GPRS Billing analysis

GPRS, as a transition from second-generation mobile communication to third generation mobile communication, has taken an important step in mobile internet. As a new business, its billing system is closely combined with the communication Process control. On the basis of introducing the billing features and information collection points of GPRS, this paper describes the analysis and processing of GPRS billing records, and puts forward the problems that will be faced in the future GPRS billing.

Today, the second generation of mobile communications mainly to provide voice and low-speed data Services, the third generation of mobile communications on the basis of improving voice services, to provide high-speed data services and multimedia services as the main features.

At present, in mobile communication network, Internet application performance is poor, which is caused by low bandwidth usage efficiency, long connection setting time and low wireless link capacity. GPRS to improve the above several aspects, it broke through the GSM network can only provide circuit switching thinking, only by adding the corresponding functional entities and the existing base station system for partial transformation to achieve packet switching. The input of this kind of transformation is relatively not big, but the user data rate that obtains is quite considerable. GPRS supports x by reducing connection creation time. 25 and IP protocols to provide optimized use of resources.

--one, GPRS billing characteristics and information collection points

--gprs on the basis of GSM network, it adds service support node (SGSN), Gateway Support node (GGSN), Billing Gateway (CG) and other network equipments, and realizes the connection between each equipment through GPRS backbone network. SGSN and GGSN are inherently non-standard routers, and SGSN in a packet network is similar to an MSc in a circuit-switched network, while GGSN is primarily responsible for external networks such as IP networks, x. 25 network, etc.) interconnection. (Computer science)

--the network in the provision of services to users at the same time need to record the user's consumption of network resources, billing is essentially based on the user of network resources in accordance with the use of certain rules to calculate costs. Because of the different business to the network resource occupancy status, so its billing strategy is also different. GPRS billing also has a close relationship with its business characteristics.

--GPRS uses wireless access means, and wireless spectrum is a very valuable resource of the network, so the consumption of wireless resources is an important part of the billing, which is similar to the current GSM voice wireless phone bill. Although mobile network is a relatively complete network, but there is still communication with the external fixed network, so the use of external network resources is also an important component of billing, which is similar to the long-distance telephone charges in GSM voice communication. Roaming around the mobile phone has led to increased overhead for networks and operators to manage their mobile phones, and there is a complex cost-clearing between operators, which ultimately comes in the form of roaming fees.

--gprs is most proud of the wireless access link to achieve a packet transmission. Packet data billing is generally based on the amount of data.

There are 5 types of call detail records (CDR)--gprs, i.e. S-cdr,m-cdr,g-cdr,s-smo-cdr and S-SMT-CDR. In addition to the 5 kinds of g-cdr by GGSN, the other 4 kinds of records are produced by SGSN. S-cdr reflects the use of wireless resources, G-CDR reflects the use of external data network resources, M-CDR reflects the cost of the system in the mobile management, S-SMO-CDR and S-SMT-CDR These two kinds of message records using GPRS-hosted SMS service.

--GPRS system will spend a lot of overhead on mobile management, although it is also true in GSM system, but in GSM system, only the roaming problem is charged, the mobile phone mobile may trigger the position update, the handoff and even the handover of service fee. Theoretically, when a mobile phone is at a basic static and high-speed movement (which may occur a number of transitions and position updates), the length of the call is the same, but the two vary greatly in terms of system overhead. The GPRS m-cdr has a change of Location that records the RAI that the mobile phone is experiencing, that is, once a routing zone update (Routing area updating) occurs, the corresponding Rai is recorded. The system provides M-CDR as the basis of billing is reasonable. The billing principle of GSM system has certain inertia to the user's mentality, so it is unfavorable to choose M-cdr.

--To sum up, GPRS billing based on the SGSN produced by the S-CDR and GGSN produced g-cdr.

--second, GPRS billing record analysis and processing

In Figure 1, the entities associated with GPRS billing are SGSN,GGSN, billing gateways and Billing systems (BS). The g-cdr of SGSN in S-cdr and GGSN is the basis of billing, which reflects the amount of wireless data and external data respectively.

