H. Henniger, O. Wilfert [references] [full-text] [Download Citations]
An Introduction to Free-space Optical Communications

Over the last two decades free-space optical communication (FSO) has become more and more interesting as an adjunct or alternative to radio frequency communication. This article gives an overview of the challenges a system designer has to consider while implementing an FSO system. Typical gains and losses along the path from the transmitter through the medium to the receiver are introduced in this article. Detailed discussions of these topics can be found in this special issue of the Radioengineering Journal.

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32. EPPLE, B. A simplified channel model for simulation of free-space optical communications. Journal of Optical Communications and Networking, 2010, vol. 2, no. 5, p. 293 – 304.
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Keywords: Free-space optical communications, link budget, turbulence, fading.

M. S. Awan, E. Leitgeb, Marzuki, T. Plank [references] [full-text] [Download Citations]
A Study of Fog Characteristics using Free-Space Optical Wireless Links

A technique for modeling the fog droplet size distributions using modified gamma distribution has been demonstrated by considering two separate radiation fog events recorded in Graz (Austria) and Prague (Czech Republic). The measurement of liquid water content (LWC) and the optical attenuations at visible wavelength are used to form equations to obtain the three parameters of the modified gamma distribution i.e., the slope (Λ), the intercept (N0 ) and the shape parameter (m). Calculated attenuation or LWC from the retrieved parameters are in excellent agreement with attenuation or LWC obtained from the measurement. Hence this method is useful in the study of fog microphysics and in modeling the fog attenuations for terrestrial FSO links in situations when our measurement data contains values of attenuations only, or liquid water content only or both at a particular location. For the two case studies, Graz and Prague, we obtained the DSD parameters Λ=3.547 ± 1.935, N0 =3.834 ± 2.239, m=6.135 ± 2.692 and Λ=5.882 ± 2.889, N0 =13.41 ± 3.875, m=5.288 ± 3.113, respectively. It is evident that the observed behavior of computed modified gamma distribution parameters for Graz and Prague is closely the same and is consistent with the previous literature for the radiation (continental) fog. Moreover, we observed the variation of the computed DSD parameters at the different stages of fog (formation, maturity and dissipation phases) indicating different microphysical processes at each stage.

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Keywords: Free-space optics, optical attenuations, continental fog, droplet size distribution, modeling

F. Nadeem, E. Leitgeb [references] [full-text] [Download Citations]
Dense Maritime Fog Attenuation Prediction from Measured Visibility Data

The benefits of Free Space Optics (FSO) motivate to use it for future high data rate demanding communication applications. However, widespread growth of the technology has been hampered by reduced availability due to weather influences on the link. The fog has been analyzed as the most detrimental for FSO communication. There are some models that predict fog attenuation in terms of visibility. These models are compared with measured attenuation data of dense maritime fog. The comparison has been in terms of Sum of Square Error (SSE) and Root Mean Square Error (RMSE). A new model has been proposed that gives the least SSE and RMSE for the measured data.

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Keywords: FSO, Attenuation, Simulation, Fog, Model comparison

S. S. Muhammad, M. S. Awan, A. Rehman [references] [full-text] [Download Citations]
PDF Estimation and Liquid Water Content Based Attenuation Modeling for Fog in Terrestrial FSO Links

Terrestrial Free-space optical communication (FSO) links have yet to achieve a mass market success due to the ever elusive 99.999% availability requirement. The terrestrial FSO links are heavily affected by atmospheric fog. To design systems which can achieve high availability and reliability in the presence of fog, accurate and better models of fog attenuation need to be developed. The current article puts forth appropriate probability density function estimates for received signal strength (hereafter RSS) under fog conditions, where variations in the RSS during foggy events have been statistically characterized. Moreover, from the surface observations of fog density, liquid water content (hereafter LWC) of fog is estimated. The actual measured optical attenuations are then compared with the optical attenuations estimated from LWC. The results presented suggest that fog density measurements carried out are accurate representation of the fog intensity and the attenuation predictions obtained by the LWC estimate match the actual measured optical attenuations. This suggests that the LWC is a useful parameter besides visibility range to predict optical attenuations in the presence of hydrometeors.

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28. GULTEPE, I., TARDIF, R., MICHAELIDES, S. C., CERMAK, J., BOTT, A., BENDIX, J., MULLER, M. D., PAGOWSKI, M., HANSEN, B., ELLROD, G., JACOBS, W., TOTH, G., COBER, S. G. Fog research: A review of past achievements and future perspectives. Pure Applied Geophysics, 2007, vol. 164, p. 1121 – 1159.
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Keywords: Free Space Optics (FSO), Fog Modeling, Probability Density Function (PDF), Liquid Water Content (LWC), Drop Size Distribution (DSD)

J. Pesek, O. Fiser, J. Svoboda, V. Schejbal [references] [full-text] [Download Citations]
Modeling of 830 nm FSO Link Attenuation in Fog or Wind Turbulence

This study is focused on the experimental research of the atmosphere impact on FSO link attenuation. Experiment is performed on a mountain observatory Milesovka of severe weather conditions. The empirical relationships on 830 nm only between FSO attenuation A on one hand and atmospheric visibility V or wind turbulent energy ET on the other hand are presented and discussed. In the fog case it was found A= 401.4V-0.5738- 1.462 dB/60m (V in meters) while for the attenuation due to the wind turbulence ET it holds A = 2.112 - 2.213 exp(-0.2867ET) dB/60m (ET in m2s-2, it was derived for 830 nm wave length). A discussion concerning problems of the “clear air attenuation,” atmospheric turbulences and sun shine impact, which was observed as a maximum 2 dB attenuation for a few minutes with a period of 24 hours is added.

1. FISER, O. et al. Attenuation measurement on dual-wavelength optical free-space link. In Proc. of SPIE, session Atmospheric Optics: Models, Measurements and Target-in-the-Loop propagation III. San Diego (USA), 3-4 August 2009, pp. 7463-1 - 7463-11.
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3. KIM, I., MCARTHUR, B., KOREVAAR, E. Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications. In Proc. of SPIE – vol. 4214 Optical Wireless Communications III. Ed. Eric J. Korevaar, February 2001, pp. 26-37.
4. ANDREWS, L. C., PHILLIPS, R. L. Laser Beam Propagation through Random Media. SPIE Press, June 1998

Keywords: Free Space Optics propagation, fog attenuation, wind turbulence attenuation, turbulent energy

G. Soysal, M. Efe [references] [full-text] [Download Citations]
Kalman Filter Aided Cooperative Optical Beam Tracking

In free-space optical communication between mobile terminals relative motion of the terminals requires an active mechanism to maintain optical alignment between the stations. Cooperative optical beam tracking could be used to address this problem. In this alignment scheme, each station tracks the arrival direction of its impinging beam to employ it as a guide to precisely point its own beam toward the opposite station. Tracking is achieved at each station by a quadrant photodetector which generates simultaneous azimuth and elevation error voltages. In this study a Kalman filtering assisted cooperative optical beam tracking has been proposed and its suitability to cooperative beam tracking is discussed. In this method, Kalman filter is employed to predict the alignment error that is used to produce appropriate control signals for re-alignment. Performance of the proposed method has been demonstrated through simulations.

