Performance of Soft Decision Digital Matched Filter in Direct-Sequence Spread-Spectrum Communication Systems

Nobuhisa KATAOKA  Toshiharu KOJIMA  Makoto MIYAKE  Tadashi FUJINO  

IEICE TRANSACTIONS on Communications   Vol.E74-B   No.5   pp.1115-1122
Publication Date: 1991/05/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Spread Spectrum Techniques and Its Applications)

Full Text: PDF(574KB)>>
Buy this Article

This paper considers the problem of realizing excellent performance of rapid acquisition in direct-sequence spread-spectrum communication systems. In this paper, we consider a scheme of digital matched filter (DMF) combined with soft decision function, which has potential capability of improving the characteristics of hard decision function by about 2dB in the environment of additive white Gaussian noise (AWGN) channel and is capable of handling long PN codes by means of simple LSIs. Analysis is made on the performance in the environment of AWGN channel and results of experiments are provided. It is confirmed that the scheme provides attractive means for acquisition of direct-sequence spread-spectrum signals. Namely, soft decision DMF achieves rapid acquisition; the dwell time for soft decision DMF in the process of acquisition is half of that for hard decision DMF. In addition, it is shown that the correlator output signal produced by the acquisition circuit can also be used for the purpose of demodulation; excellent performance of bit error probability is experimentally observed.