Patent Application
20240172156
The present disclosure relates to communication system.
The present invention relates to a wireless communication system and devices thereof operating according to the 3rd Generation Partnership Project (3GPP) standards or equivalents or derivatives thereof. The disclosure has particular but not exclusive relevance to improvements relating to the so-called ‘5G’ (or ‘Next Generation’) systems employing a non-terrestrial portion comprising airborne or spaceborne network nodes.
Under the 3GPP standards, a NodeB (or an ‘eNB’ in LTE, ‘gNB’ in 5G) is a base station via which communication devices (user equipment or ‘UE’) connect to a core network and communicate to other communication devices or remote servers. Communication devices might be, for example, mobile communication devices such as mobile telephones, smartphones, smart watches, personal digital assistants, laptop/tablet computers, web browsers, e-book readers, and/or the like. Such mobile (or even generally stationary) devices are typically operated by a user (and hence they are often collectively referred to as user equipment, ‘UE’) although it is also possible to connect IoT devices and similar MTC devices to the network. For simplicity, the present application will use the term base station to refer to any such base stations and use the term mobile device or UE to refer to any such communication device.
The latest developments of the 3GPP standards are the so-called ‘5G’ or ‘New Radio’ (NR) standards which refer to an evolving communication technology that is expected to support a variety of applications and services such as Machine Type Communications (MTC), Internet of Things (IoT)/Industrial Internet of Things (IIoT) communications, vehicular communications and autonomous cars, high resolution video streaming, smart city services, and/or the like. 3GPP intends to support 5G by way of the so-called 3GPP Next Generation (NextGen) radio access network (RAN) and the 3GPP NextGen core (NGC) network. Various details of 5G networks are described in, for example, the ‘NGMN 5G White Paper’ V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, which document is available from https://www.ngmn.org/5g-white-paper.html.
End-user communication devices are commonly referred to as User Equipment (UE) which may be operated by a human or comprise automated (MTC/IoT) devices. Whilst a base station of a 5G/NR communication system is commonly referred to as a New Radio Base Station (‘NR-BS’) or as a ‘gNB’ it will be appreciated that they may be referred to using the term ‘eNB’ (or 5G/NR eNB) which is more typically associated with Long Term Evolution (LTE) base stations (also commonly referred to as ‘4G’ base stations). 3GPP Technical Specification (TS) 38.300 V16.4.0 and TS 37.340 V16.4.0 define the following nodes, amongst others:
3GPP is also working on specifying an integrated satellite and terrestrial network infrastructure in the context of 5G. The term Non-Terrestrial Networks (NTN) refers to networks, or segments of networks, that are using an airborne or spaceborne vehicle for transmission. Satellites refer to spaceborne vehicles in Geostationary Earth Orbit (GEO) or in Non-Geostationary Earth Orbit (NGEO) such as Low Earth Orbits (LEO), Medium Earth Orbits (MEO), and Highly Elliptical Orbits (HEO). Airborne vehicles refer to High Altitude Platforms (HAPs) encompassing Unmanned Aircraft Systems (UAS)—including tethered UAS, Lighter than Air UAS and Heavier than Air UAS—all operating quasi-stationary at an altitude typically between 8 and 50 km.
3GPP Technical Report (TR) 38.811 V15.4.0 is a study on New Radio to support such Non-Terrestrial Networks. The study includes, amongst others, NTN deployment scenarios and related system parameters (such as architecture, altitude, orbit etc.) and a description of adaptation of 3GPP channel models for Non-Terrestrial Networks (propagation conditions, mobility, etc.). 3GPP TR 38.821 V16.0.0 provides further details about NTN.
Non-Terrestrial Networks are expected to:
Satellite or aerial vehicles may generate several beams over a given area to provide respective NTN cells. The beams have a typically elliptic footprint on the surface of the Earth.
With satellite or aerial vehicle keeping position fixed in terms of elevation/azimuth with respect to a given earth point e.g. GEO and UAS, the beam footprint is earth fixed.
