近年來，正交分頻多工(Orthogonal Frequency Division Multiplexing,
OFDM)系統已經是一項越來越熱門的技術，現今也常有研究將其與多重輸入多重
輸出(Multiple-input Multiple-output, MIMO)做結合，其中又以空頻區塊編碼之正
交分頻多工(Space-frequency Block Code-OFDM, SFBC-OFDM)系統以及空時區
塊編碼之正交分頻多工(Space-time Block Code-OFDM, STBC-OFDM)系統為最多
人所探討研究的對象。此兩系統各有其非常重要之前提，即在空頻區塊編碼之正交
分頻多工系統中，相鄰的編碼子載波上的通道頻率響應(Channel Frequency
Response, CFR)必須大致相等，而在空時區塊編碼之正交分頻多工系統中，相鄰的
編碼符元的通道狀況也應保持不變。由於這兩項假設在多數的無線通訊環境中是不
成立的，於是干擾於焉產生。故本論文提出在正交空頻區塊編碼之正交分頻多工系
統中，利用拉格朗日乘數法(Lagrange Multiplier Method)與常用於干擾消除之特徵
值(Eigenvalue)問題求解法兩種方法來消除由於相鄰的編碼子載波上的通道頻率響
應不相等，造成正交空頻區塊編碼的正交性失去所產生的干擾。在本論文之中，我
們藉由電腦模擬的結果，可以驗證我們所採用的方法可以有效的消除干擾。

Orthogonal frequency division multiplexing (OFDM) is the major technique
for next generation wireless communication system because of its high spectral
efficiency. In addition, multiple-input multiple-output (MIMO) technique is
usually used to further increase system capacity. There are two major coding
schemes adopted in MIMO-OFDM systems, i.e. space-time block code (STBC) and
space-frequency block code (SFBC). This thesis investigates the
orthogonal-space-frequency block code OFDM (OSFBC-OFDM) system.
In SFBC-OFDM systems, the channel frequency response is usually assumed
to be the same for adjacent subcarriers. However, this assumption is not valid in
frequency-selective fading environment. Therefore, the orthogonality of code
structure is destroyed, leading to substantial increase in interference and
significant decrease in system performance.
This thesis proposes a receiver equalizer which adopts an interference
cancellation (IC) mechanism to maximize the signal to interference plus noise ratio
(SINR). Both the Lagrange multiplier method and eigenvalue method are adopted
in the interference cancellation. Simulation experiments are conducted to verify
the system performance and results demonstrate that the SINR performance is
dramatically improved.

致謝 .................................................................................................................................. I
中文摘要 .......................................................................................................................... II
ABSTRACT .................................................................................................................... III
CONTENTS ................................................................................................................... IV
LIST OF FIGURES ........................................................................................................ VI
Chapter 1 Introduction .............................................................................................. 1
1.1 Introduction to OFDM Systems ..................................................................... 2
1.2 Introduction to MIMO Systems ...................................................................... 4
1.3 Motive of Research ......................................................................................... 5
1.4 Notations ......................................................................................................... 6
Chapter 2 System Model ........................................................................................... 7
2.1 OSFBC-OFDM System with Two Transmit Antennas ................................... 8
2.2 OSFBC-OFDM System with Three Transmit Antennas .............................. 10
Chapter 3 Proposed Filter Based on Maximum SINR ......................................... 12
3.1 System Model with Proposed Filter ............................................................. 12
3.2 Lagrange Multiplier Method ........................................................................ 13
3.3 SINR in Matrix Form at nth Subcarrier ........................................................ 20
3.4 Generalized Eigenvalue Method .................................................................. 23
Chapter 4 Simulation Results ................................................................................. 25
4.1 Simulation Results of Two Transmit Antennas ............................................ 28
4.2 Simulation Results of Three Transmit Antennas .......................................... 31
Chapter 5 Conclusions and Future Works ............................................................ 32
5.1 Conclusions .................................................................................................. 32
5.2 Future Works ................................................................................................. 33
APPENDIX ..................................................................................................................... 34
REFERENCE .................................................................................................................. 37
ABBREVIATIONS ......................................................................................................... 41

