Abstract: In order to give a quantitative description of the noisy multiuser performance of digital communications using chaos‚a new approach is proposed to analyze the noisy multiuser performance of a coherent DCSK system in this paper‚based on discrete-time chaotic sequences．The expressions of error performance and its upper bound for multiuser and single user are given theoretically and verified by the simulation results．Theoretical and simulation results show that the noise performance is reduced rapidly by increasing the number of the mult-i user‚and that there is a bound for noisy multiuser performance of coherent DCSK．The approach to increasing the performance is to produce a set of orthogonal chaotic signals．

Key words: coherent DCSK, communication system, multiuser, error performance