WCDMA access technology development

Currently, the WCDMA access technology is very mature, but there are also many problems. Here we mainly introduce the GSM user upgrade and ARD signing, this section describes speech service switching, WCDMA/GSM services, and load control. It is of great significance to achieve coordinated development of WCDMA/GSM and integration strategies, and to make full use of GSM network resources to achieve rapid network construction of WCDMA access technology. In the coordinated development of WCDMA/GSM systems, we can adhere to the one-network principle to achieve balanced user transition and smooth network evolution.

For a long period of time, the WCDMA access technology and the GSM network need to implement coverage extension and load balancing between networks through interoperability to provide seamless coverage for users. The following principles must be followed for inter-system interoperability: to minimize the upgrade of existing GSM/GPRS networks; to minimize the number of inter-system switching; to enable users of the WCDMA access technology to enjoy the services of the WCDMA network; use the GSM/GPRS network to expand the coverage of WCDMA access technology and maintain the business continuity of WCMDA users.

1. GSM user upgrade and ARD signing

There are two methods to distinguish GSM and WCDMA users: Identification and signing by number segments. The identification based on the number segment has little impact on the GSM network, but the original GSM users cannot carry the number as WCDMA users, which is not conducive to business and market development. The WCDMA/GSM User Access Control ID (AccessRestrictionData) is a new HLR signing data field defined by 3GPPR6. It can be used to distinguish WCDMA/GSM users and facilitate the coexistence of WCDMA/GSM networks, service is differentiated for different types of users to enable the transfer of GSM user numbers to WCDMA users. The GSM core network does not need to identify this identifier. The WCDMA core network can identify GSM/WCDMA users based on the mark. Requests for registering a two-mode terminal (without the ARD sign) that has not signed the WCDMA service will be rejected.

2. Terminal resident Policy

For users of WCDMA access technology, the priority of staying in the WCDMA network allows users of WCDMA to fully enjoy new WCDMA services, especially services not provided by GSM, such as videophone, HSPA, and concurrent services. In addition, the network capacity is low at the initial stage of the establishment of the WCDMA access technology. The user selects the WCDMA access technology network method to reduce the capacity pressure of the GSM network. The GSM network can be preferentially deployed to make full use of existing GSM network resources. Judging from the current construction of global WCDMA commercial and experimental networks, most of them choose the priority to stay in WCDMA.

In terms of the implementation scheme, there are two methods to preferentially reside in the WCDMA network: PLMN reselection and cell reselection. Judging from the current industry situation, the reselect solution of the residential area is the first choice of mainstream operators in the industry. The return time from GSM to WCDMA is fast and the user experience is good, the PLMN solution is suitable for carriers with many difficulties in changing the GSM current network.

3. voice service switching

Inter-system speech service switching includes switching from WCDMA to GSM voice and switching from GSM to WCDMA voice. In terms of demand, in the early stage of WCDMA network construction, the coverage of WCDMA needs to be expanded using the GSM network in areas not covered by WCDMA, and the switch from WCDMA access technology to GSM must be supported. When a WCDMA user initiates a voice service on the GSM network and enters the WCDMA coverage area, due to the excellent GSM coverage and voice quality, there is basically no need to switch the voice of the GSM network to the WCDMA access technology, after the speech service is completed, the WCDMA access technology users can re-select the target community and re-reside in the WCDMA access technology network.

In terms of user experience, the relatively low success rate between GSM and WCDMA voice switching (especially between different manufacturers) will inevitably bring about poor QoS, such as dropped calls, and increase user complaints. In the current situation of excellent GSM coverage and voice quality, there is no need to implement GSM-to-WCDMA voice switching. Therefore, to reduce the impact on the current GSM network and enhance user experience, the voice service can only support one-way switching from WCDMA to GSM to meet the voice business continuity requirements.

4. reselect Data Services

Inter-System Data Service re-selection includes two aspects: WCDMA access technology to GPRS data service reselection and GPRS to WCDMA access technology data service reselection. In terms of requirements and user experience, for grouped data services, when WCDMA is not covered, you should consider re-selecting the residential area into the GPRS network. On the other hand, the data service capability of WCDMA is much higher than that of GPRS networks (especially after the introduction of HSDPA). In order for WCDMA users to experience the high-quality services provided by the WCDMA broadband bearer network, it is also necessary to support reselection from GPRS to WCDMA. Therefore, to improve the experience of WCDMA users, group businesses are reselected in two-way.

5. WCDMA/GSM business and load control

In the middle and late stages of WCDMA operation, it is necessary to implement traffic guidance and balance between systems through service and load control between WCDMA and GSM. The main business and load control policies include:
1) Load-Based Switching: when the Community load of a network increases to meet the load control conditions, load control is enabled, and services are switched from one network to another. Load-Based Switching includes switching from WCDMA to GSM and from GSM to WCDMA.
2) Direct retry: When the cell load of a network increases to meet the conditions for direct retry, new incoming calls, the wireless network controller can start the directedretry process to directly retry the call to another network when receiving the specified message. Direct retry includes direct retry from WCDMA to GSM and direct retry From GSM to WCDMA.
3) Service-Based Switching: enables specific services to be carried in a specific network to give full play to the respective advantages of the WCDMA access technology network and the GSM network. For example, the WCDMA access technology mainly carries data, GSM mainly carries voice and so on.
4) QoS-based switching: implements QoS-based service quality switching (such as BLER, downlink power, and terminal uplink transmission power) to improve user experience.