Williamson–Hadamard spreading sequences for DS‐CDMA applications
Jennifer Seberry, Beata Joanna Wysocki, Tadeusz Antoni Wysocki · Wireless Communications and Mobile Computing · 2003
Abstract Orthogonal bipolar spreading sequences are used in direct sequence code division multiple access (DS‐CDMA) systems for both spectrum spreading and channel separation. The most commonly used sequences are Walsh–Hadamard sequences of lengths being an integer power of 2. A construction based on Williamson's arrays leading to sequences of lengths N≡4 (mod 8) is presented in the paper. Aperiodic correlation characteristics, for example sequence sets of lengths 12–252 are presented. The correlation properties of the sequence sets are later improved using a diagonal modification technique. Copyright © 2003 John Wiley & Sons, Ltd.