• ETRI Journal
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• v.37 no.2
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• pp.380-386
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• 2015

Guaranteeing quality of service over a multihop wireless network is difficult because end-to-end (ETE) delay is accumulated at each hop in a multihop flow. Recently, research has been conducted on network coding (NC) schemes as an alternative mechanism to significantly increase the utilization of valuable resources in multihop wireless networks. This paper proposes a new section-based joint NC and scheduling scheme that can reduce ETE delay and enhance resource efficiency in a multihop wireless network. Next, this paper derives the average ETE delay of the proposed scheme and simulates a TDMA network where the proposed scheme is deployed. Finally, this paper compares the performance of the proposed scheme with that of the conventional sequential scheduling scheme. From the performance analysis and simulation results, the proposed scheme gives more delay-and energy-efficient slot assignments even if the NC operation is applied, resulting in a use of fewer network resources and a reduction in ETE delay.

• Journal of information and communication convergence engineering
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• v.15 no.1
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• pp.28-36
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• 2017

The medium access control (MAC) protocol based on dynamic time division multiple access/time division duplex (TDMA/TDD) is responsible for random access control and radio resource allocation in dynamic traffic environments. These functions of random access and resource allocation are very important to prevent wastage of resources and improve MAC performance according to various network conditions. In this paper, we propose new random access and resource allocation schemes to guarantee quality of service (QoS) and provide priority services in a dynamic TDMA/TDD system. First, for the QoS guarantee, we propose an adaptive random access and resource allocation scheme by introducing an access probability. Second, for providing priority service, we propose a priority-based random access and resource allocation scheme by extending the first adaptive scheme in both a centralized and a distributed manner. The analysis and simulation results show that the proposed MAC protocol outperforms the legacy MAC protocol using a simple binary exponential backoff algorithm, and provides good differential performance according to priorities with respect to the throughput and delay.

• Journal of Communications and Networks
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• v.18 no.5
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• pp.784-795
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• 2016

In this paper, we investigate the resource allocation problem in time-varying heterogeneous wireless networks (HetNet) with multi-homing user equipments (UE). The stochastic optimization model is employed to maximize the network utility, which is defined as the difference between the HetNet's throughput and the total energy consumption cost. In harmony with the hierarchical architecture of HetNet, the problem of stochastic optimization of resource allocation is decomposed into two subproblems by the Lyapunov optimization theory, associated with the flow control in transport layer and the power allocation in physical (PHY) layer, respectively. For avoiding the signaling overhead, outdated dynamic information, and scalability issues, the distributed resource allocation method is developed for solving the two subproblems based on the primal-dual decomposition theory. After that, the adaptive resource allocation algorithm is developed to accommodate the timevarying wireless network only according to the current network state information, i.e. the queue state information (QSI) at radio access networks (RAN) and the channel state information (CSI) of RANs-UE links. The tradeoff between network utility and delay is derived, where the increase of delay is approximately linear in V and the increase of network utility is at the speed of 1/V with a control parameter V. Extensive simulations are presented to show the effectiveness of our proposed scheme.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1236-1245
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• 2000

This paper propose a novel scheme, called Mobiel Terminal Initiated Scheme(MTIS), in which mobile terminal initiates the backward handover by sending handover request message with the list of target radio ports. In this scheme, the old ATM switch suporting end-user mobility, denoted by EMAS\ulcorner, checks whether each EMAS\ulcorner, managing the target radio port, has its available resources. If it has, the EMAS\ulcorner performs the path rerouting between CrossOver Switch (COS) and itself after deciding the most suitable target radio port. Therefore, the MT initiates the handover after deciding the most suitable target radio port through the beacon signal of Wireless Access Point (WAP). The EMAS\ulcorner have only to check the resource availability of the target radio port. It is no need to waste time to decide the suitable target radio port. Also, once receiving the request of the resource availability, the EMAS\ulcorner can reduce the rerouting delay time due to perform the path rerouting to the COS. In comparison with that of the ATM-Forum procedure, our proposed MTIS handover delay time reduced 14~21%, and end-to-end transfer delay time reduced 2~9%, as a result of the simulation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.16 no.11
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• pp.3680-3693
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• 2022

The handover procedure of IEEE 802.11 wireless local area networks (WLANs) introduces significant delay, which can degrade the quality of service (QoS) especially for delay-sensitive applications. Although studies have been conducted to support handover in SDN-based WLAN, there is no research to reduce the channel scanning procedure that takes up the most delay time in the handover process. The channel scanning procedure is essential to determine the appropriate access point (AP). To mitigate this problem, this paper proposes a SWITCH: SDN-WLAN integrated handover scheme for QoS-Guaranteed mobile service. In SWITCH, each AP periodically broadcasts beacon frames through different channels in a predetermined order that includes the operating channel information of the AP. This allows mobile stations (MSs) to receive the beacon frames of nearby APs, and therefore they can determine the appropriate APs for handover without the channel scanning procedure. By reporting the information of the newly moved AP to the SDN controller, a flow rule is installed in advance to provide fast handover, and packet loss is reduced by buffering data destined for MS. In addition, the proposed scheme can adaptively operate SWITCH to consider the user location and QoS requirement of flow to save radio resource overhead. Performance evaluation results demonstrate that SWITCH can reduce the handover delays, flow table utilization ratio and radio resource overhead while improving the network throughput.

