Wimax standards and Security The Wimax

Modes of Operation

WiMAX was designed to support both point-to-point (P2P) and point-to- multipoint (PMP) topologies. While P2P can be used to support wireless net- work backbones, PMP is what the standard was mainly designed for. In a PMP scenario a base station distributes traffic to many subscriber stations. To yield a high efficiency, WiMAX uses a scheduling method in which base stations can only transmit in their time-slots and do not contend with one another. This works quite efficiently because, unlike 802.11 hotspots, which usually have bursty traffic, stations can aggregate traffic from several computers, producing a steady flow. WiMAX also supports a mesh mode of opera- tion, allowing service providers to use NLOS operation by having subscriber stations communicate directly to each other and relay traffic. Figure 11.1 illus- trates the use of mesh mode in WiMAX to provide NLOS service to residential customers [1].





FIGURE 11.1
WiMAX overview.
WiMAX’s design allows it to be used in many different operating envi- ronments. The ability to provide last mile broadband access to consumers was one major consideration during development. With a focus on standard- ization and interoperability, WiMAX may provide a low-cost solution. Figure

1. 
   illustrates the possible uses of WiMAX, including reliable business access, residential access, and high-speed connectivity for mobile users.
   

WiMAX’s ability to provide high transfers rates allows it to be used as a network backbone. Specifically, developers envision using WiMAX as a backbone for 802.11 hotspots to provide Internet access. In this configuration, users would connect to a nearby 802.11 base station. The base station would then relay the user’s data to a central WiMAX base station, which is connected to the Internet. This would provide citywide Internet access without having to run cables to each 802.11 hotspot.
Another access method would be to allow users to directly connect to the WiMAX base station, allowing citywide Internet access with a single point of attachment, without the need for any 802.11 base stations. Although possi- ble, it may not use bandwidth as efficiently as the previous example. This is due to the scheduling algorithm WiMAX uses, which is designed for steady and smooth traffic and not for the bursty traffic created by individual users.

Also, it is likely that base stations may only have a range of 5–6 mi. instead of 30 mi. due to the increased vulnerability of the links from the user mobility.

Developers also had cellular applications in mind when they designed WiMAX. The first use of WiMAX for cellular applications will be a tower backhaul service. Once the IEEE 802.16e standard is implemented, which is optimized to support handoffs and roaming at speeds of up to 75 mph, WiMAX can be used to connect directly to cell phones and other mobile devices.
Many government agencies see the value of using WiMAX for both home- land security and its use in emergency situations. Agencies could deploy WiMAX-enabled devices to monitor high-value infrastructures and transmit the information to a central operations center for processing [3]. Emergency mobile wireless networks are another important use for the government. Dur- ing a disaster, where all communications have been lost, a WiMAX network could be quickly set up. This would allow organizations like FEMA, Red Cross, and NATO to communicate important information that may be crucial to rescue operations [4].

2.