• Current Optics and Photonics
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• v.1 no.4
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• pp.325-335
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• 2017

Hybrid radio frequency/free space optical (RF/FSO) wireless mesh networks have attracted increasing attention for they can overcome the limitations of RF and FSO communications and significantly increase the throughput of wireless mesh networks (WMNs). In this article, a resource assignment optimization scheme is proposed for hybrid RF/FSO wireless mesh networks. The optimization framework is proposed for the objective of maximizing throughput of overall hybrid networks through joint transmission slot assignment, FSO links allocation and power control with the consideration of the fading nature of RF and FSO links. The scheme is formulated as an instance of mixed integer linear program (MILP) and the optimal solutions are provided using CPLEX and Gurobi optimizers. How to choose the appropriate optimizer is discussed by comparing their performance. Numerous simulations are done to demonstrate that the performance of our optimization scheme is much better than the current case of having the same topology.

• Journal of Communications and Networks
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• v.13 no.6
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• pp.639-654
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• 2011

In this paper, we present a channel access mechanism, referred to as the enhanced mesh coordinated channel access (eMCCA) mechanism, for IEEE 802.11s-based wireless mesh networks. The current draft of IEEE 802.11s includes an optional medium access control (MAC), denoted as MCCA, which is designed to provide collision-free and guaranteed channel access during reserved periods. However, the MCCA mechanism fails to achieve the desired goal in the presence of contending non-MCCA nodes; this is because non-MCCA nodes are not aware of MCCA reservations and have equal access opportunities during reserved periods. We first present a probabilistic analysis that reveals the extent to which the performance of MCCA may be affected by contending non-MCCA nodes. We then propose eMCCA, which allows MCCA-enabled nodes to enjoy collision-free and guaranteed channel access during reserved periods by means of prioritized and preemptive access mechanisms. Finally, we evaluate the performance of eMCCA through extensive simulations under different network scenarios. The simulation results indicate that eMCCA outperforms other mechanisms in terms of success rate, network throughput, end-to-end delay, packet-loss rate, and mesh coordinated channel access opportunity-utilization.

• Proceedings of the Korean Information Science Society Conference
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• 2007.10d
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• pp.556-559
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• 2007

Due to its ease of deployment, low cost, self-configuring and self-healing capabilities, Wireless Mesh Networks (WMNs) have emerged as a key technology to be used in a wide scale applications in personal, local, campus, and metropolitan areas. Security and more specifically privacy is an important issue in this type of multi-hop WMN which has given a little attention in the research community. We focus on privacy compromise of a mesh client in a community mesh network that may lead an attacker to reveal mesh clients identity. his other profiles and gain information about mobility. In this paper. we have presented an authentication mechanism with the aid of blind signature that ensures a mesh client to anonymously authenticate itself with a nearby mesh router and thereby preserve identity privacy We have also presented the security and performance analysis of the proposed scheme.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.385-389
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• 2009

Multi-hop wireless mesh networks (WMNs) suffer from significant packet losses due to insufficient available bandwidth and high channel error probability. To conquer packet losses, end-to-end (E2E) error control schemes have been proposed. However, in WMNs, E2E error control schemes are not effective in adapting to the time-varying network condition due to large delay. Thus, in this paper, we propose a network-adaptive error control for video streaming over WMNs that flexibly operates E2E and hop-by-hop (HbH) error control according to network condition. Moreover, to provide lightweight support at intermediate nodes for HbH error control, we use path-partition-based adaptation. To verify the proposed scheme, we implement it and evaluate its transport performance through MPEG-2 video streaming over a real IEEE 802.11a-based WMN testbed.

• 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.

• Journal of KIISE
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• v.44 no.9
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• pp.976-985
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• 2017

Wireless mesh network (WMN) is a promising technology for building a cost-effective and easily-deployed wireless networking infrastructure. To efficiently utilize limited radio resources in WMNs, packet transmissions (particularly, redundant packet transmissions) should be carefully managed. We therefore propose a lightweight traffic redundancy elimination (LTRE) scheme to reduce redundant packet transmissions in software-defined wireless mesh networks (SD-WMNs). In LTRE, the controller determines the optimal path of each packet to maximize the amount of traffic reduction. In addition, LTRE employs three novel techniques: 1) machine learning (ML)-based information request, 2) ID-based source routing, and 3) popularity-aware cache update. Simulation results show that LTRE can significantly reduce the traffic overhead by 18.34% to 48.89%.

