Al-Dhahir, Naofal

Permanent URI for this collectionhttps://hdl.handle.net/10735.1/6342

Naofal Al-Dhahir is an Erik Jonsson Distinguished Professor of Electrical Engineering. He is also a Fellow of the IEEE. His research interests include:

  • Machine/Deep learning applications
  • Smart grid
  • V2X communications
  • PHY security
  • Broadband wireless (cellular and WiFi)
  • Wireline (DSL and powerline) communications

News

Recipient of the Signal Processing and Communications Electronics Technical Recognition Award from the Institute of Electrical and Electronics Engineers (December 2019)

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Recent Submissions

Now showing 1 - 3 of 3
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    Security-Enhanced SC-FDMA Transmissions Using Temporal Artificial-Noise and Secret Key Aided Schemes
    (IEEE-Inst Electrical Electronics Engineers Inc, 2019-01-19) Marzban, Mohamed F.; El Shafie, Ahmed; Al-Dhahir, Naofal; Hamila, Ridha; 0000-0002-7214-0745 (Marzban, MF); 0000-0002-7315-8242 (EL Shafie, A); 113149196515374792028 (Al-Dhahir, N); Marzban, Mohamed F.; El Shafie, Ahmed; Al-Dhahir, Naofal
    We investigate the physical-layer security of uplink single-carrier frequency-division multiple-access (SC-FDMA) systems. Multiple users, Alices, send confidential messages to a common legitimate base-station, Bob, in the presence of an eavesdropper, Eve. To secure the legitimate transmissions, each user superimposes an artificial noise (AN) signal on the time-domain SC-FDMA data symbol. We reduce the computational and storage requirements at Bob's receiver by assuming simple per-sub-channel detectors. We assume that Eve has global channel knowledge of all links in addition to high computational capabilities, where she adopts high-complexity detectors such as single-user maximum likelihood (ML), multi-user minimum-mean-square-error, and multi-user ML. We analyze the correlation properties of the time-domain AN signal and illustrate how Eve can exploit them to reduce the AN effects. We prove that the number of useful AN streams that can degrade Eve's signal-to-noise ratio is dependent on the channel memories of Alices-Bob and Alices-Eve links. Furthermore, we enhance the system security for the case of partial Alices-Bob channel knowledge at Eve, where Eve only knows the precoding matrices of the data and AN signals instead of knowing the entire Alices-Bob channel matrices, and propose a hybrid security scheme that integrates temporal AN with channel-based secret key extraction.
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    Power Splitting-Based SWIPT with Dual-Hop DF Relaying in the Presence of a Direct Link
    (Institute of Electrical and Electronics Engineers Inc.) Ye, Y.; Li, Y.; Zhou, F.; Al-Dhahir, Naofal; Zhang, H.; Al-Dhahir, Naofal
    This letter investigates the outage performance of dual-hop decode and forward relay systems in the presence of a direct link between the source and the destination, where simultaneous wireless information and power transfer is exploited at the relay by using a static/dynamic power splitting (PS) scheme. An analytical expression for the outage probability is derived to determine the optimal static PS ratio. Moreover, we study the dynamic PS scheme and derive a closed-form expression for the optimal dynamic PS ratio to minimize the outage probability at a given target rate. Furthermore, an analytical expression for the outage probability with the optimal dynamic PS ratio is also presented. It is shown that a full diversity gain can be achieved in the investigated system with static/dynamic PS scheme, and that the dynamic PS scheme outperforms the static PS scheme. ©2018 IEEE
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    Outage Probability of Single Carrier NOMA Systems under I/Q Imbalance
    (Institute of Electrical and Electronics Engineers Inc.) Selim, B.; Muhaidat, S.; Sofotasios, P. C.; Sharif, B. S.; Stouraitis, T.; Karagiannidis, G. K.; Al-Dhahir, Naofal; 113149196515374792028 (Al-Dhahir, N); Al-Dhahir, Naofal
    Non-orthogonal multiple access (NOMA) has been recently proposed as a viable technology that has the potential to improve the spectral efficiency of fifth generation (5G) wireless networks and beyond. However, in practical communication scenarios, transceiver architectures inevitably suffer from radio-frequency (RF) front-end related impairments that can lead to non-negligible degradation of the overall system performance. In this context, in-phase/quadrature-phase imbalance (IQI) constitutes a major impairment in direct-conversion transceivers. Based on this, the present contribution quantifies the effects of IQI on the performance of NOMA based systems under multipath fading conditions. This is realized by first deriving novel analytic expressions for the signal-to-interference-plus-noise ratio and the outage probability of NOMA systems subject to IQI at the transmitter and/or the receiver sites. Capitalizing on these results, we demonstrate that the effects of IQI differ considerably between the different NOMA users and depending on the considered system's parameters. © 2018 IEEE.

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