Infrastructure Architectures | Basics of Wi-Fi

Because an access point cannot cover an entire building, Wi-Fi mobility networks require the concept of an infrastructure. The wireless infrastructure takes into account the entire set of access points, and whatever management tools are used.

Because large campuses can have thousands of access points, there is a natural tendency for these access points to be deployed at the same time, and often to be from one vendor. The different styles of architectures reflect the different vendors' approaches to creating a network that provides the necessary functions. The ways in which wireless architectures are described often varies from source to source and from time to time. Here, we will lay out the common terms and explain how they relate to the different architectures.

There are two different ways to look at the different architectures. One way is to focus on how the wireline architecture of the wireless network is structured. It may seem odd to look at how wireless architectures work over the wire, and it is, but, for historical reasons, this is still a common framework. The wireline categorizations look as follows:

• Standalone
• Controller-based
• Controllerless
• Directly connected

The second way is to focus on the over-the-air behavior of the network. This breaks down as follows:

• Static Microcell
• Dynamic or Adaptive Microcell
• Layered
• Virtualized

We'll explore all categories. Keep in mind that some wireline categories currently only exist with certain over-the-air categories, and that will be pointed out when appropriate.

Table 1 lists many of the vendors, both major and minor, and what architectures are possible, as of the time of writing, with each.

Table 1: Selection of vendors and architectures 

Vendor	Wireline Architecture	Over-the-Air Architecture
Aerohive	Controllerless	Dynamic Microcell
Aruba Networks	Controller	Dynamic Microcell
Belden/Trapeze	Controller	Dynamic Microcell
Cisco Systems	Standalone (IOS),	Static Microcell,
	Controller (LWAPP/CAPWAP)	Dynamic Microcell
Extricom	Directly Connected	Layered
Hewlett-Packard/Colubris	Controller	Dynamic Microcell
Meru Networks	Controller	Layered, Virtualized
Motorola/Symbol	Controller	Dynamic Microcell
Xirrus	Standalone	Static Microcell, Dynamic
		Microcell

Before we get too far into this discussion, I should take a moment to reveal my own biases. Having been one of the inventors of two of the architectures embraced by the industry(layered and virtualized) and being heavily involved in the various standards bodies for the industry and having authored or contributed to a number of the techniques necessary for voice over Wi-Fi, I have a strong interest in certain problems in wireless that may have a solution in the techniques I helped create. But I mention those problems and solutions in sincere belief that the problems of voice mobility that you may experience, and of wireless networking in general, can be solved. In any event, I will not pull any punches, and will address strategies for every architecture you may happen to run across in modern networks.