Chapter 6
Phase 3 of WIA-COMM-005 covers what happens when satellite-internet traffic crosses a boundary. The boundaries are between a terminal and a moving satellite, between one operator and another, between an operator and the ITU, and between a live link and a safety obligation in orbit. Phase 1 defined the envelope shapes and Phase 2 exposed them over HTTPS. Phase 3 defines the exchanges that carry those envelopes across trust boundaries. It does this for four protocol families: handover management, frequency coordination, orbital mechanics, and debris mitigation.
Each exchange is wire-level and protected against replay. Envelopes carry a 96-bit nonce, a 300-second clock-skew window, and a 600-second seen-nonce cache. Conjunction warnings are the highest-priority traffic class in the standard, ahead of routine operational messages.
A LEO satellite is visible to a given terminal for only 4–7 minutes, so a terminal's service is a relay race between satellites. The standard gives the visibility window as
t_visible = 2 × arccos(R_e / (R_e + h)) / ωwhere R_e is Earth's radius (6,371 km), h is the satellite altitude (550 km in the reference case), and ω is the satellite's angular velocity. The exact duration within the 4–7 minute range depends on the elevation angle at which the pass occurs. Because the end of every pass is predictable, handover can be planned rather than reacted to.
The standard distinguishes three handover types:
| Type | Frequency | Trigger | Next satellite |
|---|---|---|---|
| Intra-plane | Every 4–7 minutes | Elevation falls below a threshold | Same orbital plane |
| Inter-plane | Every 20–40 minutes | Better SNR available | Different orbital plane |
| Gateway | Variable | Traffic optimisation; satellite switches gateways | Transparent to the user |
The protocol runs in three phases:
The worked trace in the standard shows how these phases map onto envelope traffic between the terminal, the constellation controller, and the two satellites:
T+0 Terminal sees Sat-A above 25° elevation; link active.
T+90s Terminal sees Sat-A descending; predicted handover within 30s.
T+105s Terminal sends handover-request envelope to constellation
controller naming Sat-A (source) and Sat-B (predicted destination).
T+106s Controller acks; Sat-A and Sat-B receive coordinated handover
envelopes with synchronised timestamps.
T+108s Terminal switches its phased array to Sat-B; link continues.
T+109s Sat-A confirms link release; Sat-B confirms link establishment.
Audit envelopes flow to operations dashboard.Two details matter for integrators. The controller sends the two satellites synchronised timestamps, so source and destination agree on the instant of the switch. The release confirmation from Sat-A and the establishment confirmation from Sat-B are separate events, each producing an audit envelope. If a customer later reports a stall, an operations team can see whether the delay was in the request, the controller acknowledgement, the beam switch, or the confirmations. The end-to-end handover latency target is 5 seconds or less. Any handover that exceeds it emits a warning envelope to operations.
The timers in the handover protocol follow from orbital physics, and the standard states the underlying relations explicitly. Circular-orbit velocity and period are
v = √(GM / r)
T = 2π√(r³ / GM)with G = 6.674 × 10⁻¹¹ m³/kg·s², M = 5.972 × 10²⁴ kg, and r = R_e + h. The reference values for the three orbit classes are:
| Orbit | Altitude | Velocity | Period |
|---|---|---|---|
| LEO | 550 km | 7.59 km/s | 95.6 minutes |
| MEO | 8,000 km | 4.84 km/s | 6.0 hours |
| GEO | 35,786 km | 3.07 km/s | 23.93 hours |
A GEO satellite appears nearly stationary and needs no handover. A LEO satellite crosses the sky in minutes, which is why handover, Doppler tracking, and continuous beam steering are central to this phase.
The Doppler shift on the carrier is
Δf = (v / c) × f₀ × cos(θ)where v is the satellite velocity (7.59 km/s for the 550 km case), c is the speed of light (299,792 km/s), f₀ is the carrier frequency (28 GHz in the reference calculation), and θ is the angle between the velocity vector and the user. At maximum alignment:
Δf_max = (7590 / 299792) × 28 × 10⁹ = ±710 kHzA fixed receiver tuned to the nominal carrier would lose the signal at this offset. The standard also gives a Doppler rate of roughly 10–50 kHz/s, so the offset keeps changing during a pass. A terminal therefore cannot correct once and forget. It must track continuously, and it must pre-compute the offset for the next satellite during the measurement phase, so the frequency adjustment at execution time is already known when the beam switches.
The standard describes three deployment patterns that recur among production operators. Each stresses a different part of the protocol layer.
Customers and regulators compare operators using published numbers. Conformant operators release benchmarks quarterly: median round-trip time per region, 95th-percentile RTT, sustained throughput per terminal class, handover success rate, and fade-event MTBF (Mean Time Between Failures). Handover success rate and fade-event MTBF come straight from the Phase 3 protocol events, so the audit envelopes serve as the data source for these market-facing figures.
Spectrum is the shared resource every operator depends on. The standard lists three bands:
| Band | Role | Uplink | Downlink |
|---|---|---|---|
| Ka | Primary for LEO | 27.5–30.0 GHz | 17.7–20.2 GHz |
| Ku | Legacy, GEO | 12.75–13.25 and 13.75–14.5 GHz | 10.7–11.7 and 11.7–12.75 GHz |
| V | Future high-throughput | 47.2–50.2 GHz | 37.5–42.5 GHz |
For Ka-band, user and gateway links use the same ranges: 27.5–30.0 GHz up and 17.7–20.2 GHz down. V-band offers up to 10 GHz of total bandwidth.
