A first access node of a first network utilizes code sequences, assigned to different user devices, to distinguish at least acknowledgements received in parallel or sequentially from those user devices. The first access node determines from received signaling that a root sequence of the code sequences is in use by a second access node of a second network, then changes that root sequence of the code sequences assigned to the different user devices. In certain examples the access nodes are WLAN access points APs and the acknowledgements are received in response to a group probe/poll. In various embodiments the first AP monitors its neighbors' group probes/polls to learn the root sequences/basic service sets in use in those neighbor networks, or the AP's own stations monitor and send the information in neighbor reports. This latter option can be initiated by the stations themselves, or by the AP.