Direct Sequence Spread Spectrum Communication System MATLAB Simulation and Source Code
I. Introduction
Direct sequence spread spectrum communication technology is one of the important technologies in modern communication field. It spreads the original data at the transmitting end to make the signal bandwidth very wide, so as to achieve the purpose of increasing channel capacity, improving anti-noise performance, and realizing multi-user sharing.
This article will introduce the MATLAB simulation process of the direct sequence spread spectrum communication system in detail, and provide the corresponding source code.
2. The principle of direct sequence spread spectrum communication system
The direct sequence spread spectrum communication system consists of three parts: source, spreader and despreader. Wherein, the signal source generates the digital signal to be transmitted, the frequency spreader performs frequency spreading processing on the signal, and the despreader restores the signal after frequency spreading to the original signal.
There are many ways to implement the spreader, the most commonly used one is the spread spectrum method based on pseudo-random codes. Specifically, the spreader uses a pseudo-random code to perform XOR operation on the original data to obtain a spread spectrum code sequence, and then multiplies the original data by the spread spectrum code sequence to finally obtain a spread spectrum signal.
The despreader is the opposite of the spreader, it uses the same pseudo-random code to XOR the received spread signal to restore the original data.
Three, MATLAB simulation steps
- generate source data
In this simulation, we use an 8-bit text as the source data. First convert the text to binary code and expand it to the length that needs to be transmitted.
str = 'hello'; % text x1 to be transmitted
= str2bin(str); % convert text to binary code
N = 200; % length after expansion
x = reshape(repmat(x1, N/length(x1), 1 ), 1, N);
- generate pseudorandom code
Pseudo-random code sequence is an important part of spread spectrum. In this simulation, we use a pseudo-random code of length 7. Among them, the pseudo-random code is