The 802.11b spec allows for the wireless transmission of approximately 11 Mbps of raw data at indoor distances from several dozen to several hundred feet and outdoor distances of several to tens of miles as an unlicensed use of the 2.4 GHz band. The 802.11b specification started to appear in consumer form in mid-1999, with Apple Computer’s introduction of its AirPort components, manufactured in conjunction with Lucent’s WaveLAN division. (The division changed its named to Orinoco and was spun off to the newly formed Agere Corporation with a variety of other Lucent assets in early 2001; these assets were resold to Proxim Corporation in June 2002, although Agere continues to make chips.)
802.11b uses several types of modulation. Barker Code Direct Sequence Spread Spectrum with BPSK or QPSK modulation is used to transmit at 1 and 2 Mbps respectively, while Complimentary Code Keying is used to support speeds of 5.5 and 11 Mbps. Multiple users are supported by the use of Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA).
Wed, 2010-09-01 07:54
- Login or register to post comments
»