Farhang-Boroujeni,Behrouz
Email Address
elefarhg@nus.edu.sg
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Publication Performance comparison of detectors for DVD channel impaired by bloom and transition noise(1999) Gopalaswamy, Srinivasan; Kee, Ng See; Farhang-Boroujeny, B.; ELECTRICAL ENGINEERINGThe performance of several detectors for digital video disk (DVD) channel suffering from linear intersymbol interference, bloom, transition noise and additive Gaussian noise was evaluated. The detectors include the non-Viterbi detectors which exploit the d = 2 run-length constraint of the EFMPlus code in the DVD channel, and also the Viterbi detectors following equalization to certain partial response targets. The proposed detection scheme uses a partial response target of memory 6, but accounts for the resulting destructive interference through run-length corrections.Publication Experimental study of semi-blind channel identification/equalization through pilot signals(1996) Farhang-Boroujeny, B.; ELECTRICAL ENGINEERINGWe present a pilot-based channel identification scheme with a unimodal performance surface which guarantees its convergence towards an unbiased estimate of the channel response. A computationally efficient least squares channel identification algorithm is then proposed. We also introduce three different implementation strategies for data receivers which may use the proposed scheme for semi-blind equalization of communication channels. The reliability of the proposed scheme is tested through computer simulations.Publication Performance of LMS-based adaptive filters in tracking a time-varying plant(1996) Farhang-Boroujeny, B.; Gazor, S.; ELECTRICAL ENGINEERINGThis correspondence gives a general analysis of the LMSbased adaptive filters when used for tracking a class of time varying plants. The algorithms covered are the conventional LMS, the transformdomain normalized LMS, and the LMS/JNewton algorithm. An important fact that we observe is that in comparing these algorithms, better initial convergence does not necessarily mean better tracking. A few special cases are presented that show the contrary. © 1996 IEEE.Publication Adaptive filtering in subbands: Design issues and experimental results for acoustic echo cancellation(1997-09) Farhang-Boroujeny, B.; Wang, Z.; ELECTRICAL ENGINEERINGSubband adaptive filters are studied and the related design issues are addressed in detail. We focus on the delay introduced by the analysis and synthesis filters. The specifications that should be satisfied by these filters arc discussed and a design method which fulfills these specifications and at the same time can greatly reduce the delay is proposed. A design example which demonstrates the effectiveness of the proposed design technique is presented and tested with real signals for implementation of an acoustic echo canceler. © 1997 Elsevier Science B. V.Publication An IIR adaptive line enhancer with controlled bandwidth(1997) Farhang-Boroujeny, B.; ELECTRICAL ENGINEERINGA previously proposed IIR adaptive line enhancer (ALE) is explored further. We propose a mechanism for controlling the bandwidth of the ALE in an adaptive manner. The proposed mechanism increases the bandwidth of the ALE whenever its peak is not close to a spectral line of the input signal to assure its fast convergence and decreases the bandwidth of the ALE when its peak matches a spectral line of the input signal to enhance that spectral line further. In addition, a new algorithm for robust adaptation of the ALE is proposed. © 1997 IEEE.Publication Analysis and optimum design of the FFB(1994) Lim, Yong Ching; Farhang-Boroujeny, B.; ELECTRICAL ENGINEERINGA low complexity high selectivity fast filer bank (FFB) which does not involve down-sampling and up-sampling of signals has been developed in [8]. Since a single sampling rate is used throughout the filtering process, aliasing problem does not exist. In [8], the FFB was derived from the FFT. In this paper, we present an alternative derivation for the FFB. This alternative derivation renders detail analysis of the performance of the FFB possible. This in turn leads to the optimum design of the FFB. In this paper, we also show by means of an example that the computational complexity of the FFB is significantly less than that of a single-rate polyphase filter.Publication On statistical efficiency of the LMS algorithm in system modeling(1993-05) Farhang-Boroujeny, B.; ELECTRICAL ENGINEERINGThe conventional least mean square (LMS) algorithm is compared with the ideal LMS/Newton (ILMSN) algorithm. It is shown that, although, under certain conditions, for similar misadjustment, the output mean square error (MSE) of the ILMSN algorithm may converge much faster than the MSE of the LMS algorithm, the difference between the two algorithms may not be that great if misalignments of the adaptive filter tap-gains are compared. Analytical results are presented, with computer simulations that support their validity.Publication Design of multilevel decision feedback equalizers(1997) Mathew, G.; Farhang-Boroujeny, B.; Wood, R.W.; ELECTRICAL ENGINEERINGMultilevel decision feedback equalization scheme (MDFE) is an efficient and simple realization of the fixed-delay tree search with decision feedback (FDTS/DF) for channels using RLL(1, k) codes. In MDFE, the entire tree-search is replaced with a 2-tap transversal filter and a binary comparator with negligible loss in performance. This 2-tap filter can be combined with the forward and feedback equalizers resulting in a structure that is physically identical to DFE but requires very different equalizer settings. This paper focuses on equalizer design for MDFE. It is first shown that the MDFE scheme can also be derived without using the principle of tree-search by exploiting the run-length constraints imposed by the RLL(1, k) code in conjunction with the maximization of an appropriately defined signal-to-noise ratio (SNR). Recognizing that a multilevel eye is formed at the comparator, we define this SNR as the eye-opening divided by noise plus intersymbol interference. This formulation directly leads to a novel adaptive scheme based on the well known LMS algorithm. The relationship between this work and the earlier derivation of MDFE is then clarified. We also develop a noniterative analytical approach for the optimum equalizer design. Because of the economy of implementation, there is particular interest in the design of continuous-time forward equalizers. A noniterative analytic design approach, which does not suffer from local minima problems, is developed for such equalizers. Computer simulation results are presented for comparing the different design approaches. © 1997 IEEE.Publication Variable-step-size LMS algorithm: new developments and experiments(1994-10) Farhang-Boroujeny, B.; ELECTRICAL ENGINEERINGThe variable-step-size least-mean-square (VSLMS) algorithm is explored and adopted for tracking of time-varying environments. Two implementations of the VSLMS algorithm are proposed. The emphasis is on the implementations with different step sizes at various taps of the adaptive filter. General analysis of the VSLMS algorithm appears to be somewhat involved. However, for one implementation a limited analysis of the algorithm is found possible. For this implementation it is shown that, when the input samples to the adaptive filter are zero-mean. Gaussian and uncorrelated with one another, the VSLMS algorithm can adapt itself to select the optimum set of step sizes which results in the best-tracking performance. Simulation experiments with the VSLMS algorithm show that, under fairly mild conditions, both of the proposed implementations adapt toward the optimum step sizes.Publication Analysis and efficient implementation of partitioned block lms adaptive filters(1996) Farhang-Boroujeny, B.; ELECTRICAL ENGINEERINGThe frequency domain block LMS (FBLMS) algorithm used for efficient implementation of adaptive filters whose length may exceed n few thousands of taps is explored further by Asharif et fil.. To reduce the latency of such filters, it has been proposed that the adaptive filter convolution sum be partitioned into a few smaller sums and then the FBLMS be applied. In this correspondence, we show that the scheme proposed by Asharif et al. suffers from a serious eigenvalue spread problem. We identify the source of this problem and propose a solution to that. © 1996 IEEE.