在本論文中，我們所考慮的是一個受到瑞雷衰退通道影響的多載波分碼多工系統，論文主要的目的是設計一個直接線性限制性常模反向QR分解(LCCM-IQRD)的方法來做多重接取干擾(MAI)消除以及對抗因為通道估測不準確所造成不匹配(mismatch)的問題。在傳統中有兩種檢測器被用來做多使用者干擾消除(multiuser interference suppression)，其中一個是盲目適應性演算法(blind adaptive algorithm)，另一個是線性限制性分開線性干擾消除(linearly constrained PLIC)逼近法。 盲目適應性演算法在輸出訊號對干擾及雜訊的性能尚可，但因為這個方法有鏡像問題(mirror effect)而使得它的位元錯誤率提高，當通道參數無法完美估測的時候，適應性線性限制性分開線性干擾消除的方法會產生不匹配(mismatch)的問題而降低到這個方法的性能，不論是利用最小均方演算法或是遞迴式最小平方演算法。
為了解決這個不匹配的問題，利用線性限制性常模的準則(constant modulus criterion)被提出，然而梯度(gradient)的方法收斂速度較慢而無法適用於即時無線通訊系統，為了要解決收斂慢及不匹配的問題，我們設計了一個直接強韌線性限制性常模反向QR分解(robust LCCM-IQRD)的方法，這個方法可以有效的對抗多重接取干擾消除及不匹配的問題，進而比傳統的方法在位元錯誤率及輸出訊號對干擾及雜訊得到更好的性能。

In this thesis, the multi-carrier (MC) code division multiple access (CDMA) system is considered in Rayleigh fading channel. The main concern of this thesis is to devise a new direct linearly constrained constant modulus (LCCM) inverse QRD-RLS algorithm for multiple access interference (MAI) cancellation and the problem due to the mismatch of the channel estimator. In the conventional approach, two significant detectors are applied to the system for multiuser interference suppression, one is the blind adaptation algorithm and the other is adaptive linearly constrained PLIC approach. However, the mirror effect may occur when the blind adaptation algorithm is employed. It might affect the performance in terms of bit error rate (BER), although the desired signal to interference (due to other users) improvement is still acceptable. Moreover, in case that the channel coefficients could not be estimated perfectly, the mismatch problem may occur to degrade the performance of the adaptive linearly constrained PLIC approach with the LMS or RLS algorithm.
To overcome the mismatch problem, the conventional approach is to use the LCCM criterion with gradient algorithm. However, the convergence rate of the gradient algorithm is too slow to be implemented in real-time wireless communication system. In this thesis, to have fast convergence rate and to circumvent the mismatch problem, the robust LCCM-IQRD algorithm is devised and applied to the MC-CDMA system in Rayleigh fading channel. The proposed robust LCCM-IQRD algorithm has shown to be more effective in terms of MAI cancellation and the mismatch due to imperfect channel estimator. The performance, in terms of BER, of the proposed algorithm is superior to that of the conventional PLIC based algorithms, the blind adaptation algorithm, and the conventional LCCM gradient algorithm.

Acknowledgement i
Abstract ii
Contents iii
List of Figures and Tables v
Chapter 1 Introduction 1
Chapter 2 Description of Multi-Carrier CDMA System and System Model
2.1 Introductio 4
2.2 Overview of Multi-Carrier CDMA System 5
2.3 System Model 9
2.4 Conventional Receivers for MC-CDMA System 13
2.4.1 Maximum Ratio Combining 14
2.4.2 Blind Adaptation Algorithm 15
2.4.3 Partitioned Linear Interference Canceller Approach 18
Chapter 3 Linearly Constrained Constant Modulus Criterion under Mismatch Problem
3.1 Introduction 24
3.2 Conventional Linearly Constrained CM Gradient Detector 25
3.3 Robust Direct Linearly Constrained CM IQRD Detector 26
3.3.1 Constrained Cost Function of Constant Modulus Approach 27
3.3.2 Linearly Constrained CM with IQRD-RLS Algorithm 27
3.3.3 Robust LCCM-IQRD Algorithm 31
3.4 Computer Simulation Results 36
3.4.1 Without Mismatch Case 37
3.4.2 Mismatch Case 38
Chapter 4 Conclusions 50
Appendix A 52
Appendix B 54
Appendix C 56
References 58

