Raffaello Tesi

On the UWB system coexistence with GSM900, UMTS/WCDMA, and GPS

This paper evaluates the level of interference caused by different ultra-wideband (UWB) signals to other various radio systems, as well as the performance degradation of UWB systems in the presence of narrowband interference and pulsed jamming. The in-band interference caused by a selection of UWB signals is calculated at GSM900, UMTS/wideband code-division multiple-access (WCDMA), and Global Position System (GPS) frequency bands as a function of the UWB pulsewidth. Several short-pulse waveforms, based on the Gaussian pulse, can be used to generate UWB transmission. The two UWB system concepts studied here are time hopping and direct sequence spread spectrum. Baseband binary pulse amplitude modulation is used as the data modulation scheme. Proper selection of pulse waveform and pulsewidth allows one to avoid some rejected frequency bands up to a certain limit. However, the pulse shape is also intertwined with the data rate demands. If short-pulses are used in UWB communication the high-pass filtered waveforms are preferred according to the results. The use of long pulses, however, favors the generic Gaussian waveform instead. An UWB system suffers most from narrowband systems if the narrowband interference and the nominal center frequency of the UWB signal overlap. This is proved by bit-error rate simulations in an additive white Gaussian noise (AWGN) channel with interference at global system for mobile communication (GSM) and UMTS/WCDMA frequencies.

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.

On the UWB system performance studies in AWGN channel with interference in UMTS band

This paper studies the performances of ultra wideband (UWB) systems in an AWGN channel when interference in the UMTS/WCDMA band is present. The interfering band in the frequency division duplexing mode has been considered to be fully covered for both uplink and downlink cases. The interference is actually modelled as sinc-pulse jamming having a spectrum in a predefined UMTS band. The uncoded UWB system performance is studied through the bit-error-rate as a function of signal-to-noise 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 overlap. UWB systems based on the time hopping concept seem to outperform those based on the corresponding direct sequence concepts. However, for high values of interfering power, the UWB performances are converging.

UWB coexistence with IEEE 802.11a and UMTS in modified Saleh-Valenzuela channel

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. All the interference signals are equally powered at the UWB receiver input. The system under interest is a single band and single user UWB link operating at a data rate of 100 Mbps without error correction coding. UWB pulse waveforms are the 5/sup th/ and the 6/sup th/ derivatives of a Gaussian pulse to meet the FCC regulations. Both coherent and non-coherent UWB receiver algorithms are used. The former gives a best performance due to its capability to utilize the maximum available energy at the detection process when maximum ratio combining is utilized. The results show that the UWB system is sensitive to RF interference coming from the same frequency band.

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.

On the performance comparison of different UWB data modulation schemes in AWGN channel in the presence of jamming

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 other studied modulation schemes in the AWGN channel when a jamming signal is present. The simulation results showed that the rank order of the studied modulation schemes in the AWGN channel in the presence of jamming is time-hopping binary pulse amplitude modulation. direct sequence based binary pulse amplitude modulation, time hopping pulse position modulation and direct sequence based on-off-keying.

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.

On the multi-user interference study for ultra wideband communication systems in AWGN and modified Saleh-Valenzuela channel

This paper studies the effects of multiple access interference (MAI) for ultra wideband (UWB) systems in AWGN and multipath fading channels. Time hopping (TH) and direct sequence (DS) based UWB spreading approaches are performed, utilizing binary pulse amplitude modulation (PAM) and pulse shape modulation (PSM). Both the possibilities of having synchronous and asynchronous users have been taken into account. In the fading channel case, different coherent and non-coherent detection methods have been considered. Simulated performance results are depicted for the above mentioned UWB systems when a variable number of equally powered users are operating in the channel. Results show that in both the AWGN and fading channel the DS system performance shows sensibly different results in the synchronous and asynchronous case. This is due to the continuous time transmission of the different users. This problem does not occur in systems using TH spreading since the different users are less overlapped in time, due to the spreading approach used. In the fading channel, TH systems show a general higher performance loss in all cases compared to DS, in contrast to what happens in the AWGN case. That is, the allocation of the TH codes creates a higher interfering effect due to MAI in the presence of multipath fading. In general, DS-based systems outperform the corresponding TH ones.

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.

Design and performance of contention based MAC protocols in WBAN for medical ICT using IR-UWB

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, slotted Aloha (S-Aloha) and preamble sense multiple access (PSMA) are studied in terms of throughput and energy consumption. This paper has two main objectives: 1) to address realistic performance of the two selected MAC protocols, accounting for false alarm, miss-detection and capture effect, when using IR-UWB; 2) to obtain feedback information on the design of medical networks that use the IEEE 802.15.4 beacon-enabled star topology. Therefore, the performances are obtained increasing the number of active sensors, varying in parallel typical superframe parameters as beacon order and superframe order to test the reaction of the network at the introduction of an inactive period.