Browsing by Author "Panayirci,E."

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Em-Based Joint Data Detection and Channel Estimation for Uplink Mc-Cdma Systems Over Frequency Selective Channels;
(2007) Doǧan,H.; Panayirci,E.; Çirpan,H.A.; Fleury,B.H.
This paper is concerned with joint channel estimation and data detection for uplink multicarrier code-division multipleaccess (MC-CDMA) systems in the presence of frequency fading channel. The detection and estimation algorithm, implemented at the receiver, is based on a version of the expectation maximization (EM) technique which is very suitable for the multicarrier signal formats. Application of the EM-based algorithm to the problem of iterative data detection and channel estimation leads to a receiver structure that also incorporates a partial interference cancelation. Computer simulations show that the proposed algorithm has excellent BER end estimation performance.
Energy-Efficient Design for Reconfigurable Intelligent Surface Aided Cell-Free Ultra Dense Hetnets
(Institute of Electrical and Electronics Engineers Inc., 2023) Li,B.; Hu,Y.; Dong,Z.; Panayirci,E.; Jiang,H.; Wu,Q.
In this article, we investigate the energy efficiency (EE) of reconfigurable intelligent surfaces (RISs) aided cell-free ultra-dense HetNets (CFUDN). To maximize the EE of CFUDN, users (UEs) association and clustering, RISs subsurface (SSF) associations are carefully designed. Then, the phase shift matrix of RISs and transmission power of base stations (BSs) are jointly optimized. Due to the non-convexity and high complexity of the formulated problem, this jointly optimized problem is usually difficult to solve. At present, the most commonly adopted method to deal with joint optimization problems is the block coordinate descent (BCD) algorithm based on an alternative optimization framework. However, as we all know, the BCD algorithm has some degree of performance loss due to the alternate optimization of variables. To overcome this challenging issue, a novel joint optimization framework based on Riemannian product manifolds (RPM) is proposed, in which the phase shift matrix of RISs and transmission power of BSs can be simultaneously optimized rather than alternating ways. The simulation results and computational complexity analysis demonstrate that the joint optimization framework based on the RPM exhibits superior performance and lower complexity compared to the joint optimization algorithm based on the BCD. © 2023 IEEE.
Energy-Efficient Design for Ris-Aided Cell-Free Ultra Dense Hetnets
(Institute of Electrical and Electronics Engineers Inc., 2023) Li,B.; Hu,Y.; Dong,Z.; Panayirci,E.; Jiang,H.; Wu,Q.
In this article, we investigate the energy efficiency of reconfigurable intelligent surfaces (RISs) aided full-duplex cellfree ultra dense hetNets (CFUDN), which has the advantages of both cell-free massive MIMO (CF-MMIMO) and ultra-dense hetNets (UDN). To maximize the EE of full-duplex CFUDN, users association and clustering, RISs subsurface associations are carefully designed. Then, the phase shift matrix of RISs and transmission power of base stations are jointly optimized. Due to the non-convexity and high complexity of formulated problem, it is extremely difficult to solve this problem. At present, the block coordinate descent (BCD) algorithm is the most commonly used method for joint optimization problems. However, as we all know, the BCD algorithm has some degree of performance loss due to alternate optimization. To overcome this challenging issue, a novel joint optimization framework based on Riemannian product manifolds (RPM) is proposed. © 2023 IEEE.
Joint Visible Light Communications and Positioning with Dimming;
(Institute of Electrical and Electronics Engineers Inc., 2023) Bayman,I.Ö.; Çiçek,M.A.; Kumaş,M.B.; Demiryürek,T.; Arsan,T.; Panayirci,E.
In this paper, a novel visible light communication (VLC) and three-dimensional (3D) positioning (VLP) algorithm based on spatial modulation (SM) with dimming capability is proposed. With the help of the signal and pilot symbols observed by a user with two photodetectors (PD) on the receiver, the detection of the transmitted data with the estimated channel and dimming coefficients is performed, and at the same time, the position of the user represented in 3D is determined. The computer simulations conclude that the root mean square (RMS) values of the proposed algorithm in 3D position determination are very low, and the bit error rate (BER) performance is very high. © 2023 IEEE.
