WO2021058111A1

WO2021058111A1 - Method, arrangement, and computer program product for inter-satellite links to reuse the resources of feeder and service links

Info

Publication number: WO2021058111A1
Application number: PCT/EP2019/076211
Authority: WO
Inventors: Lianghai JI; Hans Thomas HÖHNE; István Zsolt KOVÁCS
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2019-09-27
Filing date: 2019-09-27
Publication date: 2021-04-01

Abstract

According to an aspect, there is disclosed a method comprising identifying two or more satellites as forming a temporary satellite group capable of intersatellite communications; determining a radio resource pool containing radio resources to be used by said temporary satellite group for said inter-satellite communications, the determined radio resource poolbeing valid for a first duration of time; and allocating a subset of radio resources from said radio resource pool for use by at least a subgroup of said temporary satellite group for said inter-satellite communications, the allocation being valid for a second duration of time within said first duration of time.

Description

METHOD, ARRANGEMENT, AND COMPUTER PROGRAM PRODUCT FOR INTER-SATELLITE LINKS TO REUSE THE RESOURCES OF FEEDER AND SERVICE LINKS

TECHNICAL FIELD

The present application generally relates to the field of wireless communications. In particular, the present application relates to an apparatus for wireless communication in space, and a related method and a com puter program.

BACKGROUND

A communications satellite is equipped for set ting up and maintaining wireless communication links with one or more network nodes on the ground, often referred to as non-terrestrial network gateways or NTN- GWs for short. Additionally the communications satellite is equipped for setting up and maintaining wireless com munication links with a large number of user devices, for which the designation user equipment or UE is used. If there are multiple satellites on sufficiently similar orbits, they may additionally set up and maintain inter satellite links.

The optimal use of radio resources is an actual question in all such devices that are capable of other than the most basic, fixed ways of wireless transmission and reception. Radio resources is a general term that covers quantities such as time, frequencies, power, al- locatable hardware, processing capacity, and spreading codes, or anything that may constitute a bottleneck for achieving some desired performance in communications. Optimal decisions about the use of radio resources are key to communications performance in particular when there are multiple devices and multiple communications channels that essentially compete for the total of radio resources available. SUMMARY

An example embodiment of a method comprises: identifying two or more satellites as forming a temporary satellite group capable of inter-satellite communications; determining a radio resource pool containing radio resources to be used by said temporary satellite group for said inter-satellite communications, the de termined radio resource pool being valid for a first duration of time; and allocating a subset of radio resources from said radio resource pool for use by at least a subgroup of said temporary satellite group for said inter-satellite com munications, the allocation being valid for a second duration of time within said first duration of time.

In an example embodiment, at least some of the radio resources in the determined radio resource pool are radio resources for use in communications between a satellite and at least one terrestrial station.

In an example embodiment, alternatively or in addition to the above-described embodiments, said iden tifying of said two or more satellites comprises ex changing first information concerning inter-satellite communications between at least some of said two or more satellites, and selecting the satellites for said tem porary satellite group based at least partly on said exchanged first information.

In an example embodiment, alternatively or in addition to the above-described embodiments, said first information comprises at least one of: locations of at least some of said two or more satellites; moving directions of at least some of said two or more satellites; satellite-to-satellite distances of at least some of said two or more satellites; orientations of at least some of said two or more satellites; satellite-to-satellite directions of at least some of said two or more satellites; conditions of signal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and volumes of communication handled by at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, said iden tifying of said two or more satellites comprises provid ing second information indicative of a predicted need for inter-satellite communications between at least some of said two or more satellites, and selecting the sat ellites for said temporary satellite group based at least partly on said second information.

In an example embodiment, alternatively or in addition to the above-described embodiments, said providing of second information comprises at least one of: calculating locations of at least some of said two or more satellites based on their orbit data; calculating moving directions of at least some of said two or more satellites based on their orbit data; calculating satellite-to-satellite distances of at least some of said two or more satellites based on their orbit data; calculating orientations of at least some of said two or more satellites; calculating satellite-to-satellite directions of at least some of said two or more satellites based on their orbit data; observing and/or predicting conditions of sig nal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and observing and/or predicting volumes of commu nication handled by at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the method further comprises: determining one of said two or more satellites as a head of said temporary satellite group; and performing said allocating of at least a subset of radio resources through actions of the satellite de termined as the head of said temporary satellite group.

In an example embodiment, alternatively or in addition to the above-described embodiments, the method is a method to be executed in that one of said two or more satellites that is determined as the head of said temporary satellite group; and said determining of a radio resource pool comprises receiving a radio resource pool allocation from a device or network infrastructure external to said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the method further comprises, before said determining of a radio resource pool, aggregating group information indicative of identities of the two or more satellites and of a need for satellite-to-satellite communications among the temporary satellite group, and sending the aggre gated group information to said external device or net work infrastructure.

In an example embodiment, alternatively or in addition to the above-described embodiments, said ag gregated group information comprises at least one of: information indicative of conditions of signal propagation on links between at least some of the two or more satellites and respective terrestrial stations, information indicative of volumes of communi cation handled by at least some of said two or more satellites orientations of at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the method further comprises, before said determining of a radio resource pool, sending a request for radio resource pool allocation to said external device or network infra structure.

In an example embodiment, alternatively or in addition to the above-described embodiments, said re quest for radio resource pool allocation is sent to said external device or network infrastructure separately from said aggregated group information.

In an example embodiment, alternatively or in addition to the above-described embodiments, said re quest for radio resource pool allocation is sent to said external device or network infrastructure together with said aggregated group information.

In an example embodiment, alternatively or in addition to the above-described embodiments, the method is a method to be executed in a device or network in frastructure external to said two or more satellites; and said allocating of a subset of radio resources from said radio resource pool comprises indirectly allocating said subset by allowing one of said two or more satel lites make a decision of said allocating.

In an example embodiment, alternatively or in addition to the above-described embodiments, the method further comprises, before said determining of a radio resource pool, performing said providing of second in formation and said selecting of the satellites for said temporary satellite group, so that said providing of second information and said selecting of the satellites are performed through actions of said device or network infrastructure external to said two or more satellites.

An example embodiment of an apparatus com prises: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to at least perform: identifying two or more satellites as forming a temporary satellite group capable of inter-satellite communications; determining a radio resource pool containing radio resources to be used by said temporary satellite group for said inter-satellite communications, the de termined radio resource pool being valid for a first duration of time; and allocating a subset of radio resources from said radio resource pool for use by at least a subgroup of said temporary satellite group for said inter-satel lite communications, the allocation being valid for a second duration of time within said first duration of time.

