Ncs Cc/Les Tdm Channel - Furuno FELCOM 15 Service Manual

1. NCS CC/LES TDM Channel

The NCS common channel and LES TDM channels share a common overall structure.
The TDM channels are based on fixed-length frames of 10368 symbols tarnsmitted at
1200 symbols/s giving a frame time of 8.64S. 10,000 frames are transmitted every day
(8.64s x 10000= 24 hours).
Each frame carries a 639 byte information field, followed by a flush byte (all 0s).
The first packet in the information field is always the Bulletin Board (BB) packet.
The bulletin board contains information on the network configuration and the correct
frame number.
TDM Frame
Frame Format
8 7 6 5 4 3 2 1
1
Bulltin Board Packet
14
Signalling Channel
Descriptor Packet
Message
or Signlling Packet
640
8.64sec (10368 TDM symbols)
TDM Frame
Fig. AP1.3.1 TDM frame configuration
AP1-18
AP1.3 Channel types and Signal processing
TDM Frame
8 7 6 5 4 3 2 1
Type Length
0
Network Version
Frame Number
2-F
Sig Channel
E Spare
Count
Local Spare
Channel
Origin ID
Status
Services
Rnd Interval
Check sum
8 7 6 5 4 3 2 1
Type Length
0
A C D S L A E
Spare
Satellite Freq. Code
28 x 2bit
Slot State
Markers
Check sum
Packet descriptor
1
0 (gero) when in
CES TDM
Frame descriptor
TDM descriptor
Service descriptor
Randomizing Interval
14
1
Packet descriptor
Indicating the channel of the
signalling channel
13