• Title/Summary/Keyword: spectral efficiency

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On the Application and Optimization of M-ary Transmission Techniques to Optical CDMA LANs (Optical CDMA 근거리망을 위한 M-진 전송기술에 대한 연구)

  • 윤용철;최진우;김영록
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.8C
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    • pp.1086-1103
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    • 2004
  • Most research efforts on the OCDMA technology assume single-bit-per-symbol transmission techniques such as on-off keying. However, achieving high spectral efficiency with such transmission techniques is likely to be a challenging task due to the "unipolar" nature of optical signals. In this paper, an M-ary transmission technique using more than two equally-weighted codes is proposed for OCDMA local area networks, and ie BER performance and spectral efficiency are analyzed. Poison frame arrival and randomly generated codes are assumed for the BER analysis, and the probability of incorrect symbol detection is analytically derived. From the approximation, it is found that there exists an optimal code weight that minimizes the BER, and its physical interpretation is drawn in an intuitive and simple statement. Under the assumption of this optimized code weight and sufficiently large code dimension, it is also shown that the spectral efficiency of OCDMA networks can be significantly improved by increasing the number (M) of symbols used. Since the cost of OCDMA transceivers is expected to increase with the code dimension, we finally provide a guideline to determine the optimal number of symbols for a given code dimension and traffic load.

High SNR Analysis of User-Multiplexing Technique Provisioning Delay QoS in OFDMA Systems (OFDMA 시스템에서 지연 QoS를 지원하는 2-D 사용자 다중화 기법에 대한 높은 SNR영역에서의 성능 분석)

  • Ahn, Seong-Woo;Hong, Dae-Sik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.4
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    • pp.77-83
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    • 2011
  • In this paper, we study the throughput-delay tradeoff of OFDMA systems in context of 2-dimensional resource allocation, and analyze the effect of frequency diversity and user-multiplexing in time domain that has on delay QoS performance. Based on the analysis results, we investigate the impacts of delay QoS on spectral efficiency. In high SNR regime, the optimal DoM (degree of multiplexing) maximizing the spectral efficiency is identified. The results of the high SNR analysis can give us an intuition on an efficient resource allocation policy. Finally, through the simulation results, we verify that our approach with its optimal DoM yields substantial capacity gain.

An Experimental Study on Combustion Characteristics of Radiant Burner (복사 버너의 연소특성에 관한 실험적 연구)

  • Wie, Jae-Hyug;Lee, Dae-Rae;Kim, Young-Soo;Jeon, Chung-Hwan
    • 한국연소학회:학술대회논문집
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    • 2006.04a
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    • pp.19-25
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    • 2006
  • Energy efficient and low pollution combustion systems the use gaseous fuels have been in great demand in recent year. Radiant burner in many different forms are emerging as very desirable combustion systems for same reason. Porous radiant burners are used in drying, preheating and curing, and in other type of materials processing and manufacturing processes. However, little knowledge is available about the operating characteristics and the structure of flames in porous ceramic fiber radiant burners. The objective of the present work is to investigate the global performance characteristics of the ceramic fiber burner. A detailed study which includes the spectral intensity, gas temperature, radiation efficiency and global pollutant emissions. Another objective is to study the flame structure of the ceramic fiber burner by measuring the local gas temperature. The results indicate that ceramic fiber burner do offer a 19-44% gain in radiant efficiency. The ceramic fiber burner exhibit significant spectral intensity peaks in the band at $2.0-2.5{\mu}m$. The local temperature distribution inside the mat and near the mat surface as a function of the equivalence ratio can be reasonably interpreted by the relation of the heat balance in the mat and movement of the reaction zone. Nox emission from ceramic fiber burner is less than 25ppm throughout the operating range.

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A Study on D-MSSTC-SM (D-MSSTC-SM 기법에 관한 연구)

  • Jeon, Chanyong;Lee, Jeong Woo
    • Journal of IKEEE
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    • v.21 no.1
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    • pp.89-91
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    • 2017
  • We proposed a spatial modulation (SM) scheme to improve spectral efficiency of multi-input multi output (MIMO) systems by using double multi-strata space-time codes (D-MSSTC). For improving the performance of proposed scheme, we allocate transmit power and phase to layers in each MSSTC, and assign rotation angle to SM codebooks. Additionally, we jointly optimize power, phase and rotation angle to maximize the minimum coding gain distance of D-MSSTC-SM. It is observed that the proposed scheme shows better error performance with high spectral efficiency than conventional schemes in simulation results.

Double Quadrature Spatial Modulation

  • Holoubi, Tasnim;Murtala, Sheriff;Muchena, Nishal;Mohaisen, Manar
    • International Journal of Internet, Broadcasting and Communication
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    • v.11 no.3
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    • pp.27-33
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    • 2019
  • Quadrature spatial modulation (QSM) utilizes the in-phase and quadrature spatial dimensions to transmit the real and imaginary parts, respectively, of a single signal symbol. Improved QSM (IQSM) builds upon QSM to increase the spectral efficiency by transmitting the real and imaginary parts of two signal symbols using antenna combinations of size of two. In this paper, we propose a double QSM (DQSM) scheme that transmits the real and imaginary parts of two signal symbols independently through any of the transmit antennas. The two signal symbols are drawn from two different constellations of the same size with the first symbol drawn from any of the conventional modulation sets while the second is drawn from an optimally rotated version of the first constellation. The optimum rotation angle is obtained through extensive Monte Carlo simulations to minimize the bit error rate (BER) of the system. Simulation results show that for a given spectral efficiency, DQSM performsrelatively close to IQSM while requiring a smaller number of transmit antennas, and outperformsIQSM by up to 2 dB when the same number of antennas are used.

