RSRQ measurement in LTE

[rmahant]

TS 36.133 in section 9.1.7 states the RSRQ range to be between -19.5 to -3 dB...However field measurements indicate otherwise, for eg.

From field:
RSSI = -79 dBm RSRP = -93 dBm

Using RSRQ = #ofRB in BW * (RSRP/RSSI) we have for 10 Mhz BW:
RSRQ = 10*log(50) + (-93+79) = 17 dB + -14 = 3dB which is what my field result displays for RSRQ...

I'm confused as to the statement in TS 36.133 and my measured value of RSRQ??

What also confuses me is EPRE for Reference Signal is 1/600 of the power allocated to the whole BW (assuming a 10 Mhz channel with 600 subcarriers) - so is it not prudent to state that the measured RSRP should be 1/600 of the RSSI?

[ykhaled]

TS 36.133 in section 9.1.7 states the RSRQ range to be between -19.5 to -3 dB...However field measurements indicate otherwise, for eg.

From field:
RSSI = -79 dBm RSRP = -93 dBm

Using RSRQ = #ofRB in BW * (RSRP/RSSI) we have for 10 Mhz BW:
RSRQ = 10*log(50) + (-93+79) = 17 dB + -14 = 3dB which is what my field result displays for RSRQ...

I'm confused as to the statement in TS 36.133 and my measured value of RSRQ??

What also confuses me is EPRE for Reference Signal is 1/600 of the power allocated to the whole BW (assuming a 10 Mhz channel with 600 subcarriers) - so is it not prudent to state that the measured RSRP should be 1/600 of the RSSI?

Hi,
Your RSRP seems a bit too high so check your measurements settings.
RSRP would be something like: [EIRP/(REs) - Prop losses]
REs = 600 for 10MHz as you noted, unless you have RSRP boost

RSSI is the total power seen in 10 MHz bandwidth seems fine.

Let me know your findings

[ykhaled]

Also, I would like to raise another issue ifsomeone can help:
I cant re-produce the -3dB, I don't understand how they came out with this number. I made my own derivation:
RSRQ = N RSRP/RSSI
Best RSSI over one resource block would be 4 x RSRP, No data transmission and no thermal noise or interference. 4 is the number of Resource elements carrying reference symbols.
Hence,
RSRQ = N x [RSRP]/[RSRP x 4 x N] = 4 = -6 dB :|
Many references write whole paragraphs and concluding -3dB but no one put it down in an equation. They seem to copy it from 3GPP.

[wahaha]

Hi, recently i have performed LTE static test and found out that RSRQ reading can exceed -3dB from the UE visualization tool... The reading obtain is RSRP = -55dBm, RSRQ = 10dB.... i still pending relevant party explanation on this.....

If you have more info or explanation, please share it :)

[ykhaled]

Hi, recently i have performed LTE static test and found out that RSRQ reading can exceed -3dB from the UE visualization tool... The reading obtain is RSRP = -55dBm, RSRQ = 10dB.... i still pending relevant party explanation on this.....

If you have more info or explanation, please share it :)

I heard that its possible to selectively boost the REs transmitting RS. That can maximize N x RSRP. But 10dB is un-realistic. I thinks thats SINR what you have. N x RSRP is a portion of RSSI so its strictly negative. RSSI measurements might be invalid and not taking the whole spectrum. If you can share settings/setup measurements I would be grateful.
If you ignore the time domain scheduling and think about it in FDM; the eNodeB spectrum would look like this:
|F1|RSRP|F2|F3|RSRP|F3|F4|F5|

RSRQ = N*RSRP/N*[F1+F2+F3+2RSRP+F4+F5+others]

Spectrum analyzer can measure RSSI simply by tuning it to the centre frequency and settings the bandwidth accordingly.
One possible reason is that the LTE receiver's bandwidth is operating at a narrower bandwidth and hence rejecting some frequencies and their corresponding power. This is contributing for lower RSSI while RSRP is un-affected because its an average value of a typical reference symbol received on R0.