|Session:||Session 4A02P - Ultrawideband Propagation Modelling (12b)|
|Date:||Thursday, November 09, 2006|
|Time:||08:30 - 12:30|
|Chair:||Wiesbeck & Jensen|
Frequency Dependence of Correlation Coefficients in Ultra Wideband Antenna Arrays
Sturm, C.; Soergel, W.; Kuhnert, C.; Wiesbeck, W.
Universitńt Karlsruhe, GERMANY
II. WAVE PROPAGATION SIMULATIONS
III. SIMULATION RESULTS
Double Directional UWB Channel Modeling Using Scatter Distribution Imaging
Romeu, J.1; Gonzalez, J.M.1; Miskovsky, P.2; Jofre, L.1; Blanch, S.1
1AntennaLab, Dpt. Signal Theory and Communications, UPC, Barcelona, SPAIN;
2CTTC, Barcelona, SPAIN
The full characterization of a wideband multi-antenna channel requires to state both the temporal and directional properties of the channel. This leads to the double-directional response of the channel that can be seen as the superposition of the contributions from the more significant multipath components. Starting from the SISO impulse response :
A Deterministic Indoor UWB Space-Variant Multipath Radio Channel Modelling Compared to Measurements on Basic Configurations
Many studies have been initiated around the world on indoor communication systems based on ultra wide band signals. European projects (Ultrawaves, Pulsers) have been initiated in the past three years. Each project contains at least a sub-workpackage dealing with the "indoor UWB channel characterisation" showing first the importance of the topic and second the fact that this channel has not been fully understood yet. Many channel sounders have been deployed. A few statistical models have appeared. These preliminary results have indicated how complex the topic is.
We believe the proposed method is complementary for some aspects to the IEEE 802.15.3a channel model, which was useful for the selection process of the new standard for UWB high-data rate communications [A. Molisch, "Channel models for ultrawideband personal area networks", IEEE Wireless Com., Dec. 2003, Vol. 10, n°6].
The proposed paper will show the novelty and the maturity of the approach by clearly explaining the process. Measurements were carried out in indoor environments. Comparisons between the obtained Impulse Response simulations and measured signals will be described and analysed. It shows good results and gives some ideas to enhance further the modelling. The measurements were specified to analyse specific phenomena like diffraction or reflections in a corridor, multifloor propagation as this will be illustrated in the proposed paper. The simulated result appears to be less dense that the measured one (mainly because the richness of the real scene is not fully represented by the modelled scene e.g. pieces of furniture, interior of cupboards). The amplitude of the simulated cluster may be tuned to adapt the model to the environment. But the main contributions (time and shape of cluster arrival) are well retrieved. The inserted figures show the main rays determined by the proposed model. The measured and non-tuned simulated responses in a corridor are represented.
Channel Simulation of Time Reversal for UWB Communications
Aubert, L. M.; Tchoffo Talom, F.; Uguen, B.
IETR-INSA Rennes, FRANCE
For the last few years, UWB techniques have been envisioned for low and high data rate indoor communications. The main advantage of UWB techniques is the great diversity provided by the available bandwidth. UWB solutions traditionally investigated are a trade-off between the exploitation of the available diversity and the receiver complexity. To increase data rate and take full advantage of channel diversity without making the receiver more complex, time reversal techniques can be applied to UWB communications. These techniques consists in transmitting the time-reversed version of the channel response. The reciprocity of the time invariant channel ensures both temporal and spatial focusing of the signal at the receiver side. Time reversal techniques have been successfully used in acoustic and underwater areas for many years . More recently, papers have demonstrated the relevance of these techniques in electromagnetic area and their feasibility in a UWB context [2-3]. Theoretically, this system provides similar performances compared to traditional impulse radio coherent systems. In practical cases, time reversal performances are highly dependant on propagation channel properties.
In this paper, we study the characteristics of the propagation channel for transmitted reference combined with UWB communications.
