GB2576054A

GB2576054A - Improvements in and relating to positioning reference signal configuration in a telecommunication system

Info

Publication number: GB2576054A
Application number: GB1812705.0A
Authority: GB
Inventors: Qi Yinan
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2018-08-03
Filing date: 2018-08-03
Publication date: 2020-02-05
Also published as: GB201812705D0

Abstract

A method of configuring a positioning reference signal (PRS) in a telecommunication system comprises distributing a plurality of positioning reference signals on a per-slot, per-mini slot or per-subframe basis. The positioning reference signals (PRS) may be distributed across a plurality of aggregated mini slots, or a subframe of two slots and may avoid collision with CORESET or PDCCH. If there is a collision, one or more PRS are punctured or shifted. A location index of PRS resource elements may follow a pseudo-random sequence. PRS from different cells may be coordinated and where each cell allocates PRS to resource blocks which do not mutually overlap. Resource blocks other than PRS may be blanked to maximize the hearability of the PRS.

Description

Improvements in and relating to Positioning Reference Signal Configuration in a telecommunication system

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 positioning technologies: Extended Cell ID (ECID), Assisted Global Navigation Satellite System (AGNSS), 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.

Further in Release 11, Uplink Observed Time Different of Arrival (UOTDA) has been adopted using 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.

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 mapping of positioning reference signals (normal cyclic prefix) according to the prior art;

Figure 2 shows mapping of positioning reference signals (extended cyclic prefix) according to the prior art;

Figure 3 shows CORESET positioning according to the prior art;

Figure 4 shows PRS configuration on slot/mini slot basis according to an embodiment of the invention;

Figure 5 shows PRS configuration on aggregated slot/mini slot basis according to an embodiment of the invention;

Figure 6 shows PRS configuration on subframe basis according to an embodiment of the invention;

Figure 7 PRS configuration on slot/mini slot basis with randomized subcarrier according to an embodiment of the invention;

Figure 8a shows PRS configuration without PDCCH transmission according to an embodiment of the invention;

Figure 8b shows PRS configuration considering CORESET according to an embodiment of the invention;

Figure 9 shows PRS configuration with CORESET (PRS punctured) according to an embodiment of the invention;

Figure 10 shows PRS configuration with CORESET and PDCCH according to an embodiment of the invention;

Figure 11 shows PRS configuration in frequency domain with interleaving for multiple cell/cell groups according to an embodiment of the invention;

Figure 12 shows PRS from multiple cells including one serving cell and multiple coordinating cells according to an embodiment of the invention;

Figure 13 shows co-ordinated PRS RB allocation according to an embodiment of the invention;

Figure 14 shows co-ordinated PRS RB allocation according to an embodiment of the invention; and

Figure 15 shows configuration of PRS with multiple antenna ports according to an embodiment of the invention.

Embodiments of this invention aim to provide methods and apparatus associated with PRS Configuration in New Radio (NR) in particular, but which may be applicable to other systems.

PRS is cell specific in LTE (i.e. the prior art) and its pattern is shown in Figure 1 (normal cyclic prefix) and Figure 2 (extended cyclic prefix) (both derived from TS 36.211).

The reasons for such patterns are as follows:

1) PRS is configured on subframe basis;

2) No PRS in the first N symbols to avoid collision with PDCCH, which occupies the whole bandwidth;

3) PRS should not collide with CRS in symbol;

4) Distance between two PRS subcarriers is 6 so that the UE can receive maximum 6 simultaneous PRS from 6 different cells with different offset values, e.g., 1-5. The orthogonality of the PRS from different cells reduces the interference so that the arrival time difference estimation is more accurate;

5) The diagonal pattern of PRS allows the configuration to benefit from frequency diversity.

For NR, according to embodiments of the invention, the configuration can also be cellspecifically defined so that the same configuration, e.g., bandwidth (BW), periodicity, duration, etc., is applied to all UEs within one cell. However there are a few significant differences as follows:

1) One slot can contain 14 symbols, similar to a subframe in LTE and the mini slot (7, 4 or 2 OFDM symbols) is introduced with less than 14 symbols;

2) There is no CRS in NR;

3) PDCCH no longer occupies the whole bandwidth but only some of the resource elements (REs) within one or multiple Control Resource Sets (CORESET), which only occupy partial bandwidth as shown in Figure 3.

For features 1) and 2) above, PRS can be configured in one of the following alternatives:

• 1: PRS is configured on slot/mini slot basis, i.e., PRS pattern is repeated on slot/mini slot basis as shown in Fig. 4;

• 2: Slots/mini slots can be aggregated and the PRS configuration is applied on aggregated slots/mini slots basis as shown in Fig. 5, which shows an aggregation level of 3;

• 3: PRS is configured on a subframe basis and one subframe can consists of N_siot slots/mini slots as shown in Fig. 6.

