9 SIGNALING IN MOBILE NETWORKS

Transcription

1 Signalling in Mobile Network 9 SIGNALING IN MOBILE NETWORKS STRUCTURE 9.1 INTRODUCTION 9.2 OBJECTIVE 9.3 SIGNALING DEFINITIONS AND USES 9.4 SIGNALING TYPES 9.5 COMMON CHANNEL SIGNALING SYSTEM NUMBER OSI REFERENCE MODEL VS. CCS7 PROTOCOLS 9.7 CCS7 PROTOCOLS IN VARIOUS NETWORK ELEMENTS 9.8 SUMMARY 9.9 SELF ASSESSMENT QUESTIONS 9.10 REFERENCES AND SUGGESTED FURTHER READINGS 9.1 INTRODUCTION GSM, signaling is any transfer of data that enables speech and data connection between users and supports mobility management and GSM services handling. 9.2 OBJECTIVE The objective of this chapter is to understand the need and development of GSM Signaling. On completion of this chapter, the trainee will get: Overview about CCS 7. To know about use of signaling in GSM, To know about the various Application Part of CCS SIGNALING DEFINITIONS AND USES PSTN needs signaling for call establishing, call release and call maintaining. In GSM, signaling can also be independent from speech. The different functions of signaling are call control, control of services, and charging control. Mobile networks have some special functions, such as location update, handover, subscriber administration, and short message service. GSM signaling can be divided into three main categories: o Speech and data connection (set up, supervise and release a call) o Mobility management (location update, handover) o Subscriber administration (including all basic and supplementary GSM services) EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 1 of 25

2 Signalling in Mobile Network 9.4 SIGNALING TYPES Signaling messages can be categorized into two main types. o Circuit-related Signaling o Non-circuit-related Signaling CIRCUIT-RELATED SIGNALING Circuit-related Signaling occurs when the Signaling message contains information about the circuit to be signaled and the origin and destination of the message. An example of circuit-related Signaling is call-setup Signaling between two exchanges NON-CIRCUIT-RELATED SIGNALING Non-circuit-related Signaling occurs when the Signaling message does not contain information about the circuit, but instead contains other information depending on the use of the Signaling. LAI data and (TMSI)/ (IMSI) in case of location update Short messages in case of sending or receiving a short message Forwarding numbers in case of activation of the call forward supplementary service B-Mobile Subscriber International ISDN Number (MSISDN) in the Send Routing Information (HLR Inquiry). 9.5 COMMON CHANNEL SIGNALING SYSTEM NUMBER 7 Common Channel Signaling (CCS) is a Signaling method that uses addressed messages to convey Signaling information over a single channel. CCS supports both circuit-related and non-circuit-related Signaling. Common Channel Signaling System Number 7 can be abbreviated CCS7, CCS#7, SS7 and SS No. 7. CCS7 is the abbreviation used in this training document. CCS7 is an internationally standardized CCS system that is optimized for operation in digital telecommunication networks such as GSM. One of the main advantages of CCS7 is that the Signaling does not have to go along the same path as the speech. Therefore, CCS7 can support both circuit-related and noncircuitrelated Signaling. 9.6 OSI REFERENCE MODEL VS. CCS7 PROTOCOLS Originally, CCS7 consisted of two parts. The first part, the MTP, was responsible for transferring messages within a Signaling network. The second part, the User Part (UP), was the user of the MTP. The UP was only used for circuit-related Signaling. However, CCS7 was created for GSM-type networks. In GSM, CCS7 is also divided into two parts, but they are called the Functional Part (FP) and the MTP. The user is the functional part that sends, receives, and acts depending on received Signaling EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 2 of 25

