Orthogonal frequency division multiplexing (OFDM) has recently received considerable interest for its advantages in high-bit-rate transmissions over frequency-selective fading channels. Space-time block coding (STBC) has emerged as a powerful approach to exploit spatial diversity and to combat fading in multiple-input multiple-output (MIMO) wireless communication systems. However, OFDM systems with direct-conversion RF receivers are very sensitive to non-idealities at the front-end of receiver, such as I/Q imbalance and carrier frequency o&;#8629;set (CFO). These non-idealities at the receiver result in intercarrier interference (ICI). Accurate estimates of the non-idealities and channel response are required in OFDM systems. This thesis studies the blind CFO and I/Q imbalance estimation for OFDM systems with multiple transmit antennas. The thesis consists of three parts. In the first part, we review an existing CFO and I/Q imbalance estimation method based on rank criterion. This method though gives good performance but not for joint estimation, it cannot estimate the I/Q imbalance in the presense of CFO. In order to solve this issue, we propose an improved method. In the second part, we propose a new rank criteron and group method for joint CFO and independent I/Q imbalance estimation. The proposed method exploits the redundant information in OSTBC for joint blind CFO and I/Q imbalance estimation. In the third part, we extend the proposed method to the estimation of frequency dependent I/Q imbalance in the presence of CFO. We also provide numerical simulation to verify the performance of the proposed methods.

List of Tables vii

List of Figures viii

Abstract xiii

Acknowledgements xv

1 Introduction........................................................... 1
2 I/Q Imbalance and Carrier Frequency Offset in OFDM Systems............. 5
2.1 Introduction to OFDMSystems.......................................... 6
2.2 Orthogonal STBC MIMO-OFDM Systems Model.............................. 10
2.3 The Phenomenon of I/Q Imbalance and CFO ............................. 11
2.4 I/Q Imbalance and CFO on the Received Baseband Signal Model.......... 12
2.5 Compensation of I/Q Imbalance and Carrier Frequency Offset........... 15
2.6 Simulation Result and Comparison .................................... 18
2.7 Concluding Remark.................................................... 21
3 Review of Blind I/Q Imbalance and CFO Estimation in OSTBC-OFDM Systems. 23
3.1 Review of OSTBC-OFDM Systems with 3 Transmit Antennas................ 24
3.2 Blind CFO Estimation Algorithms Based on Rank Criterion.............. 28
3.2.1 Proposed CFO Estimation Method Using Rank Criterion................ 28
3.2.2 SimulationResultandComparison ............... 30
3.3 Blind I/Q Imbalance Estimation Algorithms Based on Rank Criterion 33
3.3.1 Blind Estimation for Independent I/Q Imbalances . . . . . . . 33
3.3.2 Blind Estimation for Dependent I/Q Imbalances . . . . . . . 34
3.3.3 SimulationResultandComparison ............... 36
3.4 ConcludingRemark............................ 41
4 Joint Blind Estimation of I/Q Imbalance and CFO in OSTBC-OFDM Systems 43
4.1 Blind Independent I/Q Imbalance Estimation with CFO Based on
RankCriterionandGroupMethod ................... 44
4.2 Blind CFO Estimation with Independent I/Q Imbalance Compensation
BasedonRankCriterion......................... 51
4.3 SimulationResultandComparison ................... 52
4.4 ConcludingRemark............................ 60
5 Joint Blind Estimation of Frequency Dependent I/Q Imbalance and CFO in OSTBC-OFDM Systems 61
5.1 Blind Frequency Dependent I/Q Imbalance Estimation with CFO . . 62
5.1.1 ProposedSearchMethod..................... 64
5.1.2 ProposedIterativeMethod.................... 65
5.2 SimulationResultandComparison ................... 70
5.3 ConcludingRemark............................ 86
6 Conclusion 87
Bibliography 89

