Implementing of a New Software-Defined Radio Receiver Used for DSSS-CDMA Data Signals

In this paper a new software-defined radio receiver used for DSSS-CDMA data signals is presented. The proposed radio receiver is intended for the reception of data signals with DSSS-CDMA modulation transmitted in the FM radio broadcasting infrastructure according to different scenarios of vehicular communications. For detecting of the data signal the circuit proposed in this paper is based on a carrier synchronization loop, operating at baseband and a DSSSCDMA demodulator. These stages are controlled by a symbol timing synchronization loop, which provides the maximum effect points (of both received DSSS-CDMA and DEQPSK signals) by using the Early Late timing error detector (ELTED) algorithm. The proposed circuit has been implemented in MATLAB/Simulink for an input data rate of $2375 \mathrm{bit} / \mathrm{s}$ and simulated under the conditions of different offset values of both carrier frequency and data rate on an AWGN communication channel, and also using an experimental setup that includes two USRP devices of type N210. In order to validate the simulation results, the bit error rate depending on signal-to-noise ratio of the radiofrequency DSSS-CDMA signal has been plotted for different communication scenarios.