EP4197111A1

EP4197111A1 - Method and apparatus for channel estimation based on beamforming

Info

Publication number: EP4197111A1
Application number: EP20803470.2A
Authority: EP
Inventors: Hanwen Cao; Josef Eichinger; Malte Schellmann
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2020-11-05
Filing date: 2020-11-05
Publication date: 2023-06-21
Also published as: WO2022096095A1; CN116458078A

Abstract

The present disclosure relates to method and apparatus for channel estimation based on beamforming. Particularly, the present disclosure relates to a user equipment, UE (150, 160), comprising: a processor (101), configured to: auto-correlate a reference signal, RS (181), transmitted by a base station, BS (180), with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV (111, 112, 113, 114), wherein the BFV is formed by one from a set of second network devices (110, 120, 130) with the period of repetition, and the BFV shaping the RS with a spatial filter; and a transceiver (101), configured to: transmit, to the BS (180), one or more results of the auto-correlation.

Description

METHOD AND APPARATUS FOR CHANNEL ESTIMATION BASED ON BEAMFORMING

TECHNICAL FIELD

The present disclosure relates to method and apparatus for channel estimation based on beamforming, in particular based on a period of repetition of a beamforming vector formed by a network device. The disclosure particularly relates to channel probing and estimation for factory deployments of intelligent reflecting surfaces (IRSs).

BACKGROUND

With the recent introduction of an intelligent reflecting surface (IRS) by “C. Huang et al., “Energy efficient multi-user MISO communication using low resolution large intelligent surfaces,’’ in IEEE GLOBECOM, Abu Dhabi, UAE, Dec. 2018’’, a novel technology has emerged which offers the potential to shape the channel environment according to desired conditions.

In an existing communication scenario, a base station (BS) transmits information or signal via the IRS to a User Equipment (UE), where the IRS has N antenna elements. Channel estimation is implemented by using N orthogonal phase shift sequences applied to an antenna array in N consecutive time slots, e.g. by using Hadamard or DFT sequences, plus one extra measurement for the direct channel between BS and UE. As N may be very large, e.g. in the order of 100, this method creates large overhead for channel estimation. However, it is argued that the application is meant for quasi-static UEs, and hence full channel estimation needs to be performed infrequently only, which is why the large amount of overhead is not considered to be an issue.

SUMMARY

It is the object of this disclosure to provide techniques for providing efficient channel estimation via reflecting surfaces that are suitable for application in time-varying environments, such as 5G radio communication and industrial Internet of things (lloT). It is a particular object of this disclosure to provide reduced-overhead schemes for channel estimation via reflecting elements. This object is achieved by the features of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

A basic idea of this disclosure is using a communication system in which different IRSs use specific repetition periods and delay shifts for probing a set of predefined beamforming vectors (BFV), which allow to identify the IRS which reflects the strongest LOS-like BFV, simply by letting a receiving UE auto-correlates the probing signals for the corresponding periods and detect the autocorrelation signal creating the largest peak value. To enable this, the base station (BS) needs to configure the different IRS’s with specific repetition periods and delay shifts, and then the UE can report the period and peak position of the autocorrelation signal having created largest or qualified peak value. This information actually needs to be specified in a corresponding standard. The base station can use the information reported by the UEto identify which IRS provides the strongest or qualified LOS- like BFV to that UE.

Hence, the key points of this disclosure are the following:

(1) Configuring each IRS for the channel probing phase to activate its configuration of phase shifts (which form the BFVs) with a fixed repetition period and fixed delay shift, where these parameters provide a unique differentiable signature to the BFVs reflected by each IRS, and thus allow multiple IRSs to be active at the same time during probing.

(2) Transmitting reference signals from the BS to all IRSs during probing phase, where the BFVs reflected by those IRSs are imprinted with each IRS’s unique signature defined by the above parameters.

