LoRa Mesh Networking Glossary

Quick reference definitions for terminology used throughout this wiki. Terms are organized alphabetically.

A

ACK (Acknowledgment)

A confirmation packet sent by the receiving node to confirm a message was received. Meshtastic uses ACKs for unicast (direct) messages; channel (broadcast) messages do not generate per-recipient ACKs - instead the sender gets an implicit ACK when it hears another node rebroadcast the packet.

Advertisement

MeshCore term for a broadcast packet that announces a node's name, position, and public encryption key (the advert is also signed to prevent spoofing). Client nodes send adverts manually when the user initiates it; repeaters and room servers send them periodically (every 12 hours by default). Similar in purpose to Meshtastic's NodeInfo broadcast.

ARES (Amateur Radio Emergency Service)

A volunteer organization affiliated with the ARRL that provides amateur radio communications support during emergencies. Some ARES groups have begun experimenting with LoRa mesh as a supplemental data layer.

Airtime

The duration a LoRa radio is transmitting a packet. Determined mainly by Spreading Factor, Bandwidth, and message length (coding rate and preamble length also contribute). Longer airtime = more range but lower network capacity. At SF12/BW125, a short message can take 1-2 seconds of airtime; at SF7/BW500, milliseconds.

B

Bandwidth (BW)

The frequency width of a LoRa signal in kHz. Common values: 62.5, 125, 250, 500 kHz. Wider bandwidth = faster data rate, slightly less range. One of the three parameters that define a modem preset.

BMS (Battery Management System)

A circuit that protects a lithium battery from overcharge, overdischarge, overcurrent, and short circuit. Essential for bare lithium cells; many integrated battery packs include a BMS.

Broadcast storm

A network condition where packets are retransmitted indefinitely, consuming all available airtime. Prevented in LoRa mesh by hop count limits and packet deduplication.

C

Channel

In Meshtastic: a named communication group with a shared Pre-Shared Key (PSK). Nodes on the same channel can communicate. Up to 8 channels can be configured on one node. In MeshCore: the public or private channel with shared encryption key.

Channel utilization

The percentage of time the LoRa channel is occupied by transmissions. Displayed in Meshtastic app. Values above 25% indicate congestion; above 50% the network becomes unreliable.

Coding Rate (CR)

A LoRa parameter that adds forward error correction overhead. Common values: 4/5, 4/6, 4/7, 4/8. Higher coding rate provides better noise immunity at the cost of reduced data rate. One of three parameters in a modem preset.

Conducted power

Transmit power measured at the antenna connector of the radio. FCC Part 15 limits this to 1W (30 dBm) for 902-928 MHz spread spectrum.

D-E

dBi

Decibels relative to an isotropic radiator. A measure of antenna gain. Higher dBi means more focused signal in some directions. 0 dBi means gain equal to a hypothetical isotropic antenna that radiates equally in all directions; real antennas always have some directionality.

dBm

Decibels relative to 1 milliwatt. Used to express absolute power levels. 0 dBm = 1 mW; 30 dBm = 1W; -120 dBm = approximate LoRa sensitivity at low spreading factors, while at SF12 sensitivity reaches roughly -137 dBm (BW125) to -148 dBm.

ECDH (Elliptic Curve Diffie-Hellman)

A key exchange algorithm that allows two parties to derive a shared secret over an insecure channel without transmitting the secret. Used by MeshCore for all direct messages, and by Meshtastic DMs in firmware 2.5.0+.

EIRP (Effective Isotropic Radiated Power)

Total radiated power accounting for antenna gain and cable loss. EIRP = Conducted Power + Antenna Gain - Cable Loss. FCC 15.247 caps conducted power at 1 W (30 dBm) and requires dB-for-dB power reduction only for antenna gain above 6 dBi - with a 6 dBi antenna this works out to about 36 dBm (4 W) EIRP, though fixed point-to-point links are allowed higher EIRP.

F-H

Flood routing

The routing method used by Meshtastic for broadcasts: it uses managed flooding, where a node rebroadcasts a packet unless it first hears another node rebroadcast it. Since firmware 2.6, direct messages use next-hop routing instead of flooding. Simple but can cause congestion at scale.

Fresnel zone

An elliptical region around the direct path between two antennas. For reliable communication, approximately 60% of the first Fresnel zone should be free of obstructions. Trees, buildings, and terrain within the Fresnel zone cause signal loss even if the visual line-of-sight is clear.

Gateway

A node that connects the local mesh network to the internet (via WiFi, cellular, or wired connection), enabling MQTT uplink/downlink and access to map services and remote monitoring.

Hop

One radio transmission between adjacent nodes. A message that travels from Node A to Repeater B to Node C has taken 2 hops.

Hop limit

The maximum number of hops a packet may take before being discarded. Decremented at each relay. Default 3 in Meshtastic; prevents broadcast storms.

