• Journal of Information Processing Systems
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• 제5권4호
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• pp.229-236
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• 2009

Sensors are deployed to gather physical, environmental data in sensor networks. Depending on scenarios, it is often assumed that it is difficult for batteries to be recharged or exchanged in sensors. Thus, sensors should be able to process users' queries in an energy-efficient manner. This paper proposes a spatial query processing scheme- Minimum Bounding Area Based Scheme. This scheme has a purpose to decrease the number of outgoing messages during query processing. To do that, each sensor has to maintain some partial information locally about the locations of descendent nodes. In the initial setup phase, the routing path is established. Each child node delivers to its parent node the location information including itself and all of its descendent nodes. A parent node has to maintain several minimum bounding boxes per child node. This scheme can reduce unnecessary message propagations for query processing. Finally, the experimental results show the effectiveness of the proposed scheme.

• Journal of information and communication convergence engineering
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• 제13권4호
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• pp.280-285
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• 2015

Double random phase encryption (DRPE) is one of the well-known optical encryption techniques, and many techniques with DRPE have been developed for information security. However, most of these techniques may not solve the fundamental security problem caused by using fixed phase masks for DRPE. Therefore, in this paper, we propose a key phase mask updating scheme for DRPE to improve its security, where a spatial light modulator (SLM) is used to implement key phase mask updating. In the proposed scheme, updated key data are obtained by using previous image data and the first phase mask used in encryption. The SLM with the updated key is used as the second phase mask for encryption. We provide a detailed description of the method of encryption and decryption for a DRPE system using the proposed key updating scheme, and simulation results are also shown to verify that the proposed key updating scheme can enhance the security of the original DRPE.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제2권2호
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• pp.82-102
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• 2008

Packet losses tend to occur during short error bursts separated by long periods of relatively error-free transmission. There is also a significant spatial correlation in loss among the receiver nodes in a multicast session. To recover packet transmission errors at the transport layer, tree-based protocols construct a logical tree for error recovery before data transmission is started. The current tree construction scheme does not scale well because it overloads the sender node. We propose a scalable recovery tree construction scheme considering these properties. Unlike the existing tree construction schemes, our scheme distributes some tasks normally handled by the sender node to specific nodes acting as repair node distributors. It also allows receiver nodes to adaptively re-select their repair node when they experience unacceptable error recovery delay. Simulation results show that our scheme constructs the logical tree with reduced message and time overhead. Our analysis also indicates that it provides fast error recovery, since it can reduce the number of additional retransmissions from its upstream repair nodes or sender node.

• 한국정보처리학회논문지
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• 제6권4호
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• pp.841-850
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• 1999

히스토그램을 이용한 질의 술어의 선택도 추정은 상용 데이터베이스 시스템의 비용 기반 최적화기에서 가장 널리 사용되는 방법이다. 공간 데이터베이스 관리 시스템의 경우 객체간의 위상 관계를 이용한 술어가 주어지며, 질의 최적화를 위해서는 공간 위상 술어의 선택도 추정이 필수적이다. 이를 이해 본 논문에서는 기존의 다차원 히스토그램 기법에 차원 변환 기법을 적용한 공간 위상 술어 추정 기법을 제안한다. 제안된 기법은 차원 변환 공간상의 점으로 대응된 공간 객체로부터 두가지 분할 전략을 이용하여 공간 히스토그램을 생성한 수 변환 공간이 가지는 위상 관계를 이용하여 공간 위상 술어의 선택도를 추정한다. 제안된 기법은 공간 질의 최적화기에서 비교적 작은 메모리와 부가적인 입출력 없이 공간 위상 술어의 선택도를 추정할 수 있다.

• ETRI Journal
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• 제39권5호
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• pp.707-717
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• 2017

This paper presents a novel generalized quadrature spatial modulation (GQSM) transmission scheme using antenna grouping. The proposed GQSM scheme combines QSM and conventional spatial multiplexing (SMux) techniques in order to improve the spectral efficiency (SE) of the system. Analytical and simulation results show that the proposed transmission scheme has minimal losses in terms of the average bit error probability along with the advantage of an increased SE compared with previous SM and QSM schemes. For the case studies, this advantage represents a reduction of up to 81% in terms of the number of required transmit antennas compared with QSM. In addition, a detection architecture based on the ordered successive interference cancellation scheme and the QR decomposition is presented. The proposed QRD-M adaptive algorithm showed a near-maximum-likelihood performance with a complexity reduction of approximately 90%.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권1호
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• pp.426-445
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• 2012

Conventional rate control (RC) schemes for H.264 video coding usually regulate output bit rate to match channel bandwidth by adjusting quantization parameter (QP) at fixed full frame rate, and the passive frame skipping to avoid buffer overflow usually occurs when scene changes or high motions exist in video sequences especially at low bit rate, which degrades spatial-temporal quality and causes jerky effect. In this paper, an active content adaptive frame skipping scheme is proposed instead of passive methods, which skips subjectively trivial frames by structural similarity (SSIM) measurement between the original frame and the interpolated frame via motion vector (MV) copy scheme. The saved bits from skipped frames are allocated to coded key ones to enhance their spatial quality, and the skipped frames are well recovered based on MV copy scheme from adjacent key ones at the decoder side to maintain constant frame rate. Experimental results show that the proposed active SSIM-based frameskip scheme acquires better and more consistent spatial-temporal quality both in objective (PSNR) and subjective (SSIM) sense with low complexity compared to classic fixed frame rate control method JVT-G012 and prior objective metric based frameskip method.