In an example embodiment, the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform said allocation so that at least some of the radio resources in the determined radio resource pool are radio resources for use in communications be tween a satellite and at least one terrestrial station.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform said identifying of said two or more satellites by exchanging first information concerning inter-satellite communications between at least some of said two or more satellites, and selecting the satellites for said temporary satellite group based at least partly on said exchanged first information.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform said exchanging of first information by exchanging at least one of: locations of at least some of said two or more satellites; moving directions of at least some of said two or more satellites; satellite-to-satellite distances of at least some of said two or more satellites; orientations of at least some of said two or more satellites; satellite-to-satellite directions of at least some of said two or more satellites; conditions of signal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and volumes of communication handled by at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform said identifying of said two or more satellites by providing second information indicative of a predicted need for inter-satellite com munications between at least some of said two or more satellites, and selecting the satellites for said tem porary satellite group based at least partly on said second information.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform said providing of second information by performing at least one of: calculating locations of at least some of said two or more satellites based on their orbit data; calculating moving directions of at least some of said two or more satellites based on their orbit data; calculating satellite-to-satellite distances of at least some of said two or more satellites based on their orbit data; calculating orientations of at least some of said two or more satellites; calculating satellite-to-satellite directions of at least some of said two or more satellites based on their orbit data; observing and/or predicting conditions of sig nal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and observing and/or predicting volumes of commu nication handled by at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform: determining one of said two or more satellites as a head of said temporary satellite group; and performing said allocating of at least a subset of radio resources through actions of the satellite de termined as the head of said temporary satellite group.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus is an apparatus to be included in that one of said two or more satellites that is determined as the head of said temporary satellite group; and the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform said determining of a radio resource pool by receiving a radio resource pool allocation from a device or network infrastructure external to said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform, before said determining of a radio resource pool, aggregating group information indicative of identities of the two or more satellites and of a need for satellite-to-satellite communications among the temporary satellite group, and sending the aggregated group information to said external device or network infrastructure.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform said aggregating of group information by aggregating at least one of: information indicative of conditions of signal propagation on links between at least some of the two or more satellites and respective terrestrial stations, information indicative of volumes of communi cation handled by at least some of said two or more satellites orientations of at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform, before said determining of a radio resource pool, sending a request for radio resource pool allocation to said external device or net work infrastructure.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least send said request for radio re source pool allocation to said external device or net work infrastructure separately from said aggregated group information.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least send said request for radio re source pool allocation to said external device or net work infrastructure together with said aggregated group information.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus is an apparatus to be included in a device or network infrastructure external to said two or more sat ellites; and the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform said allocating of a subset of radio resources from said radio resource pool by indirectly allocating said subset by allowing one of said two or more satellites make a decision of said allocating.

In an example embodiment, alternatively or in addition to the above-described embodiments, the at least one memory and the computer program code are con figured to, with the at least one processor, cause the apparatus to at least perform said providing of second information and said selecting of the satellites for said temporary satellite group before said determining of a radio resource pool, so that said providing of second information and said selecting of the satellites are performed through actions of said device or network infrastructure external to said two or more satellites.

An example embodiment of a computer program comprises instructions for causing an apparatus to per form the method of any of the above example embodiments.

An example embodiment of a computer readable medium comprises program instructions for causing an apparatus to perform the method of any of the above example embodiments.

An example embodiment of an apparatus comprises means for performing: identifying two or more satellites as forming a temporary satellite group capable of inter-satellite communications; determining a radio resource pool containing radio resources to be used by said temporary satellite group for said inter-satellite communications, the de termined radio resource pool being valid for a first duration of time; and allocating a subset of radio resources from said radio resource pool for use by at least a subgroup of said temporary satellite group for said inter-satel lite communications, the allocation being valid for a second duration of time within said first duration of time.

In an example embodiment, the apparatus com prises means for performing said determining of at least some of the radio resources in the determined radio resource pool so that the determined radio resources are radio resources for use in communications between a sat ellite and at least one terrestrial station.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for performing said identifying of said two or more satellites so that it comprises exchanging first information concerning inter-satellite communications between at least some of said two or more satellites, and selecting the satellites for said tem porary satellite group based at least partly on said exchanged first information.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for providing said first infor mation so that said first information comprises at least one of: locations of at least some of said two or more satellites; moving directions of at least some of said two or more satellites; satellite-to-satellite distances of at least some of said two or more satellites; orientations of at least some of said two or more satellites; satellite-to-satellite directions of at least some of said two or more satellites; conditions of signal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and volumes of communication handled by at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for performing said identifying of said two or more satellites by providing second in formation indicative of a predicted need for inter-sat ellite communications between at least some of said two or more satellites, and selecting the satellites for said temporary satellite group based at least partly on said second information. In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for providing said second infor mation by performing at least one of: calculating locations of at least some of said two or more satellites based on their orbit data; calculating moving directions of at least some of said two or more satellites based on their orbit data; calculating satellite-to-satellite distances of at least some of said two or more satellites based on their orbit data; calculating orientations of at least some of said two or more satellites; calculating satellite-to-satellite directions of at least some of said two or more satellites based on their orbit data; observing and/or predicting conditions of sig nal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and observing and/or predicting volumes of commu nication handled by at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for performing: determining one of said two or more satellites as a head of said temporary satellite group; and performing said allocating of at least a subset of radio resources through actions of the satellite de termined as the head of said temporary satellite group.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus is an apparatus to be included in that one of said two or more satellites that is determined as the head of said temporary satellite group; and the apparatus comprises means for performing said determining of a radio resource pool by receiving a radio resource pool allocation from a device or network infrastructure ex ternal to said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for performing: before said determining of a radio resource pool, aggregating group information indicative of iden tities of the two or more satellites and of a need for satellite-to-satellite communications among the tempo rary satellite group, and sending the aggregated group information to said external device or network infra structure.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for providing said aggregated group information by providing at least one of: information indicative of conditions of signal propagation on links between at least some of the two or more satellites and respective terrestrial stations, information indicative of volumes of communi cation handled by at least some of said two or more satellites, orientations of at least some of said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for performing: before said determining of a radio resource pool, sending a request for radio resource pool alloca tion to said external device or network infrastructure.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for sending said request for radio resource pool allocation to said external device or net work infrastructure separately from said aggregated group information.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for sending said request for radio resource pool allocation to said external device or net work infrastructure together with said aggregated group information.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus is an apparatus to be included in a device or network infrastructure external to said two or more sat ellites; and the apparatus comprises means for perform ing said allocating of a subset of radio resources from said radio resource pool by indirectly allocating said subset by allowing one of said two or more satellites make a decision of said allocating.

In an example embodiment, alternatively or in addition to the above-described embodiments, the appa ratus comprises means for performing: before said determining of a radio resource pool, performing said providing of second information and said selecting of the satellites for said temporary satellite group, so that said providing of second in formation and said selecting of the satellites are per formed through actions of said device or network infra structure external to said two or more satellites.

In an example embodiment, alternatively or in addition to the above-described embodiments, the means comprises at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus. DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the embodiments and constitute a part of this specification, illustrate embodiments and together with the description help to explain the principles of the embodiments. In the draw ings:

FIG. 1 illustrates a terrestrial and a satel lite-based mobile network.

FIG. 2 illustrates satellites, gateways, and user equipment and their communications links.

FIG. 3 illustrates a method.

FIG. 4 illustrates a method.

FIG. 5 illustrates a method.

FIG. 6 illustrates a method.

Like reference numerals are used to designate like parts in the accompanying drawings.

DETAILED DESCRIPTION

Reference will now be made in detail to embod iments, examples of which are illustrated in the accom panying drawings. The detailed description provided be low in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the pre sent example may be constructed or utilized. The de scription sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

Fig. 1 shows a comparison between a terrestrial mobile network (in the lower part of fig. 1) and a satellite-based mobile network (in the upper part of fig. 1). Real-life systems are vastly more complicated in terms of the number of devices involved, but a sim plification is considered here in order to highlight certain important concepts.

In the terrestrial system mobile devices 101 and 102, also referred to as User Equipment (UE), set up and maintain wireless communication links with fixed base stations 103 and 104, often known by the acronym gNB (next generation Node B). Each base station is in turn connected to a core network 105 or 106, which may provide a further connection to a data network such as the Internet. Various designations are used for the in terfaces between the network elements, depending on which generation of mobile networks is in question. One example is shown in fig. 1, where the interface between a UE and a gNB is the Uu interface, and the interface between a gNB and a core network is the NG interface. In some cases the gNBs may have direct communications between them, through what is shown as the Xn interface in fig. 1.

