Transcript Communication Protocol Engineering Lab. Mobile Prepaid Services

Mobile Prepaid Phone Service
2003. 5. 13.
Kim Myung Jo
([email protected])
Communication Protocol Engineering Lab.
Myung Jo. Kim.
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Communication
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Contents
 Mobile Prepaid Services
 Wireless Intelligent Network Approach
 Service Node Approach
 Hot Billing Approach
 Handset-Based Approach
 Comparison of the Prepaid Solution
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Communication
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Overview
 Traditionally prepaid phone
– A telecommunication service that requires a customer to pay before
making calls
– Public phone (use coin)
– Public phone (use prepaid card)
 Prepaid telecommunication services
– Offered in Europe and Asia in 1982
– Became popular in the United States in 1992
• More than 30 prepaid solution vendors are currently competing for carrier
business
 Mobile prepaid service
– Has been growing exponentially all over the world
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Advantage and Characteristic
 Service provider
– Reduce the business operation costs
 Customer
– Provide immediate service without the need for long-term contracts
• Many end users just want to enjoy the service
• Do not want to fill in subscription forms
 Difference of two type of prepaid service (fixed vs mobile)
– A fixed telephone service provider knows nothing about the prepaid
customers
– Fixed prepaid service allows outgoing calls only, whereas mobile
prepaid service allows both incoming and outgoing calls
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Mobile Prepaid Services (1/2)
 In GSM prepaid service
– A customer subscribes with prepaid credit
• Coded into the subscriber identity module (SIM) card or kept in the
network
– Initialization of a prepaid customer must be completed within a certain
number of days after subscription
– If the balance is depleted
• The customer cannot originate calls
• Allowed to receive phone calls for a predetermined period
– To recover the prepaid service
• The balance has to be recharged by purchasing a top-up card , which is
similar to a lottery scratch card
• The system verifies and refreshes the account if it is a valid code
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Mobile Prepaid Services (2/2)
 Mechanism in the mobile prepaid service
– An extra billing system for mobile prepaid service is required
– A real-time usage metering function must be built in the prepaid
service system to monitor the amount of remaining credit on the
customer account
– Sales taxed are generally collected at the point of sale (POS) for
prepaid service
– A customer care mechanism maintains items including customer
activation and deactivation times, credit value, remaining time period,
PIN
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Communication
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Wireless Intelligent Network Approach
 WIN (Wireless Intelligent Network Approach)
– A complete solution to prepaid service
– A P-SCP (Prepaid Service Control Point) communicates with the M
SC through SS7 signaling network
– Several WIN triggers are defined
– All billing information for a prepaid customer is stored in the P-SCP
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WIN Call Origination
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Solid Lines : Voice Trunk
Dached Lines : Signaling
Intelligent
Peripheral
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P-SCP
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MSC
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SSP
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WIN Call Termination (called-party-pays billing)
P-SCP
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GMSC
SSP
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MSC
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WIN Prepaid Recharging
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P-SCP
Intelligent
Peripheral
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MSC
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Service Node Approach (1/3)
 The service node approach
– The most widely deployed prepaid service solution at the initial stage
of prepaid service provisioning
– To deploy the prepaid service without interrupting the existing call
models
• Most mobile service providers implement service nodes in their networks
to externally control prepaid billing
– The service node is implemented using CTI (Computer Telephony
Integration) techniques and PC-controlled PBX (Private Branch
Exchange)
– The same platform can be used to implement the prepaid service
node effectively
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Service Node Approach (2/3)
 CTI
– Utilize computer intelligence to manage telephone calls
– APIs (Application Programming Interfaces)
• TAPI (Telephony Applications Programming Interface)
• TSAPI (Telephone Services Application Programming Interface)
– Support general APIs that allows fast deployment
 PC-controlled PBX
– The software (C++) in the call control layer can be modified to
implement various telecommunication applications
– Provide larger and more cost-effective solutions than CTI switching
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Service Node Approach (3/3)
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MSC
SSP
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PBP
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Service
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PBP : Prepaid Billing Platform
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Hot Billing Approach (1/2)
 Hot billing
– Uses CDRs (Call Detail Records) to process prepaid usage
– The prepaid CDR is created in the MSC
– The information in a CDR
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Type of service
Date/ time of usage
User identification
The destination of the call
Location information
– These records are generated when the calls are completed, and are
transported from the MSC to the prepaid service center
– The balance of the customer’s account is decremented according to
the CDRs
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Communication
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Hot Billing Approach (2/2)
 When customer uses up the prepaid credit
– The HLR and the AuC are notified to prevent further service access
– The prepaid service center instructs the network to route the next
prepaid call attempt to an IVR
• To play an announcement indicating that the balance has been depleted
– The IVR can communicate with the customer to replenish the prepaid
credit by using a top-up card, a credit/ debit card, or a credit transfer
from a bank account
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Hot Billing Architecture and Interfaces
PSC
TCP/IP
IVR
CMISE
CMISE
SS7 ISUP
HLR
AuC
GSM MAP
MSC
PSC : Prepaid Service Center
IVR : Interactive Voice Response
CMISE : Common Management Information Service Element
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Hot Billing Prepaid Service Initialization
 Step1
– The customer subscribes to the prepaid service center at the POS or
