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Adaptive Power Allocation Scheme for Mobile Satellite Systems Using LTE-Advanced (LTE-Advanced 기반 이동 위성 시스템을 위한 적응형 전력 할당 방식)

  • Yeo, Sung-Moon;Kang, Kun-Seok;Kim, Soo-Young;Ku, Bon-Jun
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.49 no.6
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    • pp.1-7
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    • 2012
  • Due to the increasing demand of network convergence, in future, hybrid/integrated satellite and terrestrial systems will play an important role. In that case, compatibilities between the satellite and terrestrial systems are very important for efficiency of the systems. 3GPP Long Term Evolution (LTE) is one of the 4G system. Therefore, in this paper, we introduce the design of interleaver for mobile satellite system based 3GPP LTE specification. The 4G system including the LTE specification adopted adaptive modulation and coding (AMC) schemes for efficient usage of resources, and the updating interval of resource allocation is an order of msec. However, because of the long round trip delay of satellite systems, we cannot employ the same AMC scheme specified for the terrestrial system, and thus it cannot effectively counteract to short term fadings. Therefore, in order to overcome these problems, we propose an interleaver scheme combined with AMC. We present the interleaver design results considering mobile satellite system based on the LTE and analyze the simulation results.

An Accelerated Approach to Dose Distribution Calculation in Inverse Treatment Planning for Brachytherapy (근접 치료에서 역방향 치료 계획의 선량분포 계산 가속화 방법)

  • Byungdu Jo
    • Journal of the Korean Society of Radiology
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    • v.17 no.5
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    • pp.633-640
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    • 2023
  • With the recent development of static and dynamic modulated brachytherapy methods in brachytherapy, which use radiation shielding to modulate the dose distribution to deliver the dose, the amount of parameters and data required for dose calculation in inverse treatment planning and treatment plan optimization algorithms suitable for new directional beam intensity modulated brachytherapy is increasing. Although intensity-modulated brachytherapy enables accurate dose delivery of radiation, the increased amount of parameters and data increases the elapsed time required for dose calculation. In this study, a GPU-based CUDA-accelerated dose calculation algorithm was constructed to reduce the increase in dose calculation elapsed time. The acceleration of the calculation process was achieved by parallelizing the calculation of the system matrix of the volume of interest and the dose calculation. The developed algorithms were all performed in the same computing environment with an Intel (3.7 GHz, 6-core) CPU and a single NVIDIA GTX 1080ti graphics card, and the dose calculation time was evaluated by measuring only the dose calculation time, excluding the additional time required for loading data from disk and preprocessing operations. The results showed that the accelerated algorithm reduced the dose calculation time by about 30 times compared to the CPU-only calculation. The accelerated dose calculation algorithm can be expected to speed up treatment planning when new treatment plans need to be created to account for daily variations in applicator movement, such as in adaptive radiotherapy, or when dose calculation needs to account for changing parameters, such as in dynamically modulated brachytherapy.

Transmission Schemes for Ka band Satellite Broadcasting Signals by Rainfall Rate (Ka대역 위송방송 신호의 강우강도에 따른 전송기법)

  • Yoon, Ki-Chang;Kim, Seung-Chul;Sohn, Won
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2009.11a
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    • pp.101-104
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    • 2009
  • 이 연구는 Ka대역 위성 HDTV 방송 서비스를 제공하기 위해 강우강도에 따른 전송방안을 제안하였다. Ka대역은 Ku대역에 비하여 강우에 취약하기 때문에 이를 안정적으로 활용하기 위해서는 강우감쇠를 효과적으로 경감시키는 기술개발이 필수적이다. 유럽위성방송 표준인 DVB-S2에서는 강우감쇠에 대한 대처방안으로 채널상황에 따라 여러 변조방식과 채널 부호 율을 이용하는 적응형 변복조 방식을 지원하고 있으며, 이 논문에서는 DVB-S2기반의 전송방식과 Ka대역 중계기의 규격을 적용하여 강우강도에 따른 전송방안을 제안하였다. 이를 위하여 ITU-R P.618-9 강우감쇠 추정 모델과 기상청에서 측정한 1998년부터 2007년까지의 최근 10년간 국내 주요지역의 30분 누적강우량을 이용하여 지역별 강우 감쇠값을 도출하였고 강우강도와 시간 율 관계분석을 통하여 강우강도에 따른 강우감쇠 값을 획득하였다. 획득한 강우감쇠 값을 무궁화 위성 3호의 링크 설계에 적용하여 강우강도에 따른 적용 가능한 전송방안을 도출하였다. 이 연구를 바탕으로 강우의 지역적 편이가 높은 우리나라의 강우 특성을 유연하게 반영하여 각 지역에 맞는 적응적인 전송 방식을 고려할 수 있다.

