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Find the answers to some of the most common questions we receive at GateHouse SatCom.

About GateHouse SatCom

What is our business?

We at GateHouse SatCom are a software only company, and don´t offer any hardware related products. More than 15 different software solutions for space connectivity have been developed by us. Currently, we are developing the bi-directional 5G NB-IoT NTN software (the NodeB), which will be compliant to the 3GPP standard. It can be used in satellite systems for GSO / MEO / LEO satellites, user terminals, and ground infrastructure, supporting up- and downlink. 5G Broadband software (New Radio), as well as Inter Satellite Links are on our roadmap as well.

Besides being software developers, we are doing feasibility studies (consultancy services), to help our customers (space companies) understanding how they can approach 5G NB-IoT for their satellite system.

Who are our customers?

For the 5G NB-IoT software (the NodeB), our main customers are satellite operators, who wish to bring 5G NB-IoT connectivity services into their portfolio. Besides the standard software development, we are always eager to develop proprietary space software as well (e.g. for military projects).

We also help ground infrastructure providers to understand how they can support 5G NB-IoT for space.

Has GateHouse completed any live OTA trials of NTN NB-IoT in LEO/GEO?

GateHouse is developing a waveform for NB-IoT and we have successfully sent NB-IoT synchronization signals on a 800MHz carrier to a GEO satellite from the ground back in 2021.

Would GateHouse engage in exclusivity agreements?

In principle no as GateHouse delivers products horizontal to the market. GateHouse acknowledges that some customers are developing specialized solutions and may on exceptional basis agree to a limited exclusivity for a specified market or technology.

Do you provide connectivity services to private users?

No. We are a software development company, developing software protocols for businesses (e.g. satellite operators), who can use the software to offer connectivity services.

Are you recruiting people from telecom domain or only from satcom?

Yes, we recruit from telecom as well. We currently have several open job listings on our website. The engineering and management teams at GateHouse are very diverse, not only having extensive experience in the domains of telecom and satcom, but they are also industry leaders in specific technical areas, such as eNodeB, gNodeB, waveforms and system architecture within the non-terrestrial network technology area. The majority of the team holds a Master´s Degree, while other colleagues have a PHD background specialized in telecom or satcom.

Would GateHouse invest in customer projects or companies?

Yes indeed, GateHouse aims for business models where success reflects on both our customers and GateHouse.

5G Non-Terrestrial Networks

What does the expected market for 5G NB-IoT look like – what are use cases?

The 5G NB-IoT NTN market is expected to be in the area of half a billion of connected devices. These NTN services are expected in all verticals, which include IoT devices which send small amounts of data and that need connectivity even in the remotest areas.

The need for 5G NB-IoT NTN can range from public services verticals (e.g. rescue), to logistics, agriculture, oil and gas or mining.​

Conrete use cases could be for example​ (1) emergency cars entering remote areas, which still need to communicate with the hospital​, (2) connected cars, or logistics on land, telling you when a container would arrive​, (3) IoT sensors in a farm, measuring fertilizer levels and thereby ensuring a smart supply chain​, or (4) sensors to monitor oil pipelines and continuously send small amounts of data for control.

When will the 5G NB-IoT standard be available?

According to the standardization group´s timeline, the complete 5G NB-IoT standard will be commercially available by the beginning of 2024 (for Rel. 18 – regenerative mode). Rel.17 (transparent mode) will already be commercially available by mid-2022.

Should you wait with looking into 5G NB-IoT, until the standard is commercially available?

It all depends on your business strategy. If the IoT market, especially with devices that only send small amounts of data (Narrowband-IoT) could be an interesting asset to your service portfolio, we recommend lookng into 5G NB-IoT already today.

The reason for this is that it takes some time until you have analyzed your system set-up – to understand any requirements or changes (e.g. for designing a new satellite fleet, or how to adjust your current ones) that you need to realize your 5G strategy.

We recommend starting with this today, to make sure you are ready, once the 5G market takes off. We will be happy to support you with your system assessment.

How do we help satellite operators realize their 5G strategy?

