GB2630975A

GB2630975A - Coexistence of terrestrial and non-terrestrial cellular radio access networks

Info

Publication number: GB2630975A
Application number: GB2309009.5A
Authority: GB
Inventors: Lister David; Chesmer Rowan
Original assignee: Vodafone Group Services Ltd
Current assignee: Vodafone Group Services Ltd
Priority date: 2023-06-16
Filing date: 2023-06-16
Publication date: 2024-12-18
Anticipated expiration: 2043-06-16
Also published as: GB2630975B; WO2024256796A1

Abstract

Non-terrestrial cellular wireless communication networks may be provided in areas with no (or limited) conventional terrestrial network coverage, using satellite or High Altitude Platforms (HAP) operating in radio frequency bands allocated for the Mobile Satellite Service (MSS); however, these are limited in power and bandwidth. Terrestrial and non-terrestrial cellular Radio Access Networks (RAN) may coexist, and the ITU (International Telecommunications Union) has allocated certain frequency bands as shared between Mobile Satellite Service (MSS) and terrestrial mobile telecommunications. Configuring network stations for effective use of coexisting terrestrial and non-terrestrial Radio Access Networks (RAN) having shared frequency bands, whereby: the network station is operated based on a cell of the terrestrial cellular RAN using a first uplink frequency in a non-shared radio frequency band and a first downlink frequency in a non-shared radio frequency band; and then configured such that a User Equipment (UE), receiving service from the cell of the terrestrial cellular RAN, is provided a secondary downlink from the cell of the terrestrial cellular RAN using a second downlink frequency in the radio frequency band that is shared with the non-terrestrial cellular RAN. The provision of a secondary downlink in the terrestrial RAN cell, using a shared downlink frequency band, facilitates coexistence of the terrestrial and non-terrestrial RANs by providing for restriction of interference from the terrestrial to the non-terrestrial RAN.

Description

Coexistence of Terrestrial and Non-Terrestrial Cellular Radio Access Networks

Technical Field of the Disclosure

The present disclosure is concerned with configuring a network station to operate with a terrestrial cellular Radio Access Network (RAN) using a radio frequency band that is shared with a non-terrestrial cellular RAN. A network station so-configured is also considered.

Background to the Disclosure

Cellular wireless communication networks provide wide geographical coverage by allowing user (mobile) terminals or User Equipment (UE) to access the network through a Radio Access Network (RAN) formed of cells, each cell having a specific geographical coverage area. In this context, a cell refers to a base station (RAN access node) having a cell identifier (Cell ID), for example as used in Third Generation Partnership Project (3GPP) standards. Coverage areas of cells may overlap and this may assist to avoid areas without coverage. Nevertheless, there are still certain areas without cellular wireless network coverage, for example where the deployment of cells is hazardous, difficult, costly or a combination of these. This may particularly occur in rural areas and developing countries.

Conventional cellular networks have been terrestrial (that is, with access nodes located on the Earth's surface). Non-terrestrial cellular networks have been proposed more recently, for example using an aerial platform or a High Altitude Platform (HAP) or satellite to provide cells. This allows coverage on the ground as it would be by a typical (terrestrial) Mobile Network Operator (MNO) site, allowing access by the same user or mobile terminals supporting this RAN in the terrestrial networks, in particular using 4G or 5G. In this context, a satellite could be considered a type of HAP and, for the purposes of this disclosure, the term HAP could include any type of aerial and/or radio platform, typically operating above 20km in altitude and possibly at a specified, nominal, fixed point relative to the Earth. A RAN provided by an aerial platform, HAP or satellite infrastructure involves complexities.

Referring first to Figure 1, there is shown a schematic architecture for an exemplary non-terrestrial cellular RAN, in this case provided through a satellite 10. The satellite 10 acts as a repeater between a baseband system 30 and the end users (for example, any SIM-based devices including mobile terminals, not shown). The baseband system 30 generates radio signals for transmission by the satellite 10 and also processes baseband signals received by the satellite 10. Thus, the baseband system 30 provides lower level base station functions (and may be virtualized or non-virtualized) and transmits one or more intermediate signals to the satellite 10. Each intermediate signal represents a baseband carrier signal for a respective cell, each carrier signal having a respective bandwidth. These are provided to a satellite gateway antenna unit 50, which acts as a mixer, multiplexer and ground station radio. The transmission frequency between the gateway antenna unit 50 and the satellite 10 is typically in the Ku-band or Q-band. The communication between the baseband system 30 and the satellite 10 is thereby made through the antenna 50. The intermediate signals (which for Long Term Evolution, LTE signals, also termed 4G, would be Orthogonal Frequency Division Multiplexed, OFDM, signals) are advantageously transmitted to the satellite 10 multiplexed in frequency. Each intermediate signal may thus define a respective carrier signal.

