• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1091-1098
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• 2009

In this paper, we designed the authentication system for home network service and applied it to actual sensor nodes. The pair-wise pre-distribution key skim is applied for prevention of authentication key from sniffing on the wireless sensor networks. The authentication key and data are encrypted by using the CBC mode RC5 algorithm based on the SPINS. The experimental environment consists of a base station (BS)and sensor nodes and each sensor node sends both sensing data and the encrypted authentication key to the BS. For simulations we set up some what-if scenarios of security menaces in home network service.Slightly modified the TOS_Msg data arrays of TinyOS is suggested to store 8-byte authentication key which can enable data encryption and authentication at the each sensor node. As a result, malfunction caused by communication between BS and nodes of other groups of added nodes having malicious purpose can be protected. Also, we confirmed that a critical data of home networking service like vital signal can be transmitted securely through this system by encryption technique.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.157-170
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• 2005

The combination of multiple antennas and multi-carrier code division multiple-access (MC-CDMA) is a strong candidate for the downlink of the next generation mobile communications. The study of such systems in scenarios that model real-life trans-missions is an additional step towards an optimized achievement. We consider a realistic MIMO channel with two or four transmit antennas and up to two receive antennas, and channel state information (CSI) mismatches. Depending on the mobile terminal (MT) class, its number of antennas or complexity allowed, different data-rates are proposed with turbo-coding and asymptotic spectral efficiencies from 1 to 4.5 bit/s/Hz, using three algorithms developed within the European IST-MATRICE project. These algorithms can be classified according to the degree of CSI at base-station (BS): i) Transmit space-frequency prefiltering based on constrained zero-forcing algorithm with complete CSI at BS; ii) transmit beamforming based on spatial correlation matrix estimation from partial CSI at BS; iii) orthogonal space-time block coding based on Alamouti scheme without CSI at BS. All presented schemes require a reasonable complexity at MT, and are compatible with a single-antenna receiver. A choice between these algorithms is proposed in order to significantly improve the performance of MC-CDMA and to cover the different environments considered for the next generation cellular systems. For beyond-3G, we propose prefiltering for indoor and pedestrian microcell environments, beamforming for suburban macrocells including high-speed train, and space-time coding for urban conditions with moderate to high speeds.

• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.100-109
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• 2005

A Mobile Ad-Hoc Network (MANET) supports a multi-hop wireless network without any prepared base station (BS). The MANET is capable of building a mobile network automatically without any help from DHCP servers for address allocation or routers to forward or route messages. Many routing protocols have been proposed for the MANET, but these specify the most optimized or shortest path from a source to a destination, and they assume that nodes are pre-configured before communication. To make up for this, address allocation algorithms, such as MANETConf [1] and prophet address allocation algorithm [2], have been proposed. Especially, MANETConf proposes address allocation algorithm with duplication address check. In this paper, we present a dynamic node configuration protocol based on 2-tierd hierarchical network architecture for mobile ad-hoc network, modified from [1]. Especially, it reduces the number of broadcast message exchange between nodes when a new node somes into a network, which lessens network overhead, remarkably. This protocol is based on two-tired structure, and it ensures address allocation with simple duplication address defection mechanism.

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.581-588
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• 2002

In this paper, we newly propose the optical CDMA routing scheme for the radio access network. At the radio base station (RBS), the received radio signals are multiplied by the PN codes and converted to the CDMA radio signals. In the next optical CDMAS are performed and multiplxed by using the PN codes which are the addresses of the routing mobile switching center (MSC). At the MSC, the CDMA radio signals are routined to another MSC by the CDM receiver at the routing node. In the case MSC is equal to the desired MSC, the radio signal is correlated by the two-layerd spectrum despreading at a time. Finally we theoretically analyze the signal-to-interference and noise power ratio of regenerated signal and the routing error probability and show the availability of proposed scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.10A
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• pp.1057-1064
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• 2007

Cognitive radio(CR) technique which utilizes empty frequency bands allocated to private business but not being used temporally has been researched. According to the standard, CR users detect the primary user using the same channel, CR users should move to the another channel to guarantee the primary user's decodability. Thus, CR systems cannot use the same channel and support the CR user's QoS(Quality of Service) during the channel moving time. In this paper, we propose a radio resource sharing method that CR basestation controls the transmission power with the primary user's SNR(Signal to Noise Ratio) to increase the spectral efficiency of area and to minimize the outage of CR users. In addition, computer simulation demonstrates show that the proposed method improved spectral efficiency of area and decreased outage probability of CR users.

