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Öğe Anatomical region-specific in vivo wireless communication channel characterization(IEEE-Inst Electrical Electronics Engineers Inc, 2017) Demir, Ali Fatih; Abbasi, Qammer H.; Ankaralı, Zekeriyya Esat; Alomainy, Akram; Qaraqe, Khalid; Serpedin, Erchin; Arslan, HüseyinIn vivo wireless body area networks and their associated technologies are shaping the future of health-care by providing continuous health monitoring and noninvasive surgical capabilities, in addition to remote diagnostic and treatment of diseases. To fully exploit the potential of such devices, it is necessary to characterize the communication channel, which will help to build reliable and high-performance communication systems. This paper presents an in vivo wireless communication channel characterization for male torso both numerically and experimentally (on a human cadaver) considering various organs at 915 MHz and 2.4 GHz. A statistical path loss (PL) model is introduced, and the anatomical region-specific parameters are provided. It is found that the mean PL in decibel scale exhibits a linear decaying characteristic rather than an exponential decaying profile inside the body, and the power decay rate is approximately twice at 2.4 GHz as compared to 915 MHz. Moreover, the variance of shadowing increases significantly as the in vivo antenna is placed deeper inside the body since the main scatterers are present in the vicinity of the antenna. Multipath propagation characteristics are also investigated to facilitate proper waveform designs in the future wireless health-care systems, and a root-mean-square delay spread of 2.76 ns is observed at 5 cm depth. Results show that the in vivo channel exhibit different characteristics than the classical communication channels, and location dependence is very critical for accurate, reliable, and energy-efficient link budget calculations.Öğe Bio-inspired filter banks for frequency recognition of SSVEP-based brain-computer interfaces(Institute of Electrical and Electronics Engineers, 2019) Demir, Ali Fatih; Arslan, Hüseyin; Uysal, İsmailBrain-computer interfaces (BCIs) and their associated technologies have the potential to shape future forms of communication, control, and security. Specifically, the steady-state visual evoked potential (SSVEP) based BCIs have the advantages of better recognition accuracy, and higher information transfer rate (ITR) compared to other BCI modalities. To fully exploit the capabilities of such devices, it is necessary to understand the underlying biological features of SSVEPs and design the system considering their inherent characteristics. This paper introduces bio-inspired filter banks (BIFBs) for improved SSVEP frequency recognition. SSVEPs are frequency selective, subject-specific, and their power gets weaker as the frequency of the visual stimuli increases. Therefore, the gain and bandwidth of the filters are designed and tuned based on these characteristics while also incorporating harmonic SSVEP responses. The BIFBs are utilized in the feature extraction stage to increase the separability of classes. This method not only improves the recognition accuracy but also increases the total number of available commands in a BCI system by allowing the use of stimuli frequencies that elicit weak SSVEP responses. The BIFBs are promising particularly in the high-frequency band, which causes less visual fatigue. Hence, the proposed approach might enhance user comfort as well. The BIFB method is tested on two online benchmark datasets and outperforms the compared methods. The results show the potential of bio-inspired design, and the findings will be extended by including further SSVEP characteristics for future SSVEP based BCIs.Öğe In vivo communications: Steps toward the next generation of implantable devices(IEEE-Inst Electrical Electronics Engineers Inc, 2016) Demir, Ali Fatih; Ankaralı, Zekeriyya Esat; Abbasi, Qammer H.; Liu, Yang; Qaraqe, Khalid; Serpedin, Erchin; Arslan, Hüseyin; Gitlin, Richard D.In vivo wireless medical devices have the potential to play a vital role in future healthcare technologies by improving the quality of human life. In order to fully exploit the capabilities of such devices, it is necessary to characterize and model the in vivo wireless communication channel. Utilization of this model will have a significant role in improving the communication performance of embedded medical devices in terms of power, reliability and spectral efficiency. In this paper, the state of the art in this field is presented to provide a comprehensive understanding of current models. Such knowledge will be used to optimize the design and selection of various in vivo wireless communication methods, operational frequencies, and antenna design. Finally, open research areas are discussed for the future studies.