SHORT MESSAGE SERVICE(SMS)

MOBILE COMPUTING OVER SMS

• GSM supports data access over CSD(Circuit Switched Data).

• GSM – digitized not packetized.

• CSD – circuit is established & user is charged based on time – the circuit is active & not on the no. Of pkts. Transacted.

• GPRS – also known as 2.5G, - next phase within the evolution of GSM, supports data over packets.

• WAP – data service supported by GPRS & GSM to access Internet & remote data services.

• GSM also include Group 3 facsimile – appropriate fax adapter.

• Unique data service of GSM – SMS – enables sending and receiving text messages to & from, GSM mobile phones.

SMS

• On December 3, 1992, a scientist named Neil Papworth at Sema, a British technology company, sent the first text message “Merry Christmas” to the GSM Operator Vodafone.

• Today SMS – most popular data bearer/service within GSM with an average of 1 billion SMS messages(end of 2002) transacted everyday around the world.

• Each short message is upto 160 characters in length, when 7-bit Eng. Characters are used.

STRENGTHS OF SMS

• UNIQUE CHARACTERISTICS OF SMS :

• 1) Omnibus nature of SMS : uses SS7 signaling channel, - available throughout the world.

• Only bearer – allows a subscriber to send a long distance SMS without – long distance subscription.

• Eg., can’t make a voice call to a mobile phone in UK – unless have international calling facility.

• But send a SMS to a subscriber in – not having international call facility.

• 2) Stateless : sessionless & stateless - every SMS – unidirectional & independent of any context.

• Best bearer for notifications, alerts & paging.

• Used for Push & unsolicited response.

• 3) Asynchronous: In HTTP – there is a request & response pair – is synchronous.

• But SMS – asynchronous – ie., even if recipient is out of service – transmission not be abondoned - used as message queues.

• 4) Self-configurable & last mile problem resistant : Self-configurable.

• In WAP or Web – no trivial task to connect to a service from a foreign n/w without any change in the configuration or preference setting.

• SMS – no constraints. Can access SMS bearer without any change in the phone settings.( even SMSC or SC are not available).

• 5) Non-repudiable : SMS message carries SC & the source MSISDN as part of the message header.

• An appln. Connected to SMS – handcraft an MSISDN address like “999” or “MYBANK” .

• But an appln. Not handcraft the SC address.

• 6) Always connected : this bearer media is always on.

• User can’t SWITCH OFF, BAR or DIVERT any SMS mess.

• Eg., when a phone is busy, a voice, data or FAX call is in progress.

• SMS delivered to MS without any interruption to the call.

SMS ARCHITECTURE

• 1) SMS ARCHITECTURE – fig. 6.1

• 2) SMMT(SHORT MESSAGE MOBILE TERMINATED) – fig. 6.2

• 3) SMMO(SHORT MESSAGE MOBILE ORIGINATED) – fig. 6.3

• 4) SMS AS AN INFORMATION BEARER

• Very popular bearer – person-to-person, point-to-point, mobile-to-mobile messaging domain.

• Gaining popularity in enterprise applns., services provided by independent service providers (ASP) & notification services

• Fig . 6.4.

• To use SMS – as a bearer- connect the services running on the Enterprise Origin Server to the SC thru’ SME (Short Message Entity) or ESME (External Short Message Entity).

• SME – generally an SMS g/w.

Operator-centric Pull

• For SMMO – SC is mandatory.

• Operators offer diff. Inf. On demand & entertainment services.

• Done via connecting an Origin Server to SC via an SMS g/w.

• These service provider known – MVNO(Mobile Virtual N/w Operators).

• Virtual Operators develop diff. Sys, services & applns.,

• Many enterprises uses MVNOs – to serve to mobile phone users.

• Ie.,few banks in India to offer balance enquiry.

• Eg., HDFC – customer needs to use these services , thus register for the service.

• During registration, the HDFC customer needs to mention the MSISDN of the phone.

• Once user registered – he enters “HDFCBAL” & sends a mess. To a service no. Like 333 as an MO mess.

• SC – delivers MO to SME connected to this service.

• Response is from the enterprise appln. – delivered to MS as an MT mess. From SME.

• Std. Protocols used for this communication.

• 1) SMPP – Short Message Peer to Peer.

• 2) CIMD

• 3) between SME & Origin Server – SOAP (Simple Object Access Protocol)

• HTTP – helps user to get inf. From internet via SMS.

• SMS queries are keywords driven like “CRI” for live cricket score , etc.,

Operator-independent Push

• Similar to MO, an MT mess. – delivered from a n/w in India to an MS of UK roaming in Germany.

• Fig. 6.5

• Ie., Push – any alert , notification or even response from a pull mess. Generated by an appln., - serviced by any n/w. & delivered to any GSM phone.

• Eg., some credit cardcompanies in India send SMS notifications to its cardholders in diff. n/ws using operator-independent push.

VALUE ADDED SERVICES THRU’ SMS• VAS defined as services – share one or more of the foll. Characteristics :

• 1) Supplementary service but adds value to total service offering.

• 2) Stimulates incremental demand for core services offering.

• 3) Stands alone in terms of profitability and revenue generation potential.

• 4) Can sometimes stand-alone operationally.

