Publications without Fulltext
Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3
Browse
82 results
Search Results
Publication Metadata only Frequency-domain model of microfluidic molecular communication channels with graphene BioFET-based receivers(Institute of Electrical and Electronics Engineers Inc., 2024) Department of Electrical and Electronics Engineering; Kuşcu, Murat; Abdalı, Ali; Department of Electrical and Electronics Engineering; College of Engineering; Graduate School of Sciences and EngineeringMolecular Communication (MC) is a bio-inspired communication paradigm utilizing molecules for information transfer. Research on MC has largely transitioned from theoretical investigations to practical testbed implementations, harnessing microfluidics and sensor technologies. Accurate models for input-output relationships on these platforms are crucial for optimizing MC methods and understanding the impact of physical parameters on performance. Our study focuses on a practical microfluidic MC system with a graphene field effect transistor biosensor (bioFET)-based receiver, developing an end-to-end frequency-domain model. The model provides insights into the dispersion, distortion, and attenuation of received signals, thus potentially informing the design of new frequency-domain MC techniques, such as modulation and detection methods. The accuracy of the developed model is verified through particle-based spatial stochastic simulations of pulse transmission and ligand-receptor reactions on the receiver surface.Publication Metadata only Noise modulation(IEEE-Institute of Electrical and Electronics Engineers, 2024) Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; College of EngineeringInstead of treating the noise as a detrimental effect, can we use it as an information carrier? In this letter, we provide the conceptual and mathematical foundations of wireless communication utilizing noise and random signals in general. Mainly, the concept of noise modulation (NoiseMod) is introduced to cover information transmission by both thermal noise and externally generated noise signals. The performance of underlying NoiseMod schemes is evaluated under both additive white Gaussian and fading channels and alternative NoiseMod designs exploiting non-coherent detection and time diversity are proposed. Extensive numerical and computer simulation results are presented to validate our designs and theoretical derivations.Publication Metadata only Coordinate interleaved OFDM with repeated in-phase/quadrature index modulation(IEEE-Inst Electrical Electronics Engineers Inc, 2024) ; Department of Electrical and Electronics Engineering; Tuğtekin, Ömer Furkan; Doğukan, Ali Tuğberk; Arslan, Emre; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; ; Graduate School of Sciences and Engineering; College of Engineering; Communications Research and Innovation Laboratory (CoreLab)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.Publication Metadata only Index modulation-based information harvesting for far-field RF power transfer(IEEE-Inst Electrical Electronics Engineers Inc, 2024) İlter, Mehmet C.; Wichman, Risto; Hamalainen, Jyri; Department of Electrical and Electronics Engineering; Pıhtılı, Mehmet Ertuğ; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; ; Graduate School of Sciences and Engineering; College of Engineering; Communications Research and Innovation Laboratory (CoreLab)As wireless information transmission (WIT) progresses into its sixth generation (6G), a challenge arises in sustaining terminal operations with limited batteries for Internet-of-Things (IoT) platforms. To address this, wireless power transfer (WPT) emerges as a solution, empowering battery-less infrastructures and enabling nodes to harvest energy for sustainable operations. Thus, the eclectic integration of WPT with WIT mechanisms becomes crucial to mitigate the need for battery replacements while providing secure and reliable communication. A novel protocol that amalgamates WIT and WPT called Information Harvesting (IH) has recently been proposed to effectively handle challenges in wireless information and power transfer (WIPT) by employing index modulation (IM) techniques for data communication atop the existing far-field WPT mechanism. This paper presents a unified framework for IM-based IH mechanisms and evaluates their energy harvesting capability, bit error rate (BER), and ergodic secrecy rate (ESR) performance for diverse IM schemes. The findings indicate the significant potential of the IM-based IH mechanism in facilitating reliable data communication within existing far-field WPT systems while underscoring promising refinements in green and secure communication paradigms for next-generation IoT wireless networks. AuthorsPublication Metadata only Reconfigurable intelligent surfaces for 6G: emerging hardware architectures, applications, and open challenges(IEEE-Institute of Electrical and Electronics Engineers, 2024) Alexandropoulos, George C.; Liu, Yuanwei; Wu, Qingqing; Jin, Shi; Yuen, Chau; Dobre, Octavia A.; Schober, Robert; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; College of EngineeringReconfigurable intelligent