Security Challenges and Solutions in Wireless Mesh Networks

Minseok Oh(오민석) 한국정보기술학회 2012 한국정보기술학회논문지 Vol.10 No.2

A promising, low-cost alternative for providing last-mile wireless connectivity is the concept of Wireless Mesh Networks (WMN). The true potential of any network, however, cannot be exploited without considering and adequately addressing the security issues. The broadcast nature of transmission and the dependency on the intermediate nodes for routing the user traffic leads to security vulnerabilities making the WMN prone to various attacks. In this paper, we will discuss the security vulnerabilities in multi-hop wireless networks that are relevant to the WMN. We will consider the attacks in the MAC layer in the WMN in detail and the possible solution mechanisms in the MAC layer to prevent and detect these attacks.

Provisioning Transmission Paths Given Alarm Collecting Agents

Minseok Oh 한국정보기술학회 2009 한국정보기술학회논문지 Vol.7 No.2

For a reliable communication, all the alarms generated from a node should be delivered to a network management center. In general, before a management center receives alarms, they are collected through agents. It may be ideal for an agent to reside in every communication node, but it will use up the node's resource, such as processing power and communication bandwidth, as well as increase the cost of the node. When agents are deployed in a few selected nodes, however, there are chances that multiple fault may prohibit alarms from reaching the alarm collecting agents assuming the alarms travel along the provisioned path, as does usually in a WAN, such as in SDH/SONET. This paper investigates a way of finding the shortest path while a newly provisioned path does not cause multiple faults to block alarms basing on Bellman-Ford algorithm, and the proposed algorithm is proven mathematically.

Gap Analysis on Wireless Transmission Technologies for VR HMDs

Minseok Oh 한국정보기술학회 2018 한국정보기술학회논문지 Vol.16 No.6

Virtual reality (VR) is gaining popularity due to its ability to engage users on a level which cannot be reached before. However, so far today’s many immersive VR systems have relied on a bothersome tether to send power and high fidelity contents to the headset. To overcome this issue, currently great efforts in development and standardization are being made to provide a wireless connection between a PC console and a VR HMD (head mounted displays). A gap analysis between the requirements for wireless VR HMDs and the capabilities of wireless transmission technologies may help close the gaps for technologies and standards developers. Thus in this paper the technical requirements for a reliable operation of wireless VR HMDs are listed and the capabilities of several candidate technologies for wireless portion of the devices are investigated. Finally areas which require more attention are discussed.

Performance Evaluation of BSS Color and Adaptive Power and Sensitivity Threshold Schemes for WLAN

Minseok Oh(오민석),Youn-Kwan Kim(김윤관) 한국정보기술학회 2017 한국정보기술학회논문지 Vol.15 No.6

Many efforts have been made to obtain high data rate in IEEE 802.11, which is experienced by the users, so that a station may be affected less by the neighboring devices in a Wi-Fi station dense area. The IEEE 802.11ax TG (Task Group) is currently working these effort, called HEW (High Efficiency WLAN). To reduce the effect of neighboring devices, the TG adopted a scheme, called Adaptive Sensitivity Threshold (AST), which changes the CCA (Clear Channel Assessment) threshold dynamically. Another way is to use BSS Coloring in a preamble signal to differentiate the signals from other BSS (Basic Serivce Set). In this paper we analyze the performance of AST and BSS Coloring schemes in various density of APs/STAs through simulation and show that both schemes help improve the throughput performance over 802.11ac.

A Modulation Scheme for Less Flicker in Visible Light Communications

Minseok Oh 한국정보기술학회 2013 한국정보기술학회논문지 Vol.11 No.2

Visible light communications (VLCs) is gaining increasing attention in the field of indoor wireless network as well as outdoor applications. LEDs (light-emitting diodes) in VLC systems serve as a dual role in providing both illumination and wireless connectivity. This paper proposes a way of providing a less flicker data transmission in VLC using a pulse dual slope modulation (PDSM) scheme. Due to its moderately increasing and decreasing pulse characteristic, PDSM effectively reduces the flicker compared to PWM and PPM, the pulse edges of which are abruptly changing. A PDSM can also be used even in an extremely low light condition by additionally controlling the amplitude. And finally a binary symbol detection scheme for the proposed PDSM is provided and an analysis for brightness sensitivity for the pulse slope change is performed for a smooth brightness control. The result indicates that the slope change rate for the same brightness variation are different when the pulse has a flat portion and when it has not.

