隨著用戶對於多媒體服務需求的逐漸增加，未來的無線通訊系統除提供多用戶使用語音服務之外，同時也必須提供如圖片、影像及網際網路等各種不同速率信號之傳輸。多重速率(Multi-rate)之直接序列/分碼多工(Direct Sequence/Code Division Multiplexing Access, DS/CDMA)系統即是一個提供多用戶且多重速率信號傳輸的無線通訊系統。其中，多處理增益(Variable Processing Gain, VPG)系統以及多展頻碼(Multi-code, MC)系統最被廣泛討論及研究，而兩者皆具有單一切片速率(Chip Rate) 之傳輸信號。
基於高階統計量(Higher Order Statistics, HOS)之反濾波器準則(Inverse Filter Criteria, IFC)已被廣泛應用於離散時間多輸入多輸出(Multi-input Multi-output, MIMO)線性非時變(Linear Time Invariant, LTI)系統的盲蔽等化。而利用基於HOS之IFC所得到的等化輸出信號為其中一個未知的輸入信號，並具有未知量度因子(Scale Factor)以及未知時間延遲 (Time Delay)。本論文提出了一個基於HOS之IFC之多重速率盲蔽多用戶等化演算法(Blind Multiuser Equalization Algorithm, BMEA)，可有效地抑制干擾並同時抽出所有想要的虛擬用戶信號，並從抽出之虛擬用戶信號重建所屬之原用戶信號，而所提出之多重速率BMEA同時具有超指數的收斂速度並保證收斂的優點。此外，本論文亦提出一個多重速率盲蔽多用戶等化-盲蔽最大比例結合演算法(Multi-rate BMEA-BMRC Algorithm)，藉由使用多根接收天線系統獲得空間分集增益(Space Diversity Gain)，以提升系統容量、改善連線品質。
最後經由模擬結果，驗證本論文所提出之多重速率盲蔽多用戶等化演算法及多重速率盲蔽多用戶等化-盲蔽最大可能性結合演算法之效能。

Higher-order statistics (HOS) based inverse filter criteria (IFC) have been widely used for blind equalization of discrete-time multi-input multi-output (MIMO) linear time-invariant channels with non-Gaussian measurements but the equalization output turns out to be an unknown permutation and an unknown phase rotation of one of the driving inputs. In this thesis, a blind multi-user equalization algorithm (BMEA) for multi-rate (variable processing gain or multi-code) DS/CDMA systems in multi-path is proposed which is an extension of the single-rate BMEA proposed by Chi et al. by converting real multi-rate users into single-rate virtual users. The proposed multi-rate BMEA also shares the merit of super-exponential convergence rate of Chi et al.'s single-rate BMEA. Then the proposed multi-rate BMEA in conjunction with Chi et al.'s blind maximum ratio combining (BMRC) algorithm, called multi-rate BMEA-BMRC algorithm, is proposed with multiple receive antennas used for space diversity gain. Finally, some simulation results are presented to support the efficacy of the proposed multi-rate BMEA and multi-rate BMEA-BMRC algorithm.

[1] M. Zeng, A. Annamalai, and V. K. Bhargava, “Harmonization of global third-generation mobile
systems,” IEEE Commun. Mag., vol. 38, pp. 94-104, Dec. 2000.
[2] T. Ojanpera and R. Prasad, “An overview of air interface multiple access for IMT-2000/UMTS,”
IEEE Commun. Mag., vol. 36, pp. 82-86, Sept. 1998.
[3] C.-L. I. and R. D. Gitlin, “Multi-code CDMA wireless personal communications networks,” in Proc.
IEEE Int. Commun. Conf., vol. 2, Seattle, WA, June 1995, pp. 1060-1064.
[4] T. Ottosson and A. Svensson, “Multi-rate schemes in DS/CDMA systems,” in Proc. IEEE 45th Veh.
Technol. Conf., vol. 2, Chicago, IL, July 1995, pp. 1006-1010.
[5] M. K. Tsatsanis, Z. Xu, and X. Lu, “Blind multiuser detectors for dual rate DS-CDMA systems over
frequency selective channels,” Proc. Eur. Signal Proc. Conf., Tampere, Finland, Sept. 2000, vol. 2,
pp. 631-634.
[6] J. Ma and J. K. Tugnait, “Blind detection of multirate asynchronous CDMA signals in multipath
channels,” IEEE Trans. Signal Processing, vol. 50, pp. 2258-2272, Sept. 2002.
[7] S. Roy, H. Yan, “Blind channel estimation in multi-rate CDMA systems,” IEEE Trans. Communications,
vol. 50, pp. 995-1004, June, 2002.
[8] M. Saquib, R. Yates, and A. Ganti, “An asynchronous multirate decorrelator,” IEEE Trans. Communications,
vol. 48, pp. 739-742, May, 2002.
[9] M. Saquib, R. Yates, and A. Ganti, “A decision feedback decorrelator for a dual rate synchronous
DS/CDMA system,” Wireless Networks, vol. 4, pp. 497-506, 1998.
[10] A. -L. Johansson and A. Svensson, “Successive interference cancellation in multiple data rate
DS/CDMA systems,” in Proc. IEEE 45th Veh. Technol. Conf., vol. 2, Chicago, IL, July 1995, pp.
704-708.
[11] U. Mitra, “Comparison of maximum-likelihood-based detection for two multirate access schemes for
CDMA signals,” IEEE Trans. Communications, vol. 47, pp. 64-77, Jan., 1999.
[12] S. Verdu, Multiuser Detection. Cambridge, U.K.: Cambridge Univ. Press, 1998.
