Do you know how 5G is charged? Come and see where your money is spent

What is billing?

Billing is the process of keeping accounts and collecting money. When you use a service, you need to pay the corresponding fee based on the service content and duration. This is billing.

We use mobile phones every day, and we also need to recharge our phones. So, have you ever thought about how the mobile communication system charges?

In today’s article, let’s learn about 2/3/4/5G billing-related knowledge.

     What is a Call Record (CDR)?     

Let’s start with the basics.

The first concept to be introduced is the call record.

The call bill in communication professional terminology and the call bill we usually refer to are two different concepts.

The phone bills we usually refer to, such as those found through operator apps, are bills and detailed bills.

The bill is a detailed breakdown of the total monthly expenses. The detailed bill is a specific record of daily calls or Internet access. In simple terms, the bill is a summary settlement of the detailed bill.

bill

Detailed list

The call record in the professional terminology of our communications industry is called CDR (Call Detail Record).

CDR is a file data transmitted within the communication system, recording the information of each original communication record.

Example of a call log file. Each file has many records.

Each record is composed of different fields, including serial number, user ID, calling number, called number, start time, end time, call duration, Internet traffic, call nature and other information.

It is difficult to understand the CDR file directly. It must be interpreted (translated) according to the call record format specifications of each operator.

To put it bluntly, CDRs are not for people to see, but for the operator's business account BOSS platform to see. The BOSS here does not mean "boss", it refers to the Business & Operation Support System (Business Operation Support System).

The BOSS system parses the conversation slip, then generates a detailed slip and an invoice, sends it to the mobile phone user, and charges the fee.

There are many types of CDR bills, including voice bills, SMS bills, and data service bills (Internet bills). As long as your mobile phone uses a service, a bill will be generated.

     Offline and online charging     

So, how do 2/3/4G communication systems generate, transmit and store CDRs?

In general, there are two methods, namely offline billing and online billing.

Offline billing is a non-real-time billing method. It generates CDRs in real time based on the user's service usage and stores them locally, and uploads them to the Billing System regularly. The operator settles the bill charges regularly.

Offline billing does not have a real-time impact on the service process, and is a typical "use the service first, pay later" model. It's like you surf the Internet in an Internet cafe and settle the bill when you want to leave.

Early communication services (such as home phone calls) were all paid in this way, and many corporate packages are also paid in this way.

The following figure shows the framework of offline charging and the functions of each functional entity:

Now let’s look at online billing.

Online billing is a real-time interactive billing method, generally for "prepaid" services. The mobile phone billing method currently used by everyone, as well as some early phone card services, are all based on online billing.

Online charging requires users to deposit a certain amount of money into their accounts before using the service. OCS (Online Charging System) will monitor the user's account in real time and calculate your balance. When the balance is insufficient, the service will be stopped immediately.

It's like when you go to an Internet cafe and deposit 10 yuan, once it's all used up, the computer will be locked immediately and you won't be able to use it anymore.

Online billing has a more complicated implementation principle, but it can effectively control the risk of arrears and avoid losses to operators and users.

The tragedy of renting a house in one night will not happen under OCS.

The following figure shows the framework of online charging and the functions of each functional entity:

     Converged Billing     

Well, in the 5G era, how should billing be done?

In the 5G era, the core network architecture has undergone great changes.

The 5G core network adopts the SBA microservice architecture, which looks a bit like a bus architecture. Traditional communication network elements become many NFs (Network Functions).

These NFs can be independent and autonomous to achieve automatic management. NFs can communicate with each other as needed.

5G core network architecture. The orange box is the core network NF

In order to adapt to the SBA architecture, a new billing method has emerged, that is, Converged Charging System (CCS).

Online or offline charging first obtains charging information and then sends it to different functional entities. The converged charging system integrates online and offline charging functions and uses a unified service-oriented interface Nchf to connect with each NF on the network element side.

Converged Billing Architecture

Functions of Convergent Billing Functional Entities

CHF is a fusion of CDF for offline charging and OCF for online charging. It supports both offline and online charging. On the one hand, it generates billing call records, and on the other hand, it completes quota management to control the available amount of services used by the current user.

CDF and OCF merge into CHF

The advantages of converged billing are very obvious.

First, it merged the two original independent billing systems into one, unified the interface, achieved "slimming down", simplified the billing process, reduced the difficulty of operation and maintenance, and saved network resources.

Secondly, the SBA architecture of integrated billing allows itself to meet the needs of more business scenarios. In the 5G era, all kinds of billing needs can be found in it.

Finally, converged billing brings higher security. The SBA architecture has a variety of security measures, such as access authentication and encrypted transmission, which can effectively ensure the security of billing information transmission.

After talking about so much, what exactly is the convergent billing process? Which NFs play a role in the process?

Please see the following converged billing business process diagram:

SMF (Session Management Function) PCF (Policy Control Function) CHF (Charging Function) CCS (Converged Charging System) UPF (User Plane Function) AMF (Access and Mobility Management Function) NR (New Radio) CGF (Charging Gateway Function) ABMF (Account Balance Management Function) RF (Rate Function)

1. The charging trigger function CTF is built into the SMF on the 5GC network side. Therefore, SMF is a user of converged charging services. After SMF detects the use of network resources, it triggers the charging function and obtains the charging policy from PCF. 2. SMF initiates a request to establish a charging session to CHF, and the CCS side starts recording the billing call. 3. SMF selects UPF and establishes a data plane transmission channel, and sends/activates the billing rules at the same time. 4. SMF sends the service quota obtained from CHF to UPF for monitoring. 5. UPF reports the usage information of UE to SMF. 6. SMF reports the received information to CHF again. After CCS completes the online deduction and synchronously generates the billing call information, it allocates a new share to SMF again to start a new round of quota monitoring.

It seems a bit complicated, it doesn’t matter if you don’t understand it, haha.

For a long time in the future, we will be in a state of 2/3/4/5G coexistence. Therefore, we need to implement billing functions for 2/3/4G and 5G at the same time.

To this end, ZTE has proposed a 2/3/4/5G integrated core network billing solution.

In the solution, each network element cooperates with each other and adopts different billing methods for different access methods:

For 2/3G access: the traditional billing interface is still provided.

For 5G access: Provide a converged charging interface Nchf that complies with 3GPP standards.

For 4G access: By accurately identifying whether the user has 5G capabilities, the traditional billing interface or the new Nchf interface can be selected.

Flexible billing solutions can provide multiple 5G billing evolution routes. The ultimate evolution goal of these routes is to "withdraw from 2/3G networks and all users sign up for 5G." However, this will be a long process.

ZTE launches two 5G billing evolution routes

Well, the above is the knowledge about 2/3/4/5G billing. Do you all understand it?