In order to estimate the signal parameters accurately for mobile systems, it is necessary to estimate a system's propagation characteristics through a medium. Propagation analysis provides a good initial estimate of the signal characteristics. The ability to accurately predict radio-propagation behavior for wireless personal communication systems, such as cellular mobile radio, is becoming crucial to system design. Since site measurements are costly, propagation models have been developed as a suitable, low-cost, and convenient alternative. Channel modeling is required to predict path, loss and to characterize the impulse response of the propagating channel. The path loss is associated with the design of base stations, as this tells us how much a transmitter needs to radiate to service a given region. Channel characterization, on the other hand, deals with the fidelity of the received signals, and has to do with the nature of the waveform received at a receiver. The objective here is to design a suitable receiver that will receive the transmitted signal, distorted due to the multipath and dispersion effects of the channel, and that will decode the transmitted signal. An understanding of the various propagation models can actually address both problems. This paper begins with a review of the information available on the various propagation models for both indoor and outdoor environments. The existing models can be classified into two major classes: statistical models and site-specific models. The main characteristics of the radio channel - such as path loss, fading, and time-delay spread - are discussed. Currently, a third alternative, which includes many new numerical methods, is being introduced to propagation prediction. The advantages and disadvantages of some of these methods are summarized. In addition, an impulse-response characterization for the propagation path is also presented, including models for small-scale fading, Finally, it is shown that when two-way communication ports can be defined for a mobile system, it is possible to use reciprocity to focus the energy along the direction of an intended user without any explicit knowledge of the electromagnetic environment in which the system is operating, or knowledge of the spatial locations of the transmitter and the receiver.

A survey of various propagation models for mobile communication

On-body communication channels are of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper describes investigations into channel characterization and antenna performance at 2.45 GHz. It is shown that significant channel fading occurs during normal activity, due primarily to the dynamic nature of the human body, but also due to multipath around the body and from scattering by the environment. This fading can be mitigated by the use of antenna diversity, and gains of up to 10 dB are obtained. Separation of the antenna's performance from the channel characteristics is difficult, but results show that for many channels, an antenna polarized normal to the body's surface gives the best path gain. Simulation and modeling present many challenges, particularly in terms of the problem's scale, and the need for accurate modeling of the body and its movement.

Antennas and propagation for on-body communication systems

In this paper, the on-body performance of a range of wearable antennas was investigated by measuring |S 21| path gain between two devices mounted on tissue-equivalent numerical and experimental phantoms, representative of human muscle tissue at 2.45 GHz. In particular, the study focused on the performance of a compact higher mode microstrip patch antenna (HMMPA) with a profile as low as lambda/20. The 5- and 10-mm-high HMMPA prototypes had an impedance bandwidth of 6.7% and 8.6%, respectively, sufficient for the operating requirements of the 2.45-GHz industrial, scientific, and medical (ISM) band and both antennas offered 11-dB higher path gain compared to a fundamental-mode microstrip patch antenna. It was also demonstrated that a 7-dB improvement in path gain can be obtained for a fundamental-mode patch through the addition of a shortening wall. Notably, on-body HMMPA performance was comparable to a quarter wave monopole antenna on the same size of groundplane, mounted normal to the tissue surface, indicating that the low-profile and physically more robust antenna is a promising solution for bodyworn antenna applications.

Antennas for Over-Body-Surface Communication at 2.45 GHz

A portable multiple-vital signs monitor unit of the described apparatus is of ultra-light weight, e.g. less than one pound. In its preferred embodiment, the portable unit takes the form of a right parallelepiped enclosure the volume of which is only approximately 40 in 3 having operator display and control panels and body lead jacks on its face and periphery, respectively, and providing wireless remote full-function communication with an in situ base unit with which the portable monitor may optionally be docked. The base unit communicates via a single telephone line with a remote, typically central location including a host computer and a health care provider, preferably via concurrent voice and data transmission. In its preferred embodiment, the invented apparatus includes in the portable unit the capability for diagnostic quality ECG and pulse oximetry monitoring and in its base unit the capability diagnostic quality blood pressure monitoring.

