The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Christian Vogel - One of the best experts on this subject based on the ideXlab platform.
-
Efficiency Optimization for Burst-Mode Multilevel Radio Frequency Transmitters
2014Co-Authors: Shuli Chi, Student Member, Peter Singerl, Christian Vogel, Senior MemberAbstract:Abstract—The utilization of a burst-mode power amplifier (PA) together with pulse-width modulation (PWM) is a promising concept for achieving high efficiency in radio frequency (RF) Transmitters. Nevertheless, such a Transmitter architecture requires bandpass filtering to suppress side-band spectral com-ponents to retrieve the wanted signal, which reduces the transmit power and the Transmitter efficiency. High efficiency can only be expected with the maximum transmit power and signals with low peak-to-average-power ratios (PAPRs). To boost efficiency for signals with high PAPRs and signals at variable transmit power levels, the burst-mode multilevel Transmitter architecture has been widely discussed as a potential solution. This paper presents an efficiency optimization procedure of burst-mode multilevel Transmitters for signals with high PAPRs and signals at variable transmit power levels. The impact of the threshold value on the Transmitter efficiency is studied, where the optimum threshold value and the maximum Transmitter efficiency can be obtained according to input magnitude statistics. In addition, the relation between the threshold value and the efficiency expression of burst-mode multilevel Transmitters and those of Doherty PAs is investigated. It is shown that the obtained optimum threshold value, although originally designed for burst-mode Transmitters, can also be applied to Doherty and multistage Doherty PAs to achieve maximum Transmitter efficiency. Simulations are used to validate the efficiency improvement of the optimized burst-mode multilevel Transmitters compared to two-level and non-optimized multilevel Transmitters. Index Terms—Burst-mode operation, efficiency optimization, multilevel radio frequency (RF) Transmitter, probability density function (pdf), pulse-width modulation (PWM). I
-
efficiency optimization for burst mode multilevel radio frequency Transmitters
IEEE Transactions on Circuits and Systems, 2013Co-Authors: Shuli Chi, Peter Singerl, Christian VogelAbstract:The utilization of a burst-mode power amplifier (PA) together with pulse-width modulation (PWM) is a promising concept for achieving high efficiency in radio frequency (RF) Transmitters. Nevertheless, such a Transmitter architecture requires bandpass filtering to suppress side-band spectral components to retrieve the wanted signal, which reduces the transmit power and the Transmitter efficiency. High efficiency can only be expected with the maximum transmit power and signals with low peak-to-average-power ratios (PAPRs). To boost efficiency for signals with high PAPRs and signals at variable transmit power levels, the burst-mode multilevel Transmitter architecture has been widely discussed as a potential solution. This paper presents an efficiency optimization procedure of burst-mode multilevel Transmitters for signals with high PAPRs and signals at variable transmit power levels. The impact of the threshold value on the Transmitter efficiency is studied, where the optimum threshold value and the maximum Transmitter efficiency can be obtained according to input magnitude statistics. In addition, the relation between the threshold value and the efficiency expression of burst-mode multilevel Transmitters and those of Doherty PAs is investigated. It is shown that the obtained optimum threshold value, although originally designed for burst-mode Transmitters, can also be applied to Doherty and multistage Doherty PAs to achieve maximum Transmitter efficiency. Simulations are used to validate the efficiency improvement of the optimized burst-mode multilevel Transmitters compared to two-level and non-optimized multilevel Transmitters.
Poor H. Vincent - One of the best experts on this subject based on the ideXlab platform.
