Wimax standards and Security The Wimax

802.16 Mesh Networking

We have shown in the previous section that the 802.16 mesh standard has cross-layer design features, such as centralized scheduling, that cross the boundary between the MAC layer and the IP layer on the mesh nodes. These types of cross-layer features can be used to enhance the QoS in the mesh if they are taken advantage of. In this section, we show how to design the addressing in the network layer so that the network takes full advantage of QoS available with 802.16 MAC and yet the 802.16 mesh routers can be simple, in line with the mesh network application scenarios outlined in Section 8.1. We also design the CS, which allows the network layer to access 802.16 QoS features.

1. 
   802.16 MAC Connections
   

The 802.16 mesh standard uses a combination of a 16-bit mesh identifier (ID) and a 16-bit connection identifier (CID) to identify the source and

destination of every transmission. Mesh ID is a unique mesh node identifier obtained during the authentication process and is assigned by the base sta- tion. The CID is calculated dynamically and it depends on the type of channel the transmission is in. In the data channel, the CID refers to a logical data connection between two neighbors. In this case, the CID is a combination of an 8-bit link ID and an 8-bit QoS description for the connection. The 8-bit link ID identifies the receiver of the connection, relative to the sender of the packet. In the basic channel and the broadcast channel, the CID is a combi- nation of an 8-bit network ID and 0xFF (meaning any link ID). In the basic channel, the receiver of the transmission is identified with its 16-bit mesh ID in the MSH-NENT packet, deviating from the way receivers are identified in data channel unicast connections.

Data connections are established between neighbors with a sender-initiated
negotiation. First, the sender initiates a link creation with a request in one of its MSH-NCFG packets. The request includes a hashed message authentication code (HMAC) for the request message, obtained by applying a network-wide secret key obtained during the authentication process [15]. The receiver checks the request and if it can recalculate the HMAC, it responds with a positive response in one of its MSH-NCFG packets. Finally, the initiator sends an 8-bit link ID it will use to refer to the connection in subsequent data transmissions. In subsequent data transmissions, the 8-bit link ID is extracted from the CID so that a node can identify its packets.
A unicast data connection between two mesh nodes can be in one of four states after it is created. First, it could have no bandwidth allocated to it. In this case, the connection cannot be used to transfer data, so it is in the DOWN state (Figure 8.8). Second, it could have bandwidth allocated to it with the central- ized scheduling protocol. In this case, it is in the UP-CSCH state. Third, it could have bandwidth allocated to it with the decentralized scheduling protocol.

MSH-DSCH MSH-CSCH