Reference Signal Received Quality or with abbreviated version RSRQ is quality of the received signal. Here the “received signal” is reference signal (RSRP). But, how do we see the RSRQ value as negative in drive-test tools and why do we need RSRQ ?
RSRQ value might be used for some scenarios such as cell selection, cell reselection and handover. Regarding to the negative value of RSRQ, then let’s have a look following basic calculation:
In this example we will see theoretical calculation of RSRQ:
RSRQ = (N * RSRP) / RSSI
RSSI = Received Signal Strength Indication: total received power in the certain bandwidth including traffic channel power, control channel power, thermal noise and etc…
RSRP (Rx) = Reference Signal Received Power: average received power of reference signal which is carried on Resource Element (RE).
N: number of PRB in certain bandwidth (e.g. 100 PRB and 1200 subcarriers are exist in 20Mhz).
e.g.
Bandwidth: 20 MHz
PRB: 100
RRU Power: 20 W = 20000 mW (milliWatt)
Subcarriers: 1200
Power in each subcarrier: 20000mW / 1200 = 16.66mW (milliWatt)
Based on calculation, transmission power for each Resource Element is 16.66mW. Let’s assume that all RE powers are same like Rx Power (RSRP).
Then
RSRQ = (N * RSRP) / RSSI = (100 * 16.66) / (1200 * 16.66) = 1/12 = 0.083 mW
Conversion to dB
RSRQ = 0.083mWatt = 10*log(0.083) ≈ −10.8 dB
* In this calculation Antenna Gain, Feeder Loss, Path Loss was not taken into account, you can refer to RSRP tag for details.
Good Afternoon.
Need some answers i think you might be the right person to ask. We have something called iris on our machines. Which they use sim cards and we are using AT&T network. Getting asked to check the signal strength in the shop.
I was wondering in your opinion what would you consider good signal strength. Now looking at the RSRP i am averaging around 85 to 105 depending where i am at in the shop. Which appears to be good to fair depending on which website you look at. RSSI also appears to be between the good and fair as well. But the RSRQ is high from -12 to -17. Does that make a difference. Would that cause problems in activating anything?
Thanks
Dave
Dear David,
There might be different reasons such as network load or inappropriate RS power settings.
I am suggesting you to check SINR or CINR (you can consider it as same with little difference) value. If this measurement is also not good (less than 2-3) then following items should be checked:
– Interference
– Hardware Issue (Receiver and Transmitter)
– Network Load