• Journal of the Korea Society of Computer and Information
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• v.24 no.12
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• pp.43-50
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• 2019

In this paper, we designed a dynamic TDMA scheme for smooth tactical data distribution in TDMA tactical datalinks. Since the existing tactical datalinks use fixed time radio resources, it is impossible to change the resource status according to network conditions during operation. To overcome these limitations, we designed, implemented, and simulated the DTDMA processing and related messages such as initial timeslot allocation, intermediate time slot allocation, time slot return, and timeslot retrieval. As a result, it was shown that the method of effectively allocating and using timeslot resources according to the situation is applicable. Therefore, we will continue research to manage DTDMA communication on tactical data link in the future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.79-86
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• 2015

Recently, broadcasting environment is dramatically changed due to adopt digital method in broadcasting technology. numerous country is adopting technology for converting analog to digital. However, in the case of South Korean, standard is still indefinite. In this paper, when it broadcast using DAB system, in oder to avoid interference caused by the frequency resource shortage, DAB system is substituted narrow bandwidth DRM+ system. Therefore it considers the way that solve interference. Interference analysis simulation result shows to solve high interference area in DAB environment

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1719-1721
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• 2015

In this paper, we investigate a frequency assignment problem from graph theory for military communications. We propose an algorithm based on the graph coloring theory and confirm that we utilize 0.77 times lower number of frequencies. We also propose a hybrid algorithm that facilitates a trade-off between the range and the spectrum utilization gain.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.7
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• pp.2530-2547
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• 2015

In the recent years, femtocell technology has received a considerable attention due to the ability to provide an efficient indoor wireless coverage as well as enhanced capacity. However, under the spectrum sharing between femtocell user equipment (FUEs) and the owner of spectrum macrocell user equipment (MUEs), both may experience higher uplink interference to each other. This paper proposes a novel distributed power control algorithm for the interference management in two-tier femtocell networks. Due to the assignment of licensed radio frequency to the outdoor macrocell users, the access priority of MUEs should be higher than FUEs. In addition, the quality of service (QoS) of MUEs that is expressed in the target signal-to-interference-plus-noise ratio (SINR) must always be achieved. On the other hand, we consider an efficient QoS provisioning cost function for the low-tier FUEs. The proposed algorithm requires only local information and converges even in cases where the frontiers of available power serve the target SINRs impossible. The advantage of the algorithm is the ability to implement in a distributed manner. Simulation results show that the proposed algorithm based on our cost function provides effective resource allocation and substantial power saving as compared to the traditional algorithms.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.137-142
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• 2015

This paper analyzed the background and status of studies for WRC-15 agenda item which considers additional frequency allocations to the fixed-satellite service in Ku-band and considered national future countermeasures. Satellite frequency can be acquired through compliance with the Radio Regulations for international registration and it has been recognized as the limited natural resource, and which leads to intensifying the competition among countries for the preoccupancy of it. Under the circumstances, WRC-15 is going to consider additional allocations to the fixed-satellite service in Ku-band and it is necessary to cope with the situation taking into account adequate protection of the existing services and future plan of frequency usage by the fixed-satellite service.

• The Transactions of the Korea Information Processing Society
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• v.7 no.8S
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• pp.2722-2728
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• 2000

현재의 인터넷 망을 이용하여 음성, 화상 정보를 실시간으로 이용하고자 하는 다양한 응용이 시도되고 있다. 차세대 통신으로 주목 받고 있는 IMT-2000에서도 기존의 회선 교환망 대신 인터넷 망을 이용함으로써 경제성, 관리의 편의성, 새로운 서비스의 창출이 가능한 등의 이점이 있다. 인터넷 망이 최선의 노력(best effort)만을 제공하기 때문에 발생되는 신뢰성과 지연의 문제는 이미 많은 연구가 있어왔고 현재 어느 정도의 서비스 품질을 획득하여 VoIP(Voice Over Internet Protocol)와 같은 서비스가 실제로 이용되고 있다. 그러나 무선 통신의 경우는 이에 더하여 무선 구간에서의 자원 할당의 문제가 남아 있다. 본 연구에서는 코어 망으로 인터넷 프로토콜을 사용하는 차세대 All-IP 망에서, 무선 이동단말 간의 멀티미디어 서비스가 가능하도록 효율적인 주파수 할당을 지원하는 QoS 관리자를 설계하였다. 제안한 QoS(Quality Of Service)관리자는 요구 대역폭이 다른 멀티미디어 호 요청에 대해 융통성 있는 주파수 할당이 가능하도록 대국의 QoS 관리자와의 협상을 통해 제한된 범위 내에서 서비스 품질을 조절하여 보다 많은 호 연결 요청이 성공할 수 있도록 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.04a
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• pp.530-533
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• 2015

