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A number of different technologies are available to build wireless computer networks. Most commercial solutions are proprietary to certain vendors or do not use low cost hardware.

The IEEE 802.11 standard (called WiFi in the commercial world) allows users to network their machines using radio technology. Different sub-standards have been formed specifying the bandwidth or radio frequency the networks operate on. The standard defines a number of operation modes which allow for ad-hoc, point to point and point to multi point networking. Though the standard calls for two transmission technology standards: Direct Spread Spectrum (DSS) and Frequency Hopping Spread Spectrum (FHSS), the market has by and large standardized on DSS for indoor and outdoor point to multi-point use. FHSS, which is more robust against certain types of interference and densely packed endpoints, is currently only seen on long point to point connections where interference and frequency allocations are at a premium, for example, at an aggregation point.

In this project we have chosen the 802.11b as primary standard mostly because of the availability of equipment, open source drivers and the cost of the hardware. IEEE 802.11b is a DSS radio technology supporting link speeds of 1,2,5.5 and 11 Mbit/s. The standard uses the 2.4 GHz frequency band and is initially designed for home and office use but with special measures (antennas) it is also applicable to crossing longer distances outdoors (up to a maximum of approximately 15 Km line of sight). [WirelessNet,WirelessComm]

next up previous
Next: Topology Up: Method Previous: Introduction
Rudi van Drunen 2003-04-08