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8. BERNHARD, E. Using a GPS-aided inertial system for coarsepointing of free-space optical communication terminals. In Proceedings of the SPIE Free Space Laser Communications V, 2006, Vol. 6304.
9. YOSHIDA, K., TSUJIMURA, T. Tracking control of the mobile terminal in an active free-space optical communication system. In Proceedings of the SICE-ICASE International Joint Conference. Busan (Korea), 2006, p. 369-374.
10. SOFKA, J., NIKULIN, V. V., SKORMIN, V. A., HUGHES, D.H., LEGARE, D. J. Laser communication between mobile platforms. IEEE Transactions on Aerospace and Electronic Systems, 2009, vol. 45, no. 1, p. 336 - 346.
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Keywords: Free space optical communication, Kalman filtering, cooperative beam tracking, fine pointing

Y. Takayama, M. Toyoshima, N. Kura [references] [full-text] [Download Citations]
Estimation of Accessible Probability in a Low Earth Orbit Satellite to Ground Laser Communications

The accessible probability of a low-orbit satellite from ground is estimated by using images taken by a meteorological satellite and by analyzing visible passes of the satellite. The study indicates that the blockage by clouds in satellite-ground laser communications is almost avoidable by properly distributing several optical ground stations. For the calculation, we use an orbit information of a low-earth orbit satellite, the Optical Inter-orbit Communications Engineering Test Satellite (OICETS), as the counterpart of the optical ground stations. The calculation of the cumulative accessible probability shows the required time to achieve over 99% accessibility between the low orbit satellite and the optical ground stations.

1. JONO, T., TAKAYAMA, Y., OHINATA, K., KURA, N., KOYAMA, Y., ARAI, K., SHIRATAMA, K., SODNIK, Z., BIRD, A., DEMELENNE, B. Demonstrations of ARTEMIS- OICETS inter-satellite laser communications. In Proceedings of AIAA 24th International Communications Satellite Systems Conference. San Diego (USA), 2006, AIAA2006-5461, p. 1-7
2. TOYOSHIMA, M., TAKAHASHI, T., SUZUKI, K., KIMURA, S., TAKIZAWA, K., KURI, T., KLAUS, W., TOYODA, M., KUNIMORI, H., JONO, T., TAKAYAMA, Y., ARAI, K. Laser beam propagation in ground-to-OICETS laser communication experiments. In Proceedings of SPIE Defence and Security. Orland (USA), 2007, vol. 6551, 65510A, p.1-12.
3. PERLOT, N., KNAPEK, M., GIGGENBACH, D., HORWATH, J., BRECHTELSBAUER, M., TAKAYAMA, Y., JONO, T. Results of the optical downlink experiment KIODO from OICETS satellite to optical ground station Oberpfaffenhofen (OGS-OP). In Proceedings of SPIE Free-Space Laser Communication Technologies. San Jose (USA), 2007, vol. 6457, 645704, p. 1-8.
4. LANGE, R., SMUTNY, B., Homodyne BPSK-based optical intersatellite communication links. In Proceedings of SPIE Free-Space Laser Communication Technologies. San Jose (USA), 2007, vol. 6457, 645703, p. 1-9.
5. SMUTNY, B., LANGE, R., KAAMPFINER, H., DALLMANN, D., GREGORY, M., MUHLNIKEL, G. High data rate optical inter-satellite links. In Proceedings of ICSOS. Tokyo (Japan), 2009, pp. 1-5.
6. WILSON, K., KOVALIK, M., BISWAS, A., WRIGHT, M., ROBERTS, T., TAKAYAMA, Y., YAMAKAWA, S. Preliminary results of the OCTL to OICETS optical link experiment (OTOOLE). In Proceedings of SPIE Free-Space Laser Communication Technologies. San Francisco (USA), 2010, vol. 7587, 758703, p. 1-13.
7. TAKAYAMA, Y., TOYOSHIMA, M., SHOJI, Y., KOYAMA, Y., KUNIMORI, H., SAKAUE, M., YAMAKAWA, S., TASHIMA, Y., KURA, N. Expanded laser communications demonstrations with OICETS and ground stations. In Proceedings of SPIE Free-Space Laser Communication Technologies. San Francisco (USA), 2010, vol. 7587, 758712, p. 1-8.
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Keywords: Satellite-ground laser communications, optical ground stations, low earth orbit, OICETS

V. Kvicera, M. Grabner, O. Fiser [references] [full-text] [Download Citations]
Propagation Characteristics and Availability Performance Assessment for Simulated Terrestrial Hybrid 850 nm/58 GHz System

Results of a propagation study on a free space optical link at 850 nm on a path 853 meters long and on a parallel 58 GHz radio link obtained over a 3-year period of observation are presented. The cumulative distributions of attenuation due to all of the hydrometeors combined as well as due to individual hydrometeors were obtained for both paths. The availability performances of the FSO link, the RF link and the simulated hybrid FSO/RF system were assessed. Significantly higher availability performance was achieved for the simulated hybrid FSO/RF system than for the FSO link alone. The diversity improvement factor reached significant values for attenuation greater than 5 dB and a significant diversity gain was obtained for the percentages of time smaller than 2%.

1. KOREVAAR, E., KIM, I. I., McARTHUR, B. Atmospheric propagation characteristics of highest importance to commercial free space optics. In Proc. of SPIE, 2003, vol. 4976, p.1-12.
2. GEBHART, M., LEITGEB, E., MUHAMMAD, S. S., FLECKER, B., CHLESTIL, C. Measurement of light attenuation in dense fog conditions for FSO applications. In Proc. of SPIE, 2005, vol. 5891, p. 1-11.
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5. LEITGEB, E., GEBHART, M., BIRNBACHER, U., KOGLER, W., SCHROTTER, P. High availability of hybrid wireless networks. In Proc. of SPIE, 2004, vol. 5465, p. 238-249.
6. AKBULUT, A., EFE, M., CEYLAN, A. M., ARI, F., TELATAR, Z., ILK, H. G., TUGAC, S. An experimental hybrid FSO/RF communication system. In Proceeding (393) Communication Systems and Networks, 2003. Available at: http://www.actapress.com/PaperInfo.aspx?PaperID=13974&reaso n =500.
7. NADEEM, F., KVICERA, V., AWAN, M. S., LEITGEB, E., MUHAMMAD, S. S., KANDUS, G. Weather effects on hybrid FSO/RF communication link. IEEE Journal on Selected Areas in Communications, 2009, vol. 27, no. 9, p. 1687-1697.
8. KVICERA, V., GRABNER, M., FISER, O. Visibility and attenuation due to hydrometeors at 850 nm measured on an 850 m path. In Proc. of the Sixth International Symposium on Communication Systems, Networks and Digital Signal Processing (CSNDSP08). Graz (Austria), 2008, p. 270-272.
9. Rec. ITU-R P.1814 Prediction methods required for the design of terrestrial free-space optical links. ITU, Geneva (Switzerland), 2008.
10. Rec. ITU-R F.592-4 Vocabulary of terms for the fixed service. ITU, Geneva (Switzerland), 2008.
11. Rec. ITU-R P.530-12 Propagation data and prediction methods required for the design of terrestrial line-of-sight systems. ITU, Geneva (Switzerland), 2008.
12. Rec. ITU-R P.1410-3 Propagation data and prediction methods required for the design of terrestrial broadband millimetric radio access systems operating in a frequency range of about 20-50 GHz. ITU, Geneva (Switzerland), 2006.

