Cell Broadcast » History » Version 15
laforge, 09/29/2018 09:40 AM
1 | 1 | laforge | h1. Cell Broadcast |
---|---|---|---|
2 | 7 | fixeria | |
3 | {{>toc}} |
||
4 | 1 | laforge | |
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. |
||
6 | |||
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. |
||
8 | |||
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 |
||
10 | |||
11 | 2 | laforge | h2. Use Cases |
12 | 1 | laforge | |
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 |
||
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. |
||
16 | |||
17 | More recently, SMS-CB is seeing some uptake by various desaster warning systems, such as |
||
18 | * CMAS (Commercial Mobile Alert System), later renamed to WEA ("Wireless Emergency Alerts":https://en.wikipedia.org/wiki/Wireless_Emergency_Alerts) in the US. |
||
19 | * EU-Alert in the European union |
||
20 | * Messer Ishi (Rocket Alert) in Israel |
||
21 | * ETWS (Earthquake and Tsunami Warning System) in Japan |
||
22 | * KPAS (Korean Public Alert System) |
||
23 | |||
24 | 10 | laforge | h2. Osmocom Cell Broadcast support |
25 | 1 | laforge | |
26 | 6 | laforge | * [[OsmoBTS:]] implements the "SMS BROADCAST COMMAND" Message in RSL according to Section 8.5.8 of 3GPP TS 08.58 *but not all hardware targets support this yet, see #1617. osmo-bts-sysmo and osmo-bts-octphy are fine.* |
27 | 1 | laforge | * [[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 |
28 | 8 | laforge | ** you (obviously) first need to enable a timeslot/channel combination on the BTS that actually includes a CBCH, i.e. ccch+sdcch4+cbch or sdcch8+cbch |
29 | 1 | laforge | |
30 | 4 | laforge | !osmocom-cbs.png! |
31 | |||
32 | 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 |
33 | 1 | laforge | |
34 | 10 | laforge | h3. How to test/use it |
35 | |||
36 | You need to perform two steps: |
||
37 | |||
38 | h4. make sure your related BTS is configured to use a channel combination with CBCH |
||
39 | |||
40 | For using a combined CCCH with SDCCH/4 and CBCH you can use the following example snippet as part of osmo-bsc.cfg: |
||
41 | |||
42 | <pre> |
||
43 | network |
||
44 | bts 0 |
||
45 | trx 0 |
||
46 | timeslot 0 |
||
47 | phys_chan_config CCCH+SDCCH4+CBCH |
||
48 | </pre> |
||
49 | |||
50 | h4. telnet to osmo-bsc at port 4242, and enter something like |
||
51 | |||
52 | <pre> |
||
53 | enable |
||
54 | bts 0 smscb-command 1 001000320f1141660c344dd3cba09a0c |
||
55 | </pre> |
||
56 | |||
57 | where "1" is the number of blocks required (each 22 bytes need one block) |
||
58 | and the hex-dump at the end is the encoded GSM 04.12 message to be broadcast. |
||
59 | |||
60 | 1 | laforge | h3. What's missing (for production operation in larger networks) |
61 | |||
62 | * mechanism to broadcast one (set of) cell broadcast messages from the BSC to multiple/all BTSs, rather than one BTS individually |
||
63 | * BTS reporting of current CBCH load |
||
64 | * BSC scheduler scheduling multiple alternating sets of CBCH messages based on the current CBCH load reported by BTS |
||
65 | 10 | laforge | * external interface from BSC to a Cell Broadcast Center (CBC), e.g. according to 3GPP TS 48.049 (CBSP) |
66 | 1 | 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 |
67 | 10 | laforge | |
68 | |||
69 | |||
70 | 3 | laforge | |
71 | 2 | laforge | h2. Message Structure |
72 | |||
