Comparisons between Common and Dedicated Reference Signals for MIMO Multiplexing Using Precoding in Evolved UTRA Downlink

Hidekazu TAOKA  Yoshihisa KISHIYAMA  Kenichi HIGUCHI  Mamoru SAWAHASHI  

IEICE TRANSACTIONS on Communications   Vol.E92-B    No.5    pp.1669-1679
Publication Date: 2009/05/01
Online ISSN: 1745-1345
DOI: 10.1587/transcom.E92.B.1669
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Radio Access Techniques for 3G Evolution)
Evolved UTRA,  OFDM,  MIMO,  precoding reference signal,  downlink,  

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This paper presents comparisons between common and dedicated reference signals (RSs) for channel estimation in MIMO multiplexing using codebook-based precoding for orthogonal frequency division multiplexing (OFDM) radio access in the Evolved UTRA downlink with frequency division duplexing (FDD). We clarify the best RS structure for precoding-based MIMO multiplexing based on comparisons of the structures in terms of the achievable throughput taking into account the overhead of the common and dedicated RSs and the precoding matrix indication (PMI) signal. Based on extensive simulations on the throughput in 2-by-2 and 4-by-4 MIMO multiplexing with precoding, we clarify that channel estimation based on common RSs multiplied with the precoding matrix indicated by the PMI signal achieves higher throughput compared to that using dedicated RSs irrespective of the number of spatial multiplexing streams when the number of available precoding matrices, i.e., the codebook size, is less than approximately 16 and 32 for 2-by-2 and 4-by-4 MIMO multiplexing, respectively.