Layer23 » History » Revision 6
Revision 5 (laforge, 02/19/2016 10:49 PM) → Revision 6/11 (laforge, 02/19/2016 10:49 PM)
[[PageOutline]] = layer23 = The ''layer23'' program is the playground we use for developing the GSM Protocol layers 2 and 3 (GSM TS 04.05, 04.06, 04.08) Using the layer23 program, you can: * Connect to /tmp/osmocom_l2 socket created by [wiki:osmocon] to exchange data from [wiki:L1A_L23_Interface]. * Receive GSM Layer1 frames. * Dump received GSM Layer1 frames and print some analysis. * Send the Layer1 frames as GSMTAP packets to wireshark (see [wiki:WiresharkIntegration]) * forward the Layer1 frames to the Layer2 / LAPDm implementation inside layer23 * forward them from Layer2 into Layer3 code inside layer23. * receive outgoing frames from Layer3 * process them through layer2 * send them as uplink frames to GSMTAP * send them to the Layer1 on the phone The ''layer23'' program is used in combination with the [wiki:layer1.bin] firmware. === Usage === {{{ ./layer23 -a 871 -i 127.0.0.1 }}} where {{{-a 871}}} indicates the GSM ARFCN to which layer1 shall tune, and {{{-i 127.0.0.1}}} indicates the IP address to which the GSMTAP messages are to be sent. This will connect to the [wiki:osmocon] application and will receive GSM Layer1 frames. The receiving is done in the src/main.c and the frames will be passed to src/l1ctl.c, from there into src/lapdm.c and finally into src/layer3.c The output of the layer23 application is currently looking like this: {{{ Found CCCH burst(s): TDMA: (0003/08/39) tc:3 49 06 1b 3b 80 62 f2 20 01 3a c8 07 0a 15 65 04 b9 00 00 80 00 02 1b si: 0x1b SI3 on wrong TC Found sync burst: SNR: 16384 TDMA: (0003/15/46) bsic: 49 Found sync burst: SNR: 16384 TDMA: (0003/25/05) bsic: 49 Found sync burst: SNR: 16384 TDMA: (0003/09/15) bsic: 49 Found sync burst: SNR: 16384 TDMA: (0003/19/25) bsic: 49 Found CCCH burst(s): TDMA: (0003/07/39) tc:4 31 06 1c 62 f2 20 01 3a 65 04 b9 00 00 80 00 53 2b 2b 2b 2b 2b 2b 2b si: 0x1c SI4 on wrong TC Found sync burst: SNR: 16384 TDMA: (0003/14/46) bsic: 49 Found sync burst: SNR: 16384 TDMA: (0003/24/05) bsic: 49 Found sync burst: SNR: 16384 TDMA: (0003/08/15) bsic: 49 Found sync burst: SNR: 16384 TDMA: (0003/18/25) bsic: 49 Found CCCH burst(s): TDMA: (0003/06/39) tc:5 01 06 00 b0 00 58 47 eb 4a 92 53 40 62 84 eb 2b 2b 2b 2b 2b 2b 2b 2b si: 0x0 SI13 on wrong TC }}} === Goals === The goal for the layer2+ application is to turn it into a complete GSM Stack for Mobile stations. Mobilestations. This will include handling of GSM Layer2 (LAPDm, GSM 04.06), GSM Layer3 (GSM 04.08). The basic functionality will be to scan the channels, then receive information on the BCCH, listen on the paging channel, respond to paging, generate messages for the RACH and more...
