Features - Motorola DSP56305 User Manual

13.2

FEATURES

The following VCOP features support the GSM standard:
• Implements MLSE machine using Viterbi algorithm, for both channel decoding
and channel equalization
1
• Ungerboeck
• Manhattan metrics for channel decoding
• Constraint length of 4, 5, 6, or 7 (8, 16, 32 or 64 trellis states)
• Uses fixed trellis depth of 36
• Decision depth greater than five times the greatest constraint length (36)
• Code rates of 1/2, 1/3, 1/4, or 1/6
• Up to 6 polynomial tap registers
• Ability to specify INIT_STATE, END_STATE, INIT_METRIC
• 8-bit (256 level) soft-decision input for channel decoding
• Punctured codes derived from the supported 1/n rate codes
• Hard decision output (16-bits wide) when performing channel decoding and
equalization
• Number of bit errors corrected during channel decoding when required
• Window Error Detection function (as required for GSM half-rate code)
• Access to intermediate path metrics for the implementation of differential metric
3
scheme , and channel parameters adaptations model
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References: The following articles will be cited as reference sources in several sections of
this chapter. These references are duplicated as endnotes to this chapter, for the reader's
convenience.
1. Ungerboeck, Gottfried 1974. Adaptive Maximum-Likelihood Receiver for Carrier-Modulated
Data-Transmission Systems. IEEE Transactions on Communications vol. COM-22, no.
5:624–636. May 1974.
2. Forney, G. David, Jr. 1973. The Viterbi Algorithm. Proceedings of the IEEE, vol. 61 no.
3:268–278. March 1973.
3. Koch, Wolfgang, and Baier, Alfred 1990. "Optimum and Sub-optimum Detection of Coded Data
Disturbed by Time-varying Intersymbol Interference," in Communications: Connecting the Future,
vol. 3:1679–1684. Global Telecommunications Conference and Exhibition, San Diego, Dec. 2–5,
1990. (IEEE catalog number 90CH2827–4).
MOTOROLA
metrics for channel equalization
DSP56305 User's Manual
VITERBI CO-PROCESSOR
Features
13-5