GB2633819A

GB2633819A - Position estimation

Info

Publication number: GB2633819A
Application number: GB2314559.2A
Authority: GB
Inventors: Barbu Oana-Elena
Original assignee: Nokia Technologies Oy
Current assignee: Nokia Technologies Oy
Priority date: 2023-09-22
Filing date: 2023-09-22
Publication date: 2025-03-26
Also published as: GB202314559D0

Abstract

An apparatus (e.g. user equipment, UE) obtains first signal samples (e.g. downlink position reference signals, DL PRS), this may be from a gNB. The apparatus obtains second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein the second signal samples are obtained over respective second channels between the second and first device (e.g. via sidelink). The apparatus comprises a means for generating compensated second signal samples from the second signal samples by compensating for effects (e.g. gain or delay) of the respective second channel on the second signal samples. The apparatus comprises means for generating location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal samples. The location information may comprise carrier phase information and may further comprise a propagation delay between transmitter and first device. The first sample signals may be generated by demodulating the received downlink reference signals.

Description

Position Estimation

Field

Example embodiments may relate to systems, methods and/or computer programs for generating position estimates, or data for use in generating position estimates, for example based on received reference signals.

Background

The present specification relates to generating position estimates (or data for use in generating position estimates) using downlink reference signals (such as positioning reference signals) in systems having multiple devices in communication with one or more network nodes of a mobile communication system. The devices may have different capabilities.

Summary

The scope of protection sought for various embodiments of the invention is set out by the independent claims. The embodiments and features, if any, described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

In a first aspect, this specification describes an apparatus comprising: means for obtaining first signal samples based on a downlink reference signal (e.g. a positioning reference signal) as received at a first device, over a first channel, from a transmitter (e.g. a gNB) of a mobile communication system; means for obtaining second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein said second signal samples are obtained over respective second channels (e.g. sidelink channel(s)) between the respective second devices and the first device; means for generating compensated second signals samples from said second signal samples by compensating for effects of the respective second channel on said second signal samples; and means for generating location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal samples. The apparatus may, for example, be, or may form part of, the first device.

The said location information may comprise carrier phase information. Alternatively, or in addition, the said location information may comprise a propagation delay between the transmitter and the first device. Thus, at least one of carrier phase information or delay information may be generated. Other information (such as angle of departure data) could also be generated.

The apparatus may further comprise means for providing said location information (e.g. at least one of carrier phase information or delay information) to a location management function. For example, an LPP report may be provided.

The said means for obtaining said first signal samples may comprise: means for receiving said downlink reference signals; and means for demodulating the received downlink reference signals to generate said first signal samples.

One or more (e.g. all, although note that there may be only one such channel) of the respective second channels may be sidelink channels. In some example embodiments, one or more alternative wireless channels (e.g. Bluetooth) may be used. In some example embodiments, one or more wired channel may be used. Note that different technologies (e.g. different wireless technologies) may be used for different second channels.

In some example embodiments, an effect of the second channel comprises a gain or a delay of a dominant path of the respective second channel, or both. The apparatus may further comprise means for obtaining (e.g. estimating, determining or retrieving) the delay and the gain of the dominant path of the or each second channel.

The apparatus may further comprise means for generating an estimate of the first channel. Moreover, the apparatus may further comprise means for generating the location information based, at least in part, on the generated estimate of the first channel.

The said downlink reference signal may be a positioning reference signal. In some example embodiments, some other downlink reference signal may be used.

In a second aspect, this specification describes a system comprising an apparatus as described herein (including as described above with reference to the first aspect) and further comprising said one or more second devices.

In a third aspect, this specification describes a method comprising: obtaining first signal samples based on a downlink reference signal as received at a first device, over a first channel, from a transmitter of a mobile communication system; obtaining second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein said second signal samples are obtained over respective second channels (e.g. sidelink channel(s)) between the respective second devices and the first device; generating compensated second signals samples from said second signal samples by compensating for effects of the respective second channel on said second signal samples; and generating location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal samples. The method may be implemented at the first device (e.g. a user device, such as a mobile phone). In some example embodiments, at least some of the method may be implemented elsewhere (e.g. at a server remote from the first device).

