• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12A
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• pp.933-940
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• 2009

This paper proposes a robust detection scheme for quasi-orthogonal space-time block code over time-selective fading channels. The proposed detector performs interference cancellation and decision feedback equalization to remove the inter-antenna interference and inter-symbol interference when the channel varies from symbol to symbol. Cholesky factorization is used on the channel Gram matrix after performing interference cancellation to obtain feed forward equalizer and feedback equalizer. It is shown by simulations that the proposed detection scheme outperforms the conventional detection schemes and the exiting detection schemes to time-selectivity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.1C
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• pp.82-91
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• 2005

This paper introduces an efficient affine projection algorithm(APA) using iterative hyperplane projection. Among various fast converging adaptation algorithms, APA has been preferred to be employed for various applications due to its inherent effectiveness against the rank deficient problem. However, the amount of complexity of the conventional APA could not be negligible because of the accomplishment of sample matrix inversion(SMI). Moreover, the 'shifting invariance property' usually exploited in single channel case does not hold for the application of space-time decision-directed equalizer(STDE) deployed in single-input-multi-output(SIMO) systems. Thus, it is impossible to utilize the fast adaptation schemes such as fast transversal filter(FlF) having low-complexity. To accomplish such tasks, this paper introduces the low-complexity APA by employing hyperplane projection algorithm, which shows the excellent tracking capability as well as the fast convergence. In order to confirm th validity of the proposed method, its performance is evaluated under wireless SIMO channel in respect to bit error rate(BER) behavior and computational complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.7A
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• pp.629-634
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• 2002

The next generation of wireless communication system is expected to provide users with wireless multimedia services such as high speed internet access and wireless mobile computing. Depending on the Quality of Service(QoS) requirements and different applications per user, many wireless communication systems have been proposed. The simple decoding algorithm of space-time block coding is based on the assumption of flat fading channel, where no intersymbol interference exists. In this paper, we propose to combine space-time transmit diversity with adaptive equalizer. The proposed system effectively eliminates interference caused by multipath environment. Simulation results show that the proposed system provides improved bit error rate performance.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1042-1050
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• 2014

The performance of underwater acoustic(UWA) communication system is sensitive to the Inter-Symbol Interference(ISI) due to delay spread develop of multipath signal propagation. And due to limited frequency using acoustic wave, UWA is a low transmission rate. Thus, it is necessary technique of Space-time code, equalizer and channel code to improve transmission speed and eliminate ISI. In this paper, UWA communication system were analyzed by simulation using these techniques. In the result of simulation, the proposed Turbo Equalization method based on layered Space Time Codes has improved performance compared to conventional UWA communication.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.405-408
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• 2013

The performance of underwater acoustic(UWA) communication system is sensitive to the Inter-Symbol Interference(ISI) due to delay spread develop of multipath signal propagation. And due to limited frequency using acoustic wave, UWA is a low transmission rate. Thus, it is necessary technique of Space-time code, equalizer and channel code to improve transmission speed and eliminate ISI. In this paper, UWA communication system were analyzed by simulation using these techniques. In the result of simulation, the proposed Space-time code, Turbo code, and Zero forcing techniques is shown that improved performance than conventional UWA communication.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.402-404
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• 2013

The wireless communication channel different speed by depth of water or salt and it is influenced by multi-path according underwater. In the paper, MIMO(Multi-input-Multi-Output) system used turbo Equalizer combining Equalizer with Turbo codes for data rates by multi-path channel. we proposed and simulated that the Decision-Directed method used for phase offset. The simulation of proposed method show that the bit-error rate performance can be severely affected by phase errors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.623-630
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• 2004

The adaptive modulation along with SFBC transmit diversity is a very effective method to increase the capacity of an OFDM system. However, severe performance degradation is resulted when inter-symbol interference is applied due to frequency-selective fading in mobile communications. In this paper, we have proposed and analyzed an OFDM system with SFBC transmit diversity and adaptive modulation scheme based on pre-equalization methods, in order to increase the data transmission rate in the downlink without much increase in system complexity. By introducing subchannel grouping and the pre-equalization method among adjacent subchannels, we could enhance the efficiency of the adaptive modulation a lot. By computer simulation, it has been proven that the proposed schemes show a better BER and throughput performance than the conventional schemes under severely time-varying multipath fading channel.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.504-511
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• 2016

In this paper, MIMO system based on turbo equalization techniques which LDPC codes were outer code and space time trellis codes (STTC) were employed as an inner code are studied. LDPC decoder and STTC decoder are connected through the interleaving and de-interleaving that updates each other's information repeatedly. In conventional turbo equalization of MIMO system, BCJR decoder which decodes STTC coded bits required two-bit wise decoding processing. Therefore duo-binary turbo codes are optimal for MIMO system combined with STTC codes. However a LDPC decoder requires bit unit processing, because LDPC codes can't be applied to these system. Therefore this paper proposed turbo equalization for MIMO system based on LDPC codes combined with STTC codes. By the simulation results, we confirmed performance of proposed turbo equalization model was improved about 0.6dB than that of conventional LDPC codes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.547-553
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• 2010

In this paper, novel approximated closed-form expressions of the SER(Symbol Error Rate) and BER(Bit Error Rate) are presented for the multi-input multi-output space-time block coding(MIMO-STBC) system employing two transmit and N receive antenna(s) in Rayleigh fading channels. Assuming a zero-forcing equalizer and a single-symbol maximum-likelihood (ML) decoder, the formulas are derived for the SER and BER, and then their approximated counterparts are also derived. In the derivation of the approximated expressions, acurve-fitting model is adopted that can eliminate the integral operators in the exact expressions.