Orthogonal Frequency Division Multiplexing With Index Modulation
(2013) Basar,E.; Aygolu,U.; Panayirci,E.; Poor,H.V.
In this paper, a novel orthogonal frequency division multiplexing (OFDM) scheme, called OFDM with index modulation (OFDM-IM), is proposed for operation over frequency-selective and rapidly time-varying fading channels. In this scheme, the information is conveyed not only by $M$-ary signal constellations as in classical OFDM, but also by the indices of the subcarriers, which are activated according to the incoming bit stream. Different low complexity transceiver structures based on maximum likelihood detection or log-likelihood ratio calculation are proposed and a theoretical error performance analysis is provided for the new scheme operating under ideal channel conditions. Then, the proposed scheme is adapted to realistic channel conditions such as imperfect channel state information and very high mobility cases by modifying the receiver structure. The approximate pairwise error probability of OFDM-IM is derived under channel estimation errors. For the mobility case, several interference unaware/aware detection methods are proposed for the new scheme. It is shown via computer simulations that the proposed scheme achieves significantly better error performance than classical OFDM due to the information bits carried by the indices of OFDM subcarriers under both ideal and realistic channel conditions. © 2013 IEEE.
Physical Layer Security Under the Effect of Dimming in Visible Light Communications;
(Institute of Electrical and Electronics Engineers Inc., 2023) Yeşilirmak,Y.E.; Işikver,Ç.; Gökhan,R.B.; Arsan,T.; Panayirci,E.
Visible Light Communication (VLC) is a promising option for 6G wireless systems to increase performance and provide a high-speed data rate compared to radio frequency (RF). Dimming control is one of the most important aspects to be considered in VLC. It is very critical for the future of VLC to adjust the brightness of the light source to be used in communication and to ensure that the light source, with a changing brightness, maintains the desired communication performance due to the situation and environment. This work proposes a novel pilot-aided estimation method for channel and dimming coefficients in spatial modulation (SM)-VLC systems. As a result, in the VLC system running with the PLS algorithm, while the information transmitted to the legal user is received with an excellent BER performance, it is observed that the BER performance of the eavesdropper is around 0.5, which is the worst possible situation for the illegal user. © 2023 IEEE.
Power Control and Resource Allocation in Tdd-Ofdm Based Femtocell Networks With Interference
(Institute of Electrical and Electronics Engineers Inc., 2018) Altabbaa,M.T.; Arsan,T.; Panayirci,E.
Femtocell technology is a promising solution for different dilemmas in cellular networks. In femtocell power control, the interference experienced by the network is divided into two main tiers according to the type of network whose signal is interfering with another network. In utilizing the functionality of a two-tier network where femtocell technology is deployed, a major challenge is in sharing the frequency resource of a macrocell. This paper proposes an enhanced dynamic algorithm bounded by two constraints to optimize the transmission powers of femtocell users in TDD-OFDM based femtocell networks, taking into consideration rate enhancement of femtocell mobile stations. We compare our algorithm with the macrocell guard system, which allows femtocells to occupy only the subchannels unoccupied by the macrocell. © 2017 IEEE.
Trellis code design for spatial modulation
(2011) Başar,E.; Aygölü,Ü.; Panayirci,E.
In this paper, we propose a novel MIMO transmission scheme, called trellis coded spatial modulation (TC-SM) in which the trellis (convolutional) encoder and the spatial modulation (SM) mapper are jointly designed similar to the conventional trellis coded modulation (TCM). A soft decision Viterbi decoder, which is fed with the soft information supplied by the optimal SM decoder, is used at the receiver. We derive the pairwise error probability (PEP) upper bound for the TC-SM scheme in uncorrelated quasi-static Rayleigh fading channels. From the PEP upper bound, code design criteria are given and then used to obtain new 4-, 8- and 16-state TC-SM schemes using QPSK (quadrature phase-shift keying) and 8-PSK modulations for 2 bits/s/Hz and 3 bits/s/Hz spectral efficiencies, respectively. We show by computer simulations that the proposed TC-SM schemes achieve significantly better error performances than their counterparts at the same spectral efficiency with reduced decoding complexity. © 2011 IEEE.