3 Signalling in Mobile Network information. A comparison of the Open System Interconnection (OSI) reference model and the CCS7 protocols is shown in Figure. The functional part of CCS7 is divided into two parts: User part (common part) Application part (GSM specific part). 9.7 CCS7 PROTOCOLS IN VARIOUS NETWORK ELEMENTS When a subscriber makes a call, a functional part in the BSC sends the dialed number to a functional part in the MSC. The functional part in the BSC is the BSSAP and the functional part in the MSC is also the BSSAP. After the MSC analyses the dialed number, the MSC knows that the call has to be routed to the PSTN because it is a PSTN number. Thus, another functional part in the MSC will start sending call setup message (the dialed number together with the CIC are included) to the PSTN. The ISUP is the functional part in the MSC and in the PSTN in this case. Another Example is the location update message is sent from the mobile to the VLR via the BSC. The BSSAP is a functional part in both the BSC and VLR. If the VLR needs to ask subscriber data from the HLR, another functional part will be used in the VLR and HLR. This functional part is used only in the NSS area it is a GSM specific functional part. As a result, a MAP is used in both the VLR and the HLR. The CCS7 protocols are shown in Figure. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 3 of 25

4 Signalling in Mobile Network Base Station Subsystem Application Part The Base Station Subsystem Application Part (BSSAP) is responsible for transferring the GSM-specific messages between the MSC and BSC, and between the MSC and a mobile station. The BSSAP can be divided into two subparts DTAP and BSSMAP. DTAP (Direct Transfer Application Part) handles the transfer of the Signaling information between the MSC and the MS such as call setup, alerting, and location update request messages. They are all sent transparently via the BSC to the MS. BSSMAP (Base Station System Management Application Part) handles the Signaling functions between the MSC and the BSS and performs other procedures such as handover control and paging. The messages used in these procedures are sent directly from the MSC to the BSC. Mobile Application Part The Mobile Application Part (MAP) is a GSM-specific protocol for only non circuitrelated applications inside the NSS area. AP procedures can be location registration, handling of supplementary services, HLR inquiry, Inter-MSC handover, authentication, International Mobile Equipment Identity (IMEI) checking, and support of short message services. The operations defined within the MAP protocol are sent through the signaling network by using TCAP, SCCP, and MTP services. For SCCP, MAP uses only a connectionless service. Intelligent Network Application Part The Intelligent Network Application Part (INAP) protocol is part of the Intelligent Network (IN) implementation used for communication between a Service Switching Point (SSP) and a Service Control Point (SCP). Both the SSP and SCP are part of the basic IN network architecture. Signaling Connection Control Part, SCCP To be able to transfer messages from both user parts and application parts, there are two levels that perform the routing function: the MTP level for user part messages and the SCCP level for application part messages. Since the MTP was defined for general digital telecommunications networks such as the PSTN, the MTP is well suited for the TUP and NUP. But because the BSSAP, MAP, and INAP are defined especially for GSM, a special protocol has to be established between the application parts and the MTP level. This special protocol is called the Signaling Connection Control Part, SCCP. 9.8 SUMMARY In GSM, CCS no 7 signaling is used and it can also be independent from speech. The different functions of CCS 7 in GSM are call control, control of services, and charging control. GSM networks have some special functions, such as location update, handover, subscriber administration, and short message service which is handled by CCS 7. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 4 of 25

5 Signalling in Mobile Network 9.9 SELF ASSESSMENT QUESTIONS 1. Signalling in mobile networks have some special functions, such as,,, and. 2. GSM signalling can be divided into three main categories 3. Signaling messages can be categorized into two main types & 4. Circuit-related Signaling occurs when the Signaling message contains information about the to be signaled and the of the message. 5. Originally, CCS7 consisted of parts. The first part, the, was responsible for transferring messages within a Signaling network. The second part, the, was the user of the. 6. The Base Station Subsystem Application Part (BSSAP) is responsible for transferring the GSM-specific messages between the &, and between the and. The BSSAP can be divided into two subparts &. 7. The Mobile Application Part (MAP) is a GSM-specific protocol for only applications inside the NSS area. 8. Inter-MSC handover, authentication, International Mobile Equipment Identity (IMEI) checking, and support of short message services. The operations defined within the protocol 9. The Intelligent Network Application Part (INAP) protocol is part of the Intelligent Network (IN) implementation used for communication between a &. 10. SCCP stands for REFERENCES AND SUGGESTED FURTHER READINGS The GSM system for mobile communication-michel Mouly & Marie- Bernadette Pautet. GSM system Engineering-Asha Mehrotra (Artech House Publisher). EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 5 of 25

