• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.8
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• pp.1088-1094
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• 2021

This paper proposes a partial BMA (Broadcasting Multiple Access) network structure and D-ARP (Distributed Address Resolution Protocol) method in order to support full mesh routing function in the DAMA (Demand Assigned Multiple Access)-based MF-TDMA (Multi Frequency-Time Division Multiple Access) satellite system. The partial BMA network enables legacy router devices and routing protocols to be adopted in the satellite communication system, and decreases the amount of routing protocol overhead. In addition, we introduce the D-ARP method that help a spoke satellite node acquiring the MAC (Media Access Control) address from remote satellite nodes in none BMA satellite network. The D-ARP method provides the MAC address of remote nodes to each other nodes through the broadcasting-enabled satellite channel. And we lastly evaluate and analysis the network performance of the proposed approach.

• Journal of Digital Convergence
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• v.12 no.10
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• pp.317-327
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• 2014

To improve the efficiency of wireless channel, IEEE 802.11ac uses the DL MU-MIMO MAC scheme through which an AP transmits multiple frames to different mobile nodes simultaneously. IEEE 802.11ac DL MU-MIMO MAC needs a new step, called as TXOP sharing, between legacy IEEE 802.11n DL SU-MIMO's two operations, the obtaining an EDCA TXOP and the transmitting multiple frames for EDCA TXOP. In the TXOP sharing operation, both wireless channel destinations and frames transmitted for its TXOP period should are determined. So this paper deals with the TXOP sharing for improving IEEE 802.11ac MAC performance. However, the EDCA priority based method mentioned by IEEE 802.11ac standard document not fair among the buffers and the frames of buffers, and occurs in high_loss rate and high_delay about specific buffers. In this paper, we propose a new scheme of the TXOP sharing with sequencing p-AC, s-AC in similar properties, and all S-AC. This method provides a differentiated service without damage of EDCA characteristics.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2B
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• pp.98-106
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• 2006

In order to provide a realtime transmission over a wireless LAM, we here present a new jamming based retransmission mechanism. In a legacy wireless LAN system, all stations use the binary exponential backoff algorithm to avoid collisions among frames. It is well known that the backoff algorithm causes more collisions as the numbers of active stations increases. This makes transmission of real time traffic hard. In the proposed scheme, when each station senses collisions, it promptly allows to send a jamming signal during a unique jamming window period which is determined by its own channel access count database(CACDB). This jamming windows is chosen not to be overlapped each other by using of CACDB, and thus channel access of another station is prevented. Hereafter the station gets the ownership of the medium when the wireless medium becomes idle after sending the jamming signal and sensing carrier, and then sends frame in medium. In our proposal, repeating collisions is never happened. We here assume that real time traffic use a frame of fixed length in order to make the time for receiving its ACK frame same. Comparing the proposed jamming-based retransmission scheme with the the 802.11 and 802.11e MAC by simulation. one can find that the proposed scheme have advantages in terms of delay, average backoff time, and average number of collisions per frame. One can find that the proposed scheme might be practically applicable to several applications of realtime traffic transmission in wireless LAN systems.

• Journal of Broadcast Engineering
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• v.15 no.1
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• pp.29-39
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• 2010

This paper presents and analyzes laboratory test results of distributed translator (DTxR) for distributed frequency network (DFN) in the ATSC (Advanced Television Systems Committee) terrestrial digital TV broadcasting system. The DTxR laboratory test is classified to receiving part test and transmitting part test. The receiving part test includes dynamic range, random noise, single echo, and adjacent channel interference. The transmitting part test includes quality of output signal (out-of channel emission, quality of transmitting signal, and phase noise), frequency synchronization among output signals, and TxID (Transmitter Identification) signal's affect to the legacy receiver. By the laboratory test results, the receiving part of DTxR eliminates average -2.5 dB of single echo and has average 17.5 dB at TOV (Threshold of Visibility) under random noise environment. In addition, the transmitting part of DTxR satisfies the specification of US FCC (Federal Communications Commission), and frequency difference among DTxR output signals is less than 0.001 Hz.

• Journal of Navigation and Port Research
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• v.40 no.6
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• pp.385-390
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• 2016

ELoran Systems can provide Position, Navigation, and Time services with comparable performance to Global Positioning Systems (GPS) as a back up or alternative system. High timing and navigation performance can be achieved by eLoran signals because eLoran receivers use "all-in-view" reception. This incorporates Time of Arrival (TOA) signals from all stations in the service range because each eLoran station is synchronized to Coordinated Universal Time (UTC). Transmission station information and the differential Loran correction data are transmitted via an additional Loran Data Channel (LDC) on the transmitted eLoran signal such that eLoran provides improved Position Navigation and Timing (PNT) over legacy Loran. In this paper, we propose a technique for adapting the delay time compensation values in eLoran timing receivers to provide precise time comparison. For this purpose, we have designed a system that measures time delay from the crossing point of the third cycle extracted from the current transformer at the end point of the transmitter. The receiver delay was measured by connecting an active H-field, an E-field and a passive loop antenna to a commercial eLoran timing receiver. The common-view time transfer technique using the calibrated eLoran timing receiver improved the eLoran transfer time. A eLoran timing receiver calibrated by this method can be utilized in the field for precise time comparison as a GNSS backup.

