• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.2A
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• pp.114-126
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• 2011

Video streaming over wireless multi-hop networks(WMNs) contains the following challenges from channel fading and variable bandwidth of wireless channel, and it cause degradation of video streaming performance. To overcome the challenges, currently, WMNs can use Forward Error Correction (FEC) mechanism. In WMNs, traditional FEC schemes, E2E-FEC and HbH-FEC, for video streaming are applied, but it has long transmission delay, high computational complexity and inefficient usage of resource. Also, to distinguish network status in streaming path, it has limitation. In this paper, we propose monitoring-based coordination of network-adaptive hop-to-end(H2E) FEC scheme. To enable proposed scheme, we apply a centralized coordinator. The coordinator has observing overall monitoring information and coordinating H2E-FEC mechanism. Main points of H2E-FEC is distinguishing operation range as well as selecting FEC starting node and redundancy from monitored results in coordination. To verify the proposed scheme, we perform extensive experiment over the OMF(Orbit Measurement Framework) and IEEE 802.1la-based multi-hop WMN testbed, and we carry out performance improvement, 17%, from performance comparison by existing FEC scheme.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11A
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• pp.1076-1084
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• 2006

In this paper, we first review a concept of hybrid division duplexing (HDD) scheme, which has been proposed as a new type of duplexing scheme useful for a next generation mobile communication system and its implementation issues, including the unified radio resource management for HDD scheme. The HDD scheme maintains the advantages of both TDD and FDD at the same time while providing a useful structure to control the inter-cell interference, caused by an asymmetric traffic load of multimedia services over uplink and downlink in the TDD scheme. Employing two frequency bands, one for TDD scheme and the other for FDD scheme, uplink is operating under the TDD scheme only, while downlink is operating under the TDD or FDD scheme, depending on the location of mobile station. In the HDD scheme, therefore, it must determine a type of duplexing scheme to employ in the downlink and futhermore, a ratio of uplink and downlink duration to meet a given traffic load of asymmetric service, which requires some unified radio resource management for handling the subsequent inter-cell interference. In this paper, we propose a distributed adaptive control approach as a means of unified radio resource management for a HDD system that maximizes the overall system efficiency by fully utilizing the resource in TDD band, while minimizing the inter-cell interference.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.96-107
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• 2015

VANET technologies provide real-time traffic information for mitigating traffic jam and preventing traffic accidents, as well as in-vehicle infotainment service through Telematics/Intelligent Transportation System (ITS). Due to the rapid increasement of various requirements, the vehicle communication with a limited resource and the fixed frame architecture of the conventional techniques is limited to provide an efficient communication service. Therefore, a new flexible operation depending on the surrounding situation information is required that needs an adaptive design of the network architecture and protocol for efficiently predicting, distributing and sharing the context-aware information. In this paper, Vehicle-to-Infrastructure (V2I) based on communication between vehicle and a Road Side Units (RSU) and Vehicle-to-Vehicle (V2V) based on communication between vehicles are effectively combined in a new MAC architecture and V2I and V2V vehicles collaborate in management. As a result, many vehicles and RSU can use more efficiently the resource and send data rapidly. The simulation results show that the proposed method can achieve high resource utilization in accordance. Also we can find out the optimal transmission relay time and 2nd relay vehicle selection probability value to spread out V2V/V2I collaborative schedule message rapidly.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.23-32
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• 2011

