Ministry of Education and Science of Russia

federal state budgetary educational institution
higher professional education
"St. Petersburg State Technological Institute
(Technical University)"

UGS (code, name) 080000

Direction of training (code, name) 080500.62

Profile (name) electronic business

Faculty of Economics and Management

Department of Business Informatics

Academic discipline IT-enterprise infrastructure

Course 1 Group 6219

ABSTRACT

Subject : “How does mobile operator billing work?”

Student Platonova N.V.

Supervisor,

Job title Khaidarov A. G.

(signature, date) (initials, surname)

Grade

(signature of the manager)

Saint Petersburg
2012

Introduction. 3

1. What is billing? 4

2. Billing system. 5

3. Billing functions in the enterprise. 6

3.1. Settlement operations. 7

3.1.1. Prepaid. 8

3.1.2. Postpaid. 8

3.2. Information service. 9

3.3. Financial services. 9

4. Classification of billing by purpose.. 9

4.1. For transnational telecom operators. 9

4.2. Customized on a national scale. 10

4.3. Middle class systems for regional networks. 10

5. Billing organization scheme. eleven

Conclusions... 12

List of references used.. 16

Introduction

In this work I will try to find out how cellular operator billing works. To do this, I set a number of goals, the achievement of which will be the result of my work:

1. find out what billing is,

2. find out what the billing system is,

3. find out what functions billing performs,

4. find out what types of billing there are,

5. see an example of how billing works.

1. What is billing?

Billing (in telecommunications) is a set of processes and solutions at communications enterprises responsible for collecting information about the use of telecommunications services, their tariffication, invoicing subscribers, and processing payments.

Billing is an essential component of the activities of any commercial telecommunications operator, regardless of the type of telecommunications: fixed and mobile operators, Internet telephony, virtual operators, Internet providers, transit digital traffic operators, digital television providers - cannot exist without billing, thanks to which invoices are issued to consumers of their services and the economic component of their activities is ensured.

For billing systems in telecommunications, the Russian language also uses the term automated settlement system (ACP), in particular, this term is used in official documents of the Russian Ministry of Communications, which prescribe mandatory certification of billing systems.

2. Billing system

Systems that calculate the cost of communication services for each client and store information about all tariffs and other cost characteristics that are used by telecommunications operators to bill subscribers and make settlements with other service providers are called billing systems, and the cycle of operations performed is abbreviated as billing. It should be emphasized right away: such systems are created not only on the basis of customer requirements. There are a number of international ITU documents regulating their main functions and ways of implementing these functions. For example, the E230, E260, and E1001 series documents discuss the technical aspects of calculating call duration, recording calls for various types of communication, and determining the billable call duration of subscribers. Descriptions of the basic principles of tariffing for mobile communication services and connection scenarios are given in the recommendations of the D103, D110 and D93 series. Similar documents were issued by the State Committee for Communications of the Russian Federation: these are “General technical requirements for Automated systems of settlements with users for telecommunication services” (June 1998).

3. Billing functions

In relation to communication systems, billing systems are designed to perform the following tasks:

· Control and structuring of corporate communication costs
Structuring costs allows you to get a real picture of the use of such an important and valuable corporate resource as communications. Barsum allows you to detail communication costs for any administrative unit, down to a department or individual employee.

· Accounting for expenses by clients and projects Barsum allows you to automatically keep track of expenses made in the interests of clients and issue consolidated invoices to clients. Accounting for expenses of temporary project teams can be carried out in parallel with the main corporate accounting.

· Issuing telephone bills in hotels and business centers. Barsoom can be used as part of a PMS in hotels and business centers. In this case, it automatically charges telephone conversations and issues this information to the PMS for inclusion in the client’s bill.

· Analysis and optimization of the use of communication channels (financial aspect). Using a pricing system allows for “what if?” analysis. The results of such an analysis may show that using a dedicated channel or changing the operator will significantly reduce communication costs.

