• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2323-2340
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• 2012

Recent advances in cognitive radio technology have drawn immense attention to higher layer protocols above medium access control, such as transmission control protocol (TCP). Most proposals to improve the TCP performance in cognitive radio (CR) networks have assumed that either all nodes are in CR networks or the TCP sender side is in CR links. In those proposals, lower layer information such as the CR link status could be easily exploited to adjust the congestion window and improve throughput. In this paper, we consider a TCP network in which the TCP sender is located remotely over the Internet while the TCP receiver is connected by a CR link. This topology is more realistic than the earlier proposals, but the lower layer information cannot be exploited. Under this assumption, we propose an enhanced TCP protocol for CR networks called TCP for cognitive radio (TCP-CR) to improve the existing TCP by (1) detection of primary user (PU) interference by a remote sender without support from lower layers, (2) delayed congestion control (DCC) based on PU detection when the retransmission timeout (RTO) expires, and (3) exploitation of two separate scales of the congestion window adapted for PU activity. Performance evaluation demonstrated that the proposed TCP-CR achieves up to 255% improvement of the end-to-end throughput. Furthermore, we verified that the proposed TCP does not deteriorate the fairness of existing TCP flows and does not cause congestions.

• ETRI Journal
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• 제23권3호
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• pp.111-120
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• 2001

For scalable multicast transport, one of the promising approaches is to employ a control tree known as acknowledgement (ACK) tree which can be used to convey information on reliability and session status from receivers to a root sender. The existing tree configuration has focused on a 'bottom-up' scheme in which ACK trees grow from leaf receivers toward a root sender. This paper proposes an alternative 'top-down' configuration where an ACK tree begins at the root sender and gradually expands by including non-tree nodes into the tree in a stepwise manner. The proposed scheme is simple and practical to implement along with multicast transport protocols. It is also employed as a tree configuration in the Enhanced Communications Transport Protocol, which has been standardized in the ITU-T and ISO/IEC JTC1. From experimental simulations, we see that the top-down scheme provides advantages over the existing bottom-up one in terms of the number of control messages required for tree configuration and the number of tree levels.

• 통상정보연구
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• 제9권3호
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• pp.287-304
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• 2007

Determination of the time and place of dispatch and receipt of electronic messages is an important element of the operation of many rules of law, particularly the timing of formation of the contract. In this paper, I reviewed interpretation and application of time and place of dispatch and receipt of electronic records in electronic transactions under the UNCITRAL(United Nations Commission on International Trade Law) Model Law on Electronic Commerce, USA Uniform Electronic Transactions Act and Korea Electronic Transactions Act. Time of dispatch and time of receipt are effective when received. The sender has the burden to prove that the electronic record is sent successfully to the information process system of the recipient. Therefore, to safety electronic transactions, the sender needs to request a confirm notice for receipt to the recipient when the electronic record is sent like the provisions of UNCITRAL Model Law on Electronic Commerce and Korea Electronic Transactions Act. By requesting the above, the sender is able to take precautionary measures for damage according to the failure of dispatch and receipt of the electronic records.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제10권10호
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• pp.4642-4660
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• 2016

One major concern of applying Multipath TCP (MPTCP) to data delivery in heterogeneous wireless networks is that the utilization of asymmetric paths with diverse networking-related parameters may cause severe packet reordering and receive buffer blocking (RB²LOC). Although many efforts are devoting to addressing MPTCP's packet reordering problems, their sender-controlled solutions do not consider balancing overhead between an MPTCP sender and receiver, and their fully MPTCP mode cannot make MPTCP achieve a desired performance. This paper proposes a novel receiver-centric buffer blocking-aware data scheduling strategy for MPTCP (dubbed MPTCP-rec) necessitating the following aims: (1) alleviating MPTCP's packet reordering and RB²LOC problems, (2) improving the MPTCP performance, and (3) balancing load between the MPTCP sender and receiver. Simulation results show that the proposed MPTCP-rec solution outperforms the existing MPTCP solutions in terms of data delivery performance in heterogeneous wireless networks.

