Research on roaming handoff strategy for 2G operators to build 3G network

December 24, 2003, one of the world's top 500 of the United Arab Emirates Telecom (Emirates Telecommunications Corporation, referred to as Etisalat) officially announced that The WCDMA network from China's Huawei Technology Co., Ltd. was formally put into commercial application, and Huawei, as its exclusive supplier, contracted the National WCDMA Commercial network of the UAE telecom. The cooperation between the two sides will make the UAE telecom become the first in the Middle East and the Arab countries to launch WCDMA commercial services operators, but also the world's first to achieve 2g/3g perfect interoperability of the commercial network. Saleh Al Abdooli, general manager of Etisalat Mobile systems, points out that Huawei's leading wireless technology, tailor-made innovative services and applications, and a deep understanding of the global telecommunications market can help Etisalat bring products and services to market quickly, Establish and maintain a leading edge in the 3G field.

Huawei helped Etisalat deploy the world's first truly GSM, WCDMA coexistence commercial network, which has accumulated a lot of experience for GSM operators to build 3G networks.

To reduce the impact on the GSM network, Etisalat and Huawei decided to implement the "enhanced switching between systems" solution: GSM MSC no need to upgrade, WCDMA MSC enhancements, the implementation of WCDMA to GSM one-way switch. But in the packet network part, in the industry generally thought that the grouping domain system switch is not enough mature, both sides after the thorough discussion, has formulated "according to the coverage implementation bidirectional switching, the bearing rate adaptive adjustment" the plan. This scheme is very effective to solve the problem of "inter-network encryption, temporary link identification number, RRM algorithm", which restricts the success rate of handoff among packet domain systems.

In order to achieve the user in the 3G network can be managed, can be controlled, Etisalat developed a 3G network of access to the user authentication and roaming restrictions, the function is to ensure that the GSM users to upgrade to 3G users can easily access 3G network, but also limited the user does not apply for business in the 3G network roaming, So that operators have a firm grasp of the network "right to use." (Computer science)

Guiding Principles and implementation strategies

Interoperability between systems is introduced because: in the early 3G construction, WCDMA network is difficult to achieve nationwide coverage (but in the WCDMA service area must be a continuous film coverage). In this case, it is necessary to make use of the interoperability functions between systems (refer to switching, roaming) to ensure the continuity and availability of the user's business. When considering the interoperability features between systems, the following guidelines should be followed:

• Try to avoid the upgrade of the current network 2g/2.5g;

• Minimizing the number of transitions between systems;

• Try to allow 3G users to enjoy the 3G network services;

• Use 2G Network to expand 3G coverage to keep the voice business continuity of 3G users.

In view of the continuous coverage of GSM network and the network condition of WCDMA network with limited continuous coverage, in order to reduce the impact on GSM current network, improve the success rate of switching, avoid the ping-pong switch and the cell re-election, reduce the signaling interaction.

Solution and Network Construction operation mode

User migration Policies

Under normal circumstances, GSM users to 3G migration has four kinds of scenarios:

Programme I: Upgrade the current network HLR Way

Scenario Two: A scheme using signaling routing registers (SRR).

Programme III: Use of the Intelligent Network programme or the unconditional forward-turn programme

Plan four: Huawei NLR number carrying plan

Huawei and Etisalat After consultation, think you can choose the following solutions: Upgrade current network HLR, users apply for 3G business, directly increase the 3G contract data, do not need to replace the SIM card, customers do not need to go to the business hall, through the voice telephone IVR way. Roaming restrictions are used to differentiate between ordinary users and 3G users, to prevent "users directly buy 3G mobile phones, do not sign up to enjoy 3G services, the 3G network Impact", so as to ensure that the 3G network can be planned and manageable.

Business migration and upgrade plan

UAE mobile communication penetration rate has been very high, basically saturation, so the introduction of 3G network is the first significance of business enhancements, so that the end of the customer to bring unprecedented business experience.

Etisalat Original Mobile communication network has two brands: GSM, Wasel, respectively corresponding to postpaid, prepaid two kinds of payment methods. After the opening of its 3G network, add a new brand: Mubashir. Mubashir is Arabic English, its meaning is "immersive", that is to emphasize 3G video phone can be face2face communication, very image. Mubashir is also divided into postpaid, prepaid, respectively, by the GSM users, Wasel users upgraded.