· Optimization of telecommunications infrastructure (technical aspect). Using statistical traffic data allows you to identify bottlenecks in an enterprise's telecommunications infrastructure. Optimal infrastructure configuration will improve the quality of communication without additional costs.

Billing functions at an enterprise are grouped into three main blocks: settlement operations, information services, and financial services.

In a broad sense, when considering billing in integration with revenue management, additional functions such as revenue assurance, subscriber profitability management, and fraud control are highlighted.

3.1. Settlement operations

The calculation operations block includes functions such as determining consumption (for example, receiving detailed information about calls from switches, processing data from switching equipment on traffic consumption, receiving data from a mediation system), estimating consumption (determining the calculated characteristics of consumption data), aggregation estimates and formation of charges for subscribers, calculation of taxes, discounts, additional charges, adjustments, issuing invoices for payment, ensuring delivery or familiarization of subscribers with invoices for payment, managing personal accounts of subscribers.

The implementation of the calculation block can vary significantly both for different types of communications and in different models of relationships with subscribers.

There are 2 main types of calculation:

· advance system (prepaid), when money is paid in advance.

· postpaid - issuing an invoice for a period based on its results (postpaid)

3.1.1. Prepaid

Prepaid (prepayment) is a model of settlements with subscribers and agents, which involves the preliminary deposit of funds into your personal account of a communication service operator, which are subsequently spent on paying for the services received. Prepaid settlement systems usually keep records in real time, directly managing the process of providing services; upon reaching the lower threshold of the amount of funds in the counterparty’s account, the mode of providing services can be changed (up to complete termination). The amount of funds in the account, the duration of maintaining a positive balance, the size and regularity of receipts can serve as tariff parameters when calculating the cost, quality and quantity of services provided.

The functionality to support restricted access to real-time communications services with a prepaid billing model is sometimes referred to as hot billing.

3.1.2. Postpaid

Postpaid is a payment model in which the operator first provides services to a subscriber or agent under an agreement concluded with him, and then carries out tariffing and invoicing for payment. The process of tariffing and invoicing is planned and regular and usually covers the calendar period of time specified in the contract (most often a month, sometimes a week, quarter, year). The counterparty is obliged to pay the amount of the invoice within the period of time specified in the contract; in case of late payment, the methods of working with the debtor specified in the contract are applied to him, as part of the processes for collecting receivables.

3.2. Information service

Information services include functions to support operational information about subscribers, about products and services, including their tariffs, restrictions, possible combinations, as well as configuration data about billing in general (for example, billing and billing schedules, managing subscriber notification events, auditing and aging settings information, acceptable characteristics of subscribers).

3.3. Financial services

Financial services cover the functions of processing payments, reconciling them for issued invoices and services, managing receivables of subscribers and the process of collection, processing tax data.

4. Classification of billing by purpose

Based on the functionality of such systems, they can be divided into three classes - intended for transnational telecom operators, custom-made on a national scale, and so-called middle-class systems for regional networks.

4.1. For multinational telecom operators

Products belonging to the first class must ensure interoperability of networks at the international level and operation in different time zones, i.e. have a multi-currency and multi-lingual interface and take into account tax differences in different countries. They are characterized by a heterogeneous structure and close integration with accounting systems.

4.2. Customized on a national scale

Custom-made systems on a national scale are created if there are specific operator requirements for the functioning of the system itself, the characteristics of the communication network, or the need to use a non-standard interface with existing settlement systems. Therefore, such systems are characterized by high development and maintenance costs.

4.3. Mid-range systems for regional networks

Regionally, standard billing requirements are usually quite acceptable. Such systems almost always have a classic client-server architecture and (especially recently) often use a Web interface. However, we should not forget that they must provide scalability and functional expansion.

5. Billing organization scheme

The billing organization scheme (Fig. 1) is quite simple: information about connections and their duration is recorded by the switch and, after preliminary processing, is transferred to the billing system. Its programs “know” all the tariffs for communication lines possible in a particular telecommunications network, “identify” the identity of the calls and perform the necessary calculations, generating subscriber accounts.

