Gsm Prepaid

ENGINEERING INSTRUCTION PREPAID SERVICE (GSM) Through “IN” PLATFORM No. GSM/IN/A-007 No of Pages.

16

Issue No.

01

Issued By:

T&D, Circle

Approved By:

CGM T&D Circle

Date of Issue

12-03-2005

Amendment No (If Any)

NIL

No of Pages Issued by: Approved By: Date of Issue Restricted use by BSNL Employees only

All efforts have been made to incorporate all relevant up to date information available, any discrepancies or need for addition or deletion is felt necessary, may please be intimated to this office for further improvement, on E-mail Id [email protected].

BHARAT SANCHAR NIGAM LIMITED (A Govt. of India Enterprise) TECHNICAL & DEVELOPMENT CIRCLE, SANCHAR VIKAS BHAWAN, RESIDENCY ROAD, JABALPUR, MP-482001

ENGINEERING INSTRUCTIONS

ELECTORNIC SWITCHING GSM /IN/A-007

PREPAID SERVICE (GSM) Through “IN” PLATFORM 1. Scope This engineering instruction describes in brief about the prepaid service through IN platform in GSM. 2. General The Pre Paid Service (PPS) in GSM offers a quick and easy solution to cashless calling and ensures the service provider and the network operator the guaranteed payment for the calls because a service subscriber pays in advance for his calls. For a prepaid service the subscriber pays a certain amount in advance to his prepaid account. He is subsequently able to make calls for this amount without having to pay a (monthly) basic fee. The charging of prepaid type services is performed on-line at the SCP of the IN platform. The calculation of the applicable tariff is based on a tariff model, which incorporates certain parameters such as date and time, originating/terminating network operator, origination and destination (Aparty, B-party) of the call or the dialed number. The prepaid account is simply updated each time a call is made. Prepaid accounts are of interest to network operators and service providers for several reasons. Advance payment ensures a steady cash flow and paper-free processing reduces administration costs to a minimum. In addition, Prepaid Service is highly attractive to a wide target group - for example, parents looking to put an upper ceiling on the family phone bill and travelers domiciled for a short period in a foreign country. Subscribers are offered new and safe online charging methods. Vouchers can be purchased and easily used in order to recharge the account. Since the Prepaid Service is planned to be used with low initial values, fraud and administration procedures are kept to a minimum. Thus PPS is a lucrative business and ideally suited as a mass service. 3. ARCHITECTURE Prepaid service in GSM is implemented by means of Intelligent Network (IN) platform. The CAMEL (Customized Applications for Mobile Enhanced Logic) is the standard defined by ETSI to migrate proprietary IN towards standardized GSM network solutions. The CAMEL functions are introduced in several phases. These phases are steps towards integrating IN into a GSM PLMN/GPRS PLMN. With the help of CAMEL, national and international roaming for IN services in a multi vendor environment has become a reality. CAMEL standardizes communications between a Mobile SSP/VLR and the subscriber's HLR across national borders where the HLR and M-SSP/VLR are from different vendors. The SCP, a mandatory component of IN platform, is called CSE (CAMEL Service Environment) in GSM. The working MSC (Mobile Switching Center) of the GSM-PLMN, or the SGSN (Serving GPRS support node) of the GPRS-PLMN will be the M-SSP (Mobile Service Switching Point) and all other mandatory/optional components of IN are implemented separately. However, the IP is accommodated in the M-SSP and connected to it. Voucher management system (VOMS) maintaining database of recharge coupons is implemented separately and is in LAN with SCP/CSE. In this IN/CAMEL Network architecture, the following components are available for handling IN/CAMEL services. Mobile service switching point (M-SSP) Service control point/CAMEL service environment (CSE) Service management point (SMP) Service creation environment (SCE) Intelligent peripheral (IP) The Figure-1 shows a typical basic IN/CAMEL network architecture for circuit-switched GSM.

