GB2578634A

GB2578634A - Improvements in and relating to positioning in a telecommunication network

Info

Publication number: GB2578634A
Application number: GB1817925.9A
Authority: GB
Inventors: Qi Yinan
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2018-11-02
Filing date: 2018-11-02
Publication date: 2020-05-20
Also published as: GB201817925D0

Abstract

A transmitter in a telecommunication system is arranged to transmit data arranged into a plurality of slots, with each of the plurality of slots having a plurality of symbols and a plurality of subcarriers, whereby over a certain number of slots, a majority of the plurality of subcarriers include a reference signal for positioning. The reference signal for positioning may be one of a Positioning Reference Signal (PRS) and a Tracking Reference Signal (TRS). The majority of the plurality of subcarriers may be all of the plurality of subcarriers. A pattern and/or density of reference signals for positioning may be configured by means of Positioning Protocol (LPP), Radio Resource Control (RRC), Downlink Control Information (DCI) and/or Physical Downlink Control Channel (PDCCH). Line of Sight (LOS) links may only be considered when determining UE position. The link may be determined to be LOS if the Angle of Arrival (AoA) at one entity substantially equals the Angle of Departure (AoD) at another entity, wherein each entity is either a UE or a base station, gNB.

Description

Improvements in and relating to positioning in a telecommunication network The present invention relates to improvements in a positioning and measurement system in a telecommunication network. It relates particularly, but not exclusively, to Fifth Generation (5G) or New Radio (NR) systems.

Demand for mobile services is growing rapidly and one of the fastest growing segments is Location Based Services (LBS), primarily driven by two major requirements: emergency services and commercial applications. In response to these needs, second and third generation networks (VVCDMA, GSM, CDMA) have added support for several positioning technologies, which vary in their accuracy and Time to First Fix (TIFF) performance. 3GPP Release 9 for LTE defines support for positioning technologies: Extended Cell ID (ECID), Assisted Global Navigation Satellite System (A-GNSS), Observed Time Different Of Arrival (OTDOA) and LTE Positioning Protocol (LPP), a new positioning protocol. A new reference signal, i.e., positioning reference signal (PRS) has been defined in LTE. Further in Release-11, Uplink Observed Time Different of Arrival (UTDOA) has been adopted using SRS measurement. 3GPP Release-15 defines support for some RAT-independent positioning techniques, such as Real Time Kinematic (RTK) GNSS, to improve the accuracy of LTE positioning.

Embodiments of the present invention aim to address problems with the prior art, whether mentioned here or not.

According to the present invention there is provided an apparatus and method as set forth in the appended claims. Other features of the invention will be apparent from the dependent claims, and the description which follows.

According to a first aspect of the present invention, there is provided a method of configuring reference signals for positioning, within a telecommunication system, wherein a transmitter in the telecommunication system is arranged to transmit data arranged into a plurality of slots, with each of the plurality of slots comprising a plurality of symbols and a plurality of subcarriers, whereby over a certain number of slots, a majority of the plurality of subcarriers include a reference signal for positioning.

In an embodiment, the reference signal for positioning is one of PRS and TRS.

In an embodiment, the majority of the plurality of subcarriers is all of the plurality of subcarriers.

In an embodiment, a pattern and/or density of reference signals for positioning in configured by means of Positioning Protocol, LPP, and/or Radio Resource Control, RRC, and/or Downlink Control Information and/or Physical Downlink Control Channel, DCI.

In an embodiment, the configuration comprises a number indicating the number of symbols to include reference signals for positioning or a bitmap indicating the symbols to include reference signals for positioning.

In an embodiment, only Line of Sight, LOS, links are considered when determining User Equipment, UE, position.

In an embodiment, a link is determined to be LOS if Angle of Arrival, AoA, at one entity substantially equals Angle of Departure, AoD, at another entity, wherein each entity is either a UE or a base station, gNB.

In an embodiment, a link is determined to be LOS according to measurements made and reported by a UE and a gNB respectively.

