MATLAB Implementation of CDMA Downlink Demodulation with Despreading Algorithm

This MATLAB program implements CDMA downlink signal despreading, which is the process of recovering original signals from received spread-spectrum transmissions. The core algorithm involves using despreading codes to eliminate the effects of spreading codes through correlation operations. The implementation will include generating local despreading sequences (typically Walsh codes) and performing synchronous correlation with the received signal. The code structure will feature key functions including signal synchronization, correlation calculation, and decision logic. The program demonstrates the complete workflow from receiving spread-spectrum signals to obtaining original downlink data through despreading code processing. By comparing signal characteristics before and after despreading, users can experimentally verify the restoration of signal bandwidth and signal-to-noise ratio improvement. Implementation details will cover critical aspects such as: - Handling timing synchronization between received signals and local despreading codes - Calculating correlation values using MATLAB's dot product operations - Implementing threshold detection for data decision making - Visualizing signal transformations through time-domain and frequency-domain plots This program serves as an educational tool for understanding CDMA demodulation principles while providing practical experimentation capabilities for algorithm verification and parameter tuning.