Den där artikeln lade jag upp en gång men det finns ett fel i den.
Actually, for RSSI and RSRP, you don't count carriers but Resource blocks. At 20 MHz bandwidth, there are 100 resource blocks but 600 carriers. Ten times 10 log100 is 20, which is the figure you use for 2600. At 10 MHz bandwidth, as it is used in Europe on 800 and 900 LTE, you count 50 resource blocks, which gives 10x1,79=17,9.
See more
http://www.jdsu.com/ProductLiterature/l … _tm_ae.pdf
With 5MHz bandwidth, you arrive at about 14.
So the way to do it is to resolve the bandwidth in kHz with AT command LTESCINFO. If you get 5000 KHz, BI is 14, for 10000 it is about 18 and for 20000 it is 20.
RSRQ is RSRP + RSSI - BI, where BI is the bandwidth index as given above (there is no official denomination afaik of this index). It is easier to calculate with positive (absolute) figures. Example: 110 (RSRP) -80 (RSSI) -20 (BI for 20000 kHz at 2600) = 10 (RSRQ). Just remember that the result is negative, -10 dB. RSRQ can not be positive, because in that case, a subdivision of the whole bandwidth would be stronger than the compounded signal. Actually, RSRQ can not be better than -3 dB and if you have a non disturbed and interference free signal, you end up with something like -5 or -6 dB.
In the Sprint example, bandwidth is 5MHz and BI is about 14 (ten times 10log 25). Not 20 as the article states
LTE testare på 4G 2600, 1800, 900, 800 med Fritzbox AVM 6890, AVM6840, AVM6842, AVM 6820 och AVM 7590/7490/7390 samt diverse mifis från ZTE och Netgear. Några huaweimodem på hyllan.