The method may further comprise providing said location information to a location management function. For example, an LPP report may be provided.

Obtaining said first signal samples may comprise: receiving said downlink reference signals; and demodulating the received downlink reference signals to generate said first signal samples.

In some example embodiments, an effect of the second channel comprises a gain or a delay of a dominant path of the respective second channel, or both. The method may further comprise obtaining (e.g. estimating, determining or retrieving) the delay and the gain of the dominant path of the or each second channel.

The method may further comprise generating an estimate of the first channel. Moreover, the method may further comprise generating the location information based, at least in part, on the generated estimate of the first channel.

In a fourth aspect, this specification describes computer-readable instructions which, when executed by a computing apparatus, cause the computing apparatus to perform (at least) any method as described herein (including the method of the third aspect described above).

In a fifth aspect, this specification describes a computer-readable medium (such as a non-transitory computer-readable medium) comprising program instructions stored thereon for performing (at least) any method as described herein (including the method of the third aspect described above).

In a sixth aspect, this specification describes an apparatus comprising: at least one processor; and at least one memory including computer program code which, when executed by the at least one processor, causes the apparatus to perform (at least) any method as described herein (including the method of the third aspect described above).

In a seventh aspect, this specification describes a computer program comprising instructions which, when executed by an apparatus, cause the apparatus to: obtain first signal samples based on a downlink reference signal as received at a first device, over a first channel, from a transmitter of a mobile communication system; obtain second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein said second signal samples are obtained over respective second channels (e.g. sidelink channel(s)) between the respective second devices and the first device; generate compensated second signals samples from said second signal samples by compensating for effects of the respective second channel on said second signal samples; and generate location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal samples.

In an eighth aspect, this specification describes: a first input of a user device (or some other means) for obtaining first signal samples based on a downlink reference signal as received at a first device, over a first channel, from a transmitter of a mobile communication system; a second input of the user device (or some other means) for obtaining second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein said second signal samples are obtained over respective second channels between the respective second devices and the first device; a processor (or some other means) for generating compensated second signals samples from said second signal samples by compensating for effects of the respective second channel on said second signal samples; and the processor (or some other means) for generating location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal samples.

In an eighth aspect, this specification describes an apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the processor, causes the apparatus to perform: obtaining first signal samples based on a downlink reference signal as received at a first device, over a first channel, from a transmitter of a mobile communication system; obtaining second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein said second signal samples are obtained over respective second channels between the respective second devices and the first device; generating compensated second signals samples from said second signal samples by compensating for effects of the respective second channel on said second signal samples; and generating location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal samples.

Brief Description of the Drawings

Example embodiments will now be described by way of non-limiting example, with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a system in accordance with an example embodiment; FIG. 2 is a block diagram of a system in accordance with an example embodiment; FIG. 3 is a flowchart of a method in accordance with an example embodiment; FIG. 4 is a flowchart of a method in accordance with an example embodiment; FIG. 5 shows a message flow sequence in accordance with an example embodiment; FIG. 6 is a block diagram showing a method in accordance with an example embodiment; FIG. 7 is a block diagram showing a method in accordance with an example embodiment; FIG. 8 is a schematic diagram of components of one or more of the example embodiments described previously; and FIG. 9 shows tangible media for storing computer-readable code which when run by a computer may perform methods according to example embodiments described herein.

Detailed Description

In the description and drawings, like reference numerals refer to like elements throughout.

FIG. 1 is a block diagram of a system, indicated generally by the reference numeral 10, in accordance with an example embodiment. The system 10 comprises a network node 12, a first device 14 and a second device 16. The first and second devices are each in two-way communication with the network node 12. The second device 12 may have limited capabilities (e.g. limited power, intelligence and/or processing ability) when compared with the first device 12. The first and second devices 12 and 14 may be referred to as "primary" and "secondary" devices respectively.

