Iterative rake receiver with map channel estimation for ds-cdma systems - Récepteur en râteauiteratif avec estimation de canal au maximum a posteriori pour systèmes amrc
نویسندگان
چکیده
We propose an iterative rake receiver structure using an optimum semi-blind channel estimation algorithm for DS-CDMA mobile communication systems. This receiver performs an iterative estimation of the channel according to the maximum a posteriori criterion, using the expectation-maximization algorithm. This estimation process requires a convenient representation of the discrete multipath fading channel based on the Karhunen-Lobve orthogonal expansion theorem. The rake receiver uses pilot as well as unknown control and data symbols optimally for improving channel estimation quality. Moreover, it can take into account the coded structure of all unknown transmitted symbols when channel estimation quality is poor or unsatisfactory. The validity of the proposed method is highlighted by simulation results obtained for the FDD mode of the UMTS interface. R6sum6 Une structure de rdcepteur en rCtteau fonctionnant de manibre itdrative est propos~e, elle utilise un algorithme optimal d'estimation semi-aveugle de canal, pour les syst&nes de radiocommunication avec les mobiles de type AMRC avec sdquence directe. Ce dispositif effectue une estimation itdrative du canal selon le crit~re du maximum a posteriori, en se servant de l' algorithme EM. Cette estimation ndcessite une representation convenable du canal multitrajet avec dvanouissements discrets, bas6e sur le thdor&ne de d~veloppement orthogonale de Karhunen-Lobve. Ce dispositif utilise, de manikre opti-male, les symboles pilotes et les symboles inconmts de contr6le et d'information pour amdliorer la qualit6 de l'estimation de canal. De phts, il peut prendre en compte la structure cod6e de tousles symboles inconnus lrans-mis quand la qualitd de l'estimation de canal n 'est pas satisfaisante. L'int6r6t de l'approche proposd est illustrd par des r~sultats de simulation obtenus dans le cadre applicatif du mode FDD de la norme UMTS. Contents I. Introduction II. Transmitted signal characteristics III. Multipath fading channel characteristics IV. Signal model at the output of rake fingers V. Convenient representation of the discrete multipath fading channel VI. Semi-blind maxinTum a posteriori discrete channel estimation VII. Decoding information symbols VIII. Simulation results IX. Conclusion Appendix References (7 ref)
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ورودعنوان ژورنال:
- Annales des Télécommunications
دوره 54 شماره
صفحات -
تاریخ انتشار 1999