Furuno FELCOM 12, Service Manual

Page: 39 / 118

2-8
The first 64 symbols of convolutional encorder 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 asccending order of column position; that is, the two indentical 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 = (j
×
39) modulo 64
1 st output j = 0 : i = (0
×
3S) modulo 64 = 0
2 st output j = 1 : i = (1
×
3S) modulo 64 = 39
3 st output j = 2 : i = (2
×
3S) modulo 64 = 14
Modulo 64 is the remainder of division by 64.
0 1 2....................................161
0
1
2
63
62
...............
Column
Row
25
row
0
row
1
2
3
64
65
66
67
128
10177
10177
10177
10240
10239
63 127
39
row
.................
(
1st frame
) (
Last frame
)
Figure 2-10 Permuting
Preambling
The SES message channel is quasi–continuous therefore a preamble is added to aid
acquisition. The maximum message length is 32k bytes (about 32000 characters), as
about 50 frames can be sent consecutively.
Preamble
carrier recovery : 128bits
all = 1 clock regeneration :
64bits
UW DATA UW DATA UW DATA ...............
1sd frame 2nd frame
n frame
(max : 50)
10240bits 128bits
Figure 2-11 Preambling
Permute Matrix