Multiplex communications – Communication over free space – Combining or distributing information via code word channels...
Patent
1997-02-28
1999-10-26
Pham, Chi H.
Multiplex communications
Communication over free space
Combining or distributing information via code word channels...
370441, 375200, 375209, H04B 726
Patent
active
059740426
ABSTRACT:
A radiotelephone (121) employs a service detection circuit (125) comprising at least one chip-rate detector (109) that measures the energy of the autocorrelation of a received composite CDMA signal and employs a different time delay for each measurement of the energy. A threshold detection circuit (127) combines the measured energies and determines that service is available if the combined energies exceeds a threshold, and determines service is unavailable otherwise. The chip-rate detectors (109) can be coupled in parallel to provide simultaneous measurements of the energy of the autocorrelation of the received composite CDMA signal, or a single chip-rate detector (109) can serially measure the energy of the autocorrelation of the received composite CDMA signal.
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Kuehls et al., IEEE Journal on Selected Areas in Communications, "Presence Detection of Binary-Phase-Shift-Keyed and Direct-Sequence Spread-Spectrum Signals Using a Prefilter-Delay-and-Multiply Device", vol. 8, No. 5, Jun. 1990, pp. 915-933.
Peterson et al., Introduction to Spread Spectrum Communications, Section 10-6: Estimation of Spread-Spectrum Signal Parameters, IEEE, 1988, pp. 605-611.
Reed et al., IEEE Transactions on Communications, "Minimization of Detection of Symbol-Rate Spectral Lines by Delay and Multiply Receivers", 1988, pp. 118-120.
M. A. Wickert, Appendix A: The Calculation of the Delay and Multiply Receiver Output Power Spectral Density, University of Colorado thesis paper, pp. A-1 to A-22.
Frank Colin D.
Honkisz Jennifer A.
Storm Brian D.
Duong Frank
Kordich Donald C.
Motorola Inc.
Pham Chi H.
Williams Lalita P.
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