Glossary

Alphabetical list of acronyms and terms used across the rfgen documentation. Click any cross-link to reach the authoritative concept page.

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ABC: Abstract Base Class. A Python class that uses abc.ABC (or abc.ABCMeta) to declare abstract methods, preventing direct instantiation and enforcing a contract on every concrete subclass. The rfgen framework defines one primary ABC per layer (e.g., BaseEmitter, BaseChannel).

AGC: Automatic Gain Control. A feedback circuit that adjusts receiver amplifier gain to maintain a roughly constant output power level across a wide input-power range. In rfgen, AGC is the hardware-plane receiver transformation modeled by BaseAGCStage.

AoA: Angle of Arrival. The incident direction of a radio wave at a receive antenna, typically measured in azimuth and elevation. Required for TDOA, beamforming, and direction-finding tasks. See Channels / Propagation for which backends preserve joint spatial correlation across RX antennas.

AWGN: Additive White Gaussian Noise. A standard noise model where each sample is drawn independently from a Gaussian distribution with flat power spectral density. In rfgen, additive thermal noise is no longer a standalone stage; it enters as LNA_NOISE on the receiver’s capture plane via BaseThermalNoiseStage, where the noise power is set by the LNA noise figure and the receiver bandwidth. See Concepts / Channels / RX capture.

BS: Base Station. A fixed radio access node (e.g., a cellular tower or Wi-Fi access point). In 3GPP terminology, BS refers to the network side; the mobile side is the UE.

CDL: Clustered Delay Line. A 3GPP TR 38.901 small-scale fading model that adds angular cluster structure (angles of arrival and departure) on top of a tapped delay line. Useful when antenna arrays, beamforming, or MIMO decoding are part of the downstream task. Sionna exposes this as sionna.phy.channel.tr38901.CDL. See Concepts / Channels / Propagation.

TDL: Tapped Delay Line. A 3GPP TR 38.901 small-scale fading model for SISO simulation. Each tap fades independently; no spatial information. Simpler than CDL; preferred for controlled link-level experiments. Sionna exposes this as sionna.phy.channel.tr38901.TDL.

CIR: Channel Impulse Response. The set of complex path gains and delays a multipath channel applies to a transmitted signal. rfgen’s Sionna statistical and ray-traced graph nodes publish a typed, dimensionless unit-transfer CIR; the separate apply_cir node applies it to an independently power-scaled volts waveform, while cir_to_cfr evaluates its oracle frequency response. The v1 contract is one link and one TX/RX stream. See Node channel-response seam.

PDP: Power-Delay Profile. The distribution of a multipath channel’s average received power as a function of excess delay: which delayed copies of the signal carry how much power. declared_power_delay_profile publishes either of rfgen’s two analytic exponential profiles (not transcribed from a measurement campaign); pdp_rayleigh_fading performs the separate seeded gain draw. See Node channel-response seam.

RMS delay spread: Root-Mean-Square Delay Spread. The power-weighted standard deviation of a channel’s excess delays, summarizing how spread out in time a multipath channel’s energy is; a larger value means more delay spread and, for a fixed bandwidth, more inter-symbol interference risk. Computed from a PDP’s tap delays and powers (Rappaport, Wireless Communications: Principles and Practice, 2nd ed., Sec. 5.4, eq. 5.5/5.6).

CFO: Carrier Frequency Offset. A small difference between the nominal TX carrier frequency and the frequency the receiver synthesizer locks to, caused by reference-oscillator drift. CFO appears as a slow phase ramp on the received IQ. In rfgen, CFO is applied per emitter as the CFO transformation inside Group.TX via BaseCFO.

EIRP: Effective Isotropic Radiated Power. Total power radiated by a transmitter relative to an isotropic antenna, equal to conducted power times antenna gain. Used to characterize the TX power budget in link budget calculations. Configured through emitter and scene power parameters.

ENOB: Effective Number of Bits. A measure of the actual resolution of an ADC or DAC, accounting for distortion and noise. Lower ENOB means more quantization noise. Modeled in rfgen through BaseDACQuantization on the TX side and BaseADCQuantizationStage on the RX side.

EW: Electronic Warfare. The use of the electromagnetic spectrum for military purposes: jamming, spoofing, detection, and interception.

FEC: Forward Error Correction. Channel coding that adds redundancy to transmitted bits so receivers can correct errors without retransmission. rfgen exposes FEC as an explicit, caller-selectable coding family in exactly one emitter, FECConstellationEmitter (rfgen.waveforms.fec_constellation), which encodes bits with a real Sionna encoder (sionna.phy.fec.ldpc.LDPC5GEncoder, .polar.Polar5GEncoder, .turbo.TurboEncoder, or .conv.ConvEncoder) before mapping them to a pulse-shaped QAM constellation. NRPuschEmitter also performs real LDPC transport-block encoding, but only as a fixed, non-configurable step inside its delegated 3GPP PUSCH pipeline, not as a selectable coding family; no other rfgen emitter applies FEC in any form. See Emitter API.

