Methods and apparatus are provided for structured resource allocation signaling. In one novel aspect, an 8-bit RU allocation filed is allocated in the HE-SIG-B common field for each 20 MHz. The structured resource signaling supports more than four MU-MIMO users. In one embodiment, the STA decodes the 8-bit RU allocation signal following a structured resource unit (RU) allocation rule, and determines the RU. In one embodiment, the STA decodes the first two bits of the 8-bit RU allocation signal to determine a first category of the RU allocation. The categories of the RU allocation includes a large RU size category indicating larger than or equal to 20 MHz RUs exist, a two 106-tone category indicating two 106-tone RUs exist, and a no-large-RU category indicating only smaller-than-242-tone RUs exist. The STA further decodes based on the category. A lookup table (LUT) for RU allocation is built and decoded based on a structured signaling rule.