• Journal of Electrical Engineering and Technology
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• v.4 no.3
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• pp.405-409
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• 2009

A polarization-independent multiwavelength-switchable fiber filter is proposed based on a polarization beam splitter and fiber coupler, which can function as a polarization-independent transmission or reflection-type interleaving filter. The proposed filter consists of a polarization beam splitter and a Sagnac birefringence loop composed of a 50:50 coupler, high birefringent fibers, and two quarter-wave plates. In the proposed filter, a transmission-type interleaver with a channel isolation > 18 dB or a reflection-type one with a channel isolation of ${\sim}3$ dB, whose channel spacing and switching displacement were 0.8 and 0.4 nm in common, respectively, could be obtained. A channel interleaving operation could be performed by the proper control of waveplates within the Sagnac birefringence loop.

• Transactions on Electrical and Electronic Materials
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• v.8 no.1
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• pp.21-25
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• 2007

A two-dimensional TCAD MEDICI simulator was used to examine the voltage transfer characteristics, on-off switching properties and latch-up of a CMOS inverter as a function of the n-channel length and doping levels. The channel in a LDMOSFET encloses a junction-type source and is believed to be an important parameter for determining the circuit operation of a CMOS inverter. The digital logic levels of the output and input voltages were analyzed from the transfer curves and circuit operation. The high and low logic levels of the input voltage showed a strong dependency on the channel length, while the lateral substrate resistance from a latch-up path in the CMOS inverter was comparable to that of a typical CMOS inverter with a guard ring.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.7
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• pp.36-46
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• 1994

In the realization of interface between subscriber and network, D-channel may deteriorate the performance of switching system in handling subscriber. Thus, D-channel must be designd in a way to interface efficiently with the system while maintaining exciting performance. This objective can be obtained by through consideration of the structure of the system. This paper shows the method to design D-channel, which has significant relation with the structure of the system whenrealizing the interface between subscriber and network, in adding ISDN function. The goal of performance is also proposed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.1
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• pp.50-67
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• 2015

The Cognitive Radio (CR) paradigm in tactical ad hoc networks is an important element of future military communications for network-centric warfare. This paper presents a novel Cognitive Link State Routing protocol for CR-based tactical ad hoc networks. The proposed scheme provides prompt and reliable routes for Primary User (PU) activity through procedures that incorporate two main functions: PU-aware power adaptation and channel switching. For the PU-aware power adaptation, closer multipoint relay nodes are selected to prevent network partition and ensure successful PU communication. The PU-aware channel switching is proactively conducted using control messages to switch to a new available channel based on a common channel list. Our simulation study based on the ns-3 simulator demonstrates that the proposed routing scheme delivers significantly improved performance in terms of average end-to-end delay, jitter, and packet delivery ratio.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.10
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• pp.1034-1040
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• 2004

The latch-up current and switching characteristics of MOS-Controlled Thyristor(MCT) are studied with variation of the channel length and impurity concentration. The proposed MCT power device has the lateral structure and P-epitaxial layer in substrate. Two dimensional MEDICI simulator is used to study the latch-up current and forward voltage-drop from the characteristics of I-V and the switching characteristics with variation of impurity concentration. The channel length and impurity concentration of the proposed MCT power device show the strong affect on the anode current and turn-off time. The increase of impurity concentration in P and N channels is found to give the increase of latch-up current and forward voltage-drop.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.2
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• pp.33-48
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• 2018

In this paper, we characterise the joint interference alignment and power allocation strategies for a K-user multicell multiple-input multiple-output (MIMO) Gaussian interference channel. We consider a MIMO interference channel with a blind interference alignment through staggered antenna switching on the receiver. We explore the power allocation and the feasibility condition for cooperative cell-edge (CE) mobile users (MUs) by assuming that the channel state information is unknown. The new insight behind the transmission strategy of the proposed scheme is premeditated (randomly generated transmission strategy) and partial cooperative CE MUs, where the transmitter is equipped with a conventional antenna, the receiver is equipped with a reconfigurable multimode antenna (staggered antenna switching pattern), and the receiver switches between preset T modes. Our proposed scheme assists and aligns the desired and interference signals to cancel the common interference signals, since the received signal must have a corresponding independent signal subspace. The sum capacity for a K-user multicell MIMO Gaussian interference channel with reconfigurable multimode antennas is completely characterised.

