Research on BPSK-CSK message modulation and demodulation algorithm

For signals that have higher requirements on the information transmission rate, such as precision positioning signals, a combined binary phase shift keying-code shift keying (BPSK-CSK) modulation method is proposed to solve the problem of the high demodulation computational complexity of the traditional code shift keying (CSK). This method subdivides the modulated message into polar bits and code phase bits, so that the receiver converts demodulating message by correlating and summation into two steps to complete the message demodulation through less times of correlating summation and subcode matching. It reduces the number of correlators required for the receiver to demodulate the message and reduces the data magnitude involved in the operation. When the number of polar bits is 1 or 2, compared with the CSK, the performance of bit error rate is negligible, and the computational complexity is reduced to 50% or 25% of the computational complexity of the original method. When the number of polar bits is greater than 2, the computational complexity will be reduced at the expense of the bit error rate, but at this time, combined with the error-correcting coding, BPSK-CSK can still reduce the bit error rate under the same computational complexity.