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7 GSM Subscriber Creation 10 GSM SUBSCRIBER CREATION STRUCTURE 10.1 INTRODUCTION 10.2 OBJECTIVES 10.3 ROLE OF CSC 10.4 MAIN CATEGORIES OF SUBSCRIBER 10.5 IMPORTANT FACTS 10.6 GETTING NEW CONNECTION 10.7 NEW CONNECTION WORK FLOW 10.8 SAMPLE CAF FOR PREPAID SUBSCRIBER 10.9 SUMMARY SELF ASSESSMENT QUESTIONS 10.1 INTRODUCTION In the highly competitive environment of Mobile Communication Operations, Subscriber handling is one of the key issues that needs at most attention and care. For better customer care every Mobile Service provider gives high importance to the smooth and effective functioning of CSCs (Customer Service Centre). The mobile subscriber base of any mobile service operator depends on How well the CSCs are handling the subscriber requirements / needs OBJECTIVES After reading this unit, you should be able to: Understand two basic types of subscriber category. Understand Preliminary steps in subscriber creation. Understand the basic role of CCN, CSR and CRM ROLE OF CSC Technically speaking CSC can be referred as Customer Care Node (CCN). The executive at CSC are referred as Customer Service Representatives. The main tasks of Customer Service Centre are:- Sale of New SIMs. Handling of requests from customers regarding telephony services and billing queries. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 1 of 25

8 GSM Subscriber Creation Activation / deactivation of mobile numbers. Inventory and SIM management. Provisioning / de-provisioning of various services to the subscribers. Swapping of SIM and MSISDN. Payment and Collection MAIN CATEGORIES OF SUBSCRIBER There are two main category of Mobile Subscriber:- Post-paid Subscriber- Bill is dispatched after usage period (one month period). Post paid SIMs are plain SIM, need post data feeding (Creation). Pre-Paid Subscriber- Bill amount is deducted from the pre available balance after every usage. Pre-Paid SIMs are pre-created and are in deactivated state, need activation from CCN. In BSNL, one Activation server is employed for this purpose IMPORTANT FACTS The pre activated pre-paid SIM have IMSI and MSISDN mapped and associated with SIM serial number. (SIM serial number is printed on the back side of the SIM) On the network side subscriber is created in HLR by creating MSISDN and then mapping it with the available IMSI. So in HLR we can find the IMSI and MSISDN of the subscriber. IMSI and associated authentication data of the mobile subscriber resides in AuC at the network side GETTING NEW CONNECTION 1. The Customer goes to CSC for giving request for new mobile connection. 2. CSR give Customer Agreement form (CAF) to the customer as per his request. 3. (a) Customer completely fill the CAF as per his requirement of services. (b) It is ensured by CSR that customer is aware of terms and condition mentioned on the back side of CAF. The signature of the customer is taken on both side of the CAF. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 2 of 25

9 GSM Subscriber Creation 4. (a) Using the CAF details the CSR creates a new customer using the SIM provided to CCN and a MSISDN available in the inventory. (b) The new customer will be created in Customer relation management (CRM) application. In BSNL Kenan FX software (of Comverse) is used for CRM and Billing purpose. 5. After all the data entry by CSR and activation process initiation, the new SIM is handed over to the customer. 6. Mobile services get activated within 24 hrs and now new customer becomes new subscriber of BSNL Mobile Services NEW CONNECTION WORK FLOW Figure 1 The interrogation of subscriber related parameters is done from CSC. To process the change of Mobile Number request received from the existing mobile subscriber, the necessary instructions are initiated from the CSC. Moreover using Kenan FX the CSR can Add / Delete facilities, change billing Plans on customer account as per the customer request at any point of time SAMPLE CAF FOR PREPAID SUBSCRIBER EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 3 of 25

