• Journal of Advanced Navigation Technology
• /
• v.14 no.4
• /
• pp.495-503
• /
• 2010

The clustering is an important mechanism thai provides information for mobile nodes efficiently and improves the processing capacity for routing and the allocation of bandwidth. This paper proposes a clustering scheme based on the fuzzy relevance degree to solve problems such as node distribution found in the dynamic property due to mobility and flat structure and to enhance the routing performance. The proposed scheme uses the fuzzy relevance degree, ${\alpha}$, to select the cluster head for clustering in FSV (Fuzzy State Viewing) structure. The fuzzy relevance ${\alpha}$ plays the role in CH selection that processes the clustering in FSV. The proposed clustering scheme is used to solve problems found in existing 1-hop and 2-hop clustering schemes. NS-2 simulator is used to verify the performance of the proposed scheme by simulation. In the simulation the proposed scheme is compared with schemes such as Lowest-ID, MOBIC, and SCA. The simulation result showed that the proposed scheme has better performance than the other existing compared schemes.

• Journal of Advanced Navigation Technology
• /
• v.20 no.3
• /
• pp.238-245
• /
• 2016

There are technological, operational and environmental constraints at tactical edge, which are disconnected operation, intermittent connectivity, and limited bandwidth (DIL), size, weight and power (SWaP) limitations, ad-hoc and mobile network, and so on. To overcome these limitations and constraints, we use service-oriented architecture (SOA) based technologies. Moreover, the operation environment is highly dynamic: requirements change in response to the emerging situation, and the availability of resources needs to be updated constantly due to the factors such as technical failures. In order to use appropriate resources at the right time according to the mission, it needs to find the best resources. In this context, we identify ontology-based mission service model including mission, task, service, and resource, and develop capability-based matching in tactical edge environment. The goal of this paper is to propose a capability-based semantic matching for dynamic resource allocation. The contributions of this paper are i) military domain ontologies ii) semantic matching using ontology relationship; and (iii) the capability-based matching for the mission service model.

• Journal of Advanced Navigation Technology
• /
• v.13 no.1
• /
• pp.54-61
• /
• 2009

In this paper, Switching to digital TV broadcasting and mobile operators license expiration period of the frequency, time and 700MHz, 800MHz and 900MHz frequency band plan for the redistribution is actively being discussed. Redistribution policy direction of these frequency 800MHz (bandwidth 10MHz) integrated command frequency for wireless networks(i.e TETRA) is expected to be considered a redistribution. These Integrated Wireless Network Infrastructure configurations at the time and data communication capabilities of the system unwilling TETRA Release 2 standard for the system is presented. This system is analyzed that Release 1 of the existing system takes up more than 6 times the increase of frequency bands. Therefore, integration of the frequency band assigned to the command of a wireless network with the introduction of advanced systems will not be able to do. In this paper to the digital TV transition, and the policy based on analysis of trends in the 700MHz band for the integration of wireless networks, provides policy direction for the allocation plan.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.7B
• /
• pp.668-678
• /
• 2006

In designing a video-on-demand (VoD) system, one of the major challenges is how to reduce the viewer's waiting time maintaining a given bandwidth allocation and how to reduce the client's buffer requirements. To solve these problems, many VoD schemes were proposed. However, most VoD schemes require managing many segments of a video, frequency channel hopping, and using many channels at the same time. Therefore, to the complexity is a barrier to implementation. In this paper, we propose a fast staggered broadcasting scheme which has a simple structure and substantially improved VoD efficiency. The numerical results demonstrate that the viewer's waiting time of the fast staggered broadcasting scheme is close to the fast broadcasting scheme and the buffer requirements of this can be adapt for demanding rate by adjusting the short front part of a video sizes.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.5A
• /
• pp.433-440
• /
• 2007

In this paper, we have proposed WiBro receiver structure employing joint adaptive antenna scheme at the base station (BS) and the mobile station (MS) and evaluated its performance. In WiBro system, the joint use of transmit beamforming at BS and receive beamforming at MS can improve the SINR significantly and increase the capacity compared to the conventional system. Moreover, power allocation level can be decreased because channel variation can be reduced by using the jointly updated weight. However, it needsthe calculation of the antenna weights in every subcarrier for performance improvement. This could imply an enormous computational burden. However, the computational complexity can be reduced significantly by using the same set of the antenna weights for the adjacent subcarriers instead of calculating antenna weights for every subcarrier. We have analyzed the impact of subcarrier grouping for weight calculation on the system performance.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.3B
• /
• pp.325-338
• /
• 2004