With satellite circulating around the earth (e.g. LEO) or on an elliptical orbit around the earth (e.g. HEO) the beam footprint may be moving over the Earth with the satellite or aerial vehicle motion on its orbit. Alternatively, the beam footprint may be Earth-fixed (or quasi-Earth-fixed) temporarily, in which case an appropriate beam pointing mechanism (mechanical or electronic steering) may be used to compensate for the satellite or aerial vehicle motion.
The term Timing Advance (TA) refers to a parameter that is used for controlling the timing of transmission of signals on the uplink towards the base station to ensure that the signals arrive at the base station at the appropriate time. The greater the value of the TA the earlier the UE needs to transmit a signal in order for that signal to reach the base station at the correct time. In NTN systems signals need to travel longer distances than in non-NTN radio networks since they are relayed via satellites. Thus, the UE's applicable Timing Advance (TA) may be affected by (changes in) one or more of: the UE's position; the serving satellite's position; and the applicable timing offset.
The UE's uplink TA may be adversely effected when communicating via NTN because LEO and MEO satellites are moving at a high speed. Although it is not clear how fast satellites are getting closer/farther away from the UE, it will be appreciated that the associated round trip delay (RTD) will change faster in NTN than in legacy network (i.e. non-NTN networks). For example, in terrestrial NR networks, UE uplink timing is updated by the base station (gNB) via a closed loop using the so-called Timing Advance Command (parameter NTA_offset). However, this method would result in an incorrect timing advance value being applied after a very short time (a few seconds).
Incorrect time alignment has an adverse impact on decodability of uplink signals at the base station due to inter-system interface (ISI) and/or frame ambiguity. Moreover, the TA value is also used for applying an appropriate timing offset between the UE and the base station, for example, for scheduling of a UE for the uplink and for determining the start of the response window in the downlink.
The inventors have realised that with the more frequent TA adjustments needed in NTN systems there is an increase in associated signalling between the UE and its serving base station. Whilst it is possible for the UE to derive an appropriate TA value on its own, there are concerns regarding the accuracy of such self-calculated TA values, and additional signalling may be necessary from the network to the UE for TA refinement (e.g. during initial access and/or TA maintenance).
Moreover, the UE and the base station need to have the same Timing Offset. However, the information on which the Timing Offset is based is not symmetrical without reporting by the UE or without using legacy closed loop adjustment by the base station, which methods would be inefficient in NTN or they would be wasteful of resources. If the UE determines the applicable Timing Offset implicitly (e.g. from a TAC (Timing Advance Command)), it is not clear what happens if the UE misses a TAC and/or if the base station needs to send multiple TACs (which may also result in non-symmetrical level of knowledge at the UE and the base station).
The currently proposed methods for maintaining appropriate time alignment require excessive signalling between the UE and the base station (e.g. TA reporting by UE to maintain uplink alignment at gNB side) and/or additional processing/increased battery use at the UE (e.g. open-loop TA maintenance by the UE based on Global Navigation Satellite System (GNSS) positioning).
Accordingly, the present invention seeks to provide methods and associated apparatus that address or at least alleviate (at least some of) the above described issues.
Although for efficiency of understanding for those of skill in the art, the invention will be described in detail in the context of a 3GPP system (5G networks including NTN), the principles of the invention can be applied to other systems as well.
In one aspect, the invention provides a method performed by a user equipment (UE) configured to communicate via a non-terrestrial network, the method comprising: obtaining information identifying a threshold associated with a timing advance value applicable for communications with a network node via the non-terrestrial network; acquiring a timing advance value for said communications with the network node; and determining whether to transmit a timing advance report to the network node based on the timing advance value and the threshold.
In one aspect, the invention provides a method performed by a user equipment (UE) configured to communicate via a non-terrestrial network, the method comprising: obtaining information for use in predicting a timing advance value to be used for communicating with a network node; acquiring a timing advance value, and deriving a predicted timing advance value based on the obtained information; and determining whether to transmit a timing advance report to the network node based on the acquired timing advance value and the predicted timing advance value.