We help satellite operators understand if and how their system set-up can support 5G NB-IoT, with our background in satcom software and integration knowledge. Because our goal is to make our customer´s 5G strategy a success.

We do this by jointly designing an individual pre-assessment or feasibility study based on the operator´s individual needs and system set-up. The goal is to verify the viability of supporting 5G NB-IoT, and to calculate the system capacity and business case for example.

For this, we bring in our expertise for simulations of the link budget, and the assessment of the system capabilities. Pilot projects are also on our agenda, with the goal to develop a commercial 5G NB-IoT system for satellite operators.

How can I as a ground station infrastructure provider support 5G NB-IoT services for satellites?

Your ground station infrastructure needs edge computing capabilities to support 5G. For more details, please reach out to us.

When is the 5G NB-IoT waveform (NodeB) ready?

We are developing the 5G NB-IoT software as part of the official 3GPP standardization group. This means that the NodeB will be commercially available adhering to the standardization´s timeline. This is the beginning of 2024 (for Rel. 18 – for regenerative mode). Rel.17 (transparent mode) will already be commercially available by Mid 2022.

To be ready when 5G NB-IoT kicks off officially, we recommend reviewing your system set-up and satellite fleet already today. We will be happy to guide you through that.

How does your software differ from what other players are doing within 5G NB-IoT?

GateHouse has a long history developing protocols for the SatCom industry, and we have a vast experience with the complexities that communication via satellite connectivity includes.

We are part of the 3GPP standardization group developing the 5G standards and we bring our understanding of satellite connectivity to the 3GPP work.

GateHouse also offers assessments of future 5G satellite systems for Satellite Service providers to help push 5G technology to the market.

What projects and studies have you done for satellite 5G NB-IoT?

We are contributing to the 3GPP standardization group as an active member. ESA projects, together with other NTN players, are another important success ingredient for us.

We have conducted lab- and In-Orbit-demonstrations (IoD) for LEO satellites, and have a planned GSO IoD with ESA and another LEO IoD early 2022.

When will terminals be available? / Are there indications for market adoption? Do you know if UE modem manufacturers already announced chips that support Rep-17 for NTN use cases?

With 3GPP Release 17 standards for development of user terminals are available. Several enterprises in user terminal supply chain like GateHouse SatCom have been active in the standardization work and are quite advanced in their product offerings. However, the exact timing will be balanced with demand and priorities. And of course the availability of satellite networks supporting the release 17 Non-terrestrial services. GateHouse SatCom is not aware of any chipsets currently supporting 3GPP Release 17 NTN services.

When do you recommend starting looking into 5G?

With Rel-17´s protocol coding freeze in June this year, we recommend looking into 5G as soon as possible. Based on this timeline, software protocols for the UE and the satellite side will be available for first lab tests and proof of concepts shortly thereafter, until they are expected to be commercially available in Mid 23. We recommend using the time until then, to understand your system set-up and requirements, and the time for testing and proofing the concept within your infrastructure, so that you are ready when Rel-17 can be implemented into commercial systems.

What devices are required to adopt the system and what is the cost?

It is expected that standard, off-the-shelf chipsets will be used, alongside with standard NB-IoT supporting devices which we know from terrestrial networks today. The 5G NB-IoT for space needs to be able to run on them, which will be enabled by supporting chipsets. As we are not a chipset company, we cannot say anything in regards to the costs. But similar costs to TN supporting chipsets are expected.

When can we expect commercial devices rollout for direct satellite communication?

With Rel-17 being frozen this June, UE software will be commercially available shortly thereafter. Then it depends on chipset companies to have chipsets supporting non-terrestrial networks. Adaptations are not expected to be major, but they need to be done. And the question is when chipset companies see a market in the 5G NB-IoT NTN technology. We expect that it is only a matter of time, as companies are publishing trials as we speak.

Which use cases for 5G NB-IoT would work best for GEO vs non-GEO sats?

The use-case would be delay-tolerant applications for both LEO and GEO and GEO has the advantage of providing terrestrial-like cells while LEO has the advantage of providing global (discontinuous) coverage and a lower propagation delay. It is cheaper to launch satellites into LEO than GEO, so typically a GEO payload can be more expensive and justify an increased power budget compared to LEO satellite payloads. The new space-race with cube-sats is especially allowing for low-cost LEO payloads to be launched.

