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84 lines
3.4 KiB
Plaintext
84 lines
3.4 KiB
Plaintext
[[overview]]
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== OsmoCBC Overview
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=== The 3GPP Cell Broadcast Centre
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Within the 3GPP cellular network, the Cell Broadcast Centre is the central
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instance for managing all Cell Broadcast and Emergency Warning functions.
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It acts as a gateway between external applications / users, such as government
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authorities for civil protection, and the various components within the 3GPP
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network to actually deliver those broadcast and/or emergency messages.
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.Role of the CBC inside the 3GPP network architecture (3GPP TS 23.041 §3)
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[graphviz]
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----
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include::../images/cbc-in-network.dot[]
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----
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[[about]]
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=== About OsmoCBC
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OsmoCBC is the Osmocom implementation of a Cellular Broadcast Centre (CBC). It
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implements:
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- the BSC-CBC interface using the CBSP protocol
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- The MME-CBC interface using the SBc-AP protocol
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- a HTTP/JSON/RESTful interface for external applications
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- a telnet-based command line interface for configuration and introspection called VTY
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OsmoCBC provides mainly the following functionality:
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- establishing communication with the various Radio Access Network elements such as BSCs within the network
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- receiving requests to start or remove CBS and ETWS messages from external applications
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- distributing the CBS and/or ETWS messages to the various RANs of the 3GPP cellular network
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Future versions of OsmoCBC are expected to contain the RNC-CBC interface with
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the SABP protocol. Should you be interested in contributing to this effort,
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please contact the author of this document.
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=== CBSP implementation
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CBSP is a Layer 5 protocol operating on top of TCP/IP, established
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between the CBC and the various BSCs of a cellular network.
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According to 3GPP, the CBSP is typically established from the CBC to the
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BSC. This means that the CBSP operates as TCP client and the BSCs
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operate as TCP servers. The disadvantage of this is that it requires
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the CBC to have out-of-band, prior knowledge about all the BSCs in the
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network, as well as their IP addresses.
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OsmoCBC also supports a slightly modified mode of operation, where the
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CBC operates as TCP server, and the BSCs as TCP clients. This means
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that all BSCs need to know the IP address of the CBC. In this situation,
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the CBC doesn't need to know each and every BSC in the network. It
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simply only accepts incoming CBSP connections.
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For more information, see <<config-cbsp>> on how CBSP is configured.
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=== SBc-AP implementation
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SBc-AP (SBc Application Part) is the interface between the Mobility Management
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Entity (MME) and the Cell Broadcast Centre (CBC) in 4G networks. It is also the
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interface between the Public Warning System – Inter Working Function (PWS-IWF)
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and the CBC in 5G networks. It is specified in 3GPP TS 29.168.
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Similarly to what's done with CBSP, OsmoCBC also supports operating SBc-AP as an
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SCTP client or an SCTP server. In the first case, OsmoCBC must be passed a list
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of MMEs to connect to, while in the second one it will only accept incoming SCTP
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connections.
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For more information, see <<config-sbcap>> on how SBc-AP is configured.
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=== ECBE REST interface
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3GPP does not specify the external interface by which competent
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authorities can submit SMSCB and/or ETWS messages to a CBC.
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Hence, a non-standard, Osmocom specific HTTP/REST/JSON based interface
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is offered for external entities to create and delete SMSCB and ETWS
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messages within the CBC. This interface is called ECBE.
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For more information, see <<ecbe>> on the ECBE API definition and <<config-ecbe>>
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on how it is configured.
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