In the satellite-based mobile network the UEs 111 and 112 each set up and maintain wireless communi cation links with respective communications satellites 113 and 114 that orbit the Earth. These links are fre quently referred to as service links, and the communi cations interface may be called for example the NR-Uu interface. The satellites 113 and 114 set up and main tain wireless communication links with respective ground stations 115 and 116 through what are known as feeder links. A communications satellite meant here is a so- called regenerative satellite, which means that it is not a mere relay station but includes more advanced capabilities such as cross-connecting capability with other satellites. The ground stations 115 and 116 may be called Non-Terrestrial Network Gateways, or NTN Gate ways, or just GWs for short. In this simplified example the GWs are shown as connected to core networks 117 and 118 from which there may be further connections to e.g. data networks. A GW may also include some functionali ties in itself that could be considered core network functionalities .

While the interface from the core networks 117 and 118 to the GWs 115 and 116 is the NG interface, the interface between a GW and a satellite to which it has a feeder link is NG-over-SRI, where SRI comes from Sat ellite Radio Interface. The regenerative satellites 113 and 114 can be compared to the gNBs of the terrestrial system because they have many similar functionalities. Inter-satellite links (ISL) are possible through what is here shown as Xn over ISL.

In terrestrial mobile networks adjacent gNBs may detect each other, for direct communications through the Xn interface, through preconfiguration or a mecha nism known as the automatic neighbor relation function (ANRF). However, here it must be remembered that the terrestrial gNBs are fixedly installed. Terrestrial gNBs may also be constructed with relatively large freedom concerning their physical characteristics like availa ble power and built-in transmission hardware that have an effect on the use of radio resources.

Satellites that orbit the Earth may move at speeds of several kilometers per second in relation to each other, so their 3D spatial configuration and mutual orientation are constantly changing. This means that mechanisms that are known from terrestrial systems for setting up and maintaining communication links between neighboring gNBs may be ill suited for similar purposes between satellites. Satellites must also be constructed with extremely tight budgets on power, weight, and ro bustness, which means that their capability of using radio resources may be much more limited than what is encountered in terrestrial gNBs.

Fig. 2 illustrates schematically an example that highlights some ways in which satellites may need and utilize radio resources for inter-satellite commu nications. Two GWs 201 and 202 are shown as an example, as are three gNB satellites 211, 212, and 213 as well as four UEs 221, 222, 223, and 224. Two satellites 211 and 212 maintain feeder links with the first GW 201, while the third satellite 213 maintains a feeder link with the second GW 202. One satellite 211 maintains service links with two UEs 221 and 222, while the two other satellites 212 and 213 are shown with one service link each, between satellite 212 and UE 223 and between satellite 213 and UE 224. Possible ISLs are shown be tween all satellites 211, 212, and 213.

For the sake of clarity it may be noted that throughout this text the use of numerical qualifiers like "first", "second", or "third" does not imply an order of any kind, but these are just names used for unambiguous reference.

While communicating with the first GW 201 through the respective feeder link, the first satellite 211 may experience deteriorating feeder link quality for example because of bad weather along the signal propa gation path that connects the two communicating sta tions, or due to the feeder link being not available by design. Additionally or alternatively the first satel lite 211 may receive, from one of the UEs 221 and 222 it is communicating with, a sudden request for a service that requires very high data transmission capacity. Both of these cases are examples of how the first satellite 211 may find that the data transmission capacity of its feeder link to the first GW 201 is not sufficient. An ISL with one or more other satellites can provide a solution to the problem, together with the feeder link that such other satellite (s) has or have with their respective GWs. The first satellite 211 might e.g. route some of the data traffic required by the UEs 221 and 222 through the second satellite 212 and its respective feeder link with the first GW 201, taken that the pos sible deteriorating link quality does not affect that feeder link in the same way as the feeder link of the first satellite 211.

Another case to be considered is dual connec tivity. As an example, the second UE 222 may want to set up a further simultaneous service link with another sat ellite, like the second satellite 212, if such another satellite has the second UE 222 conveniently within its coverage area. In this case the ISL between the first and second satellites 211 and 212 may be used to transfer data packets originating from and/or destined to the second UE 222. Yet another example of a case in which an increase of transmissions needed through an ISL may become actual is an inter-satellite handover, for exam ple when the third UE 223 would like to change its service link to going through the third satellite 213 instead of the second satellite 212.

Two somewhat interlinked factors that need to be considered in setting up and maintaining ISLs are interference and the availability of radio resources. Satellites have a limited amount of power available for handling transmissions, and there are limited amounts of also other radio resources like time and frequency bandwidth. If the radio resources for the service links, feeder links, and ISLs come from a common radio resource pool, radio resources that are used for one type of communications, like service and feeder links, may limit the availability of radio resources for communications through ISLs. Concerning interference it should be en sured that transmissions through ISLs interfere as lit tle as possible with transmissions on service and feeder links, or at least that such interference remains at a tolerable level. Additionally it should be ensured that - particularly if there are multiple groups of satel lites in the sky, each group communicating through ISLs between satellites in the group - inter-satellite in terference and inter-group interference remains at ac ceptable level. Of these concepts, inter-satellite in terference refers to interference caused by one ISL to another ISL within the same satellite group, while in ter-group interference refers to interference caused by ISL transmissions of one satellite group to the ISL transmissions of another satellite group. Educated de cisions about how to optimally utilize radio resources also help to avoid interference, because said decisions direct for example the utilization of a common frequency band at various instances of time by various stations at various locations.

In terrestrial mobile networks it has been cus tomary that coordinated decisions about the use of radio resources are not made at the level of gNBs but deeper in the network, in a suitable central network entity. In the example case of fig. 2 one possibility is to make decisions about the utilization of radio resources in the GWs 201 and 202. Each satellite would request for the transmission and reception resources from its serv ing GW. However, in such a case each satellite must send resource request messages frequently to its serving GW, which introduces a large signaling overhead and addi tional latency, considering the long signal propagation distances involved. The serving GW would also need to frequently and dynamically exchange information with other GWs regarding the resource allocation, in order to enable controlling interference that the use of some allocated resources may cause to some other communica tions. Given that the two GWs 201 and 202 could be located even on two different continents, frequent in formation exchange between the GWs in real time will be challenging. The inherent propagation delays in the ter restrial communication between the GW would need to be handled/mitigated. This creates certain restrictions on how fast the ISL/GW-gNB radio resource allocation scheme would be able to react.

FIG. 3 illustrates an example embodiment of the subject matter described herein, illustrating a method for making decisions about the utilization of radio re sources in a mobile network that comprises satellites. After beginning at step 301 the method comprises iden tifying two or more satellites at step 302 as forming a temporary satellite group, in which the satellites are capable of inter-satellite communications. Advantageous embodiments for such identifying of two or more satel lites are described in more detail later in this text. The satellites may be for example located closer to each other than some predefined threshold distance, so that they are capable of receiving some beacon signals of each other at some sufficient received signal strength. Since satellites orbit the Earth on orbits the charac teristics of which are relatively easy to calculate in advance, identifying the satellites may comprise making calculations about which satellites will be where in space at which instant of time. There may be also some preliminary exchange of information between said two or more satellites, based on which it is considered to select certain satellites as forming the temporary group.

