Peerapol Yuvapoositanon

Adaptive step-size constant modulus algorithm for DS-CDMA receivers in nonstationary environments

A new adaptive step-size constant modulus algorithm for direct-sequence code division multiple access receivers is presented for application in nonstationary channel conditions. The algorithm is derived upon the basis of adapting the step-size to minimise the constant modulus criterion and its convergence is verified analytically. Simulations show the superior performance of the proposed method over similar adaptive receivers and its robustness to different settings of the initial step-size.

An adaptive step-size code-constrained minimum output energy receiver for nonstationary CDMA channels

The adaptive step-size (AS) code-constrained minimum output energy (CMOE) receiver for nonstationary code-division multiple access (CDMA) channels is proposed. The AS-CMOE algorithm adaptively varies the step-size in order to minimise the CMOE criterion. Admissibility of the proposed method is confirmed via the reformulation of the CMOE criterion as an unconstrained optimisation. The ability of the algorithm to track sudden changes of the channel structure in multipath fading channels is assessed. Sensitivity to the initial values of step-size and the adaptation rate of the algorithm is also investigated.

A Mixed-Tone RLS algorithm with orthogonal projection for Per-Tone DMT equalisation

A methodology of mixed-tone recursive least squares algorithm development based on an orthogonal projection approach is presented for per-tone equalisation in discrete multitone systems. A mixed-tone cost function described as the sum of weight-estimated errors is minimised to achieve the solutions for different per-tone equalisers simultaneously. Simulation results reveal improvement of achievable bit rate and signal to noise ratio performance as compared to the PTEQ exploiting conventional RLS algorithm.

An Adaptive Step-size Order Statistic Time Domain Equaliser for Discrete Multitone Systems

In this paper, an adaptive step-size order statistic time domain equaliser (TEQ) for discrete multitone (DMT) systems is presented. The authors have shown that the TEQ and target impulse response (TIR) solutions of a costly constrained optimisation can be cheaply obtained by means of a variant of the well-known low-complexity normalised least mean square (NLMS) algorithm. An algorithm for adapting step-size of an order statistic NLMS TEQ is presented. Simulation results reveal that the trajectories of step-size parameters of the proposed algorithm converge to their own equilibria despite large variations in initial step-size settings. Robustness of proposed TEQ with different types of disturbations such as additive white Gaussian noise (AWGN) and near-end crosstalk (NEXT) is also shown as a comparison with the existing minimum mean square error-TEQ (MMSE-TEQ)

Low complexity adaptive step-size filtered gradient-based per-tone DMT equalisation

In this paper, a low complexity adaptive step-size filtered gradient-based scheme for per-tone equalisation is investigated for discrete multitone systems. A variant of the filtered gradient adaptive algorithms has been presented in literature for the normalised version of the orthogonal gradient adaptive algorithm which employs the mixed-tone exponentially weighted least squares criterion. A low complexity adaptive step-size approach is proposed by exploiting an estimate of autocorrelation between previous and present weight-estimated error to control step-size update. In order to ensure good tracking and convergence speed, the step-size is adjusted recursively for different per-tone equalisers. Simulation results show that the trajectories of step-size of the proposed algorithm converge to its own equilibrium despite large variations in initial step-size settings. The proposed algorithm achieves superior performance, faster convergence rate and lower computational complexity than the existing algorithms.

Mixed-tone normalised orthogonal gradient adaptive per-tone DMT equalisation

A mixed-tone normalised orthogonal gradient adaptive algorithm is introduced for per-tone equalisation in discrete multitone systems. We describe briefly about the normalised orthogonal gradient adaptive algorithm that is formulated from the filtered gradient adaptive algorithm by introducing an orthogonal constraint between the direction vectors. By means of the mixed-tone cost function, the sum of weight-estimated errors is minimised in order to achieve the solutions for different per-tone equalisers. Simulation results reveal that bit rate performance can be improved in comparison with the existing recursive least squares algorithm.

Bit rate maximising per-tone equalisation with adaptive implementation for DMT-based systems

We present a bit rate maximising per-tone equalisation (BM-PTEQ) cost function that is based on an exact subchannel SNR as a function of per-tone equaliser in discrete multitone (DMT) systems. We then introduce the proposed BM-PTEQ criterion whose derivation for solution is shown to inherit from the methodology of the existing bit rate maximising time-domain equalisation (BM-TEQ). By solving a nonlinear BM-PTEQ cost function, an adaptive BM-PTEQ approach based on a recursive Levenberg-Marquardt (RLM) algorithm is presented with the adaptive inverse square-root (iQR) algorithm for DMT-based systems. Simulation results confirm that the performance of the proposed adaptive iQR RLM-based BM-PTEQ converges close to the performance of the proposed BM-PTEQ. Moreover, the performance of both these proposed BM-PTEQ algorithms is improved as compared with the BM-TEQ.

Chromosome classification for metaphase selection

Identification of good metaphase spread is an important step in chromosome analysis for genetic disorder detection. In this paper, we propose a rule for chromosome classification to identify good metaphase spreads. The chromosome shapes were classified into four main classes. The first and the second classes refer to individual chromosomes with straight and bended shapes, respectively. The third class is characterized as those chromosomes with overlapping bodies and the forth class is for the non-chromosomal artifacts. Good metaphase spreads should largely contain the first and the second classes while the number of the third class should be kept minimal. Several image parameters were examined and used for creating rule-based classification. The threshold value for each parameter is determined using statistical model. We observed that the empirical probability density function of the parameters can be represented by Gaussian model and, hence, the threshold value can be easily determined. The proposed rules can efficiently and accurately classify the individual chromosome with > 90% accuracy.

Reduced-complexity Rao-Blackwellised Particle Filtering for fault diagnosis

We explore an approach for complexity reduction for fault diagnosis problems. The underlying algorithm is a sequential Monte Carlo method known as the Rao-Blackwellised Particle Filter or RBPF. In this paper, we show that the complexity of the RBPF algorithm can be reduced by applying the Kalman updating step to only one representative particle of a group particles gathering in a particular state. The time consumption for the algorithm to complete computation is substantially reduced especially for systems employing large number of particles. Simulation results reveal that the performance of the proposed reduced-complexity algorithm or RC-RBPF in terms of percentage estimation errors is identical to that of the standard RBPF which in turn much better than that of the particle filtering.

Recursive Levenberg-Marquardt Per-Tone Equalisation for Discrete Multitone systems

Recursive Levenberg-Marquardt (RLM) algorithm is presented for per-tone equalisers in discrete multitone systems. We introduce how to formulate the proposed RLM algorithm for non-linear adaptive filter. Simulation results show that the proposed RLM algorithm can improve bit rate performance and Signal to Noise Ratio improvement as compared to the existing recursive least squares-based algorithms and matched filter bound.