Can your simulator be used by cellular operators to find out which satellite gives good coverage and capacity in a specific location?

The feasibility study allows for ascertaining system level KPIs (Sytem capacity, UE QoS (Throughput, latency) and UE energy consumption. This is done on the basis of the scenario definition – so it is indeed possible to define a specific geographic area, say the Himalayas and ascertain the performance of a Cell or a UE in that location.

What is the upcoming 3GPP 5G NB-IoT standard about?

The standardization group 3GPP is known for standardization especially in the mobile industry, with technologies such as 2G, 3G, 4G and now 5G. With 5G, the 3GPP group will include standardized satellite protocols as something new. This is, when implemented, quite ground breaking for the satellite industry, as this market has historically been characterized by proprietary systems.

One impact of this will be that connectivity can be offered even in the most remote areas, where terrestrial connectivity is not available today, but with hybrid networks expected to take over. This means that IoT devices will be able to switch between terrestrial and non-terrestrial connectivity, to have constant connectivity.

Due to being a standard with mass market volume, the costs for connectivity are expected to drastrically go down. Satellite connectivity will not keep the same prices as today. With this merge of mobile and satcom industry taking place, a new world will open up with endless new opportunities.

How will LEO satellites work with Rel-17?

3GPP Release 17 supports Non-Terrestrial connectivity using, for example, satellites in transparent mode. While connected in transparent mode, both service and feeder link must be active simultaneously to obtain service. Signals are mirrored by the satellite between user terminal and ground station. In the case of LEO satellites, connectivity to a ground station must be established before service can be provided to user terminals. Hence, connectivity is provided while the satellite is visible.

How can we be sure that our GEO system will be able to run Rel-17 compliant services?

Being able to support 5G NB-IoT services with a GEO system depends on various factors, all going back to your system infrastructure and set-up (e.g what bands you are operating on, what capacity you have, what user devices, which antennas are required, etc.). We can help you in generating a neutral, third party answer to this, with our 3GPP and NTN expertise we apply when developing the software for those systems. More specifically, we can help you in answering this question, by designing an individual pre-assessment or feasibility study based on your individual needs and system set-up. The goal is to verify the viability of supporting 5G NB-IoT, and to calculate the system capacity and business case, for example.

For this, we bring in our expertise for simulations of the link budget, and the assessment of the system capabilities. Pilot projects (lab tests, proof of concepts, and in orbit demonstrations) are also on our agenda, with the goal to pave your way to a commercial 5G NB-IoT NTN system.

Are 3GPP going to implement and approve DVB-S into 5G NR?

GateHouse SatCom has no insight into future evolutions of 5G. Changes and additions to the standards are agreed upon between contributing participants. In some backhauling solutions DVB-S is used over the satellite link to connect remote NodeB to the Core Network.

How complex is the integration of Cellular Core with Satellite core? 5G NR is still not deployed in different geographies, do you have any comments on this?

GateHouse SatCom is building NodeB to be integrated in Satellite networks in three different scenarios:

1) on the ground supporting transparent mode,

2) in the satellite supporting in-orbit processing and regenerative mode, and

3) at the remote side supporting backhauling of 5G services establishing a remote cell.

We are working with suppliers of LTE and 5G Core Network, but unfortunately we have no insight into the complexity of integrating a Cellular Core into a Satellite Core.

There are already existing satellite core networks build on 3G and 4G cell core networks offering mobile data services.

What has GHS / 3GPP done to minimize signaling overhead?

NB-IoT is a LPWAN, that is a low power wide area networks, such protocols are optimized for long-range transmissions of small data packets. Thus NB-IoT already has comparatively little signaling overhead compared to other protocols (which is why the feature set is also minimized). Further, GH is implementing DoNAS in it’s waveform and it is already implemented in the analysis.

Are there standardized models for fading simulation made by 3GPP as well?

Yes, 3GPP has standardized CDL and TDL fading models for NTN based on the “IST winner II” model.

How does the 5G NB-IoT software protocol differ for NGSO and GSO satellites?

