• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.4
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• pp.940-949
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• 1998

The paper proposes an effective mechanism hiring the adaptive buffer control schemes on the mobile seceiver's side that can resolve the problems of delay spikes caused by the handover process onthe cell boundaries when they transmit real-time moving images through the high speed wireless channels. to confirm the effectiveness of the proposed schemes, we have modeled the characteristics of the random errors on the wireless channels, the burst errors and that of the transmission delay by the handover. We also compared the rate of the delay-adaptation of the receive buffers caused by the delay and delay spikes. the comparison was done by testing the suggested schemes against the existing schemes by applying tehm to the packet delay model. We also could identify the noticable reduction of the casesof buffer delay and overflow compared with the conventional schemes, by applying the suggested algorithm to the video image compressed by H.263.

• Journal of Digital Contents Society
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• v.8 no.3
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• pp.371-376
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• 2007

Many modules such as controller, sensor, telematics terminal, navigation, audio and video are connected each other via vehicle network (CAN, MOST, etc). Futhermore, users can have ITS or internet services in moving by connecting to wireless mobile network. These network capabilities can cause a lots of security issues such as data hacking, privacy violation, location tracking and so on. Some possibilities which raise a breakdown or accident by hacking vehicle operation data (sensor, control data) are on the increase. In this paper, we propose a security module which has encryption functionalities and can be used for vehicle network system such as CAN, MOST, etc. This security module can provide conventional encryption algorithms and digital signature processing functionality such as DES, 3-DES, SEED, ECC, and RSA.

• Journal of Korean Academy of Nursing
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• v.51 no.5
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• pp.573-584
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• 2021

Purpose: This study aimed to develop an untact visit service based on an application that can be utilized in the pediatric intensive care unit (PICU) during COVID-19. Methods: This study adopted the double diamond process of service design comprising the discovery, defining, and development stages. Results: We developed an untact visit service based on an application that considered the child's status, schedule, photo, and video messages, and so on. Moreover, we derived a service flow regarding the required roles and the type of flow shown between each stakeholder. Conclusion: Considering the ongoing pandemic, the untact visit service is designed to increase rapport and participation of parents, share the child's information in real-time, and provide one-stop service without increasing healthcare providers' work. It will be a useful visit service that can be applied and evaluated in various hospital settings and the PICU.

• Journal of the Korea Society of Computer and Information
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• v.19 no.3
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• pp.63-71
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• 2014

We analyze the execution time of Reed-Solomon coding, which is the MAC-layer forward error correction scheme used in CDMA2000 1xEV-DO broadcast services, under different air channel conditions. The results show that the time constraints of MPEG-4 cannot be guaranteed by Reed-Solomon decoding when the packet loss rate (PLR) is high, due to its long computation time on current hardware. To alleviate this problem, we propose three error control schemes. Our static scheme bypasses Reed-Solomon decoding at the mobile node to satisfy the MPEG-4 time constraint when the PLR exceeds a given boundary. Second, dynamic scheme corrects errors in a best-effort manner within the time constraint, instead of giving up altogether when the PLR is high; this achieves a further quality improvement. The third, video-aware dynamic scheme fixes errors in a similar way to the dynamic scheme, but in a priority-driven manner which makes the video appear smoother. Extensive simulation results show the effectiveness of our schemes compared to the original FEC scheme.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.75-80
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• 2013

In this paper, the Ka-band maritime satellite communication systems for mobile terminals are proposed. The design includes the link budget analysis, determination of modulation and coding schemes and the overall structure of a transmitter. To avoid the harmful effects on the existing DVB-S2 services, the proposed maritime satellite system using the same spectrum with DVB-S2 at the same time employs the very wideband spreading transmission. Additionally, omni-directional low-gain antennas should be equipped in a mobile terminal to reduce the system cost. These two considerations limit the maximum transmission rate of the proposed system. Due to the limitations, the proposed system includes 36 dB or 39 dB spreading gain depending on the modulation scheme and a link-adaptive repetition method depending on the level of rain attenuation. To support short packets with minimal performance loss, the turbo code used in 3GPP instead of LDPC(low density parity check code) is adopted. By combining them, the overall structure of low-rate maritime satellite communication system is designed.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.7 no.1
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• pp.15-22
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• 2007

