m3 with the predetermined receiving power threshold m to determine whether to generate the cts packet from the terminal b for responding to the terminal a if the value of m3 is larger than that of m the terminal b will generate a first cts packet for responding to the terminal a the first cts packet is transmitted from the terminal b to the terminal a via the communication protocol it is to be noted that the present invention takes advantages of the ieee 802 11 for the transmissions of rts and cts to ensure the safety transmission of the data packets the terminal a transmits a null data packet to the terminal b via the communication protocol after receiving the cts packet from the terminal b then the terminal b responds an acknowledge packet ack to the terminal a under such a condition the terminal a starts over the process and repeatedly transmits the detecting packet rts to the terminal b sequentially using the variety of transmission powers preferably from low to high or from l1 to l3 via the communication protocol in one embodiment the predetermined receiving power threshold m at the terminal b remains a constant in another embodiment the value of the threshold m may be dynamically modified along with the multiple transmission power levels at the terminal a and the distance between the two terminals in the example set forth above only the value of.