Sometimes Size Does Matter

A side effect of increased channel width is reduction in the number of available channels for RF planning. Traditionally, a  minimum of three non-overlapping channels are necessary to minimize co-channel interference (CCI); this is not a major
concern in that with currently available 5GHz spectrum there are 22-20MHz channels , 10-40MHz channels and only -80MHz
channels available for planning. HOWEVER, the wider the base channel, the higher the risk of co-channel interference. For
example, let’s say that a network was designed around an 80MHz wide design which results in a reduction of options for AP
deployment for maximum client density. With a traditional multiple-channel approach, a base 40MHz design would result in
more APs to deploy for the higher client density. This approach, for typical Wi-Fi solutions, forces a choice between client density and data rate.

Some pundits1 have proposed an 802.11ac hybrid solution to attempt maximizing client density and minimizing CCI. This
approach could use a 40MHz deployment strategy that uses all 10 available 5GHz channels and allows for maximum AP packing. This approach DOES maximize throughput while minimizing co-channel interference, but employs a complex planning effort with potential added expense for additional APs. These same pundits also state support for 80MHz wide traffic will be on a “best-effort” basis! WHAT?!

I just don’t get it! In this model, a customer purchases brand-new access points to only gain a potential 25% data rate
increase for existing clients and only a “best-effort” basis for the highest data rate clients. This approach only provides
an incrementally faster (through 256 QAM) 802.11n-class network! Additionally, attempts to utilize the 80MHz wide channels will result in “airtime un-fairness” for these (potentially more expensive) 802.11ac devices.

The best way to realize the promise of 802.11ac higher data rates is to attack the CCI problem head-on. Meru has been doing this in our products from day one! A single channel architectural (SCA) approach must, by definition, manage interference in a consistent manner. The width (or size) of the channel is of little consequence; whether 20, 40, 80, or 160MHz wide, the Meru base architecture doesn’t change. Additionally, deploying an 80MHz network requires the same effort as deploying a 20MHz network – same level of simplicity. Meru’s approach also transparently supports 20MHz, 40MHz and 80MHz traffic under the same airtime fairness mechanism; there is no “best-effort” for Meru’s support of 80MHz (or 160MHz) wide channels.

Don’t design a network with smaller channel size just to work around a base architectural problem. Address the base problem and use the maximum channel size the standard allows to give ALL clients the maximum data rate experience. Meru will give you the best experience with 802.11ac.

1 http://revolutionwifi.blogspot.com/2013/03/safely-using-80-mhz-channels-with.html