DS525 Datasheet, PDF (5/13 Pages) –

802.16e CTC Encoder v3.0
Functional Description
Constituent Encoder
The schematic of the constituent encoder and the polynomials for the first register input X and parity
outputs Y and W are shown in Figure 2.
Figure Top x-ref 2
D_A
+
X
S1
+
S2
+
S3
is_B
c₊
ont _{X(D) = 1 + D + D3}
+
Y(D) = 1 + D² + D³
Y
W
W(D) = 1 + D³
in_{Figure 2: CRSC Constituent Encoder}
u _{The constituent encoder produces a double-binary Circular Recursive Systematic Convolutional}
(CRSC) code. This code is more efficient than a basic Recursive Systematic Convolutional (RSC) code,
e ^{because it does not require three tail bit periods to flush the encoder at the end of each block. Instead,}
the CRSC is pre-loaded with a circulation state at the start of each block.
d ^{The CRSC is double-binary. It handles two data bits at a time, and the parity bits are functions of both}
input bits.
Calculation of the circulation state for the constituent encoder is performed as follows.
I ^{1. Initialize the encoder to state 0. Encode the input sequence (in either interleaved or uninterleaved}
P ^{order as required), and obtain the final state of the encoder.}
2. Apply a look up table to obtain the circulation state.
In the CTC encoder core, the above operations are performed in parallel by the two precoders.
DS525 April 24, 2009
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Product Specification