Patent Application
20210080532
The present invention relates to an apparatus, a method and a computer program product by which a coordinated precoding and beamforming of position purpose signals can be achieved.
The following meanings for the abbreviations used in this specification apply:
Embodiments of the present invention, although not limited to this, relate to positioning of devices such as UEs.
Accurate positioning of User Equipment (UE) with sub-meter accuracy becomes more and more important in many evolving use cases. As an example, the need of sufficient protection of Vulnerable Road Users (VRU), e.g., pedestrians, wheelchairs, and cyclists, from autonomously driving vehicles is widely discussed. For that, accurate and real-time positioning of both VRU and vehicle is required.
Embodiments of the present invention address this situation and aim to improve accuracy of the UE positioning.
According to a first aspect of the present invention an apparatus, for use in a transmission device, is provided which comprises at least one processor, at least one memory including computer program code, and the at least one processor, with the at least one memory and the computer program code, being arranged to cause the apparatus at least to prepare at least one beamforming and/or precoding pattern for transmitting a positioning purpose signal via a plurality of antennas connectable to the apparatus, the positioning purpose signal serving to position at least one user equipment, and transmit the positioning purpose signal from the plurality of antennas according to the beamforming and/or precoding pattern.
According to a second aspect of the present invention a method, for use in a transmission device, is provided which comprises
According to a third aspect of the present invention, an apparatus is provided which comprises at least one processor, at least one memory including computer program code, and the at least one processor, with the at least one memory and the computer program code, being arranged to cause the apparatus at least to create a coordination scheme by which beamforming and/or precoding of transmissions of positioning purpose signals from a plurality of transmission devices each having a plurality of antennas is coordinated, wherein the positioning purpose signals serve to position at least one user equipment, and to forward information indicating the coordination scheme to the transmission devices involved in the coordination scheme.
According to a fourth aspect of the present invention a method is provided which comprises
According to a fifth aspect of the present invention, an apparatus, for use in a user equipment, is provided which comprises at least one processor, at least one memory including computer program code, and the at least one processor, with the at least one memory and the computer program code, being arranged to cause the apparatus at least to receive information indicating a coordination scheme, the coordination scheme specifying coordination of beamforming and/or precoding of transmissions of positioning purpose signals from a plurality of transmission devices each having a plurality of antennas, wherein the positioning purpose signals serve to position the user equipment, and receive at least one positioning purpose signal from at least one transmission device based on the coordination scheme.
According to a sixth aspect of the present invention a method, for use in a user equipment, is provided which comprises
The first to sixth aspects of the present invention may be modified as set out in the dependent claims.
According to a seventh aspect of the present invention a computer program product is provided which comprises code means for performing a method according to the second aspect, the fourth aspect or the sixth aspect and/or their modifications when run on a processing means or module. The computer program product may be embodied on a computer-readable medium, and/or the computer program product may be directly loadable into the internal memory of the computer and/or transmittable via a network by means of at least one of upload, download and push procedures.
According to an eighth aspect of the present invention an apparatus is provided which comprises
According to a ninth aspect of the present invention an apparatus is provided which comprises
According to a tenth aspect of the present invention an apparatus is provided which comprises
These and other objects, features, details and advantages will become more fully apparent from the following detailed description of embodiments of the present invention which is to be taken in conjunction with the appended drawings, in which:
In the following, description will be made to embodiments of the present invention. It is to be understood, however, that the description is given by way of example only, and that the described embodiments are by no means to be understood as limiting the present invention thereto.
However, before describing the embodiments, the problem underlying the present application is described in some more detail.
Two major methods are utilized for positioning today.
The first one is positioning based on Global Navigation Satellite Systems (GNSS) with the Global Positioning System (GPS) being the most prominent technology. GPS works well in open areas with line-of-sight to a sufficiently large number of satellites. However, in certain situations (e.g., in tunnels, under bridges, in parking garages, next to buildings, under dense foliage) unhindered line-of-sight may be limited or even excluded. Therefore, positioning information can be inaccurate, and in consequence the required QoS for VRU protection cannot be guaranteed in all situations. Thus, GNSS can just serve as a complementary technology.