10 GSM Subscriber Creation 10.9 SUMMARY The Customer Care Nodes or the Customer Service Centre, provides assistance to the mobile subscriber for his Billing, GSM add-on services and GPRS related requests. The activation, deactivation suspension of EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 4 of 25

11 GSM Subscriber Creation subscribers, provisioning / de-provisioning of various services to the subscribers is also done at CSC SELF ASSESSMENT QUESTIONS 1. Write the full form of CAF and CRM. 2. SIM serial number is never printed on the SIM.(True / False) 3. On the network side subscriber is created in VLR.(True / False) 4. Authentication data of the mobile subscriber resides in. 5. Kenan FX software is used for and purpose. 6. After all the data entry by and activation process initiation, the is handed over to the customer. 7. Draw the new connection network flow diagram. 8. The pre activated pre-paid SIM have and mapped and associated with SIM serial number. (SIM serial number is printed on the back side of the SIM) 9. Write down the various categories of mobile subscriber and briefly describe them. 10. Analyse the mobile market, which category of subscriber is higher and why? EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 5 of 25

12 Mobile Services VAS 11 MOBILE SERVICES VAS, ACTIVATION / DE- ACTIVATION. STRUCTURE 11.1 INTRODUCTION 11.2 OBJECTIVE 11.3 VAS 11.4 WHY VAS 11.5 MARKET SIZE AND REVENUE POTENTIAL 11.6 VAS VALUE CHAIN 11.7 VAS : AN END USER PERSPECTIVE 11.8 GPRS ( GENERAL PACKET RADIO SERVICE) BASED SERVICES 11.9 NEW VAS IN 3G REGULATORY FRAMEWORK FOR VAS CONCLUSION: SELF ASSESSMENT QUESTIONS 11.1 INTRODUCTION In India, Mobile VAS has become a big part of the mobile user's life today. With huge mobile phone subscribers in India today and having the second largest subscriber base in the whole world - Indian Telecom Industry has started witnessing an era when Users buy mobile phones not just to be in touch, but to express themselves, their attitude, feelings and interests OBJECTIVE Today mobile phones have moved beyond their fundamental role of voice communications and are increasingly being used to provide a number of value added services. Proliferation of mobile services has given an opportunity to service providers to develop new VAS applications and generate new revenue streams. Customers continuously want more application and services from their phone. They use their cellular phones to play games, read news headlines, surf the Internet, keep a tab on astrology, and listen to music, make others listen to their music, or check their bank balance VAS Value Added Services are those services which are not part of basic voice but are availed by telecom service providers to enrich their offerings. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 6 of 25