-
Relay-Aided Secure Broadcasting for Visible Light Communications
'Institute of Electrical and Electronics Engineers (IEEE)', 2019Co-Authors: Arafa Ahmed, Panayirci Erdal, Poor H. VincentAbstract:A visible light communication broadcast channel is considered, in which a Transmitter luminaire communicates with two legitimate receivers in the presence of an external eavesdropper. A number of trusted cooperative half-duplex relay luminaires are deployed to aid with securing the transmitted data. Transmitters are equipped with single light fixtures, containing multiple light emitting diodes, and receiving nodes are equipped with single photo-detectors, rendering the considered setting as a single-input single-output system. Transmission is amplitude-constrained to maintain operation within the light emitting diodes' dynamic range. Achievable secrecy rate regions are derived under such amplitude constraints for this multi-receiver wiretap channel, first for direct transmission without the relays, and then for multiple relaying schemes: cooperative jamming, decode-and-forward, and amplify-and-forward. Superposition coding with uniform signaling is used at the Transmitter and the relays. Further, for each relaying scheme, secure beamforming vectors are carefully designed at the relay nodes in order to hurt the eavesdropper and/or benefit the legitimate receivers. Superiority of the proposed relaying schemes, with secure beamforming, is shown over direct transmission. It is also shown that the best relaying scheme depends on how far the eavesdropper is located from the Transmitter and the relays, the number of relays, and their geometric layout
-
Secrecy Performance Analysis of Distributed CDD Based Cooperative Systems with Jamming
IEEE, 2018Co-Authors: Kim, Kyeong Jin, Marco Di Renzo, Liu Hongwu, Orlik Philip, Poor H. VincentAbstract:International audienceIn this paper, a cooperative cyclic-prefixed single carrier (CP-SC) system to improve physical layer security is investigated. By considering a distributed cyclic delay diversity (dCDD) scheme, a jamming method is proposed to maximize the signal-to-noise ratio (SNR) over the channels from the Transmitters to the legitimate user, while degrading the signal-to-interference-plus-noise ratio (SINR) over the channels from the Transmitters to the illegitimate user. A CDD Transmitter among the set of CDD Transmitters is selected as the sentinel Transmitter, and it transmits a jamming signal to the illegitimate user. The sentinel Transmitter is the Transmitter that provides the best channel gain in order to maximize the SNR at the legitimate user and minimize the SINR at the non-legitimate users. This allow us to enhance the security of the CP-SC system. New closed form expressions for the SNR and SINR for the dCDD protocol are derived for frequency selective fading channels. Monte-Carlo simulations are conducted to verify the analytic derivations of the performance metrics for various simulation scenarios
-
Secrecy Performance Analysis of Distributed CDD Based Cooperative Systems with Jamming
'Institute of Electrical and Electronics Engineers (IEEE)', 2018Co-Authors: Kim, Kyeong Jin, Marco Di Renzo, Liu Hongwu, Orlik Philip, Poor H. VincentAbstract:International audienceIn this paper, a cooperative cyclic-prefixed single carrier (CP-SC) system to improve physical layer security is investigated. By considering a distributed cyclic delay diversity (dCDD) scheme, a jamming method is proposed to maximize the signal-to-noise ratio (SNR) over the channels from the Transmitters to the legitimate user, while degrading the signal-to-interference-plus-noise ratio (SINR) over the channels from the Transmitters to the illegitimate user. A CDD Transmitter among the set of CDD Transmitters is selected as the sentinel Transmitter, and it transmits a jamming signal to the illegitimate user. The sentinel Transmitter is the Transmitter that provides the best channel gain in order to maximize the SNR at the legitimate user and minimize the SINR at the non-legitimate users. This allow us to enhance the security of the CP-SC system. New closed form expressions for the SNR and SINR for the dCDD protocol are derived for frequency selective fading channels. Monte-Carlo simulations are conducted to verify the analytic derivations of the performance metrics for various simulation scenarios. Index Terms-Distributed single carrier system, physical layer security, distributed cyclic delay diversity, sentinel Transmitter, frequency selective fading
Shuli Chi - One of the best experts on this subject based on the ideXlab platform.
