Shaimaa ElSayed

@modern-academy.edu.eg

Electronics and communications
Modern Academy for Engineering and Technology in Maadi

Shaimaa ElSayed


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https://researchid.co/shaimaa_elsayed

RESEARCH, TEACHING, or OTHER INTERESTS

Signal Processing, Electrical and Electronic Engineering, Engineering, Statistics and Probability
8

Scopus Publications

Scopus Publications

  • Enhancing the performance of NOMA-based VLC systems using a proposed adaptive superimposed constellation Algorithm with an exact SER analysis
    Androw Sobhy, Shaimaa ElSayed, Hala Abd El-kader Mansour, Maher Abdelrasoul, Esraa M. Eid
    Optics Communications, 2025
  • Orthogonal beamforming technique for massive MIMO systems
    Marwa Abdelfatah, Abdelhalim Zekry, Shaimaa ElSayed
    Annales Des Telecommunications Annals of Telecommunications, 2025
    Beamforming represents a pivotal technology in massive multiple-input multiple-output (MIMO) systems, as it facilitates the regulation of transmission and reception operations. Beamforming techniques’ categorization is based either on their hardware architecture or implementation strategy. This paper proposes an orthogonal beamforming technology founded on a specific implementation method that utilizes predetermined orthogonal beams to serve users. The suggested approach incorporates numerous orthogonal beams relying on a substantial number of antennas at the base station. The primary objective of this approach is to enhance the performance of massive MIMO systems by augmenting spectral efficiency and accommodating more users. The proposed beamforming approach is well suited for millimeter frequency bands. The purpose of this paper is to explore the suggested orthogonal beamforming technology. The concept of this approach is described at first and then followed by an evaluation of its efficacy for a single user through the allocation of orthogonal beams. The suggested approach is also examined in the context of multiuser systems, and the results are compared with the adaptive ZF beamforming technique. Furthermore, the paper presents solutions to the issues that may arise in multiuser systems, for example, ensuring that each orthogonal beam is assigned to only one user. The simulations conducted in this study demonstrate that the suggested approach outperforms the ZF technique in terms of both the spectral efficiency and the number of serviced users. Specifically, the suggested approach can enhance SE by approximately 40.6% over the ZF technique, and it can support up to double the number of users when compared to the ZF approach.
  • Generic 5G NR LDPC Encoder Architecture Optimized for Area and Throughput
    Muhammed Tarek, Eman Mohamed, Shaimaa ElSayed, Nahla Elashkar
    Journal of Electrical and Computer Engineering, 2025
    Physical Downlink Shared Channel (PDSCH) in 5G New Radio (NR) uses LDPC codes as the channel coding solution for their efficient error‐correcting performance and suitability for high‐speed communications. To meet the high‐throughput requirements of the 5G NR technology, this paper discusses different 5G NR LDPC encoder architectures that enable different parallel encoding schemes and optimizes the design for specific metrics. The recent architectural designs might lack effective design metrics that ensure high throughput, low area and gate counts, and full compatibility with the 5G NR standard. The suggested architecture aims to a generic design with flexible controller that is fully compatible with all the supported code block sizes and code rates in the 5G NR standard. The design is implemented in ASIC using NanGate‐15 nm standard cells CMOS technology with The Cadence Genus synthesis solution. The proposed architecture targets high‐throughput encoding operations with a low‐area hardware design. The synthesis of the suggested encoder resulted in a maximum frequency of 1.71 GHz and gate counts of 491.8 K gates with all the code block sizes and code rates in 5G NR standard supported. For the largest code length, the proposed architecture’s throughput is up to 451.44 Gbps. Among the discussed previous works, there is one that targets a very high throughput of 257.9 Gbps but implemented using very high gate counts of 1126 K gates for only one code‐word size (25344, 8448). This previous work implements encoding operation in a sub‐matrix‐by‐sub‐matrix encoding scheme. To balance between gate counts and throughput, another previous encoder architecture work, designed for only one code‐word size (23232, 7744), achieved a relatively high throughput of 202.4 Gbps and gate counts of 486.4 K gates. This architecture conducts parallel encoding operation in a row‐by‐row scheme. The results confirmed that the proposed architecture achieves suitable balance between high throughput, gate counts, and 5G NR compatibility compared to the previous works. The postsynthesis results showed a throughput improvement of 123% and 75.04% compared to row‐by‐row and submatrix‐based schemes, respectively. They also show a gate count reduction of 56% and 23.1% compared to submatrix‐based and column‐based schemes, respectively.
  • User Selection Methods for Overcoming Growing Number of Served Users in Massive MIMO Systems
    Marwa Abdelfatah, Abdelhalim Zekry, Shaimaa ElSayed
    IEEE Access, 2023
    Massive MIMO is dominant in the current wireless communication systems. Massive MIMO system uses a massive number of antennas to serve multi-users simultaneously. The growth of served users in the system will increase the interference between them and affect the system’s performance. To maintain the qualified service for the growing number of users, user selection techniques can be used to separate users into groups to be served well. This paper proposes three user selection methods named Mean Step User Selection (MSUS), Second Null User Selection (SNUS), and Interference Threshold User Selection (ITUS) methods. These three user selection methods aim to serve users with the best possible performance. The performance of these proposed user selection methods will be evaluated and compared with the performance of the system without selection and with the system using other user selection methods such as Random User Selection (RUS), Semi-orthogonal User Selection (SUS), and Inter-Channel Interference Based Selection (ICIBS) methods. The simulation shows that the proposed MSUS, SNUS, and ITUS methods provide an improvement in the spectral efficiency of 75.39%, 92.13%, and 153.71% when compared with the system without the selection method. The proposed user selection methods also improve performance compared to other user selection methods.
