Mohamed Salah Ibrahim

Astana Medical University

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Nicholas D. Sidiropoulos

University of Virginia

Giovanni Del Galdo

Technische Universität Ilmenau

Reiner S. Thomä

Technische Universität Ilmenau

Aritra Konar

KU Leuven

Florian Roemer

Fraunhofer Institute for Nondestructive Testing

Florian Römer

Fraunhofer Institute for Nondestructive Testing

Mihaela Beluri

InterDigital (United States)

Akshay Malhotra

InterDigital (United States)

Wen Xu

Huawei Technologies (Germany)

Ahmed S. Zamzam

National Renewable Energy Laboratory

Cooperative Institutions

Technische Universität Ilmenau

Oldenburger Institut für Informatik

Fraunhofer Institute for Integrated Circuits

Huawei Technologies (Germany)

Nile University

Huawei German Research Center

Fraunhofer Society

InterDigital (United States)

University of Minnesota

University of Virginia

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Audio-Enhanced Video-to-Audio Retrieval Using Text-Conditioned Feature Alignment

Anuj Razdan Praveen Kumar Shaveta Bhatia Nripendra Narayan Das Alibek Orynbek

Audio analyzer

Feature (linguistics)

Video retrieval

Audio mining

10.1109/iccsc62048.2024.10830345

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Unsupervised Learning for Pilot-free Transmission in 3GPP MIMO Systems

arXiv (Cornell University) (2023)

Omar M. Sleem Mohamed Salah Ibrahim Akshay Malhotra Mihaela Beluri Philip Pietraski

Reference signals overhead reduction has recently evolved as an effective solution for improving the system spectral efficiency. This paper introduces a new downlink data structure that is free from demodulation reference signals (DM-RS), and hence does not require any channel estimation at the receiver. The new proposed data transmission structure involves a simple repetition step of part of the user data across the different sub-bands. Exploiting the repetition structure at the user side, it is shown that reliable recovery is possible via canonical correlation analysis. This paper also proposes two effective mechanisms for boosting the CCA performance in OFDM systems; one for repetition pattern selection and another to deal with the severe frequency selectivity issues. The proposed approach exhibits favorable complexity-performance tradeoff, rendering it appealing for practical implementation. Numerical results, using a 3GPP link-level testbench, demonstrate the superiority of the proposed approach relative to the state-of-the-art methods.

Boosting

Spectral Efficiency

Channel state information

10.48550/arxiv.2302.02191

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A Simple and Practical Underlay Scheme for Short-Range Secondary Communication

IEEE Transactions on Wireless Communications (2022)

Mohamed Salah Ibrahim Paris A. Karakasis Nicholas D. Sidiropoulos

The unprecedented growth in wireless Internet-of-Things and WiFi devices has renewed interest in mechanisms for efficient spectrum reuse. Existing schemes require some level of primary-secondary coordination, cross-channel state estimation and tracking, or activity detection– which complicate implementation. For low-power short-range secondary communication, the main impediment is strong and time-varying (e.g., intermittent) interference from the primary system. This paper proposes a practical underlay scheme that permits reliable secondary communication in this regime. The secondary transmitter merely has to send its signal twice, at very low power - a few dBs above the noise floor, but far below the primary's interference. Exploiting the repetition structure, reliable and computationally efficient recovery of the secondary signal is possible via canonical correlation analysis (CCA). Experiments using a software radio testbed reveal that, for a secondary user with only two receive antennas, reliable detection of the secondary signal is possible for signal to interference plus noise ratio (SINR) in the range of −20 to −40 dB. The approach works with unknown time-varying channels, digital or analog modulation, it is immune to carrier frequency offset, and, as a side-benefit, it provides means for accurate synchronization of the secondary user even at very low SINR.