The PRS subcarrier number for each symbol can be chosen as one of the following alternatives:

• For symbol N+1, the subcarrier number is offset from symbol N by a constant l_offsetvalue as shown in Fig. 4-6 (l_offeet =1). One special case is where offset value l_offset is 0, so that the same subcarrier is chosen for PRS;

• For symbol N+1, the subcarrier number is offset from symbol N by a variable l_offset value and this value can either be pre-defined, or upper layer configured, e.g., RRC/LPP configured, or generated based on a certain pseudo-random sequence, e.g., Gold code, in a cell-specific manner, e.g., based on Physical cell ID (PCI);

• The subcarrier number for each symbol is either based on predefined values, or upper layer configured, e.g., RRC/LPP configured, or on certain pseudo-random sequence, e.g., Gold code, and generated in a cell-specific manner, e.g., based on Physical cell ID (PCI) as shown in Fig. 7.

•

As can be seen from above figures, there is no CRS present (unlike in LTE) so that PRS can be configured for every symbol.

In order to avoid collision with CORESET/PDCCH, the following alternatives can be considered:

• 1: No PRS for the first N symbols that may be occupied by CORESET even though the CORESET may not occupy the whole bandwidth. Note that N is either fixed to equal the maximum number of symbols occupied by CORESET or it can be implicitly derived from RRC configuration by the UE and, thus, variable;

• 2: PRS is configured within the partial bandwidth not occupied by CORESET, i.e., PRS will be configured in the REs of PDSCH as shown in Fig. 8b;

• 3: PRS is configured within the entire slot but will be punctured when colliding with CORESET as shown in Fig. 9;

• 4: Within a CORESET, there may be some REs available to PDSCH, e.g., REs not assigned to PDCCH, and the PRS can be configured in these REs as shown in Fig. 10. PRS can then either be configured around PDCCH as in Figure 8b or punctured when colliding with PDCCH as in Figure 10;

• If no PDCCH is transmitted, the PRS can start from the first symbol, as shown in Figure 8a.

It should be noted that for alternatives 2, 3 and 4, above, there might be a need for the positioning protocol, e.g., LPP, to know the configuration of CORESET, which can configured by upper layers, e.g., RRC, or lower layers, e.g., DCI. In this regard, the CORESET configuration information should be conveyed to and known by the positioning protocols, e.g., LPP or positioning units or Location Measurement Unit (LMU).

The information relevant to CORESET configuration is in the PDCCH-Config IE as defined in TS 38.331. As such, the location of CORESET should be known by positioning protocols. It should be noted that the information exchange may happen between the UE and the cell, e.g., gNB orTRP, or within the cell but between two protocols, e.g., between RRC and LPP.

It should also be noted that there might be some REs not available to PDSCH, as defined in TS 38.211-214, and such REs can be treated in the same way as CORESET, as set out above.

PRS configuration within one resource block (RB) is discussed in the previous sections. In the following PRS RB mapping in the frequency domain will be described. N_PRS RBs can be configured for PRS and N_PRS is configured by upper layers.

There are alternative configurations which can be considered:

• 1: Consecutive RBs are configured with PRS by one cell/cell group;

• 2: RBs with PRS from multiple cells/cell groups are discontinuous and interleaved either based on pre-defined pattern or a pseudo-randomly generated pattern as shown in Fig. 11.

Option 2 above can benefit from frequency diversity but requires more configuration parameters to be configured by upper layers, e.g., size of each RB sub-group, interleave pattern, etc.

As mentioned above, for cell-specific PRS configuration, the same configuration is applied to all UEs within one cell regardless of whether the UE needs to do positioning or not, which will cause significant overhead. In order to reduce the overhead, PRS configuration can be UE specific, e.g., based on UE specific parameters such as Radio Network Temporary Identifier (RNTI).

The UE needs to receive PRS from multiple cells as shown in Fig. 12 to measure the difference in arrival times. In this regard, the UE PRS configuration should be coordinated for all cells via the X2 interface.

There are a few options for coordinated resource allocation as follows.

• 1: Each cell allocates resources for PRS independently based on measurement results such as Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), etc. Each cell always allocates the resources with the strongest signal strength to the UE. There are two sub-options:

o a: RBs for PRS of cell i can overlap with data or PRS RBs from other cells as shown in Fig. 13 (a);

o b: RBs for PRS of cell i are blanked by other cells to reduce interference. This can be achieved by configuring zero power (ZP) PRS as shown in Fig. 13 (b).

