Following code will help in you to check the network availability for 3G and 4G connection

const char *host_name = "google.com";
    BOOL _isDataSourceAvailable = NO;
    Boolean success;

    //Creates a reachability reference to the specified
    //network host or node name.
    SCNetworkReachabilityRef reachability =
    SCNetworkReachabilityCreateWithName(NULL,host_name);

    //Determines if the specified network target is reachable
    //using the current network configuration.
    SCNetworkReachabilityFlags flags;

    success = SCNetworkReachabilityGetFlags(reachability, &flags);
    _isDataSourceAvailable = success &&
    (flags & kSCNetworkFlagsReachable) &&
    !(flags & kSCNetworkFlagsConnectionRequired);

    CFRelease(reachability);
    return _isDataSourceAvailable;