• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.247-250
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• 2007

There are three main kinds of service standards for 3G(Third-Generation) wireless communication as WCDMA, CDMA2000 and TD-SCDMA(Time Division-Synchronous Code Division Multiple Access). Compare with WCDMA and CDMA2000, TD-SCDMA system has distinguished technical characters. It is a TDD(Time Division Duplexing) based technology and deploys several advanced but in some respects complex technologies such as smart antenna, joint-detection and baton-handoff, etc. Therefore to analyze and design TD-SCDMA wireless network, it needs more efficient and systematic simulation tool. General simulation tool has so many analysis functions including path loss prediction, capacity and coverage analysis. For more suitable for TD-SCDMA, new additional technologies have to be implemented in simulation tool. Especially as the wireless network highly advancing focused on data service, it more needs to research and develop on the reliability of the simulation tool. In this paper, to give the concrete process and skill about how to implement TD-SCDMA simulation tool, we define the kinds of simulation tool and list basic analysis functions available for TD-SCDMA network design at first. And then we explain how to consider the effects of new technologies of TD-SCDMA and give the solutions about theses considerations.

• Journal of Broadcast Engineering
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• v.14 no.6
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• pp.721-732
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• 2009

AT-DMB system has been developed to increase data rate up to double of conventional T-DMB in same bandwidth while maintaining backward compatibility. The AT-DMB system adopted hierarchical modulation which adds BPSK signal or QPSK signal as enhanced layer to existing DQPSK signal. The enhanced layer signal should be small enough to maintain backward compatibility and to minimize the coverage loss of existing T-DMB service area. But this causes the enhanced layer signal of AT-DMB susceptible to fading effect in transmission channel. A turbo code which has powerful error correction capability is applied to the enhanced layer signal of the AT-DMB system for compensating channel distortion. We developed the prototype AT-DMB transmitter and receiver systems for performance evaluation. LAB test for analysing the effect of constellation ratio between existing base layer signal and enhancement layer signal, was conducted and the measurement results are shown with analysis comments.

• Journal of IKEEE
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• v.19 no.3
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• pp.288-294
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• 2015

CRC function has been built into the high-speed semiconductor memory device in order to increase the reliability of data for high-speed operation. Also, DBI function is adopted to improve of data transmission speed. Conventional CRC(ATM-8 HEC code) method has a significant amounts of area-overhead(~XOR 700 gates), and processing time(6 stage XOR) is large. Therefore it leads to a considerable burden on the timing margin at the time of reading and writing of the low power memory devices for CRC calculations. In this paper, we propose a CRC method for low cost and high speed memory, which was improved 92% for area-overhead. For low-cost implementation of the CRC scheme by the DBI function it was supplemented by data bit error detection rate. And analyzing the error detection rate were compared with conventional CRC method.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.156-162
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• 2013

In the communication between satellite and ground station, data rate can be determined from the data volume and required transmission time. Increasing data rate can be limited according to the available bandwidth. For the reason, it has been popularly studying on high spectral-efficient modulation scheme in large volume data application such as digital video broadcasting service. This paper presents the conceptual design of UHRIT broadcasting in GEO-KOMPSAT-2A (GK2A) mission by using DVB-S2 standard. Based on the recently determined data rate, UHRIT bandwidth was calculated at the various modulation schemes and code rates of DVB-S2 standard. Receiving performance of global user station was also evaluated thorough link analysis by considering that user station is located at the edge of beam coverage. Finally, maximum data rate was analyzed in a situation that COMS HRIT bandwidth should be alternatively applied for UHRIT downlink.

