A co-existence method is described. The method comprises setting a priority level of a slot based on the likelihood that the slot will be required by a first radio and signalling the priority level to radio which is co-located with the first radio and which shares a resource with the first radio. The slot may, for example, be a re-transmission slot following a primary transmission slot or may be a sniff anchor point. The likelihood may be determined based on one or more factors, such as historical data or knowledge of the activity of a peer of the first radio.