Loran-C is a navigational aid that relies on the ability to make correct estimates of the Times of Arrival (TOAs) of signals received over a noisy radio channel. How good is the performance of Loran-C in this respect? Is it close to... more
Loran-C is a navigational aid that relies on the ability to make correct estimates of the Times of Arrival (TOAs) of signals received over a noisy radio channel. How good is the performance of Loran-C in this respect? Is it close to optimal? Are there perhaps better estimation techniques available than we currently employ? In this paper we use Estimation Theory to find the optimal limit of the accuracy of TOA estimates, for a given signalto-noise ratio (SNR). Specifically, we compute the Cramer-Rao Lower Bound (CRLB) which specifies the absolute minimum error variance that can be achieved by an unbiased estimator. From the CRLB we can estimate the best repeatable accuracy that can be attained using a set of TOAs. We compute here the CRLBs for the TOA of a Loran-C signal with both Additive White Gaussian Noise (AWGN) and Additive Coloured Gaussian Noise (ACGN). We then employ the Maximum Likelihood Estimator (MLE) and compare its results with that of CRLB. Simulation results show tha...
Analysis of Depolarizing Effects and Impact on the Performance of a Multiple Satellite System Employing Polarization Diversity
Research Interests:
The amount of radiation emitted from most cell phones is minute. However, given the close proximity of the phone to the head, it might be possible for the radiation to cause harm. If you want to be on the safe side, the easiest way to... more
The amount of radiation emitted from most cell phones is minute. However, given the close proximity of the phone to the head, it might be possible for the radiation to cause harm. If you want to be on the safe side, the easiest way to minimize the radiation you are exposed to is to place the antenna as far as possible from your head. Utilizing a hands-free kit, a car-kit antenna or a cell phone whose antenna is even a couple of inches farther from the head can do this most effectively. The main objective of this paper is to investigate the possibility of applying adaptive active control methods with the aim of lowering the electromagnetic field power flow density at a specific volume in space using the superposition principle and the full space-time processing (i.e. multiple antennas at both the transmitter and receiver side or MIMO) antenna system setup. In this paper we will present the different active control signal processing algorithms (e.g., the Filtered X-LMS, Filtered X-NLM...
Research Interests:
The Impact of Depolarizing Effects on a Multiple HAP System Employing Polarization Diversity
Analytical Multiple-Input Multiple-Output (MIMO) models are often attractive due to their low complexity when analyzing possibilities and limitations in the system. In this paper we outline a a possible dual link extension of an... more
Analytical Multiple-Input Multiple-Output (MIMO) models are often attractive due to their low complexity when analyzing possibilities and limitations in the system. In this paper we outline a a possible dual link extension of an analytical MIMO channel model and investigate its suitability based on measurements of a dual link MIMO scenario. The extension is based on the correlation matrix distance (CMD) as a gauge to generate correlation matrices for the additional links of the multi-link scenario.
Research Interests:
Loran-C is a navigational aid that relies on the ability to make correct estimates of the Times of Arrival (TOAs) of signals received over a noisy radio channel. How good is the performance of Loran-C in this respect? Is it close to... more
Loran-C is a navigational aid that relies on the ability to make correct estimates of the Times of Arrival (TOAs) of signals received over a noisy radio channel. How good is the performance of Loran-C in this respect? Is it close to optimal? Are there perhaps better estimation techniques available than we currently employ? In this paper we use Estimation Theory to find the optimal limit of the accuracy of TOA estimates, for a given signal-to-noise ratio (SNR). Specifically, we compute the Cramer-Rao Lower Bound (CRLB) which specifies the absolute minimum error variance that can be achieved by an unbiased estimator. From the CRLB we can estimate the best repeatable accuracy that can be attained using a set of TOAs. We compute here the CRLBs for the TOA of a Loran-C signal with both Additive White Gaussian Noise (AWGN) and Additive Coloured Gaussian Noise (ACGN). We then employ the Maximum Likelihood Estimator (MLE) and compare its results with that of CRLB. Simulation results show th...