The other method is utilizing the cellular access technology, e.g., LTE, for positioning. However, there are several impairments that limit the achievable positioning accuracy in the order of tens of meters, see for example Qualcomm Technologies, “Observed Time Difference of Arrival (OTDOA) Positioning in 3GPP LTE”, White Paper, 2014. The most critical ones are:
Insufficient number of measurable base stations in the area of interest
According to some embodiments of the present invention, it is focused on the latter issue. The main problem caused by an insufficient number of measurable base stations is the bad performance of the multilateration algorithm determining the UE position depending on a set of OTDOA measurements with a Maximum Likelihood (ML) or a Maximum-A-Posteriori (MAP) estimator. In principle three base stations, i.e., two OTDOA measurements, suffice for 2D-positioning (x-y-coordinates or latitude/longitude), however each additional available measurement decreases the area that is characterized by a high probability that the true location is within this area. In other words, the positioning error decreases with increasing number of measurable base stations. However, in a given deployment, the number of base stations is fixed. Consequently, there may be areas where the QoS requirements of the abovementioned use cases cannot be fulfilled.
The best existing solution to increase the number of measurable base stations is Positioning Reference Signal (PRS) muting (see, for example, 3GPP TS 36.355 V14.4.0 (2017 December)). This feature was recently enabled in the Verizon network nationwide in the US. According to a configured muting pattern the base stations transmit at a subset of the PRS opportunities with “zero power”. If the PRS of the serving base station, normally received with highest signal strength, is muted, the PRS from a more distant base station sent on the same time-frequency resources becomes “measurable”, i.e. its SINR becomes high enough so that the UE can take an OTDOA measurement from the distant base station.
The main drawback of PRS muting is the reduced update rate of the OTDOA measurement with respect to one particular base station, i.e. the measurements are likely to become outdated if the UE moves with high velocity, which again mitigates the positioning accuracy, e.g., for a car. Therefore, in this invention submission we aim at a scheme avoiding or, at least, minimizing any PRS muting.
Another straightforward solution is to deploy additional transmission points in the cell aiming to increase the number of measurable base station. Two basic principles can be distinguished:
The first basic principle is that transmission points use LTE as radio access technology and transmit solely PRS. Advantages are that the radio access network has full control over the transmission points, and that it is ensured that the UEs fully support this extended positioning because from their perspective the transmission points appear just as additional base stations for OTDOA measurements.
However, the number of non-overlapping time-frequency patterns, where PRS can be sent, is limited to M (see 3GPP TS 36.211 V15.0.0 (2017 Decemebr), for example, where M=6). In other words, both base stations and additional transmission points in the deployment share in total M different time-frequency patterns for PRS. Two transmission points transmitting their PRS on the same time-frequency pattern suffer from some residual interference as the PRS are pseudo-random sequences without perfect orthogonality in the code domain. The presence of additional transmission points for PRS densifies the reuse pattern (smaller distance between two PRS transmitters utilizing the same pattern) and thus increases the mean interference level on the PRS. PRS muting can be applied to reduce the interference with the same drawback as described before.
The second basic principle is that transmission points use any other Radio Access Technology (RAT), e.g., WLAN, Bluetooth, Terrestrial Beaconing System. Regarding the addressed Intelligent Transportation System (ITS) use cases, a couple of severe drawbacks may occur:
For example, a combination of different RATs comes along with enhanced signalling overhead between the radio access network, its base stations, the supporting transmission points using a different RAT and the UEs that must be aware of that.
Moreover, it is not ensured that the UEs support the RAT of the transmission points. At least it is additional effort for the UE. Eventually the UE has to switch permanently between two different frequency bands during measuring.
Furthermore, as the transmission points typically transmit the supporting positioning signal in an unlicensed band, it may happen that measurements are significantly falsified through superimposed transmissions originating from another source, not involved in the positioning.
