Develop Reference

How to discover devices within a certain distance

As explained in the following thread:
How to find the devices in the range by using bluetooth?
An android app can get a list of devices in the range (bluetooth enabled)
My question is that if there is any way to limit the discovery range to a certain radius e.g. 1 meter?
Thanks,
Ben

You could use BluetoothDevice.EXTRA_RSSI to get the signal strength.
Nevertheless, it won't be very accurate because it's variable.
private final BroadcastReceiver receiver = new BroadcastReceiver(){
#Override
public void onReceive(Context context, Intent intent) {
String action = intent.getAction();
if(BluetoothDevice.ACTION_FOUND.equals(action)) {
short rssi = intent.getShortExtra(BluetoothDevice.EXTRA_RSSI, Short.MIN_VALUE);
System.out.println("RSSI: " + rssi + "dBm");
}
}
};
The value you obtain is in dBm. A really close device would have a rssi between around -20 dBm and -40 dBm depending of the device (built-in Bluetooth device, antenna, actual orientation of device). You can test the values you get to define an average 'dBm-range' for 1 meter. The closer the value is to 0, the stronger the received signal has been.

GSM RSSI and LTE RSSI and RSRP

I am looking to create an app that gets information about the phones connection to the cellular network.
My understanding is that RSSI is a measure of cellular signal with GSM and RSRP is a good measure for LTE.
To keep it consistent, is it possible to get a RSSI measure for LTE?
I am confused about what classes to use to get some of this information. At the moment, I am using the phone state listener which gives me a SignalStrength object. Using this object, I can call the two string method that provides me the following information when i split it. I am a little confused on what some of this means.
String ssignal = signalStrength.toString();
String[] parts = ssignal.split(" ");
The parts[] array will then contain these elements:
part[0] = "Signalstrength:" _ignore this, it's just the title_
parts[1] = GsmSignalStrength
parts[2] = GsmBitErrorRate
parts[3] = CdmaDbm
parts[4] = CdmaEcio
parts[5] = EvdoDbm
parts[6] = EvdoEcio
parts[7] = EvdoSnr
parts[8] = LteSignalStrength
parts[9] = LteRsrp
parts[10] = LteRsrq
parts[11] = LteRssnr
parts[12] = LteCqi
parts[13] = gsm|lte|cdma
parts[14] = _not really sure what this number is_
What is part 8 providing? RSSI?
Also, when you look at the signal strength in the android settings, it gives you the RSSI for GSM. When connected to LTE, is it giving us the RSRP or RSSI? It seems its providing RSRP.
My understanding is that part[1] provides the RSSI when connected on GSM. However, i am unsure, and interested about, part[2] (what is the rate measured against? what unit of time), part[8] (what does it measure exactly?), part[10] and part [11](what unit is it measured in and what is the unit range)
I understand this thread is all over the place. Hopefully it makes a little bit of sense and someone can clear something up.
Cheers guys!

To put it simply, RSSI and RSRP are signal level measurements for GSM and LTE, respectively. They are not exactly the same, because GSM and LTE are very different technologies. However, they both indicate the same type of information. RSRP holds no meaning in GSM and RSSI means something different in LTE.
This question may be worth reading:
How to get LTE signal strength in Android?
Most of what you are looking for, I was able to find here: https://developer.android.com/reference/packages.html
GsmSignalStrength - GSM Signal Strength, valid values are (0-31, 99) as defined in TS 27.007 8.5
GsmBitErrorRate - GSM bit error rate (0-7, 99) as defined in TS 27.007 8.5
CdmaDbm - CDMA RSSI value in dBm
CdmaEcio - CDMA Ec/Io value in dB*10
EvdoDbm - EVDO RSSI value in dBm
EvdoEcio - EVDO Ec/Io value in dB*10
EvdoSnr - Signal to noise ratio. Valid values are 0-8. 8 is the highest.
I could not locate the following, but here is what I suspect:
LteSignalStrength - LTE Signal Strength in ASU (0-31, 99)
LteRsrp - LTE RSRP value in dBm
LteRssnr - LTE SINR value in dB
LteCqi - LTE CQI (no units)
gsm|lte|cdma - Network type

Android MCC and MNC

I'm trying to get the mcc and mnc after a SIM LOADED state, in order to check if the SIM card did change without READ PHONE STATE permissions, in order to disable the app requests for some networks and in some countries that the user do not want.
Since getSimOperator() may change according to the current carrier (e.g. when the user is on roaming or not) I decided to use the getNetworkOperator().
Although this method can return null even if the SIM is LOADED and may return different results e.g. a lycamobile card with GSM only connection is giving me mnc = 01 and when I take the SIM card out and put it again it gives me mnc = 04.
Does some one know why the mnc gives different results for the getNetworkOperator()? Which method is better, getNetworkOperator() or getSimOperator() for this case?
Also, I cannot use getResources().getConfiguration().mcc because it gives a int number which might remove the 0 before e.g. gives 4 instead of 04.
This is my code to check a SIM state change:
#Override
public void onReceive(final Context context, Intent intent) {
if (intent != null) {
Bundle extras = intent.getExtras();
if (extras != null) {
String ss = extras.getString(EXTRAS_SIM_STATUS);
if (ss != null && (ss.equals("LOADED"))) {
TelephonyManager telephonyManager = ((TelephonyManager) context.getSystemService(Context.TELEPHONY_SERVICE));
if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M && hasPermissions(READ_PHONE_STATE)) {
//here I get the imsi
}else{
L.d("NetworkOperator result %s", telephonyManager.getNetworkOperator());
//saving in shared preferences in order to check if the sim is allowed or not
//this is also called on application onCreate() so I can check the current SIM
}
}
}
}
}
PS: the SIM card that I'm using only has GSM connection. Also I tried with an other card (with 4g capabilities) and everything works as expected the mnc is the same 01 for a vodafone card.

