A satellite may be visible to a phone, but that does not mean the phone can use its signal. The frequency must match the phone's RF hardware, the cellular interface and the spectrum arrangement for that location.
This page focuses on conventional D2C using existing cellular handset capabilities. The main question is how a satellite can use mobile spectrum while sharing the radio environment with terrestrial networks. See D2C versus standardized NTN for the scope distinction.
- Which Spectrum Does the Phone Use ?
- How Do Uplink and Downlink Fit Together ?
- The Feeder Link Uses a Different Radio
- Why Is Terrestrial Coexistence Difficult ?
- Is Lower Frequency Always Better ?
- Spectrum Permission Is Geographical
- What to Record in a D2C Spectrum Plan
- References
Which Spectrum Does the Phone Use ?
The phone uses the service link: the radio path between handset and satellite. In the conventional D2C approach discussed here, that link uses a cellular band already supported by the intended phone.
A terrestrial mobile operator can provide access to spectrum that matches its subscriber devices. That helps with RF compatibility, but it does not automatically authorize satellite transmission. The actual frequency block, geographical rights and satellite authorization must fit together.
Band, Licensed Block and Radio Channel
A band number describes a standardized operating range. An operator may hold only part of that range in a particular area. The network then configures one or more channels inside the usable block.
Level | What it tells us | What it does not establish |
|---|---|---|
Cellular band | Frequency ranges and duplex arrangement supported by a radio specification | Ownership, permission to transmit or service availability |
Licensed / authorized block | Which frequencies may be used under the applicable geographical and operating conditions | The bandwidth allocated to one user's data |
Configured channel | Carrier frequency and nominal channel bandwidth used by the cell | Guaranteed throughput or compatibility with every phone |
So ?the phone supports the band? is only the first check. It still needs the relevant RAT, channel configuration, software support and network access. A band shared by two operators also does not mean their subscribers can use both networks.
Examples of Conventional LTE Bands
The table below gives three familiar FDD bands to illustrate handset frequency compatibility. These are standardized band limits, not a list of satellite allocations or a claim that every D2C operator uses them.
LTE band | Handset transmit / uplink | Handset receive / downlink |
|---|---|---|
2 | 1850-1910 MHz | 1930-1990 MHz |
5 | 824-849 MHz | 869-894 MHz |
8 | 880-915 MHz | 925-960 MHz |
These long-established ranges are in TS 36.101, Table 5.5-1 [1]. The cited edition is used for these band definitions only. It is not a satellite compliance specification or a complete modern band list.
How Do Uplink and Downlink Fit Together ?
In an FDD example, the phone transmits in the uplink part of the band and receives in the downlink part. Moving the access point into space does not reverse the phone's transmit and receive filters.
Worked Example: A Paired 5 MHz Channel
Assume an illustrative Band 2 allocation permits a nominal 5 MHz uplink channel centered at 1872.5 MHz and a paired downlink channel centered at 1952.5 MHz. These are teaching values, not a commercial assignment.
Quantity | Value | Meaning |
|---|---|---|
Uplink nominal channel edges | 1870-1875 MHz | Phone transmits; satellite access system receives |
Downlink nominal channel edges | 1950-1955 MHz | Satellite transmits; phone receives |
Duplex separation | 1952.5 - 1872.5 = 80 MHz | Difference between the two carrier centers |
Paired bandwidth | 2 x 5 MHz | 5 MHz per direction; not a single 10 MHz downlink channel |
Nominal channel edges are not a brick-wall emission boundary. The occupied resource grid, guard regions and emission mask are different concepts. Adjacent-channel protection still matters outside the nominal channel.
Doppler changes the frequency seen at the receiver, but it does not give the network another allocation. Network compensation and receiver tracking must handle that shift while emissions remain compatible with the operating conditions.
What About TDD ?
TDD shares a frequency channel between uplink and downlink at different times. That removes the paired-frequency arrangement, but makes direction switching and timing coordination especially important across the satellite and terrestrial paths.
A distant signal can still be arriving while a local system has switched direction. The resulting transmitter-to-receiver interference must be evaluated with propagation delay included. A handset supporting a terrestrial TDD band does not by itself prove that a satellite deployment is feasible in that band.
The Feeder Link Uses a Different Radio
The satellite-to-gateway link is not the phone's radio link. A gateway can use a large directional antenna and a different frequency range, while the phone continues to use its supported cellular band.
For example, a published 2022 system description proposed Q/V-band feeder links to ground gateways alongside mobile-operator spectrum for handset access [2]. That is a dated architecture example, not a universal feeder-band choice.
The phone does not need a Q/V-band receiver to use such a system. The satellite payload connects the two radio paths through its relay or onboard processing arrangement. Likewise, an optical inter-satellite link is transport inside the space network; it does not change the handset's cellular band.
