• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.3
• /
• pp.207-215
• /
• 2013

This paper is channel assignment and scheduling techniques for efficient wireless AMI network. In AMI system, the multi-channel cluster network to be proposed defines the communication channel between NC (Network Coordinator) and CDA (Clustered Data Aggregator) as the network channel. CDA and OMD(Out Meter display) and communication channel between SMD(Smart Meter Device) are defined as the group channel. AMI network of the multi-channel cluster based in which the network channel and group channel is mixed increases the administration efficiency through the physical/logical consumer channel clustering. The reliability of inspection data through the channel use distinguished between the adjacent cluster is enhanced. In addition, the fast aggregation of data is possible and the size of a metering network is increased through the channel allocation of the multichannel cluster based.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.22 no.2
• /
• pp.87-95
• /
• 2018

The pressure loss in a cooling channel was investigated by conducting a numerical analysis, which was performed with a different channel angle in the axial direction, velocity of flow, and diameter of channels. The pressure loss did not change much with respect to the different channel angle. However, the pressure loss tended to decrease if the diameter of the channel increased and the velocity of the flow decreased. The results were quantified by a nondimensional method and compared to an existing experimental equation to validate them. The data obtained by this study would be helpful in the design process of a cooling channel considering the pressure loss.

• The Journal of the Korea Contents Association
• /
• v.14 no.2
• /
• pp.161-171
• /
• 2014

This research aims to analyze the characteristics of the channel brand components, identities in accordance with the organizational strategies of the programmes, and brand structures of the comprehensive programming channels. The channels promote themselves mobilizing a variety of channel brand components and, ecxept Channel A, JTBC, TV Chosun, and MBN coined its names which are reminiscent of their parents corporations. The organizational strategies of the programmes are related with the channel identities. TV Chosun, for instance, branded themselves as 'conservative advocate' while focusing on news programs, and Channel A also takes conservative bias strategy focusing on the news programmes, especially after the 2012 presidential election. JTBC, however, organizes drama and entertainment programmes intensively being equivalent to that of terrestrial broadcasting programmes, and MBN positioned neutral and center with the news and cultural programmes. Referring to the brand architecture, which reveals the structural system of the brand, it is argued that TV Chosun and MBN take the integrated corporate brand strategy, while JTBC tries to mix and balance the brands of the parent corporation and its own independent one. Channel A, exceptionally, doesn't take a name of its parent corporation 'Dong-A'. In conclusion, it is argued that the comprehensive programming channels utilize and take the parent corporate brand, mixed brand, and independent brand in accordance with the brand power and circumstances of their own parent corporates.

• Journal of Distribution Research
• /
• v.12 no.2
• /
• pp.23-49
• /
• 2007

Recently, mobile marketing is becoming one of the major topics of interest to the marketing discipline. Emerging from rapid developments in mobile technology, it has created opportunities for new and innovative mobile services. Also, it is enabling to conduct always-on connections that consumers can interact anytime and anywhere. Especially, mobile devices place themselves to the core means of mobile-commerce which to execute a function as a distribution channel in mobile environments. Although the adoption researches about innovative services or technologies had executed in marketing areas over the past decades, most researches just expanded or modified existing theories and explanation models. There has been little study on the comprehensive and systematic review of adoption process. Therefore, it deserves to be considered prior usage experiences of the existing channels(CL) and attractiveness of the new channel(CLalt) based on social exchange theory. In order to address this void, this study unifies components of perceived attributes in the each dimensions (ie. benefit, cost, and risk dimensions) and explores prior usage experiences of the existing channels on adoption intention in electronic financial service channels through developing comprehensive model and employing empirical test for the hierarchy of effects model. Based on these empirical results, this study suggests managerial implications for new channel management in electronic financial service areas by focusing on the prior usage experiences of the existing objects on adoption intention and perceived attributes of ubiquitous-based mobile service channel.

• Korean Chemical Engineering Research
• /
• v.53 no.6
• /
• pp.818-823
• /
• 2015

In this study, FT reaction in a microchannel was simulated using computational fluid dynamics(CFD), and sensitivity analyses conducted to see effects of channel geometry variables, namely, process channel width, height, gap between process channel and cooling channel, and gap between process channels on the channel temperature profile. Microchannel reactor considered in the study is composed of five reaction channels with height and width ranging from 0.5 mm to 5.0 mm. Cooling surfaces is assumed to be in isothermal condition to account for the heat exchange between the surface and process channels. A gas mixture of $H_2$ and CO($H_2/CO$ molar ratio = 2) is used as a reactant and operating conditions are the following: GHSV(gas hourly space velocity) = $10000h^{-1}$, pressure = 20 bar, and temperature = 483 K. From the simulation study, it was confirmed that heat removal in an FT microchannel reactor is affected channel geometry variables. Of the channel geometry variables considered, channel height and width have significant effect on the channel temperature profile. However, gap between cooling surface and process channel, and gap between process channels have little effect. Maximum temperature in the reaction channel was found to be proportional to channel height, and not affected by the width over a particular channel width size. Therefore, microchannels with smaller channel height(about less than 2 mm) and bigger channel width (about more than 4 mm), can be attractive design for better heat removal and higher production.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.12B
• /
• pp.1050-1057
• /
• 2008

