Research Project: Gelecek Nesil Wi-Fi Standartları İçin Özgün Fiziksel Katman Tasarımları
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Contributors
Funders
ID
TB.00505
Authors
Başar, Ertuğrul
Faculty Member
Publications
Efficient indexing schemes for quadrature reflection modulation in RIS-Based BackCom
(Institute of Electrical and Electronics Engineers Inc., 2024) Başar, Ertuğrul; Tufail, Ahmad; Department of Electrical and Electronics Engineering; CoreLab (Communications Research and Innovation Laboratory); Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Laboratory
Besides steering the incoming signals toward a receiver, a reconfigurable intelligent surface (RIS) can simultaneously serve as a backscatter node to communicate additional data by modulating the same signal. Quadrature reflection modulation (QRM) is a promising contender among index modulation (IM)-based techniques for implementing RIS-based backscatter communications (RIS-BackCom). In this paper, we demonstrate that the error performance of RIS-QRM heavily relies on the employed indexing scheme, which configures each RIS element into one of the two orthogonally-reflecting modes of QRM to encode the transmitted data onto the reflection pattern of RIS elements. In this context, we present an efficient guideline for designing indexing schemes that ensure the resulting channel-dependent QRM symbols are evenly spaced with maximum separation. Following this guideline, we propose two specific indexing techniques: the incremental and uniform indexing schemes, both of which substantially enhance the error performance of RIS-QRM without increasing detection complexity. We derive a closed-form expression for the bit error probability (BEP) of RIS-QRM with the incremental indexing scheme. Furthermore, we propose a low-complexity detector for RIS-BackCom systems employing RIS-QRM. Extensive computer simulations illustrate the effectiveness of our proposed schemes in improving the error performance of RIS-QRM-based BackCom systems.
Coordinate interleaved OFDM with power distribution index modulation
(Institute of Electrical and Electronics Engineers (IEEE), 2022) Başar, Ertuğrul; Doğukan, Ali Tuğberk; Tuğtekin, Ömer Furkan; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
Orthogonal frequency division multiplexing with index modulation (OFDM-IM), which transmits information bits via M-ary constellation symbols and indices of the active subcarriers, is a promising OFDM-based multicarrier transmission scheme. Recently, several new schemes have been proposed by utilizing the flexibility of the OFDM-IM to meet the diverse needs of 5G networks. Coordinate interleaved OFDM-IM (CI-OFDM-IM) that conveys the real and imaginary part of the data symbols over different subcarriers and OFDM with power distribution IM (OFDM-PIM) that transmits the data symbols over high and low power subcarriers, are two OFDM-IM based schemes with additional diversity gain and improved bit error rate (BER) performance. In this letter, we propose a novel transmission scheme named as coordinate interleaved OFDM with power distribution IM (CI-OFDM-PIM), which applies coordinate interleaving and power distribution in subcarriers to achieve a higher diversity gain. The average bit error probability (ABEP) for the CI-OFDM-PIM is derived and the superior error performance of the proposed scheme over benchmarks are shown via computer simulations.
Coordinate interleaved OFDM with repeated in-phase/quadrature index modulation
(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Arslan, Emre; Başar, Ertuğrul; Doğukan, Ali Tuğberk; Tuğtekin, Ömer Furkan; Department of Electrical and Electronics Engineering; Graduate School of Sciences and Engineering; CoreLab (Communications Research and Innovation Laboratory); Yes; College of Engineering; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING; Laboratory
Orthogonal frequency division multiplexing with index modulation (OFDM-IM), which transmits information bits through ordinary constellation symbols and indices of active subcarriers, is a promising multicarrier transmission scheme and has attracted the attention of researchers due to numerous benefits such as flexibility and simplicity. Nonetheless, OFDM-IM cannot satisfy the needs of future wireless communication services such as superior reliability, high data rates, and low complexity. In this article, we propose a novel OFDM-IM scheme named coordinate interleaved OFDM with repeated in-phase/quadrature IM (CI-OFDM-RIQIM), which provides superior error performance and enhanced spectral efficiency due to its diversity order of two and clever subcarrier activation pattern (SAP) detection mechanism, respectively. In addition, CI-OFDM-RIQIM is further extended to coordinate interleaved OFDM with in-phase/quadrature IM (CI-OFDM-IQIM) by doubling information bits transmitted by IM. Furthermore, log-likelihood ratio (LLR) based low-complexity detectors are designed for both proposed schemes. Theoretical analyses are performed and an upper bound on the bit error probability is derived. Comprehensive computer simulations under perfect and imperfect channel state information (CSI), are conducted to compare the proposed and reference schemes. It is shown that CI-OFDM-RIQIM and CI-OFDM-IQIM show superior results and can be considered promising candidates for next-generation wireless communication systems.
RIS-based Dual-Mode Receive Spatial Modulation for Low-Complexity Wireless Access Points
(Institute of Electrical and Electronics Engineers Inc., 2025) Tufail, Ahmad; Başar, Ertuğrul; Tufail, Ahmad; CoreLab (Communications Research and Innovation Laboratory); Department of Electrical and Electronics Engineering; Yes; College of Engineering; Research Center
The emerging technology of reconfigurable intelligent surface-based access points (RIS-APs) shows excellent potential as it effectively replaces conventional RF front ends with passive RISs. This paper introduces RIS-based dual-mode receive spatial modulation (RDM-RSM), a low-complexity scheme designed to improve the spectral efficiency and error performance of RIS-APs. Both versions of the proposed RDM-RSM scheme configure the RIS to simultaneously enhance the RF signals at two different receive antennas while synthesizing distinct modulation symbols from two separate constellations at each antenna, thereby enabling efficient transmission of two parallel, conventionally-modulated data-streams. Additionally, by selecting two antennas and assigning each a distinct constellation mode, more bits can be encoded per index-modulated symbol. The first version, RDM-RSM-Independent (RDM-RSMI), operates by maximizing the energy of the synthesized signals independently for each antenna. In contrast, RDM-RSM-Joint (RDM-RSMJ) optimizes the reflection phase of each RIS element to maximize an objective function that considers the signals at both antennas jointly, resulting in stronger received signals compared to RDM-RSMI, where only half of the elements can serve each antenna. A low-complexity detector is proposed, with its theoretical performance rigorously analyzed by modeling the conditional reflection phases of the RIS elements as von-Mises distributed, providing a tractable and insightful framework. © 2002-2012 IEEE.
