Blind Index Modulation Detection for Pilot-Free Short-Packet Communications

A short packet transmission is a key feature for ultra-reliable and low-latency communications in 5G. In the short packet transmission, a pilot overhead for the channel estimation is a major limiting factor that decreases the spectral efficiency. In this paper, a blind detection technique is presented for a pilot-free short packet transmission method when using OFDM with index modulation (OFDM-IM). One key finding is that a maximum a posteriori (MAP) blind detection for OFDM-IM is equivalent to a simple power detection method. Using order statistics, an analytical expression for the symbol-vector-error probability (SVEP) is derived for the proposed blind detection method. Simulation results demonstrate that the proposed non-coherent detection method provides a SVEP gain compared to the conventional coherent detection method for a short packet transmission.