在設計無線展頻分碼多工（CDMA）系統時，消除窄頻干擾（NBI）的技術是很重要的，尤其是在窄頻干擾很大時候，能夠有效的消除這些干擾，就能改善系統的效能。在過去，有關這方面所提出來的技術，都只考慮每個使用者的功率都是相等的，也就是沒有考慮到遠近效應的環境，因為在實際的傳輸環境中，由於每個使用者對基地台的距離並非都是等距離的，一定會有遠近的差別，那麼基地台所收到的訊號就會因為距離的關係，使得近的使用者所發出的訊號會干擾到遠的使用者所發出的訊號。所以我們將提出一個可以解決這個問題的方法，以便能夠更實際的應用在實際的環境中。在本論文中，我們先介紹一些既有的方法，然後提出一個更有效的方法—提高偏移式預測器。這個方法是修正學長所提的修正偏移式預測器的演算法，使其在遠近效應的環境下，能夠有好的效果。電腦模擬的結果顯示，在低訊號雜訊比時，提高偏移式預測器的方法比傳統線性濾波器優越很多，也比學長所提出之方法還好；另一方面，與近似條件平均（ACM）非線性濾波器比較時，在低訊號雜訊比的情況下亦具有不錯之性能。接下來我們探討窄頻干擾在展頻分碼多工系統中的影響，所以我們將結合消除窄頻干擾的技術與展頻分碼多工偵測器，架構出完整的展頻分碼多工系統，應用前述之消除窄頻干擾的方法和學長所提出來的渦輪部分平行干擾消除方法合併在一起，分別具有消除窄頻干擾和來自別的使用者之干擾的效果。由模擬出來的結果可看出，加上了消除窄頻干擾的技術確實會使展頻分碼多工系統的效果更好；且消除窄頻干擾能力愈強者，其效果愈好。我們所提出來的提高偏移式預測器有相當不錯的性能。

Narrowband interference (NBI) suppression plays an important role in the performance of a direct-sequence code-division multiple-access (DS-CDMA) system. Although it is well known that a CDMA system possesses the feature of resistance to narrowband interference to some extent, it has been shown that employing interference suppression filters prior to signal despreading can further enhance the performance of a DS-CDMA system. Over the past two decades, there have been many researches concerned with the development of techniques for active NBI suppression. But, most of the NBI suppression techniques were not considered for near-far environments. In this thesis, we propose an enhanced offset predictor for NBI suppression in a near-far situation. The proposed scheme has better performance than the previous techniques. Finally, we discuss a combination of NBI suppression and multiuser detection, where turbo partial parallel interference cancellation is considered for combining with the proposed NBI suppression scheme. From simulation results, it is shown that the proposed NBI suppression method is essential for improving the performance of a CDMA system.

[1] H. V. Poor and L. A. Rusch, “Narrowband interference suppression in spread spectrum CDMA,” IEEE Personal Communications, pp. 14-27, Third Quarter 1994.
[2] A. Duel-Hallen, J. Holtzman, and Z. Zvonar, “Multiuser detection for CDMA systems,” IEEE Personal Communications, pp. 46-58, April 1995.
[3] L. B. Milstein, “Interference rejection techniques in spread spectrum communications,” Proc. of the IEEE, vol. 76, NO. 6, pp. 657-671, June 1988.
[4] P. Patel and J. Holtzman, “Analysis of a simple successive interference cancellation scheme in a DS/CDMA system,” IEEE Journal on Selected Areas in Communications, vol. 12, No. 5, pp. 796-807, June 1994.
[5] E. Masry, “Closed-from analytical results for the rejection of narrowband interference in PN spread spectrum systems – part I: Linear prediction filters,” IEEE Transactions on Communications, vol. COM-32, pp. 886-896, Aug. 1984.
[6] E. Masry, “Closed-from analytical results for the rejection of narrowband interference in PN spread spectrum systems – part II: Linear interpolation filters,” IEEE Transactions on Communications, vol. COM-33, pp. 10-19, Jan. 1985.
[7] E. Masry and L. B. Milstein, “Performance of DS spread-spectrum receiver employing interference-suppression filters under a worst-case jamming condition,” IEEE Transactions on Communications, vol. COM-34, pp. 13-21, Jan. 1986.
[8] R. A. Iltis and L. B. Milstein. “An approximate statistical analysis of the widrow LMS algorithm with application to narrow-band interference rejection,” IEEE Transactions on Communications, vol. COM-33, pp. 121-130, Feb. 1985.
