• Journal of Satellite, Information and Communications
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• v.5 no.1
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• pp.22-26
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• 2010

In this paper, we propose an effective method for detecting signals among multi-user in cooperative communication system. Spread sequence is inserted to NULL space of synchronization channel to synchronize between each user among frame formats of the cooperative communication and then transmitted. In the receiver, the wanted signal is detected by using correlation among the inserted spread sequences. As simulation results, correlations among the signals using Kasami/Walsh sequence in AWGN, Rician, and Rayleigh channel are shown. Using the simulation results in this paper, we expect a reliable cooperative communication.

• 한국HCI학회:학술대회논문집
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• 2009.02a
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• pp.538-541
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• 2009

In this paper, we explain a haptic based video and audio streaming method. The proposed method is to stream tactile and vibration information along with video and audio information. The video screen is divided into a grid, and each cell has tactile information which is corresponding to the content. At the same time, the sound stream is also analyzed and vibration information is applied. These data are streamed to clients and displayed through a haptic device and a vibration interface. So, a client will be more immersed into the video and audio by touching and getting vibrations.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.252-255
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• 2010

고해상도의 동영상 서비스가 보편화 되면서 동영상을 빠르게 처리를 위한 연구가 활발히 이루어 지고 있다. 그리고 멀티코어 프로세서의 사용이 증가 하고 멀티코어 시스템에서 H.264/AVC 디코더를 구현하기 위하여 다양한 병렬화 방법이 제안되고 있다. 하지만 H.264/AVC디코더의 병렬화를 진행하는 과정에서 각 스레드에서 처리하는 데이터의 처리시간 차이로 인하여 스레드의 동기를 확인 해야 한다. 이로 인하여 병렬화를 통한 성능 향상의 걸림돌이 된다. 우리는 이러한 병렬화 과정에서 발생하는 문제점을 고려하여 효과적으로 H.264/AVC 디코더를 병렬화 하는 방법에 대하여 연구하였다. 우리가 제안하는 Frame Partition based Parallelization (FPP) 방법은 프레임을 매크로 블록 묶음으로 나누어 병렬화 한다. 그리고 병렬화 과정에서 스레드를 처리하는 방법을 개선하여 성능을 향상 시켰다. 본 논문에서는 FFmpeg H.264/AVC 디코더를 이용하여 실험 하였고 인텔 쿼드 코어 기반의 멀티코어 시스템에서 멀티 스레드로 구현하였다. 우리는 FPP 방법을 적용하여 병렬화 방법 적용 전 H.264/AVC 디코더와 비교하여 최대 53%의 성능 향상을 보였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5C
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• pp.519-533
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• 2006

The number of channels specified in IEEE 802.15.4 Low-Rate Wireless Personal Area Networks(LRWPANs) is too few to operate many applications of WPANs in the same area. To overcome this limit, we introduce Virtual Channel, a novel concept to increase the number of available channels when various WPAN applications coexist. Basically, a virtual channel is a newly-created channel via superframe scheduling within the inactive period of a logical channel preoccupied by other WPANs. To maximize the coexistence capability of WPANs using virtual channels, we propose Least Collision superframe scheduler(LC-scheduler), its less complex heuristics both for a given single channel, and Virtual Channel Selector(VCS) to efficiently manage multiple available logical channels. In addition, a simple but practical synchronization method is developed to compensate different time drifts among coexisting WPANs. The simulation results demonstrate that a remarkable improvement on the coexistence capability of the 802.15.4 can be achieved through the proposed schemes.

• Journal of KIISE:Computing Practices and Letters
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• v.9 no.4
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• pp.369-380
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• 2003

With the proliferation of a wireless support and the advances of mobile devices, there is a growing need of making it available for a wireless network as well. Low bandwidth of a wireless network is one of the major issues that should be considered for extending a synchronous collaboration system developed for a wired network to supuort a wireless network. We propose a priority-based view synchronization scheme, exploiting the relaxed synchronization. The proposed scheme leverages the fact that mobile users need not have the exactly same view as the users in a wired network since they usually have a limited screen size and thus focus only on part of a whole document. We evaluate the performance of a simple group editor with the propose scheme using ns -2. The performance results show that the proposed scheme keeps the message transmission delay low so that mobile users can have synchronous colloboration with wired users without signification delay. The proposed scheme is designed and implemented as a framework to support various kinds of realtime groupware applications, exploiting the existing groupware framework, Habanero. As a client program, we implemented a simple group text editor.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.6 s.348
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• pp.1-8
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• 2006

