Real-time-Signal-Processing

In this project I have modelled a Lifi scenario where data is transmitted via visible light (special LED lights) using a non-linear modulation technique called CDMA (Code Division Multiple Access). To do this, I first created a Walsh-Hadamard matrix with values of either 1 or -1. Then I replaced the -1 values with 0, since the intensity of the LED light can't be negative. After that, we choose a number of rows that represent near orthogonality and are used as source code for each user. One of the selected rows is given to each user. For each user (e.g. #user=4) we generated random data bits and modulated the data bits with the assigned code sequence. Then all the modulated signals from each user are added together and transmitted through the modelled LED light with intensity modulation (LED ON = 1, LED OFF = 0). There are several parameters to set the transmission scheme, such as frequency, AWGN noise, code length, etc. After successful transmission, the received data is demodulated and the corresponding user data is extracted. Finally, the bit error rate (BER) is calculated using various parameters and the best parameters are used for the actual transmission.