Convolutional Coder - Safran CORTEX CRT Quantum User Manual

For all the bits non concerned by the differential encoding, we have then: ��

3.3.6.3.4. Convolutional Coder

The convolutional coder used to implement the trellis is depicted in Figure 21. This code corresponds to one of
the "best" codes for phase transparency.
The systematic coder is implemented with the following characteristics:

number of states: 64 states,

constraint length: K = 7
The convolutional encoder is specified by the following polynomial in octal: h3 = 050, h2 = 024, h1 = 006, h0 =
103. Figure 21 shows the recommended convolutional encoder. The shift registers of the encoder are clocked at
the rate of RChS/4.
The number of coded bits is the same for the four modulation efficiencies (i.e., the same structure is used for 2,
2.25, 2.5, and 2.75 bits/channel-symbol), only the number of uncoded bits is changed. The advantage of this
coder is its optimized performance and the reduced internal rate which is equal to 1/8, 1/9, 1/10, or 1/11 of the
information rate
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Ref. DTU 100042
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Date: Dec.
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