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