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Uwb antenna for on-body communications
We who also investigate the problem of optimal redundancy allocation between the blocks of such heterogeneous coding structures. Another objective of this research is to apply iterative processing on advanced quantization methods such as trellis coded quantization. Abstract, there is a great interest in the automotive and military sectors for small and broadband antennas that meet modern communication needs. These needs require ultra-wide bandwidth ( 10:1) uwb antennas, such as the spiral english antenna. However, the physical size at the low-frequency end typically becomes too large for practical applications. To reduce the size of the antenna, miniaturization techniques must be employed such as the use of high-contrast dielectric materials. Size reduction using high-contrast materials has been demonstrated for narrowband antennas, such as patch antennas, but not for broadband antennas to our knowledge. Therefore, the concept of miniaturizing a broadband spiral antenna using dielectric materials will be investigated experimentally and sues that arise from dielectric loading such as impedance reduction will also be addressed. It will be shown using the results from these studies that there are practical limitations to the amount of miniaturization which can be achieved.
Turbo Space-time Equalization for wimax system. Team: Mutlu koca, we consider space-time turbo equalization methods for complex coded modulation signals transmitted over broadband wireless channels, which is characterized by severe multipath fading as envisioned by ieee 802.16 standard. The multipath fading channel, protected by an encoder/decoder pair, is described as a convolutional encoder and the received signal is viewed as the output of a serially concatenated coding system. It is well known that in the narrowband transmission case, the equivalent encoder model for the channel can be represented by reasonable complexity and optimum symbol detection is achieved by iterative equalization/decoding schemes where soft-information is shared between the constituent decoders. However, for fixed wireless systems operating at high data rates, the multipath delay spread becomes large which makes direct application of trellis based equalization methods impossible. Turbo Processing for Video over. Team: ceyhan Kasap, mutlu koca, we investigate the joint use of multiple description coding and channel coding for systems transmitting data over heterogeneous networks so as to achieve resilience against packet losses and protection against channel errors. Observing that the two coding blocks form a serial concatenated code, we consider a turbo decoding scheme passing gps soft messages between a siso channel decoder and a source reconstructor.
By introducing additional diversity, user cooperation improves capacity and decreases outage probability. In this project we investigate different yardage ways of implementing cooperative communications in diary uwb systems. Major challenge is the frequency selective nature of the uwb channel, which introduces isi and breaks down the orthogonality of the signals transmitted from different users. Space-time-polarization Codes, team: Onur ozyesil, mutlu koca, mimo communications systems employing space-time codes are known to have huge performance gains over single antenna systems. The capacity of the mimo systems can be further increased -theoretically doubled- if the systems use dual polarized antennas. For this reason, in this project we investigate the use of dual polarized antennas in space-time block coded systems and evaluate the theoretical limits of the performance and design iterative receiver architectures which overcome the cross-polar interference, channel fading and spatial and polarization correlation effects. Multitone Interference in mimo-ofdm systems. Team: Celal Esli, hakan Delic, we consider mimo ofdm systems subject to mult-tone interference and derive the analytical bounds for the anti-jamming performance of space-frequency coding in these systems. We also design iterative receivers for joint interference cancellation and space-frequency detection for ostbc coded ofdm systems.
Team: Ersen Ekrem, mutlu koca, hakan Delic. The research conducted for this thesis aims to find robust solutions to timing acquisition and channel estimation for ultra wideband systems subject to non-gaussian noise. Low power constraints on the uwb systems, using very short pulses to obtain higher rates and the multipath channel with extreme delay spread makes these problems more challenging with respect to other spread spectrum systems. For timing acquisition, noncoherent methods,. The methods that do not employ a priori channel knowledge, are investigated and for channel estimation, frequency-domain techniques inspired by single-carrier frequency domain equalization are explored. For robust detection and estimation, minimax robust techniques such as m-estimates, least favorable pair, are employed. Ultra-wideband User cooperative networks, team: Ozgur Dalkilic, cumhur oazan Yalcin, mutlu koca. Ultra wideband communication devices, which are restricted in size and power, can achieve some benefits of the mimo systems by means of user cooperation. Cooperation between single-antenna users involves transmission of the same data by partners hence creation of a virtual antenna array.
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The receiver performance is analyzed via exit charts. As another solution to reduce the receiver complexity, a space-time pre-equalizer is proposed for cpm. The proposed method preserves the spectral efficiency by allowing small envelope variations. Since the channel equalization functions are moved to the transmitter, the receiver performs cpm demodulation only. For coded cpm, further performance gain can be obtained by exploiting demodulation/decoding iterations at the receiver.
