CODEWITHSUNDEEP
android
publicknowledge
publicknowledge

Reputation: 644

Android how to get SNR (Signal to Noise Ratio)

I was wondering if anyone knew how to programmatically get the SNR or signal to noise ratio of LTE/WCDMA signals in Android phones. The SNR can be viewed from a secret code *#0011# in Samsung models but not in other phones such as Nexus 5. I was thinking if there isn't an actual API, maybe a calculation from existing APIs?

I know for a fact you can get detailed information on signals with the SignalStrength API but I've parsed the parts I saw and can't seem to find any SNR readings.

Any help or suggestions is greatly appreciated!

Thanks!

Additional Information:

I should add that I've been tinkering around with Signal Strength from this thread [link] How to get LTE signal strength in Android? and so that's my starting point for my question.

My results are for the following are:

LteSignalStrength -> fluctuates between around 15-30 depending on location, no idea what this is..

LteRsrp -> shows the dBm, I guess this is how phones determine signal quality (roughly anyway).

LteRsrq -> shows -7 to -11, not sure

LteRssnr -> always 300 for some reason, no idea why...

LteCqi -> Channel Quality Indicator? some huge number that seems to be the max 32-bit integer value, not sure

Is there a way to get to SNR from this API or am I looking for a nonexistent needle in a haystack?

Screenshot of Samsung GalaxyNote2 with SNR reading from *#0011# secret code: enter image description here

Upvotes: 9

Views: 16239

Answers (2)

noam
noam

Reputation: 124

I use the following to get the SNR:

public class PhoneStateListener extends android.telephony.PhoneStateListener
{
    @Override
    public void onSignalStrengthsChanged(SignalStrength signalStrength)
    {
        double snr = (double) SignalStrength.class.getMethod("getLteRssnr").invoke(signalStrength)/10D;
    }
}

You just need to register for signal events:

TelephonyManager mTelephonyManager = (TelephonyManager) getSystemService(TELEPHONY_SERVICE);
PhoneStateListener mPhoneStateListener = new PhoneStateListener();
mTelephonyManager.listen(mPhoneStateListener, PhoneStateListener.LISTEN_SIGNAL_STRENGTHS);

Upvotes: 3

Marcelo
Marcelo

Reputation: 2095

I'm researching this subject intensively since Aug-2014. Firstly, I hope that you're familiar with some telecom knowledge and Android Open Source Project (AOSP). Well, based on my researches, I state that:

  1. By looking at AOSP internal native classes, it seems that Android gives SignalStrength values by parceling returned values from AT+CSQ command (please, check AOSP native class reference-ril.c) over the modem. And only from it. The problem is that this command only gives the signal quality coupled with block error rate (BLER), and do not inform anything about other incoming signals; In LTE modem it seems to be OK in some devices, but when you change to UMTS network, things become unclear/inconsistent;
  2. You may calculate incoming interference (SNR and others) by using some derivations from telecom formulas (relating RSSI, RSCP, EcNo, and so on...) by yourself with received signal strengths from other cells, or with the AT+CGREG and AT+CREG (again, please check reference-ril.c class).;
  3. I digged all AOSP internal classes, tracing and diagraming method calls related with telephony. I've looked all from the SDK layer (where we use TelephonyManager and PhoneStateListener API classes), over to the native radio interface layers classes written in c/c++. In any moment I have found a SNQ calculation truly based in other cells, but only passed as a value obtained from the modem with AT+CSQ (this command gives only signal quality and BLER). It sounds strange for me, because interference is a value calculated with other received signals, inclusively those ones that are not from GSM. So, for me, the incoming SNR got from Android API is somewhat lame or incomplete.

Based on the above, I suppose that:

  1. Google is not 3GPP. And 3GPP is not Google. Android is a huge and complex project with more than 12 million lines of code. It is very plausible that communication/theoretical informations may be missed among Android and telecom;
  2. In particular I'm searching for CQI, and I suspect that CQI is in the context of LQR (Link Quality Report), calculated in the L2 PPP (Point-to-Point Protocol);
  3. The subject of this thread is really problematic. There will be no holy grail, because different devices owns different (maybe closed) hardware drivers. We'll need to support different softwares for each different device. Maybe, you'll need to recompile an entire Android ROM for each device, if you need to have a correct value for all device.

I hope that it brings some light to you. If you have any additional information, please share it here.

Upvotes: 12

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