How is ASU calculated?

[mikejeep]

I have been trying to educate myself about "asu" as it relates to signal strength.. it appears that that GSM and LTE use different calculations for asu, and the few formulas I have found are consistent with each other. However, none of the sites I found were terribly reliable.. and SignalCheck is pulling far different values directly from some LTE devices.  GSM data appears to be correct though.

 

Here are the formulas that I am trying to confirm are accurate:

 

GSM

ASU = (RSSI + 113) / 2

[valid ASU is in the range of 0-31; 99 = unknown]

 

LTE

ASU = RSRP + 140

[valid ASU is in the range of 0-97; 99 = unknown]

 

Now here are conflicting examples on LTE connections that I have seen recently:

 

Samsung Galaxy Victory

-93 dBm, 2 asu (status screen) [should be 47 asu?] **EDIT: Its showing the 1X RSSI. Huh.

-116 dBm, 11 asu (SignalCheck) [should be 24 asu based on formula above?]

 

Nexus 7 2013

-106 dBm, 34 asu (status screen) [appears correct?]

-105 dBm, 17 asu (SignalCheck) [should be 35 asu?]

 

EVO 4G LTE

-108 dBm, 13 asu [should be 32 asu?] (SignalCheck)

-112 dBm, 13 asu [should be 28 asu?] (SignalCheck)

-117 dBm, 10 asu [should be 23 asu?] (SignalCheck)

 

I am guessing that because GSM has been around longer than LTE, any bugs in those calculations have long since been ironed out, so there aren't any conflicts with those numbers.  It looks like the SignalCheck LTE ASU values are roughly halved, perhaps as a result of a blend of the GSM equation with the LTE one.  Hard to go with that theory until I can confirm that the equations I found are correct though.

 

-Mike

[ansars]

Mike,

 

I was also wondering about asu and rssi/rsrp. I have a sprint galaxy S3. I have actually noticed the asu number change even when then rsrp (as being reported by SignalCheck Pro) is steady. My phone is sitting right next to the window, and currently LTE is at RSRP of -103. However, the asu has been moving between 18 and 21 asu. According to the formula above asu should be at 37?

 

Not sure if the 21 was an aberration, but seems like for the last few minutes, RSRP is between -102 and -103 and ASU is between 18 and 19, although the 18 and 19 numbers occur at -102 as well as at -103.  

 

The RSRP now dropped to -96 and asu is at 20.

 

Salman

[WiWavelength]

I think ASU calculates on the Pac-12 refs making a big mistake in order to secure the win.

 

 

AJ

[koiulpoi]

So, perhaps ASU is an amalgamation of both RSSI/RSRP and SNR? So it's basically a copy of the "bars".

[mikejeep]

I think ASU calculates on the Pac-12 refs making a big mistake in order to secure the win.

 

 

AJ

 

Don't quit your day job.

 

 

 

 

-Mike

 

P.S. I know you must know the truth behind ASU.. you know everything.. spill it!

[WiWavelength]

Don't quit your day job.

Yes, I believe that is what the Pac-12 told the officiating crew after they worked the recent ASU game.

 

P.S. I know you must know the truth behind ASU.. you know everything.. spill it!

I suppose I should, but honestly, I do not care. RSSI, Ec/Io, SINR, RSRP, and RSRQ are more than enough for me.

 

One thing to add to this thread, though, is a brief definition of "ASU" for the uninformed. If I recall correctly, the acronym stands for Absolute Signal Units.  That runs in contrast to most/all other signal metrics, which are relative measurements.

 

Basically, it boils down to the difference between having your audio preamp or receiver display 0 dB vs 100 as the highest volume setting.

 

AJ

[afazel]

Yes, I believe that is what the Pac-12 told the officiating crew after they worked the recent ASU game.

 

I suppose I should, but honestly, I do not care. RSSI, Ec/Io, SINR, RSRP, and RSRQ are more than enough for me.

 

One thing to add to this thread, though, is a brief definition of "ASU" for the uninformed. If I recall correctly, the acronym stands for Absolute Signal Units.  That runs in contrast to most/all other signal metrics, which are relative measurements.

 

Basically, it boils down to the difference between having your audio preamp or receiver display 0 dB vs 100 as the highest volume setting.

 

AJ

 

Huh. I thought it had something to do with signal attenuation.

[koiulpoi]

One thing to add to this thread, though, is a brief definition of "ASU" for the uninformed. If I recall correctly, the acronym stands for Absolute Signal Units.

Really? I always figured it was "arbitrary signal unit"

[WiWavelength]

Really? I always figured it was "arbitrary signal unit"

 

It may be.  But it is also an absolute scale.  Certain kinds of minds prefer an absolute scale to a relative scale.

 

http://www.youtube.com/watch?v=NrVCjnRdB_k

 

AJ