The method comprises determining a radio re source pool at step 303, containing radio resources to be used by the temporary satellite group for inter satellite communications. The determined radio resource pool is valid for a certain duration of time, which is here called the resource pool validity period and marked as T_Rep0 · The concept of a radio resource pool means that the determining made at step 303 identifies certain ra dio resources for use, without specifying yet, which station (s) are to use which of the radio resources in cluded in the pool. A very simple example definition of a radio resource that could be included in a radio re source pool could comprise a certain radio frequency band that can be used for wireless communications for the duration of the resource pool validity period. A somewhat more elaborate example might combine frequency and time based definitions, so that certain frequency band can be used in certain time slots that occur re currently during the resource pool validity period. As the concept of defining accurately identifiable radio resource is well known in the field of wireless commu nications, it is not necessary to go into more detail about how the radio resources included in the radio resource pool are defined and identified at step 303.

The method comprises allocating a subset of radio resources from the radio resource pool at step 304, for use by at least a subgroup of the temporary satellite group formed earlier at step 302. The allo cated radio resources are to be used for inter-satellite communications, and the allocation is valid for a second duration of time within the resource pool validity pe riod. The allocating involves one or several more de tailed decisions about which communicating station is allowed to use which radio resource (s) included in the pool.

The check at step 305 and its two possible outcomes reflect the fact that the (second) duration of time, for which the allocation made at step 304 remains valid, occurs within the (first) duration of time for which the radio resource pool determining made at step

303 remains valid. Within said first duration time there may occur one, two or more rounds of allocating radio resources according to step 304. A transition from step

304 to step 305 means that one allocation made at step 304 has come to an end. If the determining of the radio resource pool made at step 303 is still valid, i.e. if the timer for the resource pool validity is still run ning, a return to step 304 occurs for the next round of allocating radio resources from the pool. If not, the method proceeds from step 305 to step 306.

The check at step 306 and its two possible outcomes reflect the fact that after the expiry of the resource pool validity period the same group of satel lites may still have a continuing need for radio re sources available for inter-satellite communications. This is the case meant by the positive outcome from step, which causes the method to return to step 303. A radio resource pool may be determined anew, containing the same or some other radio resources as those con cerned on the previous round of determining the radio resource pool. A new resource pool validity period may or may not be given. If one is given, the execution of the inner loop consisting of steps 304 and 305 is again repeated once or several times as needed, before the expiry of the new resource pool validity period. A neg ative outcome at step 306 means that the definition of the satellite group is outdated, causing the method to end at step 307.

The idea of the two-tier decision-making is that the resource pool can be determined somewhat more loosely at step 303, without having to know each accu rate detail about the quickly changing resource needs of individual satellites, however supported with infor mation about what can and what cannot be done for example with reference to expected interference between differ ent satellite groups. The allocating decisions made at step 304 can be made based on the most accurate and most actual information about the needs of individual satel lites. Preferably the allocating decisions of step 304 are made as close to the satellites themselves, both in the sense of physical distance and in the sense of delays in communications, so that even the most recent and the most rapidly occurring changes in their radio resource needs can be accounted for. At least some of the radio resources in the radio resource pool determined at step 303 may be radio resources that one or more satellites in the group could also use for communications between the satellite and at least one terrestrial station. In other words, the determining of a radio resource pool at step 303 may redirect at least some radio resources from being used in service or feeder links to being used in ISL, and/or allow the simultaneous use of some radio resource (s) both for service or feeder links and for ISL. For example if a satellite experienced a need for enhanced inter satellite communications because its feeder link was cut out by bad weather, it may use in the inter-satellite communications those radio resources that it currently cannot use for communications with its own GW anyway. Similarly if a satellite has a certain default alloca tion of radio resources for use in service links and there are not enough active UEs currently within its coverage area to exhaust that default allocation, some of those radio resources may be temporarily redirected for use in inter-satellite communications.

Identifying the two or more satellites that are to form the temporary satellite group in step 302 may utilize real time knowledge (like real time knowledge exchanged among satellites), prediction, or both. In the following we consider the first option, which involves utilizing real time knowledge. In this option step 302 may comprise exchanging information concerning inter satellite communications between at least some of said two or more satellites, and selecting the satellites for said temporary satellite group based at least partly on said exchanged information. In order to facilitate fur ther unambiguous reference to the concept we may call the exchanged information the first information.

Examples of first information of the kind meant above comprise, but are not limited to information in dicative of: - locations of at least some of the two or more sat ellites;

- moving directions of at least some of said two or more satellites;

- satellite-to-satellite distances of at least some of the two or more satellites;

- orientations of at least some of said two or more satellites;

- satellite-to-satellite directions of at least some of said two or more satellites;

- conditions of signal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and

- volumes of communication handled by at least some of said two or more satellites.

The significance of locations and satellite- to-satellite distances of the satellites is related to the physical possibility of setting up and maintaining the ISLs, because as in all wireless communications, distance between the communicating stations causes at tenuation of signal power. Orientations and satellite- to-satellite directions of the satellites have signif icance, because satellites typically employ directional antennas for wireless communications, and the location and structure of the antennas may impose restrictions concerning the directions in which the satellites are capable of transmitting and receiving efficiently. Con ditions of signal propagation between satellites and their respective terrestrial stations affect the way in which the feeder and service links can be utilized. Volumes of communication is a general term that covers both instantaneous traffic load and data amounts accu mulated over time. Information indicative of volumes of communication covers, in general terms, all ways in which one can describe, how much information needs to be communicated. Next we will consider the second option, which involves utilizing prediction in identifying the two or more satellites that are to form the temporary satellite group in step 302. Utilizing prediction may be described as providing information indicative of a predicted need for inter-satellite communications between at least some of said two or more satellites, and selecting the sat ellites for said temporary satellite group based at least partly on such information. In order to facilitate further unambiguous reference to the concept we may call such information the second information.

Examples of providing second information of the kind meant above comprise, but are not limited to:

- calculating locations of at least some of said two or more satellites based on their orbit data;

- calculating moving directions of at least some of said two or more satellites based on their orbit data;

- calculating satellite-to-satellite distances of at least some of said two or more satellites based on their orbit data;

- calculating orientations of at least some of said two or more satellites;

- calculating satellite-to-satellite directions of at least some of said two or more satellites based on their orbit data;

- observing and/or predicting conditions of signal propagation between at least some of said two or more satellites and respective terrestrial sta tions they are communicating with; and

- observing and/or predicting volumes of communica tion handled by at least some of said two or more satellites .

The calculating of locations, satellite-to- satellite distances, orientations, and satellite-to- satellite directions of the satellites is relatively straightforward, because an orbiting satellite obeys the Keplerian laws of planetary motion, augmented with the effect of dedicated means of orbit and orientation con trol devices such as thrusters, flywheels, electromag netic coils, tethered masses, and the like. Conditions of signal propagation can be predicted by observing the known locations and movements of severe weather areas and other pertinent effects, and observing how the known orbital movement of the satellites will affect the oc currence of such effects on the signal propagation paths. Volumes of communication may be predicted for example by observing regular changes that may occur in the data traffic requirements of certain devices, caused by their periodic use or other recurrent effects that can be assumed to continue also in the future.

How the steps of the method of fig. 3 are im plemented in practice may depend on how the responsi bilities are distributed between the different devices that take part in the operation. Also here there are several possibilities. Next an embodiment is considered, where considerable responsibility is given to at least one of the satellites themselves, with reference to fig. 4.