I-L

ISM band

Industrial, Scientific and Medical radio bands. In the US, license-free communications devices (FCC Part 15) may also operate in these bands. US bands include 902-928 MHz, 2.4 GHz (WiFi), and 5.8 GHz; in Europe, 863-870 MHz is used for LoRa.

LiFePO4 (Lithium Iron Phosphate)

A lithium battery chemistry with superior DISCHARGE temperature tolerance (-20°C to 60°C), long cycle life (2,000-4,000 cycles), and high thermal stability (far more resistant to thermal runaway than LiPo, though not immune). Charging below 0°C damages the cells, so outdoor solar nodes need a low-temperature charge cutoff or a heated/self-heating battery. Recommended for outdoor LoRa deployments.

Link budget

The accounting of all gains and losses in a radio link. Received power = TX power + TX antenna gain - cable losses - path loss + RX antenna gain. Link margin = received power - receiver sensitivity; a positive margin means a workable link.

LMR-200 / LMR-400

Trade names for low-loss coaxial cable commonly used for LoRa antenna connections. LMR-200 is flexible and low-loss for runs under 10m. LMR-400 is larger, lower-loss, preferred for runs over 10m at 915 MHz.

LoRa

Long Range radio modulation technology using Chirp Spread Spectrum (CSS). Not a network protocol - just the radio layer. Used by Meshtastic, MeshCore, LoRaWAN, and other systems.

LoRaWAN

A centralized IoT network protocol that uses LoRa radio. NOT the same as Meshtastic or MeshCore. LoRaWAN requires gateways connected to a network server; it does not support peer-to-peer mesh networking.

M-P

MeshCore

An open-source peer-to-peer LoRa mesh networking protocol using path-based routing (path discovery/acknowledgment) and ECDH encryption for direct messages. Distinct from and incompatible with Meshtastic.

Meshtastic

An open-source peer-to-peer LoRa mesh networking project using flood-based routing. The most widely deployed LoRa mesh protocol globally.

MPPT (Maximum Power Point Tracking)

A charge controller technique that continuously adjusts load to extract maximum power from a solar panel. MPPT typically harvests 10-30% more energy from the same panel than a PWM controller (vendor data; the exact gain depends on conditions), which matters most for small panel/battery systems.

NodeInfo

Meshtastic packet type that broadcasts a node's name, hardware type, and short name. Sent periodically and when the node first joins the network. Creates entries in other nodes' contact databases.

nRF52840

A Nordic Semiconductor microcontroller with integrated Bluetooth 5 and low-power design. Used in RAK4631, T-Echo, and T114 LoRa boards. Draws substantially less power than ESP32-based boards (sleep behavior and the radio dominate the difference), making it preferred for battery-powered deployments.

PSK (Pre-Shared Key)

A cryptographic key shared among all members of a group before communication begins. Meshtastic channels use PSKs for AES-256-CTR channel encryption (the PSK itself may be 128- or 256-bit). All nodes on a channel must have the same PSK to decrypt messages.

R-Z

RAK4631

A WisBlock LoRa module based on nRF52840 and SX1262 radio. One of the most popular nRF52840-based boards for MeshCore and Meshtastic deployments, valued for its low power consumption and external antenna support.

Room server

A MeshCore node running room-server firmware that acts as a shared message board (BBS): it stores posts and forwards them to clients when they connect, enabling asynchronous delivery. It does not require internet connectivity.

RSSI (Received Signal Strength Indicator)

Measured in dBm (negative values). The power level of a received radio signal. More negative = weaker signal. LoRa can decode signals as weak as -120 to -148 dBm depending on Spreading Factor.

SNR (Signal-to-Noise Ratio)

The ratio of signal power to noise floor, measured in dB. LoRa can decode at negative SNR values (down to about -20 dB), which is why it achieves such long range despite low signal strength.

Spreading Factor (SF)

A LoRa parameter, typically 7-12 (newer SX126x radios support 5-12). Higher SF = longer range, more airtime, lower data rate. Each step roughly doubles airtime. SF12 has roughly 30x more airtime than SF7 (at the same bandwidth) but much greater sensitivity.

T-Beam

A popular ESP32-based LoRa development board by TTGO/LilyGO featuring an integrated GPS module and 18650 battery holder. The antenna connector varies by version (SMA on classic v1.x boards, U.FL on the T-Beam Supreme/S3-Core). Available in 915 MHz (US) and 868 MHz (EU) variants.

T-Echo

A nRF52840-based LoRa device by LilyGO with an e-ink display, integrated GPS, and excellent battery life. Recommended for portable/handheld Meshtastic use.

UART

Universal Asynchronous Receiver-Transmitter. A serial communication interface. Used to connect GPS modules, serial sensors, and external hardware to LoRa boards.