GB2582893A - Positioning reference signal - Google Patents

Abstract

In a wireless communication system, position reference signals (PRS) are mapped to the bandwidth parts (BWP) of one or more user equipments (UE). Where bandwidth parts for two UEs fully overlap, the PRS may be mapped across the larger or the smaller bandwidth part. Where the bandwidth parts do not overlap, the PRS patterns and densities may be configured independently or jointly. Where there is a partial overlap, the PRS may be mapped in a joint configuration with a uniform pattern across the overall band. Alternatively, separate configurations may be used, and where collisions occur, an offset or puncturing may be applied. In a second embodiment, the PRS is mapped to predefined positions which may be within or near the central region of the system bandwidth. The configuration may be switched based on a UE capability report, indicating whether the UE can operate with the full system bandwidth. In a third embodiment, the PRS is mapped around the synchronisation signal block (SSB). The communication system may be a fifth generation (5G) New Radio (NR) network.

Description

Positioning Reference Signal

BACKGROUND OF THE INVENTION

Field of the Invention

Certain examples of the present disclosure provide methods, apparatus and systems for providing a Positioning Reference Signal (PRS) for allowing the position of a User Equipment (UE) to be determined in a wireless communication system. For example, certain examples of the present disclosure provide methods, apparatus and systems for providing PRS in 3rd Generation Partnership Project (3GPP) 5th Generation (5G) New Radio (NR).

Description of the Related Art

In wireless communication systems, it is often useful to be able to determine the position of a User Equipment (UE), for example to provide location-based services and emergency call positioning.

One example of a positioning method is Observed Time Difference Of Arrival (OTDOA). This technique is used, for example, in the 3' Generation Partnership Project (3GPP) Long-Term Evolution (LTE) standard (e.g. as specified in Release-8, Release-9 and subsequent documents). In this technique, a UE measures the Time Of Arrival (TOA) of signals received from multiple base stations (eNBs) and the position of the UE is determined based on these measurements, as well as the known positions of the base stations, using geometry.

Although the OTDOA technique may, in principle, be performed based on any DownLink (DL) signals (e.g. synchronisation signals), in practice specific positioning signals are sometimes used, for example to improve performance. For example, in the LTE standard, Positioning Reference Signals (PRS) were introduced in Release-9. The PRS signals of LTE comprise pseudo-random sequences that are mapped to certain Resource Elements (REs) (e.g. REs that are not allocated to Physical Broadcast Channel (PBCH)). The UE may correlate the received PRS sequences with local copies of the sequences and determine the corresponding ranges (distances) to the base stations based on the positions of the correlation peaks.

The 3GPP 9' Generation (5G) standard is a new standard currently under development and intended to succeed 4G (including LTE) and earlier systems. 5G New Radio (NR) is an air interface developed by 3GPP for the 5G mobile network. NR UE-positioning mechanism is a study item in the current RAN 1 (Radio Layer 1) Release-16 agenda, and is seen as a main area to be completed for 5G-NR to be compliant with Enhanced 9-1-1 (E911) and other emergency services requirements.

What is required is a positioning mechanism suitable for use in 5G-NR. For example, a technique using PRS with enhanced performance for 5G-NR requirements is desirable.

The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.

SUMMARY OF THE INVENTION

It is an aim of certain examples of the present disclosure to address, solve and/or mitigate, at least partly, at least one of the problems and/or disadvantages associated with the related art, for example at least one of the problems and/or disadvantages described above. It is an aim of certain examples of the present disclosure to provide at least one advantage over the related art, for example at least one of the advantages described below.

The present invention is defined in the independent claims. Advantageous features are defined in the dependent claims.

Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, disclose examples of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, and features and advantages of certain embodiments and aspects of the present invention will be more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which: Figures la-c illustrate exemplary PRS mapping patterns; and Figures 2a-c illustrate exemplary cases of overlapping, non-overlapping and partially overlapping BandVVidth Parts (BWP).

