GB2595978A - Positioning reference signal - Google Patents

Abstract

A first method, for a User Equipment (UE), for transmitting Position Reference Signals (PRS) in a wireless communication system comprises: measuring the signal strength from one or more base stations; and transmitting PRS with a power determined based on the measurements. The power may be based on the weakest link or an average link quality. An offset may also be applied. A second method comprises: receiving signalling from a base station; and transmitting PRS with a power determined based on the signalling. The signalling may comprise an indication to transmit at full power or may comprise an offset or multiple TPC signals.

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 1.

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 and 2b illustrate exemplary PRS mapping patterns in the case that PRS and data/control signals are spatially multiplexed.

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: * Dedicated NR DL PRS resources -time-frequency grid at resource block level o PRS transmitted in one cell may or may not collide with PRS transmissions in other cell * e.g. frequency vShifUcomb-offset is the same or different for two different PRSs in the same RB o There is no data/control transmission in time-frequency grid of dedicated NR-DL PRS resources o FDM multiplexing with other signals at RE level inside of PRS time-frequency grid is precluded o FFS interference randomization techniques across PRS signals * FFS shared in time/frequency NR DL PRS resources with other transmissions including data/control o FFS which physical channel/signals can share resources with NR DL PRS o FFS interference randomization techniques for PRS transmission with other signals Agreement: FFS: At least the following aspects for NR UL PRS design * Use of UL beam sweeping at FR2 o Beam sweeping includes possibility of quasi-omni transmission * Use of UL beam alignment at FR2 through DL reception and beam correspondence * UL Power control aspects * UL timing advance aspects 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). FDM refers to Frequency Division Multiplexing. 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 WD are as follows.

* Study and evaluate potential solutions of positioning technologies based on the above identified requirements, evaluation scenarios/methodologies [RANI] a 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 Of 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 power boosting and power control for NR positioning signals. 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 apply power boosting and power control for positioning signals other than PRS of NR or LTE.

In the following, a power boosting technique for DownLink (DL) PRS, and a power control technique for UpLink (UL) PRS are described.

Downlink Power Boosting 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. 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. U Es).

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 (PR B). The frame may be divided into a number of consecutive symbols forming the POOCH and a number of consecutive symbols forming the PDSCH.

One type of mapping scheme is comb-k pattern, in which PRS are mapped to every kth subcarrier of each symbol or RB, 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. The skilled person will appreciate that other mapping schemes may be used.

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 any other suitable schemes at the RB level may be used.

In some examples, PRS may be mapped to only a subset of symbols. For example, the symbols to which PRS are mapped may be symbols to which PDSCH is allocated. PRS may not be mapped to symbols to which PDCCH is allocated. For example, in Figures la and lb, PRS are mapped to symbols with indices 0-2 (to which POOCH is allocated), but PRS are mapped to symbols with indices 3-13 (to which PDSCH is allocated).

A certain total power may be used to transmit a symbol, and a certain proportion of this total power (per-carrier/RE power) may be used to transmit each RE/carrier in the symbol. For example, when the power boosting techniques described herein are not used, the power used to transmit each RE (per-carrier/RE power) may be the total power for transmitting a symbol divided by the total number of carriers (activated or not) in the symbol. In some systems, the average power does not vary across subcarriers. The per-carrier/RE power, for example determined in the manner described above, when the power boosting techniques described herein are not used may be regarded as a normal power or reference power.

According to certain examples of the present disclosure, the power of the REs not occupied by PRS can be used to boosting the power of PRS (i.e. relative to the normal/reference power). For example, the power allocated to one or more or all REs occupied by PRS may be increased (i.e. relative to the normal/reference power), while the power allocated to one or more or all REs not occupied by PRS may be decreased (i.e. relative to the normal/reference power).

In some examples, the amount of power allocated to different REs occupied by PRS may be the same or may be different. In some examples, the increase in power (i.e. the power boosting level or factor) applied to different REs occupied by PRS may be the same or may be different.

In certain examples, one or more power boosting rules may be applied. For example, for a comb-k pattern, the power of PRS REs may be boosted by k times (i.e. relative to the normal/reference power). In this case, REs not containing PRS may be transmitted with zero power.

In certain examples, the comb pattern may take both subcarrier level comb pattern (see Figures la and 1 b) and RB level comb pattern (see Figure 1c) into account. For example, for a comb-k subcarrier pattern and a comb-m RB pattern, the power of PRS may be boosted by k*m times (i.e. relative to the normal/reference level).

