OsmocomBB源码分析
GSM协议栈
基于接口，GSM信令协议组装成三个通用层：
- 第1层：物理层。 它使用空中接口上的通道结构。
- 第2层：数据链路层。 在Um接口上，数据链路层是用于ISDN中的D信道（LAPD）协议的链路访问协议的修改版本，在Dm信道上称为链路访问协议（LAPDm）。 在A接口上，使用消息传输部分（MTP），SS7的第2层。
- 第3层：GSM信令协议的第三层分为三个子层：
- 无线电资源管理（RR Radio Resouce）
- 流动性管理（MM Mobile Management）
- 连接管理（CM Connection Management）
业务逻辑和接口
NAS层分为CC（Call Control) SS (Supplementary Service) SMS (Short Message Service) REG (register service)
各层逻辑框图和接口
osmocon代码分析
osmocon 是一种控制台工具，用于将手机上的基带固件与主机PC中的应用程序接口。
它还可用于通过串行线路将固件或引导程序下载到电话中，当前已针对CompalE88（C118/C120/C121/C123），CompalE99（C155）实现了该程序。
目前支持的Bootloader是CompalRamloader和CalypsoRomloader。
上载固件后，它将变成HDLC多路复用器/多路解复用器，从而允许与设备进行多通道通信。
电话控制台位于一个这样的通道上，并将被重定向到运行osmocom的终端（stdout）。
可以通过以下unix域套接字访问其他几个HDLC通道：
- / tmp / osmocom_l2为L1A_L23_Interface 13759 移动，ccch_scan和其它主机程序
- / tmp / osmocon_loader用于引导程序
一般用法
使用HardwareSerialCable（2.5mm耳机插孔上的3.3V RS232）将电话 UART 连接到PC的串行端口。
选择要加载的固件，具体取决于要运行的主机程序。
将固件加载到手机，如下所示运行osmocon。用您的值填写电话类型和固件名称。
$ ./osmocon -p / dev / ttyUSB0 -m c123xor ../../target/firmware/board/PHONE_TYPE/FIRMWARE.compalram.bin
确保手机关机。 短暂按一下手机的开机按钮（短按，不像普通的手机开机！）。避免在使用osmocon时为手机充电，否则可能会限制加载程序。
观察类似于以下内容的输出：
got 2 bytes from modem, data looks like: 2f c8
got 5 bytes from modem, data looks like: 1b f6 02 00 41
got 1 bytes from modem, data looks like: 01
got 1 bytes from modem, data looks like: 40
Received PROMPT1 from phone, responding with CMD
read_file(../../target/firmware/board/compal_e88/loader.compalram.bin): file_size=13404, hdr_len=4, dnload_len=13411
got 1 bytes from modem, data looks like: 1b
got 1 bytes from modem, data looks like: f6
got 1 bytes from modem, data looks like: 02
got 1 bytes from modem, data looks like: 00
got 1 bytes from modem, data looks like: 41
got 1 bytes from modem, data looks like: 02
got 1 bytes from modem, data looks like: 43
Received PROMPT2 from phone, starting download
handle_write(): 1023 bytes (1023/13411)
handle_write(): 768 bytes (1791/13411)
handle_write(): 768 bytes (2559/13411)
handle_write(): 768 bytes (3327/13411)
handle_write(): 768 bytes (4095/13411)
handle_write(): 768 bytes (4863/13411)
handle_write(): 768 bytes (5631/13411)
handle_write(): 768 bytes (6399/13411)
handle_write(): 768 bytes (7167/13411)
handle_write(): 768 bytes (7935/13411)
handle_write(): 768 bytes (8703/13411)
handle_write(): 768 bytes (9471/13411)
handle_write(): 768 bytes (10239/13411)
handle_write(): 768 bytes (11007/13411)
handle_write(): 768 bytes (11775/13411)
handle_write(): 768 bytes (12543/13411)
handle_write(): 768 bytes (13311/13411)
handle_write(): 100 bytes (13411/13411)
handle_write(): finished
got 1 bytes from modem, data looks like: 1b
got 1 bytes from modem, data looks like: f6
got 1 bytes from modem, data looks like: 02
got 1 bytes from modem, data looks like: 00
got 1 bytes from modem, data looks like: 41
got 1 bytes from modem, data looks like: 03
got 1 bytes from modem, data looks like: 42
Received DOWNLOAD ACK from phone, your code is running now!
