Contention-based Grant-free Transmission with Independent Multi-pilot Scheme

Contention-based grant-free transmission is very promising for future massive machine-type communication (mMTC). In contention-based transmission, the random pilot collision becomes a challenge. To solve it, multi-pilot scheme is proposed. However, the existing work relies on the low correlation of spatial channels, and cannot be applied when the number of antennas is relatively small. This paper proposes a novel independent multi-pilot scheme, which utilizes the diversity of multiple pilots, instead of the spatial correlation. The interference cancellation of both data symbols and multiple pilots is utilized to improve the performance. The simulation results show that the proposed scheme significantly improves the performance in high-overloading mMTC and outperforms the existing work in a massive antenna array case.