In some examples, one or more constraints may be applied to the power boosting. For example, if symbols are transmitted with a fixed overall power, then the power boosting applied to PRS REs (and power reduction applied to non-PRS REs) in a symbol should be controlled so as to maintain the overall fixed transmission power. The skilled person will appreciate that a reduction in power applied to non-PRS REs allows a corresponding increase in power applied to PRS REs while maintaining an overall transmission power at or below a certain threshold.

The PRS with boosted power can improve the hearability of the UE. However, in some examples the power boosting may need to be subject to a limit, for example imposed by hardware. In this case, a cap may need to be imposed on the power boosting (i.e. a power cap for individual REs containing PRS). For example, the power of PRS may be chosen as min{Pboost, Rap}, where Pboost is the normal boosting power and Pcap is a power cap (i.e. a threshold, which may be predetermined or dynamically configurable for example).

In some examples PRS may be always transmitted with full transmission power (e.g. maximum available power) without taking the PRS mapping scheme (e.g. comb pattern) into consideration. For example, even if a comb-k pattern is applied to PRS mapping, the PRS may be boosted (i.e. the transmission power may be increased) so as to be transmitted with full transmission power rather than being boosted by k times.

In the above examples, PRS are mapped to REs according to a certain pattern in the time-frequency domain. In other examples, PRS may be mapped to REs according to a certain pattern additionally in the spatial domain as described in the following.

Some systems may apply spatial multiplexing techniques, for example Multi User (MU)-Multiple-Input-Multiple-Output (MIM0). Such spatial multiplexing techniques may be used to enable transmissions to multiple physically separate devices or other entities using the same time and frequency resources. For example, this may be achieved by using beamforming techniques to generate a relatively narrow transmission beam for transmission to a particular device. Different beams may be generated for different devices. If the beams are directed in different directions then there is relatively low interference between the beams, even if the same time and/or frequency resources are used in each beam. A beam may also be referred to as a layer.

When PRS and data/control are spatial multiplexed, e.g. in an MU-MIMO manner, some transmission layers/beams can be used for PRS and other transmission layers/beams can be used for data/control. If the multiplexing is orthogonal in the time/frequency domain, the energy of data/control layer can be used to further boost PRS. The PRS can be further boosted based on the number of layers.

Figures 2a and 2b illustrate exemplary PRS mapping patterns in the case that PRS and data/control signals are spatially multiplexed. There are two transmission layers/beams in this example, although the skilled person would appreciate that any suitable number of layers may be provided. As shown in Figure 2a, in the first layer, PRS are mapped to REs according to a comb-k pattern On this example a comb-6 pattern) in a similar manner illustrated in Figure 1 b.

The skilled person will appreciate that other mapping patterns may be applied. As shown in Figure 2b, in the second layer, data/control signals are mapped to REs indicated by the dark shaded portion. In the second layer, data/control signals are not mapped to REs corresponding to (i.e. having the same time and frequency indices as) REs in the first layer to which PRS are mapped. Rather, these REs are used to boost the PRS in the first layer. In particular, the power used to transmit REs in the first layer containing PRS may be further boosted (i.e. increased), while the power used to transmit corresponding REs in the second layer may be reduced (for example to zero power).

In the example of Figures 2a and 2b, the PRS in the first layer can be boosted by a factor of 2. However, in other examples in which there are more layers, the PRS may be boosted by higher factors. For example, PRS mapped to REs in a certain layer may be boosted by corresponding REs in n other layers, resulting in a boosting factor of n.

Uplink Power Control For UL PRS, the transmission power is an important consideration since the hearability depends on the transmission power. Sounding Reference Signal (SRS) is expected to be received by multiple Transmit-Receive Points (TRPs)/base stations (gNBs)/Location measurement unit ([MU) but the current power control scheme is only based on the serving cell link quality. In this regard, a modified power control mechanism is desirable. Accordingly, in certain examples of the present disclosure one or more of the following techniques may be applied for power control of UL PRS.

In some examples, 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.

Various techniques may be categorised as open loop power control or closed loop power control. For example, open loop power control may be based on measurements made at the UE, while closed loop power control may be controlled by the base station.

One or more of the following techniques may be used for open loop power control of positioning signals. The skilled person will appreciate that these techniques can be used as alternatives or in any suitable combination.

