Improvements on latency are achieved for highest priority messaging and channel utilization in a time-slotted access channel structure. New superframe structures are presented where scheduled, but unused access slots can be utilized by secondary nodes. The messaging is accomplished by defining user priorities for nodes and the nodes sensing an ongoing transmission in the network. The time slotted channel access structure has at least one access phase which is divided into access slots. In the beginning of the access phase the nodes sense if a highest priority transmission exist and if not, another node with a lower user priority may initiate transmission.