• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.4
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• pp.605-610
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• 2021

Wireless charging method using a laser is considered as the most efficient method at a long distance of the wireless charging method. Combining long-range laser wireless charging technology with wireless communication technology will make it possible to use it for a variety of applications. Accordingly, this paper shows the results of research and experiments on wireless charging and wireless communication simultaneously based on a laser. This technique uses a laser as a light source for E/O(: Electric-to-Optical) conversion at the transmitter for optical wireless power transmission. In the experimental results, the optical power transmission using a 100 mW laser transmitter and a solar cells receiver showed a DC-to-DC efficiency of 1.9 %, wireless optical communication showed a transmission speed of up to 90 kbps when the transmission distance is 15 m.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.9
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• pp.4223-4239
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• 2016

In this paper, we consider an amplify-and-forward (AF) full-duplex relay network (FDRN) using simultaneous wireless information and power transfer, where a battery-free relay node harvests energy from the received radio frequency (RF) signals from a source node and uses the harvested energy to forward the source information to destination node. The time-switching relaying (TSR) protocol is studied, with the assumption that the channel state information (CSI) at the relay node is imperfect. We deliver a rigorous analysis of the outage probability of the proposed system. Based on the outage probability expressions, the optimal time switching factor are obtained via the numerical search method. The simulation and numerical results provide practical insights into the effect of various system parameters, such as the time switching factor, the noise power, the energy harvesting efficiency, and the channel estimation error on the performance of this network. It is also observed that for the imperfect CSI case, the proposed scheme still can provide acceptable outage performance given that the channel estimation error is bounded in a permissible interval.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.1
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• pp.1-19
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• 2020

In an underlay cognitive simultaneous wireless information and power transfer (SWIPT) network, communication from secondary user (SU) to secondary destination (SD) is accomplished with decode-and-forward (DF) relays. Multiple energy-constrained relays are assumed to harvest energy from SU via power splitting (PS) protocol and complete SU secure information transmission with beamforming. Hence, physical layer security (PLS) is investigated in cognitive SWIPT network. In order to interfere with eavesdropper and improve relay's energy efficiency, a destination-assisted jamming scheme is proposed. Namely, SD transmits artificial noise (AN) to interfere with eavesdropping, while jamming signal can also provide harvested energy to relays. Beamforming vector and power splitting ratio are jointly optimized with the objective of SU secrecy capacity maximization. We solve this non-convex optimization problem via a general two-stage procedure. Firstly, we obtain the optimal beamforming vector through semi-definite relaxation (SDR) method with a fixed power splitting ratio. Secondly, the best power splitting ratio can be obtained by one-dimensional search. We provide simulation results to verify the proposed solution. Simulation results show that the scheme achieves the maximum SD secrecy rate with appropriate selection of power splitting ratio, and the proposed scheme guarantees security in cognitive SWIPT networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.8
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• pp.1560-1566
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• 2015

To enable the efficient use of energy, the environment where unscheduled receivers can harvest energy from the transmitted signal is considered in next-generation wireless communication systems. In this paper, we propose a scheme for allocating subchannel and power to maximize the system throughput and harvested energy simultaneously using optimization techniques. Through simulations, we verify that the proposed scheme can increase the system throughput and harvested energy harmoniously. In particular, the proposed scheme improves the harvested energy remarkably with a negligible degradation of system throughput, compared with conventional scheme, as a result, energy can be used efficiently in the system.

• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.209-214
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• 2007

In this paper, we proposed a new MANET (Mobile Ad hoc Networks) technology of routing protocol. The MANET has a mobility formation of mobile nodes in the wireless networks. Wireless network have two types architecture: the Tree based multicast and shared tree based. The two kind's architecture of general wireless networks have difficult to solve the problems existing in the network, such as connectivity, safety, and reliability. For this purpose, as using that ADDMRP (Ad hoc network Doppler effect-based for Dynamic Multicast Routing Protocol), this study gives the following suggestion for new topology through network durability and Omni-directional information. The proposed architectures have considered the mobility location, mobility time, density, velocity and simultaneous using node by Doppler effects and improved the performance.

