Papers by Matti Hämäläinen
International Symposium on Medical ICT, 2018
In this paper, the impact of the sternotomy wires and aortic valve implant on the ultra wideband ... more In this paper, the impact of the sternotomy wires and aortic valve implant on the ultra wideband (UWB) channel characteristics is studied. The evaluations are performed by calculations, measurement data analysis, and power flow simulations. The aim is to show that implants, which consist of steel, titanium, and other highly conductive materials, do have clear effect on the signal propagation even inside the tissues. This impact should be taken into account when using in-body or on-body communications devices, such as capsule endoscopes, etc.
International conference on Body Area Networks, 2018
This paper presents for the first time a simulation study on the impact of the sternotomy wires o... more This paper presents for the first time a simulation study on the impact of the sternotomy wires on the ultra wideband (UWB) channel characteristics. The simulations are based on the finite integration technique (FIT). The simulation results are verified with the propagation path calculations as well as with the measurement data. It is found that there is a clear correspondence between the simulated and measurement results as well as with the propagation path calculations which allows smooth transceiver algorithm investigation.
The technological innovation has enabled the spread of safety-related systems in many domains, su... more The technological innovation has enabled the spread of safety-related systems in many domains, such as public transport, energy, and medical devices. In these applications, security is one of the primary concerns. This paper proposes a watermark-based blind physical layer security (WBPLSec) utilizing a jamming receiver in conjunction with spread spectrum watermarking technique. The outage probability of the secrecy capacity is analytically derived, being regardless of the eavesdropper position. Results indicate the WBPLSec a valuable technique for deploying physical layer security creating a secure region around the receiver, such as the legitimate medical device.
2015 9th International Symposium on Medical Information and Communication Technology (ISMICT), 2015
Medical ICT is one of the most interesting and challenging research areas for both industry and a... more Medical ICT is one of the most interesting and challenging research areas for both industry and academia. Wireless body area network (WBAN) applications for health-care systems are rapidly being developed and deployed. In an unlicensed frequency band like industrial, scientific and medical (ISM) band, WBANs will encounter tough competition for resources because several other wireless technologies share the band. Spectrum occupancy evaluations (SOEs) provide a statistical insight into the resource utilization patterns. This research work is focused on stochastic modeling of such spectrum occupancies in order to statistically describe the possible interference a WBAN may face. Modeling is based upon the measurement data acquired from accident and emergency ward, Oulu University hospital. Stochastic models for channel occupancies and spectrum resource occupancy are provided. The consistency of model produced data with actual data is validated through exact and asymptotic statistical hypothesis tests.
Proceedings of the 9th International Conference on Body Area Networks, 2014
In this paper we describe an overhauled, robust approach for spectrum occupancy evaluations (SOE)... more In this paper we describe an overhauled, robust approach for spectrum occupancy evaluations (SOE) at industrial, scientific and medical (ISM) band in a hospital environment for interference free, dynamic spectrum access (DSA). A novel bandwidth and center frequency estimation algorithm is presented in order to distinguish among various coexisting systems. Different results are inferred by processing data obtained from a day long measurement campaign including channel occupancies, frequency band occupancy, and spectrum resource occupancies.
2015 9th International Symposium on Medical Information and Communication Technology (ISMICT), 2015
Spectrum occupancy evaluations (SOEs) provide statistical insight regarding frequency resource ut... more Spectrum occupancy evaluations (SOEs) provide statistical insight regarding frequency resource utilization patterns for a given frequency band. In modern health-care systems, wireless solutions are trending and a number of wireless body area network (WBAN) applications are being developed. Industrial, scientific and medical (ISM) band is an unregulated, license free band where WBANs will co-exist with several other wireless technologies. This particular research work is focused upon SOEs from the standpoint of WBANs in 2.35-2.50 GHz band. A week long SOE campaign was undertaken at Oulu University Hospital emergency ward. SOE metrics evaluated include channel occupancies and spectrum resource occupancies.
2009 IEEE International Conference on Ultra-Wideband, 2009
Wireless body area networks (WBAN) are being considered as one of the most suitable technologies ... more 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 complex shape of the human body and 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 TM . To minimize the effects of the environment the measurements were conducted in an anechoic chamber.