In one aspect, the invention provides a method performed by a network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the method comprising: transmitting, to the UE, information identifying a threshold associated with a timing advance value applicable for communications with the UE via the non-terrestrial network; acquiring a timing advance value for said communications with the UE; and receiving a timing advance report from the UE based on the threshold and a timing advance value acquired by the UE.
In one aspect, the invention provides a method performed by a network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the method comprising: transmitting, to the UE, information for use in predicting a timing advance value to be used for communications between the UE and the network node; and receiving a timing advance report from the UE based on a timing advance value acquired by the UE and the predicted timing advance value.
In one aspect, the invention provides a user equipment (UE) configured to communicate via a non-terrestrial network, the UE comprising: means for obtaining information identifying a threshold associated with a timing advance value applicable for communications with a network node via the non-terrestrial network; means for acquiring a timing advance value for said communications with the network node; and means for determining whether to transmit a timing advance report to the network node based on the timing advance value and the threshold.
In one aspect, the invention provides a user equipment (UE) configured to communicate via a non-terrestrial network, the UE comprising: means for obtaining information for use in predicting a timing advance value to be used for communicating with a network node; means for acquiring a timing advance value, and for deriving a predicted timing advance value based on the obtained information; and means for determining whether to transmit a timing advance report to the network node based on the acquired timing advance value and the predicted timing advance value.
In one aspect, the invention provides a network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the network node comprising: means for transmitting, to the UE, information identifying a threshold associated with a timing advance value applicable for communications with the UE via the non-terrestrial network; means for acquiring a timing advance value for said communications with the UE; and means for receiving a timing advance report from the UE based on the threshold and a timing advance value acquired by the UE.
In one aspect, the invention provides a network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the network node comprising: means for transmitting, to the UE, information for use in predicting a timing advance value to be used for communications between the UE and the network node; and means for receiving a timing advance report from the UE based on a timing advance value acquired by the UE and the predicted timing advance value.
In one aspect, the invention provides a user equipment (UE) configured to communicate via a non-terrestrial network, the UE comprising a processor, a transceiver, and a memory storing instructions; wherein the controller is configured to: obtain information identifying a threshold associated with a timing advance value applicable for communications with a network node via the non-terrestrial network; acquire a timing advance value for said communications with the network node; and determine whether to transmit a timing advance report to the network node based on the timing advance value and the threshold.
In one aspect, the invention provides a user equipment (UE) configured to communicate via a non-terrestrial network, the UE comprising a processor, a transceiver, and a memory storing instructions; wherein the controller is configured to: obtain information for use in predicting a timing advance value to be used for communicating with a network node; acquire a timing advance value, and derive a predicted timing advance value based on the obtained information; and determine whether to transmit a timing advance report to the network node based on the acquired timing advance value and the predicted timing advance value.
In one aspect, the invention provides a network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the network node comprising a processor, a transceiver, and a memory storing instructions; wherein the controller is configured to: control the transceiver to transmit, to the UE, information identifying a threshold associated with a timing advance value applicable for communications with the UE via the non-terrestrial network; acquire a timing advance value for said communications with the UE; and control the transceiver to receive a timing advance report from the UE based on the threshold and a timing advance value acquired by the UE.
In one aspect, the invention provides a network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the network node comprising a processor, a transceiver, and a memory storing instructions; wherein the controller is configured to control the transceiver to: transmit, to the UE, information for use in predicting a timing advance value to be used for communications between the UE and the network node; and receive a timing advance report from the UE based on a timing advance value acquired by the UE and the predicted timing advance value.
Aspects of the invention extend to corresponding systems, apparatus, and computer program products such as computer readable storage media having instructions stored thereon which are operable to program a programmable processor to carry out a method as described in the aspects and possibilities set out above or recited in the claims and/or to program a suitably adapted computer to provide the apparatus recited in any of the claims.
Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently of (or in combination with) any other disclosed and/or illustrated features. In particular but without limitation the features of any of the claims dependent from a particular independent claim may be introduced into that independent claim in any combination or individually.
Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which:
In this system 1, users of mobile devices 3 (UEs) can communicate with each other and other users via access network nodes respective satellites 5 and/or base stations 6 and a data network 7 using an appropriate 3GPP radio access technology (RAT), for example, an E-UTRA and/or 5G RAT. As those skilled in the art will appreciate, whilst three mobile devices 3, one satellite 5, and one base station 6 are shown in
It will be appreciated that a number of base stations 6 form a (radio) access network or (R)AN, and a number of NTN nodes 5 (satellites and/or UAS platforms) form a Non-Terrestrial Network (NTN). Each NTN node 5 is connected to an appropriate gateway (in this case co-located with a base station 6) using a so-called feeder link and connected to respective UEs 3 via corresponding service links. Thus, when served by an NTN node 5, a mobile device 3 communicates data to and from a base station 6 via the NTN node 5, using an appropriate service link (between the mobile device 3 and the NTN node 5) and a feeder link (between the NTN node 5 and the gateway/base station 6). In other words, the NTN forms part of the (R)AN, although it may also provide satellite communication services independently of E-UTRA and/or 5G communication services.
Although not shown in
The data (or core) network 7 (e.g. the EPC in case of LTE or the NGC in case of NR/5G) typically includes logical nodes (or ‘functions’) for supporting communication in the telecommunication system 1, and for subscriber management, mobility management, charging, security, call/session management (amongst others). For example, the data network 7 of a ‘Next Generation’/5G system will include user plane entities and control plane entities, such as one or more control plane functions (CPFs) and one or more user plane functions (UPFs). The data network 7 is also coupled to other data networks such as the Internet or similar Internet Protocol (IP) based networks (not shown in
Due to the satellites' movement along their orbit, the distance between the UE 3 and its current NTN node 5 is changing relatively rapidly, which causes the characteristics (such as delay) of the service link to change accordingly. The characteristics of the feeder link change in a similar fashion due to the distance changing between the NTN node 5 and the base station 6 with the satellites' movement. These changes have an effect on the overall RTD between the UE 3 and the base station 6 and they require appropriate adjustments to the timing advance/time offset employed between them.
In order to support appropriate time and frequency synchronization between the UE 3 and the base station 6, when the UE 3 is connected via an NTN node 5 (in RRC Connected state) it is configured to perform UE specific TA calculations based at least on its GNSS-acquired position and the serving satellite's ephemeris. In order to update its TA in RRC Connected state, the UE 3 may use an open control loop (e.g. UE autonomous TA estimation, common TA estimation, etc.) or a closed control loop (e.g. received TA commands), or a combination thereof.
Specifically, the UE 3 is configured to employ one of the following approaches:
Beneficially, the above techniques allow reducing/minimising the signalling associated with TA update without causing misalignment between the UE 3 and the base station 6. Moreover, a reduced/more efficient timing offset signalling can be achieved by employing an implicit offset derivation technique from the UE's reported and/or predicted TA.
For example, in case of a UE 3 with good GNSS/autonomous TA update, no signalling is required (no TA reporting), unless the TA has an impact on the timing offset. The base station 6 may configure an appropriate (flexible) TAT value for the UE 3 depending on the situation which can further reduce signalling needed and/or improve TA correction by the UE 3.
Since the timing offset is derived from the (full) TA, if both the UE 3 and the base station 6 has this information, then there is no need to use signalling for the indicating the actual Timing Offset (implicit solution). If a prediction model is used, the timing offset can be updated with reduced/removed signalling.
The communications control module 43 is responsible for handling (generating/sending/receiving) signalling messages and uplink/downlink data packets between the UE 3 and other nodes, including NTN nodes 5, (R)AN nodes 6, and core network nodes. The signalling may comprise control signalling related to time and frequency synchronization between the UE 3 and the base station/gateway 6.
The communications control module 63 is responsible for handling (generating/sending/receiving) signalling between the NTN node 5 and other nodes, such as the UE 3, base stations 6, gateways, and core network nodes (via the base stations/gateways). The signalling may comprise control signalling related to time and frequency synchronization between the UE 3 and the base station/gateway 6.