DETAILED DESCRIPTION

The following description of examples of the present disclosure, with reference to the accompanying drawings, is provided to assist in a comprehensive understanding of the present invention, as defined by the claims. The description includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the examples described herein can be made without departing from the scope of the invention.

The same or similar components may be designated by the same or similar reference numerals, although they may be illustrated in different drawings.

Detailed descriptions of techniques, structures, constructions, functions or processes known in the art may be omitted for clarity and conciseness, and to avoid obscuring the subject matter of the present invention.

The terms and words used herein are not limited to the bibliographical or standard meanings, but, are merely used to enable a clear and consistent understanding of the invention.

Throughout the description and claims of this specification, the words "comprise", "include" and "contain" and variations of the words, for example "comprising" and "comprises", means "including but not limited to", and is not intended to (and does not) exclude other features, elements, components, integers, steps, processes, operations, functions, characteristics, properties and/or groups thereof.

Throughout the description and claims of this specification, the singular form, for example "a", "an" and "the", encompasses the plural unless the context otherwise requires. For example, reference to "an object" includes reference to one or more of such objects.

Throughout the description and claims of this specification, language in the general form of "X for Y" (where Y is some action, process, operation, function, activity or step and X is some means for carrying out that action, process, operation, function, activity or step) encompasses means X adapted, configured or arranged specifically, but not necessarily exclusively, to do Y. Features, elements, components, integers, steps, processes, operations, functions, characteristics, properties and/or groups thereof described or disclosed in conjunction with a particular aspect, embodiment, example or claim of the present invention are to be understood to be applicable to any other aspect, embodiment, example or claim described herein unless incompatible therewith.

Certain examples of the present disclosure provide methods, apparatus and systems for providing Positioning Reference Signals (PRS) for allowing the position of a User Equipment (UE) to be determined in a wireless communication system. For example, certain examples of the present disclosure provide methods, apparatus and systems for providing PRS in 3GPP 5G-NR. However, the skilled person will appreciate that the present invention is not limited to these examples, and may be applied in any suitable system or standard, for example one or more existing and/or future generation wireless communication systems or standards.

LTE positioning has been discussed in Release-9 and Release-11. In Release-15 LTE, some Radio Access Technology (RAT)-dependent positioning techniques were agreed. NR-positioning mechanism is a study item in current RANI Release-16 agenda. Observed Time Difference Of Arrival (OTDOA) has been identified as a method for achieving positioning for both DownLink (DL) and UpLink (UL).

In 3GPP TSG RAN WG1 Meeting Ad-Hoc Meeting 1901, Taipei, Taiwan, 21' -25th January, 2019, RAN1 Chairman's Notes, Section 7.2.10, "Study on NR positioning support", the following agreements have been made: Agreement: NR DL PRS design for FR1 and FR2 supports: * Configurable NR DL PRS signal bandwidth o FFS granularity of configuration, relationship with BWP5, whether the configuration is cell and/or UE specific Agreement: * NR UL SRS is used as a starting point for design and analysis of UL PRS o Further study if and which enhancements are needed o FFS: NR UL PRS relationship with UL BWP and component carrier FR1 refers to Frequency Range 1 (i.e. 450 MHz -600 MHz) and FR2 refers to Frequency Range 2 (i.e. 24.25 GHz -52.6 GHz). BWP refers to BandWidth Part. SRS refers to Sounding Reference Signal. FFS refers to For Further Study.

In 3GPP Release-16 a Study Item Description (SID)/Work Item Description (WID) on NR positioning is approved. In particular, in RP-181399; 3GPP TSG RAN Meeting #80, La Jolla, USA, June 11-14, 2018, "New SID: Study on NR positioning support", the objectives of this WID are as follows.

* Study and evaluate potential solutions of positioning technologies based on the above identified requirements, evaluation scenarios/methodologies [RANI] o The solutions should include at least NR-based RAT dependent positioning to operate in both FR1 and FR2 whereas other positioning technologies are not precluded.

o Minimum bandwidth target (e.g. 5MHz) of NR with scalability is supported towards general extension for any applications.

