• Journal of Communications and Networks
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• v.18 no.1
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• pp.75-83
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• 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.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.359-360
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• 2011

In this work. a new receiver-driven channel rendezvous mechanism is proposed for multi-channel communication in Wireless sensor networks (WSNs). The work is a light-weight scheduled scheme. seems to be incurring less overhead in compare to traditional common control channel based rendezvous mechanisms.

• The Journal of Information Systems
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• v.22 no.1
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• pp.181-200
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• 2013

Electronic channel of automobile insurance has emerged as an attractive way of lowering costs and saving time to do the transaction for customers. Electronic channel refers to using web sites to find useful information on insurance products, buy automobile insurance, and ask for services related to the insurance. This study suggests a modified model of the UTAUT and examines the factors influencing intention to use electronic channel in the transaction of automobile insurance. Based on 203 responses from potential automobile insurance buyers, the results showed that performance expectancy, effort expectancy, social influence, service expectancy, and security risk are significantly related to intention to use electronic channel. The results also showed that age as a moderator influences the effects of performance expectancy and effort expectancy on intention to use electronic channel. The study results would improve the understanding of the factors to which managers of insurance companies should pay attention in order to increase their sales through electronic channel.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.4
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• pp.484-490
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• 1990

In speech coding scheme, because information bits have different error sensitivities over channel errors, the channel coder for combining with speech coding should be realized by the variable coding rate considering the bit importance of speech information bits. In realizing the 4 kbps channel coder for 12kbps speech, this paper have chosen the channel coding method by analyzing the hard-decision post-decoding error rate of RCPC(Rate Compatible Punctured Convolutional) codes and bit error sensitivity of 12 kbps speech. Under the coherent QPSK and Rayleigh fading channel, the performance analysis has showed that 10dB gain was obtained in speech SEGSNR by 4-level uneuqal error protection, which was compared with the caseof no channel coding at 7dB channel SNR.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.4C
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• pp.384-391
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• 2003

Blind channel identification and equalization attempt to identify the communication channel and to remove the inter-symbol interference caused by a communication channel without using any known trainning sequences. In this paper, we propose a blind adaptive channel identification and equalization algorithm with phase offset compensation for single-input multiple-output (SIMO) channel. It is based on the one-step forward multichannel linear prediction error method and can be implemented by an RLS algorithm. Phase offset problem, we use a blind adaptive algorithm called the constant modulus derotator (CMD) algorithm based on condtant modulus algorithm (CMA). Moreover, unlike many known subspace (SS) methods or cross relation (CR) methods, our proposed algorithms do not require channel order estimation. Therefore, our algorithms are robust to channel order mismatch.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.10
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• pp.4034-4053
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• 2015

In order to meet various requirements for transmission quality of both primary users (PUs) and secondary users (SUs) in cognitive radio networks, we introduce a channel bonding mechanism for PUs and a channel reservation mechanism for SUs, then we propose a novel spectrum allocation strategy. Taking into account the mistake detection and false alarm due to imperfect channel sensing, we establish a three-dimensional Markov chain to model the stochastic process of the proposed strategy. Using the method of matrix geometric solution, we derive the performance measures in terms of interference rate of PU packets, average delay and throughput of SU packets. Moreover, we investigate the influence of the number of the reserved (resp. licensed) channels on the system performance with numerical experiments. Finally, to optimize the proposed strategy socially, we provide a charging policy for SU packets.

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.79-82
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• 2004

In this paper, we analyze the performance of high-rate OFDM(Orthogonal Frequency Division Multiplexing) in the JTC(Joint Technical Committee) channel models using transmit diversity. In this thesis, each independent channel characteristic antennas in the transmitter are analyzed. Also, Equalization method through the channel estimation in the realistic fading channel environments is applied for BEE 802.11a WLAN system performance. From the simulation results, BER through transmit diversity of WLAN system is evaluated in AWGN channel and multipath channel environments.

• Journal of Broadcast Engineering
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• v.11 no.3 s.32
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• pp.311-319
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• 2006

Platform operators adopted ATSC standard send only their own channel program schedule information, so in order for the viewer to see other channel information, they have to tune the channel to the other. This issue arises from the operators' lack of bandwidth and the business interest conflicts between the platform operators. This paper guides how ATSC standard could be used within Xlet based application to display other channel information through the ISG (Integrated Scheduling Guide) technology via interactive return channel services. Its own channel information can be displayed by using on-air PSIP (Program and System Information Protocol) data.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.1
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• pp.108-122
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• 2014

Massive antenna array is an attractive candidate technique for future broadband wireless communications to acquire high spectrum and energy efficiency. However, such benefits can be realized only when proper channel information is available at the transmitter. Since the amount of the channel information required by the transmitter is large for massive antennas, the feedback is burdensome in practice, especially for frequency division duplex (FDD) systems, and needs normally to be reduced. In this paper a novel channel feedback reduction scheme based on the theory of distributed compressive sensing (DCS) is proposed to apply to massive antenna arrays with spatial correlation, which brings substantially reduced feedback load. Simulation results prove that the novel scheme is better than the channel feedback technique based on traditional compressive sensing (CS) in the aspects of mean square error (MSE), cumulative distributed function (CDF) performance and feedback resources saving.

• Journal of Korea Society of Digital Industry and Information Management
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• v.6 no.3
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• pp.103-109
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• 2010

Total performance is improved by minimizing the channel interference between links in wireless mesh networks (WMNs). The paper refines on the CB-CA [1] to be suitable for multi-radio multi-channel (MRMC) WMNs. The CB-CA is the cluster-based channel assignment algorithm for one radio three channel WMN based on IEEE 802.11b/g. The CB-CA does not perform the channel scanning and the channel switching between the cluster heads (CHs) and the edge gateway nodes (EGs). However, the use of co-channel for links between CHs and EGs brings the problem of channel interference among many nodes. We propose and evaluate an improved CB-CA algorithm to solve this problem in MRMC WMNs. The proposed algorithm discriminates between transmission channel and receive channel and assigns channels to each interface randomly and advertises this information to neighbor clusters in order to be assigned no-interference channel between clusters. Therefore, the proposed algorithm can minimize the interference between clusters and also improve QoS, since it can use multiple interfaces and multiple channels.