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 WiMAX: Air Interface and Core Network
 aspects

Wireless Interoperability in Microwave Access (WiMax) is a trade name (owned by WiMax? Forum, an industry consortium) used for products, services compliant to IEEE 802.16 set of standards, notably, the 802.16d and 802.16e standards. Additionally, the WiMax? Forum has published a set of recommendations for core network aspects including mobility, authentication, authorization and accounting among others. These are the stage 2/3 Network specifications authored by the Network Working Group within WiMax? Forum.

Section 1: Overall Network Architecture

Figure below shows the overall network architecure in wimax.

The figure indicates the various elements and interfaces defined in the specifications. The 802.16d/e specification is limited to the Air Interface i.e. the R1 interface. IEEE specifies the Physical and Media Access layers for wimax and rest of the interface points/elements are described by the stage 2/3 specifications of the wimax Forum. These specifications also describe the interworking mechanisms/flows with other core networks such as 3G or IMS. An excellent introduction to the rationale behind wimax indicates the reasons, mainly from Air Interface perspective for the adoption of wimax technology.

Section 2: Media Access Layer

The wimax Media Access Control layer is a collection of procedures for transferring a higher layer SDU to its peer layer at the basestation. The following figure illustrates the layers and the Service Access Points (SAPs) within the MAC layer.

The higher layer PDU (ATM/IP) is sent to a convergence sublayer (CS) at the top of the MAC layer. The role of the convergence Sublayer is:

1. Accepting the higher layer PDU
2. Classification of the higher layer PDU
3. Performing some operation based on the classification on the received PDU
4. Delivering the processed PDU to the appropriate MAC SAP
5. Receipt of the MAC-PDU

specifically, the role of Packet Convergence Sublayer (one used for IP traffic) is:

1. Classification of the higher layer PDU into the appropriate connection?
2. Suppression of header information (optional)?
3. delivery of resulting CS-PDU to the MAC SAP associated with the Service Flow for delivery to peer MAC SAP?
4. Receipt of the CS-PDU from the MAC SAP?
5. rebuilding of the suppressed header information (optional)?

Section 3: ASN-GW

ASB GW is a WiMAX network element providing a Point of connectivity to the Core network. Its provides following macro level functionality:

1. full mobility
2. seamless handoffs
3. user plane forwarding
4. bridging and tunnel switching
5. Radio Resource control
6. QoS enforcement and classification functions
7. security management

Further information on ASN GW is available at ASN Gateway

Categories: Wimax

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