Q

Will my 802.11 access point interoperate with 802.11b?

We have an 802.11 Symbol Spectrum24 access point. It's the plain Jane 802.11 at 2 Mb. Will existing 802.11b cards work with this unit? I guess what I'm asking is, are 802.11b devices backwards compatible with 802.11 devices?
I'll answer your general question first, then address the specific product that you're asking about.

The 802.11b standard still includes DSSS operation at 1-2 Mbps and the long preamble defined by the original 802.11

standard. 802.11b also includes new DSSS high-rate/short preamble features, and rules for interoperation between old and new radios.

An older 802.11 DSSS AP will announce its supported rates in Beacon and Probe Response frames. Based on this information, 802.11b cards should automatically adjust to using 2 Mbps with a long preamble when attempting to associated with your AP. Data rate and preamble are configurable options for some cards, so check these card settings when an 802.11b card has trouble associating with an older DSSS AP.

These older DSSS data rates are mandatory in both 802.11b and 802.11g standards. However, neither 802.11b or 802.11g includes the other (non-DSSS) PHY options defined by the original 802.11 standard: specifically, FHSS and infrared.

Which brings us to your specific AP: I suspect that you have the Symbol Spectrum24 Frequency Hopping (FHSS) AP. If so, then the answer is NO, your FHSS AP will NOT interoperate with 802.11, 802.11b, or 802.11g DSSS cards. It will only interoperate with 802.11 FHSS cards, like the Symbol Spectrum24 LA3021.

This was first published in December 2003

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