In fig. 4 it is assumed that the method com prises determining one of the two or more satellites as a head of the temporary satellite group. In this example the GH or Group Head is satellite #1, while the two other illustrated satellites are Group Members (GMs). The serving GW shown in fig. 4 is a serving GW of the satellite determined as the Group Head. The method il lustrated in fig. 4 comprises performing the allocating of at least a subset of radio resources, i.e. step 304 of fig. 3, through actions of the satellite determined as the Group Head. In the following description the whole method of fig. 3 can be considered as being es sentially executed in the satellite determined as the Group Head. This interpretation requires that step 303 of fig. 3, i.e. the determining of a radio resource pool, is understood as comprising the reception of a radio resource pool allocation from the serving GW. More generally, the radio resource pool allocation can be received from a device or network infrastructure exter nal to the two or more satellites that form the temporary satellite group.

The method of fig. 4 comprises, before said determining of a radio resource pool, aggregating group information indicative of identities of the two or more satellites and of a need for satellite-to-satellite com munications among the temporary satellite group. The method comprises also sending the aggregated group in formation to said external device or network infrastruc ture. This takes place in steps 401 to 405 of fig. 4. Of these, step 401 comprises exchanging first infor mation concerning inter-satellite communications be tween at least some of the two or more satellites that are to form the temporary satellite group, and selecting the satellites for said temporary satellite group based at least partly on said exchanged first information.

Taken that the expected resource pool alloca tion has not yet been determined at this point, the exchanging of first information should utilize radio resources that the satellites have available for inter satellite communications even without the expected re source pool allocation. Here it is assumed that such radio resources are available as a default, in order to facilitate at least basic inter-satellite communica tions at data rates that are low enough so that addi tional radio resource allocations of the kind described above are not yet needed. The default resources may be called the dedicated ISL resources.

Step 401 could also be described as the upper communication layers, like the RRC (radio resource con trol) layer and/or some layer (s) above the RRC layer for example, in the regenerative satellites deciding to tem porarily group particular satellites and to enable or extend their mutual Xn interface functions via ISL, based on the collected ("first") satellite information. This is different from what happens in terrestrial com munications systems, where the detection of another base station is based on either pre-configuration or the au tomatic neighbor relation function.

The information exchanged at step 401 may com prise network-related parameters, such as an IP (Inter net Protocol) address or other network address of each satellite, and a transmit power consumption of each sat ellite. It may also comprise non-network related param eters, like parameters indicative of controlling the hardware of the satellite. As an example, satellite #1 may already have ISLs with satellites #2 and #3, but the existing ISLs do not have a large enough capacity due to lack of resources, and there is no ISL between sat ellites #2 and #3. In this case, the higher layers (e.g. RRC layer and/or one or more layers above the RRC layer) at satellite #1 can detect different events, such as:

- The different satellites are approximately at the same altitude, meaning that ISLs will be directed essentially horizontally, so that reusing some re sources originally meant for service and/or feeder links will not introduce a prohibitive amount of interference to the essentially vertically ori ented links.

- There is a need for more resources in order to better support its ISLs with satellite #2 and sat ellite #3, e.g. to enable/extend the Xn interface functions .

- There is a need to use ISL for relaying the NG-CN connection to another satellite, whose feeder link towards its GW is blocked due to bad weather.

- There is a need for setting up an Xn interface between satellite #2 and satellite #3, since they partially cover the same area in their service links. As a result of processing for example infor mation of the kind explained above, satellite #1 can decide to form a temporary satellite group and request more resources for supporting the information exchange inside the group.

Concerning step 402, a GH satellite can be se lected with or without interaction with other GM satel lites. For instance, in the example case outlined above satellite #1 can nominate itself as the GH satellite, since it already has the ISLs with the other GM satel lites. Alternatively satellite #1 can propose another satellite to act as the GH satellite, for example by sending a request message to that satellite. The request message can contain some group information for assisting the targeted satellite in making its decision. In an advantageous embodiment a response message will be transmitted back to the proposing satellite to acknowledge acting as a GH satellite.

Whatever the selection method, the selected GH satellite can configure the GM satellites to report their local information either periodically or non-pe- riodically based on some triggering events. This con figuration can take place either in a separate step or already during the previous steps explained above. Based on that configuration, each GM satellite sends its local network information to the GH satellite, which is il lustrated as steps 403 and 404 in fig. 4. The local information may comprise e.g. information indicative of radio conditions on the service and/or feeder links, information indicative of traffic load, and the like.

The GH satellite aggregates its own network information with the information it received from the GM satellites. Step 405 represents the GH satellite sending a resource request message to its serving GW, or more generally to an external device or network in frastructure that is responsible for making decisions about radio resource pool allocations for satellites. The resource request message may contain the aggregated group information. Alternatively, the request can be sent to said external device or network infrastructure separately from the aggregated group information.

Based on the received request message, the GW (or other external device or network infrastructure) executes a resource pool allocation algorithm at step 406. The resource pool allocation algorithm may consider the co-existence of other satellite groups, in order to coordinate the resources among the different groups and mitigate any inter-group interference. In addition, the resource pool allocation algorithm may derive the re source pool validity period T_RePo . Aspects that may be considered in deriving the value of T_Rep0 may comprise e.g. the known mobility patterns of the satellites in the group, known or expected oncoming resource alloca tions to other satellite groups, and the like. The value of T_Rep0 could be set to up to several seconds or even longer.

At step 407 the GW or other external device or network infrastructure sends the resource pool config uration information to the GH satellite. The resource pool allocation is valid from this moment until the expiry of the resource pool validity period T_Rep0. Before T_Repo expires, the GH satellite will need to send the updated real-time group information and request for re source pool allocation again. The GW can also send the configuration information to one or more other GWs on Earth for awareness (not shown in fig. 4).

Step 408 represents the GH satellite allocating one or more subsets of radio resources from the radio resource pool for use by at least a subgroup of the temporary satellite group. The allocating is valid for a second duration or time within the resource pool va lidity period T_Rep0. This second duration may be called the allocation validity period and marked as Tp_A. The GH satellite can coordinate and dedicate a specific radio resource from the allocated resource pool to any ISL within the group for the allocation validity period T_RA. The dedicated resource allocation may take account of any real-time information of the different GM satellites. For instance, if two satellites have overlapping coverage area in their service links and there is a heavy traffic load in that coverage area, more resources could be allocated to their ISL. The resource configurations are transmitted from the GH sat ellite to each GM satellite at steps 409 and 410, and each ISL in the group can apply the configured resource for transmission and reception at step 411.

Before the allocation validity period T_RA ex pires the GM satellites may send their updated real time information to the GH satellite again for request ing maintaining and/or updating their dedicated resource allocations. Such transmissions take place at steps 412 and 413 in fig. 4. The value of T_RA may be much smaller than the value of T_Rep0, in order for the GH satellite to preserve the ability to dynamically adjust the resource allocation based on changes revealed by the updated the real-time information (e.g. traffic load, ISL radio con dition, etc.). Steps 414, 415, and 416 represent a new round of dedicated resource allocating that resembles that of steps 408, 409, and 410 above but takes into account the updated local information received at steps 412 and 413.