2010 IEEE 21st International Symposium on Personal, Indoor and Mobile Radio Communications Workshops, 2010
This paper focuses on wireless body area networks (WBAN) targeted for medical ICT applications. T... more This paper focuses on wireless body area networks (WBAN) targeted for medical ICT applications. The studied network follows a typical IEEE 802.15.4 beacon-enabled star topology. We simulate the collection of medical data from patients using wireless sensors. Impulse radio ultra wideband (IR-UWB) is chosen as a physical layer technology, in compliance with the IEEE 802.15.4a standard. Two random access methods,
IEEE Radio and Wireless Symposium formerly, 2002
This paper studies the performance of ultra wideband (UWB) communication systems in AWGN channels... more This paper studies the performance of ultra wideband (UWB) communication systems in AWGN channels. The studied UWB systems are utilizing different kinds of modulation schemes. The propagating information signal is jammed with a signal having a spectrum in the UMTS or in the GSM band. The simulations showed that the time hopping UWB system utilizing binary PAM modulation outperforms the
Ultra Wideband Systems and …, 2002
This paper studies the performances of ultra wideband (UWB) systems in AWGN channel when the inte... more This paper studies the performances of ultra wideband (UWB) systems in AWGN channel when the interference in UMTS/ WCDMA band is present. The interfering band in the frequency division duplexing mode has been considered as a fully covered for both uplink or downlink cases. The interference is actually modelled as a sinc-pulse jamming having a spectrum in a predefined UMTS band. The uncoded UWB system performances are studied through the bit-error-rate as a function of signal-tonoise ratio as well as jamming-to-signal power ratio. Several modifications of a generic Gaussian pulse have been selected for the deeper study. The UWB systems are based on time hopping and direct sequence spread spectrum techniques, which utilizes a binary baseband pulse amplitude data modulation. The results showed that UWB system performance degradation is the highest when the interfering signal and the nominal center frequency of the UWB system are overlapping. UWB systems based on time hopping concept seem to outperform the corresponding direct sequence concepts. However, for high values of interfering power, the UWB performances are converging.
The study for this paper focuses on searching the optimal number of fingers to be used by a Selec... more The study for this paper focuses on searching the optimal number of fingers to be used by a Selective-Rake receiver using different ultra wideband systems. The presence of multipath fading has been taken into account using a modified Saleh-Valenzuela model. Coherent and non-coherent detection has been performed within different combining approaches. Non-coherent techniques have been implemented with and without power estimation. Results show that in non-coherent systems the optimal number of fingers D opt required for the detection is lower than for coherent ones. On the other side, an increase of signal-to-noise ratio causes D opt to get higher, which is the same trend noticed while passing from a line-of-sight (LOS) channel to a non-LOS one.
Wireless body area networks (WBAN) are expected to be a breakthrough technology in healthcare are... more Wireless body area networks (WBAN) are expected to be a breakthrough technology in healthcare areas such as hospital and home care, telemedicine, and physical rehabilitation. Because the human body has a complex shape consisting of different tissues it is expected that the nature of the propagation of electromagnetic signals in the case of WBAN to be very different than the one found in other environments, e.g. offices, streets, etc. There have been several previous experimental studies aimed to characterize the nature of the Ultra-Wideband (UWB) channel for the case of WBANs. In this paper we describe our contribution to expand the knowledge of the UWB channel by taking measurements in the frequency range of 3-11 GHz in realistic scenarios expected to be found in medical applications. We also present channel models that have been developed using the experimental results.
This paper compares the performances of an ultra wideband (UWB) system in additive white Gaussian... more This paper compares the performances of an ultra wideband (UWB) system in additive white Gaussian noise (AWGN) channel in presence of a pulsed jamming or a coloured Gaussian noise allocated in the UMTS-FDD (FDD = Frequency Division Duplex) uplink band. Several modulation schemes have been implemented in order to analyze the efficiency and the robustness of different UWB systems when the studied interferences are present in the channel. Results showed that the particular UWB modulation scheme chosen doesn't affect effectively the degradation of performances introduced by the interference, giving a precise rank order for the different UWB concepts. Nevertheless, due to the band allocation of the interference, the pulsed jamming source worsens the performance of the system more significantly than the coloured noise for low interference power. For high values, instead, the behaviour is inverted.
