Case Study: Inter-Protocol Transcoder

Overview

A UK-based telecommunications company offering integrated mobile and unified communications faced significant challenges with VoIP call features due to architectural constraints. Users were unable to access essential functionalities such as call transfer or real-time presence information (BLF - Busy Lamp Field). To address this, an innovative Inter-Protocol Transcoder (IPT) solution was developed using open-source technologies, bridging the gap and enhancing communication for subscribers.

Background

The existing architecture relied on proprietary backend systems that were only partially compatible with standard SIP protocols. This limitation restricted access to key telephony features, leading to frustration among end users who expected more from their VoIP service.

Challenges

The main challenge was integrating standard SIP-based call features and presence information into a proprietary PBX environment. The architecture's constraints prevented direct access to call transfer and BLF functionality, creating a mismatch between user expectations and system capabilities. A real-time translation mechanism was required to maintain call quality and feature integrity while ensuring cross-protocol compatibility.

Solution

The IPT system was developed as a middleware layer between client devices and the PBX, enabling seamless interoperability. It delivered two core capabilities:

• SIP Call Feature Integration: Advanced SIP call functionalities, including call transfer and conferencing, were converted into a format compatible with the proprietary protocol, ensuring smooth interoperability.
• Real-Time Presence Synchronisation: BLF presence information from SIP devices was integrated with the PBX and backend systems, providing real-time visibility of call states.

This approach allowed users to access standard VoIP features without requiring changes to the existing infrastructure, significantly improving usability and satisfaction.

Technology Stack

IPT utilised an open-source technology stack to ensure efficient protocol conversions with minimal impact on call latency:

• Kamailio: Served as the SIP server, routing and manipulating call control messages in real time.
• FreeSWITCH: Handled media streams, supporting various codecs essential for voice transmission.
• Lua: Embedded within FreeSWITCH and Kamailio for custom logic scripting and dynamic call flow.
• Node.js: Facilitated rapid data processing at the middleware layer, minimising latency.

Results & Benefits

The implementation of IPT introduced critical SIP-native functionalities that were previously unavailable:

• Call Transfer Functionality: Native SIP call transfer capabilities reduced support tickets related to call control issues by 22%, easing operational demands.
• Presence Information (BLF): Full access to presence information led to a 15% reduction in complaints about call disruptions, enhancing user interactions.
• High Reliability: The system achieved a 99.99% success rate for SIP call feature usage, ensuring consistent performance and minimising disruptions.

Impact

The introduction of IPT delivered measurable improvements across the organisation:

• Enhanced User Experience: Subscribers gained access to previously unavailable features, increasing satisfaction and reducing frustration.
• Operational Efficiency: Fewer support tickets and complaints allowed the support team to allocate resources more effectively.
• Future-Ready Infrastructure: The solution positioned our client to adapt to evolving communication technologies and user expectations.
• Competitive Advantage: By resolving long-standing limitations, the company strengthened its reputation for reliability and innovation in the telecommunications sector.

Conclusion

The IPT solution transformed the VoIP infrastructure by introducing essential core functionalities and improving overall user satisfaction. By overcoming architectural limitations, the telecommunications company is now better equipped to meet evolving communication needs and deliver a more reliable, user-friendly telephony service.

* The testimonials on this page are paraphrased and based on client feedback. Names, roles, and identifying details have been removed to protect confidentiality.