The IP addresses of the satellites exchanged in step 401 can be used to set up a transport network layer (TNL) between two regenerative satellites in the temporary group. This is different from the practice of terrestrial mobile networks where the IP address of a neighboring BS is obtained by either predefined config uration or querying over the SI interface. In fig. 4 it is assumed that at least some need for additional radio resources for use in ISL communi cations remains in the temporary satellite group even when the expiry of the resource pool validity period T_Rep0 approaches. The information exchange that has taken place between the satellites in the group, for example at steps 412 and 413 of fig. 4, enables the GH satellite to send a renewed resource request, possibly together with at least some of the updated group information, to the GW or other external device or network infrastruc ture at step 417. The three-dot symbol before that in fig. 4 illustrates the fact that there may be an arbi trary number of dedicated resource allocation rounds before that, as long as a corresponding number of allo cation validity periods fits in the resource pool va lidity period T_Rep0. The resulting round of (possibly updated) resource pool allocation and transmission to the GH satellite are shown as steps 418 and 419 in fig. 4.

If the GH satellite is moving out of the group or it is not suitable for acting as the GH satellite any more for some other reason, it can autonomously nominate another satellite to act as the new GH satellite, based on the collected real-time information. Following that, it may send a message together with the group configu ration information to the new GH satellite, including the resource allocation information.

If the GH satellite moves from the currently serving ("source") GW towards another ("target") GW, the GH satellite may change its feeder link to the target GW. Since two GWs might be far away from each other, e.g. even on two continents, it is advantageous to avoid any unnecessary information exchange between them. In an advantageous embodiment the GH satellite sends its current group information to the target GW, enabling the target GW to take over the control functionality for the Xn interfaces in the satellite group. Fig. 5 illustrates an embodiment in which the method is a method to be executed in the GW, or more generally in a device or network infrastructure external to the two or more satellites that are to form the temporary satellite group. It should be noted that in this embodiment the concept of allocating a subset of radio resources from the radio resource pool comprises indirectly allocating the subset by allowing one of the satellites make a decision of the actual allocating, as is explained in more detail below.

In the embodiment of fig. 5 the initiative for forming a temporary satellite group and allocating radio resources for temporary use in ISLs is at the GW (or other external device or network infrastructure). Step 501 corresponds to identifying two or more satellites that could benefit from becoming members of the satel lite group. It comprises providing second information indicative of a predicted need for inter-satellite com munications between at least some of said two or more satellites, and selecting the satellites for said tem porary satellite group based at least partly on said second information.

Since locations of satellites can be calculated and the signal propagation between two nearby satellites in space is line-of-sight with no surprising attenuating factors, path loss between two nearby satellites can be predicted relatively accurately. Thus, based on the pre- dictively calculated locations of satellites and the ISL channel conditions, the upper layers at a GW can detect and recognize a constellation pattern of satellites and, therefore, decide for setting up a satellite group and enabling/extending the Xn interface functions by reusing the resources of the service and feeder links. In addi tion, the GW can select a GH satellite from that group using different methods, e.g. selecting the one closest to the central position of the group. Moreover, the GW also allocates the resource pool and derives the valid ity period of the resource pool allocation, i.e. T_Rep0 · The resource pool configuration may be based on the predicted satellite information, which may contain not only the information of the satellites in the group, but also information of the nearby satellites not belonging to the group and/or moving towards the group. In this way the inter-group interference could be controlled.

At step 502 the GW sends the group information together with the resource pool configuration to the GH satellite. The group information may contain IDs and IP addresses of the satellites belonging to the group, and also an indication if there should be an Xn interface via the ISL between two GM satellites. Before T_Rep0 ex pires, based on the predicted information at that point, the GW will run its group detection and resource allo cation algorithm again to send the updated resource pool configuration information (see steps 510 and 511 in fig. 5).

By sending the group information and the re source pool configuration at step 502 the GW delegates the allocating of dedicated radio resources to the GH satellite. This way also the method of fig. 5 can be said to comprise such allocating, even the allocating made by the GW is indirect.

Upon receiving the resource pool configuration the GH satellite can coordinate and dedicate a specific resource from the resource pool to each ISL at step 503 for an allocation validity duration ¾ . The resource allocation should take account of the predicted infor mation of the different GM satellites. For instance, if two satellites are nearby and the ISL between them has a low pathloss, they could use a modulation and coding scheme with higher spectral efficiency. Thus, the GH satellite can provide less resource to that ISL while providing more resources to the ISLs with high pathloss values. This consideration is naturally valid also for the other embodiments described earlier with reference to fig. 4.

The GH satellite sends the resource configura tion information to the other GM satellites at steps 504 and 505. For each Xn link between two GM satellites, the resource configuration information may contain the IDs and IP addresses of the two satellites and also indicate the allocated subset of resources for that link. Before T_RA expires, the GH satellite updates the dedicated re source allocation and sends that information to the GM satellites again (see steps 507, 508, and 509 in fig. 5).

Based on the received configuration infor mation, each GM satellite can start its ISL transmission and reception by reusing the resources of the service and the feeder links at step 506.

According to an embodiment the provided IP ad dresses of the satellites in steps 502, 504, and 505 can be used to set up a transport network layer (TNL) between two regenerative satellites. This is different from a practice employed in terrestrial mobile networks where the IP address of a neighboring BS is obtained by either predefined configuration or querying over the SI inter face.

In this approach, if the GH satellite is moving out of the group or it is otherwise not suitable for acting as the GH satellite any more, it can send a notification message to the serving GW. The serving GW may arrive at the same conclusion also at its own motion, by making the calculations of the movements of the sat ellites on orbit. Following that, the serving GW can select a new GH satellite and send the new configuration information to that satellite, as shown in steps 502 and 511 of fig. 5.

Similar to what has been described earlier with reference to fig. 4, if the GH satellite moves from the current ("source") GW towards another ("target") GW, the GH satellite will change its feeder link to the target GW. The GH satellite may send its current group infor mation to the target GW, in order to avoid direct in formation transfer between two possibly far-away GWs. The target GW can take over the control functionality for the Xn interfaces in the group based on the infor mation it received from the GH satellite.

Features from the example embodiments de scribed so far can be combined in various ways. Fig. 6 illustrates a combined embodiment that begins as in fig. 5 but continues as in fig. 4. In other words, the orig inal initiative for forming a temporary group of satel lites for inter-satellite communications is based on predicted ("second") information and comes from the GW, but at least some of the actual allocation of radio resources takes place on the basis of ("first") real time time information exchanged between the satellites.

Steps 501 to 506 in fig. 6 proceed as in fig. 5 above. During the first T_RA the GH satellite exchanges with the other GM satellites information concerning in ter-satellite communications between at least some of the satellites in the group. This exchanging of infor mation is represented as steps 412 and 413 in fig. 6, and it may involve at least some similar elements as steps 401 - 404 and 412 - 413 in fig. 4. Thus at the expiry of the first T_RA the GH satellite may have more accurate information about the latest radio resource needs and other affecting aspects of the GM satellites, and it can make even more optimal allocation decisions at step 414. In fig. 6 it is assumed that also the remaining part of the method proceeds as in fig. 4, for example so that before the GW (or other external device or network infrastructure) makes its decision about the continued resource pool allocation at step 418 it re ceives the updated group information from the GH satel lite at step 417. Alternatively, the continued resource pool allocation may be carried out in the same way as in step 501, i.e. so that step 417 would not be needed in fig. 6 for the serving GW to perform the resource pool allocation at step 418.

Another possible combination embodiment is such where after step 502, i.e. after the GH satellite received the initial group and resource pool allocation from the GW, it first initiates a round of collecting local ("first") information from the GM satellites be fore making even the first decision about dedicated re source allocation at step 503.

