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Permute symbols using shift registers


intrlved = convintrlv(data,nrows,slope)
[intrlved,state] = convintrlv(data,nrows,slope)
[intrlved,state] = convintrlv(data,nrows,slope,init_state)


intrlved = convintrlv(data,nrows,slope) permutes the elements in data by using a set of nrows internal shift registers. Before the function begins to process data, it initializes all shift registers with zeros. If data is a matrix with multiple rows and columns, the function processes the columns independently. For information about delays, see Delays of Convolutional Interleaving and Deinterleaving.

[intrlved,state] = convintrlv(data,nrows,slope) returns a structure that holds the final state of the shift registers. state.value stores any unshifted symbols. state.index is the index of the next register to be shifted.

[intrlved,state] = convintrlv(data,nrows,slope,init_state) initializes the shift registers with the symbols contained in init_state.value and directs the first input symbol to the shift register referenced by init_state.index. The structure init_state is typically the state output from a previous call to this same function, and is unrelated to the corresponding deinterleaver.


The example below shows that convintrlv is a special case of the more general function muxintrlv. Both functions yield the same numerical results.

x = randi([0 1],100,1); % Original data
nrows = 5; % Use 5 shift registers
slope = 3; % Delays are 0, 3, 6, 9, and 12.
y = convintrlv(x,nrows,slope); % Interleaving using convintrlv.
delay = [0:3:12]; % Another way to express set of delays
y1 = muxintrlv(x,delay); % Interleave using muxintrlv.

The output below shows that y, obtained using convintrlv, and y1, obtained using muxintrlv, are the same.

ans =


Another example using this function is in Effect of Delays on Recovery of Convolutionally Interleaved Data Using MATLAB.

The example on the muxdeintrlv reference page illustrates how to use the state output and init_state input with that function; the process is analogous for this function.

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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 nrows argument

  • slope is the register length step and equals the value of the slope argument

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.

General convolutional interleaver showing the set of shift registers, the delay values D(1), D(2),..., D(N) for each register, and a commutator to switch input and output symbols through registers


[1] Heegard, Chris and Stephen B. Wicker. Turbo Coding. Boston: Kluwer Academic Publishers, 1999.

Version History

Introduced before R2006a