• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7B
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• pp.673-685
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• 2002

In this paper, we analyze the pros and cons of the fast power control to the forward link in the environments where mixed traffics of voice and data produce the transmitted/received power difference. We propose the Zone-based power control scheme that can improve the performance of the fast power control scheme in the viewpoint of the resource allocation. The proposed scheme is a mechanism that controls both the power and rate of non-realtime data traffics according to location distribution of the mobile stations. The scheme is based on the conventional fast power control scheme in the CDMA systems, and it adaptively controls the transmission rate of each data traffic. Zone-based rate control of data call brings about somewhat power margin to the call. As a result, the proposed scheme saves the power consumption of portables and reduces the amount of interference. With the proposed scheme, not only be extended the service coverage of high-rate traffic to the entire cell service coverage, but also the QoS of low-rate traffic can keep going through the service time, especially, in the situation that the amount of incoming interference is much larger. The experimental results show that the proposed scheme yields a improved performance compared with the conventional scheme in terms of the power consumption and traffic throughput of portables, especially, with the increasing number of high-rate data traffics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.4
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• pp.762-768
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• 2015

D2D communication as an underlaying LTE-Advanced network has proven to be efficient in improving the network performance and decreasing the traffic load of eNodeB(enhanced NodeB). However large amount of interference can be caused by sharing the resources between the cellular users and D2D pairs. So, a resource allocation for D2D communication to coordinate the interference is necessary. Related works for resource allocation that D2D can reuse the resources of more than one cellular user with best CQI(Channel Quality Indicator) have been proposed. D2D communications may still cause interference to the primary cellular network when radio resource are shared between them. To avoid this problem, we propose a radio resource allocation algorithm with low computational complexity for D2D communication in OFDM-based wireless cellular networks. Unlike the previous works, the proposed algorithm utilizes unused ones of the whole resource. The unused resource allocate to on D2D pair can be shared only with other D2D pairs. In other words, if the distance between the D2D pairs is sufficient, we allowed more than two D2D pairs to share the same resources. The simulation results have proven that the proposed algorithm has up to 11 times lower computational complexity than the compared one according to the number of D2D.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.121-127
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• 2010

In this paper, we propose a computationally efficient scheduling algorithm that can arbitrarily control the throughput-fairness tradeoff in a multiuser wireless communication environment. As a new scheduling criterion, we combine linearly two well-known scheduling criteria such as one of achieving the maximum sum throughput and the other of achieving the maximum fairness, so as to control the relative proportion of the throughput and the fairness according to a control factor. For linear combining two different criteria, their optimization directivenesses and the units should be unified first. To meet these requirements, we choose an instantaneous channel capacity as a scheduling criterion for maximizing the sum throughput and the average serving throughput for maximizing the fairness. Through a unified linear combining of two optimization objectives with the control factor, it can provide various throughput-fairness tradeoffs according to the control factors. For further simplification, we exploit a high signal-to-noise ratio (SNR) approximation of the instantaneous channel capacity. Through computer simulations, we evaluate the throughput and fairness performances of the proposed algorithm according to the control factors, assuming an independent Rayleigh fading multiuser channel. We also evaluate the proposed algorithm employing the high SNR approximation. From simulation results, we could see that the proposed algorithm can control arbitrarily the throughput-fairness performance between the performance of the scheduler aiming to the maximum sum throughput and that of the scheduler aiming to the maximum fairness, finally, we see that the high SNR approximation can give a satisfactory performance in this situation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.10
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• pp.691-699
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• 2014

In order to increase network lifetime, duty-cycle MAC protocols which can reduce energy consumption caused by idle listening is proposed for WSNs. In common duty-cycle MAC protocols, each sensor node calculates its duty-cycle interval based on the current amount of residual energy. However, in WSNs with the capability of energy harvesting, existing duty-cycle intervals based on the residual energy may cause the sensor nodes which have high energy harvesting rate to suffer unnecessary sleep latency. Therefore, a duty-cycle scheduling scheme which adjust the duty-cycle interval based on both of the residual energy and the energy harvesting rate was proposed in our previous work. However, since this duty-cycle MAC protocol overlooked the performance variation according to the change of duty-cycle interval and adjusted the duty-cycle interval only linearly, the optimal duty-cycle interval could not be obtained to meet application requirements. In this paper, we propose three methods which calculate the duty-cycle interval and analyse their results. Through simulation study, we verify that network lifetime, end-to-end delay and packet delivery ratio can be improved up to 23%, 44% and 31% as compared to the existing linear duty-cycle scheduling method, respectively.