• KIPS Transactions on Software and Data Engineering
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• v.7 no.7
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• pp.249-258
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• 2018

The importance of software in military weapon systems is increasing, and the software structure is becoming more complicated. We therefore must thoroughly verify its reliability. In particular, the defects from the interaction of the software components that make up the weapon system are difficult to prevent only with static testing and code coverage level dynamic testing. In this paper, we classify dynamic software defect types and analyze the issues reported in the Open Source Software (OSS) used in the US department of defense weapon systems. The dynamic defects classified in this paper usually occur after integration, and it is difficult to reproduce and identify the cause. Based on this analysis, we come to the point that the software integration test must be enhanced in order to verify the reliability of the weapon system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.47-53
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• 2007

The purpose of IEEE 802.16j is to extend coverage and to enhance throughput by using relay station additionally to conventional IEEE 802.16e . The cellular system experiences performance degradation at the cell edge due to pathloss, shadow and multipath fading. We can get advantage of spatial diversity gain by using relays more than two cooperatively in the IEEE 802.16j system. Cooperative relaying using space-time code provides better performance under multipath fading and has more robustness against the shadow fading than single relaying. In this paper, we investigate the performance of IEEE 802.16j using cooperative relaying by link level simulation. We also show that the cooperative relaying system achieves better performance than the conventional single relaying system. We apply realistic shadow model considering correlations between shadow fadings of different relaying paths. It is shown that the performance of the system depends highly on the spatial location of relay stations.

• The KIPS Transactions:PartC
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• v.8C no.6
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• pp.783-792
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• 2001

It is well known that, in the near future, the lifetime of the IPv4 address space will be limited and available 32-bit IP network addresses will not be left any more. In order to solve such IPv4 address space problem in an effective way, the transition to the new version using IPv6 architecture is inevitably required. At present, it is impossible to convert IPv4 into IPv6 at a time, since the coverage and the size of today's Internet is too huge. Therefore, the coexistence of both IPv4 and IPv6 must be arranged in a special and practical fashion for rapid conversion on the whole. IP protocol translation has been proposed to ease the translation of the Internet from IPv4 to IPv6. This paper presents the design and implementation of a transparent transition service that translates packet header as they cross between IPv4 and IPv6 networks. IPv4/IPv6 Translation Protocol is written in c source code and is tested by the local test recommended by ISO, which has the most excellent error detection function. The test was processed with a test scenario and it was found that the results were successful.

• Journal of KIISE
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• v.42 no.8
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• pp.1022-1030
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• 2015

The context-awareness of mobile applications yields several issues for testing, since mobile applications should be able to be tested in any environment and under any contextual input. In previous studies of testing for Android applications as an event-driven system, many researchers have focused on using generated test cases considering only Graphical User Interface (GUI) events. However, it is difficult to find failures that could be detected when considering the changes in the context in which applications run. It is even more important to consider various contexts since the mobile applications adapt and use the new features and sensors of mobile devices. In this paper, we provide a method of systematically generating various executing contexts from permissions. By referring to the lists of permissions, the resources used by the applications for running Android applications can be easily inferred. To evaluate the efficiency of our testing method, we applied the method on two open source projects and showed that it contributes to improve the statement code coverage.

• Journal of KIISE:Information Networking
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• v.29 no.2
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• pp.141-155
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• 2002

A medium access control protocol is proposed for integrated voice and data services in the packet CDMA network with a small coverage. Uplink channels are composed of time slots and multiple spreading codes for each slot. This protocol gives higher access priority to the delay-sensitive voice traffic than to the data traffic. During a talkspurt, voice terminals reserve a spreading code to transmit multiple voice packets. On the other hand, whenever generating a data packet, data terminals transmit a packet based on the status information of spreading codes in the current slot, which is received from base station. In this protocol, voice packet does not come into collision with data packet. Therefore, this protocol can increase the maximum number of voice terminals.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.29 no.4
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• pp.807-819
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• 2019

Greybox fuzzing is known as an effective method to discover unknown security flaws reside in software and has been actively researched today. However, most of greybox fuzzing tools require an executable file. Because of this, a library, which cannot be executed by itself requires an additional executable file for greybox fuzzing. Generating such an executable file is challengeable because it requires both understanding of the library and fuzzing. In this research, we suggest the approach to generate an executable file automatically for a library and implement this approach as a tool based on the LLVM framework. This tool shows that executable files and seed files can be generated automatically by static/dynamic analysis of a unit test in the target project. A generated executable file is compatible with various greybox fuzzers like AFL because it has a common interface for greybox fuzzers. We show the performance of this tool as code coverage and discovered unknown security bugs using generated executable files and seed files from open source projects through this tool.