The WiMAX standard has defined three different profiles, Profile A, B, and C, for an Access Service Network (ASN) which consists of multiple BSs and an ASN gateway (WiMAX Forum 2008). The relation between a BS and an ASN gateway is also similar to that between a BTS and a BSC in GSM systems. A hierarchical ASN is defined in Profile A and C, whereas a flat ASN is defined in Profile B. Profile A is a hierarchical structure that is similar to traditional cellular networks.
As shown in Figure 1, the radio resource controller (RRC) and the radio resource agent (RRA) are implemented at the ASN gateway and the BS, respectively, so most radio resources are managed by the ASN gateway. In Profile B, the functionalities of a BS and an ASN gateway are co-located on the same platform/solution, which makes the architecture flat. That is, R6 defined for the link between an ASN gateway and a BS does not exist. In Profile C (Figure 2), the RRC is implemented at each BS, so all the RRM functions are performed at each BS as in a flat architecture, although it is still based on a hierarchical structure. Thus, mobility can be managed by the ASN gateway or other upper entities.
Figure 1: WiMAX ASN Profile A
Figure 2: WiMAX ASN Profile C
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