131 lines
5.0 KiB
Plaintext
131 lines
5.0 KiB
Plaintext
[[smscb]]
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== SMSCB (Cell Broadcast)
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OsmoBSC supports SMS Cell Broadcast (SMSCB) services (CBS). This
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includes the CBSP protocol to interact with a CBC (Cell Broadcast
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Centre) such as OsmoCBC, as well as the scheduling of SMSCB messages on
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both the BASIC and EXTENDED CBCH and transmission of related RSL
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messages to the attached BTS.
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More high-level information can be found at
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https://en.wikipedia.org/wiki/Cell_Broadcast and the related
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specification is <<3gpp-ts-23-041>>.
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In order to use SMSCB with OsmoBSC, you will need to
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* Configure OsmoBSC as either CBSP server or client
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* Use a channel combination including a CBCH on the BTSs
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=== Enabling a CBCH channel combination
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On the Um interface, SMSCB are transmitted via the CBCH (Cell Broadcast
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Channel). The CBCH is a separate downlink-only logical channel which
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must be activated on any of the BTSs requiring CBSP support.
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The channel combination is configured in the `timeslot` node of each TRX.
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The two `phys_chan_config` supporting CBCH are `CCCH+SDCCH4+CBCH` and
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`SDCCH/8+CBCH`. Please note that the CBCH steals one of the SDCCH, so
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a SDCCH/4 will only have three remaining SDCCH, and a SDCCH/8 will
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have only seven remaining SDCCH.
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=== Configuring the CBSP connection
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CBSP is the protocol between BSC and CBC. It operates over TCP.
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According to 3GPP TS 48.049, a BSC typically operates as a TCP server,
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and the CBC connects as TCP client. This would require the CBC to have
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out-of-band knowledge of all the BSCs in the network (and their IP
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addresses).
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In order to comply with the specifications, OsmoBSC supports this mode
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of operation as CBSP TCP server. However, to make network operation and
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configuration more simple, it also can operate in TCP client mode,
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connecting to the CBC. This way the BSCs need to know the CBC IP
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address, but not vice-versa.
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The BSC can operate in either CBSP TCP server mode or CBSP TCP client mode.
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The CBC related configuration of OsmoBSC can be found in the `cbc` configuration
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node of the VTY interface.
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The default port number for the CBSP server is 48049, according to the CBSP
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specification. Hence it normally suffices to configure only the IP addresses for
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the remote CBC server or the local CBSP server:
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.Example: Configure CBSP TCP client to connect to CBC at 1.2.3.4:48049 in osmo-bsc.cfg
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----
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cbc
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mode client
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client
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remote-ip 1.2.3.4
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----
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In server mode, the default configuration is 127.0.0.1:48049, so it suffices to
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set `mode server` to accept CBSP connections from localhost:
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----
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cbc
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mode server
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----
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To also listen for inbound CBSP connections on all interfaces, both IPv4 and
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IPv6:
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.Example: Configure CBSP TCP server to listen on all interfaces in osmo-bsc.cfg
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----
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cbc
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mode server
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server
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local-ip ::
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----
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Should non-standard port numbers be required, these can be configured with the
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`client` / `local-port` or the `server` / `remote-port` settings.
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The `client` config also supports an explicit local bind for connecting to the
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remote CBC, using `client` / `local-ip` and `local-port`.
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IP addresses for client and server can remain configured at the same time, and
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the `mode` command can be used to switch between client and server operation.
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The `mode` command takes immediate effect, no restart of OsmoBSC is required.
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After changing `cbc` IP addresses in the telnet VTY, it is required to switch
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`mode` to `disabled` and back to `client` or `server` to take effect.
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.Example: Disable the CBSP link in the telnet VTY
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----
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OsmoBSC> enable
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OsmoBSC# configure terminal
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OsmoBSC(config)# cbc
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OsmoBSC(config-cbc)# mode disabled
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OsmoBSC(config-cbc)# end
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----
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For more details on the available configuration commands, please check the OsmoBSC VTY Reference.
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=== Counters
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OsmoBSC has two Cell Broadcast related rate counter groups for each BTS:
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* the basic CBCH ("cell broadcast channel 0")
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* the extended CBCH ("cell broadcast channel 1")
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See below example for a situation where no CBS messages were received yet from the CBC,
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and hence only NULL messages have been sent on both basic and extended CBCH:
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.Example: CBCH related rate counters on a BTS that didn't receive any CBS messages
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----
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cell broadcast channel 1:
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cbch:rcvd_queued: 0 (0/s 0/m 0/h 0/d) Received + queued CBCH messages (Abis)
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cbch:rcvd_dropped: 0 (0/s 0/m 0/h 0/d) Received + dropped CBCH messages (Abis)
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cbch:sent_single: 0 (0/s 0/m 0/h 0/d) Sent single CBCH messages (Um)
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cbch:sent_default: 0 (0/s 0/m 0/h 0/d) Sent default CBCH messages (Um)
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cbch:sent_null: 31366 (0/s 45/m 2677/h 30588/d) Sent NULL CBCH messages (Um)
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cell broadcast channel 0:
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cbch:rcvd_queued: 0 (0/s 0/m 0/h 0/d) Received + queued CBCH messages (Abis)
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cbch:rcvd_dropped: 0 (0/s 0/m 0/h 0/d) Received + dropped CBCH messages (Abis)
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cbch:sent_single: 0 (0/s 0/m 0/h 0/d) Sent single CBCH messages (Um)
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cbch:sent_default: 0 (0/s 0/m 0/h 0/d) Sent default CBCH messages (Um)
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cbch:sent_null: 31366 (1/s 46/m 2676/h 30588/d) Sent NULL CBCH messages (Um)
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----
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