The communications control module 83 is responsible for handling (generating/sending/receiving) signalling between the base station 6 and other nodes, such as the UE 3, NTN nodes 5, and core network nodes. The signalling may comprise control signalling related to time and frequency synchronization between the UE 3 and the base station/gateway 6.
It will be appreciated that the Timing Advance used by the UE 3 may be affected by (changes in) one or more of: the UE's position; the serving satellite's position; and the timing offset. Regarding these parameters, the following assumptions can be made:
In this system, it is possible to reduce/minimise signalling associated with TA update due to (a combination of) one or more key features.
Downlink TAC signalling may be reduced (or completely avoided) by having an accurate calculated or estimated TA, which may be achieved by the following features:
Uplink TA reporting may be reduced (or completely avoided) using an appropriate threshold:
A benefit associated with using such prediction is that the UE 3 and the base station 6 have the same level of information, without signalling, by independently predicting the same TA. The UE 3 can be configured to make fine corrections to the TA while knowing if timing offset is affected by these corrections. The goal is to trigger fewer explicit TA or offset updates between the UE 3 and the base station 6.
The following is a description of some exemplary ways (Solutions 1 to 2b) in which the above procedure may be implemented in the system shown in
In this case the initial access procedure is used to provide more efficient signalling options for the rest of the communication. The UE 3 can indicate either implicitly or explicitly whether it will do open-loop TA control or legacy closed-loop (e.g. to avoid using GNSS). Alternatively, in the absence of such indication from the UE 3, open-loop (or closed-loop) TA control may be applied by default. The base station 6 can set an appropriate TA reporting periodicity and at least one threshold and at least one TAT value, which may also be based on initial access TA correction.
The parameters may be modified later by the base station 6 if appropriate.
In this example, the UE 3 is configured to acquire its TA autonomously and only triggers a TA report when the acquired TA would affect the timing offset, as configured by an associated threshold provided by the base station 6.
Beneficially, only minimal and necessary TA reporting is performed between the UE 3 and the base station 6. The amount of TA updates and an appropriate TAT is set during initial connection setup.
This solution also uses a prediction model. The parameters of the prediction model may be agreed upon during initial connection, they may be broadcasted, or stored in a database that the UE 3 can access. The base station 6 can update the parameters of the prediction model with time (when necessary). A few measurements (e.g. three) may be enough to provide a “U shape” interpolation curve (see
The base station 6 and the UE 3 use a predicted TA (based on the same prediction model parameters) to derive the same Timing Offset and apply this offset when communicating with each other.
The UE 3 may use an estimated TA (e.g. derived using GNSS) or a predicted TA (e.g. corrected with TACs) to apply TA and remain UL synchronised with a relatively finer granularity.
It will be appreciated that an optimal change in the estimated Timing Offset may not occur at the same time as the one predicted and common with the base station 6. However, if it this stays within a margin of error (e.g. predicted=14.9 ms→offset=17 ms but estimated=15.3 ms) then there is no need to inform the base station 6 and the current offset can still be used.
The UE 3 is able to tell if its actual TA may differ from the predicted TA to a point where the agreed upon Timing Offset would be inappropriate (e.g. predicted=14.9 ms→offset=17 ms but estimated=17.3 ms) and in this case the UE 3 can inform the base station 6 that the current offset cannot be used. A large enough margin of error (i.e. predicted=14.9 ms→offset=15, 16, 17, 18 ms?) may reduce the need for signalling but it would further increase the associated round trip delay, which is already large in NTN.
In case the UE 3 needs to inform the base station 6 that the prediction model is too inaccurate, the prediction model is required to be updated at both the UE 3 and the base station 6 to allow for the same level of knowledge (and thus timing offset derivation).
In this case, the prediction model is used for Timing Offset derivation only. Both the UE 3 and the base station 6 have access to the same level of information (initial TA and prediction model), which are not affected by potential TAC misses. The UE 3 can use other TA estimation method (e.g. GNSS) to acquire an accurate TA. The UE 3 can derive which offset is used by the base station 6 (derived from the same predicted TA) and compare it with its accurately estimated TA (or with an offset derived from the estimated TA).
