Convolutional Interleaver (`convolutional_interleaver_us`)

Takes in symbols that are of the data type, unsigned short, in a burst transmission and rearranges the order of the symbols.

Tested platforms include xsim, e31x.

Design

The convolutional interleaver component rearranges the input symbols in a burst transmission. It is used to reduce and spread out burst errors.

The convolutional interleaver is constructed by having N different delay lines with each line having a greater delay than the previous line. Each new input symbol is placed on a different delay line. The first delay line has 0 delay. The number of delay lines is defined as N and the depth of the delay line shift registers is defined as D. N should be set to a value greater than 1.

To ensure that all the input symbols make it through the convolutional interleaver, the data burst should be padded with D*N*(N-1) extra symbols.

A block diagram representation of the implementation is given in Figure 7:.

Figure 7: Block diagram outlining convolutional interleaver implementation.

Interface

<?xml version="1.0"?>
<!-- This file is protected by Copyright. Please refer to the COPYRIGHT file
     distributed with this source distribution.

     This file is part of OpenCPI <http://www.opencpi.org>

     OpenCPI is free software: you can redistribute it and/or modify it under
     the terms of the GNU Lesser General Public License as published by the Free
     Software Foundation, either version 3 of the License, or (at your option)
     any later version.

     OpenCPI is distributed in the hope that it will be useful, but WITHOUT ANY
     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
     FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
     more details.

     You should have received a copy of the GNU Lesser General Public License
     along with this program. If not, see <http://www.gnu.org/licenses/>. -->
<componentspec>
  <!-- LINT EXCEPTION: xml_004: 1: Single character name can be upper case -->
  <property name="N" type="uchar" default="12" parameter="true" description="Number of delay lines."/>
  <!-- LINT EXCEPTION: xml_004: 1: Single character name can be upper case -->
  <property name="D" type="uchar" default="17" parameter="true" description="The depth of the delay line shift registers."/>
  <port name="input" producer="false" protocol="ushort_timed_sample-prot"/>
  <port name="output" producer="true" protocol="ushort_timed_sample-prot"/>
</componentspec>

Ports

Inputs:

input: Primary input samples port.
- Protocol: ushort_timed_sample-prot
- Optional: False

Outputs:

output: Primary output samples port.
- Protocol: ushort_timed_sample-prot
- Optional: False

Opcode Handling

The convolutional interleaver interleaves data with sample opcodes only.

All other opcodes pass through this component without any effect.

Properties

N: Number of delay lines.
- Type: uchar
- Access:
  - Parameter: True
  - Writable: False
  - Initial: False
  - Volatile: False
- Default value: 12
D: The depth of the delay line shift registers.
- Type: uchar
- Access:
  - Parameter: True
  - Writable: False
  - Initial: False
  - Volatile: False
- Default value: 17

Implementations

convolutional_interleaver_us (HDL)

Implementation of a convolutional interleaver.

Example Application

<?xml version="1.0"?>
<!-- This file is protected by Copyright. Please refer to the COPYRIGHT file
     distributed with this source distribution.

     This file is part of OpenCPI <http://www.opencpi.org>

     OpenCPI is free software: you can redistribute it and/or modify it under
     the terms of the GNU Lesser General Public License as published by the Free
     Software Foundation, either version 3 of the License, or (at your option)
     any later version.

     OpenCPI is distributed in the hope that it will be useful, but WITHOUT ANY
     WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
     FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
     more details.

     You should have received a copy of the GNU Lesser General Public License
     along with this program. If not, see <http://www.gnu.org/licenses/>. -->
<application done="file_write">
  <instance component="ocpi.core.file_read" connect="convolutional_interleaver_us">
    <property name="filename" value="input.bin"/>
    <property name="messagesize" value="16384"/>
    <property name="messagesinfile" value="true"/>
  </instance>
  <instance component="ocpi.comp.sdr.communication.convolutional_interleaver_us" connect="file_write">
  </instance>
  <instance component="ocpi.core.file_write">
    <property name="filename" value="output.bin"/>
  </instance>
</application>

Dependencies

The dependencies for this worker are:

shift_reg.vhd

convolutional_delay_lines.vhd

There is also a dependency on:

ieee.std_logic_1164

ieee.numeric_std

ocpi.util.all;

Limitations

Limitations of convolutional_interleaver_us are:

None.

Testing

This component test suite uses the OpenCPI unit test framework. The unit test sends \(2^{bit\_width}\) symbols and with some zeros padding the symbols, so that all the input symbols are output by the convolutional interleaver. It is then verified to make sure that the symbols were interleaved correctly and that all the symbols made it through the convolutional interleaver.

Tested platforms: None

Component testing not completed.

Convolutional Interleaver (convolutional_interleaver_us)