• Journal of Broadcast Engineering
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• v.14 no.4
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• pp.518-536
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• 2009

To verify the performance of a Distributed Translator Network(DTxR) system in the real world conditions, 5 legacy DTV broadcasting repeater sites were implemented with 5 DTxR systems and field-tested by the DTV field test truck. The 4 DTV broadcasting repeater sites are selected in congested areas where their service areas are overlapped and the 5th site is deviated from the other sites to examine the effect of long-delayed multipath signals. First of all, we checked the receiving signal of the main station that used as a transmitting signal in 5 DTxR systems on the pre-selected 60 test points and tested every case of a DTxR system's on & off except 1 repeater site due to the already built-in DTV repeater system. The test items are received signal electric field strength, noise margin, ease of reception and subjective evaluation of the picture quality for received signals. We used 3rd, 5th, and 6th generation DTV receivers to examine the differences of the receivability by each generation of DTV receivers. Reviewing the test results, we conclude that the DTxR system can be adopted in the current DTV Repeater sites and it could improve the quality and receivability of the main signals by extending the service areas and enhancing the signal levels in the shadow areas without using the extra broadcasting channels.

• Journal of Broadcast Engineering
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• v.16 no.2
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• pp.350-359
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• 2011

Fast developments of broadcasting technologies since 1990s enabled not only High Definition Television service providing high quality audiovisual contents at home but also mobile broadcasting service providing audiovisual contents to high speed moving vehicle. Terrestrial Digital Multimedia Broadcasting (T-DMB) is one of the technologies developed for mobile broadcasting service, which has been successfully commercialized. One of the major technical breakthroughs achieved by T-DMB in addition to robust vehicular reception is an adoption of framework based on MPEG-4 System. It naturally enables integrated interactive data services by using Binary Format for Scene (BIFS) technology for scene description and representation of graphics object and Object Descriptor Framework representing multimedia service components as objects. T-DMB interactive data service has two fundamental limitations. Firstly, graphic data for interactive service should be always overlaid on top of a video not to be rendered out of it. Secondly, data for interactive service is only received by broadcasting channel. These limitations were considered as general in broadcasting systems. However, they are being considered as hard limitations for personalized data services using location information and user characteristics which are becoming widely used for data services of smart devices in these days. In this paper, the architecture of T-DMB hybrid data service is proposed which is utilizing broadcasting network, wireless internet and local storage for delivering BIFS data to overcome these limitations. This paper also presents hybrid BIFS technology to implement T-DMB hybrid data service while maintaining backward compatibility with legacy T-DMB players.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.1A
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• pp.33-43
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• 2010

Recently, users want to use real-time multimedia services, such as internet, VoIP, etc., using their IEEE 802.11 wireless lan mobile stations. In order to provide such services, a handoff among access points is essential to support the mobility of a node, in such an wide area. However, the legacy handoff methods of IEEE 802.11 technology are easy to lose connections. Also, the recognition of a disconnection and channel re-searching time make the major delay of the next AP to connect. In addition, because IEEE 802.11 decides the selection of an AP depending only on received signal strength, regardless of a node direction, position, etc., it cannot guarantee a stable bandwidth for communication. Therefore, in order to provide a real-time multimedia service, a node must reduce the disconnection time and needs an appropriate algorithm to support a sufficient communication bandwidth. In this paper, we suggest an algorithm which predicts a handoff point of a moving node by using GPS location information, and guarantees a high transmission bandwidth according to the signal strength and the distance. We implemented the suggested algorithm, and confirmed the superiority of our algorithm by reducing around 3.7ms of the layer-2 disconnection time, and guaranteed 24.8% of the communication bandwidth.

• Journal of Navigation and Port Research
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• v.37 no.4
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• pp.375-381
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• 2013

In order to establish eLoran system it needs the betterment of a receiver and a transmitter, the add of data channel to loran pulse for loran system information and the differential Loran for compensating Loran-c signal. Precise ASF database map is essential if the Loran delivers the high absolute accuracy of navigation demanded at maritime harbor entrance. In this study we developed the ASF mapping method using predicted ASFs compensated by the measured ASFs for maritime in the harbor. Actual ASF is measured by the legacy Loran signal transmitted from Pohang station in the GRI 9930 chain. We measured absolute propagation delay between the Pohang transmitting station and the measurement points by comparing with the cesium clock for the calculation of the ASFs. Monteath model was used for the irregular terrain along the propagation path in the Yeongil Bay. We measured the actual ASFs at the 12 measurement points over the Yeongil Bay. In our ASF-mapping method we estimated that the each offsets between the predicted and the measured ASFs at the 12 spaced points in the Yeongil. We obtained the ASF map by adjusting the predicted ASF results to fit the measured ASFs over Yeungil bay.

• (The) Research of the performance art and culture
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• no.22
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• pp.157-183
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• 2011

This study is to find out the legitimacy and features of Honam Choreography via Lee Mae-bang and Han Jin-ok, two of the masters, and to seek better and more creative ways to pass it down in view of regional particularities. The study looks into the traditional choreography's multi-conceptuality that is derived from various forms of art and lends it its identity with the original notion rooted in Buddhist dancing. Despite the local cultural traits of the Honam area, the fact that Lee Mae-bang is more feminine and Han Jin-ok more masculine shows the two's worlds of dancing have been created from different perspectives, though they are quite common in their roots and locales. The particularities of passing down traditional choreography are given a thought in this study with the distinction and identity taken into account. Also, it will give an opportunity to discuss the importance of localism as aesthetic consciousness and communica tion channel. In any case, there is no doubt that local difference and communica tion make a very important source of culture when we look into the originality of the choreography.