• ETRI Journal
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• v.41 no.3
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• pp.348-357
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• 2019

Fog radio access network (F-RAN) architectures provide markedly improved performance compared to conventional approaches. In this paper, an efficient genetic algorithm-based content distribution scheme is proposed that improves the throughput and reduces the transmission delay of a F-RAN. First, an F-RAN system model is presented that includes a certain number of randomly distributed fog access points (F-APs) that cache popular content from cloud and other sources. Second, the problem of efficient content distribution in F-RANs is described. Third, the details of the proposed optimal genetic algorithm-based content distribution scheme are presented. Finally, simulation results are presented that show the performance of the proposed algorithm rapidly approaches the optimal throughput. When compared with the performance of existing random and exhaustive algorithms, that of the proposed method is demonstrably superior.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.63-63
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• 2004

• Journal of Communications and Networks
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• v.18 no.5
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• pp.713-724
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• 2016

Energy consumption has become a main problem of sustainable development in communication networks and how to communicate with high energy efficiency is a significant topic that researchers and network operators commonly concern. In this paper, an energy-efficient multicast algorithm in multi-hop wireless networks is proposed aiming at new generation wireless communications. Traditional multi-hop wireless network design only considers either network efficiency or minimum energy consumption of networks, but rarely the maximum energy efficiency of networks. Different from previous methods, the paper targets maximizing energy efficiency of networks. In order to get optimal energy efficiency to build network multicast, our proposed method tries to maximize network throughput and minimize networks' energy consumption by exploiting network coding and sleeping scheme. Simulation results show that the proposed algorithm has better energy efficiency and performance improvements compared with existing methods.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.12
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• pp.1721-1735
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• 2016

Power-efficient base station (BS) operation is one of the important issues in future green cellular networks. Previously well-known BS operation schemes, the cell zooming scheme and the cell wilting and blossoming scheme, require tight cooperation between cells in cellular networks. With the previous schemes, the non-cooperative BSs of a serving cell and neighboring cells could cause coverage holes between the cells, thereby seriously degrading the quality of service as well as the power saving efficiency of the cellular networks. In this paper, we propose a novel power-efficient BS operation scheme for green downlink heterogeneous cellular networks, in which the networks virtually adjust the coverage of a serving macrocell (SM) and neighboring macrocells (NMs) without adjusting the transmission power of the BSs when the SM is lightly loaded, and the networks turn off the BS of the SM when none of active users are associated with the SM. Simulation results show that our proposed scheme significantly improves the power saving efficiency without degrading the quality of service (e.g., system throughput) of a downlink heterogeneous LTE network and outperforms the previous schemes in terms of system throughput and power saving efficiency. In particular, with the proposed scheme, macrocells are able to operate independently without the cooperation of a SM and NMs for green heterogeneous cellular networks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.5 no.1
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• pp.52-67
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• 2011

Network coding is a newly developed technology that can cause considerable improvements in network throughput. COPE is the first network coding approach for wireless mesh networks and it is based on opportunistic Wireless Network Coding (WNC). It significantly improves throughput of multi-hop wireless networks utilizing network coding and broadcast features of wireless medium. In this paper we propose a new method, called FENC, for opportunistic WNC that improves the network throughput. In addition, its complexity is lower than other opportunistic WNC approaches. FENC utilizes division and conquer method to find an optimal network coding. The numerical results show that the proposed opportunistic algorithm improves the overall throughput as well as network coding approach.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.121-127
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• 2010

