are
transmitted in ascending order of column position; that is, the two identical unique
word symbols are transmitted first. However, rows are not transmitted in a sequential
order; they are transmitted according to a permuted sequence. If the rows in the
interleave block are numbered from i = 00 to i = 63 sequentially and the transmitted
order is from j = 0 sequentially through to j = 63; then, i and j are related by
i = (jx39) modulo 64
1
st output j = 0 : i = (0x3S) modulo 64 = 0
2
st output j = 1 : i = (1x3S) modulo 64 = 39
3
st output j = 2 : i = (2x3S) modulo 64 = 14
Modulo 64 is the remainder of division by 64.
0 1 2
………………………………
161
0
1
2
63
62
:
:
:
:
:
:
:
:
Column
Row
1
2
3
…
64
…
128
65
10240
…
10177
………………
UW 64bits
UW 64bits
1
2
3
64
65
66
67
128
10177
10177
10177
10240
10239
63
127
Bit stream
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