Imperial College London

ProfessorRobertIstepanian

Faculty of MedicineInstitute of Global Health Innovation

Visiting Professor
 
 
 
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Contact

 

+44 (0)7554 342 293robert.istepanian Website

 
 
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Location

 

Central FacultyFaculty BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
to

143 results found

Banitsas KA, Tachakra S, Istepanian RSH, 2002, Operational parameters of a medical wireless LAN: Security, range and interference issues, Pages: 1889-1890, ISSN: 0589-1019

This paper provides an overview of the operational parameters of Wireless Local Area Networks (WLANs) in hospital and clinical ward environments and presents the concept of MedLAN system, dedicated to these environments. It then deals with the issues of security, range and interference with an emphasis on the first one.

CONFERENCE PAPER

D'Andrea R, Istepanian RSH, 2002, Design of full state feedback finite-precision controllers, International Journal of Robust and Nonlinear Control, Vol: 12, Pages: 537-553, ISSN: 1049-8923

In this paper, the Generalized L2 Synthesis framework is brought to bear on the problem of control design of full state feedback finite-precision controllers. In particular, we investigate the problem of designing full state feedback controllers that achieve guaranteed H-infinity performance objectives, subject to finite precision constraints on the controller. It is shown that by adopting the Generalized L2 Synthesis framework, the errors in the controller implementation can be captured as full structured uncertainty, and computationally tractable linear matrix inequality techniques used for analysis and synthesis.

JOURNAL ARTICLE

Pattichis CS, Kyriacou E, Voskarides S, Pattichis MS, Istepanian R, Schizas CNet al., 2002, Wireless telemedicine systems: An overview, IEEE ANTENNAS AND PROPAGATION MAGAZINE, Vol: 44, Pages: 143-153, ISSN: 1045-9243

JOURNAL ARTICLE

Voskarides S, Pattichis CS, Istepanian R, Kyriacou E, Pattichis MS, Schizas CNet al., 2002, Mobile health systems: A brief overview, Conference on Digital Wireless Communications IV, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, Pages: 124-131, ISSN: 0277-786X

CONFERENCE PAPER

Banitsas KA, Istepanian RSH, Tachakra S, Owens TJet al., 2001, Modelling issues of wireless LANs for accident and emergency departments, Pages: 3540-3543, ISSN: 0454-9244

The paper provides an overview of the application scenarios and modelling issues of Wireless Local Area Networks (WLAN) in hospital and clinical ward environments and presents the concept of MedLAN system, dedicated to these environments. Furthermore, it discusses the potential problems when implementing such systems.

CONFERENCE PAPER

Owens TJ, Tachakra S, Banitsas KA, Istepanian RSHet al., 2001, Securing a medical wireless LAN system, Pages: 3552-3555, ISSN: 0454-9244

This paper identifies security issues that must be addressed, if a recently proposed Medical Wireless LAN System (MedLAN) is to be accepted. Two classes of security issues are distinguished, technical and managerial.

CONFERENCE PAPER

Istepanian RSH, Woodward B, Richards CI, 2001, Advances in telemedicine using mobile communications, Pages: 3556-3558, ISSN: 0454-9244

Future telemedicine systems will exploit mobile communications technology so that patients who are free to move around at home or at work, or in emergency medical situations, can be monitored in a hospital. At present, the GSM mobile telephone cellular network is limited to 9.6 kbps, but with the introduction of the third generation (3G) network, data rates of 144 kbps will be available, giving scope for the transmission of much more biomedical data as well as voice and video data if required. The paper discusses some of the issues involved and outlines the types of system that will be viable with the new technology.

CONFERENCE PAPER

Whidborne JF, Istepanian RSH, 2001, Genetic algorithm approach to designing finite-precision controller structures, Pages: 377-382, ISSN: 1350-2379

The parameters of a digital control design usually need to be rounded when the controller is implemented with finite precision arithmetic. This often results in degradation of the closed loop performance and reduced stability margins. This paper presents a multi-objective genetic algorithm based approach to designing the structure of a finite-precision second-order state space controller implementation, which can simultaneously minimise some set of performance degradation indices and implementation cost indices. The approach provides a set of solutions that are near Pareto-optimal, and so allows the designer to trade-off performance degradation against implementation cost. The method is illustrated by the design of the structure of a PID controller for the IFAC93 benchmark problem.

