PRACH Transmission Mode Switching for Coverage

The patent implements dynamic switching between first-type and second-type PRACH transmission modes based on coverage conditions. The terminal device determines which transmission mode to use by evaluating coverage status, allowing the system to adapt from simple single-transmission mode to repeated transmission mode only when coverage is poor, thus resolving the contradiction between coverage improvement and complexity increase.

The patent applies different transmission strategies to different coverage conditions locally. In good coverage areas, the system uses first-type PRACH transmission (single transmission) to minimize time. In poor coverage areas, it switches to second-type PRACH transmission (multiple transmissions) to ensure reliability. This localized adaptation resolves the contradiction by not universally increasing transmission time, but only where coverage requires it.

The patent segments the PRACH transmission process into two distinct modes (first-type with single transmission and second-type with multiple transmissions) and provides clear determination criteria for switching between them. This segmentation with explicit decision rules simplifies the combination approach rather than increasing complexity, as the terminal device can systematically evaluate coverage conditions and select the appropriate mode without ambiguity.