• Proceedings of the KAIS Fall Conference
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• 2009.05a
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• pp.57-59
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• 2009

무선 메쉬 네트워크(Wireless Mesh Networks, WMNs)는 유비쿼터스 환경 및 무선 브로드밴드 액세스를 제공하기 위한 핵심적인 미래 기술로 대두되고 있다. WMN에서의 전체적인 성능은 채널의 간섭을 최소화함으로써 개선될 수 있다. 효율적인 채널 할당을 위해서는 채널 스캐닝 지연과 채널 의존성 문제를 고려해야 한다. 본 논문에서는 멀티채널 WMN에서의 이러한 문제점들을 해결하기 위해 클러스터 기반의 채널 할당(Cluster-Based Channel Assignment, CB-CA)을 제안한다. CB-CA에서는 클러스터 헤드 메쉬 라우터(Cluster Head Mesh Router, CHMR)들 간에는 동일 채널을 사용함으로써 채널 스캐닝과 채널 스위칭을 수행하지 않는다. 해당 클러스터 멤버 라우터(Cluster Member Mesh Router, CMMR)들과의 통신에는 CHMR들 간의 통신 채널에 영향을 미치지 않는 채널을 할당함으로써 멀티채널에서 발생할 수 있는 간섭을 최소화 할 수 있다.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.6
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• pp.85-94
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• 2015

In this paper, an enhanced QoS multicast routing scheduling scheme is proposed to adapt to a dynamic mobile traffic condition for wireless mesh networks (WMNs). It handles the network QoS by controlling the delay constraints for multimedia applications. The group size will be controlled according to both the current network state and QoS requirements. The dynamic reconstruction of QoS multicast tree can be obtained from preprocessing with both the partial multicast routing scheme and the traffic estimation. Performance evaluation of the proposed scheme is carried out on randomly generated graph derived from the wireless mesh network, by choosing the optimal value related to the appropriate delay bounds. Simulation results show that the proposed scheme can improve the performance of QoS multicast routing for WMNs.

• Journal of Industrial Convergence
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• v.17 no.4
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• pp.131-137
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• 2019

In infrastructure wireless mesh networks (WMNs), in order to improve mobile users' satisfaction for the given cache hit ratio, we investigate an User centric Cache Allocation (UCA) scheme while reducing cache cost in a mesh router (MR) and expected transmission time (ETT) for content search in cache. To minimize ETT values of mobile users, a genetic algorithm based UCA (GA-UCA) scheme is provided. The goal is to maximize mobile users' satisfaction via our well defined utility, which considers content popularity and the number of mobile users. Finally, through solving optimization problem we show the optimal cache can be allocated for UCA and GA-UCA. Besides, a WMN provider can find the optimal number of mobile users for user centric cache allocation in infrastructure WMNs.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.9B
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• pp.1390-1398
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• 2010

We present the concept of applying Wireless Mesh Networking (WMN) technology into Smart Grid, which is recently rising as a potential technology in various areas thanks to its advantages such as low installation costs, high scalability, and high flexibility. Smart Grid is an intelligent, next-generation electrical power network that can maximize energy efficiency by monitoring utility information in real-time and controlling the flow of electricity with IT communications technology converged to the existing power grid. WMNs must be designed for Smart Grid communication systems considering not only the high level of reliability, QoS support and mass-data treatment but also the properties of the traditional power grid. In addition, it is essential to design techniques based on international standards to support interoperability and scalability. In this paper, we evaluate the performance of IEEE 802.11s based Smart Grid Mesh Networks by conducting preliminary simulation studies with the ns-3 simulator. We also outline some challenging issues that should be reviewed when considering WMNs as the candidate for Smart Grid communication infrastructure.