* Study of positioning architecture for location services, functional interfaces, protocol, and procedures for supporting NR dependent positioning technologies (if needed; otherwise, need to be confirmed) [RAN2, RAN3] o Rel-15 NR positioning architecture/protocol is a starting point of the discussion while the Release 16 LCS architecture enhancement study in TSG SA side is taken into account.

o Common architecture with loT and hybrid positioning.

o The positioning architectures should support standalone NR for both voice and data including loT service.

o loT use cases, including potential LPP evolution, and efficient/low-complexity signaling are considered while striving for a common architecture.

o End-to-end latency is considered to developing positioning architecture.

loT refers to Internet of Things. TSG SA refers to Technical Specification Group Service and System Aspects. LPP refers to LTE Positioning Protocol. LCS refers to Location Services.

It is likely that the PRS specified in LTE (from Release 9 onwards) will be adapted as a means to support OTDOA techniques in 5G-NR.

In view of the above agreements and objectives, certain examples of the present disclosure provide one or more techniques for defining the mapping (in particular the frequency locations) of PRS within a system band/Component Carriers (CCs). The skilled person will appreciate that the techniques disclosed herein are not limited to NR or LTE. For example, the techniques disclosed herein may be used to map positioning signals other than PRS of NR or LTE.

For DL, PRS may be mapped to Resource Elements (REs) of a frame structure according to any suitable mapping scheme. Figures la-c illustrate exemplary PRS mapping patterns, where Figures la and lb illustrate mapping patterns at the subcarrier level while Figure lc illustrates a mapping pattern at the Resource Block (RB) level.

The frame structure may be used for certain DL Physical Layer channels, for example a Physical Downlink Shared Channel (PDSCH) and a Physical Downlink Control Channel (PDCCH) for transmitting information (e.g. control signals and data) from a base station (e.g. gNB) to one or more mobile devices (e.g. UEs).

The frame may comprises a number of Orthogonal Frequency Division Multiplexing (OFDM) symbols, each OFDM symbol comprising a number of subcarriers (or Component Carriers (CCs)). Each subcarrier of each symbol may be referred to as a Resource Element (RE). The symbols may be thought of as forming a grid of REs with time along one axis of the grid (the horizontal axis in Figures 1a and 1b) and frequency along the other axis of the grid (the vertical axis in Figures la and lb). A block of REs comprising a number (e.g. 12) of adjacent subcarriers may be defined as a Physical Resource Block (PRB).

One type of mapping scheme is comb-k pattern, in which PRS are mapped to every kth subcarrier of each symbol, and in which the subcarrier indices to which PRS are mapped cyclically decrements (or increments) with increasing symbol index. Figures la and lb illustrate comb-3 and comb-6 patterns at the subcarrier level. In some examples, a mapping scheme at the RB level may be used. For example, according to a comb-m pattern at the RB level, every mth RB includes PRS while other RBs do not include PRS. Figure lc illustrates a comb-3 pattern at the RB level. The skilled person will appreciate that other mapping schemes may be used.

UL PRS may be transmitted in a frame structure used for certain UL Physical Layer channels, for example a Physical Uplink Shared Channel (PUSCH) and a Physical Uplink Control Channel (PUCCH) for transmitting information (e.g. control signals and data) from a mobile device (e.g. UE) to a base station (e.g. gNB). UL PRS may be transmitted using the same or a similar mapping pattern as for DL PRS. For example, if SRS is used then comb-2 or comb-4 may be used.

In 5G NR, a bandwidth part (BWP) is defined (e.g. in 3GPP TS 38.211 version 15.2.0 Release 15, Section 4.4.5) as a subset of contiguous common PRBs. A UE can be configured with up to four bandwidth parts in the downlink with a single downlink bandwidth part being active at a given time, and up to four bandwidth parts in the uplink with a single uplink bandwidth part being active at a given time.

