Is 4G LTE and VOLTE the same

VoLTE in the test: Telephoning over 4G / LTE

Peter Stelzel-Morawietz

After Vodafone and O2, Deutsche Telekom now also offers Voice over LTE. But what does the new technology really bring for mobile telephony, who can use it and what does it cost?

EnlargeVoice over LTE is still in its infancy.

No, VoLTE (spoken: “Volte”) is neither about evading your opponent when fencing nor about the dressage exercise when riding. Rather, the abbreviation stands for Voice over LTE. After Vodafone and O2 Telefonica, Deutsche Telekom has now also introduced the new technology for mobile telephony. Theoretically, one has to state restrictive, because there are still a few hurdles in the way of practical use in everyday life. LTE has long been the standard for mobile Internet and offers a bandwidth of up to 100 or 150 Mbit / s, which is significantly more than many DSL landline connections.

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VoLTE: differences and advantages compared to UMTS calls

In addition, LTE is no longer reserved for the more expensive term contracts of providers, but is also possible via the prepaid SIM cards of resellers such as Alditalk. Wherever the 4G network is available, you can be on the Internet quickly with an LTE-enabled smartphone.

It only looks different when it comes to telephoning, because calls in the cellular network are - overwhelmingly - still handled in the previous 2G and 3G (UMTS) network. You can recognize this immediately by the fact that the 4G symbol disappears from the display of your smartphone as soon as you call someone. That is slowly changing now. After Vodafone and O2 Telefonica introduced LTE telephony in 2015, Deutsche Telekom has now followed suit.

Voice over LTE is said to offer a number of advantages. The phone calls build up practically immediately, the voice quality is significantly better, the new technology consumes less power and thus extends the battery life, and finally you can continue to surf the web quickly while making calls, which can be important when talking via a headset, the providers promise.

Technically, VoLTE works like IP telephony in the fixed network, so the voice transmission runs in the form of data packets over the network, which are only put together again at the recipient. This also results in much better transmission and sound quality, because much more bandwidth is available for data transmission than on the previous voice channel.

EnlargeSo far, almost every LTE smartphone (above: "4G") switches back to the previous 2G or 3G network when making mobile calls (below: "H" for HSDPA).

All prerequisites must be right for use

So everything is fine, especially since Voice over LTE does not incur any additional costs or higher call charges? In principle yes, but only in principle. Because only very few people can already use the new technology because all the boundary conditions have to be right. On the one hand, there is the hardware. Far from all LTE smartphones also allow Voice over LTE. In addition, the phones - with the exception of the iPhone 6, 6 Plus, 6S and 6S Plus from iOS 9.3 - have to be provided with a kind of VoLTE update or special settings, which is currently only possible for devices with term contracts from the provider. Vodafone currently supports around 20 models, O2 Telefonica five, and Telekom ten. VoLTE will also be possible with smartphones from free trade in 2017 at the earliest.

You also need a VoLTE-compatible contract: With Vodafone these are the Red GB, Red Business + or Black tariffs, with O2 every LTE-compatible tariff and with Telekom every term contract. In addition, LTE must of course be currently available at the time of the call at both locations where the call partners are - otherwise you will be calling again via 2G or 3G.

After all, both must have a SIM card from the same provider; cross-network calls are currently just as impossible as VoLTE in the E-Plus network.

EnlargeOnly a few smartphones currently support real LTE calls. In addition, Voice over LTE has so far only worked with specially configured providers' devices, with the exception of the iPhone.

Conclusion on Voice over LTE: Every beginning is difficult

If all of the conditions apply to you, just make sure that the 4G symbol remains visible when making a call. If it also disappears when your counterpart definitely also meets all the requirements for VoLTE, you may have to have the function activated by your provider or activate it yourself in the customer center. It is positive that the data volume used for LTE calls is not taken into account.

Very few mobile phone customers benefit from the new technology, hardly anyone currently meets all the conditions that are required for real LTE calls - and then you need a conversation partner who also applies this. In addition, Telekom initially had problems with call diversion, and an international study for the past year came to the conclusion that VoLTE calls are interrupted four to five times as often as regular cell phone calls. In principle, this should not happen even in an LTE radio gap, because you should then be able to continue talking automatically via the GSM or UMTS network. In practice, however, this "circuit-switched fallback" apparently does not always work. The incompatibility of the various provider networks is currently a major hurdle to use.

It remains to be seen whether these are just difficulties at the start. In our practical test (see box), the fast connection setup was particularly convincing; the voice quality did not differ audibly from that of HD Voice over 3G. In addition, one or the other conversation was suddenly "gone" with us.

VoLTE in a practical test: light and shadow

We couldn't do systematic practical tests because of the many exclusion criteria. Our experience is based on two identical Xperia Z3 smartphones from Sony, each equipped with a VoLTE-capable SIM card.

It was initially observed that the telephones in the “LTE border area” often jump back and forth between 3G and 4G. If the fast network is constant, the connection establishment is really impressively fast. The test persons, on the other hand, found the voice quality with the Sony devices no better than with 3G (HD Voice); this is also confirmed by the analysis of the frequencies that are transmitted during the telephone call. Compared to 2G, on the other hand, the difference is enormous: While the original GSM technology does not exceed 4300 Hz, Voice over LTE transmits up to 7500 Hz on exactly the same hardware.

EnlargeCalls in the conventional cellular network stop above 4300 Hz (left: 2G), while Voice over LTE transmits up to 7500 Hz (right: 4G).

The battery test was disappointing, because both with conventional calls (2G / 3G forced) and via LTE with the same endless loop of content, the battery level fell by around six percent per hour - so no advantage for VoLTE. On the other hand, the ability to quickly continue surfing on the smartphone during an LTE call is convincing. However, you don't always use headphones or have to do something online at the same time. After all, we also had one or two breakdowns in calls, as a current study confirms. Our overall conclusion is a bit sobering: After so much praise from the network providers, we expected a little more from the new technology.