Raised Cosine Window Research Articles

Design of optimal short OFDM-type windows

One key issue of the fifth mobile communication generation (5G) is to elaborate an appropriate new waveform. Ideally, this waveform should preserve the two main advantages of the Orthogonal Frequency Division Multiplexing (OFDM) scheme, namely low latency and complexity. Along this line of thought, we propose in this paper an OFDM-type window, i.e. identical symbol time duration and equivalent spectral efficiency as OFDM. This optimal waveform with respect to the time-frequency localization criterion is analyzed using a Filtered MultiTone (FMT) framework. For this design criterion, comparisons are carried out between our optimized FMT solution, OFDM and the Root Raised Cosine window.

Adaptive Pulse Compression Technique for X-Band Phased Array Weather Radar

Weather radar commonly uses a matched filter (MF) method to improve the range resolution and signal-to-noise ratio. A X-band phased array weather radar (PAWR), which is capable of 3-D precipitation observations in less than 30 s, is in operation at the Osaka University. The PAWR uses the MF method. In weather radar systems, the magnitude of the range sidelobes is an important topic because it can cause overestimation of the received power from a target, such as precipitation or ground clutter echoes. We propose a minimum mean square error (MMSE)-based pulse compression method to reduce the range sidelobes of the PAWR. We evaluated an MF, an MF with a raised-cosine window, and MMSE methods using numerical simulations and actual measurement data obtained from the PAWR. The results show that the MMSE method is clearly superior to the MF and MF with a raised-cosine filter methods when considering the reduction in the range sidelobes.

Implementation of Multiple Macroblock Mode Overlapped Block Motion Compensation for Wavelet Video Coding

This paper proposes a hybrid video coding framework based on discrete wavelet transform and multiple macroblock mode overlapped block motion compensation (OBMC). Studying the neighborhood in multiple macroblock mode situations, we set rules for the selection of neighboring blocks in OBMC. Based on experimental results, the raised cosine window and the best neighboring blocks are chosen for their outstanding performance. The multiple macroblock mode OBMC has a good performance in reducing the blocking effect, and the coding efficiency is improved. The proposed scheme can provide a 1 dB coding gain compared to MPEG-4, and its performance is close to the latest H.264 standard. From a subjective point of view, the new framework is also better than the standards.

On the effects of receiver windowing on OFDM performance in the presence of carrier frequency offset

An exact bit error rate (BER) expression for an OFDM system with windowing reception is derived. The effects of several Nyquist windows, including the raised-cosine window, the than raised-cosine (BTRC) window, the second order continuity window (SOCW), the Franks window, and the double-jump window on the performance of the system are examined based on both BER measure and signal-to-interference (SIR) measure. It is found that the SIR comparison is not necessarily consistent with the BER comparison. The BTRC windowing gives the smallest BER among the five windowing functions considered for small to medium values of pulse roll-off factor. However, the Franks windowing or SOCW windowing shows better BER performance when the roll-off factor approaches one

Combined per tone equalization and receiver windowing in DSL receivers: WiPTEQ

In this report, a novel technique is described for the combination of per-tone equalization (PTEQ) with receiver windowing. The PTEQ is an equalization technique for discrete multitone modulation (DMT) based modems, such as asymmetric digital subscriber line (ADSL) modems and very high bitrate digital subscriber line (VDSL) modems, optimizing the SNR (and thus capacity) of each carrier separately. Windowing functions are very useful in multitone communications systems, to prevent a narrow band noise source from causing wide band interference. Combining both techniques in a windowed PTEQ (referred to as WiPTEQ) leads to a robust communication system. The described technique is especially useful in case of a trapezoidal or raised cosine window, and when the window taper length is large compared to the number of equalizer filter taps.

A Frequency Selective Filter for Short-Length Time Series

An effective and easy-to-implement frequency filter is proposed, obtained by convolving a raised-cosine window with the ideal rectangular filter response function. Three other filters, Hodrick–Prescott, Baxter–King, and Christiano–Fitzgerald, are thoroughly reviewed. A bandpass version of the Hodrick–Prescott filter is also introduced and used. The behavior of the windowed filter is compared to the others through their frequency responses and by applying them to both quarterly and monthly artificial, known-structure series and real macroeconomic data. The windowed filter has almost no leakage and is better than the others at eliminating high-frequency components. Its response in the passband is significantly flatter, and its behavior at low frequencies ensures a better removal of undesired long-term components. These improvements are particularly evident when working with short-length time series, which are common in macroeconomics. The proposed filter is stationary and symmetric, therefore, it induces no phase-shift. It uses all the information contained in the input data and stationarizes series integrated up to order two. It thus proves to be a good candidate for extracting frequency-defined series components.

