A scheduling algorithm is disclosed that allows mobile units, participating in an ongoing communications session, to temporary perform channel-demanding communications operations without ending the session and that is useful in the case of no free radio channels. The algorithm is based on selecting a radio channel for transmitting a radio block based on information of a previous radio channel, no which a previous radio block has been transmitted. The radio block and the previous radio block are based on common information. A mobile unit participating in the communications session selects whether to perform any channel-demanding communications operations on the selected radio channel. By limiting any such other channel-demanding operations to only the selected radio channel, the probability of loss of useful data for the mobile unit during the communications session is minimized.