by calling the customer care center
 Step 2
– The prepaid service center creates a subscriber data record including
IMSI, MSISDN, account of credit, period of validity tariff model, and
other authentication-related information
 Step 3
– The prepaid service center activates the prepaid service by sending
the customer data to the HLR, which then creates a record for the
customer
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Hot Billing Prepaid Call Origination
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HLR
P-SCP
AuC
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P-SCP
PSC
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MSC
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SSP
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Hot Billing Customer Query and Recharging
PSC
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MSC
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IVR
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Handset-Based Approach (1/3)
 In the handset-based approach
– The MS performs credit deduction during the call and determines
when the credit limit is reached
– The prepaid credit is stored in the MS
• In the United States => special phones are required
• For GSM => the credit is stored in the SIM card
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Handset-Based Approach (2/3)
 SIM card issues
– Two partitions of SIM memory
• Dialing numbers, short messages received, a menu of subscribed services
• Programs that can be executed to carry out simple commands
– AoC (Advice of Charge) message
• To transfer the prepaid balance information and the tariff schemes
• Provide information for the MS to produce a cost estimate of the services
used
• AoCC (Advice of Charge Charging)
• AoCI (Advice of Charge Information)
– To utilize handset-based prepaid service
• The MS must support AoCC
• AoCC is activated for every prepaid customer in an HLR which will be
used in call setup and tariff switching
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Communication
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Handset-Based Approach (3/3)
 Data fields in a SIM card
– ACM (Accumulated Call Meter)
• Accumulates the used prepaid units
– ACM* (Accumulated Call Meter Maximum)
• Records the amount of purchased prepaid credit
– PUCT (Price per Unit and Currency Table)
• The value of the home unit in a currency chosen by the subscriber
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Handset-Based Prepaid Call Origination
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MSC
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SSP
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Combined Prepaid Call Origination
P-SCP
PSC
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MSC
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SSP
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Handset-Based Prepaid Recharging
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SSP
P-SCP
PSC
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SM-SC
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MSC
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GMSC
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SM-SC : Short Message Service Center
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Roaming
 Roaming to other network
– To provide roaming to prepaid customers
• An agreement must be made between the home system and the visit
system
• This agreement is required so that the visited system can distinguish
prepaid calls from the postpaid calls generated by roamers
• Use special MSISDN
 Prepaid charging
– Cannot be performed at the visited system because the home system
and the visited system may exercise incompatible prepaid service
solutions
 Most networks
– Require the visited MSC to route the prepaid call back to the home
network
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Communication
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Roaming to Other Networks for Prepaid Service
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MSC
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SSP
GMSC
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Service
Node
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PBP
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Scalability
 The handset-based & the WIN approaches
– have good scalability
 The hot billing approach
– The size of prepaid customer population is limited to the MSC’s
capability to process and deliver CDR messages
 The service node approach
– The capacity of the trunks between the service node and the MSC
limits the prepaid customer population that can be accommodated in
the system
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Fraud risk
 The handset-based
– AoC communication is not encrypted
– It is possible to modify the credit illegally in the MS
 Poor fraud protection
 The hot billing approach
– The risk of fraud can be high
• Due to one-call exposure
 The service node approach & the WIN approaches
– Exhibit low fraud risk
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Initial system setup
 The handset-based
– Dose not require changes to the mobile network infrastructure, except that the
MSC must support AoC
– Special SIM software is required to execute rate plans in the MS
=> Average setup cost and time
 The hot billing approach
– Requires the integration of the prepaid service center, the IVR recharging
mechanism, and the MSC/HLR
=> Average setup cost and time
 The service node approach
– The mobile network not modified
=> Setup time is short and the setup cost is for the establishment of the service
node
 The WIN approaches
– The design of services and switch software development for intelligent
network is complex
=> Setup time is long and setup cost is very high
Communication
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Service Features
 Handset-based approach
– Supports limited service features
• the number of rate plans that can be stored in the SIM card is limited and
cannot be conveniently updated
 Hot billing approach
– Better than average
 The service node & the WIN approaches
– Support flexible service features
 None of the four approaches can support prepaid short
message service
– Because the short message is delivered by the SS7 TCAP, which
cannot be identified by the MSC
– Instead, charging for the short message is done at the SM-SC
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Prepaid Short Message Service
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SM-SC
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IWMSC
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GMSC
IWMSC : Interworking MSC
Service Node
Prepaid SCP
Prepaid Service Center
or SIM/MS
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Real-Time Rating
 The handset-based approach
– Real-time rating is performed at the MS
 The service node approach
– Real-time rating is performed at the service node
 The WIN approaches
– Real-time rating is performed at the P-SCP
 The hot billing approach
– Cannot support real-time rating
– The credit information update depends on the MSC capability of
sending CDRs
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