Rice. 1: billing organization system

It is obvious that such a system should store not only standards, tariffs and information about services, but also data on customers, contracts concluded with subscribers and third-party communication service providers (if the operator’s network is connected to others), as well as on the cost of transmitting information via different channels and directions. In addition, any payment system is unthinkable without a “history” of payments and invoices issued by all clients, since only this information makes it possible to organize payment control and automate the so-called activation/deactivation of subscribers. The more powerful the DBMS executive mechanism, the more large-scale and multifunctional the billing system built on its basis will be.

6. How to make payments through the billing center?

Billing (settlement) center is an organization that combines all information coming from service providers. The use of such centers makes it possible to create a unified information system and simplify many routine procedures that take up a lot of citizens’ time.

The payment acceptance procedure itself has some peculiarities. There is no need for payment documents. The payer only needs an address, telephone number or personal account number in the database. In response, the citizen is given a receipt or check on which his initials and surname, as well as other details, are indicated. Billing centers operate online with payment acceptance points, and funds are instantly transferred to the accounts of the relevant organizations. For payers, the new payment acceptance system is a clear step forward. Now at any time you can obtain information on the status of your personal account, the existence of debts, etc. The network of payment acceptance points has also been significantly expanded. Let's hope that kilometer-long queues at payment acceptance points are a thing of the past, and the unpleasant procedure for paying bills will now take a matter of minutes.

7. Example of how billing works

Each user has a cash account from which funds are debited once a day at 00:00, according to the selected tariffs if the account is not blocked. If the account has 0 rubles, then nothing is debited, the account does not go into the negative, and the Internet does not turn on. To enable, you need to top up your account. If the amount on the account is less than the selected tariff (for example: there are 5 rubles on the account, and the service costs 9 rubles per day), this amount remains in your account. The Internet will not work, since this amount is not enough to pay in advance for services for the next day. If the amount on the account is greater than the selected tariff (for example: there are 50 rubles on the account, and the service costs 30 rubles per day), then the tariff amount (30 rubles) will be debited at midnight, the Internet will work.

You deposited 50 rubles into your account at 23:00. You have a tariff of 512. When you turn on the service, you will immediately be charged 9 rubles for the provision of the service for the current day. Then at 00:00 another 9 rubles will be debited for the next day. Thus, already at 01:00 you will have 32 rubles in your account.

To avoid these moments:

Top up your account once a month by multiplying the number of days in a month by the tariff. Top up your account immediately after 00:00 or early in the morning.

The system does not recalculate by hour.

Remember: when you turn on the VPN (the system immediately debits money for the current day. This service is fully automated, which means that funds are debited automatically. No one can arbitrarily debit money from your account, the system does this according to the tariffs.

VPN (Virtual Private Network) is a generalized name for technologies that allow one or more network connections (logical network) to be provided over another network (for example, the Internet). Despite the fact that communications are carried out over networks with a lower unknown level of trust (for example, over public networks), the level of trust in the constructed logical network does not depend on the level of trust in the underlying networks due to the use of cryptography tools (encryption, authentication, public key infrastructure, to protect against repetitions and changes in messages transmitted over the logical network).

conclusions

As a result of the work done, I learned what billing is and how it works.

Who among us has not complained at the sight of tidy bills for telephone calls, doubting in our hearts the correctness of the numbers? But if a few years ago mistakes were quite possible, today they are almost impossible. It is thanks to billing that the accuracy of calculations is guaranteed by the automated tariffing of services carried out by the billing system.

Bibliography

1. Directory "Computer networks of Russia. International communication services." - M.: LLP "ELIS. LTD" 1992

2. Proceedings of the conference “Development of billing systems and information technologies for communications enterprises” December 18, 2002. Triumph Pavilion

4. Internet sites:

http://www.asks.ru/blogs/070910/57/

http://ru.wikipedia.org/wiki/%C1%E8%EB%EB%E8%ED%E3

Billing systems: basic concepts

Billing. What associations does this term evoke? Maybe there is some connection with Bill Gates? No, fortunately he has not yet “poked his nose” into the field of telecommunications. Well, that's just a joke. But to be serious, let's look at the origins of the word billing. The English word “bill” can be translated as “account” (other translations: bill, banknote). “Billing” is translated by the expression “writing an invoice.”