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Channel-Adaptive Streaming Scheme to Guarantee Media Quality in Mobile WiMAX (모바일 와이맥스에서 채널 적응적인 미디어 품질 보장 기법)

  • Kim, Dong-Chil;Chung, Kwang-Sue
    • Journal of KIISE:Computing Practices and Letters
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    • v.16 no.10
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    • pp.990-994
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    • 2010
  • Mobile WiMAX does not guarantee the media qualities because it does not consider the characteristics of video coding techniques. In this paper, PC-MCA(Priority-based Combining adaptive Modulation and Coding with ARQ), a priority based channel-adaptive streaming scheme, is proposed to guarantee media qualities. PC-MCA uses QoS scheduler by scheduling priority of the media and differentially controls modulation and coding schemes according to wireless channel condition and frame priorities. It also guarantees multimedia service quality through video decoding reliability.

Adaptive Template Receiver for Robust Powerline Communication (견실한 전력선 통신을 위한 영교차점 적응 템플릿 수신기)

  • Lee, Won-Tae;Kim, Kwan-Ho;Woo, Dae-Ho;Yu, Young-Gyu;Won, Dong-Sun;Lee, Young-Chul
    • Proceedings of the KIEE Conference
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    • 2004.07d
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    • pp.2652-2654
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    • 2004
  • 홈 네트워크나 가로등 제어에 가장 적합한 솔루션 중 하나가 전력선 통신기술이다. 전력선 통신의 사용 주파수 대역은 $50kHz{\sim}450kHz$으로, 이 주파수 대역은 잡음이 매우 많이 존재한다. 또한 시공간에 따른 변화의 요인이 많이 존재하기 때문에 채널 모델링이 매우 어려운 실정이며, 이를 극복할 수 있는 방안으로 영교차점을 이용한 전력선 모뎀을 설계하고자 한다. 변조 방식은 Chirp 심볼을 사용하고, 주파수 대역은 $100kHz{\sim}400kHz$를 사용하였다. 전력선 채널로부터 정보를 획득하기 위해서 효율적인 수신기 구조를 채택하였다. 즉 채널 상황에 적응이 가능하고, 상관에 필요한 필터의 계수를 들어오는 심볼로부터 구하는 방법으로, 다음에 들어오는 심볼과의 상관값을 구하여 정보 신호를 판별하는 형태로 구성하였다. 영교차점을 기준으로 신호를 송수신하는 형태를 취했으며, 영교차점 기준에 들어오는 잡음은 chirp의 대역 확산 특성에 의해서 억제될 수 있다. 이런 기술에 의해서 견실한 전력선 통신 모뎀구현이 가능하였다.

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An Adaptive Companding Scheme for Effective PAPR Reduction of OFDM Signals (OFDM 신호의 효율적인 PAPR 감소를 위한 적응적 Companding 기법)

  • Kim, Jae-Woon;Shin, Yo-An
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.11C
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    • pp.1067-1075
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    • 2009
  • In this paper, we propose an adaptive companding scheme to effectively reduce PAPR (Peak-to-Average Power Ratio) of the OFDM (Orthogonal Frequency Division Multiplexing) signals, while considering both complexity and BER (Bit Error Rate) performance of systems. The proposed scheme adaptively alters the compression function in the transmitter and the expanding function in the receiver to simultaneously take into account the BER performance and the PAPR reduction. In this paper, we also measure in-band and out-of-band spectra of the proposed scheme, and observe the BER performance after applying the filtering to reduce the out-of-band radiation. As compared to the conventional companding algorithm, simulation results reveal that the proposed scheme achieves more reliable BER performance in all the cases of with and without the filtering, and has a good spectrum characteristic with effective PAPR reduction.

Hardware Design of SNR Estimator for Adaptive Satellite Transmission System (적응형 위성 전송 시스템을 위한 신호 대 잡음비 추정 회로 구현)

  • Lee, Jae-Ung;Kim, Soo-Seong;Park, Eun-Woo;Im, Chae-Yong;Yeo, Sung-Moon;Kim, Soo-Young
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.2A
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    • pp.148-158
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    • 2008
  • This paper proposes an efficient signal to noise ratio (SNR) estimation algorithm and its hardware implementation for adaptive transmission system using M-ary modulation scheme. In this paper, we present the implementation results of the proposed algorithm for the second generation digital video broadcasting via satellite (DVB-S2) system, and the proposed algorithm can be tailored to the other communication systems using adaptive transmissions. We built a look-up table (LUT) using the theoretical background of the received signal distribution, and by using this LUT we need just two comparators and a counter for the hardware implementation. For this reason, the hardware of the proposed scheme produces accurate estimation results even with extremely low complexity. The simulation results investigated in this paper reveal that the proposed method can produce estimation results within the specified SNR range in the DVB-S2 system, and it requires a few hundreds of samples for average estimation error of about 1 dB.