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Fig-1 3.1.Mobile service switching point (M-SSP): When the IN/CAMEL call processing requirements and the IN/CAMEL specific switching functions are incorporated in the switching network, then the existing basic network, the MSC of GSMPLMN, will become M-SSP. When the IN/CAMEL is incorporated into the basic network the latter is not affected or disturbed. The M-SSP acts as a gateway to the CSE node. The M-SSP detects whether a service is to be processed by the CSE and places a request. Based on the reply, the service specific treatment is applied for the situation. 3.2.Service control point/CAMEL service environment (SCP/CSE): The SCP forms the IN node (or CSE forms the CAMEL node) which is responsible for the service control function (SCF) and service data function (SDF). It exercises central control over the various services. In the SCP/CSE the inquiries from the SSP are evaluated, destination directory numbers i.e. the routing & charging are determined and steps are taken to prevent overload. Statistics covering servicerelated analyses and covering connections are also collected and transmitted to the SMP. 3.3.Service management point (SMP): The SMP is responsible for service management and access function (SMAF). The SMP combines all the functions necessary for managing the IN/CAMEL services and IN/CAMEL-SCP/CSE. Service subscribers/service providers have access to their service programs via the SMP. This allows modification of service parameters or post processing of statistics and charge data. The SMP can also be connected to OS network components such as an administration billing center (ABC) or a network management center (NMC), whereby management can be performed jointly.

3.4.Service creation environment (SCE): SCE network nodes allow service providers/network operators to design their own IN/CAMEL services with suitable, easy-to use IN/CAMEL service creation tools.

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3.5.Intelligent peripheral (IP): The IP is for Service resource function (SRF). It is connected to the SSP and it paves further options for the IN/CAMEL. Implemented solutions with IP are speech output, a speech recognition system or text conversion, which can be used for recorded announcements or identifications. 4.0 INTERFACES TO EXTERNAL SYSTEMS: The interfaces concerned are: The SCP/CSE interface to the M-SSP/HLR by CCS7 providing multiple INAP protocols e.g. to support a multi – vendor Network as well as Mobile Application Part (MAP) and CAMEL Application Part (CAP) protocols for Customized Application for Mobile Network Enhanced Logic (CAMEL) Phase 1, 2 &3. The SCP/CSE interface to external data points (EDP) for a connection to external databases such as voucher management systems (VOMS) by Exticom (proprietary) protocol over TCP/IP. The Bulk Data Interface and the Dialog Interface at the SMP enabling external systems to administer services, users and service support data employing FTAM and/or CORBA. The billing and reporting interface at the SMP to transmit billing and reporting data via FTAM/FTP over TCP/IP. The O&M interface for Fault Management based on the Simple Network Management Protocol (SNMP) integrating SCP/CSE into Network Management Systems. 5.0 PPS SERVICE DESCRIPTION IN SCP/CSE: The Pre paid service (PPS) is implemented in several service parts in the SCP/CSE. Each service part is having number of service features. Since the service parts/service features in the SCP/CSE are new and interesting, a detailed description is given in the following pages. First, let us discuss the following subjects. • Access to the Service • Handling of Outgoing Calls • Handling of Incoming Calls • USSD Functions • DTMF Menu • Voucher Recharging 5.1. Access to service: The PPS supports the following access variants: • Mobile originated calls (MOC) • Mobile terminated calls (MTC) • Access via USSD (Unrestricted supplementary data) • Dialed access • Standardization of CgPA/RedPA/CdPA 5.1.1. Mobile originated calls (MOC): Each PPS subscriber is marked in his Home Location Register (HLR) with an Originating CAMEL Subscription Information (O-CSI) flag, which is used to identify a specific service at the SCP/CSE. This initiates the triggering of the MOC service part of the PPS as soon as the subscriber dials a destination number. When the M-SSP recognizes an IN trigger, an IDP (Initial detection point) operation is signaled to the SCP/CSE via INAP including the CgPA (Calling party number), the CdPA (Called party number), the service key, and the Location of the CgPA/CdPA. The subscriber number is equivalent to his Mobile Station International ISDN Number (MSISDN). The CgPA (=MSISDN) unambiguously identifies the subscriber’s number in the PPS. BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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The dialed number is interpreted relative to the VPLMN, i.e. a subscriber can dial the foreign (network) number without country code when roaming in a foreign network. The platform will add the Country Code (CC) to the dialed number (NDC + dialed destination) as prefix depending on location information. The location information within a tariff model or a rating module is used for individual charging of roaming subscribers. 5.1.2. Mobile terminated calls (MTC): Each PPS subscriber is marked in his HLR with a Terminating CAMEL Subscription Information (T-CSI) flag, which is used to identify a specific service at the SCP/CSE. This initiates the triggering of the MTC service part of the PPS during a call attempt to the subscriber. For MTC a grace period can be set exceeding the expiry date for MOC during which the subscriber is reachable. If the expiry date is reached and the grace period has expired, an announcement is played and the call is released. 5.1.3. Access via USSD: The subscriber dials a predefined Service Access Code (SAC) in order to access one of the functions such as credit enquiry, display of last call charge, or account recharge. If the USSD SAC is invalid, a USSD error message is displayed on the subscriber’s mobile phone and the dialog is released. If access via USSD has been detected by the SCP/CSE, the SAC is evaluated and the appropriate function is selected. If the SAC is found valid, the corresponding IN service is called. If voucher recharging is detected, the external voucher management system is accessed. In case of credit enquiry, the corresponding Prepaid service part will be invoked. The SAC used in BSNL are Credit enquiry : *123# Last call charge : *102# Account recharge : *111# 5.1.4.Dialed Access: The PPS can dial from any Mobile (Post paid)/Telephone a common access number to get access to his Prepaid account and make use of it. Call charges will be debited from his PPS account and not from the originating Mobile/Telephone. This access is very much useful to recharge the PPS account from any Mobile/Telephone. For Dialed access, the subscriber has to dial the common access number. The system will prompt to dial his account no. (The account no. is nothing but the MSISDN of the PPS). Now the Announcement will be to enter the PIN. After entering the PIN. The PPS will be suggested to dial any destination, he wants. For this call, the charges will be debited from the PPS account. When the system is prompting to dial the destination, one can dial 123(DTMF MENU) and select option 2 (recharge option). Then by entering the 14 digits secret code of the voucher purchased, the PPS account is recharged. The Personal Identification Number (PIN) can be used for authentication and the subscriber is able to administrate his PIN via the DTMF menu. 5.1.5. Standardization of CgPA/RedPA/CdPA: The PPS processes the CgPA internally in the international format and the CdPA in the longest unknown format. All subscriber numbers are stored in international format in the database. In case of MTC and USSD, the CdPA is converted into international format to be able to search for the subscriber in the database. The system checks whether the CgPA is in international format. If so, nothing is done. If the CgPA is not in international format, the country code is put in front of the CgPA. The RedPA (Redirecting Party Address) is the number to which the call is rerouted in case of the called party doesn’t answer. In case of call forwarding, the RedPA is standardized. The system checks whether the RedPA is in international format. If so, nothing is done. If the RedPA is not in international format, the country code is put in front of the RedPA. BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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The system checks whether the CdPA is in international format. If so, nothing is done. If the CdPA is in national format, the national escape code is substituted by the international escape code and the country code. Some of the services numbers, which need not be standardized, e.g. emergency numbers (100), DTMF access numbers (123). These numbers are stored in a separate list. The following table gives an overview of the different formats: Format National format International format Unknown format

