• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.97-100
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• 1997

Fieldbuses are used as the lowest level communication network for real-time communication in factory automation and process control systems. Data generated from field devices can be divided into three categories: sporadic real-time, periodic real-time and non real-time data. Since these data share one fieldbus network medium, it needs a method that allocate the limited bandwidth of fieldbus network to the sporadic real-time, periodic real-time and non real-time traffic. This paper introduces an implementation method of bandwidth allocation scheme introduced in [51 on PROFIBUS. Using the modified PROFIBUS FDL(Fieldbus Data Link layer), the bandwidth allocation scheme introduced in [51 is verified by the experiments.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2002.11a
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• pp.232-236
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• 2002

In this paper, a new compact PIFA, applicable to PCS system, is described. The central aim in design is to broaden the bandwidth within limited height of mobile phones. To overcome the narrow bandwidth characteristics, which is typical of a patch antenna, tapered type radiation patch is employed. The antenna is designed using CST microwave studio and its characteristics are compared with a basic PIFA with similar volume.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.484-489
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• 2002

This paper concerns the design and implementation of a Bandwidth Variable Digital Chirp Generator (DCG) for the radar altimeter. A double SRAM parallel structure is used to breakthrough the upper DCG bandwidth limited by the highest clock frequency of the digital chips. An experimental system working in the waveform storage method has been implemented. We show that the bandwidth changed according to the radar altimeter's requirement and the design released the stringent speed requirement of the chips fur making a variable wide bandwidth DCG.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.9
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• pp.963-971
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• 1992

A (4,6) block binary line code is proposed. In addition to being de-free and runlength-limited, the new code called MB46 is strictly bandwidth-limited to the Nyquist frequency, thus achieving improved bandwidth efficiency over previously known binary line code. A technique specially employed in the design of the code is described in depth, and some performance measures including the eye pattern and the power spectrum are presented as obtained by simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.380-387
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• 2011

While mobile IPTV services are supported through the mobile WiMAX networks, there must need some guaranteed bandwidth for the IPTV services especially if IPTV and non-IPTV services are simultaneously supported by the mobile WiMAX networks. The quality of an IPTV service definitely depends on the allocated bandwidth for that channel. However, due to the high quality IPTV services and to support of huge non-IPTV traffic over mobile WiMAX networks, it is not possible to guarantee the sufficient amount of the limited mobile WiMAX bandwidth for the mobile IPTV services every time. A Service Level Agreement (SLA) between the mobile IPTV service provider and mobile WiMAX network operator to reserve sufficient bandwidth for the IPTV calls can increase the satisfaction level of the mobile IPTV users. In this paper, we propose a SLA negotiation procedure for mobile IPTV users over mobile WiMAX networks. The Bandwidth Broker controls the allocated bandwidth for IPTV and non-IPTV users. The proposed dynamically reserved bandwidth for the IPTV services increases the IPTV user's satisfaction level. The simulation results state that, our proposed scheme is able to provide better user satisfaction level for the IPTV users.

• Journal of Communications and Networks
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• v.16 no.3
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• pp.322-334
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• 2014

Multimedia content is very sensitive to packet loss and therefore multimedia streams are typically protected against packet loss, either by supporting retransmission requests or by adding redundant forward error correction (FEC) data. However, the redundant FEC information introduces significant additional bandwidth requirements, as compared to the bitrate of the original video stream. Especially on wireless and mobile networks, bandwidth availability is limited and variable. In this article, an adaptive FEC (A-FEC) system is presented whereby the redundancy rate is dynamically adjusted to the packet loss, based on feedback messages from the client. We present a statistical model of our A-FEC system and validate the proposed system under different packet loss conditions and loss probabilities. The experimental results show that 57-95%bandwidth gain can be achieved compared with a static FEC approach.

• Journal of Industrial Technology
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• v.27 no.A
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• pp.131-139
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• 2007

The recent advance in wireless network technologies has enabled the streaming media service on the mobile devices such as PDAs and cellular phones. Since the wireless network has low bandwidth channels and mobile devices are actually composed of limited hardware specifications, the transcoding technology is needed to adapt streaming media to given mobile devices. Futhermore owing to the diversity of bandwidth in the wireless network by reason of mobile users' movements and environments, it is difficult to provide stable QoS. In this paper, the autonomic multimedia transcoding system is proposed in order for users to provide network adaptive QoS. Our proposed system is based on the estimation of available bandwidth in wireless network for seamless multimedia streaming service. The proposed system is designed and implemented for various mobile clients. In experiments, we evaluate its seamless multimedia streaming and the adaptation transcoding bit rate according to the changes of bandwidth in wireless network.

• Journal of the Korea Institute of Military Science and Technology
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• v.14 no.5
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• pp.842-849
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• 2011

The transponder simulator designed to simulate the transponder of military satellite communication systems in the geostationary orbit is required to have time delay function, because of 250 ms delay time, when a radio wave transmits the distance of 36,000 km in free space. But, it is very difficult to develop 250 ms time delay device in the transponder simulator of 100 MHz bandwidth, due to unstable operation of FPGA, loss of memory data for the high speed rate signal processing. Up to date, bandwidth of the time delay device is limited to 45 MHz bandwidth. To solve this problem, we propose the new time delay techniques up to 100 MHz bandwidth without data loss. Proposed techniques are the low speed down scaling and high speed up scaling methods to read and write the external memory, and the matrix structure design of FPGA memory to treat data as high speed rate. We developed the satellite link simulator in 100 MHz bandwidth using the proposed new time delay techniques, implemented to the transponder simulator and verified the function of 265 ms time delay device in 100 MHz bandwidth.

• ETRI Journal
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• v.44 no.6
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• pp.945-954
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• 2022

The 5G mobile network is promising to handle the dynamic traffic demands of user equipment (UE). Unmanned aerial vehicles (UAVs) equipped with wireless transceivers can act as flying base stations in heterogeneous networks to ensure the quality of service of UE. However, it is challenging to efficiently allocate limited bandwidth to UE due to dynamic traffic demands and low network coverage. In this study, a blockchain-enabled bandwidth allocation framework is proposed for secure bandwidth trading. Furthermore, the proposed framework is based on the Cournot oligopoly game theoretical model to provide the optimal solution; that is, bandwidth is allocated to different UE based on the available bandwidth at UAV-assisted-based stations (UBSs) with optimal profit. The Cournot oligopoly game is performed between UBSs and cellular base stations (CBSs). Utility functions for both UBSs and CBSs are introduced on the basis of the available bandwidth, total demand of CSBs, and cost of providing cellular services. The proposed framework prevents security attacks and maximizes the utility functions of UBSs and CBSs.

• KIISE Transactions on Computing Practices
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• v.20 no.12
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• pp.688-693
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• 2014

With the advent of ubiquitous environments, the smart phone has come into wide use and the demand for various content increases. Thus, in order to efficiently utilize limited resources cognitive radio technology is regarded as a possible solution. Besides spectrum sensing or access schemes, the provision of VoIP traffic service for secondary users with limited spectrum resources is a very important issue. In this paper, a resource allocation and control system for VoIP QoS provision in cognitive radio networks is proposed. Firstly, as the system model, the time structure of the network is addressed and, according to the structure, a bandwidth broker is proposed. In addition, based on available bandwidth estimated by the bandwidth broker, a connection admission control for secondary users is developed. It is demonstrated that the provision of VoIP QoS is greatly affected by channel utilization, the number of channels, and the length of timeslot.