The satellite 10 transmits the radio signals using individual, respective beams. A first carrier may be transmitted using a first beam to provide a first coverage area 61 (the upper left area shown), a second carrier may be transmitted using a second beam to provide a second coverage area 62 (the central area shown), a third carrier may be transmitted using a third beam to provide a third coverage area 63 (the top area shown), a fourth carrier may be transmitted using a fourth beam to provide a fourth coverage area 64 (the upper right area shown), a fifth carrier may be transmitted using a fifth beam to provide a fifth coverage area 65 (the lower right area shown), a sixth carrier may be transmitted using a sixth beam to provide a sixth coverage area 66 (the lower central area shown) and a seventh carrier may be transmitted using a seventh beam to provide a seventh coverage area 67 (the lower left area). Communication between the satellite 10 and the end users is in radio frequency bands allocated for the Mobile Satellite Service (MSS). which include radio frequency bands standardised by 3GPP. Each downlink carrier signal is transmitted within a respective allocated frequency channel. Uplink from the user terminals to the satellite 10 is on a separate frequency band, typical on an allocated frequency channel that is paired with the downlink allocated channel.

The satellite 10 is thereby capable of managing a large number of wireless network cells and they can be communicated (that is, transmitted and/or received) over specific areas through directive beams. However, the satellite 10 is limited in both power and bandwidth. The bandwidth limitation especially applies for the link between the satellite 10 and the antenna unit 50. The baseband dimensioning is directly linked to the number of cells to be processed. As a result, the total bandwidth available for transmission (and/or reception) by the satellite 10 in providing the RAN is limited. The same issues may apply whatever form of aerial platform, HAP or satellite is used. Different forms of non-terrestrial cellular RAN provision may also be considered, with similar issues also applying.

One or more terrestrial cellular RANs may coexist with the non-terrestrial cellular RAN. Typically, the downlink from a terrestrial cellular RAN is provided on an allocated frequency channel in a radio frequency band dedicated to the terrestrial (for example, land) mobile service. The uplink to the terrestrial cellular RAN is then usually provided on an allocated frequency channel that is paired with the downlink allocated channel. Since the terrestrial cellular RAN uses a radio frequency band dedicated to the terrestrial mobile service, interference between the terrestrial cellular RAN and the non-terrestrial cellular RAN is not usually a concern.

International Telecommunication Union (ITU) Radio Regulations allocate certain radio frequency bands as shared between the MSS and terrestrial mobile service. Radio frequency spectrum is a limited resource. It is desirable to make best use of such shared radio frequency bands.

Summary of the Disclosure

Against this background, the present disclosure provides a method for configuring a network station to operate with a terrestrial cellular Radio Access Network (RAN) using a radio frequency band that is shared with a non-terrestrial cellular RAN according to claim 1. Also provided is a network station so-configured, in line with claim 15. Preferred and/or optional features are defined in dependent claim.

It is proposed to provide a secondary downlink of a terrestrial RAN cell in a frequency band that is shared with a non-terrestrial (cellular) RAN. In other words, the terrestrial RAN cell may use the same (or adjacent) frequency channel as used by the non-terrestrial RAN, but transmits (only) a secondary carrier in the channel. This approach may permit coexistence of the non-terrestrial and terrestrial RANs, since interference from the terrestrial RAN downlink to the non-terrestrial downlink may be restricted in a range of ways, as will be discussed further below. Preferably, terrestrial RAN uses a Radio Access Technology (RAT) that is the same or interoperable with a RAT used by the non-terrestrial cellular RAN.

Approaches according to the disclosure may be implemented at a terrestrial RAN cell (or an entity controlling one or more terrestrial RAN cells) and/or at a user terminal (or UE). Such entities, nodes or devices may be more generically termed a network station. A primary downlink carrier for the cell is advantageously transmitted on another frequency channel, preferably in a frequency band that is dedicated to the terrestrial mobile (also termed International Mobile Telecommunications or IMT) service or at least not shared with a non-terrestrial mobile service. The secondary carrier may comprise no control signalling or control signalling that is (significantly) lower than for the primary carrier.

