5.9 Advanced 802.16 Functionalities
While most of the functionality described in this chapter so far needs to be implemented in both base stations and subscriber stations to form a functional network, the 802.16 standard defines a number of optional and forward-looking functionalities that can extend the range and throughput of a network. It is unlikely that the functionalities described below will be implemented in the first generation of products. However, as the technology matures and the market for wireless high-speed Internet access increases, these functionalities offer possible options for the growth of networks and the customer base.
5.9.1 Mesh Network Topology
One of the biggest problems of wireless networks is the limited coverage area of a single base station. As described in the beginning of this chapter, the coverage area of 802.16 base stations is limited to a radius of 2 to 5 km around the base station. This is similar to coverage areas of other systems like UMTS and HSDPA. The range of a base station in a conventional setup can only be increased by using directional outdoor antennas for SSs, which is not always possible. A new approach to this problem is the mesh network. In the 802.16 mesh approach, not all SSs communicate directly with the base station. Instead, distant subscriber stations communicate with neighboring SSs. These neighboring devices in turn forward their data packets to the base station or to another SS if they are too far away from the base station ...