For controlling radio transmission in a cellular network, a network node detects data traffic between the cellular network and a user equipment. The detected data traffic is based on a transport protocol which involves transmission of an acknowledgement to acknowledge successful reception of data by the user equipment. The network node estimates a time at which sending of an future acknowledgement by the user equipment is expected. On the basis of the estimated time, the network node allocates UL radio resources to the user equipment. By sending an uplink grant, the network node may indicate the allocated uplink radio resources to the user equipment.