Simulink Model of a BPSK Direct Sequence Spread Spectrum System

Model of a BPSK DSS system with two users through an AWGN channel, attached to a BER calculator.

Input is generated using the Random Integer Generator block, converted to polar (with unipolar we get 3 states after multiplication instead of 4), then multiplied with the output of a PN-Generator.
The data is modulated using BPSK then sent through an AWGN channel.
On the receiver side we multiply with the same PN sequence and demodulate.
The BER-Calculator block compares sent data with received data, and outputs a vector with count of symbols, errors, and the BER.

To add more users simply copy the whole TX and RX part and attach it to the add block after adding another input to it.