In surveying cellular "coverage" over a geographic area, one could record any of several metrics, RSSI and practical bandwidth/throughput (e.g., Speedtest) among them. I understand that RSSI is poorly defined, but please assume an apples-to-apples measurement situation. The question is, all other things being equal, will reported RSSI depend on the total user load on the cellular system at that time and location? I've been told that -- again, all other things being equal -- reported RSSI will be lower if my mobile device is being allocated less bandwidth by the cellular system due to heavy user load (or for any other reason). This doesn't make sense to me as I thought RSSI was strictly an RF measure, independent of all logical/data considerations. Can someone clarify this?
RSSI is the total received power over the whole 5Mhz UMTS carrier (if you are talking about 3G). This power includes the power of the common channels (which can be configured), the dedicated channels which have power control and the HSDPA, and the same powers coming from adjacent cells.
RSSI depends on cell load, but it also depends on many other factors and practically it can't be used to assess the cell load.
The other factors which affect the RSSI value are:
- configured CPICH power
- path loss
- adjacent cells power
RSSI is RF measure which represents the received power. In 3G, power is related to capacity. If we have a cell with max power 20W and pilot channel of 2W then the rest of the power (18W) is for users. Each user takes small part of this power until it is all consumed.