• The Journal of Korean Institute of Communications and Information Sciences
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• 제28권5B호
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• pp.369-380
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• 2003

In the CDMA wireless link, frame errors are correlated and burst because of fading. The implementation ability of RLP error recovery is dependent on the correlated frame errors. The (1,2,3) retransmission scheme, which is recommended as default in IS-707, is not adapted in high frame loss regime with strong correlations. By using the modified error recovery method, where the total number of retransmission attempts is the same and the retransmission is increased, the proposed retransmission scheme can efficiently recover frame errors than the (1,2,3) retransmission scheme. Since the modified scheme has longer transmission delay due to the increase of retransmission round, we propose the algorithm of retransmission failure prediction to improve the modified error recovery scheme. We simulate the modified error recovery scheme applying our algorithm and compare two schemes. (i.e. default scheme by IS-707 and modified scheme) not applying our algorithm. In the result, we show TCP performance improvement is better than default scheme by IS-707.

• Journal of Broadcast Engineering
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• 제20권2호
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• pp.300-309
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• 2015

In IEEE 802.11n WLANs(Wireless Local Area Networks), to support high throughput, MAC(Media Access Control) layer adopts A-MSDU(Aggregate-MAC Service Data Unit) and A-MPDU(Aggregate-MAC Protocol Data Unit). Generally, as the A-MPDU uses a selective retransmission capability, A-MPDU provides higher throughput than A-MSDU. However, although A-MPDU uses the selective re-transmission capability, if the size of MPDU within A-MPDU is smaller than the size of minimum MPDU starting spacing, A-MPDU can reduce throughput because of the overhead of retransmission owing to the addition of delimiter, that is a dummy MPDU. Therefore, to overcome the above problem, two-level Aggregation method, where the small MPDU within A-MPDU is replaced by not delimiter but A-MSDU, has been introduced. In the two-level Aggregation method, the existing re-transmission scheme retransmits only A-MPDU, but if the size of retransmission data is smaller than the size of the minimum MPDU starting spacing, the proposed retransmission scheme retransmits the aggregated retransmission data and MSDUs. Therefore, we know that the proposed retransmission scheme have better throughput that the existing retransmission scheme.

• Korean journal of communication and information
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• 제48권
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• pp.63-89
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• 2009

The contents provided by the terrestrial broadcasters have governed the market based on their excellent quality in Korea. In spite of the launching of various pay TV services focusing on multi-channel, it is not yet easy to find out the substitutionary pay TV channels for the terrestrial. Therefore, the real time retransmission of the terrestrial channels brings about the crucial effects on the pay TV's competency, especially on the new media as the invisible barrier. So it is frequently proposed to change the aim of the retransmission policy from the universal access to the promotion of media industries. The retransmission can be divided into two types as the must carry and retransmission consent. In Korean situation, keeping or reducing the must carry channel would be appropriate rather than expanding them. However, periodic investigation into the public effects of the must carry is necessary, instead of it. Moreover, the rational and fair monetary compensation for the commercial channels(MBC, SBS, KBS2) is arising as the bottle neck in the retransmission agreements between the broadcasters. The conjoint analysis was carried out to estimate the welfare growth from the retransmission, based on the stated preference from the audiences' point of view. For must carry channels, it was certified as the 'win-win' strategy for both sides and audiences. For the commercial channels, it is revealed to be beneficial to the audiences. Thereafter, the standards for the rational price were suggested to promote the retransmission. This can contribute for inspiring the dynamic vitality to the media industry by reinforcing the contents competencies and for establishing the long term growth strategies.

