Furuno FELCOM 12 Service Manual

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
UWDATAUWDATAUWDATA ...............
1sd frame2nd frame
n frame
(max : 50)
10240bits 128bits
Figure 2-11 Preambling
Permute Matrix

Furuno FELCOM 12 Specifications

General

Brand	Furuno
Model	FELCOM 12
Category	Marine GPS System
Language	English