FHSS: Frequency-Hopping Spread Spectrum. A transmission technique in which the carrier hops among many frequencies according to a pseudorandom sequence. Drone control links (e.g., OcuSync, Lightbridge) and some radars use FHSS. The hop schedule is intrinsic to the emitter waveform; in a composed scene the composer applies the additional whole-waveform placement shift and records the final absolute carrier. See Coordinate Systems.

HIL: Hardware-in-the-Loop. A validation technique that connects real radio hardware (e.g., USRP, HackRF) to the simulation so synthetic waveforms can be compared against actual SDR captures. rfgen’s HIL harness is planned for v1.5. See Background / Validation.

IF: Intermediate Frequency. A frequency to which an RF signal is shifted before final demodulation. rfgen generates and processes baseband IQ; IF stages are considered part of the analog hardware not modeled here.

IQ: In-phase / Quadrature. The standard representation of a complex baseband signal by its real (I) and imaginary (Q) components. Emitter and composition APIs use channel-first (2, N) float32; past the receiver seam a ComplexCapture instead carries arbitrary-rank complex64, with semantic axes declaring what each dimension means. See Reference / IQ Layout Policy and Observation API.

ITU: International Telecommunication Union. The United Nations agency responsible for global radio frequency allocation and telecommunications standards. ITU propagation models (ITU-R P series) inform some of the reference path-loss curves used to validate Sionna backends.

JCAS: Joint Communications and Sensing. A dual-function radio system that reuses the same waveform and hardware for both data communication and environmental sensing (e.g., radar). A planned roadmap area for rfgen’s emitter catalog.

kTBF: Thermal noise floor, computed as k × T × B × F, where k is Boltzmann’s constant (1.38 × 10⁻²³ J/K), T is temperature in Kelvin (~290 K standard), B is bandwidth in Hz, and F is the noise figure. This gives the minimum achievable noise floor at the receiver input. See Reference / Noise Floor Table.

LNA: Low-Noise Amplifier. The first active component in most receiver chains, placed immediately after the antenna to amplify the received signal before any lossy components introduce noise. LNA noise figure (NF) is the primary parameter of BaseThermalNoiseStage on the receiver’s capture plane.

LO: Local Oscillator. An oscillator within a radio that provides the reference tone for frequency translation. The scene center frequency (scene_center_frequency_hz) in rfgen corresponds to the virtual LO that defines 0 Hz in the wideband scene IQ. See Coordinate Systems.

LOS: Line of Sight. A propagation condition where transmitter and receiver have an unobstructed geometric path between them. LOS paths typically have stronger signal levels (higher K-factor) and less delay spread than NLOS.

NLOS: Non-Line of Sight. A propagation condition where the direct geometric path is blocked by obstacles. NLOS channels typically show stronger multipath and lower received power. The 3GPP UMa, UMi, and RMa scenario models include stochastic LOS/NLOS state transitions.

mAP: mean Average Precision. The primary detection metric used in object-detection benchmarks (COCO, PASCAL VOC). Averaged over IoU thresholds and object classes. Used to evaluate wideband detection models trained on rfgen datasets.

MIMO: Multiple Input Multiple Output. Radio systems with multiple transmit and receive antennas that exploit spatial multiplexing or diversity. A multi-RX rfgen scene publishes every receiver inside one record, as the per-receiver subtrees projections/<projection_id>/receivers/rx<N>/iq, so the joint tensor MIMO decoding needs is recoverable by stacking those subtrees.

mIoU: mean Intersection over Union. The primary segmentation metric: average over classes of (intersection area) / (union area) between predicted and ground-truth masks. Used to evaluate time-frequency segmentation models trained on rfgen datasets.

NF: Noise Figure. A measure of the noise added by a component, in dB above the thermal noise floor. Lower NF means less added noise. The LNA NF is the dominant NF source in the RX chain.

NR PUSCH: New Radio Physical Uplink Shared Channel (5G). The 5G NR uplink data channel. rfgen implements this through NRPuschEmitter, which delegates 5G NR uplink PHY work (resource-grid mapping, DMRS placement, transport-block encoding, OFDM modulation) to sionna.phy.nr.PUSCHTransmitter/PUSCHConfig. See Emitter API.

