SYSTEM #21 · HIGH-CONCURRENCY GSM MODEM POOL & AT-COMMAND CONTROLLER
SIMbox Explorer
Lead System Architect & Engineering Lead: Augustin Olarian
Executive Summary: SIMbox Explorer is a hardware-level telecom fleet controller engineered by Augustin Olarian to govern large arrays of physical GSM modems and SIM banks directly at the serial AT-command layer. Discovering hundreds of COM ports in milliseconds, it maps each modem to its SIM identity, carrier, and signal strength, executes raw PDU encoding with adaptive human-like cadence, resets stalled hardware automatically, and exposes the entire cellular array as a clean REST API.
Port Discovery SpeedMilliseconds Across 100+ Modems
Protocol LayerDirect Serial AT-Command & Binary PDU
Hardware ResilienceAuto Modem Reset + Instant SIM Failover
Integration InterfaceSovereign REST API & Webhooks
System Architecture & Core Engineering Innovations
- Millisecond Parallel Serial COM Port Discovery: Scans and initializes dozens or hundreds of physical USB/serial modem channels simultaneously, reading IMSI, ICCID, carrier registration, and RSSI signal metrics.
- Raw PDU Encoding & Adaptive Human-Like Routing: Encodes multipart UCS-2/GSM-7 payloads directly in binary PDU format and distributes outbound traffic across the SIM pool with adaptive pacing and instant port failover.
- Real-Time Inbound Capture & Automated USSD Management: Streams incoming SMS replies and delivery receipts in real time while executing scheduled USSD balance and carrier status checks.
- Autonomous Modem Watchdog & REST API Gateway: Detects stalled AT state machines, triggers hardware/AT resets automatically, and provides a high-availability REST webhook interface for enterprise systems.
Technology Stack & Infrastructure
Production Scope Note: The complete production system is significantly larger and encompasses additional operational subsystems; the video walkthrough and this case study highlight selected core architectural innovations.
Technical Architecture FAQ
Why operate GSM modems at the raw binary PDU and AT-command level?
High-level wrapper libraries frequently lock up under multi-port concurrency and mishandle multipart Unicode encoding or delivery receipts. Driving the serial ports directly via asynchronous AT state machines and raw PDU frames guarantees maximum throughput and instant fault recovery.
What happens if a SIM card runs out of credit or a modem drops carrier signal?
SIMbox Explorer continuously monitors signal strength and USSD balances, rerouting queued messages to healthy ports in milliseconds and resetting stalled modems automatically.