• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2C
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• pp.206-212
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• 2004

In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. STBC(Space-Time Block Coding) has been proposed as a simple diversity scheme using two transmit antennas. Also ST-OFDM(Space-Time Block Coded OFDM) and SF-OFDM(Space-Frequency Block Coded OFDM) transmission scheme, that the STBC is applied to the OFDM, has been proposed. In this paper, we propose STF-OFDM transmission scheme that to coded in time, space and frequency domain. The STF-OFDM transmission scheme that we propose in this paper is the way to improve a performance of conventional ST-OFDM, by using frequency diversity.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1066-1069
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• 2002

Orthogonal frequency division multiplexing (OFDM) is a special technique for communication systems which can support the high data rate transmission with sufficient robustness to fading channels. Tansmitter diversity with space-time block coding (STBC) is an attractive transmission scheme to improve the performance of systems. In this paper, we compare the performance of space-time block coded OFDM systems with that of conventional OFDM systems over fast fading channels. The block-interleaved (BI) STBC and frequency hopping (FH) OFDM are proposed in the study to provide the maximum achievable diversity gains. As the simulation results, the STBC OFDM, Bl-STBC OFDM and Bl-STBC FH-OFDM provide the much improved performance over the conventional OFDM. And the Bl-STBC FH-OFDM also provide the better performance than the STBC OFDM and Bl-STBC OFDM, especially, in the case of the two transmit antennas are employed while BI-STBC FH-OFDM can maintain the same data rate of 12 Mbps.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.10A
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• pp.997-1005
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• 2008

In this paper, we propose an efficient space-time block coding (STBC) scheme in a cooperative satellite-terrestrial system. The proposed STBC scheme has code rate 1 for a 3 transmit antenna scheme. Because the channel matrix of the proposed scheme is orthogonal, we can use a simple linear decoding algorithm and also can expect improved performance over the conventional scheme. The simulation results demonstrate that the proposed scheme has improved performance for bit error rates (BER) than several conventional STBC schemes. In addition, we investigate performance simulation results by power imbalance between the terrestrial repeaters and satellite.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.6A
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• pp.640-650
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• 2004

Channel estimation schemes are proposed for Multiple Input-Multiple output Orthogonal Frequency Division Multiplexing(MIMO-OFDM) systems based on the physical layer specification of the IEEE 802.1 la. By combining the space-time block coding(STBC)/ space-frequency block coding(SFBC) techniques with the transform domain interpolation, the proposed algorithms achieve more accurate channel coefficients for the MIMO channels such that improve the BER performance. The performance improvements of the proposed algorithms are evaluated by simulations under the various multipath fading channel environments and various transmission rates.

• ETRI Journal
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• v.28 no.5
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• pp.684-687
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• 2006

In this letter, we evaluate the system performance of a space-time block coded (STBC) multicarrier (MC) DS-CDMA system over a time selective fading channel, with imperfect channel knowledge. The average bit error rate impairment due to imperfect channel information is investigated by taking into account the effect of the STBC position. We consider two schemes: STBC after spreading and STBC before spreading in the MC DS-CDMA system. In the scheme with STBC after spreading, STBC is performed at the chip level; in the scheme with STBC before spreading, STBC is performed at the symbol level. We found that these two schemes have various channel estimation errors, and that the system with STBC before spreading is more sensitive to channel estimation than the system with STBC after spreading. Furthermore, derived results prove that a high spreading factor (SF) in the MC DS-CDMA system with STBC before spreading leads to high channel estimation error, whereas for a system with STBC after spreading this statement is not true.

• ETRI Journal
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• v.35 no.4
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• pp.710-713
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• 2013

We propose a new space-time block coding (STBC) for asynchronous cooperative systems in full-duplex mode. The orthogonal frequency division multiplexing (OFDM) transmission technique is used to combat the timing errors from the relay nodes. At the relay nodes, only one OFDM time slot is required to delay for a pair-wise symbol swap operation. The decoding complexity is lower for this new STBC than for the traditional quasi-orthogonal STBC. Simulation results show that the proposed scheme achieves excellent performances.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5A
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• pp.423-430
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• 2010

The performances of turbo-coded space-time block coding (STBC) schemes are subject to how soft decision detection (SDD) information are generated from the STBC decoder. For this reason, we have to pay particular attention to estimation of SDD. In this paper, we evaluate the performance of a turbo coded STBC scheme depending on the accuracy of the SDD. Recently, a new quasi orthogonal STBC (QO-STBC) scheme using a noise whitened filter was proposed in order to reduce noise enhancing effect of zero forcing detection process. This QO-STBC scheme was proven to be efficient in computational complexity compared to the other conventional QO-STBC schemes. In this paper, we first present detailed mathematical analysis on the noise whitened QO-STBC scheme, and by using the result we propose the optimum SDD method.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.426-433
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• 2008

In this paper, we present a method to improve the performance of the four transmit antenna quasi-orthogonal space-time block code (STBC) in the coded system. For the four transmit antenna case, the quasi-orthogonal STBC consists of two symbol groups which are orthogonal to each other, but intra group symbols are not. In uncoded system with the matched filter detection, constellation rotation can improve the performance. However, in coded systems, its gain is absorbed by the coding gain especially for lower rate code. We propose an iterative decoding method to improve the performance of quasi-orthogonal codes in coded systems. With conventional quasi-orthogonal STBC detection, the joint ML detection can be improved by iterative processing between the demapper and the decoder. Simulation results shows that the performance improvement is about 2dB at 1% frame error rate.

• Journal of information and communication convergence engineering
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• v.20 no.1
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• pp.1-7
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• 2022

Herein, a new space-time block coding technique is proposed for a MIMO 2 × 2 multiple-input multiple output (MIMO) system to minimize the bit error rate (BER) in Rayleigh fading channels with reduced decoding complexity using ZF and MMSE linear detection techniques. The main objective is to improve the service quality of wireless communication systems and optimize the number of antennas used in base stations and terminals. The idea is to exploit the correlation product technique between both information symbols to transmit per space-time block code and their own orthogonal Walsh-Hadamard sequences to ensure orthogonality between both symbol vectors and create a full-rate orthogonal STBC code. Using 16 quadrature amplitude modulation and the quasi-static Rayleigh channel model in the MATLAB environment, the simulation results show that the proposed space-time block code performs better than the Alamouti code in terms of BER performance in the 2 × 2 MIMO system for both cases of linear decoding ZF and MMSE.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.6C
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• pp.562-571
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• 2010

Forward error correction (FEC) coding schemes using iterative soft decision detection (SDD) information are mandatory in most of the next generation wireless communication system, in order to combat inevitable channel imparirnents. At the same time, space-time block coding (STBC) schemes are used for the diversity gain. Therefore, SDD information has to be fed into FEC decoder. In this paper, we propose efficient SDD methods for turbo-coded STBC system using high order modulation such as QAM. We present simulation results of various SDD schemes for turbo-coded STBC systems, and show that the proposed methods can provide almost approximating performance to maximum likelihood detection with much less computational load.