In an embodiment, 3D positioning is performed by means of taking vertical AoA measurements.

In an embodiment, the degree of quantization is selected according to the positioning accuracy required.

According to a second aspect of the present invention, apparatus is provided, arranged to perform the method of the first aspect.

In an embodiment, a telecommunication system is provided comprising the apparatus of the second aspect.

Although a few preferred embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes and modifications might be made without departing from the scope of the invention, as defined in the appended claims.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example only, to the accompanying diagrammatic drawings in which: Figure 1 shows TRS configuration according to the prior art; Figure 2 shows side correlation peaks, illustrating a problem in the prior ad; Figures 3a and 3b show modified TRS configurations according to an embodiment of the invention; Figures 4a and 4b shows a modified PRS configuration according to an embodiment of the invention; Figure 5 shows a modified PRS configuration according to a further embodiment of the invention; and Figure 6 shows LOS determination according to an embodiment of the invention.

In the following, Positioning Reference Signal (PRS) and Tracking Reference Signal (TRS) are referred to as specific instances of reference signals for positioning. The skilled person will appreciate that either of these or, indeed, a different signal will suffice and so when a generic reference is intended, the term "reference signal for positioning" will be used and this is intended to relate to PRS, TRS or some other signal, as required.

In prior art LTE systems, only one Positioning Reference Signal (PRS) pattern is defined. However, in NR, multiple PRS patterns/densities may be defined at least based on carrier frequency range, e.g., FR1 (<6GHz) or FR2 (>24GHz) The main reason for this is that positioning accuracy depends on two factors: available bandwidth for positioning and numerology, i.e., subcarrier spacing (SCS).

In FR1, the available bandwidth for positioning is not always large especially considering the prevalence of Internet of Things (loT) devices with 5MHz bandwidth. In addition, smaller SCS in FR1 also leads to lower positioning accuracy. In such cases, in order to achieve the required high degree of positioning accuracy, the density of PRS should, ideally, be high. On the contrary, the available bandwidth for positioning reference signals in FR2 is normally quite large and the larger SCS also improves positioning accuracy. In such cases, a lower density of PRS can be considered.

In a first embodiment, PRS pattern/density scales with carrier frequency and/or subcarrier spacing in a pre-defined manner (e.g. defined in a table), which can be configured by Positioning Protocol (LPP) and/or Radio Resource Control (RRC) and/or Downlink Control Information (DCI) / Physical Downlink Control Channel (PDCCH).

In a second embodiment, the LTE PRS pattern can be used with modification and Channel State Information Reference Signal (CSI-RS) / Tracking Reference Signal (TRS) can also be used with modification, e.g., LTE PRS for FR1 and Channel State Information Reference Signal (CSI-RS) / Tracking Reference Signal (TRS) for FR2.

In the second embodiment, LTE PRS does not occupy every subcarrier due to the existence of Cell Specific Reference Signal (CRS). However, in NR, there is no CRS and using the same pattern as in the prior art LTE system can cause a problem in that there are some subcarriers without PRS and this will lead to large side correlation peaks, which will significantly degrade positioning accuracy. Using CSI-RS/TRS will cause the same problem. TRS can be configured for 2 symbols in two consecutive slots with density 3 (in total 4 symbols for two slots) as shown in Figure 1 with only 3 subcarriers are occupied.

The fact that not all subcarriers are occupied leads to large side correlation peaks as shown in Figure 2. In situations with low Signal to Interference and Noise Ratio (SINR), the problem would be particularly pronounced.

In order to address the problem, the subcarrier used for CRS in LTE is used for PRS so that PRS can occupy all the subcarriers. For CSI-RS/TRS, a different frequency offset can be introduced so that TRS can occupy all the subcarriers in one slot or in multiple slots as shown in the Figures 3a and 3b.

In some circumstances, it may be acceptable to transmit PRS such that is occupies a simple majority of the available subcarriers. This would give an improved performance over the prior art situation, but the best performance is achieved by ensuring that each subcarrier includes PRS. The system designer can specify an acceptable level of performance and schedule PRS accordingly.

