Timer in background mode

Question

As we know there are some limitations for applications which running in background mode.For example, the NSTimer doesn't work. I tried to write a "Timer" like this which can work in background mode.

-(UIBackgroundTaskIdentifier)startTimerWithInterval:(NSTimeInterval)interval run:(void (^)())runBlock complete:(void (^)())completeBlock
{
    NSTimeInterval delay_in_seconds = interval;
    dispatch_time_t delay = dispatch_time(DISPATCH_TIME_NOW, delay_in_seconds * NSEC_PER_SEC);
    dispatch_queue_t queue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    // ensure the app stays awake long enough to complete the task when switching apps
    UIBackgroundTaskIdentifier taskIdentifier = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{

        completeBlock();

    }];

    NSLog(@"remain task time = %f,taskId = %d",[UIApplication sharedApplication].backgroundTimeRemaining,taskIdentifier);

    dispatch_after(delay, queue, ^{
        // perform your background tasks here. It's a block, so variables available in the calling method can be referenced here.
        runBlock();

        // now dispatch a new block on the main thread, to update our UI
        dispatch_async(dispatch_get_main_queue(), ^{

            completeBlock();
            [[UIApplication sharedApplication] endBackgroundTask:taskIdentifier];
        });
    });

    return taskIdentifier;

}

I called this function like this:

-(void)fire
{
    self.taskIdentifier = [self startTimerWithInterval:10
                                                   run:^{
                                                           NSLog(@"timer!");
                                                           [self fire];
                                                   }
                                              complete:^{

                                                  NSLog(@"Finished");

                                              }];

}

This timer works perfect except that there is one problem. The longest period for background task is 10 minute.(Please refer to the NSLog in startTimerWithInterval).

If there any way to make my timer work more than 10 minutes? By the way, my application is a BLE application, I set UIBackgroundModes to bluetooth-central already.