Research Interests:
Research Interests:
Abstract. In this paper we propose a new approach em-ploying adaptive active control algorithms combined with a Multiple-Input Multiple-Output (MIMO) antenna system to suppress the electromagnetic field at a certain volume in space (e.g.,... more
Abstract. In this paper we propose a new approach em-ploying adaptive active control algorithms combined with a Multiple-Input Multiple-Output (MIMO) antenna system to suppress the electromagnetic field at a certain volume in space (e.g., at the human head). We will investigate the effects of the size and number of MIMO antenna elements on the system performance and test the algorithms at dif-ferent carrier frequencies (e.g., GSM bands and UMTS).
Research Interests:
Active suppression of noise and vibrations is a well established field of research with many applications in acoustic and mechanical industries. In this report we test some of these active control methods combined with MIMO antenna system... more
Active suppression of noise and vibrations is a well established field of research with many applications in acoustic and mechanical industries. In this report we test some of these active control methods combined with MIMO antenna system in order to assess their validity and performance when applied to electromagnetic fields. The application that we evaluated is a model of a mobile phone equipped with one ordinary transmitting antenna and a number of actuator-antennas which purpose is to cancel out the electromagnetic field at a specific volume in space (e.g. at the human head) while maintaining a predefined level of the overall output power of the system. This power control is achieved through the use of a quadratic constraint on the active control algorithm. In addition, we will also investigate the impact of MIMO antenna parameters and carrier frequency on the performance of the system. Simulation results show the promise of using the adaptive control algorithms and MIMO system ...
ABSTRACT Active suppression of noise and vibrations is a well established field of research with many applications in acoustic and mechanical industries. In this paper we test some of these active control methods combined with MIMO... more
ABSTRACT Active suppression of noise and vibrations is a well established field of research with many applications in acoustic and mechanical industries. In this paper we test some of these active control methods combined with MIMO antenna system in order to assess their validity and performance when applied to electromagnetic fields. The application that we evaluated is a model of a mobile phone equipped with one ordinary transmitting antenna and two actuator-antennas which purpose is to cancel out the electromagnetic field at a specific volume in space (e.g. at the human head) while maintaining a predefined level of the overall output power of the system. This power control is achieved through the use of a quadratic constraint on the active control algorithm. Simulation results show the promise of using the adaptive control algorithms and MIMO system to attenuate the electromagnetic field power density.
Research Interests:
Active suppression of noise and vibrations is a well established field of research with many applications in acoustic and mechanical industries. In this paper we investigate the possibility of applying these adaptive active control... more
Active suppression of noise and vibrations is a well established field of research with many applications in acoustic and mechanical industries. In this paper we investigate the possibility of applying these adaptive active control methods with the aim of lowering the electromagnetic power density at a specific volume in space using the superposition principle and space-time processing employing the full MIMO (Multiple Input Multiple Output) antenna system setup. The application that we evaluated is a model of a mobile phone equipped with one ordinary transmitting antenna and two actuator-antennas whichpurpose is to cancel out the electromagnetic field at the human head while maintaining a predefined level of the overall output power of the system. This power control is achieved through the use of a quadratic constraint on the active control algorithm. Simulation results show the promise of using the adaptive control algorithms and MIMO system to attenuate the electromagnetic field ...
ABSTRACT In this paper we investigate the wave propagation effects of a short‐range wireless device, like the Bluetooth, in an indoor office environment. Specifically, we investigate line of sight (LOS) and non line of sight (NLOS)... more
ABSTRACT In this paper we investigate the wave propagation effects of a short‐range wireless device, like the Bluetooth, in an indoor office environment. Specifically, we investigate line of sight (LOS) and non line of sight (NLOS) propagation scenarios and verify the theoretical statistics of the fading using real measurements and finite element method (FEM) simulations of the environment. The simulations are also used for assessing the impact on propagation when doors are opened or closed. In addition, we also investigate the improvement in performance resulting from receive diversity gain of a system employing multiple receive antennas with various combining techniques. © 2006 American Institute of Physics
Research Interests:
Research Interests:
Research Interests:
Research Interests:
AbstractIn this paper we assess the multipath propagation effects of a short-range wireless device operating at 2.4 GHz in an indoor office environment. The investigations are carried out using FEM simulations and measurement trials for... more
AbstractIn this paper we assess the multipath propagation effects of a short-range wireless device operating at 2.4 GHz in an indoor office environment. The investigations are carried out using FEM simulations and measurement trials for NLOS and LOS propagation ...
