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Alexis Ariza

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Central European University

Università di Bologna

Yannis Hamilakis

Brown University

Field Museum

Stephen Whittle

Manchester Metropolitan University

Johns Hopkins University

University of Genova

Cosmin Sebastian Cercel

Ghent University

Hungarian Academy of Sciences

European University at St. Petersburg

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Papers by Alexis Ariza

An Unusual Complication of Laparoscopy: Pneumopericardium

Endoscopy, 1980

Case report of a 17-year-old man with acute bridging hepatitis in whom laparoscopy was followed b... more

La camisa

The Modern Language Journal, 1970

La camisa

Hispania, 1969

60 GHz short-range communications: channel measurements, analysis, and modeling

International Journal of Microwave and Wireless Technologies, 2011

60 GHz short-range communications: channel measurements, analysis, and modeling alexis paolo garc... more 60 GHz short-range communications: channel measurements, analysis, and modeling alexis paolo garcia ariza 1 , uwe trautwein 2 , robert mu ¤ ller 1 , frank wollenschla ¤ger 1 , reiner s. thoma ¤ 1 , ju ¤ rgen kunisch 3 , itziar de la torre 3 , robert felbecker 4 , michael peter 4 and wilhelm keusgen 4

60 GHz ultrawideband front-ends with gain control, phase shifter, and wave guide transition in LTCC technology

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

... 91080, Uttenreuth, Germany 1-3{mueller.robert, frank.wollenschlaeger, alexander.schulz, matth... more

60 GHz polarimetric MIMO sensing: Architectures and technology

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

ABSTRACT Millimeter-Wave (mm-W) is considered a potential technology for high-data rate wireless ... more ABSTRACT Millimeter-Wave (mm-W) is considered a potential technology for high-data rate wireless transmission and for high-resolution short-range radar, due to the 7-9 GHz bandwidth at the 60 GHz unlicensed band available worldwide. Developing ultrawideband architectures including multiple-input-multiple-output (MIMO) antenna systems at mm-W offer many advantages including jointly optimized analogue and digital signal processing at carrier frequency and baseband. This allows for flexible antenna designs and reduced losses, as many passive structures can be avoided at both sides of the link. Besides, based on flexible polarimetric approaches, the polarimetric propagation of electromagnetic waves can be exploited. In this paper we present a 60 GHz polarimetric MIMO system architecture, which includes analogue miniaturized frontends designed and manufactured by multi-layer packaging technologies. Such architecture permitted the design of compact MIMO radar and multi-dimensional channel sounding. The MIMO approach allows not only polarimetric filtering and fully polarimetric/directional signal processing to increase the signal-to-clutter-plus-noise ratio of mm-W radar systems, but also the full characterization of wireless channels including multipath with orthogonal polarizations.

A wideband 60 GHz differential stripline-to-waveguide transition for antenna measurements in low-temperature co-fired ceramics technology

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

ABSTRACT Modern communication systems require an ever increasing bandwidth for high data-rate com... more ABSTRACT Modern communication systems require an ever increasing bandwidth for high data-rate communication systems. The internationally available 60 GHz industrial, scientific and medical band permits unlicensed communication links for wireless local and personal area networks. Leveraging the advanced integration and miniaturization of end-user devices enabled by low-temperature co-fire ceramics technology (LTCC), 60 GHz antennas can be directly integrated with frontend MMICs into compact systems. We have designed, fabricated, and tested an LTCC stripline-to-waveguide transition intended for verification of planar antennas and other active or passive components at millimeter-wave frequencies.

60 GHz-Ultrawideband Real-Time Multi-Antenna Channel Sounding for Multi Giga-Bit/s Access

2010 IEEE 72nd Vehicular Technology Conference - Fall, 2010

60 GHz technology has been proposed recently for multi-Giga-bit/s access within different applica... more 60 GHz technology has been proposed recently for multi-Giga-bit/s access within different application scenarios, e.g. in crowded multi-user public transportation (PT) environments. Hence, channel sounders that are used to investigate multipath propagation and multi-user access techniques including spatial diversity and beam-forming in time-variant shadowing environments require ultra-wideband (UWB) operation, multiple antennas, and real-time. This paper presents probably the first channel

Frequency Dependent Indoor MIMO Channel Characterisation between 2 and 12 GHz Based on Full Spatial Correlation Matrices

Journal of Communications, 2008

The integration of wideband and multiple-input multiple-output (MIMO) radio technologies represen... more The integration of wideband and multiple-input multiple-output (MIMO) radio technologies represents a powerful tool for different wireless communication standards. In the test process of these systems, new strategies for MIMO channel modelling and characterisation are necessary in order to investigate how the frequency band and the bandwidth affect the system performance.

