Wireless Medical Telemetry Systems Research Articles

Electromagnetic Compatibility Issues in 400-MHz-Band Wireless Medical Telemetry Systems and Their Management Using Simplified Methods for Safe Operation.

Wireless medical telemetry systems (WMTSs) are typical radio communication-based medical devices that monitor various biological parameters, such as electrocardiograms and respiration rates. In Japan, the assigned frequency band for WMTSs is 400 MHz. However, the issues accounting for poor reception in WMTS constitute major concerns. In this study, we analyzed the effects of electromagnetic interferences (EMIs) caused by other radio communication systems, the intermodulation (IM) effect, and noises generated from electrical devices on WMTS and discussed their management. The 400-MHz frequency band is also shared by other radio communication systems. We showed the instantaneous and impulsive voltages generated from the location-detection system for wandering patients and their potential to exhibit EMI effects on WMTS. Further, we presented the IM effect significantly reduces reception in WMTS. Additionally, the electromagnetic noises generated from electrical devices, such as light-emitting diode lamps and security cameras, can exceed the 400 MHz frequency band as these devices employ the switched-mode power supply and/or central processing unit and radiate wideband emissions. Moreover, we proposed and evaluated simple and facile methods using a simplified spectrum analysis function installed in the WMTS receiver and software-defined radio for evaluating the electromagnetic environment.

Fundamental Study of Quantitative Evaluation of Radio Wave Output of Wireless Medical Telemetry Transmitters Operable in Medical Field

Wireless medical telemetry systems (WMTSs) are important medical equipment for monitoring of biological information such as the electrocardiogram of a patient in a remote location in real time. However, because WMTSs have characteristically used channels that are unique to the radio wave spectrum, many institutions have not previously managed WMTSs. Therefore, we examined a method for quantitative evaluation of the radio wave output of a wireless medical telemetry transmitter (WMTT) that can even be implemented in the medical field. In the experiments, we demonstrated the possibility of use of the method for quantitative evaluation of WMTT radio wave output in the medical field using two types of radio wave propagation model: a free-space propagation model and a two-ray ground reflection model. To determine the reference threshold value for use of each model, a breakpoint was found to be important to grasp the change point between short distance and long distance. It was indicated that the measured value was lower than the theoretical value below the breakpoint, while the measured value was slightly higher than the theoretical value beyond the breakpoint.

Effect of Wandering Sensing Systems on Wireless Medical Telemetry Systems

Effect of Wandering Sensing Systems on Wireless Medical Telemetry Systems

Electromagnetic compatibility of wireless medical telemetry systems and light-emitting diode (LED) lamps

Electromagnetic compatibility of wireless medical telemetry systems and light-emitting diode (LED) lamps

Impact of LED lamp noise on receiver sensitivity of wireless medical telemetry system

Impact of LED lamp noise on receiver sensitivity of wireless medical telemetry system

Design of robust adaptive frequency hopping for wireless medical telemetry systems

The authors propose an adaptive frequency hopping (AFH) algorithm, entitled robust adaptive frequency hopping (RAFH), for providing increased reliability of a wireless medical telemetry system (WMTS) under coexistence environment with non-medical devices. The conventional AFH scheme classifies channels into `good` or `bad` according to the threshold-based on`off decision by packet error rate (PER) measurement, and only uses good channels with a uniform hop probability. Unlike the conventional AFH scheme, RAFH is a novel technique, which solves a constrained entropy maximisation problem and assigns every channel a different hop probability as a decreasing function of the measured PER. The key novelty of RAFH over existing AFH schemes is that it reflects the relative channel condition by assigning non-uniform hop probabilities. By adopting constrained entropy maximisation, RAFH not only improves the average PER, but also reduces the PER fluctuation over time under a dynamic interference environment, both of which increase the reliability of WMTS. Through extensive simulation, we show that RAFH outperforms basic frequency hopping (FH) and the conventional AFH with respect to the PER under various scenarios of dynamic interference.

Home Telemedicine: Encryption is Not Enough

Implantable medical devices and home monitors make use of wireless radio communication for both therapeutic functions and remote monitoring of patients' vital signs. While our past work showed that lack of cryptographic protection results in disclosure of private medical data and manipulation of therapies (Halperin et al., IEEE S&P, 2008) our present work shows that even using encryption is insufficient to protect the confidentiality of patient telemetry. Our experiment analyzes the security of data traffic patterns of two sets of real medical telemetry: a corpus from PhysioNet (an online biomedical research database) and a network trace of a live disaster drill using Harvard's CodeBlue medical sensor network (Chen et al., DCOSS, 2008). Our work shows that even if a wireless medical device uses encryption, patient data can leak to unauthorized parties who need not be near the patient. Our measurements show that data packet timing information and headers distinguish the types of medical and monitoring devices even if traditional cryptographic mechanisms are used. Furthermore, the highly repetitive nature of medical data, such as ECG or respiration signals, leads to additional privacy vulnerabilities that cannot be easily mitigated by means of encryption without significant modification. Data compression technology further exposes encrypted telemetry to cryptanalysis. The information leakage of telemetry could facilitate unauthorized tracking of a patient because an ECG is known to uniquely identify a person in a predetermined group (Biel et al., IEEE I&M, 2002). Moreover, our study shows that data packet padding, encryption, authentication, and other common defenses against security threats require significant energy, storage, and computation that impose on the already scarce battery and space resources. Two of our experiments show how to automatically recover data from encrypted telemetry using Bayesian classifiers. In one experiment, we encrypted an ECG signal. By observing only the length of the digitally encrypted data, we were able to reconstruct sufficient information about the original ECG data that we determined the patient's heart rate. Using similar techniques, we recovered a leaked respiration signal that visually matches the original signal. Our findings show the weakness of using common cryptographic techniques on highly periodic and often compressed medical telemetry. Our work further discusses techniques to mitigate these security and privacy risks in wireless medical telemetry systems. However, all known techniques require extra energy, computation, and bandwidth from the medical device. The lesson learned is that encryption is not enough to protect the privacy of medical telemetry, and that reasonable assurance for security and privacy will require an energy budget. Future design of medical devices will have to make difficult tradeoffs between battery life versus security and privacy. This work was supported by NSF grants CNS-0627529, CNS-0716386, and CNS-0831244.

Medical-Grade, Mission-Critical Wireless Networks [Designing an Enterprise Mobility Solution in the Healthcare Environment

Today's healthcare environment requires an enterprise mobility solution for both patients and staff. Separate isolated networks are suboptimal from cost, management, scalability, and reliability perspectives. The wireless medical telemetry system (WMTS) does not provide sufficient bandwidth for many hospitals. Therefore, some seek to operate outside of the WMTS. Standards-based 802.11 networks with published reliability tenfold higher than conventional telemetry already meet the requirements for supporting life-critical applications. These 802.11 networks are easily supported on an enterprise scale, and they have advanced and matured to meet the needs for life-critical applications on an enterprise-wide shared network. To achieve peak performance, any network must be properly designed, installed, and validated for its intended use. To maintain peak performance, the network must be actively monitored and managed.