The Experts below are selected from a list of 819654 Experts worldwide ranked by ideXlab platform
Jian Wang - One of the best experts on this subject based on the ideXlab platform.
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terabit free space Data transmission employing orbital angular momentum multiplexing
Nature Photonics, 2012Co-Authors: Yongxiong Ren, Hao Huang, Yang Yue, Yan Yan, Nisar Ahmed, Jian Wang, Jengyuan Yang, I Fazal, Samuel J DolinarAbstract:Researchers demonstrate the ability to multiplex and transfer Data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the Data Capacity of free-space optical communications links.
E Tangdiongga - One of the best experts on this subject based on the ideXlab platform.
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high Capacity optical wireless communication using two dimensional ir beam steering
Journal of Lightwave Technology, 2018Co-Authors: Ton Koonen, K. A. Mekonnen, F M Huijskens, Zizheng Cao, Fausto Gomezagis, E TangdionggaAbstract:The free-space narrow infrared beams can offer unprecedented Data Capacity to devices individually, as they can provide non-shared connections that have a large link power budget. By means of a fully passive module based on a high port count arrayed waveguide grating router (AWGR), many infrared beams can be 2D steered individually using wavelength tuning. By applying the defocusing techniques, a compact beam steering module has been realized. A simultaneous communication at up to 112 Gbit/s PAM-4 per beam has been shown with an 80-ports AWGR, thus offering a total wireless throughput beyond 8.9 Tbit/s. The wireless provisioning of multiple ultrahigh-definition video streams has been demonstrated in a proof-of-concept laboratory setup.
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indoor ultra high Capacity optical wireless communication using steerable infrared beams
International Topical Meeting on Microwave Photonics, 2017Co-Authors: Ton Koonen, K. A. Mekonnen, F M Huijskens, Zizheng Cao, Fausto Gomezagis, E TangdionggaAbstract:Free-space infrared beams can offer unprecedented Data Capacity to devices individually, by means of unshared connections which have a large link power budget. Two solutions based on passive diffractive modules are presented which perform wavelength-controlled 2D beam steering while minimizing power consumption. Downstream capacities up to 112Gbit/s per beam were experimentally demonstrated. In a hybrid system demonstrator, 60GHz techniques provided upstream Capacity up to 5Gbit/s. Also an all-optical optical wireless communication system concept has been demonstrated, and a novel concept for an aperture-and-bandwidth-optimized integrated optical receiver is presented.
Samuel J Dolinar - One of the best experts on this subject based on the ideXlab platform.
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terabit free space Data transmission employing orbital angular momentum multiplexing
Nature Photonics, 2012Co-Authors: Yongxiong Ren, Hao Huang, Yang Yue, Yan Yan, Nisar Ahmed, Jian Wang, Jengyuan Yang, I Fazal, Samuel J DolinarAbstract:Researchers demonstrate the ability to multiplex and transfer Data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the Data Capacity of free-space optical communications links.
Chungming Wang - One of the best experts on this subject based on the ideXlab platform.
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a novel Data hiding scheme for color images using a bsp tree
Journal of Systems and Software, 2007Co-Authors: Yuan-yu Tsai, Chungming WangAbstract:In this paper, we propose a novel Data hiding technique for color images using a BSP (Binary Space Partitioning) tree. First, we treat the RGB values at each pixel as a three-dimensional (3D) virtual point in the XYZ coordinates and a bounding volume is employed to enclose them. Using predefined termination criteria, we construct a BSP tree by recursively decomposing the bounding volume into voxels containing one or several 3D virtual points. The voxels are then further categorized into eight subspaces, each of which is numbered and represented as three-digit binary characters. In the embedding process, we first traverse the BSP tree, locating a leaf voxel; then we embed every three bits of the secret message into the points inside the leaf voxel. This is realized by translating a point's current position to the corresponding numbered subspace. Finally, we transform the Data-embedded 3D points to the stego color image. Our technique is a blind extraction scheme, where embedded messages can be extracted without the aid of the original cover image. It achieves high Data Capacity, equivalent to at least three times the number of pixels in the cover image. The stego image causes insignificant visual distortion under this high Data Capacity embedding scheme. In addition, we can take advantage of the properties of tree Data structure to improve the security of the embedding process, making it difficult to extract the secret message without the secret key provided. Finally, when we adaptively modify the thresholds used to construct the BSP tree, our technique can be robust against attacks including image cropping, pixel value perturbation, and pixel reordering. But, the scheme is not robust against image compression, blurring, scaling, sharpening, and rotation attacks.
