• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5479-5486
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• 2012

In this paper, we have measured PRR, RSSI and LQI of ZigBee channels under Wi-Fi environment and have assessed channel characteristic and link quality. To confirm any relationship among RSSI, LQI values and PRR under Wi-Fi interference in overlapping and non-overlapping channels of Wi-Fi and ZigBee, the experiments were performed without Wi-Fi, with Wi-Fi and file download through Wi-Fi. Under Wi-Fi interference, We perfomed experiments to ensure channel characteristics and link quality by fixing Wi-Fi and ZigBee receiver and varying the distance between ZigBee receiver and transmitter. ZigBee transmitter sends packet of 256 bits every second to ZigBee receiver. PRR was measured from ZigBee with variance of distance between fixed Wi-Fi and ZigBee. RSSI, LQI, PRR were measured from ZigBee with fixed Wi-Fi, fixed ZigBee receiver and variance of distance of ZigBee transmitter. As a result, we confirmed decrease of PRR under Wi-Fi interference but RSSI, LQI values similar regardless of overlapped or non-overlapped channel and Wi-Fi interference. Therefore, PRR should be used for interference detection in ZigBee communication under Wi-Fi environment but RSSI and LQI are not appreciate.

• Journal of the Korea Society of Computer and Information
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• v.20 no.3
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• pp.1-8
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• 2015

The most used smart set-top box in home driven by the Android OS and based on Wi-Fi technology has to ensure nothing wrong with the Wi-Fi service regardless of the various user's installation environment. The direction test method about the nondirectional of the Wi-Fi doesn't be determined as the standard and each manufacturers devise the their own test methods and conduct the tests. In this paper, we created the 720 test cases considering 2 components of upload & download, the 10 elements of the vertical angle and the 36 elements of the horizontal angle looking at the wireless router in order to verify omni-directional Wi-Fi capability. In reality, from viewpoint in terms of cost and time constraint, it is difficult to test all the test cases. Therefore, we decided to reduce test cases by applying Pair-wise testing technique which is one of combinational testing techniques based on ISO / IEC 29119-4. And we obtained the test cases in which the Pair-wise technique was applied by Allpairs tool which output test cases automatically and conducted the test. It could be confirmed that the proposed technique shortened 48.61% of the time to be spent in progressing the existing test cases and that the trace about the part in which the problem was generated with the result of the simplified test case was possible enough.

• Journal of Global Scholars of Marketing Science
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• v.7
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• pp.283-302
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• 2001

The purpose of this study was to examine the current situation about the internet usage and advertisement attitude, to investigate the relationship between consumer characteristics and internet advertising effect, and to identify the moderating effect of consumer characteristics on the relationship between advertising types and advertising effects. For the study, a sample of 152 apparel consumers participated in this survey research. The survey of design with a questionnaire was employed. Questionnaire was developed with the html language and data collection was done at Korea though the internet on October 2000. For data analysis, descriptive statistics (i.e., frequency, percent), ANOVA with duncan tests were used. First, the major place of using internet was found as home, company, school, PC room in order and the average time of using internet was found as three times weekly. The major purpose of using internet were information search, e-mail, PC communication and program-download. The experience of internet fashion advertising was high. Second, consumer characteristics(age, job) had significant effects on attitude to the product. 20 years-old age group and specialist group were found to influence on the higher attitude toward product. Third, main effects of consumer characteristics(age, job) were found to be significant. The correlation and interaction effects of consumer characteristics and internet advertisement types were not significant.