The network node 12 may be a network node of a mobile communication system (e.g. a base station or an access point of a wireless system). The first and second devices may be radio devices (e.g. user devices or user equipments) that form part of the mobile communication system. At least one of the first and second devices may be a mobile phone.

As discussed in detail, the first and second devices 14 and 16 may receive downlink reference signals from the network node 12. The downlink reference signals may be provided for a variety of purposes. Example downlink reference signals include positioning reference signals (PRS). The skilled person will be aware of other reference signals that could be relevant to some example embodiments.

The system 10 could take many forms and could be used in many applications. An example application discussed further below is an Industrial Internet of Things (IIoT) application. The skilled person will, however, be aware of many alternative applications that could make use of the principles discussed herein (such as an extended reality (XR) or similar application). Similarly, the network node and the devices discussed herein may form part of a New Radio (NR) communication system, but the principles described herein are widely applicable to other communications systems and technologies.

FIG. 2 is a block diagram of a system, indicated generally by the reference numeral 20, in accordance with an example embodiment. The system 20 comprising a robot 21 (or some other industrial equipment). The robot 21 includes a first device 22 and a second device 24. The first and second devices may be radio devices and may be examples of the first and second devices 14 and 16 of the system 10 described above. The devices 22 and 24 may each be in communication with a network node (such as the network node 12 described above) and may be in communication with each other (e.g. using sidelink communications or some other wired or wireless communication protocol). By way of example, the second device 24 (e.g. an IIoT device) may have limited power and/or intelligence (e.g. processing ability) when compared with the first device 22.

In example implementations of the system 20 in which the first device 22 has higher power and/or processing capacity that the second device 24, in order to determine the location of the robot 21, one approach may be to trigger a localization session at the first device 22 to ensure that accurate positioning measurements are collected. This is typically suboptimal, since other devices (i.e., the second device 24 in the example system 20) is/are not involved in the positioning session, even though they could positively contribute to the measurement collection.

In example embodiments discussed in detail below, positioning estimates for the robot 21 can be determined using a single positioning session while exploiting information from multiple devices residing on the machinery (e.g. the first device 22 and the second device 24 of the robot 21), despite the heterogeneous processing capabilities of those devices.

The system 20 is described by way of example only. The principles described herein could be implemented in other systems. For example, the first and second devices may be devices of an XR or similar system, such as a user equipment (e.g. a mobile phone) and virtual reality (VR) glasses respectively. In such an example embodiment, the VR glasses may have limited power and/or intelligence (e.g. processing ability) relative to the user equipment.

FIG. 3 is a flowchart of a method. The method may be implemented using an algorithm, indicated generally by the reference numeral 30, in accordance with an example embodiment. The algorithm 30 may be implemented using the system 10 or the system 20 described above. For example, the algorithm 30 may be implemented at the first device 14 of the system 10 or the first device 22 of the system 20. This is not essential to all example embodiments; for example, some or all of the operations of the algorithm could be implemented elsewhere (e.g. at a server); in particular one or both of the operations 36 or 38 may be implemented elsewhere.

The algorithm 30 starts at operation 32 where first signal samples are obtained based on a downlink reference signal as received at a first device of a system, over a first channel, from a transmitter of a mobile communication system. The operation 32 may be implemented by receiving and demodulating downlink reference signals (e.g. positioning reference signals). The downlink reference signal may, for example, be received at the first device 14 or the first device 22 from a transmitter, such as the network node 12.

At operation 34, the first device receives second signal samples over a second channel (e.g. a sidelink channel) between respective ones of one or more second devices and the first device. The second signal samples are obtained, by the respective second device, based on the downlink reference signal as received at the respective second device (e.g. the second device 16 or the second device 24) of the system from the transmitter of the mobile communication system.

is It should be noted that although the algorithm 30 suggests that the first samples are obtained in operation 32 before the second samples are obtained in operation 34, this is not essential. The operations 32 and 34 may be implemented in a different order, or in parallel.

