A wake-up radio is configured to scan for transmissions while the radio receiver is in sleep mode. The wake-up radio detects incoming RF transmissions intended for the radio receiver by analyzing data frame characteristics in an incoming RF transmission. The data frame characteristics may contain a signature code that is unique to the radio receiver. The signature code may be based on the time duration of a sequence of orthogonal frequency division multiplex (OFDM) symbols received in a clear to send to self (CTS2S) transmission or a time duration of short interframe spaces (SIFS) used to transmit the data frames.