• Asia pacific journal of information systems
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• v.20 no.2
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• pp.157-180
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• 2010

Rapid development of information technology has generated a new industry and market. In particular, network technology such as the Internet and other computer networks made transaction activities switched from traditional offline commerce to e-commerce. Among them, digital content is bit-based object which is created and distributed through electronic environment. In particular, many entertainment contents such as the music, the movies, and the computer game softwares are main products. Although digital content commerce has high potential demand, it lacks the consideration about the factor related to maintaining existing customer such as customer loyalty and switching costs. There has been a number of research on customer loyalty and other factors affecting it in the traditional electronic commerce environment, but there is a lack of research which examines the characteristics of digital content. The study about the effect of switching costs on customer loyalty in digital content commerce is necessary because the customers of digital content commerce market are from those of other e-commerce market or traditional offline commerce market. In addition, customer loyalty and switching costs are important factors because they may build up greater customer retention. For that reason, this study focused on examining the relationships among switching costs, antecedents for switching costs, and customer loyalty in online digital music service industry. The study has three major purposes: (1) to find antecedents of switching costs on digital content commerce and examine effect of antecedents for switching costs; (2) to identify effect of switching costs on customer loyalty in digital content commerce and examine moderating effects of alternative attractiveness; (3) to identify the differences of antecedents for switching costs by contents transmission type(streaming service and downloading service). And, the online digital music service industry is selected in this study since there are many users and transactions incurring. To accomplish these purposes, a survey questionnaire was developed and distributed to 256 informants. Survey instrument was developed based on previous research and pre-established survey items. Total of 206 surveys are collected and used in the data analysis. Among the respondents, 56.8% is male and 43.2% is female. Also, 86 responses were streaming service user group and 120 responses were download service user group. These data was analyzed using regression analysis. Major findings of empirical analysis can be summarized as follows. First, switching costs have positive effect on customer loyalty in digital content commerce environment. Second, the influence of switching costs on customer loyalty increases under conditions of high alternative attractiveness. Third, DRM convenience and breadth of use have positive effect on switching costs. The findings imply that the digital content provider should pay more attention to switching costs in addition to customer satisfaction in order to attract customers. Also, increasing the convenience of DRM use by securing the convenience of user interface and expanding the support device and increasing the service use scope by providing diverse value-added service helps to create a switching barrier. The result of the study can become a practical use in marketing strategy for maintaining existing customer. In particular, switching barrier is very important under conditions of high competition in the online music service market. This study can be used as a basis for further studies about customer retention in digital content commerce.

• Journal of Broadcast Engineering
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• v.11 no.1 s.30
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• pp.66-79
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• 2006

As constant development of digital broadcasting and data broadcasting system, new technology will be introduced to digital broadcasting and new broadcasting service will be appeared. These services need to be changed and processed to suit each services and the software of the receiver need to be upgraded. Though, generally the digital broadcasting receivers are not getting updated once it's delivered to home for long time and it need to be done by hand or collected each one of them with trouble. Therefore this paper suggests a way to overcome these difficulties via broadcasting stream. This research is to describe how three modules-namely (1) Downloader, downloads new software from data carrousel stream, (2) Update Loader, installs the software received by downloader; and (3) Recoverer, recovers the former version of the software if some serious problem has been occurred during downloading and installing the software. This paper tries to realize the accommodation of terrestrial STB based on the new technique and service following ATSC A-97 agreement.

• Journal of Korea Multimedia Society
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• v.15 no.5
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• pp.651-663
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• 2012

Networked digital signage downloads necessary multimedia contents from a large-sized storage on WAN to its local disk of a limited size before starting their playback. If the required time to download the entire contents gets longer, a start time to play the contents at the digital signage could be delayed. In this paper, we propose a hybrid storage architecture that not only inserts an iSCSI storage layer between the existing local disk and the WAN storage, but offers a contents caching scheme in order to obtain all the necessary contents in digital signage rapidly. The proposed caching scheme determines how to place the downloaded contents both in the local disk and the iSCSI storage. Uniquely, the proposed caching scheme manages the iSCSI storage space by dividing it into two regions: (1) in one region, the digital signage can play the contents directly without downloading them into the local disk; (2) in the other region, the digital signage cannot. Performance evaluations on a simulator and an actual system with workloads of various contents show that a contents-downloading time of the hybrid storage architecture is at maximum three times shorter than that of the existing storage architecture.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.6
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• pp.1369-1380
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• 2011

