Application of frequency diversity to an OFDM system

Citation
T. Seki et al., Application of frequency diversity to an OFDM system, ELEC C JP 1, 85(2), 2002, pp. 17-29
Citations number
12
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Information Tecnology & Communication Systems
Journal title
ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS
ISSN journal
8756-6621 → ACNP
Volume
85
Issue
2
Year of publication
2002
Pages
17 - 29
Database
ISI
SICI code
8756-6621(2002)85:2<17:AOFDTA>2.0.ZU;2-#
Abstract
Frequency-selective fading caused by multipath interference influences sign al reception. OFDM is attracting attention as a means of dealing with this problem. In an OFDM system, equalization is easy, since the frequency-selec tive fading is assumed to be flat fading on each unit of carrier, making th e bandwidth of each carrier narrow. However, when frequency- selective fadi ng generates a deep dip, the SNR (signal-to-noise ratio) is degraded radica lly. In this case, it becomes difficult to retrieve the original informatio n correctly, even if the equalization is appropriate. Hence, we propose an OFDM system applying frequency diversity in this paper. In this system, a u nique symbol is transmitted on several carriers. These carriers are selecte d in order to compensate the degraded carrier by the enhanced carrier, or a re selected quasi-randomly. In the former case, although the receiver must feed back the channel transfer function for the transmitter, better charact eristics are expected. In the latter case, although there is a necessity on ly for sharing of the common quasi-random sequence, less gain than in the f ormer method is expected. At the receiver, symbols which are obtained from these carriers are combined so as to maximize the SNR. A simulation shows t hat the proposed system can achieve larger gain, especially in a static mul tipath environment whose D/U is smaller, or in a Rayleigh fading environmen t. (C) 2001 Scripta Technica.