Hence, it is desirable to improve the positioning accuracy. According to embodiments of the present invention, a beamforming and coordination scheme for Positioning Reference Signals (PRS) is provided that can significantly enhance the capabilities of the existing LTE positioning with Observed Time Difference of Arrival (OTDOA).
In the following, a general overview of an embodiment of the present invention is described by referring to
In particular,
In other words, by referring to the flowchart shown in
It is noted that the BS 10 is only an example for the first apparatus or transmission device. Alternatively, the apparatus may be any kind of device, which may also include a program or code that is able to transmit or to control transmission of positioning purpose signals via a plurality of antennas in a beamforming and/or precoding pattern. Moreover, the apparatus may be a controller for a transmission device such as a BS. Hence, the plurality of antennas may be part of the apparatus, or the plurality of antennas may not be part of the apparatus, but is connectable thereto.
The beamforming and/or precoding pattern may be a pattern which specifies how beamforming or precoding is to be carried out. For example, the pattern may specify center_beam_azimuth, center_beam_elevation and beam_width etc. When precoding is applied, the pattern may specify weights to be applied to the different antennas of the plurality of antennas.
The beamforming and/or precoding pattern may be prepared such that a received signal power of the positioning purpose signal is maximized in a certain area, and/or the received signal power of the positioning purpose signal is minimized in another area.
The transmission device may comprise the antenna array 14 shown in
Moreover, the beamforming and/or precoding pattern may be created based on a coordination scheme, in which beamforming of transmission of positioning purpose signals from a plurality of transmission devices are coordinated.
In other words, by referring to the flowchart shown in
The LS or localization coordinating entity is only an example for the second apparatus, and can be any other suitable network element which is able to create a coordination scheme for a plurality of transmission devices. For example, the second apparatus may also be part of a BS, eNB or the like.
In other words, by referring to the flowchart shown in
Hence, according to embodiments of the present invention, transmission devices (such as BS) perform beamforming according to a coordination scheme. In this way, certain areas may be targeted with a high received signal power, whereas other areas may be targeted with low received signal power. In this way, the number of measurable transmission devices for a UE can be increased.
In other words, according to embodiments of the present invention, beamforming or precoding of PRS transmissions is used in combination with a coordination scheme between base stations aiming at increasing the number of measurable base stations at a target UE for OTDOA measurements within a given time interval T.
It is noted that the BS 10 and the LS 20 may further comprise input/output (I/O) units or functions (interfaces) 13 connected to the processor 11, and also the LS 20 may further comprise input/output (I/O) units or functions (interfaces) 23 connected to the processor 21, in order to provide connections to other elements. In particular, the I/O units or functions 23 may receiver/transmitter units. Similarly, the UE 30 may further comprise input/output (I/O) units or functions (interfaces) 33 connected to the processor 31. For example, the I/O units or functions 33 may comprise a receiver/transmitter unit.
In the following, some more details of embodiments of the present invention are described.
According to some embodiments of the present invention the transmission of PRS from a multi-antenna base station (BS) to at least one target UE (T-UE) is beamformed or precoded aiming at
Moreover, according to some embodiments, a coordination scheme between a number N of BSs, each transmitting one out of M<N orthogonal realizations of the PRS, in the following referred to as PRS ID, is provided such that the number of measurable BSs for OTDOA measurements within a given time duration T is maximized, and their interference at all the interested T-UEs is minimized through an advantageous beamforming pattern from the N BSs, and consequently the positioning error of the T-UE is minimized. Measurable BS means that the T-UE receives the PRS from said BS with sufficiently high SINR so that it can take a meaningful OTDOA measurement. The time duration T depends on the application. As an example, a fast driving car requires a small value of T, in the order of 100 ms, to avoid outdated position estimates.
Examples for the messaging and the protocols between BS, T-UE and the localization coordinating entity, the Location Server (LS) hereafter, to configure this PRS transmission are described later.
