• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1522-1533
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• 2001

In this paper, we handle the estimation method of the received $E_{b}l1_{o}$ for forward closed-loop power control in cdma2000 systems. The estimation of MS-received $E_{b}l1_{o}$ utilizes the symbols related to the forward power control subchannel transmission. The estimation of the received bit energy and noise variance is analyzed for the frequency-selective Rayleigh fading channel. In order to improve SIR (signal-to-interference), the estimation of the received bit energy is made by the coherent combining of the rake-fingers and received I/Q symbols. And, in this paper, we evaluate the performance of forward closed-loop power control according to the mobile speed and the power adjustment step size in terms of the bit error rate (BER) and power control error. Simulation results present the optimal power adjustment step sizes according to the mobile speeds.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.809-811
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• 1993

The load impedance of power lines generally varies with time, areas, and season. Also, the harmonic noises by the power electrical equipments are scattered through the power lines. The received signal level varies with the environment and is not able to detect the PLC(Power Line Carrier) signal. For this reason, it is requried for the signal transmitter to hold the received signal level uniform independently with the variation of the load impedence. In this paper, the power lines are modeled simply and a method keeping the received signal level uniform is suggested through the analysis of the signal transmission characteritics of the PLC coupler using tank circuit.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.4
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• pp.1390-1405
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• 2014

This paper investigates optimal relay selection and power allocation under an aggregate power constraint for cooperative wireless sensor networks assisted by amplify-and-forward relay nodes. By considering both transmission power and circuit power consumptions, the received signal-to-noise ratio (SNR) at the destination node is calculated, based on which, a relay selection and power allocation scheme is developed. The core idea is to adaptively adjust the selected relays and their transmission power to maximize the received SNR according to the channel state information. The proposed scheme is derived by recasting the optimization problem into a three-layered problem-determining the number of relays to be activated, selecting the active relays, and performing power allocation among the selected relays. Monte Carlo simulation results demonstrate that the proposed scheme provides a higher received SNR and a lower bit error rate as compared to the average power allocation scheme.

• Journal of Internet Computing and Services
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• v.18 no.6
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• pp.15-23
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• 2017

Wireless power transmission (WPT) for wireless charging is currently attracting much attention as a promising approach to miniaturize batteries and increase the maximum total range of an electric vehicle. The main advantage of the laser power beam (LPB) approach is its high power transmission efficiency (PTE) over long distance. In this paper, we present the design of a laser power beam based WPT system, which has a best WPT channel selection technique at the receiver end when multiple power transmitters and single power receiver are operated simultaneously. The transmitters send their transmission channel information via optically modulated laser pulses. The receiver uses the received signal strength indicator and digitized data to choose an optimum power transmission path. We modeled a vertical multi-junction photovoltaic cell array, and conducted an experiment and simulation to test the feasibility of this system. From the experimental result, the standard deviation between the mathematical model and the measured values of normalized energy distribution is 0.0052. The error between the mathematical model and measured values are acceptable, thus the validity of the model is verified.

• ETRI Journal
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• v.38 no.1
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• pp.30-40
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• 2016

Co-channel interference between macro-femtocell networks is an unresolved problem, due to the frequency reuse phenomenon. To mitigate such interference, a secondary femtocell must acquire channel-state knowledge about a co-channel macrocell user and accordingly condition the maximum transmit power of femtocell user. This paper proposes a pilot-based spectrum sensing (PSS) algorithm for overlaid femtocell networks to sense the presence of a macrocell user over a channel of interest. The PSS algorithm senses the pilot tones in the received signal through the power level and the correlation metric comparisons between the received signal and the local reference pilots. On ensuring the existence of a co-channel macrocell user, the maximum transmit power of the corresponding femtocell user is optimized so as to avoid interference. Time and frequency offsets are carefully handled in our proposal. Simulation results show that the PSS algorithm outperforms existing sensing techniques, even at poor received signal quality. It requires less sensing time and provides better detection probability over existing techniques.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.53-59
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• 2000

In this paper, considering configuration of the earth and environment of country, it is classified a radio propagation environment Multipath propagation measuring system based on PN code correlation detection method is built to study a wave propagation characteristics of 1.95GHz. Considering the characteristic artificial structure of country, Cihwa plant superintendent area has been selected for basic and accurate measurement a radio propagation characteristic. The experiments are carried out with respect to the RMS delay Spread and the received power in the two kind of geographical areas, LOS (Line of Sight) and N-LOS (Non Line of Sight). The measurement result of that received power of LOS area is -1.6∼-28.8dBm, RMS delay spread is 0.023㎲∼0.22㎲ and received power of N-LOS area is 16∼36.5dBm and RMS delay spread is 0.068∼0.37㎲.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.265-266
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• 2006

In this paper, we propose an efficient rate control scheme based on the received power level to overcome a quality degradation of video under time varying channel condition caused by the movement of mobile devices. First, we statistically obtain the relation between the PLR and the received power level. With this information and the sequences of received power level, we calculate the transition probability for the Markov Channel Model. Then, with using Markov chain rule, we obtain the probability where the channel condition remains in a good state and finally find the efficient target bit rate by multiplying it by the offered bandwidth when the network access has begun. We use TMN8 to adjust the bit rate to our proposed outcome. Experimental results show that the proposed method can efficiently enhance the video quality and provide better PSNR performance than with only using TMN8 rate control method.

• Journal of IKEEE
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• v.2 no.2 s.3
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• pp.200-211
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• 1998

A DS/CDMA system that makes all base stations require equal received power for all mobiles can lead to the non-uniform quality of service when mobiles are non-uniformly located over a service area. In order to resolve this problem the base-received power should be controlled according to base's load in order to make the quality of service uniform, and the pilot power also has to be adjusted to maintain the balance of cell coverage between reverse link and forward link. In this paper, we propose a generalized model including Pilot Power control, base-received power control on the reverse link, transmission power allocation on multiple forward link, and soft handoff on both links. We also apply our model to an initial system design as an example.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.8
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• pp.76-82
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• 2013

We evaluate the performance of the time-reversal (TR) prefilter and the weighted TR prefilter in an indoor wireless communication system with channel estimation errors. The TR prefilter uses a time-reversed channel as a prefilter to maximize received peak power. The equivalent channel of the TR prefilter is an 공분산 of the channel and the received peak power is maximized. When there are channel estimation errors, the equivalent channel is not an 공분산 of the channel and the received peak power cannot be maximized. The weighted TR prefilter minimizes the inter-symbol interference and maintains the received peak power. Thus, even when there are some channel estimation errors, the weighted TR prefilter can guarantee the received peak power.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.5A
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• pp.409-416
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• 2007

In cellular orthogonal frequency division multiplexing (OFDM) networks, co-channel interference (CCI) leads to severe degradation in the BER performance. To solve this problem, maximum-likelihood estimation (MLE) CCI cancellation scheme has been proposed in the literature. MLE CCI cancellation scheme generates weighted replicas of the transmitted signals where weights represent the estimated channel transfer functions. The replica with the smallest Euclidean distance from the received signal is selected and data are detected. When the received power of the desired and interference signals are nearly the same, the BER performance is degraded. In this paper, we propose a closed-loop power control (PC) scheme capable of detecting the equal received power situation at the mobile station (MS) receiver by using the newly introduced parameter power ratio (PR). When this situation is detected, the MS sends a feedback to the desired base station (BS) which boosts the transmission power in the next frame. At cell edge where signal to interferer ratio (SIR) is considered to have average value between -5 dB and 10 dB, computer simulations show that the proposed CCI cancellation scheme has a gain of 7 dB at 28 Km/h.