Least squares error (LSE) method adopted recursively can be used to track the frequency and amplitude of signals in steady states and kinds of non-steady ones in power system. Taylor expansion is used to give another version of this recursive LSE method. Aided by variable-windowed short-time discrete Fourier transform, recursive LSEs with and without Taylor expansion converge faster than the original ones in the circumstance of off-nominal input singles. Different versions of recursive LSE were analyzed under various states, such as signals of off-nominal frequency with harmonics, signals with step changes, signals modulated by a sine signal, signals with decaying DC offset and additive Gaussian white noise. Sampling rate and data window size are two main factors influencing the performance of method recursive LSE in transient states. Recursive LSE is sensitive to step changes of signals, but it is in-sensitive to signals' modulation and singles with decaying DC offset and noise.

This paper presents a new feature extraction method for robust speech recognition based on the autocorrelation mel frequency cepstral coefficients (AMFCCs) and a variable window. While the AMFCC feature extraction method uses the fixed double-dynamic-range (DDR) Hamming window for higher-lag autocorrelation coefficients, which are least affected by noise, the proposed method applies a variable window, depending on the frame energy and periodicity. The performance of the proposed method is verified using an Aurora-2 task, and the results confirm a significantly improved performance under noisy conditions.

In this paper, the average error-rate characteristics are investigated as the number of users increases in the digital cellular DS/CDMA (Direct Sequence/Code Division Multiple Access) systems. Then, the performances of the various error control schemes applied to the data service of digital cellular DS/CDMA systems are compared and analyzed. That is, the performances of the conventional error control schemes such as Go-back-N ARQ (Automatic Repeat Request) and Selective-Repeat ARQ are analyzed in the circumstance of digital cellular DS/CDMA system. Also, the improved error control schemes which utilize the variable window size and/or variable data packet size are proposed and evaluated in order to improve the performances of the conventional error control scheme such as Quick-Repeat ARQ and WORM ARQ schemes in the digital cellular DS/CDMA system environments. According to the simulation results, the performances of the improved scheme with variable window and variable frame size are superior to those of the conventional scheme in the view of throughput and delay characteristics due to the robustness to the fading channel impairments.