• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.664-674
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• 1996

In high speed multi-wavelength networks, retransmission overhead due to desination conflict or control packet collision is one factor of performance degration because signal prpagation delay is much larger than the transmission time of data packet. In this paper, an efficient WDMA protocol with a collision avoidance mechanism is proposed for high speed WDM single-hop network with a passive star topology. In proposed protocol, each node has cource queues and routing table to store souting informatio. This architecture makes is possible to avoid any kind of collision when a node reserves the channel to transmit a data packet. High system thoughput and channel utilization can be achieved by proposed protocol since there are no discarded packets caused by any collision at transmission time. The performance of proposed protocol is evaluated in term of throughput and delay with variations in offered load. Simulation results show that the proposed protocol has superior performance to convertional protocols under nonuniform traffic as well as uniform traffic.

• Journal of Communications and Networks
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• v.14 no.6
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• pp.640-652
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• 2012

Many studies have investigated the smart grid architecture and communication models in the past few years. However, the communication model and architecture for a smart grid still remain unclear. Today's electric power distribution is very complex and maladapted because of the lack of efficient and cost-effective energy generation, distribution, and consumption management systems. A wireless smart grid communication system can play an important role in achieving these goals. In this paper, we describe a smart grid communication architecture in which we merge customers and distributors into a single domain. In the proposed architecture, all the home area networks, neighborhood area networks, and local electrical equipment form a local wireless mesh network (LWMN). Each device or meter can act as a source, router, or relay. The data generated in any node (device/meter) reaches the data collector via other nodes. The data collector transmits this data via the access point of a wide area network (WAN). Finally, data is transferred to the service provider or to the control center of the smart grid. We propose a wireless cooperative communication model for the LWMN.We deploy a limited number of smart relays to improve the performance of the network. A novel relay selection mechanism is also proposed to reduce the relay selection overhead. Simulation results show that our cooperative smart grid (coopSG) communication model improves the end-to-end packet delivery latency, throughput, and energy efficiency over both the Wang et al. and Niyato et al. models.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1B
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• pp.31-38
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• 2012

In this paper, we propose a method to improve cell edge users' performance in HetNet (heterogeneous network) systems by cooperatively transmitting signals using remote radio heads (RRHs) located near coverage boundaries, referred to as edge RRHs. The proposed method locates the edge RRHs in specific locations of the cell boundary and provides an efficient operational strategy by adjusting the duty cycle of the edge RRHs and base stations. The effectiveness of the method is demonstrated by experimental performance based on the system model parameters of the CoMP (coordinated multi-point transmission and reception) scenario, which is discussed in LTE-Advanced (Long Term Evolution - Advanced) standard contributions. When compared with conventional methods, utilization of edge RRHs is especially advantageous for the performance improvement of lower percentile users in terms of average throughput and effectively improves the fairness among users.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.165-173
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• 2010

WMN(Wireless Mesh Network) is an wireless backbone network technology that is an easily configurable network in the low cost compared to the wireless LAN(Local Area Network). Most of the previous researches have evaluated their algorithms by the simulations rather than by the implementation. There exist some implementation papers, however, they have the limitations of the flexibility on the link establishment and the link quality utilization. Consequently, the benefit of the WMN - configuration flexibility is degraded and the performance deterioration occurs in the multi-hop wireless environment. In this paper, we introduce a Linux-based link layer Wireless Mesh Routing System - WBMR. The design and implementation of WBMR provides the dynamic link establishment and the effective multi-channel usage. We have modified the ntroof the original WLAN operation for the dynamic link establishment, and the Linux bridge for the link layer routing. The result of performance evaluation verifies that our WBMR supports fast self-configuration and increases data transmission throughput compared to the other researches of the wireless multi-hop environment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.1
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• pp.76-82
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• 2014

In order for heterogeneous unlicensed devices to co-exist on the same frequency band, the frequency interference avoidance mechanism is necessary. In this paper, a frequency interference between WLAN and WPAN systems that operate at 2.4 GHz ISM band was analyzed in the MAC layer. We observed that WPAN systems suffer from severe interference from WLAN systems. To avoid this interference problem, we propose a new channel shift algorithm for WPAN systems. We showed that the proposed channel shift algorithm is better than the traditional WPAN system which uses a fixed channel in terms of throughput.

