• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.9A
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• pp.1359-1371
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• 1999

In this paper, we propose an efficient explicit rate (ER) feedback switch algorithm for available bit rate (ABR) flow control. In order to improve the disadvantages of existing ER feedback switch algorithms with congestion avoidance, the proposed scheme adjusts the target utilization dynamically according to the queue length and its growth rate. also, we investigate the performance of the proposed switch algorithm and compare it with ERICA and NIST switches using simulation. Simulation results show that the proposed switch algorithm can control the cell emission rate of a source rapidly according to variations of available link bandwidth by using dynamic adaptation of target utilization. It also exhibits a better performance than the existing ER feedback switches in terms of queue length and link utilization.

• Journal of Internet Computing and Services
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• v.17 no.6
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• pp.9-15
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• 2016

In this paper, we propose a smart HLS(HTTP Live Stream) platform with dynamic single buffering for the best transmission of adaptive video bit-rates. This smart HLS can optimizes the channel transition zapping-time with the monitoring of bandwidth between HLS server and OTT(Over The Top) client. This platform is designed through the control of video stream due to proper multi-bitrates and bandwidths. This proposed OTT can decode the live and VOD(Video On Demand) videos with the buffering of optimumal bitrate. And, the HLS can be cooperated with a smart OTT, and segmented for the m3u8 files of H.265 MPEG-2 TS(Transport Stream) videos. As a resullt, this single buffer based smart OTT can transmit optimal videos with the maximum data buffering according to the adaptive bit-rate depending on the network bandwidth efficiency and the decoded VOD video, too.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.5C
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• pp.338-343
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• 2005

MIMO(Multiple Input Multiple Output) systems are considered as one of the most promising systems for next generation mobile communication systems which require efficient frequency resource utilization as well as high data rate transmissions. BLAST-STTC is the MIMO system which transmits information from many of STTC encoder groups with two transmit antennas and cancels the interference from other groups in receiver. In this paper we propose a reverse-ordered iterative decoding scheme for BLAST-STTC systems which achieve full diversity gain for all groups and improve the performance of interference cancellation, and compare the error performance of the proposed scheme with general schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.10A
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• pp.1529-1539
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• 2000

The contact procedure of access channel necessary to set up the originating call has a close relation with the performance and capacity of the base station system in CDMA cellular network. This paper investigates the structure and the operation of the backward channel of IS-95 CDMA standard and explains the related system parameters. We can derive the throughput of the CDMA access channel depending on the arrivals of the access probes per access channel slot, given the system parameters such as cell radius, the maximum number of retransmission, and the error rates of the access and paging channel. It shows that the performance in throughput is much better in the CDMA IS-95 access channel than in the slotted aloha channel. It also gives the reasonable number of the trafic channels in a cell with the given blocking probability.

• Journal of KIISE
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• v.42 no.1
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• pp.130-137
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• 2015

With the rapid increase of energy consumption and environmental problems, the need for green techniques is increasing. Network coding can provide a solution by reducing unnecessary data transmission and by estimating traffic patterns. In addition, it can amplify the synergy with the cognitive radio network (CR) since the CR has recognition and optimal decision functionalities. In this paper, we propose a network coding based green cognitive radio network. With the simulations, we show that the proposed scheme is up to 25% better than the previous work.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.156-162
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• 2013

In the communication between satellite and ground station, data rate can be determined from the data volume and required transmission time. Increasing data rate can be limited according to the available bandwidth. For the reason, it has been popularly studying on high spectral-efficient modulation scheme in large volume data application such as digital video broadcasting service. This paper presents the conceptual design of UHRIT broadcasting in GEO-KOMPSAT-2A (GK2A) mission by using DVB-S2 standard. Based on the recently determined data rate, UHRIT bandwidth was calculated at the various modulation schemes and code rates of DVB-S2 standard. Receiving performance of global user station was also evaluated thorough link analysis by considering that user station is located at the edge of beam coverage. Finally, maximum data rate was analyzed in a situation that COMS HRIT bandwidth should be alternatively applied for UHRIT downlink.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.295-297
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• 2010

