• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.87-90
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• 2007

In cooperative communication systems, the source terminal transmits signal to the destination terminal with the aid of partner terminals. Therefore, the source terminal obtains extra spatial diversity gain. As a result, its performance is enhanced in term of higher achievable transmission rate, the larger coverage range, and the lower bit-error-rate (BER). Space-time codes (STCs) have been applied to cooperative communication systems in distributed fashion, in which the signal is spatially time exploited to obtain gains analogous to those provided by STCs. In this work, we consider the application of orthogonal Space-time Block Codes (OSTBCs) to the cooperative communication systems to further achieve higher diversity gain. The advances of the proposed approach are verified via computer simulations.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.8A
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• pp.775-783
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• 2006

In this paper, the new technique combining beamforming with space-time coding is proposed for an orthogonal frequency division multiplexing(OFDM) system with multi-input multi-output(MIMO). When MIMO-OFDM system is employing Nt(the number of transmitterantenna) beamfomers and one S-T decoder at Nr receiver antennas, Nt signals removed CCI are outputted at the beamformer and then diversity gain can be got through space-time decoding. As the proposed technique can reduce cochannel interference and get diversity gain in the multi-user environment, the performance of MIMO-OFDM system is very improved. BER performance improvement and convergence behavior of the proposed approach are investigated through computer simulation by applying it to MIMO-OFDM system in the multi-user environment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.3
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• pp.40-45
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• 2008

This paper proposes the signal design techniques of quasi-orthogonal space time block codes (QO-STBCS) on the multi-dimensional signal space. In the multiple antenna system(MIMO), QO-STBC achieves the full-diversity and full-rate by grouping two based-symbols. We study the condition for the full-diversity of the grouping QO-STBC geometrically and the performance analysis of codes on the multi-dimensional signal space regarding the various signal constellations. Simulation results show that the way of the performance analysis is validity.

• Journal of electromagnetic engineering and science
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• v.3 no.2
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• pp.99-103
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• 2003

For mobile multimedia systems that equip transmit diversity for a forward channel, it is well known that the Tx diversity technique is appropriate for high rate mobile multimedia communications. In this paper, we propose a STTD (Space Time Transmit Diversity) receiver, which incorporates the design of the Tx diversity receiver without the mutual interference of antenna by using a CCI cancellation technique. The new STTD receiver is simulated and its performance is analyzed in a DS-CDMA/QPSK. Adopting the proposed STTD receiver at $10^{-2}$TEX>∼$10^{-4}$TEX> in bit error rate, SNR of 0.5 ㏈∼2 ㏈ performance improvement in AWGN and Rayleigh fading environments has been achieved.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4A
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• pp.282-287
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• 2005

The space time block code(STBC) can not provide simultaneously both full diversity and full transmission rate in a transmit diversity system having more than two transmit antennas.. There are a quasi orthogonal STBC for four transmit antennas that provides full transmission rate and minimized interference. Recently, a simple correlation canceling algorithm is introduced to achieve full diversity from STBC considering four transmit antennas. In this paper, we propose a new decoding procedure using the power allocation at the transmitter and subtraction interference process at the receiver to achieve a better performance without noise enhancement.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4B
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• pp.298-307
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• 2002

This paper concentrates on developing and analyzing an advanced space-time multiuser receiver for WCDMA forward link. Through exploring the interference caused by co-channel users and delayed multipaths in CDMA, a constrained linear adaptive filter is adopted to cancel the interference. Furthermore, by utilizing the space-time diversity, an optimum diversity receiver, called a constrained adaptive space-time interference canceller (C-ASTIC), is proposed. For comparison, the statistical analysis of multiuser performance for WCDMA system with space-time diversity is described. The result of the simulation showed that C-ASTIC performs better than both the space-time diversity combining maximal ratio combiner (MRC) and the single-antenna adaptive interference canceller in a multipath fading channel. Also, the efficiency of the C-ASTIC in the multimedia communication environment is investigated under the multiuser, multi-transmit antenna, and multirate WCDMA system in a multipath fading channel. From the results, the C-ASTIC was validated to be useful for multi-rate WCDMA system through improving the performance gain by more than 3 dB at BER of 10$\^$-3/ in a half or more loaded system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.3
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• pp.403-409
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• 2000

In this paper, we measured and analyzed cross polarization discrimination(XPD), signal correlation coefficient($\rho$) and received signal level decrease, for the application of polarization diversity scheme in the up-link of microcell environments. We experimented in a dense building area, a dense residence area, a market area, a school area and etc at 1.9 GHz. Cross polarization discrimination (XPD) is about 6~11 dB, signal correlation coefficient($\rho$) is below 0.7 and received signal level decrease is smaller than 3 dB. The results of comparing polarization diversity with space diversity show that polarization diversity gain is about 2~5 dB higher in the various area. As a results, polarization diversity scheme is more effective than space diversity scheme in microcell environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.9A
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• pp.871-877
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• 2007

In this paper, we propose a new transmit diversity scheme using window functions in orthogonal frequency division multiplexing (OFDM) system. Transmit diversity of the scheme is varied with window functions and the condition of the window function to maximize transmit diversity is derived. The proposed scheme can be considered as a generalization of the diversity schemes such as cyclic delay diversity (CDD), orthogonal transmit diversity (OTD), and frequency switched transmit diversity (FSTD).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.3A
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• pp.258-264
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• 2009

In this paper, we propose an efficient cooperative diversity scheme for mobile satellite multimedia broadcasting services. The proposed scheme is a transmit diversity technique to adapt time varying channel conditions, and we do not need any channel quality information from the return link. In the proposed scheme, we utilize space-time block coding (STBC) and rate compatible turbo codes in order to realize the transmit diversity for the mobile satellite system with several repeaters. The satellite and several repeaters operate in unison to send the encoded signals, so that the receiver may realize diversity gain. The simulation results demonstrate that the proposed scheme can provide highly improved performance.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.10
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• pp.2411-2429
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• 2013

In this paper, we extend the case of information exchange error mitigation for the distributed orthogonal space-time block code (DOSTBC) for two transmit antennas to distributed quasi-orthogonal space-time block code (DQOSTBC) for four transmit antennas. A rate 1 full-diversity DQOSTBC for four transmit antennas is designed. The code matrix changes according to different information exchange error cases, so full diversity is maintained even if not all information exchange is correct. We also perform analysis of the pairwise error probability. The performance analysis indicates that the proposed rate 1 DQOSTBC outperforms rate 1/2 DOSTBC for four transmit antennas at the same transmission rate, which is confirmed by the simulation results.