• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.21-25
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• 2013

The dual-stream based stereoscopic 3D HDTV broadcasting service was launched recently. Although the dual-stream based HDTV service has been successfully provided, the 3D HDTV broadcasting system requires more bandwidth efficient transmission schemes because it should convey both left and right HD resolution images simultaneously in the finite 6MHz bandwidth. In this paper, we consider more advanced ATSC transmission schemes that use higher modulation such as 16-QAM and concatenated RS code and block LDPC codes. Compared with conventional ATSC system and the modified ATSC system in [2], the proposed system has about 2.97dB and 1.12dB SNR gain at the payload data rate of 19.44Mbps compared with the existing ATSC system and the modified ATSC system [2]. Also, the proposed scheme requires only 1.05dB power increase for the 3D HDTV service, which is reasonable SNR increase value and applicable to the advanced 3D high definition broadcasting realization in limited 6MHz bandwidth.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.11A
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• pp.1056-1063
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• 2005

In this paper, we develop a dual beam automotive laser radar system which improve the defect of conventional unipolar one beam laser scheme. We introduce an SNR improving method using bipolar signal synthesizing scheme from two unipolar signals at the receiving unit via differential structure by allocating bipolar m-sequence into the two laser wavelengths, which have similar property like 2-D OOC, and investigate its performance. Simulation results show that the proposed dual beam scheme can have 3dB SNR improvement as compared with conventional unipolar signaling laser radar system. Also, we show the simple interference rejection scheme using differential structures. The proposed scheme have a merit to obtain additional 3dB SNR gain applied into the excellent results based on unipolar optical signal studied lately.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.5
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• pp.377-384
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• 2013

In order to improve the security strength in the password based user authentication, in which the security vulnerability is increased while the same password is repeatedly used, the OTP(One-Time Password) system has been introduced. In the OTP systems, however, the user account information and OTP value may be hacked if the user PC is infected by the malicious codes, because the user types the OTP value, which is generated by the mobile device synchronized with the server, directly onto the user PC. In this paper, we propose a new method, called DTOTP(Dual Transmission OTP), to solve this security problem. The DTOTP system is an improved two-factor authentication method by using the dual transmission, in which the user performs the server authentication by typing the user account and password information onto the PC, and then for the OTP authentication the mobile device scans the QR code displayed on the PC and the OTP value is sent to the server directly. The proposed system provides more improved security strength than that of the existing OTP system, and also can adopt the existing OTP algorithm without any modification. As a result, the proposed system can be safely applied to various security services such like banking, portal, and game services.

• 한국전산유체공학회:학술대회논문집
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• 1998.11a
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• pp.90-95
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• 1998

The two-dimensional incompressible and compressible Navier-Stokes codes are developed for the computation of the viscous turbulent flow over high-lift airfoils. Incompressible code using pseudo-compressibility and dual-time stepping method involves a conventional upwind differencing scheme for the convective terms and LU-SGS scheme for time integration. Compressible code also adopts an FDS scheme and LU-SGS scheme. Several two-equation turbulence models (the standard $k-{\varepsilon}$ model, the $k-{\omega}$ model. and $k-{\omega}$ SST model) are evaluated by computing the flow over single and multi-element airfoils. The compressible and incompressible codes are validated by computing the flow around the transonic RAE2822 airfoil and the NACA4412 airfoil, respectively. Both the results show a good agreement with experimental surface pressure coefficients and velocity profiles in the boundary layers. Also, the GA(W)-1 single airfoil and the NLR7301 airfoil with a flap are computed using the two-equation turbulence models. The grid systems around two- and three-element airfoil are efficiently generated using Chimera grid scheme, one of the overlapping grid generation methods.