An Experimental Comparison of Delivery Mechanisms in a Linear Topology

Minseok Oh(오민석) 한국정보기술학회 2011 한국정보기술학회논문지 Vol.9 No.8

In this paper, we compare and analyze the performances of two mesh routing protocols (BATMAN-ADV and FLAME) and a WDS implementation of the IEEE 802.11, all of which run on Layer 2 of the OSI reference model. Sometimes the mesh network may simply form a linear topology to provide a service coverage to a line-shaped area. A linear topology can be built without any routing protocol involved using WDS. The first two routing protocols are a few protocols available in software package incorporated into the OpenWrt OS for embedded systems. Our experiments involves the throughput and delay performance measured on a linear mesh network over varying number of hops between two end nodes. We have used 5.8㎓ channel bands to avoid any interference with existing 802.11g radios. The results show that BATMAN-ADV performs best in throughput and WDS best in delay. The higher throughput of BATMAN-ADV is due to the elaborateness of the routing mechanism and the up-to-date release of BATMAN-ADV over FLAME. The lower delay of WDS is attributed to the structural efficiency of the WDS delivery mechanism.

Performance Evaluation of Dynamic CCA-ED Threshold Control Scheme for WLAN

Minseok Oh(오민석),Hyeonho Na(나현호) 한국정보기술학회 2015 한국정보기술학회논문지 Vol.13 No.12

An effort has been made to achieve and maintain a high data rate, which is actually experienced by the users and less affected by the nearby devices even in a Wi-Fi dense area. An IEEE 802.11ax TG (task group) was formed to standardize these efforts, so called HEW (high efficiency WLAN). As a way of alleviating the effect of nearby devices, the IEEE 802.11ax TG is considering a scheme which changes the CCA (clear channel assessment) threshold dynamically. In this paper we explain how the scheme tries to resolve the hidden terminal problem and the exposed terminal problem at the same time. We also analyze the performance of the dynamic CCA threshold control scheme in various density of APs/STAs through simulation.

A Performance Comparison of Two Mesh Routing Protocols

Minseok Oh 한국정보기술학회 2011 Proceedings of KIIT Conference Vol.2011 No.5

In this paper, we compare two mesh routing protocols, BATMAN-ADV and FLAME, which run on Layer 2 of the OSI reference model. Those are a few protocols available in software package incorporated into the OpenWrt OS for embedded systems. Our experiments involves the throughput and delay performance on a linear mesh network over varying number of hops between end nodes. We have used 5.8 ㎓ channel bands to avoid any interference with existing 802.11g radios. The results show that BATMAN-ADV performs better than FLAME slightly. The better performance is due to the elaborate routing mechanism and up-to-date release of BATMAN-ADV compared to FLAME.

A Binary Search Tree Algorithm for Fault Localization in the Section Layer in a SDH/SONET Ring Network Given Failure Probabilities

Minseok Oh 한국정보기술학회 2008 한국정보기술학회논문지 Vol.6 No.6

In SDH/SONET, ADMs make it possible to have a ring network. The ring topology provides certain advantages in executing a fault localization process. Each section in SDH/SONET may exhibit a different characteristic in terms of its failure, which results in different probabilities of failure. A failure in the section layer produces alarms which are consequently delivered to the fault management center. Once they are collected, those received alarms are checked to find a possible fault section. Each lookup process may be associated with a certain cost or delay, which we want to minimize in this investigation. As a sequential work from the previous study, this paper proposes a minimum cost search tree algorithm for localizing a section failure in a SDH/SONET ring network in light of the search delay, given the probability of each section.

A Hybrid Routing Protocol and Performance Evaluation in a Wireless Mesh Network

Minseok Oh 한국정보기술학회 2011 JOURNAL OF ADVANCED INFORMATION TECHNOLOGY AND CON Vol.1 No.1