**2.2 Accounting**

#### **2.2.1 The network structure of accounting**

The accounting structure of WiMAX access layer is shown in the figure below:

Fig. 8. Accounting Structure of WiMAX access layer

WiMAX accounting consists of two parts: BS collects the accounting parameters of the wireless side and ASN-GW collects the accounting parameters of the network side . BS sends the wireless side accounting parameters to ASN-GW through the interface between them. ASN-GW integrates the wireless side and network side accounting parameters into UDR and then sends it to AAA-server through RADIUS interface . AAA-server provides the interface to the accounting center and it can collect the initial voice information from AAA-server .

The interface between ASN-GW and AAA-server supports RADIUS protocol and the evolution to DIAMETER protocol. Considering the special bits of WiMAX accounting, it will use RADIUS or DIAMETER according to the producers.
