A wireless device generating a High-Efficiency (HE) PHY Protocol Data Unit (PPDU) for transmission sets a Packet Extension Disambiguity bit of an HE Signal-A (HE-SIG-A) field of the HE PPDU based on respective durations of a packet extension of the HE PPDU and a signal extension of the HE PPDU. The wireless device may determine whether a relationship T PE + ( 4 × ⌈ TXTIME - T SE - 20 4 ⌉ - ( TXTIME - T SE - 20 ) ) ≥ T SYM is satisfied, where TPE is the duration of the packet extension, TXTIME is a transmission time of the HE PPDU, TSE is the duration of the signal extension, and TSYM is a duration of symbols in a data field of the HE PPDU. The wireless device may set the Packet Extension Disambiguity bit to one when the relationship is satisfied; and to zero when the relationship is not satisfied.