• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6A
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• pp.499-509
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• 2005

The capacity of Satellite DMB(Digital Multimedia Broadcasting) system is limited mainly by the interference. So, to achieve the expected performance of Satellite DMB system and to minimize the interference from other Satellite DMB system, ACI(Adjacent Channel Interference) should be considered carefully. Satellite DMB system uses the Gap-filler for effective transmission in terrestrial environment, and the Gap-filler can use direct amplification or frequency conversion to satisfy the specific requirements. Therefore, amplified signal causes several effects on interference between System A(Eureka 147 DAB) and System E(ISDB : Integrated services Digital Broadcasting). In this paper, by using the outcome of system-level simulation considering the results of link-level simulation, we analyze the interferences between System A and System E under practical situation based on the exact parameters of ITU-R BO. 1130-4. We also propose the appropriate level of guard band and Cell Radius to optimize system capacity by adapting the spectrum mask given in the spec. and utilizing the interference analysis between System A and System E.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.6A
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• pp.484-493
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• 2009

For the flexible frequency utilization, cognitive radio technique has been prominently considered. The most important requirement in cognitive radio networks is to protect the communications of primary users. Spectrum sensing task by secondary users should be seriously considered in cognitive radio networks, since the spectrum sensing process makes their current quality of service worse. In this paper, we propose the channel sensing scheduling method that keeps the requirements for protecting the primary and guarantee the secondary user's quality of service as possible. The quality of service of secondary user is analyzed in terms of packet delay and loss while the protection-requirements in terms of sensing interval and sensing time predefined. In numerical analysis, we can get appropriate parameters which guarantee QoS in various environment. And simulation results show that this method can improve the performance, delay and the number of transmitted packets against consecutive sensing method.

• Earthquakes and Structures
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• v.3 no.2
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• pp.141-168
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• 2012

The Retrofit Yield Spectrum (RYS) is a new spectrum-based device that relates seismic demand of a retrofitted structure with the fundamental design parameters of the retrofit. This is obtained from superposition of Yield Point Spectra with design charts that summarize in pertinent spectrum-compatible coordinates the attributes of a number of alternative retrofit scenarios. Therefore, once the requirements for upgrading a given structure have been determined, the RYS enable direct insight of the sensitivity of the seismic response of the upgraded structure to the preliminary design decisions made while establishing the retrofit plan. By virtue of their spectrum-based origin, RYS are derived with reference to a single mode of structural vibration; a primary objective is to control the contribution of this mode in the retrofit design so as to produce a desirable distribution of damage at the ultimate limit state by removing soft storey formations and engaging the maximum number of structural members in deformation, in response to the input motion. Calculations are performed with reference to the yield-point, where secant stiffness is proportional to the flexural strength of reinforced concrete members. Derivation and use of the Retrofit Yield Spectra (RYS) refers to the seismic demand expressed either in terms of spectral acceleration, spectral displacement or interstory drift, at yield of the first storey. A reinforced concrete building that has been tested in full scale to a sequence of simulated earthquake excitations is used in the paper as a demonstration case study to examine the effectiveness of the proposed methodology.

• Journal of Advanced Navigation Technology
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• v.13 no.3
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• pp.378-384
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• 2009

In this paper, we consider a cyclostationary-feature-detection based spectrum sensing algorithm for ATSC signal detection. One of the proposed algorithms for IEEE 802.22 standardization organization which meet the requirements of IEEE 802.22 is Thomson's algorithm based on cyclostationary feature detection. We propose an interpolation-based spectrum sensing algorithm for ATSC signal detection, which has less computation complexity than that of Thomson's algorithm and provides no performance loss compared to Thomson's algorithm. By using zero-padding in time domain and effective sensing scanning method, the proposed algorithm requires less computational complexity and shows no performance degradation compared to Thomson's algorithm.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.79-86
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• 2007

In order to operate Low Earth Orbit(LEO) satellite on space, technical requirements and administrative procedure which are defined by the International Telecommunication Union(ITU) should be followed on satellite development. Main technical requirements to follow are purpose of use, bandwidth, Radio Frequency(RF) intensity, and constraints on new satellite network about existing satellite networks according to frequency spectrum. Such ITU's requirements are reflected and designed on system specification and space to ground interface control document. In order to have a right and protection about using the satellite network on space, the satellite network has to be registered on Master International Frequency Register(MIFR) and procedure for this has to be followed. Coordination with countries raising objection is needed in order to register. And reference and method for coordination are also needed.

