A Signal Modulation Method of Direct Sequence Spread Spectrum Based on Modulated m-sequence

To raise the spectrum utilization, a modulation and demodulation method called modulated Direct Sequence Spread Spectrum (m-DSSS) is proposed, which assign the period of m-sequence to be equal to the integer multiple of data bit. Firstly, the feasibility of m-DSSS signal acquisition is verified by numerical simulation results of correlation. Then, according to the permutation of information bits, a multi-channel signal modulation and demodulation method for m-DSSS is designed, and the mathematical model reacting the anti-interference ability of passing through the additive Gaussian white noise channel is established. Finally, the simulation and contrast test are carried out with Codes Shift Keying (CSK) modulation under the same spectrum utilization. The simulation results show that m-DSSS signal not only has lower side peak than CSK signal but also can assist signal acquisition by judging polarity when BPSK modulation is adopted. When bit error rate is better than 1e-3, m-DSSS signal has more than 2 dB advantage than CSK signal, which verifies the feasibility of m-DSSS used in DSSS system.