In 5G NR, the UE is not expected to receive PDSCH, PDCCH, or CSI-RS (except for RRM) outside an active BWP. The UE shall not transmit PUSCH or PUCCH outside an active BWP. For an active cell, the UE shall not transmit SRS outside an active BWP.

The BWP concept allows a UE to operate bandwidth adaption, wherein the UE may selectively operate using either a narrow bandwidth (reducing power consumption) or a wide bandwidth (when a higher data rate is required (e.g. bursty traffic situation)). Also, the BWP concept addresses a situation in which a UE may not be capable of utilising the entire bandwidth available in 5G.

In view of the above requirements, PRS should be mapped to a BWP. Furthermore, BWPs (BWP1 and BWP2) of two different UEs (UE1 and UE2) may completely overlap, partially overlap, or may not overlap. In the following, techniques are disclosed for determining the mapping of PRS within the overall system band, taking into account BWP utilisation. The skilled person will appreciate that the following techniques may be applied to both DL and UL PRS

First Example

In this example, DL PRS is always within the active or a pre-defined specific (e.g., lowest/highest index) BWP only and bandwidth of PRS can be the same or less than the bandwidth of the active BWP. This configuration can be UE specific configuration. The following three cases, illustrated respectively in Figures 2a-c, are considered.

Case 1: Fully overlapping BWPs (Figure 2a) In this case, the BWPs of UE1 and UE2 fully overlap. The supported PRS bandwidth can either be up to minimum bandwidth of all BWPs (e.g. the smallest bandwidth from BWP1 and BWP2 = min{Bandwidth(BWP1), Bandwidth(BWP2)}, which is UE1 BWP1 in the example of Figure 2a), or maximum bandwidth of all BWPs (e.g. the largest bandwidth from BWP1 and BWP2 = max{Bandwidth(BWP1), Bandwidth(BWP2)}, which is UE2 BWP2 in the example of Figure 2a). Accordingly, in the former case PRS may be mapped to REs within BWP1, while in the latter case PRS may be mapped to REs within BWP2. In certain situations, some UEs might not be able to support the maximum BWP. In this case, the supported PRS bandwidth may be up to maximum supported width of all BWPs. The pattern/density of PRS can be aligned with either the highest or the lowest density. For example, in BWP1 the PRS density is higher (e.g. comb-3) and in BWP2 the PRS density is lower (e.g. comb-6). The same comb pattern can be used for both BPWs. If PRS density is aligned with higher density, comb-3 may be used. If PRS density is aligned with lower density, comb-6 may be used. In some examples, UE may need to report if it is capable of operating outside BWP for positioning in a UE capability report.

Case 2: Non overlapping BWPs (Figure 2b) In this case, the BWPs of UE 1 and UE2 do not overlap.

For the non-overlapping case, PRS density/pattern can be configured independently, or jointly with common density/pattern and a reference point in frequency domain (e.g. a starting point in frequency so that the relative position of each BWP can be inferred, for example point A defined in 38.211). For example, different patterns/densities may be used for BWP1 and BWP2 in the independent case, while the same pattern/density may be used for BWP1 and BWP2 in the joint case. For example, for the independent configuration, a first PRS density/pattern may be configured for UE1 such that PRS is mapped to BWP1 according to the first PRS density/pattern, while a second PRS density/pattern may be independently configured for UE2 such that PRS is mapped to BWP2 according to the second PRS density/pattern. For the joint configuration, a common PRS density/pattern is configured for both UE1 and UE2 such that PRS is mapped to BWP1 and BWP2 according to the common PRS density/pattern.

Case 3: Partial overlapping BWPs (Figure 2c) In this case, the UE1 and UE2 BWPs partially overlap.