(3) Detecting the parameters of the unique signature at a receiving UE by identifying the maximum peak after auto-correlating the reference signal and feeding back repetition period p and the peak’s position to the BS, enabling it to identify the IRS closest to the UE and the corresponding BFV providing LOS-like conditions for that UE.

An IRS may be a planar array consisting of a large number of (nearly) passive, low-cost and low energy consuming reflecting elements with reconfigurable parameters. Each of these elements reflects an impinging radio wave with an individually configurable phase shift, which results in the formation of a reflection beam, whose direction can be actively controlled by choosing the phase shifts for the reflecting elements accordingly. One or multiple IRSs can be easily integrated into walls or ceilings of large halls and buildings. An IRS may open up additional channel propagation paths and thus enables shaping the radio channel -- without any increase of the transmit power. This way, it can create additional channel diversity, and it can establish line-of-sight (LOS)-like channel conditions for any communication device residing in the coverage area, thus enabling a better radio illumination of the entire space of radio service. In fact, an IRS acts similar to a relay, but adds no additional latency and does not emit any additional power, thus yielding a significantly improved energy efficiency.

According to a first aspect, the disclosure relates to a user equipment, UE, comprising: a processor, configured to: auto-correlate a reference signal, RS, transmitted by a base station, BS, with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter; and a transceiver, configured to: transmit, to the BS, one or more results of the auto-correlation.

Such a UE can provide efficient channel estimation by exploiting information received from the second network device. The second network device can be suitably arranged within an environment of the UE in order to provide line-of-sight conditions when line-of-sight may not be guaranteed for a beam from the base station (i.e. the first network device) to the UE. I.e., a beam formed by the second network device may directly pass the UE while a beam formed by the base station may be a non-line-of-sight beam due to possible obstacles between the BS and the UE. The auto-correlation of the reference signal can be advantageously applied in mobile environments, such as 5G radio communication and industrial Internet of things (lloT). With that scheme, the overhead for estimating several IRS compared to estimating each IRS separately (i.e., one at a time) by using dedicated RS can be reduced.

The BFVs are formed at the second network device. The second network device reflects an impinging signal (transmitted by the BS), and this reflected signal is shaped by the BFV.

The “probing phase” is the phase where the RS are sent by the BS and reflected by the IRSs which are also referred to as second network devices hereinafter. In an exemplary implementation of the UE, the set of second network devices comprises one or more second network devices, and the period of repetition for distinct second network devices is different.

This provides the advantage that the UE can easily detect from which of the second network devices a received beam was formed by evaluating the auto-correlation generated with a delay corresponding to the period of repetition.

In an exemplary implementation of the UE, the processor may be further configured to: obtain the period of repetition for auto-correlation of the RS by pre-configuration or, receive the configuration of the period of repetition from the BS.

This provides the advantage that the period of repetition can easily and flexibly be configured.

In an exemplary implementation of the UE, the results of the auto-correlation may comprise at least one of:

- one or more values of auto-correlation,

- a corresponding number of delayed symbols for the one or more values of autocorrelation,

- the number of delayed symbols,

- corresponding positions for the one or more values of auto-correlation or for the number of delayed symbols,

- a value of auto-correlation with highest correlation value,

- a value of auto-correlation with second-highest correlation value,

- a detection threshold for the auto-correlation,

- a noise threshold for the auto-correlation.

The results of the auto-correlation can also comprise any combination of items from the above list. I.e., different combinations from the list are possible. Although a basis idea of the disclosure is to provide information on the number of delayed symbols and position of the peak value from the autocorrelation signal yielding maximum value, also more sets of tuples (delayed symbols and position) may be provided to cover more than one autocorrelation yielding highest values. Although transmitting to the BS the actual “values of the autocorrelation” may be quite complex with respect to transmission resources, the BS may derive useful information from the values of the auto-correlation. A highest correlation value means the correlation signal with the highest peak. If more than one correlation signals have the same peak values, any of these correlation signals can be used for determining the specific individual parameters.

