Why do they make calls over the Internet?
VoWiFi technology allows you to make calls to a phone number outside the mobile network coverage area using Wi-Fi. Today we decided to discuss the relevance of such a service and the key ways to configure it: from OTT and UMA to untrusted access to ePDG. We will also consider the prospects for technology and the difficulties facing telecom operators offering Internet calling services.
Who uses the technology
Primarily VoWiFi technology attracts telecom operators. By offering the ability to make calls over Wi-Fi, telecoms expand the coverage of their own networks and attract customers who work in places where access is problematic, for example, in reinforced concrete office buildings or basements. Wi-Fi calling is also convenient for residents of rural areas and country houses.
At the same time, VoWiFi allows operators to reduce infrastructure costs. They don't have to install new base stations and expand coverage to operate in remote areas. In large cities, operators also have the opportunity to reduce the load on their networks. In megacities, users are close to access points not only at home. How note According to experts from the consulting firm ACG Research, thanks to VoWiFi, American telecoms save a penny on every minute of customer calls, and one large operator saved $2.2 billion over five years.
VoWiFi technology becomes also relevant in transport, where it is difficult to ensure a high-quality level of communication – for example, on trains. Special equipment receives a signal from operator towers or a satellite to an external antenna. Wi-Fi is then distributed throughout the cars using routers. This approach allows manage Internet access centrally and monitor the connection status, switching between different signal sources if necessary. This makes calling over Wi-Fi more stable than calling over a mobile network. Back in 2020, a group of Swedish engineers conducted a study and compared the quality of communication on the railway route between two major cities in Sweden – Stockholm and Gothenburg. VoWiFi showed much better results than GSM or UMTS.
Not only large operators are showing interest in Wi-Fi calling technology, but also private business. VoWiFi allows them to set up communication between employees without being tied to a mobile network. So, it’s been around since the early 2000s apply in American medical institutions for communication between doctors. Communication devices operate within a virtual local network, where data exchange occurs. According to UC Davis officials, VoWiFi technology reduces the number of communication tools by replacing voicemail, email, and faxes.
Today technology attracts ordinary enthusiastswho want to take a closer look at the nuances of how communication networks work. Yes, one engineer launched private mobile network and connected the smartphone to it. He also invited interested users to join the project to connect and communicate with friends directly.
How do internet calls work?
In general there is five ways Wi-Fi calling settings.
UMA (Unlicensed Mobile Access). Switch between mobile networks and Wi-Fi is happening using so-called GAN controllers. They receive packets from the Internet and transmit them to the telephone network as if they came from an antenna on a cell tower. Today, some of the frequencies at which UMA operates are somewhat outdated, but some market players consider the technology extremely promising. UMA is offered as a commercial service in North America and several European countries.
Connection via the operator's application. In this case, the user needs to download the operator’s special mobile application, enter a login and password. To connect even need not SIM card and this communication method can be use on older devices that do not support VoWiFi by default.
Trusted access to EPC. Settings is happening within a network built on the provider’s Wi-Fi hotspots, hence the name – trusted access. Such a trusted network provides QoS and secure user connections through authentication mechanisms and traffic encryption. Client terminals interact with mobile networks using s2b interface. But the price of subscriber equipment is quite high, so implementing trusted access to EPC and IMS may not be the most profitable approach for the operator.
Untrusted access to ePDG. The device establishes a connection to the service provider core via ePDG and is authenticated using a SIM card. Information from 3GPP servers responsible for authorization, authentication and user accounting allows you to maintain call quality and monitor QoS. If desired, the operator can limit the selection of Wi-Fi points. The technology is launched based on the existing infrastructure for VoLTE. On the market there are vendors, ready to help with implementation. For example, our solution provides a secure connection from the subscriber device to the core. The phone raises an IPSec tunnel to ePDG, which is then “shifted” to a GTP tunnel.
OTT (Over the Top). In essence, this implementation of VoWiFi represents classic calls through instant messengers like Viber and Telegram. We can say that it is not used by telecom operators.
Technology Outlook
Despite all the advantages of VoWiFi, the technology has a number of features. One of the significant limitations is related to hardware. Calling over Wi-Fi is mostly supported by mid-range and high-end phone models. At the same time, operators are unable control quality of Internet connection through third-party access points. Even a strong Wi-Fi network can be overloaded with too much traffic, and if the operator is unable to detect this before switching the call, voice quality can suffer. Thus, operators pay special attention to algorithms responsible for switching between networks, assessing the load on access points and compliance with acceptable latency levels. They try to allocate sufficient bandwidth to edge devices, and if the quality of the Wi-Fi connection is poor, they implement handover to the mobile network.
Another issue remains possible interference from radio devices when calling over public Wi-Fi networks. However, RRM algorithms are already used to protect against communication interruptions. They are constantly analyze RF data from access points to automatically optimize channel capacity, transmission power and more – including using AI systems. Finally, technologies are being developed to increase coverage and signal quality. So, a group of Spanish engineers suggested use UAVs in the form of repeaters to distribute Wi-Fi. This approach can be useful, for example, when eliminating the consequences of accidents or other emergencies far from the coverage area of operators.
At the same time, it is worth noting that VoWiFi technology is potentially vulnerable to hacker attacks. Attackers can try disrupt communication between users using DDoS attacks. In theory, they can also determine a person's IP address and call statistics if they intercept Internet packets from a vulnerable access point. Although researchers are already developing special anti-virus solutions for operators providing VoWiFi services. It can be assumed that the proliferation of such systems will contribute to the further development of VoWiFi and expand the ecosystem of vendor offerings.
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