Let me share some information with you.. It may help.
MCC, MNC, PLMN
First, you must understand MCC and MNC:
MCC - Mobile Country Code
This is the country code. It always has 3 digits. Some countries can use more than one MCC.
MNC - Mobile Network Code
This is the network code. It can have 2 or 3 digits.
MCCMNC - PLMN Number.
Those numbers are used to differentiate one carrier from another one.
For example, you can check a list at www.mcc-mnc.com:
AT&T in US has following PLMN Number:
MCC = 310
MNC = 410
PLMN = 310410
Telefonica in Brazil, for example, has following PLMN Number:
MCC = 724
MNC = 10
PLMN = 72410
Based on the information above, we can imagine that we have PLMNs with 5 or 6 digits.
Since MNC can have 2 or 3 digits, I think you can retrieve the MNC number as follows (knowing that MCC always have 3 digits):
String plmn = "33402"; // OR 334020
String mcc = plmn.substring(0,3);
String mnc = plmn.substring(3,plmn.length());
System.out.println("plmn[" + plmn + "] mcc[" + mcc + "] mnc[" + mnc + "]");
All carriers in same country share the same MCC numbers. Some countries has more than one MCC... But even then, all carriers in that country uses one of that MCC.
So, if you want to check the location of some carrier, you must read its MCC (and never its MNC).
SIM and Network
One information stored in the simcard is that PLMN number. The PLMN number is retrieved from its IMSI. Its PLMN number are the 5 or 6 first digits of its IMSI.
This way, you can determine which carrier owns that SIMCard.
On the other rand, the network tower also broadcast its PLMN.
This way, an device can search for its HOME network every time you reboot you device (or move to another location).
HOME vs ROAMING
Home situation is when PLMN Number from the simcard is the same of the current registered network.
Roaming is when the SIMCard has a different PLMN than the registered cell.
Of course, some carriers has more than one PLMN Number and phone should be considered HOME in those situations. But this is another story.
Finally getSimOperator() and getNetworkOperator()
getSimOperator() This method returns MCCMNC (PLMN) from SIMCard
getNetworkOperator() This method returns MCCMNC (PLMN) from current camped Carrier
It is up to you
Now, you know the difference between simcard and network operator. So, you have to decide how to block/allow your app.
If you block by getSimOperator() you are blocking the simcards from a specific country. This way, regarless the registered cell, feature will remain blocked (even if the user is travelling to a country with the feature enabled).
If you block by getNetworkOperator() you are blocking the feature in specific networks/Contries. This way, if the user which can use the app, may have issues when he travells to a country where the feature is blocked.

How is telephony signal strength updated to UI in android

i went though the following post to get the signal strength in android:
How to get cell service signal strength in Android?
my ques is that: how does the signal strength gets updated to the system UI. what does each bar in the strength meter signify? is there a particular threshold value for each bar?

The signal strength icon is controlled from SystemUI. It might differ in other Android versions, but in KitKat the NetworkController.java class handles which icon is shown. The SignalStrength.java is the class that returns to NetworkController.java what the current signal strength is. The signal strength is represented as a number between 0 (no signal) and 4 (great signal). The actual signal is measured in dBm, and is passed into the SignalStrength.java class as a Parcel from the (low level) radio interface layer (RIL) of the Android framework. The actual thresholds differs between the different radio technologies used.

The getGsmLevel() function in SignalStrength.java does the trick here:
int level;
int asu = getGsmSignalStrength();
if (asu <= 2 || asu == 99) level = SIGNAL_STRENGTH_NONE_OR_UNKNOWN;
else if (asu >= 12) level = SIGNAL_STRENGTH_GREAT;
else if (asu >= 8) level = SIGNAL_STRENGTH_GOOD;
else if (asu >= 5) level = SIGNAL_STRENGTH_MODERATE;
else level = SIGNAL_STRENGTH_POOR;
this function returns the level

Visualize the wifi signal strength

I was able to scan all wifi networks with the wifimanager.getScanResults().
In the next step I extracted the SSID and signal level of the wifi network.
private List<String> showOnlySSIDAndLevel(List<ScanResult> networks) {
List<String> networkList = new ArrayList<String>();
for(ScanResult result : networks){
int level = WifiManager.calculateSignalLevel(result.level, 5) + 1;
String content = result.SSID + " \tSignal strength: " + level;
networkList.add(content);
}
return networkList;
}
I have the signal level in a format, where it's between 1 - 5 (5 is the best signal level)
How can I use this to have a graphical representation of the different wifi signal levels.
I coudn't find a UI for this. Do I need a graphic for each of the 5 possible level or is there another way? How is the internal Android Settings (Wifi scan results) doing it?

I think found a better option ...
imageView.setIcon(android.R.drawable.stat_sys_wifi_signal_<strength>)
where strength is a variable in the range of 0 to 4...
For more details refer to
http://androiddrawableexplorer.appspot.com/

You can use the built-in RatingBar component. You can make it read-only by giving it a ratingBarStyleSmall or ratingBarStyleIndicator style.