If your mobile operator offers 4G services, you may already have used the 4G calling or VoLTE service on your LTE compatible mobile phone. VoLTE is a technology 4G LTE networks use to facilitate voice calls and text messages.
VoLTE stands for Voice over LTE, and it is a managed-VoIP technology in 4G LTE networks that enables voice calls and text messages (SMS) through packet-switching. 2G and 3G networks use circuit-switching for voice calls and SMS, whereas LTE uses data to deliver all services, including voice and SMS.
Voice calling is one of the most fundamental considerations when buying a mobile phone subscription. It is an essential service that mobile operators offer as part of their mobile phone solutions. If all VoLTE does is provide voice calls and SMS, do you wonder why it is such a big deal considering 2G and 3G networks have been delivering voice and texts for the last few decades?
What does VoLTE mean on your 4G phone?
VoLTE or Voice over LTE is an IP-based technology introduced by the 4G LTE networks to deliver voice calls and text messages. 4G LTE networks are data-only and utilise mobile data to facilitate voice calls and texts instead of employing conventional calling technologies that 2G and 3G use.
Conventional voice calling in 2G and 3G networks is based on circuit-switching (CS) technology. On the other hand, mobile internet in 2G and 3G networks requires packet-switching (PS) technology. As a data-only mobile network, 4G LTE uses packet-switching for all services, including voice, texts and the internet.
When making a regular voice call from your mobile phone, the mobile network needs to communicate with external networks such as the landline network (Public Switched Telephone System – PSTN) or other local mobile networks (Public Land Mobile Network – PLMN). That requires the mobile network to be integrated with PSTN, which is how a mobile network connects your call to other landline or mobile numbers.
On the other hand, internet-based voice calls such as WhatsApp do not require you to dial a phone number and rely on your phone number as a registration ID. Allowing customers to dial mobile or landline numbers through a cell phone requires integration with voice networks like PSTN or ISDN, which is achieved through circuit-switching in 2G and 3G.
VoLTE allows packet-switched 4G LTE networks to integrate with voice networks like PSTN and ISDN. VoLTE requires a new network entity, IP Multimedia Subsystem or IMS, to work with the 4G mobile core network to enable rich communications services, including voice calling. IMS is not limited to 4G networks only and is also used by 5G to enable Voice over 5G.
On your 4G LTE mobile phone, you may also see an inter-related technology, WiFi calling, that allows you to make traditional voice calls when connected to a WiFi network. WiFi calling is also called Voice over WiFi or VoWiFi, and it requires additional hardware.
How does Voice over LTE (VoLTE) work in 4G and 5G?
VoLTE uses IP Multimedia Subsystem (IMS) and 4G LTE core network (Evolved Packet Core – EPC) to enable rich communication services, including voice calls and SMS in 4G and 5G NSA. VoLTE implementation also has a 2G/3G circuit-switched fallback (CSFB) as a backup for devices that don’t support VoLTE.
For Voice over LTE (VoLTE) to work, the key requirement is a packet-switched mobile core network and IP Multimedia Subsystem (IMS). 4G LTE networks are data-only and have a packet-switched core network, Evolved Packet Core or EPC. EPC works alongside another network entity, IP Multimedia Subsystem (IMS), which provides the necessary integration with voice and multimedia networks.
There are two critical conditions for VoLTE and Wi-Fi calling to work: first, the mobile device needs to be online, and secondly, it must be connected to the mobile core network. The second part is where the real magic happens. The in-built IMS architecture and the mobile core network take care of all the integrations with PSTN and other networks to enable voice calls through the internet in a secure manner.
VoLTE is a better option for customers and mobile operators for voice calls and SMS. For an operator, it is more efficient because the calls are not engaging any of their circuits, and for customers, the call is of better quality. In 2G GSM and 3G UMTS networks, there are two parts to the mobile core network: circuit-switched and packet-switched.
Circuit-switched calls are not efficient and engage traditional circuits for the entire duration of a session, e.g. a phone call. LTE networks change that through VoLTE, but they still keep a 2G/3G fallback option so that if the network or device does not support VoLTE, voice calls and SMS can take place using circuit-switched technology.
As soon as a VoLTE or VoWiFi enabled device is connected to the mobile network, the IMS infrastructure replicates what traditional circuit-switched calling would have done using packets of data instead of circuits. Therefore mobile operators have a cost for enabling the service, which is why the calls are chargeable.
In non-standalone 5G networks, 5G NSA, the communication takes place between the 5G radio network and the 4G LTE core network (EPC). Since both 4G LTE and 5G NSA use the EPC, the VoLTE capability exists in these cellular technologies. In standalone 5G (5G SA) with a dedicated 5G core network, an equivalent technology, Voice over 5G or Voice over NR, is used.
Nowadays, mobile operators also have partnerships with fixed network providers for enabling Wi-Fi hotspots on specific mobile tariffs, which comes in handy for VoWiFi calls. Mobile Network Operators also have roaming agreements with mobile operators in other countries so that when customers travel to those countries, the partner networks can enable connectivity for them.
Is VoLTE the same as Wi-Fi calling?
WiFi calling, also known as Voice over WiFi, is not the same as VoLTE, but it is an inter-related technology that allows WiFi-connected cellular devices to become part of a 4G LTE network. For integrating Wi-Fi networks to a mobile network, an entity, Evolved Packet Data Gateway (ePDG), is used.
ePDG establishes a secure connection with the WiFi connected cellular devices using IPsec. IPsec stands for Internet Protocol Security and is a suite of protocols used for encrypting data packets. This way, ePDG becomes an integral part of the overall 4G mobile core network, the EPC to extend the network coverage by taking advantage of the WiFi networks.