Numbers 0 9443 124365 91 9443 124365 0091 9443 124365 (Longest unknown format, a complete phone number up to 20 digits)

5.2. Handling of Outgoing Calls: The purpose of the MOC service part is to process the call handling for outgoing calls to fixed or mobile networks. This section gives an overview of all service features of mobile originating calls. This section contains the following detailed descriptions. • First Call Treatment • Additional Announcements • Emergency Numbers • Connection to Call Center • Call Forwarding • Fax and Data Service Treatment • Subscriber Lock Check • Forbidden Number Handling • Charge-free Numbers • Validity Duration Monitoring • Call Credit Threshold • Rerouting of Service Connections • Granted Time Check • Recharging Reminder • PIN Check • Follow-on Calls • MOC Online Charging • Separation of Airtime and PSTN Charges • Last Call Charge Handling 5.2.1.First Call Treatment: There is parameter called “First call flag” in the PPS profile of the CSE. When the PPS is making the first call from his mobile, the service is activated, the flag will be set and his expiry date is also decided. Only MOC (charged call, charge free call, DTMF call, and call attempts to a forbidden number) is treated as first call, not MTC/USSD/SMS. When the first call is made the PPS will be addressed with welcome announcement and prompted to select the language of his choice. The system will take care not to permit MTC/USSD/SMS before the first call is made. 5.2.2.Additional Announcements: The CSE is having the facility to optionally play additional announcements to PPS during call setup.