Thus, the secondary carrier may be adapted in ways not necessarily possible for the primary carrier.

Typically, the uplink for the terrestrial RAN cell is also provided in a frequency band that is dedicated to the terrestrial mobile service or at least not shared with a non-terrestrial mobile service. Beneficially, a frequency channel allocated to the cell uplink is paired with the frequency channel allocated to the cell primary downlink. Normal operation of the terrestrial RAN may thus be otherwise unaffected by the approach of the present disclosure.

This use of a secondary downlink of a terrestrial RAN cell in shared frequency spectrum may be dependent on interference mitigation and/or a condition permitting coexistence. Thus, it may only be applied to one or more specific cells of the terrestrial RAN. By coexistence, it may be understood that interference caused by the manner in which the secondary downlink of the terrestrial RAN cell is being provided (its operative state) permits functioning of the non-terrestrial RAN downlink (its operative state). For example, the geographical coverage of non-terrestrial RAN downlink may be essentially non-overlapping with the geographical coverage of the terrestrial RAN cell secondary downlink. In other words, the secondary downlink is only provided in geographical regions where the non-terrestrial RAN downlink is (essentially) non-operative, for instance in urban areas. Additionally or alternatively, the non-terrestrial RAN downlink may be multiplexed with the terrestrial RAN secondary downlink. One or more of: time-division multiplexing; code-division multiplexing; and frequency-division multiplexing (for instance, using Orthogonal Frequency Division Multiplexing, OFDM) may be employed.

It may be possible to handover a UE from the terrestrial RAN (the cell providing the secondary downlink or another cell) to the non-terrestrial RAN. In this case, the non-terrestrial RAN downlink beneficially uses the shared radio frequency band and preferably the same frequency (channel) as used for the terrestrial RAN secondary downlink. This may allow improved handover between terrestrial and non-terrestrials cells, such that the user terminal does not need to change the downlink radio configuration significantly.

Handover may advantageously occur when coexistence between the non-terrestrial and terrestrial RANs is not possible (for example, in geographical regions where the non-terrestrial RAN downlink is operative, which may include urban areas and/or where other factors may prevent multiplexing).

The terrestrial RAN may provide information about access to the non-terrestrial RAN (for example, downlink configuration, which may include frequency) or vice versa.

This may further improve handover or just access to the other RAN where desired or needed.

The non-terrestrial RAN typically uses an uplink frequency (channel) in a radio frequency band that is dedicated or at least not shared with the terrestrial RAN. Preferably, the uplink frequency (channel) used by the non-terrestrial RAN is paired with the downlink frequency used by the non-terrestrial RAN. Thus, the normal operation of the non-terrestrial RAN may not be affected according to the presently disclosed approach.

The non-terrestrial RAN may use one or more of: a satellite; an aerial platform; and a High Altitude Platform (HAP). Any form of non-terrestrial RAN implementation may be compatible with approaches according to the present disclosure.

Brief Description of the Drawings

The approach of the disclosure may be put into practice in various ways, one of which will now be described by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a schematic architecture for an exemplary non-terrestrial cellular RAN; Figure 2 schematically depicts an example configuration permitting coexistence of terrestrial and non-terrestrial cellular RANs; Figure 3 illustrates an existing frequency band allocation for terrestrial and non-terrestrial cellular RANs; Figure 4 illustrates an example frequency channel allocation for a terrestrial cellular RAN and a non-terrestrial cellular RAN within the existing frequency band allocation according to an approach of the disclosure; and Figure 5 shows a flowchart according to an embodiment of the disclosure.

Where a drawing indicates a feature also shown in another drawing, identical reference numerals have been used.

Detailed Description of Preferred Embodiments

The disclosure is concerned with coexistence and/or interoperability between a terrestrial cellular RAN and a non-terrestrial cellular RAN (for example, provided by a satellite, HAP or aerial platform). Referring to Figure 2, there is schematically depicted an example configuration permitting coexistence of terrestrial and non-terrestrial cellular RANs. In this configuration, three terrestrial RAN cells are shown: a first cell 101; a second cell 102 and a third cell 103, each of which has a corresponding terrestrial base station.