CONFERENCE PAPER

Wu J, Chen S, Li G, Istepanian RH, Chu Jet al., 2001, An improved closed-loop stability related measure for finite-precision digital controller realizations, IEEE Transactions on Automatic Control, Vol: 46, Pages: 1162-1166, ISSN: 0018-9286

The pole-sensitivity approach is employed to investigate the stability issue of the discrete-time control system, where a digital controller, implemented with finite word length (FWL), is used. A new stability related measure is derived, which is more accurate in estimating the closed-loop stability robustness of an FWL implemented controller than some existing measures for the pole-sensitivity analysis. This improved stability measure thus provides a better criterion to find the optimal realizations for a generic controller structure that includes output-feedback and observer-based controllers. A numerical example is used to verify the theoretical analysis and to illustrate the design procedure.

JOURNAL ARTICLE

Chen S, Istepanian R, Luk BL, 2001, Digital IIR filter design using adaptive simulated annealing, DIGITAL SIGNAL PROCESSING, Vol: 11, Pages: 241-251, ISSN: 1051-2004

JOURNAL ARTICLE

Istepanian RSH, Wu J, Whidborne JF, 2001, Controller realizations of a teleoperated dual-wrist assembly system with finite word length considerations, IEEE Transactions on Control Systems Technology, Vol: 9, Pages: 624-628, ISSN: 1063-6536

This paper presents some implementation issues of finite-precision optimal and quasioptimal sparse H∞controller structures applied to a teleoperated dual-wrist assembly system. The relevant stability robustness measures and the optimization search procedures for both the optimal and the quasioptimal sparse Finite Word Length (FWL) controller realizations are described. Comparative analytical and numerical results show that the sparse FWL controller realizations provide minimum bit lengths, with maximum trivial elements in the controller coefficients and higher stability bounds compared to nonoptimal realization. The results illustrate that the FWL methodology presented provides better implementation structures, increased computational speed and FWL stability for teleoperated motion-scaling control systems.

JOURNAL ARTICLE

Istepanian RS, Hadjileontiadis LJ, Panas SM, 2001, ECG data compression using wavelets and higher order statistics methods., IEEE Trans Inf Technol Biomed, Vol: 5, Pages: 108-115, ISSN: 1089-7771

This paper evaluates the compression performance and characteristics of two wavelet coding compression schemes of electrocardiogram (ECG) signals suitable for real-time telemedical applications. The two proposed methods, namely the optimal zonal wavelet coding (OZWC) method and the wavelet transform higher order statistics-based coding (WHOSC) method, are used to assess the ECG compression issues. The WHOSC method employs higher order statistics (HOS) and uses multirate processing with the autoregressive HOS model technique to provide increasing robustness to the coding scheme. The OZWC algorithm used is based on the optimal wavelet-based zonal coding method developed for the class of discrete "Lipschitizian" signals. Both methodologies were evaluated using the normalized rms error (NRMSE) and the average compression ratio (CR) and bits per sample criteria, applied on abnormal clinical ECG data samples selected from the MIT-BIH database and the Creighton University Cardiac Center database. Simulation results illustrate that both methods can contribute to and enhance the medical data compression performance suitable for a hybrid mobile telemedical system that integrates these algorithmic approaches for real-time ECG data transmission scenarios with high CRs and low NRMSE ratios, especially in low bandwidth mobile systems.

JOURNAL ARTICLE

Woodward B, Istepanian RS, Richards CI, 2001, Design of a telemedicine system using a mobile telephone., IEEE Trans Inf Technol Biomed, Vol: 5, Pages: 13-15, ISSN: 1089-7771

This paper describes the design of a prototype integrated mobile telemedicine system that is compatible with existing mobile telecommunications networks and upgradable for use with third-generation networks. The system, when fully developed, will enable a doctor to monitor remotely a patient who is free to move around for sports medicine and for emergency situations.