At operation 36, compensated second signals samples are generated from the second signal samples obtained in the operation 34. The operation 36 compensates for effects of the respective second channel on said second signal samples. As discussed in detail below, the effects of the second channels may, for example, comprise a gain and a delay of a dominant path of the respective second channel. The operation 36 may, for example, include obtaining (e.g. estimating) the delay and the gain of the dominant path of the or each second channel (note that in some example embodiments, determining the delay and gain of the dominant path may be a separate process and may be implemented prior to the start of the algorithm 30).

At operation 38, location information relating to the first device relative to the transmitter is generated. As discussed in detail below, the location information may comprise at least one of carrier phase information or a propagation delay (which may be generated based on carrier phase information) between the transmitter and the first device. The location information may be generated (based on the first signal samples and the compensated second signal samples) by considering the first and second devices to represent a single device having multiple antennas (e.g. an emulated virtual MIMO receiver at the first device). Example implementations of the operation 38 are discussed in detail below.

The operation 38 may include generating an estimate of the first channel based on an emulated virtual MIMO receiver. The delay between the transmitter and the first device of the system may be estimated based on a carrier phase estimate, which may be generated based on the estimate of the first channel.

The output of the step 38 may then be reported, for example to a location management function (e.g. as part of an LPP report). The report may comprise an estimated delay. Alternatively, or in addition, arrier phase information could be reported.

FIG. 4 is a flowchart of a method. The method may be implemented using an algorithm, indicated generally by the reference numeral 40, in accordance with an example embodiment. The algorithm 40 may, for example, be implemented at the second device 16 of the system 10 or the second device 24 of the system 20.

The algorithm 40 starts at operation 42, where downlink reference signals (e.g. PRS) are received and processed (e.g. at the second device 16 of the system 10 or the second device 24 of the system 20). At operation 44, processed downlink reference signal samples are transferred to another device (e.g. the first device 14 of the system 10 or the first device 22 of the system 20). The operation 44 may be implemented using a sidelink connection (or some other wireless or wired connection) between the first and second devices. The downlink reference signal samples received in the operation 34 of the algorithm 30 may be the downlink reference signal samples transferred in the operation 44 of the algorithm 40.

As discussed in detail below, the signals received at the respective second devices of the system may be deemed to have been received over the first channel. For example, the channel between the transmitter and each of the first and second devices may be considered to be the same -this is often a reasonable approximation.

FIG. 5 shows a message flow sequence, indicated generally by the reference numeral 50, in accordance with an example embodiment. The message flow sequence 50 shows messages between, and actions at, a first user device (UE1) 51, a second user device (UE2) 52, a gNB 53 and a location management function (LMF) 54. The first user device 51 is an example of the first devices 14 and 22 described above. The second user device 52 is an example of the second devices 16 and 24 described above. The gNB 53 is an example of the network node 12 described above. The message flow sequence 50 shows an example implementation of the algorithms 30 and 40 discussed above.

As discussed in detail below, the message flow sequence 50 seeks to exploit DL PRS reception at one or more secondary UEs (here UE2) to emulate a positioning receiver having multiple antennas (e.g. a virtual MIMO positioning receiver) at UE1. By doing so, the number of available reference signal observations (e.g. PRS observations) at UE1 is increased (e.g. doubled -the multiplication factor depends on the number of secondary UEs), which in turn may increase the precision of the positioning measurements.

It should be noted that although a single second device (UE2) is shown in the message sequence 50 (and in the systems 30 and 40 described above), a plurality of second devices may be provided in some example embodiments.

The message sequence 50 starts at step 1, where a Location and Positioning Protocol (LPP) positioning session between the user devices 51, 52, the gNB 53 and the LMF 54 is configured.