--s-cdr mainly contains the following information: User identification, such as MSISDN,IMSI and mobile phone network capabilities (divided into three categories a,b,c); node IP address, including the IP address of the SGSN that originated the call and the IP address of the current GGSN; Packet data Protocol (PDP) information, That is, the network side initiates the PDP context mark (Network initiated PDP context), the PDP's billing identification and the PDP type (X. 25,IP), etc.; Call location, that is, the location of the launch of this call cell code (local area codes), APN information, including APN Network identification, APN operator identification, call time, that is, the launch of the call Date, time and duration, data flow and including uplink data flow, downlink data traffic and corresponding duration of time. The G-CDR record contains fields similar to the S-CDR, but does not contain mobile location information.

--gprs can use time as the standard billing, but also can use the flow as the standard billing, S-CDR and G-CDR both support the two billing methods. Time is the standard billing, that is, according to the user on the Internet as a billing standard, the flow rate as the standard billing, that is, according to the user on the Internet downloaded data volume and the amount of data uploaded as a billing standard. GPRS using packet switching technology, meaning 24h real-time online, users can get the information from the Internet at any time, so the traffic for the billing standard is more in line with the characteristics of GPRS, with the time billing standard obviously limited the user's use of GPRS, GPRS superiority can not be played.

For GPRS, the communication process is described by a PDP context. Taking the mobile phone access to extranet resources as an example, the PDP context must be established before the visit, and many signaling messages are defined around the PDP context, which are used to negotiate the QoS parameters between users and the network, dynamically assign the mobile IP address, select GGSN, distribute the external PDP legal address, Establish a tunnel between SGSN and GGSN. Once the PDP context is activated, data transfer can take place. The core of PDP context is the occupancy of the PDP address; a communication process is assigned from the PDP address, occupy to release, period SGSN may change (mobile phone movement), other parameters may also change (such as QoS, etc.), this through the PDP context update signaling to complete. For a PDP context process, there are s-cdr and g-cdr at the same time, and because the data communication duration is long and the inclusions are complex, the last session of the GPRS Business node (GSN) produces multiple partial records (Partial record), Multiple records that describe a PDP context require an identifier to indicate that they belong to a single session, which is the C-id. C-id is determined in the process of establishing a PDP context between SGSN and GGSN, thus ensuring the association of one session S-CDR with the G-CDR. The combination of GGSN and C-id is unique over a long period of time.

Traffic record is the core problem of GPRS billing. In GPRS, the uplink and downlink flow have asymmetry, so they are charged separately. GPRS supports a variety of QoS contours, its QoS is embodied in 5 aspects, namely, delay, reliability, priority, average throughput and peak throughput, there are some optional levels in each aspect. The description of traffic takes the form of a list, and the amount of data is statistically divided according to each QoS profile. Note that different users, different services for QoS requirements are different, and the wireless environment is time-varying, the network can provide QoS with user use, channel quality factors such as the uncertainty, so a session of the QoS profile will change, each change in the list to add one item.

--The original CDR record is produced in the GSN, but the GSN does not preserve the CDR for a long time, because the amount of CDR produced is too large, so the function of the billing gateway is introduced to store the CDR and preprocess the original CDR. As mentioned earlier, a PDP context corresponds to a plurality of records, and the billing gateway merges the partial records belonging to a session according to GGSN and C-id to form a complete list. The billing gateway also has functions such as single preprocessing, filtering and culling, and will be conveys to billing system after merging.

--third, the future of GPRS billing problems

In the data communication between the mobile phone and the internet, the problem of cost settlement between the mobile communication Enterprise and ICP is likely to be involved in the future. G-CDR is produced by the GGSN single record, can be used as the basis for settlement, and the current GPRS billing is generally based on S-CDR, mainly for mobile phone users charge.

At present, prepaid expense households (such as Shenzhou Line business users) is a very representative business direction, its characteristics are real-time billing. Different systems to implement card services, such as the smart phone network (including mobile intelligent network) prepaid to the sound of seventh signaling, with the information in the signaling system, the current China IP calling card service with RAS and RADIUS protocol messages carry billing information, But GPRS has not stipulated how to carry on the real-time card user billing. In fact, GPRS prepaid service than the telephone prepaid to achieve a much more difficult, which not only technical difficulties, but also billing policy factors, the uncertainty of the QoS also increases the balance of the card based on the amount of data remaining to calculate the difficulty.

--Four, the conclusion

As a transition from second-generation mobile to third-generation mobile communication,--GPRS has taken an important step in mobile internet. As a new business, its billing system is closely combined with the communication Process control. Billing also provides the original data for operators to master network condition and user behavior analysis, and it is the precondition of designing mature billing system to understand the billing characteristics of GPRS.