[9] R. A. Iltis and L. B. Milstein, “Performance analysis of narrow-band interference rejection techniques in DS spread-spectrum systems,” IEEE Transactions on Communications, vol. COM-32, pp. 1169-1177, Nov. 1984.
[10] L. M. Li and L. B. Milstein, “Rejection of narrow-band interference in PN spread-spectrum systems using transversal filters,” IEEE Transactions on Communications, vol. COM-30, pp. 925-928, May 1982.
[11] J. W. Ketchum and J. G. Proakis, “Adaptive algorithms for estimating and suppression narrow-band interference in PN spread-spectrum systems,” IEEE Transactions on Communications, vol. COM-30, pp. 913-924, May 1982.
[12] F. M. Hsu and A. A. Giordano, “Digital whitening techniques for improving spread-spectrum communications performance in the presence of narrow-band jamming and interference,” IEEE Transactions on Communications, vol. COM-26, pp. 209-216, Feb. 1978.
[13] P. B. Papajic and B. S. Vucetic, “Adaptive Structures for Asynchronous CDMA systems,” IEEE Journal on Selected Areas in Communications, vol. 12, NO. 4, pp. 685-697, May 1994.
[14] U. Mitra, and H. V. Poor, “Analysis of an adaptive decorrelating detector for synchronous CDMA Channels,” IEEE Transactions on Communications, vol. 44, NO. 2, pp. 257-268, Feb. 1996.
[15] R. Vijayan, and H. V. Poor, “Nonlinear techniques for interference suppression in spread-spectrum systems,” IEEE Transactions on Communications, vol. 38, NO. 7, pp. 1060-1065, July 1990.
[16] W. R. Wu, and F. F. Yu, “New nonlinear algorithms for estimating and suppressing narrowband interference in DS spread spectrum systems,” IEEE Transactions on Communications, vol. 44, NO. 4, pp. 508-515, April 1996.
[17] A. Y.-C. Wong and V. C. M. Leung, “Signal tone interference rejection of code-phase multiplexed direct-sequence spread-spectrum signaling,” IEEE Transactions on Communications, vol. 44, NO. 5, pp. 557-561, May 1996.
[18] D. S. Chen and S. Roy, “An adaptive multiuser receiver for CDMA systems,” IEEE Journal on Selected Areas in Communications, vol. 12, NO. 5, pp. 808-816, June 1994.
[19] Z. Zvonar and D. Brady, “Suboptimal multiuser detector for frequency-selective rayleigh fading synchronous CDMA channels,” IEEE Transactions on Communications, vol. 43, NO. 2/3/4, pp. 154-157, Feb./March/April 1995.
[20] B. Wu and Q. Wang, “New suboptimal multiuser detectors for synchronous CDMA systems,” IEEE Transactions on Communications, vol. 44, NO. 7, pp. 782-785, July 1996.
[21] S. Haykin, Adaptive Filter Theory. Upper Saddle River, NJ: Prentice-Hall, 1996.
[22] L. A. Rusch and H. V. Poor, “Narrowband interference suppression in CDMA spread spectrum communications,” IEEE Transactions on Communications, vol. 42, NO. 2/3/4, pp. 1969-1979, Feb./March/April 1994.
[23] L. A. Rusch and H. V. Poor, “Multiuser detection techniques for narrowband interference suppression in spread spectrum communications,” in Proc. Seventh IEEE European conf. Mobile Personal Communications, pp. 84-89, Brighton, England, Dec. 1993.
[24] C. J. Masreliez, “Approximate non-Gaussian filtering with linear state and observation relations,” IEEE Transactions on Automatic Control, vol. AC-20, pp. 107-110, Feb. 1975.
[25] C. F. Wang, Adaptive Narrowband Interference Cancellation in Wireless Code-Division Multiple-Access Systems, Master Thesis, Department of Electrical Engineering, National Tsing Hua University, Hsinchu, Taiwan, June 1996.
[26] C. L. Wang and C. F. Wang, and J. M. Cioffi, “Reduced-complexity nonlinear techniques for narrowband interference suppression in spread-spectrum CDMA systems,” in Proc. 1997 IEEE Global Telecommunications Conference (Globecom ’97), Phoenix, AZ, pp. 659-664, Nov. 1997.