• Journal of the Korea Society of Computer and Information
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• v.13 no.6
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• pp.25-31
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• 2008

The web has been evolving as an indispensable part of our lives since Berners Lee introduced the first web sever and browser in 1990. From the web end user's point of view, the response time is a matter of concern. Moreover the throughput is an important factor to consider for the system manager's point as well. It's not easy to estimate the performance of a web application because it depends on various elements comprising the whole operational environment of the Internet from networking, client and server computing powers, DBMS and OS capabilities, to application itself. This paper suggests a coarse grained simulation model for web application performance estimation based on the data measured by Buch and Pentkowski [1] and the analytical model proposed by Gunther [2]. The result of the simulation model almost coincides with the measured data and estimates the performance of a new environment.

• Journal of the Korea Society for Simulation
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• v.15 no.4
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• pp.143-151
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• 2006

This paper deals with the simulation model for design and operations of A-Mart logistic center for low temperature products. In developed simulation model, receiving docks, digital classification system (DCS), shipping docks, material handling devices and manual sorting stations are considered. Five types of cargo such as fruits, palletized fruits, delicatessen and fisheries, vegetables and refrigerated cargoes are considered. The simulation model and process animation are developed using the simulation package ARENA. Among various design and operation alternatives consisting of the number of workers of receiving dock, allocation of receiving docks by cargo types, DCS capacity, the number of folk-lift, the number of manual sorting operators and overall layout, the best alternatives of each subsystem are selected by simulation analysis. The major performance measures such as DCS throughput, utilization of operators at each station, receiving docks utilization and folk-lift utilization are considered for the alternative evaluation.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.409-411
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• 2013

In this paper, we used FTN(Faster than Nyquist) method that is transmission method faster than Nyquist theory. FTN signaling introduces intersymbol interference(ISI), but increases the bit rate while preserving the signaling bandwidth. Therefore, we need compensating ISI caused by FTN. In this paper, we propose decoding method for FTN signal that using BCJR Equalizer and Turbo Equalization. first ISI of inputted signal is restored by BCJR Equalizer, and then restored signal inputted in LDPC decoder, and repeat the process using the Turbo Equalization improves performance. finally, we shows performance comparison according to reduce percentage of FTN signal.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1345-1358
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• 2017

The impact of overproduction of a heterologous protein on the metabolic system of host Lactococcus lactis was investigated. The protein expression profiles of L. lactis IL1403 containing two near-identical plasmids that expressed high- and low-level of the green fluorescent protein (GFP) were examined via shotgun proteomics. Analysis of the two strains via high-throughput LC-MS/MS proteomics identified the expression of 294 proteins. The relative amount of each protein in the proteome of both strains was determined by label-free quantification using the spectral counting method. Although expression level of most proteins were similar, several significant alterations in metabolic network were identified in the high GFP-producing strain. These changes include alterations in the pyruvate fermentation pathway, oxidative pentose phosphate pathway, and de novo synthesis pathway for pyrimidine RNA. Expression of enzymes for the synthesis of dTDP-rhamnose and N-acetylglucosamine from glucose was suppressed in the high GFP strain. In addition, enzymes involved in the amino acid synthesis or interconversion pathway were downregulated. The most noticeable changes in the high GFP-producing strain were a 3.4-fold increase in the expression of stress response and chaperone proteins and increase of caseinolytic peptidase family proteins. Characterization of these host expression changes witnessed during overexpression of GFP was might suggested the metabolic requirements and networks that may limit protein expression, and will aid in the future development of lactococcal hosts to produce more heterologous protein.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.60-66
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• 2011

LTE (Long Term Evolution) supports QoS (Quality of Service) with several service classes. For each class of traffic, a big difference exists on BER (Bit Error Rate) requirement. This leads to a considerable difference in transmission power for various classes of traffic. In this paper, a novel scheduler is designed and proposed for LTE which supports CoS (Class of Service) with the consideration of priority as well as target BER. By the CQI (Channel Quality Indicator) and QCI (QoS Class Identifier), a minimum transmission power is assigned from the target BER for each class of traffic per each user. Hence, with the other information such as user's used rate in the past and the priority of traffic, the probability of occupying channels is determined. The simulation results of Service Class scheduling are compared with that of Maximum Rate and Proportional Fair. The results show that the service class-aided scheduling can improve the throughput of whole system significantly.