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The first announcement needs to be defined at Provider level. Hence this announcement will be played to all the subscribers every time during call setup. New year greetings/ marketing announcements may be assigned. The second announcement needs to be defined at the individual PPS level. This announcement will be played only once on a specified day. Birthday greetings to the PPS may be played, if we maintain PPS personal profile d/b. 5.2.3.Emergency Numbers: The network operator can define up to 10 numbers in a list of emergency numbers. An emergency call treatment is executed at each call setup before a subscriber is determined by the service. If the called party is found in the list of emergency numbers, the connection is established immediately and without any further checks. Emergency calls are always free of charge. The PPS credit balance & date criteria are not taken into account for putting through the emergency call. 5.2.4.Connection to Call Center: If the subscriber data are not found in the SCP/CSE, the call is routed to a call center automatically. If no connection to a call center is foreseen, an announcement is played and the call is released. 5.2.5.Call Forwarding: This feature allows the PPS forwarding of incoming calls to another destination. Callers can be forwarded, for example, to a mailbox or any other number. This forwarded number should be within the HPLMN may be of Mobile/landline. Even when the PPS is on roaming the C/F can be effected to his HPLMN numbers. The C/F is of unconditional and conditional. I.C/F unconditional: Case1: B party (a PPS in HPLMN) forwarded to Voicemail. No charge for B party. Case 2: B party (a PPS in HPLMN) forwarded to Number. Facility charge + MOC leg for B party. Case 3: B party (a PPS in VPLMN) forwarded to Voicemail. No charge for B party. Case 4: B party (a PPS in VPLMN) forwarded to Number. Facility charge + MOC leg for B party. I.C/F conditional: (CF BUSY, CF NR, CF Unreachable) Case1: B party (a PPS in HPLMN) forwarded to Voicemail. No charge for B party. Case 2: B party (a PPS in HPLMN) forwarded to Number. Facility charge + MOC leg for B party. Case 3: B party (a PPS in VPLMN) forwarded to Voicemail. No charge for B party. Case 4: B party (a PPS in VPLMN) forwarded to Number. Facility charge + MOC leg for B party + MTC leg for B party. In all the above cases, the A party only has to pay for the intended connection. In case of a forwarded call the forwarding subscriber’s MSISDN (RedPA-the B party) is used as CgPA to find the subscriber’s data, whereas the PPS subscriber is charged for the forwarding leg. The B-subscriber of the CF (A->B->C) will not be charged for the MTC leg as long as he is in his HPLMN where MTC is free. When he is in VPLMN and C/F conditional is activated, then he has to pay for MTC leg, if any, in addition to facility charge + MOC leg. 5.2.6.Fax and Data Service Treatment: This feature allows the PPS also to be used for fax and data connections. It applies only for the subscribed access to the service. If a fax or data service is detected, the SCP/CSE switches off all announcements or warning tones for connected calls as they might interrupt transmission. For the charging of fax or data connections the bearer capability is evaluated by the tariff Service Logic. 5.2.7.Subscriber Lock Check: This feature is used to restrict the access to the PPS for a specific subscriber, e.g. to a subscriber blocked because of fraudulent events. This feature checks whether a subscriber is locked or not. If the BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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subscriber is locked, an announcement is played and the call is released. Additionally, a fraud ticket is written. If a subscriber is not locked call processing is continued. 5.2.8.Forbidden Number Handling: Some connections cannot be charged online and network operator/providers may not want subscribers to call certain numbers. These numbers are stored in a list of forbidden numbers. To improve the flexibility of administration, forbidden numbers can be defined in a black and in a white list. Black list of forbidden numbers: First the CdPA is checked against a black list of forbidden numbers. If a match between a black list entry and the leading digits of the CdPA is found, the CdPA is checked against the white list of forbidden numbers. If no match is found in the black list, call processing is continued. White list of forbidden numbers: If the leading digits of the CdPA are found in the white list, call processing is continued. If the CdPA cannot be found in the white list, an announcement is played and the call is released. 5.2.9.Charge-free Numbers: The service provider can define a list of numbers that are free of charge. When a call is set up, the CdPA is compared with the list of charge-free numbers. If the CdPA is found in the list, the call is connected and charging within the IN is suppressed. If the CdPA is not found in the list, call processing is continued. Charge-free numbers cannot be selected as friends and family numbers. 5.2.10.Validity Duration Monitoring: The expiry date that means the validity duration of the prepaid account is set when the subscriber uses the service for the first time. A successful recharging of the prepaid account can extend the expiry date. If the service subscriber attempts a call after the expiry date, an announcement is played informing the caller that the validity of the prepaid account has expired and the call is released. A special announcement is played during a warning period near the expiry date of the prepaid account. Before the call is connected, this announcement informs the subscriber of the expiry date of his account. 5.2.11.Call Credit Threshold: This feature checks the remaining account balance of a subscriber before the call is set up. If the account value is below the call credit threshold, the call is denied. The user is informed that the call cannot be set up because of insufficient credit. If the available money is greater or equal than the call credit threshold, call processing is continued. 5.2.12.Rerouting of Service Connections: In the service logic, the service provider can administrate a list of rerouting numbers. If a subscriber dials a number of this list, it is translated into another number. This functionality can be used to reroute well-known service numbers to the correct destinations. The network operators need only to publish one number of a centralized customer care, which deals with all GSM subscribers. PPS subscribers are automatically rerouted to the PPS customer care. The service provider can also offer some value-added services using the well-known numbers of any other network simply by rerouting the call. 5.2.13.Granted Time Check: The grant time is the mandatory parameter of Apply Charging (AC) message in INAP from SCP/CSE to M-SSP. It is the reply to the Initial detection point (IDP) query from M-SSP. Based on the A location and B destination numbers available in the IDP query, by referring to the pre defined tariff tables in the SCP/CSE, it arrives at a calculated balance for a predefined grant time. Then CSE checks the actual balance with the calculated balance, and at last sends the Grant time to the M-SSP. The provider can set a threshold for the minimum granted time valid for all subscribers. Once it has been exceeded, an announcement is played and the call is released. BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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5.2.14.Recharging Reminder: This feature compares the actual account balance of a service subscriber with a threshold value. If the actual account balance is equal or below the threshold, the service subscriber is requested to recharge his account by an announcement. If the actual account balance is above the threshold, call processing is continued. The account balance is updated after each call depending on the call charges. 5.2.15. PIN Check: This feature provides an authentication of the subscriber with a special PIN. This feature is used for security reasons in order to prevent illegal use of the PPS in case of dialed access. After entering the subscriber number, the subscriber is prompted to enter his PIN. The dialed digits are collected by the MSSP and sent to the SCP/CSE. The SCP/CSE checks if the PIN exists in the subscriber data set. If the PIN is incorrect, the subscriber is prompted to re-enter his subscriber number and PIN. This procedure is repeated until the maximum number of repetitions is reached or a valid subscriber number and PIN was entered. A PIN is recognized as correct when the digits entered by the subscriber match with the administrated PIN. If the PIN is locked, a fraud ticket is written and an announcement is played. As a result the call is released. 5.2.16.Follow-on Calls: This service feature allows the service subscriber in case of dialed access to place a follow-on call to another destination without redialing the service access code and going through the authentication process. The subscriber can place follow-on calls in case of B-party busy/no answer/disconnect and network error. Follow-on calls are possible after connection to service center too, regardless of whether the connection is established from DTMF menu or during service access. The SCP/CSE monitors the events Bparty busy/no answer, network error and disconnect B party. If one of these events occurs, an announcement is played and the service subscriber can place a follow-on call. The number of follow-on calls within one call execution is limited. The SCP/CSE checks this limit. If the limit is reached the call is released after playing an announcement. 5.2.17.MOC Online Charging: This feature allows the charging of a service subscriber during the call at predefined intervals and at call release by directly deducting the charges from the service subscriber’s personal account. The applicable tariff is determined by evaluating the appropriate tariff model. To determine the tariff model, the available input parameters are • Time • Destination • Origin • Bearer type (speech, fax or data) • Tariff number (subscriber defined) • Type of call (e.g. Favorite Area (FA), Friends and Family (FnF) or Home Zone) • Quality of Service (QoS; only for GPRS) These parameters are provided to the Tariff feature during call processing via call service logic in the SCP/CSE. As a result of the tariff determination, the Tariff feature determines a certain e-parameter set applicable for the current type of tariff. This e-parameter set contains 7 e-parameter values used for charge calculation. The Tariff feature does this calculation and the result is provided to the main service function as amount of charge (Calculated balance). Using the result, the remaining call time (granted time) is evaluated by comparing the Actual balance and Calculated balance. Then the “Grant time” is sent to the MSSP along with “Connect” in the “Apply Charging” message on INAP. Definition of e-parameters: One e-parameter set defines the charging for a particular time interval and for a particular type of dialed destination numbers. BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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e1: Units/amount for subsequent time slices* e2: Duration in seconds of subsequent time slices** e3: Scaling factor (not used) e4: Units/amount for initial time slice* e5: Units/amount per data interval (not used)*** e6: Segments per data interval (not used)*** e7: Duration in seconds of initial time slice** * These e-parameter values are computed by dividing by 10,000. ** These e-parameter values are computed by dividing by 10. *** These e-parameters are used for data transfer charging. The e-parameter set may be defined as follows: (An example) E1 E2 E3 E4 E5 E6 E7 110000 300 100 110000 0 1 300 E7 = 300/10 = 30 sec E2 = 300/10 = 30 sec E4 = 11000/10000 = Rs.1.10 (INR) E1 = 11000/10000 = Rs.1.10 (INR) If the above e-parameter set is determined by the charging logic for a call, then the charging will be Rs.1.10p for the first 30 sec and for the subsequent time slice. The number of subsequent time slices (x) are depending on the total duration/ pre defined grant time (T), and are computed by the following formula:

