Communication Subsystem decomposition — V2X, telemetry, OTA, and network security

System

Autonomous Vehicle decomposition, session 167. Five of six subsystems now have full component-level decomposition in the entity graph: {{entity:Perception Subsystem}}, {{entity:Localization and Mapping Subsystem}}, {{entity:Vehicle Control Subsystem}}, {{entity:Safety and Monitoring Subsystem}}, and now {{entity:Communication Subsystem}}. The {{entity:Planning and Decision Subsystem}} remains — it has interface requirements and a diagram placeholder from prior sessions but no classified components in the SE namespace. The project stands at 107 requirements across all six documents with 101 trace links.

Decomposition

The {{entity:Communication Subsystem}} ({{hex:51F57319}}) was decomposed into five components, each classified in the SE:autonomous-vehicle namespace:

  • {{entity:V2X Communication Module}} ({{hex:D4F47219}}) — dual-mode DSRC/C-V2X radio handling BSM, SPaT, MAP, and TIM messages
  • {{entity:Telemetry and Fleet Gateway}} ({{hex:50E55219}}) — 4G/5G cellular uplink for fleet telemetry and remote commands
  • {{entity:OTA Update Manager}} ({{hex:41B77B18}}) — secure download, A/B partition deployment, and rollback for software updates
  • {{entity:In-Vehicle Network Router}} ({{hex:D4B57218}}) — central Ethernet/TSN backbone with VLAN isolation and QoS shaping
  • {{entity:Communication Security Manager}} ({{hex:40B57979}}) — PKI, HSM-backed key storage, and message authentication across all channels

The architecture places the {{entity:In-Vehicle Network Router}} as the central hub, routing traffic to the three external-facing modules. All external communication flows through the {{entity:Communication Security Manager}} for signing, encryption, or verification before leaving the vehicle.

flowchart TB
    NR["In-Vehicle Network Router"]
    V2X["V2X Communication Module"]
    TG["Telemetry and Fleet Gateway"]
    OTA["OTA Update Manager"]
    CSM["Communication Security Manager"]

    NR -->|V2X protocol frames| V2X
    NR -->|Telemetry data| TG
    NR -->|Update packages| OTA
    V2X -->|Message signing requests| CSM
    TG -->|TLS session management| CSM
    OTA -->|Payload verification| CSM

Analysis

The {{trait:Physical Object}} trait split is notable in this subsystem. The {{entity:V2X Communication Module}} and {{entity:In-Vehicle Network Router}} both classify as physical objects — they are discrete hardware with RF front-ends and Ethernet switch fabric respectively. The {{entity:Communication Security Manager}} classifies as abstract ({{hex:40B57979}}), reflecting its nature as a software service wrapping an HSM. The {{entity:OTA Update Manager}} ({{hex:41B77B18}}) also classifies abstract despite depending on flash storage — its identity is the update orchestration logic, not the storage medium.

Cross-domain similarity search on the {{entity:In-Vehicle Network Router}} returned 90.6% Jaccard with both integrated circuit and {{entity:V2X Communication Module}}. The high self-similarity within the subsystem confirms these components share a dense trait cluster around {{trait:Synthetic}}, {{trait:Powered}}, {{trait:Processes Signals/Logic}}, and {{trait:System-integrated}}. The Radio Modem entity at 87.5% from prior classification work reinforces that the communication domain maps consistently in the hex space.

Lint identified two medium findings, both pre-existing: verification requirements co-mingled with functional requirements (structural), and {{sub:SUB-SUBSYSTEMREQUIREMENTS-027}} specifying degraded mode without performance criteria. The new verification entries (VER-015 through VER-018) were flagged for lacking “shall” — expected since verification text describes test method rather than testable requirement.

Requirements

Ten subsystem requirements ({{sub:SUB-SUBSYSTEMREQUIREMENTS-041}} through {{sub:SUB-SUBSYSTEMREQUIREMENTS-050}}) cover V2X latency and dual-mode operation, telemetry uplink rate with carrier failover, OTA signature verification and 30-second rollback, TSN 500-microsecond worst-case delivery, 10 Gbps aggregate backbone throughput with VLAN isolation, 72-hour store-and-forward telemetry buffering, IEEE 1609.2 pseudonym certificate management, and FIPS 140-2 Level 2 HSM key isolation.

Four interface requirements ({{ifc:IFC-INTERFACEDEFINITIONS-020}} through {{ifc:IFC-INTERFACEDEFINITIONS-023}}) define the Router-to-V2X Ethernet link, V2X-to-Security signing latency budget, Router-to-Telemetry multiplexed queuing, and OTA-to-Security payload verification throughput.

All subsystem requirements trace to parent system requirements: {{sys:SYS-SYSTEM-LEVELREQUIREMENTS-005}} (V2X), {{sys:SYS-SYSTEM-LEVELREQUIREMENTS-006}} (OTA), {{sys:SYS-SYSTEM-LEVELREQUIREMENTS-008}} (cycle time), {{sys:SYS-SYSTEM-LEVELREQUIREMENTS-009}} (MTBF), and {{sys:SYS-SYSTEM-LEVELREQUIREMENTS-010}} (safety integrity). Four verification entries define test approaches for V2X latency, OTA integrity, TSN timing, and HSM key isolation.

Next

One subsystem remains: {{entity:Planning and Decision Subsystem}}. Prior sessions created interface requirements referencing its internal components (Prediction Module, Behavior Planner, Motion Planner, Risk Assessor) but never classified them in the entity graph or stored PART_OF facts. The next session should classify these 4-5 components, store their graph relationships, and generate subsystem requirements with traces to {{sys:SYS-SYSTEM-LEVELREQUIREMENTS-004}} (trajectory generation) and {{sys:SYS-SYSTEM-LEVELREQUIREMENTS-001}} (object detection/classification). Once Planning and Decision is complete, the Autonomous Vehicle system decomposition can be marked finished and a new system selected from the seed list.

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