The first cell 101, second cell 102 and third cell 103 may provide coverage across an urban area, for instance. A satellite 10 also provides a non-terrestrial RAN cell 110. The non-terrestrial RAN cell 110 provides a coverage area outside the coverage areas of the first cell 101, second cell 102 and third cell 103, for example in a non-urban or rural area. It will be appreciated that this schematic depiction is an illustrative example only. In reality, coverage areas may not have a clear demarcation and/or may overlap. Also, the shape of a coverage area is rarely regular in nature. The size of a cell (and/or the number of cells) provided by a non-terrestrial RAN will likely differ significantly from that shown, which is simplified for illustrative purposes.

A user terminal (which may equivalently be termed a mobile terminal or using 3GPP terminology, a User Equipment or UE) 120 may be receiving service from the terrestrial RAN, for example from the first cell 101, due to the location of the user terminal 120. If the user terminal 120 moves within the coverage areas provided by the terrestrial RAN, for example from the first cell 101 to the second cell 102 or the third cell 103, handover allows the user terminal 120 to receive continuous and/or uninterrupted service from the terrestrial RAN.

If the user terminal 120 leaves the coverage areas provided by the terrestrial RAN, for example entering the coverage area of the non-terrestrial RAN cell 110, handover is beneficially also possible from the terrestrial RAN (for instance, the first cell 101) to the non-terrestrial RAN cell 110. This may be achieved in accordance with existing arrangements, for instance as discussed with reference to Figure 1 above or using other known approaches. Advantageously, the non-terrestrial RAN need not provide coverage within the coverage area of the terrestrial RAN. Indeed, a key benefit of the non-terrestrial RAN may be to provide coverage in regions where the terrestrial RAN cannot.

Both the terrestrial and non-terrestrial RANs are typically implemented using a Frequency Division Duplex (FDD) approach. As previously discussed, this means that each cell is allocated a frequency channel for downlink transmissions and a separate frequency channel for uplink transmissions (which may therefore occur simultaneously). The frequency channel for uplink transmissions is provided within a first frequency band and the frequency channel for downlink transmissions is provided within a second frequency band. The first and second frequency bands are typically separated by a guard band, not used by the RAN (although it may be used by other devices, systems or networks).

Referring now to Figure 3, there is illustrated an existing frequency band allocation for terrestrial and non-terrestrial cellular RANs. To aid understanding, specific frequencies have been included on this drawing, but it should be clear that these frequencies are simply examples and alternative frequency band structures and frequencies could be used. A terrestrial uplink frequency band 201 and a non-terrestrial (satellite) uplink frequency band 211 are defined. Frequency channels may be defined within these frequency bands.

Similarly, a terrestrial downlink frequency band 202 and a non-terrestrial (satellite) downlink frequency band 212 are defined. Again, frequency channels may be defined within these frequency bands. Each frequency channel defined within an uplink frequency band is advantageously paired with a respective frequency channel defined within the corresponding downlink frequency band. In this way, FDD operation of a cell may be implemented by allocating the cell a pair of frequency channels (one for uplink and one for downlink), the frequency band in which the channels are allocated depending on whether the cell is terrestrial or non-terrestrial.

It has been recognised that the non-terrestrial downlink frequency band could beneficially be used for a terrestrial RAN as well. Sharing this downlink frequency band for both terrestrial and non-terrestrial RANs is not necessarily straightforward, due to possible interference from downlink transmissions on the terrestrial RAN to reception by a UE of downlink transmissions from the non-terrestrial RAN. For example, the power received by the UE from one or more cells of the terrestrial RAN is likely to be significantly higher than the power received by the UE from the non-terrestrial RAN.

An approach proposed by the disclosure is for one or more cells of the terrestrial RAN to provide a secondary downlink in a frequency channel of the non-terrestrial downlink frequency band 212. In other words, each of the one or more cells typically transmits a primary downlink carrier, for example using a frequency channel in the terrestrial downlink frequency band 202. The cell transmits secondary downlink carrier in a frequency channel of the non-terrestrial downlink frequency band 212. This channel may also be used by a cell of the non-terrestrial RAN. This is particularly possible where the non-terrestrial RAN does not provide coverage in the same geographical regions as the terrestrial RAN (for instance, as discussed above with reference to Figure 1), but coexistence may also be achievable due to other reasons, as will be discussed below.

