Is there a way to detect which cellular network is used on Android?

Here is a Gist of the class, so you can fork it and edited it.

package com.emil.android.util;

import android.content.Context;
import android.net.ConnectivityManager;
import android.net.NetworkInfo;
import android.telephony.TelephonyManager;

/**
 * Check device's network connectivity and speed 
 * @author emil http://stackoverflow.com/users/220710/emil
 *
 */
public class Connectivity {

    /**
     * Get the network info
     * @param context
     * @return
     */
    public static NetworkInfo getNetworkInfo(Context context){
        ConnectivityManager cm = (ConnectivityManager) context.getSystemService(Context.CONNECTIVITY_SERVICE);
        return cm.getActiveNetworkInfo();
    }

    /**
     * Check if there is any connectivity
     * @param context
     * @return
     */
    public static boolean isConnected(Context context){
        NetworkInfo info = Connectivity.getNetworkInfo(context);
        return (info != null && info.isConnected());
    }

    /**
     * Check if there is any connectivity to a Wifi network
     * @param context
     * @param type
     * @return
     */
    public static boolean isConnectedWifi(Context context){
        NetworkInfo info = Connectivity.getNetworkInfo(context);
        return (info != null && info.isConnected() && info.getType() == ConnectivityManager.TYPE_WIFI);
    }

    /**
     * Check if there is any connectivity to a mobile network
     * @param context
     * @param type
     * @return
     */
    public static boolean isConnectedMobile(Context context){
        NetworkInfo info = Connectivity.getNetworkInfo(context);
        return (info != null && info.isConnected() && info.getType() == ConnectivityManager.TYPE_MOBILE);
    }

    /**
     * Check if there is fast connectivity
     * @param context
     * @return
     */
    public static boolean isConnectedFast(Context context){
        NetworkInfo info = Connectivity.getNetworkInfo(context);
        return (info != null && info.isConnected() && Connectivity.isConnectionFast(info.getType(),info.getSubtype()));
    }

    /**
     * Check if the connection is fast
     * @param type
     * @param subType
     * @return
     */
    public static boolean isConnectionFast(int type, int subType){
        if(type==ConnectivityManager.TYPE_WIFI){
            return true;
        }else if(type==ConnectivityManager.TYPE_MOBILE){
            switch(subType){
            case TelephonyManager.NETWORK_TYPE_1xRTT:
                return false; // ~ 50-100 kbps
            case TelephonyManager.NETWORK_TYPE_CDMA:
                return false; // ~ 14-64 kbps
            case TelephonyManager.NETWORK_TYPE_EDGE:
                return false; // ~ 50-100 kbps
            case TelephonyManager.NETWORK_TYPE_EVDO_0:
                return true; // ~ 400-1000 kbps
            case TelephonyManager.NETWORK_TYPE_EVDO_A:
                return true; // ~ 600-1400 kbps
            case TelephonyManager.NETWORK_TYPE_GPRS:
                return false; // ~ 100 kbps
            case TelephonyManager.NETWORK_TYPE_HSDPA:
                return true; // ~ 2-14 Mbps
            case TelephonyManager.NETWORK_TYPE_HSPA:
                return true; // ~ 700-1700 kbps
            case TelephonyManager.NETWORK_TYPE_HSUPA:
                return true; // ~ 1-23 Mbps
            case TelephonyManager.NETWORK_TYPE_UMTS:
                return true; // ~ 400-7000 kbps
            /*
             * Above API level 7, make sure to set android:targetSdkVersion 
             * to appropriate level to use these
             */
            case TelephonyManager.NETWORK_TYPE_EHRPD: // API level 11 
                return true; // ~ 1-2 Mbps
            case TelephonyManager.NETWORK_TYPE_EVDO_B: // API level 9
                return true; // ~ 5 Mbps
            case TelephonyManager.NETWORK_TYPE_HSPAP: // API level 13
                return true; // ~ 10-20 Mbps
            case TelephonyManager.NETWORK_TYPE_IDEN: // API level 8
                return false; // ~25 kbps 
            case TelephonyManager.NETWORK_TYPE_LTE: // API level 11
                return true; // ~ 10+ Mbps
            // Unknown
            case TelephonyManager.NETWORK_TYPE_UNKNOWN:
            default:
                return false;
            }
        }else{
            return false;
        }
    }

}

Also make sure to add this permission to you AndroidManifest.xml

<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE"></uses-permission>

For all less than or equal to 100kbps speed, the network is considered to be as 2G.

For all greater than 100kbps & less than 1mbps speed, the network is considered to be as 3G.

And for all greater than 1mbps speed, the network is considered to be as 4G.

Sources for network speeds include wikipedia http://en.wikipedia.org/wiki/Comparison_of_wireless_data_standards