Vcop Support For Gsm; Introduction; Figure 13-1 Block Diagram Of A Typical Data Communication System - Motorola DSP56305 User Manual

13.1

INTRODUCTION

The Viterbi Co-Processor (VCOP) is a dedicated, programmable peripheral module,
integrated with the DSP56300 core; it is designed to perform convolutional coding and
channel equalization algorithms. It operates independently of the core, requiring
minimum CPU-time overhead. Although its original design purpose is to support base
stations for the Global System for Mobile Communication (GSM) standard, it can
support several standard convolutional coding algorithms, based on common 1/n rates
or their puncture derivatives, as used by GSM, PCN, and NADC.
The VCOP is designed for a wide range of standard applications requiring the Viterbi
algorithm for convolutional coding or channel equalization (in particular maximum
likelihood decoding) used for the following applications:
• Maximum Likelihood Sequential Estimation (MLSE) equalizer
• Channel decoder
• Convolutional encoder
In recent years, the Viterbi algorithm has been widely used in several
telecommunications areas, such as modems, cellular phone systems, and satellite
communications.
13.1.1

VCOP Support for GSM

The channel coding scheme specified by GSM is described in the following block
diagram:
Convolutional
Encoding
Speech
or Data
Convolutional
Decoding

Figure 13-1 Block Diagram of a Typical Data Communication System

The blocks using the VCOP (framed in bold, above) are convolutional encoding,
convolutional decoding, and channel equalization. The next section gives an example of
using the Viterbi algorithm for channel equalization.
MOTOROLA
Burst
Interleaving
Formatting
De- Burst
interleaving Formatting
DSP56305 User's Manual
VITERBI CO-PROCESSOR
Introduction
Modulator
Ciphering
RF Transmit
RF Receiver
De-ciphering
& Equalizer
AA1311
13-3