A compact dual-polarized wideband patch antenna array for the unlicensed 60 GHz band

The unlicensed 60 GHz industrial, scientific and medical (ISM) radio band provides a wide bandwid... more The unlicensed 60 GHz industrial, scientific and medical (ISM) radio band provides a wide bandwidth for wireless high data rate communication systems. To optimally utilize these millimeter wave data transmission channels, exploiting orthogonal polarizations is a crucial enhancement. Along with the increase in data rate, improvements of the robustness of communication links in wireless local/personal area networks (WLANs/WPANs) can be achieved adopting the dual-polarization approach. Adjustment of the proper antenna gain is essential for meeting a specific link budget. We have designed, fabricated, and characterized a patch antenna array utilizing orthogonal polarizations in planar multilayer technology.

Dual-polarized architecture for channel sounding at 60 GHz with digital/analog phase control based on 0.25µm SiGe BiCMOS and LTCC technology

Channel sounders that are used to investigate 60 GHz multipath propagation and multi-user access ... more Channel sounders that are used to investigate 60 GHz multipath propagation and multi-user access techniques under time-variant shadowing environments require challenging technical characteristics, e.g., ultra-wideband (UWB) real-time operation (7 to 9 GHz bandwidth), multiple antennas, and high dynamic range. In addition, dual-polarization and phase adjustment have become in a need not only for full channel characterization extracting polarimetric information, but also for consumer user cases under polarization mismatch and misalignment. This paper presents a novel 60 GHz UWB dual-polarized (DP) air interface architecture (AIA) incorporating 360° phase shifters on chip fulfilling the previous requirements. The AIA is based on a 0.25μm SiGe BiCMOS chip-set, and low-temperature co-fired ceramics (LTCC) technology for antennas and packaging. Measurement results using our first prototype are addressed in this paper. The phase adjustment capability is verified and also its usability for cross-polarized real-time measurements including disturbances due to human activity.

60 GHz ultrawideband hybrid-integrated dual-polarized front-end in LTCC technology

For wireless high-data-rate applications, channel sounding, and radar sensors, the unlicensed fre... more For wireless high-data-rate applications, channel sounding, and radar sensors, the unlicensed frequency band around 60 GHz is of relevant commercial interest. Currently, there is enormous progress in the field of integrating 60 GHz technology in compact systems using multilayer technology and reducing costs for mass production. For full channel characterization, but also for consumer applications, dual-polarized frontends offer many advantages for enhancement of polarization mismatch and increasing data rates. In this paper we address the design, successful implementation, and application of two dual-polarized (DP) frontend solutions using the low-temperature co-fired ceramic (LTCC) technology. These DP frontends exhibit advantageous technical properties for practical implementation, e.g., up to 9 GHz bandwidth at the 60 GHz band, low cross-talk between two channel and good heat dissipation in approximately 20 × 40 mm.

Polarimetric Ultrawideband Radar — Principles and applications

2012 IEEE International Conference on Ultra-Wideband, 2012

ABSTRACT In this article we give an overview about the principles of polarimetric Ultrawideband R... more ABSTRACT In this article we give an overview about the principles of polarimetric Ultrawideband Radar. Starting from the state of the art and a summary of the theory we analyze the calibration principles of polarized UWB Radar Data, we investigate possible imaging algorithms and we list important applications. Finally we show an example, to detect certain targets using a polarimetric MIMO UWB radar by doing an analysis of the radar cross section (RCS) of the individual targets.

Polarimetric ultrawideband MIMO radar for security check points: Detecting and classifying suspects carrying wires

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

Ultrawideband Channel Sounding within an Airbus 319

Vehicular Technology, IEEE Conference, 2010

Ultra-wideband (UWB) techniques are recently targeted as a broadband short range solution for in-... more Ultra-wideband (UWB) techniques are recently targeted as a broadband short range solution for in-flight-entertainment (IFE) systems. Despite the in-cabin channel can be considered as an indoor channel, under the current aviation regulations, and due to the usual metal cabins and cylindrical shapes, these scenarios are particular for wireless applications. In this paper is presented an experimental characterization of the UWB channel within an Airbus 319 aircraft cabin based on a real-time multiple-input-multiple-output (MIMO) UWB channel sounder. Here, the delay spread and coherent bandwidth have been calculated for different antennas configurations and distances. Besides, the in-cabin path-loss exponent has been calculated based on an extensively amount of data. Moreover, dynamic range metrics have been introduced for channel analysis and performance comparisons along the cabin.

