Open loop transmit diversity solutions for LTE-A uplink

Transmit diversity (TD) techniques are expected to be included in the uplink of the upcoming Long Term Evolution - Advanced (LTE-A) systems to boost the user performance in low Signal-to-Noise Ratio (SNR) conditions. In this paper, several open loop TD solutions based on both space frequency coding (SFC) and space time coding (STC) are evaluated in a Single Carrier Frequency Division Multiplexing (SC-FDM) system with the aim of discussing their suitability for the upcoming standard. Traditional SFC is shown to increase the Peak-to-Average Power Ratio (PAPR) of the SC-FDM signal but it also outperforms STC for high speed and high order modulation and coding schemes (MCSs). Moreover, STC suffers from reduced flexibility in the time domain encoding. Starting from the single carrier sequences in the time domain, a SFC solution keeping low PAPR is derived; it is shown to be a valid option for low delay spread channels and small amount of data to be transmitted.