I am unable to retrieve the signal strength of a 3G (Wcdma) connection using telephonyManager.requestCellInfoUpdate() :

   private fun getSignal(context: Context) {
        if (context.checkSelfPermission(Manifest.permission.ACCESS_FINE_LOCATION) == PackageManager.PERMISSION_DENIED
            || context.checkSelfPermission(Manifest.permission.READ_PHONE_STATE) == PackageManager.PERMISSION_DENIED) return

        telephonyManager.requestCellInfoUpdate(context.mainExecutor, object : TelephonyManager.CellInfoCallback() {
            override fun onCellInfo(cellInfos: List<CellInfo>) {
                for (cellInfo in cellInfos)
                    if (cellInfo.isRegistered) {
                        when (cellInfo) {
                            is CellInfoWcdma -> {
                                Log.i("LOG", cellInfo.cellSignalStrength.toString())
                            }
                        }

                        return
                    }
            }
        })
    }

The returned value is always -24 :

-24 (CellSignalStrengthWcdma: ss=-105 ber=99 rscp=-24 ecno=0 level=1)

Digging into the source code I found that getDbm() actually returns the mRscp when it is valid (which is the case), the problem is that it is never updated when called from telephonyManager.requestCellInfoUpdate() :

public int getDbm() {
    if (mRscp != CellInfo.UNAVAILABLE) return mRscp;
    return mRssi;
}

Strangely, the signal strength returned by telephonyManager.signalStrength.cellSignalStrengths[0].dbm is working fine (something like -99), but it has a latency of up to 10 seconds, which is too high for my intended use.