A Comparative Analysis of Spatial Multiplexing Techniques for Ou...

Abstract—In this paper, we analyze spatial multiplexing tech- ques for the downlink of a multiple-input–multiple-output MIMO) orthogonal frequency-divisionmultiplexing (OFDM) sys- m. Our study is focused on outdoor environments characterized y a moderate angular spread. We consider two techniques that e able to separate the downlink data streams associated with fferent users and to guarantee a fixed error probability by ploiting limited feedback from each user. The grid of beams GoBs) and the proposed adaptive GoB (AGoB) differ in the ay the precoders are designed (by adaptive or fixed processing) nd in their scheduling policy. The new AGoB is able to harness artial knowledge of the downlink channel spatial structure to etter select the users and adjust their precoders for downlink ansmission. The performances of GoB and AGoB are compared