First, we set up a general MIMO channel modeling formalism based on the ray propagation assumption. Particularly, this formalism highlights the channel reciprocity principle on which time reversal techniques rely.
Then, this formalism is implemented in a deterministic simulation tool that combines a ray tracing approach with optical geometry (OG) and uniform theory of diffraction (UTD). Prior measurements in near field chamber are used to rigorously take into account antennas in the simulator .
We use this simulator to verify the channel reciprocity property whatever the type of antennas. We also demonstrate that simulations can be exploited to analyze the spatial coherence of the channel. This characteristic determines, on the one hand, the distance that ensures focusing of the received signal, and on the other hand, the minimum gap between each antenna requisite in a MIMO situation.
 Fink, M. , "Time-reversed acoustics," Scientific American, Nov. 1999.
Ultra-Wideband Indoor Propagation Channel: Measurements, Analysis and Modeling
Irahhauten, Z.; Yarovoy, A; Janssen, G.J.M.; Nikookar, H; Ligthart, L.P.
Delft University of Technology, NETHERLANDS
Due to its potential applications like high data rate communication and positioning capabilities, UWB is gaining more interest in the field of wireless communication. However, the analysis and design of UWB communication systems need an accurate knowledge of the propagation channel characteristics. Therefore, extensive and accurate channel measurements are required. To date a limited number of measurement campaigns and channel modeling efforts have been reported to characterize the UWB channel when compared to narrowband measurements.
A large frequency band of 3.1 to 10.6 GHz is devoted to UWB wireless communication in indoor environments according to FCC. Propagation mechanisms (e.g. reflection, diffraction, scattering...) are very frequency dependent. Because of the large frequency band occupied by UWB signal, channel parameters in the whole band are frequency dependent. This important issue should be well incorporated in the modeling of the UWB channel.
A large set of UWB measurements has been performed. The measurements are carried out in indoor office environments at the campus of Delft University of Technology using a time domain technique. The generator fires a Gaussian-like pulse with duration of 50 ps. As a result, the measurements can be performed in the bandwidth of 12 GHz. The maximum measured distance was about 10 m for both LOS and NLOS situations. To characterize the small-scale and large-scale fading parameters of the sub-channels, a grid of 7x7 with a spacing of 5 cm between adjacent points was designed and used in the measurements.
In this paper the total measured band is divided into 15 sub-bands of 500 MHz. For each sub-band statistics of channel parameters are obtained. Furthermore, the frequency dependency of these statistics is investigated. The results of the statistical analysis address the frequency dependency of: amplitude fading statistics, large scale path loss, time dispersion and correlation. Major application of this study is the MB-OFDM which divides the band into several bands.
Numerical Simulation of UWB Radar Propagation Effects
Schejbal, V.; Nemec, Z.; Cermak, D.; Bezousek, P.
University of Pardubice, CZECH REPUBLIC
Vladimir SCHEJBAL, Zdenek NEMEC, Dusan CERMAK, Pavel BEZOUSEK
The UWB concept is very useful for radars and communications. A UWB engineer needs to be familiar with both the time domain and frequency domain, able to switch seamlessly from one domain to the other as the nature of problem demands. The UWB radar output signals can be substantially affected due to electromagnetic wave propagation through walls and multipath effects. The program, which allows the calculations for both frequency spectra and time responses for combinations of various receiving and transmitting antennas, input signals and obstacles (walls), has been coded using MATLAB® language. The numerical simulation of UWB radar propagation effects is briefly described.
Several combinations of receiving and transmitting antennas and input signals have been calculated and compared. It can be concluded that UWB radar output transmitted signals are formed both with transmitters and antennas. The transmitting transient responses of an ideal antenna are proportional to the time derivatives of the receiving transient responses of the same antenna. Therefore, UWB antennas should be considered as an integral part of the whole systems. Moreover, the output transmitted signals should be formed according to UWB system demands. That means that analyses should be done for very wide frequency spectrum and simultaneously, the effect of input signals should be considered both for transmitting and receiving antennas.
