The Country Information element is shown below
Fig Courtesy 802.11-2012 standard
where dot11OperatingClassesRequired is true and the First Channel Number/Operating Extension Identifier octet has a positive integer value of 201 or greater, then that triplet comprises the Operating Extension Identifier, Operating Class, and Coverage Class fields
- Operating Extension Identifier – indicates whether the Sub-band triplet contains Operating class/coverage class or not. A value of 201 or greater indicates the next two fields as operating class and coverage class
- Operating class is a set of rules that defines a set of channels , channel starting frequency, channel spacing and any specific behavior limits for the channels of that class. A couple of examples for US operating classes from the standard is shown below
Fig Courtesy: 802.11-2012 standard
- The above table is interpreted as below
- Operating class 1 in the US is mapped to global operating class 115 and so on
- Channel starting frequency – 5 GHz
- Each channel has a channel width of 20 MHz
- Channel set defines the different channels supported in each class
- Behaviour limit describes that operating class 2 are constrained according to Dynamic Frequency Selection rules and class 3 has nomadic behaviour (rules change as the device moves). <refer Annexure D in 802.11-2012 standard>
- The coverage class determines what distance each operating class covers. The information determines the BSS coverage area and at what distances the Access Points need to be placed (installed)
- A coverage class is shown below with a diagram for <1 uS air propagation time
Fig Courtesy 802.11-2012 standard
As an example, consider the above – if the air propagation time is < 1us, then the distance travelled by the WLAN signal is given by
- Distance = air propagation time X speed of light, where speed of light = 300000 km/s (approximate)
- so the distance covered for the above case will be
- Distance = 1 uS x 300000 = 300 meters
Hence, the distance calculation for the above 3 examples of coverage class is given by
| Coverage class field | aAirPropagation time (uS) | Distance in Miles | Distance in Kilometres |
| 1 | <= 1 | 0.186 | 0.300 |
| 2 | 3 | 0.538 | 0.900 |
| 3 | 6 | 1.120 | 1.800 |
The coverage class thus gives the BSS coverage details and also informs at what distances Access Points need to be installed for seamless connectivity