Journal of Electrical & Electronic Systems

This editorial examines design techniques for high-speed serial data links over wire channels. The state-of-theart of serial links over wire channels is briefly studied. The imperfections of wire channels at high frequencies and their effect on multi-Gbps serial links are examined. It is followed with a close examination of modulation schemes effective in combating the effect of the finite bandwidth of wire channels. Channel equalization, both pre-emphasis and post-equalization, are investigated with an emphasis on adaptive decision feedback equalization. Challenges and opportunities in combating ISI are explored.

The rapid development of modern communication services results in high data rate requirements from the end user. It is challenging to meet high data rate requirements because of prevailing issues such as spectrum scarcity and spectrum underutilization due to fixed spectrum assignment policy. Cognitive Radio (CR), being the enabler of dynamic spectrum management techniques, has the capability to tackle these issues by proficiently implementing spectrum sharing schemes using Multicarrier Modulation (MCM) techniques. In CR system, where the Primary User (PU) and the Secondary User (SU) co-exist in the same frequency band, mutual interference (i.e., from SU to PU and vice versa) is a limiting factor on the achievable capacity of both the PU and the SU. Power allocation in MCM based CR systems aims to dynamically control the transmit power on each subcarrier of the SU in order to reduce the mutual interference. Furthermore, combining multiple antennas with MCM is regarded as a very attractive solution for the CR communications to effectively enhance data rate without demanding additional bandwidth and transmit power.

Emitter Direction-of-Arrival (DOA) estimation is a fundamental problem in a variety of applications including radar, sonar, and wireless communications. The research has received considerable attention in literature and numerous methods have been proposed. Maximum Likelihood (ML) is a nearly optimal technique producing superior estimates compared to other methods especially in unfavorable conditions, and thus is of significant practical interest. This paper discusses in details the techniques for ML DOA estimation in either white Gaussian noise or unknown noise environment. Their performances are analyzed and compared, and evaluated against the theoretical lower bounds.

Magnetic fields can cause human health problems. Low-frequency electromagnetic fields are sometimes induced by electric currents in metallic objects that are worn or used in or on the body, and are unlike the high-frequency electromagnetic fields that produce heat. In low-frequency magnetic fields, the strength of the induced electric current is believed to be more important than the magnetic field strength in terms of effects on the health of living bodies. Electrically powered dental devices, including personal devices such as electric toothbrushes and professional devices such as curing lights for light-cured dental resins, are widely used because of their convenience, but the electric circuits and motors that power them produce low-frequency electromagnetic waves. These magnetic fields induce electric currents in teeth and in metallic appliances that are set in the oral cavity. The effects of these induced currents on human health must therefore be considered. Investigations of this issue revealed that magnetic fields from dental devices promoted the corrosion of intraoral metallic appliances via the induced currents, and this is likely to cause metallic allergies. Almost all reports on the effects of magnetic field exposure, including this corrosion phenomenon, describe harmful effects on human health. However, there may be some effective uses of the magnetic fields generated by dental devices for human health promotion. Oral bacteria were found to corrode orthodontic stainless steel appliances, but magnetic field-induced currents in these appliances could provide remarkable protection effects against this microbially induced corrosion. In this review, we discuss the results and conclusions of these investigations especially about novel ways of harmful effects and effective use of magnetic fields from dental devices, and conclude that further detailed studies are required to clarify their detailed mechanisms and to develop countermeasures for protection from or effective use of these fields.

This review paper analyzes the role of natural and man-made magnetic and electromagnetic fields in origin and evolution of life as well as the effects of contemporary magnetic/electromagnetic fields on human life. Both, hazard and benefit of these fields is discussed with the review of variety of signals that affect human life. The emphasis is on the use of electromagnetic fields in medicine for diagnostics and therapy. The paper demonstrates basic science and clinical achievements in planning and executing studies and clinical trials, as well as the perspectives for future development of magnetotherapy.

The recording of magnetic fields associated with cellular current flow in nerve and muscle fibers was first reported nearly three and a half decades ago. These magnetic fields are detected using a room-temperature toroidal pickup coil called the neuromagnetic current probe. These probes can be employed to measure action currents of biological tissues while they are resting in their own natural settings or in saline baths, thereby reducing the risk associated with elevating and drying the tissues in the air during experiments. These magnetic fields are relatively insensitive to muscle movement since these probes are not directly connected to the tissues, and distortions of the recorded data due to changes in the electrochemical interface between the probes and the tissues are minimal. In this paper, the magnetic fields of single nerve axons, muscle fibers and nerve bundles are discussed. Furthermore, one of the possible applications of the neuromagnetic current probe to the intraoperative assessment of damaged nerve bundles is discussed.

In the current radio frequency communication system, many spectrum bands are highly utilized while several remain moderately utilized or underutilized. The cognitive radio is a new paradigm to overcome the persisting problem of spectrum underutilization. Seeing the ever increasing demand of wireless applications, the radio spectrum is a precious resource and in cognitive radio systems, trustworthy spectrum sensing techniques are required to be adopted and implemented for the purpose of avoiding any harmful interference to the primary users who have authorized or licensed access to the spectrum. It is up to the secondary users to vacate the channels whenever primary users need the channel. BER and Eb/No are the performance metrics or governing parameters to affect the system performance using polyphase filter bank. The present paper deals with the study of effect of variation of number of subchannels M at fix overlapping factor K of polyphase component of Filter Bank Multicarrier cognitive radio in terms of prototype filter length at Lp=K*M-1 with K=4.

Modern clinical medicine uses a wide variety of highly technical medical devices on which advanced medicine increasingly relies. These devices often use internet and communication technology. Some medical devices pick up weak biomedical signals and others function by generating a powerful magnetic field. Wireless LAN and wireless voice communication are useful in clinical settings.
Because of the recent availability of technical reports and our educational efforts to show that medical devices and wireless communication apparatus are safe and compatible, there is reduced anxiety among medical professionals and thus demand is increasing for technically advanced systems. For safety and security reasons, it is necessary to prevent both the radiation of strong electromagnetic waves from apparatus inside the hospital and to block the invasion of electromagnetic waves from outside. These problems can be solved by the use of electromagnetic shielding technology. The above are all related to the necessity of controlling electromagnetic fields. At present, adequate techniques for the control of the fields commonly found in medical settings have not been established. The best results will be attained if collaboration is done with people from the variety of fields working on or who will work on the project, such as those involved in material, architectural, and structural engineering, as well as the medical staff.
In order to insure the safe use of wireless communications in medical settings it will be necessary to improve the EMC standards and to disseminate information about electromagnetic field control to the medical staff. To insure safety and meet the needs of this rapidly changing environment, electromagnetic field control techniques must be established and constantly improved to meet the requirements of the environment in which medical devices are used. To achieve this, interdisciplinary collaboration is indispensable.