Yalçın Şadi

Şadi, Yalçın

Name Variants

ŞADI, Yalçın
Şadi,Y.
Sadi,Y.
Yalçın Şadi
ŞADI, YALÇIN
Şadi, Y.
Sadi, Y.
Y. Sadi
Yalçın ŞADI
YALÇIN ŞADI
Sadi,Yalcin
S., Yalcin
Sadi, Yalçın
Şadi, Yalçın
Yalçın Sadi
Sadi Y.
Ş., Yalçın
Y. Şadi
Şadi, YALÇIN
Sadi, Yalcin
Yalcin, Sadi
S.,Yalcin
Şadi Y.

Job Title

Dr. Öğr. Üyesi

Email Address

yalcin.sadi@khas.edu.tr

ORCID ID

0000-0002-8378-5688

Scopus Author ID

36844802900

Full item page

Scholarly Output

23

Articles

8

Citation Count

148

Supervised Theses

4 Scholarly Output Search Results

Now showing 1 - 10 of 23

Citation Count: 1
The Effect of Codebook Design on the Conventional SCMA System Performance
(Institute of Electrical and Electronics Engineers Inc., 2020) Şadi, Yalçın; Bardakci, E.; Sadi, Y.; Erkucuk, S.
In 4G systems, Orthogonal Frequency-Division Multiple Access (OFDMA) has been used conventionally for multiple access purposes. This technique has low spectral efficiency since it allocates the resources orthogonally to each user. As an alternative to this technique, Non-orthogonal Multiple Access (NOMA) has been proposed for new generation systems as it allows different users to use the same resources and therefore, increases spectral efficiency. Sparse Code Multiple Access (SCMA) is a code-based NOMA technique and its performance depends on codebook design. In this study, a conventionally used codebook design in the literature has been considered and the system performance has been improved by increasing the distance between the signal constellation points. Considering two different design approaches, the conventional codebook has been modified and about 1dB gain has been achieved in the high signal-to-noiseratio (SNR) region. © 2020 IEEE.
Citation Count: 0
NOMA-based Radio Resource Allocation for Machine Type Communications in 5G and Beyond Cellular Networks
(IEEE, 2021) Şadi, Yalçın; Sadi, Yalcin; Erkucuk, Serhat; Okumus, F. Batuhan
In this paper, the minimum bandwidth resource allocation problem for non-orthogonal multiple access (NOMA) based machine to machine (M2M) communications in 5G and beyond cellular networks is investigated. In order to solve the problem fast and efficiently, a persistent resource allocation based polynomial-time algorithm considering NOMA and the periodicity of the machine type communication traffic is proposed. The algorithm consists of two phases. In first phase, M2M clusters are divided into NOMA sub-clusters using a technique that minimizes the number of NOMA sub-clusters for a set of devices. In second phase, NOMA sub-clusters are allocated to resource blocks (RB) considering their quality of service (QoS) requirements while achieving minimum bandwidth reservation. Through simulations, the performance of the proposed algorithm is presented in comparison to the previously proposed access grant time interval (AGTI) based radio resource allocation algorithms. It is illustrated that the proposed algorithm improves the spectrum-efficiency significantly.
Citation Count: 31
Machine type communications: key drivers and enablers towards the 6G era
(SPRINGER, 2021) Şadi, Yalçın; Boecker, Stefan; Moerman, Ingrid; Lopez, Onel A.; Munari, Andrea; Mikhaylov, Konstantin; Clazzer, Federico; Bartz, Hannes; Park, Ok-Sun; Mercier, Eric; Saidi, Selma; Osorio, Diana Moya; Jantti, Riku; Pragada, Ravikumar; Annanpera, Elina; Ma, Yihua; Wietfeld, Christian; Andraud, Martin; Liva, Gianluigi; Chen, Yan; Garro, Eduardo; Burkhardt, Frank; Liu, Chen-Feng; Alves, Hirley; Sadi, Yalçın; Kelanti, Markus; Dore, Jean-Baptiste; Kim, Eunah; Shin, JaeSheung; Park, Gi-Yoon; Kim, Seok-Ki; Yoon, Chanho; Anwar, Khoirul; Seppanen, Pertti
The recently introduced 5G New Radio is the first wireless standard natively designed to support critical and massive machine type communications (MTC). However, it is already becoming evident that some of the more demanding requirements for MTC cannot be fully supported by 5G networks. Alongside, emerging use cases and applications towards 2030 will give rise to new and more stringent requirements on wireless connectivity in general and MTC in particular. Next generation wireless networks, namely 6G, should therefore be an agile and efficient convergent network designed to meet the diverse and challenging requirements anticipated by 2030. This paper explores the main drivers and requirements of MTC towards 6G, and discusses a wide variety of enabling technologies. More specifically, we first explore the emerging key performance indicators for MTC in 6G. Thereafter, we present a vision for an MTC-optimized holistic end-to-end network architecture. Finally, key enablers towards (1) ultra-low power MTC, (2) massively scalable global connectivity, (3) critical and dependable MTC, and (4) security and privacy preserving schemes for MTC are detailed. Our main objective is to present a set of research directions considering different aspects for an MTC-optimized 6G network in the 2030-era.
Citation Count: 2
Minimum Length Scheduling for Multi-Cell Full Duplex Wireless Powered Communication Networks