Design and Implementation of Clipcast Service via Terrestrial DMB This paper outlines the system design and the implementation process of clipcast service that can send clips of video, mp3, text, images, etc. to terrestrial DMB terminals. To provide clipcast service in terrestrial DMB, a separate data channel needs to be allocated and this requires changes in the existing bandwidth allocation. Clipcast contents can be sent after midnight at around 3 to 4 AM, when terrestrial DMB viewship is low. If the video service bit rate is lowered to 352 Kbps and the TPEG service band is fully used, then 320 Kbps bit rate can be allocated to clipcast. To enable clipcast service, the terminals' DMB program must be executed, and this can be done through SMS and EPG. Clipcast service applies MOT protocol to transmit multimedia objects, and transmits twice in carousel format for stable transmission of files. Therefore, 72Mbyte data can be transmitted in one hour, which corresponds to about 20 minutes of full motion video service at 500Kbps data rate. When running the clip transmitted through terrestrial DMB data channel, information regarding the length of each clip is received through communication with the CMS(Content Management Server), then error-free files are displayed. The clips can be provided to the users as preview contents of the complete VOD contents. In order to use the complete content, the user needs to access the URL allocated for that specific content and download the content by completing a billing process. This paper suggests the design and implementation of terrestrial DMB system to provide clipcast service, which enables file download services as provided in MediaFLO, DVB-H, and the other mobile broadcasting systems. Unlike the other mobile broadcasting systems, the proposed system applies more reliable SMS method to activate the DMB terminals for highly stable clipcast service. This allows hybrid, i.e, both SMS and EPG activations of terminals for clipcast services.

• Broadcasting and Media Magazine
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• v.11 no.4
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• pp.104-117
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• 2006

In this Paper, we analyze the application of Interactive Data Broadcasting in DMB(Digital Multimedia Broadcasting) in the accordance with convergence of service and technology. With the acceleration of digital convergence in the Ubiquitous period substantial development of digital media technology and convergence of broadcasting and telecommunication industry are being witnessed. Consequently these results gave rise to newly combined-products such as DMB(Digital Multimedia Broadcasting), WCDMA(Wide-band code division multiple access), Wibro(Wireless Broadband Internet), IP-TV (Internet protocol TV) and HSDPA(High speed downlink packet access). The preparatory stage for the implementation of Interactive Data Broadcasting Service will be reached by the end of December, 2006. DMB is the first result of a successful convergence service between Broadcasting and Telecommunication in new media era. Multimedia technology and services are the core elements of DMB. The Data Broadcasting will not only offer various services of interactive information such News, Weather, Broadcasting Program etc, but also be linked with characteristic function of mobile phone such as calling and SMS(Short Message Service) via Return Channel.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.11
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• pp.44-52
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• 2011

In this article, we present a QoS-guaranteed IP mobility management scheme of Internet service for fast moving vehicles with multiple wireless network interfaces. The idea of the proposed mechanism consists of two things. One is that new wireless connections are established to available wireless channels whenever the measured data rate at the vehicle equipped with mobile gateway drops below to the required data rate of the user requirement. The other is that parallel distribution packet tunnels between an access router and the mobile gateway are dynamically constructed using multiple wireless network interfaces in order to guarantee the required data rate during the mobile gateway's movement. By doing these methods, the required data rate of the mobile gateway can be preserved while eliminating the possible delay and packet loss during handover operation, thus resulting in the guaranteed QoS. The architecture of the IETF standard HMIPv6 has been extended to realize the proposed scheme, and detailed algorithms for the extension of HMIPv6 has been designed. Finally, simulation has been done for performance evaluation, and the simulation results show that the proposed mechanism demonstrates guaranteed QoS during the handover with regard to the handover delay, packet loss and throughput.

• The Journal of the Korea Contents Association
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• v.15 no.4
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• pp.29-44
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• 2015

Digital Signage, a way of advertising or delivering information to viewers through digital displays, has expanded from being just an advertising channel in public places. Recently, it has become widely prevalent in restaurants and retail stores. Despite its wide expansion, digital signage is limited to specific usages and services and the devices it uses are also quite expensive. This study introduces a stick-type digital signage product that operates on Android OS, which addresses all the weaknesses of digital signage with much more reasonable pricing and stable operation. For stability, performance tests were executed on the hardware and applications. The results for hardware performance were extremely promising, as each scenario's maximum performance results, measured by Load Runner programs, reached target indexes. Also, as a result of the usability test, all participants, including non-digital signage system users (novices), were able to easily learn all the tasks. As a result of user satisfaction survey, positive responses were exhibited for ease of learning and usability (LEU), helpfulness and problem solving capabilities (HPSC), affective aspect and multimedia properties (AAMP), commands and minimal memory load (CMML), and control and efficiency (CE).

