comm.HelicalInterleaver

Permute input symbols using helical array

Description

The comm.HelicalInterleaver System object™ permutes the symbols in the input signal by placing them in an array in a helical arrangement and then sending rows of the array to the output port. For more information, see Algorithms.

To helically interleave input symbols:

1. Create the comm.HelicalInterleaver 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.HelicalInterleaver

intrlvr = comm.HelicalInterleaver(Name=Value)

Description

intrlvr = comm.HelicalInterleaver creates a default helical interleaver System object.

intrlvr = comm.HelicalInterleaver(Name=Value) sets properties using one or more name-value arguments. For example, NumColumns=6 sets the number of columns in the helical array to 6.

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.

NumColumns — Number of columns in helical array

6 (default) | positive integer

Number of columns in the helical array, specified as a positive integer.

GroupSize — Size of each group of input symbols

4 (default) | positive integer

Size of each group of input symbols, specified as a positive integer.

StepSize — Helical array step size

1 (default) | positive integer

Helical array step size, specified as a positive integer. Step size indicates the number of rows of separation between consecutive input groups in their respective columns of the helical array.

InitialConditions — Initial conditions of helical array

0 (default) | numeric scalar

Initial conditions of the helical array, specified as a numeric scalar value. This is the initial value stored in the helical array.

Usage

Syntax

intrlvseq = intrlvr(inputseq)

Description

intrlvseq = intrlvr(inputseq)

Input Arguments

inputseq — Sequence of symbols

column vector

Sequence of symbols, specified as a column vector. Input sequence is of size NumColumns × GroupSize.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | logical | fi

Output Arguments

intrlvseq — Interleaved sequence of symbols

column vector

Interleaved sequence of symbols, returned as a column vector with the same data type and length as the inputseq argument.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | 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

Helical Interleaving and Deinterleaving

Create helical interleaver and deinterleaver System objects.

intrlver = comm.HelicalInterleaver(GroupSize=2,NumColumns=3, ...
            InitialConditions=-1);
deintrlvr = comm.HelicalDeinterleaver(GroupSize=2,NumColumns=3, ...
            InitialConditions=-1);

Generate random data. Interleave and then deinterleave the data.

[dataIn,dataOut] = deal([]);
for k = 1:10
    data = randi(7,6,1);
    intData = intrlver(data);
    deIntData = deintrlvr(intData);
    
    dataIn = cat(1,dataIn,data);
    dataOut = cat(1,dataOut,deIntData);
end

Determine the delay through the interleaver and deinterleaver pair.

intlvDelay = finddelay(dataIn,dataOut)

intlvDelay = 
6

After taking the interleaving delay into account, confirm that the original and deinterleaved data are identical.

isequal(dataIn(1:end-intlvDelay),dataOut(1+intlvDelay:end))

ans = logical
   1

Algorithms

Array Processing of Helical Interleaver

The helical interleaver System object places the elements of inputseq in an array in a helical fashion. If you set the NumColumns property of the object to C, then the array has C columns and unlimited rows. If you set the GroupSize property to N, then the object accepts an input of length C × N and partitions the input into consecutive groups of N symbols. The object places the k^th group in the array along column k mod C. This placement is of type helical because of the reduction modulo C, and because the first symbol in the k^th group is in the row 1+(k-1) × s, where s is the value for the StepSize property. Positions in the array that do not contain input symbols have default contents specified by the InitialConditions property.

The System object outputs C × N symbols from the array by reading the next N rows sequentially. When you call the object, the output symbols can also be the InitialConditions property value, input sequence of symbols, inputseq, or symbols left in the array from a previous object call.

For example, set the properties of the object to these values.

• C = 3

• N = 2

• s = 1

• InitialConditions = -1

After receiving inputs of [1:6]', [7:12]', and [13:18]', the internal array of the System object looks like the schematic shown in this figure below. The coloring of the inputs and the array indicate how the input symbols are placed within the array.

The outputs at the first three time steps are [1;-1;-1;2;3;-1], [7;4;5;8;9;6], and [13;10;11;14;15;12].

Note that the outputs are not color-coded in the schematic.

References

[1] Berlekamp, E. R. and P. Tong. "Improved Interleavers for Algebraic Block Codes." US Patent 4559625, Dec. 17, 1985.

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).

Version History

Introduced in R2012a