• Journal of the Korea Institute of Information Security & Cryptology
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• v.6 no.4
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• pp.3-38
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• 1996

The mobile station shall convolutionally encode the data transmitted on the reverse traffic channel and the access channel prior to interleaving. Code symbols output from the convolutional encoder are repeated before being interleaved except the 9600 bps data rate. All the symbols are then interleaved, 64-ary orthogonal modulation, direct-sequence spreading, quadrature spreading, baseband filtering and QPSK transmission. The sync, paging, and forward traffic channel except the pilot channel in the forward CDMA channel are convolutionally encoded, block interleaved, spread with Walsh function at a fixed chip rate of 1.2288 Mcps to provide orthogonal channelization among all code channels. Following the spreading operation, the I and Q impulses are applied to respective baseband filters. After that, these impulses shall be transmitted by QPSK. Authentication in the CDMA system is the process for confirming the identity of the mobile station by exchanging information between a mobile station and the base station. The authentication scheme is to generate a 18-bit hash code from the 152-bit message length appended with 24-bit or 40-bit padding. Several techniques are proposed for the authentication data computation in this paper. To protect sensitive subscriber information, it shall be required enciphering ceratin fields of selected traffic channel signaling messages. The message encryption can be accomplished in two ways, i.e., external encryption and internal encryption.

• Journal of Industrial Technology
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• v.27 no.B
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• pp.43-51
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• 2007

In mobile multi-hop wireless networks, the authentication between a base station and a mobile multi-hop node, between multi-hop nodes, and between user a station and a multi-hop node is needed for the reliable and secure network operation. In this paper, we survey various authentication schemes which can be considered to be adopted in mobile multi-hop wireless networks and propose a concept of novel mutual authentication scheme applicable to mobile multi-hop network architecture. The scheme should resolve the initial trust gain problem of a multi-hop node at its entry to the network, the problem of rogue mobile multi-hop node and the problem of hop-by-hop authentication between multi-hop nodes. Effectively, the scheme is a hybrid scheme of the distributed authentication method and the centralized authentication method which are considered to be deployed in the wireless ad-hoc network and the wireless network connected to wired authentication servers, respectively.

• Journal of Hydrogen and New Energy
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• v.32 no.5
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• pp.299-307
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• 2021

In order to expand the supply of hydrogen vehicles, the first thing to be done is to build an infrastructure to supply hydrogen. There are fixed and mobile types of hydrogen refueling stations that can supply hydrogen. Mobile hydrogen refueling stations have the advantage of supplying hydrogen to two or three areas, so the introduction of mobile hydrogen refueling stations is considered at the initial stage of hydrogen vehicle dissemination. However, mobile hydrogen refueling stations have greater risks than fixed hydrogen refueling stations due to the hazard associated with movement and intensive installation of facilities in vehicle, so stricter design standards to lower the risk must be applied. Therefore, in this study, basic data for establishing safety standards for mobile hydrogen refueling stations were proposed by suggesting improvements such as the location of emergency shutoff valves, the number of gas detectors etc., using HAZOP analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.186-195
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• 2010

For the fast target base station channel decision in WiMAX networks, fast group scanning scheme was suggested, in which mobile stations in proximity of each other form a group and scan the candidate channels dispersively. However, the previous group scanning scheme does not consider the different QoS requirements of each MS in a group. In this paper we propose the enhanced group scanning scheme, so-called QoS-aware group scan scheduling scheme, that makes mobile stations in a group scan the candidate channels without deteriorating the QoS requirements. We introduce the QoS-aware channel scanning concept of a individual mobile station and show the different scanning latencies due to the different QoS requirements. With the help of the efficient channel allocation by the serving BS, in the proposed scanning scheme, a mobile station with relatively higher QoS in a group scans less amount of candidate channels than the others with relatively lower QoS, while the mobile stations in a group still guarantees the fast target base station decision. The performance results show that our proposed scanning scheme results in the fast target base station decision while considering the QoS requirements of each MS.

• Journal of the Korean Institute of Gas
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• v.25 no.6
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• pp.45-52
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• 2021

The government is converting the fuel for trucks, one of the causes of PM in Korea, form diesel to LNG. Mobile LNG station are being developed to solve the problems of insufficient charging infrastructure and facilitate the spread of LNG fuel. In this study, QRA was used th calculate the CA of the facility for a secure design prior to the development of the mobile LNG station and to predict the individual/societal risk the scenario. As a result, the danger of mobile LNG station was in ALARP.

