• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2708-2716
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• 2013

This paper presents implementation of embedded remote monitoring diagnosis system which has effective wireless channel structure and communication protocols with user-friendly UI for intelligent digital vessel. Developed system contains integrated vessel monitoring system, server, exclusive mobile terminal and smart phone. We designed an effective dual structure communication channel and simple but effective communication protocol on the monitoring system. Failures of the wireless communication are minimized and the wrong wireless communication channel is immediately replaced. In addition, we developed an effective embedded Linux UI for LCD. The implemented wireless monitoring system was tested and verified on digital vessel.

• Journal of information and communication convergence engineering
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• v.4 no.2
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• pp.71-74
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• 2006

A basic access method about IEEE 802.11 MAC layer protocol using IEEE 802.11 wireless LANs is the DCF thatis based on the CSMA/CA. But, cause of IEEE 802.11 MAC layer uses original backoff algorithm (exponential backoff method), when collision occurred, the size of contention windows increases the double size Also, a time of packet transmission delay increases and efficienty is decreased by original backoff scheme. In this paper, we have analyzed TCP packet transmission time of IEEE 802.11 MAC DCF protocol for wireless LANs a proposed enhanced backoff algorithm. It is considered the transmission time of transmission control protocol (TCP) packet on the orthogonal frequency division multiplexing (OFDM) in additive white gaussian noise (A WGN) and Rician fading channel. From the results, a proposed enhanced backoff algorithm produces a better performance improvement than an original backoff in wireless LAN environment. Also, in OFDM/quadrature phase shift keying channel (QPSK), we can achieve that the transmission time in wireless channel decreases as the TCP packet size increases and based on the data collected, we can infer the correlation between packet size and the transmission time, allowing for an inference of the optimal packet size in the TCP layer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2B
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• pp.334-344
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• 2010

Recently, due to the prevalence of various mobile devices and broadband wireless networks, a significant interests and demands for multimedia streaming services over the Internet have been increasing. However, it is difficult to transmit continuous multimedia stream when mobile terminals are moving. Therefore, in order to deploy mobile IPTV service in the broadband wireless network, efficient wireless resource utilization and seamless QoE (Quality of Experience) offers to the users are an important issue. In this paper, we propose a network based adaptive streaming scheme, called MARC (Mobile Adaptive Rate Control), which controls the quality of the video and rate of the video based on the status of the wireless channel. The proposed scheme uses awareness information of the wireless channel status and controls transmitting streaming video which is suitable for the wireless channel status and mobile station location, in order to provide a seamless video playback for mobile environment in addition to improving the quality of a streaming service. The proposed MARC scheme alleviates the discontinuity of video playback and allocates suitable client buffer in broadband wireless network. Simulation results demonstrate the effectiveness of our proposed scheme.

• Journal of Korea Multimedia Society
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• v.7 no.5
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• pp.713-720
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• 2004

In this paper we suggest error control scheme to improve CLR performance degradation on wireless ATM access networks which consist of access node and wireless channel. Based on the cell scale and hurst scale, traffic model of wireless ATM access network is analyzed. The CLR equation due to buffer overflow for wireless access node is derived for VBR traffic. the CLR equation due to random bit errors and burst errors for wireless channel is derived. Using the CLR equation for both access node and wireless channel, the CLR equation of wireless ATM access network is derived, and we evaluate the CLR performance on the wireless ATM access networks with conventional SR ARQ scheme and recommended error control scheme, that is, Type I Hybrid ARQ scheme. It is confirmed that CLR performance of the access networks with recommended error control schemes is superior to that of access networks with conventional error control scheme.

• ETRI Journal
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• v.38 no.5
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• pp.952-961
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• 2016

In this paper, we study a spectrum sharing network (SSN) where a spectrum sharing device (SSD) coexists with multiple wireless communication systems (WCSs) in the same channel. The SSD can operate with either a duty cycle (DC) channel access mechanism or a listen-before-talk (LBT) channel access mechanism, whereas WCSs operate with an LBT mechanism. An opportunistic channel selection scheme for the SSD in the SSN is first proposed to minimize the outage probability. The optimal data transmission time for the DC-based SSD is derived to further improve the outage probability. We also derive the exact and closed-form outage probability of the proposed channel selection in the SSN by assuming that the number of WCSs operating in each channel is uniformly distributed. The simulation results show that the proposed channel selection scheme outperforms other channel selection schemes. It was also observed that a DC-based SSD with an optimal data transmission time provides a better outage performance than an LBT-based SSD. As the number of available channels increases, the channel selection scheme plays an important role in minimizing the outage probability of the SSNs.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.5
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• pp.1369-1389
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• 2024