기존의 조사에 따르면 현재 소프트웨어 개발 프로젝트의 실패율은 높은 편이다. 미국의 The Standish Group의 보고서에 따르면 소프트웨어 프로젝트의 성공률은 약 32%로 낮음을 볼 수 있다. 소프트웨어 프로젝트 성공에 영향을 주는 요소 중 하나는 인력배치이다. 이는 소프트웨어 개발 프로젝트의 참여 인력 구성에 따라 생산성, 비용 및 개발기간이 달라지게 되기 때문이다. 즉 인력 구성에 따라 프로젝트 성공률에 많은 영향을 주게 될 수 있다. 프로젝트 인력할당은 WBS(Work Breakdown Structure)에 따라 PM(Project Manager) 또는 부서장이 할당하게 되는데, 이들은 프로젝트 구성원들의 상세한 정보까지 파악이 어렵기 때문에 인력구성의 어려움이 존재한다. 과거에 수행했던 개발 프로젝트에서 유사성이 높은 작업을 했음에도 불구하고 전혀 경험이 없는 작업에 할당되면 상대적으로 업무 지식습득에 어려움을 겪고 시간 지연에 따른 비용이 추가적으로 발생하게 된다. 이러한 문제를 해결하고자 본 연구는 소프트웨어 개발 프로젝트 구성원의 상세한 정보들과 소프트웨어 개발 업무와의 유사도 측정을 통해 인력을 업무에 할당하는 기법을 제안한다. 이를 위하여 제안한 기법을 프로토타입으로 구현한 후 현업에서 실제 개발되는 프로젝트에 적용하여 제안 기법의 우수함을 평가한다.

• Journal of Information Processing Systems
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• v.17 no.3
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• pp.615-629
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• 2021

With the development of mobile edge computing, how to utilize the computing power of edge computing to effectively and efficiently offload data and to compute offloading is of great research value. This paper studies the computation offloading problem of multi-user and multi-server in mobile edge computing. Firstly, in order to minimize system energy consumption, the problem is modeled by considering the joint optimization of the offloading strategy and the wireless and computing resource allocation in a multi-user and multi-server scenario. Additionally, this paper explores the computation offloading scheme to optimize the overall cost. As the centralized optimization method is an NP problem, the game method is used to achieve effective computation offloading in a distributed manner. The decision problem of distributed computation offloading between the mobile equipment is modeled as a multi-user computation offloading game. There is a Nash equilibrium in this game, and it can be achieved by a limited number of iterations. Then, we propose a distributed computation offloading algorithm, which first calculates offloading weights, and then distributedly iterates by the time slot to update the computation offloading decision. Finally, the algorithm is verified by simulation experiments. Simulation results show that our proposed algorithm can achieve the balance by a limited number of iterations. At the same time, the algorithm outperforms several other advanced computation offloading algorithms in terms of the number of users and overall overheads for beneficial decision-making.

• Journal of Communications and Networks
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• v.16 no.4
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• pp.397-406
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• 2014

Radio frequency (RF) jamming is a denial of service attack targeted at wireless networks. In resource-hungry scenarios with constant traffic demand, jamming can create connectivity problems and seriously affect communication. Therefore, the vulnerabilities of wireless networks must be studied. In this study, we investigate a particular type of RF jamming that exploits the semantics of physical (PHY) and medium access control (MAC) layer protocols. This can be extended to any wireless communication network whose protocol characteristics and operating frequencies are known to the attacker. We propose two efficient jamming techniques: A low-data-rate random jamming and a shot-noise based protocol-aware RF jamming. Both techniques use shot-noise pulses to disrupt ongoing transmission ensuring they are energy efficient, and they significantly reduce the detection probability of the jammer. Further, we derived the tight upper bound on the duration and the number of shot-noise pulses for Wi-Fi, GSM, and WiMax networks. The proposed model takes consider the channel access mechanism employed at the MAC layer, data transmission rate, PHY/MAC layer modulation and channel coding schemes. Moreover, we analyze the effect of different packet sizes on the proposed jamming methodologies. The proposed jamming attack models have been experimentally evaluated for 802.11b networks on an actual testbed environment by transmitting data packets of varying sizes. The achieved results clearly demonstrate a considerable increase in the overall jamming efficiency of the proposed protocol-aware jammer in terms of packet delivery ratio, energy expenditure and detection probabilities over contemporary jamming methods provided in the literature.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.4
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• pp.371-380
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• 2020

Video is principal information that facilitates commander's immediate command decision. Due to fading characteristics of radio link, however, it is difficult to stably transmit video in a multi-hop wireless environment. In this paper, we propose a MANET structure composed of a link adaptive routing protocol and a TDMA MAC protocol to stably transmit video traffic in a ultra-narrowband video streaming network. The routing protocol can adapt to link state change and select a stable route. The TDMA protocol enables collision-free video transmission to a destination using multi-hop dynamic resource allocation. As a result of simulation, the proposed MANET structure shows better video transmission performance than proposed MANET structure without link quality adaption, AODV with CSMA/CA, and OLSR with CSMA/CA structures.