DMRS: Demodulation Reference Signal. Known pilot symbols placed at fixed resource elements within an NR slot so a real receiver can estimate the channel before demodulating data. NRPuschEmitter places a real, full-band, single-symbol DMRS pattern (3GPP TS 38.211 mapping type A) via sionna.phy.nr.PUSCHTransmitter; the standards-shaped ConformantOFDMEmitter places a different, non-DMRS Kronecker pilot pattern instead (see that emitter’s entry in the Emitter API).

Numerology: In 3GPP NR, the combination of subcarrier spacing and symbol/slot timing a standard defines (TS 38.211 Table 4.2-1 names five: 15/30/60/120/240 kHz). A wider subcarrier spacing gives a shorter OFDM symbol and a shorter slot. NRPuschEmitter supports any of the five; ConformantOFDMEmitter fixes numerology 0 (15 kHz).

Resource block / resource grid: A resource block is 12 consecutive OFDM subcarriers (3GPP TS 38.211 section 4.4.4.1), the basic unit of frequency-domain bandwidth allocation in NR and NR-numerology-shaped waveforms. A resource grid is the full two-dimensional grid of subcarriers by OFDM symbols within one slot that carries both pilot and data resource elements. rfgen’s NRPuschEmitter and ConformantOFDMEmitter both size their resource grid from a requested resource-block count or an equivalent occupied-bandwidth override; see Emitter API.

Transport block: The unit of data a 3GPP PHY layer encodes, scrambles, and maps onto a resource grid in one slot (or slot group). NRPuschEmitter produces a genuinely sized transport block (LDPC-encoded, per 3GPP TS 38.212) via sionna.phy.nr.PUSCHTransmitter; the standards-shaped ConformantOFDMEmitter has no transport-block concept at all: its data path is uncoded bits mapped directly to QPSK.

MCS: Modulation and Coding Scheme. A 3GPP index (TS 38.214 Table 5.1.3.1-1 for NR PUSCH) that jointly selects a modulation order and a target code rate for one transmission. NRPuschEmitter’s NRPuschParams.mcs field selects this index directly; not every (resource-block count, MCS) pair is a constructible transport block (see the Emitter API).

NTIA: National Telecommunications and Information Administration. The US agency that manages federal spectrum use (the FCC manages non-federal). NTIA frequency allocation charts are useful for planning real-world RF scenarios.

OSM: OpenStreetMap. A community-maintained geographic database. Sionna RT can load OSM-derived 3D scene meshes for site-specific ray-traced propagation.

PA: Power Amplifier. The final amplifier stage in a transmitter. PA nonlinearity (modeled by the Rapp or Saleh model) causes spectral regrowth and EVM degradation, and is a key source of per-device fingerprint. In rfgen, PA nonlinearity is the PA transformation inside Group.TX via BasePANonlinearity.

PAES: Physical Attribute Extraction Score. A metric introduced in this framework for measuring annotation quality. The verifier inference pass re-extracts physical attributes (modulation, SNR, bandwidth, channel, time placement) from a text annotation and compares to ground-truth metadata. Score = fraction of attributes recovered within tolerance. Target: PAES ≥ 0.80 on the caption annotation type.

PRI: Pulse Repetition Interval. The time between the start of successive radar pulses. PRI determines the unambiguous range of a pulsed radar. rfgen’s chirp_radar emitter accepts pri_us as a parameter, the TimePlacementStrategy.PRI_PULSE_TRAIN strategy schedules pulses at the specified interval, and the coupled radar response models carry the full PRI schedule as pulse_repetition_intervals_s.

PSD: Power Spectral Density. The distribution of signal power per unit frequency (in dBm/Hz or W/Hz). Used in SNR calculations, spectral mask compliance checking, and AWGN noise floor specification.

RFML: Radio Frequency Machine Learning. The research discipline of applying machine learning to RF signal processing: modulation classification, signal detection, specific emitter identification, and related tasks. rfgen is designed to generate training data for RFML tasks.

RIS: Reconfigurable Intelligent Surface. A passive array of tunable scattering elements that can be programmed to reflect or focus radio waves. An emerging propagation technology; Sionna RT supports RIS scenes. Listed as a planned roadmap item for rfgen.

RMa: Rural Macro (3GPP). A 3GPP TR 38.901 scenario for base-station deployments in rural areas with large inter-site distances and lower building density. Implemented in Sionna as sionna.phy.channel.tr38901.RMa.

UMa: Urban Macro (3GPP). A 3GPP TR 38.901 scenario for macro-cell deployments in urban areas with base-station height around 25 m. Implemented in Sionna as sionna.phy.channel.tr38901.UMa.

UMi: Urban Micro (3GPP). A 3GPP TR 38.901 scenario for small-cell or street-canyon deployments. Implemented in Sionna as sionna.phy.channel.tr38901.UMi.

