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Ccch scan » History » Version 1

Anonymous, 02/19/2016 10:49 PM
Copied from /trac/wiki/layer23 version 8; this reflects the name change in the current code.

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[[PageOutline]]
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= ccch_scan =
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The ''ccch_scan'' program (formerly layer23) is the playground we use for developing the GSM Protocol layers 2 and 3 (GSM TS 04.05, 04.06, 04.08)
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Using the ccch_scan program, you can:
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  * Connect to /tmp/osmocom_l2 socket created by [wiki:osmocon] to exchange data from [wiki:L1A_L23_Interface].
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  * Receive GSM Layer1 frames.
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   * Dump received GSM Layer1 frames and print some analysis.
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   * Send the Layer1 frames as [wiki:GSMTAP] packets to wireshark (see [wiki:WiresharkIntegration])
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   * forward the Layer1 frames to the Layer2 / LAPDm implementation inside ccch_scan
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   * forward them from Layer2 into Layer3 code inside ccch_scan.
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  * receive outgoing frames from Layer3
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   * process them through layer2
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   * send them as uplink frames to [wiki:GSMTAP]
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   * send them to the Layer1 on the phone
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The ''ccch_scan'' program is used in combination with the [wiki:layer1.bin] firmware.
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=== Usage ===
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{{{
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./ccch_scan -a 871 -i 127.0.0.1
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}}}
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where {{{-a 871}}} indicates the GSM ARFCN to which layer1 shall tune, and {{{-i 127.0.0.1}}} indicates the IP address
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to which the [wiki:GSMTAP] messages are to be sent.
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This will connect to the [wiki:osmocon] application and will receive GSM Layer1 frames. 
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The receiving is done in the src/main.c and the frames will be passed to src/l1ctl.c,
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from there into src/lapdm.c and finally into src/layer3.c
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The output of the ccch_scan application is currently looking like this:
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{{{
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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
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        SI3 on wrong TC
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Found sync burst: SNR: 16384 TDMA: (0003/15/46) bsic: 49
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Found sync burst: SNR: 16384 TDMA: (0003/25/05) bsic: 49
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Found sync burst: SNR: 16384 TDMA: (0003/09/15) bsic: 49
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Found sync burst: SNR: 16384 TDMA: (0003/19/25) bsic: 49
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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
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        SI4 on wrong TC
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Found sync burst: SNR: 16384 TDMA: (0003/14/46) bsic: 49
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Found sync burst: SNR: 16384 TDMA: (0003/24/05) bsic: 49
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Found sync burst: SNR: 16384 TDMA: (0003/08/15) bsic: 49
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Found sync burst: SNR: 16384 TDMA: (0003/18/25) bsic: 49
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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
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        SI13 on wrong TC
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}}}
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