Network construction and the implementation of 3G and 2G network coexistence Solutions

The handoff between WCDMA and GSM system is one of the core problems for the existing GSM operator to build 3G network. From the point of view of operators ' operation demand, the paper gives the "Circuit domain: WCDMA to GSM one-way switch, group domain: WCDMA, GSM bidirectional switching, Network Load rate Adaptive adjustment, GSM network need not upgrade" solution. So far, Huawei's system switching solution, has successfully completed with Ericsson, Siemens, Alcatel and other manufacturers of the network between the verification, and formally put into business, the implementation of good results.

The basic points of this solution can be summed up as follows: Switching between the circuit domain system: Implementing the one-way switch of WCDMA to GSM, and WCDMA MSC all the signaling to be fully adapted into the GSM format. From the GSM MSC point of view, the switch "equivalent to" a common GSM switching between the two, so that 3g/2g coordination on the 2G network has the least impact. The "handoff" between the grouped domain systems performs the two-way handoff of WCDMA and GSM. There are two ways to implement this switch: first, through the process of district gravity separation, 3G and 2G respectively configure the necessary neighborhood and gravity separation condition information, and broadcast through the system information; the gravity measurement and the decision process for the specific terminals are not interfered, so this is a kind of terminal decision and initiates the switching "re-election" process The other way is to 3G network according to the measurement report of the terminal to judge, and through the different system District re-election command terminal of the order of gravity action. The two modes of implementation, are for the dual-mode terminal to use the 3G network as far as possible, so that users can more experience the WCDMA broadband hosting network to provide quality services; At the same time, in order to transmit the same number of user data, can also reduce the cost of carrier network occupancy, Because WCDMA is capable of carrying data services much higher than GSM/GPRS network.

3G Network Utilization Maximization and the unification of customer satisfaction degree maximization

Our recommendation is 3G user priority to choose 3G Network, and has been maintained in 3G network. This way can ensure that users registered in the 3G can quickly and directly enjoy the more colorful business functions based on 3G, avoid from GSM to WCDMA unnecessary switching and roaming. At the beginning of 3G construction, the network capacity is not a problem, the 3G user priority Choice 3G Network can maximize the resource utilization of 3G network.

However, in the implementation process, we also found that in accordance with the above principles, the specific problems to be specific analysis. For example, in order to achieve dual-mode users to optimize the purpose of 3G, the ideal approach is as long as the 3G signal to meet the minimum pilot strength requirements, immediately re-election to 3G network, so as to achieve the maximum 3G network requirements. But because of the randomness of the movement of the terminals (people and cars), the mobile phone is not guaranteed to receive the pilot signal that meets the minimum strength requirement. In this case, it is possible that the terminal will rapidly re-gravity the GSM network. With the fading of wireless signal, the possibility of ping-pong re-election between GSM/WCDMA is increased. This not only to be called paging success rate has an impact, if the terminal at this time to initiate a call, there will be a low connection rate, abnormal off the words and so on.

In order to improve the success rate of switching between systems, it is necessary to set up the compression mode of switching between the systems in a specific area to avoid the abnormal drop due to the sudden decline of the signal, according to the different wireless communication environment. Otherwise, in accordance with the usual practice, only when the signal attenuation to a certain absolute threshold to start switching the preparation and execution process, if you encounter a corner or serious occlusion, it is easy to drop words.

To sum up, we emphasize that 3G users priority to enjoy 3G services, as far as possible to improve the utilization of 3G network and provide 3G quality service This guiding principle, in the implementation process and based on practical experience to introduce a certain degree of flexibility to improve the end-user experience, truly achieve customer satisfaction maximization. Because of the complex characteristics of wireless networks, only solution providers with rich practical experience can achieve the unification of maximizing 3G network utilization and maximizing customer satisfaction. Huawei has built the industry's first GSM/WCDMA fully coordinated commercial 3G network, has accumulated a wealth of experience in the business Network practice, will provide Etisalat and other global partners with better services.

Conclusion

The United Arab Emirates Etisalat GSM network equipment is provided by several suppliers, Huawei's 3G equipment needs and different manufacturers of GSM equipment interoperability and functional coordination, Huawei's solutions and equipment capabilities are a test. Through the efforts of Huawei technical experts, in less than two months time, the completion of the network with a number of manufacturers interconnection interoperability, and the actual operation of WCDMA to GSM voice business to switch the success rate to meet or exceed the expected indicators. This fully demonstrates Huawei as the industry's first real and GSM with the WCDMA solution provider, in the field of advanced technology and rich practical experience. This also marks the industry has been discussed but no practical application of the network construction concept of 3G/2G with commercial deployment, 2G operators to build 3G network has accumulated valuable experience.