Prepaid System

The above sections focus on customers who use monthly services who make payments at the end of each month. After the first prepaid mobile service plan that was introduced in 1995, this service has grown rapidly, and now more than 250 wireless providers in more than 100 nations provide prepaid services. More than 600 million users use prepaid services, which is 60% of the total mobile phone users in the entire world. The percentage even exceeds 90% in some of the European nations. The so-called “prepaid” basically means a user pays a certain amount of money for the service when applying for it. Prepaid services have many advantages for the service providers:

n Prepaid services help reduce cost and increase the number of clients quickly.

n Payments are already fully made by the customers, eliminating bad debts.

n Eliminates the cost of printing and mailing bills.

n Eliminates the bad debts caused by illegal copies of SIM cards.

n Expands the potential pool of customers, including business travelers, corporations, or clients whose services were terminated due to bad credits. This also allows phone rental services.

To the customers, since they have paid for a certain length of duration for their services, they can effectively manage the amount of usage. For example, this helps parents to restrict their children’s cell phone bills. Moreover, since a receiver of a call does not need to pay for the call in Taiwan, clients who have low call volumes can save money on monthly service fees.

The prepaid system basically includes three actual types: the Billing System, the Intelligent Network, and Smart Card models. Since the most widely used system is the Intelligent Network system, we will describe its framework in Fig. A.12.

In this figure, HLR identifies whether a client is indeed a user of prepaid services since

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prepaid clients often have special fields such as Service Key, DP2 trigger, and SCP address in their HLR. Moreover, SCP is used to store customers’ basic information such as the phone number of a prepaid service, its expiry date, applicable billing plans, suitable languages, and account balance. When a prepaid user makes a call, since HLR/VLR contains DP2 trigger, MSC/SSP will look for the corresponding SCP based on the SCP address in order to inquire into the customer’s remaining balance. If the balance is insufficient, SCP will prompt the IP (Intelligent Peripheral) to send a signal of “not enough balance” back to MSC/SSP, and MSC/SSP will playback a voice recording in the IP for the client. If there is enough balance remaining, SCP will convert it into the usable minutes based on the client’s billing rate and notify MSC/SSP to let the call go through. During the call, MSC/SSP must constantly monitor to see whether the duration of the call exceeds the allowed time. When it does, IP will be activated to ask the client whether he/she wishes to add in more money or terminate the call.

When the call is ended, MSC/SSP must let SCP know the client’s remaining minutes so SCP can update the information on the remaining time. As for the source of customer information in HLR and SCP (please refer to Section A.2.2), the configuration is done by a service provider’s Service Order Provisioning after a client has applied for the prepaid service.

Fig. A.12: Framework of intelligent network prepaid system

Prepaid system’s Voucher System is used to allow a user to add in more money. The user can go to the service window of the service provider or a convenience store to buy more

“tokens” and use the code number provided by the service provider (Chunghwa’s code is 928, for example) to add in the tokens.

A.6 Summary

A good CCBS must be constantly updated, and the only thing that remains unchanged is

“continued changes.” The activation and operation of a system is not the end but rather the beginning, and workers in this field must realize that the relevant functions and technologies must continue to be improved in order to satisfy their customers’ demands. This is especially true for the integration of a large information system since it is extremely complicated.

Without proper planning, appropriate tools, actual implementations, and careful collaborations, it would not be done within a limited amount of time. This is what software engineering is constantly working on.

Although information technologies can be acquired at schools, the key to successfully developing CCBS is “domain knowledge” – especially for telecommunication services that have a very long history. Therefore, the companies of many well-known brands of this type of software in the market mostly started as telecom operators or their long-term partners. In this era of knowledge-based economy, domain knowledge has become the most cherished and valuable asset.

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Reference

[1] 3GPP. 3^rd Generation Partnership Project; Technical Specification Group Core Network;

Signalling flows for the IP multimedia call control based on SIP and SDP; Stage 3. version 5.15.0(2006-10). 3GPP TS 24.228, 2006.

[2] 3rd Generation Partnership Project, Technical Specification Group Services and System Aspects. Telecommunication Management, Charging and Billing, 3G call and event data for the Packet Switched (PS) domain. Technical Report 3GPP TS 32.015, version 3.9.0, 3GPP, Mar. 2002.

