Spectrum management is the technology used by virtualization architectures to manage the available wireless resources. Unlike radio resource management, which is focused on adjusting the available wireless resources on a per-access-point basis, to ensure that the clients of that access point receive reasonable service without regard to the neighbors, spectrum management takes a view of the entire unlicensed Wi-Fi spectrum within the network, and applies principles of capacity management to the network to organize and optimize the layout of channel layers. In many ways, spectrum management is radio resource management, applied to the virtualized spectrum, rather than individual radios.
Spectrum management focuses on determining which broad swaths of unlicensed spectrum are adequate for the network or for given applications within the network. One advantage of channel layering is that channels are freed from being used to avoid interference, and thus can be used to divide the spectrum up by purposes. Much as regulatory bodies, such as the FCC, divide up the entire radio spectrum by applications, setting aside one band for radio, another for television, some for wireless communications, and so on, administrators of virtualization architectures can use spectrum management to divide up the available channels into bands that maximize the mutual capacity between applications by separating out applications with the highest likely bandwidth needs onto separate channel layers.
The constraints of spectrum management are fairly simple. A deployment has only a given number of access points. The number and position of the access points limits the number of independent channel layers that can be provided over given areas of the wireless deployment area. It is not necessary for every channel layer to extend across the entire network—in fact, channel layers are often created more in places with higher traffic density, such as libraries or conference centers. The number of channel layers in a given area is called the network thickness. Spectrum management can detect the maximum number of channel layers that can be created given the current deployment of access points, and is then able to determine when to create multiple layers by spreading channel assignments of close access points, or when to maximize signal strength and SNR by setting close access points to the same channel. Thus, spectrum management can determine the appropriate thickness for each given square foot. For 802.1 In networks, spectrum management is able to work with channel widths, as well as band and channel allocations, and is thus able to make very clear decisions about doubling capacity by arranging channels as needed.
Spectrum management also applies the neighboring-interference-avoidance aspects that RRM uses to prevent adjacent networks from being deployed in the same spectrum, if it can at all be avoided. Because there is no per-channel performance compromise in compressing the thickness of the network, spectrum management can avoid some of the troublesome aspects of radio resource management when dealing with edge effects from multiple, independent networks. Furthermore, spectrum management is not required to react to transient interference, as the channel layering mechanism is already better suited to handle transient changes through RF redundancy. This allows spectrum management to reserve network reconfigurations for periods of less network usage and potential disruption (such as night), or to make changes at a deliberate pace that ensures network convergence throughout the process.
