Optimization of Pilot Signal Power in OFDM-Based OTFS System

Orthogonal time-frequency space modulation (OTFS) in orthogonal frequency division multiplexing (OFDM) system has advantages in high mobility scenarios due to sparse and quasi-static channel representation. To reduce channel degradation and obtain data, it is necessary to estimate and equalize the channel. Pilot signals are used to estimate the channel state. When the OTFS frame energy is limited, a small fraction of the pilot energy will lead to unreliable channel estimation, and when the fraction is large, data symbols are difficult to distinguish from noise even with reliable channel estimation. This indicates the existence of an optimal trade-off between data and pilot energies. Optimization was performed for OTFS frames of different sizes with two values of signal-to-noise ratio per bit to find the optimal value of the pilot energy fraction. A simulated dependence of the pilot energy fraction on the number of information symbols in a frame was obtained, which is inversely proportional to the square root of the number of data symbols.