Underlay

10.1109/twc.2022.3181618

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MAPPING THE CONFORMATION SPACE OF _-PROLINE BY MATRIX-ISOLATION IR SPECTROSCOPY COMBINED WITH NIR LASER INDUCED CONFORMATIONAL CHANGE AND STATE-OF-THE-ART AB INITIO COMPUTATIONS

Proceedings of the 74th International Symposium on Molecular Spectroscopy (2019)

György Tarczay Małgorzata Biczysko Mohamed Salah Ibrahim Tamás Vörös Anita Schneiker

The conformers of α-proline were studied by matrix-isolation IR spectroscopy.In order to group the vibrational bands to different conformers, conformational changes were induced by NIR laser irradiations, by exciting the OH stretching overtone of a selected conformer.For identification, the single conformer spectra were compared to state-of-the-art ab initio computations.Infrared spectra and anharmonic thermodynamic corrections have been computed by means of second order vibrational perturbation theory (VPT2), with GVPT2 and HDCPT2 models, respectively.A hybrid force-field was developed by addition of the cubic and semi-diagonal quartic B3LYP-D3/SNSD force constants to the (harmonic quadratic) B2PLYP-D3/maug-cc-pVTZ results.As the result of the spectrum analysis, seven conformers could be identified.Four of these conformers were present in the as-deposited matrix, two of them were generated by the NIR laser irradiation, and found to be stable in Ar matrix.The seventh conformer could also be produced upon the NIR laser irradiation, and it decays by H-atom tunneling to a lower energy form on the sub-second and minute timescales in Ar and N 2 matrices, respectively.

Matrix Isolation

Matrix (chemical analysis)

Conformational change

10.15278/isms.2019.ml06

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Pilot allocation trade-off for low latency and high reliability transmission

Mohamed Salah Ibrahim Wen Xu

5G is expected to support a wide variety of new services which will potentially have quite strict requirements on the wireless communication link. Currently, the standard indicator of a service requirement is its Latency/Reliability tolerance. The 5G usecases demand ultra low latency and ultra high reliability. Generally speaking, those two requirements are contradictive. Latency and reliability budgets are a function of all the parameters in the communication layers. This work investigates the latency/reliability aspect at the PHY layer. One of the most influential parameters which control latency and reliability is the pilot design. For a constrained bandwidth, increasing the pilot density will enhance reliability, but will increase latency due to the increased pilot overhead, and vice versa. Hence, there exists a trade-off pilot allocation which balances the contradicitve requirements of latency and reliability. This work proposes a practical method for the transmitter to tune the pilot spacings based on the optimal solutions of latency/reliability.

PHY

10.1109/ict.2016.7500425

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Citations (2)

A Novel Linear Precoder Design for Reliable UL/DL Detection in TDD Cellular Networks

IEEE Transactions on Communications (2022)

Mohamed Salah Ibrahim Ahmed A. Hussain Nicholas D. Sidiropoulos

The ever-growing demands on wireless connectivity, especially with the emergence of various data-intensive low-latency applications, require novel multiplexing solutions capable of reliably supporting high rates at low latency. Non-orthogonal time division duplex (TDD) coupled with multiuser detection can meet these emerging needs, provided that accurate channel state information is available. This paper proposes a new pilot-free TDD frame structure that allows designing highly effective multiuser decoders and precoders for uplink and downlink multicell systems, in an unsupervised manner. The key idea is that each user repeats and permutes its uplink data using a pre-assigned permutation code. Invoking canonical correlation analysis (CCA) at the serving BS on the two deinterleaved uplink blocks yields high quality CCA-based beamformers capable of both recovering the uplink and precoding the downlink user signals in a way that effectively mitigates interference. The paper includes a pilotless synchronization framework that leverages CCA to recover the timing and frequency offsets in an asynchronous multiuser MIMO setup, without using pilots. Simulations are used to study the performance of the proposed approach on a large-scale network with multiple users and cells, while laboratory experiments with a small-scale network of software radios are used to demonstrate that the approach works well in practice under common hardware imperfections.