QARA: Quality-Aware Rate Adaptation for Scalable Video Multicast in Multi-Rate Wireless LANs (다중 전송율 무선랜에서의 스케일러블 비디오 멀티캐스트를 위한 품질 기반 전송 속도 적응 기법)

  • Park, Gwangwoo;Jang, Insun;Pack, Sangheon
    • KIPS Transactions on Computer and Communication Systems
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    • v.1 no.1
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    • pp.29-34
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    • 2012
  • Wireless multicast service can be used for video streaming service to save the network resources by sending the same popular multimedia contents to a group of users at once. For better multimedia streaming multicast service, we propose a quality-aware rate adaptation (QARA) scheme for scalable video multicast in rate adaptive wireless networks. In QARA, transmission rate is determined depending on the content's type and users' channel conditions. First, the base layer is transmitted by a low rate for high reliability. That means we provide basic service quality to all users. On the contrary, the transmission rate for enhancement layer is adapted by using channel condition feedback from a randomly selected node. So, the enhancement layer frames in a multimedia content is sent with various transmission rates. Therefore, each node can be provided with differentiated quality services. Consequently, QARA is capable of serving heterogeneous population of mobile nodes. Moreover, it can utilize network resources more efficiently. Our simulation results show that QARA outperforms utilization of the available transmission rate and reduces the data transmission time.

A Novel Two-step Channel Prediction Technique for Adaptive Transmission in OFDM/FDD System (OFDM/FDD 시스템에서 Target QoS 만족을 위한 다단계 적응전송 채널예측기법)

  • Heo Joo;Chang Kyung-Hi
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.8A
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    • pp.745-751
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    • 2006
  • The transmitter requires knowledge of the channel status information in order to adopt the adaptive modulation and coding scheme(AMC) for OFDM system. But in the outdoor environment which the users have high mobility, the channel status information from the users is outdated, so that it induces the degradation of system throughput and packet error rate(PER) performance. To solve this problem, researches about applying channel prediction technique to the AMC scheme have been proceeded. Most channel prediction techniques assume that there is no channel variation in the predefined time duration, e.g., a slot. As a result, those techniques cannot compensate the degradation of PER performance resulting from the rapid variation of channel during the slot duration. This paper introduces a novel channel prediction technique for OFDM/FDD system to support adaptive modulation and coding scheme over rapidly time-varying multipath fading channel. The proposed channel prediction technique considers the time-varying nature of channel during the slot duration. Simulation results show that the AMC scheme of OFDM/FDD system utilizing the proposed channel prediction technique can guarantee the target PER of 1% without any loss of system throughput compared with the case supported by the conventional channel prediction under ITU-R Veh A 30km/h.

A Study about Space Vector PWM strategy For Three-Phase Four-Legged Voltage Source Inverter (3상 4레그 전압원 인버터(Three-Phase Four-Legged Voltage Source Inverter)의 공간벡터 전압변조 방식에 대한 연구)

  • Kim, Jang-Hwan;Sul, Seung-Ki
    • Proceedings of the KIEE Conference
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    • 2003.04a
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    • pp.154-156
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    • 2003
  • 3상 4레그(leg) VSI(Voltage Source Inverter)는 독립된 3개의 출력전압을 합성할 수 있다. 따라서 전압 합성에 있어서 3개의 자유도를 갖는다. 본 논문에서는 3상 4레그 VSI를 위한 PWM방법에 대해서 설명한다. 3상 4레그 VSI를 위한 기존의 PWM기술은 3-D SVPWM으로 그 구현 방법에 있어서 많은 양의 계산과 테이블을 필요로 하였다. 하지만, 본 논문에서 제안 한 방법은 3상 3레그 VSI경우에 적용되었던 옵셋(offset) 전압의 개념을 사용한다. 또한 단일 반송파를 이용하여 폴(Pole)전압과 비교함으로써 PWM을 구현하기 때문에 그 적응이 매우 간단하다. 본 논문에서는 기존의 3-D SVPWM과 제안한 방법이 해석적으로 동일한 방법임을 증명하였으며, 3상 4레그 VSI에서 합성가능한 3자유도의 전압범위를 계산하였다. 마지막으로 이를 실험을 통하여 검증하였다.

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