基于SC―FDE的频率选择性衰落信道中的空时分组编码系统性能研究

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Abstract： In the frequency selective fading channel， the orthogonal space-time block code with single-carrier frequency domain equalization （OSTBC-scfde）system can effectively combat the frequency selective fading，and achieve full diversity gain.It has attracted widespread attention. However， it does not achieve full rate transmission when more than two transmit antennas. In order to overcome the shortcomings of the program，this paper studies the rotation matrix quasi orthogonal space-time block code with single-carrier frequency domain equalizaton（RM-QOSTBC-SCFDE）. Simulation results show that when the number of transmit antennas is 4，this program not only achieve full rate transmission but also get a high diversity gain.

Keywords： orthogonal space-time block code （QOSTBC）； rotation matrix； single-carrier frequency domain equalization （SC-FDE）； frequency selective fading

Introduction

In the frequency selective fading channel，SCFDE[1]can effectively combat the frequency selective fading， and avoid high PAPR and frequency offset sensitive of the OFDM system.STBC[2] with multiple transmit and receive antennas establish multiples independent communication links to realizes the higher diversity gain. If combine the two，not only can overcome frequency selective fading of wireless channel.but also can achieve diversity gain.There is a wide application prospect in the field of broadband wireless communications.

Current research focuses on OSTBC-SCFDE， such as Naofal Al-Dhahir [3] studied the Alamouti-SCFDE technologies. But studies show that the program can not achieve full rate transmission when more than two transmit antennas. Jafarkhani

[4] and TBH[5] proposed QOSTBC by sacrificing part of the diversity gain achieved full rate transmission. However， the scheme is suitable for flat fading channels. When applied to frequency selective fading channel， the decoder and equalizer would be very complicated. Literature[6] studied RM-QOSTBC in the flat fading channel. Literature[7] proposed an improved QOSTBC-SCFDE with four transmit antennas.Although the realized full rate transmission in the frequency selective fading channel ，but the system diversity gain is only two. This paper studies RM-QOSTBC-SCFDE， through the rotation matrix to eliminate the correlation of the channel matrix that make the decoder is more simple. By this way not only overcome the frequency selective fading， to achieve full rate transmission， but also achieve higher diversity gain.

1 Based on four transmit antennas OSTBC-SCFDE technology

Where is a diagonal matrix. The value of is equal to .This shows that the diversity gain is 4. the coefficient of the MMSE-FDE in this case is equal to，where IN is N x N Xunit matrix.

2 Based on four transmit antennas RM-QOSTBC-SCFDE technology

Through the above analysis shows that 4 transmit antenna OSTBC-SCFDE technology could overcome the frequency selective fading and achieve full diversity gain in the frequency selective fading channel，but the rate is only 1/2. In order to achieve full rate transmission，high diversity and low decoding complexity，this paper studies the RM-QOSTBC-SCFDE technology. At present， the researches of QOSTBC mainly focus on flat fading channels. Based on the constellation rotation QOSTBC achieve full rate and full diversity，but the decoding and SCFDE of the receiver will become more complex.RM-QOSTBC-SCFDE.

4 conclusions

In frequency selective fading channel， the OSTBC-SCFDE technology overcomes the frequency selective fading，and achieve full diversity gain .It improves the performance of the system， and has broad application prospects. However， ， the program can achieve full transmission rate when more than two transmit antennas. This seriously affects the practical application of the system. In this paper， the RM-QOSTBC-SCFDE of four transmit antennas sacrifices some diversity gain to achieve full rate transmission. It has a certain practical value.

REFERENCES

[1]FALCONER D，ARIYAVISTAKUL S L，BENYAMIN-SEEYAR A，et al. “Frequency domain equalization for single-carrier broadband wirelss systems”. IEEE Communications Magazine，2002，40（4）：58-66.

[2]SHAO Zhao.MIMO System and STC：The Theory and Practice of Diversity[M].Publishing House of Electronics Industry. 2013，1

[3]AL-DHAHIR N. “Single-carrier frequency-domain equalization for space-time block-coded transmissions over frequency-selective fading channels”. IEEE Commun Lett，2001，5（7）：304-306.

[4]Hamid Jafarkhani. “A quasi-orthogonal space-time block code”. IEEE Trans. Commun，2001，49（1）：1-4

[5]Olav Tirkkonen，Adrian Boariu，and Ari Hottinen. “ Minimal Non-Orthogonality Rate 1 Space-Time Block Codes for 3+Tx Antennas”. IEEE International Symposium on Spread Spectrum Techniques and Applications，v 2，p 429-432，2000

[6]Uysal，Murat；Al-Dhahir，Naofal. “Time and Frequency-Domain Equalization for Quasi-Orthogonal STBC over Frequency-Selective Channels”.IEEE International Conference on Communications，v 2， p 697-701，2004 [7]

[7]Unhee Park，Sooyoung Kim. “A Novel QO-STBC Scheme with Linear Decoding for Three and Four Transmit Antennas”.IEEE COMMUNICATIONS LETTERS. 2008，12（12）：868-870

[8]NI Ying-jun，LI Ming-qi，GUO Wen-qiang. “Novel design method of quasi-orthogonal space-time block code”.Application Research of Computers. 2011，28（2）：665-668

（作者单位：中国矿业大学（北京），北京 100083）