The example embodiments illustrated above may be performed by an apparatus, which may be located for example in the GW, in some other external device or network infrastructure, or in the GH satellite. Such an apparatus may comprise one or more processors or other programmable devices, which are capable of implementing a method of a kind described above by executing machine- readable instructions stored in a memory in the form of a computer program. Further, a computer program com prising instructions for causing an apparatus to per form, may perform the illustrated example embodiments.

Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equiv alent features and acts are intended to be within the scope of the claims.

It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be un derstood that reference to 'an' item may refer to one or more of those items.

The steps of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the spirit and scope of the subject matter de scribed herein. Aspects of any of the embodiments de scribed above may be combined with aspects of any of the other embodiments described to form further embodiments without losing the effect sought.

The term 'comprising' is used herein to mean including the method, blocks or elements identified, but that such blocks or elements do not comprise an exclu sive list and a method or apparatus may contain addi tional blocks or elements.

It will be understood that the above descrip tion is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exem plary embodiments. Although various embodiments have been described above with a certain degree of particu larity, or with reference to one or more individual embodiments, those skilled in the art could make numer ous alterations to the disclosed embodiments without departing from the spirit or scope of this specifica tion.

Claims

1. A method comprising: identifying two or more satellites as forming a temporary satellite group capable of inter-satellite communications; determining a radio resource pool containing radio resources to be used by said temporary satellite group for said inter-satellite communications, the de termined radio resource pool being valid for a first duration of time; and allocating a subset of radio resources from said radio resource pool for use by at least a subgroup of said temporary satellite group for said inter-satel lite communications, the allocation being valid for a second duration of time within said first duration of time.

2. The method according to claim 1, wherein at least some of the radio resources in the determined radio resource pool are radio resources for use in communi cations between a satellite and at least one terres trial station.

3. The method according to claim 1 or 2, wherein said identifying of said two or more satellites comprises exchanging first information concerning inter-satel lite communications between at least some of said two or more satellites, and selecting the satellites for said temporary satellite group based at least partly on said exchanged first information.

4. The method according to claim 3, wherein said first information comprises at least one of: locations of at least some of said two or more satellites; moving directions of at least some of said two or more satellites; satellite-to-satellite distances of at least some of said two or more satellites; orientations of at least some of said two or more satellites; satellite-to-satellite directions of at least some of said two or more satellites; conditions of signal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and volumes of communication handled by at least some of said two or more satellites.

5. The method according to any of the preceding claims, wherein said identifying of said two or more satel lites comprises providing second information indica tive of a predicted need for inter-satellite communi cations between at least some of said two or more satellites, and selecting the satellites for said tem porary satellite group based at least partly on said second information.

6. The method according to claim 5, wherein said provid ing of second information comprises at least one of: calculating locations of at least some of said two or more satellites based on their orbit data; calculating moving directions of at least some of said two or more satellites based on their orbit data; calculating satellite-to-satellite distances of at least some of said two or more satellites based on their orbit data; calculating orientations of at least some of said two or more satellites; calculating satellite-to-satellite directions of at least some of said two or more satellites based on their orbit data; observing and/or predicting conditions of sig nal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and observing and/or predicting volumes of commu nication handled by at least some of said two or more satellites.

7. The method according to any of the preceding claims, comprising: determining one of said two or more satellites as a head of said temporary satellite group; and performing said allocating of at least a subset of radio resources through actions of the satellite de termined as the head of said temporary satellite group.

8. The method according to claim 7, wherein: the method is a method to be executed in that one of said two or more satellites that is determined as the head of said temporary satellite group; and said determining of a radio resource pool com prises receiving a radio resource pool allocation from a device or network infrastructure external to said two or more satellites.

9. The method according to claim 8, wherein: the method comprises, before said determining of a radio resource pool, aggregating group information indicative of identities of the two or more satellites and of a need for satellite-to-satellite communications among the temporary satellite group, and sending the aggregated group information to said external device or network infrastructure.

10. The method according to claim 9, wherein said ag gregated group information comprises at least one of: information indicative of conditions of signal propagation on links between at least some of the two or more satellites and respective terrestrial stations, information indicative of volumes of communi cation handled by at least some of said two or more satellites orientations of at least some of said two or more satellites.

11. The method according to any of claims 8 to 10, wherein: the method comprises, before said determining of a radio resource pool, sending a request for radio resource pool allocation to said external device or net work infrastructure.

12. The method according to claim 11, when depending on any of claims 9 or 10, wherein said request for radio resource pool allocation is sent to said external de vice or network infrastructure separately from said aggregated group information.

13. The method according to claim 11, when depending on any of claims 9 or 10, wherein said request for radio resource pool allocation is sent to said external de vice or network infrastructure together with said ag gregated group information.

14. The method according any of claims 1 to 7, wherein: the method is a method to be executed in a device or network infrastructure external to said two or more satellites; and said allocating of a subset of radio resources from said radio resource pool comprises indirectly al locating said subset by allowing one of said two or more satellites make a decision of said allocating.

15. The method according to claim 14, when depending on any of claims 5 or 6, wherein: the method comprises, before said determining of a radio resource pool, performing said providing of second information and said selecting of the satellites for said temporary satellite group, so that said provid ing of second information and said selecting of the satellites are performed through actions of said device or network infrastructure external to said two or more satellites.

16. An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer pro gram code configured to, with the at least one proces sor, cause the apparatus to at least perform: identifying two or more satellites as forming a temporary satellite group capable of inter-satellite communications; determining a radio resource pool containing radio resources to be used by said temporary satellite group for said inter-satellite communications, the de termined radio resource pool being valid for a first duration of time; and allocating a subset of radio resources from said radio resource pool for use by at least a subgroup of said temporary satellite group for said inter-satel lite communications, the allocation being valid for a second duration of time within said first duration of time.

17. The apparatus according to claim 16, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform said allocation so that at least some of the radio resources in the de termined radio resource pool are radio resources for use in communications between a satellite and at least one terrestrial station.

18. The apparatus according to claim 16 or 17, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform said identi fying of said two or more satellites by exchanging first information concerning inter-satellite communi cations between at least some of said two or more satellites, and selecting the satellites for said tem porary satellite group based at least partly on said exchanged first information.

19. The apparatus according to claim 18, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform said exchanging of first information by exchanging at least one of: locations of at least some of said two or more satellites; moving directions of at least some of said two or more satellites; satellite-to-satellite distances of at least some of said two or more satellites; orientations of at least some of said two or more satellites; satellite-to-satellite directions of at least some of said two or more satellites; conditions of signal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and volumes of communication handled by at least some of said two or more satellites.

20. The apparatus according to any of claims 16 to 19, wherein the at least one memory and the computer pro gram code are configured to, with the at least one processor, cause the apparatus to at least perform said identifying of said two or more satellites by providing second information indicative of a predicted need for inter-satellite communications between at least some of said two or more satellites, and se lecting the satellites for said temporary satellite group based at least partly on said second infor mation.

21. The apparatus according to claim 20, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform said providing of second information by performing at least one of: calculating locations of at least some of said two or more satellites based on their orbit data; calculating moving directions of at least some of said two or more satellites based on their orbit data; calculating satellite-to-satellite distances of at least some of said two or more satellites based on their orbit data; calculating orientations of at least some of said two or more satellites; calculating satellite-to-satellite directions of at least some of said two or more satellites based on their orbit data; observing and/or predicting conditions of sig nal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and observing and/or predicting volumes of commu nication handled by at least some of said two or more satellites.