As the recent rapid development of internet technology and the wide spread of multimedia communication, massive increase of network traffic causes some problems such as the lack of network paths and the bad quality of service. To resolve these problems, this paper presents a traffic control agent that can perform the dynamic resource allocation by controlling traffic flows on a DiffServ network. In addition, this paper presents a router that can support DiffServ on Linux to support selective QoS in IP network environment. To implement a method for selective traffic transmission based on priority on a DiffServ router, this paper changes the queuing discipline in Linux, and presents the traffic control agent so that it can efficiently control routers, efficiently allocates network resources according to service requests, and relocate resources in response to state changes of the network. Particularly for the efficient processing of Assured Forwarding(AF) Per Hop Behavior(PHB), this paper proposes an ACWF$^2$Q$^{+}$ packet scheduler on a DiffServ router to enhance the throughput of packet transmission and the fairness of traffic services.s.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2011.05a
• /
• pp.344-347
• /
• 2011

Unlike a terrestrial wireless sensor network which uses radio waves, UWASN(Underwater Acoustic Sensor Network) relies on acoustic waves. There are lots of ongoing researches for long latency and limited bandwidth of underwater sensor network by using acoustic wave. Packets transferred by node often colide in underwater sensor network due to long latency. To solve this kind of problem, in general, Back-off scheme which is used in wireless network is used. However, fixed Slot-time according to node allocation generates useless time delay, and this lowers network performance. In this thesis, active setting technique of Slot-time is proposed, and applied for already studied MAC protocol. At the conclusion, it was proved that the MAC protocol using the proposed scheme has better performance than existing MAC protocol as a result comparison.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.7C
• /
• pp.713-724
• /
• 2006

The purpose of this study is to design, implement and verify the pre-modulation filter with the variable -3dB cutoff frequency and linear phase response for bandlimiting the allocation of radio frequency bandwidth for PCM/FM transmission. For the design of this required filter, the digital FIR filter, DAC system and tuneable 2nd order LPF have been constructed and simulated according to the attenuation characteristic requirement of the amplitude frequency response by each stage. From these results, we have implemented the filter and verified the analog conversion hardware part which is composed of DAC system and tuneable 2nd order LPF for the interpolation of the discrete sequences. Especially this paper proposes and carries out the verification processes using the tone generator and the calibration procedures for more precise frequency response of the filter.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.27 no.8C
• /
• pp.803-811
• /
• 2002

Asynchronous Transfer Mode-Passive Optical Network(ATM-PON) Technology is one of the best solutions for implementation of broadband access network. In this paper, we propose a new Dynamic Bandwidth Allocation (DBA) algorithm for ATM-PON systems. The DBA is a key technique for data traffic management. DBA has been studied widely to allow ATM-PON to transport data traffic cost-effectively and efficiently, and currently a hot standardization issue in Full Service Access Network(FSAN) and ITU-T. The proposed DBA algorithm efficiently manages the user traffics according to their service categories. Performance of the proposed algorithm, in aspect of Cell Transfer Delay(CTD) and Cell Delay Variation(CDV), is evaluated using computer simulation.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.37 no.2A
• /
• pp.83-94
• /
• 2012

Various wireless communication devices or network such as WRAN and WLAN will coexist in the TVWS(TV White Space). Because of this coexistence, the wireless devices which use the TVWS have to avoid interfering to not only licensed TV receiver and wireless microphone but also homogeneous or heterogeneous TVBD(TV Band Device)s. In this paper, we propose two frequency sharing methods for the coexistence of WLAN and WRAN in terms of interference reduction and throughput enhancement in both homogeneous and heterogeneous networks. One is the WRAN spectrum etiquette to provide more wide bandwidth for WLAN users and the other is the WLAN frequency selection methods to improve the throughput performance. The simulation results have confirmed the throughput improvement of the proposed methods. Moreover, the proposed methods is also applicable to improve the throughput performance and reduce interference of similar systems working in a cognitive manner.