[13] J. G. Proakis, Digital Communications, 3rd ed. New York: Mc-Graw-Hill,1995.
[14] U. Madhow and M. Honig, “MMSE interference suppression for direct-sequence spread-spectrum
CDMA,” IEEE Trans. Commun., vol. 42, pp. 3178-3188, Dec. 1994.
[15] M. Honig, U. Madhow and S. Verdu, “Blind adaptive multiuser detection,” IEEE Trans. Inform.
Theory, vol. 41, pp. 994-959, July 1995.
[16] M. K. Varanasi and B. Aazhang, “Multistage detection in asynchronous code-division multiple access
communications,” IEEE Trans. Commun., vol. 38, pp. 509-519, Apr. 1990.
[17] A. D. Hallen, “Decorrelating decision-feedback multiuser detector for synchronous CDMA,” IEEE
Trans. Commun., vol. 41, pp. 285-290, Feb. 1993.
[18] M.-H. Chung, K.-C. Chen and M.Y. You, “MMSE multiuser detection for multi-rate wideband CDMA
communications ,” in Proc. IEEE Personal, Indoor and Mobile Radio Communications, vol. 1, London,
UK, Sept. 2000, pp. 534-538.
[19] S. H. Han and J. H. Lee, “Multi-stage partial PIC receivers for multi-rate DS-CDMA system with
multiple modulation,” in Proc. IEEE Wireless Communications and Networking, vol. 1, Seoul, South
Korea, Mar. 2003, pp. 591-594.
[20] R. Lupas and S. Verdu, “Near-far resistance of multiuser detectors in asynchronous channels,” IEEE
Trans. Commun., vol. 38, pp. 496-508, Apr. 1990.
[21] S. Moshavi, “Multi-user detection for DS-CDMA communicatioins,” IEEE Commun. Mag., vol. 34,
pp. 124-136, Oct. 1996.
[22] M. K. Tsatsanis and Z. Xu, “Performance analysis of minimum variance CDMA receivers,” IEEE
Trans. Signal Processing, vol. 46, pp. 3014-3022, Nov. 1998.
[23] M. Torlak and G. Xu, “Blind multiuser channel estimation in asynchronous CDMA systems,” IEEE
Trans. Signal Processing, vol. 45, pp. 137-147, Jan. 1997.
[24] S. E. Bensley and B. Aazhang, “Subspace-based channel estimation for code division multiple access
communication systems,” IEEE Trans. Commun., vol. 44, pp. 1009-1020, Aug. 1996.
[25] M. K. Tsatsanis and G. B. Giannakis, “Optimal decorrelating receivers for DS/CDMA systems: A
signal processing framework,” IEEE Trans. Signal Processing, vol. 44, pp. 3044-3055, Dec. 1996.
[26] C.-Y. Chi, C.-Y. Chen, C.-H. Chen and C.-C. Feng, “Batch processing algorithms for blind equalization
using higher-order statistics,” IEEE Signal Processing Magazine, vol. 20, pp. 25-49, Jan. 2003.
[27] M. K. Tsatsanis, “Inverse filtering criteria for CDMA systems,” IEEE Trans. Signal Processing, vol.
45, pp. 102-112, Jan. 1997.
[28] Y. Inouye and K. Tanebe, “Super-exponential algorithms for multichannel blind deconvolution,” IEEE
Trans. Signal Processing, vol. 48, pp. 881-888, Mar. 2000.
[29] L. Li and H. H. Fan, “Blind CDMA detection and equalization using linearly constrained CMA,” in
Proc. IEEE Int. Conf. Acoust., Speech, Signal Process., June 5-9, 2000, pp. 2905-2908.
[30] C. L. Nikias and A. P. Petropulu, Higher-order Spectra Analysis: A Nonlinear Signal Processing
Framework. Englewood Cliffs, NJ: Prentice-Hall, 1993.
[31] C.-Y. Chi and C.-H. Chen, “Cumulant based inverse filter criteria for MIMO blind deconvolution:
properties, algorithms, and application to DS/CDMA systems,” IEEE Trans. Signal Processing, vol.
49, pp. 1282-1299, July 2001.
[32] C.-Y. Chi, C.-H. Chen and C.-Y. Chen, “Blind MAI and ISI suppression for DS/CDMA systems using
HOS-based inverse filter criteria,” IEEE Trans. Signal Processing, vol. 50, pp. 1368-1381, June 2002.
[33] Z. Xu and P. Liu , “Code constrained CMA-based multirate multiuser detection ,” in Proc. IEEE
Signals, Systems and Computers, vol. 2, Pacific Grove, CA USA, 4-7 Nov. 2001, pp. 51455 - 1459.
[34] A. J. Paulraj and C. B. Papadias, “Space-time processing for wireless communicatin,” IEEE Signal
Processing Magazine, vol. 14, pp. 49-83, Nov. 1997.
[35] C. W. Therrien, Discrete-time Random Signals and Statistical Signal Processing. Englewood Cliffs,
NJ: Prentice-Hall, 1992.
[36] J. K. Tugnait and T. Li, “Blind detection of asynchronous CDMA signals in multipath channels using
code-constrained inverse filter criterion,” IEEE Trans. Signal Processing, vol. 49, pp. 1300-1309, July
2001.
[37] J. Ma and H. Ge, “Modified multi-rate detection for frequency selective Rayleigh fading CDMA
channels,” Proc. of PIMRC’98, Boston, MA, Sept. 8-11, 1998, vol.3, pp. 1304-1308.