GB2576033A

GB2576033A - Improvements in and relating to user equipment positioning

Info

Publication number: GB2576033A
Application number: GB1812598.9A
Authority: GB
Inventors: Qi Yinan
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2018-08-02
Filing date: 2018-08-02
Publication date: 2020-02-05
Anticipated expiration: 2038-08-02
Also published as: GB2576033B; GB2576033A8; GB201812598D0

Abstract

A method of configuring a periodicity of a positioning reference signal (PRS) transmission in a telecommunication system comprises the step of configuring the starting timing and the duration of the PRS transmission, wherein the transmission is either consecutive or interleaved on cell or cell group basis, and the configuration is numerology dependent. Periodicity may be defined on a slot or mini slot basis, a sub-frame basis or defined in absolute time units. The PRS may have a multi-level structure defining a block set comprising plural block sub-sets each further comprising plural blocks with each block comprising plural consecutive symbols, mini-slots, slots, sub-frames or frames. The block set is repeated with a defined periodicity. The positioning reference signal may be selected from one or more of SS, CS_RS, SRS, DMRS and PTRS.

Description

Improvements in and relating to User Equipment positioning

The present invention relates to improvements in Location based Services (LBS) used in mobile telecommunication networks to provide location information of a particular User Equipment (UE).

Demand for mobile services is expanding quickly and one of the fastest growing segments is Location Based Services (LBS), primarily driven by two major requirements: emergency services and commercial applications. Emergency services desire to know the location of a UE in the event of, for instance, a vehicular accident. Commercial applications desire to know the location of a UE so that the user can be presented with relevant information or advertisements such as, for instance, restaurant deals in his vicinity.

In response to these needs, second and third generation networks (WCDMA, GSM, CDMA) have added support for several positioning technologies, which vary in their accuracy and Time to First Fix (TTFF) performance. 3GPP Release 9 for LTE defines support for various positioning technologies: Extended Cell ID (ECID), Assisted Global Navigation Satellite System (A-GNSS), Observed Time Difference 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, to support this new protocol.

Further in Release 11 of LTE, Uplink Observed Time Different of Arrival (UOTDA) has been adopted using Sounding Reference Signal (SRS) measurement. 3GPP Release 15 defines support for some (Radio Access Technology) RAT-independent positioning techniques, such as Real Time Kinematic (RTK) GNSS, to improve the accuracy of LTE positioning.

There is a need to provide an improved configuration to enable the use of positioning technologies, so as to address shortcomings in the prior art location services. Embodiments of the present invention aim to address these shortcomings.

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.

Embodiments of the present invention provide system configurations, in terms of reference signal designs, which provide advantageous solutions for LBS.

Reference Signal (RS) Periodicity design for positioning can vary due to different positioning techniques applied. For OTDOA, periodicity refers to PRS transmission periodicity. For ECID or UOTDA, periodicity refers to the periodicity of other downlink (DL), e.g., synchronization signal (SS), and/or uplink (UL) signals, e.g., SRS.

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 PRS configuration for multiple cells/cell groups, according to an embodiment of the present invention; and

Figure 2 shows PRS configuration for clot 28, according to an embodiment of the present invention; and

Figure 3 shows PRS beam sweeping according to an embodiment of the present invention; and

Figure 4 shows a multi-level PRS structure according to an embodiment of the invention.

Positioning Reference Signal (PRS) periodicity is configured by upper layers, e.g., LPP/RRC, and the configuration is highly flexible so that different requirements for a variety of different use cases can be met without causing too much signalling overhead. For example, the minimum periodicity value should be smaller than required time to first fix (TTFF) and there might be other requirements imposed by different use cases. Considering that New Radio (NR) supports multiple numerology and thus multiple slot durations, the periodicity can be defined in different ways.