Wireless Mesh Networks (WMNs) have recently become a hot issue to support high link capacity in wireless access networks. The IEEE 802. I 1 standard which is mainly used for the network interface technology in WMNs supports up to 3 or 12 multiple channels according to the IEEE 802.11 specification. However, two important problems must be addressed when we design a channel assigmnent algorithm: channel dependency problem and channel scanning delay. The former occurs when the dynamic channel switching of an interface leads to the channel switching of other interfaces to maintain node connectivity. The latter happens per channel switching of the interface, and affects the network performance. Therefore, in this paper, we propose the Distance-Based Channel Assigmnent (DB-CA) scheme for multi-channel WMNs to solve such problems. In DB-CA, nodes just perform channel switching without channel scanning to communicate with neighboring nodes that operate on different channels. Furthermore, DB-CA minimizes the interference of channels being used by nodes near the gateway in WMNs. Our simulation results show that DB-CA achieves improved performance in WMNs.

• Journal of Internet Computing and Services
• /
• v.15 no.2
• /
• pp.19-31
• /
• 2014

In this paper, a parallel backoff delay procedure on multiple IEEE 802.15.4 channels and a channel searching method considering the frequency spectrum of WiFi traffic are studied for IEEE 802.15.4 nodes to avoid the interference from WiFi traffic. In order to search the channels being occupied by WiFi traffic, we analyzed the methods measuring the powers of adjacent channels simultaneously, checking the duration of measured power levels greater than a threshold, and finding the same periodicity of sampled RSSI data as the beacon frame by signal processing. In an wireless channel overlapped with IEEE 802.11 network, the operation of CSMA-CA algorithm for IEEE 802.15.4 nodes is explained. A method to execute a parallel backoff procedure on multiples IEEE 802.15.4 channels by an IEEE 802.15.4 device is proposed with the description of its algorithm. When we analyze the data measured by the experimental system implemented with the proposed method, it is observed that medium access delay times increase at the same time in the associated IEEE 802.15.4 channels that are adjacent each other during the generation of WiFi traffic. A channel evaluation function to decide the interference from other traffic on an IEEE 802.15.4 channel is defined. A channel searching method considering the channel evaluations on the adjacent channels together is proposed in order to search the IEEE 802.15.4 channels interfered by WiFi, and the experimental results show that it correctly finds the channels interfered by WiFi traffic.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.2
• /
• pp.235-243
• /
• 2012

In this paper, we propose a method to improve performance of pilot symbol assisted modulation(PSAM) channel estimation method for OFDM systems over frequency selective channel. When channel values are estimated, the low pilot density used for channel estimation increases not only the effective data rate but also power efficiency. Thus, the lower pilot density which is used for channel estimation is better for OFDM system. At first, we estimate the channel values which are located at the middle of adjacent pilots, and then all of the possible channel values are estiamted by using original pilot values and previously estimated pilot values. Furthermore, the error of estimated channel values is reduced by introducing guard interval which is designed acccording to maximum channel delay. Performance achieved with the proposed method is illustrated by simulation experiments in comparison with the existing methods in terms of mean squared error(MSE).

• The Journal of the Korea Contents Association
• /
• v.9 no.5
• /
• pp.84-90
• /
• 2009

In this paper, the new channel estimation was proposed that have the low complexity and high performance using Fuzzy inference method uses recently from various field for estimation about uncertainty in channel estimation of OFDM. Proposed method is channel estimation performance improve, calculation and interpolation for statistics character of channel using the pilot before LS channel estimation by Fuzzy inference method. Simulation result in QPSK proposed channel estimation method shows the enhancement of 5.5dB compared to the LS channel estimation and the deterioration of 1.3dB compared to the MMSE channel estimation in mean square error point $10^{-3}$. symbol error rate shows similarity performance the MMSE $10^{-1.96}$, proposed channel estimation $10^{-1.93}$ and enhancement of $10^{-0.35}$ compared to the LS channel estimation in signal to noise ratio point 20dB.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.5C
• /
• pp.519-533
• /
• 2006

The number of channels specified in IEEE 802.15.4 Low-Rate Wireless Personal Area Networks(LRWPANs) is too few to operate many applications of WPANs in the same area. To overcome this limit, we introduce Virtual Channel, a novel concept to increase the number of available channels when various WPAN applications coexist. Basically, a virtual channel is a newly-created channel via superframe scheduling within the inactive period of a logical channel preoccupied by other WPANs. To maximize the coexistence capability of WPANs using virtual channels, we propose Least Collision superframe scheduler(LC-scheduler), its less complex heuristics both for a given single channel, and Virtual Channel Selector(VCS) to efficiently manage multiple available logical channels. In addition, a simple but practical synchronization method is developed to compensate different time drifts among coexisting WPANs. The simulation results demonstrate that a remarkable improvement on the coexistence capability of the 802.15.4 can be achieved through the proposed schemes.