The secondary downlink carrier is intended to provide additional downlink capacity (which may be advantageous due to the typical asymmetric nature of the cellular network traffic). Existing approaches for providing an additional downlink carrier in this way may include Carrier Aggregation (CA) and Dual Connectivity (DC) approaches. The secondary downlink carrier may comprise no control signalling or control signalling that is significantly lower than for the primary carrier. These reduced requirements of the secondary downlink carrier in comparison with the primary downlink carrier may make coexistence more straightforward. The terrestrial and non-terrestrial cellular RANs may beneficially use the same or interoperable Radio Access Technologies (RATs), for instance based on 3GPP standards.

With reference to Figure 4, there is illustrated an example frequency channel allocation for a terrestrial cellular RAN and a non-terrestrial cellular RAN within the existing frequency band allocation. As discussed above, a terrestrial cell is allocated an uplink channel 301 in the terrestrial uplink frequency band 201 and a paired first downlink channel 302, for transmission of a primary carrier, in the terrestrial downlink frequency band 202. In addition, the terrestrial cell is allocated a second downlink channel 320, for transmission of a secondary carrier, in the non-terrestrial (or shared) downlink frequency band 212.

A non-terrestrial cell may also be allocated the second downlink channel 320, as well as the paired uplink channel 311 in the non-terrestrial (satellite) uplink frequency band 211 (which is not a shared frequency band in this approach). It will be noted that the non-terrestrial cell is the primary user of the second downlink channel 320. The terrestrial cell may use the second downlink channel 320 on the basis of non-interference. In other words, some form of coexistence condition is met to allow the terrestrial cell to use the second downlink channel 320. For instance, such a condition may be met if the non-terrestrial RAN does not generally provide service within the coverage area of the terrestrial RAN. In such cases, the same channel can be used by geographical (spatial) separation of the transmissions. Additionally or alternatively, some form of multiplexing may exist to mitigate interference. Suitable multiplexing may include one or more of: time-division (that is, using the downlink channel at different times); code-division (for instance, orthogonally encoded transmissions); and frequency division (for example, sub-dividing the channel, which may include using Orthogonal Frequency Division Multiplexing, OFDM).

In specific terms, the downlink allocation (2170-2200MHz as shown in Figure 3) may be identified as a shared band between MSS and terrestrial IMT. An intended service for MSS is to deliver mobile broadband services, for example including voice, to consumer smart-phones and cellular terminals directly from satellite. An intended service for terrestrial IMT in this band may be to deliver an additional capacity layer in urban areas on terrestrial networks.

In this approach, the downlink allocation (2170-2200MHz as shown in Figure 3) can be assigned as supplementary downlink (SDL) and used for terrestrial networks in urban areas for capacity expansion by pairing with existing IMT uplink allocations (such as LTE Band 1).

The uplink allocation (1980-2010MHz as shown in Figure 3) advantageously remains an MSS dedicated band, which may allow the satellite receiver to be protected of interference from terrestrial IMT networks, which may enable MSS services based on IMTAdvanced (4G) or IMT-2020 (5G) to be delivered complementary to terrestrial networks.

This approach is aligned with the ITU Radio Regulations that define the band as co-primary MOBILE and MOBILE-SATELLITE.

This approach can deliver much improved utilisation of spectrum. It is noted that the bandwidth and propagation characteristics of 2170-2200MHz particularly make this band attractive for consumer smart-phone devices, so an approach that supports a hybrid satellite -terrestrial approach where both use a common technology platform such as 4G/5G may be advantageous.

Finally referring to Figure 5, there is shown a flowchart according to an embodiment of the disclosure. The process described comprises configuration of a network station (for instance, a cell, an entity configured for operating or controlling the cell or a UE) to operate with a terrestrial cellular RAN. According to the process, the network station is configured to communicate (in particular, receive in the case of a UE or transmit in the case of a cell or related entity) using a radio frequency band that is shared with a non-terrestrial cellular RAN. The non-terrestrial cellular RAN may, for instance, use one or more of: a satellite; an aerial platform; and a High Altitude Platform (HAP).

