WiMAX Simulator
Figure 13.13 illustrates the protocol structure of the WiMAX mesh MAC protocol stack. One of the functionalities of the mesh network entry protocol component is selection of sponsor node, which will involve communication exchange of unicast MSH-NENT from the new entry node and broadcast MSH-NCFG control messages from
- Figure 13.13 WiMAX mesh simulator protocol structure.
the sponsor node. In the design, the network entry process has been simplified, whereby the joining node will only perform the selection of sponsor node upon entry to the mesh network. In the simulation framework, the role of the sponsor node is not being utilized for data routing, as all route setup processes are being handled by the network layer ad hoc routing protocol. Once a node has registered successfully with its sponsor node, the node will start to transmit its MSH-DSCH and MSH-NCFG messages using the mesh election algorithm to schedule the channel access for the control messages.
The WiMAX mesh protocol MAC stack is designed for multihop mesh environment using the coordinated distributed scheduling mechanism. In this mechanism, data transmissions are scheduled in a manner that does not rely on the operation of a BS. Coordinated distributed scheduling employs a three-way-handshaking procedure (REQUEST/GRANT/CONFIRM) to set up a connection with its neighbor. Distributed scheduling mechanism utilizes the distributed election scheduling algorithm to compete for channel access for the transmission of its control messages. Because other nodes may also transmit in the selected time slot in the control channel, each node will use the standard-defined mesh election algorithm to compute whether it can win the time slot or not.
As a means of increasing the robustness of MAC layer, automatic request retransmission (ARQ) is another supported feature. With ARQ, the WiMAX mesh MAC layer will perform retransmission from the MAC layer when acknowledgment fails to be received from the receiver within a certain configurable time period. To enable route setup between mesh entities (i.e., SS to SS) that are located multiple hops away, ad hoc routing protocol is utilized at the networking layer. For the framework's routing component, AODV ad hoc routing protocol, which is readily available on QualNET, is used. The network topology currently supported by the protocol stack is of mesh client architecture, with single-radio interface for each node.
Post a comment