Embodiments of a system and methods for distinguishing high-efficiency Wi-Fi (HEW) packets from legacy packets are generally described herein. In some embodiments, an access point may select a value for the length field of a legacy signal field (L-SIG) that is non-divisible by three for communicating with HEW stations and may select a value for the length field that is divisible by three for communicating with legacy stations. In some embodiments, the access point may select a phase rotation for application to the BPSK modulation of at least one of the first and second symbols of a subsequent signal field to distinguish a high-throughput (HT) PPDU, a very-high throughput (VHT) PPDU and an HEW PPDU.