ANSI SCTE-56-2011 pdf download DIGITAL MULTIPROGRAM DISTRIBUTION BY SATELLITE
3.1.2 Matched filter This universal element of a satellite IRD performs the complementary pulse shaping filtering type according to the roll-off. The use of a Finite Impulse Response (FIR) digital filter could provide equalization of the channel linear distortions in the IRD.
This universal element of a satellite IRD shall be capable of processing signal with the following shaping and roll-off factors:
Square Root Raised Cosine:
α=0.35 and 0.20
Band-limited 4th order Butterworth
Standard and Truncated-spectrum modes
Information about the template for the signal spectrum at the modulator output is given in § 5.1.
3.1.3 Convolutional decoding
This universal element of a satellite IRD performs first level error protection decoding. It will operate at an input equivalent “hard decision” BER in the order of between 10 -1 and 10 -2 (depending on the adopted code rate), and will produce an output BER about 2×10 -4 or lower. This output BER corresponds to QEF service after outer code correction. It is possible that this unit makes use of “soft decision” information. This unit is in a position to try each of the code rates and puncturing configurations until lock is acquired. Furthermore, it is in a position to resolve π/2 demodulation phase ambiguity.
The inner code has the following characteristics:
• Viterbi and puncturing
• Code constraint length K = 7
This universal element of a satellite IRD shall be capable of decoding the two different convolutional codes. The system shall allow convolutional decoding with code rates based on a rate of either 1/2 or 1/3:
• Based on a basic rate 1/2: FEC= 1/2, 2/3, 3/4, 5/6, 6/7 and 7/8.
• Based on a basic rate 1/3: FEC= 5/11, 1/2, 3/4, 2/3, 3/5, 4/5, 5/6, and 7/8.
Specific characteristics are provided in § 5.2.