In one technique, a UE measures the signal strength from multiple TRPs/gNBs. Here, the signal strength measurement may comprise any suitable measurement, for example path loss. Then, the UE transmits PRS with a power determined based on the measurements. For example, the UE may identify the weakest link and transmit based on the weakest link. For example, assuming the link quality is ranked in descending order for N TRP/gNBs as LNI, LN will be used for adjusting the UE transmission power. In another example, the UE may identify the average link quality and transmit based on the average link quality. For example, assuming the link quality is ranked in descending order for N TRP/gNBs as {L1,...,LN}, E7_, Li /N will be used for adjusting the UE transmission power. In other examples, 20 the PRS transmission power may be determined based on other factors derived from the signal strength measurements, or a combination of two or more factors (e.g. a weighted sum of the weakest link and the average link). In some examples, the UE may transmit PRS with a power determined in the manner described above as long as the power is lower than a maximum value, for example a maximum allowed transmit power per carrier (i.e. a threshold, which may be predetermined or dynamically configurable for example).

In another technique, the UE measures the signal strength of the serving TRP/gNB. As above, the signal strength measurement may comprise any suitable measurement, for example path loss. Then, the UE transmits PRS with a power determined based on the measurement. For example, the UE may transmit based on the measurement with a power offset added to its normal transmission power. In some examples, the offset may be a pre-defined offset. In other examples, the offset may be a configurable offset, for example configurable by upper layers.

In a further technique, the UE always transmits with full (or maximum) power, which could be subject to some constraints, e.g., the total transmission power of each symbol keeps the same.

One or more of the following techniques may be used for closed loop power control of positioning signals. The skilled person will appreciate that these techniques can be used as alternatives or in any suitable combination.

In a first technique, UL PRS can be indicated by gNB to ignore power control signalling and UE always transmits with full/maximum power, which could be subject to some constraints, e.g., the total transmission power of each symbol keeps the same.

In another technique, an offset may be added to UL PRS for positioning such that the boosted power is equal to the sum of a normal/reference UL power and the offset. The normal/reference UL power refers to the UL PRS transmission power based on a power control procedure of the related art, without applying the power control techniques disclosed herein. Whereas the DL normal/reference power may be constant, the UL normal/reference power may be determined by power control (e.g. a power control procedure of the related art) and thus may not be constant. The offset may be determined or selected according any suitable way. In some examples, the offset may be a pre-defined fixed offset. In other examples, the offset may be a configuration offset where the configuration is based on measurements of UL reference signals.

In another technique, the UE is allowed to receive multiple Transmission Power Control (TPC) signals and adjust the transmission power based on the received TPC signals, for example based on the maximum power, the average power, etc. For example, the TPC may give the information how transmission power should be adjusted.

In another technique, boosting may be selectively applied according to a use of the PRS. For example, when UE receives TPC signals and identifies that the UL PRS will be mainly used for positioning On some examples, since UL PRS can be SRS, PRS can also be used for channel sounding), the UE can scale the transmission power configured by the serving cell by K times. In certain examples, the transmission power may be boosted when UL PRS are used for positioning (or mainly used for positioning), whereas the transmission power is not boosted when UL PRS are not used for positioning (or not mainly used for positioning). The amount of boosting (e.g. a boosting factor K) may be determined based on the implementation.

For closed loop power control, multiple power control signalling can be issued from multiple cells. In some examples the UE is allowed to receive multiple signalling from multiple cells. If such setting is not be feasible, these signalling can be conveyed to the serving cell via the x2 interface between gNBs and can be jointly signalled to the UE.

Certain examples of the present disclosure may be provided in the form of a base station (e.g. gNB) and/or method therefor. Certain examples of the present disclosure may be provided in the form of a mobile device (e.g. UE) 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.

The skilled person will appreciate that a given process, operation and/or method step disclosed herein may be performed by a single entity (hardware and/or software), or the performance of such a process, operation and/or method step may be distributed and performed by two or more entities in cooperation. The skilled person will also appreciate that a single entity (hardware and/or software) may be configured to perform one process, operation and/or method step disclosed herein, or may be configured to perform two or more such processes, operations and/or method steps.

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.

Certain examples of the present disclosure provide one or more methods and/or base stations according to one or more of the following exemplary aspects.

According to a first aspect, there is provided a method, for a base station, for transmitting Position Reference Signals (PRS) in a wireless communication system, the method comprising: mapping PRS to Resource Elements (REs) of a frame structure; and transmitting the frame structure such that the power used to transmit REs containing PRS is higher than the power used to transmit REs not containing PRS.

According to a second aspect, there is provided a method according to the first aspect, wherein the frame structure comprises two or more multi-carrier symbols and each RE comprises a sub-carrier of a symbol, wherein the step of mapping comprising mapping PRS to a subset of REs of each symbol such that the number of REs containing PRS is a fraction 1/k of the total number of REs in each symbol, and wherein the power used to transmit REs containing PRS is a factor k higher than a reference power.

