• 전자공학회논문지B
• /
• 제32B권12호
• /
• pp.1565-1571
• /
• 1995

Misalignment of recording head position results in inter-track interference (ITI), which is a primary factor limiting radial(track) density in current digital magnetic channels. This paper proposes a multi- channel adaptive PRML for digital high-density recording channels, and compares it with the conventional single-channel PRML in the presence of ITI for the per- formance evaluation. Simulation results show that the proposed method removes ITI effectively when heal-misalignment occurs, then improving its performance significantly as compared with the single- channel PRML. As a result, it is confirmed that multi-channel adaptive PRML is well suited for high-density recording in digital magnetic channels.

• Journal of the Optical Society of Korea
• /
• 제7권2호
• /
• pp.97-101
• /
• 2003

The transmission characteristics of multi-channel long period fiber gratings (LPFGs) in terms of the physical parameters like the separation distance, grating length and number of gratings will be discussed. Their transmission characteristics such as channel spacing, number of channels, loss peak depth, and channel bandwidth can be easily controlled by physical parameters. Based on the experimental results, their applications to optical multiwavelength Raman lasers and optical sensors will be investigated. A multiwavelength Raman fiber ring laser with 9 WDM channels with 100 ㎓ spacing and 19 channels with 50 ㎓ spacing using tunable multi-channel LPFGs will be experimentally demonstrated. The fiber-optic sensing applications with high resolution and sensitivity based on multi-channel LPFGs will be also presented.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 1999년도 하계종합학술대회 논문집
• /
• pp.134-137
• /
• 1999

The MC-CDMA(Multi-Code CDMA) systems for handling various data transmission rate which is demanded in the IMT-2000 systems are effective transmission technology, which can provide the higher data service than the conventional IS-95 CDMA systems because a user takes advantage of a number of channels. The receiver of MC-CDMA systems to be provided these data service have to be structured of demodulating simultaneously a number of traffic channels. This paper is designed the merged rake receiver demodulating simultaneously a number of traffic channels in the MC-CDMA systems. The merged rake receiver is to reduce the complexity of receiver resulting a number of channels.

• 한국인터넷방송통신학회논문지
• /
• 제18권2호
• /
• pp.11-17
• /
• 2018

본 연구는 국내에서 제작된 인기 있는 YouTube 채널들의 특징들을 탐구한다. 과학과 기술이 발달함에 따라, 일반인들도 동영상을 촬영한 뒤, 자신의 영상을 업로드를 할 수 있는 상황으로 변화였다. 전 세계적으로 인기 있는 동영상 제공 서비스 사이트 YouTube에서, 국내에서 인기 높은 YouTube 채널들의 특징들을 조사한다. 구체적으로, 1) 구독자 2) 시청 항목의 인기 채널 100개를 조사 한 뒤, 1) 가장 높은 구독자/시청 숫자 2) 비디오 개수 3) 시청/구독자 숫자 4) 장르 5) 제작자로 나누어 탐구한다. 이를 통해, 한국에서 인기 있는 YouTube 채널들의 다각적인 모습뿐만 아니라 한국 멀티채널네트워크(MCN) 시장을 전망한다.

• Journal of Communications and Networks
• /
• 제14권3호
• /
• pp.267-272
• /
• 2012

In this paper, we study multi-hop cooperative transmission protocols using fountain codes. The proposed protocols can reduce the end-to-end delay and number of stages compared to those in conventional multi-hop transmission. VariousMonte-Carlo simulations are presented to evaluate and compare performance of the protocols over Rayeigh fading channels.