60 GHz-Ultrawideband Real-Time Multi-Antenna Channel Sounding for Multi GigaBit/s Access

Vehicular Technology, IEEE Conference, 2010

60 GHz technology has been proposed recently for multi-Giga-bit/s access within different applica... more 60 GHz technology has been proposed recently for multi-Giga-bit/s access within different application scenarios, e.g. in crowded multi-user public transportation (PT) environments. Hence, channel sounders that are used to investigate multipath propagation and multi-user access techniques including spatial diversity and beam-forming in time-variant shadowing environments require ultra-wideband (UWB) operation, multiple antennas, and real-time. This paper presents probably the first channel sounder architecture fulfilling these requirements. Moreover, an experimental study is described which is performed for planning purposes and deployment of 60 GHz WLAN/WPAN networks in PT scenarios. Coverage analysis based on different PHY channelization schemes, including multiple access point configurations and antennas is addressed for the Airbus 340 cabin. Additionally, distributions of time dispersion, coherent bandwidth, and Rice K-factor in the in-cabin coverage area are presented. Specifically, a brief analysis under dynamic channel conditions due to human activities is introduced. The suitability of the 60 GHz-UWB channels sounder for PT scenarios is demonstrated. Besides, some channel results for finding the most suitable system parameters for 60 GHz access deployment of in-flight-entertainment (IFE) systems are given.

60 GHz Ultrawideband Polarimetric MIMO Sensing for Wireless Multi-Gigabit and Radar

IEEE Transactions on Antennas and Propagation, 2000

Polarimetric radio wave processing becomes of increasing interest for very high-data rate wireles... more Polarimetric radio wave processing becomes of increasing interest for very high-data rate wireless transmission and for short-range radar at millimeter-waves (mm-W). This goes along with the huge bandwidth of 7 to 9 GHz, which is available worldwide in the 60 GHz unlicensed band. In this paper, we propose a 60 GHz ultra-wideband (UWB) polarimetric multiple-input-multiple-output (MIMO) sensing system architecture and polarimetric signal processing for short-range communications and radar. Demonstration measurements were made by using an UWB radar interface. By measurements in multipath rich environments it is demonstrated that tap-wise polarimetric filtering in delay domain can enhance the 60 GHz link budget by filtering some paths and then reducing shadowing due to human activity. Additionally, optimum MIMO polarimetric filtering is proposed to reduce heavy clutter for mm-W radar, increasing by about 30 dB the signal-to-clutter-plus-noise-ratio.

QoS routing with outdated network knowledge

Electronics Letters, 2000

ABSTRACT The problem of QoS routing in an inaccurate link state is studied. In particular, the ef... more ABSTRACT The problem of QoS routing in an inaccurate link state is studied. In particular, the efficiency of different link cost functions are compared in a realistic environment where the link state changes are not immediately communicated to all nodes in the network. The effects of predicting the present network state when a node must make a routing decision are also analysed. For this purpose, an optimistic and a pessimistic prediction are considered, together with a combination of these two assumptions through a multi-path search policy

Alternating projection method applied to indefinite correlation matrices for generation of synthetic MIMO channels

AEU - International Journal of Electronics and Communications, 2010

Complex correlation multiple-input multiple-output (MIMO) matrices estimated from measurements un... more Complex correlation multiple-input multiple-output (MIMO) matrices estimated from measurements under realistic propagation conditions occasionally have positive, zero and negative eigenvalues, converting them to indefinite matrices. In this framework, this paper presents a novel correction procedure (CP) based on the alternating projection (AP) method to find the Hermitian and positive definite matrix closest to an estimated indefinite full spatial correlation (FSC) MIMO matrix. This corrected matrix allows the Cholesky factorisation usually used for generation of synthetic MIMO channel samples. The applicability of the CP has been analysed using real data from non-line-of-sight (NLOS) indoor measurements. The results reported in this paper show that a proper selection of the CP parameters has not a sensitive impact on the cumulative distribution function (CDF) of the eigenvalues of the estimated FSC MIMO matrices. This characteristic makes the CP useful for channel characterisation, allowing to assess the performance of a MIMO system. As an example of the CP application, a study of ergodic and outage MIMO capacities for different array configurations is presented .

