Last Post: February 7, 2007:
Noticed on an access point, that was configured by a company which deploys WLAN networks in warehouses, the following setting on a Cisco 1231G...
speed basic-2.0 basic-5.5 basic-11.0
Not quite sure what their goal was. It appears that they have a huge number of AP's in this particular warehouse, most at 50mw power. Do they think that by disabling 1Mbps, the mobile clients will reach a roaming threshold quicker?
Also, will the AP now transmit pre-ambles and beacons at the 2Mbps rate properly. I believe they are using short-preambles.
Hey DaveFromPeg, we did something similar at our warehouses. We actually disabled anything below 24mbps. We are also using 1231G Cisco AP's. We were having problems with Intermec CK31 handhelds with slow roaming and basically "holding onto" an ap until it just couldn't see it no more before it would roam. In working with Cisco and Intermec they actually recommended those settings along with enabling WDS on the AP's.
This has seemed to make the CK31's roaming "easier" and not lose their connections.
I honestly haven't done an analysis to see if the pre-amble and beacons transmitted @ 2Mbps but I think they would still have to.
9.6 Multirate support "All frames with multicast and broadcast in the Address 1 field that have a UP of zero shall be transmitted at one of the rates included in the BSSBasicRateSet parameter, regardless of their type or subtype."
Beacons must be transmitted at a basic rate.
By vendor convention beacons are transmitted at the lowest basic rate.
By administrator convention no rate is supported lower than the lowest basic rate. If a still lower rate was supported, and a client chose that lower rate for its transmissions rather than reassociate to another AP, that client might stop receiving beacons reliably.
On another note, 1 Mbps data rate transmissions use DBPSK modulation for the data, the physical header, and the long (not short) preamble regardless of whether the transmitting device is a DSSS PHY, a HR/DSSS PHY (b), an ERP PHY (g), or an HT PHY (n), and regardless of whether the transmitting device supports short preamble as well as long.
In an environment with lots of APs available at short range, I might drop support for both 1 and 2 Mbps.
I hope this helps. Thanks. /criss
Thanks Chris and Boomer, that explained it fully