JOURNAL ARTICLE

Whidborne JF, Istepanian RSH, Wu J, 2001, Reduction of controller fragility by pole sensitivity minimization, IEEE Transactions on Automatic Control, Vol: 46, Pages: 320-325, ISSN: 0018-9286

This note presents a method for the reduction of controller fragility. The method is based on the sensitivity of closed-loop poles to perturbations in the controller parameters. By means of a state space parameterization of the controller, the closed-loop pole sensitivity can be reduced. A controller fragility measure based on the closed-loop pole sensitivity is proposed. Conditions for the optimal state-space realization of the controller are presented, along with a numerical method for obtaining the solution.

JOURNAL ARTICLE

Istepanian RSH, Sibson L, 2001, The Impact of New Wireless Telecommunication Systems on Home Telecare, Journal of Telemedicine and Telecare, Vol: 7, ISSN: 1357-633X

JOURNAL ARTICLE

Song T, Collins EG, Istepanian RH, 2001, Improved closed-loop stability for fixed-point controller realizations using the delta operator, International Journal of Robust and Nonlinear Control, Vol: 11, Pages: 41-57, ISSN: 1049-8923

A stable discrete-time control system may achieve a lower than predicted performance or even become unstable when the discrete-time control law is implemented with a fixed-point digital control processor due to the finite word length (FWL) effects, which depends on the control law state-space realization and the discrete-time operator (e.g., the delta operator or the forward-shift operator) used to represent the control law. To improve the closed-loop stability (and as a byproduct, performance) when the control law is implemented, a state-space approach that selects the control law realization to optimize a stability-related objective function is developed using the delta operator. Analytical and numerical comparison of the fixed-point performance of delta control laws with the performance of the corresponding forward-shift control laws quantifies the improved closed-loop stability of the delta realizations over those of the corresponding forward-shift realizations. It is also shown that there exists a simple mapping between the optimal FWL forward-shift control law realizations and the optimal FWL delta control law realizations. The results are illustrated by delta and forward-shift control law realizations of a discrete-time H∞ control law designed for a teleoperation motion-scaling system.

JOURNAL ARTICLE

Istepanian RS, Kyriacou E, Pavlopoulos S, Koutsouris Det al., 2001, Effect of wavelet compression on data transmission in a multipurpose wireless telemedicine system., J Telemed Telecare, Vol: 7 Suppl 1, Pages: 14-16, ISSN: 1357-633X

We have developed a novel emergency telemedicine system which allows the transmission of physiological data (electrocardiogram, oximetry, blood pressure and temperature) and still images of the patient. The transmission is performed through wireless links using either GSM mobile phones or satellite. Because of the low bandwidth available through these links, data compression is required to allow realtime transmission of electrocardiographic (ECG) data. A new integrated design approach for an optimal zonal wavelet compression (OZWC) method was implemented for the ECG data. The performance of the mobile system with compressed ECG data segments was evaluated in terms of the percentage root-mean-square difference and visual inspection. The optimum wavelet algorithm achieved a maximum compression ratio of 18:1 with low distortion.

JOURNAL ARTICLE

Pavlopoulos S, Istepanian RSH, Kyriacou E, Koutsouris Det al., 2000, Optimal wavelet biosignal compression for mobile multi-purpose telemedicine