The Charge/Calculated balance (C) for that call will be computed by the following formula: C = e4 + xe1 The SCP/CSE tariff matrix is very exhaustive for the SCP/CSE is the Charge determining point for different A-locations. A-location being his HPLMN, for different destination numbers dialed by the PPS subscribers the tariff needs to be defined in the SCP/CSE. Since national/international roaming can be availed by these PPS, the M-SSP in the VPLMN contacts the parent SCP/CSE for charging purpose. Hence, each VPLMN should be treated as A-location and with respect to that A location tariff needs to be defined in the SCP/CSE for all the destination numbers dialed by the PPS subscribers. That is why the PPS tariff definition in SCP/CSE is becoming huge than that of the Billing system catering for postpaid subscribers. 5.2.18.Separation of Airtime and PSTN Charges: Whether a PSTN subscriber is involved in the call is determined on basis of the A-Location (from where the caller is calling) and the called party number (where he is calling to). With CAP 2 the PSTN BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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tariff model is bypassed, it is only used with SINAP5m+ (proprietary). In CAP 2 implementation the second IDP with 9D for PSTN is avoided. When the Call ticket is generated on completion of the call, we could find a field called “PSTN component” in the CDR. While post processing the CDRs all such PSTN component can be sorted and can be used for IUC settlement purpose. 5.2.19.Last Call Charge Handling: The data of the last call charge are determined during the call and written into variables on the subscriber level after the end of the call. If more than one call occurs simultaneously, the last call is the call, which is released last. In follow-on calls, the last call is the last call of the follow-on package. The last call must be a valid call. If a call attempt is not successful and ends with any error, this call attempt is not valid as last call. . 5.3.Handling of Incoming Calls: This section gives an overview of all service features of Mobile Terminating Calls (MTC). The purpose of the MTC service part is to process the call handling for incoming calls from a fixed or a mobile network. Incoming calls can only be received in the following cases: • If the subscriber is not barred from I/C calls • If the subscriber already performed his first outgoing call (MOC) • If the expiry date of the prepaid account is not yet reached. This section contains the following detailed descriptions: • First Call Treatment • Call Credit Threshold • Checking the Validity Duration of the Account • Online Charging of MTC Calls 5.3.1. First Call Treatment: A PPS subscriber can only receive calls (MTC) after he has made his first MOC. If an MOC has not yet been made, the first call flag will not be set in the PPS subscriber profile. Hence for an MTC, an announcement informs the calling party that the destination cannot be reached and the call is released. This treatment is mandatory as in BSNL we offer Charge free I/C calls in HPLMN. This will avoid the use of the PPS only for I/C calls even without making the first MOC call. 5.3.2.Call Credit Threshold: I/C calls in VPLMN attract charge and hence the balance will be checked. If the account value is below the call credit threshold, the call is denied. The user is informed that the call cannot be set up because of insufficient credit. If the available money is greater or equal than the call credit threshold, call processing is continued. 5.3.3. Checking the Validity Duration of the Account: If the network operator activates this feature, the validity duration of the subscriber’s account (which start from the first MOC) is checked. During the validity period MTC is permitted. After the expiry date if an A-party attempts to call a PPS subscriber, an announcement is played and the call is released. 5.3.4.Online Charging of MTC Calls: If the subscriber is within the HPLMN (Home Public Land Mobile Network)) or if the subscriber is roaming in a VPLMN (Visitor Public Land Mobile Network)), he may be charged for the MTC call. I/C calls are charged only when the PPS subscriber is roaming in a VPLMN. This is happening in the same way as applied for MOC. But the call charges are defined in the MTC tariff model by way of eparameters. BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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ELECTORNIC SWITCHING GSM /IN/A-007