In a first embodiment, periodicity is defined on a slot or mini slot basis, i.e., periodicity can be defined as N slots/mini slots and N is selected from a group of values pre-defined, e.g., N can be chosen as K*2ⁿ and n can be from 0 to n_max.

In a second embodiment, periodicity is defined on a subframe basis, i.e., periodicity can be defined as N subframes and N is selected from a group of values pre-defined, e.g., N can be chosen as K*2ⁿ and n can be from 0 to n_max.

In a third embodiment, periodicity is defined in absolute time units, e.g., milliseconds. Periodicity can be defined as N absolute time units and N is selected from a group of values pre-defined, e.g., N can be chosen as K*2ⁿ and n can be from 0 to n_max.

K may be pre-defined and the smaller the value of K is, the finer the time resolution that can be provided. However, to serve different use cases, K can also be configured by upper layers to provide more flexibility.

For the first embodiment, above, since slot duration might be different for different numerologies, the actual periodicity, in terms of absolute time, changes with slot duration or numerology.

For the second embodiment, above, the duration of the subframe is constant for all numerologies and the actual periodicity, in terms of absolute time, does not change.

For the third embodiment, above, the actual periodicity in terms of absolute time does not change either.

Periodicity configurations for multiple numerologies can be based on one of the following alternatives:

• Uniform periodicity design for all numerology and the periodicity values can be defined in the two tables as shown below. Compared with a prior art LTE table, these tables may be expanded to meet the diverse requirements of all NR use cases as shown below.

Periodicity can be defined per numerology and for each numerology, the periodicity values can be defined in a table so that multiple tables are needed as shown below.

Numerology 2 (slots)

64K

128K

A benefit of the first alternative above is that only one table is needed. However, a disadvantage is that the table can be very large since it should include all possible values. If multiple periodicity tables are defined per numerology, each individual table can be smaller. Which table and which periodicity values to choose are configured by upper layers, e.g., LPP. In the latter case, numerology configuration is conveyed and known to the positioning protocols, e.g., LPP or units, e.g., Location Measurement Unit (LMU).

There are several options available when considering which slot, mini slot or subframe to configure with PRS as follows:

• Option 1: The slots/mini slots/subframes configured with PRS from one cell or a group of cells are consecutive in the time domain. In such a case, two parameters are needed: starting point and duration. These parameters can be configured by upper layers, e.g., LPP/RRC.

• Option 2: The slots/mini slots/subframes configured with PRS from one cell or a group of cells are discontinuous and follows a certain pattern, which could be either predefined, or generated based on cell ID, e.g., PCI or cell group ID, or configured by upper layers, e.g., LPP/RRC. However, N consecutive slots/mini slots/subframes are configured for multiple cell/cell groups and N is configured by upper layers. In this option, the starting point of the N consecutive slots/mini slots/subframes is still needed as well as the duration, i.e., N. In addition, the time domain pattern should also be known.

Fig. 1 shows an example of Option 2 above with two cell groups shown - Cell Group 1 and Cell Group 2. For NR, the cell density is expected to be much higher than LTE due to the requirement for high data rate and coverage. With Option 2, PRS can be configured to be present in more cells without causing too much interference and with the result that positioning accuracy can be improved. By defining and using Cell Groups in this manner, it is possible for the UE to receive a greater number of Reference Signals and so it is possible to calculate location to a greater degree of accuracy.

In NR, multiple slot formats are defined to provide enhanced flexibility. PRS is only configured to resources allocated for downlink (DL) transmission, i.e., PRS can not be configured for slot format 1 and 8-15, since they have no provision for DL slots. There are two possible configurations in the light of this:

• PRS is only configured to the slot formats without explicit uplink (UL) transmission, e.g., slot format 1,8-15, 19-45, and 50-61 cannot be used for PRS; or • PRS can be configured to the slot formats with explicit UL transmission except pure UL formats slot format 1 and 8-15. In such a case, the PRS are only configured to DL symbols and/or unknown symbols which can be used for DL as shown in Fig. 2, which shows, as an example, slot format 28.

