Direct Sequence Spread Spectrum

Simulates DSSS QPSK performance in presence of interference.

Description

These files provide a Direct Sequence Spread Spectrum simulation. Testing is the main program and calls the others as necessary. After running Testing once, downlink can be used to test just the downlink portion against different types of noise/interference (Reusing the same uplink signal saves a lot of time if you modify the PRN sequence to create long sequences). Compares to QPSK with no spreading.

Set data rate, frequency, chip rate, and noise offset from center freq in "testing". Modify interference levels in "noise". Carrier freq in "downlink" should match that in "testing" - noise offset can also be varied in "downlink". Low chip rate/data ratio gives better plots, but high chip rate/data ratio gives better BER (initially set at 316:1).

Outputs number of bit errors and BER for both the QPSK and DSSS.

Acknowledgements

The author wishes to acknowledge the following in the creation of this submission:
QPSK TX RX System Analysis

• MATLAB release: MATLAB 7.1.0 (R14SP3)

[Jing Wang]