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Open Source GSM network at the Burning Man festival

Since the 1990s, tens of thousands of people have gathered in the deserted Black Rock Desert in Nevada for the Burning Man counterculture festival. As usual, the eight-day event starts on the last Monday of August, at 00:01 local time. About 50,000 people came this year, but not only the record attendance is a feature of the festival. The fact is that open source hardware enthusiasts two years ago built a complete GSM network in the desert with solar batteries and free equipment. The network costs the organizers a penny, and anyone can use it for free.

Perhaps, it is the first in the world open GSM-network of such a scale. According to the engineers, their system can serve as a prototype for creating cheap GSM networks in the third world countries, including in Africa (anlim on voice traffic can cost about $ 2 per month for a mobile operator to make a good profit). In an interview with Network World and engineers talk in detail about the design of the network.

GSM base stations operate on the free OpenBTS program (AGPLv3 licensed) under Unix, which, together with Universal Software Radio Peripheral (USRP), provides a normal GSM interface for any standard GSM phone, without having to make any modifications for it. At the same time, an OpenBTS base station requires only 50 W, unlike standard commercial GSM equipment, so even solar batteries are enough for it. Such a station can fit literally in a shoebox.

Next, open IP PBX Asterisk routes calls over VoIP. From a network point of view, every GSM phone becomes a SIP client.

To build a network, the organizers had to take the official license from the FCC, as well as negotiate with the neighboring operators about the division of the frequency range. When the user enters the coverage area of ​​the Burning Man base station, he receives an SMS message to confirm his consent to the transition to the new “operator”.

You can make calls to any number, but receive calls only from other subscribers who are on the Burning Man network, because roaming agreements are not concluded with the operators. But everything is free and the network is made by hand.

In September, it is planned to launch the first commercial startup, which will be engaged in the construction of such cheap GSM-networks in different regions of the world. It is estimated that a base station on OpenBTS will cost about $ 10,000, that is, about 5-10 times cheaper than a regular base station in a commercial cellular network.

Since the beginning of this year, several similar pilot projects have already been launched at OpenBTS in India, Africa and the countries of South-East Asia.

Source: https://habr.com/ru/post/103145/

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