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wlanScramble

Scramble and descramble binary input sequence

Description

example

y = wlanScramble(bits,scramInit) scrambles or descrambles the binary input bits for the specified initial scramble state, using a 127-length frame-synchronous scrambler. The frame-synchronous scrambler uses the generator polynomial defined in IEEE® 802.11™-2012, Section 18.3.5.5 and IEEE 802.11ad™-2012, Section 21.3.9. The same scrambler is used to scramble bits at the transmitter and descramble bits at the receiver.

Examples

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Create the scrambler initialization and the input sequence of random bits.

scramInit = 93;
bits = randi([0,1],1000,1);

Scramble and descramble the bits by using the scrambler initialization.

scrambledData = wlanScramble(bits,scramInit);
descrambledData = wlanScramble(scrambledData,scramInit);

Verify that the descrambled data matches the original data.

isequal(bits,descrambledData)
ans = logical
   1

Input Arguments

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Input sequence to be scrambled, specified as a binary-valued column vector or matrix.

Data Types: double | int8

Initial scrambler state, specified as an integer in the interval [1, 127], or the corresponding binary-valued column vector of length 7.

Section 17.3.5.5 of [1] specifies the scrambling and descrambling process applied to the transmitted data. The header and data fields that follow the scrambler initialization field (including data padding bits) are scrambled by XORing each bit with a length-127 periodic sequence generated by the polynomial S(x) = x7+x4+1. The octets of the PSDU are placed into a bit stream, and, within each octet, bit 0 (LSB) is first and bit 7 (MSB) is last. This figure demonstrates the sequence generation and XOR operation.

Conversion from integer to bits uses left-MSB orientation. For the initialization of the scrambler with decimal 1, the bits are mapped to the elements shown.

ElementX7X6X5X4X3X2X1
Bit value0000001

To generate the bit stream equivalent to a decimal, use the de2bi function. For example, for the decimal 1:

de2bi(1,7,'left-msb')
ans =

     0     0     0     0     0     0     1

Example: [1; 0; 1; 1; 1; 0; 1] conveys the scrambler initialization state of 93 as a binary-valued columnm vector.

Data Types: double

Output Arguments

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Scrambled or descrambled output, returned as a binary column vector or matrix with the same size and type as bits.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Introduced in R2017b