Resource Allocation Algorithm for Multiple RIS-Assisted UAV Networks (다중 UAV-RIS 네트워크를 위한 자원 할당 알고리즘)

  • Heejae Park;Laihyuk Park
    • Journal of Platform Technology
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    • v.11 no.1
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    • pp.3-10
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    • 2023
  • Unmanned Aerial Vehicles (UAVs) have gained significant attention in 5G and 6G wireless networks due to their high flexibility and low hardware costs. However, UAV communication is still challenged by blockage and energy consumption issues. Reconfigurable Intelligent Surfaces (RISs) have emerged as a promising solution to these challenges, enabling improved spectral efficiency and reduced energy consumption by transmitting signals to users who cannot receive signals because of the obstacles. Many previous studies have focused on minimizing power consumption and data transmission delay through phase shift and power optimization. This paper proposes an algorithm that maximizes the sum rate by including bandwidth optimization. Simulation results demonstrate the effectiveness of the proposed algorithm.

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Spectral Efficient SF Block Coded Relay Transmission System without Cyclic Prefix for a Shadow Area (음영 지역을 위한 주기적 프리픽스 없는 주파수 효율적인 주파수 공간 블록 부호화 중계기 전송 시스템)

  • Won, Hui-Chul
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.11
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    • pp.7456-7462
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    • 2015
  • This paper proposes a spectral efficient space-frequency(SF) block coded single carrier-frequency division multiple access(SC-FDMA) transmission system in a relaying multi-path shadow area. The cyclic prefix(CP) is not used in the proposed system in order to prevent a loss of spectral efficiency due to the use of CP. The destruction of channel cyclicity due to the lack of CP is recovered at the receivers of relays and a destination station. Simulation results show that the performance of the proposed system without CP is almost same as that of the conventional system with full CP, thus increasing the spectral efficiency.

A Parallel Combinatory OFDM System with Weighted Phase Subcarriers

  • Zheng, Hui;Shrestha, Robin;Hwang, Jae-Ho;Kim, Jae-Mong
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.1
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    • pp.322-340
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    • 2012
  • Orthogonal Frequency Division Multiplexing (OFDM) is usually regarded as a spectral efficient multicarrier modulation technique, yet it suffers from a high peak-to-average power ratio (PAPR) problem. Among all the existing PAPR reduction techniques in OFDM systems, side information based PAPR reduction techniques such as partial transmit sequence (PTS) and selective mapping (SLM) schemes, have attracted the most attention. However, the transmission of side information results in somewhat spectral loss and this does not significantly improve the bit error rate (BER) performance. Parallel combinatory (PC) OFDM yields higher spectral efficiency (SE) and better BER performance on Gaussian channels,while is a little but not obvious PAPR improvement over the ordinary OFDM system. This investigation aimed to design a 'perfect' OFDM system. We introduce the side information to rotate the subcarrier phases of our novel PC-OFDM system structure, and call this new system the SIPC(Side information based Parallel Combinatory)-OFDM system. The proposed system achieves better PAPR and SE performance. In addition, considering the tradeoff of system parameters, the proposed system also has the properties of a higher BER.

MIMO-aided Efficient Communication Resource Scheduling Scheme in VDES

  • Sung, Juhyoung;Cho, Sungyoon;Jeon, Wongi;Park, Kyungwon;Ahn, Sang Jung;Kwon, Kiwon
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.16 no.8
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    • pp.2736-2750
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    • 2022
  • As demands for the maritime communications increase, a variety of functions and information are required to exchange via elements of maritime systems, which leads communication traffic increases in maritime frequency bands, especially in VHF (Very High Frequency) band. Thus, effective resource management is crucial to the future maritime communication systems not only to the typical terrestrial communication systems. VHF data exchange system (VDES) enables to utilize more flexible configuration according to the communication condition. This paper focuses on the VDES communication system among VDES terminals such as shore stations, ship stations and aids to navigation (AtoN) to address efficient resource allocation. We propose a resource management method considering a MIMO (Multiple Input Multiple Output) technique in VDES, which has been widely used for modern terrestrial wireless networks but not for marine environments by scheduling the essential communication resources. We introduce the general channel model in marine environment and give two metrics, spectral and the energy efficiencies to examine our resource scheduling algorithm. Based on the simulation results and analysis, the proposed method provides a possibility to enhance spectral and energy efficiencies. Additionally, we present a trade-off relationship between spectral and energy efficiencies. Furthermore, we examine the resource efficiencies related to the imperfect channel estimation.

User-Oriented Energy- and Spectral-Efficiency Tradeoff for Wireless Networks

  • Zhang, Yueying;Long, Hang;Peng, Yuexing;Zheng, Kan;Wang, Wenbo
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.7 no.2
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    • pp.216-233
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    • 2013
  • Conventional optimization designs of wireless networks mainly focus on spectral efficiency (SE) as a performance metric. However, as diverse media services are emerging, a green wireless network, which not only meets the quality of experience (QoE) requirements for users and also improves energy efficiency (EE), is the most appropriate solution. In this paper, we firstly propose the unit QoE per Watt, which is termed QoE efficiency (QEE), as a user-oriented metric to evaluate EE for wireless networks. We then analyze which is the kind of wireless resource given priority to use under different scenarios to obtain an acceptable QEE. Particularly, power, delay and data-rate related to QoE are separately addressed for several typical services, such as file download, video stream and web browsing services. Next, the fundamental tradeoffs are investigated between QEE and SE for wireless networks. Our analytical results are helpful for network design and optimization to strike a good balance between the users perceived QoE and energy consumption.