Uplink resource assignment in a wireless local area network (WLAN) by an access point (AP) to wireless stations (STAs) is herein provided using opportunistic feedback from the STAs. The AP sends a message to a first STA; the message is also observed by a second STA. Each STA can determine if it wishes to opportunistically send information concerning the message to the AP. The second STA can perform power measurements on the message and send subcarrier signal to noise ratio (SNR) or ranking information to the AP. Thus, the AP can receive, possibly without expectation, encoded or compressed information describing radio channels of the first STA and/or the second STA. Based on the received channel information the AP improves operation of a dynamic resource allocation algorithm which determines uplink grants of resource units (RUs) to the STAs.