-
Efficiency Optimization for Burst-Mode Multilevel Radio Frequency Transmitters
2014Co-Authors: Shuli Chi, Student Member, Peter Singerl, Christian Vogel, Senior MemberAbstract:Abstract—The utilization of a burst-mode power amplifier (PA) together with pulse-width modulation (PWM) is a promising concept for achieving high efficiency in radio frequency (RF) Transmitters. Nevertheless, such a Transmitter architecture requires bandpass filtering to suppress side-band spectral com-ponents to retrieve the wanted signal, which reduces the transmit power and the Transmitter efficiency. High efficiency can only be expected with the maximum transmit power and signals with low peak-to-average-power ratios (PAPRs). To boost efficiency for signals with high PAPRs and signals at variable transmit power levels, the burst-mode multilevel Transmitter architecture has been widely discussed as a potential solution. This paper presents an efficiency optimization procedure of burst-mode multilevel Transmitters for signals with high PAPRs and signals at variable transmit power levels. The impact of the threshold value on the Transmitter efficiency is studied, where the optimum threshold value and the maximum Transmitter efficiency can be obtained according to input magnitude statistics. In addition, the relation between the threshold value and the efficiency expression of burst-mode multilevel Transmitters and those of Doherty PAs is investigated. It is shown that the obtained optimum threshold value, although originally designed for burst-mode Transmitters, can also be applied to Doherty and multistage Doherty PAs to achieve maximum Transmitter efficiency. Simulations are used to validate the efficiency improvement of the optimized burst-mode multilevel Transmitters compared to two-level and non-optimized multilevel Transmitters. Index Terms—Burst-mode operation, efficiency optimization, multilevel radio frequency (RF) Transmitter, probability density function (pdf), pulse-width modulation (PWM). I
-
efficiency optimization for burst mode multilevel radio frequency Transmitters
IEEE Transactions on Circuits and Systems, 2013Co-Authors: Shuli Chi, Peter Singerl, Christian VogelAbstract:The utilization of a burst-mode power amplifier (PA) together with pulse-width modulation (PWM) is a promising concept for achieving high efficiency in radio frequency (RF) Transmitters. Nevertheless, such a Transmitter architecture requires bandpass filtering to suppress side-band spectral components to retrieve the wanted signal, which reduces the transmit power and the Transmitter efficiency. High efficiency can only be expected with the maximum transmit power and signals with low peak-to-average-power ratios (PAPRs). To boost efficiency for signals with high PAPRs and signals at variable transmit power levels, the burst-mode multilevel Transmitter architecture has been widely discussed as a potential solution. This paper presents an efficiency optimization procedure of burst-mode multilevel Transmitters for signals with high PAPRs and signals at variable transmit power levels. The impact of the threshold value on the Transmitter efficiency is studied, where the optimum threshold value and the maximum Transmitter efficiency can be obtained according to input magnitude statistics. In addition, the relation between the threshold value and the efficiency expression of burst-mode multilevel Transmitters and those of Doherty PAs is investigated. It is shown that the obtained optimum threshold value, although originally designed for burst-mode Transmitters, can also be applied to Doherty and multistage Doherty PAs to achieve maximum Transmitter efficiency. Simulations are used to validate the efficiency improvement of the optimized burst-mode multilevel Transmitters compared to two-level and non-optimized multilevel Transmitters.
Lingjiang Kong - One of the best experts on this subject based on the ideXlab platform.
-
MIMO OFDM radar IRCI free range reconstruction with sufficient cyclic prefix
IEEE Transactions on Aerospace and Electronic Systems, 2015Co-Authors: Xiang-gen Xia, Tianxian Zhang, Lingjiang KongAbstract:In this paper, we propose multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) radar with sufficient cyclic prefix (CP), where all OFDM pulses transmitted from different Transmitters share the same frequency band and are orthogonal to each other for every subcarrier in the discrete frequency domain. The orthogonality is not affected by time delays from Transmitters. Thus, our proposed MIMO OFDM radar has the same range resolution as single Transmitter radar and achieves full spatial diversity. Orthogonal designs are used to achieve this orthogonality across the Transmitters, with which it is only needed to design OFDM pulses for the first Transmitter. We also propose a joint pulse compression and pulse coherent integration for range reconstruction. In order to achieve the optimal signal-to-noise ratio (SNR) for the range reconstruction, we apply the paraunitary filterbank theory to design the OFDM pulses. We then propose a modified iterative clipping and filtering (MICF) algorithm for the designs of OFDM pulses jointly, when other important factors, such as peak-to-average power ratio (PAPR) in time domain, are also considered.With our proposed MIMO OFDM radar, there is no interference for the range reconstruction not only across the Transmitters but also across the range cells in a swath called inter-range-cell interference (IRCI) free that is similar to our previously proposed CP-based OFDM radar for single Transmitter. Simulations are presented to illustrate our proposed theory and show that the CP-based MIMO OFDM radar outperforms the existing frequency-band shared MIMO radar with polyphase codes and also frequency division MIMO radar.