What is a billing system?

Systems that calculate the cost of communication services for each client and store information about all tariffs and other cost characteristics that are used by telecommunications operators to issue invoices to subscribers and mutual settlements with other service providers are called billing systems; the cycle of operations they perform is called billing. A billing system (BS) is an accounting system, software, in other words, “software” developed specifically for operators. Which operators? Telecommunications. That is, we are not talking only about cellular operators. BSs are also used by regular (landline, wireline) communication operators. In small offices, for example, you can conduct telephony billing (analyze: who called, when, how long the conversation lasted). IP telephony is another area of ​​application of BS. What about Internet providers? They also use BS, for example, to generate invoices and record traffic. Any BS is created on the basis of a specific database management system (DBMS). Most BS in the world were created on the basis of the Oracle DBMS. Among other DBMSs, Sybase and Informix can be distinguished as designed for large volumes of information. Here are the names of some billing systems: BIS, Flagship, CBOSS, Arbor, Bill-2000-prepaid. It is worth mentioning that BS can also mean hardware involved in organizing billing.

Terminology

I will try to consider all the basic concepts and definitions related to BS. I will focus on the BS used by cellular operators. But most definitions also apply to BS used in other areas. I will try to explain it as simply as possible so that most readers can understand the material. If you have anything to add to the terms I have entered, please write to me by e-mail.

There are several names for the billing system: ACP— automated payment system; IHD— information billing system.

One of the important qualities of BS is its flexibility, that is, the ability to adapt to changed circumstances. The flexible system is adapted not only to the immediate needs of the operator; due to such qualities as customizability, modularity and openness, it allows you to solve promising problems. The more options the system has for customization, the better. What is it modularity? The modular principle of building a system is a principle in which the entire system is assembled from individual parts (modules), just like a house is assembled brick by brick. The BS also consists of such modules - subsystems. The BS includes, for example, a data pre-processing subsystem, an operational billing management subsystem, and a customer notification subsystem (read below about the structure and functions of the BS). Under openness The system implies openness of the source code of the software product, which allows the operator not to depend on the developer in the future and independently maintain and upgrade the system. Closely related to the flexibility of the BS is the next quality of automated calculation systems - scalability.

Load scalability. With the growth of the subscriber base and the appearance of additional services, there should not be a need to change or modify the software part of the BS. Increasing the capabilities of the BS should be achieved by upgrading the system hardware. What is important to consider when designing scalable systems? It is necessary to use DBMS designed for large volumes of data. The DBMS must be compatible with various computer platforms to provide support for multiprocessor operation.

Reliability- one of the main requirements for any system. The reliability of the BS is determined by the reliability of the DBMS and the technologies used in system development. Not least important is the reliability of the supplier (developer) of application software: the time it has been on the market and, as an indirect indicator, the percentage of presence of the systems it has developed on the telecommunications market. Why is the indicator indirect? Is Microsoft Windows the best and most reliable operating system?... And at the same time, it occupies a significant market share. However, the reliability of the BS is also ensured by compliance with certain standards during their development (read about this below).

Multilingual— ability to install different languages ​​for presenting information.

Multicurrency— ability to work with any currencies

Deferred billing— billing, in which payments are made after calls have taken place.

Hot billing— the account balance changes during the conversation, and information about the balance on your account can be obtained immediately after the call.

Billing optimization— improvement, improvement by the operator of his BS.

Big BS— systems used by large operators.

Posting billing— recording the results of billing calculations; After calculations, the results become available to users (sent out, printed).

What can, what should, or what is the BS responsible for?

European (origin) standard TAR appeared in 1992. It is maintained by the TADIG working group. Most European operators use TAR2, although there is a third version. Since 1995, modification TAP2, known as specification TD.27, or NAGTAP2, began to be used in the USA.

