Browsing by Author "Develi, İbrahim"

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Citation - Scopus: 1
Error Analysis of Ofdm-Im Systems for Beyond 5g: the Effect of Iqi at Transceiver
(Wiley, 2024) Ceniklioğlu, Büşra; Develi, İbrahim; Canbilen, Ayşe Elif
It is well known that hardware impairments (HWIs) can worthy reduce the wireless system performance at high carrier frequencies by showing random effects. Most current researches for 5 GB systems assume that transmitters and receivers (transceivers) are perfectly equipped. But wireless transceivers (TxRx$$ {T}_x{R}_x $$) are affected by HWIs in practice. Considering the previous studies in the literature, it is reported that HWIs have devastating effects on the performance of OFDM and OFDM-index modulation (IM) systems with fading channels. In this paper, in-phase and quadrature phase imbalance (IQI), which is the one of most HWIs between transmitter and receiver in wireless communication systems, is examined on OFDM-IM system over Rayleigh and Nakagami-m$$ m $$ fading channels. Two well-known detectors, the maximum likelihood (ML) detector and the log-likelihood ratio (LLR) detector are used under the effect of the IQI at TxRx$$ {T}_x{R}_x $$. Error performance analyzes over fading channels of the IQI effect on OFDM-IM system are realized first theoretically and then by computer simulations. Results obtained for the presence of IQI at TxRx$$ {T}_x{R}_x $$ show that a performance evaluation based only on the presence of IQI in the receiver would be optimistic and misleading in terms of the performance of real-life OFDM-IM systems. Most current researches for 5 GB systems assume that transmitters and receivers (transceivers) are perfectly equipped. In this paper, in-phase and quadrature phase imbalance (IQI), which is the one of most HWIs between transmitter and receiver in wireless communication systems, is examined on OFDM-IM system over Rayleigh and Nakagami-m fading channels. Results obtained for the presence of IQI at transceiver show that a performance evaluation based only on the presence of IQI in the receiver would be optimistic and misleading in terms of the performance of real-life OFDM-IM systems. image
Citation - WoS: 16
Citation - Scopus: 19
Error Analysis of the Joint Localization and Synchronization of Ris-Assisted Mm-Wave Miso-Ofdm Under the Effect of Hardware Impairments
(IEEE-Inst Electrical Electronics Engineers Inc, 2022) Ceniklioğlu, Büşra; Tubail, Deeb Assad; Canbilen, Ayse Elif; Develi, İbrahim; İkki, Salama S.
This work investigates the theoretical bounds of the joint localization and synchronization processes in a reconfigurable intelligent surface (RIS)-assisted system. We address the case of millimeter-wave ( $mm$ -Wave) multiple-input single-output (MISO) orthogonal frequency-division multiplexing (OFDM) with non-ideal transceivers. Considering a single antenna mobile station (MS) aims to estimate the parameters of the downlinks from the base station (BS) and the RIS by observing a known sequence received by the MS directly from the BS and indirectly through the RIS. The theoretical bounds of the estimation process are assessed by using the Fisher information matrix (FIM). A transformation matrix is then used to convert the FIM of the downlink channel parameters to the FIM of the MS joint localization and synchronization parameters. Specifically, the transformation matrix is derived based on the geometric relationships that convert the estimated downlink channels' parameters to the position coordinates and clock offset. Next, the Cramer-Rao lower bound (CRLB) matrix of the joint localization and synchronization process is obtained by using the pseudo-inverse of the FIM. Thus, the position error bound (PEB), as well as the synchronization error bound (SEB), are calculated. Computer simulation results are provided to illustrate the adverse effects of the hardware impairments (HWIs) on the accuracy of localization and synchronization. These results are given in proportion to the effective signal-to-noise ratio (SNR), the number of pilot transmissions, and the number of the RIS elements.
Citation - WoS: 34
Citation - Scopus: 37
Impact of I/Q Imbalance on Amplify-And Relaying: Optimal Detector Design and Error Performance
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2019) Canbilen, Ayşe Elif; Ikki, Salama Said; Başar, Ertuğrul; Gültekin, Seyfettin Sinan; Develi, İbrahim
Future wireless communication systems face several transceiver hardware imperfections that may significantly degrade their performance. In-phase (I) and quadrature-phase (Q) imbalance (IQI), which causes self-interference effects on the desired signal, is an important and practical example to these impairments. In this paper, a channel state information-assisted dual-hop amplify-and-forward (AF) relaying system in the presence of IQI is analyzed. The error performance of the relevant AF cooperative protocol is firstly studied by considering the traditional maximum likelihood detection (MLD) algorithm as a benchmark. Then, two compensation methods, weighting and zero-forcing, are proposed to mitigate the IQI effects. Finally, an optimal MLD solution is introduced by adapting the traditional MLD technique in compliance with the asymmetric characteristics of the IQI. The system performance is evaluated in terms of average symbol error probability (ASEP) through the computer simulations. The ASEP is calculated analytically for the optimal MLD method as well under the assumption of point-to-point communication, which has been envisioned as an allied technology of the fifth generation (5G) wireless systems, between the source and the relay nodes. A power allocation algorithm is provided for this specific case. The extensive computer simulations and analytical results prove that the proposed optimal MLD method provides the best results.
Citation - WoS: 14
Citation - Scopus: 17
Joint Impact of I/Q Imbalance and Imperfect Csi on Sm-Mimo Systems Over Generalized Beckmann Fading Channels: Optimal Detection and Cramer-Rao Bound
(IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2020) Canbilen, Ayşe Elif; Ikki, Salama Said; Başar, Ertuğrul; Gültekin, Seyfettin Sinan; Develi, İbrahim
Spatial modulation (SM) has been shown to be a promising low-complexity alternative to the state-of-art multiple-input multiple-output (MIMO) schemes due to its novel transmission approach. This paper investigates the performance of SM-MIMO systems in the presence of two practical undesirable effects, namely in-phase (I) and quadrature-phase (Q) imbalance (IQI) and imperfect channel state information (ICSI). An optimum maximum likelihood detection (MLD) method is proposed to tackle the effects of self-interference and signal distortion caused by IQI impairment by adapting the traditional MLD technique in accordance with the asymmetric characteristics of the IQI. More particularly, upper-bounds of the closed-form average pairwise error probability (APEP) and the average bit error rate (ABER) are derived for generalized Beckmann fading channels. As erroneously interpreted channel coefficients at the receiver (Rx) cause the error rate to increase and the detection to fall short, Cramer-Rao bound, which is a lower bound on the variance of the channel estimator, is utilized to assess the estimation accuracy. The system performance is evaluated by analytical derivations that are corroborated with computer simulations. The obtained results show that ICSI and IQI should be seriously considered while designing the future SM-based wireless communication systems.