Optimal two-term offset windowing for fractionaldelay

Fractional-sample delay in discrete-time systems is often provided by special FIR filters which are asymmetric about mid-sequence. Here we preserve the appeal of sine-sequence fractional delayers (simplicity and single-parameter delay tuning) by devising a two-term raised-cosine window which delivers fractional-delay filters comparable to the best obtainable by highly regarded optimisation approaches.

Modeling and identification of the combustion pressure process in internal combustion engines

We present a new model relating cylinder combustion pressure to crankshaft angular velocity in an internal combustion engine. There are three aspects to this model. First, by changing the independent variable from time to crankshaft angle, a non-linear differential equation model becomes a linear first-order differential equation. Second, a new stochastic model for combustion pressure uses the sum of a deterministic waveform and a raised cosine window amplitude-modulated by a Bernoulli-Gaussian random sequence, parametrising the pressure by the sample modulating sequence. This results in a state equation for the square of angular velocity sampled every combustion, with the modulating sequence as input. Third, the inverse problem of reconstructing pressure from noisy angular velocity measurements can now be formulated as a state-space deconvolution problem, and solved using a Kalman-filter-based deconvolution algorithm. Simulation results show that the parametrised pressure can be deconvolved at low noise levels, and combustion misfires detected, all in real time. Supporting experimental results are referenced in companion papers.

Modeling and Identification of the Combustion Pressure Process in Internal Combustion Engines: II—Experimental Results

In Connolly and Yagle (1992, 1993) we presented a new model relating cylinder combustion pressure to crankshaft angular velocity in an internal combustion engine, primarily the fluctuations in velocity near the cylinder firing frequency. There are three aspects to this model. First, by changing the independent variable from time to crankshaft angle, a nonlinear differential equation becomes a linear first-order differential equation. Second, a new stochastic model for combustion pressure uses the sum of a deterministic waveform and a raised-cosine window amplitude-modulated by a Bernoulli-Gaussian random sequence, parametrizing the pressure by the sample modulating sequence. This results in a state equation for the square of angular velocity sampled every combustion, with the modulating sequence as input. Third, the inverse problem of reconstructing pressure from noisy angular velocity measurements was formulated as a state-space deconvolution problem, and solved using a Kalman-filter-based deconvolution algorithm. Simulation results in Connolly and Yagle (1992, 1993) show that the parametrized pressure can be deconvolved at low to moderate noise levels, and combustion misfires detected, all in real time. This paper presents and discusses experimental results that confirm this model, at least at the relatively low-speed, low-to-moderate load operating conditions analyzed. They show that cyclic combustion pressure variation is fairly well modeled and may be directly estimated from angular velocity measurements. They also show that the deconvolution algorithm is able to detect misfires and possibly classify their severity. Since the experimental data are taken from an actual V-6 automobile engine, and the algorithms are simple enough to be implemented in real time, these results are directly applicable to real-world combustion pressure identification.

Spatial-frequency tuning as a function of temporal frequency and stimulus motion.

Spatial-frequency tuning at two different spatial frequencies was determined by measuring the detectability of a signal grating that was made difficult to see by low- or high-pass visual noise. The signals were vertical sinusoidal gratings of different spatial frequencies. The detectability of the signal was measured in two-alternative forced-choice tasks with different temporal envelopes: (1) a slowly changing raised-cosine (Hanning) window, (2) a rectangularly gated 2-Hz counterphase flickering envelope, and (3) a rectangularly gated 10-Hz counterphase flickering envelope. Additional measurements were made using drifting stimuli with the signal and noise drifting in the same or in opposite directions. The temporal envelopes were chosen because they have different effects on the contrast-sensitivity function and it was desired to know how temporal factors affect the spatial-frequency tuning of the relatively narrowly tuned channels thought to underlie contrast sensitivity. The results show that, for counterphase flickering stimuli, spatial-frequency tuning does not depend on temporal envelopes applied identically to the signal and to the masking noise. A similar picture emerges at slow (2.7-deg/sec) but not at fast (10.9-deg/sec) drift rates.

Sonics and ultrasonics : Ranging and data transmission using digital encoded fm-‘chirp’ surface acoustic wave filters Burnsweig, J., Wooldridge, J. SU-20 (April 1973) 190–197

In this report, a novel technique is described for the combination of per-tone equalization (PTEQ) with receiver windowing. The PTEQ is an equalization technique for discrete multitone modulation (DMT) based modems, such as asymmetric digital subscriber line (ADSL) modems and very high bitrate digital subscriber line (VDSL) modems, optimizing the SNR (and thus capacity) of each carrier separately. Windowing functions are very useful in multitone communications systems, to prevent a narrow band noise source from causing wide band interference. Combining both techniques in a windowed PTEQ (referred to as WiPTEQ) leads to a robust communication system. The described technique is especially useful in case of a trapezoidal or raised cosine window, and when the window taper length is large compared to the number of equalizer filter taps.