• Journal of Broadcast Engineering
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• v.19 no.4
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• pp.510-520
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• 2014

By adopting the MAC(Media Access Control) protocol which enables to pack multiple MPDUs(MAC-level Protocol Data Units) into a single PPDU(Physical Layer Protocol Data Unit), IEEE 802.11n WLAN supports high throughput. Up to now, there have been a lot of existing channel information-based A-MPDU schemes dynamically determining the number of MSDUs according to the wireless channel condition information which is sent from the receiver to sender. However, the channel information-based scheme has a serious drawback having a high system overhead due to the frequent channel feedback information. To reduce the system overhead, the proposed BA-base dynamic A-MPDU scheme simply chooses the number of MSDUs to be retransmitted by not the frequent channel feedback information but the BA signal representing whether MPSUs belonging to the A-MPDU are received or not. Through NS-2(Network Simulator-2), we found that the proposed scheme had higher throughput and lower packet error rate than the existing fixed A-MPDU scheme.

• Journal of KIISE:Information Networking
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• v.36 no.6
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• pp.528-535
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• 2009

This paper proposes a mechanism to increase performance using cooperative communications in IEEE 802.11 environment. Existing algorithms use one relay between a source and a destination, which is a 2 hop relay. The proposed algorithm utilizes more than one relay to complement inefficiency of using one relay. In the proposed mechanism, an AP manages network information (rate), which is used to select relays of a source by the AP. The AP notifies the selected relays to the source and neighbor nodes, and the source transmits data to the relays for cooperative communications. Moreover, relays are given to have an opportunity to send its own data right after relaying the source's data. So relays are compensated for the power to send the source's data and overall throughput is improved.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.22 no.3
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• pp.513-519
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• 2018

OFDM modulation has been used for a transmission scheme in 4G LTE (Long Term Evolution) and Wi-Fi systems to mitigate the effects of frequency selective fading channels. An OFDM modulation is a block transmission scheme because an OFDM symbol consists of multiple subcarriers with narrow bandwidth. Therefore, all OFDM symbols in a frame should be filled out with data and padding bits. Depending on the amount of data, more padding bits than information bits can occupy the last OFDM symbol. Such inefficiency causes the loss of throughput. To overcome this problem, an efficiency padding method is proposed by using the property of DFT (Discrete Fourier Transform). In the proposed method, symbol duration of the last symbol is changed depending on the number used data subcarriers in the last symbol. With numerical evaluation, it is examined that throughput enhancement achieved by the proposed method can be about 20% depending a transmission scheme and data length.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.5
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• pp.725-730
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• 2022

Named Data Networking (NDN) is a representative technology of ICN that realizes the future Internet architecture. NDN searches for data by its content and not by its host IP address. The consumer generates an interest packet and sends it to the NDN network. The NDN network uses three tables such as CS, FIB, and PIT and forwards the received interest packet to the next hop. The producer transmits the data packet to the consumer through a name-based forwarding scheme. In this paper, we design and implement an ndnSIM-based NDN network and perform performance evaluation. We analyze the ndnSIM structure and develop a 6-node congested NDN network and a 9-node grid NDN network using ndnSIM. In the simulation, the performance of latency and throughput of the interest packet rate are measured. We analyze the effect of congestion on the latency and throughput of the NDN network. This approach will help researchers in the future.

• Journal of KIISE:Information Networking
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• v.37 no.4
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• pp.272-283
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• 2010

Wireless Mesh Networks (WMNs) have gained a lot of attention recently. Based on the characteristic of WMNs as a highly connected wireless infrastructure, many efforts from research organizations are made in order to improve the performance of the flow throughput in WMNs. Therefore, it is very critical issue to establish efficient routing paths for multiple concurrent ongoing flows. In this paper, we propose a general modeling methodology to analyze the end-to-end throughput of multiple concurrent flows by analytical calculation taking into account the carrier sensing behaviors, interference and the IEEE 802.11 Distributed Coordination Function mechanism. After the comparison of the average service time for each successful transmission at each node, we analyze the bottlenecks of flows, and hence obtain the maximum end-to-end throughput of them. By using our proposed model, it is possible to predicate the throughput of several candidate routing paths for multiple concurrent ongoing data flows, so we can select the most efficient route that can achieve the highest throughput. We carry out simulations with various traffic patterns of multiple flows in WMNs to validate our modeling and our efficient route selection mechanism.