• 5) Does not cannibalize basic serive unless clearly favorable.

• 6) Can be an add-on to basic service,& as such, may be sold at a premium price.

• 7) May provide operational and/or administrative synergy b/w or among other services .

• GSM’s goal – to offer the n/w infrastructure.

• Voice, SMS – basic services provided by a GSM operator.

• Offering diff. Other services using SMS as a bearer – is VAS.

• Most popular VAS over SMS – entertainment & inf. On demand.

• Inf. On demand – has 3 categories

• 1) Static Information : not change frequently. Eg., restaurant guide.

• Contents fall in mass market category.

• 2) Dynamic Inf. : changes in days. Eg., daily horoscope changes on daily basis. Mass market content fall in this category.

• 3) Real-time Inf. : changes continually. Third-party contents fall in this category. Eg., scores in a live cricket match.

• All enterprise contents fall in this category.

• User Interface in SMS Value Added Services :

• SMS – sessionless & short transaction model.

• For a SMS based service,user interface always – keyword-based.

• eg.1, to know the latest news. Enter News & send it to VAS service.

• If business news, enter News biz.

• News – keyword

• Eg.2, RSA 2627 Bangalore New Delhi 20 01. – to find the seat availability on the Indian Railways train No. 2627 from Bangalore to New Delhi on Jan’ 20th.

• Response for this – given in book.

• If response > 160 char. – split the response into multiple mess responses.

• Advised to a seq. No. Like .....1/3,......2/3, and ..........3/3 – for 1st,2nd, 3rd mess.

• VAS EXAMPLES :

• 1) NEWS/STOCK QUOTES SERVICE :get the latest news or stock inf.

• Keyword for news – News, for stock inf. (Bombay Stock Inf.) – BSE

• For News & Stock - must have relationship with some content provider who will supply the up-to-date inf.

• Eg. Tie up with CNN – for international news, The Indian Express – general news, weather.com – weather news.

• For stock quote – tie up with Bombay Stock Exchange or National Stock Exchange.

• 2) SESSION-BASED CHAT APPLN.

• Chat service – session-oriented transaction.

• Needs to explicity log out or logged out implicitly.

• Every time user sends a chat keyword, need to know the previous trans.

• MSISDN no. Phone – used as session key.

• 3) EMAIL THRU’ SMS

• Trans. Oriented dialogue.

• User mess. Will be – eg., mail roopa@iitb.ac.in we will meet tomorrow 6:00 p.m.

• In above mess. – mail id & body of the mess. Given

• 4) HEALTH CARE SERVICES

• This needs both pull & push .

• A typical appln. – be ICU sys. – include alerts to doctor.

• Eg., in status monitoring service – doctor or nurse can enquire the status of a patient in ICU.- short trans. – pull service

• Even the doctors & nurses – notified periodically about the status of the patients. - push service.

• 5) MICRO-PAYMENT SERVICES

• Session-oriented dialogue.

• In this appln. – will be some no. Of identifier- pasted on the vending machine.

• Customer enter this no. & sends a request to purchase a product.

• Service provider – authenticate the user & check whether the user has sufficient money.

• Based upon the money trans. – approved or rejected.

• If approved – authentication mess. – sent back to the vending machine.

• Vending machine – ask the user to select the product.

• User selects product – shop dispense the product – vending machine send a mess. To VAS indicating shop that the product – dispensed.

• ALERT SERVICES

• Time-based :

• Proactive alerts sent to phones @ pre-assigned time.

• Watermark-based:

• Whenever stock price goes up or falls down to a certain level, alerts are sent.

• Other services – cricket score – periodic alert (every 10 minutes).

• LOCATION-BASED SOFTWARE :

• Eg., road direction, restaurant guide etc.,

• Some location-aware VAS services provide shopping alerts.

• In locaation-based services – only the inf. Relevant to the current location is provided.

• Eg., in shopping service – alerts on discount or sale inf. – when they pass thru’ close the shopping mall.

• In restaurant guide, if a person in his office & sends Res to VAS – then receives – restaurants in & around his office.

• For location-aware s/w – precise location needs to be determined.

• Either from the n/w or from the device.

• Using n/w – Time Advancing Technique used within the BTS.

• Using device – 1) Cell ID-based sys. 2) Global Positioning Sys.(GPS)-based sys.

• 1) In a CID-based sys. – CID of the current BTS –determined.

• Needs mapping of the cell id to the geographical loc.

• Signal strength from all the diff. CIDs - extracted from the device & sent to the server thru’ SMS.

• Loc. Of user – determined using signal strength & triangulation algs.

• 2) In a GPS-based sys. – loc. Determined thru’ GPS receiver installed within the phone.

• Computes position, velocity & time of a GPS reciever.

• Exact loc. Provided to offer direction inf.

• Based on the velocity also direction be identified.

• GPS sys. – not dependent on n/w operator.

• Fig. 6.6 – shows the architecture of VAS.

• ACCESSING THE SMS BEARER

• 2 ways of accessing:

• 1) use a mobile phone as a GSM modem & connect it to computer.

• 2) Use the SMSC of an operator thru’ SMPP or similar interface.

• GSM MODEM (OVER THE AIR)