The LPP positioning session starts with the gNB 53 providing downlink reference signals (here positioning reference signals) to the first and second user devices. The DL reference signals are received at the first user device 51 in step 2 and are received at the second user device 52 in step 3.

At step 4, the first user device 51 measures and demodulates the DL reference signals (for example, based on orthogonal frequency division multiplexing (OFDM) principles). Similarly, at step 5, the second user device 52 measures and demodulates the DL reference signals.

The second user device 52 transfers the demodulated reference signals to the first user device 51 in step 6 of the message sequence 50. This transfer may take place over a sidelink (SL) channel with known gain and delay (although other channels, such as Bluetooth, wi-fi, or wired channels could be used). The gain and delay of said sidelink (or other) channel may have been acquired when the link between the first and second user device (the UE1-UE2 link) was established. Alternatively, the gain and delay of said sidelink (or other) channel may be implemented as part of the message sequence 50.

Steps 2 and 4 of the sequence 50 may therefore implement the operation 32 of the algorithm 30. Similarly, steps 3, 5 and 6 of the sequence may implement the operations 42, 44 and 34 of the algorithms 30 and 40. 1.1

At step 7, the first user device collects the reference signal observations of the second user device 52 and removes the channel effect (e.g. sidelink channel effect) from the received signal. In some example embodiments, the compensated reference signals are then combined with the first user device reference signals into an RX array that represents a virtual MIMO receiver (step 8), thereby providing an example implementation of the operation 36 of the algorithm 30. As discussed elsewhere herein, creating a large virtual MIMO device (or some other system representation having multiple antennas, e.g. co-located antennas) can lead to an increase in positioning accuracy due to the linear increase in the number of RX signals.

In the message sequence 50, the virtual MIMO samples are processed jointly, and carrier phase and delay extraction follow (steps 9 and 10), thereby providing an example implementation of the operation 38 of the algorithm 30. Specifically, the carrier phase is extracted after estimating the DL MIMO channel impulse response and the delay information is extracted using carrier phase information and the delay profile of the estimated MIMO channel.

Finally, in step 11, the first user device 51 may provide an LPP report to the LMF 54. The LPP report may include the delay information and time of arrival data determined based on the reference signals received at the first and second user devices. The LPP report can then be processed, for example to determine a position estimate for the system (e.g. the position of the robot 21 in the example embodiments discussed above).

It should be noted that the steps 10 and 11 are provided by way of example only.

Alternative implementations are possible. For example, step 10 may be omitted and carrier phase information (as determined in step 9) may be provided to the LMF 54.

FIG. 6 is a block diagram showing a method. The method may be implemented using an algorithm, indicated generally by the reference numeral 60, in accordance with an example embodiment. The algorithm 60 is implemented in the first user device (UE1) 51 and the second user device (UE2) 52 described above. The algorithm 60 provides further details of an example implementation of the algorithms 30 and 40 and the message sequence 50.

As described above, the first user device 51 is a primary UE (UE1) and the second user device 52 is a secondary UE (UE2). UE1 and UE2 may communicate directly, for example using sidelinks (SLs) or some other connection (e.g. a wired connection or some other wireless connection). 1.2

In accordance with step 4 of the algorithm 50, UE1 51 receives a DL PRS signal. The DL PRS signals received at the UE1 are provided to an OFDM demodulator and the following RX signal samples (y1) are collected and stored: = (1) Where F is a DFT matrix with N x L entries, F(a,1)= exp(-2mj f"7-1) , where N is the total number of subcarriers and L is the number of multipath components of the channel between UE1 and the TRP sending the PRS. The column vector a has L entries and stores the complex gain of each of the multipath components, i.e. a(1) = a(1)exp(-2irj fc -r1) where a(I) is the amplitude and Ti is the delay of the l-th component, and L is the carrier frequency.

