Michael Peter - RankMe

89 papers A* 1B 8C 2Misc 1Journal 23Unranked 54

Year	Rank	Type	Title / Venue / Authors
2026	J	`jnl`	A stacking model integrating GARCH and LSTM with feature interactions for time series volatility prediction. Array Michael Peter, Silas Mirau, Emmanuel Sinkwembe, Christian Kasumo, Calisto Guambe
2025	—	`conf`	Agile Sub-Terahertz to Terahertz Broadband Time-Domain Photonic Channel Sounder. WSA Ramez Askar, Garrit Schwanke, Milan Deumer, Alper Schultze, Nico Vieweg, Thomas Puppe, Sebastian Müller, Albrecht Neudecker, Oliver Stiewe, Robert B. Kohlhaas, Shahram Keyvaninia, Robert Elschner, Colja Schubert, Ronald Freund, Michael Peter, Taro Eichler, Wilhelm Keusgen
2025	B	`conf`	D-Band Adaptive Beamforming for 6G Sub-THz Communications: Feasibility and Experimental Results. PIMRC Sven Wittig, Ramez Askar, Utku Uçak, Matthias Mehlhose, Mathis Schmieder, Jaehoon Chung, Bersant Gashi, Laurenz John, Thomas Merkle, Yonghak Suh, Jongpil Lee, Michael Peter, Thomas Haustein, Slawomir Stanczak, Arnulf Leuther
2025	—	`conf`	D-Band Dielectric Lens Antenna: Emulated Linear Array Superposition Measurements for Performance Analysis. WSA Vitor Almeida, Ramez Askar, Woo Cheol Choi, Michael Peter, Jaehoon Chung, Wilhelm Keusgen
2025	—	`conf`	Design and Validation of a Time Domain Correlation Based Channel Sounder up to 500 GHz. WSA Alper Schultze, Anton Dilg, Sven Wittig, Mathis Schmieder, Ramez Askar, Michael Peter, Wilhelm Keusgen
2025	—	`conf`	Evaluation of a Wr6.5 Rotary Joint with Two 3D-Printed TE01 Mode Transducers. WSA Mathis Schmieder, Sven Wittig, Steffen Sigwart, Michael Peter, Wilhelm Keusgen
2025	—	`conf`	Real-Time Demonstration of Integrated Sensing and Communication in the Sub-Terahertz D-Band. JC&S Sven Wittig, Ramez Askar, Rodrigo Hernangómez, Michael Peter, Slawomir Stanczak
2024	—	`conf`	Demonstration of a Real-Time Testbed for D-Band Integrated Sensing and Communication. MILCOM Sven Wittig, Rodrigo Hernangómez, Karen Vardanyan, Ramez Askar, Amr Haj-Omar, Michael Peter, Slawomir Stanczak
2024	—	`conf`	Dual-Polarized Sub-THz Channel Measurements in D-Band in an Industrial Environment. EuCNC/6G Summit Alper Schultze, Mathis Schmieder, Ramez Askar, Michael Peter, Wilhelm Keusgen, Taro Eichler
2024	J	`jnl`	Examining the interdependencies of e-government challenges using PESTELMO, DEMATEL and ANP: A case study of Tanzania. Inf. Polity Catherine G. Mkude, Michael Peter
2024	J	`jnl`	Little or No Equalization is Needed in Energy-Efficient Sub-THz Mobile Access. IEEE Commun. Mag. Lorenzo Miretti, Thomas Kühne, Alper Schultze, Wilhelm Keusgen, Giuseppe Caire, Michael Peter, Slawomir Stanczak, Taro Eichler
2024	—	`conf`	Measurement and Modeling of sub-THz Channels in the Presence of Emulated RIS. GLOBECOM (Workshops) Mathis Schmieder, Alper Schultze, Niclas Kullig, Michael Peter, Ramez Askar, Wilhelm Keusgen
2024	J	`jnl`	Mobilizing the Terahertz Beam: D-Band Analog-Beamforming Front-End Prototyping and Long-Range 6G Trials. IEEE Wirel. Commun. Ramez Askar, Jaehoon Chung, Laurenz John, Thomas Merkle, Sven Wittig, Mathis Schmieder, Yonghak Suh, Jongpil Lee, Benjamin Baumann, Michael Peter, Thomas Haustein, Wilhelm Keusgen, Slawomir Stanczak