Research Interests:
Abstract In this paper we address the potential gain of using various compact MIMO antenna array configurations in conjunction with HAP (high altitude platforms) diversity techniques in order to enhance the data rates in HAP communication... more
Abstract In this paper we address the potential gain of using various compact MIMO antenna array configurations in conjunction with HAP (high altitude platforms) diversity techniques in order to enhance the data rates in HAP communication systems. We also investigate the ...
Research Interests:
Abstract In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP diversity techniques in order to increase the data rates in HAP communication systems. Simulation results show... more
Abstract In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP diversity techniques in order to increase the data rates in HAP communication systems. Simulation results show that the MIMO system ...
Research Interests:
Abstract Correlation between different links is an essential characteristic for many of the forthcoming radio communication systems that utilize the multiple-input-multiple-output (MIMO) technology. This paper investigates the physical... more
Abstract Correlation between different links is an essential characteristic for many of the forthcoming radio communication systems that utilize the multiple-input-multiple-output (MIMO) technology. This paper investigates the physical phenomena that cause the inter-...
Research Interests:
ABSTRACT Reliable characterization of the propagation environment and channel modelling of mobile satellite communication systems is necessary in order to provide better quality of service and efficient design of these systems. In this... more
ABSTRACT Reliable characterization of the propagation environment and channel modelling of mobile satellite communication systems is necessary in order to provide better quality of service and efficient design of these systems. In this paper, the channel impairments affecting the performance and an overview of the satellite channel models are presented. The statistical distributions of the received signal that can be used to characterize the dynamic nature of these propagation channels are also presented. The main modelling parameters are investigated and simulation results show that the bit error rate (BER) performance is predominantly affected by the shadowing factor. Finally, in order to further test the channel models and the effect of the propagation environment, we investigate a novel application of using satellite diversity in conjunction with compact MIMO (multiple‐input multiple‐output) antenna array configurations in order to enhance the capacity of satellite communication links.
Research Interests:
In this paper we investigate the possibility of multiple HAP coverage of a common cell area. In particular we study the uplink system performance since it is considered as a worst case scenario. In order to obtain further enhancement... more
In this paper we investigate the possibility of multiple HAP coverage of a common cell area. In particular we study the uplink system performance since it is considered as a worst case scenario. In order to obtain further enhancement (interference mitigation) we also apply space-time diversity techniques, such as Single-Input Multiple-Output (SIMO) receive diversity or Multiple-Input Multiple-Output (MIMO) diversity, to
Research Interests:
... of Electrical and Information Technology, Lund University PO Box 118, SE-221 00 Lund, Sweden {tommy.hult, fredrik.tufvesson}@.eit.lth.se # SMARAD CoE, Aalto University, School of Science and ... [7] J. Salo, P. Suvikunnas, HM... more
... of Electrical and Information Technology, Lund University PO Box 118, SE-221 00 Lund, Sweden {tommy.hult, fredrik.tufvesson}@.eit.lth.se # SMARAD CoE, Aalto University, School of Science and ... [7] J. Salo, P. Suvikunnas, HM El-Sallabi and P. Vainikainen, Ellipticity Statistic ...
Research Interests:
... Department ofSignal Processing, Blekinge Institute ofTechnology 372 25 Ronneby, Sweden 1 tommy.hult 4bth.se 3 abbas.mohammed 4bth.se Department ofElectronics, University ofYork York, YOIO 5DD, UK 2 dg 4ohm.york.ac.uk* ... [14] MA... more
... Department ofSignal Processing, Blekinge Institute ofTechnology 372 25 Ronneby, Sweden 1 tommy.hult 4bth.se 3 abbas.mohammed 4bth.se Department ofElectronics, University ofYork York, YOIO 5DD, UK 2 dg 4ohm.york.ac.uk* ... [14] MA Vazquez-Castro, D. Belay-Zelek and ...
