Receiver design in DS-CDMA systems with aperiodic random sequences

Tan Foon Wong, Purdue University

Abstract

In this work, we investigate issues on receiver design in direct-sequence code-division multiple-access (DS-CDMA) systems with aperiodic random signature sequences. The main objective is to design receiving structures capable of rejecting multiple-access interference (MAI), which is the major channel imperfection in DS-CDMA systems. The use of aperiodic random sequences, albeit more practical, presents some difficulties over the periodic sequence assumption usually made in the design of MAI rejecting receivers. To circumvent these difficulties, we propose a decentralized linear coherent receiver, which consists of the conventional sequence-matched filter followed by a tapped delay line, to achieve the desired MAI rejection capability. The proposed receiver is capable of utilizing the diversities provided by oversampling, electronically steerable antenna arrays, or multicarrier modulation to achieve MAI rejection by suitably choosing the weights in the tapped delay line. In addition to MAI, the receiver can also combat imperfections caused by fading channel environments and narrowband interference. Our second objective concerns the implementability of the proposed receiver. To this end, we develop both adaptive and non-adaptive algorithms to obtain the weights in the tapped delay line of the receiver. We also investigate the problem of chip waveform selection, and evaluate the performance of the proposed receiver in cellular wireless environments, in which DS-CDMA systems are often employed.

Degree

Ph.D.

Advisors

Lehnert, Purdue University.

Subject Area

Electrical engineering

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