(Mdpi, 2021) Şadi, Yalçın; Sadi, Yalcin; Coleri, Sinem
Wireless powered communication networks (WPCNs) will be a major enabler of massive machine type communications (MTCs), which is a major service domain for 5G and beyond systems. These MTC networks will be deployed by using low-power transceivers and a very limited set of transmission configurations. We investigate a novel minimum length scheduling problem for multi-cell full-duplex wireless powered communication networks to determine the optimal power control and scheduling for constant rate transmission model. The formulated optimization problem is combinatorial in nature and, thus, difficult to solve for the global optimum. As a solution strategy, first, we decompose the problem into the power control problem (PCP) and scheduling problem. For the PCP, we propose the optimal polynomial time algorithm based on the evaluation of Perron-Frobenius conditions. For the scheduling problem, we propose a heuristic algorithm that aims to maximize the number of concurrently transmitting users by maximizing the allowable interference on each user without violating the signal-to-noise-ratio (SNR) requirements. Through extensive simulations, we demonstrate a 50% reduction in the schedule length by using the proposed algorithm in comparison to unscheduled concurrent transmissions.
Citation Count: 13
Minimum Length Scheduling for Full Duplex Time-Critical Wireless Powered Communication Networks
(IEEE, 2020) Şadi, Yalçın; Şadi, Yalçın; Coleri, Sinem
Radio frequency (RF) energy harvesting is key in attaining perpetual lifetime for time-critical wireless powered communication networks (WPCNs) due to full control on energy transfer, far field region, small and low-cost circuitry. In this paper, we propose a novel minimum length scheduling problem to determine the optimal power control, time allocation and schedule subject to data, energy causality and maximum transmit power constraints in a full-duplex WPCN. We first formulate the problem as a mixed integer non-linear programming problem and conjecture that the problem is NP-hard. As a solution strategy, we demonstrate that the power control and time allocation, and the scheduling problems can be solved separately in the optimal solution. For the power control and time allocation problem, we derive the optimal solution by evaluating Karush-Kuhn-Tucker conditions. For the scheduling, we introduce a penalty function allowing reformulation of the problem as a sum penalty minimization problem. Upon derivation of the optimality conditions based on the characteristics of the penalty function, we propose two polynomial-time heuristic algorithms and a reduced-complexity exact algorithm employing smart pruning techniques. Via extensive simulations, we illustrate that the proposed heuristic schemes outperform the schemes for predetermined transmission order of users and achieve close-to-optimal solutions.
Citation Count: 7
Energy efficient robust scheduling of periodic sensor packets for discrete rate based wireless networked control systems
(Elsevier, 2020) Şadi, Yalçın; Uçar, Seyhan; Şadi, Yalçın; Coleri, Sinem
Wireless networked control systems (WNCSs) require the design of a robust scheduling algorithm that meets the stringent timing and reliability requirements of control systems, despite the limited battery resources of sensor nodes and adverse properties of wireless communication for delay and packet errors. In this article, we propose a robust delay and energy constrained scheduling algorithm based on the exploitation of the mostly pre-known periodic data generation nature of sensor nodes in control systems. We first formulate the joint optimization of scheduling, power control and rate adaptation for discrete rate transmission model, in which only a finite set of transmission rates are supported, as a Mixed-Integer Non-linear Programming problem and prove its NP-hardness. Next, we propose an optimal polynomial-time power control and rate adaptation algorithm for minimizing the transmission time of a node subset. We then design a novel polynomial-time heuristic scheduling algorithm based on first determining the concurrently transmitting node subsets and then distributing them uniformly over time by a modified Karmarkar-Karp algorithm. We demonstrate the superior performance of the proposed scheduling algorithm in terms of robustness, delay and runtime on the Low-Rate Wireless Personal Area Network (LR-WPAN) simulation platform, which we developed in network simulator-3 (ns3).
Citation Count: 7
Minimum Length Scheduling for Discrete Rate Based Full Duplex Wireless Powered Communication Networks
(Springer, 2019) Şadi, Yalçın; Şadı, Yalçın; Ergen, Sinem Coleri
