THESIS
2007
xi, 52 leaves : ill. ; 30 cm
Abstract
Constant Amplitude Zero Autocorrelation (CAZAC) Sequences have found many applications in spread spectrum communications, radar signals and system identification. They are frequently employed in communication systems as preambles for timing synchronization and channel estimation.
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Constant Amplitude Zero Autocorrelation (CAZAC) Sequences have found many applications in spread spectrum communications, radar signals and system identification. They are frequently employed in communication systems as preambles for timing synchronization and channel estimation.
In this thesis, we study CAZAC sequences generated by the unified Perfect Root of Unity Sequence (PRUS) construction. New polyphase sequences of length 2m
2 are presented. They are constructed based on patterns observed from full search results for small sequence lengths. It is shown that the new sequences have better merit factors, as well as better peak-to-side-peak ratios when compared with the well known Chu sequences. In addition, they are constructed with minimum alphabet size. In particular to the special case when the sequence length is a power of 2, the new alphabet size is the square root of that of Chu sequences, making implementation in a practical system easier.
We also investigate the application of these CAZAC sequences as preambles in Orthogonal Frequency Division Multiplexing (OFDM) systems, where low Peak to Average Power Ratio (PAPR) is desired. Truncation and cyclic shift are shown to be a simple and efficient way of suppressing the PAPR of a polyphase sequence. The effect of these techniques on different polyphase sequences is analyzed. Polyphase sequences with PAPR as low as 2 dB are obtained by applying appropriate truncation and cyclic shift, showing significant improvement over well known low-PAPR sequences, such as Chu sequences and Golay sequences.
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