9.1 WCDMA CS Domain Billing Principles

9.1.1  WCDMA CS Domain Billing Architecture

The billing system of WCDMA system CS domain is consistent with that of GSM system, that is, the billing data are both generated by MSC/MSC Server and directly transported to billing center. Therefore, in view of the architecture, the billing system of CS domain consists of billing module of MSC/MSC Server and billing center. Between the billing module and billing center, bill data are transported with FTP/FTAM file transporting protocol.
Because no specific interface parameter is prescribed for MSC/MSC Server billing module in the protocol, the interface between MSC/MSC Server host system and billing module is an internal interface, and the implementation of the billing module is also diversified. 

MSC/MSC Server billing system mainly consists of host modules and Bill Administration Unit (BAU). Figure 9-1 shows the CS domain billing architecture.
Host system: The bill information is generated from the host system, and firstly buffered in the bill pool of host. The original bills in the bill pool are, in the form of packet, continuously transported to BAU with TCP/IP.
Bill Administration Unit (BAU): BAU, the processing core of MSC/MSC Server billing system, is a dual-system hot backup system. Connected to the host through local area network (LAN) and to billing center through wide area network (WAN), BAU provides FTP/FTAM interface for billing center to support Server/Client in FTP and Responder in FTAM, to transport bills to billing center.
BAU functions: After saving the original bills received from the host system, it carries out sorting and format conversion for the original bills to generate the final bill. BAU saves the final bill and transports it to billing center. Specifically:
l   Saving original bills: After receiving the bill packets from the host, unpacking and validating the packets, BAU saves the received original bills in hard disk, then sends confirmation message to the host and makes the corresponding log record, and finally carries out sorting and format conversion for the original bills.
l   Sorting bills: It means classifying bills according to a domain, to process them in different flows and save them in different physical paths. All data domains in bills can be used as the criterion for sorting.
l   Bill format conversion: The format conversion on BAU involves choosing bill domain, changing the two-digit chronology into four-digit chronology, and converting into specified text format.
l   Saving final bill: After sorting and format conversion on the original bills, BAU saves the final bills in different directories according to their classification.
Billing center: Collecting and processing final CDRs, and generating final subscriber bills based on tariffs.

9.1.2  Billing Data Generated by MSC/MSC Server

1. Bill type

MSC/MSC Server can be used as VMSC, TMSC, GMSC and SSP. Different calls may have different bill types. The major bill types are as follows:
l   Mobile calling bill: A bill generated when a local mobile subscriber initiates a call.
l   Mobile called bill: A bill generated when a local mobile subscriber is called.
l   Roaming bill: A bill generated when a subscriber of another office calls a local subscriber.
l   Gateway office outgoing bill: A bill generated when a local subscriber calls a subscriber of another network.
l   Tandem bill: A bill generated when the caller and called are not local subscribers and this office is a TMSC.
l   Substituting bill: When a non-prepaid subscriber calls prepaid subscriber and it is an OVERLAY networking, SSP will replace the originating MSC to generate this bill to charge the non-prepaid calling subscriber.
l   Forwarding bill: A bill generated when a local subscriber is called and the call is forwarded.
l   Call attempt bill: A bill generated when a call is not successful.
l   SM bill: A bill generated when an SM is originated/terminated.
l   Special service bill: A bill generated when special service call or special service emergency call is involved.

2. Bill format

The bill format that MSC/MSC SERVER BAU provides for billing center complies with Mobile Phone Billing Standard Pre-processing Bill Format. BAU can provide billing center with bills in binary or text format as required.
A bill mainly consists of the following information:
l   WCDMA/GSM/PLMN resource utilization (such as MSC number and incoming/outgoing trunk group number)
l   Basic service utilization (in accordance with source, destination, call date, call time, call duration, and bearer service)
l   Supplementary services utilization (such as call forwarding)

l   Subscriber related numbers (such as MSISDN, IMSI and MSRN)

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