• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.12-15
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• 2000

In this paper, we have evaluated the performance of an OFDM system using hierarchical 16QAM (OFDM/HL-16QAM) for achieving high quality and high speed data and image transmission in multipath fading channel. The wireless channel for performance evaluation is assumed to include AWGN and two ray multipath fading. Through simulation we have obtained the BER performance of the system according to $E_{b}$, $N_{0}$, then compared the received image quality of proposed system with that of conventional system. From the result, it is shown that the OFDM/HL-16QAM system is more effective for data and image transmission.n.n.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.1
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• pp.95-104
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• 1997

This paper deals with an analysis of multipath which affect a transmission performance in underwater acoustic channel. For the test of autonomous underwater vehicle(AUV), underwater acoustic channel with multipath structure is introduced to mathmatical modelling for a basin environment. In this paper, SMR(Signal to Multipath Ratio) which is defined as a parameter of mulipath's effect is presented as a mathmatical equation, and the equation or SMR is simulated by MATLAB program.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.05a
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• pp.598-599
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• 2015

For the wireless mesh networks, efficient routing protocol is required to transmit data from source to destination node through multi-hop transmission. Multipath routing enable the stable data transmission even in the case of traffic congestion or unstable link. In this paper, we propose partial multipath routing which does not make a full multipath but partial for some parts of unstable links. This partial multipath routing reduce the number of nodes for routing and minimized the required power.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.247-252
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• 2005

This paper proposed M-ary QAM OFDM system for efficiently transmission in multipath fading environment. And, this system have analyzed reception performance by occurred synchronization error to frequency offset in presence of multipath fading. As a result, it confirmed justification by simulation and BER theory of 64QAM OFDM of SP frame structure for the digital broadcasting.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.3
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• pp.19-29
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• 2008

Underwater acoustic(UWA) communication is one of the most difficult field in terms of severe channel environments such as multipath propagation, high temporal and spatial variability of channel conditions. Therefore, it is important to model and analyze the characteristics of underwater acoustic channel such as multipath propagation, transmission loss, reverberation, and ambient noise. In this paper, UWA communication channel is modeled with a ray tracing method and applied to image transmission. Quadrature phase shift keying(QPSK) and multichannel decision feedback equalizer(DFE) are utilized as phase-coherent modulation method and equalization technique, respectively. The objective is to improve the performance of the image transmission using vertical sensor array instead of single sensor in the viewpoint of bit error rate(BER), constellation diagram, and received image quality.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.2
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• pp.271-287
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• 2013

We propose a new multipath-based reliable routing protocol on MANETs, Multipath-based Reliable routing protocol with Fast-Recovery of failures (MRFR). For reliable message transmission, MRFR tries to find the most reliable path between a source and a destination considering the end-to-end packet reception reliability of the routes. The established path consists of a primary path that is used to transmit messages, and the secondary paths that are used to recover the path when detecting failures on the primary path. After establishing the path, the source transmits messages through the primary path. If a node detects a link failure during message transmission, it can recover the path locally by switching from the primary to the secondary path. By allowing the intermediate nodes to locally recover the route failure, the proposed protocol can handle the dynamic topological change of the MANETs efficiently. The simulation result using the QualNet simulator shows that the MRFR protocol performs better than other protocols in terms of the end-to-end message delivery ratio and fault-tolerance capability.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.6 no.12
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• pp.3081-3099
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• 2012

We propose a new multipath-based reliable routing protocol on MANETs, Multipath-based Reliable routing protocol with Fast-Recovery of failures (MRFR). For reliable message transmission, MRFR tries to find the most reliable path between a source and a destination considering the end-to-end packet reception reliability of the routes. The established path consists of a primary path that is used to transmit messages, and the secondary paths that are used to recover the path when detecting failures on the primary path. After establishing the path, the source transmits messages through the primary path. If a node detects a link failure during message transmission, it can recover the path locally by switching from the primary to the secondary path. By allowing the intermediate nodes to locally recover the route failure, the proposed protocol can handle the dynamic topological change of the MANETs efficiently. The simulation result using the QualNet simulator shows that the MRFR protocol performs better than other protocols in terms of the end-to-end message delivery ratio and fault-tolerance capability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.12A
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• pp.958-963
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• 2003

Increasing throughput using high order data modulations in the WCDMA downlink requires the elimination of multipath interferences. For this reason, Kenichi Higuchi proposed a multipath interference canceller in WCDMA downlink. However, this paper considers the downlink signal models that only contains code channels for which code information is known to the receiver. WCDMA systems contain code channels for other active users whose code information is unknown to the receiver and these code channels degrade the performance of the multipath interference canceller. Thus, this paper proposes a multipath interference mitigation scheme which removes multipath interference induced by all the code channels within a cell. Simulation results show that the proposed scheme outperforms both the RAKE receiver and the multipath interference canceller in the WCDMA downlink.

• Proceedings of the IEEK Conference
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• summer
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• pp.110-113
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• 2004

Underwater acoustic(UWA) communication is one of the most difficult field because of several factors such as multipath propagation, high temporal and spatial variability of channel conditions. Therefore, it is important to model and analyze the characteristics of underwater acoustic channel such as multipath propagation, transmission loss, reverberation, and ambient noise. In this paper, UWA communication channel is modeled with a ray tracing method and applied to image transmission. Quadrature phase shift keying(QPSK) and multichannel decision feedback equalizer(DFE) are utilized as phase-coherent modulation method and equalization technique, respectively. The objective is to improve the performance of vertical sensor array than that of single sensor in the viewpoint of bit error rate(BER), constellation output, and received image quality.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.3
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• pp.259-269
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• 2018

Multipath TCP (MPTCP) can be expected to provide improved network performance because it transmits data through multiple paths. However, Bufferbloat, which unexpectedly occurs in the transmission path, degrades not only the performance of the corresponding path but also the performance of other paths, so that the performance is worse than that of a single TCP. In this paper, we propose the transmission status monitoring method at the sender's MPTCP level and also HoL packets retransmission algorithm in order to solve the Bufferbloat problem. The proposed algorithm enables Bufferbloat detection by the sender side independently, and it can resolve the HoL blocking problem by identifying the HoL packet in the proposed transmission status monitoring buffer and retransmitting it to the normal path. Simulation results based on NS-3 show that the proposed algorithm achieves the improved throughput performance up to 22.8% compared to the existing MPTCP, and the average number of queued packets in the sender and receiver's buffers is decreased to 44.3% and 9.2%, respectively.