UCHT-based complex sequences for asynchronous CDMA system

Signal Processing by Generalized Receiver in DS-CDMA Wireless Communications Systems

“…These sequences are generated by the unified complex Hadamard transform matrix discussed in [96], the correlation properties of which are studied in [97], where it is shown that the unified complex Hadamard transform sequences possess the better autocorrelation properties in comparison with the WH sequences, which are characterrized by very poor autocorrelation properties.…”

“…They are categorized into two groups: the halfspectrum property orthogonal unified complex Hadamard transform spreading sequences and the non-half-spectrum property orthogonal unified complex Hadamard transform spreading sequences. Consider briefly how these sequences can be generated and note the main definitions and remarks discussed in [96,97].…”

“…A unified complex Hadamard transform matrix A of order n N 2  is a square matrix with elements 1  and j  , and is constructed by [96,97] [97] that the non-half-spectrum property unified complex Hadamard transform sequences have very similarly poor autocorrelation properties as WH sequences, and some of the half-spectrum property unified complex Hadamard transform sequences exhibit a reasonable compromise between the autocorrelation and cross-correlation functions. In this section, we just consider the half-spectrum property unified complex Hadamard transform sequences, i.e., j j a   or 3 .…”

Precise BER Formulas for Asynchronous QPSK-Modulated DS-CDMA Systems Using Random Quaternary Spreading Over Rayleigh Channels

“…As a benefit of their relative simplicity compared with other polyphase sequences [3], a number of quaternary spreading sequences, which are synonymously also referred to as complex-valued spreading sequences, have been proposed in [4]- [6]. Some of them were claimed to outperform gold and m-sequences in asynchronous DS-CDMA systems [5], [6]. A receiver architecture using quaternary spreading sequences and QPSK modulation was proposed in [7].…”

“…The bit-error-ratio (BER) performance of the family of DS-CDMA systems using quaternary spreading and QPSK modulation has been investigated using a variety of techniques, including precise analysis [6], [7], approximations [6], [8], [9], bounding techniques [9], or simulations [5], [8]. The achievable BER performance over both additive white Gaussian noise (AWGN) [5], [7]- [9] and Rayleigh [6] both deterministic quaternary spreading sequences [5]- [7], [9] and random quaternary spreading sequences [8] was also studied.…”