Auto Race and Service Testing

Yota is actively preparing for a full-scale launch into commercial operation as a mobile operator. Yota voice communication services are already available across the country in limited commercial operation - and as part of this test, our employees and a limited number of subscribers check the configuration of network elements in different regions, as well as the correct operation of the provided Yota services.



Ekho Moskvy radio station was the first to take part in testing the new federal mobile operator Yota as part of the Road Stories rally. A group of well-known journalists and radio hosts went by car to nine cities along the route Moscow - Kazan - Kirov - Perm - Yekaterinburg - Ufa - Orenburg - Samara - Saratov - Moscow, during the run a series of meetings were planned with listeners of Echo of Moscow from the cities of radio broadcasting . We provided all participants with Google Nexus 5 smartphones with unique Yota SIM cards , and they regularly provided feedback.



Below is a story about how the multi-day testing took place and what difficulties and technical features Yota specialists encountered.

Case on the border

During the trip, journalists regularly wrote travel notes with hashtags #echoroad and #yotamobile on social networks, posted photos. The only communication channel for these purposes was the mobile Internet. The expedition started from Moscow, at first no difficulties were observed, but the mobile Internet disappeared on the border of the Kirov region and Tatarstan. Since we were not able to diagnose the problem remotely and did not want to distract journalists from their immediate work, it was decided to send a group of technical specialists from St. Petersburg to help. At the same time, they had to conduct a thorough check of the services throughout the rest of the route, thereby speeding up routine testing in these regions. Literally in a day two crews were organized, who joined to test and accompany the Echo of Moscow rally. One crew arrived in Perm, the second - in Yekaterinburg, the next city on the route.





The cause of the problems was clarified on the spot - it turned out that the analysis of the range of Yota SIM cards was not registered in the packet network (PS-domain). After the IMSI Yota range was registered in the PS-domain of the Ural branch of the MegaFon network, the mobile Internet started working again.

Technical information : when a mobile phone is connected to a cellular network at the base station level, it is registered in two networks: a CS domain (Circuit switch, voice communication) and a PS domain (Packet switch, data transfer). This is necessary for voice calls and data transfer. And in both domains, it is necessary to prescribe an analysis of the IMSI range of each mobile operator.

Journalists regularly sent us the results of measurements of the speed of the mobile Internet - and with the exception of the described case, he was present throughout the route, without any pronounced bursts.

From dusk to dawn

From the point of view of most people, becoming a mobile operator is quite simple, only expensive. It is enough to stretch a larger cable, install more often base stations. In fact, this is a complex complex process, and it depends not only on the actions and efforts of Yota. There are a number of tasks that must be addressed by other players in the telecom market. Due to the large number of different operators, it is not easy to control the actions of each partner.

Technical background : as a new operator, Yota has its own number base. To ensure the correct operation of our services, other mobile and fixed communication operators must correctly register the routing of calls. If operator “A” does not do this with respect to the number base of operator “B”, then in this way it degrades the service for its own subscribers. Because they will not be able to make and receive calls from subscribers of operator "B".

The number base of each operator is limited to DEF codes allocated for it (a three-digit number following the country code (+7 xxx *** - ** - **). For many operators, the DEF code is tied to a specific region. However, mobile operators have one the same DEF code is used in different regions.

Between telecom operators, voice connection points are organized. Via these interfaces, voice call routing is configured. And Yota faces a very time-consuming task of coordinating the registration of routing with a large number of telecom operators throughout the country.

Shortly after the start of the expedition, Echo of Moscow journalists found that some landline numbers of callers were not correctly determined from 10 p.m. to 10 a.m. That is, instead of the Moscow number of the radio studio from which their colleagues called, other numbers were periodically determined.

It turned out that this is a problem on the side of the fixed-line provider with which the Moscow radio station works. In its routing settings, the Yota DEF code was erroneously defined as belonging to St. Petersburg. At night, a long-distance call was connected through an alternative St. Petersburg provider, which led to an incorrect identification of the calling number. The routing was quickly fixed by them, after which the numbers of the callers began to be determined correctly.

Proactive fix

Technical Reference : 2G / 3G networks consist of a CS domain and a PS domain. The LTE (4G) network consists only of a PS domain, that is, it is used exclusively for data transfer. At present, in Russia voice communication within the framework of LTE networks (VoLTE, Voice over LTE) is not certified by government agencies. Therefore, the transition technology CSFB (Circuit switch fall fall) is used. So that a subscriber located in the LTE network can make / receive voice calls, a switch is made to the 2G / 3G network, and vice versa. The procedure when a subscriber with priority is registered in a 4G network, but the system can switch it to 2G / 3G, is called combined attach (combined registration). This is one of the components of CSFB.

Only once, during two weeks, one of the crews who tested the connection encountered incorrect operation on the 4G network in Ufa. Yota specialists analyzed the traces between MME and MSC (signaling messages exchange between elements of 4G and 2G / 3G networks). It turned out that the CSFB procedure was not configured correctly, the combined attach failed. That is, the subscriber was registered in the 4G network, but it did not bind to the CS domain in 2G / 3G. Thanks to the coordinated work of Yota and MegaFon specialists, this failure was very quickly eliminated. Therefore, the journalists of Echo of Moscow did not even encounter him.

This is another example of how difficult and unique for the Russian telecom market Yota is solving, deploying a full-fledged MVNO throughout Russia. Indeed, as a 4G network, Yota uses its own dedicated segment under its carrier name, and 2G / 3G networks are provided by MegaFon. That is, all Yota-devices simultaneously operate in two different carrier networks. This is an atypical service implementation scheme. There are less than five such networks in the world. And Yota has to overcome many organizational and technical difficulties in order to ensure high-quality and uninterrupted operation of its services.

Conclusion

Yota specialists returned home to St. Petersburg, and journalists returned to Moscow, where we met them together with our colleagues. Thanks to the rally, Yota conducted a very important user testing of its services. Thanks to the coordinated work of all test participants, shortcomings that could affect subscribers were discovered and eliminated. We additionally made sure that Yota is ready for launch in a wide commercial operation.





The preparation for launching into commercial operation is greatly complicated by the uniqueness of the case - for the first time in Russia, Yota is building a federal cellular coverage with roaming-free space on the basis of the integrated Scartel and MegaFon networks. Not a single player on the Russian telecom market has yet solved such a problem. Therefore, Yota uses every opportunity to evaluate the quality of communication for its users.

We invite all interested journalists and bloggers to participate in joint testing of the services of the mobile operator Yota. Send questions and suggestions for testing to press@yotateam.com. In the summer of 2014, SIM cards will be issued:

• to users who place an order on the site and through the Android application
• to journalists and bloggers.

A little later, a press event will be held regarding the launch of the Yota operator in wide commercial operation.