Method, apparatus, and system for sending and receiving information

A method for sending and receiving information, comprising:

• determining, by a terminal device, a backoff time for a current frame, the backoff time is a backoff time before a network device performs a clear channel assessment CCA;
• listening, by the terminal device, on a channel based on the backoff time;
• and
• when the terminal device detects, over the channel, a pilot sent by the network device, receiving, by the terminal device, current-frame data sent by the network device over the channel, or sending current-frame data to the network device over the channel.

An apparatus for sending and receiving information, comprising:

• a processor, configured to determine a backoff time for a current frame and to perform a clear channel assessment (CCA) on a channel at an end moment of the determined backoff time for the current frame, and obtain an assessment result of the CCA;
• and
• a transceiver, configured to:
• when the assessment result of the CCA obtained by the processor is that the channel is in an idle state, send a pilot over the channel;
• and
• after sending the pilot, send current-frame data to a terminal device over the channel, or receive, over the channel, current-frame data sent by a terminal device.

An apparatus for sending and receiving information, comprising:

• a processor, configured to determine a backoff time for a current frame, the backoff time is a backoff time before a network device performs a clear channel assessment (CCA), and to listen on a channel based on the backoff time for the current frame;
• and
• a transceiver, configured to:
• when the processor detects, over the channel, a pilot sent by the network device, receive current-frame data sent by the network device over the channel, or send current-frame data to the network device over the channel.