Wimax standards and Security The Wimax

Connection Establishment and Maintenance

1. 
   Network Entry and Initialization
   

This is the first step when a new SS enters and registers to one sector of the WiMAX network with the PMP operation.
The procedure can be divided into the following phases:

1. 
   Scan for downlink channel and establish synchronization with the BS
   
2. 
   Obtain transmit parameters (from UCD message)
   
3. 
   Perform ranging
   
4. 
   Negotiate basic capabilities
   
5. 
   Authorize SS and perform key exchange (f) Perform registration
   

7. 
   Establish IP connectivity
   
8. 
   Establish time of day
   
9. 
   Transfer operational parameters
   
10. 
    Set up connections
    

Implementation of phases (g), (h), and (i) at the SS is optional. These phases shall only be performed if the SS has indicated in the registration request (REG-REQ) message that it is a managed SS. Each SS contains the following information when shipped from the manufacturer: (a) A 48-bit universal MAC address assigned during the manufacturing process. This is used to identify the SS to the various provisioning servers during initialization. (b) Security information used to authenticate the SS to the security server and authenticate the responses from the security and provisioning servers.

2. 
   Connection Maintenance
   

Ranging is a collection of processes by which the SS and BS maintain the quality of the RF communication link between them. Distinct processes are used for managing uplink and downlink. Also, some PHY modes support ranging mechanisms unique to their capabilities.
The channel descriptors are transmitted at regular intervals by the BS. Each descriptor contains the configuration change count, which shall remain



FIGURE 3.2
SS request/grant procedure.

unchanged as long as the channel descriptor remains unchanged. All UL-MAP and DL-MAP messages allocating transmissions and receptions using burst profiles defined in a channel descriptor with a given configu- ration change count value shall have a UCD/DCD count value equal to the configuration change count of the corresponding channel descriptor. The BS may add an SS to a multicast polling group by sending an MCA-REQ message with the join command. Upon receiving an MCA-REQ message, the SS shall respond by sending an MCA-RSP message.

The BS may establish a downlink multicast service by creating a connection with each SS to be associated with the service. Any available traffic CID value may be used for the service. To ensure proper multicast operation, the CID used for the service is the same for all SSs on the same channel that partic- ipate in the connection. The SSs need not be aware that the connection is a multicast connection. The data transmitted on the connection with the given CID shall be received and processed by the MAC of each involved SS. Thus, each multicast SDU is transmitted only once per BS channel. Since a multicast connection is associated with a service flow, it is associated with the QoS and traffic parameters for that service flow.
ARQ is not applicable to multicast connections. If a downlink multicast connection is to be encrypted, each SS participating in the connection shall have an additional security association (SA), allowing that connection to be encrypted using keys that are independent of those used for other encrypted transmissions between the SSs and the BS.

3.