Major differences are on the satellites´ infrastructure. One example is the different location of the NodeB functionality.

For help in assessing how your satellite system set-up can support 5G NB-IoT connectivity, please do contact us.

Is 5G NB-IoT not more suitable for NGSOs than GSOs?

The 5G NTN standard is working with two different satellite configurations – the 1) Transparent mode, and 2) Regenerative mode.

The 3GPP 5G standardization group has started with the specification of the transparent mode in Rel-17, where the regenerative mode is planned for future releases. The transparent mode fits to both GEO and NGSO satellites.

The standard also looks into the supported frequencies. E.g. the higher the frequency, the more challenges are expected for the performance, as the frequency influences the antenna size. If you want to assess how your satellite set-up is suitable for supporting 5G NB-IoT, please contact us.

In what frequencies does NTN 5G NB-IoT operate?

Even though current operational satellite frequency bands can be used, from 3GPP directive, the S-band (2-4 GHz) is set as an exemplary band.

That´s why we are currently developing the software with L- and S-band reference. However, with Ka and Ku band present in many traditional GSO satellites, we are also looking into this case. The higher frequencies will require a bigger antenna. We will be happy to support you with understanding and assessing exact requirements and potential use cases.

What link budget is anticipated for NTN NB-IoT?

There will often be direct line-of-sight between satellite and device but the Free-Space-Path-Loss for NTN NB-IoT is higher, due to longer distance. The link budget is calculated separately for up- and downlink. Uplink is favored by the use of single-tone transmission which theoretically adds up to 17 dB gain. Antennas on GSO satellites are typically having a large gain (around 50 dBi) while it is less for LEO satellites. This results in LEO and GSO link-budgets with comparable dB ranges. Calculation on a small-sat LEO case indicates that SNR range for downlink is -5 to 0 dB while for uplink it is -2 to 3 dB (depending on elevation angle and distance between the device and satellite).

What latency level is anticipated with GSO and LEO satellites?

With GSO satellites positioned stationary at 36.000 km from Earth propagation delays up to 541 ms will occur. Comparably for a scenario with a LEO satellite on 600 km distance, this will vary between 4-26 ms depending on the position of the satellite in relation to the device for regenerative systems. For transparent systems, as focused on in 3GPP Rel-17, the LEO propagation delay is doubled (8-52 ms).

How is Doppler effect handled with NB-IoT and non stationary satellites (NGSO)?

Since NGSO satellites (e.g. LEO or MEO satellites) are moving around the earth at very high speeds (can be as fast as 28.000 km/hour), transmission signals are influenced by the Doppler-effect. Mathematical algorithms are helping to reconstruct the transmission signaling by taking into account the (moving) positions of the satellite and device. For this GNSS position information of the satellite will be transmitted within System Information Broadcast messages. The device’s location can either be fixed configured or retrieved via an embedded GNSS module. By doing this, the original signal can be recovered and the uplink transmission can be pre-compensated at the device side.

Will there be a seamless satellite handover in a LEO or GSO scenario?

Devices can stay connected to the same GSO satellite, since the satellite is stationary. LEO satellites are moving in relation to earth, and devices will need to continue reselecting different satellites. Otherwise, connection gaps will be experienced. As NB-IoT currently does not support Handover procedures, a message transfer will need to finish during the pass of a single satellite.

How will the network be managed between satellite operators on the non-terrestrial network side (NTN) and the Mobile Network Operators (MNOs) on the terrestrial network (TN) side?

The expected end-vision of the 5G standardization foresees connectivity provision handled by MNOs. This would mean that IoT customers who need connectivity for their IoT terminals, would approach their local MNO, who offers connectivity for dual mode networks (meaning terrestrial and non-terrestrial connectivity – TN and NTN). In this case, the satellite operator would have an agreement with the MNO. Until the standardization has evolved to this point, we expect satellite operators to offer 5G network directly to their customers, with the MNO brought in case by case.

Will there be spectrum / frequency available in my country?

5G NB-IoT connectivity for NTN and TN networks is expected to be a global standard. Please approach your local ITU, to obtain and apply for spectrum allocation.