OSMOCOM Calypso loader (revision f45c5ee-modified)
======================================================================
Running on compal_e88 in environment ramload
现在，您可以通过应用程序（例如mobile，ccch_scan，osmoload等）与手机进行交互，具体取决于所加载的固件。
NAS层代码分析
UE和NW之间的呼叫处理过程
CC Call Control(GSM 04.08)
主叫和被叫 call control状态转换图
呼叫控制部分代码由全局变量datastatelist的函数列表来维护。
datastatelist的不同状态对应的处理函数
| states | protocol | type | callback |
|---|---|---|---|
| /* mobile originating call establishment*/ | |||
| SBIT(GSM_CSTATE_INITIATED) | /5.2.1.3/ | GSM48_MT_CC_CALL_PROC | gsm48_cc_rx_call_proceeding |
| SBIT(GSM_CSTATE_INITIATED), SBIT(GSM_CSTATE_MO_CALL_PROC), SBIT(GSM_CSTATE_CALL_DELIVERED) | /*5.2.1.4.1*/ | GSM48_MT_CC_PROGRESS | gsm48_cc_rx_progress |
| SBIT(GSM_CSTATE_INITIATED), SBIT(GSM_CSTATE_MO_CALL_PROC) | /*5.2.1.5*/ | GSM48_MT_CC_ALERTING | gsm48_cc_rx_alerting |
| SBIT(GSM_CSTATE_INITIATED), SBIT(GSM_CSTATE_MO_CALL_PROC), SBIT(GSM_CSTATE_CALL_DELIVERED) | /*5.2.1.6*/ | GSM48_MT_CC_CONNECT | gsm48_cc_rx_connect |
| /*mobile terminating call establishment*/ | |||
| SBIT(GSM_CSTATE_NULL) | /*5.2.2.1*/ | GSM48_MT_CC_SETUP | gsm48_cc_rx_setup |
| SBIT(GSM_CSTATE_CONNECT_REQUEST) | /*5.2.2.6*/ | GSM48_MT_CC_CONNECT_ACK | gsm48_cc_rx_connect_ack |
| /*signalling during call*/ | |||
| SBIT(GSM_CSTATE_ACTIVE) | /*5.3.1*/ | GSM48_MT_CC_NOTIFY | gsm48_cc_rx_notify |
| ALL_STATES | /8.4/ | GSM48_MT_CC_STATUS_ENQ | gsm48_cc_rx_status_enq |
| ALL_STATES | /8.4/ | GSM48_MT_CC_STATUS | gsm48_cc_rx_status |
| ALL_STATES | /*5.5.7.2*/ | GSM48_MT_CC_START_DTMF_ACK | gsm48_cc_rx_start_dtmf_ack |
| ALL_STATES | /*5.5.7.2*/ | GSM48_MT_CC_START_DTMF_REJ | gsm48_cc_rx_start_dtmf_rej |
| ALL_STATES | /*5.5.7.4*/ | GSM48_MT_CC_STOP_DTMF_ACK | gsm48_cc_rx_stop_dtmf_ack |
| SBIT(GSM_CSTATE_ACTIVE) | GSM48_MT_CC_HOLD_ACK | gsm48_cc_rx_hold_ack | |
| SBIT(GSM_CSTATE_ACTIVE) | GSM48_MT_CC_HOLD_REJ | gsm48_cc_rx_hold_rej | |
| SBIT(GSM_CSTATE_ACTIVE) | GSM48_MT_CC_RETR_ACK | gsm48_cc_rx_retrieve_ack | |
| SBIT(GSM_CSTATE_ACTIVE) | GSM48_MT_CC_RETR_REJ | gsm48_cc_rx_retrieve_rej | |
| ALL_STATES-SBIT(GSM_CSTATE_NULL) | GSM48_MT_CC_FACILITY | gsm48_cc_rx_facility | |
| SBIT(GSM_CSTATE_ACTIVE) | GSM48_MT_CC_USER_INFO | gsm48_cc_rx_userinfo | |
| /*clearing*/ | |||
| ALL_STATES-SBIT(GSM_CSTATE_NULL)-SBIT(GSM_CSTATE_RELEASE_REQ)-SBIT(GSM_CSTATE_DISCONNECT_IND) | /*5.4.4.1.1*/ | GSM48_MT_CC_DISCONNECT | gsm48_cc_rx_disconnect |
| ALL_STATES | /*5.4.3.3&5.4.5!!!*/ | GSM48_MT_CC_RELEASE | gsm48_cc_rx_release |
| ALL_STATES | /*5.4.4.1.3*/ | GSM48_MT_CC_RELEASE_COMPL | gsm48_cc_rx_release_compl |
| /*modify*/ | |||
| SBIT(GSM_CSTATE_ACTIVE) | GSM48_MT_CC_MODIFY | gsm48_cc_rx_modify | |
| SBIT(GSM_CSTATE_MO_TERM_MODIFY) | GSM48_MT_CC_MODIFY_COMPL | gsm48_cc_rx_modify_complete | |
| SBIT(GSM_CSTATE_MO_TERM_MODIFY) | GSM48_MT_CC_MODIFY_REJECT | gsm48_cc_rx_modify_reject |
SS Supplementary Service(GSM 04.80)
SMS Short Message Service(GSM 04.11)
SMS Call Flow
PHY层代码
trx数据接收和发送过程
不同信道的接收发送由trx_lchan_desc全局变量的函数列表来维护，接收处理函数rx_data_fn，接收处理函数tx_data_fn。
GSM 05.03 Channel Coding
encode & decode
Y:\code\libosmocore\src\coding\gsm0503_coding.c
GSM 05.03 Interleaving
interleave & deinterleave
Y:\code\libosmocore\src\coding\gsm0503_interleaving.c
GSM 05.03 mapping
mapping & unmapping
Y:\code\libosmocore\src\coding\gsm0503_mapping.c
