All values in the Channels Table are recalculated every time a new sweep of Wi-Spy data enters or leaves the Current Time Window (CTW) and with the exception of the the Current(dBm) value, these values are based on a collection of sweeps defined by that CTW.
The NoiseFloor calculation utilizes the following information that is derived and refreshed every time the collection in the CTW changes. The following example is based on a 2.4 Ghz Full Band sweep using a Wi-Spy DBx3
In this configuration, the following parameters apply:
- 286 FrequencyPoints of 333000 Hz each
- StartFrequency = 2400000 Khz
- StopFrequency = 2495238 Khz
- RSSI values for each FrequencyPoint range from -134.0 dBm to 6.5 dBm in 0.5 dBm increments
Before calculating individual channel numbers, the AverageRSSI is calculated for each FrequencyPoint over the CTW. This averaging of RSSI values tends to weigh heavily toward the noiseFloor because of the logarithmic scaling of dBm.
Then, for each channel in view, the number of FrequencyPoints in the channel is walked for that channel.
For instance, for the 2.4Ghz Full Band using a DBx, each channel (1-14) has 66 FrequencyPoints based on 22Mhz/Channel and 0.333 Mhz/FrequencyPoint. The NoiseFloor value for each channel is the simple average of AverageRSSI values over the 66 FrequencyPoints.
In summary, the value that we calculate for Noise Floor is the simple average of the RSSI values. So, for each sweep we average all of the RSSI values for that particular frequency point over the number of sweeps in the data window. Then we take that average for each of the average of all of the frequency points in the channel to derive the number.... An average of averages.