Reconfigurable Cellular GSM Network Using USRP B200 and Openbts

2017 IEEE 13th Malaysia International Conference on Communications (MICC) Reconﬁgurable Cellular GSM Network using USRP B200 and OpenBTS for Disaster-Hit Regions

Kinjal Aggrawal Khyati Vachhani Assistant System Engineer, TCS Assistant Professor, ECE Department India Nirma University, India [email protected] [email protected]

Abstract—In this paper, we have presented a cost effective provide the real-time voice connectivity for underdeveloped technique for quick reinstatement of wireless connectivity in countries and rural areas apart from natural disasters. This pa- disaster hit areas, which face complete breakdown of prevailing per focuses on a cellular communication infrastructure which infrastructure. A test reconfigurable GSM Base Transceiver System (BTS) based on Software Defined Radio (SDR) is build can be established in a fraction of cost and time than regular using Universal Software Radio Peripheral (USRP) B200 board full-fledged GSM cellular BTS. It is based on SDR hardware, and OpenBTS. USRP B200 overcomes the necessity of an external henceforth it is reconfigurable by reverence to physical layer 10 MHz reference signal as conflicting to widely used N-series and furthermost to the Media Access Control (MAC) layers. and USRP1. After establishing cellular GSM network, short mes- SDR is supported by Asterisk, which is an open source call sage services and voice calling are executed. Besides OpenBTS, standalone typical applications-SMQueue and Asterisk are also management service and accordingly the development cost is used for correct routing of messages. It also outspreads the reduced considerably. Meanwhile the infrastructure is built connectivity to practically every individual in the disaster hit on SDR, it has tolerance with respect to center frequency areas having a GSM handset at no further cost. This low-cost and numerous other physical layer constraints. Studies have and economical deployment will encourage the government to been carried out for providing cost-effective communication appliance such models in areas hit by major cataclysm. Index Terms—GNU Radio, GSM, OpenBTS, SMS, SDR, Test solutions to people in disaster hit areas or in rural areas using Network, USRP, voice call the OpenBTS and USRP [3] [4]. The commercial deployment of the communication model is frugally sustainable. The system is portable and can be mobilized every time the full- I.INTRODUCTION fledged cellular infrastructure is hindered. Natural disasters like earthquake, storm and tsunami are All versions of USRP by Ettus Research are supported frequent phenomenon, besides they are quite unpredictable as in OpenBTS with minor or negligible modifications with well. Failure in communication system have been significant the daughter boards. The N-series USRP is termed as the in such parts of natural disasters as the breakdown of Base highest performing device with high dynamic range and low Transceiver Stations (BTS) disrupt the wireless connectivity phase error amongst its family. The implementation of GSM in the affected area. Despite the outdated infrastructure, it is Test Network using N-series USRP has been carried out in not replaced due to huge capital requirement for up-gradation. with some calibration to eventually transmit/receive GSM In case of disaster, emergency services have to depend on signals. USRP2, which is functionally identical to the N-series communication networks obliquely. requires dedicated external 10 MHz reference signal in order One of the primary standards developed for cellular net- to run OpenBTS. USRP1 does not support OpenBTS without works is Global System for Mobile Communication (GSM) the hardware modification. Unlike USRP2, USRP1 does not [1], and due to commonly deployed infrastructure and in- accept a 10 MHz reference signal but required external 52 expensive hardware it is used extensively by the majority MHz clock [5]. With the release of low-cost B200/B210, use of the world population.Endmost authorization of deploying of external 10 MHz reference signal became non-mandatory this hardware architecture and procurement of it was at the in order to run OpenBTS. This became an advantage in directive of funded organizations of government bodies only. terms of establishing GSM system with no prior hardware This confines the testing and analysis of GSM protocols and modifications. In this paper, a comparatively inexpensive B200 infrastructure. Though, due to modern advancements of several USRP board is used to create a Test Network as against reconfigurable architectures and open-source tools like Soft- the previous work carried out on N-series or USRP1/USRP2 ware Defined Radio (SDR), it is now probable to implement platform. The 56 MHz clock rate of B200 can be changed to GSM technology by using utmost hardware with real-time GSM specific 52 MHz by redefining the firmware of USRP software applications. Using low-cost SDR devices such as Hardware Driver (UHD) file. Universal Software Radio Peripherals (USRP), the OpenBTS The paper is organized as follows: Section 2 describes the is one such prevalent software application which can emulate GSM and OpenBTS architecture. In Section 3, the hardware complete GSM stack [2]. This has remained contributory to software suite required for setting up the GSM test network has