Attaphongse Taparugssanagorn

UWB channel modelling for wireless body area networks in a hospital

This paper describes an experimental study of the ultra wideband (UWB) wireless body area network (WBAN) channel in a hospital environment. The measured data are used to develop statistical models for the channel, which can then be used to design efficient and safe communication networks. WBANs are expected to be used in the healthcare field to enable concepts such as telemedicine. The human body has a complex shape and consists of different tissues. It is then expected that the propagation of the electromagnetic waves near a patients body will have unique characteristics. In a hospital environment, there are also a variety of electronic devices and specialised medical equipment, which have impact on the electromagnetic propagation. To properly design WBANs is then necessary to have a good understanding of the characteristics of the radio channel in the proximity of the human body within a hospital.

Measurement Based Capacity of Distributed MIMO Antenna System in Urban Microcellular Environment at 5.25 GHz

In this paper, the results of distributed multiple-input multiple-output antenna system (MIMO DAS) capacity measurements are presented. Until this point, literature about MIMO DAS considers only theoretical channels. The novelty of this paper comes from applying actual measured radio channel to MIMO DAS. In MIMO DAS, the coverage is obtained by using several largely separated MIMO antenna ports (AP) in the area. This way the advantages of shadowing diversity can be exploited and the link performance can be improved as theoretically shown in Ni and Daoben (2004). The measurements for the analysis were conducted in the downtown of Oulu, Finland, by generating a 4times16 MIMO configuration with EB Propsound CStrade as a channel sounding device. The results show that the capacity of MIMO DAS is improved from the conventional system and the diversity aspect in shadowing between the separated APs is large.

Wireless medical communications using UWB

This paper introduces some of the recent activities in a medical ICT related ultra wideband (UWB) research. The paper concentrates on our proposed body area network (BAN) based system architecture for wireless medical communications, and gives also a summary on experimental UWB wireless BAN (WBAN) radio channels modeling activities. The network architecture under discussion consists of parts that have already been implemented and also parts that require studies in more details before their utilization and implementation into operative healthcare services. For detailed communication system designs, accurate close body channel models are needed. This paper gives also a summary on UWB radio channel models that are suitable to be applied in wireless body area network research. Experiments for UWB radio channel models have been done in real end-user environments.

A comparison of UWB WBAN receivers in different measured hospital environments

Wireless technology has been developing fast for years and is spreading to new areas of everyday life. One of the newest areas is healthcare and welfare sector where it can be a significant way to save costs and improve existing procedures. The coming years are going to be challenging as the population, in the developed countries especially, is aging fast and more patients are going to need treatment but with the same or even smaller number of nursing staff than nowadays. Therefore there is a clear need for both improvement of methods and cutting down the costs. In this paper, the performance of different ultra wideband (UWB) receivers implemented following the IEEE 802.15.4a requirements are being compared in different hospital environments. Wireless body area network (WBAN) radio channel models used in the simulations are based on the measurements carried out in a real hospital environment in Oulu, Finland.

Effect of body motion and the type of antenna on the measured UWB channel characteristics in medical applications of wireless body area networks

Wireless body area networks (WBAN) are being considered as one of the most suitable technologies for remote health monitoring. This technology has the potential to increase the quality of medical care as well as keeping under control the associated costs. Due to the complexity of the human organisms and the nature of its different tissues it is expected that the propagation characteristics of the radio channel, when measured in close proximity of a human body, to be different than those found in other scenarios. The work described in this papers aims to expand the knowledge of the ultra-wideband (UWB) channel in the frequency range of 3.1–10 GHz, for the case of WBANs, under static and dynamic scenarios. Two different type of antennas are used, the SkyCross SMT-3TO10M-A and the P200 BroadSpec™. To minimize the effects of the environment the measurements were conducted in an anechoic chamber.

UWB supporting medical ICT applications

In this paper, the utilization of ultra wideband (UWB) technology is reviewed for medical wireless ICT applications. As a low power technique, UWB is capable to operate in underlay fashion with other existing radio and medical systems. At hospital site, this is one of the major requirements set to the electrical devices. UWB makes it possible to utilize both high and low data rate applications and accurate positioning.

