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Terminology

Core terms and definitions used throughout this wiki. Use terms consistently when reporting issues or discussing deployments — it reduces ambiguity and speeds up troubleshooting.

MeshCore protocol terms

  • Node: any device participating in the mesh, regardless of role
  • Companion node: personal portable node that sends and receives messages; does not forward traffic from other nodes; connects to the mobile app via BLE or USB
  • Fixed node: stationary companion node deployed at home or a fixed site for persistent local coverage
  • Repeater / relay: node configured to forward packets, extending network reach; infrastructure backbone of any deployment; no app interface, managed via CLI
  • Room Server: store-and-forward message board node; holds messages for offline recipients; login-based access control
  • Sensor node: transmit-only node that broadcasts telemetry (GPS, environmental data) in CayenneLPP format; no user interface
  • Terminal Chat: CLI-only companion node; useful for headless Linux devices and development
  • KISS Modem: firmware that exposes a MeshCore radio as a standard KISS TNC interface for APRS and AX.25 integration
  • Channel: a group communication namespace defined by a 32-byte shared secret; not related to radio frequency; all nodes sharing the secret can decrypt group messages on that channel
  • Contact: a known node stored locally with its public key, cached routing path, and derived shared secret
  • Advertisement (ADVERT): a signed broadcast packet that announces a node's identity, type, name, and optionally GPS coordinates; used for discovery and routing

Routing terms

  • Flood (ROUTE_TYPE_FLOOD): routing mode where a packet propagates to all nodes; used for initial discovery
  • Direct (ROUTE_TYPE_DIRECT): routing mode using a cached explicit path; used for subsequent messages to a known contact
  • Path: ordered sequence of 1-byte node IDs that describes the hops between sender and destination
  • Path caching: storing the returned path from a flood discovery for reuse in direct routing
  • Hop limit (flood_max): configurable maximum number of hops a flood packet may traverse before being dropped
  • Duplicate suppression: mechanism that prevents the same packet from being forwarded more than once by any node
  • ACK (acknowledgement): a 4-byte CRC response confirming receipt of a message
  • TRACE: diagnostic packet that collects per-hop SNR data as it traverses the mesh

RF terms

  • RSSI: received signal strength indicator — the power level of the received signal in dBm; more negative = weaker signal
  • SNR: signal-to-noise ratio — the signal level relative to the background noise floor in dB; negative SNR means the signal is below the noise floor but may still be decodable due to LoRa processing gain
  • Noise floor: baseline RF power level at a receiver in the absence of a signal; elevated noise floor reduces effective range
  • LoS (Line of Sight): unobstructed optical path between two points; near-LoS is sufficient for LoRa links
  • Fresnel zone: elliptical volume around the straight-line path between two antennas; partial obstruction of this zone causes diffraction loss
  • EIRP: effective isotropic radiated power — the transmitted power accounting for antenna gain and cable loss, referenced to an isotropic radiator
  • ERP: effective radiated power — similar to EIRP but referenced to a dipole (3 dB less than EIRP)
  • SWR (standing wave ratio): ratio measuring antenna/feedline impedance match; high SWR (>2:1) indicates significant reflected power and potential efficiency loss
  • Spreading Factor (SF): LoRa parameter controlling the number of chirp symbols per bit; higher SF = longer range, longer airtime, more power
  • Bandwidth (BW): LoRa channel width in kHz; narrower bandwidth improves sensitivity but reduces data rate
  • Coding Rate (CR): LoRa forward error correction ratio (⅘ to 4/8); higher coding rate improves error resilience at the cost of data rate
  • CAD (Channel Activity Detection): LoRa feature that checks for on-air activity before transmitting, reducing collisions
  • Duty cycle: proportion of time a transmitter is allowed to transmit; regulated in some regions (e.g., EU 1–10% for certain sub-bands)

Cryptography terms

  • Ed25519: elliptic curve signature algorithm used for node identity keypairs and advertisement signing
  • ECDH / X25519: elliptic curve Diffie-Hellman key exchange used to derive a shared secret between two nodes from their public keys
  • AES-128-ECB: symmetric encryption algorithm used for message confidentiality; ECB mode means no IV/nonce
  • HMAC-SHA256: hash-based message authentication code providing message integrity and authenticity
  • Shared secret: 32-byte value derived from ECDH between two nodes; used as the encryption and MAC key for their private messages
  • Channel secret: 32-byte shared key material used for group channel encryption and authentication
  • MAC (message authentication code): 2-byte truncated HMAC tag appended to encrypted messages to verify integrity

Operations terms

  • Uptime: proportion of time a node is available and functioning; tracks reliability over time
  • Last-seen: timestamp of the most recent advertisement or message received from a node; primary availability indicator
  • Change window: planned period when configuration or firmware modifications are made to infrastructure nodes
  • Rollback: process of returning a node to a previous known-good firmware version or configuration after a failed change
  • Baseline config: the set of region, frequency, bandwidth, spreading factor, and coding rate settings that all community nodes share for interoperability
  • Commissioning: the process of deploying, configuring, and validating a new node before handing it over to normal operation
  • Decommissioning: controlled removal of a node from service, including removal from monitoring and the network map
  • Err flags: bitmask in node statistics indicating fault conditions (stuck radio, CAD timeout, queue overflow, etc.)