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steganography on 3d models using a spatial subdivision technique
Computer Graphics International, 2006Co-Authors: Yuan-yu Tsai, Chungming Wang, Yuming Cheng, Chunghsien Chang, Pengcheng WangAbstract:This paper proposes a new steganography algorithm for 3D models using a spatial subdivision technique. Our algorithm first decomposes the bounding volume of the cover model into voxels based on a Binary Space Partitioning (BSP) tree. The voxels are then further categorized into eight subspaces, each of which is numbered and represented as three-digit binary characters. In the embedding process, we first traverse the BSP tree, locating a leaf voxel; then we embed every three bits of the payload message into the vertex inside the leaf voxel. This is realized by translating a vertex's current position to the corresponding numbered subspace. This technique is a substitutive blind extraction scheme, where messages embedded can be extracted without the aid of the original cover model. This technique achieves high Data Capacity, equivalent to at least three times the number of the embedded vertices in the cover model. In addition, the stego model has insignificant visual distortion. Finally, this scheme is robust against similarity transformation attacks.
Ferran Martin - One of the best experts on this subject based on the ideXlab platform.
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near field chipless rfid system with high Data Capacity for security and authentication applications
IEEE Transactions on Microwave Theory and Techniques, 2017Co-Authors: Cristian Herrojo, Javier Matacontreras, Alba Nunez, Ferran Paredes, Eloi Ramon, Ferran MartinAbstract:A high Data Capacity chipless radio frequency identification (chipless-RFID) system, useful for security and authentication applications, is presented in this paper. Reading is based on the near-field coupling between the tag, a chain of identical split-ring resonators (SRRs) printed on a (typically flexible) dielectric substrate (e.g., liquid crystal polymer, plastic, and paper), and the reader. Encoding is achieved by the presence or absence of SRRs at predefined (equidistant) positions in the chain, and tag identification (ID) is based on sequential bit reading. Namely, the tag must be longitudinally displaced, at short distance, over the reader, a microstrip line loaded with an SRR and fed by a harmonic signal. By this means, the harmonic signal is amplitude modulated, and the (ID) code is contained in the envelope function, which can be obtained by means of an envelope detector. With this system, tag reading requires proximity with the reader, but this is not an issue in many applications within the domain of security and authentication (e.g., secure paper for corporate documents and certificates). Several circularly shaped 40-bit encoders (implemented in a commercial microwave substrate), and the corresponding reader, are designed and fabricated as proof-of-concept demonstrators. Strategies for programming the tags and a first proof-of-concept chipless-RFID tag fabricated on plastic substrate through inkjet printing are included in this paper.
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near field chipless rfid encoders with sequential bit reading and high Data Capacity
International Microwave Symposium, 2017Co-Authors: Cristian Herrojo, Javier Matacontreras, Ferran Paredes, Ferran MartinAbstract:This paper presents a novel and unconventional approach for the implementation of chipless RFID systems with high Data Capacity, suitable for authentication and security applications. Contrarily to previous time-domain or frequency-domain chipless RFID tags, where encoding is achieved either by generating defects (reflectors) in a transmission line (producing echoes in an input pulsed signal), or by etching multiple resonators (each tuned to a different frequency) in a dielectric substrate (providing a unique spectral signature), respectively, the chipless tags proposed in this paper consist of a set of identical resonators conveniently aligned and etched (or printed) on a dielectric layer (e.g., liquid crystal polymer, paper, etc). The resonators are located at predefined equidistant positions in such a way that the presence or absence of resonators in such positions corresponds to the ‘1’ or ‘0’ logic states, respectively. The reader is simply a coplanar waveguide (CPW) transmission line fed by a harmonic signal tuned to the frequency of the resonant elements. In a reading operation, the tag must be mechanically guided and transversally displaced over the CPW, so that the resonant elements modulate the amplitude of the feeding harmonic signal (through electromagnetic coupling) as they cross the axis of the CPW transmission line. This sequential bit reading alleviates the spectral bandwidth limitations of previous multi-resonator chipless RFID tags since the resonators are all identical in the proposed encoders. Therefore, the Data Capacity (number of bits) can be substantially enhanced since it is only limited by the area occupied by the resonant elements. The necessary close proximity between the tag and the reader is not an issue in certain applications such as authentication and security (e.g., secure paper), where the reading distances can be sacrificed in favor of a high number of bits. The design of 10-bit encoders based on this approach, and implemented by means of S-shaped split ring resonators (S-SRRs) etched on a flexible microwave substrate, is reported. The area of the encoders is as small as 1.35 cm2. The number of bits can be significantly increased by simply adding further S-SRRs to the codes. Thus, high Data Capacity can be achieved without penalizing the complexity of the reader.