Research Interests:
Abstract The evaluation of uplink performance of delivering WiMAX services from high altitude platforms (HAPs) is presented. System performance is assessed in terms of coexisting capability with terrestrial WiMAX system, employing... more
Abstract The evaluation of uplink performance of delivering WiMAX services from high altitude platforms (HAPs) is presented. System performance is assessed in terms of coexisting capability with terrestrial WiMAX system, employing directive antenna models ...
Research Interests:
Abstract Antennas that are able to direct the transmitted and received signals' energy are of great interest for future wireless communication systems. The directivity implies reduced transmit power and interference, and hence... more
Abstract Antennas that are able to direct the transmitted and received signals' energy are of great interest for future wireless communication systems. The directivity implies reduced transmit power and interference, and hence potential for increased capacity. In this paper ...
Research Interests:
... Tommy Hult (Lund University, Sweden), and Abbas Mohammed (Blekinge Institute of Technology, Sweden) Sample PDF | More details... ... Automated Solar Feature Detection for Space Weather Applications (pages 207-225). David Pérez-Suárez... more
... Tommy Hult (Lund University, Sweden), and Abbas Mohammed (Blekinge Institute of Technology, Sweden) Sample PDF | More details... ... Automated Solar Feature Detection for Space Weather Applications (pages 207-225). David Pérez-Suárez (Trinity College Dublin, Ireland ...
ABSTRACT In this paper we study the depolarization effects caused weather conditions and scattering structures at ground level on the performance of a multiple satellite system employing multi-polarized compact MIMO antenna... more
ABSTRACT In this paper we study the depolarization effects caused weather conditions and scattering structures at ground level on the performance of a multiple satellite system employing multi-polarized compact MIMO antenna configurations. In order to reinforce the analysis, we first propose a novel multichannel simulator that produces realistic time-series of the fading process affecting signal transmission in satellite communication environments. The proposed simulator takes into account the temporal, spatial and polarization properties affecting these processes. Finally, we analyse the impact of depolarization on the total capacity of the tetrahedron Compact MIMO antenna system. Simulation results show a significant drop in performance as the cross polar discrimination decreases.
Abstract The subspace eigen-decomposition algorithms are applied to the problem of detecting ionospheric interfering signals affecting the performance of Loran-C receivers. In particular, we are interested in measuring the delay of these... more
Abstract The subspace eigen-decomposition algorithms are applied to the problem of detecting ionospheric interfering signals affecting the performance of Loran-C receivers. In particular, we are interested in measuring the delay of these interfering Loran-C skywave ...
... of Electrical and Information Technology, Lund University, Sweden Email: fredrik.harrysson@ ericsson.com, {tommy.hult, fredrik.tufvesson}@eit.lth.se ... For the measurements we used the MedavRUSK Lund channel sounder in the frequency... more
... of Electrical and Information Technology, Lund University, Sweden Email: fredrik.harrysson@ ericsson.com, {tommy.hult, fredrik.tufvesson}@eit.lth.se ... For the measurements we used the MedavRUSK Lund channel sounder in the frequency band 2570–2630 MHz, and the signal ...
Research Interests:
ABSTRACT In this paper we propose a multi-channel simulator that produces a realistic time-series of the fading process affecting signal transmission in satellite systems. The proposed simulator takes into account the temporal, spatial... more
ABSTRACT In this paper we propose a multi-channel simulator that produces a realistic time-series of the fading process affecting signal transmission in satellite systems. The proposed simulator takes into account the temporal, spatial and polarization properties affecting these processes. In addition, we determine the impact on the total capacity of an application that utilizes the spatial-polarization channels for high data rate transmission system using multiple satellites. A significant drop in performance can be seen in the system as the cross polar discrimination decreases.