Keywords: free space optical link, radio link, hybrid system, availability performance

F. Nadeem, S. Chessa, E. Leitgeb, S. Zaman [references] [full-text] [Download Citations]
The Effects of Weather on the Life Time of Wireless Sensor Networks Using FSO/RF Communication

The increased interest in long lasting wireless sensor networks motivates to use Free Space Optics (FSO) link along with radio frequency (RF) link for communication. Earlier results show that RF/FSO wireless sensor networks have life time twice as long as RF only wireless sensor networks. However, for terrestrial applications, the effect of weather conditions such as fog, rain or snow on optical wireless communication link is major concern, that should be taken into account in the performance analysis. In this paper, life time performance of hybrid wireless sensor networks is compared to wireless sensor networks using RF only for terrestrial applications and weather effects of fog, rain and snow. The results show that combined hybrid network with three threshold scheme can provide efficient power consumption of 6548 seconds, 2118 seconds and 360 seconds for measured fog, snow and rain events respectively resulting in approximately twice of the life time with only RF link.

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9. DENG, S., LIAO, J., RENA HUANG, Z., HELLA, M., CONNOR, K. Wireless connections of sensor network using RF and free space optical links. In Proc. SPIE vol.6773, 2007, pp. 677307-1- 677307-11.
10. FLECKER, B., GEBHART, M., LEITGEB, E., SHEIKH MUHAMMAD, S., CHLESTIL, C. Results of attenuation- measurements for Optical Wireless Channel under dense fog conditions regarding different wavelengths. In Proc. SPIE vol. 6303, 2006.
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34. http://news.thomasnet.com/fullstory/452488 as seen on 16.11.09
35. NADEEM, F., CHESSA, S., LEITGEB, E., AWAN, M. S., KANDUS, G. Comparing the life time of hybrid network using optical wireless and RF links to only RF link for terrestrial wireless sensor networks. Presented at IWCMC 09, France.
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Keywords: FSO, Fog, Hybrid network, Wireless sensor networks, Simulation.

A. Akbulut, H. A. Ilgin, M. Efe [references] [full-text] [Download Citations]
Adaptive Bit Rate Video Streaming Through an RF/Free Space Optical Laser Link

This paper presents a channel-adaptive video streaming scheme which adjusts video bit rate according to channel conditions and transmits video through a hybrid RF/free space optical (FSO) laser communication system. The design criteria of the FSO link for video transmission to 2.9 km distance have been given and adaptive bit rate video streaming according to the varying channel state over this link has been studied. It has been shown that the proposed structure is suitable for uninterrupted transmission of videos over the hybrid wireless network with reduced packet delays and losses even when the received power is decreased due to weather conditions.

1. CARBONNEAU, T. H., WISELY D. R. Opportunities and challenges for optical wireless; the competitive advantage of free space telecommunication links in today’s crowded marketplace. In SPIE Conference on Optical Wireless Communications. Massachusetts, 1998, p. 119-128.
2. WISELY, D. R., McCULLAGH, M. J., EARDLEY, P. L., SMYTH, P. P., LUTHRA, D., DE MIRANDA, E. C., COLE, R. S. 4-km terrestrial line-of-sight optical free-space link operating at 155 Mbit/s. Free Space Laser Communication Technologies VI, Proceedings of SPIE, vol. 2123, 1994, p. 108-119.
3. AKBULUT, A., EFE, M., CEYLAN, A. M., ARI, F., TELATAR, Z., ILK, H. G. An experimental hybrid FSO/RF communication system. In Proceedings of the IASTED International Conference on Communication System and Networks, CSN 2003, p. 406-411.
4. SMOLYANINOV, I., WASICZKO, L., CHO, K., DAVIS, C. Long-distance 1.2 Gb/s optical wireless communication link at 1550 nm. Free-Space Laser Communication and Laser Imaging, Proceedings of SPIE, vol. 4489, 2002, p. 241-250.
5. YIN, F. Optical interconnects for telecommunication and data communications. Optical Interconnects for Telecommunication and Data Communications, Proceedings of SPIE, vol. 4225, 2000, p. 223-227.
6. TAN, Y., GUO, JIAN-ZHONG. Study of channel model of freespace laser communications system. Free-Space Laser Communications V, Proceedings of SPIE, vol. 5892, 2005, pp.223 to 227.
7. MAJUMDAR, A. K., RICKLIN, J. C. Effects of the atmospheric channel on free-space laser communications. Free-Space Laser Communications V, Proceedings of SPIE, 2005, vol. 5892, p. 58920K.1-58920K.
8. MANOR, H., ARNON, S. Performance of an optical wireless communication system as a function of wavelength. Applied Optics, vol. 42 (21), 2003, p. 4285-4294.
9. NADEEM, F., LEITGEB, E., SALEEM AWAN, M., KANDUS, G. FSO/RF hybrid network availability analysis under different weather conditions. In Third International Conference on Next Generation Mobile Applications, Services and Technologies, IEEE Computer Society Press, p. 239-244, 2009.
10. ZHANG, W., HRANILOVIC, S., CE SHI. Soft-switching hybrid FSO/RF links using short-length raptor codes: Design and implementation. IEEE Journal on Selected Areas in Communications, vol. 27, no. 9, p. 1-11, December 2009.
11. NADEEM, F., LEITGEB, E., AWAN, M. S., KHAN, M. S., KANDUS, G. Throughput efficient solution for hybrid wireless network. In IEEE International Workshop on Satellite and Space Communications, 2008. IWSSC 2008., p. 316-320, 2008.
12. KIM, I., KOREVAAR, E. J. Availability of free-space optics (FSO) and hybrid FSO/RF systems. In Proceedings Optical Wireless Communications IV, vol. 4530, Eric J. Korevaar, Editors, p. 84-95, 2001.
13. TZUNG-HSIEN, H., SUGIANTO, T., ANIKET, D., JAIME, L., STUART, D. M., CHRISTOPHER, C. D. Performance and analysis of reconfigurable hybrid FSO/RF wireless networks. In Proceedings Vol. 5712, Free-Space Laser Communication Technologies XVII, G. Stephen Mecherle, Editors, p. 119-130, 18 April 2005.
14. KIM, I., McARTHUR, B., KOREVAAR, E. J. Comparison of laser beam propagation at 785 nm and 1550 nm in fog and haze for optical wireless communications. Optical Wireless Communications III, Proc. SPIE, vol. 4214 (26), 2001, p. 26-37.
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Keywords: Free space laser communication, link availability, adaptive video streaming.

T. Drizdal, P. Togni, L. Visek, J. Vrba [references] [full-text] [Download Citations]
Comparison of Constant and Temperature Dependent Blood Perfusion in Temperature Prediction for Superficial Hyperthermia

The purpose of this study was to determine whether prediction of the 3D temperature profile for superficial hyperthermia using constant blood perfusion model could be matched to one with a temperature dependent blood perfusion. We compared three different constant blood perfusion scenarios with one temperature dependent blood perfusion using a layered model of biological tissue consisting of skin (2 mm), fat (10 mm) and muscle (108 mm). For all four scenarios the maximum temperature of 43 °C was found in the muscle tissue in the close proximity (1 – 3 mm) of fat layer. Cumulative histograms of temperature versus volume were identical for the region of 100x100x40 mm3 under the applicator aperture for the three constant blood perfusion models. For temperature dependent blood perfusion model, 85 % of the studied region was covered with the temperature equal or higher than 40 °C in comparison with 43 % for the constant blood perfusion models. Hence this study demonstrates that constant blood perfusion scenarios cannot be matched to one with a temperature dependent blood perfusion.