• 한국컴퓨터정보학회논문지
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• 제15권12호
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• pp.75-84
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• 2010

모바일 애드 혹 네트워크(MANET)에서 브로드캐스팅은 한 노드가 모든 다른 노드들에게 패킷을 전달하는 과정인데, Ad hoc On demand Distance Vector (AODV)와 같은 라우팅 프로토콜에서 경로를 설정하는 과정에서 제어 정보를 전달하기 위하여 많이 사용된다. 본 논문에서는 MANET에서 송수신 노드 사이의 이격 비율에 기반한 확률적 브로드캐스팅 기법을 제안하는데, 이 방법은 확률적 접근 방법과 거리에 기반한 접근 방법을 결합한 방법이다. 브로드캐스트 패킷을 수신한 이동 노드는 송신 노드로부터의 이격 비율을 고려하여 재전송 확률을 결정하는데, 이격비율은 송수신 노드사이의 거리와 무선 전파의 전달 거리를 고려하여 계산한다. 높은 이격 비율을 가진 노드는 송신자로부터 멀리 떨어진 노드로서 높은 확률값을 부여한다. 반면에 송신자에 가까운 노드는 이격 비율이 작아 낮은 재전송 확률값을 부여하여 패킷의 조기 소멸을 통해 재전송 브로드캐스트 패킷의 수를 줄이도록 한다. 플러딩 기법과 고정된 확률값 기법과의 성능 비교를 통하여 제안 기법이 다른 방법보다 우수한 성능을 보여주었는데, 제안 기법은 플러딩에 비하여 30% 이상의 패킷 전송을 감소시킬 수 있었으며, 96%에 가까운 패킷의 도착율을 보여주었다.

• 한국멀티미디어학회논문지
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• 제23권8호
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• pp.1030-1039
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• 2020

The biggest feature of the online environment is anonymity. So it is difficult to identify the sender accurately in Email. So we use PGP to enhance the security of email. PGP is an e-mail encryption program that has become the standard for email security worldwide. But PGP has a weak point in security. PGP can identify users, but it is difficult to verify reliability. In PGP, the more reliable other users guarantee that user are, the more reliable they are. In the previous study, the PGP structure was implemented by utilizing the block chain to lay the foundation, and in this paper, the structure of the previous article is applied to the e-mail environment to measure up the sender's reliability, and a system is proposed that allows users to distinguish the reliability of the message.

• 대한임베디드공학회논문지
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• 제1권2호
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• pp.64-72
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• 2006

The long propagation delay over satellite internet causes degradation of TCP performance in slow start phase. Especially, web traffic performance is greatly reduced by low throughput in slow start phase. To improve web traffic performance, we propose the Dynamic ACK Generation Scheme which generates ACKs and considers sender RTO in PEP (Performance Enhancing Proxy). The Normal ACK generation mechanism improves TCP throughput, and also decreases sender RTO. if PEP stops generating ACKs, TCP performance will be reduced by frequent RTO expiration. To solve this problem, our scheme adjusts RTO using ACK generation interval. And it supports retransmission mechanism for loss recovery in PEP. The results of the performance analysis provide a good evidence to demonstrate the efficiency of our mechanisms over satellite internet.

• 한국통신학회논문지
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• 제18권1호
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• pp.150-156
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• 1993

본 논문에서는 정보통신에 있어서 수신자가 송신자 및 송신문을 인증하는 방법으로써Galois Field에서의 다항식을 이용한 암호가 기법을 적용하여 인증에 걸리는 처리속도를 향상시켰으며, 또한 송신자에 대한 인증정보를 대화방식으로 영지식증명 절차를 이용하여 생성하고, 이를 송신문에대한 인증정보에 포함하여 전송하므로써 비밀정보 교환의 안전성을 강화하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
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• pp.130-133
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• 2001

VoIP(voice over internet protocol) technology is based on IP protocol. The IP protocol can be involved in two types of communication: unicasting and multicasting. Unicasting is the communication between one sender and one receiver. It is one-to-one communication. Multicasting is one-to-many communication. So that, many receivers can get same data from one sender simultaneously. and, the different protocol are proposed for VoIP; H.323, SIP and MGCP. MGCP is perfect server-client protocol, so MGCP is very attractive VoIP protocol to ISP. This paper uses MGCP and offers modified MGCP for conference call. So that, Modified MGCP is compatible to MGCP, and supports conference call using IP-multicast.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1904-1919
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• 2015

Deniable authentication protocol allows a sender to deny his/her involvement after the protocol run and a receiver can identify the true source of a given message. Meanwhile, the receiver has no ability to convince any third party of the fact that the message was sent by the specific sender. However, most of the proposed protocols didn't achieve confidentiality of the transmitted message. But, in some special application scenarios such as e-mail system, electronic voting and Internet negotiations, not only the property of deniable authentication but also message confidentiality are needed. To settle this problem, in this paper, we present a non-interactive identity-based deniable authenticated encryption (IBDAE) scheme using pairings. We give the security model and formal proof of the presented IBDAE scheme in the random oracle model under bilinear Diffie-Hellman (BDH) assumption.