ASN - Access Service Network.
- Establish layer 2 connections between the BS and the MS.
- Transmit AAA messages to the home NSP of the MS.
- Assist the high level to establish layer 3 connections with the MS and assign
the IP addresses.
- Perform the radio resource management (RRM).
- Perform the intra-ASN mobility management and handover.
- Perform the intra-ASN paging and location management.
- Establish and manage the tunnels between the ASN and the CSN.
- Store the list of temporary subscriber information, which is similar to the function of VLR in a 3G network.