[1] R. W. Chang, “Synthesis of band-limited orthogonal signals for multichannel data transmission,” Bell System Tech. J., vol. 45, pp. 1775–1796, Dec. 1966.
[2] Radio broadcasting system: Digital audio broadcasting DAB to mobile, portable and fixed receivers, ETSI, ETS 300 401, 1.3.2 ed. 2000.
[3] Digital video broadcasting DVB: Framing structure, channel coding and modulation for digital terrestrial television, ETSI, EN 300 744, 1.3.1 ed. 2000.
[4] IEEE Part 11: Wireless LAN medium access control MAC and physical layer PHY specifications: high-speed physical layer in the 5 GHz band, IEEE Std. 802.11a-1999,
Sep. 1999.
[5] IEEE standard for local and metropolitan area networks, IEEE Std. 802.16-2004, Oct. 2004.
[6] M. Z. Siam and M. Krunz, “An overview of MIMO-oriented channel access in wireless networks,” IEEE Wireless Commun., vol. 15, no. 1, pp. 63–69, Feb. 2008.
[7] M. Jiang and L. Hanzo, “Multiuser MIMO-OFDM for next-generation wireless systems,” Proceedings of the IEEE, vol. 95, no. 7, pp. 1430–1469, Jul. 2007.
[8] S. M. Alamouti, “A simple transmit diversity technique for wireless communications,” IEEE J. Sel. Areas Commun., vol. 16, no. 8, pp. 1451–1458, Oct. 1998.
[9] R. S. Blum, Y. Li, J. H. Winters, and Q. Yan, “Improved space-time coding for MIMO-OFDM wireless communications,” IEEE Trans. Commun., vol. 49, no. 11, pp.1873–1878, Nov. 2001.
[10] P. Dayal, M. Brehler, and M. K. Varanasi, “Leveraging coherent space-time codes for noncoherent communication via training,” IEEE Trans. Inf. Theory, vol. 50, no. 9, pp. 2058–2080, Sep. 2004.
[11] W. Su, Z. Safar, M. Olfat, and K. J. R. Liu, “Obtaining full-diversity space-frequency codes from space-time codes via mapping,” IEEE Trans. Signal Process., vol. 51, no. 11, pp. 2905–2916, Nov. 2003.
[12] K. Lee and D. Williams, “A space-frequency transmitter diversity technique for OFDM systems,” in Proc. IEEE GLOBECOM, San Francisco, CA, 2000, vol. 3, pp.
1473–1477.
[13] W. Su, Z. Safar, and K. J. R. Liu, “Full-rate full-diversity space-frequency codes with optimum coding advantage,” IEEE Trans. Inf. Theory, vol. 51, no. 1, pp. 229–249, Jan.
2005.
[14] M. Saegusa and T. Saba, “Effect of inter-code interference cancellation on STFBC-OFDM under time and frequency selective fading environments,” in Proc. IEEE GLOBECOM, Washington, DC, 2007, pp. 3995–3999.
[15] K. Lee, Y. Kim, and J. Kang, “A novel orthogonal space-time-frequency block code for OFDM systems,” IEEE Commun. Lett., vol. 13, no. 9, pp. 652–654, Sep. 2009.
[16] S. B. Weinstein and P. Ebert, “Data transmission by frequency-division multiplexing using the discrete Fourier transform,” IEEE Trans. Commun. Technol., vol. 19, no. 5, pp. 628–634, Oct. 1971.
[17] E. Feig, “Practical aspects of DFT-based frequency division multiplexing for data transmission,” IEEE Trans. Commun., vol. 38, pp. 929–932, Jul. 1990.
[18] Z. Wang and G. B. Giannakis, “Wireless multicarrier communications,” IEEE Signal Process. Mag., vol. 17, no. 3, pp. 29–48, May 2000.
[19] G. J. Foschini, “Layered space-time architecture for wireless communication in a fading environment when using multi-element antennas,” Bell Labs Tech. J., vol. Autumn, pp. 41–59, Oct. 1996.
[20] A. Stamoulis, S. N. Diggavi, and N. Al-Dhahir, “Intercarrier interference in MIMO OFDM,” IEEE Trans. Signal Process., vol. 50, no. 10, pp. 2451–2464, Oct. 2002.
[21] G. P. Villardi, G. De Abreu, and R. Kohno, “Modified orthogonal space–time block codes for time-selective fading channels,” IEEE Trans. Veh. Technol., vol. 57, no. 6, pp. 3921–3927, Nov. 2008.
[22] L. Y. Song and A. G. Burr, “Successive interference cancellation for space-time block codes over time-selective channels,” IEEE Commun. Lett., vol. 10, no. 12, pp. 837–839, Dec. 2006.
[23] F. C. Zheng and A. G. Burr, “Signal detection for orthogonal space-time block coding over time-selective fading channels: a PIC approach for the Gi systems,” IEEE Trans. Commun., vol. 53, no. 6, pp. 969–972, Jun. 2005.
[24] F. C. Zheng and A. G. Burr, “Signal detection for non-orthogonal space-time block coding over time-selective fading channels,” IEEE Commun. Lett., vol. 8, no. 8, pp. 491–493, Aug. 2004.
[25] B. Ozbek and D. Le Ruyet, “Low complexity ZF receiver for orthogonal SFBC-OFDM in broadband wireless channels,” Electron. Lett., vol. 42, no. 8, pp. 479–481, Apr. 2006.
[26] S. D. Muruganathan and A. B. Sesay, “A computationally efficient QR-successive interference cancellation scheme for simplified receiver implementation in SFBC-OFDM systems,” IEEE Trans. Wireless Commun., vol. 6, no. 10, pp. 3641–3647, Oct. 2007.
[27] A. Scaglione, P. Stoica, S. Barbarossa, G. B. Giannakis, and H. Sampath, “Optimal designs for space-time linear precoders and decoders,” IEEE Trans. Signal Process., vol. 50, no. 5, pp. 1051–1064, May 2002.
[28] T. A. Tran and A. B. Sesay, “A generalized linear quasi-ML decoder of OSTBCs for wireless communications over time-selective fading channels,” IEEE Trans. Wireless Commun., vol. 3, no. 3, pp. 855–864, May 2004.
[29] T. X. Lai, S. D. Muruganathan, and A. B. Sesay, “Performance analysis and multi-stage iterative receiver design for concatenated space-frequency block coding schemes,” IEEE Trans. Wireless Commun., vol. 7, no. 11, pp. 4208–4214, Nov. 2008.
[30] H. E. Gamal, A. R. Hammons Jr., Y. Liu, M. P. Fitz, and O. Y. Takeshita, “On the design of space-time and space-frequency codes for MIMO frequency-selective fading
channels,” IEEE Trans. Inf. Theory, vol. 49, no. 9, pp. 2277–2292, Sep. 2003.