A scheduler in a communication network comprising a communication channel which is shared by a plurality of user nodes, the communication channel having a succession of slots. The scheduler has a quality unit for receiving an indication of the quality of the communication channel for each user node. A delay unit for receiving a predetermined delay factor for each of at least some of the user nodes, the delay factor representing a level of tolerance to a time delay. A selection unit connected to the quality and delay units and being arranged to determine, for each slot, which of the user nodes is to use that slot based on the channel quality indication and the delay factors.