• Journal of Digital Convergence
• /
• v.18 no.2
• /
• pp.103-110
• /
• 2020

The fire incident of KT's Ahyun branch occurred last year indicates that hyper-connected society led by 5G technology would be a dystopia instead of a utopia unless seamless connection of 5G service is well secured. Looking backward on 1999, we could peacefully and happily greet the new millennium by making a great effort to prevent the millennium bugs(Y2K) from causing the catastrophe such as a shut-down of banking system. Likewise, we should make a great effort to keep 5G networks and 5G service continuously working without the disruption of even just a second, which would enable us to avoid facing any catastrophes caused by the disruption of 5G service. As a way to do so, it can be considered that 5G service is designated as universal service because it has the key features of public goods like telephone and high-speed internet services.

• Journal of Satellite, Information and Communications
• /
• v.8 no.1
• /
• pp.1-7
• /
• 2013

Currently satellite communication systems usually use the ACM(Adaptive Coding and Modulation) to extend the link availability and to increase the bandwidth efficiency. However, when ACM system is used for satellite communications, we should carefully consider TCP congestion control to avoid network congestions. Because MODCODs in ACM are changed to make a packet more robust according to satellite wireless link conditions, bandwidth of satellite forward link is also changed. Whereas TCP has a severe problem to control the congestion window for the changed bandwidth, then packet overflow can be experienced at MAC or PHY interface buffers. This is a reason that TCP in transport layer does not recognize a change of bandwidth capability form MAC or PHY layer. To overcome this problem, we propose the adaptive congestion control scheme of TCP for supporting ACM in Satellite PEP (Performance Enhancing Proxy) systems. Simulation results by using ns-2 show that our proposed scheme can be efficiently adapted to the changed bandwidth and TCP congestion window size, and can be useful to improve TCP performance.

• Journal of Sensor Science and Technology
• /
• v.21 no.1
• /
• pp.59-67
• /
• 2012

It was reported that the latest sensor technology allow an 65536 conductive polymer sensor array to be made with broad but overlapping selectivity to different families of chemicals emulating the characteristics found in biological olfaction. However, the supernumerary redundancy always accompanies great error and risk as well as an inordinate amount of computation time and local minima in signal processing, e.g. neural networks. In this paper, we propose a new method to reduce the number of sensor for analysis by reducing redundancy between sensors and by removing unstable sensors using the cosine similarity method and to decide on representative sensor using FCM(Fuzzy C-Means) algorithm. The representative sensors can be just used in analyzing. And, we introduce DWT(Discrete Wavelet Transform) for data compression in the time domain as preprocessing. Throughout experimental trials, we have done a comparative analysis between gas sensor data with and without reduced redundancy. The possibility and superiority of the proposed methods are confirmed through experiments.

• Journal of Internet Computing and Services
• /
• v.2 no.3
• /
• pp.51-62
• /
• 2001

Recently, as computers and networks become popular, distributing information on the Internet is common In our daily life. also, the explosion of the Internet. of wireless digital communication and data exchange on Internet has rapidly changed the way we connect with other people. The e-mail has been commonly used by users as well recognizing It as the standard of manners among users on the Internet. In the past, e-mail has been the primary choice of exchanging Information, but secure mail is gaining popularity abroad and domestically because of their nature of providing security. That is. it has been used a variety of fields such as general mail and e-mail for advertisement. But, As the data transmitted on network can be easily opened or forged with simple operations. most of existing e-mail system don't have any security on the transmitted information. Thus. security mail system need to provide security including message encryption, content Integrity, message origin authentication, and non-repudiation. In this paper, we design implement secure mail system with non-repudiation service and encryption capability to provide services for certification of delivery and certification of content as well as the basic security services. API.

• Journal of Internet Computing and Services
• /
• v.3 no.3
• /
• pp.87-93
• /
• 2002

A complex network and a parallel computer are made up of interconnected switching units. The role of a switching unit is to set up a connection between an input port and an output port, according to the routing information. We proposed our switching network with a remodeled architecture is a newly modified Banyan network with eight input and output ports. We have analysed the maximum throughput of the revised switch. Our analyses have shown that under the uniform random traffic load, the FIFO discipline is limited to 70%, The switching system consists of an input control unit, a switch unit and an output control unit. Therefore the result of the analyses shows that the results of the networking simulation with the new switch are feasible and if we adopt the new architecture of the revised model of the Banyan switch, the hardware complexity can be reduced. The FIFO discipline has increased by about 11% when we compare the switching system with the input buffer system. We have designed and verified the switching system in VHDL using Max＋plusII. We also designed our test environment including micro computers, the base station, and the proposed architecture. We proposed a new architecture of the Banyan switch for BISDN networks and parallel computers.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.5 no.12
• /
• pp.2272-2293
• /
• 2011