13 Mobile Services VAS Typically, in nineties SMS and itemized billing would be categorized as VAS. Later on with the evolution of mobile networks from GSM to GPRS and EDGE Personalized Ringtones, Caller Ringback tones(crbt), SMS based information, Multi media messaging (MMS) etc became the main value added services. VAS data services are based on bearers like SMS, USSD (Unstructured Supplementary Services Data), WAP,GPRS, EDGE and 3G WHY VAS In the fast evolving mobile telephony space, Average Revenue Per User (ARPU) from Voice services are plateauing as plain voice service is increasingly becoming commoditized. In such a scenario, innovative Value Added Services offer an opportunity to Telecom Service Providers to differentiate their offerings in the market. Service providers are bringing new value added services in order to satisfy the growing demand of Indian consumers. Many a times customers choose a particular service provider depending upon the VAS offerings from that service provider. So as the competition is becoming fierce to acquire and retain customers. Mobile service providers are making all out efforts to introduce newer and newer services to woo customers. Value Added Services used by a particular customer are often extension of his persona. Understanding needs of different segment of users is essential for offering right kind of services. Thus unlike voice business, market dynamics play an important role in VAS business. Understanding the market needs and accordingly applying the principles of Segmentation, Targeting and Positioning (STP) to decide a particular service, have a key role. These fundamental aspects about VAS can not be overlooked while formulating a strategy for VAS business. A glimpse of various types of VAS is depicted in Exhibit 1. NEWS: National, International, Business. Finance: Stocks, Forex Rates, Commodity Prices. Entertainment: Games, TV, Jokes, Bollywod Songs. Travel: Railway Airline Downloads: Logos, Ringbones, Caller Tunes Astrology Services: Horoscope/Prediction Contest: Reality Shows MMS: Picture Massages, Clippings Music on Demand: Sing a Song and download. Cricket: Cricket, Score, Clipping, Commentary GPRS/WAP/UMTS: Mobile Internet, Chat, TV, video call Call Alert: When Mobile is Switched off, Busy Health: Health, Tips, Beauty Tips m-commerce: Transaction-Based Services Miscellaneous: Devotional songs, Movies & Music Voice Based Applications. Exhibit 1: A Glimpse of Various Types VAS. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 7 of 25

14 Mobile Services VAS 11.5 MARKET SIZE AND REVENUE POTENTIAL With voice increasingly becoming a commodity and the current Mobile VAS industry being expected to earn more revenue compare to voice call revenue in mobile.mvas industry is attracting wireless operators, handset manufacturers, content developers, music & film companies, cartoon artists, game makers and musicians for ring tones, music, gaming, sports, mobile imagery, WAP, wall papers, logos, SMS based contests and streaming audio and video. Though presently VAS contributes a low percentage of revenue of mobile operators, it holds a huge potential for growth in future VAS VALUE CHAIN For the VAS to make an impact Network, Devices (Handsets) and Applications are critically important. VAS value chain primarily consists of six entities involved in the flow as depicted in Exhibit 2. Content owner owns the content and Aggregator modifies that content to suit requirement of Consumer and device capability. Software developer and Technology Enabler assist Aggregator in modifying the content. Exhibit 2: VAS Value Chain. Telecom Service Provider presently dominates the revenue share arrangement in VAS industry. Overall revenue share split of approx 70:30 applies to both GSM and CDMA operators. However this is not the case in developed countries where major share of VAS revenue is kept by content owner. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 8 of 25

15 Mobile Services VAS Exhibit 3: Present Revenue Share Arrangement VAS : AN END USER PERSPECTIVE Understanding consumer perspective of VAS is significant for correct positioning of the VAS. From end user perspective, the important considerations are- i) Services as per user need. ii) Simplicity to use. iii) Reliability, and iv) Affordability. Different segment of customers are interested in different kind of services. For younger generation entertainment may be primary, for business executives company data and financial transaction may be more important whereas middle aged people may be more interested in sports updates. This calls for Segmenting the end user according to their profile. For a service provider it is important that its offerings cater to a larger section of the end users. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 9 of 25

16 Mobile Services VAS 11.8 GPRS ( GENERAL PACKET RADIO SERVICE) BASED SERVICES These services are available on short code through content providers own WAP site. A wide range of corporate and consumer applications are enabled by non-voice mobile services such as SMS and GPRS. This section will introduce those that are particularly suited to GPRS. a) Chat b) Textual and Visual Information c) Still Images d) Moving Images e) Web Browsing f) Internet g) Vehicle Positioning h) MMS The Multimedia Messaging service (MMS). It is an advanced messaging service, which allows you to send Wallpapers, Video clips, picture message. In GPRS Network user can get the Max. /Theoretically speed upto Kbps. To use GPRS service user need the Handset setting NEW VAS IN 3G In 3 G higher bandwidth, maximum up-to 2 Mbps, would be available to end users.this will enable provisioning bandwidth hungry applications and services with rich EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 10 of 25

