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When looking at antenna range I have details of the range for 54Mbps transmission.

90 feet at 54 Mbps and 300 ft at 6 Mbps

Can I interpret these for 802.11b as

90 feet at 11 Mbps and 300 ft at 1 Mbps

Also from a standard manufacturers tables what power will these distances relate to? I understand that the more power the greater the range from the same antenna therefore without the manufacturer in this case Cisco state what power is applied to the antenna these figures cannot make sense?

Should I assume that these distances are at the max output ie 100mW of the APs and therefore half it for half power. The problem is we have a wireless installation that I have inherited and basically its a mess. APs next to each other on channels 2 and 3 etc. no specific diagram of ranges, its a bit of a nightmare.

The range numbers given by 802.11 vendors are often meaningless in the real world. So many factors contribute to the range of an 802.11 radio that it's not possible to give meaningful general numbers like, "90 feet at 54 mbps," because those numbers are not measured under controlled circumstances. Range numbers aren't really even useful for comparing two vendors to each other, since vendors don't use standard ways of calculating range.

In outdoor environments where the Fresnel zone is clear, it is possible to predict range fairly accurately. In indoor environments, predicting range requires an intimate knowledge of the structure of the building, which the vendor doesn't have when they quote range numbers. In addition, the range of an AP is hardly ever a circle or sphere in an indoor environment. Obstructions in one direction will create shadows that don't exist in other directions, so the range might be 90 feet in one direction and 20 feet in another.

The right way to calculate range is to take the transmit power of the AP, calculate path loss between the AP and the client, and find the range at which the received power has decreased to close to the client's receive sensitivity. In indoor environments, this is challenging without the help of specialized software like Wireless Valley LanPlanner. Alternatively, you can do a site survey to measure the actual range of the real APs in your environment. It sounds from your description of the network like a site survey is called for either way.

Thanks Joshua

I realise the vendor will speek in favourable terms and use an idealised model. However it is just at present to get a visualisation of what is going on and a better grasp of the subject matter.

Also it is probably the worst scenario you can imagine, lots of high bay steel racking so warehouse varies when racks are full and empty, the survey we had done was frossly inadequate, I am now trying to get it performing as well as we can, at the same time get my CWNA,

Most of the CWNA stuff I,m finding ok just a bit worried about some of the theoretical and practical aspects. Thats to say when I do a site survey making sure I can visualise coverage and understand what we can and can't achieve.