MATCHED MEDIAN DETECTORS FOR MULTIPLE-ACCESS CHANNELS

The performance of matched median detectors is studied in a coherent code-division multiple-access environment addressing asynchronous and synchronous communication. Two types of noise sources interfering with the data transmission are assumed: multiple-access interference and additive impulsive channel noise. A detector structure based on a multistage multiple-access rejection scheme and matched median filters is studied. Probability of error analysis is presented for a two-stage detector, and performance is characterized in terms of average bit-error probability. Calculations and simulations show that the multistage matched median structure performs well in situations where the energies of the code signals are different, therefore being able to combat the near-far problem characteristic of direct-sequence spread spectrum multiple-access systems.