Surprising reason Air Mobile eats smartphone batteries for breakfast — and how Afrihost fixed it

After years of complaints that Afrihost’s mobile data services seemed to drain smartphone batteries faster than MTN’s, the company has identified and mitigated the problem.

Reports of the issue first appeared on the MyBroadband forum on 1 November 2018.

Subscribers found that using Afrihost’s mobile data service doubled their smartphone’s battery consumption compared to MTN.

Afrihost’s virtual mobile network runs on MTN, and switching between the two providers to conduct such tests is relatively simple — you just change the access point name (APN) setting in your device.

The issue did not appear to affect all Afrihost Mobile subscribers equally, leading to speculation that it might only affect certain mobile phones when they connect over LTE.

However, nothing came of the complaints that Afrihost’s APN seemed to be draining batteries faster over LTE on specific devices.

Over a year later, on 15 November 2019, another subscriber reported a similar problem.

Afrihost dismissed the matter despite comprehensive testing showing the issue only occurred when connecting over its APN.

In fairness, the issue did not appear widespread at the time.

More than two years passed until the next battery-related complaint appeared on 13 January 2022.

However, the subscriber traced the problem to a badly-behaved SIM toolkit app on their smartphone that appeared after porting from Cell C to MTN (and Afrihost’s APN).

On 29 August 2022, MyBroadband forum member Jason-ZA posted a report after detailed testing that eliminated all of the previous suspected battery-draining culprits.

MyBroadband conducted its own tests using two identical Nokia 5 devices and was able to reproduce the issue.

Using the Afrihost APN, the battery drained at over 4% per hour, whereas the smartphone using MTN’s default APN consumed 0.6% or less per hour.

We conducted our tests by letting the devices lie idle for 16 hours.

To ensure it wasn’t a rogue app, we ran the test twice, swapping the SIMs and APN settings between the two devices for the second test.

The table below summarises our test results.

Test elements First test Second test
Afrihost MTN Afrihost MTN
Device Nokia 5 (Alpha) Nokia 5 (Beta) Nokia 5 (Beta) Nokia 5 (Alpha)
Start time 15:00
Battery at start 100%
End time 07:38
Battery at end 28% 90% 30% 91%
Battery usage 72% 10% 70% 9%
Test length 16.6 hours
Per-hour battery consumption 4.33% 0.60% 4.21% 0.54%

Afrihost finally resolved the problem after Jason-ZA pinpointed the exact technical reason for the battery drain.

“I think the issue is that we are being handed out a publicly routable IP instead of a CGNAT IP, which causes all the junk traffic (ICMP, bot port scans, etc.) to hit our devices, keeping the LTE radio active all the time,” Jason wrote.

“Not Afrihost’s fault at all, just the nature of having a public routable IP.”

Publicly routable Internet Protocol (IP) addresses allow devices on the Internet to communicate without an intermediary doing any translation or traffic forwarding.

Essentially, having a publicly routable IP allocated through the Afrihost APN makes it easier to host online services on the Air Mobile network.

Carrier-Grade Network Address Translation (CGNAT) gives end-user devices a private IP address and lets several subscribers share one public IP.

IP version 4 addresses are limited, and NAT lets network designers use a handful of public IP addresses to serve many clients.

It can also have the additional effect of blocking certain traffic from reaching devices.

This can be good for average end-users, who are spared from indiscriminate attack traffic. However, it is a drawback for tech-savvy customers who want to host an online service over their mobile connection.

After monitoring traffic to their device, Jason said they saw a lot of junk traffic hitting their Afrihost-assigned IP addresses.

“The normal MTN APN seems like it hands out a CGNAT IP which could possibly explain the difference in battery drain.”

MyBroadband contacted Afrihost for comment, but it did not respond by the time of publication.

However, Afrihost’s customer support representative on the MyBroadband forum did confirm Jason’s assessment.

Afrihost said Internet bots doing port scans across public IP ranges seem to keep the LTE radio active, preventing the phone from putting it to sleep even when only connected to Wi-Fi.

New Air Mobile customers will now receive a CGNAT address by default and may request to receive a publicly routable address.

Similarly, existing subscribers who receive a publicly routable address may contact Afrihost support and request to receive a CGNAT address.

Air Mobile customers experiencing extremely high smartphone battery drain while using the Afrihost APN should contact the ISP’s support and ask to be switched to a CGNAT address.

Testing conducted by Wikus Steyn. Thanks to Jason-ZA for finally getting to the bottom of this.

Now read: Afrihost overtakes RSAWeb and Webafrica in battle for top South African ISP

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Surprising reason Air Mobile eats smartphone batteries for breakfast — and how Afrihost fixed it