Deterministic Signature Sequences Research Articles

Effect of Signature Sequence on the Performance of an AsynchronousMultiple-Chip-Rate DS/CDMA System

The effects of signature sequence on the performance of an asynchronous multiple-chip-rate (MCR)-DS/CDMA system are considered. The equations for the multiple access interference (MAI) and the variance of the MAI are developed. The bit error rate is derived by using the Gaussian approximation. The deterministic signature sequences such as maximal-length sequences and Gold sequences are compared with random signature sequences in terms of the variance of the MAI and bit error rate. We find that the performance of signature sequences in an asynchronous MCR-DS/CDMA system depends not only on the crosscorrelation properties of sequences but also on the carrier frequency separation between the interfering and desired users.

MC-CDMA performance evaluation over a multipath fading channel using the characteristic function method

This letter presents an efficient and accurate performance evaluation method for binary MC-CDMA systems with deterministic signature sequences. This method is based on a formulation of the characteristic function, and does not resort to any assumption on the statistical or spectral behavior of the interference. The accuracy of the Gaussian approximation method is also considered.

Low-Complexity Performance Evaluation of Binary and Quaternary DS-SSMAover Rician Fading Channels via the Characteristic Function Method

This paper presents an efficient and accurate performance evaluation technique for binary and quaternary direct-sequence spread-spectrum multiple-access (DS-SSMA) systems with deterministic signature sequences over Rician fading channels, without resorting to any (e.g. Gaussian) assumptions with respect to the distribution of the multiple-access interference (MAI). The method is based on a reduced-complexity formulation of the characteristic function method. In previous versions of this technique, the characteristic function of the MAI component of the decision statistic was expressed in terms of a double integral over the distributions of phase and delay. The new formulation, developed herein for both binary and quaternary modulation with a correlation receiver, generates a compact expression for the characteristic function of the MAI, eliminates the need for numerical integration over the phase distribution and yields a computational complexity reduction proportional to the spreading gain. This renders the characteristic function method more attractive for application to wideband CDMA systems and by extension, to more complex transceiver structures.

Performance of binary and quaternary direct-sequence spread-spectrum multiple-access systems with random signature sequences

The performance of synchronous and asynchronous, binary and quaternary (with and without offset) direct-sequence spread-spectrum multiple-access (DS/SSMA) communication systems using random signature sequences and arbitrary chip waveforms is investigated. The average probability of error at the output of the correlation receiver is evaluated using a characteristic-function approach for these systems. Numerical results are presented that illustrate performance comparisons between systems using random and deterministic signature sequences, synchronous and asynchronous systems, systems with rectangular or sinewave chip waveforms, and binary and quaternary systems with the same data rates and bandwidth. In all cases, the accuracy of the Gaussian approximation is also examined. >