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Standards

EMI (1900.2)

IEEE 1900.2 is a recommended practice for analyzing interference and coexistence between radio systems, before a system goes into service as well as after a net goes bad. It answers the same questions the same way every time: who causes it, who suffers it, how much, and where the line for "harmful" sits. NEMESynth-EMSO uses its structure for predicted conflicts, interference reports, analysis and resolution.

Source, path, recipient

Every interference case has a source (a transmitter, a jammer, a noisy generator), a path (distance, terrain, antennas) and a recipient (the receiver, the net and the people using it). You can work it from either end. An interference analysis starts with the source's energy and follows it to the recipient. A coexistence analysis starts with the recipient's job, such as getting a call for fire through, and asks what the interference does to it. Doing both keeps you from missing an effect, and from worrying about one that doesn't matter.

Source, path and recipient, with interference analysis working forward from the source and coexistence analysis working back from the recipient's mission Source transmitter, jammer, generator, radar power, frequency, time Path distance and terrain antenna gain and pointing weather, buildings Recipient receiver and net the mission it carries the people using it Interference analysis: start from the energy and follow it to its effect Coexistence analysis: start from the mission and ask what the interference does to it Both directions, one case: a fault on either end shows up in the other
The two directions of an interference case.

When is it harmful?

Most energy that reaches a receiver does no damage. 1900.2 makes you say up front what you're measuring, what counts as an effect, and where the line is, and then give your reasons for that line. When two units disagree about a case, the disagreement narrows to one number you can argue about.

Measurement events contain interference events, which contain harmful interference Measurement events Every sample, measured or calculated, with its bandwidth, averaging time and conditions stated Interference events The samples where the source measurably hurts the recipient: lower throughput, garbled voice, dropped links, lost margin, delay Harmful interference past the threshold the analysis states and justifies, over time, users or systems
Not every measurement is interference, and not all interference is harmful.

A measurement event can be measured or calculated, so the same analysis runs on predictions from models as on reports from the field. 1900.2 then gives seven ways to say when interference events add up to harmful interference. The analysis picks one or more and states why.

CategoryHarmful whenEstablished by
ConceivableAn interference event is theoretically possible for some configuration of source and recipient. No threshold.Analysis, component measurement or laboratory experiment
ObservedAny interference event is reported in typical useExperiment or field reports
ExcessiveAny one recipient has more than a set share of its measurement events as interference events, such as more than X minutes of outage a yearPrediction or measurement, per recipient
WidespreadMore than a set share of recipients have an interference event at the same timePrediction or measurement, across recipients
Multiple widespreadWidespread interference happens for more than a set share of the timePrediction or measurement, across recipients
Multiple excessiveMore than a set share of recipients suffer excessive interferencePrediction or measurement, across recipients
Probability of interferenceMore than a set share of all measurement events, across recipients and time, are interference eventsPrediction or measurement, across recipients

1900.2 also asks who owns a receiver's protection margin, the decibels it keeps against fading. NEMESynth-EMSO computes that margin from spectrum consumption models: see power margin.

Physical and logical effects

Interference has always been treated as a physical problem: power, antennas, noise, sensitivity. A network can hide it, though. If a mesh reroutes around a jammed link and the traffic still gets through, was the net harmed? 1900.2 separates the physical domain (the radio signals) from the logical domain (routing, retransmission, scheduling, quality of service) and lets you analyze both.

NEMESynth-EMSO keeps the same split in how it understands the world. RF energy and propagation sit in the physical layer. Nets, protocols and the SFAF record sit in the logical layer, on top of it. See how NEMESynth-EMSO is layered.

From report to resolution

The interference workflow: report, characterize, analyze, resolve, record Report who, where, when, what it sounded like Characterize frequency, time, what's authorized there Analyze source, path, recipient; harmful or not Resolve retune, move, schedule, PACE switch, coordinate Record closed, with reasons, shared with the record Each step is a record in the SFAFx set, so every node sees the same case and the same outcome
An interference case from the first report to closing it out.
In NEMESynth-EMSOStatus
Interference events as records in the SFAFx set, alongside the assignments they touchDraft
Conflict pairs with interference-to-noise from the frequency assignment optimizer, so a new assignment doesn't create a caseBuilt
An interference event triggering the net's PACE plan through its decision sheetBuilt
Measured energy compared with what's authorized: a match is friendly use, and no match is a leadPlanned

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Send us an unclassified case your unit worked, and we'll walk it through NEMESynth-EMSO from the report to the resolution.

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