An Unusual Complication of Laparoscopy: Pneumopericardium

Endoscopy, 1980

Case report of a 17-year-old man with acute bridging hepatitis in whom laparoscopy was followed b... more

La camisa

The Modern Language Journal, 1970

La camisa

Hispania, 1969

60 GHz short-range communications: channel measurements, analysis, and modeling

International Journal of Microwave and Wireless Technologies, 2011

60 GHz short-range communications: channel measurements, analysis, and modeling alexis paolo garc... more 60 GHz short-range communications: channel measurements, analysis, and modeling alexis paolo garcia ariza 1 , uwe trautwein 2 , robert mu ¤ ller 1 , frank wollenschla ¤ger 1 , reiner s. thoma ¤ 1 , ju ¤ rgen kunisch 3 , itziar de la torre 3 , robert felbecker 4 , michael peter 4 and wilhelm keusgen 4

60 GHz ultrawideband front-ends with gain control, phase shifter, and wave guide transition in LTCC technology

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

... 91080, Uttenreuth, Germany 1-3{mueller.robert, frank.wollenschlaeger, alexander.schulz, matth... more

60 GHz polarimetric MIMO sensing: Architectures and technology

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

ABSTRACT Millimeter-Wave (mm-W) is considered a potential technology for high-data rate wireless ... more ABSTRACT Millimeter-Wave (mm-W) is considered a potential technology for high-data rate wireless transmission and for high-resolution short-range radar, due to the 7-9 GHz bandwidth at the 60 GHz unlicensed band available worldwide. Developing ultrawideband architectures including multiple-input-multiple-output (MIMO) antenna systems at mm-W offer many advantages including jointly optimized analogue and digital signal processing at carrier frequency and baseband. This allows for flexible antenna designs and reduced losses, as many passive structures can be avoided at both sides of the link. Besides, based on flexible polarimetric approaches, the polarimetric propagation of electromagnetic waves can be exploited. In this paper we present a 60 GHz polarimetric MIMO system architecture, which includes analogue miniaturized frontends designed and manufactured by multi-layer packaging technologies. Such architecture permitted the design of compact MIMO radar and multi-dimensional channel sounding. The MIMO approach allows not only polarimetric filtering and fully polarimetric/directional signal processing to increase the signal-to-clutter-plus-noise ratio of mm-W radar systems, but also the full characterization of wireless channels including multipath with orthogonal polarizations.

A wideband 60 GHz differential stripline-to-waveguide transition for antenna measurements in low-temperature co-fired ceramics technology

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

ABSTRACT Modern communication systems require an ever increasing bandwidth for high data-rate com... more ABSTRACT Modern communication systems require an ever increasing bandwidth for high data-rate communication systems. The internationally available 60 GHz industrial, scientific and medical band permits unlicensed communication links for wireless local and personal area networks. Leveraging the advanced integration and miniaturization of end-user devices enabled by low-temperature co-fire ceramics technology (LTCC), 60 GHz antennas can be directly integrated with frontend MMICs into compact systems. We have designed, fabricated, and tested an LTCC stripline-to-waveguide transition intended for verification of planar antennas and other active or passive components at millimeter-wave frequencies.

60 GHz-Ultrawideband Real-Time Multi-Antenna Channel Sounding for Multi Giga-Bit/s Access

2010 IEEE 72nd Vehicular Technology Conference - Fall, 2010

60 GHz technology has been proposed recently for multi-Giga-bit/s access within different applica... more 60 GHz technology has been proposed recently for multi-Giga-bit/s access within different application scenarios, e.g. in crowded multi-user public transportation (PT) environments. Hence, channel sounders that are used to investigate multipath propagation and multi-user access techniques including spatial diversity and beam-forming in time-variant shadowing environments require ultra-wideband (UWB) operation, multiple antennas, and real-time. This paper presents probably the first channel

Frequency Dependent Indoor MIMO Channel Characterisation between 2 and 12 GHz Based on Full Spatial Correlation Matrices

Journal of Communications, 2008

The integration of wideband and multiple-input multiple-output (MIMO) radio technologies represen... more The integration of wideband and multiple-input multiple-output (MIMO) radio technologies represents a powerful tool for different wireless communication standards. In the test process of these systems, new strategies for MIMO channel modelling and characterisation are necessary in order to investigate how the frequency band and the bandwidth affect the system performance.

