Research Of Charging Test Technology With Switch System

1. IntroductionThe accuracy of telecommunication charging is a hotspot of customer's complaints recently, and the problems of telecommunication provider's service quality are more concentrated on charging. In order to resolve the hotspot problems such as charging disputations, it is necessary to build quality charging systems. Before 2003, the charging systems used by telecommunication providers were not approved by any third party authority. Since there were no adequate supporting technological measures then, the administration could not provide the customer with any authoratative test report to validate the reliability of charging systems, and the providers had to invest vast labor and material resources to resolve the charging disputations. Therefore, the performance test of charging is an important task to enhance telecommunication administration, is the demand of improving the service quality and competency of providers, is the requirement of realizing faithful business, explicit consumption, and fair competition. The department of information industry launched the pilot project of performance test of telecommunication charging at Beijing in Oct. 2003. Based on the pilot project, other provinces carry out the charging test successively. Referring to the cases of telecommunication network of Jilin province, this thesis carries out further studies on the test approaches of switch systems charging and the analysis systems of message registration of Jilin province.The object of charging test is voice service presently, and the networks pertinent to voice service include PSTN and PLMN. For GSM and CDMA systems of PLMN are similar, this thesis analyze the PLMN based on GSM.2. Test approaches and charging procedure of switch systems(1) Test approaches and charging procedure of PSTNTest approaches include two types: end-to-end test and No. 7 signaling test. For end-to-end test is inaccurate for long time, has low credibility and high limitations, No. 7 signaling test is adopted as the test approach.The telecommunication connection is established by signaling, and the call period is timed by signaling to trigger charging system. Bridging the test device on charging spot with high impedance to acquire signaling data and processing the signaling data, signaling messages with the same OPC, DPC, and CIC can be synthesized as the complete call procedure, so that objective, complete, and tested-system-independent message registration can be obtained. Timing error of No. 7 signaling test is determined by the tested spot and independent of other spots and transmission links. According to presented mode of restoration control, the complete charging message (calling and called number, start time, charging period, etc.) can be acquired. Compared with the message from tested spot, the charging accuracy can be obtained.The start signaling of charging is ANC, and the stop signaling is determined by the restoration control mode. The stop signaling is CLF for calling control mode or overtime after receiving CBK, the former of CBK and CLF for independent control mode, and CBK for called control mode.The charging mode of Jilin province is the independent control mode. The charging spot for long-distance call is the long-distance office, and the charging spot for local call is the local office.(2) Test approaches and charging procedure of PLMNTest approaches include centralized monitor test, call test, and A interface signaling test. For plentiful devices, long test period, and complexity of analysis, the centralized monitor test is inappropriate for charging test.Call test utilizes the terminals as the calling end and called end for timing test. When the calling end calls the called end, the timing starts as soon as the connection is established. The timing stops when the connection is destroyed. Call test is based on the comparison of timing period for the same call between testing and tested devices. Call test is influenced by transmission delay error of establishing and destroying connection, and the network error will conceal the error of tested device.A interface signaling test records the signaling messages by bridging the test device on signaling link of A interface with high impedance. Because the test device acquires signaling close to the tested MSC link, the timing error of test device is determined by processing delay of MSC signaling. In addition, the timing error of start delay, stop delay, and rounding must be considered. If the timing period accuracy of tested device is s digits, the timing period of test device can be as accurate as ms digits. A interface signaling test avoids the influences of other parts of network, that is, the uncertainty of whole network, on the charging accuracy.Based on the above analysis, this thesis proposes that A interface signaling test should be used in charging test of PLMN.PLMN charges the calling end as well as the called end, and the charging spot is located on visiting MSC.For the calling end, charging starts when MSC receives the establishing signal of the called end from A interface (or interface between MSC and GMSC, interface between MSC and long-distance office/ TMSC), or when MSC receives the establishing confirmation signal of the calling end. For the called end, charging starts when MSC receives the establishing signal of the called end from A interface.Because the restoration control mode in PLMN is independent control mode, charging stops when MSC receives destroying signal of any end from A interface.3. Processing of charging test dataBy acquiring signaling data, decoding and analyzing data, statistically processing data based on OPC, DPC, SLC, serial number, etc., the objective, complete, and tested- system-independent message registration is obtained and stored in the database as the contrast message registration of test device. The standard message registration provided by charging center is stored in the corresponding database as the contrast message registration of office. The test report is generated by comparing the contrast message registrations of test device and office according to certain test procedure. By further analysis of test report, the test and analysis approaches appropriate for Jilin province can be determined finally.