Coordination across operators such as Starlink, Kuiper, and OneWeb follows ITU-R conventions. The ITU-R allocates spectrum. The standard defines the envelope that operators exchange with each other and with ITU-R, carrying four things: the operator identity, the requested frequency band, the geographic footprint, and the time window. Because the shape is fixed, a coordination request from one operator can be machine-read by every peer. Coordination can then happen on a timescale of minutes, rather than only through long document cycles.
The long-lead ITU filing steps still apply to new systems:
Interference mitigation combines three techniques:
Spectrum rights are also tied to place. Operators work under FCC (US), Ofcom (UK), MIC (Japan), KCC (Korea), EU member-state regulators, and ITU-R for coordination. The protocol envelopes carry the operator's licensed-jurisdiction set, so a consumer can verify that the service it requests falls inside the permitted jurisdictions before relying on it.
Compliance in this phase is about physical safety in orbit and legal accountability on the ground.
End-of-life disposal. The 25-year rule requires LEO satellites to deorbit within 25 years after end of mission. The standard lists three disposal strategies:
Collision avoidance. Operators screen daily against the TLE catalogue. An alert is raised when the probability of collision exceeds 10⁻⁴, and a maneuver is triggered when miss distance falls below 1 km. The maneuver size follows
ΔV = √(2μ/r) × Δh / (2h)where μ is Earth's gravitational parameter, r is the orbital radius, and Δh is the altitude change, typically 500–1000 m. A conjunction-warning envelope carries the predicted close-approach parameters between two satellites, or between a satellite and a debris object. It is the highest-priority traffic class precisely because the response window is short.
Design for demise. Satellites must also burn up on reentry. The standard calls for aluminium and composites in place of high-melting-point materials such as titanium and inconel. It limits component mass, targeting fewer than 5 kg of surviving components, and requires propellant tanks to be depleted before deorbit to prevent on-orbit explosions.
Records and lawful access. Audit envelopes are replicated across at least two storage backends, with retention sized to the regulatory window:
| Record class | Typical retention |
|---|---|
| Spectrum-coordination records | 5 years |
| Safety-related conjunction-warning records | 10 years |
Jurisdictions that require lawful intercept, such as the US under CALEA, the EU under ETSI ES 201 671, and Korea under its communications-secrecy law, declare the requirement in the discovery document. Sessions there emit a notice envelope at session start. The intercept itself runs through a separate signed channel that audit-logs every access, so lawful access is visible in the record and never silent.
The standard's reference list for this phase includes ISO 24113 (space debris mitigation), CCSDS 502.0-B (Orbital Ephemeris Message), CCSDS 132.0-B (TM Space Data Link Protocol), the ITU-R Radio Regulations, 3GPP NTN specifications, IETF RFC 8446 (TLS 1.3), and IETF RFC 8785 (JSON Canonicalization). An integrator can check a deployment against these using the published conformance suite.
A first implementation follows a staged runbook:
The standard suggests a first deployment that follows this path reaches production in about 90 days. Most of that time goes into audit and compliance work, which is where the effort belongs given how many sovereign boundaries the service crosses. Later deployments into additional jurisdictions reuse the same machinery with per-jurisdiction policy overlays.
Several design points deserve attention early:
Three directions follow from the material in this phase. First, V-band, with up to 10 GHz of total bandwidth, is the standard's named route to higher throughput. Its coordination and interference rules will need the same envelope discipline already used for Ka-band. Second, 3GPP NTN specifications are already in the reference list, which points toward closer alignment between satellite links and cellular architecture. Third, as constellations grow, the daily screening and conjunction-warning loop will carry more traffic and bear more weight in safety terms. The design-for-demise limits and the 25-year rule are the baseline that this growth is measured against.
The commitment that holds across all three is the split described in the standard's closing protocol note. The audit layer favours rigour, covering spectrum coordination, licensing, and debris mitigation. The operational layer favours responsiveness, with sub-5-second handover and minute-scale coordination.
This chapter followed one thread through the Phase 3 protocol layer. A LEO satellite is overhead for only 4–7 minutes, travelling at 7.59 km/s at 550 km. That produces a Doppler offset of up to ±710 kHz at 28 GHz, changing at 10–50 kHz/s. Handover therefore has to be planned in measurement, decision, and execution phases, and completed within a 5-second end-to-end target. The same constellation shares Ka-band spectrum with other operators and with legacy GEO services. It is therefore governed by ITU filing steps, polarisation and beam reuse, and exclusion zones around the GEO arc. It must also be retired safely: deorbit within 25 years, screen daily for conjunctions, and design components to demise. Each of these exchanges has a fixed envelope, so it can be audited. Records are kept for 5 years for spectrum coordination and 10 years for safety-related conjunction warnings.
The next chapter moves from these protocol exchanges to the wider ecosystem of Phase 4. There the same envelopes, handover events, and coordination records connect to other WIA family standards and to the external systems of operators, regulators, and customers.