Both VoLTE and VoWiFi use the same mobile core network to provide a high-quality audio/video calling experience to customers. As a customer, you can make phone calls to landline numbers or other mobile numbers as normal as long as you are connected to a WiFi network. It is an excellent service for those who live in areas with poor cellular coverage or who often use underground train services like Tube or Metro.
Is VoLTE good or bad for your phone?
VoLTE is the future of voice calling, and 5G New Radio (NR) networks follow the same approach. It evolves voice calls from conventional circuit-based calling to IP-based calling. VoLTE offers you a high-quality voice service without relying on 2G or 3G networks unless your device or network does not support it.
When LTE networks were launched as part of 3GPP Release 8, the main LTE driver for the customers was a higher data rate than 2G/3G networks. The 2G and 3G mobile networks had two different parts of the network operating within them; one for voice calls and SMS, and the other for all things data.
Since moving conventional voice calling to IP was a big step, especially in the beginning when 2G and 3G networks were still more widely available than 4G, LTE networks had an interim technology called circuit-switched fallback (CSFB). CSFB is the capability of LTE networks to use 2G and 3G networks for voice calls and SMS. So, for example, if you have a 4G phone and a SIM, CSFB allows you to make phone calls as normal, but in the background, it will be using 2G (e.g. GSM) or 3G (e.g. UMTS) networks.
What VoLTE does is that it takes away that dependency on 2G and 3G networks so that if you are in an area where you only have 4G or 5G network coverage, you can still make voice calls. And not just that, VoLTE is capable of providing a better and more crisp calling experience and is also more power-efficient than other VoIP services.
Do VoLTE calls cost extra?
Generally, there are no extra charges for VoLTE, and the calling minutes come out of your standard calling allowance. So, for example, if you have 500 calling minutes as part of your monthly allowance, the minutes you use for VoLTE calling will come out of those 500 minutes, just like any non-VoLTE calls.
Also, even though VoLTE uses the packet-switched part of the network, which is data-only, any data that VoLTE consumes does not come out of your monthly data allowance because mobile operators charge for it as calling minutes not data.
However, you must always check with your mobile operator to avoid any bill shocks if you are unclear. Each operator’s business and pricing model can differ, so you should speak to your mobile operator, especially if you plan to use any of the services abroad.
Should VoLTE on your mobile phone be ON or OFF?
There is no reason for not having the VoLTE feature enabled (switched on) on your mobile phone. Since VoLTE also has a circuit-switched fallback option (CSFB), if your mobile network or device does not support VoLTE, you can still make and receive phone calls through the circuit-switched 2G or 3G networks.
With 2G/3G circuit-switched fallback, if you are in a geographical location where your mobile operator does not have VoLTE support or if you have an older phone that is not VoLTE-compatible, you may still make and receive calls through 2G GSM or 3G UMTS networks.
When travelling abroad, you may want to check with your mobile operator if there are any extra charges for using VoLTE or VoWiFi when roaming. To avoid bill shock, you can use a spend-cap to take control of any such unforeseen costs. If you switch off WiFi calling or VoLTE, you will still be able to use your phone for conventional circuit-switched calling on 2G/3G networks.
How to enable or disable VoLTE on your phone?
Not all phones show a symbol on top of your phone screen when VoLTE is enabled, but it is possible to turn VoLTE off on your phone. If you want to do that, generally, you can find the VoLTE tab by going to “Settings” and then “Mobile Data” or “Mobile Networks” tab. Below are some screenshots and guidance to help you do that for iPhone and some Android phones:
iPhone
To turn off VoLTE on an iPhone, you need to go to Settings->Mobile Data->Mobile Data Options->Voice & Data. That will take you to the tab where you can use a slide button to enable/disable VoLTE.
Android phones:
You will likely find the VoLTE option on Andriod phones under the “Mobile Networks” tab. An example below for a Samsung phone:
To turn off VoLTE, go to: Settings->Connections->Mobile networks. That will take you to the following tab so you can enable/disable VoLTE:
Conclusion
VoLTE or Voice over LTE is a fourth-generation (4G) technology that enables voice calls and SMS over 4G LTE networks. In the absence of VoLTE, the only way 4G networks can facilitate voice calls is by using a 2G/3G fallback option called Circuit-Switched Fallback (CSFB), which utilises legacy networks (2G/3G) for voice calls. VoLTE is a packet-switched technology enabled by IMS (IP Multimedia Subsystem) in mobile networks. It relies on data packets instead of conventional circuits to make voice calls and send text messages (SMS). VoLTE requires the 4G LTE core network (EPC) to support voice calls and SMS in both 4G LTE and non-standalone 5G NR networks. Some key features and benefits of VoLTE:
- HD voice: High-quality (HD) voice that gives you crystal clear audio
- No extra costs: There is no additional cost, and the call minutes are deducted from your monthly calling allowance (not data allowance)
- Simultaneous voice and data: If you are using your phone as a hotspot, you can still use the voice calling service simultaneously through VoLTE
Here are some helpful downloads
Thank you for reading this post. I hope it helped you in developing a better understanding of cellular networks. Sometimes, we need extra support, especially when preparing for a new job, studying a new topic, or buying a new phone. Whatever you are trying to do, here are some downloads that can help you:
Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy, which explains the network nodes, e.g., BTS, MSC, GGSN etc.
Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and the challenges considering how quickly the industry evolves. The bigger picture comes from experience, which is why I’ve carefully put together a few slides to get you started in no time. So if you work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on the product overview and product roadmap.