In the era of 6G, the rapid increase in communication data volume poses higher demands on traditional channel estimation techniques and those based on deep learning, especially when processing large-scale data as their computational load and real-time performance often fail to meet practical requirements. To overcome this bottleneck, this paper introduces quantum computing techniques, exploring for the first time the application of Quantum Generative Adversarial Networks (QGAN) to broadband channel estimation challenges. Although generative adversarial technology has been applied to channel estimation, obtaining instantaneous channel information remains a significant challenge. To address the issue of instantaneous channel estimation, this paper proposes an innovative QGAN with a dual-module design in the generator. The adversarial loss function and the Mean Squared Error (MSE) loss function are separately applied for the parameter updates of these two modules, facilitating the learning of statistical channel information and the generation of instantaneous channel details. Experimental results demonstrate the efficiency and accuracy of the proposed dual-module QGAN technique in channel estimation on the Pennylane quantum computing simulation platform. This research opens a new direction for physical layer techniques in wireless communication and offers expanded possibilities for the future development of wireless communication technologies.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.7
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• pp.1243-1248
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• 2016

This paper investigated the channel link budget for Wireless Avionics Intra-Communication (WAIC) in 4.4GHz. The band 4.2~4.2GHz was allocated for the communication service among aeronautical applications in world radiocommunication conference (WRC). Wireless channels in aircraft was modelled by the combination of path loss, shadowing effect caused by obstacles, and fading caused by multipath signals. In addition, wireless channels in aircraft are categorized into 6 groups according to various locations of transmitter and receiver. We analyzed the channel link budget for the 6 channel groups in terms of maximum transmission distance and outage probability. Our analysis and intensive computer simulation results show that the propagation characteristics of group A, B, and F is superior to group C, D, E, and the propagation of group E is the most vulnerable. Also, these results can be utilized as basic reference for the channel analysis of intra-aircraft or similar environment.

• Journal of Convergence Society for SMB
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• v.2 no.1
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• pp.25-31
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• 2012

Recently Wireless Communication technologies are widely used in Small And Medium Business fields. Wireless mesh networks have been studied as the next generation technology to solve problem of conventional wireless networks. Wireless mesh network uses a 802.11 when make up of network. mesh clients occurs Hard handover moving between ones. This increases the handover latency of the network mobility is a very great issues. Consequently, this paper propose a channel information previously methods to reduce the handover latency selective channels. Proposed scheme accounts for more than 90% of the probe delay to minimize the client had to move the mesh based on the old channel to retrieve information. Through simulation, the proposed scheme had shorter handover delay time than transitional full scan and selective scan. Through results of evaluation, the suggest PCISS scheme more fast 6.5% than transitional scheme.

• ETRI Journal
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• v.34 no.1
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• pp.9-16
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• 2012

Precoding in the multiple-input multiple-output orthogonal frequency division multiplexing system is investigated. In conventional wideband precoding (WBP), only one precoder, obtained from the decomposition of the subcarrier independent channel matrix, is used for all subcarriers. With an investigation of the relationship between the subcarrier independent channel matrix and the temporal/frequency channels, an improved WBP scheme is proposed for practical scenarios in which a part of subcarriers are allocated to a user. The improved WBP scheme is a generalized scheme of which narrow-band precoding and conventional WBP schemes are special modes. Simulation results demonstrate that the improved WBP scheme almost achieves the optimum performance of a single precoder and outperforms the conventional WBP scheme in terms of the bit error ratio and ergodic capacity with slight complexity increase. The largest advantage of the improved WBP scheme on signal-to-noise ratio in simulation results is over 2.1 dB.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.2
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• pp.424-442
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• 2014

Most recent research on iterative solutions for interference alignment (IA) presents solutions assuming channel reciprocity based on the suppression of interference from undesired sources by using an appropriate decoding matrix also known as a receiver combining matrix for multiple input multiple output (MIMO) interference channel networks and reciprocal networks. In this paper, we present an alternative solution for IA by designing precoding and decoding matrices based on the concept of signal leakage (the measure of signal power that leaks to unintended users) on each transmit side. We propose an iterative algorithm for an IA solution based on maximization of the signal-to-leakage-and-noise ratio (SLNR) of the transmitted signal from each transmitter. In order to make an algorithm removing the requirement of channel reciprocity, we deploy maximization of the signal-to-interference-and-noise ratio (SINR) in the design of the decoding matrices. We show through simulation that minimizing the leakage in each transmission can help achieve enhanced performance in terms of aggregate sum capacity in the system.