• 2: Common resources are allocated for PRS for all cells as shown in Fig. 14. There are two sub-options:

o a: Resources with stronger signal strength in the serving cell are allocated;

o b: Resources with stronger signal strength in the coordinating cell are allocated to improve the hearability.

The PRS pattern described previously for cell-specific PRS can also be used for UE specific cases. It should also be noted that all the various alternatives described herein can be combined as required to provide more flexibility.

In addition to the features described above, there are related issues addressed by embodiments of this invention.

Cyclic Prefix (CP)

As mentioned, the UE needs to measure PRS from coordinating cells and these coordinating cells could be quite far away from the UE. In this regard, a longer cyclic prefix (CP) is needed. In the current NR specifications, extended CP can only be used for 60kHz, which might not be suitable for macro cells where 15kHz is normally used. Therefore, extended CP may be required for at least 15kHz and 30kHz for PRS.

DC tone

In LTE, PRS RBs are configured around DC tone. In embodiments for NR, three options can be considered.

• 1: PRS RBs are allocated around DC tone, which is decided by Component Carrier (CC) center;

• 2: PRS RBs are allocated around DC tone decided per bandwidth part (BWP);

• 3: PRS RBs are allocated in pre-defined manner without knowing the DC tone information.

Option 1 can be easily applied to cell-specific PRS.

Option 2 can be used for either cell-specific PRS or UE-specific PRS, where the DC tone can be decided by UE on per BWP basis. In this case, UE needs to report the position of DC tone to the base station (BS) and the report should be per BWP basis. Such information needs to be conveyed to and known by the positioning protocols, e.g., LPP or positioning units, e.g., LMU.

If DC tone information is not known, option 3 can be used.

PRS antenna port

In LTE, PRS is transmitted in antenna port 6. However, in NR, when considering multi-panel operation, especially for above 6GHz, i.e., Frequency Band 2 (FR2), one antenna port might not be feasible. There are therefore three alternatives that need to be considered:

• 1: For both below 6GHz, i.e., FR1 and above 6GHz, i.e., FR2, only one antenna port is supported;

• 2: For FR1, one antenna port is supported but for FR2, more than one antenna port are supported as shown in Fig. 15;

• 3: For both below 6GHz, i.e., FR1 and above 6GHz, i.e., FR2, more than one antenna port is supported.

For FR1, the transmission could be omni-directional and therefore one antenna port is enough. In addition, there is no need to split the power between multiple antenna ports so that the positioning accuracy is good. For FR2 with beamforming, there might be a need to use multiple beams so that the UE can be covered by one of the beams. In this regard, multiple antenna ports are needed. The number of antenna ports is configured by upper layers and beam related information is conveyed to, and known by, the positioning protocols, e.g., LPP or positioning units, e.g., LMU.

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 positioning reference signal in a telecommunication system, comprising the step of distributing a plurality of positioning reference signal on a per-slot, permini slot or per-subframe basis.

2. The method of claim 1 wherein the plurality of positioning reference signals are distributed across a plurality of aggregated mini slots.

3. The method of claim 1 wherein the plurality of positioning reference signals are distributed across a subframe comprising two slots.

4. The method of claim 1 wherein a location index of positioning reference signal resource elements follows a pseudo-random sequence.

5. The method of any preceding claim wherein the positioning reference signals are distributed so as to avoid collision with a CORESET or PDCCH.

6. The method of any preceding claim wherein the positioning reference signals are distributed such that if there is a collision with a CORESET or PDCCH, one or more positioning reference signals are punctured or shifted.

7. The method of any preceding claim further comprising the step of co-ordinating positioning reference signals arriving at a given User Equipment from different cells.

8. The method of claim 7 wherein the each cell allocated resources for the positioning reference signal based on measurement results.

9. The method of claim 8 wherein each cell allocates positioning reference signals to resource blocks which do not mutually overlap.

10. The method of claim 9 wherein resource blocks other than positioning reference signals are blanked so to maximise the hearability of the positioning reference signals.

11. The method of claim 7 wherein common resources are allocated for positioning reference signals.

12. The method of any preceding claim wherein extended Cyclic Prefix, CP, is utilised for 15KHz and 30KHz subcarrier spacing for positioning reference signal.

13. The method of any preceding claim comprising configuring positioning reference signals around a DC tone, based upon either Component Carrier, CC, centre or per Bandwidth Part, BWP.

14. The method of any preceding claim further comprising the step of configuring multiple antenna ports for positioning reference signal transmission.