When someone quotes a satellite's total spectrum bandwidth, ask which link it describes. A wide feeder channel cannot make a narrow service-link channel carry unlimited traffic. Multiple beams may reuse service-link frequencies, but each reuse needs sufficient spatial isolation. See D2C Architecture for the processing and transport paths.
Why Is Terrestrial Coexistence Difficult ?
A satellite beam can illuminate a large area containing both a coverage gap and working terrestrial cells. The intended D2C user may have no tower signal, while another receiver nearby still needs protection.
The diagram below shows the desired link into a coverage gap and unwanted illumination toward a terrestrial service area. The boundary marks an authorization area, not a physical wall that stops the radio signal.
Figure 1 : A coverage gap at one phone does not make the surrounding spectrum empty
Co-Channel and Adjacent-Channel Interference
Co-channel interference occurs when another signal uses overlapping frequencies. On downlink, a terrestrial phone can receive unwanted satellite energy. On uplink, a satellite receiver can also collect transmissions from terrestrial users over a wide area.
Adjacent-channel interference concerns energy leaking into a neighboring channel and the victim receiver's ability to reject it. Good transmitter filtering helps, but receiver selectivity and strong nearby signals also affect the result.
Spatial separation, beam shaping, power control and coordinated frequency use are tools for managing these problems. None creates a perfect beam edge. A design must include sidelobes, overlap and the aggregate contribution from multiple transmitters.
A Simple Interference Example
Suppose a receiver gets its desired signal at -110 dBm, with noise at -115 dBm. Its SNR is 5 dB. Now add one co-channel interferer at -112 dBm.
Relative to the noise, the interference is 3 dB stronger, or about twice the power. Noise plus interference is therefore about three times the noise power: -115 + 10 log10(3) = -110.23 dBm. The resulting SINR is only about 0.23 dB.
This illustrative calculation shows why a link can have sufficient received signal power and still perform poorly. Powers must be added in linear units; adding -115 dBm and -112 dBm directly would be incorrect.
Is Lower Frequency Always Better ?
At equal distance and equal antenna gains, free-space path loss increases with frequency. Comparing 850 MHz with 1900 MHz gives 20 log10(1900/850), or about 7 dB more loss at 1900 MHz.
But equal antenna gain is an assumption. For a fixed physical satellite aperture and comparable efficiency, gain increases with frequency. Beamwidth, handset antenna efficiency, available channel bandwidth and interference also change the comparison.
A lower-frequency band therefore does not automatically give the best system capacity. A larger footprint may serve more land while sharing its resources among more users. A higher-frequency design may form narrower beams, but still has to close the handset uplink and handle the required coverage geometry.
Compare complete uplink and downlink budgets with the actual antenna assumptions. Also compare the usable licensed bandwidth, rather than the total width of the standardized band. D2C Technology explains the associated antenna and link constraints.
Spectrum Permission Is Geographical
A cellular band definition is an engineering specification, not permission to operate a satellite service. The applicable authorization connects frequencies, service areas, operators and technical conditions. A satellite footprint may cross several such areas.
As a concrete example, Canada's SMCS decision ties service to the bands and areas in the SMCS agreement and the mobile provider's valid licences. It also specifies a no-interference, no-protection basis and mitigation obligations [3]. These are Canadian framework conditions, not a worldwide rule.
A UK example shows why handset permission and operator authorization should be distinguished. Ofcom's June 2026 statement describes a device licence-exemption amendment for specified 900 MHz frequencies, following a separate operator licence variation [4].
These dated examples were reviewed on 5 November 2026. They illustrate the structure of authorization; a band appearing here does not establish permission for a particular commercial service. For a deployment, identify the applicable grant and its frequency, geographical and interference conditions.
What to Record in a D2C Spectrum Plan
A useful spectrum plan should let another engineer trace the phone's radio channel through the network and identify which receivers need protection. Record these values for each service area, not just for the constellation as a whole.
- Handset interface: RAT, band, duplex mode and supported device configuration.
- Service-link channel: uplink/downlink center frequencies, nominal bandwidth and usable resource allocation.
- Spectrum rights: relevant operators, frequency blocks, service areas and authorization conditions.
- Coexistence: terrestrial users, neighboring channels, beam overlap, sidelobes and border constraints.
- Transport: feeder-link bands and optional inter-satellite links, kept separate from handset spectrum.
- Evidence: licence or grant identifier, configuration date and measurement conditions.
References
- [1] 3GPP TS 36.101 V8.10.0 : Table 5.5-1; established LTE band definitions used in the examples.
- [2] 2022 Annual Report : AST SpaceMobile; dated service-link and Q/V-band feeder-link architecture description.
- [3] Decision on a Policy, Licensing and Technical Framework for Supplemental Mobile Coverage by Satellite : ISED; service-area, agreement and interference conditions.
- [4] Direct to Device licence exemption regulations update, June 2026 : Ofcom; specified 900 MHz device exemption and relationship to operator licence variation.