Medical patient vital signs-monitoring apparatus

Method and apparatus for voice interaction between the service provider to the patient whose life signs, e.g. an electrocardiograph (ECG), concurrently are being monitored are described. Patient data and voice communication are conveyed on a single, or common, public switched telephone (PSTN) line. A life signs monitor at the patient site is connected to the patient and to a digital simultaneous voice and data (DSVD) device having the ability to digitize and compress the patient's voice and having the ability to decompress and analogize the physician's voice via a standard telephone. A modem modulates and demodulates transmitted and received data over the telephone line. At a remote monitoring site a second modem receives and transmits data over the same telephone line. The second modem is connected with a second DSVD device connected to a display- or printer-equipped receiving station for presentation in textual or graphic form to a remote service provider the patient data, e.g. in the form of an ECG trace. Thus, the service provider has the ability to overview patient life signs monitoring while in direct vocal communication with the patient, for instructing the patient or otherwise reassuring the patient of the proper use of the life signs monitor or diagnosing or prescribing in real-time response to what is gleaned from the monitoring.

Concurrent medical patient data and voice communication method and apparatus

Bodyworn antennas are found in a wide range of medical, military and personal communication applications, yet reliable communication from the surface of the human body still presents a range of engineering challenges At UHF and microwave frequencies, bodyworn antennas can suffer from reduced efficiency due to electromagnetic absorption in tissue, radiation pattern fragmentation and variations in feed-point impedance The significance and nature of these effects are system specific and depend on the operating frequency, propagation environment and physical constraints on the antenna itself This paper describes how numerical electromagnetic modelling techniques such as FDTD (finite-difference time-domain) can be used in the design of bodyworn antennas Examples are presented for 418 MHz, 916/spl middot/5 MHz and 2/spl middot/45 GHz, in the context of both biomedical signalling and wireless personal-area networking applications such as the Bluetooth/sup TM/ wireless technology

Numerical analysis of bodyworn UHF antenna systems

A novel model for indoor wireless communication, based on a dual image and ray-shooting approach, is presented. The model, capable of improved site-specific indoor propagation prediction, considers multiple human bodies moving within the environment. In a modern office at 2.45 GHz, the combined effect of pedestrian traffic and a moving receiver causes rapid temporal fading of up to 30 dB.

Hybrid image/ray-shooting UHF radio propagation predictor for populated indoor environments

Vaginal temperature sensing using UHF radio telemetry.

[Summary]: Human body effects such as antenna-body interaction and scattering caused by pedestrian movement are important indoor radio propagation phenomena at microwave frequencies. This paper reports measurements and statistical analysis of the indoor narrowband propagation channel at 5.2 GHz for two scenarios: a fixed line-of-sight (LOS) link perturbed by pedestrian movement and a mobile link incorporating a moving bodyworn terminal. Two indoor environments were considered for both types of measurements: an 18 m long corridor and a 42 m2 office. The fixed-link results show that the statistical distribution of the received envelope was dependent on the number of pedestrians present. However, fading was slower than expected, with an average fade duration of more than 100 ms for a Doppler frequency of 8.67 Hz. For the bodyworn terminal, mean received power values were dependent on whether or not the user's body obstructed the LOS. For example, in the corridor the average non-line-of-sight (NLOS) pathloss was 5.4 dB greater than with LOS

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Measured pedestrian movement and bodyworn terminal effects for the indoor channel at 5.2 GHz

Embedded systems within home appliances are not usually manufactured to operate in a networked environment; connecting supplementary hardware/software systems through a wireless, PC-controlled medium is necessary to enable full, efficient control of their functions from a remote location. Access to the home's central PC may be gained via a local web server, giving Internet-based control from almost anywhere in the world. The proposed system constitutes a significant improvement over those discussed in the literature to date, and reviewed here. It enables complex-appliance control in a secure and reliable portable-wireless environment, and was developed using ASPNet. The system was assessed for Received Signal Strength (RSS) in an environment more radio-hostile than that found in a typical household. The minimum RF level found at a transfer rate of 9.6 kbps was 8 dB above the receiver's quoted sensitivity of -103 dBm: this fading margin will increase in a normal household environment.

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N.E. Evans

Papers

Numerical analysis of bodyworn UHF antenna systems

Hybrid image/ray-shooting UHF radio propagation predictor for populated indoor environments

Vaginal temperature sensing using UHF radio telemetry.

Measured pedestrian movement and bodyworn terminal effects for the indoor channel at 5.2 GHz

Online Remote Control of a Wireless Home Automation Network