At present, when the M-SSP at the VPLMN and the SCP/CSE at the HPLMN are from the same vendor, then proprietary INAP is used for MTC trigger. When the M-SSP at the VPLMN and the SCP/CSE at the HPLMN are from different vendor, then CAP-2 (Camel application part 2) is used for MTC trigger. However care is to be taken for the balance amount in the account should not be utilized in the grace period. That is the chargeable MTC (on roaming) is not permitted in the grace period, whereas charge free MTC (in home area) is allowed. 5.4. USSD Functions: USSD (Unstructured Supplementary Service Data) functions are used to perform actions via messages that are entered via the display of the mobile telephone. Three USSD functions are supported: • Credit enquiry • Display of the last call charge • Account Recharge The subscriber has to enter a specific SAC (Service Access Code) to start the required USSD function. The advantage to the network operator in promoting the USSD feature is to avoid the usage of costly traffic channels in the air interface by the PPS subscribers. The advantage to the user is that the message is displayed in the handset and he need not listen to the announcement. During mobility the subscriber may miss a part of the announcement due to outside noise. It is worth mentioning that the USSD query initiated from the HLR towards the SCP/CSE is a MAP message on C7 protocol. 5.4.1. Credit Enquiry: The subscriber has to enter a specific Service Access Code (SAC) to display his current account balance on the display of his mobile telephone. The amount can only be displayed in the default currency (INR). If the USSD SAC is invalid, a text showing that the wrong number is called is shown and the call is released. If the USSD SAC is valid, call processing is continued. The SAC for Credit enquiry is *123#. The PPS subscriber has to enter these digits in the handset and press send button. His account balance will be displayed. Of late the display of “Expiry date” along with account balance is also made available to BSNL subscribers. 5.4.2. Display of Last Call Charge (LCC): The subscriber has to enter a specific SAC to get information about the last call charge. The last call charge is read out of the subscriber’s database and displayed on the screen of the subscriber’s mobile telephone in default currency (INR). The SAC for last call charge is *102#. It is observed that only session based charging calls the amount is appearing in the LCC enquiry. For example a MOC or a chargeable MTC. In case of event charging like SMS (originating) the amount is not appearing in the LCC enquiry. However the SMS (originating) charge is debited from his account. 5.4.3.Account Recharge: The subscriber has to enter the SAC followed by the 14 digit secret code of the recharge coupon with discriminators in between and a end string at the last, then press “send” button. The SCP/CSE contacts the Voucher management (VOMS) where the d/b of the recharge vouchers is maintained, checks the validity, updates the account balance, then a successful recharge message with updated balance is displayed to the subscriber. The SAC is * 111 * 14 digits secret code #. All these three USSD functions are possible whether the subscriber is in home area or on roaming. 5.5. DTMF Menu: The subscriber dials a special service number to be able to administer his service data via DTMF menu. The menu options depend on the subscriber's permission. After the prompt of the main menu, a welcome announcement is played, the available menu options are announced to the subscriber and he is prompted to select the appropriate function. The input of the subscriber is checked. If the input is wrong, the subscriber is prompted again to select a valid option. The number of invalid inputs is limited. BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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ENGINEERING INSTRUCTIONS

