Communication apparatus and communication method

A first communication apparatus, comprising:

• processing circuitry configured to:
• detect communications between a second communication apparatus and a third communication apparatus;
• from the detected communications, executing a determination procedure to determine an estimated time length until the communications produce a communication synchronization error to fall within a predetermined error range;
• generate a calculated time length based on the estimated time length;
• make a determination result of if the first communication apparatus shared the calculated time length with the third communication apparatus;
• based on the determination result being true, select either a frame of a first format including a training signal, or a frame of a second format not including a first field which is at least a part of the training signal, and generate the frame of the selected format;
• and
• communication circuitry configured to transmit the frame of the first format or the frame of the second format;
• wherein the determination procedure includes the processing circuitry being further configured to detect a time of reception of an immediate response request sent by the second communication apparatus, and to detect a time of reception of a response to the immediate response request, wherein the response was sent by the third communication apparatus.