Frequency-Domain Transmit Processing for MIMO SC-FDMA in Wideband Propagation Channels

Recently there has been considerable interest in the use of single carrier frequency division multiple access (SC-FDMA) as the uplink transmission scheme for the 3GPP long term evolution (LTE) standard. This paper investigates different multiple input multiple-output (MIMO) techniques for uplink SC-FDMA. Here we demonstrate how the transmitter can exploit the available channel information, through precoding and pre-equalization, in order to combat the frequency selective nature of the propagation channel and improve the system´s performance under fading. In this work we investigate the achievable system capacity, and the peak-to-average power ratio (PAPR) characteristics of the precoded and pre-equalized SC-FDMA waveform. We consider unitary preceding for MIMO, as well as pre-equalization for a multiple-input single-output (MISO) system with maximum ratio combining (MRC), equal gain combining (EGC), zero forcing (ZF), and minimum mean square error (MMSE) algorithms. Results reported in this paper show that ZF pre-equalization for SISO SC-FDMA is capable of achieving the Shannon Capacity limit for faded channels, with a BER performance that is identical to an AWGN channel, and that pre-equalized increases the capacity of MIMO SC-FDMA systems.