• Structural Engineering and Mechanics
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• v.14 no.6
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• pp.625-647
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• 2002

Parallel execution of computational mechanics codes requires efficient mesh-partitioning techniques. These mesh-partitioning techniques divide the mesh into specified number of submeshes of approximately the same size and at the same time, minimise the interface nodes of the submeshes. This paper describes a new mesh partitioning technique, employing Genetic Algorithms. The proposed algorithm operates on the deduced graph (dual or nodal graph) of the given finite element mesh rather than directly on the mesh itself. The algorithm works by first constructing a coarse graph approximation using an automatic graph coarsening method. The coarse graph is partitioned and the results are interpolated onto the original graph to initialise an optimisation of the graph partition problem. In practice, hierarchy of (usually more than two) graphs are used to obtain the final graph partition. The proposed partitioning algorithm is applied to graphs derived from unstructured finite element meshes describing practical engineering problems and also several example graphs related to finite element meshes given in the literature. The test results indicate that the proposed GA based graph partitioning algorithm generates high quality partitions and are superior to spectral and multilevel graph partitioning algorithms.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.12
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• pp.20-26
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• 2012

The newly introduced model of a STTC-based Distributed Wireless Communication System (DWCS) can provide the capability of joint control of the signals at multiple cells. This paper has considered the virtual cell systems: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on DWCS network. The considered system constructs DVC by using antenna selection method. Also, for multi-user high-rate data transmission, the proposed system introduces multiple antenna technology to get a spatial and temporal diversity gain and exploits space-time trellis codes known as STTC to increase a spectral efficiency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7A
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• pp.528-534
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• 2012

In order to achieve high capacity and reliable link quality of the overlay convergent networks with the cognitive networking based on the advanced capability of the mobile terminal, a Distributed Wireless Communication System (DWCS) can provide the capability of enhancing the link quality. This paper has considered virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on radio resource monitering. The considered system constructs DVC for multi-user high-rate data transmission, and the DWCS system exploits space-time trellis codes i.e., STTC to improve a spectral efficiency. The effects of imperfect CSI(channel state information) on the system performance has also been investigated.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.7C
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• pp.715-723
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• 2009

In this paper, we propose a new detection method called dual-cell combining (DCC) detection for the acquisition in time of spread spectrum codes in the presence of residual frequency offset (RFO). When the RFO exists, the correlation peak used for detection during the acquisition process is split into two neighboring peaks with smaller amplitudes, resulting in considerable degradation in the overall acquisition performance of conventional methods. In the DCC detection method, the decision variable for detection is formed by combining two consecutive correlator outputs so that the influence of the reduction in the correlation peak due to the RFO can be alleviated. Numerical results show that the DCC detection method can offer better mean-time-to-synchrouization performance than the conventional method based on the cell-by-cell detection.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6B
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• pp.483-488
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• 2012

With the fast growing data traffic, the performance of the convergent overlay network environment under the cognitive networking environment is crucial for the implementation of the efficient network structure. In order to achieve high capacity and reliable link quality in wireless communication of the overlay convergent networks with the cognitive networking based on the advanced capability of the mobile terminal, a Distributed Wireless Communication System (DWCS) can provide the capability of ambient-aware dual cell system's operation. This paper has considered virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on DWCS network. One is the Active Virtual Cell which exists for user's actual data traffic and the other is the Candidate Virtual Cell which contains a set of candidate antennas to protect user's link quality from performance degradation or interruption. The considered system constructs DVC by using cognitive ability of finding useful virtual signals. Also, for multi-user high-rate data transmission, the DWCS system exploits Space-Time Trellis Codes. The effects of changing environments on the system performance has been investigated thereafter.

• ETRI Journal
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• v.30 no.1
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• pp.113-128
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• 2008

Turbo codes are extensively used in current communications standards and have a promising outlook for future generations. The advantages of software defined radio, especially dynamic reconfiguration, make it very attractive in this multi-standard scenario. However, the complex and power consuming implementation of the maximum a posteriori (MAP) algorithm, employed by turbo decoders, sets hurdles to this goal. This work introduces an ASIP architecture for the MAP algorithm, based on a dual-clustered VLIW processor. It displays the good performance of application specific designs along with the versatility of processors, which makes it compliant with leading edge standards. The machine deals with multi-operand instructions in an innovative way, the fetching and assertion of data is serialized and the addressing is automatized and transparent for the programmer. The performance-area trade-off of the proposed architecture achieves a throughput of 8 cycles per symbol with very low power dissipation.