A method for identifying source BSS in WLAN is proposed. A high efficiency (HE) access point (AP) sends a packet containing a basic service set (BSS) color to a HE station. The HE AP also sends a packet containing an assigned association identification (AID) to a very high throughput (VHT) station. The assigned AID comprises at least part of the BSS color information. The VHT station therefore sends a packet containing the at least part of the BSS color information such that any AP or station that receives the packet can determine the BSS the VHT station is in.