The availability of prompt and expert medical care can meaningfully improve health care services at understaffed rural or remote areas. The provision of effective emergency telemedicine and home monitoring solutions are the major fields of interest discussed in this study. Ambulances, Rural Health Centers (RHC) or other remote health location, Ships navigating in wide seas and Airplanes in flight are common examples of possible emergency sites, while critical care telemetry and telemedicine home follow-ups are important issues of telemonitoring. In order to cover the above different growing application fields a novel Emergency Telemedicine System has been developed. The system allows the transmission of vital biosignals (3-12 lead ECG, SPO2, NIBP, IBP, Temp) and still images of the patient. The transmission is performed through wireless links both GSM and satellite. Due to the low-bandwidth available through these links (max 9600 bps), data compression is required to allow real-time transmission of ECG data. A new integrated design approach for an optimal zonal wavelet-based ECG data compression (OZWC) method has been implemented and the performance of the mobile system with compressed ECG data segments selected from the MIT-BIH arrhythmia data base has been evaluated in terms of Bit Error rate (BER), Percent Root-mean-square Difference (PRD) and visual clinical inspection. The optimal wavelet algorithm achieved a maximum compression ratio of 18:1 with low PRD ratios. Using this approach the next generation multi-purpose Mobile Telemedicine Systems with wavelet compression techniques can be developed.

CONFERENCE PAPER

Wu J, Chen S, Li G, Istepanian RH, Chu Jet al., 2000, Shift and delta operator realisations for digital controllers with finite word length considerations, IEE Proceedings: Control Theory and Applications, Vol: 147, Pages: 664-672, ISSN: 1350-2379

The implementation issues of digital controllers with finite word length (FWL) considerations are addressed. Both the shift and delta operator parameterisations of a general controller structure are considered. A unified formulation is adopted to derive a computationally tractable stability related measure that describes FWL closed-loop stability characteristics of different controller realisations. Within a given operator parameterisation, the optimal FWL controller realisation, which maximises the proposed stability related measure, is the solution of a nonlinear optimisation problem. The relationship between the z-operator and δ-operator controller parameterisations is analysed, and it is shown that the δ parameterisation has a better FWL closed-loop stability margin than the z-domain approach under a mild condition. A design example is included to verify the theoretical analysis and to illustrate the proposed optimisation procedure. © IEE, 2000.

JOURNAL ARTICLE

Laxminarayan S, Istepanian RSH, 2000, UNWIRED E-MED: The next generation of wireless and internet telemedicine systems, IEEE Transactions on Information Technology in Biomedicine, Vol: 4, Pages: 195-199, ISSN: 1089-7771

The movement of telemedicine to wireless and mobile Internet applications is imminent in the next few years. This migration from desktop platforms to wireless and mobile configurations will have a significant impact on future healthcare delivery systems and their globalization. Recent telecommunications and biomédical computing advances will significantly enhance the current methodologies of telemedicine and telecare systems. This editorial will present some of the evolutionary issues and important aspects that have to be considered in developing technologies for the next generation of Internet and third generation of mobile systems geared for future telemedical applications. These will provide new dimensions to existing medical services and areas of outreach that are not possible with the current generation that will have tremendous impact on how healthcare delivery will be shaped for the 21st century. © 2000 IEEE.

JOURNAL ARTICLE

Istepanian RS, Petrosian AA, 2000, Optimal zonal wavelet-based ECG data compression for a mobile telecardiology system., IEEE Trans Inf Technol Biomed, Vol: 4, Pages: 200-211, ISSN: 1089-7771

A new integrated design approach for an optimal zonal wavelet-based ECG data compression (OZWC) method for a mobile telecardiology model is presented. The hybrid implementation issues of this wavelet method with a GSM-based mobile telecardiology system are also introduced. The performance of the mobile system with compressed ECG data segments selected from the MIT-BIH arrhythmia data base is evaluated in terms of bit error rate (BER), percent rms difference (PRD), and visual clinical inspection. The compression performance analysis of the OZWC is compared with another wavelet-based (Discrete Symmetric Wavelet Compression) approach. The optimal wavelet algorithm achieved a maximum compression ratio of 18: 1 with low PRD ratios. The mobile telemedical simulation results show the successful compressed ECG transmission at speeds of 100 (km/h) with BER rates of less than 10(-15), providing a 73% reduction in total mobile transmission time with clinically acceptable reconstruction of the received signals. This approach will provide a framework for the design and functionality issues of GSM-based wireless telemedicine systems with wavelet compression techniques and their future integration for the next generation of mobile telecardiology systems.