What antenna is required for an NTN 5G NB-IoT device?

It is desirable and possible to use the same kind of omnidirectional antennas which are used in terrestrial IoT devices. To compensate for the low device antenna gain, the satellite shall be equipped with a directional antenna with a higher gain. It will still be beneficial and possible for some devices to use a higher gain antenna to obtain a better link-budget.

Which chipsets are expected for TN/NTN dualmode 5G NB-IoT operations?

To support NTN 5G NB-IoT connectivity, common chipsets that can support multiple access technologies, as well control carriers on multiple frequencies, are expected to be used.

For LEO satellites, the chipsets will need to be able to control the timing and frequency drifting, caused by the varying time delay and Doppler due to the satellite’s motion.

How will the regenerative mode help out on LEO networks?

Compared to the transparent mode (Rel-17), the regenerative mode will include enhancements and optimizations for NGSO satellite systems, considering the moving of the non-Geostationary satellites, enabling efficient blind search of user devices, etc. The regenerative will enable UEs to communicate with the NodeB even when a feeder link is not active, and makes communication everywhere on the globe possible. In the regenerative mode, the NodeB will be located on the satellites themselves.

What are your thoughts on power consumption and Line of Sight going to affect hybrid connectivity?

The 3GPP standards specify multimode user terminals that are capable of obtaining service without modifications on both terrestrial and non-terrestrial networks. Tests have been conducted with hardware conforming to earlier releases where only software was modified to obtain service. Hence, power consumption is expected to be equal to previous releases for user terminals working in hybrid mode. To close the link budget user terminals are expected to have line of sight visibility to satellites when used on satellite based networks.

Can you comment on the solutions to the synchronization in the presence of Dopper spread also considering the relatively short satellite visibility time?

With help of the NPSS, NSSS and NRS, a signal can be detected, and during the decoding of it, the frequency offset can be determined. That this frequency offset can be very high, and becomes lower the closer the satellite comes to the UE can be calculated and resolved by the processing algorithm.

Will it be possible to use the satellites for data transmission in connected mode or is connectivity restricted to disconnected mode vie the random access procedure?

There are no changes to the protocol or services available under 3GPP release 17 for non-terrestrial networks. A PDP Context can be established and maintained for data transmission as for terrestrial networks. Hence it is not needed to apply the random access procedure as long as the connection is not broken. For NGSO communication, the transmission will be likely a few minutes, and for GEO transmission the context can be kept longer active.

Will there be issues with the use of transparent mode in NGSO systems?

We see two issues with the use of transparent mode in NGSO systems. 1) As the satellites are only visible from both ground station and user terminals in a relatively short time period it is only possible to obtain service in smaller time intervals. 2) Since ground stations must be located in the same satellite footprint as the user terminals there will be large parts of the earth surface like the oceans where is not possible to obtain services.

The 5G handover from one to the next overflying satellite, is this not something ground users uplinking/downlinking signals needs to handle (maybe by having the 2nd link up before the 1st one is lost)?

Handover of traffic connections resulting from moving NGSO satellites is not supported in release 17 and in transparent mode there is no on-board processing. The procedure and algorithms for handover currently implemented in standard compliant user terminals will not be able to support setting up a 2nd link for handover of the traffic. We expect this to come as part of one of the following releases.

Can you explain the difference between 5G NTN and 6G?

6G will be an evolution of 5G. 6G has not been defined and is expected to incorporate even more of the NTN capabilities. The first 3GPP release that will  incorporate 6G is expected with release 21 in 2029.

How do you know that your models are performing / simulating “real-life-scenarios”?

In essence, the realism of the feasibility study depends on the configuration of the scenario (input parameters) and the results are generally approximation, worst/best-case results and where applicable they have been compared to similar SoTA results. All modelling is an attempt to deconstruct or approximate reality in a way that we can more easily deal with. In our feasibility-study we have divided the RAN (radio access network) in three major parts the fading channel, the link-level and the system level. We can develop fading channels based on Ray-tracing, which will be very realistic or use a more abstract/generalized model – or 3GPP standardized models depending on choice. On the Link-level we do extensive monte-carlo simulations to find the link performance given the chosen fading model. On the system level we have rigorous analytical models, which account for many protocol aspects and signaling overheads (e.g. the various message sequences) – and this level relies on the realism of the two layers below.