It can be seen in Figure 3a that TRS is positioned such that, over 2 slots, TRS appears on each subcarrier. This is achieved by adjusting the placements of TRS compared to the prior art situation shown in Figure 1, without increasing the actual number of TRS transmissions per se.

In Figure 3b, the number of TRS transmissions per slot is increased, compared to Figure 1. The effect is such that TRS is transmitted on every subcarrier by means of a repeating patters over 4 symbols.

The different configuration of TRS according to embodiments of the invention can be configured semi-persistently by upper layer signaling, e.g., LPP and/or RRC and/or dynamically by lower layer signaling, e.g. DCI.

One of the most important features used widely NR is beamforming, especially for FR2. In order to improve hearabilty, beam sweeping is utilised for the transmission of PRS. In addition, stringent latency requirements impose another limit to the duration of one positioning occasion. The number of symbols which can be used in one positioning occasion is made configurable in the following embodiments. Positioning occasion refers to the duration of local correlation to measure time difference of arrival (tdoa).

In a first embodiment, all the symbols for one positioning occasion are in the same slot as shown in Figure 4a and the duration can be configured semi-persistently by upper layer signaling, e.g., LPP and/or RRC and/or dynamically by lower layer signaling, e.g. DCI.

In Figure 4b, two different beam positions are shown, each associated with 2 different sets of 3 symbols. This results in 2 poisoning occasions within the slot shown.

In a second embodiment, the symbols for one positioning occasion occur across multiple slots as shown in Figure 5 and the duration can be configured semi-persistently by upper layer signaling, e.g., LPP and/or RRC and/or dynamically by lower layer signaling, e.g. DCI.

In either case, the duration can either be signalled as a single value indicating the number of symbols with positioning or a bitmap indicating the symbols carrying PRS. For each positioning occasion, different beams can be supported as shown in the below figure.

The performance of positioning largely depends on Line of Sight (LOS) condition. It is implicitly assumed that all links are LOS links so that if any of the links is actually a Not LOS (NLOS) link, the positioning performance will be significantly degraded. Therefore, it is important to identify which links are NLOS links so that these links are not taken into consideration for positioning purposes.

One solution to determine LOS condition is to use Angle of Arrival (AoA) and/or Angle of Departure (AoD) information. Most of the user terminals (UE) are equipped with an Inertial Measurement Unit (IMU) sensor so that the UE antenna array orientation can be obtained.

The base station (gNB) antenna array orientation is fixed so this information is also available. With such information, it is possible to compare the AoA/AoD angle at the UE and gNB and if they match, e.g., AoA/AoD of gNB = AoA/AoD of UE, as shown in Figure 6, the link is determined to be a LOS link and, if not, it is a NLOS link.

A first embodiment uses AoA/AoD measurement based solutions, and comprises two options. Firstly, the gNB measures AoA; the UE reports its AoD; and the LOS decision is made at gNB if the AoA=AoD.

Alternatively, theUE measures AoA; the gNB reports its AoD; and the LOS decision is made at the UE.

A second embodiment uses beam measurement and report-based solutions. This, too, comprises two options.

Firstly, the gNB determines the reception beam and detects the UE transmission beam, and the LOS decision is made at gNB.

Alternatively, the UE determines the reception beam and the gNB signals its transmission beam, and the LOS decision is made at UE.

In each of these cases, one of the network entities makes the determination based on either AoA/AoD considerations or via reports and measurements. Which particular entity makes the LOS determination and which technique is to be used may be configured as required.