surfaces (RISs) are rapidly gaining prominence in the realm of 5G-advanced and predominantly 6G mobile networks, offering a revolutionary approach to optimizing wireless communications. This article delves into the intricate world of the RIS technology, exploring its diverse hardware architectures and the resulting versatile operating modes. These include RISs with signal reception and processing units, sensors, amplification units, transmissive capability, multiple stacked components, and dynamic metasurface antennas (DMAs). Furthermore, we shed light on emerging RIS applications, such as index and reflection modulation, noncoherent modulation, next-generation multiple access (NGMA), integrated sensing and communications (ISAC), energy harvesting (EH), as well as aerial and vehicular networks. These exciting applications are set to transform the way we will wirelessly connect in the upcoming era of 6G. Finally, we review recent experimental RIS setups and present various open problems of the overviewed RIS hardware architectures and their applications. From enhancing network coverage to enabling new communication paradigms, RIS-empowered connectivity is poised to play a pivotal role in shaping the future of wireless networking. This article unveils the underlying principles and potential impacts of RISs, focusing on cutting-edge developments of this physical-layer smart connectivity technology.Publication Metadata only Pairwise sequency index modulation with OTSM for green and robust single-carrier communications(IEEE-Institute of Electrical and Electronics Engineers, 2024) Doosti-Aref, Abed; Masouros, Christos; Arslan, Huseyin; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; College of EngineeringIn this letter, inspired by the fundamental thoughts of sequency index modulation (SeIM) and orthogonal time sequency multiplexing (OTSM), a novel technique is introduced for green and robust single-carrier communications in wireless networks. More specifically, pairwise SeIM (PSeIM) is proposed as a novel indexing scheme making SeIM robust to error propagation and significantly reduces the peak power of SeIM-based systems with a lower complexity of detection. Analytical results are presented for the bit error rate (BER), peak-to-average power ratio (PAPR), and spectral efficiency to reveal the trade-off and advantages in PSeIM-OTSM. Simulation and analytical results verify that for 4-QAM uncoded data, PSeIM-OTSM outperforms OTSM by 50% in terms of both PAPR and complexity of detection along with 125.32% energy efficiency improvement to achieve a BER of 10-8 in high mobility doubly spread channels.Publication Metadata only Index modulation aided fragmented spectra centralization in OTFS systems(IEEE-Institute of Electrical and Electronics Engineers, 2024) Zhang, Bo; Mei, Lin; Du, Zhaopeng; Teh, Kah Chan; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; College of EngineeringBy selecting various active-silent combinations, classical frequency-domain index modulation (IM) generates numerous energy-free subcarriers dispersed across subblocks, which we refer to as the fragmented spectra. This letter proposes a novel IM approach aimed at collecting the fragmented spectra in subblocks to form a completely unused frequency band, called the IM-aided fragmented spectra centralization (IM-FSC). Specifically, within each subblock, if the last subcarrier is to be activated, we transfer this active position to the first unactivated subcarrier and employ a distinguishable constellation to modulate the symbol on this subcarrier. Through this approach, each subblock contributes one energy-free subcarrier, and the unused frequency band can be obtained accordingly by combining these fragmented spectra from multiple subblocks. We designate this unoccupied frequency band as zero padding (ZP) and guard interval for interference cancellation and channel estimation in orthogonal time frequency space (OTFS) system. The closed-form expressions of bit error rate (BER) and generalization guidelines are also derived. Simulation results demonstrate the promising communication capability and channel estimation accuracy of the proposed scheme.Publication Metadata only Multi-scenario broadband channel measurement and modeling for Sub-6 GHz RIS-assisted wireless communication systems(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Sang, Jian; Zhou, Mingyong; Lan, Jifeng; Gao, Boning; Tang, Wankai; Li, Xiao; Jin, Shi; Li, Cen; Cheng, Qiang; Cui, Tie Jun; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Department of Electrical and Electronics Engineering; ; College of Engineering; Communications Research and Innovation Laboratory (CoreLab)Reconfigurable intelligent surface (RIS)-empowered communication, has been considered widely as one of the revolutionary technologies for next generation networks. However, due to the novel propagation characteristics of RISs, underlying RIS channel modeling and measurement research is still in its infancy and not fully investigated. In this paper, we conduct multi-scenario broadband channel measurements and modeling for RIS-assisted communications at the sub-6 GHz band. The measurements are