17 Mobile Services VAS multimedia content to customers. BSNL has planned Video on Demand (VoD), video streaming and other multi-media applications in 3 G network. BSNL Live is a WAP Portal which offers one stop shop for all Information, Entertainment, and Communication related requirements. Through BSNL Live one can access on demand Videos clips for various categories like Bolloywood, Astrology, recipes/ cookery, entertainment, cricket, comics/ animation, Movies and Movie trailers, Music, Multimedia games and wallpapers, and different tones/tunes etc. It enables us to get many Value Added Services in much simpler and friendly way. BSNL Live provides a variety of services to suit our every day mood. To name a few following services are on offer- Movies: Movies will be streamed on demand i.e. the content will be played in real time on your mobile from BSNL Live directly without first getting stored. Videos: Video clips of 3-5 minutes on an average are available on demand. We can choose videos and download from the available huge library of content. The categories of content varies from astrology, recipes/ cookery, entertainment, cricket to beauty tips/ clips, comics/ animation, Movies and Movie trailers, Music, Multimedia games and wallpapers, and other different tones/tunes. Music - Full track song download: You can download full track audio songs (mp3) of our choice through BSNL Live. Games: Various Categories of Games viz. Regular (Simple & premium) and multiplayer branded games are available. We can see only games which are compatible with our handsets. Thus one needs not to worry about compatibility of games. At the time of download the customer will be required to pay charges of games. Accessing BSNL Live : Any handset with WAP browsing capability can be used to access BSNL Live. BSNL Live can be accessed by all GSM (2.5 G and 3G) subscribers. However the videos, movies and full track songs and multiplayer games are heavy on data and to access these services one needs to have a 3G connection otherwise his experience will be greatly reduced and the downloads for audio and video clips will take longer time. Before one can access the BSNL Live, one needs to have correct settings in his mobile. APN Settings may be got done in the following way:- The Handset setting is required to access the different GPRS/ 3G services by user. a) All the settings required to access BSNL Live & avail different services on BSNL Live will be pushed to your handset by BSNL. b) One can also ask for the settings by sending <make> space <model> of your handset to by SMS e.g. <Nokia> space <N79> to After you send the SMS you will in response get several settings on your handset viz. bsnllive / bsnlstream /bsnl mms/bsnlnet etc. c) One may also call BSNL Customer Care Center 1503 (Toll Free) to know the settings. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 11 of 25

18 Mobile Services VAS d) To get the setting via Internet,Go to internet site: And Click on GPRS/MMS Settings(Red arrow). EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 12 of 25

19 Mobile Services VAS Once we get all the settings, we have to save all of them. Out of these several settings the one pertaining to BSNL Live (will appear as bsnllive ) should be saved as default. In some handsets the word Bookmark is used instead of default. Thereafter whenever one wants to access BSNL Live one can click on his Web browser in his mobile; the BSNL Live bookmark will be visible and clicking on it will leads to the Welcome page. Settings for movie streaming (will appear as bsnlstream ) may also be saved in mobile REGULATORY FRAMEWORK FOR VAS With a move to lay down regulation for VAS players, TRAI had issued a consultation paper for licensing VAS. At present, VAS providers are neither regulated nor licensed and mainly they act as channel partners of telecom operators. Telecom service providers by virtue of being owners of the network have near monopolistic advantage in revenue share agreement. Concerns have been raised about security related issues with respect to VAS. Recently there was a standoff between the Department of Telecom and RIM (the maker of the BlackBerry smart phone). RIM ( Research In Motion), the Canadian company, was under scrutiny after security agencies had expressed fear that terror group might exploit this loophole as data sent between BlackBerry devices bypassed the network of Indian telecom service providers and therefore could not be monitored by the country s intelligence agency. The appropriate regulatory regime for VAS is likely to provide clarity and transparency in tracking the source. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 13 of 25