In the asynchrous OFCDM(Orthogonal Frequency and Code Division Multiplexing) system, a three-step cell search algorithm is performed for the initial synchronization in the following three steps: OFCDM symbol timing, i.e., Fast Fourier Transform(FFT) window timing is estimated employing guard interval (GI) correlation in the first step, then the frame timing and CSSC (Cell Specific Scrambling Code) group is detected by taking the correlation of the CPICH(Common Pilot Channel) based on the property yeilded by shifting the CSSC phase in the frequency domain. Finally, the CSSC phase within the group is identified in the third step. This paper proposes a modification code(PCSSCG:Patial Cell Specific Scrambling Code Group) of the conventional CPICH based cell search algorithm in the second step which offers MS(Mobile Station) complexity reductions with the nearly same performance. The proposed method is to be compared and verified through the computer simulation.

• The Journal of the Acoustical Society of Korea
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• v.20 no.7
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• pp.101-108
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• 2001

In this paper we focus on dynamic reservation slot allocation scheme for supporting QoS of a voice traffic in WATM MAC. Especially, voice traffic is the most important real-time object, and so we propose a new MAC protocol for voice traffic over WATM networks in the multimedia environment. According to the characteristics of voice traffic which is repeatedly in silent state and active state, new protocol allocates reservation slots dynamically with respect to the number of silent voice source of which starting time is stored to the state table in base station (BS). The simulation results show that the proposed protocol has better performance than slotted ALOHA in average access delay, collision rate, better than NC-PRMA(Non Collision Packet Reservation Multiple Access) in band width efficiency, and can provide a certain level of QoS requirement by the given slot assignment even though the number of voice terminals is increased.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.4
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• pp.80-87
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• 2007

In this paper, link-level performance of a OFDMA technique, which has been considered as a standard for 802.16, 802.20, 3G-LTE, WiMax, and WiBro, is evaluated for next-generation wireless communication systems. While many researches have focused on uncoded forward-link performances, this paper provides a coded performance of a reverse-link OFDMA system. Performance degradation due to time offset among reverse-link users and frequency offset during FFT process is investigated. Transmitter and receiver antenna diversity techniques are used to overcome performance degradation. Performance of a OFDMA system is compared with a CDMA system in terms of FER and throughput to emphasize the advantage of OFDMA system for a reverse-link. Finally, under given specification, Eb/No required to achieve the maximum throughput of a reverse-link is proposed considering various coded rates and antenna permutations.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.121-126
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• 2006

This paper report on the design and implementation of a 9.6kbps DSSS CDMA modem for a medium speed wireless link. The proposed modem provides a general purpose I/O interface with a microprocessor. The I/O interface consists of 8-bit data bus, chip enable, read/write, and interrupt pins. In transmit block, the 8-bit data delivered from the I/O interface buffer is converted to 9.6kbps serial data, which are spreaded into 76.8kcps with 8-bit PN code generated inside the modem by direct sequence method. An 8-bit training sequence is preceded in the data frame for data synchronization in receiver. In receiver block the PN code is synchronized from the received data spreaded to 76.8kcps and find the data timing from the 8-bit training sequence. We have used the Early-and-Late integration method. The modem has been implemented and verified using a Xilix FPGA board and has been fabricated as an ASIC CHIP through Hynir $0.25{\mu}m$ CMOS. The multiple accessing method is DSSS CDMA.

• Journal of Broadcast Engineering
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• v.17 no.4
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• pp.596-610
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• 2012

This paper proposes a method to provide the high quality 3D broadcasting service in a mobile broadcasting system. In this method, audio and video data are delivered through a heterogeneous network, consisting of a mobile network as well as a broadcasting network, due to the limited bandwidth of the broadcasting system. However, it is more difficult to synchronize the left and right video frames of a 3D stereoscopic service, which come through different types of networks. The proposed method suggests the use of the offset from the initial timestamp of RTP (Real Time Protocol) to determine the order of frames and to find the pair of a left and a right frame that must be played at the same time. Additionally, a new signaling method is introduced for a mobile device to request a 3D service and to get the initial RTP timestamp.