Altera Viterbi Compiler - Manual (Page 23)

Figure 3-5: Implementation of the Viterbi Decoder as a Trellis Decoder
decdat0
Viterbi
Decoder
Trellis Mode
Rate 1/2
Convolutional
Encoder
Trellis
Output
Demapper
decdat1
Branch
Metric
Rotate
Delay
Sector
Number
ROM
(I, Q)
to
Branch
Metric
and
Sector
Number
Rotate
Sector
Number
I
Q
About Converting Received Signals
The Viterbi decoder calculates the distances to the nearest four symbol points as an unsigned number in
the range 0...00 to 1...11 (number of softbits).
Where the range is equal to the radius of the symbol map. The decoder works with accumulative metrics
(not Euclidean metrics), so the decoder inverts these distances (000 becomes 111; 001 becomes110).
UG-VITERBI
2014.12.15
About Converting Received Signals 3-5
Viterbi IP Core Functional Description Altera Corporation
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