Figure 2 shows slot format 28 as an example of a slot format which can accommodate PRS. As shown, PRS is present in a repeating pattern of OFDM symbols and subcarriers with the overall slot structure. It is not, however, present in the final symbol (k=13) since that is provisioned for UL symbols only. Since PRS is available as shown in DL, the UE can measure PRS and report back to the network which is then able to determine its position.

In both of the above cases, the slot format configuration information should be conveyed and known to the positioning protocols, e.g., LPP or units, e.g., LMU. It should be noted that the information exchange may happen between the UE and the cell ( e.g. gNB or TRP), or within the same cell but between two protocols (e.g. between RRC and LPP).

The periodicity design can be applied to all the UEs within one cell/cell group (called herein cell-specific periodicity). However, if PRS is UE-specific, the following issues should be considered additionally.

Considering the very diverse use cases in NR, as well as the vastly different requirements imposed by these use cases, it is possible that different UEs might need different periodicity values. Periodicity values are configured by positioning protocols, i.e., LPP, but from the UE perspective, the periodicity is configured by RRC which wraps the LPP protocol data unit (PDU).

When periodicity is cell-specifically configured, only one periodicity value is needed for one cell/cell group per numerology and this may not be able to meet the requirements for all UEs covered in this cell. For example, for a UE moving at high speed, the periodicity should be small so that the UE location can be updated more frequently, but for a pedestrian case, a longer periodicity is feasible.

Since a small periodicity will cause high signalling overhead and thus lead to capacity loss, it is not desirable to configure a small periodicity for all the UEs. In such a case, LPP should configure multiple periodicity values per numerology as candidates and the cell can then configure suitable periodicity values to each individual UE based on their requirements, e.g., latency and positioning accuracy. This gives rise to three possible alternatives:

• The UE does not report its current status, e.g., moving speed, or requirements and the cell just configures the smallest periodicity to the UE based on numerology;

• The UE reports partial or full information regarding its current status and requirements and the cell configures suitable periodicity based on the report;

• The cells (i.e. all cells involved in positioning) jointly derive the UE information implicitly, e.g., frequency of handover, and exchange the information via X2 interface, then configure suitable periodicity to the UE.

PRS can be configured as periodic, aperiodic, or semi-persistent. Both aperiodic and semipersistent PRS can be triggered by upper layers, e.g., LPP/RCC or DCI.

Another issue for PRS is that beamforming is needed in Frequency Band 2 (FR2, 24.24GHz 52.6GHz) so that PRS might also be beamformed and, in such a case, the PRS beam 100 should sweep to cover all possible directions as shown in Fig. 3, so that each of UEs 1, 2, 3 are able to receive the associated transmission.

In order to support beam sweeping, it is possible to define a multi-level PRS block set 200 which consists of n consecutive symbols/mini slots/slots/subframes/frames. Within each PRS block set 200, multiple PRS block sub-sets 210 can be defined and each PRS block sub-set consists of multiple PRS blocks 220 which could have either the same or different beam patterns. The multi-level structure is shown in Fig. 4.

A UE assumes that reception occasions of a PRS block are in consecutive symbols/mini slots/slots/subframes/frames. If the UE has not been provided dedicated higher layer parameters, the UE may assume that the subcarrier spacing of PRS is the same as SS/PBCH blocks, otherwise, it can be signalled explicitly by upper layers or by means of broadcast information. The indexes for candidate PRS can be determined according to the subcarrier spacing of PRS.

