Signal transmission method and apparatus

A signal transmission apparatus, wherein the apparatus comprises:

• at least one processor;
• at least one memory coupled to the at least one processor and storing programming instructions for execution by the at least one processor to spread a preamble symbol based on a first spreading code sequence to generate a first signal, wherein the first spreading code sequence comprises a plurality of spreading code groups, each spreading code group comprises a plurality of same spreading codes and at least one guard symbol, at least one of a first bit or a last bit of each spreading code group is a guard symbol, and the plurality of spreading code groups comprise at least two spreading code groups with different spreading codes, and wherein the first signal is used to determine a channel impulse response;
• and
• a transmitter configured to send the first signal to a receiver.