2024	J	`jnl`	Quasi-Deterministic Modeling for Industrial IoT Channels Based on Millimeter Wave Measurements. IEEE Internet Things J. Jingya Yang, Yiru Liu, Ke Guan, Mathis Schmieder, Dan Fei, Michael Peter, Wilhelm Keusgen, Ning Wang, Yi Wang, Bo Ai
2024	J	`jnl`	Reconfigurable Intelligent Surfaces for 6G Mobile Networks: An Industry R&D Perspective. IEEE Access Maik Sode, Michael Ponschab, Lucas N. Ribeiro, Sven Haesloop, Ehsan Tohidi, Michael Peter, Slawomir Stanczak, Bilal H. Mohamed, Wilhelm Keusgen, Heinz Mellein, Eslam Yassin, Bernd Schröder
2024	B	`conf`	Sub-THz D-Band Integrated Analog Beamforming Front-End Prototyping and 6G Outdoor Trials. WCNC Ramez Askar, Mathis Schmieder, Jaehoon Chung, Laurenz John, Thomas Merkle, Sven Wittig, Yonghak Suh, Jongpil Lee, Michael Peter, Thomas Haustein, Wilhelm Keusgen, Slawomir Stanczak
2024	—	`conf`	W-Band Beamforming Front-End Implementation and Outdoor Trials for Mobile Backhaul and Access. ICC Mathis Schmieder, Ramez Askar, Alper Schultze, Mehrnoosh Mazhar Sarmadi, Michael Peter, Dirk Schwantuschke, Wilhelm Keusgen
2023	—	`conf`	Outdoor Transmission Trials in the W-Band for 6G Mobile Access Scenarios. VTC2023-Spring Mehrnoosh Mazhar Sarmadi, Ramez Askar, Mathis Schmieder, Michael Peter, Dirk Schwantuschke, Wilhelm Keusgen
2023	B	`conf`	TEEVseL4: Trusted Execution Environment for Virtualized seL4-Based Systems. RTCSA Borna Blazevic, Michael Peter, Mohammad Hamad, Sebastian Steinhorst
2022	—	`conf`	Angle-Resolved THz Channel Measurements at 300 GHz in an Industrial Environment. VTC Spring Alper Schultze, Mathis Schmieder, Sven Wittig, Henrik Klessig, Michael Peter, Wilhelm Keusgen
2022	J	`jnl`	Little or no equalization is needed in energy-efficient sub-THz mobile access. CoRR Lorenzo Miretti, Thomas Kühne, Alper Schultze, Wilhelm Keusgen, Giuseppe Caire, Michael Peter, Slawomir Stanczak, Taro Eichler
2022	—	`conf`	Self-Interference Channel Measurements Utilizing mmWave Phased Arrays for Full-Duplex IAB Scenario. GLOBECOM (Workshops) Ramez Askar, Mathis Schmieder, Michael Peter, Wilhelm Keusgen, Thomas Haustein
2021	—	`conf`	Angle-Resolved THz Channel Measurements at 300 GHz in an Outdoor Environment. ICC Workshops Fabian Undi, Alper Schultze, Wilhelm Keusgen, Michael Peter, Taro Eichler
2021	—	`conf`	Channel Measurements and Large Scale Parameter Estimation in a Production Hall. VTC Fall Mathis Schmieder, Henrik Klessig, Alper Schultze, Sven Wittig, Michael Peter, Wilhelm Keusgen
2021	—	`conf`	Over-the-Air Verification of Angle-of-Arrival Estimation in Millimeter-Wave Channel Sounders. VTC Fall Sven Wittig, Alper Schultze, Michael Peter, Wilhelm Keusgen
2021	—	`conf`	The Fraunhofer CCIT Smart Intersection. ITSC Michael Klöppel-Gersdorf, Friedrich Trauzettel, Konstantin Koslowski, Michael Peter, Thomas Otto
2020	—	`conf`	Investigation of Theoretical limits for Unconditional AoA Estimations in multi-element antenna arrays by simulations. ICIT Olesya Bolkhovskaya, Alexander Maltsev, Victor Sergeev, Wilhelm Keusgen, Michael Peter
2020	—	`conf`	THz Channel Sounding: Design and Validation of a High Performance Channel Sounder at 300 GHz. WCNC Workshops Mathis Schmieder, Wilhelm Keusgen, Michael Peter, Sven Wittig, Thomas Merkle, Sandrine Wagner, Michael Kuri, Taro Eichler