Two PRS in different BWPs may have different density/pattern. In one example, there is a joint configuration considering the overall band, e.g., a uniform PRS density/pattern can be configured to BWP1+BWP2-overlapping part (i.e. the non-overlapping parts of BWP1 and BWP2). In another example, there is a separate configuration. However, if there are different PRS density/pattern in the overlapping part (i.e. the PRS density/pattern for BWP1 is different from the PRS density/pattern for BWP2), two PRS may collide (i.e. PRS for UE1 and PRS for UE2 may use the same time/frequency resources and hence interfere). One or more of the following examples may be used to resolve potential collisions.

* 1. Align the density/pattern with lower/higher pattern/density (i.e. same as in the full overlapping case 1 described above); * 2. Introduce an offset when collision happens (e.g. an offset is added to the mapped RE index of a colliding PRS so that the PRS is shifted to a different RE thus avoiding collision); * 3. Puncture one of the PRS patterns (i.e. puncturing may be applied at REs at which collision occurs); * 4. Allow collision but introduce further interference mitigate schemes. Second Example In this example, PRS can be mapped to pre-defined positions, e.g., within the central region of the system bandwidth, or a region close (or closest) to the central region of the system bandwidth. The PRS bandwidth may be configured according to one or more of the following examples.

* 1. PRS can be configured up to system bandwidth of one CC. In this case, UE should be allowed to operate with full system bandwidth.

* 2. PRS can be configured within one or more BWPs. The same methods discussed above can be used but may have additional constraint that the BWP(s) is/are the BWP(s) containing the subcarrier(s) at the pre-defined position.

* 3. The above two examples (1 and 2) can be switched based on UE capability report, e.g., whether or not the UE can operate with full system bandwidth.

Third Example

In this example, PRS may be mapped around Synchronization Signal Block (SSB), e.g. with SSB in the centre or in the BWP containing SSB. In the former case, PRS is not necessarily mapped in the BWP. In the latter case, PRS can also be mapped around SSB with SSB in the centre. In case of multiple SSBs are configured, PRS may be mapped to the main SSB with Remaining Minimum System Information (RMSO/Control Resource Set (CORESET) information or the SSB closest to the central of the full system bandwidth. The bandwidth of PRS may be configured using one or more of the examples 1-4 in the "First Example" described above. In certain examples, PRS should avoid collision with SSB, e.g., puncturing PRS or SSB or adding an offset.

UE capability report In one or more or all of the above examples, UE might need to operate outside its configured BWP. For example, the PRS bandwidth may be larger than the BWP bandwidth configured to the UE. In this case, UE may indicate if such operation is feasible in its capability report and such report can be per BWP or per SCS. The maximum bandwidth on which a UE can operate can be included in this capability report.

The skilled person will appreciate that the above techniques are not limited to application to BWP. For example, the techniques described herein may be applied to Carrier Components (CCs).

The skilled person will appreciate that the examples disclosed herein may be combined and the BWP mentioned is not necessarily the active BWP. In general, the "First Example" described above may be a UE specific configuration, and the "Second Example" and the "Third Example" described above may be either a UE specific or cell specific configuration. The combination of all Examples may be enabled. In certain examples, by default, cell specific configuration is used as a baseline, but UE specific can be enabled when necessary. For example, by default, PRS position density/pattern may be predefined or mapped to SSB on a per cell basis, but UE specific configuration may be enabled when necessary.

Certain examples of the present disclosure may be provided in the form of a base station and/or method therefor. Certain examples of the present disclosure may be provided in the form of a mobile device and/or method therefor. Certain examples of the present disclosure may be provided in the form of a system comprising one or more base stations and one or more mobile devices, and/or method therefor.

The techniques described herein may be implemented using any suitably configured apparatus and/or system. Such an apparatus and/or system may be configured to perform a method according to any aspect, embodiment, example or claim disclosed herein. Such an apparatus may comprise one or more elements, for example one or more of receivers, transmitters, transceivers, processors, controllers, modules, units, and the like, each element configured to perform one or more corresponding processes, operations and/or method steps for implementing the techniques described herein. For example, an operation of X may be performed by a module configured to perform X (or an X-module). The one or more elements may be implemented in the form of hardware, software, or any combination of hardware and software.

