Title :
Polyphase Scrambled Walsh Codes for Zero-Correlation Zone Extension in QS-CDMA
Author :
Choi, Kwonhue ; Liu, Huaping
Author_Institution :
Dept. of Inf. & Commun. Eng., Yeungnam Univ., Gyeongsan, South Korea
fDate :
4/1/2012 12:00:00 AM
Abstract :
Polyphase complex scrambling patterns are designed to extend the zero-correlation zone (ZCZ) of a family of user spreading sequences, called properly scrambled Walsh-Hadamard (PSW) codes, recently proposed for quasi-synchronous (QS) code-division multiple-access systems. The merits of the binary (ZCZ equals 2) and quadri-phase (ZCZ equals 4) PSW codes over the existing QS spreading codes are still retained in the proposed polyphase PSW codes. Scrambling patterns for the case of ZCZ of 8 are derived first. Then, the scrambling pattern design rules are generalized for greater ZCZs and a structured procedure to generate polyphase PSW codes for any ZCZ is developed. Finally, the cross-correlation properties of the proposed spreading codes are evaluated.
Keywords :
Hadamard codes; binary codes; code division multiple access; QS code-division multiple-access system; QS spreading codes; QS-CDMA; ZCZ; binary PSW codes; polyphase PSW codes; polyphase complex scrambling pattern; polyphase scrambled Walsh code; properly scrambled Walsh-Hadamard codes; quadriphase PSW codes; quasisynchronous CDMA; user spreading sequences; zero-correlation zone extension; Correlation; Educational institutions; Fading; Indexes; Interference; Multiaccess communication; Phase shift keying; Quasi-synchronous CDMA; orthogonal spreading codes; scrambling; zero-correlation zone (ZCZ);
Journal_Title :
Communications Letters, IEEE
DOI :
10.1109/LCOMM.2011.112311.111380
