• ANALYSIS OF CYCLOSTATIONARY AND SPECTRAL CORRELATION OF FEHER-KEYING (FK) SIGNALS

      Chang, Soo-Young; Gonzalez, Maria C.; McCorduck, James A.; Feher, Kamilo; University of Suwon; University of California; Digcom, Inc. (International Foundation for Telemetering, 2002-10)
      Feher Keying (FK) signals are clock shaped baseband waveforms with the potential to attain very high spectral efficiencies. Two FK signals which have different level rectangular waveforms (named as FK-1) or sinusoidal waveforms (named as FK-2) for two binary symbols are considered in this paper. These signals have periodic components in the time domain. Therefore they have cyclostationary properties. This means that spectral correlation exists in the frequency domain. For each type of waveforms, spectral correlation has been investigated. FK signals can be expressed mathematically into two parts in the frequency domain – discrete part and continuous part. The discrete part has one or more discrete impulse(s) in their spectra and the continuous part has periodically the same shape of harmonics in their spectra. The correlations of their spectra have been obtained mathematically and by simulation. It is shown that FK signals have high correlation related to the symbol rate. Finally, some suggestions how these properties can be used to improve their performance by devising better demodulators are discussed. These properties can be used for interference rejection at the receiver, which results in low bit error rate performance.
    • SPECTRAL EFFICIENCY/BIT ERROR RATE OF FQPSK AND OTHER NON-COHERENT SYSTEMS SUPERIOR TO COHERENT SYSTEMS FOR SMS AND BURSTED TDMA AND CDMA SYSTEMS

      McCorduck, James A.; Feher, Kamilo; MatrixSat, Inc.; University of California; Digcom, Inc. (International Foundation for Telemetering, 2002-10)
      For faster acquisition in bursted environments for SMS (Short Messaging Service) and other lower-bit rate applications, non-coherent detection techniques are proposed. Non-Coherent detection demodulators are proposed because faster acquisition capability in bursted environments can result in a reduced amount of preamble bits in the messaging frame, i.e. less overhead, resulting in an effective increase in spectral efficiency. Reducing the preamble can also provide performance enhancement opportunities for Feher Quadrature Phase Shift Keying (FQPSK) [1] and for other systems. The preamble can also be varied to provide for better Bit Error Rate (BER) performance. The lower bit rate environment also gives the opportunity to employ simpler architectures in lieu of preamble modification. Several non-coherent detection alternatives are described.