• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.5
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• pp.872-878
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• 2003

In this paper, we developed a simulator which can generate the polarization waves for the indoor wireless communications based on three dimensional ray tracing technique and verified the simulation results comparing with the measured data in indoor wireless propagation environments. Using the developed simulator, we analyzed the channel characteristic and polarization diversity reception characteristic for the vertical, horizontal and circularly polarized waves. From the analysis results, in the case of using circularly polarized wave it can be clearly seen that the multipath fading is markedly reduced compared to the vertical and horizontal polarized waves due to the reception characteristic of removing the odd time reflected waves.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.457-461
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• 2007

In many applications, received signal strength indicator is used for location tracking and sensor nodes localization. For location finding, the distances between sensor nodes can be estimated by converting received signal's power into distance using path loss prediction model. Many researches have done the analysis of power-distance relationship for radio channel characterization. In indoor environment, the general conclusion is the non-linear variation of RSSI values as distance varied linearly. This has been one of the difficulties for indoor localization. This paper presents works on indoor RSSI characterization based on statistical methods to find the overall trend of RSSI variation at different places and times within the same room From experiments, it has been shown that the variation of RSSI values can be determined by both spatial and temporal factors. This two factors are directly indicated by the two main parameters of path loss prediction model. The results show that all sensor nodes which are located at different places share the same characterization value for the temporal parameter whereas different values for the spatial parameters. Using this relationship, the characterization for location estimation can be more efficient and accurate.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8C
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• pp.814-821
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• 2009

In an ultrawide band (UWB) indoor wireless localization, time of arrival (TOA) parameter estimation techniques have some difficulties in acquiring a reasonable TOA estimate because of the clustered multipath components overlapping or random time intervals mainly due to non line-of-sight (NLOS) environment. In order to solve that problem and achieve an excellent UWB indoor wireless localization, we propose a UWB signal model and a robust TOA parameter estimation technique that has little effect on the clustered problems unlike the conventional technique. Through simulation studies, the validity of the proposed model and the TOA estimation technique are examined. The performance of estimation error is also analyzed.

• 한국ITS학회:학술대회논문집
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• 2008.11a
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• pp.132-136
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• 2008

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.39-39
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• 2004

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.47-52
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• 2013

In this paper, The existing interference alignment algorithms were analyzed in Rayleigh fading channel environment. The interference alignment techniques are divided to two parts. First thing is Iterative-method, another is Linear-method. Iterative method needs local channel info, but it has the constraint of iteration. On the other hand Linear-method must have global channel info, but has free of iteration and better performance. This paper evaluates the performance of interference alignment algorithms in Rayleigh fading channel of outdoor environment and WLAN channel based on IEEE 802.11n of indoor environment.

• Journal of Advanced Navigation Technology
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• v.6 no.3
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• pp.203-210
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• 2002

In this paper, the BER performance of IEEE 802.11a OFDM WLAN system is obtained by simulation and it is shown that the proposed modified channel estimation algorithm improves the channel estimation performance of the system. The wireless channel used in channel simulation includes AWGN and delay spread channel implemented by TDL model. At first, the performance of OFDM WLAN system according to data rate and coding rate defined in standard is evaluated in AWGN channel. Then, imperfect channel estimation in indoor wireless channel is considered. After the performance of conventional channel estimation scheme using only two long training symbols is evaluated, and that of proposed modified channel estimation scheme using additional 8 short training symbol is compared with it. From the simulation results, it is shown that modified channel estimation scheme provides reduced channel estimation error and improves the channel estimation performance due to noise averaging effect with the same preamble format as defined in specification.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.53-58
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• 2016

A ray tracing method to analyze the propagation channel characteristics for a millimeter-wave indoor wireless communication system is presented. Reflected rays from planar as well as rough surfaces are included. Transmitted rays though a thin dielectric slab are considered. Maps representing received power levels and RMS delay spread from a transmitter in a rectangular room are shown. The received power levels in the empty room for bottom's roughness factors of 0 and 0.13 are represented. The simulation results are well consistent with the calculation of Friis equation with reflection coefficient. Any size of furniture the shape of plane form can be positioned anywhere in the room.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.943-950
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• 2000

In this paper, an asynchronous multi-rate optical wireless pulse position modulation-code division multiple access (PPM-CDMA) is proposed for an indoor non-directed diffuse channel. As a signature sequence for CDMA, an optical orthogonal code (OOC) is used and an interference cancellation scheme is applied to improve the bit error rate. It is known that the optical PPM-CDMA has advantages due to its power efficiency. Moreover, it provides multi-rate services by varying the modulation level with fixed pulse duration. In the proposed multi-rate PPM-CDMA system with fixed pulse duration, chip rate and sampling time do not change for each transmission rate and this simplifies overall system structure.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5C
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• pp.472-478
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• 2010

In the environment of wireless communication system of IEEE 802.15.3a UWB standard, the angle of arrival(AOA) estimation technique for the indoor wireless positioning algorithms, based on the AOA parameter estimation which fits well for the wireless communication channel and shows high estimation accuracy, is proposed. After the UWB signal model, based on the IEEE 802.1.3a standard, is constructed, the average weighted MUSIC technique is proposed, which shows better estimation accuracy than those of conventional estimation technique. Through the simulation studies, the environment of the indoor wireless positioning system including the IEEE 802.15.3a channel is configured and we demonstrate better estimation results by the proposed AOA estimation technique than those from the conventional method.