1. OVERGAARD, J., GONZALEZ GONZALEZ, D., HULSHOF, M. C. C. H., ARCANGELI, G., DAHL, O., MELLA, O., BENTZEN, S. M. Hyperthermia as an adjuvant to radiation therapy of recurrent or metastatic malignant melanoma. A multicentre randomized trial by the European Society for Hypertermic Oncology. International Journal of Hyperthermia, 2009, vol. 25, no. 5, p. 323 – 334.
2. VAN DER ZEE, J., OVERGAARD, J. Hyperthermia classic commentary: 'Hyperthermia as an adjuvant to radiation therapy of recurrent or metastatic malignant melanoma. A multicentre randomized trial by the European Society for Hyperthermic Oncology' by J. Overgaard, D. Gonzalez Gonzalez, M.C.C.H. Hulshof, G. Arcangeli, O. Dahl, O. Mella & S.M. Bentzen, International Journal of Hyperthermia 1996;12:3–20. International Journal of Hyperthermia, 2009, vol. 25, no. 5, p. 335 – 337.
3. VERNON, C. C., HAND, J. W., FIELD, S. B., MACHIN, D., WHALEY, J. B., VAN DER ZEE, J., VAN PUTTEN, W. L. J., VAN RHOON, G. C., VAN DIJK, J. D. P., GONZALEZ, D. G., LIU, F., GOODMAN, P., SHERAR, M. Radiotherapy with or without hyperthermia in the treatment of superficial localized breast cancer: Results from five randomized controlled trials. International Journal of Radiation Oncology Biology Physics, 1996, vol. 35, no. 4, p. 731 – 744.
4. JONES, E., OLESON, J. R., PROSNITZ, L. R., SAMULSKI, T. V., VUJASKOVIC, Z., YU, D., SANDERS, L. L., DEWHIRST, M. W. Randomized trial of hyperthermia and radiation for superficial tumors. Journal of Clinical Oncology, 2005, vol. 23, no. 13, p. 3079 – 3085.
5. FRANCKENA, M., STALPERS, L., KOPER, P., WIGGENRAAD, R., HOOGENRAAD, W., VAN DIJK, J., WARLAM-RODENHUIS, C., JOBSEN, J., VAN RHOON, G., VAN DER ZEE, J. Long-term improvement in treatment outcome after radiotherapy and hyperthermia in locoregionally advanced cervix cancer: An update of the Dutch Deep Hyperthermia Trial. International Journal of Radiation Oncology Biology Physics, 2008, vol. 70, no. 4, p. 1176 – 1182.
6. ARUNACHALAM, K., MACCARINI, P., JUANG, T., GAETA, C., STAUFFER, R. P. Performance evaluation of a conformal thermal monitoring sheet sensor array for measurement of surface temperature distributions during superficial hyperthermia treatments. International J. Hyperthermia, 2008, vol. 24, no. 4, p. 313 – 325.
7. VAN DER ZEE, J., RIETVELD, P. J. M., BROEKMEYER-REIRINK, M. P., WIELHEESEN, D. H. M., VAN RHOON, G. C. Hyperthermia in recurrent breast cancer: From experimental oncology to standard practice. Experimental Oncology, 2002, vol. 24, no. 1, p. 45 – 50.
8. DE BRUIJNE, M., WIELHEESEN, D. H. M., VAN DER ZEE, J., CHAVANES, N., VAN RHOON, G. C. Benefits of superficial hyperthermia treatment planning: Five case study. International Journal of Hyperthermia, 2007, vol. 23, no. 5, p. 417 – 429.
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10. VAN RHOON, G. C., RIETVELD, P. J. M., VAN DER ZEE, J. A 433 MHz Lucite cone waveguide applicator for superficial hyperthermia. International Journal of Hyperthermia, 1998, vol. 14, no. 1, p. 13 – 27.
11. RIETVELD, P. J. M., PUTTEN, W. L. J., VAN DER ZEE, J., VAN RHOON, G. C. Comparison of the clinical effectiveness of the 433 MHz Lucite cone applicator with that of a conventional waveguide applicator in applications of superficial hyperthermia. International Journal of Radiation Oncology Biology Physics, 1999, vol. 43, no. 3, p. 681 – 687.
12. GELVICH, E. A., MAZOKHIN, V. N. Contact flexible microstrip applicators (CFMA) in a range from microwaves up to short waves. IEEE Transaction on Biomedical Engineering, 2002, vol. 49, no. 9, p. 1015 – 1023.
13. KOK, H. P., DE GREEF, M., CORREIA, D., ZUM VORDE SIVE VORDING, P. J., VAN STAM, G., GELVICH, E. A., BEL, A., CREZEE, J., FDTD simulations to asses the performance of CFMA- 434 applicators for superficial hyperthermia. International Journal of Hyperthermia, 2009, vol. 25, no. 6, p. 462 – 476.
14. STAUFFER, P. R., ROSSETTO, F., LEONCINI, M., GENTILLI, G. B., Radiation patterns of dual concentric conductor microstrip antennas for superficial hyperthermia. IEEE Transaction on Biomedical Engineering, 1998, vol. 45, no. 5, p. 605 – 613.
15. JOHNSON, J. E., NEUMAN, D. G., MACCARINI, P. F., JUANG, T., STAUFFER, P. R., TURNER, P. Evaluation of a dual-arm archimedean spiral array for microwave hyperthermia. International Journal of Hyperthermia, 2006, vol. 22, no. 6, p. 475 – 490.
16. VAN WIERINGEN, N., WIERSMA, J., ZUM VORDE SIVE VORDING, P. J. , OLDENBORG, S., GELVICH, E. A., MAZOKHIN, V. N., VAN DIJK, J. D. P., CREZEE, J. Characteristic and performance evaluation of the capacitive Contact Flexible Microstrip Applicator operating at 70 MHz for external hyperthermia. International Journal of Hyperthermia, 2009, vol. 25, no. 7, p. 542 – 553.
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19. LANG, J., ERDMANN, B., SEEBASS, M. Impact of nonlinear heat transfer on temperature control in regional hyperthermia. IEEE Transaction on Biomedical Engineering, 1999, vol. 46, no. 9, p. 1129 – 1138.
20. SONG, CH. W., LOKSHINA, A., RHEE, J. G., PATTEN, M, LEVITT, S. H. Implication of blood flow in hyperthermia treatment of tumours. IEEE Transaction on Biomedical Engineering, 1984, vol. 31, no. 1, p. 9 – 16.
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22. VAN DER GAAG, M. L., DE BRUIJNE, M., SAMARAS, T., VAN DER ZEE, J., VAN RHOON, G. C. Development of a guideline for the water bolus temperature in superficial hyperthermia. International Journal of Hyperthermia, 2006, vol. 22, no. 8, p. 637 – 656.
23. DE BRUIJNE, M., SAMARAS, T., BAKKER, J. F., VAN RHOON, G. C. Effects of water bolus size, shape and configuration on the SAR distribution pattern of the Lucite cone applicator. International Journal of Hyperthermia, 2006, vol. 22, no. 1, p. 15 – 28.
24. GABRIEL, S., LAU, R. W., GABRIEL, C. The dielectric properties of biological tissues: III. Parametric models for the dielectric spectrum of tissues. Physics in Medicine and Biology, 1996, vol. 41, no. 11, p. 2271 – 2293. [Online] Available at: http://niremf.ifac.cnr.it/tissprop/
25. Treatment Planning and Modeling in Hyperthermia (technical report). COMAC BMR Task Group Report. Rome (Italy): University of Rome, 1992.
26. KUMARADAS, J. C., SHERAR, M. D. Edge-element based finite element analyses of microwave hyperthermia treatments for superficial tumours on the chest wall. International Journal of Hyperther- mia, 2003, vol. 19, no. 4, p. 414 – 430.
27. DE BRUIJNE, M., SAMARAS, T., CHAVANNES, N., VAN RHOON, G. C. Quantitative validation of the 3D SAR profile of hyperthermia applicators using the gamma method. Physics in Medicine and Biology, 2007, vol. 46, no. 14, p. 3075 – 3088.
28. ARUNACHALAM, K., MACCARINI, P. F., SCHLORFF, J. L., BIRKELUND, Y., JACOBSEN, S., STAUFFER, P. R. Design of a water coupling bolus with improved flow distribution for multi- element superficial hyperthermia applicators. International Journal of Hyperthermia, 2009, vol. 25, no. 7, p. 554 – 565.
29. WYATT, C., SOHER, B., MACCARINI, P., CHARLES, H. C., STAUFFER, P., MACFALL, J. Hyperthermia MRI temperature mea- surement: Evaluation of measurement stabilisation strategies for ex- tremity and breast tumours. International Journal of Hyperthermia, 2009, vol. 25, no. 6, p. 405 – 415.
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Keywords: Superficial hyperthermia, bioheat equation, blood perfusion, SAR, temperature prediction