20 Mobile Services VAS CONCLUSION: For the orderly and fast growth of VAS industry and the entire VAS ecosystem the challenges and hurdles before the industry needs to be addressed promptly. The revenue from mobile advertising is likely to open a new revenue stream for VAS players. Mobile advertising will benefit operators, VAS players, advertisers as well as consumers. On the user front awareness is likely to remain a problem for high end VAS. However traditional VAS- SMS, CRBT and Ring-tones are likely to continue to grow with increased user awareness. A facilitating regulatory framework and transparency in allocation of the spectrum would go a long way in encouraging the service providers to aggressively push VAS. VAS players entering into partnership with handset manufactures for implementing embedded applications and service providers bundling the handsets may lead to greater adoption of VAS. Competition is really becoming fierce in VAS space and each service provider including BSNL is making all out effort to grab a share of VAS market. BSNL has introduced numerous VAS services on its 3G platform BSNL Live and other VAS services. There is a need to create awareness about recently introduced services and to popularize the services SELF ASSESSMENT QUESTIONS 1. What are VAS services? How the differ from normal voice and SMS services. 2. Why VAS is used in mobile network? 3. What is the principle of STP in VAS services? 4. List any five VAS services. 5. What are STK services? 6. Write four APNs of BSNL and there uses. 7. List GPRS based VAS services? 8. Explain VAS Value Chain? 9. List and explain the end user perspective & the important considerations for VAS. 10. Explain Regulatory Framework for VAS? EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 14 of 25

21 GSM Call Flow STRUCTURE 12 GSM CALL FLOW 12.1 INTODUCTION 12.2 OBJECTIVE 12.3 MOBILE ORIGINATED (MO) CALL 12.4 MOBILE TERMINATED (MT) CALL 12.5 SHORT MESSAGE SERVICE (SMS) 12.6 SUMMARY 12.7 SELF ASSESSMENT QUESTIONS 12.8 REFERENCES AND SUGGESTED FURTHER READINGS 12.1 INTODUCTION In this we will discuss the call processing aspect and look into specifics case of a mobile originated (MO) call and a mobile terminated (MT) call. We also look into short message (SMS) 12.2 OBJECTIVE The objective of the chapter is to understand the concept of call flow in GSM network. On completion of this chapter, the trainee will get: To know about use of RF channel in Call setup, To know about the MO call, MT call and SMS 12.3 MOBILE ORIGINATED (MO) CALL There are four distinct phase of a mobile originated call- 1. Setup phase. 2. Ringing phase. 3. Conversation phase. 4. Release phase. Out of these phases the setup phase is the most important phase and includes authentication of the subscriber, Ciphering of data over radio interface, validation of mobile equipment, validation of subscriber data at VLR for requests service and assignment of a voice channel on A-interface by MSC. Whenever MS wants to initiate an outgoing call or want to send an SMS it requested for a channel to BSS over RACH. On receiving request from MS, BSS assigns a stand-alone dedicated control channel (SDCCH) to MS over access grant channel (AGCH). Once a SDCCH has been allocated to MS all the call set up information flow takes place over SDCCH. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 15 of 25

22 GSM Call Flow MS now sends a Call Set up Request to the MSC/VLR certain check are performed at MSC/VLR like- whether the requested service is provisioned for the subscriber or not, whether the dialed digits are sufficient or not after this MSC sends Assignment command to the BSS which contains a free voice channel on A-interface On getting this message BSS allocates a free TCH to the MS and informs the MS to attach to it. MS on attaching to this TCH informs the BSS about it. On receiving a response from the BSS, MSC switches the speech path toward the calling MS. Thus at the end of Assignment the speech path is through from MS to MSC. After assignment MSC sends a network set-up message to the PSTN requesting that a call be set up. The PSTN may involve several switching exchanges before finally reaching the final local exchange responsible for applying the ringing tone to the destination phone. The local exchange will generate the ringing tone over the trunk, or series of trunk (if several intermediate switching exchange are involved), to the MSC. At this point in time MS will hear ringing tone. This is ringing phase. When the destination party goes off hook, PSTN informs the MSC of this event. At this point, MS is connected to the destination party and billing is started. This is the conversation phase Under normal condition, the termination of a call is MS initiated or network initiated. In this scenario, we have assumed that MS initiates the release of the call by pressing end button and MS send a disconnect message to the MSC and All the resources between MSC and the MS are released MOBILE TERMINATED (MT) CALL The different phases of a mobile terminated call are EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 16 of 25