The propagation of electromagnetic waves through obstacles has been analyzed, where wall parameters are given both for brick and concrete walls with various thicknesses and S11 and S21 can be found using numerical simulations for these cases. The responses (input and output signals calculated using IFFT) have been extensively analyzed as well. The ringing (due to boundary multiple reflections) can be clearly observed. Naturally, the interferences of multiple reflections are much smaller for very short pulses than for CW and narrow-band applications.
The method can be used for analyses of multipath propagation due to reflections (such as ground or wall reflections). Multipath effects are analyzed and simulated numerically for various cases with several heights and distances. The output transmitted signal is usually formed according to UWB system requirements. Various cases show delays (due to propagation through wall and various paths of direct and reflected rays) and the ringing (similar to UWB propagation through wall). Certainly, these phenomena are much more pronounced for reflected rays. On the other hand, the interference effects of multiple reflections and multipath effects are much smaller for UWB signals than for CW narrow-band applications as interference minima and maxima do not occur for the same frequencies. Moreover for very short pulses, the individual pulses are received at various times and can be distinguished more easily.
Measurement of Local Enviromental Effects in UWB Channels
Atilim University, TURKEY
Understanding of local environmental conditions near the terminals is important for determining system performance and possible interference in UWB channels[1,2]. Objects like desks and cabinets scatter the radio waves and thereby cause spatial fading as a result of multipath as well as shadowing due to blockage. When people move in the vicinity of the link they cause additional fading, which may be the result of body blockage or multipath interference due to body scattering. On line of sight (LOS) links body blockage is found to produce deep fades, while on obscured links the effect of body scattering are found to be most significant. This difference is observed both in the time dependence of the excess path loss as people move, and in the statistical distribution of the fading for indoor propagation [3,4,5]. In this study, measurement results for local enviromental effects in UWB channels are presented. Effecs of objects in and around the radio link particularly human body shadowings are studied for UWB channels. Fully computer controlled measurement setup includes a signal generator, two identical triangular monopoles and a spectrum analyzer that is connected to a PC (Figure 1). All measurements including outdoor calibrations are performed in Atilim University campus area. Measurement setup and preliminary results involving human body blockage when crossing the radio link at different frequencies are presented in Figure 2-4. 1.Roy, S. et al.,"Ultrawideband Radio Design: The promise of high-speed, short-range wireless connectivity", Proceedings of the IEEE, vol.92, No.2, 2004. 2.UWB Channel Modeling, IEEE P802.15 Working Group Document. 3.Obayashi, S., and Zander, J., "A body-shadowing model for indoor radio communication environments", IEEE Trans. on Antennas and Prop., vol. 46, no.6, pp.920-927, 1998. 4.Hafezi, P. et al., "An experimental investigation of the impact of human shadowing on temporal variation of broadband indoor radio channel characteristics and system performance", IEEE VTC-Fall Vehicular Technology Conference, vol.1, pp.37-42, 2000. 5.Kara, A. and Bertoni, H.L., "Blockage/shadowing and polarization measurements at 2.45 GHz for interference evaluation between Bluetooth and IEEE 802.11 WLAN", IEEE APS/URSI Symposium, vol. 3, pp. 376-379, 2001.
Multihop Channel Model in UWB Ad Hoc Networks at 60 GHz
Bendjaballah, A.1; Clavier, L.2; Rolland, N.1; Rolland, P. A.1
1IEMN DHS-CSAM, FRANCE;
2GET ľ INT ľ TÚlÚcom Lille 1, FRANCE
Multipath evolution with the number of hops:
|Abstracts assigned without a sequence or a sequence number beyond maximum presentation slots available:|
|10 - 357468 - UWB Tracking for Sports and Entertainment|