The UE 3 informs the base station 6 only if it determines that the derived offset at the base station 6 will not be appropriate (i.e. the prediction model is too far off). In most cases, even a slightly wrong prediction model with enough margin of error in the offset can still yield good results that would make the predicted offset appropriate.
A benefit associated with this solution is that it can further reduce (or completely remove) signalling related to TA reporting.
In this case, the prediction model is also used for actual TA adjustment. Both the UE 3 and the base station 6 have access to the same level of initial information (prediction model and initial TA). The UE 3 uses the predicted model to apply the TA. Consistent failure to decode TAC may cause a misalignment of TA information between the base station 6 and the UE 3 (e.g. the base station 6 may think the UE 3 corrected the TA three times, based on three TAC, when the UE failed to decode twice and only corrected once). However, misalignment of TA information will not affect the applied Timing Offset as it is derived from the prediction model.
Benefits associated with this solution include reduced signalling between the UE 3 and the base station 6, improves UE battery consumption (because no GNSS is required after initial access), and no need for GNSS related measuring gaps.
TA adjustment protocol: Initialisation (common to every solution)
The following initialisation procedure is common to the three solutions previously described, with the exception of the prediction model signalling at steps 2/7 which are optional in case of Solution 1.
In more detail, the initialisation stage comprises the following steps:
The threshold to trigger TA reporting can be configured by the base station 6 (e.g. in step 7 above) or it may be a preconfigured for the UE 3. The threshold can be given as e.g. a certain difference in TA (value or percentage) since the last reporting or periodic timer. For instance, the threshold can be a point where a TA update would cause/require a Timing Offset change (which corresponds to the TA having changed by approximately 1 ms since last update).
This stage comprises the following steps:
In this case both the UE 3 and the base station 6 update the timing offset from the predicted model independently. Beneficially, the trigger to update TA can be looser and the UE 3 has the possibility to only report its TA if necessary (e.g. when inaccurate information at gNB side would impact validity of the offset). For instance, instead of “TA having changed by a certain value (e.g. 1 ms) since last update” the trigger may be “TA being farther than a certain value (e.g. 1 ms) compared to predicted TA”.
This stage comprises the following steps:
TA adjustment protocol: During RRC_CONNECTED (Solution 2b) In this case the UE 3 uses its predicted TA for actual TA adjustment and the Timing offset is derived from a prediction model (instead of a predicted and corrected TA as above). This approach may be followed for example when an incremental TA adjustment is inaccurate due to the UE 3 missing or failing to decode one or more TACs. Beneficially, updates/corrections of the prediction model ensure an appropriate Timing Offset is always used.
This stage comprises the following steps:
In this example, the base station or gNB 6 signals NTN satellite information to the UE 3 in step SOL. The NTN satellite information includes feeder link information, information relating to satellite movement with regards to a reference location.
Optionally, in step S02, the gNB 6 may also transmit the UE 3 information related to an RTT prediction model to be used in the NTN cell, and an appropriate formula for deriving a Timing Offset from TA. The information transmitted to the UE 3 may depend on the solution being used.
In step 503, the UE 3 calculates an optimum uplink TA (‘UE-specific TA’) based e.g. upon its current location (derived using GNSS if applicable), broadcast information, and the obtained NTN satellite information.
In step 504, the UE 3 derives and applies a Timing Offset based on the TA, then reports the TA to the gNB 6 in step S05 (e.g. as part of a RACH procedure).
Optionally, as generally shown in step S06, the UE 3 may also transmit information regarding the TA update mechanism and prediction model to be used.
Based on the TA from the UE 3, the gNB 6 also derives and applies a Timing Offset in step S07, and indicates an appropriate dedicated TAT value (optionally a TA reporting periodicity as well) to the UE 3 in step S08.