The third generation mobile communications system requiring the reliable multimedia data transmission has provided with the reliable voice, data and video services over the variable propagation environment. However the broadband wireless multiple access technologies cause Inter Symbol Interference(ISI) or Multiple Access Interference(MAI) to degrade the performance of CDMA(Code Division Multiple Access) system. Constant Modulus Algorithm which is frequently used as the adaptive blind equalizers to remove the interfering signal has ill-convergence phenomenon without proper initialization. In this paper, new blind equalization method based on conventional CMA is proposed to improve the channel efficiency, and through computer simulation this is tested over the time varying fading environment of mobile communication system. consequently, new blind equalization method into concatenated Kalman filter with CMA is verified better than conventional CMA through adopting minimum mean square errors and eye- pattern obtained from algorithm are compared.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.36-45
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• 1998

This paper discusses multiple access control aspects for a wireless extension of high-speed asynchronous transfer mode(ATM) networks. One challenging requirement is that mobile systems convey of diverse types of information including voice, computer data, facsimile, and video data that have different quality of service constraints. Basically, a centralized control scheme for a coordinated multiple access is required in order to efficiently accommodate multimedia traffic on wireless links. The proposed scheme dynamically scheduling the mobile terminal, which has data to transfer according to the service, types at base station. In this scheme, the scheduling algorithm is performed on the basis of traffic descriptors and QoS parameters, which required in the connection set up phase. As a consequence, the transmission scheduling is very flexible and can account for the different traffic rate and delay constraints that emerge from voice and data integration. The simulation result shows that the proposed scheme has better performance over other scheduling algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.1A
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• pp.19-27
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• 2011

WiBro is a wireless mobile communication system which supports a high data rate and high mobility in anywhere and anytime. Although WiBro system provides multimedia service including data, audio and video services, customers require better service quality in WiBro system. But, many researches have theoretically evaluated the performance of WiBro system without systematic studies by simulation. Therefore, in this paper, we evaluate a performance of WiBro system using OPNET simulator. We analyze system performance according to various modulation and coding schemes, and propose Adaptive Modulation and Coding (AMC) profile to support quality of services for user requirements. Also we evaluate the performance of WiBro system using AMC and Hybrid-Automatic Repeat Request (H-ARQ) technologies, and confirm that the proposed AMC profile can be applied to WiBro system with high performance.

• Journal of Information Technology Services
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• v.14 no.2
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• pp.315-335
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• 2015

The New Way of Working (NWOW) is changing the world in which we work today. The principles of NWOW are based on freedom of time and place to work, and steering on output (results) instead of input (presence). As NWOW is a relatively new phenomenon, research on the effect of NWOW on knowledge sharing in organizations is scarce. In this research two multiple-case studies were performed to investigate the effect of the New Way of Working on knowledge. In the first study (A) different knowledge sharing scenarios were used at organizations that were in the process of implementing NWOW. This provided the opportunity to compare the sharing of knowledge between 'NWOW workers' and employees that still worked in the traditional way (non-NWOW workers). In total 216 scenario results were evaluated to determine differences in channel choice between the traditional and new work environment. For the second study (B) a Knowledge Sharing Framework was developed, based on the theories of Nonaka and Alavi & Leidner. This framework was used to determine the type of knowledge shared, e.g. tacit or explicit knowledge, in 84 situations. Additionally, to measure the level of NWOW adoption, a NWOW Analysis Monitor was used. The results show that NWOW workers use more different communication channels than traditional workers. When knowledge workers become more mobile, they will exchange knowledge less explicit (codified) and more tacit (personalized), use less face-to-face communication, but more video calls and e-mail. The adoption of the principles of NWOW seems to have a balancing effect on the knowledge that is shared in a tacit and explicit way, which in the view of Scheepers et al. is an effective knowledge sharing strategy. The research results show organizations need to realize that the New World of Working is affecting the way knowledge is shared. Missing out on this development may result in the loss of important knowledge and impact the operation of organizations.

• The Journal of the Korea institute of electronic communication sciences
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• v.5 no.4
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• pp.450-456
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• 2010

In the high-speed packet service, next generation mobile communication system has emerged as a major feature. If the fire of these high-speed kit services and non-continuous transmission of data due to the symmetrical nature of daeyiteo traffic for D-CDMA system has been actively studied. Small amounts of data moving in the uplink, but the real-time video downlink transmission, such as downloading large files to move data and services to those with asymmetric traffic characteristics, a system that can efficiently handle the data requirements be. Of 3GPP TDD(Time Division Duplex) scheme based on CDMA and TDMA in a way by introducing the concept through the proper allocation of time slots that can handle asymmetric traffic efficiently, has an advantage. TD-CDMA system by considering the characteristics of the frame configuration of transmission methods, such as physical channel structure and channel coding has been investigated. In addition, the HARQ scheme TD-CDMA system performance is analyzed by comparing them.