OFDM Learning Journey

Objective:

These days began to get ready to engage in OFDM and the like, do not move the first MATLAB simulation, here I will slowly update, is basically my own learning sentiment bar < to be continued >

First, PRBS

PRBS is the abbreviation for Pseudo random binary Sequence, meaning "pseudo-random binary sequence". The PRBS code has a "random" feature, is because in the PRBS stream, the binary number "0" and "1" is random, but it and the real meaning of the random code, this "random" feature is only local, that is, within the cycle, "0" and "1" is random (after the code stream generation function and the initial code is determined,　　The order of the code stream is also fixed), but the code flow in each period is exactly the same, so we call it "" pseudo-random code. The period length of PRBS code is related to its order number, and the order number is 7, 9, 11, 15, 20, 23, 31, which we often say PRBS7, PRBS9, PRBS11, PRBS15, PRBS20, PRBS23, PRBS 31. Common order Digital Flow parameter statistics: tr>

PRBS n	initial value	primitive polynomial
PRBS 7	0 0 0 0 0 0 1	x7+x6 + 1
PRBS 9	0 0 0 0 0 0 0 0 1	x9+x5+1
PRBS	0 0 0 0 0 0 0 0 0 0 0 0 0 0 1	x15+x14+1
PRBS	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1	x16+x14+x13+x11+1
PRBS	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1	x20+x17+1
PRBS	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1	x21+x19+1
PRBS	0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1	x23+x18+1

In the high-speed signal link error test, basically use PRBS code stream to simulate the real network code flow environment, because in the online network, all the data are random, there is no rule to say, and PRBS stream to some extent with this "random data" characteristics, binary "0" and "1" Randomly appearing, its spectral characteristics are very close to the white noise.　　The higher the order of the PRBS stream, the richer the pattern it contains, the closer it is to the real network environment, the more accurate the test results. A PRBS sequence can be strung/converted into multiple paths (2, 4, 8, 16 ... , the rate of each output decreases, but still retains all the characteristics of the original sequence; Conversely, the same clock source low-rate multi-channel (2, 4, 8, 16 ...　　The PRBS of the same n number can be converted to a high rate of N-order PRBS by A/string. The PRBS pattern generator consists of a shift register and XOR Gate (XOR), for example:

Code See below:

%PRBS Generating input signal% f (x) =1+x^6+x^7;%%prbs7_initial= [1 1 1 1 1 1 1]; Prbs7_data=prbs7_initial;%generates data for 1 rows of totbits columns Prbs7_out= Zeros (1, totbits); Prbs_reg= Zeros (1,2);%Store XOR value forData_bit =1: Totbits prbs7_out (data_bit)= Prbs7_data (7); %assigns the 7th bit to prbs7_out all data%%use the generated formula to shift the 6, 7-bit data to the right or back loop Prbs_reg= Prbs7_data (6:7);%6th, 7-bit assignment Prbs7_data (2:7) = Prbs7_data (1:6);%1-6-bit data is moved backwards by one prbs7_data (1) = XOR (Prbs_reg (1), Prbs_reg (2));%An xor assignment of the 6\7 bit to the end prbs7_data of the first bit;% is a random sequence of generated PRBS7

PRBS7

OFDM Learning Journey