This completes the initialisation stage after which the UE 3 and the gNB 6 have applied the same TA value/Timing Offset and they have the same level of knowledge for subsequently updating the TA in accordance with the applicable TA adjustment protocol.
Detailed embodiments have been described above. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above embodiments whilst still benefiting from the inventions embodied therein. By way of illustration only a number of these alternatives and modifications will now be described.
It will be appreciated that the above embodiments may be applied to both 5G New Radio and LTE systems (E-UTRAN). A base station (gateway) that supports E-UTRA/4G protocols may be referred to as an ‘eNB’ and a base station that supports NextGeneration/5G protocols may be referred to as a ‘gNBs’. It will be appreciated that some base stations may be configured to support both 4G and 5G protocols, and/or any other 3GPP or non-3GPP communication protocols.
LEO satellites may have steerable beams in which case the beams are temporarily directed to substantially fixed footprints on the Earth. In other words, the beam footprints (which represent NTN cell) are stationary on the ground for a certain amount of time before they change their focus area over to another NTN cell (due to the satellite's movement on its orbit). From cell coverage/UE point of view, this results in cell changes happening regularly at discrete intervals because different Physical Cell Identities (PCIs) and/or Synchronization Signal/Physical Broadcast Channel (PBCH) blocks (SSBs) have to be assigned after each service link change, even when these beams serve the same land area (have the same footprint). LEO satellites without steerable beams cause the beams (cells) moving on the ground constantly in a sweeping motion as the satellite moves along its orbit and as in the case of steerable beams, service link change and consequently cell changes happen regularly at discrete intervals.
Similarly to service link changes, feeder link changes also happen at regular intervals due to the satellite's movement on its orbit. Both service and feeder link changes may be performed between different base stations/gateways (which may be referred to as an ‘inter-gNB radio link switch’) or within the same base station/gateway (‘intra-gNB radio link switch’). The above described methods may be performed at service and/or feeder link changes, if appropriate.
It will be appreciated that there are various architecture options to implement NTN in a 5G system, some of which are illustrated schematically in
An appropriate TAT value may be configured by default in system information block type 1 (SIB 1) and it can be reconfigured when necessary, as described in 3GPP TS 38.331 V16.3.1. Specifically, the TAT can be (re)configured using an appropriate information element (IE) of the RRC Reconfiguration message (e.g. rrcReconfiguration IE>secondaryCellGroup IE>CellGroupConfig IE>mac-CellGroupConfig IE>TAG-Config IE>tag-ToAddMod IE>timeAlignmentTimer IE).
The value of the TimeAlignmentTimer field is given in milliseconds. This allows a UE to be configured with a dedicated TAT (for a given cell/carrier) ranging between 500 ms to 10240 ms, or infinity.
In the above description, the UE, the NTN node (satellite/UAS platform), and the access network node (base station) are described for ease of understanding as having a number of discrete modules (such as the communication control modules). Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the invention, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities. These modules may also be implemented in software, hardware, firmware or a mix of these.
Each controller may comprise any suitable form of processing circuitry including (but not limited to), for example: one or more hardware implemented computer processors; microprocessors; central processing units (CPUs); arithmetic logic units (ALUs); input/output (IO) circuits; internal memories/caches (program and/or data); processing registers; communication buses (e.g. control, data and/or address buses); direct memory access (DMA) functions; hardware or software implemented counters, pointers and/or timers; and/or the like.
In the above embodiments, a number of software modules were described. As those skilled in the art will appreciate, the software modules may be provided in compiled or un-compiled form and may be supplied to the UE, the NTN node, and the access network node (base station) as a signal over a computer network, or on a recording medium. Further, the functionality performed by part or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of the UE, the NTN node, and the access network node (base station) in order to update their functionalities.
The above embodiments are also applicable to ‘non-mobile’ or generally stationary user equipment. The above described mobile device may comprise an MTC/IoT device and/or the like.
The method performed by the UE may further comprise deriving a timing offset for the communications with the network node based on the timing advance value.
The method performed by the UE may further comprise transmitting a timing advance report to the network node when it is determined that the timing advance value has changed over the threshold.