Instead of a conclusion

You take your cell phone out of your pocket, dial the number, press “call” and... the conversation takes place. Now you can't wait to find out your account balance. If the billing system is “hot”, you are immediately informed of this amount. “I calculated everything accurately, it’s a good billing system,” you think. Meanwhile, the other subscriber finds out that he has just reached his time limit and has been disconnected. “Why do I need this “hot” billing! Stupid billing system!” he complains... Yes, you can’t please everyone at the same time!

Special thanks for information support to Bolshovaya Galina, magazine columnist

At the same time, information about the account status is available at any time during the billing period, which provides the subscriber with constant control over their expenses.

When concluding an agreement with each subscriber, a personal account is assigned to which an advance payment is made; accordingly, communication services are provided to the subscriber as long as the account balance is positive. The depletion of funds in the personal account leads to the suspension of the provision of communication services to the subscriber until the account is replenished.

In this material we will try to explain how funds are debited from a personal account.

Billing is a procedure for calculating the use and pricing of communication services. In other words, the billing system determines:

Possibility of providing communication services to the subscriber, i.e. availability of funds in the personal account;
- type of calls, their direction, cost;
- availability and cost of services used by the subscriber.

All calculations are carried out in conventional units that correspond to US dollars. Payment is made by the subscriber in rubles, funds are credited to the account at the rate of the Central Bank of the Russian Federation on the day of payment. Payment is considered made if the funds are received in the current account or at the cash desk.

3. At what points are funds debited from the account?

Periodic services - services provided continuously over a certain period, for example, subscription fees, network and additional services, for which you must pay monthly.
One-time services - services provided and paid for once, as needed, for example, replacing a SIM card or adding the Voicemail service.

4. Billing groups

Funds are debited from the subscriber's personal account depending on the services provided and in accordance with the billing rules.

The company has three settlement (billing) periods:

The first corresponds to the calendar month, i.e. starts on the 1st and ends on the last day of the month;
- the second begins on the 10th of the current month and ends on the 9th of the next month;
- the third begins on the 20th of the current month and ends on the 19th of the next month.

Accordingly, within 10 days after the end of the billing period, a monthly invoice is generated and printed, which reflects information about the funds debited from the subscriber’s personal account for all types of services provided.

5. Why is there a difference between the exact balance and balance information in ACCA?

The easiest and most common way to find out the status of your personal account is to call the Automatic Subscriber Service at 088011 (the call is free on your home network). Perhaps every subscriber, having listened to the information about the balance, asked the question “How accurate is the information in ACCA?”

However, despite the obvious advantages, the advance method of mutual settlements has one feature that “overshadows” it and raises numerous questions from subscribers. We are talking about a technological delay between the time of provision of communication services to the subscriber and the moment of their accounting and tariffication in the settlement system (billing). The duration of such a delay is determined by the load on the network switching equipment and the degree of optimization of technological processes in the billing system.

6. Types of accounts

As already mentioned, at the end of each billing period, the subscriber (for each personal account) is issued an invoice for payment, which is a kind of report to the subscriber for all charges made in the past billing period. In addition, the monthly invoice contains information about payments made and the recommended amount for prepayment.

To receive an invoice for payment, you must order and pay for the "Invoice Delivery" service in accordance with the selected tariff plan. Invoices can be delivered by email, fax, mail or courier (within Moscow and the Moscow region). You can also arrange the delivery method "In hand", i.e. The subscriber has the opportunity to independently collect issued invoices by contacting the Financial Control Service personally. In addition, you can order an invoice for payment via ACCA by fax at 0880141 or via ISSA by fax or email (invoice delivery is free).

Prepayment invoice

If necessary, you can order an invoice for prepayment in the amount indicated by the subscriber himself or recommended by the billing system from the financial control service or through ACCA, ISSA. The prepayment invoice is calculated free of charge.