[3] Anderson, M. M. Financial Service Markup Language (FSML) Version 1.17.1. Technical Report Financial Services Technology Consortium, October 1998.

[4] Andreasen, F. and Foster, B. Media Gateway Control Protocol (MGCP) Version 1.0 IETF RFC3435, 2003.

[5] Arteta, A. Prepaid Billing Technologies - Which One is for you? Billing World, pages 54–61, Feb. 1998.

[6] Asokan, N., Janson, P. A., Steiner, M., and Waidner, M. The State of the Art in Electronic Payment Systems. IEEE Computer, 30(9):28-35, September 1997.

[7] Barreto, P., Kim, H., Bynn, B., and Scott, M. Efficient Algorithms for Pairing-Based Cryptosystems. Proceedings of 22nd Annual International Cryptology Conference Santa Barbara, 2442:354-368, Springer-Verlag 2002.

[8] Barreto, P. S. L. M., Ben, L., and Michael, S. Efficient Implementation of Pairing-Based Cryptosystems. Journal of Cryptology, 17(4):321-334, 2004.

[9] Bellare, M., Garay, J., Hauser, R., Herzberg, A., Krawczyk, H., Steiner, M., Tsudik, G., Herreweghen, E., and Waidner, M. Design, Implementation and Deployment of a Secure Account-Based Electronic Payment System. IEEE Journal on Selected Areas in Communications, 18:611-627, April 2000.

[10] Boly, J. P., Bosselaers, A., Cramer, R., Michelsen, R., Mjolsnes, S. F., Muller, F., Pedersen, T. P., P_tzmann, B., Rooij, P. de, Schoenmakers, B., Schunter, M., Vallee, L., and Waidner, M. The ESPRIT Project CAFE-High Security Digital Payment Systems.

Proceedings of ESORICS, pages 217-230, 1994.

[11] Boneh, D. and Franklin, M. Identity-Based Encryption from Weil Pairing. Proceedings

of Crypto 2001, 2139:213-229, 2001.

[12] Cai, Y. et.al. Authorization mechanisms for mobile commerce implementations in enhanced prepaid solutions. Bell Labs Technical Journal, 8(4):121–131, Feb. 2004.

[13] Camenisch, J., Maurer, U., and Stadler, M. Digital Payment Systems with Passive Anonymity-Revoking Trustees. Proceedings of ESORICS, pages 33-43, 1996.

[14] CCITT. Numbering Plan for the ISDN Era. Technical Report Recommendation E. 164 (COM II-45-E), ITU-T, 1991.

[15] Chang, M.-F., Lin, Y.-B., and Pang, A.-C. vGPRS: A Mechanism for Voice over GPRS.

ACM Wireless Networks, 2001.

[16] Chang, M.-F., Lin, Y.-B. and Yang, W.-Z. Performance of Hot Billing Mobile Prepaid Service. Computer Networks Journal, 36(2):269–290, Jul. 2001.

[17] Chang, M.-F., Yang, W.-Z. and Lin, Y.-B. Performance of Service-Node Based Mobile Prepaid Service. IEEE Transactions on Vehicular Technology, 51(3):597–612, May 2002.

[18] Chen R.-J. Hwu, J.-S. and Y.-B. Lin. An identity-based cryptosystem for end-to-end mobile security. IEEE Transactions on Wireless Communications, 2006. Accepted for publication.

[19] Daemen, J., Borg, S., and Rijmen, V. The Design of Rijndael: AES - The Advanced Encryption Standard. Springer-Verlag, 2002.

[20] Davies, W. Moving Wireless Office. Taiwan Telecommunication Magazine, pages 93–97, Dec. 2001.

[21] Davies, W. Who’s Ready for GPRS. Telecommunications, Feb. 2002.

[22] D.L. Lu. presented in Chunghwa Telecom Co., Ltd. Apr. 2002.

[23] Fancher, C. H. In Your Pocket: Smartcards. IEEE Spectrum, 34:47-53, February 1997.

[24] Ferreira, L. and Dahab, R. A Scheme for Analyzing Electronic Payment Systems.

Proceedings of ACSAC, pages 137-146, 1998.