For a certain case, with specific subcarrier spacing, the time location of PRS blocks can be defined by the following equation: A+B*n , where A defines the starting location of PRS block 220 and belongs to a set with size ofthe PRS block within one PRS block sub-set 210; B defines the step of PRS block subset in time domain and can be defined per sub-carrier; and n defines the number of PRS block sub-sets 220 within one PRS block set 200. With this multi level PRS block structure, there may be a need to define multi-level periodicity, each corresponding to one level. For example, PRS block set periodicity 230 should be defined as shown in Fig. 4. In addition, PRS block sub-set periodicity and PRS block periodicity may be defined by configuring the value of A, B and n as needed. This multi-level structure can either be configured by upper layers or pre-defined based on factors such as carrier frequency, numerology, etc. It is also possible that multiple PRS blocks are transmitted simultaneously and these PRS blocks can be either overlapping in the same time-frequency resources but differentiated by SDM or FDM.

It should be noted that this multi-level structure can be quite flexible. The embodiment shown here in Figure 4 has three levels but it can be reduced to two or extended to more than three levels as required.

For ECID, UE needs to measure signal strength, e.g. Reference Signal Received Power (RSRP) of synchronization signal (SS) in the DL and the cell/cell group needs to measure angle of arrival (AoA) in UL. For UL link AoA measurement, SRS is used for LTE. For NR, SRS, DMRS, PTRS can be considered. The problem associate with DMRS and PTRS is that they are only configured when there is data to be transmitted. However, considering positioning normally happens when UE is RRC_Connected, it is still feasible to use DMRS and PTRS. For all the above alternatives, the periodicity can be configured by upper layers based on requirements.

For DL, things are different from two perspectives:

• SS periodicity is changed in NR and depends on numerology;

• In addition, UE can measure RSRP of Channel State Information Reference Signal (CSI-RS) in NR.

If SS is measured, the periodicity is configured in the cell-specific manner. However, if CSI-RS is measured, the periodicity is configured in the UE-specific manner by upper layers, e.g., RRC, and thus can be more flexible.

For UOTDA, the cell group measures the difference of time of arrival from the UE based on reference signals of the UE. Similar to ECID (described above), SRS, DMRS and PTRS can be considered in NR and the periodicity can be configured by upper layers based on particular requirements.

For both of the above cases, periodicity can be configured by LPP and then the information is exchanged between LPP and RRC.

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

1. A method of configuring a periodicity of a positioning reference signal transmission in a telecommunication system comprising the step of configuring the starting timing and the duration of the positioning reference signal transmission, wherein the transmission is either consecutive or interleaved on cell or cell group basis, and the configuration is numerology dependent.

2. The method of claim 1 wherein the step of configuring comprises configuring a multilevel structure fora positioning reference signal.

3. The method of claim 2 wherein beamforming and beam sweeping is used to transmit the positioning reference signal.

4. The method of claim or 3 wherein the multi-level structure comprises the steps of defining a positioning reference signal block set, comprising a plurality of block sub-sets, each further comprising a plurality of blocks, with each block comprising a plurality of consecutive symbols or mini slots or slots or subframes or frames.

5. The method of claim 4 wherein the positioning reference signal block set is repeated with a defined periodicity.

6. The method of claim 5 wherein the location of a positioning reference signal block is defined by the equation A+B*n , where A defines the starting location of the positioning reference signal block and belongs to a set with size of the block within one block sub-set; B defines the step of the block subset in time domain; and n defines the number of block subsets within one block set.

7. The method of any preceding claim wherein multiple positioning reference signal are transmitted simultaneously but differentiated by SDM or FDM.

8. The method of any preceding claim wherein the configuration of positioning reference signals is arranged to avoid symbols for uplink transmission in a selected slot format.

9. The method of any preceding claim wherein the configuration of positioning reference signals is User Equipment, UE, specific, based on explicit UE reports or by implicit derivation by Base Stations, gNBs.

10. The method of any preceding claim wherein the reference signal used for positioning is selected from one or more of SS, CSI-RS, SRS, DMRS, PTRS.

11. The method of any preceding claim wherein the configuration information of positioning

5 reference signals is exchanged between upper layer protocols, such as RRC and LPP, and/or exchanged between measurement units, such as LMU.