Viterbi IP Core User Guide

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ID 683280
Date 11/06/2017
Public
Document Table of Contents
Document Table of Contents x
1. About the Viterbi IP Core 2. Viterbi IP Core Getting Started 3. Viterbi IP Core Functional Description A. Viterbi IP Core User Guide Document Archives 4. Document Revision History
1. About the Viterbi IP Core x
1.1. Intel® DSP IP Core Features 1.2. Viterbi IP Core Features 1.3. DSP IP Core Device Family Support 1.4. DSP IP Core Verification 1.5. Viterbi IP Core Release Information 1.6. Viterbi IP Core Performance and Resource Utilization
2. Viterbi IP Core Getting Started x
2.1. Installing and Licensing Intel® FPGA IP Cores 2.2. IP Catalog and Parameter Editor 2.3. Generating IP Cores ( Intel® Quartus® Prime Pro Edition) 2.4. Simulating Intel® FPGA IP Cores 2.5. DSP Builder for Intel® FPGAs Design Flow
2.1. Installing and Licensing Intel® FPGA IP Cores x
2.1.1. Intel® FPGA IP Evaluation Mode 2.1.2. Viterbi IP Core Intel® FPGA IP Evaluation Mode Timeout Behavior
2.3. Generating IP Cores ( Intel® Quartus® Prime Pro Edition) x
2.3.1. IP Core Generation Output ( Intel® Quartus® Prime Pro Edition)
3. Viterbi IP Core Functional Description x
3.1. Decoder 3.2. Convolutional Encoder 3.3. Trellis Coded Modulation 3.4. Viterbi IP Core Parameters 3.5. Viterbi IP Core Interfaces and Signals
3.3. Trellis Coded Modulation x
3.3.1. Half-Rate Convolutional Codes 3.3.2. Trellis Decoder 3.3.3. About Converting Received Signals 3.3.4. Trellis Termination 3.3.5. Trellis Initialization
3.4. Viterbi IP Core Parameters x
3.4.1. Architecture 3.4.2. Code Sets 3.4.3. Viterbi Parameters 3.4.4. Test Data
3.4.1. Architecture x
3.4.1.1. BER Estimator 3.4.1.2. Node Synchronization
3.4.3. Viterbi Parameters x
3.4.3.1. Soft Symbol Input 3.4.3.2. State Metrics 3.4.3.3. Throughput Calculator 3.4.3.4. Latency Calculator
3.4.4. Test Data x
3.4.4.1. External Puncturing
3.5. Viterbi IP Core Interfaces and Signals x
3.5.1. Avalon-ST Interfaces in DSP IP Cores 3.5.2. Global Signals 3.5.3. Avalon-ST Sink Signals 3.5.4. Avalon Source-ST Signals 3.5.5. Configuration Signals 3.5.6. Status Signals 3.5.7. Viterbi IP Core Timing Diagrams
1. About the Viterbi IP Core
2. Viterbi IP Core Getting Started
3. Viterbi IP Core Functional Description
A. Viterbi IP Core User Guide Document Archives
4. Document Revision History

3.3.4. Trellis Termination

Block decoders must properly decode the last bits of the block and adapt to the convolutional encoder.

Tail-biting feeds the convolutional encoder with a block and terminates it with (L – 1) unknown bits taken from the end of the block. Tail-biting sets the initial state of the convolutional encoder with the last (L – 1) information bits. Tail-biting is decoded by replicating the block at the decoder or double feeding the block into the decoder. By decoding in the middle point, the trellis is forced into the state that is both the initial state and the end state. From the first decoding block, you can take the last half of the block; from the second decoded block (or second pass through the decoder), you can obtain the first half of the bits of the block.

Note: In tail-biting, the block size must be large enough to train the decoder, otherwise you may see BER loss.

Alternatively, if you initialize the convolutional encoder to zero, the initial state of the trellis is zero. The decoder knows the last (L – 1) bits to the convolutional encoder. They bring the convolutional encoder to a known end state. The decoder then uses this information to set the end state of the trellis with tr_init_state, which is derived from the last (L – 1) bits of the block in reverse order. For example, for a block that ends in: ...000101 If L = 5 and the decoder knows the last (L – 1) = 4 bits, it sets tr_init_state as 0101, which reversed and in binary is 1010, or 10 in decimal. The wizard generates tr_init_state as if it knows the last (L – 1) bits of each block.

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