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Harald Welte gerrit-no-reply at lists.osmocom.orgReview at https://gerrit.osmocom.org/2790 Add chapter on Cell Broadcast Support in Osmocom (to BSC+NITB manual) Change-Id: I2c621def499dc0564d31eb9440e22e79948a5466 --- M OsmoBSC/osmobsc-usermanual.adoc M OsmoNITB/osmonitb-usermanual.adoc A common/chapters/cell-broadcast.adoc A common/chapters/osmocom-cbs.msc 4 files changed, 91 insertions(+), 0 deletions(-) git pull ssh://gerrit.osmocom.org:29418/osmo-gsm-manuals refs/changes/90/2790/1 diff --git a/OsmoBSC/osmobsc-usermanual.adoc b/OsmoBSC/osmobsc-usermanual.adoc index 25bd35b..9323373 100644 --- a/OsmoBSC/osmobsc-usermanual.adoc +++ b/OsmoBSC/osmobsc-usermanual.adoc @@ -27,6 +27,8 @@ include::../common/chapters/control_if.adoc[] +include::../common/chapters/cell-broadcast.adoc[] + include::../common/chapters/port_numbers.adoc[] include::../common/chapters/bibliography.adoc[] diff --git a/OsmoNITB/osmonitb-usermanual.adoc b/OsmoNITB/osmonitb-usermanual.adoc index ec219d9..73166fa 100644 --- a/OsmoNITB/osmonitb-usermanual.adoc +++ b/OsmoNITB/osmonitb-usermanual.adoc @@ -31,6 +31,8 @@ include::../common/chapters/control_if.adoc[] +include::../common/chapters/cell-broadcast.adoc[] + include::../common/chapters/abis.adoc[] include::../common/chapters/port_numbers.adoc[] diff --git a/common/chapters/cell-broadcast.adoc b/common/chapters/cell-broadcast.adoc new file mode 100644 index 0000000..d439128 --- /dev/null +++ b/common/chapters/cell-broadcast.adoc @@ -0,0 +1,75 @@ +[[cell_broadcast]] +== Cell Broadcast + +Normally, all user plane data in GSM/GPRS networks are sent in +point-to-point channels from the network to the user. Those are called +"dedicated" radio channels which exist between the network and one +given phone/subscriber at a time. + +Cell Broadcast is an exception to that rule. It permits user data +(so-called SMS-CB data) to be broadcast by the network in a way that +can be received by all phones in the coverage area of the given BTS +simultaneously. + +More high-level information can be found at +https://en.wikipedia.org/wiki/Cell_Broadcast and the related +specification is <<3gpp-ts-23-041>>. + +=== Use Cases + +Cell Broadcast was used for various different use cases primarily in +the 1990ies and early 2000s, including + +* advertisement of the GPS position of the cell tower you're currently camping on +* advertisement of the calling codes of your current "home zone", i.e. a + "lower cost short distance" call zone travelling with you as you roam around. + +More recently, SMS-CB is seeing some uptake by various disaster +warning systems, such as + +* CMAS (Commercial Mobile Alert System), later renamed to WEA (Wireless Emergency Alerts) in the US. +* EU-Alert in the European union +* Messer Ishi (Rocket Alert) in Israel +* ETWS (Earthquake and Tsunami Warning System) in Japan +* KPAS (Korean Public Alert System) + +=== Osmocom Cell Broadcast support + +* OsmoBTS implements the "SMS BROADCAST COMMAND" Message in RSL + according to Section 8.5.8 of 3GPP TS 08.58 +* OsmoNITB and OsmoBSC implement a VTY command + `bts <0-255> smscb-command <1-4> HEXSTRING` to send a given hex-formatted cell + broadcast message to a specified BTS + +[mscgen] +---- +include::osmocom-cbs.msc[] +---- + +==== What'a miaaing + +What's missing (for production operation in larger networks) + +* mechanism to broadcast one (set of) cell broadcast messages from the + BSC to multiple/all BTSs, rather than one BTS individually +* OsmoBTS reporting of current CBCH load +* BSC scheduler scheduling multiple alternating sets of CBCH messages + based on the current CBCH load reported by BTS +* external interface from BSC to a Cell Broadcast Center (CBC), e.g. + according to 3GPP TS 48.049 +* an Osmocom implementation of the Cell Broadcast Center (OsmoCBC) + which can manage and distribute messages to multiple BSCs and which + has an external interface by which cell-broadcast can be entered + into the network + +If you would like to contribute in any of those areas (by means of +code or funding), please reach out to us any time. + +=== Message Structure + +* Each message has a meximum of 15 pages +* Each page is 82 bytes of data, resulting in 93 characters in GSM + 7-bit default alphabet +* Messages are broadcast on logical channels (more like an address) +* Subscribers can activate/deactivate selective addresses + diff --git a/common/chapters/osmocom-cbs.msc b/common/chapters/osmocom-cbs.msc new file mode 100644 index 0000000..f4fd297 --- /dev/null +++ b/common/chapters/osmocom-cbs.msc @@ -0,0 +1,12 @@ +msc { + hscale="2"; + ms [label="MS"], bts [label="BTS"], bsc [label="BSC"], user [label="User"]; + + user -> bsc [label="Establish VTY connection"]; + user -> bsc [label="VTY command"]; + bsc -> bts [label="08.58 RSL SMS BROADCAST CMD"]; + bts -> ms [label="04.12 SMS BC REQ (1st block)"]; + bts -> ms [label="04.12 SMS BC REQ (2nd block)"]; + bts -> ms [label="04.12 SMS BC REQ (3rd block)"]; + bts -> ms [label="04.12 SMS BC REQ (4th block)"]; +} -- To view, visit https://gerrit.osmocom.org/2790 To unsubscribe, visit https://gerrit.osmocom.org/settings Gerrit-MessageType: newchange Gerrit-Change-Id: I2c621def499dc0564d31eb9440e22e79948a5466 Gerrit-PatchSet: 1 Gerrit-Project: osmo-gsm-manuals Gerrit-Branch: master Gerrit-Owner: Harald Welte <laforge at gnumonks.org>