J. Lacik [references] [full-text] [Download Citations]
Filtering Technique for Stabilization of Marching-on-in-Time Method

In this paper, digital filters are used for the stabilization of the marching-on-in-time (MOT) method. A methodology of designing a proper filter using optimization techniques is proposed here. Since the proposed procedure considers the important part of the spectrum of the excitation signal, the designed filter does not degrade the accuracy of the MOT method. Further, the procedure for the efficient stabilization of the MOT method by a set of filters is proposed and verified on the examples.

1. RAO, S. M., Time Domain Electromagnetics. London: Academic Press, 1999, ch. 2 – 5.
2. CHUNG, Y. S., et al. Solution of time domain electric field integral equation using the Laguerre polynomials. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 9, p. 2319 – 2328.
3. WANG, X., WILDMAN, R. A., WEILE, D. S., MONK, P. A finite discretization delay modeling approach to the discretization of the time domain integral equations of electromagnetism. IEEE Transactions on Antennas and Propagation, 2008, vol. 56, no. 8, p. 2442 - 2452.
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5. MANARA, G. et al. A space-time discretization criterion for a stable time-marching solution of the electric field integral equation. IEEE Transactions on Antennas and Propagation, 1997, vol. 45, no. 3, pp. 527 - 532.
6. WEILE, S. D., PISHARODY, G., CHEN, N. - Y., SHANKER, B., MICHIELSSEN, E. A novel scheme for the solution on the time- domain integral equations of electromagnetics. IEEE Transactions on Antennas and Propagation. 2004, vol. 52, no. 1, p. 283 – 295.
7. VECHINSKI, A. D. et al. A stable procedure to calculate the transient scattering by conducting surfaces of arbitrary shape. IEEE Transactions on Antennas and Propagation. 1992, vol. 40, no. 6, p. 661 - 665.
8. DAVIS, P. J. On the stability of time-marching schemes for the general surface electric field integral equation. IEEE Transactions on Antennas Propagation, 1996, vol. 44, no. 11, p. 1467 – 1473.
9. SADIGH, A., ARVAS, E. Treating the instabilities in marching- on-in-time method from a different perspective. IEEE Transactions on Antennas Propagation, 1993, vol. 41, no. 12, p. 1695 – 1702.
10. JAN, J. Digital Signal Filtering, Analysis and Restoration. Brno: Brno University of Technology, 1997, ch. 5. (In Czech).
11. ROBINSON, J., RAMAT-SAMII, Y. Particle swarm optimization in electromagnetics. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 2, p. 397 – 407.
12. MAKAROV, S. N. Antenna and EM Modeling with Matlab. New York: John Wiley & Sons, 2002, ch. 7.

Keywords: Time domain electric field integral equation, method of moments, marching on in time method, stability, filtering technique.

J. Puskely, Z. Novacek [references] [full-text] [Download Citations]
Exploiting of the Compression Methods for Reconstruction of the Antenna Far-Field Using Only Amplitude Near-Field Measurements

The novel approach exploits the principle of the conventional two-plane amplitude measurements for the reconstruction of the unknown electric field distribution on the antenna aperture. The method combines a global optimization with a compression method. The global optimization method (GO) is used to minimize the functional, and the compression method is used to reduce the number of unknown variables. The algorithm employs the Real Coded Genetic Algorithm (RCGA) as the global optimization approach. The Discrete Cosine Transform (DCT) and the Discrete Wavelet Transform (DWT) are applied to reduce the number of unknown variables. Pros and cons of methods are investigated and reported for the solution of the problem. In order to make the algorithm faster, exploitation of amplitudes from a single scanning plane is also discussed. First, the algorithm is used to obtain an initial estimate. Subsequently, the common Fourier iterative algorithm is used to reach global minima with sufficient accuracy. The method is examined measuring the dish antenna.

1. JUNKIN, G., BENNET, J. C., HUANG, T. Holographic near-field /far-field for therahertz antenna testing. In Proceedings of 19th Antenna Measurement Tech. Assoc. Meet. Symposium. Boston (USA, MA), Nov. 1997, p. 419 - 423.
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4. YACCARINO, R. G., RAHMAT-SAMII, Y. Phaseless bi-polar planar near-field measurements and diagnostics of array antennas. IEEE Transactions on Antennas and Propagation, 1999, vol. 47, no. 3, p. 574 – 583.
5. PUSKELY, J., NOVACEK, Z. Application of the global optimization approaches to planar near-field antenna phaseless measurements. Radioengineering, 2009, vol. 18, no. 1, p. 9 - 17.
6. TKADLEC, R., NOVACEK, Z. Radiation pattern reconstruction from the near-field amplitude measurement on two planes using PSO. Radioengineering, 2005, vol. 14, no. 4, p. 63 - 67.
7. RAZAVI, S. F., RAHMAT-SAMII, Y. A new look at phaseless planar near-field measurements: limitations, simulations, measurements, and a hybrid solution. IEEE Antennas and Propagation Magazine, 2007, vol. 49, no. 2, p. 170 - 178.
8. COSTANZO, S., DI MASSA, G., MIGLIORE, M. D. A novel hybrid approach for far-field characterization from near-field amplitude-only measurements on arbitrary scanning surfaces. IEEE Transactions on Antennas and Propagation, 2005, vol. 53, no. 6, p. 1866 - 1874.
9. LAS-HERAS, F., SARKAR, T.-K. A direct optimization approach for source reconstruction and NF-FF transformation using amplitude-only data. IEEE Transactions on Antennas and Propagation, 2002, vol. 50, no. 4, p. 500 - 510.
10. PUSKELY, J., NOVACEK, Z. New look to Real Valued Genetic Algorithm used to reconstruct radiation patterns. In Proceedings of the 15th Conference Radioelektronika 2009. Bratislava (Slovakia), 2009, p. 299 - 302.
11. PUSKELY, J., NOVACEK, Z. Reconstruction of antenna radiation pattern at 310 GHz using image compression methods. In Proceedings of the 4th European Conference on Antennas and Propagation EuCAP 2010, 2010.
12. VON LERBER, A., VIIKARI, V., LISENO, A., ALA- LAURINAHO, J., RAISANEN, A. V. A feasibility study of phase retrieval algorithms at sub-millimeter wavelengths. In Proceedigns of the 27th Annual Antenna Measurement Techniques Association (AMTA) Meeting & Symposium. Newport (RI, USA), 2005, p. 79 to 84.
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Keywords: Planar near-field scanning, near-field far-field transform (NF-FF), global optimization, compression method, Fourier iterative algorithm

