Reliability-based hybrid automatic repeat request （HARQ） （RB-HARQ） is a recently developed form of incremental-redundancy ARQ. It achieves good performance whereas large retransmission request packets should be fe...Reliability-based hybrid automatic repeat request （HARQ） （RB-HARQ） is a recently developed form of incremental-redundancy ARQ. It achieves good performance whereas large retransmission request packets should be fed back. In this paper, in order to reduce the number of the fed back bits, we propose a HARQ scheme applied in time duplex division orthogonal frequency division multiplexing （TDD- OFI）M） system over the slow fading channel which is named channel-based HARQ （CB-HARQ）. Because one bit which meets deep fading is always with small value of log likelihood ratio （LLR） during the process of decoding of LDPC code, the bits transmitted on the carrier with deep fading are retransmitted. At the receiver, the decoder will compute the locations of retransmission bits according to the channel fading values which are gotten by utilizing the feature of channel symmetry in TDD mode. So the indices of retransmission bits are avoided to be transmitted. Simulation results show that this method achieves better BER performance and requires much smaller request packets in feedback link.展开更多
Functionality represents a blueprint of a product and plays a crucial role in problem-solving such as design.This article discusses the model representation from the angle of functional ontology by function deployment...Functionality represents a blueprint of a product and plays a crucial role in problem-solving such as design.This article discusses the model representation from the angle of functional ontology by function deployment.We construct a framework of functional ontology which decomposes the function and contains a library of vocabulary to comprehensively represent the conceptual design model.The ontology enables the automatic identification system to search in the functional space.Furthermore,the functional ontology can form a systematic representation for the model so that it can be reused in the conceptual design and can be applied in the domain of knowledge fusion in our further work.展开更多
基金the National High Technology Research and Development Programme of China(No.2003AA12331004)
文摘Reliability-based hybrid automatic repeat request （HARQ） （RB-HARQ） is a recently developed form of incremental-redundancy ARQ. It achieves good performance whereas large retransmission request packets should be fed back. In this paper, in order to reduce the number of the fed back bits, we propose a HARQ scheme applied in time duplex division orthogonal frequency division multiplexing （TDD- OFI）M） system over the slow fading channel which is named channel-based HARQ （CB-HARQ）. Because one bit which meets deep fading is always with small value of log likelihood ratio （LLR） during the process of decoding of LDPC code, the bits transmitted on the carrier with deep fading are retransmitted. At the receiver, the decoder will compute the locations of retransmission bits according to the channel fading values which are gotten by utilizing the feature of channel symmetry in TDD mode. So the indices of retransmission bits are avoided to be transmitted. Simulation results show that this method achieves better BER performance and requires much smaller request packets in feedback link.
基金the National Natural Science Foundation of China (Nos.50575142,50775140 and 60304015)the National High Technology Research and Development Program (863) of China (No.2008AA04Z113)+2 种基金the National Basic Research Program (973) of China (No.2006CB705400)the Shanghai Committee of Science and Technology (Nos.08JC1412000,09DZ1121400 and 07XD14016)the Research Fund for the Doctoral Program of Higher Education (No.200802480036)
文摘Functionality represents a blueprint of a product and plays a crucial role in problem-solving such as design.This article discusses the model representation from the angle of functional ontology by function deployment.We construct a framework of functional ontology which decomposes the function and contains a library of vocabulary to comprehensively represent the conceptual design model.The ontology enables the automatic identification system to search in the functional space.Furthermore,the functional ontology can form a systematic representation for the model so that it can be reused in the conceptual design and can be applied in the domain of knowledge fusion in our further work.