When the UE reports back its measurement results, e.g., time difference of arrival (tdoa) / time of arrival (toa) and AoA/AoD, the values are quantized, as in all in digital communications. The quantization granularity used determines the quantization error, which also impacts the positioning accuracy. Essentially, the higher the quantization granularity, the more accurate the positioning is. However, very high quantization granularity will also create a large signaling overhead and may increase the positioning latency. As such, the quantization granularity is determined by the required positioning accuracy. In an embodiment, multiple quantization granularities are supported. For cases where higher accuracy is required, a finer quantization granularity is configured and, for cases with a lower accuracy requirement, a coarser granularity can be configured to reduce signaling overhead. Such configuration can be done by upper layer signaling, e.g., LPP and/or RRC.

As mentioned, AoA measurements are performed to support positioning in NR. In order to support 3D positioning, vertical AoA measurement are required, in addition to measurements in the horizontal plane. Vertical AoA measurements may be defined as: the estimated angle of a user or network node, e.g., gNB with respect to a reference direction. The reference direction for this measurement shall be the geographical vertical to the ground, positive in a counter-clockwise direction.

The AoA is determined at the gNB antenna for an Uplink (UL) channel corresponding to a particular UE or at the UE antenna for a Downlink (DL) channel corresponding to transmitting gNB. It should be noted that AoA/AoD measurement can also be done via beams if, with each beam indication or report, the angle of the beam is also indicated or reported.

At least some of the example embodiments described herein may be constructed, partially or wholly, using dedicated special-purpose hardware. Terms such as 'component', 'module' or unit' used herein may include, but are not limited to, a hardware device, such as circuitry in the form of discrete or integrated components, a Field Programmable Gate Array (FPGA) or Application Specific Integrated Circuit (ASIC), which performs certain tasks or provides the associated functionality. In some embodiments, the described elements may be configured to reside on a tangible, persistent, addressable storage medium and may be configured to execute on one or more processors. These functional elements may in some embodiments include, by way of example, components, such as software components, object-oriented software components, class components and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuitry, data, databases, data structures, tables, arrays, and variables. Although the example embodiments have been described with reference to the components, modules and units discussed herein, such functional elements may be combined into fewer elements or separated into additional elements. Various combinations of optional features have been described herein, and it will be appreciated that described features may be combined in any suitable combination. In particular, the features of any one example embodiment may be combined with features of any other embodiment, as appropriate, except where such combinations are mutually exclusive. Throughout this specification, the term "comprising" or "comprises" means including the component(s) specified but not to the exclusion of the presence of others.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

CLAIMS1. A method of configuring reference signals for positioning, within a telecommunication system, wherein a transmitter in the telecommunication system is arranged to transmit data arranged into a plurality of slots, with each of the plurality of slots comprising a plurality of symbols and a plurality of subcarriers, whereby over a certain number of slots, a majority of the plurality of subcarriers include a reference signal for positioning.
2. The method of claim 1 wherein the reference signal for positioning is one of PRS and TRS.
3. The method of claim 1 or 2 wherein the majority of the plurality of subcarriers is all of the plurality of subcarriers.
4. The method of any preceding claim wherein a pattern and/or density of reference signals for positioning in configured by means of Positioning Protocol, LPP, and/or Radio Resource Control, RRC, and/or Downlink Control Information and/or Physical Downlink Control Channel, DCI.
5. The method of claim 4 wherein the configuration comprises a number indicating the number of symbols to include reference signals for positioning or a bitmap indicating the symbols to include reference signals for positioning.
6. The method of any preceding claim wherein only Line of Sight, LOS, links are considered when determining User Equipment, UE, position.
7. The method of claim 6 wherein a link is determined to be LOS if Angle of Arrival, AoA, at one entity substantially equals Angle of Departure, AoD, at another entity, wherein each entity is either a UE or a base station, gNB.
8. The method of claim 6 wherein a link is determined to be LOS according to measurements made and reported by a UE and a gNB respectively.
9. The method of any preceding claim wherein 3D positioning is performed by means of taking vertical AoA measurements.
10. The method of any of claims 7 to 9 wherein the degree of quantization is selected according to the positioning accuracy required.
11. Apparatus arranged to perform the method of any preceding claim.
12. A telecommunication system comprising the apparatus of claim 11.