Browsing by Author "Vaidyanathan, PP"

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A kaiser window approach for the design of prototype filters of cosine modulated filterbanks
(1998-06-01)
Lin, YP
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Vaidyanathan, PP
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電控工程研究所
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Institute of Electrical and Control Engineering
The traditional designs for the prototype filters of cosine modulated filterbanks usually involve nonlinear optimizations. We propose limiting the search of the prototype filters to the class of filters obtained using Kaiser windows. The design process is reduced to the optimization of a single parameter. An example will be given to show that very good designs can be obtained in spite of the limit of search.
Discrete multitone modulation with principal component filter banks
(2002-10-01)
Vaidyanathan, PP
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Lin, YP
;
Akkarakaran, S
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Phoong, SM
;
電控工程研究所
Discrete multitone (DMT) modulation is an attractive method for communication over a nonflat channel with possibly colored noise. The uniform discrete Fourier transforn (DFT) filter bank and cosine modulated filter bank have in the past been used in this system because of low complexity. We show in this paper that principal component filter banks (PCFB) which are known to be optimal for data compression and denoising applications, are also optimal for a number of criteria in DMT modulation communication. For example, the PCFB of the effective channel noise power spectrum (noise psd weighted by the inverse of the channel gain) is optimal for DMT modulation in the sense of maximizing bit rate for fixed power and error probabilities. We also establish an optimality property of the PCFB when scalar prefilters and postfilters are used around the channel. The difference between the PCFB and a traditional filter bank such as the brickwall filter bank or DFT filter bank is significant for effective power spectra which depart considerably from monotonicity. The twisted pair channel with its bridged taps, next and fext noises, and AM interference, therefore appears to be a good candidate for the application of a PCFB. This will be demonstrated with the help of numerical results for the case of the ADSL channel.
On the duality of optimal DMT systems and biorthogonal subband coders
(2000)
Lin, YP
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Vaidyanathan, PP
;
Akkarakaran, S
;
Phoong, SM
;
電控工程研究所
The discrete multitone modulation (DMT) systems have been widely used in various applications. The DMT system can be considered as a dual of a subband coder, obtained by using the synthesis bank as the transmitter and analysis bank as the receiver. In designing optimal subband coders, the objective is to minimize output quantization noise, whereas in the problem of designing optimal DMT system, the objective function to be minimized is the transmitted power. In this paper we will show that the design of optimal DMT systems can be formulated as a hypothetical design problem of optimal subband coders. The solution of optimal DMT system can be obtained using existing design methods for optimal biorthogonal subband coders.
Periodically nonuniform sampling of bandpass signals
(1998-03-01)
Lin, YP
;
Vaidyanathan, PP
;
交大名義發表
;
National Chiao Tung University
It is known that a continuous time signal x(t) with Fourier transform X(nu) band-limited to u < Theta/2 can be reconstructed from its samples x(T(o)n) with T-o = 2 pi/Theta. In the case that X(nu) consists Of two bands and is band-limited to nu(o) < u < nu(o) + Theta/2, successful reconstruction of x(t) from x(T(o)n) requires an additional condition on the band positions, When the two bands are not located properly, Kohlenberg showed that we can use two sets of uniform samples, x(2T(o)n) and x(2T(o)n+d(1)), with average sampling period T-o, to recover x(t). Because two sets of uniform samples are employed, this sampling scheme is called Periodically Nonuniform Sampling of second order [PNS(2)], In this paper, we show that PNS(2) can be generalized and applied to a wider class, Also, Periodically Nonuniform Sampling of Lth-order [PNS(L)] will be developed and used to recover a broader class of band-limited signals, Further generalizations will be made to the two-dimensional case and discrete time case.