[25] Grimaldi, R. Discrete and Combinational Mathematics, Fifth Edition. Addison-Wesley, 1999.

[26] Heikki, K., Ari, A., Lauri, L., Siamak, N., and Valtteri, N. UMTS Networks-Architecture, Mobility & Services. John Wiley & Sons, Inc., 2002.

[27] Herzberg, A. and Yochai, H. Mini-Pay: Charging Per Click on the Web. Proceedings of

94

the Sixth International World Wide Web Conference, Santa Clara, California, pages 301-307, April 1997.

[28] Hess, F. E_cient Identity Based Signature Schemes Based on Pairings. Proceeding of Selected Areas in Cryptography: 9th Annual International Workshop, 2595:310-324, August 2002.

[29] IEEE. IEEE Std 802.11-1997 Information Technology-Telecommunications and Information Exchange between Systems-Local and Metropolitan Area Networks-Specific Requirements-Part 11: Wireless Lan Medium Access Control (MAC) and Physical Layer (PHY) Specifications. Technical Report IEEE Std 802.11-1997, 1997.

[30] IEEE. IEEE Standard for Local and Metropolitan Area Networks-Part 16: Air Interface for Fixed Broadband Wireless Access Systems. Technical Report IEEE Std 802.16-2004, 2004.

[31] INFOCOMM. Intelligent Prepaid System (IPS) Functional Description. Technical Report PDIPS-00-00001-FD, INFOCOMM, 1998.

[32] ITU. Packet-based Multimedial Communications Systems. Technical Report ITU-T H.323, Version 5, International Telecommunication Union, 2003.

[33] Jonsson, J. and Kaliski, B. Public-Key Cryptography Standards (PKCS) #1: RSA Cryptography Specifications Version 2.1. Technical Report RFC 3447, 2003.

[34] Lai, Y.-C., Lin, P., and Huang, Y.-T. Design and Implementation of a Wireless Internet Remote Access Platform. Journal of Wireless Communications and Mobile Computing, 6(4):413-429, January 2006.

[35] Lee, Z.-Y., Yu, H.-C., and Ku, P.-J. An Analysis and Comparison of Di_erent Types of Electronic Payment Systems. Proceedings of Portland International Conference on Management of Engineering and Technology, 2001. PICMET'01, 2:38-45, 2001.

[36] Lin, P. et.al. Credit Allocation for UMTS Prepaid Service. Accepted and to appear in IEEE Trans. on Veh. Technol.

[37] Lin, Y.-B. Introduction to Telephony. Vekeg, 1997.

[38] Lin, Y-B. Telephone Network and PBX Software. Wei-Keg, 1999.

[39] Lin, Y.-B. and Chlamtac, I. Wireless and Mobile Network Architectures. John Wiley &

Sons, Inc., 2001.

[40] Liu, C.-H. et. al. CAMEL Evolution and PPS Evaluation. IEEE intelligent network workshop, pages 9–13, May 2001.

[41] Low, S., and Maxemchuk, N. Anonymous Credit Cards. Proceedings of 2nd ACM Conference on Computer and Communications Security, pages 108-117, 1994.

[42] Mastercard and Visa. SET Secure Electronic Transactions Protocol, version 1.0 edition, Book One: Business Speci_cations, Book Two: Technical Speci_cation, Book Three: Formal Protocol Definition. May 1997.

[43] Medvinsky, F. and Neuman, B. NetCash: A Design for Practical Electronic Currency on the Internet. Proceedings of the First ACM Conference on Computer and Communications Security, pages 102-106, 1993.

[44] Menezes, A., Oorschot, P. V., and Vanstone, S. Handbook of Applied Cryptography;

[Online] Available: http://citeseer.ist.psu.edu/428600.html, 1999.

[45] Rao, H.C.-H., Lin, Y.-B., and Chou, S.-L. iGSM: VoIP Service for Mobil Networks.

IEEE Communications Magazine, 4(38):62-69, 2000.

[46] Rivest, R. L. and Shamir, A. PayWord and MicroMint: Two Simple Micropayment Schemes. IEEE Transactions on Vehicular Technology, 52(1):132-141, 2003.

