In a method for improving the transmission efficiency in a communication system with a layered protocol stack, data packets are processed on an upper protocol layer. Data packets are forwarded to a lower protocol layer for transmission and the transmission is performed with variable channel access delays. The upper protocol layer is notified by the lower protocol layer when a transmission is started to allow a synchronization of timers in the upper protocol layer. If a layer performs a scheduling of data packets for the transmission, a rescheduling is performed alternatively or in addition during a channel access delay. Devices and software programs embodying the invention are also described.