Draft 2.0 802.11n network performance is dependent on so many variables that it can be challenging to get your head around just what to expect with the next-generation Wi-Fi LAN systems. However, Wi-Fi chipmaker Atheros has shared some ballpark throughput numbers based on hypothetical modeling it has conducted in-house.

The table provides estimates of the downlink throughput likely to be realized in Atheros-based networks at various distances and depending on how many antennas and spatial streams are in play. The lion’s share of Wi-Fi systems use Atheros chipsets; many also use the Atheros reference design. Cisco is a notable exception.

In addition to the core chips and system implementation, some other key contributors to actual throughput include the following:

* Architecture of the WLAN system.
* The mix of clients in your environment and their degree of “stickiness.”
* The mix of mandatory and optional 802.11n features supported in the pre-standard 802.11n devices you use.
* How many antennas are used in the system and how many spatial streams are supported (see "MIMO, antennas and streams - oh, my!" and "What 802.11n tech specs mean").
* Whether you operate in 40MHz dual-channel mode or in 20MHz single-channel mode.
* Whether 11n APs are serving 802.11a, b or g clients as well as n clients.

And so on. In the coming months, we’ll take a look at each of these items a bit more under the microscope.

Joanie Wexler is an independent networking technology writer/editor in Silicon Valley.