Patent ID: 7299063

Claim:
A wireless communication system including wireless units at least some of which are configured to perform data information transmission during a predetermined data communication period portion of a predetermined transmission frame period and to perform a distance measurement between particular wireless units during a ranging period portion of said predetermined transmission frame period separate from the data communication period portion, wherein, during the ranging period portion of said predetermined transmission frame period separate from the data communication period portion, a first wireless unit configured to perform data information transmission during the predetermined data communication period portion of the predetermined transmission frame period and to perform the distance measurement between particular wireless units during the ranging period portion of said predetermined transmission frame period separate from the data communication period portion is further configured to transmit a ranging signal to a second wireless unit, said second wireless unit is configured to receive the ranging signal and responds thereto by transmitting a response signal to said first wireless unit after a lapse of a predetermined delay period after said second wireless unit receives the ranging signal, and said first wireless unit includes a reception gate configure to prevent reception of signals for a predetermined masking time period during the ranging period portion having a predetermined duration necessary for masking reception of signals due to reflection of waves from an unintended object and to permit reception of the response signal from the second wireless unit after the predetermined masking time period elapses so as to then measure a distance between said first wireless unit and said second wireless unit according to an elapsed time measured from when said first wireless unit transmits the ranging signal until the first wireless unit receives the response signal from the second wireless unit after the predetermined masking time period elapses.