[27] C. L. Wang and K. M. Wu, “A New Narrowband Interference Suppression Scheme for Spread-spectrum CDMA Communications,” IEEE Transactions on Signal Processing, vol. 49, pp. 2832-2838, Nov. 2001.
[28] B. Aazhang and H. V. Poor, “Performance of DS/SSMA communications in impulsive channel-part I: Linear correlation receivers,” IEEE Transactions on Communications, vol. Com-35, pp. 1179-1188, Nov. 1987.
[29] P. K. Enge and D. V. Sarwate, “Spread spectrum multiple access performance of orthogonal codes: Linear receivers,” IEEE Transactions on Communications, vol. Com-35, Dec. 1987.
[30] E. A. Geraniotis and M. B. Pursley, “Error probability for direct-sequence spread spectrum multiple access communications-part II: Approximations,” IEEE Transactions on Communications, vol. 30, pp. 985-995, May 1992.
[31] M. K. Varanasi and B. Aazhang, “Multistage detection in asynchronous code-division multiple-access communications,” IEEE Transactions on Communications, vol. 38, pp. 509-519, April 1990.
[32] D. Divsalar, M. K. Simon, and D. Raphaeli, ”Improved parallel interference cancellation for CDMA,” IEEE Transactions on Communications, vol. 46, pp. 258-268, Feb. 1998.
[33] N. S. Correal, R. M. Buehrer, and B. D. Woerner, “A DSP-based DS-CDMA multiuser receiver employing partial parallel interference cancellation,” IEEE J. Select. Areas Communications, vol. 17, pp. 613-630, April 1999.
[34] C. L. Wang and K. M. Wu, “Multiuser Detection Using Partial Parallel Interference Cancellation for DS-CDMA Systems,” submitted to IEEE Transactions on Wireless Communications.
[35] C. L. Wang and C. F. Wang, “Adaptive narrowband interference cancellation in wireless code-division multiple-access systems,” Master Thesis, Department of Electrical Engineering, National Tsing Hua University, ROC, June 1996.
[36] S. Theodosidis et. al., “Interference rejection in PN spread spectrum systems with LS linear-phase FIR filters,” IEEE Transactions on Communications, vol. 37, pp. 991-994, Sep. 1989.
[37] Y. K. Cho and J. H. Lee, “Performance of narrowband interference suppression filters in a direct sequence code division multiple access system,” in IEEE 5th International Conference on Universal Personal Communications, vol. 1, pp. 169-173, 1996.
[38] P. Kalidas and K. M. M. Prabhu, “An improved LMS adaptive algorithm for narrowband interference suppression in direct sequence spread spectrum,” IEEE Trans. Aerosp. And Electronic Syst., vol. 31, pp. 1198-1201, July 1995.
[39] J. G. Proakis, “Interference suppression in spread spectrum systems,” in IEEE 4th International Symposium on Spread Spectrum Techniques and Applications Proceedings, vol. 1, pp. 259-266, Sept. 1996.
[40] X. Huang and H. Leung, “Narrowband interference cancellation in a chaotic CDMA communication system,” in IEEE Pacific Rim Conference on Communications, Computers, and Signal Processing, pp. 437-440, May 1995.
[41] A. Ansari and R. Viswanathan, “On SNR as a measure of performance for narrowband interference rejection in direct sequence spread spectrum systems,” IEEE Transactions on Communications, vol. 43, pp. 1318-1322, Feb./Mar./April 1995.
[42] A. Ranheim, “Narrowband interference rejection in direct-sequence spread-spectrum system using time-frequency decomposition,” IEE Proc.-Commun., vol. 142, NO. 6, pp. 393-400, Dec. 1995.
[43] S. D. Sandberg, “Adapted demodulation for spread-spectrum receivers which employ transform-domain interference excision,” IEEE Transactions on Communications, vol. 43, NO. 9, pp. 2502-2510, Sep. 1995.
[44] R. Rifkin, Comments on “Narrow-band interference rejection using real-time Fourier transforms,” IEEE Transactions on Communications, vol. 39, NO. 9, pp. 1292-1294, Sep. 1991.
[45] U. Madhow and M. Honig, “MMSE interference suppression for direct-sequence spread-spectrum CDMA,” IEEE Transactions on Communications, vol. 42, pp. 3178-3188, Dec. 1994.
[46] H. V. Poor and S. Verdu, “Probability of error in MMSE multi-user detection,” IEEE Trans. Inform. Theory, vol. 43, pp. 858-881, May 1997.