Last Post: December 14, 2005:
I am doing the timing tests for a wireless card driver. The driver supports the three modes 802.11a/b & g .. !!
The problem I am facing is with 11a data rates. Since, I need maximum efficiency for the timing tests. When I use higher data rates (54 mbps), the sniffer shows that each packet is retransmitted atleast once as the first frame had an invalid checksum. Because of these errors, the STA reduces its rate to 24 mbps. This is why the results don't show any significant difference for a/b and g modes. If I disable the rate control feature we get even slower rates.
I am using the Cisco AP. I have checked the major settings and have also tried the tests after changing the position of the AP. Still, the rates did not improve.
Is there anyone who had faced this problem before and can help me in the higher rates?
all things being equal, you should be able to get the same rates for 802.11a and 802.11g (b is the slow one :-) ).
I can't offer any advise on your checksum problem though, sorry.
The first thing I would do is do a true throughput test. You can easily download free software to test throughput to the device. One that comes to mind is NetPerSec.
The other thing, sometimes sniffers will have issues with their captures and show entirely too many CRC errors than is really happening. The new version of Airopeek that I am using will sometimes have this issue. Every data packet having to be retransmitted is almost unheard of (but not impossible).
In the end, I would like to know what the true throughput you are acheiving. In a clean RF enrionment with 11a, it should be around 20 - 22 Mbps.
Let us know how it works out.