• Journal of KIISE:Information Networking
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• v.37 no.2
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• pp.85-93
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• 2010

WLAN virtualization can make multiple simultaneous experiments, each of which is conducted by a separate researcher, share scarce wireless resources in an IEEE 802.11 WLAN. The experiment performed in a virtualized WLAN should be consistent with that in a non-virtualized WLAN. The more similar these two experimental results, the better the consistency. To this end, we propose a novel virtualization scheme that has good consistency by preventing multiple simultaneous experiments from interacting with one another, without any modifications to the IEEE 802.11 standard. Through an intensive simulation study, we confirm that the consistency depends not only on the number of simultaneous experiments but also on wireless channel characteristics such as Doppler frequency and Ricean factor. According to such dependencies, the proposed scheme is optimized, so that it supports good consistency.

• Journal of Communications and Networks
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• v.13 no.2
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• pp.86-94
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• 2011

In recent years, there has been a rise in epidemiological evidence suggesting the health benefits of a physically active lifestyle. However, it is not always easy for individuals to personally recognize the optimal conditions for exercise and physical activity. Wearable acceleration-based pedometers have become widely used in estimating the amount of physical activity, and to a limited extent, providing information regarding exercise intensity, but they have never been used to assess adaptation to exercise. In order to realize simultaneous activity monitoring for multiple users exercising outdoors, we developed a prototype wireless local area network (WLAN) based system. In our system, a WLAN is deployed outside, and a user wearing a smart phone and monitoring device exercises freely within the coverage area of the wireless network. By doing so, the developed system is able to monitor the activity of each user andmeasures various parameters including those related to exercise adaptation. In a demonstration experiment, the developed system was evaluated and used to monitor users enjoying a Nordic walk, after which users were immediately able to receive their exercise report. In this paper, we discuss the requirements and issues in developing an activity monitoring system and report the findings we obtained through the demonstration experiment.

• Journal of KIISE:Information Networking
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• v.35 no.1
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• pp.56-66
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• 2008

Contention-based forwarding in wireless ad-hoc networks reduces transmission failure rate by selecting one receiver with good channel among multiple receivers. However, contention-based forwarding may increase transmission latency due to the collision problem caused by the simultaneous transmission among multiple receivers. In this paper, we present an analytic model that reflects the delay and collision rate of contention-based forwarding in lossy wireless links. Through the analytic model, we calculate the expected delay and progress in one-hop transmission under given wireless link model and delay model. Based on the analytic results, we observe that delay model should be adapted to wireless link model for optimal performance in contention-based forwarding.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.5
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• pp.2701-2722
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• 2017

Key generation is essential for protecting wireless networks. Based on wireless channel reciprocity, transceivers can generate shared secret keys by measuring their communicating channels. However, due to non-simultaneous measurements, asymmetric noises and other interferences, channel measurements collected by different transceivers are highly correlated but not identical and thus might have some discrepancies. Further, these discrepancies might lead to mismatches of bit sequences after quantization. The referred mismatches significantly affect the efficiency of key generation. In this paper, an efficient key generation scheme leveraging wireless channel reciprocity is proposed. To reduce the bit mismatch rate and enhance the efficiency of key generation, the involved transceivers separately apply discrete cosine transform (DCT) and inverse discrete cosine transform (IDCT) to pre-process their measurements. Then, the outputs of IDCT are quantified and encoded to establish the bit sequence. With the implementations of information reconciliation and privacy amplification, the shared secret key can be generated. Several experiments in real environments are conducted to evaluate the proposed scheme. During each experiment, the shared key is established from the received signal strength (RSS) of heterogeneous devices. The results of experiments demonstrate that the proposed scheme can efficiently generate shared secret keys between transceivers.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.1
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• pp.24-29
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• 2009

In this paper, we show the implementation of the low-cost RF transceiver module for parking control system. Super regenerative receiver scheme was adopted for this module due to its simplicity, low-cost, low power consumption and small number of components to improve reliability of the systems. For improving communication error rate by collision and in-band noise, dual-channel hopping scheme was adopted. Testing prototypes under the environment of simultaneous transmissions, we verified that the designed scheme is able to improve the success rate of data transmission of wireless parking control system cost effectively.