M. Pokorny, Z. Raida [references] [full-text] [Download Citations]
Transmission Line on Semiconductor Substrate with Distributed Amplification

In order to compensate losses in metal strips, an active microstrip line on a semiconductor substrate is proposed, and its finite element model is presented. The active medium is provided by A3B5 semiconductor in highintensity electric field. The simple model of the active media is developed and used for calculation of the propagation properties of the fundamental mode and for the thermal analysis of the device. The problem of system self-oscillation is discussed and empirical stability criteria are introduced. A proper heat-sink is proposed to provide the operation in a continuous regime.

1. LYUBCHENKO, V. E. The Science and Technology of Millimetre Wave Components and Devices. Electrocomponent Science Monographs, vol. 12. London: Taylor & Francis, 2003.
2. LIOUBTCHENKO, D., TRETYAKOV, S., DUDOROV, S. Millimeter-Wave Waveguides. Boston: Kluwer Academic Publishers, 2003.
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5. POKORNY, M., RAIDA, Z. Active semiconductor waveguides and antennas. In Proceedings of 4th Workshop on Antenna Systems and Sensors for Information Society Technologies. Dublin, Trinity College (Ireland), 2008, p. 132 – 137
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7. ZHANG, M., WU, C., WU, K., LITVA, J. Losses in GaAs microstrip and coplanar waveguide. In Proceedings of Microwave Symposium Digest, 1992, IEEE MTT-S International, 1-5 June 1992, vol. 2, p. 971 - 974.
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Keywords: GaAs, active, mictrostrip, millimeter-wave, Gunn’s effect, thermal, COMSOL

Z. Kejik, J. Drinovsky, V. Ruzek [references] [full-text] [Download Citations]
Estimation of the EMI Filter Circuitry from the Insertion Loss Characteristics

The paper deals with the EMI filter models for the calculation of the insertion loss characteristics. The insertion loss is in fact the basic EMI filter property. Unfortunately it is not easy to precisely define and measure this parameter in a wide frequency range due to variability of terminating impedances. The uncertainty of the potential impedance termination really complicates the measurements and also comparison of the performance of filters. A model with spurious components is introduced in this paper. The procedure model design is also added up. The spurious components make together with the real ones form resonant circuits. The resonance frequencies make breakages in the insertion loss characteristic. Their resonance frequencies were identified by the analysis of equivalent circuits of the filter for different measuring systems. The calculation of the values of spurious components, based on knowledge of resonance frequencies, is mentioned at the end of the paper.

1. CSN CISPR 17: Methods of Measurement of the Suppression Characteristics of Passive Radio Interference Filters and Suppression Components. Czech Technical Standard. Prague: Czech Normalization Institute, 2000. 27 pages. (in Czech).
2. Schaffner, Switzerland. Using 50 Ω Attenuation Curves to: Compare Filter Performances; Select Second Sources; Do Incoming Inspection. (application note). [Online] Cited 2009-08-08. Available at http://www.schaffner.com/components/en/ pdf/ technical informations/.
3. DRINOVSKY, J., OLIVA, L. Modeling of performance of EMI filter. In Zvule 2007. Brno (Czech Republic): FEEC BUT, 2007, p. 20 – 23. (in Czech).
4. DRINOVSKY, J., SVACINA, J., RAIDA, Z. Simple models of EMI filters for low frequency range. Radioengineering, 2008, vol. 17, no. 3, p. 8 – 14.
5. BIOLEK, D. Solving Electrical Circuits. Prague: BEN, 2004. (in Czech).
6. DRINOVSKY, J., SVACINA, J. Estimation of EMI filter performance for the “worst-case” system. Radioengineering, 2006, vol. 15, no. 4, p. 16 – 21.
7. TIHANYI, L. Electromagnetic Compatibility in Power Electronics. The IEEE Press, 2004.
8. ROBINSON, J., RAHMAT-SAMII,Y. Particle swarm optimization in electromagnetics. IEEE Transactions on Antennas and Propagation, 2004, vol. 52, no. 2, p. 397 – 407.

Keywords: Insertion loss, EMI filter, current compensated inductor, spurious component, MNVM, Modified Nodal Voltage Method

K. H. Yeap, C. Y. Tham, K. C. Yeong, H. J. Woo [references] [full-text] [Download Citations]
Wave Propagation in Lossy and Superconducting Circular Waveguides

We present an accurate approach to compute the attenuation of waves, propagating in circular waveguides with lossy and superconducting walls. A set of transcendental equation is developed by matching the fields at the surface of the wall with the electrical properties of the wall material. The propagation constant kz is found by numerically solving for the root of the equation. The complex conductivity of the superconductor is obtained from the Mattis-Bardeen equations. We have compared the loss of TE11 mode computed using our technique with that using the perturbation and Stratton’s methods. The results from the three methods agree very well at a reasonable range of frequencies above the cutoff. The curves, however, deviate below cutoff and at millimeter wave frequencies. We attribute the discrepancies to the dispersive effect and the presence of the longitudinal fields in a lossy waveguide. At frequencies below the gap, the superconducting waveguide exhibits lossless transmission behavior. Above the gap frequency, Cooper-pair breaking becomes dominant and the loss increases significantly.

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Keywords: Circular waveguides, superconductor, propagation constant, dispersive effect, Cooper-pair

J. Horng, H. Lee, J. Wu [references] [full-text] [Download Citations]
Electronically Tunable Third-Order Quadrature Oscillator Using CDTAs

A current/voltage-mode third-order quadrature oscillator based on current differencing transconductance amplifiers (CDTAs) is presented in this paper. Outputs of two current-mode and two voltage-mode sinusoids each with 90o phase difference are available in the quadrature oscillator circuit. The oscillation condition and oscillation frequency are independently controllable. The proposed circuit employs only grounded capacitors and is ideal for integration. Simulation results are included to confirm the theoretical analysis.