In contrast to the existing solution operating with PRS muting only, according to embodiments of the present invention, a subset of the PRS
IDs with sharp beams pointing to adjacent cells is transmitted as indicated in
The purpose is that, for example, the T-UE located in cell 7C can take an OTDOA measurement from BS site 5, which would not be possible with the existing solution without muting the respective PRS ID at BS site 7. A PRS ID corresponds to one of the beams P41 to P46 indicated in
Moreover, it is noted that the PRS in the downlink, as standardized for positioning purposes at the moment, is only an example for a positioning purpose signal. That is, the positioning purpose signal is not limited to PRS, and can be any kind of radio signal transmitted for the purpose of positioning. That is, according to some embodiments of the present invention, a general concept of precoding/beamforming the transmission of any other radio signals transmitted for the purpose of positioning is provided to increase the number of measurable transmitters, limiting the interference from not-desired transmitters in the process. One example for that is a Supporting PRS (S-PRS) signal sent from a Supporting UE (S-UE) to the T-UE on sidelink resources. Lampposts along a street can be equipped with these S-UEs, each of them transmitting advantageously beamformed/precoded S-PRS to a car driving by.
In the following, some more details of the above embodiments are described.
As mentioned above, it is an aim to increase the number of measurable BSs at a T-UE to increase the number of OTDOA measurements from these BSs within the given time duration T, achieving highly accurate positioning of the T-UE.
First of all, thanks to beamforming gains one can extend the range of these PRS in the interested direction that the system wants to monitor.
In doing so, the following degrees of freedom are achieved:
A: Each BS transmits one out of M different PRS IDs. These M PRS IDs are mutual orthogonal in the sense that disjoint sets of time-frequency resources, so called patterns, are utilized. As an example, the M=6 PRS patterns defined in 3GPP TS 36.355 V14.4.0 (2017 December) can be used.
B: According to the present embodiment, the possibility is provided that each BS steers the transmitted PRS in a preferred area A, and/or avoids transmitting any signal power in a non-preferred area B by beamforming or precoding of the PRS. The beamforming/precoding decisions can depend on a coordination scheme.
This coordination scheme between a number N of BS aims to
i) maximizing the SINR on received PRS in a certain area, or for certain T-UEs,
ii) drastically reducing the interference power produced by BS X in a certain preferred area of BS Y, both transmitting the same PRS ID. This can be done to temporarily increase the number of BS illuminating the same T-UE, since BS far away from the T-UE can transmit a sharp beam in that T-UE's direction, without impacting a huge area around (e.g. see
iii) not transmitting in an area B where the BS has strong NLOS degradation, but still can bring some interference to few positions in B.
The beamforming/precoding decisions can furthermore depend on rough knowledge of the T-UEs' position at the BS or LS, and/or prediction of future positions of at least one T-UE at the BS or the LS based on previous positions or supporting information like a street map.
C: Periodicity of PRS transmissions
According to a preferred embodiment of the invention, the abovementioned parameters are selected (e.g., by the LS) jointly in such a way that the number of OTDOA measurements from measurable BSs within a given time period T is maximized and the interference brought to other users is minimized. A measureable (detectable) BS is defined as a BS whose PRS is received at the T-UE with a SINR higher than a threshold y, depending on the BS and the T-UE's position. T is defined by the application and may range in the orders of magnitude between 10 ms and 10 s. The higher the speed of the T-UE, the shorter must be chosen T in order to get accurate position estimates in real time.
The so called PRS beamforming pattern is defined as the set of all
The PRS beamforming is coordinated between the N cells which can mean that in each PRS transmission slot a different PRS beamforming pattern is utilized. As an example, the sharply beamformed PRS IDs may rotate over time in order to illuminate different target areas in the adjacent cells, while illumination of the target area from multiple BS sending the same PRS ID is avoided. For example, the signaling may comprise the rotation speed (e.g. +30 degree every transmission) and behavior (e.g. maximum and minimum angle).
