Project

General

Profile

FakeTRX » History » Revision 37

Revision 36 (fixeria, 04/19/2019 06:09 PM) → Revision 37/44 (fixeria, 04/19/2019 06:20 PM)

h1. FakeTRX (Virtual Um-interface) 

 FakeTRX is a virtual Um-interface implementation written in Python, that which allows you to connect both [[OsmocomBB:]] and [[OsmoBTS:]] without the actual RF hardware. The main purpose of this software is to facilitate and simplify the development and testing process. In other words, you don't need to physically run your GSM network nor use any kind of special hardware - just run a few scripts and do anything you want / need in your virtual GSM network! 

 h2. Source code 

 FakeTRX is a part of [[OsmocomBB:]]. The source code is available at git.osmocom.org. 

 You can browse it via cgit: https://git.osmocom.org/osmocom-bb/tree/src/target/trx_toolkit, and download using git: 

 <pre> 
 $ git clone git://git.osmocom.org/osmocom-bb.git 
 </pre> 

 Contributions are welcome via [[cellular-infrastructure:Gerrit]]. 

 h2. FAQ 

 

 h3. What is the difference from [[cellular-infrastructure:Virtual_Um|VIRT-PHY]]? 

 The main difference is that FakeTRX basically works on GSM L1 and deals with bursts, while [[cellular-infrastructure:Virtual_Um|VIRT-PHY]] works on GSM L2, using GSMTAP and multicast sockets to exchange MAC-blocks. FakeTRX provides the [[TRX Interface]] for both [[OsmocomBB:]] and [[OsmoBTS:]], and forwards GSM bursts between both sides. So, there is no need to do any modifications in the [[OsmoBTS:]] source code, just use osmo-bts-trx. 

 

 h3. Python? 

 Of course, Python is slower than C, for example. But it's more than enough for exchanging UDP messages between [[OsmocomBB:]] and [[OsmoBTS:]], and vice versa. Moreover, it can be easily reimplemented in C, if someone interested in better performance. 

 Once multiple instances are supported, we can benchmark to see what's the preformance bottleneck. 

 h3. What about RSSI and ToA (Timing of Arrival)? 

 Since we are talking about the virtual interface, it's possible to emulate any values for both RSSI and ToA. 

 

 h3. Can I run multiple BTS and / or multiple MS instances? 

 Yes (since #3667 is done)! 

 

 h2. Running 

 This guide assumes that you already have the Osmocom GSM [[cellular-infrastructure:|network side stack]] compiled and installed. If not, the simplest way is to use the [[osmonitb:|Network in the Box]]. 

 {{graphviz_link() 
 digraph G { 
     rankdir = LR; 
     subgraph cluster_M { 
         L23APP1 [label="L2&3 app (e.g. mobile)"]; 
         L23APP2 [label="L2&3 app (e.g mobile)"]; 
         TTCN3MS [label="TTCN-3 TC (MS side)"]; 
         TRXcon1 [label="trxcon"]; 
         TRXcon2 [label="trxcon"]; 
         TRXcon3 [label="trxcon"]; 
         label = "Mobile side"; 
     } 

     FakeTRX [label="FakeTRX"]; 

     subgraph cluster_N { 
         OsmoBSC; 
         TTCN3NET [label="TTCN-3 TC (BTS side)"]; 
         OsmoBTS1 [label="osmo-bts-trx"]; 
         OsmoBTS2 [label="osmo-bts-trx"]; 
         OsmoBTS3 [label="osmo-bts-trx"]; 
         label = "Network side"; 
     } 

     L23APP1 -> TRXcon1 [label="L1CTL"]; 
     L23APP2 -> TRXcon2 [label="L1CTL"]; 
     TTCN3MS -> TRXcon3 [label="L1CTL"]; 

     TRXcon1 -> FakeTRX [label="TRX Interface"]; 
     TRXcon2 -> FakeTRX [label="TRX Interface"]; 
     TRXcon3 -> FakeTRX [label="TRX Interface"]; 

     FakeTRX -> OsmoBTS1 [label="TRX Interface"]; 
     FakeTRX -> OsmoBTS2 [label="TRX Interface"]; 
     FakeTRX -> OsmoBTS3 [label="TRX Interface"]; 
     OsmoBTS1 -> OsmoBSC; 
     OsmoBTS2 -> OsmoBSC; 
     OsmoBTS3 -> TTCN3NET; 
     } 
 } 
 }} 

 [[TRX Interface]] is a part of the upstream [[OsmocomBB:]], just make sure that you have compiled the latest version of [[TRX Interface#The-trxcon-application|trxcon]] application. FakeTRX is a part of TRX toolkit, that is located in 'src/target/trx_toolkit/'. See README for more details. 

