• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.1
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• pp.47-58
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• 2018

The heterogeneous cellular network (HCN) is most significant as a key technology for future fifth generation (5G) wireless networks. The heterogeneous network considered consists of randomly macrocell base stations (MBSs) overlaid with femtocell base stations (BSs). The stochastic geometry has been shown to be a very powerful tool to model, analyze, and design networks with random topologies such as wireless ad hoc, sensor networks, and multi- tier cellular networks. The HCNs can be energy-efficiently designed by deploying various BSs belonging to different networks, which has drawn significant attention to one of the technologies for future 5G wireless networks. In this paper, we propose switching off/on systems enabling the BSs in the cellular networks to efficiently consume the power by introducing active/sleep modes, which is able to reduce the interference and power consumption in the MBSs and FBSs on an individual basis as well as improve the energy efficiency of the cellular networks. We formulate the minimization of the power onsumption for the MBSs and FBSs as well as an optimization problem to maximize the energy efficiency subject to throughput outage constraints, which can be solved the Karush Kuhn Tucker (KKT) conditions according to the femto tier BS density. We also formulate and compare the coverage probability and the energy efficiency in HCNs scenarios with and without coordinated multi-point (CoMP) to avoid coverage holes.

• International Journal of Internet, Broadcasting and Communication
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• v.10 no.1
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• pp.11-15
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• 2018

The application of Wireless Sensor Networks requires a wise utilization of limited energy resources. Therefore, a wide range of routing protocols with a motivation to prolong the lifetime of a network has been proposed in recent years. Hierarchical clustering based protocols have become an object of a large number of studies that aim to efficiently utilize the limited energy of network components. In this paper, the effect of mismatch in parameter estimation is discussed to evaluate the robustness of a distanced based algorithm called distributed clustering protocol in homogeneous and heterogeneous environment. For quantitative analysis, performance simulations for this protocol are carried out in terms of the network lifetime which is the main criteria of efficiency for the energy limited system.

• Journal of Information Processing Systems
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• v.6 no.3
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• pp.269-294
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• 2010

The interconnection of mobile devices in urban environments can open up a lot of vistas for collaboration and content-based services. This will require setting up of a network in an urban environment which not only provides the necessary services to the user but also ensures that the network is secure and energy efficient. In this paper, we propose a secure, energy efficient dynamic routing protocol for heterogeneous wireless sensor networks in urban environments. A decision is made by every node based on various parameters like longevity, distance, battery power which measure the node and link quality to decide the next hop in the route. This ensures that the total load is distributed evenly while conserving the energy of battery-constrained nodes. The protocol also maintains a trusted population for each node through Dynamic Trust Factor (DTF) which ensures secure communication in the environment by gradually isolating the malicious nodes. The results obtained show that the proposed protocol when compared with another energy efficient protocol (MMBCR) and a widely accepted protocol (DSR) gives far better results in terms of energy efficiency. Similarly, it also outdoes a secure protocol (QDV) when it comes to detecting malicious nodes in the network.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1023-1026
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• 2005

In the ubiquitous computing environment, an intelligent vehicle is defined as a sensor node with a capability of intelligence and communication in a wire and wireless network space. To make it real, a lot of problems should be addressed in the aspect of vehicle mobility, in-vehicle communication, common service platform and the connection of heterogeneous networks to provide a driver with several intelligent information services beyond the time and space. In this paper, we present an intelligent information system for managing in-vehicle sensor network and a vehicle gateway for connecting the external networks. The in-vehicle sensor network connected with several sensor nodes is used to collect sensor data and control the vehicle based on CAN protocol. Each sensor node is equipped with a reusable modular node architecture, which contains a common CAN stack, a message manager and an event handler. The vehicle gateway makes vehicle control and diagnosis from a remote host possible by connecting the in-vehicle sensor network with an external network. Specifically, it gives an access to the external mobile communication network such as CDMA. Some experiments was made to find out how long it takes to communicate between a vehicle's intelligent information system and an external server in the various environment. The results show that the average response time amounts to 776ms at fixed place, 707ms at rural area and 910ms at urban area.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.77-88
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• 2010

Wireless Mesh Networks are consist of mobility mesh clients and mesh routers. WMNs can communicate with heterogeneous networks such as IEEE 802.11, IEEE 802.15, IEEE 802.16 and sensor networks. WMNs which is based on ad hoc network are on research and developing to enhance WLANs, WPANs, or WMANs. WMNs can offer environment to serve human, service to person area, campus, and metro. But WMNs has many problems to solve about enhancing performance and generalization. Among them, Existing protocol layers has many problems enhancing to optimize WMNs. This document issues problems about WMNs in protocol layer and suggest the solutions. Also, suggests the requirements and the methods of QoS supporting issue.

• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.73-76
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• 2005

The advanced information and communication technology gives vehicles another role of the third digital space, merging a physical space with a virtual space in a ubiquitous society. In the ubiquitous environment, the vehicle becomes a sensor node, which has a computing and communication capability in the digital space of wired and wireless network. An intelligent vehicle information system with a remote control and diagnosis is one of the future vehicle systems that we can expect in the ubiquitous environment. However, for the intelligent vehicle system, many issues such as vehicle mobility, in-vehicle communication, service platform and network convergence should be resolved. In this paper, an in-vehicle gateway is presented for an intelligent vehicle information system to make an access to heterogeneous networks. It gives an access to the server systems on the internet via CDMA-based hierarchical module architecture. Some experiments was made to find out how long it takes to communicate between a vehicle's intelligent information system and an external server in the various environment. The results show that the average response time amounts to 776ms at fixec place, 707ms at rural area and 910ms at urban area.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06b
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• pp.441-445
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• 2008

기존 무선 센서 네트워크 분야에서의 연구는 단일기종 환경이라는 가정하에서 진행되었다. 최근 정보수집 기법이나 라우팅 프로토콜의 경우 클러스터링 기반의 이기종 환경에서 더 높은 에너지 효율을 보이고 있다. 네트워크의 수명이 길어지고, 이를 기반으로 동작하는 응용에 대한 요구가 다양해 짐에 따라 동적 재구성에 대한 요구도 높아지고 있다. 본 논문에서는 이기종 환경을 기반으로 보다 효율적인 동적 재구성 기법을 제안한다. 제안한 기법은 무선 센서 네트워크의 특성을 반영하며, 대규모의 네트워크를 지원할 수 있도록 설계했다. 시뮬레이션 결과를 통해, 제안한 기법이 기존의 기법에 비해 우수하다는 것을 검증한다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11b
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• pp.373-375
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• 2005

디지털 홈이 구체화되면서 실내 환경조절, 방법, 가전기기 제어, 건강 모니터링 분야에서 센서 네트워크가 활용됨에 따라 이질적인 센서 네트워크간의 정보교환에 대한 요구가 증대하고 있다. 본 논문에서는 이러한 홈 환경에서 이질적인 센서 네트워크간 정보교환을 위한 메카니즘으로 홈 서버를 이용한 상호운영성 미들웨어 구조(Interoperable Middleware Architecture)를 제안한다. 이를 위하여, 홈 서버와 센서 네트워크 미들웨어 구조를 소개하고, 미들웨어가 상호운영성을 제공하기 위한 정보교환 메시지 포맷을 정의한다. 메시지 교환 양식은 XML 문서를 이용하고, 메시지 전송을 위한 프로토콜로 SOAP(Simple Object Access Protocol)을 선정한다. 본 논문의 적절성을 검증하기 위하여 홈 환경에서 이종 센서 네트워크간 점보교환 사례연구를 실시하고 이를 통해 확장성과 유연성을 보유한 정보교환 메카니즘의 효과를 확인한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.612-614
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• 2012

센서 네트워크는 센싱 기능과 데이터 처리 그리고 무선 통신기능을 갖춘 많은 노드로 이루어져 있다. 센서 노드는 제한적인 CPU, 배터리 그리고 저장공간과 같은 제약사항을 가지고 있기 때문에 시간이 지날수록 노드의 수명이 다해 전체 적인 네트워크의 성능은 감소하게 된다. 본 논문에서는 이기종 센서 네트워크에서 노드 개수에 따른 작업 수행 시간의 분석을 통해 센서 네트워크의 수명을 판단한다. 성능 평가 결과 계층 기반의 라우팅 기법의 경우 클러스터 수의 비율이 네트워크의 수명에 큰 영향올 주는 것을 알 수 있다.

• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.958-961
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• 2008

유비쿼터스 컴퓨팅 기술의 진보로 무선 센서 네트워크의 관심이 높아지고 있다. 센서 네트워크는 MAC 프로토콜에서 정해진 전송 스케줄에 따라 주기적인 수면(sleep)을 통해 에너지를 절약하는 연구가 진행되어 왔다. 그리고 센서 노드가 센싱한 데이터를 BS(Base Station)로 전달하기 위한 라우팅 경로 기법과 클러스터링 기법 등이 제시되고 있다. 센서 네트워크에서 가장 중요한 이슈중의 하나는 제한된 자원 즉, 센서 노드에 주어진 에너지를 활용하여 네트워크의 수명을 최대로 연장 하는 것이다. 본 논문에서는 S-MAC 프로토콜의 스케줄관리 기법을 이용하여 무선 센서 네트워크에서 서로 다른 그룹 간의 통신을 원활하게 하기 위한 통신기법을 제시한다.