• 대한전자공학회논문지SP
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• 제38권2호
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• pp.218-226
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• 2001

MPEG-2 비디오 부호화 과정에서 비트율 제어를 위해 MPEG-2 Test Model 5 (TM5) 알고리즘이 널리 사용되고 있지만, 실제로는 각 화면에 할당되는 목표 비트수와 실제 부호화된 비트수가 잘 맞지 않아 한 GOP의 마지막 부분에서 버퍼 넘침 현상과 화질의 급격한 열화 현상이 발생할 수 있다. 본 논문에서는 부호화하고자 하는 블록의 이전 블록에서 실제 발생된 비트수와 예측에 의한 비트수 사이의 관계를 이용하여 정확한 비트수를 할당함으로써, 각 화면의 목표 비트수와 실제 발생되는 부호화 비트수를 정합시키는 새로운 비트율 제어 알고리즘을 제안한다. 제안된 알고리즘은 화면내에서 일관된 화질을 유지하며, 실시간 처리도 가능하다.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2004년도 하계종합학술발표회논문초록집
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• pp.275-275
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• 2004

• 한국통신학회논문지
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• 제22권1호
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• pp.53-63
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• 1997

In this paper, we present a new macroblock-based bit allocation scheme in multiple MPEG-1 video encoders system and a single multiplexer over a single channel. The proposed scheme models the relations between fate(Bits/MB) and distortion(MSE/MB), rate and quantizer parameter(QP), distortion and quantizer parameter, respectively, in the same form. By using these relations, we minimize the Larangian cost function to obtain a bit allocation scheme based on macroblock unit. Experimental results show that the proposed scheme can reduce MSE compared to other conventional buffer-based rate control methods, i.e. independent buffer control method and shared common buffer control one. And we confirmed, through computer simulation, that the proposed scheme can be effectively modified to maintain the objective quality of a specific video service at a constant level.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권1호
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• pp.20-39
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• 2020

This paper considers a downlink multi-carrier cooperative non-orthogonal multiple access (NOMA) transmission, where no direct link exists between the far user and the base station (BS), and the communication between them only relies on the assist of the near user. Firstly, the BS sends a superimposed signal of the far and the near user to the near user, and then the near user adopts simultaneous wireless information and power transfer (SWIPT) to split the received superimposed signal into two portions for energy harvesting and information decoding respectively. Afterwards, the near user forwards the signal of the far user by utilizing the harvested energy. A minimum data is required to ensure the quality of service (QoS) of the far user. We jointly optimize power allocation, subcarrier allocation, time allocation, the power allocation (PA) coefficient and the power splitting (PS) ratio to maximize the number of data bits received at the near user under the energy causality constraint, the minimum data constraint and the transmission power constraint. The block-coordinate descent method and the Lagrange duality method are used to obtain a suboptimal solution of this optimization problem. In the final simulation results, the superiority of the proposed NOMA scheme is confirmed compared with the benchmark NOMA schemes and the orthogonal multiple access (OMA) scheme.

• 한국통신학회논문지
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• 제33권11A호
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• pp.1095-1104
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• 2008

다중 사용자 OFDM 시스템에서 제한된 자원을 효율적으로 사용하기 위해서는 부반송파와 비트의 할당은 중요한 역할을 한다. 하지만 부반송파와 비트의 할당문제는 비선형적 문제로 모든 경우의 수를 계산하여 최적의 값을 얻기에는 사실상 불가능하다. 본 논문에서는 비선형적 문제의 효율적인 자원 활용을 위해서 새로운 유전자 알고리즘을 사용하였다. 논문에서 제안된 알고리즘은 기존의 정형화된 유전자 알고리즘보다 다양한 조합을 참고하여 해를 찾게 된다. 따라서 수치적 시뮬레이션 결과들을 통해서 기존의 알고리즘들과 제안된 알고리즘을 비교해 볼 때, 제안한 알고리즘이 기존의 알고리즘들보다 뛰어난 성능을 보임을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권12호
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• pp.3037-3054
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• 2013

Interference between primary user (PU) and secondary user (SU) transceivers should be mitigated in order to implement underlay spectrum sharing in cognitive radio networks (CRN). Considering this scenario, an improved joint subcarrier and bit allocation scheme for cognitive user with primary users' cooperation (PU Coop) in CRN is proposed. In this scheme, the optimization problem is formulated to minimize the average interference power level at the PU receiver via PU Coop, which guarantees a higher primary signal to interference plus noise ratio (SINR) while maintaining the secondary user total rate constraint. The joint optimal scheme is separated into subcarrier allocation and bit assignment in each subcarrier via arith-metric geo-metric (AM-GM) inequality with asymptotical optimization solution. Moreover, the joint subcarrier and bit optimization scheme, which is evaluated by the available SU subcarriers and the allocated bits, is analyzed in the proposed PU Coop model. The performance of cognitive spectral efficiency and the average interference power level are investigated. Numerical analysis indicates that the SU's spectral efficiency increases significantly compared with the PU non-cooperation scenario. Moreover, the interference power level decreases dramatically for the proposed scheme compared with the traditional Hughes-Hartogs bit allocation scheme.

