SOVA equalization for multi-code CDMA system with low spreading factor

In a CDMA system, the RAKE receiver is commonly used to attain the diversity gain by taking advantage of the good correlation properties of the spreading codes. However, at low spreading gains the good correlation properties of the spreading codes are lost and the RAKE receiver performance is severely degraded by interpath interference (IPI). In the case of multi-code CDMA system, the multi-code interference (MCI) exists in the system. In order to suppress MPI and MCI, a novel receiver based on soft-output Viterbi algorithm (SOVA) equalization is proposed in this paper. The SOVA equalization is applied to symbol sequences after RAKE combining and MCI cancellation to effectively eliminate the IPI during transmission of high rate data in wideband DS-CDMA systems. Simulation results show that the proposed receiver significantly outperform the traditional RAKE and RAKE-VA receivers.

[1]  K. Hooli,et al.  Inter-path interference suppression in WCDMA systems with low spreading factors , 1999, Gateway to 21st Century Communications Village. VTC 1999-Fall. IEEE VTS 50th Vehicular Technology Conference (Cat. No.99CH36324).

[2]  Chunming Zhao,et al.  Reduced-complexity soft-output Viterbi equalizer , 1998, ICCT'98. 1998 International Conference on Communication Technology. Proceedings (IEEE Cat. No.98EX243).

[3]  H. Boujemaa,et al.  On the RAKE receiver performance , 2000, Vehicular Technology Conference Fall 2000. IEEE VTS Fall VTC2000. 52nd Vehicular Technology Conference (Cat. No.00CH37152).

[4]  Joachim Hagenauer,et al.  A Viterbi algorithm with soft-decision outputs and its applications , 1989, IEEE Global Telecommunications Conference, 1989, and Exhibition. 'Communications Technology for the 1990s and Beyond.

[5]  Gerhard Fettweis,et al.  On interpath interference suppression by MLSE detection in DS/SS systems , 2003, 14th IEEE Proceedings on Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003..

[6]  Peter Adam Hoeher.  TCM on frequency-selective fading channels: a comparison of soft-output probabilistic equalizers , 1990, [Proceedings] GLOBECOM '90: IEEE Global Telecommunications Conference and Exhibition.

[7]  Kwang Bok Lee,et al.  Performance analysis of low processing gain DS/CDMA systems with random spreading sequences , 1998, IEEE Communications Letters.

[8]  Asrar U. H. Sheikh,et al.  Joint multipath diversity combining and MLSE equalization (RAKE-MLSE receiver) for WCDMA systems , 2000, VTC2000-Spring. 2000 IEEE 51st Vehicular Technology Conference Proceedings (Cat. No.00CH37026).

[9]  Xiaohu You,et al.  Joint receiving scheme of RAKE combining and Viterbi equalization for low spreading factor wideband DS-CDMA systems , 2003, 14th IEEE Proceedings on Personal, Indoor and Mobile Radio Communications, 2003. PIMRC 2003..