S. Chen

The comparative performance of mobile telemedical systems based on the IS-54 and GSM cellular telephone standards

The performance of mobile telemedical communications links based on the IS-54 and GSM cellular telephone standards the most widely used commercial systems in North America and Europe, respectively was studied by computer simulations. A photoplethysmography signal was used to investigate the transmission of medical data over simulated mobile phone channels. Various conditions were simulated in the communications path between a mobile transmitter and receiver, from perfect to distorted conditions. The results showed successful transmission, with bit error rates of better than 10-7 at the receiver for the IS-54 standard. The performance of the IS-54 standard was superior to that of GSM in terms of minimum path delay variations, especially in builtup urban areas.

Optimizing stability bounds of finite-precision PID controllers using adaptive simulated annealing

Based on a lower bound stability measure for sampled-data controller structures subject to finite-word-length (FWL) constraints, the optimal realization of the digital PID controller with FWL considerations is formulated as a nonlinear optimization problem. An efficient strategy based on adaptive simulated annealing is adopted to solve this complex optimization problem. A numerical example of optimizing the finite-precision PID controller for a steel rolling mill system is used to demonstrate the effectiveness of the proposed method.

Optimal finite-precision controller realization of sampled-data systems

We investigate the sensitivity of closed-loop stability with respect to finite word length (FWL) effects in the implementation of digital controller coefficients. The optimal realization of digital controller structures with finite precision consideration is formulated as the solution of a constrained nonlinear optimization problem. A sophisticated optimization strategy involving the adaptive simulated annealing (ASA) optimizer is developed to provide an efficient computational method for searching the optimal FWL controller realization with maximum stability bound and minimum bit length requirement. A numerical simulation example is presented to illustrate the effectiveness of the proposed strategy.

Sparse realizations of optimal finite-precision teleoperation controller structures

We study the finite word length (FWL) implementation of digital controller structures with sparseness consideration. A FWL stability measure is derived, taking into account the number of trivial elements in a controller realization. The controller realization that maximizes a lower bound of this measure is first obtained, and a stepwise algorithm is then applied to make the realization sparse. A test case involving a dual wrist assembly shows that the proposed design procedure yields a computationally efficient controller realization with good FWL closed-loop stability performance.

Signal processing applications using adaptive simulated annealing

Many signal processing applications pose optimization problems with multimodal and nonsmooth cost functions. Gradient methods are ineffective in these situations. The adaptive simulated annealing (ASA) offers a viable optimization tool for tackling these difficult nonlinear problems. We demonstrate the effectiveness of the ASA using three applications, infinite-impulse-response (IIR) filter design, maximum likelihood (ML) joint channel and data estimation and evaluation of minimum symbol-error-rate (MSER) decision feedback equalizer (DFE).

Postprocessing for image coding applications using neural network visual model

We present a neural network visual model (NNVM) which extracts multi-scale edge features from the decompressed image and uses these visual features as input to estimate and compensate the coding distortions. Our approach is a generic postprocessing technique and can be applied to all the main coding methods. Experimental results involving post-processing four coding systems show that the NNVM significantly improves the quality of reconstructed images, both in terms of the objective peak signal to noise ratio and subjective visual assessment.