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 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)