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Service Area Broadcast » History » Version 1

laforge, 07/24/2017 03:24 PM

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h1. Service Area Broadcast
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Normally, all user plane data in UMTS 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.
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Service Area 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 Service Area (group of cells) simultaneously.
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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
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Service Area Broadcast is the UMTS successor of the GSM [[Cell_Broadcast]]
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h2. Use Cases
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More recently, SMS-CB is seeing some uptake by various desaster warning systems, such as
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* 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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* EU-Alert in the European union
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* Messer Ishi (Rocket Alert) in Israel
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* ETWS (Earthquake and Tsunami Warning System) in Japan
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* KPAS (Korean Public Alert System)
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h2. Architecture as per 3GPP specs.
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See Section 6.2 of 3GPP TR 25.931.  Basically, the CBC (Cell Broadcast Centre) is issuing SABP (Service Area Broadcast Protocol, 3GPP TS 25.419) requests via the Iu-BC interface towards the RNC.  The RNC then schedules the transmission of CBS messages on the CTCH (Common Traffic Channel)
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h2. Osmocom Service Area Broadcast support
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Currently it is not yet supported by any of the Osmocom components.  We would love to implement it, but somebody would have to contribute related code and/or funding.
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Assuming that the NodeB+RNC connected to [[OsmoMSC:]] or the hNodeB connected to [[OsmoHNBGW:]] implement SABP, all we'd need to do is to implement a kind of SABP multiplexor inside [[OsmoHNBGW:]] so that the CBC has to talk only once to the HNBGW, which then takes care of distributing that information to all hNodeB in the service area.
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We would also want to implement a simplistic CBC which implements SABP on Iu-BC towards the RNC/HNBGW, as well as 3GPP TS 48.049 for GSM.  This way one could easily configure certain CBS / SMS-CB messages on the CBC, and the CBC would distribute it to all BSCs/RNCs/HNBGWs in the respective service area, who in turn communicate the messages to the MSs.
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