• Journal of Broadcast Engineering
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• v.18 no.4
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• pp.572-588
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• 2013

In this paper, 4K-UHDTV or 8K-UHDTV and UHD-3DTV that the next generation broadcasting implementation and the possibility of direct receiving environment construction is analyzed on the terrestrial broadcasting. Particularly, we investigated the possibility by analyzing the previous and related works with regard to UHDTV transmission by DVB-T2 that is one of the best commercialized transmission mode. In order that the UHDTV broadcasting succeeds once again after completion of digital terrestrial switch over at the end of 2012, the ultra high resolution image transfer is important. However, the direct, the indoor and ubiquitous receiving environment is important in not only TV but also the personal type multimedia terminal in the sense of UHDTV service penetration. Therefore, in this paper, by using SFN and high error-correcting mode in DVB-T2 standard, the efficient frequency utilization and effective reception environment construction is illustrated. Particularly, SFN network constitution by 2 mutually different frequencies including the VHF bandwidth and UHF band, and etc. is shown. And the method that builds the free wireless receive environment by using SFN low power radio repeater and for home use gap filler is proposed. And the effect and frequency amount required are presented, when UHDTV broadcasting use 10MHz bandwidth.

• The Journal of the Acoustical Society of Korea
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• v.23 no.8
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• pp.554-561
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• 2004

As the technologies of semiconductor and multimedia communication have been improved. the high-quality video and the multi-channel audio have been highlighted. MPEG Audio Layer 3 decoder has been implemented as a Processor using a standard. Since the synthesis filter of MPEG-1 Audio Layer 3 decoder requires the most outstanding operation in the entire decoder. the synthesis filter that can reduce the amount of operation is needed for the design of the high-speed processor. Therefore, in this paper, the synthesis filter. the most important part of MPEG Audio, is materialized in FPGA using the method of DAULT (distributed arithemetic look-up table). For the design of high-speed synthesis filter, the DAULT method is used instead of a multiplier and a Pipeline structure is used. The Performance improvement by 30% is obtained by additionally making the result of multiplication of data with cosine function into the table. All hardware design of this Paper are described using VHDL (VHIC Hardware Description Language) Active-HDL 6.1 of ALDEC is used for VHDL simulation and Synplify Pro 7.2V is used for Model-sim and synthesis. The corresponding library is materialized by XC4013E and XC4020EX. XC4052XL of XILINX and XACT M1.4 is used for P&R tool. The materialized processor operates from 20MHz to 70MHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.443-451
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• 2010

This paper describes a fully integrated CMOS low-IF mobile-TV RF tuner for Band-III T-DMB/DAB applications. All functional blocks such as low noise amplifier, mixers, variable gain amplifiers, channel filter, phase locked loop, voltage controlled oscillator and PLL loop filter are integrated. The gain of LNA can be controlled from -10 dB to +15 dB with 4-step resolutions. This provides a high signal-to-noise ratio and high linearity performance at a certain power level of RF input because LNA has a small gain variance. For further improving the linearity and noise performance we have proposed the RF VGA exploiting Schmoock's technique and the mixer with current bleeding, which injects directly the charges to the transconductance stage. The chip is fabricated in a 0.18 um mixed signal CMOS process. The measured gain range of the receiver is -25~+88 dB, the overall noise figure(NF) is 4.02~5.13 dB over the whole T-DMB band of 174~240 MHz, and the measured IIP3 is +2.3 dBm at low gain mode. The tuner rejects the image signal over maximum 63.4 dB. The power consumption is 54 mW at 1.8 V supply voltage. The chip area is $3.0{\times}2.5mm^2$.