comm.ConvolutionalInterleaver

Permute symbols using set of shift registers with specified delays

Description

The comm.ConvolutionalInterleaver System object™ permutes the symbols in the input sequence by using a set of shift registers, each with its own delay value. For information about delays, see Delays of Convolutional Interleaving and Deinterleaving.

To permute symbols using a set of shift registers with specified delays:

1. Create the comm.ConvolutionalInterleaver object and set its properties.

2. Call the object with arguments, as if it were a function.

To learn more about how System objects work, see What Are System Objects?

Creation

Syntax

intrlvr = comm.ConvolutionalInterleaver

intrlvr = comm.ConvolutionalInterleaver(Name=Value)

Description

intrlvr = comm.ConvolutionalInterleaver creates a default convolutional interleaver System object.

intrlvr = comm.ConvolutionalInterleaver(Name=Value) sets Properties using one or more name-value arguments. For example, NumRegisters=10 specifies 10 internal shift registers.

Properties

Unless otherwise indicated, properties are nontunable, which means you cannot change their values after calling the object. Objects lock when you call them, and the release function unlocks them.

If a property is tunable, you can change its value at any time.

For more information on changing property values, see System Design in MATLAB Using System Objects.

NumRegisters — Number of internal shift registers

6 (default) | positive integer

Number of internal shift registers, specified as a positive integer.

Data Types: double

RegisterLengthStep — Number of additional symbols that fit in each successive shift register

2 (default) | positive integer

Number of additional symbols that fit in each successive shift register, specified as a positive integer. The first register holds zero symbols.

Data Types: double

InitialConditions — Initial conditions of shift registers

0 (default) | scalar | column vector

Initial conditions of the shift registers, specified as one of these options.

• Scalar — All shift registers, except the first one, store the same specified value.

• Column vector — If the length of the column vector equals the value of the NumRegisters property, then the kth shift register stores the kth element of the specified vector.

You do not need to specify a value for the first shift register, which has zero delay. Because the first shift register has zero delay, the object ignores the first element of this property.

Data Types: double

Usage

Syntax

intrlvseq = intrlvr(inputseq)

Description

intrlvseq = intrlvr(inputseq) permutes the input sequence of symbols by using a set of shift registers. The object outputs the interleaved sequence of symbols.

For information about delays, see Delays of Convolutional Interleaving and Deinterleaving.

Input Arguments

inputseq — Sequence of symbols

column vector

Sequence of symbols, specified as a column vector.

Data Types: numeric | logical | fi

Output Arguments

intrlvseq — Interleaved sequence of symbols

column vector

Interleaved sequence of symbols, returned as a column vector of the same data type and size as the inputseq input.

Data Types: numeric | logical | fi

Object Functions

To use an object function, specify the System object as the first input argument. For example, to release system resources of a System object named obj, use this syntax:

release(obj)

Common to All System Objects

step	Run System object algorithm
release	Release resources and allow changes to System object property values and input characteristics
reset	Reset internal states of System object

Examples

Convolutionally Interleave and Deinterleave Sequence

Create a convolutional interleaver System object, specifying the number of shift registers and register length step.

intrlvr = comm.ConvolutionalInterleaver(NumRegisters=2, ...
                                        RegisterLengthStep=3);

Create a convolutional deinterleaver System object, specifying the number of shift registers and register length step.

deintrlvr = comm.ConvolutionalDeinterleaver(NumRegisters=2, ...
                                            RegisterLengthStep=3);

Generate a random data sequence. Pass the data sequence through the interleaver and then the deinterleaver.

data = (0:20)';
intrlvData = intrlvr(data);
deintrlvData = deintrlvr(intrlvData);

Display the original sequence, interleaved sequence, and restored sequence.

[data,intrlvData,deintrlvData]

ans = 21×3

     0     0     0
     1     0     0
     2     2     0
     3     0     0
     4     4     0
     5     0     0
     6     6     0
     7     1     1
     8     8     2
     9     3     3
    10    10     4
    11     5     5
    12    12     6
    13     7     7
    14    14     8
      ⋮

The delay through the interleaver and deinterleaver pair is equal to the product of the NumRegisters and RegisterLengthStep properties.

intrlvDelay = intrlvr.NumRegisters*intrlvr.RegisterLengthStep

intrlvDelay = 
6

After accounting for this delay, verify that the original and deinterleaved data are identical.

numSymErrors = symerr(data(1:end-intrlvDelay), ...
                      deintrlvData(1+intrlvDelay:end))

numSymErrors = 
0

More About

Delays of Convolutional Interleaving and Deinterleaving

The total delay due to a convolutional interleaver and deinterleaver pair is N × slope × (N – 1).

• N is the number of registers and equals the value of the NumRegisters property

• slope is the register length step and equals the value of the RegisterLengthStep property

This diagram shows the structure of a general convolutional interleaver comprised of a set of shift registers, each having a specified delay shown as D(1), D(2),..., D(N), and a commutator to switch input and output symbols through registers. The kth shift register holds D(k) symbols, where k = 1, 2, 3, … N. The kth shift register has a delay value of ((k–1) × slope). With each new input symbol, the commutator switches to a new register and shifts in the new symbol while shifting out the oldest symbol in that register. When the commutator reaches the Nth register, upon the next new input, the commutator returns to the first register.

For more information, see Interleaving.

References

[1] Clark, George C., and J. Bibb Cain. Error-Correction Coding for Digital Communications. Applications of Communications Theory. New York: Plenum Press, 1981.

[2] Forney, G., D., Jr. "Burst-Correcting Codes for the Classic Bursty Channel." IEEE Transactions on Communications, vol. COM-19, October 1971. 772-781.

[3] Ramsey, J. L. "Realization of Optimum Interleavers." IEEE Transactions on Information Theory, IT-16 (3), May 1970. 338-345.

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

See System Objects in MATLAB Code Generation (MATLAB Coder).

HDL Code Generation

Generate VHDL, Verilog and SystemVerilog code for FPGA and ASIC designs using HDL Coder™.

The software supports double and single data types for simulation, but not for HDL code generation.

To generate HDL code from predefined System objects, see Generate HDL Code for IIR Filter (DSP HDL Toolbox).

Version History

Introduced in R2012a