. . . . . "N}, is a device such as a notebook computer, personal digital assistant (PDA), tablet PC, etc. that transmits radio signals to and receives radio signals from other stations in local-area network 100 via access point 101. [0008] Access point 101 and stations 102-1 through 102-N transmit data in units referred to as frames over a shared-communications channel such that if two or more stations (or a" . .