The method performed by the UE may further comprise obtaining a Time Alignment Timer (TAT) associated with the timing advance value.
The method performed by the UE may further comprise indicating whether the UE is configured to use an open-loop timing advance control or a closed-loop timing advance control.
The method performed by the UE may further comprise acquiring the timing advance value based on a location of the UE obtained using a Global Navigation Satellite System (GNSS). The method performed by the UE may further comprise acquiring the timing advance value based on a prediction model relating to at least one of a service link and a feeder link associated with said communications with the network node via the non-terrestrial network.
The information for use in predicting a timing advance value may comprise a set of parameters for predicting the timing advance (e.g. a prediction model). The set of parameters may be used for deriving a timing offset for communicating with the network node. The information (or parameters) for use in predicting a timing advance value may be transmitted by the network node at initial access or upon receiving a timing advance report from the UE.
The method performed by the network node may further comprise transmitting a TAT associated with the timing advance value to the UE.
The network node may comprise a gateway, a base station apparatus, or a satellite having a gateway or base station functionality.
Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.
For example, the whole or part of the exemplary embodiments disclosed above can be described as, but not limited to, the following supplementary notes.
(Supplementary Note 1)
A method performed by a user equipment (UE) configured to communicate via a non-terrestrial network, the method comprising:
(Supplementary Note 2)
The method according to note 1, further comprising deriving a timing offset for the communication based on the timing advance value.
(Supplementary Note 3)
The method according to note 1 or 2, further comprising:
(Supplementary Note 4)
The method according to any one of notes 1 to 3, further comprising receiving, from the network node, a Time Alignment Timer (TAT) associated with the timing advance value.
(Supplementary Note 5)
The method according to any one of notes 1 to 4, further comprising transmitting, to the network node, information indicating whether the UE is configured to use an open-loop timing advance control or a closed-loop timing advance control.
(Supplementary Note 6)
The method according to any one of notes 1 to 5, wherein the acquiring the timing advance value is performed based on a location of the UE obtained using a Global Navigation Satellite System (GNSS).
(Supplementary Note 7)
The method according to any one of notes 1 to 6, wherein the acquiring the timing advance value is performed based on a prediction model relating to at least one of a service link and a feeder link associated with the communication.
(Supplementary Note 8)
A method performed by a user equipment (UE) configured to communicate via a non-terrestrial network, the method comprising:
(Supplementary Note 9)
The method according to note 8, wherein the information includes a set of parameters for predicting the timing advance.
(Supplementary Note 10)
The method according to note 9, wherein the set of parameters is used for deriving a timing offset for the communication.
(Supplementary Note 11)
The method according to any one of notes 8 to 10, wherein the receiving the information is performed at initial access or in response to the transmitting the timing advance report.
(Supplementary Note 12)
A method performed by a network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the method comprising:
(Supplementary Note 13)
The method according to note 12, further comprising transmitting a time alignment timer (TAT) associated with the timing advance value to the UE.
(Supplementary Note 14)
A method performed by a network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the method comprising:
(Supplementary Note 15)
The method according to note 14, wherein the transmitting the information is performed at initial access or upon receiving the timing advance report.
(Supplementary Note 16)
The method according to any one of notes 12 to 15, wherein the network node includes a gateway, a base station, or a satellite having a gateway or base station functionality.
(Supplementary Note 17)
A user equipment (UE) configured to communicate via a non-terrestrial network, the UE comprising:
(Supplementary Note 18)
A user equipment (UE) configured to communicate via a non-terrestrial network, the UE comprising:
(Supplementary Note 19)
A network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the network node comprising:
(Supplementary Note 20)
A network node configured to communicate with a user equipment (UE) via a non-terrestrial network, the network node comprising:
This application is based upon and claims the benefit of priority from Great Britain Patent Application No. 2104780.8, filed on Apr. 1, 2021, the disclosure of which is incorporated herein in its entirety by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2104780.8 | Apr 2021 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2022/012480 | 3/17/2022 | WO |
