• Title/Summary/Keyword: Channel allocation

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Multicast VOD System for Interactive Services in the Head-End-Network (Head-End-Network에서 대화형 서비스를 위한 멀티캐스트 VOD 시스템)

  • Kim, Back-Hyun;Hwang, Tae-June;Kim, Ik-Soo
    • The KIPS Transactions:PartB
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    • v.11B no.3
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    • pp.361-368
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    • 2004
  • This paper proposes an interactive VOD system to serve truly interactive VCR services using multicast delivery, client buffer and web-caching technique which implements the distributed proxy in Head-End- Network(HNET). This technique adopts some caches in the HNET that consists of a Switching Agent(SA), some Head-End-Nodes(HEN) and many clients. In this model, HENs distributively store the requested video under the control of SA. Also, client buffer dynamically expands to support various VCR playback rate. Thus, interactive services are offered with transmitting video streams from network, HENs and stored streams on buffer. Therefore this technique makes the load of network occur In the limited area, minimizes the additional channel allocation from server and restricts the transmission of duplicated video contents

Symbol Error Probability of a Physical Layer Network Coded System in Nakagami Fading Channels (나카가미 페이딩 채널에서 물리 계층 네트워크 부호화 시스템의 심볼 오류율)

  • Do, Phu Thinh;Wang, Jin-Soo;Park, Jin-Bae;Kim, Yun-Hee
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.37 no.8C
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    • pp.645-654
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    • 2012
  • In this paper, we consider a two-way relay (TWR) system, where two user nodes exchange their information within two transmission phases, by the help of a relay node adopting physical layer network coding. In the system, two users transmit their binary phase shift keying symbols simultaneously in the first phase, and the relay node decodes the XORed version of two user data and broadcasts it back to two users in the second phase. The performance of the system is analyzed in terms of the average end-to-end symbol error probability in Nakagami-m fading channels, for which a tight upper bound is derived in a closed form to provide an accurate and handy estimate on the performance. The results show that our upper bounds are almost indistinguishable from simulation results for various channel and system configurations. In addition, the optimal relay location and power allocation for various conditions can be obtained quickly with our analysis.

An On/Off Power Control for OFDM Transmission Scheme in a Cochannel Interference Environment (동일 채널 간섭 환경에서 OFDM 전송 방식을 위한 온/오프 송신 전력 제어)

  • Park, Jin-Kyu;Lim, Chang-Heon;Kim, Jin-Yul
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.11A
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    • pp.1182-1189
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    • 2007
  • Frequency reuse in a cellular wireless communication environment gives rise to a phenomenon of cochannel interference. This paper introduces a power control strategy for OFDM based communication systems operating in such an environment. Among the existing power control schemes, IWF(iterative waterfilling) is known to exhibit relatively good performance. However, it requires feedback of power level and bit allocation information for each subcarrier from a receiver to its associated transmitter, which can lead to a considerable overhead, especially for the case of employing large number of subcarriers. Motivated by this, we present a simplified power control scheme with reduced overhead feedback, which allocates some nonzero identical power to the subcarriers of which channel conditions are above a certain threshold and zero power to the other ones. Computer simulations show that the proposed strategy produces a good approximation to the performance of the IWF in terms of the transmission power level while it requires less overhead feedback.

Performance Analysis of DVC Scheme with Adaptive Gray Code for Frame Difference Signal (화면 간 차이신호에 대한 적응적 그레이코드를 이용한 분산 비디오 부호화 기법의 성능 분석)

  • Kim, Jin-Soo;Kim, Jae-Gon;Choi, Hae-Chul
    • Journal of Broadcast Engineering
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    • v.17 no.5
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    • pp.876-890
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    • 2012
  • In this paper, we investigated the performances of the distributed video codec with adaptive Gray code to apply for frame-difference signal. That is, the best cases and the worst cases were analyzed and compared by considering the statistical characteristics of the frame difference signal in view of the Gray code allocation. Through computer simulations, if 9-bit data for frame difference signal is generated for luminance signal with 8-bit definition and so n-bit is allocated to the quantized coefficient, we were able to find the best method to reduce the virtual channel noise by adding $256+2^{9-n-1}$ to the frame difference signal. Through computer simulation with test video sequences, it was shown that the performance difference between the best cases and the worst cases is larger than about 1.5dB at same rate. It is expected that the results in this paper are applicable for the transform-domain scheme as well as the pixel-domain scheme.

Effect of SIC Errors to Cooperative NOMA systems (SIC 에러가 협동 NOMA 시스템에 미치는 영향)

  • Kim, Nam-Soo
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.17 no.5
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    • pp.35-42
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    • 2017
  • NOMA (Non-orthogonal multiple access) system is the most promising multiple access technology to satisfy the requirements of the spectral efficiency and the performance of 5G cellular systems. NOMA system simultaneously serves multiple users in the power domain, and adapts SIC (Successive interference cancellation) at the receivers to cancel the interference from multiple users. Since in a realistic wireless fading channel the perfect SIC is impossible, the study of the effect of the imperfect SIC to a NOMA system is necessary. This paper considers a cooperative NOMA system with SIC error, and the performance of the system is analytically derived. And the optimum power allocation to minimize the system performance is obtained. When the transmit power is fixed, the distances between a base station and the relay is considered for different SIC errors. The derived analytical results are verified through Monte Carlo simulation, and the results are perfectly matched.