The "Detailed bill" service is a transcript of the subscriber's conversations for the billing period. It indicates the date, time of the call, the telephone number to which the subscriber called, or from which the call was received, if

Billing is an automated process that uses professional software. It analyzes how the signal passes through each cell, then it is sorted and calculated what the cost of services will be for a particular owner. It is telephone billing that generates payment for telephone communications. After the call, he debits as much money as indicated in your tariff plan.

Billing systems

Mobile phone billing is a complex process that requires modern, high-quality and powerful tools. Software, banking and legal support are components of new technologies. It is because of this that phone billing programs exist only in large companies that engage in e-commerce and, of course, in regional cellular companies.

The function of this new system is that it calculates the price for mobile communication services separately for each person. Programs save information about the time when the user called, duration and other characteristics of conversations for a certain period (for a year or six months). Phone billing involves professional software that is used in the accounting calculations of telecommunications operators.

Load distribution

As a rule, mobile operators cooperate with each other. They install one station and use it together without spending additional money on software and Typically, in each city, one operator installs a separate tower for itself. In rural areas and highways, several companies use one. There will be only one owner of this mobile station, but other operators pay him for rent, its cost is calculated based on the number of calls.

Internet traffic is also handled by billing systems. In this case, the subscriber is charged at a separate rate. Each company is different. In one, you need to pay for the time spent on the Internet, in the other, for transmitted and received information packets.

Billing functions

Phone billing is based on a fairly simple principle. The switching node records all data, namely the duration and characteristics of the call. Then all the information received is sent to the central station, where the calculation is made.

The software, which is installed in the central office, processes all data and monitors regulations, tariffs and prices. Phone billing contains all information about the user (tariff, availability of bonuses, prices for certain areas).

These modern databases store information about all payments made by each customer. This allows you to calculate withdrawals. Billing stations are equipped with high-quality and powerful computers that allow you to make calculations very quickly. Due to this, subscribers’ requests for account status receive results almost instantly.

The software also monitors the user's account status. The system has the ability to deactivate a subscriber. If a person has not topped up his account for a long time and does not use the services of a mobile company, then he is simply turned off.

As you may have guessed, due to cell phone billing, a message pops up stating that the system cannot establish a connection when the bill is zero. If you top up your phone balance, you can immediately use the services; the system connects them automatically.

Most mobile operators create a feedback function. It also controls cell phone billing. With its help, by logging into your personal account, you can replenish, disable, connect various services, change your tariff and much more.

If you go to your mobile operator's website, you can see your activity for the last month through your phone billing. You can see who you had conversations with, for what duration, and how much money they charged you for it.

Additional billing options: mobile surveillance

The mobile phone that we use for communication, like a camera, video camera, beacon, has some other functions. Nowadays, most crimes are investigated using billing. This system is able to track all calls.

How can phone billing help in a murder investigation? It's simple, this system records when we log on to the Internet and where this happens, call or send SMS.

With the help of new technologies, namely billing, many high-profile crimes have already been investigated and the culprits found.

The subscriber is always available

The mobile phone is a great achievement of man, a new technology that has advanced progress. Unfortunately, this technology can be used not for good, since a cell phone is a kind of radio beacon that will help track a person’s location.

As we have already found out, the entire territory where there is mobile communication is divided into cells. There are towers and special stations that have a specific address.

If you analyze the signal from a mobile phone, you can determine at what distance and where a person is (in a car, at home, on the street). It is also not difficult to determine the subscriber’s movement. You can take several towers and find out a person’s route with a small error.

Private billing

The first to use billing for investigations were private detectives. Of course, their actions violated the Criminal Code.

If it's prohibited, how did they get the information? The first way is to purchase data from employees of a mobile company. But now it is not so simple, services have begun to struggle with information leakage.

Now, to get the data to detectives, you will need to pay $500. And in order to analyze it, to find out the movement of a person, you need to pay 1,500 dollars. In most cases, in order for a cellular company employee to become interested in this “business,” you need to constantly learn numbers in large quantities.

Another way is to ask familiar operatives to find out about the mobile phone and the person to whom it belongs. But this is quite long, the investigation may drag on.