H.264/AVC 무손실 인트라 압축을 위하여 사용되는 픽셀 예측 방법은 Sample by Sample DPCM (SbS DPCM) 으로서 이 방법에서는 각각의 픽셀을 주변 픽셀로부터 예측하고 그 오차를 전송한다. 본 논문에서는 $4{\times}4$ 블록에 대한 Multiple Partition 예측과 SbS DPCM을 이용하여 H.264/AVC 의 무손실 인트라 압축 효율을 증가시키는 방법을 제안한다. 제안하는 방법은 각 $4{\times}4$ 블록을 $4{\times}4$, $4{\times}2$, $2{\times}4$, $2{\times}2$, $1{\times}1$ 크기의 sub-partition 을 가지는 다양한 partition 으로 예측한다. 이 때 각 sub-partition 들은 SbS DPCM을 이용하여 예측되고 이 때 사용하는 예측 방향의 개수는 예측 방향 정보량을 고려하여 sub-partition 크기에 따라 조절한다. 실험 결과에 의하면 제안하는 방법은 기존 H.264/AVC에 비하여 최대 17.02 %p, 평균 13.29 %p 의 압축율 개선을 보여주며 SbS DPCM만 사용하는 방법에 비하여 최대 4.74 %p, 평균 3.62 %p 정도의 압축율 개선을 보여준다.

• Proceedings of the Korean Nuclear Society Conference
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• 1998.05b
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• pp.783-788
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• 1998

발전소 운영자는 운전 시작시점에서 수명 종료시점까지 발전소 과도상태 종류별 횟수가 설계 제한치를 넘지 않도록 감시하여야 하며 이를 위해서는 발전소 운전 과도상태 기록유지가 필요하다. 그러나 현재와 같은 발전소 운전 Strip Chart나 Log Sheet를 이용하는 방식으로는 과도상태 발생여부 판단이 어려울 뿐만 아니라 카운팅 자체에도 많은 시간이 소요되어 좀더 편리한 방법의 도입이 필요하다. 본 연구에서는 발전소 주전산기의 운전 데이타를 이용한 과도상태 데이터 수집 및 지능형 과도상태 판단방법을 개발하여 시범 적용하였다. 과도상태 데이터 수집은 전송되는 데이터와 이전 데이터를 비교하여 변화가 있을 시에만 데이터 압축방식을 이용하여 저장하였고, 최대/최소온도, 최대/최소압력, 온도/압력기울기 등의 운전 데이타를 기 설정된 과도상태의 전체 변수와 비교하여 오차율 범위내에 들면 동일한 과도상태로 판단하였다. 원자로 냉각재 계통의 온도 및 압력과 같이 계기 오차가 비교적 작은($\pm$1$^{\circ}C$) 운전변수는 과도상태 판단이 용이하나 오차가 큰 운전변수의 경우에는 과도상태 판단을 위한 보다 상세한 알고리즘의 개발이 필요하다.

• The Transactions of the Korea Information Processing Society
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• v.4 no.7
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• pp.1770-1780
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• 1997

Our problem is improvement of image quality because it is inevitable cell loss of image data when traffic congestion occurs. If cells are discarded indiscriminately in transmission of MPEG video data, it occurs severe degradation in quality of service(QOS). In this paper, to solve this problem, we propose two method. The first, we analyze the traffic characteristics of an MPEG encoder and generate high priority and low priority data stream. During network congestion, only the least low priority cells are dropped, and this ensures that the high priority cells are successfully transmitted, which, in turn, guarantees satisfactory QoS. In this case, the prioritization scheme for the encoder assigns components of the data stream to each priority level based on the value of a parameter ${\beta}$. The second, Number of high priority cells are increased when value of ${\beta}$ is large. It occurs the loss of high priority cell in the congestion. To prevent it, this paper is regulated to data stream rate as buffer occupancy with UPC controller. Therefore, encoder's bandwidth can be calculated renegotiation of the encoder and networks. In this paper, the encoder's bandwidth requirements are characterized by a usage parameter control (UPC) set consisting of peak rate, burstness, and sustained rate. An adaptive encoder rate control algorithm at the Networks Interface Card(NIC) computes the necessary UPC parameter to maintain the user specified quality of service. Simulation results are given for a rate-controlled VBR video encoder operating through an ATM network interface which supports dynamic UPC. These results show that dynamic bandwidth renegotiation of prioritized data stream could provided bandwidth saving and significant quality gains which guarantee high priority data stream.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.610-617
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• 2009

This paper proposes a cross-layer design combining adaptive modulation and coding (AMC) with truncated hybrid automatic repeat request (HARQ) for wireless multicast transmission, in order to increase the spectral efficiency while meeting the target quality-of-service (QoS). In the design, we provide the selection criterion of AMC so as to satisfy the target packet error rate (PER) of all users when the multicast data is received through the common channel and the number of retransmission is limited by the delay constraint of the service. The analytically derived results show that the cross-layer design using HARQ provides a better spectral efficiency than the AMC without HARQ by allowing retransmission and code combining. It is also observed that the design for multicast outperforms that for unicast in the mid to high signal-to-noise ratio region.