[1] S. Hara and R. Prasad, “Overview of Multicarrier CDMA,” IEEE Commun.
Mag., pp. 126–133, Dec. 1997
[2] S. Kondo and L. B. Milstein, “Performance of Multicarrier DS CDMA
Systems,” IEEE Trans. on Commun., vol. 44, pp. 238–246, Feb. 1996
[3] Richard van Nee and Ramjee Prasad, “OFDM Wireless Multimedia
Communications”, Artce House, 2000
[4] Tat M. Lok, Tan F. Wong and James S. Lehnert, “Blind Adaptive Signal
Reception for MC-CDMA Systems in Rayleigh Fading Channels” IEEE Trans. on
Commun., vol. 47, No. 3, pp.464-471, March 1999
[5] T. F. Wong, T. M. Lok, J. S. Lehnert, and M. D. Zoltowski, “Spread-
Spectrum Signaling Techniques with Antenna Arrays and Blind Adaptation,”
IEEE Proc. MILCOM’96, vol. 1, pp. 194–198, 1996
[6] T. F. Wong, T. M. Lok, J. S. Lehnert, and M. D. Zoltowski, “A Linear
Receiver for Direct-Sequence Spread-Spectrum Multiple-Access Systems with
Antenna Arrays and Blind Adaptation,” IEEE Trans. on Inform. Theory, vol.
44, pp. 659–676, Mar. 1998
[7] J. G. Proakis, “Digital Communications”, 3rd, New York: McGraw-Hill, 1995
[8] Jeffrey B. Schodorf and Douglas B. Williams, “A Constraint Optimization
Approach to Multiuser Detection,” IEEE Trans. on Signal Processing, vol.
45, No.1, January 1997
[9] M. Honig, U. Madhow, and S. Verd’ u, “Blind Adaptive Multiuser
Detection,” IEEE Trans. on Inform. Theory, pp. 944–960, July 1995
[10] L. J. Griffiths and C. W. Jim, “An Alternative Approach to Linearly
Constrained Adaptive Beamforming,” IEEE Trans. on Antennas Propagat., pp.
27-34, Jan. 1982
[11] Haykin, “Adaptive Filter Theory”, 3rd, Englewood Cliffs, NJ: Prentice
Hall, 1996
[12] S. T. Alexander and A. L. Ghirnikar, “ A Method for Recursive Least
Squares Filtering Based upon an Inverse QR Decomposition,” IEEE Trans. on
Signal Processing, vol. 41, No.1, pp. 20-30, Jan. 1993
[13] L. S. Resende, J. T. Romano, and M. G. Bellanger, “ A Fast Least-Squares
Algorithm for Linearly Constrained Adaptive Filtering,” IEEE Trans. on
Signal Processing, vol. 44, No. 5, May 1996
[14] S. J. Chern, “Adaptive Array Processing with Application to Mobile
Communications,” Report of the 38th Research Fellowship of National
Science Council, Taiwan, R.O.C.
[15] C. Y. Chang and S. J. Chern, “Adaptive Linearly Constrained Inverse QRD-
RLS Beamformer for Multiple Jammers Suppression,” The Third IEEE Signal
Processing Workshop on Signal Processing Advances in Wireless
Communications, Westin Resort, Ta-Shee, Taoyuan, Taiwan, R.O.C., pp. 294-
297, March 20-23, 2001
[16] S. J. Chern and C. Y. Chang, “Adaptive Linearly Constrained Inverse QRD-
RLS Beamforming Algorithm for Moving Jammers Suppression,” IEEE Trans. on
Antennas Propagat. (revised)
[17] S. J. Chern, C. Y. Chang and T. Y. Liao, “Adaptive Multiuser Interference
Cancellation with Robust Constrained IQRD-RLS Algorithm for MC-CDMA
System,” submitted to IEEE ISPACS2001
[18] O. L. Frost III, “An Algorithm for Linearly Constraint Adaptive Array
Processing,” Proc. IEEE, vol. 60, No.8, pp. 926-935, Aug. 1972
[19] Jeffrey B. Schodorf and Douglas B. Williams, “Array Processing Techniques
for Multiuser Detection,” IEEE Trans. on Commun., vol. 45, No. 11,
November 1997
[20] J. Miguez, and L. Castedo, “Blind Multiuser Interference Cancellation in
Multicarrier CDMA: A Linearly Constrained Constant Modulus Approach,”
The Ninth IEEE International Symposium on Personal, Indoor and Mobile
Radio Communications, vol. 2, pp. 523 –527, 1998
[21] J. Miguez, and L. Castedo, “A Linearly Constrained Constant Modulus
Approach to Blind Adaptive Multiuser Interference Suppression,” IEEE
Commun. Letters, vol.2, No. 8, Aug. 1998
[22] R. Pickholtz, and K. Elbarbary, “The Recursive Constant Modulus
Algorithm; A New Approach for Real-Time Array Processing,” Signals,
Systems and Computers. IEEE Conference on Record of The Twenty-Seventh
Asilomar, vol. 1, pp. 627-632, 1993