1,721,121 research outputs found
Comments on "Orthogonal multiple carrier data transmission"
No full textIn a paper from 1992, Fliege introduced a novel multicarrier modulation scheme claiming to obtain an implementation that is computationally more efficient and has a simpler filter bank structure with respect to those previously presented in the literature. Being understood the correctness and valuability of the ideas expressed in that paper, nevertheless we would like to point out that an implementation with the same computational complexity had already been presented by Hirosaki in 1981, and that the optimization of the filter bank structure is based on an incorrect ste
On the realization of minimum noise and low-noise frequency sampling FIR filters
No full textIn this work the finite precision effects issue connected to the frequency sampling realization of FIR filters is considered. In particular, the performance of the frequency sampling filters is evaluated in terms of noise gain for the following three different realizations of the second-order elementary sections: the canonical direct form, the minimum roundoff noise structure, and the suboptimal state-space structure introduced by Bomar. An interesting property on the design of minimum noise second-order sections embedded in the frequency sampling structure, is given. The results obtained show that the realizations via minimum noise structures and Bomar's structures greatly outperform the realizations via canonical direct form structures, and, for very narrow-band filters, have noise gain comparable to that of nonrecursive direct realization
OFDM-OQAM multicarrier transmission systems
No full textAn OFDM-OQAM digital base band transmission and reception system with filters for the multiplexing of N complex sequences each with symbol frequency F/2 and spacing F between the frequencies of the adjacent subcarriers is embodied with f0=0 where f0 means the frequency of the subcarrier of order 0. An OFDM-OQAM digital pass band transmission and reception system with filters for the multiplexing of N complex sequences each with symbol frequency F/2 and spacing F between the frequencies of the adjacent subcarriers is embodied with f0=0 where f0 means the base band equivalent frequency of the subcarrier of order 0
Filter design for the conjugate OFDM-OQAM system
No full textWe present a filter design procedure for a novel multicarrier modulation scheme, the conjugate OFDM-OQAM, which only requires amplitude tailoring of the prototype filter frequency response, regardless of its phase. It achieves good interchannel interference (ICI) and intersymbol interference (ISI) rejection, while still maintaining maximum spectral efficiency and a good time-frequency localization of the transmission pulses. Loosening the phase constraint allows the use of an effective technique for matched filter design, developed by Samueli (1988). Through this technique we are able to design a system with higher performance than standard OFDM-OQAM systems with the same prototype filter length
Channel Impulse Response Estimation in IEEE 802.11p via Data Fusion and MMSE Estimator
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Efficient Implementations and Alternative Architectures for OFDM-OQAM Systems
No full textWe derive new implementations for baseband and passband orthogonal frequency-division multiplexing based on offset QAM (OFDM-OQAM), which nearly halve the number of arithmetic operations required every symbol period by exploiting the symmetries in the transmitted sequences. We also propose a novel scheme, named conjugate, that employs two different filters being the time-reversed version of each other: one in the modulator for the even subchannels and in the demodulator for the odd ones, and the other in the modulator for the odd subchannels and in the demodulator for the even ones. We formulate both baseband and passband versions of this scheme in which the constraints for the filter design are loosened, requiring only amplitude tailoring of its frequency response. We derive efficient implementations for the conjugate scheme, which exhibit a significantly lower complexity than previous implementations of the traditional OFDM-OQAM schem
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