What is USSI USSD simulation service in IMS

USSI: Bringing USSD Functionality to IMS Networks

In the realm of mobile communication, USSI (USSD Simulation Service in IMS) bridges the gap between traditional USSD (Unstructured Supplementary Service Data) functionality and the IP Multimedia Subsystem (IMS) architecture. Here's a detailed technical explanation:

Core Function:

• USSD is a widely used service in GSM and UMTS networks for user interaction with network services through text-based codes. However, IMS networks, primarily designed for data and multimedia communication, lacked a native USSD implementation.
• USSI steps in to simulate USSD functionality within the IMS framework. It allows mobile subscribers using IMS to interact with network services in a similar way they would with traditional USSD.

Technical Challenges:

• Traditional USSD relies on dedicated signaling channels within the circuit-switched domain of GSM/UMTS networks. IMS, on the other hand, operates primarily in the packet-switched domain using protocols like SIP (Session Initiation Protocol).
• This fundamental difference in network architectures posed a challenge for directly implementing USSD in IMS.

USSI Solution:

• USSI overcomes this challenge by simulating the USSD interaction. Here's how it works:
  1. USSD Code Dialing: The user dials a USSD code on their mobile phone.
  2. IMS Network Interception: The IMS core network intercepts the USSD code instead of routing it through traditional signaling channels.
  3. USSD to SIP Conversion: The USSD code is converted into a format compatible with the IMS architecture, often encapsulated within a SIP message.
  4. Network Service Interaction: The SIP message containing the USSD information is sent to a specific network service entity capable of processing the request.
  5. Response Generation: The network service retrieves the requested information or performs the desired action based on the USSD code.
  6. Response Delivery: The response is sent back to the UE through the IMS network, typically formatted as a text message displayed on the user's phone screen.

Benefits of USSI:

• Preserves User Experience: USSI maintains the familiar USSD user experience for subscribers migrating to IMS networks.
• Leverages Existing Infrastructure: Network operators can utilize existing USSD infrastructure and services, minimizing the need for significant network upgrades.
• Cost-Effective Solution: Implementing USSI can be a more cost-effective approach compared to developing entirely new service interfaces for IMS.

Limitations of USSI:

• Potential Performance Overhead: Converting USSD messages and interacting with network services via SIP could introduce some additional processing overhead compared to native USSD implementations.
• Security Considerations: Adapting USSD security mechanisms to the IMS environment might require additional security measures.

Evolution and Future Directions:

• USSI represents a transitional solution for maintaining USSD functionality in the evolving mobile network landscape.
• Future advancements might focus on:
  • Native IMS USSD Solutions: Developing native USSD implementations within the IMS architecture, potentially utilizing SIP-based signaling for a more streamlined approach.
  • Enhanced User Interfaces: Exploring richer user interfaces beyond text-based messages for interacting with network services, possibly leveraging mobile apps or web portals.

Conclusion:

USSI plays a crucial role in ensuring a smooth transition for users accustomed to USSD functionality as they move to IMS-based networks. By simulating USSD interactions within the IMS framework, USSI bridges the gap between traditional and next-generation mobile communication architectures. However, as technology evolves, we might see native IMS USSD solutions or entirely new user interfaces emerge to meet the future needs of mobile subscribers.