GSM 1X Technologies and ZTE´s Gateway Solution

ZXC10-FLR/AUC（Foreign Mode Location Register/Authentication Center）is the first GGG gateway product in the world.

    It connects with the CDMA network according to the IS-41 protocol of No.7 signaling (SS7), and with the GSM network according to SS7 GSM-MAP protocol, supporting SS7 MTP, SCCP and TCAP. This product’s open signaling interface not only follows relevant GSM and CDMA specifications and standards to provide standard interfaces to connect with HLR/AUC, SC and MSC/VLR of both GSM and CDMA, but also provides standard interfaces to PLMN, PSTN, ISDN and PSPDN.

    ZXC10-FLR/AUC adopts advanced technology of Very Large Scale Integration (VLSI). It features open signaling interface, highly reliable database system, flexible networking, large capacity, excellent reliability, strong disaster recovery capability, perfect maintenance and powerful signaling handling capability.

Facing keen competition in telecom markets worldwide, global mobile operators are looking for the best solution that can not only make full use of existing network resources, but also introduce new technologies for new service provision.

    The CDMA network features great capacity, strong anti-jamming functionality, good voice quality and low power consumption of terminals, with which CDMA operators can reduce their investment in equipment and cost of network operation and maintenance. In addition, when transiting to 3G, the CDMA system can implement smooth evolution from IS-95A to CDMA2000 1X and then to CDMA2000 1xEV with low cost.

    According to the statistics from Morgan Stanley, in South Korea, it took only 20% of resources to upgrade CDMA2000 1x to 3G; in Japan, KDDI spent only 75% of the investment that NTT DoCoMo spent in building its WCDMA network to upgrade its network to CDMA2000 1xEV-DO; in the United States, it just cost 8 dollars every point of presence (POP) for Sprint PCS to realize network evolution to CDMA2000 1xEV-DO, while other operators would spend 24 dollars to upgrade their networks to WCDMA. Thus CDMA technologies have been adopted widely, and CDMA2000 has become the optimal technology for mobile operators to build their 3G networks.

    But the GSM networks occurred earlier than CDMA, so the CDMA network covers much less than GSM does. For CDMA network operators, their subscribers’ global roaming is a very pressing problem. They hope that CDMA subscribers could use GSM networks with wider coverage when roaming internationally. For those operators who have both networks of CDMA and GSM, since the CDMA 2000 1X network can provide more data services than GSM, they urgently want to provide special data services of CDMA for GSM subscribers to improve service quality of the GSM network, better satisfy their subscribers and make full use of existing network resources . The GSM 1X technology can make these dreams come true.

1 GSM 1X Technology
The GSM 1X technology developed by Qualcomm combines GSM core network and the wireless access part of the CDMA 1X network.

    The technology supports roaming between networks of GSM and CDMA and helps subscribers use services of the accessed network, and GSM/CDMA handsets with one integrated card or two single- or dual-mode cards. When an operator with both GSM and CDMA networks offers data services for subscribers of both networks through upgrading its CDMA 1X network, with a GSM/CDMA handset and without changing his mobile phone number, the GSM subscriber can share CDMA 1X data services and the CDMA subscriber can enjoy roaming on the GSM network. GSM 1X helps GSM/CDMA operators make full use of the investment in their existing networks, reduce operation cost, improve network competence with differentiated services, and balance the development of two networks.

    Proposed by Qualcomm and Spatial Wireless, the solution called MSN (Mobile Switch Node) converges CDMA wireless access network and GSM-MAP core network. A new network entity is introduced to realize this convergence and the core network needs partial modification to its architecture. The solution enables one-way roaming of GSM subscribers to the CDMA network, however, it cannot support two-way roaming. Therefore, this solution is more suitable for GSM operators to build new CDMA networks.

    In order to implement two-way roaming, ZTE Corporation proposes a GGG gateway solution. A special gateway between the two networks is built up to exchange subscribers’ location messages and implement protocol conversion between MAP messages and IS-41 messages. In this solution, no modification is made to the existing core network. By using a GSM/CDMA handset, on one hand, GSM subscribers can roam to the CDMA network to share CDMA high-rate data and multimedia services when keeping GSM voice services; on the other hand, CDMA subscribers can share the international roaming service and GPRS high-rate data services offered by the GSM network. The GGG gateway solution enables two-way roaming and is suitable for various operators.

2 ZTE’s Gateway Product
Launched by ZTE Corporation, ZXC10-FLR/AUC（Foreign Mode Location Register/Authentication Center）is the first GGG gateway product in the world. With this product, the subscribers can share both GSM and CDMA services without changing their mobile phone numbers. And the real two-way convergence of GSM and CDMA networks has come true.

    ZXC10-FLR/AUC connects with the CDMA network according to the IS-41 protocol of No.7 signaling (SS7), and with the GSM network according to SS7 GSM-MAP protocol, supporting SS7 MTP, SCCP and TCAP. This product’s open signaling interface not only follows relevant GSM and CDMA specifications and standards to provide standard interfaces to connect with HLR/AUC, SC and MSC/VLR of both GSM and CDMA, but also provides standard interfaces to Public Land Mobile Network (PLMN), Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN) and Packet Switched Public Data Network (PSPDN).
ZXC10-FLR/AUC adopts advanced technology of Very Large Scale Integration (VLSI). It features open signaling interface, highly reliable database system, flexible networking, large capacity, excellent reliability, strong disaster recovery capability, perfect maintenance and powerful signaling handling capability.The GGG gateway connects with advanced Signaling Transfer Points (STP) only through signaling, as shown in figure 1.