• The Journal of Information Technology
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• v.4 no.4
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• pp.65-72
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• 2001

This paper investigates the Performance of MSA l (group partition based reservation scheduling algorithm) and MSA ll (group based reservation scheduling algorithm) for multicast service in single-hop WDM networks. Simulation results show that MSA l produces lower mean packet delay than MSA ll when the channel resource is sufficient. However, when the channel resource is limited, MSA ll produces lower mean packet delay than MSA I when traffic load is heavy.

• ETRI Journal
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• v.45 no.4
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• pp.627-635
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• 2023

In vehicular edge computing (VEC) networks, the rapid expansion of intelligent transportation and the corresponding enormous numbers of tasks bring stringent requirements on timely task offloading. However, many tasks typically appear within a short period rather than arriving simultaneously, which makes it difficult to realize effective and efficient resource scheduling. In addition, some key information about tasks could be learned due to the regular data collection and uploading processes of sensors, which may contribute to developing effective offloading strategies. Thus, in this paper, we propose a model that considers the deterministic demand of multiple tasks. It is possible to generate effective resource reservations or early preparation decisions in offloading strategies if some feature information of the deterministic demand can be obtained in advance. We formulate our scenario as a 0-1 programming problem to minimize the average delay of tasks and transform it into a convex form. Finally, we proposed an efficient optimal offloading algorithm that uses the interior point method. Simulation results demonstrate that the proposed algorithm has great advantages in optimizing offloading utility.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.2
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• pp.67-74
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• 2018

Resource leveling minimizes resource fluctuations by deferring the earliest start times (ESTs) of non-critical activities within their corresponding total float. The intentional float-consumption for resource leveling purpose reduces the schedule delay contingency. This paper presents a method called Genetic Algorithm based Resource Leveling (GARL) that minimizes resource fluctuations and float-consumption impact over project duration. It identifies activities that are less sensitive to float-consumption and performs resource leveling using those activities. The study is of value to project scheduler because GARL identifies the set of activities to be deferred and the number of shift day(s) of each and every activities in the set within its total float expeditiously. It contributes to establish a baseline schedule which implements an optimal resource leveling plan. A case study is presented to verify the validity and usability of the method. It was confirmed that GARL satisfies the project duration constraint by considering resource fluctuations and float-consumption over project duration.

• Journal of the Korea Computer Industry Society
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• v.2 no.9
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• pp.1163-1174
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• 2001

A general goal of the ATM(Asynchronous Transfer Mode) network is to support connections across various networks. ABR service using EPRCA(Enhanced Proportional Rate Control Algorithm) switch controls traffics in ATM network. EPRCA switch, traffic control method uses variation of the ACR(Allowed Cell Rate) to enhance the utilization of the link bandwidth. However, in ABR(Available Bit Rate) service, different treatments are offered according to different RTTs(Round Trip Times) of connections. To improve the above unfairness, this paper presents ABR DELAY mechanism, in which three reference parameters for cell delay are defined, and reflect on the messages of RM(Resource Management) cells. To evaluate our mechanism, we compare the fairness among TCP connections between ABR DELAY mechanism and ABR RRM mechanism. And also we execute simulations on a simple ATM network model where six TCP connections and a background traffic with different RTTs share the bandwidth of a bottleneck link. The simulation results, based on TCP goodput and efficiency, clearly show that ABR DELAY mechanism improves the fairness among TCP connections.

• Journal of Korea Multimedia Society
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• v.10 no.1
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• pp.83-93
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• 2007

WFQ (Weighted Fair Queuing) is the most popular fair queuing algorithm, but it had the inherent drawback of a poet bandwidth utilization, particularly under the traffic requiring a low rate but tight delay bound such as internet phone. It was recently identified that the poor utilization is mainly due to the non-optimized latency of a flow and then LOFQ(Latency-Optimized Fair Queuing) to overcome the drawback was introduced. In this paper, we improve the performance of LOFQ by introducing an occupied resource optimization function and reduce the implementation complexity of recursive resource transformation by revising the transformation scheme. We also prove the superiority of LOFQ over WFQ in terms of utilization. The simulation result shows that the improved LOFQ provides $20{\sim}30%$ higher utilization than that in the legacy LOFQ.