DIY Building Basic OpenBTS

January 24th, 2012 | 65 views | Posted in Computer Gadget, Tips Tricks | No Comments »

Open Base Transceiver Station, or OpenBTS, is a software-based GSM base stations, allowing users to receive calls GSM mobile phone or send short messages (SMS), without using a commercial service provider’s network.

That is, with this technology the user can call or sms without the need to pay. In fact, by assembling this OpenBTS, you actually build your own mobile operator. Only a limited signal range, and could only communicate with other phones that are connected with this OpenBTS network.

Application OpenBTS in Indonesia are being encouraged by the practitioners of information technology Onno W. Purbo. Here are the basics of equipment and software required to use this technology as presented by Onno at his place.

Hardware

A set of computers, can be a desktop or notebook. Then, for minimal version OpenBTS , the hardware required to emit radio signal is called the Universal Software Radio Peripheral (USRP) and two types of antennas, the transmitter and receiver antennas.

USRP is to replace the role of the transmitter at the commercial Base Transceiver Station (BTS) by cellular carriers. USRP minimal version can be bught online for around $15,000.

Through the USB cable, connect the computer to the USRP. After that, there are two wires of USRP are connected to the two antennas.

Software

At the moment the computer has to be running Linux operating system. Other operating systems like Windows or Mac can not be used to run OpenBTS. All software used for this OpenBTS can be downloaded for free, and everything is open source software.

Use the GNU Radio software, to control the USRP. Then OpenBTS software to control the BTS operation. And also there is software called Asterisk central telephone. This software is commonly used for central telephone generation 4G technology.

The protocol used by Asterisk is the Session Initiation Protocol (SIP). This kind of protocol is also used by commercial cellular operators such as Indosat, Telkomsel, XL, Axis, and others.

USRP hardware logic thinking

Logical thinking in OpenBTS USRP is approximately like a sound card of the computer. A sound card must be programmed to issue an audio signal.

Well, so does the USRP is programmed to issue a radio signal. Not just a radio signal, USRP can be adjusted to issue AM, FM, or TV signals. All signals were programmed through the software.

This is what causes OpenBTS can be assembled at a cheap price since the transmitter is controlled via software. If the transmitter is control via hardwares, this will cost million of dollars.

OpenBTS minimal version can only reach 5 to 10 meters. Because, the power consumption only 100 milli watts. If the power amplifier is changed to 10 watts the range can reach 5 kilometers or more. More power means longer distance. Try to compare it with the mobile operator’s base stations. For a similar version, will cost $150,000 dollars. [kompas.com]