The scope of this document is to define the logical link control layer, or LLC layer, of the wideband air interface (WAI). The wideband air interface called U_W is the interface between the fixed network equipment (FNE) and the subscriber units, or directly between subscriber units in a wideband system. The general wideband system model is shown in Figure 1 and illustrates the Radio to FNE Mode of operation. A Vehicular Repeater (VR) may additionally act as a relay between FS and MR when coverage limitations require the use of this local coverage area extension.

The Wideband Air Interface (WAI) reference point Uw is between the BR 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 LLC layer is the highest sublayer of OSI layer 2 and directly interfaces with the MAC/RLA layer.

This document concentrates on the wideband air interface logical link control layer, whose function is to define the procedures and message formats that permit virtually error free (optional) transmission of LLC frames over the point-topoint or point-to-multipoint MRC to FNE, or MRC to MRC RF link.

The functions allocated to the LLC layer include the following major aspects:

• Reliable and unreliable payload and control data transmission

• Logical link management

• Segmentation and re-assembly of packets

• Data flow control