802.11n without Channel Bonding is Just Stupid

802.11n is a good choice. 802.11n without channel bonding is not.

Perhaps the most important thing (in addition to MIMO and frame aggregation) that makes 802.11n 802.11n is 40Mhz channelization, aka channel bonding.

Channel bonding boosts bandwidth by combining two adjacent 20 MHz channels into a single 40 MHz channel. The throughput increase is actually a bit more than double since the guard band between the two bonded channels can also be removed.

Since only three non-overlapping 20 MHz channels are available in the 2.4 GHz (2.4 GHz to 2.4835 GHz) spectrum band used by the IEEE 802.11b and IEEE 802.11g WLAN communication standards, channel bonding is often thought to be difficult in noisy environments with dumb Wi-Fi systems that have no proper adaptive controls.

But here's the real deal. Without channel bonding 802.11n is handicaped. Limiting clients (e.g. Centrino and other laptops) to 20MHz-only is essentially misguided and actually hurts 802.11n as a whole. People that think that 40MHz operation causes extra interference don't actually understand RF issues.

Yes, 40Mhz operation consumes twice the bandwidth, but the packets are half as long (relative to time) so there is no net increase in interference. APs and clients should be smart enough to dynamically determine the correct mode of operation.  Smart Wi-Fi systems do just that.

Smart Wi-Fi systems continuously pay attention or listen to (my engineer says i must say "monitor") the RF environment, picking the best performing signal paths and RF transmission parameters for a given client.

This results in less interference since the link is occupied for a shorter period of time.  There you go.  Now tell someone who really cares.

Comments

[primemover]

This blog entry effectively addresses the fear, uncertainty and doubt that companies are spreading by WLAN companies who remain flat-footed on delivering 802.11n products and others who are simply, sadly uninformed.

Here is an example of such mis-guiding from the VP of Marketing @ Extricom:

"In fact, 802.11n, with its wide 40MHz channels, could wreck non-blanket Wi-Fi systems, he said - at least in the 2.4GHz band, where it reduces the number of non-overlapping channels from three to one, and makes it impossible for every access point to have a different channel to the next one."

Tell a friend ...

[Devin Akin]

First, a 40 MHz channel uses the same mask as a 20 MHz channel, and therefore "channel bonding" is a misnomer. They aren't actually two side-by-side channels, but rather one large channel. Your comment about being able to take advantage of the guard band between what used to be two 20 MHz channels is both correct and proof of this. :)

Using three HT 20 MHz channels in 2.4 GHz is a much better solution than using either one 40 MHz channel and a 20 MHz channel or two 40 MHz channels. The reason is co-channel and adjacent channel interference. If you want to take a look at the real effects, I would suggest using the latest version (802.11n capable) of AirMagnet Wi-Fi Analyzer Pro and take a look at the Channel Occupancy feature. I've done this in a Ruckus deployment, and the interference is staggeringly bad between channels when ANY 40 MHz channels are deployed in 2.4 GHz.

There are still many distinct advantages to 802.11n in 2.4 GHz without 40 MHz channels, especially using Ruckus's TxBF features. I highly suggest to everyone to deploy 802.11n in 2.4 GHz (whether using an MCA or SCA system), but never with 40 MHz channels - which should be reserved for the UNII bands.