Communication technology of future networks is predicted to provide a large variety of services including WiFi service in vehicular network. In this paper, we assume that vehicles are embedded with WiMAX antenna and in-vehicle terminals receive WiMAX traffic through WiFi interface. This assumption will impose severe performance degradation due to interference among mobile BSSs when WiFi access points (APs) are densely located. Existing interference avoidance techniques cannot properly resolve the above problems and do not cope with dynamically moving vehicular scenario since they focus only on the fixed network topology. In this paper, we propose a mobility-aware interference avoidance scheme for WiFi services. The proposed scheme computes the interference duration by exploiting mobility vector and location information of neighboring APs. If the interference duration is not negligible, our scheme searches for another channel in order to avoid interference. However, if the interference duration is negligible, our scheme continues to use the channel to reduce switching overhead. To measure the effectiveness of the proposed scheme against other existing techniques, we evaluated performance by using OPNET simulator. Through the simulation, we obtained about 60% reduction in the maximum interference frequency and about 67% improvement in throughput. Furthermore, our scheme provides fair channel usage.

• Journal of Internet Computing and Services
• /
• v.8 no.1
• /
• pp.1-14
• /
• 2007

IF handoff events are occurred during the transmission of multimedia traffic, the efficient resource allocation and handoff procedures are necessary to maintain the same QoS of transmitted multimedia traffic because the QoS may be defected by some delay and information loss, This paper proposes a handoff scheme to accommodate multimedia traffic based on the resource reservation procedure using direction estimation, This scheme uses a novel mobile tracking method based on Fuzzy Multi Criteria Decision Making, in which uncertain parameters such as PSS (Pilot Signal Strength), the distance between the mobile and the base station, the moving direction, and the previous location are used in the decision process using the aggregation function in fuzzy set theory, With the position information, the moving direction is determined, The handoff requests for real time sessions are handled based on the direction prediction and the resource reservation scheme, The resources in the estimated adjacent cells should be reserved and allocated to guarantee the continuity of the real time sessions, Through simulation results, we show that our proposed resource reservation method provides a better performance than that of the conventional method.

• Journal of the Korea Society of Computer and Information
• /
• v.12 no.2 s.46
• /
• pp.209-220
• /
• 2007

Mobile devices become a pak of our daily life due to their versatility, such as the wireless phone calls, the wireless accessibility to Internet, the display of multimedia content, and the communication with nearby mobile devices. Third generation telecommunication service provides an easy access to the Internet for nubile devices. Mobile users pay a fee charged by the telecommunication provider based on the amount of data transferred. This paper introduces a special ad hoc network in which mobile devices cooperate each other to download an interesting content from the Internet in order to reduce the telecommunication cost. The mobile devices, called the peers, in the ad hoc network are assigned a portion of the target file, and are responsible for downloading the portion using their 3G connection. Then, the peers exchange their downloaded portion with other participating peers using their cost-free ad hoc connection in order to reconstruct the whole content. According to the simulation results, large number of participating peers saves the telecommunication cost up to 90% with as few as 10 peers, although it slightly increase the overall content reconstruction time.

• Journal of the Institute of Convergence Signal Processing
• /
• v.1 no.1
• /
• pp.7-14
• /
• 2000

Recently, the technologies of adaptive noise cancellation(ANC) are developed fast and widely due to the highly sophisticated digital signal processing algorithms and the high-speed communication networks and devices. But, thousand numbers of the adaptive filter taps are required to obtain the satisfying results in the fields of the adaptive noise cancellation and echo cancellation. In the paper, performance comparisons based on the real-time processing between frequency domain adaptive filter(FDAF) and multi-delay frequency domain adaptive filter(MDF) are carried. Those algorithms provide us with the reductions of the computational burdens and the increase of the convergence rate for the lengthy Fill adaptive filters. The time delay due to the long taps of FDAF can be reduced by adopting the MDF algorithms. The conventional ANC and cross talks ANC using FDAF are implemented on the dSP ACE 1103 real-time signal processing board.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.15 no.1
• /
• pp.99-106
• /
• 2011

The emerging of ubiquitous computing and healthcare technologies provides us a strong platform to build sustainable healthcare applications especially those that require real-time information related to personal healthcare regardless of place. We realize that system stability, reliability and data protection are also important requirements for u-healthcare services. Therefore, in this paper, we designed a u-healthcare system which can be attached to the patient's body to measure vital signals, enhanced with USN secure sensor module. Our proposed u-healthcare system is using wireless sensor modules embedded with NLM-128 algorithm. In addition, PS-LFSR technique is applied to the NLM-128 algorithm to enable faster and more efficient computation. We included some performance statistical results in term of CPU cycles spent on NLM-128 algorithm with and without the PS-LFSR optimization for performance evaluation.