Robust Multiuser Detection in Ultra-wideband Systems. Team: nazli guney, hakan Delic, uwb transmission, where information is sent over impulse-like radio (IR) waveforms, has emerged as an exciting technology for commercial wireless communication systems essay and local area networking. Despite their advantages especially in short range, such as low power consumption, carrier-free transmission, utilization of low-complexity transceivers, capability to co-exist with existing broadband systems, ultra wideband systems can only be realized after major design issues have been solved. Our research in this area involves the design low-power uwb multiple access schemes with low complexity multi-user receivers. Our investigation involves code optimization for multiple access protocols, transceiver design for uwb systems employing time-hopping and multi-band orthogonal pulses, design of low complexity demodulation and decoding structures and interference cancellation algorithms, space-time signal processing to enable the use of multiple transmit/receive antennas in uwb. Robust Signal Acquisition and Detection in Ultra-wideband Systems.
Months 10-12, assessment and characterization of fabb-ed antenna(s). Priliminary results, months 13-16, redesign and fab of best antenna based on previous assessment. Measured results, months 17-18, final writeup. Thesis/publication, veiledere: Tor sverre lande, ifi. Kristian Kjelgård, ifi, mats høvin, ifi, publisert.
Below is a list of current or recent research topics we work on with brief summaries. For details please contact to any of the team members listed under each project. Advanced Transceiver Design for Continuous Phase modulation. Team: Baris Ozgul, mutlu koca, hakan Delic. This research aims to propose efficient transmitter and receiver designs for continuous phase modulation (cpm which is a non-linear modulation scheme with excellent power and bandwidth properties. The research topics include the application of iterative receiver algorithms, precoding, and space-time processing for cpm as mentioned below. The optimal joint equalization/demodulation of cpm signals over frequency-selective multipath fading channels encounter computational problems because of the intensive search performed over a single super trellis. In the thesis, soft-input soft-output linear time-domain/frequency-domain equalizer algorithms are devised for coded cpm, which are followed by cpm demodulator and the channel decoder. Near optimum performance is attained with low-complexity by employing iterative processing.
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The users at iris will be involved in antenna assessment. The project the is suitable for fuller students with background in electromagnetics and with interest in real world used involving modeling and measurements with advanced rf equipment. Workplan periode task, results, month 1-3, study for literature and understand requirements for matched antenna. Learn to use instruments in MilliLab. Potential antenna shapes and sizes. Months 3-6, modeling and simulation of antennas in 3d em tools. Months 7-9, detailed model for 3D fabrication, first fabricated antenna.
Normally the relative dielectric constant is used as describing rf properties of materials (vacuum1). Provided the observed material time does not have too high relative dielectric constant, ensuring proper coupling using matched antennas, surface reflections are removed and significant energy is penetrating the material. In general, antennas close to the material ( quarter wavelength) provide coupling, but such rf radiators tend to have wide beams giving wide exposure and minimal gain. Focused antenna are growing in depth and are often called horn antennas. The exposing material must be extended into the horn (hard to do with a stone or the human body). However, suitable foam may be used ensuring proper antenna match. Such antennas are rarely found in the literature and are a good topic for. Project with significant potential for good science (publishable). The project will be carried out in the milliLab facilities at ifi in collaboration with antenna manufacturing at the robin group.
emerged. One of them came from ifi and is now commercially available from novelda. Unlike traditional radar, these systems are small and suited for short-range sensing and imaging. In order to detect object, these reflection are desirable and useful. However, radiowaves also have interesting penetration properties. We know even weak gps signals in mobile devices are detectable even inside concrete buildings. However, some materials like metals are highly conductive and absorb radiated energy converting it to currents. Other materials like concrete and stone may also be good rf shields.
In order to avoid such reflections, dedicated antennas matched for the material to expose are required. Then air/material reflections are removed and rf energy is released into the material provided minimal air is present in the signal path (coupled antenna). The Iris research Institute in Stavanger reviews home) is exploring radar inspection of sandstone to determine salt-water saturation. Even detection of water-front in the porous stone during the saturation process is interesting as well as saturation profile. Project will model, design a directional antenna matched for sandstone water saturation using microwave rf signals. Both conductance as well as permittivity may provide indications. A suitable antenna will be fabricated either in aluminum or on a 3D printer coated with conductive paint. The measurements will be analyzed with researchers from the iris institute.
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Infoscience Infoscience latest documentsenFri, 13:27:44 gmtinvenio 360125gInfoscience search search this site:p/search. Focused and matched antenna for pulsed radar in different matter. The use of radar technology as sensors has emerged lately because miniaturized radar solutions operational at short range have become available. The sensing capability of radar is based on backscattering (reflection) of radiowaves (RF) from object, a phenomena happening with radiowaves are travelling in air/vacuum and hit some surface with different dielectric properties. New technology has enabled small and accurate radar systems suitable for short-range operation. Such resumes miniaturization opens for new and interesting applications of radar exploring rf penetration abilities for inspecting solid or opaque objects. However, penetration of heavy materials is prevented due to reflections (scattering) from the air/material dielectric differences.