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Öğe Blind numerology identification for mixed numerologies(IEEE - Institute of Electrical and Electronics Engineers, Inc, 2021) Jaradat, Ahmad; Memişoğlu, Ebubekir; Arslan, Hüseyin5G New Radio (NR) introduces new flexibility that different numerologies can be selected to meet the requirements of a wide variety of services. For this new structure, blind numerology identification can increase system efficiency. Therefore, we propose a blind identification method for mixed numerologies. An autocorrelation method is applied in the time domain by correlating the cyclic prefix (CP) signal of the candidate numerology in the received composite signal for numerology type identification. Then, the location of each numerology in the frequency domain is identified by the variance difference in the power spectral density (PSD) of the subbands, on which different numerologies are occupied. The simulation results are obtained under additive white Gaussian noise (AWGN) and frequency-selective channels. The obtained results show that the proposed method has a robust identification accuracy and a satisfactory BER performance as compared to the non-blind identification approach in the conventional mixed-numerology system.Öğe CSI-Based NOMA for integrated sensing and communication(IEEE-Institute of Electrical and Electronics Engineers Inc., 2023) Memişoğlu, Ebubekir; Türkmen, Halise; Ak Özbakış, Başak; Arslan, HüseyinIntegrated sensing and communication (ISAC) is a key enabler of beyond fifth-generation networks and a multitude of futuristic applications. However, the coexistence, scheduling and spectrum scarcity issues due to additional sensing signals are valid concerns. A communicating device requiring sensing can use its communication signal for sensing. However, a non-communicating device requiring sensing will need to transmit additional sensing signals, increasing traffic in the network. Thus, in this letter, a novel ISAC with iterative channel estimation (ISAC-ICE) method is proposed to provide spectral efficiency while maintaining sensing and communication performance. The proposed method attains this by enabling the multi-channel estimation from received non-orthogonal communication and sensing signals for uplink transmission. The simulation results and complexity analysis demonstrate that the proposed method enables non-orthogonal multiple accessing (NOMA) of ISAC with a linearithmic complexity.Öğe Exploiting OTFS frame structure for PAPR reduction(Institute of Electrical and Electronics Engineers Inc., 2022) Sümer, Ahmet Sacid; Yılmaz, Talha; Memişoğlu, Ebubekir; Arslan, HüseyinWireless technologies have always been the cornerstone of industrial progress. However, as industrial technologies have improved and advanced services have emerged, the demands of industry have meant that wireless technologies have had to adapt. When throughput was the only major concern in previous generations, orthogonal frequency division multiplexing (OFDM) provided an excellent solution for frequency-selective channels. However, the current era of technologies also requires extensive mobility support, resulting in doubly selective channels. As a robust waveform in doubly dispersive channels, orthogonal time-frequency space (OTFS) has been proposed in the literature recently. However, like other multicarrier schemes, OTFS suffers from high a peak-to-average power ratio (PAPR). High PAPR can lead to inter-modulation distortion due to the non-linearity, resulting in severe degradation of detection performance. Therefore, we present a novel PAPR reduction method that exploits the unique OTFS frame structure. Simulation results show that this method can reduce PAPR by up to 2.4 dB, with minimal loss of detection performance compared to conventional OTFS transmission.Öğe Fading-aligned OFDM with index modulation for mMTC services(Elsevier B.V., 2019) Memişoğlu, Ebubekir; Başar, Ertuğrul; Arslan, Hüseyin5th generation (5G) of wireless networking is coming with diverse use cases, such as enhanced-Mobile BroadBand (eMBB), Ultra Reliable and Low Latency Communications (URLLC), and massive Machine Type Communications (mMTC). As a result, 5G wireless networks require flexible physical layer solutions through new radio access technologies (RATs). At this point, orthogonal frequency division multiplexing with index modulation (OFDM-IM) appears a flexible solution to satisfy the diverse user demands. Considering the strict requirements of mMTC services, such as low throughput, low power consumption, and low cost design, we propose fading-aligned OFDM-IM for more spectrum- and energy-efficient communication. In the proposed method, inactive subcarriers in OFDM-IM are cleverly utilized to avoid deep fading sub-channels, because the deep fading of the active subcarriers decreases bit error rate (BER) performance significantly. Computer simulation results demonstrate that more than 10 dB gain is obtained for a reference BER value of 10 -4 at the same spectral efficiency with conventional OFDM. Moreover, the proposed method is compared with convolutional coded (CC) OFDM at the same spectral efficiency, and it is shown that the proposed scheme performs better in terms of BER performance. Furthermore, theoretical error performance of the proposed method is investigated to support our computer simulations.