L64704 LSI Logic Corporation, L64704 Datasheet - Page 155

• Manufacturer Part Number: L64704
• Description: Satellite Decoder Technical Manual 5/97
• Manufacturer: LSI Logic Corporation

Figure 7.10
Percent Channel
Symbol Errors vs.
Eb/No for
Rate = 7/8 Code
Equation 7.1
7.2
Deinterleaver
Module
% Channel Symbol Errors
10.0
You must select a value for the ratio VMBEC/VMDC1 that is in between
the in-synchronization and the out-of-synchronization curves. For exam-
ple, for a rate equal to 1/2 code, a value of 0.24, or 24%, for
VMBEC/VMDC1 establishes a valid decision threshold over the entire
Eb/No range shown.
Symbol Error Percentages.
Figure 7.11
leaver is a device that rearranges the ordering of a sequence of symbols
in a deterministic manner. A (B, N) Periodic Interleaver has the following
characteristics:
This scheme is also called a convolutional Interleaver/Deinterleaver.
Deinterleaver Module
Channel Symbol Error Rate
8.0
6.0
4.0
2.0
0.0
2
The minimum separation at the Interleaver output is B symbols for
any two symbols that are separated by less than N symbols at the
Interleaver input.
If the channel inserts any burst of less than B errors, single errors
occur at the Deinterleaver output.
2.5
outlines the interleaving/deinterleaving operation. The Inter-
3
3.5
Eb/No (dB)
Equation 7.1
4
=
128 VMBEC
--------------------------------------------- -
4.5
256 VMDC 1
shows the computation of Channel
Rate 7/8
5
+
5.5
32
6
7-11