• The Korean Journal of Air & Space Law and Policy
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• v.27 no.1
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• pp.123-156
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• 2012

This study focuses on the satellite licenses and the requirements for satellite spectrum management (i.e. frequency allocation) in Korean satellite industry via comparative analyses against those cases in other developed countries, in order to provide complementary measures to the domestic satellite policies. The satellite industry is one of the main pursuits of a nation's efforts, and it shows distinct characteristics depending on various factors such as national defense and security. In addition, the industry is determined by the nation's market size as well as its international relationship. Consequently, the present study considers examples from various organizations and nations - including U.S.A, Japan, and ITU - and provides a hybrid policy that is well customized for the domestic market. This study looks at similarities between policies of other countries, and finds any supplements for domestic polices by specifying similar cases in others and analyzing their results. The main purpose of this study, therefore, is to find the best agreement for domestic policy with internal interpretation, rather accepting others. While the licensing method for domestic satellites need not be distinct from that of other nations, the case of using non-Korean licensed satellites must be complemented by the conditions in the domestic market. Furthermore, the spectrum management is essential to the nation's satellite industry since the spectrum is a scarce resource. As such, spectrum management that is carefully designed to incorporate the rapidly changing international market demand is crucial to provide a sufficient supply for domestic space industry. In the present study, we find that auction-like market based approaches together with measures to avoid exclusive uses of the scarce resource (e.g. share, leas and reallocation) would provide an excellent method for the domestic satellite industry.

• Journal of Satellite, Information and Communications
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• v.2 no.2
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• pp.22-28
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• 2007

Spectrum spreading, in its general form, can be conceived as an artificial expansion of the signal bandwidth with respect to the minimum Nyquist band required to transmit the desired information. Spreading can be functional to several objectives, including resilience to interference and jammers and reduction of power spectral density levels. In the paper, signal spreading is manly used for increasing the received energy, thus satisfying link budget constraints, for terminals with low aperture antennas, without increasing the transmitted EIRP. As a matter of fact, in many mobile scenarios, even when MODCOD configurations with very low spectral efficiency (i.e. QPSK-1/4) in DVB-S2 standard, are used, the link budget cannot be closed. Spectrum spreading has been recently proposed as a technique to improve system performance without introducing additional MODCOD configurations under the constraint of fixed power spectrum density level at the transmitter side. To this aim, the design of spectrum spreading techniques shall keep into consideration requirements such as spectrum mask, physical layer performance, link budget, hardware reuse, robustness, complexity, and backward compliance with existing commercial equipments. The proposed implementation allows to fully reuse the standard DVB-S2 circuitry and is inserted as an 'inner layer' in the standard DVB-S2 chain.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.68-78
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• 2013

In this paper, we propose an early spectrum sensing(ESS) as an advance preparation for radio-access trial, which enables multi-mode terminals to access the most appropriate radio-access system in a cloud-conceptual base station system where multiple radio access technologies(RATs) coexist. Prior to a random access to one of RATs, a multi-mode terminal conducts a spectrum sensing over entire frequency bands of whole RATs, then select the RAT with the lowest sensing power, that is likely to have the most available spectrum. Thus, an access failure caused by that the selected RAT has no available radio spectrum could be avoidable in advance. In computer simulation, we consider as various RATs as possible. First, circuit and packet systems are taken into consideration. In addition, the packet systems are classified according to the feasibility of carrier aggregation(CA). In case of terminal, three modes are considered with circuit-only, packet-only, and multi-mode. Subsequently, packet traffic is classified into real-time and non-real-time traffic with three different tolerable delay levels. The simulation includes a call process starting with a call generation and ending up with a resource allocation reflecting individual user's QoS requirements and evaluates the proposed scheme in terms of the successful access probability, system access time, system balancing factor and packet loss probability.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.3
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• pp.21-27
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• 2016

The static and dynamic structural integrity qualification was performed through the seismic analysis of a small-size Savonius-type vertical wind turbine at dead weight plus wind load and seismic loads. The ANSYS finite element program was used to develop the FEM model of the wind turbine and to accomplish static, modal, and dynamic frequency response analyses. The stress of the wind turbine structure for each wind load and dead weight was calculated and combined by taking the square root of the sum of the squares (SRSS) to obtain static stresses. Seismic response spectrum analysis was also carried out in the horizontal (X and Y) and vertical (Z) directions to determine the response stress distribution for the required response spectrum (RRS) at safe-shutdown earthquake with a 5% damping (SSE-5%) condition. The stress resulting from the seismic analysis in each of the three directions was combined with the SRSS to yield dynamic stresses. These static and dynamic stresses were summed by using the same SRSS. Finally, this total stress was compared with the allowable stress design, which was calculated based on the requirements of the KBC 2009, KS C IEC 61400-1, and KS C IEC 61400-2 codes.

• Journal of the Korea Computer Industry Society
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• v.2 no.4
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• pp.537-546
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• 2001

Griffth's and LCCMA which are Single-user detection adaptive algorithm are proposed for mitigate MAI(multiple access interference) and the near-far problem in direct-sequence spread-spectrum CDMA system and MOE Algorithm is proposed for MMSE(Minimum Mean-Square Error). This paper pertains to three types of Blind adaptive algorithms which can upgrade system functionality without the requirements from training sequence. It goes further to compare and analyze the functionalities of the algorithms as per number of interfering users or data update rate of the users. The simulation results was that LCCMA algorithm was superior to other algorithms in both areas. Blind application enabled a more flexible network design by eliminating the necessity of training sequence.