• International Journal of Computer Science & Network Security
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• v.21 no.3
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• pp.48-54
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• 2021

Security is an important issue for wireless communications and poses many challenges. Most security schemes have been applied to the upper layers of communications networks. Since in a typical wireless communication, transmission of data is over the air, third party receiver(s) may have easy access to the transmitted data. This work examines a new security technique at the physical layer for the sake of enhancing the protection of wireless communications against eavesdroppers. We examine the issue of secret communication through Rayleigh fading channel in the presence of an eavesdropper in which the transmitter knows the channel state information of both the main and eavesdropper channel. Then, we analyze the capacity of the main channel and eavesdropper channel we also analyze for the symbol error rate of the main channel, and the outage probability is obtained for the main transmission. This work elucidate that the proposed security technique can safely complement other Security approaches implemented in the upper layers of the communication network. Lastly, we implement the results in Mat lab

• Journal of the Korea Society of Computer and Information
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• v.13 no.5
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• pp.179-186
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• 2008

In proportion as the growth of the wireless sensor network applications, we need for more accuracy wireless channel information. In the case of indoor or outdoor wireless sensor networks, multipath propagation causes severe problems in terms of fading. Therefore, a path-loss model for multipath environment is required to optimize communication systems. This paper deals with log-normal path loss modeling of the indoor 2.4 GHz channel. We measured variation of the received signal strength between the sender and receiver of which separation was increased from 1 to 30m. The path-loss exponent and the standard deviation of wireless channel were determined by fitting of the measured data. By using the PRR(Packet Reception Rate) of this model. Wireless sensor channel is defined CR(Connect Region), DR(Disconnected Region). In order to verify the characteristics of wireless channel, we performed simulations and experiments. We demonstrated that connection ranges are 24m in indoor, and 14m in outdoor.

• Proceedings of the KIEE Conference
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• 2004.05a
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• pp.65-67
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• 2004

Change of state of Channel between two wireless terminals which is caused by noise and multiple environmental conditions for happens frequently from the Wireles Network. So, When it is like that planning a wireless network protocol or performance analysis, it follows to change of state of time-varying channel and packet the analysis against a transmission efficiency is necessary. In this paper, analyzes transmission time of a packet and a packet in a time-varying and packet based Wireless Network. To reflecte the feature of the time-varying channel, we use a Signal Flow Graph model. From the model the mean of transmission time and the mean of queue length of the packet are analyzed in terms of the packet distribution function, the packet transmission service time, and the PER of the time-varying channel.

• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.943-949
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• 2009

In this paper, the 5.9GHz WAVE(Wireless Access in Vehicular Environments) channel modeling is used by the Jakes channel model for the suitability of the fast wireless channel fluctuation. The performance analysed the fading signal constellation and the spectrum in the IEEE 802.11p spectrum mask, the Doppler effect, the modulation scheme. In addition, the vehicular speed, exactly the performance analysis the WAVE communication systems follow the Doppler effect.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.4
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• pp.651-669
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• 2013

In this paper, we study a novel routing algorithm based on load balancing for multi-channel wireless mesh networks. In order to increase the network capacity and reduce the interference of transmission streams and the communication delay, on the basis of weighted cumulative expected transmission time (WCETT) routing metric this paper proposes an improved routing metric based on load balancing and channel interference (LBI_WCETT), which considers the channel interference, channel diversity, link load and the latency brought by channel switching. Meanwhile, in order to utilize the multi-channel strategy efficiently in wireless mesh networks, a new channel allocation algorithm is proposed. This channel allocation algorithm utilizes the conflict graph model and considers the initial link load estimation and the potential interference of the link to assign a channel for each link in the wireless mesh network. It also utilizes the channel utilization percentage of the virtual link in its interference range as the channel selection standard. Simulation results show that the LBI_WCETT routing metric can help increase the network capacity effectively, reduce the average end to end delay, and improve the network performance.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.5A
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• pp.355-362
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• 2009