• Asia pacific journal of information systems
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• v.16 no.3
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• pp.67-93
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• 2006

Some consumers prefer online and others prefer offline. What makes them prefer online or offline? There has been a lack of theoretical development to adequately explain consumers' channel switching behavior between traditional physical stores and new virtual stores. Through consumers' purchase decision processes, this study examined the reasons why consumers changed channels depending on purchase process stages. Consumer's purchase decision process could be divided into three stages: pre-purchase stage, purchase stage, and post-purchase stage. We used the intention of channel selection as a surrogate dependent variable of channel selection. And some constructs, that is, channel function, channel benefits, customer relationship benefits, and perceived behavioral control, were selected as independent variables. In buying look-and-feel products, it was identified that consumers preferred virtual stores to physical stores at pre-purchase stage. To put it concretely, all constructs except channel benefits were more influenced to consumers at virtual stores. This result implied that information searching function, which is a main function at pre-purchase stage, was better supported by virtual stores than physical stores. In purchase stage, consumers preferred physical stores to virtual stores. Specially, all constructs influenced much more to consumers at physical stores. This result implied that although escrow service and trusted third parties were introduced, consumers felt that financial risk, performance risk, social risk, etc. still remained highly online. Finally, consumers did not prefer any channel at post-purchase stage. But three independent variables, i.e. channel function, channel benefits, and customer relationship benefits, were significantly preferred at physical stores rather than virtual stores at post-purchase stage. So we concluded that physical stores were a little more preferred to virtual stores at post-purchase stage. Through this study, it was identified that most consumers might switch channels according to purchase process stages. So, first of all, sales representatives should decide that what benefits should be given them through virtual stores at the pre-purchase stage and through physical stores at the purchase and post-purchase stages, and then devise collaborative channel strategies.

• Journal of IKEEE
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• v.15 no.2
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• pp.179-189
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• 2011

This paper presents an SVC based multi-channel transmission technique. Transmission of high definition multimedia and its service efficiency can be significantly improved by the proposed method. In this method, the HD stream is divided into the two layer streams, i.e., a base layer stream and an enhancement layer stream. The divided streams are transmitted through a primary channel and an auxiliary channel, respectively. The proposed technique provides a noble mode switching technique which enables a seamless service of HD multimedia even under the conditions of abrupt and intermittent deterioration of the auxiliary channel. When the enhancement layer stream is disrupted by the channel monitoring in the mode switching algorithm, the algorithm works further to maintain the spatial and time resolution of the HD multimedia by upsampling and interpolating the base layer stream, consequently serving for the non disrupted play of the media. Moreover, the adoption of an adaptive switching algorithm significantly reduces the frequency of channel disruption avoiding the unnecessary switching for the short period variations of the channel. The feasibility of the proposed technique is verified through the simulation study with an example application to the simultaneous utilization of both Ku and Ka bands for HD multimedia broadcasting service. The rainfall modeling and the analysis of the satellite channel attenuation characteristics are performed to simulate the quality of service performance of the proposed HD broadcasting method. The simulation results obtained under a relatively poor channel (weather) situations show that the average lasting period of enhancement layer service is extended from 9.48[min] to 23.12[min] and the average switching frequency is reduced from 3.84[times/hour] to 1.68[times/hour]. It is verified in the satellite example that the proposed SVC based transmission technique best utilizes the Ka band channel for the service of HD broadcasting, although it is characterized by its inherent weather related poor reliability causing severe limitations in its independent application.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.7
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• pp.3747-3765
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• 2017

Existing authentication mechanisms in cellular mobile communication networks are realized in the upper layer by employing cryptographic techniques. Authentication data are broadcasted over the air in plaintext, enabling attackers to completely eavesdrop on the authentication and get some information about the shared secret key between legitimate nodes. Therefore, reusing the same secret key to authenticate several times results in the secret key's information leakage and high attacking rate. In this paper, we consider the most representative authentication mechanism, Authentication and Key Agreement (AKA), in cellular communication networks and propose an enhanced AKA scheme based on Physical Layer Authentication (AKA-PLA). Authentication responses generated by AKA are no longer transmitted in plaintext but masked by wireless channel characteristics, which are not available to adversaries, to generate physical layer authentication responses by a fault-tolerant hash method. The authenticator sets the threshold according to the authentication requirement and channel condition, further verifies the identity of the requester based on the matching result of the physical layer authentication responses. The performance analyses show that the proposed scheme can achieve lower false alarm rate and missing rate, which are a pair of contradictions, than traditional AKA. Besides, it is well compatible with AKA.

• Journal of information and communication convergence engineering
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• v.6 no.1
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• pp.47-50
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• 2008

A novel high channel efficiency transceiver based on a fast acquisition frequency synthesizer has been designed. The direct digital synthesis (DDS) technique is applied and a simple memory look-up table is incorporated to expedite channel acquisition. The technique simplifies the frequency control process in the transceiver and thus reduces the channel switching time. As a result, the channel efficiency is improved. The designed transceiver is ideal for frequency hopping mobile communication applications.