Cell Broadcast » History » Version 4
laforge, 05/29/2017 06:37 PM
1 | 1 | laforge | {{>toc}} |
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3 | h1. Cell Broadcast |
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5 | 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 whcih exist between the network and one given phone/subscriber at a time. |
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7 | 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. |
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9 | More high-level information can be found at https://en.wikipedia.org/wiki/Cell_Broadcast and the related specification is found at "3GPP TS 23.041 Technical realization of Cell Broadcast Service (CBS)":http://www.3gpp.org/ftp/Specs/html-info/23041.htm |
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11 | 2 | laforge | h2. Use Cases |
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13 | 2 | laforge | Cell Broadcast was used for various different use cases primarily in the 1990ies and early 2000s, including |
14 | * advertisement of the GPS position of the cell tower you're currently camping on |
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15 | * 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. |
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17 | More recently, SMS-CB is seeing some uptake by various desaster warning systems, such as |
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18 | * CMAS (Commercial Mobile Alert System), later renamed to WEA ("Wireless Emergency Alerts":https://en.wikipedia.org/wiki/Wireless_Emergency_Alerts) in the US. |
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19 | * EU-Alert in the European union |
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20 | * Messer Ishi (Rocket Alert) in Israel |
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21 | * ETWS (Earthquake and Tsunami Warning System) in Japan |
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22 | * KPAS (Korean Public Alert System) |
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24 | 1 | laforge | h2. Osmocom Cell Broadcast support |
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26 | * [[OsmoBTS:]] implements the "SMS BROADCAST COMMAND" Message in RSL according to Section 8.5.8 of 3GPP TS 08.58 |
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27 | * [[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 |
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29 | 4 | laforge | !osmocom-cbs.png! |
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31 | 2 | laforge | This is sufficient for manual transmission of cell-broadcast messages in a lab environment or in small networks. The functionality has been developed and "used at the 31st annual CCC congress (31C3) to deliver spoofed _Presidential Level Alert_ messages":https://twitter.com/2b_as/status/549695235207737344/photo/1 |
32 | 1 | laforge | |
33 | h3. What's missing (for production operation in larger networks) |
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35 | * mechanism to broadcast one (set of) cell broadcast messages from the BSC to multiple/all BTSs, rather than one BTS individually |
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36 | * BTS reporting of current CBCH load |
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37 | * BSC scheduler scheduling multiple alternating sets of CBCH messages based on the current CBCH load reported by BTS |
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38 | 2 | laforge | * external interface from BSC to a Cell Broadcast Center (CBC), e.g. according to 3GPP TS 48.049 |
39 | 3 | laforge | * an Osmocom implementation of the Cell Broadcast Center (OsmoCBC) which can manage and dsitribute messages to multiple BSCs and which has an external interface by which cell-broadcast can be entered into the network |
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41 | 2 | laforge | h2. Message Structure |
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43 | * Message has maximum 15 pages |
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44 | * Each page is 82 bytes of data, resulting in 93 characters in GSM 7-bit default alphabet |
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45 | * Messges are broadcast on logical channels (more like an address) |
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46 | * Subscribers can activate/deactivate selective addresses |
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48 | h2. Further Reading |
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50 | * ITU-T SG2 (Standardization of CB Channels) |
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51 | * 3GPP TS 23.041 Cell Broadcast |
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52 | * ETSI 102 444 |
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53 | * "3GPP TS 22.268 PWS: Public Warning System (PWS) requirements":http://www.etsi.org/deliver/etsi_ts/122200_122299/122268/14.00.00_60/ts_122268v140000p.pdf |
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55 | h3. EU-Alert |
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57 | * ETSI/EMTEL TS 102 900 |
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59 | h3. CMAS |
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61 | * ATIS/TIA Standards J-STD-100, 101, 102 |
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63 | h3. ETWS |