[47] Shamir, A. Identity-Based Cryptosystems and Signature Schemes. Proceedings of CRYPTO 84 on Advances in cryptology, pages 47-53, 1985.

[48] Skype. http://www.skkype.com, 2007.

[49] Smith, C. and Collins, D. 3G Wireless Networks. McGraw-Hill, 2002.

[50] Stallings, W. Cryptography and Network Security: Principles and Practice, Second Edition. Prentice-Hall, 1999.

[51] Tracey, L. V. Prepaid Calling: Market Update. Telecommunications, Apr. 1999.

[52] Vriendt, J. D. et.al. Mobile Network Evolution: A Revolution on the Move. IEEE Communications Magazine, pages 104–111, Apr. 2002.

[53] Wang, H. and Guo, H. Fair Payment Protocols for E-Commerce. Proceedings of the 22th Annual Symposium on Principles of Distributed Computing, pages 227-245, 2004.

[54] Yang, Z., Lang, W., and Tan, Y. A New Fair Micropayment System Based on Hash Chain. Proceedings of IEEE International Conference on e-Technology, e-Commerce and e-Service. EEE'04, pages 139-145, 2004.

[55] Yen, S.-M. PayFair: A Prepaid Internet Micropayment Scheme Ensuring Customer Fairness. Proceedings of IEE Computers and Digital Techniques, 148(6):207-213, November 2001.

96

[56] Y. Zhang and Y. Fang. ARSA: an attack-resilient security architecture for multi-hop wireless mesh networks. IEEE Journal on Selected Areas in Communications, 2006. Accepted for publication.

[57] Y. Zhang and Y. Fang. A secure authentication and billing architecture for wireless mesh networks. ACM Wireless Networks, 2006. Accepted for publication.

[58] Y. Zhang, W. Liu, W. Lou, and Y. Fang. Anonymous handshakes in mobile ad hoc networks. IEEE Transactions on Wireless Communications, 2006. Accepted for publication.

[59] Y. Zhang, W. Liu, W. Lou, and Y. Fang. Location-based security mechanisms in wireless sensor networks. IEEE Journal on Selected Areas in Communications, 24(2):247-260, February 2006.

[60] Y. Zhang, W. Liu, W. Lou, and Y. Fang. Securing mobile ad hoc networks with certificateless public keys. IEEE Transactions on Dependable and Secure Computing, Accepted for publication.

Curriculum Vitae

Lu, Fang-Sun was born in Taipei, Taiwan, R.O.C., in 1960. He received the B.S. degree in applied mathematics, the M.S. degree in mathematics from Fu-Jen University in 1983 and 1985, respectively. He is currently a PhD candidate in the Department of Computer Science and Information Engineering at National Chiao Tong University. Since 1985, he has been with the Customer Service Systems Laboratory of Telecommunication Laboratories, Chunghwa Telcom Co., Ltd, where he is currently a Distinguished Researcher and a project manager. His research interests include design and analysis of personal communications services network, development of telecommunication operation support systems, and performance modeling.

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Publication List

l Journal Publications

1. Wei-Zu Yang, Fang-Sun Lu*, Ming-Feng Chang. “Performance Modeling of an Integrated Mobile Prepaid Services.” IEEE Transaction on Vehicular Technology, 56(2):899-906, 2007.

2. Phone Lin, Hong-Yueh Chen, Yuguang Fang, Jeu-Yih Jeng, Fang-Sun Lu*, “A Secure Mobile Electronic Payment Architecture Platform for Wireless Mobile Networks.”

accepted and to appear in IEEE Transaction on Wireless Communications.

l Conference Papers

1. Wei-Zu Yang, Fang-Sun Lu*, Ming-Feng Chang. “Performance Modeling of an Integrated Mobile Prepaid Services.” The 10^th Mobile Computing Workshop, pp.128-133, March, 2004.

l Book

1. 鄭枸澺, 呂芳森*, “第十三章 電信客戶服務與帳務系統 (Customer Care & Billing

System for Telecommunication).” 個人通訊服務網路. 教育部顧問室「通訊科技人才培

育先導型計畫」 維科圖書有限公司 2006 l In Preparation

1. Meng-Fang Chang, Fang-Sun Lu* and Chung-Yung Chia , " A Callback Mechanism for Private Telecommunications Network."