A Study on PEP based on Cross-layer and Network Coding in DVB-RCS Networks (DVB-RCS 네트워크에서 Cross-layer 및 네트워크 코딩 기반 PEP 연구)

  • Lee, Kyu-Hwan;Jung, Hyun-Ki;Kim, Jae-Hyun
    • Journal of the Institute of Electronics and Information Engineers
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    • v.52 no.3
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    • pp.25-31
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    • 2015
  • In this paper, we propose PEP based on cross-layer and network coding in digital video broadcasting-return channel via satellite (DVB-RCS) networks. In particular, we propose not only a scheme of cross-layer information exchange for interaction between TCP and the resource allocation (RA) scheme in the link layer but also a tuning algorithm for the TCP contention window (CWND) by using information on the RA in the link layer and the redundancy rate for network-coded packets. The simulation results show that TCP CWND can be adjusted by RA information in the proposed protocol. Furthermore, through the transmission of network-coded packets and the proposed CWND tuning algorithm, TCP throughput is enhanced in lossy environment due to user mobility without the unnecessary resource overhead.

Overall Cell Data Rates Analysis for Heterogenous Network Under Adaptive Modulation (이종 네트워크에서 적응변조 사용시 주파수 공유에 따른 데이터 전송률 분석)

  • Kwon, Tae-Hoon
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.11 no.4
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    • pp.394-400
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    • 2018
  • A heterogenous network is the one of key technologies for 5G, where one cell is divided into small cells in order to extend coverage and support high data rates. Divided cells aggravates the intercell interference problem as the cell edge increases. In order to avoid the intercell interference, it is the best to allocate the different spectrum for each cells. However, it also decreases the spectral efficiency. Therefore, the trade-off between the spectral efficiency gain and the signal quality loss by the interference should be considered for an efficient spectrum sharing in the heterogenous network. The adaptive modulation is the method to change the transmitted bit according to the channel quality, which is adopted as the standard in the most practical communication systems. It should be considered to applied the performance analysis into the practical systems. In this paper, the overall cell data rates is analyzed for the heterogenous network under the adaptive modulation. The Monte Carlo simulation results verify the correctness of the analysis.

Analysis on the Interference from HAPS Airship into P-MP FWA System (HAPS 비행선에서 P-MP FWA 시스템으로의 간섭 분석)

  • Choi, Mun-Hwan;Ham, Hyoung-Il;Kang, Young-Heung
    • Journal of Advanced Navigation Technology
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    • v.9 no.2
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    • pp.177-184
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    • 2005
  • In this paper, we have analyzed the effects of the interference from HAPS airship stations to P-MP FWA base station and to P-MP FWA terminal station, using more detail parameters such as a new interference model, a realistic HAPS scenario, practical antenna patterns for both HAPS system and FWA system. The analysis results show that, in the case of interference from HAPS AS into the P-MP FWA BS, compatibility between two systems can be obtained by using a sectored BS antenna with the boresight directed away from the nadir. However, in the case of Interference from HAPS AS into the P-MP FWA TS, the two systems cannot operate effectively in the same bands unless the separation distance is guranteed and/or some form of interference mitigation technique is employed such as dynamic channel allocation.

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A Bitrate Control considering Interframe Variance of Image for H.264/AVC (화면간 영상 변화량을 고려한 H.264/AVC 비트율 제어 방법)

  • Son Nam-Rye;Lee Guee-Sang
    • The KIPS Transactions:PartB
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    • v.13B no.3 s.106
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    • pp.245-254
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    • 2006
  • In this work, a new rate control algorithm for transmission of H.264/AVC video bit stream through CBR(constant bit rate) channel is proposed. The proposed algorithm predicts target bit rate and MAD(mean of absolute difference) for current frame considering image complexity variance between neighboring backward and current images. In details, respective linear regression analysis for MAD and encoded bit rate against image complexity variance produce correlation parameters. Additionally, it uses frame skip technique to maintain bit stream within a manageable range and protect buffer from overflow or underflow. Implementation and experimental results show that the proposed algorithm can provide accurate bit allocation, and can effectively visual degradation after scene changes. Also our proposed algorithm encodes the video sequences with less frame skipping compared to the existing rate control for H.264/AVC.

An OFDMA-Based Next-Generation Wireless Downlink System Design with Hybrid Multiple Access and Frequency Grouping Techniques

  • Lee Won-Ick;Lee Byeong Gi;Lee Kwang Bok;Bahk Saewoong
    • Journal of Communications and Networks
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    • v.7 no.2
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    • pp.115-125
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    • 2005
  • This paper discusses how to effectively design a next-generation wireless communication system that can possibly provide very high data-rate transmissions and versatile quality services. In order to accommodate the sophisticated user requirements and diversified user environments of the next-generation systems, it should be designed to take an efficient and flexible structure for multiple access and resource allocation. In addition, the design should be optimized for cost-effective usage of resources and for efficient operation in a multi-cell environment. As orthogonal frequency division multiple access (OFDMA) has turned out in recent researches to be one of the most promising multiple access techniques that can possibly meet all those requirements through efficient radio spectrum utilization, we take OFDMA as the basic framework in the next-generation wireless communications system design. So, in this paper, we focus on introducing an OFDMA-based downlink system design that employs the techniques of hybrid multiple access (HMA) and frequency group (FG) in conjunction with intra-frequency group averaging (IFGA). The HMA technique combines various multiple access schemes on the basis of OFDMA system, adopting the multiple access scheme that best fits to the given user condition in terms of mobility, service, and environment. The FG concept and IFGA technique help to reduce the feedback overhead of OFDMA system and the other-cell interference (OCI) problem by grouping the sub-carriers based on coherence band-widths and by harmonizing the channel condition and OCI of the grouped sub-carriers.