Single-carrier frequency-division multiplexing (SC-FDM) has been adopted as the uplink (UL) waveform in the 3GPP LTE standards due to its various desirable features. One key benefit of SC-FDM is its low peak-to-average-power ratio (PAPR), which is highly desirable in the UL to lower down the cost of the power amplifier (PA) in the user equipment (UE). In order to preserve the low PAPR, current LTE specification only allows one SC-FDM symbol to contain either all data or all pilots, but not both. This is insufficient and inflexible for scenarios like high Doppler. In this paper, we introduce one novel scheme to flexibly multiplex data and pilots within a single SC-FDM symbol while not distorting the single-carrier waveform. In the case of high Doppler, without increasing the pilot overhead, we can apply this scheme to multiplex pilots onto the data symbols to allow coherent channel estimation all the time. Numerical simulations demonstrate significant performance improvements over current LTE designs.
['Xiliang Luo']
Low-PAPR Multiplexing of Data and Pilots