73 | * Message has maximum 15 pages |
||
74 | * Each page is 82 bytes of data, resulting in 93 characters in GSM 7-bit default alphabet |
||
75 | * Messges are broadcast on logical channels (more like an address) |
||
76 | * Subscribers can activate/deactivate selective addresses |
||
77 | |||
78 | h2. Further Reading |
||
79 | |||
80 | * ITU-T SG2 (Standardization of CB Channels) |
||
81 | * ETSI 102 444 |
||
82 | 9 | laforge | * "3GPP TS 23.041 GSM: Technical realization of Cell Broadcast Service (CBS)":https://www.etsi.org/deliver/etsi_ts/123000_123099/123041/15.02.00_60/ts_123041v150200p.pdf |
83 | * "3GPP TS 48.049 GSM: Baste Station Controller - Cell Broadcast Centre (BSC-CBC) interface specification; Cell Broadcast Service Protocol (CBSP)":https://www.etsi.org/deliver/etsi_ts/148000_148099/148049/15.00.00_60/ts_148049v150000p.pdf |
||
84 | 2 | laforge | * "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 |
85 | 1 | laforge | * "3GPP TS 44.012 GSM: Short Message Service Cell Broadcast (SMSCB) support on the mobile radio interface":https://www.etsi.org/deliver/etsi_ts/144000_144099/144012/15.00.00_60/ts_144012v150000p.pdf |
86 | 14 | laforge | * "Whitepaper on Displaying Cell Broadcast":https://www.one2many.eu/assets/files/19_displaying-cb-messages.pdf |
87 | 2 | laforge | |
88 | h3. EU-Alert |
||
89 | |||
90 | 13 | laforge | * "ETSI/EMTEL TS 102 900":https://www.etsi.org/deliver/etsi_ts/102900_102999/102900/01.01.01_60/ts_102900v010101p.pdf |
91 | 2 | laforge | |
92 | h3. CMAS |
||
93 | |||
94 | 12 | laforge | * "FCC 08-99: First Report and Order":https://www.one2many.eu/assets/files/16_first-report-and-order.pdf |
95 | * "FCC 08-164: Second Report and Order":https://www.one2many.eu/assets/files/17_second-report-and-order.pdf |
||
96 | * "FCC 08-184: Third Report and Order":https://www.one2many.eu/assets/files/18_third-report-and-order.pdf |
||
97 | 15 | laforge | * "ATIS/TIA Standard J-STD-100 (Mobile Device Behavior)":https://global.ihs.com/doc_detail.cfm?&document_name=TIA%20J-STD-100 |
98 | * "ATIS/TIA Standard J-STD-101 (Federal Alert Gateway to CMSP Gateway Interface Spec)":https://global.ihs.com/doc_detail.cfm?&document_name=TIA%20J-STD-101 |
||
99 | * "ATIS/TIA Standard J-STD-102 (Federal Alert Gateway to CMSP Gateway Interface Test Spec)":https://global.ihs.com/doc_detail.cfm?&document_name=TIA%20J-STD-102 |
||
100 | 14 | laforge | * "ATIS 0700006 eWEA via GSM/UMTS Cell Broadcast Service Spec":https://global.ihs.com/doc_detail.cfm?document_name=ATIS%200700006 |
101 | * "ATIS 0700007 Implementation Guidelines and Best Practises for GSM/UMTS Cell Broadcast Service":https://global.ihs.com/doc_detail.cfm?document_name=ATIS%200700007 |
||
102 | * "ATIS 0700008 Cell Broadcast Entity (CBE)-to-Cell Broadcast Center (CBC) Interface Specification":https://global.ihs.com/doc_detail.cfm?document_name=ATIS%200700008 |
||
103 | * "ATIS 0700010 Enhanced Wireless Emergency Alert (eWEA) via EPS Public Warning System Specification":https://global.ihs.com/doc_detail.cfm?document_name=ATIS%200700010 |
||
104 | 2 | laforge | |
105 | h3. ETWS |
||
106 | 11 | laforge | |
107 | * "3GPP TS 22.168: ETWS Requirements Stage 1":https://www.etsi.org/deliver/etsi_ts/122100_122199/122168/08.03.00_60/ts_122168v080300p.pdf |
||
108 | * various modifications to TS 23.038, 23.401, 25.304, 25.331, see http://www.3gpp.org/DynaReport/WiCr--370051.htm |