Space-time processing techniques have emerged as one of the most promising areas of research and development in wireless communications. Space-time processing signifies the signal processing performed on a system consisting of several... more
Space-time processing techniques have emerged as one of the most promising areas of research and development in wireless communications. Space-time processing signifies the signal processing performed on a system consisting of several antenna elements, whose signals are processed adaptively in order to exploit both the spatial (space) and temporal (time) dimensions of the radio channel. Space-time processing techniques can be applied at the transmitter, the receiver or both. The use of space-time signal processing can significantly improve average signal power, mitigating fading, and reduce inter-symbol interference and co-channel interference. This can significantly improve capacity, coverage and quality of wireless systems. In this thesis we expand the scope of space-time processing by proposing novel applications in wireless communications. These include the reduction of possibly harmful electromagnetic radiation from mobile phones, enhancing link quality for Bluetooth links in i...
Loran-C is a navigational aid that relies on the ability to make correct estimates of the Times of Arrival (TOAs) of signals received over a noisy radio channel. How good is the performance of Loran-C in this respect? Is it close to... more
Loran-C is a navigational aid that relies on the ability to make correct estimates of the Times of Arrival (TOAs) of signals received over a noisy radio channel. How good is the performance of Loran-C in this respect? Is it close to optimal? Are there perhaps better estimation techniques available than we currently employ? In this paper we use Estimation Theory to find the optimal limit of the accuracy of TOA estimates, for a given signal-to-noise ratio (SNR). Specifically, we compute the Cramer-Rao Lower Bound (CRLB) which specifies the absolute minimum error variance that can be achieved by an unbiased estimator. From the CRLB we can estimate the best repeatable accuracy that can be attained using a set of TOAs. We compute here the CRLBs for the TOA of a Loran-C signal with both Additive White Gaussian Noise (AWGN) and Additive Coloured Gaussian Noise (ACGN). We then employ the Maximum Likelihood Estimator (MLE) and compare its results with that of CRLB. Simulation results show th...
Research Interests:
In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with High Altitude Platforms (HAPs) diversity techniques in order to increase the capacity in HAP communication systems. For... more
In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with High Altitude Platforms (HAPs) diversity techniques in order to increase the capacity in HAP communication systems. For this purpose, we also propose a novel compact MIMO antenna which we denote as the "MIMO-Octahedron" and compare its performance with the vector element antenna. Simulation results show that the MIMO-Octahedron antenna provides superior performance to the vector element antenna and the single HAP case.
Research Interests:
In this paper we propose a novel combination of orthogonal frequency division multiplexing (OFDM) and the orbital angular momentum (OAM) of the electromagnetic field to produce a novel orthogonal momentum division multiplexing (OMDM)... more
In this paper we propose a novel combination of orthogonal frequency division multiplexing (OFDM) and the orbital angular momentum (OAM) of the electromagnetic field to produce a novel orthogonal momentum division multiplexing (OMDM) technique. This OMDM technique is applied to a satellite diversity system employing three satellites. Simulation results show that the proposed OMDM-satellite diversity system can achieve a theoretic N-fold increase in system capacity as compared with a system utilizing OFDM only.
ABSTRACT In this paper we study the depolarization effects caused by rain and ice particles in the troposphere on the performance of a multiple HAP (high altitude platforms) system employing multi-polarized compact MIMO antenna... more
ABSTRACT In this paper we study the depolarization effects caused by rain and ice particles in the troposphere on the performance of a multiple HAP (high altitude platforms) system employing multi-polarized compact MIMO antenna configurations. In order to reinforce the analysis, we first propose a novel multi-channel simulator that produces realistic time-series of the fading process affecting signal transmission in HAP systems. The proposed simulator takes into account the temporal, spatial and polarization properties affecting these processes. Finally, we analyse the impact of depolarization on the total capacity of the system. Simulation results show a significant drop in performance as the cross polar discrimination decreases.
Research Interests:
Abstract In this paper we address the potential gain of using various compact MIMO antenna array configurations in conjunction with HAP (high altitude platforms) diversity techniques in order to enhance the data rates in HAP communication... more
Abstract In this paper we address the potential gain of using various compact MIMO antenna array configurations in conjunction with HAP (high altitude platforms) diversity techniques in order to enhance the data rates in HAP communication systems. We also investigate the ...
