Analysis of spectrum requirements for cooperative intelligent transport systems based on cellular vehicle to everything communications셀룰러 차량 사물 통신 기반의 차세대 지능형 교통 시스템을 위한 주파수 소요량 연구

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With the development of fifth generation of wireless communication technologies that meet the requirements of high reliability and low latency, C-ITS service applying cellular vehicle-to-everything communication technology is getting closer to reality. In recent years, a variety of C-ITS applications that enhance driving experience and safety of users by attaching various sensors on vehicles and sharing the information obtained through these sensors with surrounding vehicles. As the C-ITS services evolve, a driving support system that send warning messages to drivers in emergency situations has been proposed to enhance the driving safety, and furthermore, autonomous driving service that monitors surrounding vehicles and driving environment and automatically controls the vehicle are proposed. In order to support these applications, it is essential to secure an appropriate spectrum by estimating the spectrum required for the C-ITS services. As C-ITS service is directly related to the safety of drivers and pedestrians, it is important to estimate spectrum requirements that will ensure high reliability. Even though ITU-R has previously developed several methodologies of estimating spectrum requirements for wireless communications, it is not suitable to apply the ITU-R methodologies directly to C-ITS. The previous mobile communication did not consider critical communication service which is closely related to user safety, thus ITU-R methodologies did not sufficiently consider the quality of service for individual users. To overcome the weakness, a methodology of estimating spectrum requirements applying signal-to-interference-plus-noise-ratio probability distribution is proposed. As the ITU-R methodology uses only mean spectral efficiency of the cell, identical spectra are estimated if the mean spectral efficiencies are identical, even in different channel environments. Therefore, the ITU-R methodology may not satisfy the data reliability for some users in poor channel status. Different from the ITU-R methodology, the proposed methodology adaptively reflects the channel status of each user to guarantee the quality of service for all users. The wireless channel status for users is classified into several levels depending on SINR ranges, and the spectral efficiency is derived for each channel level. Based on the SINR probability obtained from a realistic 5G deployment, the probability of satisfying the corresponding spectral efficiency in each channel level is obtained. By applying these values, the proposed methodology adaptively estimates larger spectra in lower channel levels and smaller spectra in higher channel levels. Also, the probability of retransmission due to errors is also considered to estimate the spectrum requirements reflecting the practical service circumstance. For the evaluation of the proposed methodology, the spectrum requirements for C-ITS are estimated by using both the proposed methodology and ITU-R methodology for various cases. In order to guarantee the reliability of the results, traffic data obtained from various combination of parameters are applied in urban and freeway traffic models at two carrier frequencies. As the proposed methodology adaptively estimates the spectrum requirement by reflecting the channel status of each user in the cell, the results estimated by using the two methodologies under the same conditions show different tendency. In the proposed methodology, the lower the channel level, the smaller the spectral efficiency. In addition, as spectral efficiency is greatly decreased as the channel level is lower, much larger spectra are required at low channel levels to ensure the quality of service for users. Therefore, the spectra estimated by using the proposed methodology are larger than those estimated by using the ITU-R methodology. Furthermore, the spectrum requirement estimated by the proposed methodology increases as the carrier frequency increases. On the other hand, the spectrum requirement estimated by ITU-R decreases because the mean spectral efficiency at higher carrier frequency is higher than the value at the at lower carrier frequency. As the ITU-R methodology only reflects the mean spectral efficiency, the QoS at low channel levels is not sufficiently considered. These results show that the proposed methodology is appropriate for C-ITS and can guarantee the QoS for all users in the cell, regardless of channel level. In addition, various BLER and latency depending on the data type are applied for estimation of spectrum requirements in order to provide the optimized results according to the various service scenarios. For the purpose, the parameters are subdivided and a modified methodology was applied to apply the expanded parameters. Accordingly, spectrum requirements for various C-ITS applications are estimated in various scenarios. The estimation spectrum requirements are very sensitive to the assumptions on data characteristics and application environments, thus the estimated results need to be handled carefully according to the considered scenarios. We expect the results to be utilized as a guideline for spectrum allocation for C-ITS service.
Ahn, Seungyoungresearcher안승영researcher
한국과학기술원 :조천식녹색교통대학원,
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학위논문(박사) - 한국과학기술원 : 조천식녹색교통대학원, 2020.8,[ix, 110 p. :]


Spectrum requirements▼aC-ITS; SINR▼aprobability distribution▼aC-V2X; 주파수 소요량▼a차세대 지능형 교통 시스템▼a신호 대 간섭 잡음비▼a확률분포; 셀룰러 기반 차량 사물 통신

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