• Journal of Digital Contents Society
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• v.17 no.3
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• pp.135-142
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• 2016

When video service is performed in simulation using NS-2(Network Simulation-2), the video replay is performed as the received frame order. In the existing video replay method based on the received frame order, as the frame orders of receiver and transmitter are different, the receiver buffer does not have the effect that the packets between the frames of transmitter buffer holds a regular size and packet dense and sparsity phenomenon in the receiver buffer is made by the irregular packet size due to the unpredictable reversed order of received partial frames. The above dense and sparsity phenomenon increases the probability of buffer overflow and underflow generation. To prevent these problems, the proposed frame receive order relocation method adds an extra replay buffer which rearranges the order of receive frame as the order of transmit frame, so it has the effect that the packets between the transmit frames keeps a regular size. Through the simulation using NS-2 and JSVM(Joint Scalable Video Model), the generation number of buffer overflow and underflow, and PSNR(Required Peak Signal to Noise Ratio) performance between the existing method and proposed method were compared. As a result, it was found that the proposed method would have better performance than the existing method.

• Journal of Digital Convergence
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• v.11 no.3
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• pp.415-426
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• 2013

Smart work has recently introduced as a way to solve problems such as greenhouse gas emissions, low birth rate and aging as well as to improve productivity. Because of development of ICT infrastructure and the proliferation of smart devices, the mobile office has the most commonly used within types of smart work in Korea. But the adoption of the mobile office in small businesses is only half of that of large corporations. The security issue appears to be one of the biggest obstacles to the introduction of smart work in small businesses. Therefore, the purpose of this study is to analyze the information security factors that should be considered when the mobile office is introduced to small businesses. By analyzing the previous studies, the information security factors of the mobile office are classified 5 groups composed of 24 factors. 5 groups are terminals, applications and platforms, networks, servers and users. According to the survey result using AHP, 'User' was drawn to the most important group, and 'Data Encryption', 'Wireless LAN Control' and 'Terminal Recovery When Leaving' were drawn to the important information security factors of the mobile office among 24 factors.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.146-149
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• 2013

For in recently years, global cellular network service is changing rapidly to 4G. However, the fast introducing of 4G has been going with not enough research about security threat, it could be many kind of vulnerability. Therefore the research about security threat on 4G network is ongoing in external countries, but not sufficient in domestic. particularly in domestic situation of rapidly increased subscribers, The security threats which are hindering stability and usability could make a fatal effect on many users. 4G network should be considered about the feature of mobile network to protect 4G network stable. Mobile network has limited radio resources, it releases the radio resource which is not used in selected time and reallocate when detected the data transmission. Many signaling messages are transferred in the network entities to allocate or release the radio resource. In this paper, it will be introduced the technology to detect signaling DoS traffic hindering the stability and usability of network entities managing the radio resources by huge signaling message from the repetitive wireless connection/release message.

• Information Systems Review
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• v.6 no.2
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• pp.285-305
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• 2004

This study is based on providing core infrastructure to make or extend an ERP strategy to make the proper model to cope effectively with various customer requirements and market changes through ERP improvement. The purpose of this study is to support making a competitive advantage by raising productivity and reducing costs as a result of making and applying the "mobile real time connection to ERP"model which is accessible anywhere and anytime using PDA and wireless LAN on the basis of mobile business concept. The model is implemented as the "mobile Material Management System" on the area of material management of ERP in the enterprise which already implemented ERP system. This model is also applied into other divisions of the enterprise. This case study shows that the proper application of ERP reduces costs by reducing business process lead time, increase productivity and customer satisfaction through mobility and instant connectivity and easiness of the system. It is recommended to apply this model into the ERP system which is used in most enterprise, to make a competitive advantage. To sum up, the model in this study can be applied into the enterprise which wants to reduce costs, increase productivity and customer satisfaction through ERP improvement.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2008.11a
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• pp.763-766
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• 2008

The success of a construction project depends on efficient construction supply chain and service informationalization as types and quantities of materials in construction industry geometrically increase because the size of the construction industry increasingly becomes huge, high-rise, and complex. However, the omission of data for each step and the lower effect occurs because of uncertainty and inaccuracy of information as compared to other industries. In addition, it takes many hours to manage the present material states. Currently, IT technology and various mobile devices are being developed through the automation system of next generation intelligent construction supply chain management for the effective supply chain information management but the confusion regarding the recognition and transmission of the supply chain information between the multiple materials and transportation equipment using the IT and wireless network technology occurred. Therefore, the objective of this study is to propose the recognition mechanism which can deduce processes which caused the confusion of the recognition and transmission with supply chain information and solve the problems originated from the processes so as to solve the problems related to the confirmation and the communication of the correct supply chain information.

• Journal of Korean Society for Geospatial Information Science
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• v.23 no.3
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• pp.69-75
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• 2015

Road facilities for safe driving were designed for drivers to distinguish them during day and night, but they cannot play their role when the weather becomes worse. Recently, the road facilities have been designed by using electric and electronic technology so that they can be displayed well at a long distance, but they should be replaced very often due to their frequent breakdown. So, there are many problems in traffic calming and maintenance. In this study, to solve the above problems, semi-permanent LED beacon light was installed in the area where traffic accident are frequent, and monitoring system was developed so that the LED beacon light can be maintenanced by connecting with system. For the above installation and development, system was based on window operating system and it was developed for worker to operate it by using P.C. through connecting with wireless local area network. The result of this study led to analyzing state information on the battery of field-installed LED beacon light in real time, and manegement to effectively by predicting their life cycle.