Öğe In vivo wireless channel modeling(Institution of Engineering and Technology, 2016) Demir, Ali Fatih; Ankaralı, Zekeriyya Esat; Liu, Yang; Abbasi, Qammer Hussain; Qaraqe, Khalid; Serpedin, Erchin; Arslan, Hüseyin; Gitlin, RichardTechnological advances in biomedical engineering have significantly improved the quality of life and increased the life expectancy of many people. In recent years, there has been increased interest inwireless body area networks(WBANs)research with the goal of satisfying the demand for innovative biomedical technologies and improved healthcare quality [1, 2]. One component ofsuch advanced technologiesisrepresented bythe devicessuch aswirelessin vivo sensors and actuators, e.g., pacemakers, internal drug delivery devices, nerve stimulators, wireless capsule endoscopes (WCEs), etc. In vivo wireless medical devices and their associated technologies represent the next stage of this evolution and offer a cost efficient and scalable solution along with the integration of wearable devices. In vivo-WBAN devices (Figure 7.1) are capable of providing continuous health monitoring and reducing the invasiveness of surgeries. Furthermore, patient information can be collected over a larger period of time, and physicians are able to perform more reliable analysis by exploiting big data [3] rather than relying on the data recorded in short hospital visits.Öğe Innovative telecommunications training through flexible radio platforms(Institute of Electrical and Electronics Engineers, 2019) Demir, Ali Fatih; Peköz, Berker; Köse, Selçuk; Arslan, HüseyinThe everchanging telecommunication industry is in severe need of a highly skilled workforce to shape and deploy future generation communication systems. This article presents innovative telecommunication training that is designed to satisfy this need. The training focuses on hardware layers of the open systems interconnection model. It integrates theory, numerical modeling, and hardware implementation to ensure complete and long-lasting understanding. The key telecommunication concepts that are covered in the fundamental training phase are detailed along with best teaching practices. In addition, methods that enrich the learning experience, such as gamified microtasks and interactive use of daily telecommunication devices, are featured. The project development case studies that cultivate creative thinking and scientific interest are highlighted. Also, a well-established guideline to compose the teaching environment that emphasizes hands-on experience is provided. Therefore, the presented training can be exemplary to other institutions that share the same mission to educate the distinguished engineers of the future.Öğe Inter-numerology interference management with adaptive guards: A cross-layer approach(IEEE - Institute of Electrical and Electronics Engineers, Inc., 2020) Demir, Ali Fatih; Arslan, HüseyinThe next-generation communication technologies are evolving towards increased flexibility in various aspects. Although orthogonal frequency division multiplexing (OFDM) remains as the waveform of the upcoming fifth-generation (5G) standard, the new radio provides flexibility in waveform parametrization (a.k.a. numerology) to address diverse requirements. However, managing the peaceful coexistence of mixed numerologies is challenging due to inter-numerology interference (INI). This paper proposes the utilization of adaptive guards in both time and frequency domains as a solution along with a multi-window operation in the physical (PHY) layer. The adaptive windowing operation needs a guard duration to reduce the unwanted emissions, and a guard band is required to handle the INI level on the adjacent band. The guards in both domains are jointly optimized with respect to the subcarrier spacing, use case (i.e., service requirement), and power offset between the numerologies. Also, the multi-window approach provides managing each side of the spectrum independently in case of an asymmetric interference scenario. Since the allowed interference level depends on the numerologies operating in the adjacent bands, the potential of adaptive guards is further increased and exploited with a medium access control (MAC) layer scheduling technique. The proposed INI-based scheduling algorithm decreases the need for guards by allocating the numerologies to the available bands, considering their subcarrier spacing, power level, and SIR requirements. Therefore, INI management is performed with a cross-layer (PHY and MAC) approach in this study. The results show that the precise design that accommodates such flexibility reduces the guards significantly and improves the spectral efficiency of mixed numerology systems.