RT: Ray Tracing. The propagation simulation method that traces discrete geometric paths between TX and RX, potentially accounting for interactions with scene geometry. In rfgen, Sionna RT (SionnaRT) forwards only los, specular_reflection, diffuse_reflection, and refraction. Sionna’s diffuse scattering is optional through diffuse_reflection; rfgen does not expose or pass Sionna diffraction, edge-diffraction, or diffraction-lit-region controls, and its solver outputs are not field-calibrated. See Concepts / Channels / Propagation.

SDR: Software-Defined Radio. A radio communication system that implements typical hardware components (amplifiers, modulators, mixers) in software. Hardware SDRs (USRP, HackRF, ADALM-PLUTO) are used in rfgen’s HIL validation harness.

SEI: Specific Emitter Identification. The RFML task of identifying a specific physical radio device from its waveform, relying on subtle hardware impairments (CFO, IQ imbalance, phase noise, PA nonlinearity) that are device-specific.

SFO: Sample Frequency Offset. A small mismatch between the nominal and actual sampling clock frequency, causing the received IQ to appear to run at a slightly different rate than expected. The SEI literature treats it as a TX-side oscillator impairment that manifests as a small fractional resample. In rfgen it exists as a per-device prior, FingerprintParams.sfo_ppm, that no shipped transformation currently consumes; the general mechanism that would realize such an offset is a (1 + ε) resample inside BaseResamplerStage on the receiver’s capture plane. Do not confuse it with SRO below: SampleRateOffsetStage is a caller-configured, per-instance RX-side offset that reads nothing from the device-fingerprint registry. See Reference / Algorithms / Fingerprint Math for the math and Background / RF Fingerprinting (SEI) for context.

SigMF: Signal Metadata Format. An open standard for recording RF captures as paired binary data (.sigmf-data) and JSON metadata (.sigmf-meta). rfgen accepts SigMF captures as read-only input for HIL validation and replay emitters.

SNR: Signal-to-Noise Ratio. The ratio of signal power to noise power, typically expressed in dB. In rfgen, SNR is specified as a per-emitter target; the realized noise floor is set by LNA_NOISE on the receiver’s capture plane via BaseThermalNoiseStage, and the per-emitter realized SNR is recorded in SignalMetadata.snr_db and SceneMetadata.realized_snr_distribution.

SRO: Sample-Rate Offset, also called clock drift. A fixed fractional difference between the transmitter and receiver sampling clocks, quoted in parts per million, which leaves the receiver sampling on a time grid that is slightly stretched or compressed. SRO is the timing-axis counterpart of CFO, and is distinct from the per-device SFO fingerprint prior above. In rfgen, SRO is applied as the RESAMPLER transformation on the receiver’s capture plane via BaseResamplerStage, whose concrete SampleRateOffsetStage performs a length-preserving (1 + ppm * 1e-6) resample. See Concepts / RX capture § Sample-rate offset (clock drift).

SSL (machine learning): Self-Supervised Learning. A family of ML training approaches that derive supervisory signal from the data itself without human labels, often by predicting masked or augmented versions.

SSL (networking): Secure Sockets Layer. A cryptographic protocol for securing network communications, superseded by TLS. The two SSL acronyms are unrelated; context disambiguates them.

Stage: Retired. In the previous channel pipeline, Stage was a five-member IntEnum (TX_HARDWARE, FREQUENCY_SHIFT, PROPAGATION, RX_FRONTEND, AWGN) tagged onto every BaseChannel implementation. The current design replaces it with two finer-grained enums: Group (four members partitioning the chain at the pre-sum / post-sum boundary) and Transformation (fourteen members naming individual operations within a group). See Background / Design Decisions for the rationale and Concepts / Channels for the current model.

TDOA: Time Difference of Arrival. A localization technique that estimates the position of a transmitter by comparing the arrival time of its signal at multiple receivers. Requires the arrival times at several receivers to stay in one record: a multi-RX rfgen scene keeps them there, as the per-receiver subtrees projections/<projection_id>/receivers/rx<N>/iq.

TX / RX: Transmit / Receive. TX denotes the transmitter side (emitter, BS downlink, or UE uplink); RX denotes the receiver side. In 3GPP cellular contexts, TX and RX roles depend on direction: uplink means UE transmits, BS receives; downlink means BS transmits, UE receives.

UE: User Equipment. The mobile terminal in a cellular network (phone, modem, IoT device). In 3GPP uplink scenarios the UE is the transmitter; in downlink it is the receiver.

V2X: Vehicle-to-Everything. Encompasses V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), and related vehicular communications. V2X scenarios with distributed TX positions are a motivating use case for ChannelApplicationMode.PER_EMITTER in rfgen.