The scope of this document is to define the Media Access Control / Radio Link Adaptation layer, or MAC/RLA layer, of the Wideband Air Interface (WAI). The WAI called UW is the interface between the Fixed Network Equipment (FNE) and the Mobile Radio (MR), or directly between MRs in a wideband system. The general wideband system model is shown in Figure 1 and illustrates the Radio to FNE Configuration as defined in [1]. A Vehicular Repeater (VR) may additionally act as a relay between Fixed Station (FS) and MR when coverage limitations require the use of this local coverage area extension.

The WAI reference point UW is between the FS and MR, or MR to MR, and is used for wireless communications between these functional groups. OSI layers 1 and 2 are the specified scope of the implementation of the UW services. The MAC layer is the lowest sub layer of OSI layer 2 and directly interfaces with the physical layer.

This document concentrates on the WAI MAC, whose function is to define the procedures and message formats that allow multiple MRs to efficiently share the physical and logical radio channel(s). The functions allocated to the MAC layer include the following major aspects:

• Frequency configurations, logical channels, and synchronization

• Channel access, allocation of channel resources, and contention resolution

• Dynamic radio link adaptation control

• Radio power, and energy conservation management

• Radio channel encryption and scrambling

• MAC layer services, procedures, and PDU definitions

This standard does not include any specific functions that may be required for the VR link configuration operation. The specific MAC/RLA operation in the VR configuration will be defined in a future standard.