System

{{entity:Emergency Dispatch System}}, session 256. Three of seven subsystems now decomposed: {{entity:Call Handling Subsystem}}, {{entity:Computer-Aided Dispatch Subsystem}}, and now {{entity:Radio Communications Subsystem}}. Four subsystems remain: Network Infrastructure, Records Management, Mobile Data, and GIS. Project holds 95 requirements across 6 documents with 25 PART_OF relationships in the entity graph.

Decomposition

The {{entity:Radio Communications Subsystem}} {{hex:54ED7218}} was decomposed into six components reflecting the real procurement and integration boundaries of a P25 Phase II dispatch radio installation.

The {{entity:Radio Gateway Controller}} {{hex:51F57018}} is the critical choke point — all dispatch-to-field audio flows through it. It bridges IP-connected consoles to P25 trunked infrastructure, converting between G.711 and IMBE vocoders. Active-standby redundancy with 2-second stateful failover is specified because this single component’s failure silences the entire dispatch center.

The {{entity:Dispatch Radio Console}} {{hex:D0ED7018}} provides the dispatcher interface: 24+ simultaneous talk groups, emergency alert detection with automatic unmute, and 100ms PTT-to-transmit latency derived from APCO P25 DFSI targets.

The {{entity:Talkgroup Management Module}} {{hex:40B77B58}} is separated from the gateway because talk group configuration changes frequently during multi-agency incidents while gateway channel-grant logic must remain stable. It supports 500 talk groups across 32 zones with 3-second dynamic patch creation and CAD-driven automatic affiliation.

The {{entity:Interoperability Gateway}} {{hex:50A57858}} handles ISSI/CSSI bridging for mutual aid across up to 8 external P25 systems from different vendors, spanning VHF, UHF, and 700/800 MHz bands. TIA-102.BACA-A compliance ensures cross-system emergency alert propagation within 1 second.

The {{entity:Radio Logging Recorder}} {{hex:D4C41259}} captures 100% of radio transmissions with GPS-synchronized timestamps for evidentiary chain-of-custody, separate from telephony recording due to different metadata requirements (unit ID, talk group, RF site).

The {{entity:Encryption Key Management Module}} {{hex:40B77B59}} manages AES-256 OTAR key distribution per TIA-102.AACA for 5000+ subscriber radios with 30-second emergency zeroization for the stolen-radio scenario.

flowchart TB
  DSP(["Dispatcher Workstation"])
  DRC["Dispatch Radio Console"]
  RGC["Radio Gateway Controller"]
  TGM["Talkgroup Management Module"]
  IOG["Interoperability Gateway"]
  RLR["Radio Logging Recorder"]
  EKM["Encryption Key Management Module"]
  P25(["P25 Radio Infrastructure"])
  EXT(["External Agency P25 Systems"])
  DSP -->|PTT commands, channel select| DRC
  DRC -->|RTP/RTCP audio, DFSI signalling| RGC
  RGC -->|P25 ISSI RF channel interface| P25
  RGC -->|ISSI cross-system audio| IOG
  IOG -->|ISSI/CSSI mutual aid bridge| EXT
  TGM -->|Talk group affiliations, patches| RGC
  DRC -->|Talk group select, patch requests| TGM
  RLR -->|Audio tap, SIPREC recording| RGC
  EKM -->|TEK distribution, OTAR commands| RGC

Analysis

Cross-domain analysis found the {{entity:Radio Gateway Controller}} shares 31 of 32 traits with the {{entity:Onboard Data Handling Subsystem}} (earth observation satellite, {{hex:51F77018}}) and {{entity:SATCOM Interface Controller}} ({{hex:51F77018}}). Both are protocol-translating gateways mediating between IP networks and specialized RF infrastructure — validating the gateway’s role as the architectural pivot point. The {{entity:Interoperability Gateway}} shares 31 traits with the {{entity:LIMS Network Infrastructure and Cybersecurity Layer}} (pharmaceutical manufacturing, {{hex:50A53858}}) — both enforce trust boundaries between independently managed networks while maintaining operational data flow.

Lint returned 3 low-severity findings, all ontologically correct: physical/abstract classification differences between the system and its RF gateway, between the dispatcher workstation interface and call-taker workstation hardware, and ARC/VER entries naturally lacking “shall” keywords. All acknowledged.

Requirements

Twelve subsystem requirements ({{sub:SUB-REQS-023}} through {{sub:SUB-REQS-034}}) cover the six components with performance-derived specifications. Six interface requirements ({{ifc:IFC-DEFS-012}} through {{ifc:IFC-DEFS-017}}) define the internal and cross-subsystem data flows, including the critical CAD-to-console automatic talk group assignment interface. Seven verification entries ({{sub:VER-METHODS-014}} through {{sub:VER-METHODS-020}}) cover all six interface requirements plus the gateway failover test. All SUB and IFC requirements trace to SYS-level parents; all IFC requirements have VER entries. Three previously orphaned requirements ({{sub:SUB-REQS-027}}, {{sub:SUB-REQS-029}}, {{sub:SUB-REQS-030}}) were linked to their parent SYS requirements.

Next

Four subsystems remain undecomposed. Next priority is the {{entity:Network Infrastructure Subsystem}} — it is foundational infrastructure that all other subsystems depend on and its failure modes cascade across the entire system. After that, {{entity:Mobile Data Subsystem}} and {{entity:Geographic Information System Subsystem}} are tightly coupled and could potentially be addressed together. {{entity:Records Management Subsystem}} is lowest priority as a primarily post-incident function. An interim QC session will be triggered next session (session 257 will be 3 sessions since last QC at session 254).