Hardware/Software VoWiFi SIM Management

Description:
We are looking for experienced hardware and software engineers to design and develop a custom solution for managing physical SIM cards using a hybrid approach.
Project Overview:
We currently use traditional GSM gateways that require continuous connection to cellular towers. We want to develop a better system with the following behavior:
Initial Registration Phase: SIMs must first register on the mobile network through cellular towers (like a normal smartphone).
Main Operation Phase: After successful registration, the SIMs should operate primarily over the internet using VoWiFi (WiFi Calling), receiving SMS and calls via IP without continuous dependence on cell towers.
Key Requirements:
Support for physical SIM cards
Scalable architecture (from dozens to hundreds of SIMs)
Centralized management software / web panel
Ability to switch between cellular registration mode and VoWiFi mode
Modular / rack-mountable hardware preferred (1U or 2U)
Reliable SMS and call reception
We are open to the technical architecture. We want the engineering team to propose the best approach based on their expertise (hardware design, modules, software stack, etc.).
Looking for:
Hardware engineers with experience in cellular modules, embedded systems, and SIM management
Software engineers with experience in VoWiFi / IMS, SIP, and device management platforms
Ideally, candidates or teams who can handle both hardware and software development
Please include:
Relevant experience
Proposed technical approach
Estimated timeline
Budget range

The system should allow SIMs to switch between cellular registration mode and VoWiFi operation mode.
We are open to technical recommendations regarding modules, architecture, and design approach. Looking for engineers with strong experience in embedded systems, cellular modules, and PCB/hardware design.
Please share your portfolio and proposed technical approach.
 ... Show more