A Method for Modulation Parameters Estimation of Co-Channel Multi-Signals based on Cyclic Spectrum

Modulation parameters estimation of co-channel multi-signals has become a new subject of communication signals processing. In the non-cooperative communication fields, it is the key step and base of subsequent processes, such as modulation recognition, signal demodulation and so on. As is well known, signals exhibite cyclostationary character after modulation, pulse formation and sampling, which is different for those time-frequency overlapped co-channel multi-signals whose modulation parameters are often different from each other. Making use of the character mentioned above, this paper presented a method based on cyclic spectrum and discrete spectrum-line abstraction to estimate the modulation parameters, including carrier frequency and chip rate. The method utilized the relationship between modulation parameters and cyclic frequency, extracted the discrete spectrum line corresponding to the carrier frequency and chip rate in the cyclic spectrum profile to estimate the parameters of each time-frequency overlapped signals. Using BPSK and 8QAM as overlapped simulation signals, Matlab simulation results proved the method effective and accurate. Even when the dispersion of carrier frequencies is very small compared to the chip rate, this method can also be used. Additionally, it is robust to noise and spectrum overlapping extent; at the same time, the sum of computation is small as well.