Ad-hoc wireless networks limited to 11mbps!

 

There are basically 2 types of wireless networks. Infrastructure and ad-hoc (also known as peer to peer). Infrastructure is when you have a wireless router and all computers “talk” with the router. Ad-hoc is when one computer talks directly to another.

I was fiddling with some wireless networks, and discovered that indeed the ad-hoc type of wireless networks have a maximum speed of 11 mbps!

from http://labs.pcw.co.uk/2005/03/adhoc-wireless.html

Ad-hoc wireless connections limited to 11mbps

Reader Ian Longdon has drawn our attention to a little-known limitation of ad-hoc (peer-to-peer) wireless networks, typically used between two or more notebooks with Wi-Fi adapters. The IEEE 802.11 standard specifies that performance in ad-hoc mode must achieve 11Mbits/sec, but no more, regardless of whether the adapter is 802.11b or 802.11g. There's no requirement for manufacturers to exceed the 11Mbits/sec specification, and as Ian found with his D-Link cards, some don't.

We asked D-Link and the Wi-Fi Alliance about this problem. D-Link replied:

"Unfortunately we only meet the standard and don't exceed it. D-Link wireless products follow the IEEE 802.11 standards. The 802.11b and 802.11g standards specify that Ad-Hoc mode only needs to support up to 11Mbps. For best results, use an access point or wireless router and set your adapters to Infrastructure (station) mode."

The Wi-Fi Alliance told us that as the standard only specifies a maximum of  11Mbits/sec performance in ad-hoc mode, testing above this speed is not performed as part of the Wi-Fi certification procedure.

While it's arguably unfair to criticise vendors for not exceeding a standard, they certainly don't go out of their way to let users know about this. Some products do appear to connect at higher rates in ad-hoc mode, but it's certainly not advertised and it's very much a 'suck it and see' process to find out. Netgear is one of the few companies with a public statement on the issue.

We'll certainly be keeping an eye out in future when products come through the labs. Thanks again to Ian for informing us about this.