22. The apparatus according to any of claims 16 to 21, wherein the at least one memory and the computer pro gram code are configured to, with the at least one processor, cause the apparatus to at least perform: determining one of said two or more satellites as a head of said temporary satellite group; and performing said allocating of at least a subset of radio resources through actions of the satellite de- termined as the head of said temporary satellite group.

23. The apparatus according to claim 22, wherein: the apparatus is an apparatus to be included in that one of said two or more satellites that is determined as the head of said temporary satellite group; and the at least one memory and the computer pro gram code are configured to, with the at least one pro cessor, cause the apparatus to at least perform said determining of a radio resource pool by receiving a radio resource pool allocation from a device or network infrastructure external to said two or more satellites.

24. The apparatus according to claim 23, wherein: the at least one memory and the computer pro gram code are configured to, with the at least one pro cessor, cause the apparatus to at least perform, before said determining of a radio resource pool, aggregating group information indicative of identities of the two or more satellites and of a need for satellite-to-sat- ellite communications among the temporary satellite group, and sending the aggregated group information to said external device or network infrastructure.

25. The apparatus according to claim 24, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus to at least perform said aggregating of group information by aggregating at least one of: information indicative of conditions of signal propagation on links between at least some of the two or more satellites and respective terrestrial stations, information indicative of volumes of communi cation handled by at least some of said two or more satellites orientations of at least some of said two or more satellites.

26. The apparatus according to any of claims 23 to 25, wherein: the at least one memory and the computer pro gram code are configured to, with the at least one pro cessor, cause the apparatus to at least perform, before said determining of a radio resource pool, sending a request for radio resource pool allocation to said ex ternal device or network infrastructure.

27. The apparatus according to claim 26, when depending on any of claims 24 or 25, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the appa ratus to at least send said request for radio resource pool allocation to said external device or network infrastructure separately from said aggregated group information.

28. The apparatus according to claim 26, when depending on any of claims 24 or 25, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the appa ratus to at least send said request for radio resource pool allocation to said external device or network infrastructure together with said aggregated group information.

29. The apparatus according any of claims 16 to 22, wherein: the apparatus is an apparatus to be included in a device or network infrastructure external to said two or more satellites; and the at least one memory and the computer pro gram code are configured to, with the at least one pro cessor, cause the apparatus to at least perform said allocating of a subset of radio resources from said radio resource pool by indirectly allocating said subset by allowing one of said two or more satellites make a decision of said allocating.

30. The apparatus according to claim 29, when depending on any of claims 20 or 21, wherein: the at least one memory and the computer pro gram code are configured to, with the at least one pro cessor, cause the apparatus to at least perform said providing of second information and said selecting of the satellites for said temporary satellite group before said determining of a radio resource pool, so that said providing of second information and said selecting of the satellites are performed through actions of said device or network infrastructure external to said two or more satellites.

31. A computer program comprising instructions for caus ing an apparatus to perform the method of any of claims 1 - 15.

32. A computer-readable medium comprising a computer program comprising instructions for causing an appa ratus to perform the method of any of claims 1 - 15.

33. An apparatus comprising means for performing: identifying two or more satellites as forming a temporary satellite group capable of inter-satellite communications; determining a radio resource pool containing radio resources to be used by said temporary satellite group for said inter-satellite communications, the de termined radio resource pool being valid for a first duration of time; and allocating a subset of radio resources from said radio resource pool for use by at least a subgroup of said temporary satellite group for said inter-satel lite communications, the allocation being valid for a second duration of time within said first duration of time.

34. The apparatus according to claim 33, comprising means for performing said determining of at least some of the radio resources in the determined radio re source pool so that the determined radio resources are radio resources for use in communications between a satellite and at least one terrestrial station.

35. The apparatus according to claim 33 or 34, compris ing means for performing said identifying of said two or more satellites so that it comprises exchanging first information concerning inter-satellite communi cations between at least some of said two or more satellites, and selecting the satellites for said tem porary satellite group based at least partly on said exchanged first information.

36. The apparatus according to claim 35, comprising means for providing said first information so that said first information comprises at least one of: locations of at least some of said two or more satellites; moving directions of at least some of said two or more satellites; satellite-to-satellite distances of at least some of said two or more satellites; orientations of at least some of said two or more satellites; satellite-to-satellite directions of at least some of said two or more satellites; conditions of signal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and volumes of communication handled by at least some of said two or more satellites.

37. The apparatus according to any of claims 33 to 36, comprising means for performing said identifying of said two or more satellites by providing second in formation indicative of a predicted need for inter satellite communications between at least some of said two or more satellites, and selecting the satellites for said temporary satellite group based at least partly on said second information.

38. The apparatus according to claim 37, comprising means for providing said second information by per forming at least one of: calculating locations of at least some of said two or more satellites based on their orbit data; calculating moving directions of at least some of said two or more satellites based on their orbit data; calculating satellite-to-satellite distances of at least some of said two or more satellites based on their orbit data; calculating orientations of at least some of said two or more satellites; calculating satellite-to-satellite directions of at least some of said two or more satellites based on their orbit data; observing and/or predicting conditions of sig nal propagation between at least some of said two or more satellites and respective terrestrial stations they are communicating with; and observing and/or predicting volumes of commu nication handled by at least some of said two or more satellites.

39. The apparatus according to any of claims 33 to 38, comprising means for performing: determining one of said two or more satellites as a head of said temporary satellite group; and performing said allocating of at least a subset of radio resources through actions of the satellite de termined as the head of said temporary satellite group.

40. The apparatus according to claim 39, wherein: the apparatus is an apparatus to be included in that one of said two or more satellites that is determined as the head of said temporary satellite group; and the apparatus comprises means for performing said determining of a radio resource pool by receiving a radio resource pool allocation from a device or net work infrastructure external to said two or more satel lites.

41. The apparatus according to claim 40, comprising means for performing: before said determining of a radio resource pool, aggregating group information indicative of iden tities of the two or more satellites and of a need for satellite-to-satellite communications among the tempo rary satellite group, and sending the aggregated group information to said external device or network infra structure.

42. The apparatus according to claim 41, comprising means for providing said aggregated group information by providing at least one of: information indicative of conditions of signal propagation on links between at least some of the two or more satellites and respective terrestrial stations, information indicative of volumes of communi cation handled by at least some of said two or more satellites orientations of at least some of said two or more satellites.

43. The apparatus according to any of claims 40 to 42, comprising means for performing: before said determining of a radio resource pool, sending a request for radio resource pool alloca tion to said external device or network infrastructure.

44. The apparatus according to claim 43, when depending on any of claims 41 or 42, comprising means for sending said request for radio resource pool allocation to said external device or network infrastructure sepa rately from said aggregated group information.

45. The apparatus according to claim 43, when depending on any of claims 41 or 42, comprising means for sending said request for radio resource pool allocation to said external device or network infrastructure to gether with said aggregated group information.

46. The apparatus according any of claims 33 to 39, wherein: the apparatus is an apparatus to be included in a device or network infrastructure external to said two or more satellites; and the apparatus comprises means for performing said allocating of a subset of radio resources from said radio resource pool by indirectly allocating said subset by allowing one of said two or more satellites make a decision of said allocating.

47. The apparatus according to claim 46, when depending on any of claims 37 or 38, comprising means for per forming: before said determining of a radio resource pool, performing said providing of second information and said selecting of the satellites for said temporary satellite group, so that said providing of second in formation and said selecting of the satellites are per formed through actions of said device or network infra structure external to said two or more satellites.

48. The apparatus of any of claims 33 to 47, wherein the means comprises at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.