Characteristics of Short-Term Phase Noise of MIMO Channel Sounding and Its Effect on Capacity Estimation

Multi-input-multi-output (MIMO) radio channel sounders commonly employ a time-division-multiplexing (TDM) technique to switch between transmit (TX) and receive (RX) antennas. The TDM-based switching enables very cost-effective solutions. Nevertheless, it can cause measurement errors due to phase noise in the local oscillators. In typical MIMO applications with a relatively small number of TX and RX antennas, the measurement cycle for a single snapshot of a MIMO radio channel is so short that independent or white Gaussian noise samples cannot be assumed. Indeed, the characteristics of the phase noise depend on the observing-time scale and the local oscillator design in the TX and the RX. In free-running systems, in which the local oscillators of the TX and the RX employ their own clocks, the properties of the phase noise have a strong dependence on the scale of the observing time. In particular, the short-term characteristics of the phase noise have not been considered in literature regarding MIMO measurements. In this paper, the characteristics of the short-term phase noise in time-switched MIMO radio channel measurements are disclosed. We show also that the Allan deviation, which commonly characterizes the frequency stability of the local oscillators, does not apply well to the short-term scale. Instead, an autoregressive model that is well suited for modeling of correlated noise is applied to characterize the short-term behavior of the phase noise. Finally, the effect of short-term phase noise on the estimation of MIMO channel capacity is analyzed. We also derive an upper bound for the ergodic channel capacity and show that it is dependent on the distribution of the largest eigenvalue of the noise covariance matrix. The results reveal that the effect of short-term phase noise always overestimates MIMO channel capacity.

P-rake receivers in different measured WBAN hospital channels

In wireless applications, power consumption has been, and will be, one of the important characteristics when designing any wireless device. This is the case especially in sensor networks where a single sensor may be functioning, hopefully for very long time, without external power source. Generally, the architecture complexity reduces the battery life, but the performance increases with complexity. The best performance is achieved with the most complex devices which, however, consume a lot of power. Rake receivers can offer a good tradeoff between complexity and performance. In the near future, due to the aging of population, personal medical applications are most likely increasing in number and gaining more attention in industry. This paper presents simulation results for IEEE 802.15.4a ultra wideband (UWB) rake receivers in measured hospital channel. Oulu University Hospital in Oulu, Finland, was the location of the wireless body area network (WBAN) channel model measurements.

Preliminary UWB channel study for wireless body area networks in medical applications

Ultra wideband (UWB) communications is a promising technology for wireless body area networks (WBAN) due to its very low power emission and robustness against multipath fading characteristics. The use of WBANs in the areas of healthcare and telemedicine is being seriously considered as a way of increasing the quality of medical services and of keeping under control the associated costs. Because the human body has a complex shape and consists of different tissues it is expected that the propagation of electromagnetic signals will have different characteristics than the ones found in other environments, e.g., offices, streets, etc. The contribution of the work described in this paper is to expand the knowledge of the UWB channel, for WBAN applications, in the frequency range of 3-11 GHz under scenarios expected to be found in the medical care field. The experimental measurements are used to develop UWB channel models which can then be applied to the design of efficient communications protocols.

On the energy detector, P- and s-rake receivers in a measured UWB channel inside a hospital

Medical industry is potentially a big market for the wireless applications in the coming years. As the number of elder people is increasing, the need for various wireless body monitoring and measurement equipment is increasing as well. However, having any kind of electronic device next to the human body, or even inside of a body, faces challenges. For wireless body area network (WBAN) solutions, the battery life needs to be long, the equipment has to be safe to use and un-harmful also for other electronic devices. From power usage point of view, the most complex high performance receivers are not the best option since they tend to have high power consumption, thus short battery life. In this paper, the performances of receiver types suitable for low cost WBAN solutions are compared in a real hospital environment. The ultra wideband (UWB) transceiver system has been implemented by following the IEEE 802.15.4a standard requirements. The WBAN channel model is based on the measurements carried out in a regular hospital room in Oulu University Hospital, Finland.