In the following, two examples to schedule such directional PRS with beamforming/precoding pattern are described. One is stationary with respect to the T-UEs position and cell history, and only updated once in a while, e.g. every hour, by the LS. The other is updating the beamforming pattern very quickly, based on T-UEs positions and QoS requirements.
In the following, an embodiment is described according to which a stationary beamforming pattern scheduling is applied.
The beamforming pattern in this case is independent from the T-UEs positions and demands. This is the case when a lot of different T-UEs must be tracked simultaneously, with a sufficient number of advantageously placed BSs.
In
The example shown in
Each BS always transmits 3 PRS in its 120 degrees sectors.
Furthermore, each BS transmits the 3 other beamformed PRS, achieving a beamforming gain and sharpening the area where the PRS signal can be perceived. Please note that these beamformed PRS are intentionally steered in neighboring cells to allow T-UEs located in these neighboring cells taking OTDOA measurements with respect to the transmitting BS. These three beams start with an offset of 0, 120, 240 degrees respectively, and then rotate with 120/K degrees at the next PRS transmission slot, e.g. 40 degrees with K=3. Therefore, the periodicity of the PRS measurement coming from the same BS site in the same area is K=3. In
The configuration of the beamforming pattern could be shared also with the T-UE. Hence, according to an embodiment, the location server (LS) and/or the base station (BS) include means to inform the T-UE about the beamforming pattern configuration. This can be achieved by an extension of the existing LTE Positioning Protocol (LPP) (see 3GPP TS 36.355 V14.4.0 (2017 December)), i.e. adding respective new information fields. However, the invention is not limited to LPP, but can be applied on other kind of positioning protocol as well, for example also in a New Radio (NR) positioning protocol.
As one can see, with this simple scheme, without the need of any muting pattern, the T-UE can sense the BS5 (as well as two other BS not shown in the Figure, from yellow and grey PRS), that could not be sensed with a typical broadcast-like transmission of M=6 PRS without applying muting.
According to another embodiment of the present invention, an on the fly beamforming pattern scheduling is applied.
In particular, according to this embodiment, the beamforming pattern is adapted based on rough previous position estimates in the case that only few T-UEs should be tracked.
In this way, the scheduler of the BS of interest can act as depicted in
In
The invention is not limited to the specific embodiments described above, and various modifications are possible.
For example, according to some embodiments, the localization coordinating entity or Location Server (LS) has been described as a separate entity (dedicated network control element) for controlling the BSs in the coordination scheme. However, alternatively the localization coordinating entity may also be a part of one of the BSs involved, or may be a part of another suitable network control element.
Moreover, the base stations (BSs) are only examples for transmission devices for transmitting positioning purpose signals in a beamforming and/or precoding pattern from a plurality of antennas.
Furthermore, according to some embodiments, it is described that the PRS with different ID (1, . . . , M) are orthogonal to each other if transmitted in the same time/frequency, however the invention is not limited to these sequences. That is, one can use signals to take OTDOA/Carrier Phase measurements that are not fully orthogonal in time/frequency, but are separated by the fact that they are transmitted in different space, applying beamforming.
Moreover, according to some embodiments, it is described that transmission of a signal is beamformed/precoded that can be used to perform OTDOA. However, the invention is not limited to this. That is, also any other measurements can be performed by using the beamformed/precoded transmission of these signals, e.g. carrier phase.
In general, various embodiments of the UE can include, but are not limited to, mobile stations, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.
The memories 12, 22 and 23 may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The processors 11, 21 and 32 may be of any type suitable to the local technical environment, and may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on a multi core processor architecture, as non-limiting examples.
Further, as used in this application, the term “circuitry” refers to all of the following:
(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and
(b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and
(c) to circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present.
This definition of “circuitry” applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term “circuitry” would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term “circuitry” would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.
It is to be understood that the above description is illustrative of the invention and is not to be construed as limiting the invention. Various modifications and applications may occur to those skilled in the art without departing from the true spirit and scope of the invention as defined by the appended claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/053390 | 2/12/2018 | WO | 00 |
