Run YateBTS with USRP N210 or bladeRF x40/x115 Hopefully this tutorial will let you skip straight to the right SDR/base station pair and avoid some of the pain (and cost). Tried using the bladeRF x40 for srsLTE as srsLTE mentioned “bladeRF support”, but to no avail.Ended up having to buy the bladeRF x40 (older model) and use an older FPGA image to get devices to connect. Had multiple issues due to YateBTS writing their own radio driver instead of using the official bladeRF libraries. Tried to get the bladeRF 2.0 xA4 working with YateBTS because it mentioned it was supported.Spent a while going through commit logs to find an old working revision that supported UHD. Tried to get the USRP N210’s working with YateBTS latest checkout only to realize that they dropped support for the UHD driver.It could in theory work with other clock rates by performing resampling, but it does not do this. Spent a month trying to get these to work only to realize that srsLTE needs an SDR with a base clock that is a multiple of 1.92MHz (100MHz is not). Bought two USRP N210’s to setup srsLTE.Here’s a list of the main issues we encountered: Well every step along the way revealed some obscure software or hardware incompatibility that left us having try out many different configurations. So why didn’t we just stick with one SDR? These are both open source and their code is relatively easy to compile and hack on. Here are the SDRs we purchased (keep reading, you don’t need all of these): Nameįor the base stations we chose YateBTS for GSM and srsLTE for LTE. SDRs & Softwareįor our SDRs we used four different kinds across two base station implementations when trying to get our testbed working properly. With the disclaimers out of the way, lets dive in. Please still exercise caution to minimize risk to you and those around you and don’t use this for malicious purposes. When it comes to SDRs, rules or not, the genie is out of the bottle and laws won’t stop everyone. DO perform experiments in an RF-shielded environment (Faraday cage) or with the minimum required power.DO consult all applicable laws and regulations for your country/state/county/company before experimenting.DO NOT infer with any other transmitting devices, especially critical infrastructure like other commercial towers.DO NOT transmit on any frequency that you do not have the license(s) for. In general some maxims to follow include, but are not limited to: Some of you may even have your amateur radio tech/general/extra class license, but transmitting potentially encrypted cellular traffic is still prohibited to the best of my knowledge. Even if you did have the required spectrum licenses to transmit (which is highly unlikely), you could still cause serious harm if you by accident intercept or infer with emergency calls from legitimate subscribers. Some laws in other countries are so strict that even possessing an SDR, let alone transmitting, can get you thrown into jail. Violations of FCC regulations can at best land you a hefty fine. This means you need to be ethical when performing cellular, or any radio-based research for that matter. Technically there are the industrial, scientific and medical (ISM) band frequencies, but even these don’t give you free reign to transmit devices (and humans) transmitting in these bands still need FCC approval and testing. Well sorry, this is one of those “if you have to ask you can’t afford it” deals. But wait, what if you don’t have a license? Do you really need one and how can you get one? If you have the equipment and are properly licensed, you’ll legally be able to setup a cell site of your own. To get a base station up and running you need two things: a software defined radio (SDR) for the radio frontend and a software station implementation that can talk to your SDR. In cellular terminology these are known as the BTS and eNodeB for GSM and LTE respectively, but throughout we’ll stick with base station. In this tutorial we’re going to detail the exact steps my guest author Tyler Tucker and I took to get a 2G (GSM) and 4G (LTE) testbed up and running. Without a background in signal processing, cellular protocol conventions, or the right equipment, debugging why a cellular testbed isn’t working can be a pain, to say the least. Understanding and setting up a cellular testbed for this kind of exploration can be a difficult and frustrating process. Have you ever wondered how your smartphone communicates over-the-air? How calls and SMSs reach your phone from across the world? What about how your phone decodes over-the-air messages? Does it do it correctly and what happens if it doesn’t? Well these answers and more lie within the 2 - 5G cellular protocols and their implementations.
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