Most existing mobile distance learning systems are asynchronous ones that allow students to download lecture video and presentation material. However, there are a few synchronous real-time mobile distance learning systems that support slide, annotation, feedback from student, and lecture video and audio at the same time. These live mobile distance learning systems have an advantage of supporting real-time interaction between students and a lecturer thereby making students understand the lecture better. But, they also have a disadvantage in the sense that they don't allow students to experience the past lecture. This problem can be solved by recording and replaying lecture session. So far, there are few mobile distance learning systems that support session recording and replay. This paper presents a synchronous mobile distance learning system that supports video and audio, slide with annotation, and real-time feedback from students, as well as session recording and replay, which is not supported by the existing mobile distance learning systems. The evaluation of the system among students shows that 61.3% of them were satisfied while 3.2% weren't.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.429-440
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• 2004

Recently, real time data acquisition become important for space weather forecast and research. In this work, we have developed the data acquisition tools and their applications for space weather monitoring. We have developed programs to download the space weather data using IDL as well as programs to interactively display the image and data using ION (IDL on the Net). By using these tools, we have constructed the mirror site of Active Region Monitor (ARM) which summarizes several different solar activities, and developed ION programs to display TEC(Total Electron Contents) maps from GPS data at the passage of Korean satellites. At present, the KAO ARM mirror site (http://sun.kao.re.kr/arm) is successfully updated in every thirty minutes. The TEC maps from GPS data are expected to be used for monitoring the space environment of Korean satellites.

• Journal of Korea Multimedia Society
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• v.11 no.10
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• pp.1409-1419
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• 2008

Inauthentic resources can be easily spread by P2P (Peer-to-Peer) participants due to the openness and anonymity of P2P networks. A possible way to restrict the distribution of inauthentic resources and prevent malicious peers from joining P2P networks is to exploit peers' reputation which reflect their past behaviors and are also helpful to predict peers' future behaviors. There is a possibility that some peers intentionally plays along with other peers in order to increase/decrease its reputation through false feedback exchanges. Therefore, we propose a new reputation management scheme, called TrustRRep (Trustable Resource sharing service using Reputation) scheme, which improves the trustworthiness and efficiency of P2P networks by identifying peers who give false feedback. The TrustRRep scheme is also capable of providing peers with the trustworthiness of shared resources by discriminating resources distributed by malicious peers. We implement the proposed TrustRRep scheme on the NS-2 simulator for evaluating its performance compared to the recent reputation management work available in literature. A case study on simulations shows that the proposed reputation management scheme yields efficient performance in terms of the minimal download ratio and dissemination of inauthentic resources, the efficient identification of peers who give false feedback, and the provisioning of the trustworthiness of peers' reputation. It also shows that the proposed TrustRRep scheme imposes the restrictions of participating P2P networks on a malicious peers by diminishing its trust value.

• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.514-524
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• 2007

Recent advances in the speed of multi-rate wireless local area networks (WLANs) and the proliferation of WLAN devices have made rate adaptive, opportunistic scheduling critical for throughput optimization. As WLAN traffic evolves to be more symmetric due to the emerging new applications such as VoWLAN, collaborative download, and peer-to-peer file sharing, opportunistic scheduling at the downlink becomes insufficient for optimized utilization of the single shared wireless channel. However, opportunistic scheduling on the uplink of a WLAN is challenging because wireless channel condition is dynamic and asymmetric. Each transmitting client has to probe the access point to maintain the updated channel conditions at the access point. Moreover, the scheduling decisions must be coordinated at all clients for consistency. This paper presents JUDS, a joint uplink/downlink opportunistic scheduling for WLANs. Through synergistic integration of both the uplink and the downlink scheduling, JUDS maximizes channel diversity at significantly reduced scheduling overhead. It also enforces fair channel sharing between the downlink and uplink traffic. Through extensive QualNet simulations, we show that JUDS improves the overall throughput by up to 127% and achieves close-to-perfect fairness between uplink and downlink traffic.