In this study, we consider a wireless powered communication network where multiple users with radio frequency energy harvesting capabilities communicate to a hybrid energy and information access point in full duplex mode. We characterize an optimization framework for minimum length scheduling to determine the optimal rate adaptation and transmission scheduling subject to energy causality and traffic demand constraints of the users considering discrete-rate transmission model. We first formulate the problem as a mixed integer nonlinear programming problem which is hard to solve for a global optimum in polynomial-time. Then, based on an analysis on the characteristics of the optimal solution, we derive optimality conditions for rate adaptation and scheduling using which we propose a fast polynomial-time complexity heuristic algorithm. We illustrate through numerical analysis that the proposed algorithm performs very close to optimal for various network scenarios.
Citation Count: 3
Scheduling and Relay Selection for Full-Duplex Wireless Powered Cooperative Communication Networks
(Institute of Electrical and Electronics Engineers Inc., 2020) Şadi, Yalçın; Syed, Kazmi Abbas Adil; Coleri, Sinem; Sadi, Yalçın
In this manuscript, we consider a full-duplex wireless powered cooperative communication system where the users communicate with a hybrid access point through relays. We formulate an optimization problem with the objective to minimize the total transmission time through user scheduling and relay selection while considering the traffic demand, energy causality and initial battery levels of the users. The formulated optimization problem is a mixed integer non-linear programming problem, hence difficult to solve for the global optimal solution. As a solution strategy, we decompose the problem into sub problems: time allocation, scheduling and relay selection. In the time allocation problem; the schedule and relays are assumed to be pre-known, we derive the optimal solution by using the optimality analysis. For the scheduling problem; we assume that users know their relays, we determine the optimal schedule. For the relay selection problem; users transmit their information in a pre-determined order, we determine the optimal relays for each user. For the overall scheduling and relay selection problem, we propose a heuristic algorithm which iteratively determines the scheduling and relay selection in polynomial time by using the optimal solutions of the individual relay selection and scheduling problems. Through simulations, we demonstrate that the scheduling length can be significantly reduced through proper scheduling and relay selection. The proposed algorithm performs very close to the optimal solution for different maximum user transmit power, network densities, initial battery levels and hybrid access point power levels. © 2020 IEEE.
Citation Count: 1
Flexible radio resource allocation for machine type communications in 5G cellular networks
(Institute of Electrical and Electronics Engineers Inc., 2018) Şadi, Yalçın; Şadi, Yalçın
The fast growth of machine-to-machine (M2M) communications in cellular networks brings the challenge of satisfying diverse Quality-of-Service (QoS) requirements of massive number of machine type communications (MTC) devices with limited radio resources. In this study we first introduce the minimum bandwidth resource allocation problem for M2M communications in 5G and beyond cellular networks. NP-hardness of the problem is proven. Then we propose a fast and efficient polynomial-time algorithm exploiting the periodicity of the MTC traffic based on persistent resource allocation. We prove a mathematical performance result for this algorithm considering a special case of the problem. Simulations show that the proposed algorithm outperforms the previously proposed clustering based radio resource algorithm significantly and performs very close to optimal. © 2018 IEEE.
Citation Count: 18
Physical-layer security in visible light communications
(Institute of Electrical and Electronics Engineers Inc., 2020) Şadi, Yalçın; Çoğalan, Tezcan; Erküçük, Serhat; Şadi, Yalçın; Panayırcı, Erdal; Haas, Harald; Poor, Harold Vincent
Optical wireless communications (OWC) and its potential to solve physical layer security (PLS) issues are becoming important research areas in 6G communications systems. In this paper, an overview of PLS in visible light communications (VLC), is presented. Then, two new PLS techniques based on generalized space shift keying (GSSK) modulation with spatial constellation design (SCD) and non-orthogonal multiple access (NOMA) cooperative relaying are introduced. In the first technique, the PLS of the system is enhanced by the appropriate selection of a precoding matrix for randomly activated light emitting diodes (LEDs). With the aid of a legitimate user's (Bob's) channel state information (CSI) at the transmitter (CSIT), the bit error ratio (BER) of Bob is minimized while the BER performance of the potential eavesdroppers (Eves) is significantly degraded. In the second technique, superposition coding with uniform signaling is used at the transmitter and relays. The design of secure beamforming vectors at the relay nodes along with NOMA techniques is used to enhance PLS in a VLC system. Insights gained from the improved security levels of the proposed techniques are used to discuss how PLS can be further improved in future generation communication systems by using VLC.