• 한국CDE학회논문집
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• 제5권4호
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• pp.380-392
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• 2000

This paper proposes a qualitative reasoning approach for the spatial configuration of mechanisms that could be applied in the early phase of the conceptual design. The spatial configuration problem addressed in this paper involves the relative direction and position between the input and output motion, and the orientation of the constituent primitive mechanisms of a mechanism. The knowledge of spatial configuration of a primitive mechanism is represented in a matrix form called spatial configuration matrix. This matrix provides a compact and convenient representation scheme for the spatial knowledge, and facilitates the manipulation of the relevant spatial knowledge. Using this spatial knowledge of the constituent primitive mechanisms, the overall configuration of a mechanism is described and identified by a spatial configuration state matrix. This matrix is obtained by using a qualitative reasoning method based on sign algebra and is used to represent the qualitative behavior of the mechanism. The matrix-based representation scheme allows handling the involved spatial knowledge simultaneously and the proposed reasoning method enables the designer to predict the spatial behavior of a mechanism without knowing specific dimension of the components of the mechanism.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권8호
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• pp.3641-3655
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• 2016

Wireless sensor networks (WSNs) provide a promising approach to monitor the physical environments, to prolong the network lifetime by exploiting the mutual correlation among sensor readings has become a research focus. In this paper, we design a hierarchical network framework which guarantees layered-compression. Meanwhile, a data sorting-based adaptive spatial compression scheme (DS-ASCS) is proposed to explore the spatial correlation among signals. The proposed scheme reduces the amount of data transmissions and alleviates the network congestion. It also obtains high compression performance by sorting original sensor readings and selectively discarding the small coefficients in transformed matrix. Moreover, the compression ratio of this scheme varies according to the correlation among signals and the value of adaptive threshold, so the proposed scheme is adaptive to various deploying environments. Finally, the simulation results show that the energy of sorted data is more concentrated than the unsorted data, and the proposed scheme achieves higher reconstruction precision and compression ratio as compared with other spatial compression schemes.

• 한국통신학회논문지
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• 제35권4A호
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• pp.322-331
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• 2010

본 논문에서는 폐루프 다중입출력 무선통신 환경을 위한 새로운 공간 다중화 기법을 소개한다. 기존에 제안되 었던 직교 공간 다중화 (OSM; orthogonalized spatial multiplexing) 방식을 확장하여, 우리는 임의의 수의 데이터 스트림을 동시에 전송하기 위한 새로운 방식을 제안한다. 이를 위하여 우리는 데이터 스트림을 두 개 이상의 그룹으로 나누고 수신기에서 블록 대각화 과정을 수행한다. 제안하는 기법은 적은 피드백 정보량을 가지며 심볼 단위의 ML (maximum likelihood) 검출을 통해 복잡도를 최소화한다. 실험 결과를 통해 제안하는 기법은 기존의 설계 기법들에 비하여 비트에러율 관점에서 큰 성능 이득을 제공함을 확인한다. 또한 추가적인 피드백을 통해 수신 그룹의 선택을 최적화함으로써 성능을 더욱 향상시킬 수 있음을 관찰한다.

• 한국통신학회논문지
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• 제34권7A호
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• pp.515-522
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• 2009

본 논문에서는 채널 부호회된 OFDM (orthogonal frequency division multiplexing) 시스템을 위한 공간 변조를 이용한 새로운 전송 기법을 제안한다. 공간 변조라 불리는 개루프 (open-loop) 방식의 다중 안테나 기술은 업력 데이터를 안테나 인텍스(index) 신호와 데이터 신호로 나누고, 안테나 인텍스 신호에 따라 다수의 송신안테나 중 하나의 송신안테나를 선택하여 데이터 신호를 전송한다. 공간 변조는 수신기에서 송신된 신호가 어떤 안테나로부터 보내졌는지를 의미하는 안테나 인텍스를 검출해야 하는데, 이를 위해서 채널 행렬의 직교성이 보장되어야 한다. 실제 채널은 무시하지 못할 정도의 채널 상관도로 인해 직교성을 유지하지 못한다. 또한 기존 공간 변조를 위한 수신기는 경판정 방식을 취하고 있으므로, 실제 시스템에 이를 활용하기가 어렵다. 본 논문에서는 기존의 공간 변조 기법이 연판정 수신을 할 수 있도록 소프트 출력 디맵퍼 (soft-output demapper)를 유도하고, 기존 기법의 수신 성능을 개선하기 위해 새로운 구조의 전송 기법을 제안한다.