[1] 3GPP TS 36.211 v8.0.0. 3-rd Generation Partnership Project Technical Specifica- tion Group Radio Access Network Evolved Universal Terrestrial Radio Access(E- UTRA) Physical channels and modulation (Realease 8),Sept. 2007.
[2] European Telecommunication Standards Institude, “Digital audio broadcasting (DAB) to mobile protable and fixed receiverd,” EST 300 401, 1994.
[3] European Telecommunication Standards Institude, “Digital vedio broadcasting; framing, structure, channel coding and modulation for digital terrestrial television (DVB-T),” EST 300 744, 1997.
[4] Lawrence Der, and Behzad Razavi, “A 2-GHz CMOS image-reject receiver with LMS calibration,” IEEE J. Solid-State Circuits, vol. 38, no. 2, pp. 167-175, Febru- ary 2003.
[5] P. Zhang, T. Nguyen, C. Lam, D. Gambetta, C. Soorapanth, B. Cheng, S. Hart, I. Sever, T. Bourdi, A. Tham, B. Razavi, “A direct conversion CMOS transceiver for IEEE 802.11a WLANs,” in IEEE Int. Solid-State Circuits Conf. Dig Technical papers, February 2003.
[6] D. D. Lin, R. A. Pacheco, T. J. Lim, and D. Hatzinakos, “Joint estimation of channel response, frequency offset, and phase noise in OFDM,” IEEE Transactions on Signal Processing, vol. 54, no. 9, September 2006.
[7] Q. Zou, A. Tarighat, and A. H. Sayed, “Compensation of phase noise in OFDM wireless systems,” IEEE Transactions on Signal Processing, vol. 55, no. 11, Novem- ber 2007.
[8] S. Wu, and Y. B. -Ness, “OFDM channel estimation in the presence of frequency offset and phase noise,” IEEE International Conference on Communications, vol. 5, pp. 3366-3370, May 2003.
[9] Y. Yao, and Giannakis, “Blind carrier drequency offset estimation in SISO,MIMO and multiuser OFDM systems,” IEEE Trans.Signal Process., vol. 51, no,3 pp. 602- 613,May 2003.
[10] B. Razavi, RF Microelectronics. Englewood Cliffs, NJ: Prentice-Hall, 1998.
[11] Y.-P. Lin and S.-M. Phoong, “BER minimized OFDM systems with channel
independent precoders,” , volume 51, issue 9, pp. 2369-2380, September 2003.
[12] L.-H. Lee, “Performance Study of OFDM and SC-CP Systems in Nonideal Trans-
mission Environment,” Master thesis, National Taiwan University, June 2005.
[13] M. J. M. PELGROM,A. C. J. DUINMAIJER,, and A. P. G. WELBERS, “Match- ing properties of MOS transistors,” IEEE J. Solid-State Circuits, vol. 24, no. 5, pp. 1433-1439, October 1989.
[14] L. L. Jr, M. Kurosaki, and H. Ochi, “Low Complexity Compensation of Fre- quency Dependent I/Q Imbalance and CFO for Direct Conversion Receivers,” Cir- cuits and Systems (ISCAS),June 2010.
[15] S. M. Alamouti, “A simple transmit diversity technique for wireless communica- tions,” IEEE Transactions on Communications, vol. 16, pp. 1451-1458, Oct. 1998.
[16] V. Tarokh ,and H. Jafarkhani, “SpaceVTime Block Codes from Orthogonal De- signs,” IEEE TRANSACTIONS ON INFORMATION THEORY, vol. 45, no. 5, July. 1999.
[17] Z.-T Huang, “Estimation of I/Q Imbalance and Carrier Frequency Offset for Or- thogonal Space-Time Block Coded OFDM Systems,” National Taiwan University Graduate Institute of Communication Engineering Master Thesis, June. 2012.
[18] L. Wu, X.-D. Zhang, P.-S. Li,and Y.-T. Su, “A Closed-form Blind CFO Estimator Based on Frequency Analysis for OFDM Systems,” IEEE Transactions on Wireless Communication, vol. 57, pp. 1634-1637, June 2009.
[19] T. Roman,S. Visuri, V. Koivunen, “Blind Frequency Synchronization in OFDM via Diagonality Criterion,” IEEE Transactions on Signal Processing, vol. 54, no. 8, August 2006.
[20] Q. Zhu, W. Wang and Y. Liu, “A New Fast CFO Tracking Algorithm for OFDM Systems,” International Wiress Communications Networking and Mobile Comput- ing (WiCOM) Conf., pp.1-3,2010.2010 6th
[21] L. Anttila,M. Valkama, “Circularity-Based I/Q Imbalance Compensation in Wideband Direct-Conversion Receivers,” IEEE Transactions on Vehicular Tech- nology, vol. 57, no. 4, July 2008.