• ETRI Journal
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• 제33권2호
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• pp.184-193
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• 2011

Tailored for wireless local area networks, the present paper proposes a cross-layer resource allocation scheme for multiple-input multiple-output orthogonal frequency-division multiplexing systems. Our cross-layer resource allocation scheme consists of three stages. Firstly, the condition of sharing the subchannel by more than one user is studied. Secondly, the subchannel allocation policy which depends on the data packets' lengths and the admissible combination of users per subchannel is proposed. Finally, the bits and corresponding power are allocated to users based on a greedy algorithm and the data packets' lengths. The analysis and simulation results demonstrate that our proposed scheme not only achieves significant improvement in system throughput and average packet delay compared with conventional schemes but also has low computational complexity.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(4)
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• pp.29-32
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• 2002

In typical block-based video coding, the objective of RC(Rate Control) is to select the quantization parameters so that the encoder produces bits at the rate of the channel and the overall distortion is minimized. To reduce the huge amount of computations required for offline RC, there have been significant efforts to speed up the process of video encoders. Those efforts have been mainly focused on the modes for bit rate and distortion in types of coders, in terms of the quantization parameters. Because previous works related to model based online RC are based on statistics of previous frame, it occurs the problem such that allocates bits unequally without regard to current frame statistics. In this thesis, an equal bit allocation scheme using current frame statistics is proposed.

• 한국통신학회논문지
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• 제19권7호
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• pp.1256-1271
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• 1994

본 논문에서는 Gbit 매체접근데어 프로토콜인 HMR(High-speed Multimedia Ring)의 퀘타 할당방법을 변형 적용하여 B-ISDN의 GFC(Generic Flow Control) 프로토콜로 제안하고 시뮬레이션을 통하여 제안된 프로토콜의 성능을 분석하였다. HMR 프로토콜은 Gbit ATM-LAN으로 제안되었지만 버스, 링, 스타버스 형태의 토폴로지에 적용할 수 있도록 고려되었을뿐 아니라 멀티미디어 트래픽 수용을 위한 다단계의 우선순위 제어기능을 가지고 있으므로 수정없이 GFC 프로토콜로 적용이 가능하다. 그러나 기존의 HMR 프로토콜에서 제안되었던 정적퀘타할당 방법은 버스트성이 큰 트래픽에 대하여는 엑세스지연이 과다하게 되는 단점이 있었다. 따라서 본 논문에서는 큐의 크기를 고려한 동적퀘타할당 방식을 적용한 HMR 프로토콜을 제안하고 CCITT에서 제안한 7사지 GFC 시험절차를 적용하여 시뮬레이션을 수행하였다. 동적 퀘타할당 방식을 적용한 HMR 프로토콜은 정적퀘타할당 방식을 적용한 HMR에 비하여 개선된 성능을 나타내었다. 또한 HMR-GFC 프로토콜은 ATMR에 비하여 우수한 성능을 나타내며, DQDB와는 대등한 정도의 성능을 나타탬을 확인하였다.

• Journal of Communications and Networks
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• 제18권3호
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• pp.387-396
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• 2016

Multiuser communication has been an important research area of underwater acoustic communications and networking. This paper studies the use of adaptive orthogonal frequency-division multiple access (OFDMA) in a downlink scenario, where a central node sends data to multiple distributed nodes simultaneously. In practical implementations, the instantaneous channel state information (CSI) cannot be perfectly known by the central node in time-varying underwater acoustic (UWA) channels, due to the long propagation delays resulting from the low sound speed. In this paper, we explore the CSI feedback for resource allocation. An adaptive power-bit loading algorithm is presented, which assigns subcarriers to different users and allocates power and bits to each subcarrier, aiming to minimize the bit error rate (BER) under power and throughput constraints. Simulation results show considerable performance gains due to adaptive subcarrier allocation and further improvement through power and bit loading, as compared to the non-adaptive interleave subcarrier allocation scheme. In a lake experiment, channel feedback reduction is implemented through subcarrier clustering and uniform quantization. Although the performance gains are not as large as expected, experiment results confirm that adaptive subcarrier allocation schemes based on delayed channel feedback or long term statistics outperform the interleave subcarrier allocation scheme.