In a first step 400, the network station is operated based on (or in accordance with) a cell of the terrestrial cellular RAN using: a first uplink frequency in a non-shared radio frequency band; and a first downlink frequency (for a primary downlink carrier, for instance) in a non-shared radio frequency band. References to a frequency in respect of this process may be equally understood to mean a frequency channel. Beneficially, the first uplink frequency and the first downlink frequency are allocated for paired operation. A UE may then receive service from the cell of the terrestrial cellular RAN.

In a second step 410, the network station is configured such that the UE is provided a secondary downlink from the cell of the terrestrial cellular RAN. The secondary downlink is provided using a second downlink frequency. The second downlink frequency is in the radio frequency band that is shared with the non-terrestrial cellular RAN. The downlink of the non-terrestrial cellular RAN advantageously also uses the second downlink frequency. Although this step is discussed with reference to a single cell, it may be applied to multiple cells (and likewise, the first step may be applied to more than one cell). Optionally, the secondary downlink is provided by carrier aggregation or dual connectivity.

-10 -It should be noted that the non-terrestrial cellular RAN is preferably configured to use a second uplink frequency in a non-shared radio frequency band. The second uplink frequency and the second downlink frequency are typically allocated for paired operation.

The second step 410 of configuring the network station may (only) be performed if a coexistence condition is met for the cell of the terrestrial cellular RAN. The coexistence condition is typically a condition indicative that interference caused by an operative state of the secondary downlink of the cell of the terrestrial cellular RAN permits an operative state of a downlink of the non-terrestrial cellular RAN. One option for the coexistence condition may be that a geographical coverage of a downlink of the non-terrestrial cellular RAN is (essentially) non-overlapping with a geographical coverage of the secondary downlink of the cell of the terrestrial cellular RAN. Another option may be that a downlink of the non-terrestrial cellular RAN and the secondary downlink of the cell of the terrestrial cellular RAN operate a multiplexing arrangement. The two options may be combined.

When the UE receives service from the cell of the terrestrial cellular RAN, the cell may communicate to the UE information about access to the non-terrestrial cellular RAN.

Thus, the cell may transmit such information and/or the UE may receive it. The information may include, for example, information about the downlink and/or uplink frequency (channel) used by the non-terrestrial cellular RAN and/or a cell identifier (CeIIID). For the sake of completeness, it should be noted that, additionally or alternatively, the non-terrestrial cellular RAN may communicate to the UE information about access to the cell of the terrestrial cellular RAN. Again, a cell of the non-terrestrial cellular RAN may transmit such information and/or the UE may receive it. The information may include, for example, information about the downlink and/or uplink frequency (channel) used by the terrestrial cellular RAN and/or a CeIIID.

In a third step 420, handover of the UE is performed from the terrestrial cellular RAN to the non-terrestrial cellular RAN. In this case, a downlink of the non-terrestrial cellular RAN advantageously uses the radio frequency band that is shared with the non-terrestrial cellular RAN. More preferably, the downlink of the non-terrestrial cellular RAN uses the second downlink frequency (as suggested above). The handover process for the downlink radio equipment may be less complex in such a case. The handover step 420 may take place from the cell (or one of the cells) using the second downlink frequency to provide the secondary downlink or from another cell (that does not use the second downlink frequency).

The handover step 420 may be carried out in response to a determination that the UE can no longer receive service from the cell of the terrestrial cellular RAN for which the coexistence condition is met. For example, the UE may be leaving (or have left) the coverage area of that cell. Alternatively, the cell may no longer meet the technical and/or service requirements of the UE. If the coexistence condition is no longer met for the cell, the cell may cease use of the second downlink frequency to provide the secondary downlink. In that case, the non-terrestrial cellular RAN may use the second downlink frequency instead.

The method may be implemented as a network station for operation with a terrestrial cellular RAN, the network station being configured to operate in accordance with the method. As noted above, examples of a network station in this context may include a cell, an entity configured for operating or controlling the cell or a UE. Other examples may include a network node of a cellular network (for example, a eNB or gNB). For example, the network station or network node may include a processor and at least one communication interface, particularly comprising one or both of a transmitter and receiver. A UE may likewise include a processor and at least one communication interface, particularly comprising one or both of a transmitter and receiver. A controller for a network station or node may also be considered.

Any of the methods described herein may be implemented as a computer program. The computer program may be configured to control a MS, UE and/or a network node or entity to perform any method according to the disclosure.

