Similar to previous iOS updates, over 50% of Apple device users upgraded their device to iOS 7 within 2-3 days of its release, 30% upgrading within the first day. Apple made improvements to their software release process to ensure mobile networks are protected from these techno-hungry iPhone users. Specifically, the notification announcing availability of the new iOS is staggered over a few days to help spread out the signaling load. They also implemented a “no-greater than 100 MB app size” policy which restricts apps over that size from downloading over mobile networks. And Apple’s iOS 7 update came with a mandatory WiFi-based upgrade path. So, quiet day on mobile networks on September 18th? Not quite – iOS 7 update came with a hidden cost to mobile operators. But, only systems correlating signaling, volume, applications and device data – down to the iOS version – could detect these trends. In this Analytics Beat blog, we report on Apple iOS update trends discovered using the Alcatel-Lucent 9900 WNG on mobile networks worldwide.

Source: 9900 Wireless Network Guardian

General upgrade cycle observations

The upgrade cycle started a few hours prior to the iOS 7 release when applications notified users of to upgrade their app to be IOS 7 compatible. Next, users were notified that iOS itself was available – the small red bubble on the “Settings icon.” Users connected their mobile devices to WiFi to upgrade. During that time, we observed a decrease in per user data volume from the Apple device population over the mobile network. Then, a portion of users soon resumed their mobility and received notification to upgrade their app to synchronize with the upgraded OS. Many opted to download these apps over the mobile network.

Manageable paging day

The notification process starts with locating the device (paging it) and then forwarding the alert. Apple staggered their alerts to iPhone users when iOS7 became available. A number of applications also alerted that a new version of their software was available; the latter is what we term “iTunes” signaling.

The iOS 7 availability notification load was equivalent to adding an extra 12-20% paging over a typical iTunes day. iTunes itself experienced a paging increase of up to 35%. Together, they contributed a 22-49% increase in paging compared to typical daily iTunes rate. Yet, the impact on the overall signaling across the network for these two days was negligible, in great part due to the policies Apple implemented to spread out signaling. It worked.

The cellular downloading loophole & post-iOS application update

Next, we noticed traffic coming from Apple’s servers tasked with providing the iOS 7 upgrade software. Given the mandatory WiFi upgrade, we did not expect any volume over the mobile network from those servers. We were puzzled about this mystery traffic, especially given its volume. In some networks during peak time, iOS 7 upgrade over the cellular network generated as much traffic as all of iTunes could on a typical day! How to explain traffic of this magnitude when none was expected? Combining this OS update traffic with iTunes app upgrade traffic triggered by OS synchronization drove iTunes traffic 1.8 – 3 times above normal baselines. This resulted in a staggering overall network bandwidth increase of 5-10% the day after the release.

Were it not for tagging IP flows with the data received from signaling (IP address, device type, and device OS), that fact would have been relegated to the annals of “Odd and Unexplained Occurrences.” However, we discovered a loophole to the mandatory WiFi upgrade. The MAC or PC used for upgrading Apple devices is allowed to have its internet connection over WiFi or the cellular network. Using a mobile device to provide internet connectivity to a laptop is called tethering and is used to provide connectivity when not in range of a WiFi connection. Tethering is used by 4-12% of users depending on geography, plans and promotions. During the iOS 7 upgrade, we discovered that some users tethered their laptop with Android devices and were able to receive the IOS update over the mobile networks. A loophole that defeated Apple’s WiFi-only upgrade policy.

While relatively few users choose this connectivity method, those who did downloaded a large iOS 7 file of 750 MB minimum. This certainly accounts for the large amount of traffic observed, but can also result in bill shock. To put in perspective, the average 3G user in North America generates 17 MB of data per day.

Conclusion

Apple has clearly improved its mobile savviness by implementing smart policies for software delivery. Barely noticeable signaling increase is great progress. But continued cooperation is greatly needed. These improvements are only possible when service providers have the right data in hand to discover inefficiencies and to understand their causes before initiating optimization discussions with the equipment vendor.

We also noticed a wide variation in overall network traffic and signaling statistics. This phenomenon depends on how heavily invested a service provider is with a particular OS. Device OS homogeneity means that a large percentage of phones will exhibit the same pattern, all concurrently. Another factor is what applications users downloaded to their phones. Not all applications had an update synchronized with the iOS 7 availability. So while trends were similar all over the world, the exact impact varied significantly across service providers.

Over the next few weeks, users will tryout the new iOS 7 features. Our next blog will compare the performance of this latest iOS version with previous ones and determine if usage of new feature drive changes in overall signaling, volume and airtime.

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Our Analytics Beat studies examine a representative cross-section of mobile data customers using the 9900 Wireless Network Guardian and are made possible by the voluntary participation of our customers. Collectively, these customers provide mobile service to millions of subscribers worldwide.