Öğe Numerical characterization of in vivo wireless communication channels(Institute of Electrical and Electronics Engineers Inc., 2014) Demir, Ali Fatih; Abbasi, Qammer Hussain; Ankaralı, Zekeriyya Esat; Serpedin, Erchin; Arslan, HüseyinIn this paper, we numerically investigated the in vivo wireless communication channel for human male torso at 915 MHz. Results show that in vivo channel is different than the classical communication channel and location dependency is very critical for link budget calculations. A statistical path loss model based on angle, depth and body region is introduced for near and far field regions. Furthermore, multipath characteristics are investigated using a power delay profile as well.Öğe Short paper: Experimental characterization of in vivo wireless communication channels(Institute of Electrical and Electronics Engineers, 2015) Demir, Ali Fatih; Abbasi, Qammer Hussain; Ankaralı, Zekeriyya Esat; Qaraqe, Marwa; Serpedin, Erchin; Arslan, HüseyinIn vivo wireless medical devices have a critical role in healthcare technologies due to their continuous health monitoring and noninvasive surgery capabilities. In order to fully exploit the potential of such devices, it is necessary to characterize the in vivo wireless communication channel which will help to build reliable and high-performance communication systems. This paper presents preliminary results of experimental characterization for this fascinating communications medium on a human cadaver and compares the results with numerical studies.Öğe The impact of adaptive guards for 5G and beyond(Institute of Electrical and Electronics Engineers Inc., 2017) Demir, Ali Fatih; Arslan, HüseyinThe next generation communication systems are evolving towards an increased flexibility in different aspects. Enhanced flexibility is the key in order to address diverse requirements. This paper presents the significance of adaptive guards considering a windowed-OFDM system which supports a variety of services operating asynchronously under the same network. The windowing approach requires a guard duration to suppress the out-of-band emissions (OOBE), and the guard band is required to handle the adjacent channel interference (ACI) along with the windowing. The guards in both time and frequency domains are optimized with respect to the use case and power offset between the users. To fully exploit and further increase the potential of adaptive guards, an interference-based scheduling algorithm is proposed as well. The results show that the precise design that facilitates such flexibility reduce the guards significantly and boost the spectral efficiency.Öğe Time-frequency warped waveforms(IEEE-Inst Electrical Electronics Engineers Inc, 2019) İbrahim, Mostafa; Demir, Ali Fatih; Arslan, HüseyinThe forthcoming communication systems are advancing toward improved flexibility in various aspects. Improved flexibility is crucial to cater diverse service requirements. This letter proposes a novel waveform design scheme that exploits axis warping to enable peaceful coexistence of different pulse shapes. A warping transform manipulates the lattice samples non-uniformly and provides flexibility to handle the time-frequency occupancy of a signal. The proposed approach enables the utilization of flexible pulse shapes in a quasi-orthogonal manner and increases the spectral efficiency. In addition, the rectangular resource block structure, which assists an efficient resource allocation, is preserved with the warped waveform design as well.Öğe Waveform design for 5G and beyond(Wiley, 2018) Demir, Ali Fatih; Elkourdi, Mohamed H.; İbrahim, Mostafa N.; Arslan, Hüseyin5G is envisioned to improve major key performance indicators (KPIs), such as peak data rate, spectral efficiency, power consumption, complexity, connection density, latency, and mobility. This chapter aims to provide a complete picture of the ongoing 5G waveform discussions and overviews the major candidates. It provides a brief description of the waveform and reveals the 5G use cases and waveform design requirements. The chapter presents the main features of cyclic prefix-orthogonal frequency-division multiplexing (CP-OFDM) that is deployed in 4G LTE systems. CP-OFDM is the baseline of the 5G waveform discussions since the performance of a new waveform is usually compared with it. The chapter examines the essential characteristics of the major waveform candidates along with the related advantages and disadvantages. It summarizes and compares the key features of different waveforms.
