• Journal of Advanced Navigation Technology
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• v.10 no.3
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• pp.213-218
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• 2006

In this paper, we analyzed the performance of orthogonal frequency division multiplexing/ frequency hopping multiple access(OFDM/FHMA) hybrid system that in impulsive interference and broadband wireless communication channel then we applied the turbo code scheme to make satisfied in data and voice transmission service. Also, we compared the bit error rate(BER) performance of turbo coded diversity scheme in the OFDM/FHMA hybrid system. As a result of simulation, proposed OFDM/FHMA hybrid system shows the enhancement of 10 times compared to the general OFDM/FHMA system.

• Journal of Communications and Networks
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• v.7 no.3
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• pp.307-312
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• 2005

In this work, we study the performance of a serial concatenated scheme comprising a convolutional code (CC) and an orthogonal space-time block code (STBC) separated by an inter-leaver. Specifically, we derive performance bounds for this concatenated scheme, clearly quantify the impact of using a CC in conjunction with a STBC, and compare that to using a STBC code only. Furthermore, we examine the impact of performing antenna selection at the receiver on the diversity order and coding gain of the system. In performing antenna selection, we adopt a selection criterion that is based on maximizing the instantaneous signal-to­noise ratio (SNR) at the receiver. That is, we select a subset of the available receive antennas that maximizes the received SNR. Two channel models are considered in this study: Fast fading and quasi-static fading. For both cases, our analyses show that substantial coding gains can be achieved, which is confirmed through Monte-Carlo simulations. We demonstrate that the spatial diversity is maintained for all cases, whereas the coding gain deteriorates by no more than $10\;log_{10}$ (M / L) dB, all relative to the full complexity multiple-input multiple-output (MIMO) system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.968-975
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• 2006

Research about the mode of MIMO that can get a coding benefit at the same time with a diversity benefit using a multiple antenna at the fading channel for a high-speed data transmission have been processed actively But the analysis about the interference of UWB system comes not to consist yet. So this paper analyzed the performance of the interference of UWB system to SFBC-OFDM and SFTC-OFDM system that applied a space block code which has a space diversity characteristic to OFDM system at MIMO channel. We shelved the performance that SFTC-OFDM system is robuster than SFBC-OFDM system under MB-OFDM UWB Interference.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.29-37
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• 2005

One of the principal disadvantages of multicarrier modulation technique is the sensitivity to the frequency offset introduced by Doppler shift. This frequency offset introduces inter-carrier interference (ICI) among the multiplicity of carriers in the multicarrier modulated signal. However, Doppler spread induced by temporal channel variations can Provide another means for diversity. In this paper, we propose a modified multicarrier code division multiple access (CDMA) system to exploit Doppler diversity as well as multipath diversity. The key work of our framework is a canonical time-frequency-based decomposition of the mobile wireless channel into series of independent fading channel. The decomposition naturally leads to a time-frequency generalization of the Rake receiver that exploits both multipath and Doppler diversity.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.190-195
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• 2004

In this paper, Error rate performance of Convolution coded DS-CDMA 16 QAM signal is analyzed using selective combining diversity reception techniques and maximal ratio combining diversity reception techniques under the environments of Rician fading. With the results of analysis, maximal ratio combining diversity reception techniques provides the performance improvement of about 3-8[㏈] over selective combining diversity reception techniques for the good error performance lot data communication. And it is found that a synergistic performance improvement is show to both diversity reception and Convolution coding, techniques overcoming mobile wireless data communication channel environment.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.41-46
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• 2000

In this paper, we analyze the performance of W-CDMA systems using turbo code in the wideband multipath channel. The strength of each multipath component is assumed to be Rayleigh distributed. Turbo codes of long block sizes have been known to show very good performance in a AWGN channel. Recently, turbo codes of short block sizes suitable for real time communication systems have attracted a lot of attention. Thus, in this paper we consider the turbo code of 1/3 code rate and short frame size of 192 bits in wideband mobile multipath channel. We analyze the performance of W-CDMA systems with 10MHz bandwidths in the case of employing RAKE receiver with not only MRC diversity but also turbo code.

• Journal of information and communication convergence engineering
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• v.2 no.1
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• pp.5-8
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• 2004

DS-COMA is now a matured multiple access technology that utilizes spreading codes for user separation. In this paper, we attempt to improve the performance of a multiuser DS-COMA system with a unique chip shaping code called Carrier Interferometry (CI) code. The CI codes exhibit an excellent correlation property that can be used in many applications. In DS-COMA with CI codes (CI/DS-COMA), the symbols are spread by a spreading code and then the chip signals are shaped using a CI code. Due to the correlation property of the CI code, a diversity gain from the shaped chip signals is achieved and the performance of DS-COMA is significantly improved. Comparison study demonstrates that the DS-COMA with CI outperforms the conventional DS-COMA system in multiuser environments.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.41-45
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• 2007

Multi-input multi-output (MIMO) system can increase data rate, capacity and bit error rate (BER) performance compare to traditional single antenna system. However MIMO technique is pointed out the problem that has high complexity to design receiver. So a recent trend of research on the MIMO system pays more attention to simplified implementation of receiver structure. In this paper, we propose differential space time block code (STBC) for MIMO system with cyclic delay diversity (CDD). This structure can provide a very close performance to that of the conventional diversity scheme with maximum likelihood (ML) detection without channel estimation block while the receiver structure is highly simplified. Bit error rate (BER) performance of the proposed system is simulated for an AWGN channel by theoretical and simulated approaches. The results of this paper can be applicable to the 4G mobile multimedia communication systems.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11A
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• pp.1237-1243
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• 2004

This paper presents and analyses the closed-form expression of the average bit error rate (BER) for an asynchronous direct-sequence code division multiple access (DS-CDMA) system with coherent binary phase shift keying (BPSK) modulation scheme using a maximal ratio combining (MRC) diversity over a Rician fading channel. In addition to the average BER, outage probability, and user capacity of system are estimated as performance measures. The results are general enough so that it includes Rayleigh fading and nonfading channel with zero and infinite Rician factor, respectively, as special cases. The effects of various channel models, processing gains, and diversity orders on the system performances are also considered for the typical multipath delay profiles characterized by Rician fading channel.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.153-154
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• 2008

In this paper, we propose a diversity-enhancing scheme in a single link fading channel using repetition QPSK symbol code. The proposed scheme can be converted to rate outage formula and obtains enhanced diversity performance while guaranteeing the required data rate. Simulation result shows that the proposed scheme improves the rate outage performance compared to the conventional BPSK diversity schemes.