• Journal of the Korea Society of Computer and Information
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• v.14 no.1
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• pp.107-115
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• 2009

The cryptological key which is used in WiMAX environment is used at regular intervals by mobile nodes (laptop computer, PDA, cell-phone) which is in the range of base station coverage. But it is very weak at local attack like man-in-the-middle when the mobile node is off the range of base station or enters into the range to communicate with base station because the communication section is activated wirelessly. This paper proposes a distribution key building protocol which can reuse security key used by nodes to reduce cryptological security attack danger and communication overhead which occurs when mobile node tries to communicate with base station. The proposed distribution key establishing protocol can reduce overhead which occurs between base station and mobile node through key reusing which occurs during the communication process and also, makes security better than IEEE 802.16 standard by creating shared key which is required for inter-certification through the random number which node itself creates.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.5
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• pp.1075-1082
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• 1997

In this paper, we propose a channel assignment scheme for reducing call blocking rate in a base station(BS) of DS-CDMA cellular systems. The proposed scheme can e applied to the case where the capacity of reverse radio link is enough, but not are the available traffic channels performing the digital modulation and demodulation functions between a mobile station and the base station. The proposed scheme takes advantage of the feature of soft handoff in which a mobile station keeps its communication link even if one of the two communication links is released. The scheme estimates the mean and variance of the received power level measured at the base station before assigning a traffic channel for a new call request. The BS makes decision based on the estimated balues whether the new call request will be accepted or not. If it is decided that the capacity of reverse radio link is enough, but all traffic channels are not available, then the BS increases the soft handoff parameter T_DROP to release the traffic channels of mobile stations loactedin soft handoff area. The BS assigns the released traffic channel to anew call or a handoff call. The performance of the proposed channel assignment scheme is evaluated by computer simulation. The results show that the call blocking rate for new calls and handoff calls is reduced.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.1177-1190
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• 2009

In this paper, we propose a fuzzy proxy cache scheme for caching web documents in mobile base stations. In this scheme, a mobile cache model is used to facilitate data caching and data replication. Using the proposed cache scheme, the individual proxy in the base station makes cache decisions based solely on its local knowledge of the global cache state so that the entire wireless proxy cache system can be effectively managed without centralized control. To improve the performance of proxy caching, the proposed cache scheme predicts the direction of movement of mobile hosts, and uses various cache methods for neighboring proxy servers according to the fuzzy-logic-based control rules based on the membership degree of the mobile host. The performance of our cache scheme is evaluated analytically in terms of average response delay and average energy cost, and is compared with that of other mobile cache schemes.

• The Journal of Information Technology
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• v.12 no.2
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• pp.1-12
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• 2009

China first started its mobile phone services in 1987, and the number of users has exponentially increased so that it reached 700 millions in January 2009. Currently China's 2G(GSM) users is 650 millions. These 2G (GSM) services have an advantage of the capability to use the mobile phone with a SIM (Subscriber Identity Modul) card, one kind of smart cards, inserted into it. However, due to the security vulnerability of SIM cards being used within China's 2G (GSM) services, SIM cards cloning. Problems concerning mobile phone surveillance towards a designated person by illegal cloning ESN and IMSI have recently risen to be a massive social issue within Korea as well. These studies have experimented the possibility of SIM cards clone in various mobile communication corporations using 2G (GSM) in China, and hence discovered the security vulnerability such as the incoming outgoing, SMS service and additional services on mobile phones using clone SIM cards.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.661-663
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• 2021

Network performance is degraded when the UE is disconnected because the outage occurs at the base station in a mobile communication system. Therefore it is important to detect and recover the outage. In this paper, detecting the outage base station by using the KPI and the network scanning in the neighbor base station, and increasing the transmit power and changing the frequency band to recovery the outage scheme is proposed. The proposed scheme uses not only the KPI of the base station but also the network scanning of the neighbor base stations to detect the outage base station, so that it is possible to detect the outage base station more accurately. In addition, when the outage occurred, the neighbor base station changes the transmit power and frequency band to recover the outage with less signal interference.