• 한국정보처리학회논문지
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• 제3권4호
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• pp.938-946
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• 1996

계층적 구조를 갖는 서브밴드 코덱은 그 구조의 간단성과 모듈적인 특성으로 인하여 데이타 압축/복원 시스템에 많이 쓰여왔다. 최근까지 연구되어 오고 있는 대부분의 계층적 서브밴드 코덱은 주로 양자화 영향을 고려하지 않은 상태에서 출력단에서 입력 신호를 복원하기 위한 완전복원(perfet Reconstruction)시스템에 제한되어 왔다. 그러나 실제적인 서브밴드 코덱 시스템에서는 분석 필터 뱅크를 통한 입력 신호가 양자화기를 거쳐 합성필터 뱅크에 전송되므로, 양자화 오차가 발생하게 되어 완전복 원은 불가능하게 된다. 따라서, 이러한 양자화 오차를 최소화하여 출력단에서 가능한 한 원 입력신호에 가깝게 재생할 수 있는 최적의 코덱 시스템을 필요로 하게 된다. 본 논문에서는 그 동안 수학적 이론과 코덱구조의 복합성 때문에 고려되지 않았던 양자화기에 위한 양자화 오차를 수학적으로 분석하여 최적화된 계층적 구조를 갖는 서브밴드 코덱의 설계를 제안한다. 본 논문에서의 최적화의기준은 코덱에서 양자화 기에 의해 발생하는 평균 제곱 오차를 최소화하는 계층적 분석/합성 필터 뱅크와 양자화기의 설계에 있다. 구체적인 최적화 설계 예제는 레벨-1. 레벨-2 계층적 구조를 갖는 코덱에 실제 적용되었으며, 설계된 코덱은 컴퓨터 모의 실험을 통하여 검증하였다.

• Journal of Information Processing Systems
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• 제9권1호
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• pp.53-68
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• 2013

We investigate the rate-compatible punctured convolutional (RCPC) codes concatenated with hierarchical QAM for designing a cross-layer unequal error protection scheme for H.264 coded sequences. We first divide the H.264 encoded video slices into three priority classes based on their relative importance. We investigate the system constraints and propose an optimization formulation to compute the optimal parameters of the proposed system for the given source significance information. An upper bound to the significance-weighted bit error rate in the proposed system is derived as a function of system parameters, including the code rate and geometry of the constellation. An example is given with design rules for H.264 video communications and 3.5-4 dB PSNR improvement over existing RCPC based techniques for AWGN wireless channels is shown through simulations.

• 한국통신학회논문지
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• 제41권7호
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• pp.747-749
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• 2016

본 논문에서는 시분할 다중 접속 릴레이 채널을 고려한다. 여기서 두 개의 송신 노드들은 서로 다른 데이터율을 가진 데이터를 네트워크 코딩을 수행하는 단일 릴레이 노드를 통해 단일 수신 노드에게 전송한다. 하지만 이러한 비대칭한 데이터율 때문에 릴레이 노드는 수신한 비트에 대하여 XOR 기반의 네트워크 코딩을 효율적으로 수행할 수 없다. 따라서 본 논문에서는 위와 같은 문제를 해결하기 위해 제로 패딩(Zero Padding) 방식과 계층 16QAM 방식을 개별적으로 네트워크 코딩과 결합하여 성능비교를 수행한다.

• Journal of Communications and Networks
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• 제12권2호
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• pp.122-129
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• 2010

Energy conservation is one of the most important issues for evaluating the performance of wireless sensor network (WSN) applications. Generally speaking, hierarchical clustering protocols such as LEACH, LEACH-C, EEEAC, and BCDCP are more efficient in energy conservation than flat routing protocols. However, these typical protocols still have drawbacks of unequal and high energy depletion in cluster heads (CHs) due to the different transmission distance from each CH to the base station (BS). In order to minimize the energy consumption and increase the network lifetime, we propose a new hierarchical routing protocol, distance aware intelligent clustering protocol (DAIC), with the key concept of dividing the network into tiers and selecting the high energy CHs at the nearest distance from the BS. We have observed that a considerable amount of energy can be conserved by selecting CHs at the nearest distance from the BS. Also, the number of CHs is computed dynamically to avoid the selection of unnecessarily large number of CHs in the network. Our simulation results showed that the proposed DAIC outperforms LEACH and LEACH-C by 63.28% and 36.27% in energy conservation respectively. The distance aware CH selection method adopted in the proposed DAIC protocol can also be adapted to other hierarchical clustering protocols for the higher energy efficiency.