Öğe Guard band reduction for 5G and beyond multiple numerologies(IEEE, 2020) Memişoğlu, Ebubekir; Kihero, Abuu Bakari; Başar, Ertuğrul; Arslan, HüseyinThe existence of inter-numerology interference (INI) is a major drawback for the flexible multi-numerology frame structure proposed for the upcoming fifth generation New Radio (5G-NR). Insertion of a guard band (GB) between adjacent numerologies has been widely used in the literature as one of the effective ways to reduce the INI. However, the conventional way of implementing GBs is inefficient in terms of spectrum usage. In this letter, we exploit the inherent INI characteristics of the scalable multi-numerology structure to propose a more spectrally efficient way of implementing GBs. It is shown through simulations that the proposed GB insertion technique enhances the GB utilization up to 50% while achieving the same bit error rate performance as the conventionally implemented GB.Öğe Identification of distorted RF components via deep multi-task learning(Institute of Electrical and Electronics Engineers Inc., 2022) Aygül, Mehmet Ali; Memişoğlu, Ebubekir; Çırpan, Hakan Ali; Arslan, HüseyinHigh-quality radio frequency (RF) components are imperative for efficient wireless communication. However, these components can degrade over time and need to be identified so that either they can be replaced or their effects can be compensated. The identification of these components can be done through observation and analysis of constellation diagrams. However, in the presence of multiple distortions, it is very challenging to isolate and identify the RF components responsible for the degradation. This paper highlights the difficulties of distorted RF components' identification and their importance. Furthermore, a deep multi-task learning algorithm is proposed to identify the distorted components in the challenging scenario. Extensive simulations show that the proposed algorithm can automatically detect multiple distorted RF components with high accuracy in different scenarios.Öğe Joint estimation of multiple RF impairments using deep multi-task learning(IEEE-Institute of Electrical and Electronics Engineers Inc., 2022) Aygül, Mehmet Ali; Memişoğlu, Ebubekir; Arslan, HüseyinRadio-frequency (RF) front-end forms a critical part of any radio system, defining its cost as well as communication performance. However, these components frequently exhibit non-ideal behavior, referred to as impairments, due to the imperfections in the manufacturing/design process. Most of the designers rely on simplified closed-form models to estimate these impairments. On the other hand, these models do not holistically or accurately capture the effects of real-world RF front-end components. Recently, machine learning-based algorithms have been proposed to estimate these impairments. However, these algorithms are not capable of estimating multiple RF impairments jointly, which leads to limited estimation accuracy. In this paper, the joint estimation of multiple RF impairments by exploiting the relationship between them is proposed. To do this, a deep multi-task learning-based algorithm is designed. Extensive simulation results reveal that the performance of the proposed joint RF impairments estimation algorithm is superior to the conventional individual estimations in terms of mean-square error. Moreover, the proposed algorithm removes the need of training multiple models for estimating the different impairments.Öğe Low complexity peak-to-average power ratio reduction in OFDM-IM(Institute of Electrical and Electronics Engineers Inc., 2018) Memişoğlu, Ebubekir; Başar, Ertuğrul; Arslan, HüseyinOrthogonal frequency division multiplexing with index modulation (OFDM-IM) employs the indices of the active subcarriers for information transmission, as an alternative to conventional OFDM. It offers high spectral efficiency and high energy efficiency in comparison to OFDM thanks to the information bits conveyed by IM. However, OFDM-IM has the drawback of high peak-to-average power ratio (PAPR) similar to OFDM, and this important problem has not been studied well in the literature. Active constellation extension (ACE), which is one of the well-known PAPR reduction methods, can be used to solve