Jari Iinatti

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.

On the threshold setting principles in code acquisition of DS-SS signals

This paper compares the meaning of different threshold setting principles in the code acquisition process of a direct sequence (DS) spread spectrum (SS) receiver. The consideration is made mainly in one-path additive white Gaussian noise (AWGN) channel. A consideration to a fixed multipath channel is given to see its effect on the results. Also, a consideration for a certain type of fading is given in a case where the signal power is assumed to be considerably lower, i.e., faded, part of the time. For the possible performance measures of code acquisition, the main interest is in the mean acquisition time T/sub MA/. The probability of the acquisition in a given observation interval P/sub acq/ is also considered to see if different measures have different demands. A matched filter (MF) acquisition is used with and without a verification mode using an active integration. In the comparisons, fixed thresholds, thresholds based on constant false alarm rate (CFAR) criteria, and optimal thresholds in the sense to give either the minimum T/sub MA/ or the maximum P/sub acq/ are used. The results, which are obtained by using a method of selecting the maximum value at the output of the MF, are compared to the threshold cases. The results can be summarized as follows: when the performance measure is T/sub MA/, the best results are obtained by using CFAR-based threshold comparison. By a proper selection of the probability of a false alarm, the same performance is obtained as by using the optimal thresholds. When the performance measure is P/sub acq/, the maximum-selection method is the best choice.

In-band interference power caused by different kinds of UWB signals at UMTS/WCDMA frequency bands

This paper studies in-band interference caused by different kinds of ultra wideband signals in UMTS frequency bands as a function of UWB pulse width. UWB frequency spectra are produced by using several types of narrow pulse waveforms. Due to the extremely wide bandwidth these signals will spread over the frequency bands allocated to other RF-systems. Study revealed that one can reduce interfering UWB power by using different waveforms and pulse widths to avoid UMTS frequencies without any additional filtering. The simulations did not make a significant difference between time hopping and direct sequence concepts when interference was calculated at the UMTS bands.

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.

Evaluation of LoRa LPWAN technology for remote health and wellbeing monitoring

Low power consumption, low transceiver chip cost and large coverage area are the main characteristics of the low power wide area networks (LPWAN) technologies. We expect that LPWAN can be part of enabling new human-centric health and wellness monitoring applications. Therefore in this work we study the indoor performance of one LPWAN technology, namely LoRa, by the means of real-life measurements. The measurements were conducted using the commercially available equipment in the main campus of the University of Oulu, Finland, which has an indoor area spanning for over 570 meters North to South and over 320 meters East to West. The measurements were executed for a sensor node operating close to human body that was periodically reporting the sensed data to a base station. The obtained results show that when using 14 dBm transmit power and the largest spreading factor of 12 for the 868 MHz ISM band, the whole campus area can be covered. Measured packet success delivery ratio was 96.7 % without acknowledgements and retransmissions.

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.

Different experimental WBAN channel models and IEEE802.15.6 models: Comparison and effects

In this paper, a summary of the IEEE802.15.6 wireless body area network (WBAN) radio channel models is given and the models are compared to the corresponding results obtained from the measurements carried out at the Oulu University hospital, Oulu, Finland. CWC has done a set of experimental UWB on-body channel modeling independently of the measurements that are behind the IEEE model. Being statistically more reliable, CWCs results correspond with the models presented by the IEEE806.15.6 task group. Different scenarios for the WBAN link setups have been considered in both campaigns.

Two-dimensional code acquisition in time and angular domains

The extension of conventional delay-domain code acquisition to the angular domain is explored. The uncertainty region is partitioned into a number of delay and angular cells. In single-path channels where the interference is modeled as temporarily and spatially white, there exists an optimum number of angular cells minimizing the mean acquisition time. Mean acquisition times up to three times shorter can be attained with the two-dimensional approach. A rather similar behavior is in general found in Lth-order equal amplitude multipath channels, where paths are contiguous in the delay or angular domains. The strategy employed to search through the uncertainty region may have a considerable impact on acquisition performance. The results reveal that the search should proceed not in the direction of the multipath spread but in the other available domain. Proper selection of the search strategy can reduce the synchronization time by a factor of up to two. Two-dimensional code acquisition in scenarios with spatially nonuniform interference is also investigated. In general, the acquisition performance is degraded by the presence of nonuniform interference in the angular domain.

Effect of the antenna-human body distance on the antenna matching in UWB WBAN applications

In this paper, the interaction between the ultra wideband (UWB) antenna and human body is considered and demonstrated in the range of 0-30 mm above the body surface, which could be practical operation distance for the on-body antenna. Two different planar UWB antennas (loop and dipole) are used for the examinations. First, the antenna performance in free space (FS) is shown. Then, the effect of the antenna-body distance on the antenna operation is analysed in the terms of the matching, i.e., reflection coefficient S11. Measurements are carried out in the proximity of a real human body while the simulations are run by using the whole body model having a frequency-dependent behaviour. Observations are concluded to commensurate with the antenna field regions and the size of antennas reactive near-field was satisfied to be an important factor in the evaluation of an acceptable on-body operation. No significant differences between different antennas were observed through investigations. Both antennas perform satisfactory when the distance is high enough. The results of this study are helpful to engineers and designers evaluating antennas for the use in UWB wireless body area network (WBAN) applications.

Design study for a CDMA-based LEO satellite network: downlink system level parameters

The performance analysis of a new concept of a code-division multiple-access (CDMA) based low Earth orbit (LEO) satellite network for mobile satellite communications is presented and discussed. The starting point was to analyze the feasibility of implementing multisatellite and multipath diversity reception in a CDMA network for LEO satellites. The results are used to specify the design parameters for a system experimental test bed. Due to the extremely high Doppler, which is characteristic of LEO satellites, code acquisition is significantly simplified by using a continuous wave (CW) pilot carrier for Doppler estimation and compensation. The basic elements for the analysis presented are: the channel model, the pilot carrier frequency estimation for Doppler compensation, and multipath and multisatellite diversity combining.