ISSN : 1796-2021
Volume : 4    Issue : 3    Date : April 2009

On the Feasibility of Precoded Single User MIMO for LTE-A Uplink
Gilberto Berardinelli, Luis Ángel Maestro Ruiz de Temiño, Simone Frattasi, Troels B.Sørensen,
Preben Mogensen, and Kari Pajukoski
Page(s): 155-163
Full Text:
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The 3rd Generation Partnership Project (3GPP) is currently specifying the system requirements for
Long Term Evolution - Advanced (LTE-A), having as a target peak data rates of 1 Gbit/s in local
areas and 100 Mbit/s in wide areas. To meet these ambitious requirements for the uplink,
multiple-input-multiple-output (MIMO) antenna techniques are expected to be deployed. In this
paper, several channel-aware MIMO precoding techniques are presented. Specifically, precoded
single user spatial multiplexing for both Orthogonal Frequency Division Multiplexing (OFDM) and
Single Carrier Frequency Division Multiplexing (SCFDM) is studied, and its feasibility in a LTE-A
uplink system is discussed. Particular emphasis is given to the limited feedback precoding, where
a codebook generation method based on the Lloyd algorithm is proposed. Results show that, when
full channel knowledge is available at both the transmitter and the receiver, precoding leads to a
spectral efficiency gain up to 4 dB over open loop transmission; furthermore, OFDM slightly
outperforms SC-FDM because of its higher robustness to the noise. Limited feedback precoding
has been shown to be effective and consistently robust to the subcarrier grouping in a urban micro
scenario. However, the performance is severely degraded in the blind precoding case, where
transmitter and receiver compute the precoding matrix independently, due to the high sensitivity to
the delay. Finally, the precoding operation over the SCFDM signal is shown to increase its Peak to
Average Power Ratio (PAPR), thus reducing its advantage with respect to OFDM.

Index Terms
LTE-A, MIMO, OFDMA, PAPR, SCFDMA, precoding, spatial multiplexing, transmit diversity