If this number is reached, the call is released. If the subscriber selected a valid option, he is branched to the appropriate menu option. The PPS subscribers have to dial “123” for DTMF menu. The following figure gives an overview of all DTMF menu options, which will be played on dialing 123. Access to main menu (123)

(Options)

1 Credit & exp date enquiry

2 Voucher recharg

3

4

Modify account

Feature menu

5

6

Last call enquiry

Call center

8 Help

When option 1(123 – 1) is selected, the account balance and the expiry date will be fetched from SCP/CSE and it will be played as announcement to the PPS subscriber. When option 2 (123 – 2) is selected, the user is prompted to enter the 14 digit secret code of the recharge coupon. It will be validated then the PPS account will be updated accordingly. The updated balance amount after successful recharge and the new expiry date will be played as announcement to the PPS subscriber. When option 3 (123 – 3) is selected, the system will play the sub menus of “Modify account”.

123

Option 3

(Sub menus) 1

2

Tariff change

PIN change

3 Language change

In the sub menus of “Modify account”, Option 1 (123 – 3 – 1) is for “tariff change”. There can be number of tariff plans which can be selected by the subscriber himself if he is entitled to do. Option 2 (123 – 3 – 2) is for “PIN change”. In “Dialed access” feature, the subscriber will be asked to enter the PIN number to check the authenticity of the user. The subscriber can administer such a PIN number for his PPS account by this option. Option 3 (123 – 3 – 3) the PPS subscriber will be prompted to select language among English, Hindi, & Regional language for entire future announcement, when the first call was made. However, there is a provision by this DTMF menu option to change the language of the announcement in between the life cycle of the PPS. When option 4 (123 – 4) is selected, the system will play the sub menus of “feature menu”.