The platform processes InitialDP 37 ms; the subscriber listened to beeps for 10 seconds; The duration of the conversation is a little more than 5 minutes.

Billing collects information about the use of telecommunications services, their tariffs, and is responsible for billing subscribers and processing payments.

There are 2 main types of calculation:

• Postpay- issuing an invoice for the period based on its results (postpaid)
• And advance system(prepaid), when money is paid in advance.

Postpayment appeared historically earlier, but prepayment turned out to be more convenient for customers (more controllable - if something goes wrong, a disconnection occurs, rather than a large bill being issued).

Postpaid system

When a postpaid payment system subscriber uses the services of an operator, special CDR (Charging Data Record) files are generated on the switches. Essentially, these are ordinary logs that indicate the subscriber number, date, call time/volume of downloaded traffic, etc. Billing, at a certain time (for example, once a day) connects to the switch, downloads CDRs, calculates the cost of services and saves everything in a database (usually Oracle). The subscriber is then issued a total invoice at the end of the month.

Scheme of interaction of the Postpaid platform with the core of the operator’s network.
CSN- circuit switching network; Represented by channel switches (MSC).
PSN– packet switching network; Represented by packet switches and gateways (SGSN and GGSN, respectively).

The principle of operation of the postpaid system is relatively simple, because it does not require a real-time response from the platform: after all, the subscriber does not need to be warned about reaching zero (and, accordingly, there is no need to change the nature of the network’s interaction with him).

Advance system

In the case of advance charging, the telecom operator, in addition to taking into account the volume of services provided, needs to solve the problem of tracking the subscriber’s current account and, if it reaches zero, inform the subscriber/disable the provision of the service. Therefore, such systems are also called Online Charging System (OCS).

Since the operator provides different types of services and different types of networks are used (channel/packet switching system), the billing system has to use different charging protocols to solve the problem of controlling the subscriber’s account, for example the following:

Scheme of interaction of the prepaid platform with the operator’s network.

Let's look at these protocols in more detail.

CAP

CAP(CAMEL Application Part) is an application layer protocol of the SS7 stack that implements intelligent services in GSM/UMTS networks (for example, prepaid).

Place of the protocol on the stack. The figure also shows a popular option using SIGTRAN technology (an SS7 extension that allows the use of the “seven” protocols over an IP network).

Using this protocol, OCS communicates with the circuit switching network. Here is an example of outgoing voice call pricing:

Charging dialog using the CAP protocol, dotted lines show ISUP messages.

1. First, the billing system receives a message (Initial Detection Point) from the MSC1 switch, which transmits the subscriber’s parameters. These are incoming and outgoing numbers, the cell address of the called subscriber and others. Based on this, it is possible to begin analyzing the call. Billing creates a certain Detection Point - that is, the state of the call. OCS determines whether the subscriber can make a voice call (whether there are funds in the account), if so, then for what maximum time.
2. After this, OCS responds to the switch with a Request Report BCSM Event (“I have initialized the Detection Point, I am waiting for further information from you about the status of the call”). And sends Apply Charging (“the subscriber has funds in his account, I authorize the call”). The maximum time that the subscriber can use is also sent there.
3. The switch, having received permission from OCS, initiates a voice connection between subscribers using the ISUP protocol, sending an IAM (Initial Address Message) message to MSC2.
4. MSC2 responds to MSC1 with an ACM (Address Complete Message) message, in this case it means “yes, my subscriber, he is now online, I’m starting to call him.” Having received this message, MSC1 turns on long beeps to subscriber A.
5. Subscriber B picks up the phone, MSC2 sends MSC1 the message ANM (Answer Message) - “my subscriber picked up the phone, connect them.”
6. MSC1 connects subscriber A and B, a conversation begins. MSC1 sends an Event Report BCSM (O_Answer) message to the OCS. OCS changes the call status for this subscriber. From this moment, charging begins (taking into account that the first 3 seconds are free).
7. While subscribers are communicating, MSC1 monitors the call time. If there is little time left, the MSC warns the subscriber with an audible signal.
8. In our case, subscriber B hangs up first, MSC1 and MSC2 make a friendly handshake using REL (Release Message) and RLC (Release Complete Message) messages.
9. MSC1 sends the message Event Report BCSM (O_Disconnect - “subscribers successfully disconnected”) and Apply Charging Report (how many seconds the conversation lasted) to OCS.
10. OCS accepts this data and responds that the session can now be closed.