In real-time communication services, delay constraints are among the most important QoS (Quality of Service) factors. In particular, it is difficult to guarantee the delay requirement over wireless channels, since they exhibit dynamic time-varying behavior and even severe burst-errors during periods of deep fading. Channel throughput may be increased, but at the cost of the additional delays when ARQ (Automatic Repeat Request) schemes are used. For real-time communication services, it is very essential to predict data deliverability. This paper derives the delay distribution and the successful delivery probability within a given delay budget using a priori channel model and a posteriori information from the perspective of queueing theory. The Gilbert-Elliot burst-noise channel is employed as an a Priori channel model, where a two-state Markov-modulated Bernoulli process $(MMBP_2)$ is used. for a posteriori information, the channel parameters, the queue-length and the initial channel state are assumed to be given. The numerical derivation is verified and analyzed via Monte Carlo simulations. This numerical derivation is then applied to a rate control scheme for real-time video transmission, where an optimal encoding rate is determined based on the future channel capacity and the distortion of the reconstructed pictures.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.3
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• pp.390-394
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• 2003

It is very important to simulate various mobile communication channels for the reliable system design and performance tests. Therefore, a new method is proposed in this paper to improve the conventional one for the purpose of the efficient channel simulation having various characteristics. A newly proposed method can simulate any narrow band channel very efficiently from the given Doppler power spectrum model. Also, it has many simulation advantages considering the variety of wireless channel conditions since parameters related with channel characteristics, such as a signal power, signal to noise ratio, direct signal power ratio, etc., can be easily changed according to various propagation environments to be tested.

• Journal of Korea Multimedia Society
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• v.12 no.6
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• pp.824-832
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• 2009

Multi-radio multi-channel Wireless Mesh Network requires an effective management policy to control the assignment of channels to each radio. We concentrated our investigation on modeling method and solution to find a dynamic channel assignment scheme that is adapted to change of network traffic. Multi-path routing scheme was chosen to overwhelm the unreliability of wireless link. For a particular traffic state, our optimization model found a specific traffic distribution over multi-path and a channel assignment scheme that maximizes the overall network throughput. We developed a simple heuristic method for channel assignment by gradually removing clique load to obtain higher throughput. We also presented numerical examples and discussion of our models in comparison with existing research.

• Journal of electromagnetic engineering and science
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• v.12 no.1
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• pp.77-84
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• 2012

This paper introduces our development of a MIMO-OTA system with simplified configuration. The key element of our proposal is the adoption of an antenna branch-controlled configuration for generating multipath delayed waves. The signal processing is carried out on IF band signal with an FPGA in a fading-emulator-type MIMO-OTA measurement system. The proposed scheme is largely different from available system configurations for the fading simulator method of constructing the OTA test environment. We describe the principle of the proposed scheme, channel model incorporated in the system, basic configuration of the developed system, and its performance.

• Journal of Advanced Navigation Technology
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• v.26 no.6
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• pp.481-486
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• 2022

The recent rapid growth of the IoT(Internet of Things) is leading to the spread of low-power wireless technology. A major challenge in designing IoT wireless networks is to achieve coexistence between different wireless technologies that share the 2.4 [GHz] ISM (Industrial Scientific Medical) frequency band. Therefore, there is a need for research on improving the reliability of wireless networks and coexisting operation between wireless networks. In particular, it is necessary to study an interference model and performance for mutual service coexistence in a BLE (Bluetooth Low Energy) wireless network environment, which is expected to be widely used as a connection medium between devices in various industrial fields. In this paper, the co-channel interference model with the IEEE 802.15.4 system is established focusing on the physical layer of the BLE system widely used in residential and industrial wireless applications, and the performance of the BLE wireless communication system is analyzed in the co-channel interference environment. As a result of the analysis, as the distance between the interference source and the BLE system increases in an environment where noise and co-channel interference exist, the amount of co-channel interference decreases and the error rate performance of the BLE system improves.