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-== OsmoBTS software architecture
-
-=== OsmoBTS PHY interface abstraction
-
-The OsmoBTS PHY interface serves as an internal abstraction layer
-between given PHY hardware (as provided by the bts_model) and the actual
-logical transceivers (TRXs) of a BTS inside the OsmoBTS code base.
-
-
-==== PHY link
-
-A PHY link is a physical connection / link towards a given PHY. This
-might be, for example,
-
-* a set of file descriptors to device nodes in the /dev/ directory
- (sysmobts, litecell15)
-* a packet socket for sending raw Ethernet frames to an OCTPHY
-* a set of UDP sockets for interacting with OsmoTRX
-
-Each PHY interface has a set of attribute/parameters and a list of 1 to
-n PHY instances.
-
-PHY links are numbered 0..n globally inside OsmoBTS.
-
-Each PHY link is configured via the VTY using its individual top-level
-vty node. Given the different bts-model / phy specific properties, the
-VTY configuration options (if any) of the PHY instance differ between
-BTS models.
-
-The PHY links and instances must be configured above the BTS/TRX nodes
-in the configuration file. If the file is saved via the VTY, the code
-automatically ensures this.
-
-
-==== PHY instance
-
-A PHY instance is an instance of a PHY, accessed via a PHY link.
-
-In the case of osmo-bts-sysmo and osmo-bts-trx, there is only one
-instance in every PHY link. This is due to the fact that the API inside
-that PHY link does not permit for distinguishing multiple different
-logical TRXs.
-
-Other PHY implementations like the OCTPHY however do support addressing
-multiple PHY instances via a single PHY link.
-
-PHY instances are numbered 0..n inside each PHY link.
-
-Each PHY instance is configured via the VTY as a separate node beneath each
-PHY link. Given the different bts-model / phy specific properties, the
-VTY configuration options (if any) of the PHY instance differ between
-BTS models.
-
-
-==== Mapping PHY instances to TRXs
-
-Each TRX node in the VTY must use the 'phy N instance M' command in
-order to specify which PHY instance is allocated to this specific TRX.
-
-=== Internal control flow
-
-==== start-up / sequencing during OsmoBTS start
-
-.Control flow at OsmoBTS start-up procedure
-[options="header",cols="10%,35%,55%"]
-|===
-| section | function | description
-| bts-specific | main() | Entering main() from glibc
-| common | bts_main() | initialization of talloc contexts
-| common | bts_log_init() | initialization of logging
-| common | handle_options() | common option parsing
-| bts-specific | bts_model_handle_options() | model-specific option parsing
-| common | gsm_bts_alloc() | allocation of BTS/TRX/TS data structures
-| common | vty_init() | Initialziation of VTY core, libosmo-abis and osmo-bts VTY
-| common | main() | Setting of scheduler RR priority (if configured)
-| common | main() | Initialization of GSMTAP (if configured)
-| common | bts_init() | configuration of defaults in bts/trx/s object
-| bts-specific | bts_model_init | ?
-| common | abis_init() | Initialization of libosmo-abis
-| common | vty_read_config_file() | Reading of configuration file
-| bts-specific | bts_model_phy_link_set_defaults() | Called for every PHY link created
-| bts-specific | bts_model_phy_instance_set_defaults() | Called for every PHY Instance created
-| common | bts_controlif_setup() | Initialization of Control Interface
-| bts-specific | bts_model_ctrl_cmds_install() | Install model-specific control interface commands
-| common | telnet_init() | Initialization of telnet interface
-| common | pcu_sock_init() | Initialization of PCU socket
-| common | main() | Installation of signal handlers
-| common | abis_open() | Start of the A-bis connection to BSC
-| common | phy_links_open() | Iterate over list of configured PHY links
-| bts-specific | bts_model_phy_link_open() | Open each of the configured PHY links
-| common | write_pid_file() | Generate the pid file
-| common | osmo_daemonize() | Fork as daemon in background (if configured)
-| common | bts_main() | Run main loop until global variable quit >= 2
-|===
-
-
-==== At time of OML establishment
-
-.Control flow at time of OML establishment
-[options="header",cols="10%,35%,55%"]
-|===
-| section | function | description
-| bts-specific | bts_model_oml_estab() | Called by core once OML link is established
-| bts-specific | bts_model_check_oml() | called each time OML sets some attributes on a MO, checks if attributes are valid
-| bts-specific | bts_model_apply_oml() | called each time OML sets some attributes on a MO, stores attribute contents in data structures
-| bts-specific | bts_model_opstart() | for NM_OC_BTS, NM_OC_SITE_MANAGER, NM_OC_GPRS_NSE, NM_OC_GPRS_CELL, NMO_OC_GPRS_NSVC
-| bts-specific | bts_model_opstart() | for NM_OC_RADIO_CARRIER for each trx
-| bts-specific | bts_model_opstart() | for NM_OC_BASEB_TRANSC for each trx
-| bts-specific | bts_model_opstart() | for NM_OC_CHANNEL for each timeslot on each trx
-| bts-specific | bts_model_change_power() | change transmit power for each trx (power ramp-up/ramp-down)
-|===
-
-==== At time of RSL connection loss
-
-.Control flow at time of RSL connection loss
-[options="header",cols="10%,35%,55%"]
-|===
-| section | function | description
-| bts-specific | bts_model_abis_close() | called when either one of the RSL links or the OML link are down
-|===