Similarly, in accordance with step 3 of the algorithm 50, UE2 52 receives the same DL PRS signal. The DL PRS signal received at UE2 are provided to an OFDM demodulator and the following signal samples (y2) are collected and stored: Y2 = Fa2 ± "2 (2) The DL-PRS signals received at UE1 and UE2 are provided by the same transmission-reception point (TRP), such as the gNB 53. Since the TRP-to-UE1 distance and the TRP-to-UE2 distance are similar, and much larger than the distance between UE1 and UE2, we hypothesize that both UEs see the same channel towards the TRP. Thus, we approximate a2 a. This allows us to recast (2) as the following approximation: Y2 = Fa + n2 (2) Next, in accordance with step 6 of the algorithm 50, UE2 transfers the RX signal samples yz to UE1 via the SL channel (or some other channel). That channel typically consists of a single dominant path with gain fl and delay T much smaller than the propagation delay from the TRP. We assume that the SL channel is known (at least to a reasonable approximation). For example, the channel may have been learnt in a separate procedure, during the establishment of the SL connection.

Given the above, UE1 receives from UE2 the signal samples: T2 = PEra + P172 (3).

Where F.,.(a,b) = exp(-2Trj fi)F(a,b) is a rotated version of F. By enabling the direct transfer operation above, we enable a virtual MIMO receiver in UE1 which now possess two sets of samples i.e. (1) and (3). The virtual MIMO UE1 then 1.3 now combines the samples as following: y = [1.21 = Aa + (4) Where: s A = [Id is a virtual MIMO dictionary matrix; and the total noise term = [finn12] is considered AWGN with subcarrier-based variance o-2.

Using the approximate model in (4), we can now use a suitable channel estimator (e.g., orthogonal matching pursuit, tools from sparse Bayesian learning, etc.) and compute an estimate of a, denoted as a.

Next, we identify the dominant entry in the vector a e.g., the component with maximum amplitude. The index of the dominant component is k i.e.: = max(161) (5).

Following, we extract the carrier phase of the dominant component: cp(k,2) = phase(a(k)) + 21-11. (6) Since the phase is periodic with periodicity 2z, we may resolve the integer ambiguity A before converting the phase to delay domain.

To do that, we can assess the k-th column of matrix F and extract the approximate delay information, e.g.: phase(F (a, k)) dk -la * (7) fa Then, using (6, 7), we find A: A arg mini exp(-2n] fc, cik) -exp(Jrp(k, A)) I (8) Finally, we can now extract the delay from the carrier phase information: cp(k,1) 2a f.-.

Which, in accordance with step 11 of the algorithm 50, is sent by UE1 to the location management function (LMF), such as the LMF 54 of the system 50 described above. LMF.

Alternatively, as noted above, step 11 of the algorithm 50 may be implemented by 1.4 providing the carrier phase information (e.g. as defined above in Equation 6) to the LMF.

In the example embodiments described above, the second device UE2 transfers the RX signal samples yz to UE1 (e.g. via a sidelink channel channel). This is not essential to all example embodiments. For example, the second device may transfer the RX signal samples y2 to a remote processor that also receives the first signal samples yi in order to use the virtual MIMO receiver principles describes herein to generate the required delay information. In this case, the remote processor may process yz using models (2) and (3) to obtain r, and then proceed to combine yi with r by following the same method as presented above. The remote processor may have learned in the past the direct channel between the UEs (e.g. including gain p and delay T), or may, for example, estimate the channel based on an approximate distance between the UEs.

FIG. 7 is a block diagram showing a method. The method may be implemented using an algorithm, indicated generally by the reference numeral 70, in accordance with an example embodiment. The algorithm 70 is implemented by the first user device (UE1) 51 and the second user device (UE2) 52 described above. The algorithm 70 provides further details of an example implementation of the algorithms 30 and 40 and the message sequence 50.

The algorithm 70 includes the features of the algorithm 60 and additionally enables the first user device 51 to update the SL channel parameters (fl, T) before the start of the DL positioning session. This update may be implemented using existing SL DMRS channel estimation. This updating can be provided so that the dictionary A remains up to date.