Research Interests:
... Networks (pages 1-13). Seema Ansari (Karachi Institute of Economics and Technology, Pakistan), Syeda Fariha Hasnain (Karachi ... Sciences, Pakistan), Waseem Shahzad (National University of Computer and Emerging Sciences, Pakistan),... more
... Networks (pages 1-13). Seema Ansari (Karachi Institute of Economics and Technology, Pakistan), Syeda Fariha Hasnain (Karachi ... Sciences, Pakistan), Waseem Shahzad (National University of Computer and Emerging Sciences, Pakistan), and Farrukh Aslam Khan (National ...
Research Interests:
ABSTRACT In this paper we assess the effects of multipath propagation on the link performance of a short-range wireless device, like the Bluetooth, in an indoor office environment. Specifically, we analyze the non line of sight (NLOS)... more
ABSTRACT In this paper we assess the effects of multipath propagation on the link performance of a short-range wireless device, like the Bluetooth, in an indoor office environment. Specifically, we analyze the non line of sight (NLOS) propagation scenario and confirm the theoretical statistics of the fading using real measurements and finite element method (FEM) simulations of the environment. The simulations are also used for assessing the impact of multipath propagation when doors are opened or closed. In addition, we also investigate the improvement in performance resulting from receive diversity gain of a system employing multiple receive antennas with various combining techniques.
Research Interests:
ABSTRACT In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with satellite diversity techniques in order to increase the data rates in satellite communication systems. Simulation... more
ABSTRACT In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with satellite diversity techniques in order to increase the data rates in satellite communication systems. Simulation results show that by exploiting the additional multiple polarization channels and satellite diversity we can achieve considerable capacity gain compared to the single satellite case.
Research Interests:
... Tommy Hult, Abbas Mohammed Blekinge Institute of Technology, 372 25 Ronneby Sweden Email:tommy.hult@bth.se, Email: abbas.mohammed@bth.se ABSTRACT ... 127-137, June 2001. Page 5. [6] Thornton, J., Grace, D., Spillard, C., Konefal, T.... more
... Tommy Hult, Abbas Mohammed Blekinge Institute of Technology, 372 25 Ronneby Sweden Email:tommy.hult@bth.se, Email: abbas.mohammed@bth.se ABSTRACT ... 127-137, June 2001. Page 5. [6] Thornton, J., Grace, D., Spillard, C., Konefal, T. and Tozer, TC “Broadband ...
Research Interests:
Abstract In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with satellite diversity techniques in order to increase the data rates in satellite communication systems. We will... more
Abstract In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with satellite diversity techniques in order to increase the data rates in satellite communication systems. We will also investigate the effects of separation ...
Research Interests:
In this paper we investigate the possibility of multiple HAP coverage of a common cell area. In particular we study the uplink system performance since it is considered as a worst case scenario. In order to obtain further enhancement... more
In this paper we investigate the possibility of multiple HAP coverage of a common cell area. In particular we study the uplink system performance since it is considered as a worst case scenario. In order to obtain further enhancement (interference mitigation) we also apply space-time diversity techniques, such as Single-Input Multiple-Output (SIMO) receive diversity or Multiple-Input Multiple-Output (MIMO) diversity, to
Research Interests:
... Ericsson Research, Sweden {mikael.coldrey,patrik.c.persson}@ericsson.com Lund University, Sweden tommy.hult@eit.lth.se Chalmers University of Technology, Sweden andreas.wolfgang@ chalmers.se ... Kolmonen, T. Riihonen, R. Wichman, P.... more
... Ericsson Research, Sweden {mikael.coldrey,patrik.c.persson}@ericsson.com Lund University, Sweden tommy.hult@eit.lth.se Chalmers University of Technology, Sweden andreas.wolfgang@ chalmers.se ... Kolmonen, T. Riihonen, R. Wichman, P. Vainikainen, JI. ...
Research Interests:
Abstract In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP diversity techniques in order to increase the data rates in HAP communication systems. Simulation results show... more
Abstract In this paper we address the potential gain of using compact MIMO antenna array configurations in conjunction with HAP diversity techniques in order to increase the data rates in HAP communication systems. Simulation results show that the MIMO system ...