On what frequency band are your simulations derived?

The carrier frequency (band of operation) is a parameter for the configuration of the feasibility study. In general the frequency will change the link budget and the Doppler characteristics.

What bandwidth can be reached (in bits per second)?

The peak throughput is a bit less than for terrestrial NB-IoT around 258 kbits/s in PDSCH(DL) and the same in PUSCH(UL) at the link-level without accounting for propagation time. In reality the obtainable throughput will depend heavily on the link-budget throughout the cell and this is a function of the satellite payload. In our feasibility study we can take this evaluation one step further to account for overhead in terms of static signaling and the dynamic message exchanges (an application payload is embedded in a larger message exchange, eg. RA+)

Does the beam center move with the satellite movement in NGSO or does it “track” the location of the NB-IOT devices in FOV?

There are two scenarios defined by 3GPP in the NGSO case: 1) Earth-fixed cells, where an NGSO satellite steers its beams such that the cell projected on the ground does not move and 2) Earth-moving cells, where an NGSO satellite has a fixed beam direction, such that the cell moves around with the satellite.

Why is this based on 5G? Is there a technical limitation that prevented this NB-IoT to work with 4G standards?

5G is a set of requirements for networks – as was 4G. In 5G one of the targeted use-cases is massive machine type communications (mMTC). The requirement for a 5G mMTC technology is that it must be able to service 1 million devices per km2 sending 32bytes of L2 data every 2 hr. After the requirements had been set, the development of the new technologies for 5G started. It was quickly found that NB-IoT and eMTC were sufficient for this requirement (terrestrially) given enough channels. Therefore these radio access networks are 5G compliant and hence now called 5G. In the backbone of the network there is a core network, here the 5G variant is called 5GC (5G core) and the 4G variant is called EPC (evolved packet core). Even though the RAN remains largely the same (but has developed over the 3GPP releases) there are some differences in base-station depending on whether it is interfacing with 5GC or EPC.

Have you done any study concerning potential interference between terrestrial component and NTN component within the same network?

We have not studied interference between TN and NTN. The networks should be separated in frequency with appropriate guard bands handling Doppler shift in the NGSO case. The bands and channels allocated for NTN and TN are being determined by standardization organizations like ITU, 3GPP and ETSI. As a general rule you can count on interference not being allowed.

Is it possible to emulate 5G NB-IoT network links?

Yes, real life testing w. in-orbit emulator.

How is system coping w. finding satellites when both devices and sats are moving?

3GPP has defined functionality wrt. the channel raster such that UEs will always be able to look for, find and appropriately identify any available channel. The trick is to find an available cell by searching for that particular channel while in coverage of a serving satellite. This can be helped by satellite assistance information, which is a feature that is expected to be settled and included n Rel-17.

How are your simulations handling dynamics of moving sats?

In the case of a GEO sat the cell will have a static link-budget and the elevation angle toward the satellite does not vary throughout the cell. In the case of NGSO earth-fixed cell, the cell has a fixed position and so would a stationary UE within it, but the link-budget and elevation angles are dynamic and change overt time, so we compute these for a satellite pass. In case of a earth-moving cell NGSO we have a cell which moves within the cell the linkbudget and elevation angles are static, but the cell moves over the UE. This is equivalent to a UE travelling within a GEU cell (at approximately 7.3km/s or so 🙂 )

Does 5G NB-IoT work on Ka/Ku band?

Rel-17 will work on the S-band, but preliminary work has already been started on the Ka-band. It is likely that higher bands will be supported in future releases. The higher frequencies are a source of wider spectrum/bandwidth for the NTN networks, but there are major challenges involved with higher frequencies – in particular dealing with the increased signal propagation. It could very well be unfeasible to launch ka/Ku band on cubesat payloads due to the limited power budget.

Apart from UEs and satlinks, is there any need for ground infrastructure to establish 5G IoT communication?

