3471-ddc.ib.rev2.doc
page 4 of 20
17/10/2007
Applications:
•
Block length indication and error detection.
•
Interface to test equipment.
•
Interfacing to Telecoms switched data network.
•
Interfacing various MPEG2 TS formats.
•
Interleaving or de-interleaving. *
•
Reed Solomon insertion & correction. *
•
Spectrum dispersion correction. *
•
Signal monitoring for remote alarm indications.
* DDC-3471 only.
Application
Processes which may be performed by the DDC-3471 are:
Baseband interfacing and sync
This unit adapts the data structure to the format of the signal source. This may be a DDC-3460 or simply the input
interface of the DDC-3471. The framing structure is in accordance with MPEG-2 transport layer including sync
Bytes.
Sync 1 inversion and randomisation
(Scrambling)
The Sync 1 Byte is inverted according to the MPEG-2 framing structure, and the data stream randomised for
spectrum shaping purposes.
Reed-Solomon (RS) encoder
A shortened Reed-Solomon (RS) code is applied to each randomised transport packet to generate an error-protected
packet. This code is also applied to the Sync Byte itself.
Convolutional interleaver
This part performs a depth I = 12 convolutional interleaving of the error-protected packets. The periodicity of the
sync Bytes remains unchanged.
Block diagram
DDC-3471
Scrambling
Reed-Solomon
Insert
Convolutional
Interleaver
Alarms & Indications
SCRAMBLED
RS PRESENT
188 BYTE BLOCK
204 BYTE BLOCK
SYNC ERROR
INPUT LOSS
RS ERROR
Convolutional
De-Interleaver
Reed-Solomon
Correction
De-S
crambling
LVDS
NRZ
NRZ
LVDS
8B
10B
8
8
Input
(270 Mb/s) coax
SPI
SPI
ASI-C
Outputs
IRT
Communications
www.irtcommunications.com