A compact dual-polarized wideband patch antenna array for the unlicensed 60 GHz band

The unlicensed 60 GHz industrial, scientific and medical (ISM) radio band provides a wide bandwid... more The unlicensed 60 GHz industrial, scientific and medical (ISM) radio band provides a wide bandwidth for wireless high data rate communication systems. To optimally utilize these millimeter wave data transmission channels, exploiting orthogonal polarizations is a crucial enhancement. Along with the increase in data rate, improvements of the robustness of communication links in wireless local/personal area networks (WLANs/WPANs) can be achieved adopting the dual-polarization approach. Adjustment of the proper antenna gain is essential for meeting a specific link budget. We have designed, fabricated, and characterized a patch antenna array utilizing orthogonal polarizations in planar multilayer technology.

Dual-polarized architecture for channel sounding at 60 GHz with digital/analog phase control based on 0.25µm SiGe BiCMOS and LTCC technology

Channel sounders that are used to investigate 60 GHz multipath propagation and multi-user access ... more Channel sounders that are used to investigate 60 GHz multipath propagation and multi-user access techniques under time-variant shadowing environments require challenging technical characteristics, e.g., ultra-wideband (UWB) real-time operation (7 to 9 GHz bandwidth), multiple antennas, and high dynamic range. In addition, dual-polarization and phase adjustment have become in a need not only for full channel characterization extracting polarimetric information, but also for consumer user cases under polarization mismatch and misalignment. This paper presents a novel 60 GHz UWB dual-polarized (DP) air interface architecture (AIA) incorporating 360° phase shifters on chip fulfilling the previous requirements. The AIA is based on a 0.25μm SiGe BiCMOS chip-set, and low-temperature co-fired ceramics (LTCC) technology for antennas and packaging. Measurement results using our first prototype are addressed in this paper. The phase adjustment capability is verified and also its usability for cross-polarized real-time measurements including disturbances due to human activity.

60 GHz ultrawideband hybrid-integrated dual-polarized front-end in LTCC technology

For wireless high-data-rate applications, channel sounding, and radar sensors, the unlicensed fre... more For wireless high-data-rate applications, channel sounding, and radar sensors, the unlicensed frequency band around 60 GHz is of relevant commercial interest. Currently, there is enormous progress in the field of integrating 60 GHz technology in compact systems using multilayer technology and reducing costs for mass production. For full channel characterization, but also for consumer applications, dual-polarized frontends offer many advantages for enhancement of polarization mismatch and increasing data rates. In this paper we address the design, successful implementation, and application of two dual-polarized (DP) frontend solutions using the low-temperature co-fired ceramic (LTCC) technology. These DP frontends exhibit advantageous technical properties for practical implementation, e.g., up to 9 GHz bandwidth at the 60 GHz band, low cross-talk between two channel and good heat dissipation in approximately 20 × 40 mm.

Polarimetric Ultrawideband Radar — Principles and applications

2012 IEEE International Conference on Ultra-Wideband, 2012

ABSTRACT In this article we give an overview about the principles of polarimetric Ultrawideband R... more ABSTRACT In this article we give an overview about the principles of polarimetric Ultrawideband Radar. Starting from the state of the art and a summary of the theory we analyze the calibration principles of polarized UWB Radar Data, we investigate possible imaging algorithms and we list important applications. Finally we show an example, to detect certain targets using a polarimetric MIMO UWB radar by doing an analysis of the radar cross section (RCS) of the individual targets.

Polarimetric ultrawideband MIMO radar for security check points: Detecting and classifying suspects carrying wires

2012 6th European Conference on Antennas and Propagation (EUCAP), 2012

Ultrawideband Channel Sounding within an Airbus 319

Vehicular Technology, IEEE Conference, 2010

Ultra-wideband (UWB) techniques are recently targeted as a broadband short range solution for in-... more Ultra-wideband (UWB) techniques are recently targeted as a broadband short range solution for in-flight-entertainment (IFE) systems. Despite the in-cabin channel can be considered as an indoor channel, under the current aviation regulations, and due to the usual metal cabins and cylindrical shapes, these scenarios are particular for wireless applications. In this paper is presented an experimental characterization of the UWB channel within an Airbus 319 aircraft cabin based on a real-time multiple-input-multiple-output (MIMO) UWB channel sounder. Here, the delay spread and coherent bandwidth have been calculated for different antennas configurations and distances. Besides, the in-cabin path-loss exponent has been calculated based on an extensively amount of data. Moreover, dynamic range metrics have been introduced for channel analysis and performance comparisons along the cabin.