3 Opportunities Brought by ZTE’s GGG Gateway Product
At present, more than one hundred countries including China and European countries have GSM networks while more than thirty countries including China, the United States and South Korea have built CDMA networks. All the major developed countries have GSM networks. As GSM/CDMA mobile operators, China Unicom, Telstra (Australia), Telefonica (Spain), Huchison (Hong Kong SAR) and Tata (India) are always balancing the development of the two networks and looking for a breakthrough in differentiated operation.

    For GSM/CDMA operators, the GGG Gateway solution is a good evolution solution to the two networks at the same time. On one hand, it helps the GSM network upgrade to realize the services complement of the two networks. On the other hand, it ensures the international roaming of CDMA subscribers, making their dream of roaming in over 100 countries come true.

3.1 Investment Scale
Take Chinese operators as an example. It may cost RMB 140 million to build up a GGG gateway office with the capacity of 1 million subscribers.

3.2 Attraction of Global Roaming
The GGG Gateway can help subscribers enjoy real international roaming.

    For example, most high-end subscribers in China need global roaming services. They take up to 2% of China Mobile’s GSM subscribers, 0.57% of China Unicom’s GSM subscribers and 2.3% of its CDMA subscribers. It is estimated that, by offering the global roaming service, China Unicom could not only strengthen the stability of existing 1 million high-end subscribers, but also attract about 3 million new high-end subscribers from other operators.

    ARPU of these high-end subscribers is about RMB 600 Yuan. If an operator attracts 20% of the users from other operators, his revenue may increase RMB 43.2 billion annually.

3.3 Attraction of Value-Added Services
Besides global roaming, value-added services such as special high-rate data services and gpsOne positioning services offered by the CDMA2000 1X network are also very attractive.

    Comparing with the GPRS’ data transmission rate of 30 kb/s, the CDMA 2000 1X network supports a much higher rate of 70-80 kb/s, which is very useful for high-end subscribers to check emails and browse Websites.

3.4 Subscriber Growth
Let’s take a Chinese operator as an example to analyze the subscriber growth brought by the GGG Gateway.

    (1) Stage 1: Building up Subscriber’s Trust
    After the GSM 1X project finished and relevant services was available, the operator first began to develop subscribers’ confidence in the system. The main method was to offer free terminals to potential users. Experiencing the services, the users had a deep impression on the advantages of international roaming and value-added services. This stage took about 3 months.

    (2) Stage 2: Rapid Growth of Subscribers
    After the first stage, with relevant service promotion and propagation, subscribers began to quickly increase. This stage lasted for about one year. The number of GSM/CDMA dual-mode subscribers rose by 20 000 per month, out of which 37% came from the No.1 mobile operator in China and 63% from the No.2.

    (3) Stage 3: Steady Growth of Subscriber
    GSM/CDMA subscribers tended to growth steadily after 15 months. As time went by, the price of GSM/CDMA terminals decrease continually, so more and more common users could enjoy the service. At this stage, the subscriber growth rate kept 250 000 per month.

4 GGG Gateway Application Cases
The GSM 1X technology brings GSM/CDMA operators a new business model and revenue growth point. The GGG Gateway implements the real convergence of CDMA and GSM networks. The utilization of GSM resources can be greatly improved, and the GSM/CDMA operators will play a more and more important role in the global mobile communication industry.

    The following cases are examples of the commercial applications of ZTE’s GGG Gateway.
    (1) Case 1: China Unicom
    As the No.3 mobile operator in the world, China Unicom has over 100 million mobile subscribers. ZTE was responsible for its GGG Gateway project with the capacity of 3 million subscribers. ZTE’s ZXC10-FLR/AUC passed the trial test and was put into commercial use in August 2004. China Unicom has added a new group of GSM 1X subscribers besides the GSM subscriber group and CDMA group.

    (2) Case 2: VIVO
    VIVO is the largest mobile operator in Brazil with over 17 million mobile subscribers. In the first phase of its GGG Gateway project, ZTE Corporation provided the gateway equipment with a capacity of 50 000 subscribers. Now the project is in test, and expected to be put into commercial use soon.

    (3) Case 3: Indosta
    Indosta is the second largest mobile operator in Indonesia with over 3.4 million mobile subscribers. It has a CDMA network with a capacity of 500 000 subscribers. In the first phase of its GGG Gateway project, ZTE offered the equipment with a capacity of 50 000 subscribers. Now the project is in test, and will be put into commercial use soon.

    (4) Case 4: Delta Telecom
    Delta Telecom is the largest CDMA 450 operator in Russia with 200 000 subscribers. ZTE has agreed to provide it with the gateway equipment with a capacity of 20 000 subscribers. Now the project is in progress, and the system will be put into commercial use before the end of this year.

    Having launched the first commercial GSM 1X product, ZXC10-FLR/AUC, in the world, ZTE will strengthen the cooperation with mobile operators and other manufactures in technology standardization and marketing promotion to bring operators with more benefits.

Manuscript Received 2004-09-14