1. SEDRA, A. S., SMITH, K. C. Microelectronic Circuits. 4th edition. New York: Oxford University Press, pp. 984-986, 1998.
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6. SOLIMAN, A. M. Synthesis of grounded capacitor and grounded resistor oscillators. Journal of the Franklin Institute, 1999, vol. 336, p. 735-746.
7. HORNG, J. W. Current differencing buffered amplifiers based single resistance controlled quadrature oscillator employing grounded capacitors. IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, 2002, vol. E85-A, p. 1416-1419.
8. HORNG, J. W. Current-mode quadrature oscillator with grounded capacitors and resistors using two DVCCs. IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, 2003, vol. E86-A, p. 2152-2154.
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14. HORNG, J. W., HOU, C. L., CHANG, C. M., CHENG, S. T., SU, H. Y. Current or/and voltage-mode quadrature oscillators with grounded capacitors and resistors using FDCCIIs. WSEAS Transactions on Circuits and Systems, 2008, vol. 7, p. 129-138.
15. KESKIN, A. U., AYDIN, C., HANCIOLU, E., ACAR, C. Quadrature oscillator using current differencing buffered amplifiers (CDBA). Frequenz, 2006, vol. 60, p. 21-23.
16. TANGSRIRAT, W., PISITCHALERMPONG, S. CDBA-based quadrature sinusoidal oscillator. Frequenz, 2007, vol. 61, p. 102- 104.
17. KESKIN, A. U., BIOLEK, D. Current mode quadrature oscillator using current differencing transconductance amplifiers (CDTA). IEE Proc.-Circuits, Devices and Systems, 2006, vol. 153, p. 214- 218.
18. JAIKLA, W., SIRIPRUCHYANUN, S., BAJER, J., BIOLEK, D. A simple current-mode quadrature oscillator using single CDTA. Radioengineering, 2008, vol. 17, p. 33-40.
19. BIOLEK, D. CDTA-Building block for current-mode analog signal processing. In Proceedings of the ECCTD’03, Krakow, Poland, 2003, vol. III, p. 397-400.
20. KESKIN, A. U., BIOLEK, D., HANCIOGLU, E., BIOLKOVA, V. Current-mode KHN filter employing current differencing transconductance amplifiers. AEU International Journal of Electronics and Communications, 2006, vol. 60, p. 443-446.
21. TANGSRIRAT, W., TANJAROEN, W. Current-mode multiphase sinusoidal oscillator using current differencing transconductance amplifiers. Circuits, Systems and Signal Processing, 2008, vol. 27, p. 81-93.
22. BIOLEK, D., BIOLKOVA, V., KESKIN, A. Current mode quadrature oscillator using two CDTAs and two grounded capacitors. In Proceedings of the 5th WSEAS Int. Conf. on System Science and Simulation in Engineering. Tenerife, Canary Islands, (Spain), December 16-18, 2006, p. 368-370.
23. TANGSRIRAT, W. Current differencing transconductance amplifier-based current-mode four-phase quadrature oscillator. Indian Journal of Engineering and Material Sciences, 2007, vol. 14, p. 289-294.
24. HORNG, J. W. Current-mode third-order quadrature oscillator using CDTAs. Active and Passive Electronic Components, 2009, Article ID 789171, p. 1-5.
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Keywords: Current differencing transconductance amplifiers, quadrature oscillator, current-mode, voltage-mode, active circuit

Z. Tothova, J. Polec [references] [full-text] [Download Citations]
A Novel Technique of Error Concealment Method Selection in Texture Images Using ALBP Classifier

There are many error concealment techniques for image processing. In the paper, the focus is on restoration of image with missing blocks or macroblocks. Different methods can be optimal for different kinds of images. In recent years, great attention was dedicated to textures, and specific methods were developed for their processing. Many of them use classification of textures as an integral part. It is also of an advantage to know the texture classification to select the best restoration technique. In the paper, selection based on texture classification with advanced local binary patterns and spatial distribution of dominant patterns is proposed. It is shown, that for classified textures, optimal error concealment method can be selected from predefined ones, resulting then in better restoration. For testing, three methods of extrapolation and texture synthesis were used.

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14. SHU LIAO, CHUNG, A. C. S. Texture Classification by using Advanced Local Binary Patterns and Spatial Distribution of Dominant Patterns. In Acoustics, Speech and Signal Processing, ICASSP 2007. 15-20 April 2007, vol. 1, p.I-1221-I-1224.
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23. POLEC, J., POHANCENIK, M., ONDRUSOVA, S., KOTULIAKOVA, K., KARLUBIKOVA, T. Error concealment for classified texture images. In EUROCON 2009: International IEEE Conference devoted to the 150-Anniversary of Alexander S. Popov. Saint Petersburg (Russia), 2009, p. 1348-1353.
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25. POLEC, J., KARLUBIKOVA, T. Discrete orthogonal transform for gappy image extrapolation. In Proceedings of Computer Vision and Graphics International Conference, ICCVG 2004. Warsaw (Poland), September 2004, Proceedings, Series: Computational Imaging and Vision, vol. 32, Springer, 2005, pp. 222-227.
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Keywords: Error concealment, re-synthesis, inpainting, texture, extrapolation, classification

R. Stukavec, T. Kratochvil [references] [full-text] [Download Citations]
Simulation and Measurement of the Transmission Distortions of the Digital Television DVB-T/H (Part 1: Modulator for Digital Terrestrial Television)

The paper deals with the first part of results of the Czech Science Foundation research project that was aimed into the simulation and measurement of the transmission distortions of the digital terrestrial television according to DVB-T/H standards. In this part the modulator performance characteristics and its simulation and laboratory measurements are presented with focus on typical DVB-T/H broadcasting scenario – large SFN network for fixed reception. The paper deals with the COFDM modulator imperfections and I/Q errors influence on the DVB-T/H signals and the related I/Q constellation analysis. Impact of the modulator imperfections on Modulation Error Rate from I/Q constellation and Bit Error Rates before and after Viterbi decoding in DVB-T/H signal decoding are evaluated and discussed.

1. REIMERS, U. Digital Video Broadcasting, The Family of International Standards for Digital Television. 2nd ed. Berlin: Springer, 2004.
2. FISHER, W. Digital Video and Audio Broadcasting. A Practical Engineering Guide. 2nd ed. Berlin: Springer, 2008.
3. ETSI EN 300 744 V1.6.1 (2009-01). Digital Video Broadcasting (DVB), Framing structure, channel coding and modulation for digital terrestrial television. European Standard. Sophia Antipolis (France): ETSI, 2009.
4. ETSI TS TS 101 191 V1.4.1 (2004-06). Digital Video Broadcasting (DVB), Mega-frame for Single Frequency Network (SFN) synchronization. Technical Specification. Sophia Antipolis (France): ETSI, 2004.
5. ETSI TR 101 290 V1.2.1 (2001-05). Digital Video Broadcasting (DVB), Measurement guidelines for DVB systems. Technical Report. Sophia Antipolis (France): ETSI, 2001.
6. ETSI EN 302 304 V1.1.1 (2004-11). Digital Video Broadcasting (DVB), Transmission system for handheld terminals. European Standard. Sophia Antipolis (France): ETSI, 2004.
7. ETSI TR 102 377 V1.4.1 (2009-06). Digital Video Broadcasting (DVB), Implementation guidelines for DVB handheld services. Technical Report. Sophia Antipolis (France): ETSI, 2009.
8. BUCHOLZ, M., SCHUCHERT, A., HASHOLZNER, R. Effects of tuner IQ imbalance on multicarrier-modulation systems. In Proceedings of the 2000 Third IEEE International Caracas Conference on Devices, Circuits and Systems. Cancun (Mexico), 2000, p. T65/1 – T65/6.
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Keywords: I/Q modulator, I/Q modulation error, Amplitude Imbalance, Phase Error, Carrier Suppression, COFDM, DVB-T/H