Indeed, the radio access network (RAN) NB-IoT, LTE, LoRaWAN, etc. are just the communication link between UEs and satellites. To make this link useful a link to the core-network on earth should be established. This latter link is known as the feeder link in SatCom terminology and is established between the satellite and large ground-stations. The service link must provide sufficient capacity for the cumulative RAN information (and then some other telemetry) to be exchanged which is why ground-station typically have large steerable antennas and a large transmission power.

What are considerations for latency for IoT use case?

The latency in NTN is larger than in terrestrial networks due to the larger propagation delay. In some satellite constellations coverage can not be provided continuously on the ground either. So IoT devices for NTN must be delay tolerant.

Are there any satellite crosslink capabilities providing global Satcom coverage vice just connectivity within one satellite footprint?

Yes, inter-satellite links (ISL) can be used for networking and routing between satellites. However in Rel-17 the focus has been on bent-pipe satellite payloads, i.e.. satellites that act as relays where the ground-station is the actual base-station – so first the focus in a future release needs to switch to regenerative payloads i.e.. base-stations onboard the satellite – and then to ISL later. Nothing hinders ISL at them moment – it is just not standardized.

What are the typical messages lengths (in kilobytes) that can be sent and received via satellite NB-IoT? Does it compare with cellular NB-IoT?

The transport block sizes in NTN NB-IoT are the same as in NB-IoT so the difference is in the fading model and the link budget. Provided that the link budget of a satellite payload is comparable to that of a satellite cell the typical message lengths will be comparable between TN and NTN. Basically, you should in most cases be able to expect TN-like performance if the satellite payload is well designed.

How does the signaling overhead compare for the satellite assistance SIB in LEO vs GEO configurations?

In short, GEO will have little overhead while NGSO and especially LEO will see more overhead, but we expect at most a few percent overhead on the anchor channel. Two SIBs are defined for NTN IoT, the first being for uplink synchronization and the second (to be defined in May) is for helping UEs to predict coverage in discontinuous coverage scenarios, to better enable mobile originating (MO)-traffic. The fist SIB has a fixed size regardless of the use-case, but in LEO it may be necessary to transmit for example once per second (but this will depend on the Orbit, satellite payload GNSS and the band of interest) where in GEO a UE need only receive it once. Overall this SIB should at most take up a few percent of the anchor channel. The SIB for satellite assistance information (SAI) is not defined yet, but we expect it to be of a variable size with plenty of optional parameters. This SIB-SAI is optional and should not be an overhead in GEO. SIB SAI should be expected as overhead in discontinuous NGSO only. The SIB SAI need only be received by UEs once, but the overhead here will again be larger for LEO where the satellite will move faster – a rate of once per 5 or 10 sec should be feasible.

Do you apply beamforming in reception? If yes how do you keep beams in the right direction elevation and azimuth?

In NTN IoT the goal is to reuse the hardware platforms of terrestrial cellular. So the UEs are essentially similar to handheld devices with an omnidirectional antenna. Beamforming may be applied from the satellite site to orient the beam towards a specific geolocation for the ‘earth-fixed cell’ scenario.

What are the currently considered strategies for dealing with the Doppler drift in the NGSO setting? Are UE supposed to precompensate the Doppler?

Yes, in Rel-17 the UE will handle the compensation. In the downlink the UE will synchronize to the Doppler shifted NPSS/NSSS signals as usual, it will then decode an ephemeris (a description of the serving satellite’s orbit accurate for a moment, say 1 sec) which will allow the UE to precompensate for the Doppler effect when it transmits in the uplink direction (RACH/PUSCH). This will be the way for NTN IoT (NB-IoT and eMTC) and also NTN NR.

Is there a difference between cell size and beam size?

Yes, a ‘beam’ refers to the RF or ‘physical’ power from the TX side, which is a continuous function. A ‘cell’ is a logical entity on the RX side in a cellular network and is determined as an area within the ‘beam’ where certain criteria are met: Synchronization and SNR above threshold.

Can ray tracing be done for different areas, mountains, ocean, desert?

Yes, ray tracing can be done for different terrain and geographic locations. We can also create specific scenarios or use 3GPP fading models.