For completeness, FIG. 8 is a schematic diagram of components of one or more of the example embodiments described previously, which hereafter are referred to generically as a processing system 300. The processing system 300 may, for example, be the apparatus referred to in the claims below.

The processing system 300 may have a processor 302, a memory 304 closely coupled to the processor and comprised of a RAM 314 and a ROM 312, and, optionally, a user input 310 and a display 318. The processing system 300 may comprise one or more network/apparatus interfaces 308 for connection to a network/apparatus, e.g. a modem which may be wired or wireless. The network/apparatus interface 308 may also operate as a connection to other apparatus such as device/apparatus which is not network side apparatus. Thus, direct connection between devices/apparatus without network participation is possible.

The processor 302 is connected to each of the other components in order to control operation thereof.

The memory 304 may comprise a non-volatile memory, such as a hard disk drive (HDD) or a solid state drive (SSD). The ROM 312 of the memory 304 stores, amongst other things, an operating system 315 and may store software applications 316. The RAM 314 of the memory 304 is used by the processor 302 for the temporary storage of data. The operating system 315 may contain code which, when executed by the processor implements aspects of the algorithms and message sequences 30, 40, 50, 60 and 70 described above. Note that in the case of small device/apparatus the memory can be most suitable for small size usage i.e. not always a hard disk drive (HDD) or a solid state drive (SSD) is used.

is The processor 302 may take any suitable form. For instance, it may be a microcontroller, a plurality of microcontrollers, a processor, or a plurality of processors.

The processing system 300 may be a standalone computer, a server, a console, or a network thereof. The processing system 300 and needed structural parts may be all inside device/apparatus such as IoT device/apparatus i.e. embedded to very small size.

In some example embodiments, the processing system 300 may also be associated with external software applications. These may be applications stored on a remote server device/apparatus and may run partly or exclusively on the remote server device/apparatus. These applications may be termed cloud-hosted applications. The processing system 300 may be in communication with the remote server device/apparatus in order to utilize the software application stored there.

FIG. 9 shows a tangible media, in the form of a removable memory unit 365, storing computer-readable code which when run by a computer may perform methods according to example embodiments described above. The removable memory unit 365 may be a memory stick, e.g. a USB memory stick, having internal memory 366 storing the computer-readable code. The internal memory 366 may be accessed by a computer system via a connector 367. Of course, other forms of tangible storage media may be used, as will be readily apparent to those of ordinary skilled in the art. Tangible media can be any device/apparatus capable of storing data/information which data/information can be exchanged between devices/apparatus/network.

Embodiments of the present invention may be implemented in software, hardware, application logic or a combination of software, hardware and application logic. The software, application logic and/or hardware may reside on memory, or any computer media. In an example embodiment, the application logic, software or an instruction set is maintained on any one of various conventional computer-readable media. In the context of this document, a "memory" or "computer-readable medium" may be any non-transitory media or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer.

Reference to, where relevant, "computer-readable medium", "computer program product", "tangibly embodied computer program" etc., or a "processor" or "processing circuitry" etc. should be understood to encompass not only computers having differing architectures such as single/multi-processor architectures and sequencers/parallel architectures, but also specialised circuits such as field programmable gate arrays FPGA, application specify circuits ASIC, signal processing devices/apparatus and other devices/apparatus. References to computer program, instructions, code etc. should be understood to express software for a programmable processor firmware such as the programmable content of a hardware device/apparatus as instructions for a processor or configured or configuration settings for a fixed function device/apparatus, gate array, programmable logic device/apparatus, etc. The term "means" as used in the description and in the claims may refer to one or more individual elements configured to perform the corresponding recited functionality or functionalities, or it may refer to several elements that perform such functionality or functionalities. Furthermore, several functionalities recited in the claims may be performed by the same individual means or the same combination of means. For example performing such functionality or functionalities may be caused in an apparatus by a processor that executes instructions stored in a memory of the apparatus.

