When I set the basic rates of a Cisco AP to 1.0, 2.0, 5.5 and 11.0, does it allow the clients 802.11b to shift their rates to lower than
11Mbps when it works further from the AP and the signal becomes weak ?Or does it mean that the AP will require all the clients MUST ALWAYS work at 11mpbs ?
Thanks,
DT
No. Client will auto-shift if necessary
No. Client will auto-shift if necessary
Merv schrieb:
What you say isn't false, the client will fallback. But the AP will disassociate a station not capable of tx/rx at 11mbit/s. Even if this is for a very short moment.
Setting a rate as "basic-rate" requires all basic rates at all times the client communicates with this ap.
Other vendors call this setting something like "microcell". Forced roaming the best AP. Even with slow moves you won't be able to reassociate to an AP with the setting. Usually it's not a good idea, until you really knows what this setting means.
When you expect a throughput gain from this setting: Not worth. The preamble is always transmitted with 1mbit (2mbit for short preamble)
My recommendation: setting 1 and 2 to basic the rest to allowed. Perhaps
5.5 to basic.On a "g" radio setting any OFDM rate to basic blocks all "b" only stations from associating.
Uli, thanks for your reply. Does it mean that in the case of there is only *one* AP and all clients are 802.11b, then setting basic rates to 11 will be the same as settings basic rate to 1,2,5.5 and 11 ? 5.5 will not be used because it will cause a disassociate when 11 is a baic rate . ACK will reply on 11 because it is on the basic rate and the clients use 11 for transmitting.
Thanks,
DT
snipped-for-privacy@yahoo.com schrieb:
No. Setting basic-rate to 11mb with 1 2 and 5.5 deactivated won't work at all.
Why are you so sure about this? The basic-rate has not much to do with the unicast datarates used for transmitting the data. Basic Rate is the rate for the infrastructure.
Uli, thanks for bearing with me.
I made a test with an AP 1200 ( 1230B ) and a client with Intel Pro/2200BG which is set to working on 802.11b only.
The test is repeated with the command "speed bacsic-xx" ( i.e only one speed is chosen at a time ) with xx is 1.0, 2.0, 5.5 and 11. Each time the command is issued, the client shows the speed change correspodningly, and I am still able to access to the network. A protocol analysis shows the beacons are transmitted at the AP speed also. This is done with each speed separately.
The difference in two cases with basic rate = 11 and basic rate = {1,2,5.5,11} is in the later case, the beacon is transmitted at 1Mbps ( or the lowest basic rate ) , and in the former case it uses 11Mbps.
I think the basic rates apply to both unicast and multicast/broadcast frames, with the exception the unicast can also transmitted on "enabled" rates if the client is capable to work on the "enabled" rate.
DT
snipped-for-privacy@yahoo.com schrieb:
Receiving the beacons is a must for joining an infrastucture. After missing a given number of beacons the station scans (== listens for beacons from another MAC of a radio in Master role, it scans all allowed channels) for a better AP.
beacons are unencrypted multicast/broadcast to the group of associated or scanning clients.
Since the beacons are small the frame overhead and preamble leverages the gain of the shorter transmission time at the higher rate.
The interference to neighbouring cells isn't smaller. Physically the cell has a much smaller coverage but equal interference/disturbance area of neighbouring cells.
So if you want max bandwidth with more but smaller cells you need less interference by lowering output level by AP *and* stations or load balancing.
If your AP is 3 meters away in line of sight from you notebook standing still on the table, you won't see problems with 11mbit/s basic-rate.
Your notebook will frequently drop and get back connection when in motion (at faster walking speed).
Uli, thanks a lot for the explanation again.
DT
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