This paper compares the performances of an ultra wideband (UWB) system in additive white Gaussian... more This paper compares the performances of an ultra wideband (UWB) system in additive white Gaussian noise (AWGN) channel in presence of a pulsed jamming or a coloured Gaussian noise allocated in the UMTS-FDD (FDD = Frequency Division Duplex) uplink band. Several modulation schemes have been implemented in order to analyze the efficiency and the robustness of different UWB systems when the studied interferences are present in the channel. Results showed that the particular UWB modulation scheme chosen doesn't affect effectively the degradation of performances introduced by the interference, giving a precise rank order for the different UWB concepts. Nevertheless, due to the band allocation of the interference, the pulsed jamming source worsens the performance of the system more significantly than the coloured noise for low interference power. For high values, instead, the behaviour is inverted.
Oppermann/UWB: Theory and Applications, 2004
In hospitals patients and other medical facilities have various levels of mobility, e.g., walking... more In hospitals patients and other medical facilities have various levels of mobility, e.g., walking, wheelchairing, eating, etc. There is also growing evidence that for most medical conditions having patients move or walk, as much as they can tolerate, will improve their health. With keeping this in mind, not only static wireless body area network (WBAN) radio channels usually investigated, but also dynamic scenarios due to the effect of body motion must be considered. The contribution of the work described in this paper is to expand the knowledge of the ultra-wideband (UWB) channel in the frequency range of 3.1-10 GHz in close proximity of a dynamic human body. Based on experimental measurements a two-state alternating Weibull renewal process is modelled for the dynamic fade characteristics of the channel. The model can then be used to better design communication network protocols for WBANs.
Wireless body area networks (WBAN) are expected to be a breakthrough in healthcare, leading to co... more Wireless body area networks (WBAN) are expected to be a breakthrough in healthcare, leading to concepts like "telemedicine" becoming real, since the sensor nodes in WBANs, communicating through wireless technologies, can transmit data from the body to a home base station, from where the data can be forwarded to a hospital, clinic or elsewhere, real-time. WBANs have not only the potential to increase the quality of the medical care but also to keep under control the associated costs. The characteristics of radio propagation, in the case of WBANs, is expected to be distinct from the ones found in other environment, since the human body has a complex shape and consists of different tissues. In a reality, patients have various levels of mobility, e.g. walking, wheelchairing, eating, etc. It is a fact that for most medical conditions patients are encouraged to walk or move as much as they can tolerate in order to improve their recovery. The fluctuations of the radio channels in the proximity of a human body under dynamic situations should then be well understood for proper design of these body are networks. Our contribution in this paper is to elaborate the knowledge of the ultra-wideband (UWB) channel in the frequency range of 3.1-10 GHz, for the case of WBANs, in real hospital environments under both static and dynamic scenarios.
The study for this paper focuses on searching the optimal number of fingers to be used by a Selec... more The study for this paper focuses on searching the optimal number of fingers to be used by a Selective-Rake receiver using different ultra wideband systems. The presence of multipath fading has been taken into account using a modified Saleh-Valenzuela model. Coherent and non-coherent detection has been performed within different combining approaches. Non-coherent techniques have been implemented with and without power estimation. Results show that in non-coherent systems the optimal number of fingers D opt required for the detection is lower than for coherent ones. On the other side, an increase of signal-to-noise ratio causes D opt to get higher, which is the same trend noticed while passing from a line-of-sight (LOS) channel to a non-LOS one.
IEEE Conference on Ultra Wideband Systems and Technologies, 2004
Ultra wideband (UWB) system performance is studied in the presence of multiband interference. The... more Ultra wideband (UWB) system performance is studied in the presence of multiband interference. The interference sources considered are IEEE 802.11a and UMTS which are operating simultaneously with their maximum system bandwidths. The channel model used in the study is a modified Saleh-Valenzuela model which is adopted to be used as a reference UWB channel by the IEEE 802.15.3a study group.
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Papers by Matti Hämäläinen