Dynamic QRDM ReceiversforMIMO Beamforming Systemswith Imperfect Channel StateInformation

Formultiple-input multiple-output (MIMO)an- tennasystems, ifperfect channel state information (CSI) isavail- ableatthetransmitter andreceiver sides, advanced beamforming (ABF)canbeapplied atbothsides sothatthetransmitted datastreams canbedecoupled easily, andadaptive modulation canbeutilized tomaximize thethroughput. When theavail- ableCSIisimperfect, however, thedatastreams cannotbe decoupled completely withlinear receive beamforming. Inthis paper, adynamic QR decomposition basedM-Algorithm (QRDM receiver) isproposed forrecovering thedatastreams delivered by MIMO beamforming systems withadaptive modulation designed byimperfect CSI.We alsopropose a schemetodetermine thedecoding orderforassisting theQRDM operation. The proposed schemescanalsobeapplied tomultiuser MIMO systems withrandomtransmit beamforming wheretherandom beamsarehardly matchthedesired user's CSIexactly. Computer simulations haveshownthattheproposed receiver isveryrobust totheCSImismatch ascompared toconventional linear receivers. Keywords-MIMO,beamforming, Maximum likelihood detection, QR decomposition, lowcomplexity receiver.

[1]  Kiho Kim,et al.  A random beamforming technique in MIMO systems exploiting multiuser diversity , 2003, IEEE J. Sel. Areas Commun..

[2]  Ying-Chang Liang,et al.  Random beamforming for MIMO systems with multiuser diversity , 2004, 2004 IEEE 15th International Symposium on Personal, Indoor and Mobile Radio Communications (IEEE Cat. No.04TH8754).

[3]  Giuseppe Caire,et al.  On maximum-likelihood detection and the search for the closest lattice point , 2003, IEEE Trans. Inf. Theory.