In this paper, we propose a computationally efficient scheduling algorithm that can arbitrarily control the throughput-fairness tradeoff in a multiuser wireless communication environment. As a new scheduling criterion, we combine linearly two well-known scheduling criteria such as one of achieving the maximum sum throughput and the other of achieving the maximum fairness, so as to control the relative proportion of the throughput and the fairness according to a control factor. For linear combining two different criteria, their optimization directivenesses and the units should be unified first. To meet these requirements, we choose an instantaneous channel capacity as a scheduling criterion for maximizing the sum throughput and the average serving throughput for maximizing the fairness. Through a unified linear combining of two optimization objectives with the control factor, it can provide various throughput-fairness tradeoffs according to the control factors. For further simplification, we exploit a high signal-to-noise ratio (SNR) approximation of the instantaneous channel capacity. Through computer simulations, we evaluate the throughput and fairness performances of the proposed algorithm according to the control factors, assuming an independent Rayleigh fading multiuser channel. We also evaluate the proposed algorithm employing the high SNR approximation. From simulation results, we could see that the proposed algorithm can control arbitrarily the throughput-fairness performance between the performance of the scheduler aiming to the maximum sum throughput and that of the scheduler aiming to the maximum fairness, finally, we see that the high SNR approximation can give a satisfactory performance in this situation.

• Journal of Communications and Networks
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• v.16 no.3
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• pp.293-300
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• 2014

As energy harvesting communication systems emerge, there is a need for transmission schemes that dynamically adapt to the energy harvesting process. In this paper, after exhibiting a finite-horizon online throughput-maximizing scheduling problem formulation and the structure of its optimal solution within a dynamic programming formulation, a low complexity online scheduling policy is proposed. The policy exploits the existence of thresholds for choosing rate and power levels as a function of stored energy, harvest state and time until the end of the horizon. The policy, which is based on computing an expected threshold, performs close to optimal on a wide range of example energy harvest patterns. Moreover, it achieves higher throughput values for a given delay, than throughput-optimal online policies developed based on infinite-horizon formulations in recent literature. The solution is extended to include ergodic time-varying (fading) channels, and a corresponding low complexity policy is proposed and evaluated for this case as well.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1A
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• pp.34-43
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• 2007

In the IEEE 802.15.3 Medium Access Control (MAC) protocol, Simultaneously Operating Piconets (SOPs) are linked by the parent/child (P/C) or parent/neighbor (P/N) configuration, which work on a Time Division Multiple Access (TDMA) basis. This provides interference mitigation but the overall throughput is limited because the SOPs share the channel time exclusively. The protocol is not efficient for SOPs if we focus on the combination of interference mitigation and high throughput maintenance. In this paper Public Channel Time Allocation (Public CTA) is proposed, which is able to greatly reduce the inter-piconet interference (IPI) and achieve greater throughput without much loss of link success probability (LSP) in the SOPs. The simulation results based on the SOPs of Direct Sequence Ultra Wideband (DS-UWB) system demonstrate that the proposed scheme effectively supports the coexistence of SOPs, and it can not only significantly improve the overall throughput of SOPs but also maintain high LSP.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1066-1072
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• 2001

ALOHA Multi-Carrier DS-CDMA systems in the multipath Rayleigh fading channel. The throughput of two systems are compared according to the length of a packet in the fast Rayleigh and the slow Rayleigh multipath fading. As a result, we have known that Multi-Carrier DS-CDMA system has less capacity than wideband DS-CDMA system in the same bandwidth, but throughput of Multi-Carrier DS-CDMA system is higher than that of wideband DS-CDMA system. And in Multi-Carrier DS-CDMA systems, higher throughput can be obtained through shortening the length of packet in the fast Rayleigh fading, and it is efficient to control the length of a packet adequately or increase the system capacity of Multi-Carrier DS-CDMA system in the slow Rayleigh fading.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.675-679
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• 2001

In this paper, throughput is derived for slotted ALOHA wideband DS-CDMA and slotted ALOHA Multi-Carrier DS-CDMA systems in the multipath Rayleigh fading channel. The throughput of two systems are compared according to the length of a packet in the fast Rayleigh and the slow Rayleigh multipath fading. As a result, we have known that Multi-Carrier DS-CDMA system has less capacity than wideband DS-CDMA system in the same bandwidth, but throughput of Multi-Carrier DS-CDMA system is higher than that of wideband DS-CDMA system. And in Multi-Carrier DS-CDMA systems, higher throughput can be obtained through shortening the length of packet in the fast Rayleigh fading and it is efficient to control the length of a packet adequately or increase the system capacity of Multi-Carrier DS-CDMA system in the slow Rayleigh fading.