-
MIMO OFDM Radar IRCI Free Range Reconstruction with Sufficient Cyclic Prefix
arXiv: Information Theory, 2014Co-Authors: Xiang-gen Xia, Tianxian Zhang, Lingjiang KongAbstract:In this paper, we propose MIMO OFDM radar with sufficient cyclic prefix (CP), where all OFDM pulses transmitted from different Transmitters share the same frequency band and are orthogonal to each other for every subcarrier in the discrete frequency domain. The orthogonality is not affected by time delays from Transmitters. Thus, our proposed MIMO OFDM radar has the same range resolution as single Transmitter radar and achieves full spatial diversity. Orthogonal designs are used to achieve this orthogonality across the Transmitters, with which it is only needed to design OFDM pulses for the first Transmitter. We also propose a joint pulse compression and pulse coherent integration for range reconstruction. In order to achieve the optimal SNR for the range reconstruction, we apply the paraunitary filterbank theory to design the OFDM pulses. We then propose a modified iterative clipping and filtering (MICF) algorithm for the designs of OFDM pulses jointly, when other important factors, such as peak-to-average power ratio (PAPR) in time domain, are also considered. With our proposed MIMO OFDM radar, there is no interference for the range reconstruction not only across the Transmitters but also across the range cells in a swath called inter-range-cell interference (IRCI) free that is similar to our previously proposed CP based OFDM radar for single Transmitter. Simulations are presented to illustrate our proposed theory and show that the CP based MIMO OFDM radar outperforms the existing frequency-band shared MIMO radar with polyphase codes and also frequency division MIMO radar.
Armin Dammann - One of the best experts on this subject based on the ideXlab platform.
-
data association among physical and virtual radio Transmitters with visibility regions
Vehicular Technology Conference, 2019Co-Authors: Markus Ulmschneider, Christian Gentner, Armin DammannAbstract:In multipath assisted positioning, multipath components (MPCs) are exploited for positioning as they are regarded as line-of-sight (LoS) signals from virtual Transmitters. With simultaneous localization and mapping (SLAM), the locations of physical and virtual Transmitters are estimated jointly with and relative to the user position. A robust data association scheme is crucial for the robustness of SLAM. In multipath assisted positioning, data association refers to the question which MPCs correspond to which Transmitters. We say that a physical or virtual Transmitter is visible to the user if the user is in LoS to the Transmitter. Within this paper, we propose to map information on the visibility of physical and virtual Transmitters in addition to their locations, and use such information for a reliable data association. Visibility information may stem from previous observations of a user, or from a visibility map of the scenario obtained from another user or a central entity. Our simulations in an indoor scenario show that information on the visibility of Transmitters considerably improves the positioning performance by increasing the robustness of data association.
-
multipath assisted positioning with simultaneous localization and mapping
IEEE Transactions on Wireless Communications, 2016Co-Authors: Christian Gentner, Armin Dammann, Wei Wang, Thomas Jost, Siwei Zhang, Uwecarsten FiebigAbstract:This paper describes an algorithm that exploits multipath propagation for position estimation of mobile receivers. We apply a novel algorithm based on recursive Bayesian filtering, named Channel-SLAM. This approach treats multipath components as signals emitted from virtual Transmitters, which are time synchronized to the physical Transmitter and static in their positions. Contrary to other approaches, Channel-SLAM considers also paths occurring due to multiple numbers of reflections or scattering as well as the combination. Hence, each received multipath component increases the number of Transmitters resulting in a more accurate position estimate or enabling positioning when the number of physical Transmitters is insufficient. Channel-SLAM estimates the receiver position and the positions of the virtual Transmitters simultaneously; hence, the approach does not require any prior information, such as a room-layout or a database for fingerprinting. The only prior knowledge needed is the physical Transmitter position as well as the initial receiver position and moving direction. Based on simulations, the position precision of Channel-SLAM is evaluated by a comparison to simplified algorithms and to the posterior Cramer-Rao lower bound. Furthermore, this paper shows the performance of Channel-SLAM based on measurements in an indoor scenario with only a single physical Transmitter.