INVOKE --- A1 TAG: A1h 1B LEN: 27 --- INVOKE ID --- 02 TAG: 02h INTEGER 01 LEN: 1 02 INVOKE ID: 2 === CAP === --- INVOKE --- -- - OPERATION --- 02 TAG: 02h INTEGER 01 LEN: 1 23 OPERATION: 35 = applyCharging --- APPL CHARG --- 30 TAG: 30h SEQUENCE 13 LEN: 19 --- ACH BCC --- 80 TAG: 80h 0C LEN: 12 --- TDC --- A0 TAG: A0h 0A LEN: 10 --- MAX C P D --- 80 TAG: 80h 03 LEN: 3 01 19 40 MAX C P D: 4370

This is part of the trace. We see that the applyCharging message was sent via the CAP protocol, the maximum conversation time (MAX CPD - Maximum Call Period Duration) is 437.0 seconds.

I’ll duplicate the picture before the kata: this is an example of communication using the CAP protocol. Timestamps can be estimated: the platform processes InitialDP 37 ms; the subscriber listened to beeps for 10 seconds; The duration of the conversation is a little more than 5 minutes.

But here the call is long and you can see how the system itself requests the status of the call (activityTest) from MSC every 6 minutes. This was done so that, in the event of any error, the conversation would not last for days (until all the subscriber’s money is debited).

The CAP protocol can charge not only voice calls - it is also capable of charging Internet connections, SMS, MMS, and so on. Although in practice, specially tailored protocols (DIAMETER/OSA) are most often used for these needs.

O.S.A.

O.S.A.(Open Service Access) is an open software interface developed by the 3GPP and ETSI consortium, often used for charging VAS services and mobile Internet.

Let's consider the operation of this protocol using the example of tariffing for mobile Internet services:

1. When an attempt is made to activate the PDP Context (the phone obtains an IP address in the mobile operator’s network), GGSN asks the platform whether this subscriber can activate a charging session (CreateChargingSessionReq).
2. In our case, everything is fine (the subscriber is in the database, there are funds), the platform creates a charging session and allows the PDP Context to be activated (CreateChargingSessionResp).
3. Now the subscriber wants to start downloading data. To allow him to do this, GGSN contacts the platform with a request to reserve funds (ReserveUnitReq). In general, unit is an abstract thing, it can be anything - a kilobyte of data, a text message, a second of conversation, a ruble, a pizza, a barrel, and so on. In our case, unit is 100 kB.
4. The platform checks whether a given subscriber, in accordance with his tariff, has funds for 100 kB of traffic and responds with the message ReserveUnitResp (“funds are reserved”). Having received this message from the platform, GGSN allows the subscriber to download traffic.
5. When the subscriber has downloaded the reserved portion of traffic, GGSN contacts the platform with the message DebitUnitReq (“you can write off the reserved funds”).
6. The platform debits the funds and responds with the message DebitUnitResp (“funds successfully debited”).
7. The ReserveUnitReq-DebitUnitResp cycle is repeated until the subscriber downloads the entire Internet and closes the Internet session.
8. When PDP Context is deactivated, GGSN sends a message to the platform indicating the end of the charging session; the memory allocated for this session is freed.

Request debitUnitReq; OSA commands are wrapped in the SOAP protocol, which in turn is encapsulated by the HTTP protocol.

Conclusion

Changing customer needs (including an increase in the volume of transmitted data), the creation of new types of services, entails the evolution of the mobile operator’s network, primarily in the field of VAS platforms and billing systems.

If the topic of AAA family protocols is interesting to you, then later I will talk about RADIUS, DIAMETER and other interesting things.