JOURNAL ARTICLE

Laxminarayan S, Istepanian RS, 2000, UNWIRED E-MED: the next generation of wireless and internet telemedicine systems., IEEE Trans Inf Technol Biomed, Vol: 4, Pages: 189-193, ISSN: 1089-7771

The movement of telemedicine to wireless and mobile Internet applications is imminent in the next few years. This migration from desktop platforms to wireless and mobile configurations will have a significant impact on future healthcare delivery systems and their globalization. Recent telecommunications and biomedical computing advances will significantly enhance the current methodologies of telemedicine and telecare systems. This editorial will present some of the evolutionary issues and important aspects that have to be considered in developing technologies for the next generation of Internet and third generation of mobile systems geared for future telemedical applications. These will provide new dimensions to existing medical services and areas of outreach that are not possible with the current generation that will have tremendous impact on how healthcare delivery will be shaped for the 21st century.

JOURNAL ARTICLE

Chen S, Istepanian RH, Wu J, Chu Jet al., 2000, Comparative study on optimizing closed-loop stability bounds of finite-precision controller structures with shift and delta operators, SYSTEMS & CONTROL LETTERS, Vol: 40, Pages: 153-163, ISSN: 0167-6911

JOURNAL ARTICLE

Istepanian RH, Chen S, Wu J, Whidborne JFet al., 2000, Optimal finite-precision controller realization of sampled-data systems, INTERNATIONAL JOURNAL OF SYSTEMS SCIENCE, Vol: 31, Pages: 429-438, ISSN: 0020-7721

JOURNAL ARTICLE

Whidborne JF, Wu J, Istepanian RSH, Chu JAet al., 2000, Comments on "On the structure of digital controllers with finite word length consideration", IEEE TRANSACTIONS ON AUTOMATIC CONTROL, Vol: 45, Pages: 344-344, ISSN: 0018-9286

JOURNAL ARTICLE

Whidborne JF, Wu J, Istepanian RSH, 2000, Finite word length stability issues in an l(1) framework, INTERNATIONAL JOURNAL OF CONTROL, Vol: 73, Pages: 166-176, ISSN: 0020-7179

JOURNAL ARTICLE

Istepanian RH, Wu J, Chen S, 2000, Sparse realizations of optimal finite-precision teleoperation controller structures, 2000 American Control Conference (ACC 2000), Publisher: IEEE, Pages: 687-691, ISSN: 0743-1619

CONFERENCE PAPER

Bauer P, Sichitiu M, Istepanian R, Premaratne Ket al., 2000, The mobile patient: Wireless distributed sensor networks for patient monitoring and care, Joint Meeting of the 3rd IEEE EMBS International Conference on Information Technology Applications in Biomedicine/3rd Workshop of the Int-Telemedical-Information-Society, Publisher: IEEE, Pages: 17-21, ISSN: 1049-3565

CONFERENCE PAPER

Istepanian RS, Nikogosian H, 2000, Telemedicine in Armenia., J Telemed Telecare, Vol: 6, Pages: 268-272, ISSN: 1357-633X

Telemedicine in Armenia began with the US Telemedicine Space Bridge programme, which was introduced following the disastrous earthquake in 1988. More recently educational programmes have been established between the School of Medicine at Boston University and the Emergency Hospital in Yerevan. There are also telemedicine activities involving the Internet, for example at the Diagnostica Medical Centre in Yerevan. The future integration of telemedicine and telehealth services within the health services in Armenia will produce significant benefits. Current telemedicine activities in Armenia represent models for collaborative projects in other former Soviet republics with the aim of providing greater access to health-care at higher quality and lower cost.

JOURNAL ARTICLE

Chen S, Istepanian RH, Wu J, 1999, Optimizing stability bounds of finite-precision PID controllers using adaptive simulated annealing, Pages: 4316-4320, ISSN: 0743-1619

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 (ASA) 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.

CONFERENCE PAPER

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