• 디지털산업정보학회논문지
• /
• 제6권3호
• /
• pp.103-109
• /
• 2010

Total performance is improved by minimizing the channel interference between links in wireless mesh networks (WMNs). The paper refines on the CB-CA [1] to be suitable for multi-radio multi-channel (MRMC) WMNs. The CB-CA is the cluster-based channel assignment algorithm for one radio three channel WMN based on IEEE 802.11b/g. The CB-CA does not perform the channel scanning and the channel switching between the cluster heads (CHs) and the edge gateway nodes (EGs). However, the use of co-channel for links between CHs and EGs brings the problem of channel interference among many nodes. We propose and evaluate an improved CB-CA algorithm to solve this problem in MRMC WMNs. The proposed algorithm discriminates between transmission channel and receive channel and assigns channels to each interface randomly and advertises this information to neighbor clusters in order to be assigned no-interference channel between clusters. Therefore, the proposed algorithm can minimize the interference between clusters and also improve QoS, since it can use multiple interfaces and multiple channels.

• 한국IT서비스학회지
• /
• 제11권2호
• /
• pp.291-306
• /
• 2012

Recently, Wireless Mesh Network (WMN) technology recently has been used in various industries. Especially, a number of multi-channel assignment schemes have been presented to improve the throughput of IEEE 802.11-based multi-hop WMN. However, performance of the conventional multi-channel assignment schemes is not enough to satisfy the industry requirements. We, thus, should study more about the multi-channel assignment scheme in order to enhance the performance. This paper proposes a novel channel assignment scheme that employs Multi-channel and Multi-Interface in the WMN. The proposed scheme can obtain the traffic information of the network and the efficient channel assignment result without any message exchanges. We verify the efficiency of the proposed scheme through the mathematical modeling and the real-world experiments. The results show that the proposed scheme improves the throughput of the network compared with the conventional schemes.

• 한국군사과학기술학회지
• /
• 제14권5호
• /
• pp.880-887
• /
• 2011

The Wireless Mesh Network(WMN) technology is able to provide an infrastructure for isolated islands, in which it is difficult to install cables or wide area such as battlefield. Therefore, WMN is frequently used to satisfy needs for internet connection and active studies and research on them are in progress. However, as a result of increase in number of hops under hop-by-hop communication environment has caused a significant decrease in throughput and an increase in delay. Considering the heavy traffic of real-time data, such as voice or moving pictures to adaptive WMN, in a military environment. Such phenomenon might cause an issue in fairness index. In order to resolve this issue, we proposed a Cluster Based Multi-channel Assignment Scheme(CB-MAS) for adaptive tactical wireless mesh network. In the CB-MAS, the communication between the Cluster-Head(CH) and cluster number nodes uses a channel has no effect on channels being used by the inter-CH links. Therefore, the CB-MAS can minimize the interference within multi-channel environments. Our Simulation results showed that CB-MAS achieves improved the throughput and fairness index in WMN.

• 한국정보과학회논문지:정보통신
• /
• 제29권5호
• /
• pp.459-465
• /
• 2002

동적 토폴로지 특성을 가지는 애드-혹 네트워크에서의 응용들 중 많은 부분이 그룹 통신을 기반으로 하고 있다. 그러나 현재의 멀티캐스팅은 각 그룹에 대하여 트리나 메쉬와 같은 멀티캐스트 하부 구조를 기반으로 동작하므로, 동적으로 토폴로지가 변화하는 환경에서는 많은 오버헤드를 야기시킨다. 따라서 본 논문에서는 응용의 특성상 소규모 그룹 통신이 주종을 이루는 애드-혹 네트워크 환경에서 멀티캐스트 하부 구조를 구축하지 않고 유니캐스트 라우팅 테이블만을 기반으로 멀티캐스팅 서비스를 제공하는 새로운 기법을 제안한다.

• Journal of Information Technology Applications and Management
• /
• 제15권1호
• /
• pp.261-270
• /
• 2008

Wireless Mesh Networks (WMNs) have emerged as one of the new hot topics in wireless communications. WMNs have been suggested for use in situations in which some or all of the users are mobile or are located in inaccessible environments. Unconstrained transmission in a WMN may lead to the time overlap of two or more packet receptions, called collisions or interferences, resulting in damaged useless packets at the destination. There are two types of collisions; primary collision, due to the transmission of the stations which can hear each other, and hidden terminal collision, when stations outside the hearing range of each other transmit to the same receiving stations. For a WMN, direct collisions can be minimized by short propagation and carrier sense times. Thus, in this paper we only consider hidden terminal collision while neglecting direct collisions. To reduce or eliminate hidden terminal collision, code division multiple access (CDMA) protocols have been introduced. The collision-free property is guaranteed by the use of spread spectrum communication techniques and the proper assignment of orthogonal codes. Such codes share the fixed channel capacity allocated to the network in the design stage. Thus, it is very important to minimize the number of codes while achieving a proper transmission quality level in CDMA WMNs. In this paper, an efficient heuristic code assignment algorithm for eliminating hidden terminal collision in CDMA WMNs with general topology.