this drawback of OFDM-IM. Owing to the fact that this PAPR reduction method is less effective for OFDM-IM, we propose the extension of the constellation over inactive subcarriers through adding clipped signals over them. These subcarriers have a signal power limited by an upper bound, and this causes a slight degradation in the bit error rate (BER) performance. Computer simulation results demonstrate that our proposed method has a better PAPR reduction performance than the ACE method for OFDM and OFDM-IM while being more energy efficient with a very slight degradation in BER performance when a proper clipping threshold level is selected. Additionally, it is shown that the proposed method and ACE can be further combined, and this provides an improved PAPR reduction. In order to decrease the computational complexity of the PAPR reduction method to the linear-logarithmic level, smart gradient projection (SGP) is employed.Öğe Numerology scheduling for PAPR reduction in mixed numerologies(IEEE-Institute of Electrical and Electronics Engineers Inc., 2021) Memişoğlu, Ebubekir; Duranay, Ahmet Enes; Arslan, HüseyinThe flexible mixed-numerology structure with orthogonal frequency division multiplexing (OFDM) waveform is a key enabler to meet the requirements of various applications in fifth-generation (5G) and beyond wireless networks. However, the high peak-to-average power ratio (PAPR) is still one of the main drawbacks and conventional numerology selection can only provide PAPR reduction for the time-domain numerology multiplexing. In this letter, a novel numerology scheduling (NS) method is proposed to provide PAPR reduction for both time-domain and frequency-domain numerology multiplexing scenarios. For the proposed method, the signal with minimum PAPR is selected from a set of signals with different NS. The simulation results and complexity analysis demonstrate that the proposed method with a linearithmic complexity improves PAPR reduction compared to conventional numerology selection.Öğe Orthogonal coexistence of overlapped radar and communication waveforms(Institute of Electrical and Electronics Engineers Inc., 2022) Memişoğlu, Ebubekir; Şahin, Mehmet Mert; Arslan, HüseyinWith revolutionary new services and applications, integrated sensing and communication has been essential for recent and future wireless communication systems. For the communication systems, the cyclic prefix - orthogonal frequency division multiplexing (CP-OFDM) is a widely used waveform in various wireless standards due to its high spectral efficiency and resilience to static multi-path channel conditions. On the other hand, the frequency modulated continuous-wave (FMCW) is a popular waveform in radar-sensing applications, especially for autonomous vehicles. Although communication signals over the air are utilized for sensing applications, such as passive radars, however, these systems have limited sensing capabilities. Also, several coexistence schemes are introduced for these different systems, communication and radar-sensing that separately allocate time, frequency and space resources. Unlike these approaches, a novel waveform design by overlapping on the same time and frequency resources is proposed to provide orthogonal coexistence for joint radar and communication (JRC) systems. For the proposed design, the channel estimation and bit-error rate (BER) performances are compared with the conventional CP-OFDM systems, and it is demonstrated that the same performance can be obtained in the proposed coexistence. Therefore, this waveform design due to the overlapping achieves a better spectral efficiency compared to separate resource sharing approaches.Öğe Phase rotation approach with mixed-numerology architecture for PAPR reduction in 5G and beyond(Institute of Electrical and Electronics Engineers Inc., 2023) Duranay, Ahmet Enes; Memişoğlu, Ebubekir; Özbakış, Başak; Arslan, HüseyinFor a wide range of service requirements, the 5G-NR offers significant flexibility based on OFDM with numerous numerologies. However, OFDM is recognized to have a significant disadvantage due to a high PAPR. On the other hand, the PAPR reduction for mixed-numerology OFDM has received little attention compared to single-numerology OFDM, despite there being possible challenges and advantages such as computational complexity and new structure opportunity, respectively. In this paper, the phase rotation PAPR reduction approach on mixed-numerology OFDM is proposed for the first time. Unlike the single-numerology approach, the need for additional IFFT and side information overhead is eliminated, and the mixed-numerology transmitter structure is exploited to provide three novel approaches, namely proposed numerology-based (Proposed-NB), proposed symbol-based (Proposed-SB), and proposed location-based (Proposed-LB). Proposed-NB has the same PAPR performance with a lower complexity compared to the partial transmit sequence (PTS) method for single-numerology OFDM. Moreover, the new ability to use multiple phase factors for the same numerology symbols in the defined largest symbol length enhances the PAPR reduction performance further using Proposed-SB. While all symbols are jointly optimized in the Proposed-SB, Proposed-LB drives a sub-optimal solution developed by optimizing the selected symbols. Due where the presence of different symbols duration between numerologies and also consecutive symbols in the same numerology, PAPR reduction performance in Proposed-LB almost reaches the optimum Proposed-SB performances with a lower computational complexity compared to Proposed-SB. The conducted numerical results validate the superiority of the proposed methods for 5G and beyond compared to PTS and numerology scheduling methods.Öğe Power-efficient time-domain scheduling for isac beamforming(2024) Memişoğlu, Ebubekir; Janjua, Muhammad Bilal; Arslan, HüseyinPower efficiency is a critical metric for a sustainable 6G network. The emergence of integrated sensing and communication (ISAC) services leads to significant power consumption due to additional signal transmission for sensing. An ISAC beamforming is an efficient transmission method for reducing power consumption in mmWave multi-input multi-output (MIMO) systems while meeting the requirements of communication users (CUs) and sensing users (SUs). This approach is only feasible when both users are within the coverage of the same beam. Otherwise, separate beams are required which results in high power consumption. In this letter, we propose a novel time-domain scheduling method for ISAC beamforming to achieve high-power efficiency. The performance gains compared to conventional scheduling method are demonstrated for the different number of users, periodicity values, and user distribution ratios.Öğe Public safety network design for broadband wireless access(Frontiers Media SA, 2023) Sümer, Ahmet Sacid; Yılmaz, Talha; Memişoğlu, Ebubekir; Akkurt, Arif; Arslan, HüseyinPublic protection and disaster relief (PPDR) agencies rely on wireless communications to respond in the event of emergencies. Public safety networks (PSNs) provide the wireless network used by emergency services. PSN is used to support push-to-talk services with some data transmission by employing land mobile radios. However, PPDR agencies are increasingly relying on additional information such as videos that require higher bandwidths. Therefore, many countries are transitioning or integrating their public safety networks with advanced broadband wireless communication systems such as fourth-generation (4G) long-term evolution (LTE) and planning to evolve to fifth-generation (5G) new radio (NR) in the future. The paper investigates infrastructure sharing mechanisms and deployment strategies in the transition of PSNs to a 4G LTE network, including a roadmap for cost analysis. Additionally, the paper examines LTE-based PSN deployment scenarios in various countries and engages in a discussion of the advantages and disadvantages of different sharing mechanisms and coexistence schemes. Finally, the challenges within the Public Safety Broadband Network (PSBN) are addressed and potential future research directions in this domain are deliberated.Öğe Waveform design with constellation extension for OFDM dual-functional radar-communications(Institute of Electrical and Electronics Engineers Inc., 2023) Memişoğlu, Ebubekir; Yılmaz, Talha; Arslan, HüseyinOrthogonal frequency division multiplexing (OFDM) is widely used and works efficiently for the communication, but emerging applications requires OFDM to be flexible to meet sensing requirements. The time-frequency waveform design of OFDM for dual-functional radar-communications (DFRC) is critical to achieve the future communication and sensing requirements. Therefore, we propose a novel method to minimize Cramér-Rao bounds (CRBs) of the delay and Doppler estimation to improve radar performance of an OFDM DFRC system. Although some methods are proposed in the literature to improve the CRBs, these methods either require feedforward signaling or subcarrier reservation. However, it is possible to exploit the constellation extension of quadrature amplitude modulation (QAM) to achieve lower CRBs without these requirements. Therefore, the proposed method provides a transparent communication along with the CRB minimization for conventional OFDM systems. For the evaluation of the proposed method, CRB and symbol error rate (SER) are considered in the simulation results. Furthermore, the theoretical SER analysis of the proposed method is derived to understand the effects of CRB minimization on the communication performance.