2020	—	`conf`	Time Dispersion Parameters of Indoor Self-Interference Radio Channels in Sub-7-GHz Bands. WCNC Workshops Ramez Askar, Mehrnoosh Mazhar Sarmadi, Fabian Undi, Michael Peter, Wilhelm Keusgen, Thomas Haustein
2020	—	`conf`	Time Dispersion Parameters of Outdoor Cross-Polar Self-Interference Radio Channels in sub-8-GHz Bands. ICC Workshops Ramez Askar, Mehrnoosh Mazhar Sarmadi, Fabian Undi, Michael Peter, Wilhelm Keusgen, Thomas Haustein
2019	J	`jnl`	A Comprehensive Study on mmWave-Based Mobile Hotspot Network System for High-Speed Train Communications. IEEE Trans. Veh. Technol. Junhyeong Kim, Mathis Schmieder, Michael Peter, Hee-Sang Chung, Sung-Woo Choi, Ilgyu Kim, Youngnam Han
2019	—	`conf`	Accurate Iterative Algorithm for Detection and the Signal AoA Estimation in Low SNR Region. ICCCS Olesya Bolkhovskaya, Alexander Maltsev, Victor Sergeev, Wilhelm Keusgen, Michael Peter
2019	J	`jnl`	Design, Calibration, and Evaluation of a Backpack Indoor Mobile Mapping System. Remote. Sens. Samer Karam, George Vosselman, Michael Peter, Siavash Hosseinyalamdary, Ville V. Lehtola
2019	B	`conf`	Directional Wideband Channel Measurements at 28 GHz in an Industrial Environment. GLOBECOM Mathis Schmieder, Fabian Undi, Michael Peter, Ephraim Koenig, Wilhelm Keusgen
2019	—	`conf`	Polarimetric Characterization of MIMO Sub-6-GHz Self-Interference Indoor Radio Channels. PIMRC Workshops Ramez Askar, Mehrnoosh Mazhar Sarmadi, Fabian Undi, Rodrigo Silva Rezende, Michael Peter, Wilhelm Keusgen, Thomas Haustein
2019	—	`conf`	Polarimetric Characterization of Sub-6-GHz Self-Interference Indoor Radio Channels. ICC Workshops Ramez Askar, Fabian Undi, Rodrigo Silva Rezende, Michael Peter, Wilhelm Keusgen
2019	—	`conf`	Time Dispersion Characteristics of Cross-Polarized 2X2 MIMO Self-Interference Indoor Radio Channels. VTC Fall Ramez Askar, Mehrnoosh Mazhar Sarmadi, Fabian Undi, Michael Peter, Wilhelm Keusgen, Thomas Haustein
2018	J	`jnl`	Indoor Tracking, Mapping, and Navigation: Algorithms, Technologies, and Applications. J. Sensors Jacky C. K. Chow, Michael Peter, Marco Scaioni, Mohamad Al-Durgham
2018	J	`jnl`	Minimizing Event-Handling Latencies in Secure Virtual Machines. CoRR Janis Danisevskis, Michael Peter, Jan Nordholz
2018	J	`jnl`	Semantic Interpretation of Mobile Laser Scanner Point Clouds in Indoor Scenes Using Trajectories. Remote. Sens. Shayan Nikoohemat, Michael Peter, Sander Oude Elberink, George Vosselman
2018	J	`jnl`	Space Subdivision in Indoor Mobile Laser Scanning Point Clouds Based on Scanline Analysis. Sensors Yi Zheng, Michael Peter, Ruofei Zhong, Sander Oude Elberink, Quan Zhou
2018	J	`jnl`	Space Subdivision of Indoor Mobile Laser Scanning Data Based on the Scanner Trajectory. Remote. Sens. Ahmed Elseicy, Shayan Nikoohemat, Michael Peter, Sander Oude Elberink
2017	J	`jnl`	Challenges & Solutions for above 6 GHz Radio Access Network Integration for Future Mobile Communication Systems. CoRR Marcin Rybakowski, Krystian Safjan, Venkatkumar Venkatasubramanian, Arnesh Vijay, Laurent Dussopt, Ali A. Zaidi, Michael Peter, Jian Luo, Maria Fresia, Mehrdad Shariat