• Journal of Communications and Networks
• /
• 제18권1호
• /
• pp.75-83
• /
• 2016

In this paper, we propose a multi-channel medium access control (MAC) protocol, named underwater multi-channel MAC protocol (UMMAC), for underwater acoustic networks (UANs). UMMAC is a split phase and reservation based multi-channel MAC protocol which enables hosts to utilize multiple channels via a channel allocation and power control algorithm (CAPC). In UMMAC, channel information of neighboring nodes is gathered via exchange of control packets. With such information, UMMAC allows for as many parallel transmissions as possible while avoiding using extra time slot for channel negotiation. By running CAPC algorithm, which aims at maximizing the network's capacity, users can allocate their transmission power and channels in a distributed way. The advantages of the proposed protocol are threefold: 1) Only one transceiver is needed for each node; 2) based on CAPC, hosts are coordinated to negotiate the channels and control power in a distributed way; 3) comparing with existing RTS/CTS MAC protocols, UMMAC do not introduce new overhead for channel negotiation. Simulation results show that UMMAC outperforms Slotted floor acquisition multiple access (FAMA) and multi-channel MAC (MMAC) in terms of network goodput (50% and 17% respectively in a certain scenario). Furthermore, UMMAC can lower the end-to-end delay and achieves a lower energy consumption compared to Slotted FAMA and MMAC.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제5권1호
• /
• pp.68-82
• /
• 2011

Wireless mesh networks (WMNs) provide high-speed backbone networks without any wired cable. Many researchers have tried to increase network throughput by using multi-channel and multi-radio interfaces. A multi-radio multi-channel WMN requires channel assignment algorithm to decide the number of channels needed for each link. Since the channel assignment affects routing and interference directly, it is a critical component for enhancing network performance. However, the optimal channel assignment is known as a NP complete problem. For high performance, most of previous works assign channels in a centralized manner but they are limited in being applied for dynamic network environments. In this paper, we propose a simple flow estimation algorithm and a hybrid channel assignment algorithm. Our flow estimation algorithm obtains aggregated flow rate information between routers by packet sampling, thereby achieving high scalability. Our hybrid channel assignment algorithm initially assigns channels in a centralized manner first, and runs in a distributed manner to adjust channel assignment when notable traffic changes are detected. This approach provides high scalability and high performance compared with existing algorithms, and they are confirmed through extensive performance evaluations.

• 한국통신학회논문지
• /
• 제26권11B호
• /
• pp.1540-1545
• /
• 2001

This paper is concerned with the reverse link performance of multi-code CDMA systems in multipath fading environments. The degree of orthogonality loss among multiple spreading code channels is characterized as the orthogonality factor. It depends on various system parameters including multipath power profiles of propagation channels and the number of Paths resolved at a Rake receiver. The effect of the parameters on the system performance is then investigated in terms of bit error rate and required signal quality. The results show that multipath delay power profiles dominantly affect mutual interference among multi-code channels and multipath combining gain by bandwidth expansion is not so great due to the increase of the mutual interference. Moreover, the orthogonality factor is derived as the value of between (1/m) and 1.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2008년도 하계종합학술대회
• /
• pp.175-176
• /
• 2008

Exploiting block diagonal geometric mean decomposition (BD-GMD) for the multi-user MIMO broadcast channels, each user can achieve identical received SNRs for its subchannels. Thus, equal rate modulation can be applied to each user. Using BD-GMD, we can apply an adaptive modulation to each user with the required bit error rate (BER). In this paper, we propose an adaptive modulation algorithm for the multi-user MIMO broadcast channels with BD-GMD to maximize the system throughput satisfying the required BER performance.

• 경영과학
• /
• 제33권2호
• /
• pp.89-115
• /
• 2016

Recent trends in online commerce shows that multi-channels including offline and online become prevailing as a standard type of channel. However, literature survey revealed that there exist few studies about how an individual negative emotion such as neuroticism affects trust transfer between channels, and usage continuance intention. To fill the research void like this, this study proposes an research model where trust transfer between offline and online channels is included, and neuroticism is also adopted as a moderating variable between trust transfer, satisfaction, and usage continuance intention. Empirical results with valid 406 questionnaires revealed that neuroticism has a negative influence on online commerce users' perceived usage continuance intention.