06-12-2002 07:45 PM - edited 07-04-2021 11:14 PM
06-12-2002 07:49 PM
Half-Duplex, just like 802.11 and 802.11b.
That means that the 22Mbps maximum *actual* throughput (vs. 54Mbps signalling rate or nominal throughput) is both half-duplex and shared between all active users. Of course, that's roughly comparable to shared 100BaseTX.
Matthew Wheeler
07-23-2002 09:21 PM
Actually, some 802.11a technology utilizes 2 radios in both the AP and the client in a "proprietary Speed-Doubling mode", one for "send" and one for "receive", thereby making the network Full-Duplex. Also, the data rates for the 802.11a equipment I have tested has come closer to 36Mbps *actual* throughput, as opposed to the 22Mbps you are stating.
07-25-2002 12:37 PM
There are 5GHz dual-radio bridges out there (not APs), but they are NOT 802.11a. Products such as the Full-Duplex Tsunami 10 and 45 bridges use two 5.8GHz channels or one 5.8 and one 5.3 under the ISM and U-NII regulations.
Products based on the Atheros chipset offer a proprietary 'Turbo' mode rated at 72 or 108Mbps, with actual throughput of 36Mbps, however in 802.11a-compatible mode, they run about 22Mbps.
I have not heard any comments from Cisco on a 'Turbo' mode for their chipset.
Matthew Wheeler
Chief Wireless Architect
07-25-2002 12:23 PM
Mr. Wheeler is correct. 802.11, .11b and .11a are all half duplex. Even the vendors that support multiple radios are still only operating at half duplex. Since the client cards can only send OR receive at any given time, they are only half duplex.
They are both correct in regard to typical speeds. Different vendor products perform differently with speeds ranging from around 20 Mbps to around 30 Mbps.
The proprietary 2x modes that some vendors offer do not place the cards into full duplex. They use different modulation techniques to achieve higher data rates, though they are usually only a minimal increase. Typical speeds in 2x mode are around 35 Mbps.
Hope this helps.
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