Methods, apparatus, systems, architectures and interfaces for determining whether sidelink resources of a sidelink radio bearer are available, and for reserving resources of any number of sidelink radio bearers for transmission of periodic data are provided. The method includes determining any of a size, a period, or a pattern of a resource reservation for periodic data that is to be transmitted by the WTRU via the sidelink radio bearer; determining sidelink resources available for transmission of the periodic data via any number of sidelink radio bearers; and transmitting a message including the resource reservation including information indicating reservation of the available sidelink resources for transmission of the periodic data by the WTRU according to any of the size, the period, or the pattern of a resource reservation, wherein the message includes any of a bearer identifier (ID) or Quality of Service (QoS) information.