Architecture NamingBy CWNP On 12/28/2007 - 11 Comments
There are two distinct types of architectures in today's WLAN infrastructures. Each goes by several different names. Today's WLAN newcomers can be easily confused by having several names for the same thing as well as trying to understand the nuance between each vendor's implementation. I'd like to clarify some common terminolgy.
First, we need some plain old definitions:
Single Channel Architecture (SCA) – A WLAN architecture where uplink and downlink transmissions are coordinated by a WLAN Controller on a single 802.11 channel in such a manner that the effects of co-channel and adjacent channel interference are minimized.
Multiple Channel Architecture (MCA) – A WLAN architecture where three or more channels are used in a tiled pattern within a frequency band (2.4 or 5 GHz) for the purpose of minimizing co-channel and adjacent channel interference. This is often referred to as “channel reuse” or “micro-cell” architecture.
Channel Stacking / Channel Spanning / Channel Blankets™– When a Single Channel Architecture (SCA) is used, WLANs may be co-located in the same physical area on different 802.11 channels for the purpose of high-density / high-capacity client deployments. Scalability is accomplished through adding additional coordinated channels in the same physical space.
Virtual BSSID / Virtual Cell – When 2 or more access points coordinated by a WLAN Controller appear to be the same access point (have the same BSSID).
These names are some that we made up and some that we borrowed from vendor partners. These definitions are our own and are likely missing some of the discriptive marketing language that you would expect from vendors trying to sell their warez. They are not considered perfect, but are generally accepted as accurate.
There are currently only two manufacturers who make SCA equipment: Meru Networks and Extricom. Both OEM to other vendors (e.g. Meru > Foundry and Extricom > Belden). With SCA equipment, scalability comes as a result of stacking/spanning/blanketing multiple channels in the same physical area by using one or more APs rather than reusing channels in a tiling pattern like MCA does. MCA is where the market has been for a number of years; deploying APs on different channels in a tile-like pattern to avoid as much co-channel and adjacent channel interference as possible.
"Which is better?" is an on-going industry debate that is often more volatile than discussing politics or religion.
There are other architectures on the market, but these two are currently the most dominent. Others include: Arrays (i.e. Xirrus), Cooperative Control (Aerohive), and Mesh (Firetide, Tropos, Strix, etc). Some vendors support multiple architectures. For example, Cisco, Aruba, Motorola, Colubris, Trapeze, and Bluesocket all support MCA and Mesh. Meru supports SCA and Mesh.
More or less, there's an architecture for every occassion, but within the more dominent architectures (MCA and SCA), we thought it important to sort out some details.