• Journal of Computing Science and Engineering
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• 제5권4호
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• pp.324-330
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• 2011

To avoid collisions, IEEE 802.11 medium access control (MAC) uses predetermined inter-frame spaces and the random back-off process. However, the retransmission strategy of IEEE 802.11 MAC results in considerable time wastage. The hidden node problem is well known in wireless networks; it aggravates the consequences of time wastage for retransmission. Many collision prevention and recovery approaches have been proposed to solve the hidden node problem, but all of them have complex control overhead. In this paper, we propose a fast retransmission scheme as a recovery approach. The proposed scheme identifies collisions caused by hidden nodes and then allows retransmission without collision. Analysis and simulations show that the proposed scheme has greater throughput than request-to-send and clear-to-send (RTS/CTS) and a shorter average waiting time.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제29권2B호
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• pp.203-209
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• 2004

In OBS networks, the burst dropping due to contention significantly affects the performance of TCP, but existing drop policies have not considered this problem and researches related to TCP have been mainly studied on burst assembling. We propose the drop policy considering retransmission of TCP to improve the performance of TCP in OBS networks. The proposed drop policy is the Retransmission Count-based DP that regards retransmission count of bursts as priority when it selects dropping burst. This paper evaluates the performance of RC-based DP model and general DP model using ns-2. The metrics of performance evaluation are TCP throughput, maximum sequence number of received TCP packets and drop rate of packet as simulation time increases.

• Proceedings of the IEEK Conference
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(3)
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• pp.93-96
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• 2001

In this paper, we propose a delay-constrained retransmission method to control packet error or loss in common internet. The Delay Regulator(or Jitter Buffer) which is used to control errors caused by unreliable UDP connection, stores received data packets fDr a small amount of time to prevent network jitter from affecting display quality, which causes constant delay. In this paper, we propose a retransmission method to increase efficiency of ARQ(Automatic Repeat reQuest) by using characteristic of delay regulator.

• Proceedings of the Korea Information Processing Society Conference
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• 한국정보처리학회 2003년도 추계학술발표논문집 (중)
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• pp.939-942
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• 2003

TCP Westwood[1]는 송신측에 수신된 ACK를 통해서 대역폭을 계산하여 데이터를 전송하는 기법이다. 위성망 같이 손실률이 매우 높은 환경을 위해 TCP Westwood에서는 기존의 Bu]k Retransmission[2] 기법을 보안 하였다. 하지만 Bulk 재 전송 기법은 불필요한 데이터도 함께 재전송하기 때문에 성능이 저하되게 된다. 이 논문에서는 재 전송 패킷의 수를 적절히 조절하는 Adaptive Bulk Retransmission 기법을 제안하고자 한다.

• Journal of Industrial Technology
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• 제28권A호
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• pp.113-117
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• 2008

Wireless carrier sense multiple access (CSMA) systems are widely used but show extremely different transmission efficiency according to the operation environment. Simulation or prototype deployment is needed to see the transmission efficiency of a wireless CSMA system with the partial packet retransmission scheme. The lower bound for the transmission efficiency of such a system is found mathematically in this work. This shows how much the partial packet retransmission scheme improves the transmission efficiency quantitatively. It also shows that the maximum throughput is obtained at higher offered load compared to the conventional CSMA system without the partial packet transmission. The result of this work can be applied to IEEE 802.11 networks or wireless mesh networks.

• Journal of Communications and Networks
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• 제12권6호
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• pp.577-581
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• 2010

We introduce a novel packet retransmission technique which improves the efficiency of automatic retransmission query (ARQ) protocols in the context of satellite broadcast/multicast systems. The proposed coded ARQ technique, similarly to fountain coding, performs transmission of redundant packets, which are made by linear combinations of the packets composing the source block. Differently from fountain codes, the packets for the linear combinations are selected on the basis of the retransmission requests coming from the user terminals. The selection is performed in a way that, at the terminals, the source packets can be recovered iteratively by means of simple back-substitutions. This work aims at providing a simple and efficient alternative to reliable multicast protocols based on erasure correction coding techniques.

• Journal of Broadcast Engineering
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• 제19권3호
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• pp.415-418
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• 2014

The CBS methodology has been standardized in order to make a rapid broadcast of emergency alert message for cellular users. However, the standard does not specify a retransmission request mechanism in the case that the users fail in receiving the alert message. Therefore, we propose a retransmission request scheme based on cognitive radio for the CBS technology in this letter. The simulation results confirm that our proposed scheme is very suitable for the retransmission method in CBS-based emergency alert broadcast systems.