wlanScramble
Scramble and descramble binary input sequence
Description
y = wlanScramble(bits,scramInit) 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
Input Arguments
bits — Input sequence
column vector | matrix
Input sequence to be scrambled, specified as a binary column vector or matrix.
Data Types: double | int8
scramInit — Initial state of scrambler
integer from 1 to 127 | 7-by-1 binary column vector
Initial state of the scrambler, specified as an integer from 1 to 127, or a corresponding 7-by-1 column vector of binary bits.
The scrambler initialization used on the transmission data follows the process described in IEEE Std 802.11-2012, Section 18.3.5.5 and IEEE Std 802.11ad-2012, Section 21.3.9. 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 (Physical Layer Service Data Unit) are placed into a bit stream, and within each octet, bit 0 (LSB) is first and bit 7 (MSB) is last. The generation of the sequence and the XOR operation are shown in this figure:
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.
| Element | X7 | X6 | X5 | X4 | X3 | X2 | X1 |
|---|---|---|---|---|---|---|---|
| Bit Value | 0 | 0 | 0 | 0 | 0 | 0 | 1 |
To generate the bit stream equivalent to a decimal, use de2bi. For example, for decimal
1:
de2bi(1,7,'left-msb')
ans =
0 0 0 0 0 0 1Same scramInit is applied across all the columns of
bits when the input is a matrix.
Example: [0 0 0 0 0 0 1]'
Data Types: double