MATCHED MEDIAN DETECTORS FOR MULTIPLE-ACCESS CHANNELS

The performance of matched median detectors is studied in a coherent c ode-division multiple-access environment addressing asynchronous and s ynchronous communication. Two types of noise sources interfering with the data transmission are assumed: multiple-access interference and ad ditive impulsive channel noise. A detector structure based on a multis tage multiple-access rejection scheme and matched median filters is st udied. Probability of error analysis is presented for a two-stage dete ctor, and performance is characterized in terms of average bit-error p robability. Calculations and simulations show that the multistage matc hed median structure performs well in situations where the energies of the code signals are different, therefore being able to combat the ne ar-far problem characteristic of direct-sequence spread spectrum multi ple-access systems.