• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.876-884
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• 2012

This paper introduces two multi-hop delay factors which can be caused by conventional TDMA scheduling; queueing delay and delay by random link scheduling, and proposes a new sequential scheduling scheme to resolve these two factors. We also simulate the TDMA network with the proposed link scheduling scheme and compare it with conventional(random) link scheduling scheme in terms of end-to-end packet transmission delay. From the simulation results, the more the average hop distance increases, the more the difference of the delay performance of both scheduling schemes increases. When the average number of hops is 2.66, 4.1, 4.75, and 6.3, the proposed sequential scheduling scheme reduces the average end-to-end delay by about 22%, 36%, 48%, and 55% respectively when compared to the random scheduling scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.10
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• pp.674-683
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• 2014

Multi-hop wireless networks has become common phenomenon according to a development of wireless communications and an increase of usage of wireless link. ARQ is one of the common protocols in link layer and can improve a link performance recovering packet loss in wireless link. However, ARQ cannot sufficient to assure a end-to-end performance because ARQ only manages the ARQ's own link. In this paper, we propose a new retransmission persistence for ARQ in multi-hop wireless network to satisfy the end-to-end performance. The proposed scheme can aware a bottleneck link according to the exchange of link information between ARQs and can support the end-to-end performance by managing a retransmission persistence. OPNET simulator is used to evaluate the performance of the proposed scheme and results show that proposed scheme can improve the end-to-end performance with satisfying a requirement of entire wireless section.

• Journal of Industrial Convergence
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• v.18 no.2
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• pp.69-75
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• 2020

Industrial IoT has much interested in wireless mesh networks (WMNs) due to cost effectiveness and coverage. According to the advance in caching technology, WMNs have been researched to overcome the throughput degradation of multihop environment. However, there is few researches of cache power consumption models for WMNs. In particular, a wired line based cache power consumption model in content-centric networks is not still proper to WMNs. In this paper, we split the amount of cache power from the idle power consumption of CPU, and then the cache hit ratio proportional power consumption model (CHR-model) is proposed. The proposed CHR-model provides more accurate power consumption in WMNs, compared with the conventional cache power efficiency based consumption model (CPE-model). The proposed CHR-model can provide a reference model to improve energy-efficient cache operation for Industrial IoT.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.618-633
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• 2014

Relay technology is becoming more important for mobile communications and wireless internet of things (IoT) networking because of the extended access network coverage range and reliable quality of service (QoS) it can provide at low power consumption levels. Existing mobile multihop relay (MMR) technology uses fixed-point stationary relay stations (RSs) and a divided time-frame (or frequency-band) to support the relay operation. This approach has limitations when a local fixed-point stationary RS does not exist. In addition, since the time-frame (or frequency-band) channel resources are pre-divided for the relay operation, there is no way to achieve high channel utilization using intelligent opportunistic techniques. In this paper, a different approach is considered, where the use of mobile/IoT devices as RSs is considered. In applications that use mobile/IoT devices as relay systems, due to the very limited battery energy of a mobile/IoT device and unequal channel conditions to and from the RS, both minimum energy consumption and QoS support must be considered simultaneously in the selection and configuration of RSs. Therefore, in this paper, a mobile RS is selected and configured with the objective of minimizing power consumption while satisfying end-to-end data rate and bit error rate (BER) requirements. For the RS, both downlink (DL) to the destination system (DS) (i.e., IoT device or user equipment (UE)) and uplink (UL) to the base station (BS) need to be adaptively configured (using adaptive modulation and power control) to minimize power consumption while satisfying the end-to-end QoS constraints. This paper proposes a minimum transmission power consuming RS selection and configuration (MPRSC) scheme, where the RS uses cognitive radio (CR) sub-channels when communicating with the DS, and therefore the scheme is named MPRSC-CR. The proposed MPRSC-CR scheme is activated when a DS moves out of the BS's QoS supportive coverage range. In this case, data transmissions between the RS and BS use the assigned primary channel that the DS had been using, and data transmissions between the RS and DS use CR sub-channels. The simulation results demonstrate that the proposed MPRSC-CR scheme extends the coverage range of the BS and minimizes the power consumption of the RS through optimal selection and configuration of a RS.

• The Journal of the Korea Contents Association
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• v.18 no.3
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• pp.611-625
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• 2018

With innovative advances in wireless communication technology, many researches for extending network lifetime in maximum by using energy harvesting have been actively performed on the area of network resource optimization, QoS-guaranteed transmission, energy-intelligent routing and etc. As known well, it is very hard to guarantee end-to-end network delay due to uncertainty of the amount of harvested energy in multi-hop RF(radio frequency) energy harvesting wireless networks. To minimize end-to-end delay in multi-hop RF energy harvesting networks, this paper proposes an energy efficient routing metric based on interference aware and protocol which takes account of various delays caused by co-channel interference, energy harvesting time and queuing in a relay node. The proposed method maximizes end-to-end throughput by performing avoidance of packet congestion causing load unbalance, reduction of waiting time due to exhaustion of energy and restraint of delay time from co-channel interference. Finally simulation results using ns-3 simulator show that the proposed method outperforms existing methods in respect of throughput, end-to-end delay and energy consumption.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2004-2010
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• 2009

The characteristic of the backbond for distribution service in WMNs(Wireless Mesh Networks) is that WMNs has multiple links connected to mesh points and dynamic routing protocol such as AODV to establish routing paths. When the terminal is communicating with the service through new AP, mobile nodes can resume communication by setting only the link between new AP and mobile node in the case of existing WLANs, but WMNs needs path establishment process in multihop networks. Our goal in this paper is to support the seamless communication service by eliminating path establishment delay in WMNs. We present the method that eliminates the handover latency by predicting the location of handover using GPS information and making the paths to their destination in advance. We implement mesh nodes using embedded board that contains proposed handover method and evaluate performance of handover latency. Our experiment shows that handover delay time is decreased from 2.47 to 0.05 seconds and data loss rate is decreased from 20~35% in the existing method to 0~10% level.