It will be appreciated that examples of the present disclosure may be implemented in the form of hardware, software or any combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage, for example a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape or the like.

It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs comprising instructions that, when executed, implement certain examples of the present disclosure. Accordingly, certain example provide a program comprising code for implementing a method, apparatus or system according to any example, embodiment, aspect and/or claim disclosed herein, and/or a machine-readable storage storing such a program. Still further, such programs may be conveyed electronically via any medium, for example a communication signal carried over a wired or wireless connection.

While the invention has been shown and described with reference to certain examples, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention, as defined by the appended claims.

Claims (18)

1. Claims 1. A method for mapping Position Reference Signals (PRS) in a wireless communication system comprising a first User Equipment (UE) and a second UE, the method comprising: identifying a first Bandwidth Part (BWP) for the first UE and a second BWP for the second UE; and mapping PRS to one or both of the first BWP and the second BWP.
2. 2. A method according to claim 1, wherein, when the first BWP and the second BWP fully overlap, the PRS are mapped in a PRS bandwidth up to the minimum bandwidth of the first and second BWPs, or the maximum bandwidth of the first and second BWPs.
3. 3. A method according to claim 2, wherein the PRS bandwidth is up to a maximum supported bandwidth of the first and second BWPs.
4. 4. A method according to claim 2 or 3, wherein the pattern and/or density of the PRS mapping is aligned with the highest density or lowest density.
5. 5. A method according to claim 1, wherein, when the first BWP and the second BWP do not overlap, the patterns and/or densities of the PRS mapping in the first and second BWPs are configured: independently; or jointly with a common pattern and/or density.
6. 6. A method according to claim 1, wherein, when the first BWP and the second BWP partially overlap, the PRS are mapped according to: a joint configuration based on the overall band; or separate configurations.
7. 7. A method according to claim 6, wherein, when the PRS are mapped according to a joint configuration, a uniform PRS density and/or pattern is configured to the non-overlapping part of the first and second BWPs.
8. 8. A method according to claim 6 or 7, wherein the method further comprises one or more of: aligning the PRS mapping densities and/or patterns with lower and/or higher pattern and/or density; adding an offset to a mapped Resource Element (RE) index of a colliding PRS; applying puncturing at REs at which collision occurs; and applying one or more interference mitigation schemes.
9. 9. A method for mapping Position Reference Signals (PRS) in a wireless communication system, the method comprising: mapping PRS to predefined positions within a PRS bandwidth.
10. 10. A method according to claim 9, wherein the predefined positions are within the central region of the system bandwidth, or a region close (or closest) to the central region of the system bandwidth.
11. 11. A method according to claim 9 or 10, wherein the PRS bandwidth is configured according to: configuring PRS up to system bandwidth of one CC, wherein a UE operates with full system bandwidth; or configuring PRS within one or more BWPs, wherein the BWP(s) is/are the BWP(s) containing the subcarrier(s) at pre-defined position
12. 12. A method according to claim 11, further comprising switching the configuring based on a UE capability report (e.g. indicating whether or not the UE can operate with full system bandwidth).
13. 13. A method for mapping Position Reference Signals (PRS) in a wireless communication system, the method comprising mapping the PRS around Synchronization Signal Block (SSB).
14. 14. A method according to claim 13, wherein the PRS are mapped with SSB in the centre or in the BWP containing SSB.
15. 15. A method according to claim 14, wherein, when multiple SSBs are configured, the PRS are mapped to the main SSB with Remaining Minimum System Information (RMSI)/Control Resource Set (CORESET) information or the SSB closest to the central of the full system bandwidth.
16. 16. A base station configured to perform the method of any of claims 1 to 15.
17. 17. A User Equipment (UE) configured to perform the method of any of claims 1 to 15.
18. 18. A system comprising one or more base stations according to claim 16 and one or more user equipment according to claim 17.