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ELECTORNIC SWITCHING GSM /IN/A-007

The sub menus of “Feature menu” will be useful when the SCP/CSE is released with additional features like Friends & Family (FnF), Favorite area (FA), Mobile local call (MLC), and Home zone (HZI). If such features are available & provisioned to the PPS subscribers, then it can be administrated by this option. When option 5(123 – 5) is selected, the Last call amount will be fetched from SCP/CSE and it will be played as announcement to the PPS subscriber. When option 6(123 – 6) is selected, SCP/CSE will route the call to a predefined Call Center number. When option 8(123 – 8) is selected, SCP/CSE will advise IP to play the entire options available with DTMF menu in detail to the PPS subscriber. 5.6. Voucher Recharging: This feature allows the PPS subscriber to add money to his account. As a result of this operation, the expiry date of the PPS may be postponed. To recharge his account, the subscriber may select any of the two methods either DTMF menu (123-2) or USSD recharge (*111* 14 digits secret code #). This leads to a connection to an external voucher management system (VoMS). The functional range and the execution of recharging therefore depend on the VOMS. The external VOMS is in LAN with other IN components as shown in the figure below.

6.0 Global Prepaid architecture The vouchers database is located in the VoMS. In a cluster configuration of VOMS, the database is located on an external disk array and all processes run on only one of the servers as shown in the figure below. The SCP/CSE and IVR always connect to the active server.

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ELECTORNIC SWITCHING GSM /IN/A-007

Fiber cat Cluster architecture The communication links shown below are used during a recharge request.

6.1 Communication links The subscriber chooses the voucher recharging function and enters the 14 digit secret code. The SCP/CSE sends a “RESERVATION” command there by presents the 14-digit secret code to the VOMS. The VOMS replies with a “RESERVATION ACKNOWLEDGEMENT” after checking the secret code in its database. Case 1: VOMS may send a ‘negative acknowledgement’ if there is an error in the VOMS system itself, or may be due to subscriber initiated errors like attempting with ‘expired/used/locked/not found vouchers’. In all these subscriber-initiated errors, fraud counter is incremented for that PPS subscriber in the SCP/CSE. Case 2: VOMS will send a ‘positive acknowledgement’, if the coupon is a valid one by marking the status of the coupon as ‘pending’. This will contain the amount and the validity period of the recharge coupon. With this, the SCP/CSE checks whether the subscriber will exceed the ‘max credit limit’. If it is exceeding, then inform VOMS to discontinue the session and the status of the coupon will be “available”. The subscriber is informed of the unsuccessful attempt with proper announcement. If the subscriber has not reached the ‘max credit limit’ with this recharge the SCP/CSE sends a “CONFIRMATION” to the VOMS. Now, the status of the coupon in VOMS will be ‘used’ and replies to SCP/CSE by a “CONFIRMATION ACKNOWLEDGEMENT”. Now the SCP/CSE adds the recharging amount and enters a new expiry date to the subscribers account. After successful recharging, the subscriber is informed about his new account balance and expiry date. Each voucher recharging operation via SCP-VOMS is documented in tickets including among other things information about the subscriber (e.g. MSISDN), the voucher ID, the time, the transaction ID, and the error code. These tickets are needed to get a history of all recharging attempts. 7.0 CONCLUSION: The PPS is attractive and the subscriber base is more than that of Postpaid. The secret lies in its “on line charging” features, which privilege the user to monitor his usage. Though “on line charging” is achieved for MOC/ MTC. For SMS/GPRS it is not so. Either we should go for “ off line charging” or “messaging gateway”. We adopt “off line charging” with the help of one “Off line server”. BHARAT SANCHAR NIGAM LIMITED A Govt of India Enterprises Restricted to Telecom Staff

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ELECTORNIC SWITCHING GSM /IN/A-007

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The Off line server will collect CDR from SMSC then send a file to the SCP/CSE to deduct the amount from the PPS account. The pooling of CDR from SMSC and sending files to SCP/CSE will not happen instantaneously and hence this process is called off line charging. As for as SMS charging is concern, on line charging is achieved by CAP1 (Camel application part 1) implementation within the Zones of BSNL, where equipments are from a single vendor. Even then we cannot dispense with the ‘off line server’. Since the PPS subscribers are with National roaming, for an SMS, the M-SSP of another vendor cannot speck with the home SCP/CSE in any of the existing protocol. So we seek the help of ‘off line server’ for SMS charging, for SMS made on roaming in other zones. To conclude, SMS/GPRS on line charging will happen, when all the M-SSP & SCP/CSE in GSM of BSNL are implemented with CAP3 (Camel application part 3) where messages similar to IDP for MOC/MTC, namely IDP_SMS and IDP_GPRS are standardized.

THE END

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