A cell within cellular network includes user equipments (UEs) that transmit data to a base station (eNB). Over a period of time, not all of the UEs will have data to transmit. The UEs are tracked as a scheduled portion and an unscheduled portion, wherein a UE is included in the scheduled portion in response to receiving a scheduling request from the UE. Synchronization is maintained between the eNB and each UE in the scheduled portion by sending a timing adjustment (TA) command if needed. Synchronization is maintained between the eNB and each UE in the unscheduled portion by allocating a periodic reference signal (sync-RS) to each UE in the unscheduled portion and by sending a respective timing adjustment (TA) command if needed to each respective UE in the unscheduled portion in response to a respective sync-RS received from each UE in the unscheduled portion.