• Smart Media Journal
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• v.9 no.3
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• pp.71-79
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• 2020

Mobile network is used by many users worldwide for diverse services, including phone-call, messaging and data transfer over the Internet. However, this network may experience massive damage if it is exposed to cyber-attacks or denial-of-service attacks via wireless communication interference. Because the mobile network is also used as an emergency network in cases of disaster, evaluation or verification for security and safety is necessary as an important nation-wide asset. However, it is not easy to analyze the mobile core network because it's built and serviced by private service providers, exclusively operated, and there is even no separate network for testing. Thus, in this paper, a virtual mobile network is built using OpenAirInterface, which is implemented based on 3GPP standards and provided as an open source software, and the structure and protocols of the core network are analyzed. In particular, the S1AP protocol messages captured on S1-MME, the interface between the base station eNodeB and the mobility manager MME, are analyzed to identify potential security threats by evaluating the effect of the messages sent from the user terminal UE to the mobile core network.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10B
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• pp.891-899
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• 2006

Generally, a geographical area consists of many regions called cells in wireless networks. Each mobile host(MH) in a cell communicates with a base station(BS) located in the center of the cell. The BSs are connected to each other by a static wired network. Since users are expected to move around during communication sessions, one of the most important QoS factors is related to the handoff. But, the handoff could fail due to unavailability of sufficient bandwidth in the next cell. As the individual cell size gradually shrinks to accommodate increasing the number of MHs, the probability of successful handoffs can be dropped. In this paper, we suppose a bandwidth reservation method to guarantee MHs against connection failure in case of frequent handoffs. This method predicts the mobility based on the geographical information and assigns the bandwidth reservation in proportion to the speed of MHs' motion. As a result, we can expect more exact moving path of MH and to reduce the waste of bandwidth.

• Journal of Digital Contents Society
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• v.16 no.1
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• pp.43-51
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• 2015

South Korea decided to use the public safety long term evolution (PS-LTE) method to build a wireless communications network for national disaster. The move will allow all disaster management agencies, including police, firefighters and the military to use multimedia information, including videos, in addition to voice to carry out rescue operations from 2017. The Ministry of Science, ICT and Future Planning said Thursday that it adopted PS-LTE as the technology method for national disaster management system following a national policy coordination meeting last month. PS-LTE is a method integrating group communication, direction communication between terminals and independent base station function with existing LTE technology. Until now, disaster management agencies used technology that only allowed voice communication. However, transmission of multimedia information is possible using PS-LTE.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.6
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• pp.648-653
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• 2011

In this paper, coordinated space division multiple access(SDMA) technology is proposed to mitigate inter-cell interference by using partial channel state information in cooperative wireless communications system with limited feedback. Each AT selects an optimal cluster transmission mode and sends it back to a cluster scheduler, and at the cluster scheduler, ATs are scheduled within a AT group with the identical cluster transmission mode, and the optimal transmission mode and the corresponding scheduled ATs are determined to maximize scheduling priority. Also, in order to enhance multiuser diversity gain, an extended transmission feedback method is proposed to feed back multiple preferred cluster transmission modes at each AT. It is shown that the proposed coordinated SDMA scheme outperforms existing non-coordinated SDMA schemes in terms of the average system throughput.

• The Journal of the Korea Contents Association
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• v.10 no.12
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• pp.101-108
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• 2010

Many works on energy-efficient cluster event detection schemes have been done considering the energy restriction of sensor networks. The existing cluster event detection schemes transmit only the boundary information of detected cluster event nodes to the base station. However, If the range of the cluster event is widened and the distribution density of sensor nodes is high, the existing cluster event detection schemes need high transmission costs due to the increase of sensor nodes located in the event boundary. In this paper, we propose an energy-efficient cluster event detection scheme using the minimum boundary polygons (MBP) that can compress and summarize the information of event boundary nodes. The proposed scheme represents the boundary information of cluster events using the MBP creation technique in the large scale of sensor network environments. In order to show the superiority of the proposed scheme, we compare it with the existing scheme through the performance evaluation. Simulation results show that our scheme maintains about 92% accuracy and decreases about 80% in energy consumption to detect the cluster event over the existing schemes on average.