60 GHz-Ultrawideband Real-Time Multi-Antenna Channel Sounding for Multi GigaBit/s Access

Vehicular Technology, IEEE Conference, 2010

60 GHz technology has been proposed recently for multi-Giga-bit/s access within different applica... more 60 GHz technology has been proposed recently for multi-Giga-bit/s access within different application scenarios, e.g. in crowded multi-user public transportation (PT) environments. Hence, channel sounders that are used to investigate multipath propagation and multi-user access techniques including spatial diversity and beam-forming in time-variant shadowing environments require ultra-wideband (UWB) operation, multiple antennas, and real-time. This paper presents probably the first channel sounder architecture fulfilling these requirements. Moreover, an experimental study is described which is performed for planning purposes and deployment of 60 GHz WLAN/WPAN networks in PT scenarios. Coverage analysis based on different PHY channelization schemes, including multiple access point configurations and antennas is addressed for the Airbus 340 cabin. Additionally, distributions of time dispersion, coherent bandwidth, and Rice K-factor in the in-cabin coverage area are presented. Specifically, a brief analysis under dynamic channel conditions due to human activities is introduced. The suitability of the 60 GHz-UWB channels sounder for PT scenarios is demonstrated. Besides, some channel results for finding the most suitable system parameters for 60 GHz access deployment of in-flight-entertainment (IFE) systems are given.

60 GHz Ultrawideband Polarimetric MIMO Sensing for Wireless Multi-Gigabit and Radar

IEEE Transactions on Antennas and Propagation, 2000

Polarimetric radio wave processing becomes of increasing interest for very high-data rate wireles... more Polarimetric radio wave processing becomes of increasing interest for very high-data rate wireless transmission and for short-range radar at millimeter-waves (mm-W). This goes along with the huge bandwidth of 7 to 9 GHz, which is available worldwide in the 60 GHz unlicensed band. In this paper, we propose a 60 GHz ultra-wideband (UWB) polarimetric multiple-input-multiple-output (MIMO) sensing system architecture and polarimetric signal processing for short-range communications and radar. Demonstration measurements were made by using an UWB radar interface. By measurements in multipath rich environments it is demonstrated that tap-wise polarimetric filtering in delay domain can enhance the 60 GHz link budget by filtering some paths and then reducing shadowing due to human activity. Additionally, optimum MIMO polarimetric filtering is proposed to reduce heavy clutter for mm-W radar, increasing by about 30 dB the signal-to-clutter-plus-noise-ratio.

QoS routing with outdated network knowledge

Electronics Letters, 2000

ABSTRACT The problem of QoS routing in an inaccurate link state is studied. In particular, the ef... more ABSTRACT The problem of QoS routing in an inaccurate link state is studied. In particular, the efficiency of different link cost functions are compared in a realistic environment where the link state changes are not immediately communicated to all nodes in the network. The effects of predicting the present network state when a node must make a routing decision are also analysed. For this purpose, an optimistic and a pessimistic prediction are considered, together with a combination of these two assumptions through a multi-path search policy

Alternating projection method applied to indefinite correlation matrices for generation of synthetic MIMO channels

AEU - International Journal of Electronics and Communications, 2010

Complex correlation multiple-input multiple-output (MIMO) matrices estimated from measurements un... more Complex correlation multiple-input multiple-output (MIMO) matrices estimated from measurements under realistic propagation conditions occasionally have positive, zero and negative eigenvalues, converting them to indefinite matrices. In this framework, this paper presents a novel correction procedure (CP) based on the alternating projection (AP) method to find the Hermitian and positive definite matrix closest to an estimated indefinite full spatial correlation (FSC) MIMO matrix. This corrected matrix allows the Cholesky factorisation usually used for generation of synthetic MIMO channel samples. The applicability of the CP has been analysed using real data from non-line-of-sight (NLOS) indoor measurements. The results reported in this paper show that a proper selection of the CP parameters has not a sensitive impact on the cumulative distribution function (CDF) of the eigenvalues of the estimated FSC MIMO matrices. This characteristic makes the CP useful for channel characterisation, allowing to assess the performance of a MIMO system. As an example of the CP application, a study of ergodic and outage MIMO capacities for different array configurations is presented .