A satellite-based non-terrestrial cellular RAN has been considered herein.

Preferred embodiments may be concerned with a non-terrestrial cellular RAN provided using a Low Earth Orbit (LEO) satellite. A LEO satellite may deliver a network round-trip-time similar to that of terrestrial networks, advantageously improving the inter-operability of satellite and terrestrial RANs and a similar data connection quality to be met across both systems. However, the non-terrestrial cellular RAN may alternatively be based on a Medium Earth Orbit (MEO) satellite, Geostationary Earth Orbit (GEO) satellite, an aerial platform, drones, High Altitude Platform (HAP) or very high altitude platforms.

Although specific embodiments have now been described, the skilled person will understand that various modifications and variations are possible. For example, whilst the disclosure is described in relation to existing network architecture, it will be understood that changes to the architecture (and/or nomenclature) are possible, but the present disclosure may still be applicable in this case. Also, combinations of any specific features shown with reference to one embodiment (or aspect) or with reference to multiple embodiments (or aspects) are also provided, even if that combination has not been explicitly detailed herein.

Claims

-12 -CLAIMS1. A method for configuring a network station to operate with a terrestrial cellular Radio Access Network (RAN) using a radio frequency band that is shared with a non-terrestrial cellular RAN, the method comprising: operating the network station based on a cell of the terrestrial cellular RAN using a first uplink frequency in a non-shared radio frequency band and a first downlink frequency in a non-shared radio frequency band; configuring the network station such that a User Equipment (UE), receiving service from the cell of the terrestrial cellular RAN, is provided a secondary downlink from the cell of the terrestrial cellular RAN using a second downlink frequency in the radio frequency band that is shared with the non-terrestrial cellular RAN.
2. The method of claim 1, wherein the step of configuring the network station is performed if a coexistence condition is met for the cell of the terrestrial cellular RAN.
3. The method of claim 2, wherein one or both of: the coexistence condition is a condition indicative that interference caused by an operative state of the secondary downlink of the cell of the terrestrial cellular RAN permits an operative state of a downlink of the non-terrestrial cellular RAN; and the coexistence condition comprises one or more of: a geographical coverage of a downlink of the non-terrestrial cellular RAN is essentially non-overlapping with a geographical coverage of the secondary downlink of the cell of the terrestrial cellular RAN; and a downlink of the non-terrestrial cellular RAN and the secondary downlink of the cell of the terrestrial cellular RAN operate a multiplexing arrangement.
4. The method of any preceding claim, further comprising: performing handover of the UE from the terrestrial cellular RAN to the non-terrestrial cellular RAN, a downlink of the non-terrestrial cellular RAN using the radio frequency band that is shared with the non-terrestrial cellular RAN.
5. The method of claim 4, wherein the downlink of the non-terrestrial cellular RAN uses the second downlink frequency.
-13 - 6. The method of claim 4 or claim 5, wherein the step of performing handover is from the cell of the terrestrial cellular RAN.
7. The method of any one of claims 4 to 6 when dependent on claim 2, wherein the step of performing handover is carried out in response to a determination that the UE can no longer receive service from the cell of the terrestrial cellular RAN for which the coexistence condition is met.
8. The method of any preceding claim, further comprising: communicating from the cell of the terrestrial cellular RAN to the UE information about access to the non-terrestrial cellular RAN; and/or communicating from the non-terrestrial cellular RAN to the UE information about access to the cell of the terrestrial cellular RAN.
9. The method of any preceding claim, wherein the secondary downlink is provided by carrier aggregation or dual connectivity.
10. The method of any preceding claim, wherein the first uplink frequency and the first downlink frequency are allocated for paired operation.
11. The method of any preceding claim, wherein the non-terrestrial cellular RAN is configured to use a second uplink frequency in a non-shared radio frequency band.
12. The method of claim 11, wherein the second uplink frequency and the second downlink frequency are allocated for paired operation.
13. The method of any preceding claim, wherein the non-terrestrial cellular RAN uses one or more of: a satellite; an aerial platform; and a High Altitude Platform (HAP).
14. The method of any preceding claim, wherein the network station is one of: the UE; an entity configured for operating or controlling the cell; and the cell.
15. A network station for operation with a terrestrial cellular Radio Access Network (RAN), the network station configured to operate in accordance with the method of any preceding claim.