• 한국통신학회논문지
• /
• 제40권8호
• /
• pp.1469-1476
• /
• 2015

본 논문은 원형배열 안테나를 사용하는 무선 메쉬 네트워크 환경에서 코드북을 이용한 다중 섹터 빔 형성시 섹터간 SIR 향상 빔 선택 알고리즘을 제안한다. 제안된 빔 선택 알고리즘은 피드백 되는 코드북 인덱스 조합에 따라 상호간 SIR을 향상시키는 빔 선택방법과 QoS를 보장하는 방법에 관한 내용이다. 전산 모의 실험을 통해 노드들이 섹터경계에 있을 경우 제안한 방법이 기존의 코드북 선택 방법보다 SIR이 4.42dB 우수함을 보였다. QoS를 위해 PF를 적용할 경우 기존보다 SIR이 1.70dB만큼 향상됨을 보였고 사용자간 QoS도 만족시킴을 보였다.

• 제어로봇시스템학회논문지
• /
• 제22권11호
• /
• pp.984-990
• /
• 2016

In wireless mesh sensor networks (WMSNs), sensor nodes are connected in the form of a mesh topology and transfer sensor data by multi-hop routing. A data aggregation method for WMSNs is required to minimize the number of routing hops and the energy consumption of each node with limited battery power. This paper presents a shortest path data aggregation method for WMSNs. The proposed method utilizes a simple hash function based on shuffled row major indexing for addressing sensor nodes. This allows sensor data to be aggregated without complex routing tables and calculation for deciding the next hop. The proposed data aggregation algorithms work in a fractal fashion with different mesh sizes. The method repeatedly performs gathering and moves sensor data to sink nodes in higher-level clusters. The proposed method was implemented and simulations were performed to confirm the accuracy of the proposed algorithms.

• 전기학회논문지
• /
• 제68권1호
• /
• pp.207-214
• /
• 2019

A large-capacity wireless power system is a technology that transmits electric power of kW or more in a noncontact type. Electric cars, electric buses, and electric railways. In order to increase the power transmission efficiency, a resonance method using a frequency of kHz is applied and the efficiency is 80 ~ 90%. In this case, the loss is 10 ~ 20% other than efficiency, and corresponds to several hundreds of W to several kW in kW class wireless power transmission. 35 kW wireless feed system environment, and induced current in the nearby conductive part was measured. As a result of analysis, it was confirmed that induction phenomenon is higher as the loop configuration of the conductive part per area is dense. The increase of the induced current in the mesh loop is characterized by the density of the nearby conductive part having a permeability per unit area. The concentration of the magnetic field by the permeability is increased and the induction phenomenon causing the induction current is increased. It was confirmed that induction phenomenon increases by about 2.7 times when 9 times dense structure is formed.

• 한국정보처리학회:학술대회논문집
• /
• 한국정보처리학회 2011년도 춘계학술발표대회
• /
• pp.844-847
• /
• 2011

Wireless mesh network (WMN) is a type of mobile ad-hoc network consists of wireless router, mobile clients and gateway which connects the network with the Internet. To provide security in the network it is required to encrypt the message sent among the communicating nodes in such way so that only legitimate user can retrieve the original data. Several security mechanisms have been proposed so far to enhance the security of WMN. However, there still exists a need for a comprehensive mechanism to prevent attacks in data communication. Considering the characteristic of mesh network, in this paper we proposed a public key cryptography based security architecture to establish a secure key agreement among communicating nodes in mesh network. The proposed security architecture consists of two major sections: client data protection and network data protection. Client data protection deals with the mutual authentication between the client and the access router and provide client to access router encryption for data confidentiality using standard IEEE 802.11i protocol. On the other hand, network data protection ensures encrypted routing and data transfer in the multi hop backbone network. For the network data protection, we used the pre-distributed public key to form a secure backbone infrastructure.

• 인터넷정보학회논문지
• /
• 제15권3호
• /
• pp.63-69
• /
• 2014

IEEE 802.11p 차량 네트워크 환경 (WAVE)에서는 차량 운전자의 안전을 위해서 주기적으로 안전 메시지를 전송하도록 되어 있다. 차량 안전 메시지의 전송을 통해 도로상의 안전과 주행 효율을 제공하기 위해서 WAVE 표준에서는 멀티 채널 멀티 라디오 환경을 제안하고 있다. 그러나 WAVE 표준안은 안전메세지를 하나의 물리 디바이스에 하나의 채널을 이용하여 제어하고 전송하는 것으로 정의되어 있어서 다중 라디오 환경과 안전 메시지 전송 효율성을 고려하지 않았다. 또한 네트워크 무선상에서 서로 충돌이 일어나지 않는 채널을 할당하는 채널 할당은 네트워크 망구성방식을 잘 알고 있거나 모든 노드들이 같은 전송률을 가지는 무선 대역에 있어도 NP-hard한 문제로 잘 알려져 있다. 본 논문에서는 최신 802.11p와 1609.4 802.11p 표준을 이용해서 다중 채널 다중 라디오 WAVE 환경을 무선 메쉬 네트워크로 가정하여 Nash 협상 게임을 통해서 서로 간섭이 없는 채널을 할당하는 방법을 제안하고자 한다. 본 제안된 알고리즘은 시뮬레이션을 통해서 검증하였고 해당 알고리즘이 8채널 3 라디오 환경에서 랜덤 채널 할당 방법이나 Tabu 알고리즘 보다 효율성이 좋다는 것을 입증하였다.