7 research outputs found

    A review of commercialisation mechanisms for carbon dioxide removal

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    The deployment of carbon dioxide removal (CDR) needs to be scaled up to achieve net zero emission pledges. In this paper we survey the policy mechanisms currently in place globally to incentivise CDR, together with an estimate of what different mechanisms are paying per tonne of CDR, and how those costs are currently distributed. Incentive structures are grouped into three structures, market-based, public procurement, and fiscal mechanisms. We find the majority of mechanisms currently in operation are underresourced and pay too little to enable a portfolio of CDR that could support achievement of net zero. The majority of mechanisms are concentrated in market-based and fiscal structures, specifically carbon markets and subsidies. While not primarily motivated by CDR, mechanisms tend to support established afforestation and soil carbon sequestration methods. Mechanisms for geological CDR remain largely underdeveloped relative to the requirements of modelled net zero scenarios. Commercialisation pathways for CDR require suitable policies and markets throughout the projects development cycle. Discussion and investment in CDR has tended to focus on technology development. Our findings suggest that an equal or greater emphasis on policy innovation may be required if future requirements for CDR are to be met. This study can further support research and policy on the identification of incentive gaps and realistic potential for CDR globally

    PAPR Analysis in OFDM-IQ-IM Systems

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    One of the key disadvantages of OFDM system, implemented already in 4G and 5G is high PAPR. For this reason, it is very important to evaluate the PAPR performance of any potential multiplexing technique candidate for upcoming generations. Due to the superior performance over OFDM considering BER performance, spectral efficiency, energy efficiency, OFDM-IQ-IM is one of the promising multiplexing techniques for upcoming generations of wireless technology. Therefore, the PAPR performance of OFDM-IQ-IM system has been analysed here. In deterministic approach, subcarriers are considered to be modulated by symbols with highest power and the upper limit of the PAPR of OFDM-IQ-IM system has been formulated. Using statistical distribution, a probabilistic approach has been taken to determine the PAPR performance of the OFDM-IQ-IM and OFDM-IM systems. The distribution of PAPR of OFDM-IQ-IM and OFDM-IM systems has been evaluated considering the discrete time baseband signals for both in-phase and quadrature components as independent Gaussian random variables. A comparative analysis of the PAPR of OFDM, OFDM-IM and OFDM-IQ-IM systems has been made in both deterministic and probabilistic approach. Thus improved PAPR performance has been noticed in OFDM-IQ-IM system compared to OFDM-IM and OFDM systems for same spectral efficiency

    A Study on Weighted Multiband Communication Method Based on Iterative Coding for Long Range Underwater Acoustic Communication

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    Recently, underwater acoustic communication is an essential technology for underwater communication in marine research, and its application field is expanding. In addition, with the development of military AUV capable of long-distance movement, there is an increasing need to develop a technology capable of reliably communicating over a long distance for efficient marine surveillance. In the long distance acoustic communication, as the transmission distance increases, the bandwidth decreases and the throughput efficiency decreases. Multiband transmission technique is an efficient method to improve the transmission distance and performance in long-range underwater acoustic communication. However, sometimes the performance of multiband is lower than that of single bands. This is because in the transceiver model using the conventional multiband transmission technique, signals of different frequency bands are combined with the same weight and input to the decoder, so that performance degradation of a specific frequency band affects the total band. Accordingly, this thesis propose a weighted multiband transceiver model to improve the performance of the multiband transceiver model. In the weighted multiband transceiver model, the transmitter uses a convolution code and a turbo code of 1/3 coding rate, and receiver uses a decision feedback equalizer to compensate for multipath distortion after compensating for frequency and phase offsets in each band. And, by applying the turbo equalization technique, the equalizer and the decoder is connected to each other to update the information iteratively to improve performance as the number of iteration increases. In addition, the threshold detector adds weights by setting threshold values through preamble BER(Bit Error Rate) of each band. The weighting method according to the threshold value for each band can improve the performance by reducing the influence of the band having low performance in the total band. Simulation results show that the performance improves as the number of bands increases when the multiband transmission technique is applied. The performance of the proposed weighted multiband transceiver model analyzed through short and 90 km long-range sea experiments. In the short-range sea experiment, it confirmed that the performance improved with the increase of the number of bands, and that the performance was improved by applying the proposed weighted multiband structure to the data with low performance when the number of bands was four. In addition, the 90 km long-range sea experiment applied a weighted multiband transceiver model for data that did not completely correct errors within 5 iterations in the conventional multiband. As a result, it confirmed that the performance is further improved when the weighted multiband is applied.List of Tables ii List of Figures iii Abstract iv 제 1 장 서론 1 제 2 장 수중음향통신에서 고려되는 전송 기법 3 2.1 채널 부호화 기법 4 2.2 단일밴드 전송 기법 6 2.3 다중밴드 전송 기법 9 제 3 장 가중화된 다중밴드 통신 12 3.1 임계값 및 가중치 설정 알고리즘 12 3.2 가중화된 다중밴드 기반의 송·수신구조 15 제 4 장 시뮬레이션 및 실험 결과 분석 17 4.1 시뮬레이션 17 4.2 단거리 해양 실험 20 4.3 장거리 해양 실험 26 제 5 장 결 론 35 참고문헌 37 감사의 글 40Maste
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