Step-by-step transition from a carrier's VoIP to a Softswitch

PSTN has been serving users for decades as a high-quality network that provides voice communication. However, with the rapid development of technology and the increasing demand for diversified services, it will eventually be replaced by the next generation network with Softswitch as the core. The Softswitch Network implements call and service control and voice and data transmission through IP-based transmission protocol, which not only solves the existing problems of PSTN, more importantly, it skillfully combines the exchange network and the data network, and proposes a variety of flexible and rich business provision methods. However, in this evolution process, operators must consider how to protect the interests of PSTN voice service users so that the VoIP service based on Softswitch can be smoothly promoted. Therefore, through the Access Gateway, integrated access devices, and other common POTS terminal access methods, through the relay Gateway provides a way to communicate with the PSTN, is essential. This article focuses on how to gradually transition the operator's VoIP service to the softswitch network.

During the evolution of the PSTN to the softswitch network, the current focus is on how to build a more reasonable network architecture and what special services are provided, however, the ultimate goal of building an advanced network is to provide better services to users. Therefore, in the process of evolution, we should consider from the user's perspective, that is, to provide users with richer services, at the same time, we should try our best to avoid any inconvenience caused to users.

Provides a wide range of softswitch services for PSTN users.

The Softswitch technology is still in an immature stage and is still under discussion in many aspects. Considering the abundant network resources and a large amount of investment, it is impossible for the company to discard all of them and completely replace the softswitch network. Therefore, during the evolution of the PSTN to the softswitch network, the PSTN and the softswitch network will coexist for a long period of time. At this stage, we should consider making full use of the new Softswitch technology to not only provide services for Softswitch users, but also provide richer services for PSTN users, this not only gives full play to the advantages of softswitch, enrich the types of PSTN services, but also makes full use of existing network resources to protect existing investment, thus extending the service period of PSTN. The services that Softswitch can provide for PSTN users include Unified Communication, color calls (call background music), phone message-to-Email, and Internet services.

To achieve this goal, the basic idea is to use the softswitch network as a value-added service platform of the PSTN. The call requests from users who have applied for the softswitch service will be routed to the softswitch network to provide services. There are several possible solutions:

Solution 1: for users who have applied for the softswitch service to re-allocate a number with the characteristics of the softswitch service (such as a special character Crown), the PSTN switch routes it to the softswitch through number analysis, this triggers the business. This solution requires users to change their numbers, which may cause inconvenience to users.

Solution 2: Set the user's Softswitch service attribute ID in the switch or user Attribute Database of the PSTN network. The switch routes the call to the softswitch based on this information. This solution can quickly provide users with rich services without any changes.

Ensure smooth migration of PSTN users

In the process of gradually replacing PSTN with Softswitch, on the one hand, it may be from the operator's point of view that the softswitch replaces the existing switch due to outdated equipment, network optimization, evolution, and other reasons, on the other hand, some PSTN users may need to migrate to the softswitch network due to the attraction of the rich services of SoftSwitch. In this case, the operator should consider how to ensure smooth migration from the PSTN to the softswitch network. Smooth migration has two meanings: the original phone number can still be used without changing and the original contracted business. To ensure that the user number remains unchanged, there are several possible solutions:

Solution 1: Perform unconditional call transfer (CFU) on the switch to which the user belongs. when calling the user, the user must first go from the original switch, then, it is transferred to the user's current Softswitch based on the Business ID. This scheme only displays the new Softswitch number when the user calls it. It is not a permanent solution because the number remains unchanged and occupies the original switch resources.

Solution 2: Introduce the NP (number portability) database, which stores the correspondence between the user numbers of the original PSTN and the user numbers of the existing Softswitch Network, the vswitch or Softswitch obtains the information about the gateway or route by querying the database. This solution can completely keep the user number unchanged, which is a good solution.

There are several possible solutions to ensure the continuity of the user's contracted business:

Solution 1: The operator transfers the smart service data related to the user in the original SCP to the business platform of the existing Softswitch, but this will consume a lot of time and manpower, in addition, data reliability is not guaranteed.

Solution 2: the service is still provided by the original SCP, and the service is still triggered by the original access code. The Softswitch triggers the service by inserting the corresponding access code before the attribute setting, this solution can quickly and effectively provide services.

Currently, Softswitch is under active deployment and will gradually replace the existing PSTN. In this evolution process, users, as the final service objects of telecom networks, should consider more from their perspectives, this ensures that users can maintain their original usage habits as much as possible during network evolution and provide them with more flexible and richer services, so as to improve the service quality of users, enhance the core competitiveness of telecom operators.

1. Introduction to the two major directions and development status of VoIP technology
2. Application of softswitch in emerging carriers