Vehicular Metropolitan Area Network Systems Architecture: The WiMAX Network Reference Model

10.1 Introduction

Based on WiMAX Forum Network Architecture definition (Stage 2: Architecture Tenets, Reference Model and Reference Points (Juo et al., 2008)) (Stage 3: Detailed Protocols and Procedures (WiChorus, 2009)), the WiMAX network reference model includes the logical functional entities and reference points. Figure 1 shows the WiMAX network reference model containing reference points, functional entities, and some important basic elements like Network Service Provider (NSP) and Network Access Provider (NAP).

Figure 1.

WiMAX network reference model

The functional entities contains Subscriber Station (SS)/Mobile station (MS), ASN(Access Service Network) and CSN(Connectivity Service Network). As in Fig 10.1, the network reference model depicts telecommunication’s operations. Access Service Network is managed by NAP (Network Access Provider). CSN is managed by NSP (Network Service Provider). CSN provides IP connectivity, links out with the internet and combines with its Home-ASP (Application Service Provider). Basically, the overall architecture can be divided into three parts. The first part (left position in Figure 10.1) is MS/SS equipments, and it’s also called the end users. The second part (center position in Figure 10.1) is ASN. ASN supports wireless communication and air-interface to MS/SS. The third part is CSN where inner management servers locate (such as Home Agent, Location Register, AAA server and so on).

Based on Figure 1, we give an introduction for these functional entities and reference points:

ASN(Access Service Network): It links with WiMAX Customer Premises Equipment (CPE) e.g. MS, SS. Access Service Network (ASN) functions support WiMAX Layer2 connectivity, AAA messages forwarding, WiMAX NSP selection, Layer-3 link tunneling (BS-SS) and Radio Resource Management (RRM). The operations can be seen in the ASN-GW function.

ASN-GW(ASN Gateway): As in Figure 2, we can observe the ASN-GW functions which contain reference points and functional entities in ASN. ASN-GW not only manages IP Data Forwarding in ASN, but also links with the other function entities inside or outside the ASN-GW. It tunnels data and packets to the suitable BS. ASN-GW Control plane handles all of the radio-independent control and includes authorization, authentication, and accounting (AAA), context management, profile management, service flow authorization, paging, radio resource management, and handover. Data plane feature set includes mapping radio bearer to the IP network, packet inspection, tunneling, admission control, policing, QoS and data forwarding.

Figure 2.

ASN-GW reference model

ASP(Application Service Provider): ASP provides basic network service and manages applications with IP-network. An application service provider (ASP) is a business that provides computer-based services to customers over a network. Software offered using an ASP model is also sometimes called On-demand software.

CSN(Connectivity Service Network): The CSN contains several functional elements and tasks for supporting IP-Network connectivity to CPE. The following lists the major tasks in CSN network:

• 1.

  MS/SS IP address assignment.

• 2.

  Internet access.

• 3.

  AAA Server management.

• 4.

  Tunnel supported (between CSN and SS).

• 5.

  Accounting /pricing service.

• 6.

  Users roaming across ASNs/ CSNs.

• 7.

  Mobility management between MS and ASN.

NAP (Network Access Provider): ASP provides basic network service and manages applications with IP network. Moreover, it provides radio link resource to one or more NSPs. One NAP can also contain one or more ASN network. For example as Figure 10.1 shown, the NAP function contains two ASN networks.