carried out in three scenarios covering outdoor, indoor, and outdoor-to-indoor (O2I) environments, which suffer from non-line-of-sight (NLOS) propagation inherently. Three propagation modes including intelligent reflection with RIS, specular reflection with RIS and the mode without RIS, are taken into account in each scenario. In addition, considering the cascaded characteristics of RIS-assisted channel by nature, two modified empirical models including floating-intercept (FI) and close-in (CI) are proposed, which cover distance and angle domains. The measurement results rooted in 2096 channel acquisitions verify the prediction accuracy of these proposed models. Moreover, the propagation characteristics for RIS-assisted channels, including path loss (PL) gain, PL exponent, spatial consistency, time dispersion, frequency stationarity, etc., are compared and analyzed comprehensively. These channel measurement and modeling results may lay the groundwork for future applications of RIS-assisted communication systems in practice.Publication Metadata only A unified framework for multi-hop wireless relaying with hardware impairments(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Soleimani-Nasab, Ehsan; Department of Electrical and Electronics Engineering; Ergen, Sinem Çöleri; Department of Electrical and Electronics Engineering; ; College of Engineering;Relaying increases the coverage area and reliability of wireless communications systems by mitigating the fading effect on the received signal. Most technical contributions in the context of these systems assume ideal hardware (ID) by neglecting the non-idealities of the transceivers, which include phase noise, in-phase/quadrature mismatch and high power amplifier nonlinearities. These non-idealities create distortion on the received signal by causing variations in the phase and attenuating the amplitude. The resulting deterioration of the performance of wireless communication systems is further magnified as the frequency of transmission increases. In this paper, we investigate the aggregate impact of hardware impairments (HI) on the general multi-hop relay system using amplify-and-forward (AF) and decode-and-forward (DF) relaying techniques over a general bf H-fading model. bf H-fading model includes free space optics, radio frequency, millimeter wave, Terahertz, and underwater fading models. Closed-form expressions of outage probability, bit error probability and ergodic capacity are derived in terms of bf H-functions. Following an asymptotic analysis at high signal-to-noise ratio (SNR), practical optimization problems have been formulated with the objective of finding the optimal level of HI subject to the limitation on the total HI level. The analytical solution has been derived for the Nakagami-m fading channel which is a special case of bf H-fading for AF and DF relaying techniques. The overall instantaneous signal-to-noise-plus-distortion ratio has been demonstrated to reach a ceiling at high SNRs which has a reciprocal proportion to the HI level of all hops' transceivers on the contrary to the ID.Publication Metadata only Performance analysis of OTSM under hardware impairments and imperfect CSI(IEEE-Inst Electrical Electronics Engineers Inc, 2024) Doosti-Aref, Abed; Masouros, Christos; Zhu, Xu; Arslan, Hüseyin; Department of Electrical and Electronics Engineering; Başar, Ertuğrul; Ergen, Sinem Çöleri; Department of Electrical and Electronics Engineering; College of EngineeringOrthogonal time sequency multiplexing (OTSM) has been recently proposed as a single-carrier waveform offering similar bit error rate to orthogonal time frequency space (OTFS) and outperforms orthogonal frequency division multiplexing (OFDM) in doubly-spread channels (DSCs);however, with a much lower complexity making it a potential candidate for 6G wireless networks. In this paper, the performance of OTSM is explored by considering the joint effects of multiple hardware impairments (HWIs) such as in-phase and quadrature imbalance (IQI), direct current offset (DCO), phase noise, power amplifier non-linearity, carrier frequency offset, and synchronization timing offset for the first time in the area. First, the discrete-time baseband signal model is obtained in vector form under all mentioned HWIs. Second, the system input-output relations are derived in time, delay-time, and delay-sequency (DS) domains in which the parameters of all mentioned HWIs are incorporated. Third, analytical expressions are derived for the pairwise and average bit error probability under imperfect channel state information (CSI) as a function of the parameters of all mentioned HWIs. Analytical results demonstrate that under all mentioned HWIs, noise stays additive white Gaussian, effective channel matrix is sparse, DCO appears as a DC signal at the receiver interfering with only the zero sequency, and IQI redounds to self-conjugated sequency interference in the DS domain. Simulation results reveal the fact that by considering the joint effects of all mentioned HWIs and imperfect CSI not only OTSM outperforms OFDM by 29%in terms of energy of bit per noise but it performs same as OTFS in high mobility DSCs. IEEE