• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.525-530
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• 2008

There are a few core technologies to enable high-performance $4^{th}$ generation (4G) broadband wireless communication system. A multiple input multiple output (MIMO) provides high-rate transmission through expended channels by multiple array antennas in both sender and receiver side. Also orthogonal frequency division multiplexing (OFDM) is well-known as the most appropriate technique for high data rate transmission such as Mobile WiMAX and WLAN. Efficient decrease of inter-carrier interference (ISI) and inter-carrier interference (ICI) are the reasons for why OFDM is suitable for high-performance transmission, 4G mobile communication. In this paper, we mainly focus on two of objects, combination between MIMO and OFDM, and OFDM channel simulator using Ray-tracing algorithm. The results of this paper can be used implementation of a Wireless Software Platform for 4G Mobile Communication Systems.

• Journal of Digital Convergence
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• v.13 no.3
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• pp.1-10
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• 2015

Carrier billing services market is growing according to the technical development. This study investigated the limiting factor in carrier billing services and suggested the improvement factor for it using the Delphi Method. The amount money to use in carrier billing charges should be provided in their credit based and the accumulated payment using a text message is displayed and also telecommunications carriers and carrier billing firms are the least responsible for consumer harm. It also provides administrative responsibility for communications carriers and billing services company for non recognition and payment. The service provider to prove negligence not proven by consumer and telecommunications billing service delinquency rate is applied at a rate such as a credit card and it also should integrate retail payment and service fee. This study will contribute to the communication billing services market growth through improved communication billing service. Further research is needed to continue the study of the factors that emerged from communication and billing services due to emerging technologies and services.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.11
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• pp.987-995
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• 2016

One of evaluation indicators of candidate waveforms for 5G mobile communication is spectral efficiency improvement by OOB(Out of Band) power reduction technique. In this paper, time-frequency resource allocation characteristic of UFMC(Universal Filtered Multi-Carrier), FBMC(Filter Bank Multi-Carrier), and W-OFDM(Weighted Orthogonal Frequency Division Multiplexing) system is evaluated and analyzed. As simulation results, spectral efficiency characteristic of these systems have been improved according to time resource allocation. In this paper, we can confirm that each system has similar time-frequency efficiency characteristic when the number of transmission bit is same and four symbols are transmitted with the linear system condition. Also, we can conclude that FBMC system has the lowest time-frequency resource efficiency under the nonlinear condition.

• Journal of Communications and Networks
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• v.8 no.2
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• pp.182-186
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• 2006

Previous approaches to sizing the carrier spacing for voice-oriented cellular systems have been based on the outage requirement. However, such a design paradigm needs to be changed as the performance of most upcoming cellular systems employing adaptive modulation and coding (AMC) techniques is more sensitive to throughput than outage. In this paper, we propose a novel approach to determining the carrier spacing which is based on a throughput criterion. The proposed method reflects well the characteristics of throughput-sensitive cellular systems that transport multimedia traffic. Numerical results show that our approach requires less carrier spacing, thus leading to more efficient spectrum utilization.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.8A
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• pp.815-820
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• 2008

Carrier frequency offset (CFO) is one of the most important problems in an orthogonal frequency division multiplexing (OFDM) system, which seriously degrades the performance of the systems due to its time-variant behavior. In this paper, the performance of a pilot-assisted fine CFO estimator in OFDM-based mobile WiMAX systems is analyzed. Analytical closed-form expression of the mean square error (MSE) of the post-FFT based CFO synchronization scheme is reported for time-variant fading channels. Taking into account the frame structure of the IEEE802.16e standard, simulation results are used to verify the theoretical analysis developed in this paper.

• Journal of Advanced Marine Engineering and Technology
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• v.36 no.6
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• pp.823-829
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• 2012

Data communications networks at sea in the future can be modelled by overlapped MANET networks with Broadband Wireless Access carriers. A novel routing scheme (CPLR) is proposed in this paper, which finds out an optimal route by selecting an optimal carrier for each hop in routes based on carrier preferences of each application, and locations of ships as well. As distances between each ships and destination ships are considered in this scheme, routing can be done much faster. Performance is compared with that of the CPR (only Carrier Preference-based Routing Scheme), and it shows some improvements.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.4
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• pp.167-174
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• 2018

Presently, the exploration of an unknown environment is an important task for the development of mobile robots and mobile robots are navigated by means of a number of methods, using navigating systems such as the sonar-sensing system or the visual-sensing system. To fully utilize the strengths of both the sonar and visual sensing systems, In mobile robotics, multi-sensor data fusion(MSDF) became useful method for navigation and collision avoiding. Moreover, their applicability for map building and navigation has exploited in recent years. In this paper, as the preliminary step for developing a multi-purpose autonomous carrier mobile robot to transport trolleys or heavy goods and serve as robotic nursing assistant in hospital wards. The aim of this paper is to present the use of multi-sensor data fusion such as ultrasonic sensor, IR sensor for mobile robot to navigate, and presents an experimental mobile robot designed to operate autonomously within indoor environments. Simulation results with a mobile robot will demonstrate the effectiveness of the discussed methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.6
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• pp.1056-1061
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• 2001

In this paper we have evaluated the degree of performance improvement in Multi-Carrier CDMA system adopting CCI canceller against MUI under mobile channel coexisting MU which is a major interference degrading the performance of Multi-carrier CDMA system. As a result of analysis, BER performance was improved by adopting CCI canceller and it was found that the amount of performance improvement was largely increased as Eb/No became higher. As an example, in case that data service BER = 10$^{-5}$ must be achieved with $E_{b/}$ $N_{o}$ = 12 ㏈, 4 users could be supported without CCI canceller while 30 users could be supported with CCI canceller, Also, we found that performance improving effect of 5$\times$10$^{-3}$ in a point of view BER could be achieved by adopting CCI canceller with fixed $E_{b/}$ $N_{o}$. o/. o/.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.27 no.8
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• pp.725-734
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• 2016

Recently, novel candidate waveform techniques for spectral efficiency improvement was proposed in order to satisfy key performance indicators(KPIs) of 5th generation(5G) mobile communication. Multi-carrier based universal filtered multi-carrier(UFMC) and filter bank multi-carrier(FBMC) are very famous as 5G candidate waveform techniques. Also, weighted orthogonal frequency division multiplexing (W-OFDM) that has low-complexity is receiving the spotlight slowly. In this paper, firstly, we describe a basic OFDM system. And then, we also describe UFMC, FBMC, and W-OFDM system. Next, we evaluate and analyze spectrum and BER performance of these systems under the nonlinear high power amplifier(HPA) environment. As simulation results, spectrum characteristic and BER performance of UFMC, FBMC, and W-OFDM are similar to each other. Therefore, under the nonlinear HPA environment, W-OFDM system is more advantageous because W-OFDM system uses a simple time-domain windowing technique and has similar characteristics to the others.

• Journal of Digital Contents Society
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• v.5 no.3
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• pp.187-191
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• 2004

Rapid time variations of the mobile communication channel have a dramatic effect on the performance of multi-carrier modulation. This paper analyzed the bit error rate (BER) performance for multi-carrier code division multiple access (MC-CDMA) network, and derived the equivalent signal-to-total noise plus interference(SNIR) of MC-CDMA system in the reverse link, the performance of MC-CDMA/BPSK signal is evaluated taking into account the fraction of partial-band interference and interference power. and the effect of partial-band interference is comprehensively studied in order to further improve the Qos of multi-carrier multimedia system.