Browsing by Author "Silva, H. J. A. da"
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- Generalized Chu polyphase sequencesPublication . Pereira, J. S.; Silva, H. J. A. daThe perfect sequences are so ideal that all out-ofphase autocorrelation coefficients are zero. A method to generate a prime number N of perfect sequences with length N is presented. Moreover, these new sets have one more perfect sequence than Chu polyphase sets with the same maximum absolute value of periodic cross-correlation, and are slightly better for asynchronous direct sequence code division multiple access (DS-CDMA). The new sequences are more robust than Chu sequences when used with M-ary quadrature amplitude modulation (QAM). The reason for this improvement is that the new sequences are designed to be orthogonal to the M-ary QAM carriers. Other sequence transformations are also suggested and may be used to obtain many other perfect sequences with the same correlation properties. For example, the new sequences can be transformed into quadriphase sequences, also with good correlation properties.
- Perfect DFT sequences transformed into orthogonal sequencesPublication . Pereira, J. S.; Silva, H. J. A. daIn this paper, we present a method and a code generator to transform perfect DFT (discrete Fourier transform) sequences into orthogonal sequences and into bipolar codes, with good correlation properties. These new sequences or codes produce a low peak-to-average power ratio (PAPR) and a low error probability in a code-division multiple access (CDMA) system. All these codes can also be useful in a pre-coded version of an orthogonal frequency-division multiplexing (OFDM) system.