this is the header file

#import <CoreTelephony/CTTelephonyNetworkInfo.h>

code

CTTelephonyNetworkInfo *telephonyInfo = [CTTelephonyNetworkInfo new];
    NSLog(@"Current Radio Access Technology: %@", telephonyInfo.currentRadioAccessTechnology);
    [NSNotificationCenter.defaultCenter addObserverForName:CTRadioAccessTechnologyDidChangeNotification
                                                    object:nil
                                                     queue:nil
                                                usingBlock:^(NSNotification *note) {
        NSLog(@"New Radio Access Technology: %@", telephonyInfo.currentRadioAccessTechnology);
    }];

this fast function

- (BOOL)isFast:(NSString*)radioAccessTechnology {
    if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyGPRS]) {
        return NO;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyEdge]) {
        return NO;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyWCDMA]) {
        return YES;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyHSDPA]) {
        return YES;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyHSUPA]) {
        return YES;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMA1x]) {
        return NO;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORev0]) {
        return YES;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORevA]) {
        return YES;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyCDMAEVDORevB]) {
        return YES;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyeHRPD]) {
        return YES;
    } else if ([radioAccessTechnology isEqualToString:CTRadioAccessTechnologyLTE]) {
        return YES;
    }
    
    return YES;
}

after ios7

2G

CTRadioAccessTechnologyGPRS 
CTRadioAccessTechnologyEdge

3G

CTRadioAccessTechnologyWCDMA 
CTRadioAccessTechnologyHSDPA  
CTRadioAccessTechnologyHSUPA
CTRadioAccessTechnologyCDMA1x
CTRadioAccessTechnologyCDMAEVDORev0
CTRadioAccessTechnologyCDMAEVDORevA 
CTRadioAccessTechnologyCDMAEVDORevB
CTRadioAccessTechnologyeHRPD

4G

CTRadioAccessTechnologyLTE