Broadband interference excision for software-radio spread-spectrumcommunications using time-frequency distribution synthesis

摘要

A new method is introduced for interference excision innspread-spectrum communications that is conducive to software-radionapplications. Spare processing capacity in the receiver permits the usenof time-frequency techniques to synthesize a nonstationary interferencenfrom the time-frequency domain using least squares methods. Thensynthesized signal is then subtracted from the incoming data in the timendomain, leading to jammer removal and increasednsignal-to-interference-and-noise ratio at the input of the correlator.nThe paper focuses on jammers with constant modulus that are uniquelyndescribed by their instantaneous frequency characteristics. With this anpriori knowledge, the jammer signal amplitude is restored by projectingneach sample of the synthesized signal to a circle representing itsnconstant modulus. With the phase matching provided by the least squaresnsynthesis method and amplitude matching underlying the projectionnoperation, a significant improvement in receiver performance/bit-errornrates is achieved over the case where no projection is performed.nSoftware-radio aspects including computational complexity and processingnmodes are also discussed