  • A Study on the Basics Processes of Massive MIMO
    Marwa Abdelfatah, Shaimaa ElSayed, Abdelhalim Zekry
    Journal of Communications, 2022
    Massive Multiple Input Multiple Output (MIMO) is a key technique used in 5G mobile communication systems; it aims to efficiently increase the spectral efficiency of the communication systems. Massive MIMO is a MIMO system with a massive number of antennas in the base station, it uses its large number of antennas to efficiently transmit and receive the signals between the base stations and the user equipment and maximize the spectral efficiency of the system. Massive MIMO is mainly composed of three important processes: channel estimation, uplink transmission (receive beamforming), and downlink transmission (transmit beamforming). Based on the effective channel estimation methods, the base station can process the signal to make efficient transmit and receive beamforming and provide good transmission and reception quality, which is measured by the spectral efficiency of the system. Many references present the basics of massive MIMO processes, including channel estimation, transmit beamforming and receive beamforming. This paper aims to present a cleared and concluded study on these basics massive MIMO processes. It presents different channel estimation methods and evaluates its performance based on the normalized mean square error. It also presents different receive and transmit beamforming techniques and evaluates its performance based on spectral efficiency.
  • Enhancing the performance of optical VLC system based on asymmetric symmetric subcarriers OFDM
    Androw Sobhy, Shaimaa ElSayed, Abdelhalim Zekry
    International Journal of Communication Systems, 2020
    SummaryRecently, visible light communications (VLCs) based on the orthogonal frequency‐division multiplexing (OFDM) technique play an important role in the field of wireless communications. Researches in that field found techniques to improve performance and reduce the system complexity. This paper proposes a system named asymmetric symmetric subcarriers enhanced optical (ASSEO)‐OFDM applied to VLC based on OFDM technique. The proposed system enhances the transmitted data rate by a factor of 1/8 compared with other existing systems. Keeping the same transmitted data rate as the comparable techniques, simulation results show an enhancement of the Eb/No for the proposed system by at least 0.65 dB than asymmetrically and symmetrically clipping optical (ASCO)‐OFDM, by at least 2 dB than asymmetrically clipped optical (ACO)‐OFDM and FLIP‐OFDM, and by at least 0.9 dB than DC‐biased optical (DCO)‐OFDM system at bit error rate (BER) of 10−4. An analytical description of the ASSEO proposed system is also introduced in this paper besides a comparative study with other existing systems.
  • Performance enhancement of an indoor localization system based on visible light communication using rssi/tdoa hybrid technique
    Marina Karmy, Shaimaa ElSayed, Abdelhalim Zekry
    Journal of Communications, 2020
    This work introduces an enhanced optical wireless Line of Sight (LOS) indoor localization system based on Visible Light Communication (VLC) technology using Light-Emitting Diodes (LEDs) as optical sources. Although Received Signal Strength Indication (RSSI) localization algorithm is simple and needs no extra hardware to be installed, but its performance is poor at some received areas compared to Time Difference of Arrival (TDOA) technique. That is because RSSI technique depends on the received power strength which is degraded towards room corners. Therefore, the proposed system is a combination between RSSI and TDOA algorithms and the target position is estimated using RSSI only at places with acceptable received electrical power (1.04x10W or between 6.53x10 to 9.92x10W) while TDOA will be used at the other positions. Thus, this hybrid localization system will decrease the root mean-squared-error (RMSE) from 7.34cm using RSSI technique only on the whole received area to 5.81cm (using this hybrid system) and will save time. Some parameters that affect the performance of both RSSI and TDOA techniques are also included in this work in order to select the suitable values in the hybrid localization system. This work is evaluated by using MATLAB software version 2013. 
  • C15. CFO mitigation in OFDM systems with a comparative analysis to CP-based estimator technique
    Shaimaa ElSayed, K.A. ElBarbary, Ragab M. El-Sagheer
    National Radio Science Conference NRSC Proceedings, 2015
    The sensitivity of Orthogonal Frequency Division Multiplexing (OFDM) systems to Carrier Frequency Offset (CFO) is a major disadvantage. Researchers have proposed various CFO compensation techniques. One method is to use the inherent construction of the OFDM symbol by estimating the value of CFO using the cyclic prefix (CP) part then compensate for it. The estimated CFO range of this method does not exceed half the value of the subcarrier spacing. One of the major competitions between researchers is to enlarge the estimation range. Our proposed scheme enlarges this range by four times at least compared to the CP-based technique keeping low complexity. This is done at the expense of reducing, slightly, the transmitted data rate. This paper discusses the proposed scheme in both cyclic-prefix and zero-padding systems with a comparative analysis to the CP-based estimator technique. The simulations are done for Rayleigh multipath fading channels using MATLAB.