• Journal of Satellite, Information and Communications
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• v.12 no.3
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• pp.8-14
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• 2017

In 4G mobile communication, data services of mobile communication began to be provided in earnest. As a result, services such as the internet and multimedia including the video have become the main contents in the recent wireless traffic. Accordingly, research on 5G mobile communication with higher transmission rate has been actively carried out. 5G mobile communication is expected to be based on 4G for compatibility with existing terminals. Therefore, the simulation of this paper is based on 4G and we propose a new user scheduling scheme based on the Max throughput scheduling algorithm to improve system performance. This paper derives the frequency efficiency and fairness to compare the existing user scheduling algorithm with the proposed user scheduling algorithm. The proposed scheme shows better frequency efficiency and fairness than Max throughput in all situations. This paper contributes to the research for improving the system performance of 5G mobile communication technology, and I hope that it will help some of the ongoing standardization work.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6A
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• pp.455-464
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• 2005

In this paper, we implement resource allocation algorithm based on the WiBro system which including OFDMA, TDD, and we propose the algorithm in order to increase bandwidth efficiency. In this algorithm, data is allocated from the subchannel which has large channel gain to the subchannel which has small channel gain with maximum modulation order. The moment total power is more than available power, the modulation order of the latest subchannel is adjusted. The problem of decreasing of throughput in large channel attenuation environment is solved by allocating additional power. Still, this algorithm has large bandwidth efficiency.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.121-127
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• 2016

Satellite communication is a communication method using a satellite as a repeater communication on the air and have a communication range is wide and is possible to transmit high-speed data, so Satellite communication has been highlighted as the next generation communication. However, because the distance between the ground and the satellite is far away, there is a disadvantage that propagation delay time is very long and packet is damaged. Therefore, this study was applied to Link Relay H-ARQ system in order to complement the damage to the packet. Furthermore, we propose the Modified Link Relay H-ARQ scheme is a new scheme to supplementation the delay time. By applying the Markov channel for implementing a channel of satellite communications, the results of analyzing the performance, when applying the Link Relay HARQ scheme, BER and PER performance was improved, when applying the Modified Link Relay H-ARQ scheme, Throughput performance was confirmed improvement.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.3
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• pp.303-308
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• 2016

Recently, as the rapid development of network technology and the increase of services required high bandwidth such as multimedia service, the network traffic dramatically increases. This massive increase of network traffic causes some problems such as the degradation of QoS and the lack of network resources and, to solve these problems, various research to guarantee QoS have been performing. Currently, The most representative method to guarantee the QoS is the DiffServ(: Differentiated Service). The DiffServ defines the AF(: Assured Forwarding) PHB(: Per Hop Behavior) and statistically ensures the throughput over the certain level of data rate. However, the TCP congestion control method that make up the majority of the Internet traffic is not fundamentally suitable to the DiffServ that guarantees the throughput without managing the individual flow. Therefore, in this paper, we present this mismatch through the simulation as an example and propose the solution by controlling the TCP of the terminal in the network. The proposed scheme utilizes the information of the reception window size included in the ACK frame and does not require any modification of the TCP algorithms currently in use.

• Journal of Korea Port Economic Association
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• v.29 no.3
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• pp.1-23
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• 2013

This paper estimates and forecasts the container throughput of Busan port using the monthly data for years 1992-2011. To do this, this paper uses the several seasonal multiplicative ARIMA models. Among several ARIMA models, the seasonal multiplicative ARIMA model $(1,0,1){\times}(1,0,1)_{12}$ is selected as the best model by AIC, SC and Hannan-Quin information criteria. According to the forecasting values of the selected seasonal multiplicative ARIMA model $(1,0,1){\times}(1,0,1)_{12}$, the container throughput of Busan port for 2013-2020 will increase steadily annually, but there will be some volatile variations monthly due to the seasonality and other factors. Thus, to forecast the future container throughput of Busan port and to develop the Busan port efficiently, we need to use and analyze the seasonal multiplicative ARIMA model $(1,0,1){\times}(1,0,1)_{12}$.