 _Tip: feel free to use tmux or screen to avoid a mess with multiple windows_ 

 1. Run the network side stack you have. In this example we will use the [[osmonitb:|Network in the Box]]: 

 <pre> 
 $ osmo-nitb -c ./openbsc.cfg -l ./hlr.sqlite3 -P -C --debug=DRLL:DCC:DMM:DRR:DRSL:DNM 
 </pre> 

 2. Run the fake_trx.py: 

 <pre> 
 $ cd osmocom-bb/src/target/trx_toolkit/ 
 $ python ./fake_trx.py 
 </pre> 

 3. Start [[OsmoBTS:]]: 

 <pre> 
 $ osmo-bts-trx -c ./osmo-bts.cfg 
 </pre> 

 Congratulations! Now you have a virtual GSM network running. As you can see, the virtual transceiver emulates the clock source, as this is required for [[OsmoBTS:]]. Also, it handles only a few important commands, such as RXTUNE and TXTUNE, but ignores other irrelevant ones. 

 4. In order to "bridge" [[Host_Software|L2&3 applications]] with FakeTRX, you need to run [[TRX Interface#The-trxcon-application|trxcon]]: 

 <pre> 
 $ cd osmocom-bb/src/host/trxcon/ 
 $ ./trxcon 
 </pre> 

 5. Finally, run any L2&3 application, e.g. ccch_scan: 

 <pre> 
 $ cd osmocom-bb/src/host/layer23/src/misc/ 
 $ ./ccch_scan -a ARFCN -i 127.0.0.1 
 </pre> 

 Please note that ARFCN value should match the one your BTS configured to. 

 At this stage, you should see the broadcast messages coming from the virtual network, like in case of a real one. You can use Wireshark to analyze them. 

 

 h2. Running [[mobile]] application 

 As you should already know, [[mobile]] applications implements a simple mobile phone with SMS, USSD and voice calls. In the virtual network we can benefit from using a virtual SIM card. Just configure one according to your network configuration, see the example below. If you are starting with the default config from the source tree (@osmocom-bb/doc/examples/mobile/default.cfg@), make sure to change @sim reader@ to @sim test@ in the @ms 1@ section. 

 <pre> 
 test-sim 
   imsi 901700000000000 
   no barred-access 
   rplmn 901 70 
 </pre> 

 Make sure you have the virtual network running, then run mobile the same way as in case of a Calypso based phone: 

 <pre> 
 $ cd osmocom-bb/src/host/layer23/src/mobile/ 
 $ ./mobile -i 127.0.0.1 
 </pre> 

 Now you can use mobile's telnet interface to manage your virtual phone: 

 <pre> 
 $ telnet localhost 4247 
 $ ... 
 </pre> 

 h2. Multiple transceivers 

 It's possible to handle multiple MS and/or BTS connections in a single [[FakeTRX]] process using _--trx_ option. 

 Additional MS-/BTS-side transceiver: 

 <pre> 
 $ ./fake_trx.py --trx 127.0.0.1:6703 
 </pre> 

 Two child transceivers of the main BTS: 

 <pre> 
 $ ./fake_trx.py --trx 127.0.0.1:5700/1 --trx 127.0.0.1:5700/2 
 </pre> 

 Additional transceiver with name: 

 <pre> 
 $ ./fake_trx.py --trx foo@127.0.0.1:5703 
 </pre> 

 Additional transceiver with IPv6 address: 

 <pre> 
 $ ./fake_trx.py --trx ipv6@[2001:0db8:85a3:0000:0000:8a2e:0370:7334]:5700/5 
 </pre> 

 

 h2. Demo 

 https://www.youtube.com/watch?v=Uxdaui8EkjY 

 

 h2. Project status 

 Supported: 

 * Simulation and randomization of both RSSI and ToA 
 * Multiple MS / BTS transceivers (see #3667) 
 * Burst capture to file (see data_dump.py) 
 * Injection of bursts and commands
Add picture from clipboard (Maximum size: 48.8 MB)