C. Tao, J. Qiu, L. Liu [references] [full-text] [Download Citations]
A Novel OFDM Channel Estimation Algorithm with ICI Mitigation over Fast Fading Channels

Orthogonal frequency-division multiplexing (OFDM) is well-known as a high-bit-rate transmission technique, but the Doppler frequency offset due to the high speed movement destroys the orthogonality of the subcarriers resulting in the intercarrier interference (ICI), and degrades the performance of the system at the same time. In this paper a novel OFDM channel estimation algorithm with ICI mitigation based on the ICI self-cancellation scheme is proposed. With this method, a more accurate channel estimation is obtained by comb-type double pilots and then ICI coefficients can be obtained to mitigate the ICI on each subcarrier under the assumption that the channel impulse response (CIR) varies in a linear fashion. The theoretical analysis and simulation results show that the bit error rate (BER) and spectral efficiency performances are improved significantly under high-speed mobility conditions (350 km/h – 500 km/h) in comparison to ZHAO’s ICI self-cancellation scheme.

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6. KIM, B. C., LU, I. T. Doppler diversity for OFDM wireless mobile communications. Part I: Frequency domain approaches. In Proceedings of IEEE Vehicular Technology Conference. Florida (USA), 2003, vol. 4, p. 2677 – 2681.
7. GE, R., SUN, S. ICI Performance analysis for all phase OFDM systems. Journal of Electromagnetic Analysis and Applications, 2009, p. 118 – 123.
8. LIU, Y., JIANG, W., YAO, C., et al. Doubly selective channel estimation based on fractional basis expansion model. Acta Scientiarum Naturalium Universitatis Pekinensis, 2008, vol. 44, no. 1, p. 87 – 91.
9. PAATZOLD, M. Mobile Fading Channels Modelling, Analysis and Simulation. West Sussex (UK): Wiley, 2002.
10. JEON, W. G., CHANG, K. H., CHO, Y. S. An equalization technique for orthogonal frequency division multiplexing systems in time-variant multipath channels. IEEE Transaction on Communications, 1999, vol. 47, no. 1, p. 27 – 32.
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12. LIU, L., TAO, C., QIU, J. H., et al. A novel comb-pilot transform domain frequency diversity channel estimation for OFDM system. Radioengineering, 2009, vol. 18, no. 4, p. 497 – 502.
13. MOSTOFI, Y., COX, D. C., BAHAI, A. ICI mitigation for mobile OFDM receivers, In Proceedings of IEEE International Conference on Communications (ICC). Alaska (USA), 2003, vol. 5, p. 3351 – 3355.
14. NAKAMURA, M. T., SEKI, M., ITAMI, K. et al. New estimation and equalization approach for OFDM under Doppler-spread channel. In Proceedings of Indoor Mobile Radio Communications (PIMRC). Lisbon (Portugal), 2002, vol. 2, p. 555 – 560.
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Keywords: OFDM system, channel estimation, high-speed mobility, ICI mitigation

M. R. Islam, J. Kim [references] [full-text] [Download Citations]
Quasi Cyclic Low Density Parity Check Code for High SNR Data Transfer

An improved Quasi Cyclic Low Density Parity Check code (QC-LDPC) is proposed to reduce the complexity of the Low Density Parity Check code (LDPC) while obtaining the similar performance. The proposed QC-LDPC presents an improved construction at high SNR with circulant sub-matrices. The proposed construction yields a performance gain of about 1 dB at a 0.0003 bit error rate (BER) and it is tested on 4 different decoding algorithms. Proposed QC-LDPC is compared with the existing QC-LDPC and the simulation results show that the proposed approach outperforms the existing one at high SNR. Simulations are also performed varying the number of horizontal sub matrices and the results show that the parity check matrix with smaller horizontal concatenation shows better performance.

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14. LAN, L., ZENG, L., TAI, Y. Y., CHEN, L., LIN, S., GHAFFAR, K. A. Construction of Quasi-Cyclic LDPC Codes for AWGN and binary erasure channels: A finite field approach. IEEE Transactions on Information Theory, July 2007, vol. 53, no. 7.
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19. ZHAO, S., ZHENG, B., WANG, W. Construction of quantum Low Density Parity Check Code based on quasi-cyclic sparse sequence. In International Conference on Communications and Networking in China, 2008.
20. WU, X., YOU, X., ZHAO, C. A necessary and sufficient condition for determining the girth of Quasi-Cyclic LDPC Codes. IEEE Transactions on Communications, June 2008, vol. 56, no. 6, pp. 854-857.
21. MALEMA, G., LIEBELT, M. Quasi-cyclic LDPC codes of column-weight two using a search algorithm. EURASIP Journal on Advances in Signal Processing, 2007. doi:10.1155/2007/45768.
22. WANG, Y., YEDIDIA, J. S., DRAPER, D S. C. Construction of high-girth QC-LDPC codes. In International Symposium on Turbo Codes and Related Topics, 2008.
23. KIM, S., NO, J. S., CHUNG, H., SHIN, D. J. Cycle analysis and construction of protographs for QC LDPC codes with girth larger than 12. In IEEE International Symposium on Information Theory, June 2007.
24. KIM, J., RAMAMOORTHY, A., MCLAUGHLIN, S. W. Design of Efficiently-Encodable Rate-Compatible Irregular LDPC Codes. ICC, 2006.
25. WU, X., LING, C., JIANG, M., XU, E., ZHAO, C., YOU, X. Towards understanding weighted bit-flipping decoding. In IEEE International Symposium on Information Theory, June 2007.
26. ZHANG, J., FOSSORIER, M. A modified weighted bit-flipping decoding of low-density parity-check codes. IEEE Communication Letter, 2004, pp. 165–167.

Keywords: Low Density Parity Check codes, Quasi Cyclic Low Density Parity Check codes, SNR, bit error rate, circulant sub matrix, parity check matrix, generator matrix

J. Hajny [references] [full-text] [Download Citations]
Anonymous Authentication for Smartcards

The paper presents an innovative solution in the field of RFID (Radio-Frequency IDentification) smartcard authentication. Currently the smartcards are used for many purposes - e.g. employee identification, library cards, student cards or even identity credentials. Personal identity is revealed to untrustworthy entities every time we use these cards. Such information could later be used without our knowledge and for harmful reasons like shopping pattern scanning or even movement tracking. We present a communication scheme for keeping one’s identity private in this paper. Although our system provides anonymity, it does not allow users to abuse this feature. The system is based on strong cryptographic primitives that provide features never available before. Besides theoretical design of the anonymous authentication scheme and its analysis we also provide implementation results.

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19. SCHAFFER, M., SCHARTNER, P. Anonymous authentication with optional shared anonymity revocation and linkability. In Seventh Smart Card Research and Advanced Application IFIP Conference CARDIS 2006. Tarragona (Spain), 2006, p. 206 – 221.
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Keywords: RFID, privacy, anonymity, cryptography, authentication, smartcards