2017	—	`conf`	Dense matching quality evaluation - an empirical study. JURSE Zhenchao Zhang, Markus Gerke, Michael Peter, Michael Ying Yang, George Vosselman
2017	J	`jnl`	Millimeter-Wave Channel Measurements and Analysis for Statistical Spatial Channel Model in In-Building and Urban Environments at 28 GHz. IEEE Trans. Wirel. Commun. Junghoon Ko, Yeon-Jea Cho, Sooyoung Hur, Taehwan Kim, Jeongho Park, Andreas F. Molisch, Katsuyuki Haneda, Michael Peter, Dong-Jo Park, Dong-Ho Cho
2017	J	`jnl`	On the Frequency Dependency of Radio Channel's Delay Spread: Analyses and Findings From mmMAGIC Multi-frequency Channel Sounding. CoRR Sinh Le Hong Nguyen, Jonas Medbo, Michael Peter, Aki Karttunen, Katsuyuki Haneda, Aliou Bamba, Raffaele D'Errico, Naveed Iqbal, Cheikh Diakhate, Jean-Marc Conrat
2016	—	`conf`	5G systems: The mmMAGIC project perspective on use cases and challenges between 6-100 GHz. WCNC Workshops Miurel Tercero, Peter von Wrycza, Aditya Amah, Joerg Widmer, Maria Fresia, Valerio Frascolla, Javier Lorca, Tommy Svensson, Marie-Hélène Hamon, Sandrine Destouet Roblot, Arnesh Vijay, Michael Peter, Victoria Sgardoni, Mythri Hunukumbure, Jian Luo, Nikola Vucic
2016	B	`conf`	5G systems: The mmMAGIC project perspective on use cases and challenges between 6-100 GHz. WCNC Miurel Tercero, Peter von Wrycza, Aditya Amah, Joerg Widmer, Maria Fresia, Valerio Frascolla, Javier Lorca, Tommy Svensson, Marie-Hélène Hamon, Sandrine Destouet Roblot, Arnesh Vijay, Michael Peter, Victoria Sgardoni, Mythri Hunukumbure, Jian Luo, Nikola Vucic
2016	—	`conf`	Challenges & solutions for above 6 GHz radio access network integration for future mobile communication systems. ICC Workshops Marcin Rybakowski, Krystian Safjan, Venkatkumar Venkatasubramanian, Arnesh Vijay, Laurent Dussopt, Ali A. Zaidi, Michael Peter, Jian Luo, Maria Fresia, Mehrdad Shariat
2016	J	`jnl`	Channel Measurement and Modeling for 5G Urban Microcellular Scenarios. Sensors Michael Peter, Richard J. Weiler, Baris Göktepe, Wilhelm Keusgen, Kei Sakaguchi
2016	J	`jnl`	Environment Induced Shadowing of Urban Millimeter-Wave Access Links. 440-44 IEEE Wirel. Commun. Lett. Richard J. Weiler, Michael Peter, Wilhelm Keusgen, Kei Sakaguchi, Fabian Undi
2016	J	`jnl`	Investigation of MPC Correlation and Angular Characteristics in the Vehicular Urban Intersection Channel Using Channel Sounding and Ray Tracing. IEEE Trans. Veh. Technol. Panagiotis Ch. Paschalidis, Jörg Nuckelt, Kim Mahler, Michael Peter, Andreas Kortke, Mike Wisotzki, Wilhelm Keusgen, Thomas Kürner
2016	J	`jnl`	Quasi-deterministic millimeter-wave channel models in MiWEBA. EURASIP J. Wirel. Commun. Netw. Richard J. Weiler, Michael Peter, Wilhelm Keusgen, Alexander Maltsev, Ingolf Karls, Andrey Pudeyev, Ilya Bolotin, Isabelle Siaud, Anne-Marie Ulmer-Moll
2016	—	`conf`	Virtual Antenna Array Methodology for Outdoor Millimeter-Wave Channel Measurements. GLOBECOM Workshops Alexander Maltsev, Andrey Pudeyev, Richard J. Weiler, Michael Peter, Wilhelm Keusgen, Ilya Bolotin
2015	J	`jnl`	A Secure System Architecture for Measuring Instruments in Legal Metrology. Comput. Daniel Peters, Michael Peter, Jean-Pierre Seifert, Florian Thiel
2015	—	`conf`	A secure software framework for Measuring Instruments in legal metrology. I2MTC Daniel Peters, Florian Thiel, Michael Peter, Jean-Pierre Seifert