If desired, the different functions discussed herein may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the above-described functions may be optional or may be combined. Similarly, it will also be appreciated that the flow diagrams, message sequences and block diagrams of Figures 3 to 7 are examples only and that various operations depicted therein may be omitted, reordered and/or combined.

It will be appreciated that the above described example embodiments are purely 1.7 illustrative and are not limiting on the scope of the invention. Other variations and modifications will be apparent to persons skilled in the art upon reading the present specification.

Moreover, the disclosure of the present application should be understood to include any novel features or any novel combination of features either explicitly or implicitly disclosed herein or any generalization thereof and during the prosecution of the present application or of any application derived therefrom, new claims may be formulated to cover any such features and/or combination of such features.

Although various aspects of the invention are set out in the independent claims, other aspects of the invention comprise other combinations of features from the described example embodiments and/or the dependent claims with the features of the independent claims, and not solely the combinations explicitly set out in the claims.

It is also noted herein that while the above describes various examples, these descriptions should not be viewed in a limiting sense. Rather, there are several variations and modifications which may be made without departing from the scope of the present invention as defined in the appended claims.

Claims

Claims: 1. An apparatus comprising: means for obtaining first signal samples based on a downlink reference signal as received at a first device, over a first channel, from a transmitter of a mobile communication system; means for obtaining second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein said second signal samples are obtained over respective second channels between the respective second devices and the first device; means for generating compensated second signals samples from said second signal samples by compensating for effects of the respective second channel on said second signal samples; and means for generating location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal samples.
2. An apparatus as claimed in claim 1, wherein said location information comprises carrier phase information.
3. An apparatus as claimed in claim 1 or claim 2, wherein said location information comprises a propagation delay between the transmitter and the first device.
4. An apparatus as claimed in any of the preceding claims, further comprising means for providing said location information to a location management function.
5. An apparatus as claimed in any of the preceding claims, wherein said means for obtaining said first signal samples comprises: means for receiving said downlink reference signals; and means for demodulating the received downlink reference signals to generate said first signal samples.
6. An apparatus as claimed in any of the preceding claims, wherein one or more of the respective second channels are sidelink channels.
7. An apparatus as claimed in any of the preceding claims, wherein an effect of the second channel comprises a gain or a delay of a dominant path of the respective second channel, or both. 1.9
8. An apparatus as claimed in claim 7, further comprising: means for obtaining the delay and the gain of the dominant path of the or each second channel.
9. An apparatus as claimed in any of the preceding claims, further comprising: means for generating an estimate of the first channel.
10. An apparatus as claimed in claim 9, further comprising: means for generating the location information based, at least in part, on the generated estimate of the first channel.
11. An apparatus as claimed in any of the preceding claims, wherein the downlink reference signal is a positioning reference signal.
12. An apparatus as claimed in any of the preceding claims, wherein the apparatus is, or forms part of, the first device.
13. A system comprising an apparatus as claimed in any of claims 1 to 12 and further comprising said one or more second devices.
14. A method comprising: obtaining first signal samples based on a downlink reference signal as received at a first device, over a first channel, from a transmitter of a mobile communication system; obtaining second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein said second signal samples are obtained over respective second channels between the respective second devices and the first device; generating compensated second signals samples from said second signal samples by compensating for effects of the respective second channel on said second signal samples; and generating location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal 35 samples.
15. A computer program comprising instructions which, when executed by an apparatus, cause the apparatus to: obtain first signal samples based on a downlink reference signal as received at a first device, over a first channel, from a transmitter of a mobile communication system; obtain second signal samples based on the downlink reference signal as received at one or more second devices from the transmitter of the mobile communication system, wherein said second signal samples are obtained over respective second channels between the respective second devices and the first device; generate compensated second signals samples from said second signal samples by compensating for effects of the respective second channel on said second signal samples; and generate location information relating to the first device relative to the transmitter based on the first signal samples and the compensated second signal samples.