Browsing by Author "Pereira, J. S."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- 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.
- Orthogonal perfect DFT Golay codesPublication . Lanza-Gutierrez, J. M.; Ferreira, M.; Gomez-Pulido, J. A.; Priem-Mendes, S.; Pereira, J. S.; Silva, H. J. A.Deciding about which coding sequences should be used is an important issue in many communication systems, such as those employing Code Division Multiple Access (CDMA). In this paper, we propose a cascading electronic codec based on a recursive algorithm for the generation of perfect sequences, derived from an Inverse Discrete Fourier Transform (IDFT) of Golay codes. The sequences generated have a low Peak-to-Average Power Ratio (PAPR), around 3 dB, which is the PAPR of a sine wave. The proposal is compared to the original Golay codes, verifying that our codec provides better crosscorrelation and autocorrelation results, crucial to gain immunity to multi-path interference.