Duplex (building)

10.1109/tcomm.2022.3217129

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Citations (3)

On Numerology and Capacity of the Self-Contained Frame Structure

2022 IEEE Globecom Workshops (GC Wkshps) (2016)

Mohamed Salah Ibrahim Wen Xu

The advent of 5G will enable further diverse types of services to be supported, some of which have different requirements from the radio access architecture such as extreme low latency, ultra-high reliability and massive connectivity. With the scarcity of the available bandwidth, careful design of radio frame structures is essential in order to efficiently support the challenging requirements of 5G. The flexible numerology design of the PHY layer frame structure is a key tool in achieving low latency and high reliability. In this paper, we present a methodology to compute the optimal numerology for a given set of requirements from the PHY layer. It is shown that during low mobility and high SNR regimes, the choice of the numerology becomes more critical than at high mobility and low SNR regimes.

PHY

10.1109/glocomw.2016.7848974

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Citations (4)

Weak Target Detection in MIMO Radar via Beamspace Canonical Correlation

Mohamed Salah Ibrahim Nicholas D. Sidiropoulos

Reliable detection and accurate estimation of weak targets and their Doppler frequencies is a challenging problem in MIMO radar systems. Reflections from such targets are often overpowered by those from stronger nearby targets and clutter. Considering a 3-D data model where the coherent processing interval comprises multiple pulses, a novel weak target detection and estimation approach is proposed in this paper. The proposed method is based on creating partially overlapping spatial beams, and performing canonical correlation analysis (CCA) in the resulting beamspace. It is shown that if a target is present in the overlap sector, then its Doppler profile can be reliably estimated via beamspace CCA, even if hidden under much stronger interference from nearby targets and clutter. Numerical results are included to validate this theoretical claim, demonstrating that the proposed Beamspace Canonical Correlation (BCC) method yields considerable performance improvement over existing approaches.

Canonical correlation

Radar detection

10.1109/sam48682.2020.9104284

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Citations (5)

A Frame Structure with Precoding for Bidirectional Low Latency Applications

2022 IEEE Globecom Workshops (GC Wkshps) (2017)

Mohamed Salah Ibrahim Wen Xu

The advent of 5G will introduce new classes of services which demand different requirements compared to traditional radio systems. Of particular interest is the Ultra-Reliable Low Latency Communication (URLLC), which restricts the PHY layer to short deadlines for delivering the radio message. For OFDM based systems, the radio frame structure should be able to support large variations in data rates of any two given communicating nodes. Legacy radio frame structures did not take such restrictions into account. In this paper, we present a flexible radio frame structure where, under low latency constraints, large variations in the bi-directional data rates can be easily supported using time and frequency duplexing. As such, a fair subdivision of the radio resources which fit into the exact requested data rates becomes possible. To maintain high spectral efficiency, the bi-directional traffics are packed close to each other in frequency domain, which leads to considerable amount of cross talk. To suppress this interference, we introduce a novel precoder which mitigates the cross talk interference in baseband.

PHY

10.1109/glocomw.2017.8269138

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On the Capacity Region of the Deterministic Y-Channel with Common and Private Messages

Mohamed Salah Ibrahim Mohammed Nafie Yahya Mohasseb

In multi user Gaussian relay networks, it is desirable to transmit private information to each user as well as common information to all of them. However, the capacity region of such networks with both kinds of information is not easy to characterize. Prior art exploits the linear deterministic models to approximate the capacities of these Gaussian networks. This paper studies the capacity region of the deterministic Y-channel with private and common messages. In this channel, each user aims at delivering two private messages to the other two users in addition to a common message directed towards both of them. As there is no direct link between the users, all messages must pass through an intermediate relay. We present outer-bounds on the rate region using genie-aided and cut-set bounds. Then, we develop a greedy scheme to define an achievable region and show that at a certain number of levels at the relay, our achievable region coincides with the upper bound. Finally, we argue that these bounds for this setup are not sufficient to characterize the capacity region.

Private information retrieval

10.1109/ieeeconf44664.2019.9048781

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Citations (1)