2015	—	`conf`	Automotive MILS. GI-Jahrestagung Jean-Pierre Seifert, Michael Peter
2015	—	`conf`	Millimeter-Wave Small-Cell Backhaul Measurements and Considerations on Street-Level Deployment. GLOBECOM Workshops Michael Peter, Richard J. Weiler, Thomas Kühne, Baris Göktepe, Jasminka Serafimoska, Wilhelm Keusgen
2015	—	`conf`	Millimeter-wave channel sounding of outdoor ground reflections. RWS Richard J. Weiler, Michael Peter, Wilhelm Keusgen, Andreas Kortke, Mike Wisotzki
2015	Misc	`conf`	Uncloaking Rootkits on Mobile Devices with a Hypervisor-Based Detector. ICISC Julian Vetter, Matthias Junker-Petschick, Jan Nordholz, Michael Peter, Janis Danisevskis
2015	—	`conf`	Undermining Isolation Through Covert Channels in the Fiasco.OC Microkernel. ISCIS Michael Peter, Matthias Petschick, Julian Vetter, Jan Nordholz, Janis Danisevskis, Jean-Pierre Seifert
2015	—	`conf`	XNPro: Low-Impact Hypervisor-Based Execution Prevention on ARM. TrustED@CCS Jan Nordholz, Julian Vetter, Michael Peter, Matthias Junker-Petschick, Janis Danisevskis
2014	—	`conf`	Achieving Software Security for Measuring Instruments under Legal Control. FedCSIS (Position Papers) Daniel Peters, Ulrich Grottker, Florian Thiel, Michael Peter, Jean-Pierre Seifert
2014	—	`conf`	Enabling 5G backhaul and access with millimeter-waves. EuCNC Richard J. Weiler, Michael Peter, Wilhelm Keusgen, Emilio Calvanese Strinati, Antonio De Domenico, Ilario Filippini, Antonio Capone, Isabelle Siaud, Anne-Marie Ulmer-Moll, Alexander Maltsev, Thomas Haustein, Kei Sakaguchi
2014	A*	`conf`	MapGENIE: Grammar-enhanced indoor map construction from crowd-sourced data. PerCom Damian Philipp, Patrick Baier, Christoph Dibak, Frank Dürr, Kurt Rothermel, Susanne Becker, Michael Peter, Dieter Fritsch
2014	B	`conf`	On the choice of carrier frequency and bandwidth for 5G small cell deployments. PIMRC Richard J. Weiler, Wilhelm Keusgen, Hung-Anh Nguyen, Michael Peter
2014	B	`conf`	Outdoor millimeter-wave access for heterogeneous networks - Path loss and system performance. PIMRC Richard J. Weiler, Michael Peter, Wilhelm Keusgen, Hidekazu Shimodaira, Gia Khanh Tran, Kei Sakaguchi
2014	—	`conf`	Quasi-deterministic approach to mmWave channel modeling in a non-stationary environment. GLOBECOM Workshops Alexander Maltsev, Andrey Pudeyev, Ingolf Karls, Ilya Bolotin, Gregory Morozov, Richard J. Weiler, Michael Peter, Wilhelm Keusgen
2014	J	`jnl`	Undermining Isolation through Covert Channels in the Fiasco.OC Microkernel. IACR Cryptol. ePrint Arch. Michael Peter, Jan Nordholz, Matthias Petschick, Janis Danisevskis, Julian Vetter, Jean-Pierre Seifert
2013	—	`conf`	Image based 3D Reconstruction in Cultural Heritage Preservation. ICINCO (1) Alessandro Cefalu, Mohammed Abdel-Wahab, Michael Peter, Konrad Wenzel, Dieter Fritsch
2013	—	`conf`	Realistic IEEE 802.11p Transmission Simulations Based on Channel Sounder Measurement Data. VTC Fall Kim Mahler, Panagiotis Ch. Paschalidis, Andreas Kortke, Michael Peter, Wilhelm Keusgen
2013	C	`conf`	Refinement of coarse indoor models using position traces and a low-cost range camera. IPIN Michael Peter, Ali Mohammad Khosravani, Dieter Fritsch
