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There is currently considerable interest in the development of high-speed radio local area networks (LAN). In particular, the HIPERLAN/2 standard is currently under development. The modulation technique for this standard is orthogonal frequency division multiplexing (OFDM). OFDM transmission in a time-dispersive radio channel requires the insertion of a guard interval to combat intercarrier interference (ICI). This insertion of a guard interval reduces transmission efficiency. Recently, a combined OFDM-equalization strategy has been developed by the authors. This strategy employs a pre-FFT equalizer to supplement or replace the guard interval and thereby achieve a more efficient transmission. This paper presents the equalizer design and two measured radio transmission channels for test purposes. The paper also discusses the potential performance improvements over conventional OFDM offered by a combined OFDM-equalization strategy for a range of transmission rates. It is demonstrated that the combined OFDM-equalization method offers an increase in transmission efficiency relative to the conventional OFDM method. This increase improves with the transmission rate and the radio channel's RMS delay spread. For long delay spreads, efficiency can be improved by nearly 20%. Furthermore, the combined OFDM-equalization technique is capable of operating under delay spread conditions which would require conventional OFDM to employ prohibitively long guard intervals
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Name of Conference: 10th International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC)
Venue of Conference: Osaka, Japan