Quantum and Evolution Series Installation and Operating Handbook
13-6
13.6 Intelsat Reed-Solomon Codec and Custom Option Specifications
Parameter
Modem
Format
Concatenated Reed-Solomon outer codec to IESS-
308/310
Code Rate
Default n, k, t = (126, 112, 7) depth 4.
Automatically switches to:
(225, 205, 10) depth 4 for 1544kbps IDR mode or
(219, 201, 9) depth 4 for 2048kbps IDR mode and
TCM<=1544kbps or
(219, 201, 9) depth 8 for TCM >1544kbps.
Processing Delay
Combined encoder and decoder: 8 x (2n-k+60)
Combined Interleaver/De-Interleaver: 8 x n x Depth
(Calculate delay time using data rate including RS
overhead).
Custom Option
When fitted allows arbitrary selection of n and k to
provide fully variable code rate.
60<=n<=255
(n-20)<=k<=(n-2) in steps of 2.
Interleaving depth of 4 or 8.
The custom option allows use of shorter code
words to reduce interleaver/de-interleaver delay on
low data rate circuits.
Up to 10Mbps.
13.7 Drop and Insert Option Specifications
Parameter
Modem
Bearer Types
T1-D4, T1-ESF and E1-G.732
Timeslot Selection
Independent selection of arbitrary timeslots for both
drop and insert.
Bearer Generation
The terrestrial bearer may be looped through the
Drop Mux then Insert Mux, or terminated after the
Drop Mux and a new blank bearer generated by the
insert Mux. The bearer generated within the Insert
Mux provides full multiframe and CRC support and
may be generated from the Tx clock, station
reference, satellite clock or Internal reference.
Bearer Backup
In the event that the Insert Mux bearer clock is lost,
or AIS is supplied, then the Insert Mux will switch
temporarily to bearer generation mode in order to
preserve the receive traffic. The backup bearer may
be generated from the station reference, satellite
clock or internal reference.
Terrestrial CRC
Fully supported, with front panel display of
terrestrial error rate based on CRC (T1-ESF and
G.732) or Frame Alignment Word errors (all bearer
types).