2012	—	`conf`	Statistical Evaluation of Multipath Component Lifetime in the Car-to-Car Channel at Urban Street Intersections Based on Geometrical Tracking. VTC Spring Panagiotis Ch. Paschalidis, Kim Mahler, Andreas Kortke, Michael Peter, Wilhelm Keusgen
2011	—	`conf`	2 X 2 MIMO Measurements of the Wideband Car-to-Car Channel at 5.7 GHz on Urban Street Intersections. VTC Fall Panagiotis Ch. Paschalidis, Kim Mahler, Andreas Kortke, Mike Wisotzki, Michael Peter, Wilhelm Keusgen
2011	—	`conf`	L4Android: a generic operating system framework for secure smartphones. SPSM@CCS Matthias Lange, Steffen Liebergeld, Adam Lackorzynski, Alexander Warg, Michael Peter
2011	—	`conf`	Pathloss and Multipath Power Decay of the Wideband Car-to-Car Channel at 5.7 GHz. VTC Spring Panagiotis Ch. Paschalidis, Kim Mahler, Andreas Kortke, Michael Peter, Wilhelm Keusgen
2009	—	`conf`	Car-to-Car MIMO Radio Channel Measurements at 5.7 GHz in Typical Communication Scenarios. VTC Fall Panagiotis Ch. Paschalidis, Andreas Kortke, Kim Mahler, Michael Peter, Mike Wisotzki, Wilhelm Keusgen
2009	—	`conf`	Measurement-Based Investigation of 60 GHz Broadband Transmission for Wireless In-Car Communication. VTC Fall Michael Peter, Robert Felbecker, Wilhelm Keusgen, Joachim Hillebrand
2009	—	`conf`	Presentation and Evaluation of Inconsistencies in Multiply Represented 3D Building Models. QuaCon Michael Peter
2009	—	`conf`	Privacy-enabling abstraction and obfuscation techniques for 3D city models. SPRINGL Martin Kada, Michael Peter, Dieter Fritsch, Oliver Siemoneit, Christoph Hubig
2009	—	`conf`	Virtual machines jailed: virtualization in systems with small trusted computing bases. VDTS@EuroSys Michael Peter, Henning Schild, Adam Lackorzynski, Alexander Warg
2008	—	`conf`	A Design Concept for a 60 GHz Wireless In-Flight Entertainment System. VTC Fall Jian Luo, Wilhelm Keusgen, Andreas Kortke, Michael Peter
2008	—	`conf`	A Wideband Channel Sounder for Car-to-Car Radio Channel Measurements at 5.7 GHz and Results for an Urban Scenario. VTC Fall Panagiotis Ch. Paschalidis, Mike Wisotzki, Andreas Kortke, Wilhelm Keusgen, Michael Peter
2008	—	`conf`	Incabin Millimeter Wave Propagation Simulation in a Wide-Bodied Aircraft Using Ray-Tracing. VTC Fall Robert Felbecker, Wilhelm Keusgen, Michael Peter
2007	—	`conf`	Measurement and Analysis of the 60 GHz In-Vehicular Broadband Radio Channel. VTC Fall Michael Peter, Wilhelm Keusgen, Andreas Kortke, Martin Schirrmacher
2006	B	`conf`	Statistics of the Ricean K-Factor at 5.2 Ghz in an Urban Macro-Cell Scenario. PIMRC Lars Thiele, Michael Peter, Volker Jungnickel
2005	C	`conf`	The Nizza secure-system architecture. CollaborateCom Hermann Härtig, Michael Hohmuth, Norman Feske, Christian Helmuth, Adam Lackorzynski, Frank Mehnert, Michael Peter
2004	—	`conf`	Reducing TCB size by using untrusted components: small kernels versus virtual-machine monitors. ACM SIGOPS European Workshop Michael Hohmuth, Michael Peter, Hermann Härtig, Jonathan S. Shapiro
1998	—	`conf`	Common Logging Interface - Ein System zum Sammeln und Verarbeiten von Debugnachrichten in verteilten Umgebungen. Java-Informations-Tage Raimar Falke, Michael Peter, Achim Gratz, Rainer G. Spallek