23 GSM Call Flow - Routing analysis - Paging. - Call setup. - Call release. The phases of mobile terminated (MT) call are similar to a mobile originated (MO) call except routing analysis and paging phase. Call to a mobile subscriber in a PLMN first comes to gateway MSC (GMSC). GMSC is the MSC, which is the capable of querying HLR for subscriber routing information. GMSC need not to be part of home PLMN, though it is normal practice to have GMSC as part of PLMN in commercially deployed networks. GMSC Send / Routing / Info-Request (SRI request) is sent to HLR. SRI request contains MSISDN of the subscriber. HLR sends Provide / Roaming / Number-request (PRN request)to the VLR. VLR responds to PRN request with PRN response message, which carries an MSRN (mobile subscriber roaming number), which can be used for routing toward visiting MSC in the network. HLR returns MSRN to GMSC (MSC that queried HLR) in SRI response message. On getting MSRN the GMSC routes the call towards VMSC The purpose of this entire exercise is to locate where the terminating mobile subscriber is. VMSC uses the LAI provided by the VLR to determine which BSS s should page the MS. MSC transmit a message to each of these BSS requesting that a page be performed. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 17 of 25

24 GSM Call Flow Included in the message is the TMSI of the MS. Each of the BSS s broadcasts the TMSI of the mobile in a page message on paging channel (PCH). When MS detects its TMSI broadcast on the paging channel, it responds with a channel request message over Random Access Channel (RACH). Now onward case is same as we have in MO call. The mobile-to-mobile call scenario is a combination of phases encountered in mobile originated (MO) and mobile terminated (MT) call. MNP Call Scenario 12.5 SHORT MESSAGE SERVICE (SMS) SMS is a simple bearer service and acts as a bi-directional alphanumeric paging service, which allows value added service provision as well as management services provision such as advice of charge. A short message can carry at most 160 characters (it can be less depending upon the type of characters and their coding scheme). The SMS could be either in broadcast mode (via CBCH channel) or in a point-to-point mode (via either SDCCH channel if mobile is in idle state, or SACCH if the mobile is in dedicated mode) SUMMARY Mo Call includes authentication of the subscriber, Ciphering of data over radio interface, validation of mobile equipment, validation of subscriber data at VLR for requests service and assignment of a voice channel on A-interface by MSC and mobile terminated (MT) call are similar to a mobile originated (MO) call except routing analysis and paging phase EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 18 of 25

25 GSM Call Flow 12.7 SELF ASSESSMENT QUESTIONS 11. Write down the four distinct phase of a mobile originated call 12. Whenever MS wants to initiate an outgoing call or want to send an SMS it requested for a channel to BSS over. On receiving request from MS, BSS assigns a to MS over The different phases of a mobile terminated call are 14.. A short message can carry at most characters 15.. Normally in idle mode short message is carried on channel in air interface 16. Speech is carried on channel in air interface 17. The SMS could be either in broadcast mode via channel or in a point-to-point mode via either channel if mobile is in idle state, or if the mobile is in dedicated mode. 18. In MO call MSRN is used (True/False) 19. TMSI is used for routing of mobile call (True/False) 20. MSRN is a number similar to REFERENCES AND SUGGESTED FURTHER READINGS The GSM system for mobile communication-michel Mouly & Marie- Bernadette Pautet. GSM system Engineering-Asha Mehrotra (Artech House Publisher). ETSI standard ETS July 1994 on ISDN, ISDN-GSM, PLMN signalling interface. EETP/BSNL Platinum Certification Course Version 1.0 June 2014 Page 19 of 25