• International Journal of Advanced Culture Technology
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• 제2권1호
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• pp.1-13
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• 2014

In next-generation wireless networks, provisioning of IP-based network architecture and seamless transmission services are very important issues for mobile nodes. For this reason, a mobility management mechanism to support global roaming is highly regarded. These technologies bring a broader life by using a global roaming account through the connection of multiple devices or technology to mobile users; they also provide real-time multimedia services. This paper presents a comprehensive performance analysis of fast handover for hierarchical mobile IPv6 (F-HMIPv6), hierarchical mobile IPv6 (HMIPv6), Proxy Mobile IPv6 (PMIPv6), and fast Proxy Mobile IPv6 (FPMIPv6) using the fluid-flow model and random-walk model. As a result, the location update cost of the PMIPv6 and FPMIPv6 is better than that of HMIPv6 and F-HMIPv6. These results suggest that the network-based mobility management technology is superior to the hierarchical mobility management technology in the mobility environment.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권7호
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• pp.2449-2463
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• 2014

Hierarchical B-frame coding was introduced into H.264/SVC to provide temporal scalability and improve coding performance. A content analysis-based adaptive group of picture structure (AGS) can further improve the coding efficiency, but damages the inter-frame correlation and temporal scalability of hierarchical B-frame to different degrees. In this paper, we propose a group of pictures (GOP) adaptation coding method based on the positions of video cuts. First, the cut positions are accurately detected by the combination of motion coherence (MC) and mutual information (MI); then the GOP is adaptively and proportionately set by the analysis of MC in one scene. In addition, we propose a binary tree algorithm to achieve the temporal scalability of any size of GOP. The results for test sequences and real videos show that the proposed method reduces the bit rate by up to about 15%, achieves a performance gain of about 0.28-1.67 dB over a fixed GOP, and has the advantages of better transmission resilience and video summaries.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.2042-2060
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• 2013

In wireless sensor networks (WSNs), energy efficiency is one of the most essential design considerations, since sensor nodes are resource constrained. Group communication can reduce WSNs communication overhead by sending a message to multiple nodes in one packet. In this paper, in order to simultaneously resolve the transmission security and scalability in WSNs group communications, we propose a hierarchical cluster-based secure and scalable group key management scheme, called HRKT, based on logic key tree and route key tree structure. The HRKT scheme divides the group key into cluster head key and cluster key. The cluster head generates a route key tree according to the route topology of the cluster. This hierarchical key structure facilitates local secure communications taking advantage of the fact that the nodes at a contiguous place usually communicate with each other more frequently. In HRKT scheme, the key updates are confined in a cluster, so the cost of the key updates is reduced efficiently, especially in the case of massive membership changes. The security analysis shows that the HRKT scheme meets the requirements of group communication. In addition, performance simulation results also demonstrate its efficiency in terms of low storage and flexibility when membership changes massively.

• 한국통신학회논문지
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• 제35권4B호
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• pp.670-676
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• 2010

AT-DMB 수신에 적용하기 위한 PN 시퀀스 기반 시간 동기 방법을 제안한다. AT-DMB 변조 모드 정보를 전송하기 위해 PRS에 PN 시퀀스를 삽입하여 전송하는 방법을 적용할 수 있는데, 이 PN 시퀀스를 이용하여 효과적으로 AT-DMB의 시간동기를 획득할 수 있다. 제안한 PN 시퀀스 기반 시간동기 방법에 대해 이동 채널에서 BER 분석을 통해 성능 분석을 하였고 그 결과를 도시하였다.

• Journal of Electrical Engineering and Technology
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• 제9권4호
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• pp.1188-1195
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• 2014

This paper presents an analytical technique for reliability evaluation of electrical distribution network (EDN) containing distributed generation (DG). Based on hierarchical levels of circuit breaker controlling zones and feeder sections, a directed-relation-graph (DRG) for an END is formed to describe the hierarchical structure of the EDN. The reliability indices of EDN and load points can be evaluated directly using the formed DRG, and the reliability evaluation of an EDN containing DGs can also be done without re-forming the DRG. The proposed technique incorporates multi-state models of photovoltaic and diesel generations, as well as weather factors. The IEEE-RBTS Bus 6 EDN is used to validate the proposed technique; and a practical campus EDN containing DG was also analyzed using the proposed technique.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2008년도 춘계종합학술대회 A
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• pp.689-692
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• 2008

Hierarchical modulation has been considered for achieving higher data rates in Terrestrial-DMB(T-DMB) systems. And for achieving a higher data rates transmission, the low-priority (LP) data, which is used to carry additional data, such as video data, audio data and textual data, should be perfectly decoded in a certain value of $E_b/N_o$. Unfortunately, the man-made noise badly affects the high-priority (HP) symbol, which is used to carry the conventional data in the existed T-DMB system; and since the advanced T-DMB system is proposed to fit for the legacy T-DMB receivers, the low-priority symbols in the hierarchical modulation are much worse affected by the neighbors, who are both in the same quadrant. Because of the feature that mentioned previously, the turbo code has been considered to deal with the LP data. And due to the degradation which caused by the shortened symbol distance, the error performance of LP data is not sufficient by only using the turbo code. In this paper, we propose a Reed-Solomon code used outside of turbo code, and with the turbo code, it becomes a concatenated code. In this paper, there are some simulation results, within the comparison of those performances, we can see how a Reed-Solomon code is utilized for degradation of error performance which is caused by the hierarchical constellation, and how to design a Reed-Solomon code which is suitable for improving the degradation of error performance.