According to a third aspect, there is provided a method according to the first or second aspect, wherein PRS are mapped to REs according to a comb-k pattern at the sub-carrier level and the power used to transmit REs containing PRS is boosted by a factor of k, or wherein PRS are mapped to REs according to a comb-k pattern at the sub-carrier level and a comb-m pattern at the Resource Block (RB) level and the power used to transmit REs containing PRS is boosted by a factor of kxm.

According to a fourth aspect, there is provided a method according to the first, second or third aspect, wherein zero power is used to transmit REs not containing PRS.

According to a fifth aspect, there is provided a method according to any of the first to fourth aspects, wherein the power used to transmit REs containing PRS is selected so as to not exceed a certain power threshold.

According to a sixth aspect, there is provided a method according to any of the first to fifth aspects, wherein REs containing PRS are transmitted with full transmission power, which could be subject to some constraints, e.g., the total transmission power of each symbol keeps the same.

According to a seventh aspect, there is provided a method according to any of the first to sixth aspects, wherein PRS are mapped to a first set of REs in a first spatial layer, wherein a second set of R Es in a second spatial layer, corresponding to the first set of REs, are used to boost the transmission power of the first set of REs, wherein data and/or control signals are mapped a third set of REs of the second layer, where the third set of REs do not include REs of the second set of REs, and wherein the step of transmitting the frame structure comprises transmitting the first and second layers in the same or respective transmission beams.

According to an eighth aspect, there is provided a method according to any of the first to seventh aspects, wherein the PRS comprise PRS of 5G NR.

According to a ninth aspect, there is provided a base station configured to perform the method of any of the first to eighth aspects.

According to a tenth aspect, there is provided a system comprising one or more base stations according to any aspect, example, embodiment and/or claim disclosed herein and one or more user equipment according to any aspect, example, embodiment and/or claim disclosed herein.

Claims (16)

1. Claims 1. A method, for a User Equipment (UE), for transmitting Position Reference Signals (PRS) in a wireless communication system, the method comprising: measuring the signal strength from one or more base stations; and transmitting PRS with a power determined based on the measurements.
2. 2. A method according to claim 1, wherein the step of measuring comprises measuring the signal strength from two or more base stations.
3. 3. A method according to claim 2, further comprising identifying the weakest link, wherein the step of transmitting comprises transmitting the PRS based on the weakest link.
4. 4. A method according to claim 2 or 3, further comprising identifying the average link quality, wherein the step of transmitting comprises transmitting the PRS based on the average link quality.
5. 5. A method according to any preceding claim, wherein the PRS are transmitted so as to not exceed a maximum allowed transmit power per carrier. 20
6. 6. A method according to any preceding claim, wherein the step of measuring comprises measuring the signal strength of a serving base station, and wherein the step of transmitting comprises transmitting the PRS with a power determined based on the measurement with an offset.
7. 7. A method according to claim 6, wherein the offset is a pre-defined offset or a configurable offset.
8. 8. A method according to any preceding claim, wherein the step of transmitting comprises transmitting with full power.
9. 9. A method, for a User Equipment (UE), for transmitting Position Reference Signals (PRS) in a wireless communication system, the method comprising: receiving signalling from a base station; and transmitting PRS with a power determined based on the signalling.
10. 10. A method according to claim 9, wherein the signalling comprises an indication to transmit with full power, which could be subject to some constraints, e.g., the total transmission power of each symbol keeps the same.
11. 11. A method according to claim 9 or 10, wherein the signalling comprises an offset determined based on measurements of UpLink (UL) reference signals, wherein the PRS is transmitted with a power based on the offset.
12. 12. A method according to claim 9, 10 or 11 further comprising receiving multiple Transmission Power Control (TPC) signals, wherein the step of transmitting comprises adjust the transmission power based on the received TPC signals.
13. 13. A method according to any of claims 9 to 12, further comprising receiving Transmission Power Control (TPC) signals, and when identifying that the UpLink (UL) PRS will be used for positioning, scaling the transmission power configured by the serving cell by K times.
14. 14. A method according to any of claims 9 to 13, further comprising exchanging Transmission Power Control (TPC) signals among gN Bs via X2 interface.
15. 15. A User Equipment (UE) configured to perform the method of any preceding claim.
16. 16. A system comprising one or more base stations and one or more user equipment according to claim 15.