Signal transmission method, related device, and system

A network device, comprising:

• a transmitter, a receiver, a memory, and a processor coupled to the memory, wherein the processor is configured to invoke an instruction stored in the memory to control the transmitter;
• the transmitter is configured to send first indication information to a terminal, wherein the first indication information is used to indicate an uplink resource allocated by the network device to the terminal in a first bandwidth, and the uplink resource comprises one or more interlace segments corresponding to one or more subbands in the first bandwidth, wherein each one of the one or more interlace segments is a segment of an interlace located in a subband;
• and
• the receiver is configured to receive second indication information sent by the terminal, wherein the second indication information is used to indicate an idle second bandwidth that is detected by the terminal and that is used for uplink transmission, wherein uplink transmission to the receiver is performed by the terminal on the one or more interlace segments corresponding to the one or more subbands after sensing the one or more subbands to be idle.