The BFVs formed by a second network device may be based on specific individual parameters of the second network device. Specific individual parameters according to the disclosure define a unique signature of the IRS, which is imprinted on the reflected signals. Such specific individual parameters may include for example a specific beam repetition period and/or a specific delay shift for the BFVs formed by the IRS. Specific individual parameters may further include other parameters that are suitable for uniquely characterizing an IRS.

In an exemplary implementation of the UE, the processor may be further configured to: estimate one or more channels of one or more BFVs, wherein the one or more BFVs are configured by the BS, or the one or more BFVs correspond to those applied for generating the one or more results of the auto-correlation.

This provides the advantage that channels may be flexibly estimated, either for the first stage, i.e. probing phase, alone or for the first and second stages, i.e. probing phase and channel estimation phase.

The „probing phase" is a first stage of channel estimation. The probing phase aims to determine the IRS providing the best BFV (from a first set of IRSs) to the UE. The second stage of channel estimation is then for the exact channel estimation exploiting the results of the first stage, i.e. the results of the probing phase. It may be suboptimal to estimate the channels in the probing phase, since they are “contaminated” by other BFVs from the other IRSs.

That means, that the UE either estimates the BFVs which have already been used in the autocorrelation process (1^st stage), or other BFVs that have been configured by the BS.

In one scenario, the estimated channels correspond to the BFVs in the first stage as default and no further configuration from BS. The second stage can be used for beam refinement, since the first stage will most likely use quite broad beams. The choice of BFVs for the second stage does not have to depend on the “number of results”, i.e. BFVs reported by the UE. In an exemplary implementation of the UE, a set of BFVs for channel estimation is given in the second stage, and an index refers to the BFVs in this set, then the transceiver is further configured to: transmit the index of at least a strongest received BFV to the BS.

This provides the advantage that only a small amount of information, i.e. the index, is transmitted, thereby efficiently using transmission resources.

In an exemplary implementation of the UE, the one or more BFVs may be formed by one or more second network devices.

This provides the advantage that the second network elements can be used for forming BFVs that point along the line-of-sight path to the UE, thereby resulting in a better transmission quality.

In an exemplary implementation of the UE, the one or more second network devices may comprise one or more intelligent reflecting surfaces, IRS.

Such IRS have the advantage that energy efficient transmission can be guaranteed, since an IRS is purely passive and thus consumes no additional transmit power.

In an exemplary implementation of the UE, the BFVs formed by a second network device may be based on specific individual parameters of the second network device.

Transmission of the specific individual parameters enables the base station to identify the IRS of the set of IRSs providing the strongest BFV to a UE.

The specific individual parameters of an IRS define a unique signature of the IRS, which is imprinted on the reflected signals.

In an exemplary implementation of the UE, the specific individual parameters of a second network device may comprise a specific beam repetition period and/or a specific delay shift for the BFVs formed by the second network device.

This provides the advantage that based on the specific beam repetition period and/or the specific delay shift, the originating IRS or second network device, respectively, can easily be detected from the received RS after auto-correlation at the UE. In an exemplary implementation of the UE, the reference signal received by the UE comprises a superposition of multiple BFVs formed by multiple second network devices at the same time.

This provides the advantage that these many IRSs are used to cover all locations in the environment in order to find at least one IRS for serving a UE. At least one of the second network devices would have line-of-sight transmission to the UE. The probing phase according to the disclosure is efficient, as all IRSs are probed at the same time.

In an exemplary implementation of the UE, the processor may be configured to: determine the specific individual parameters from the autocorrelation signal with the highest correlation value by determining an autocorrelation period used for generating the autocorrelation signal and/or a position of the highest correlation value of the autocorrelation signal.

This provides the advantage that these parameters can be easily processed and can be used for a reliable indication of the originating IRS, that is: the IRS providing the best BFV (with LOS-like conditions) to the UE, or second network device.

In an exemplary implementation of the UE, the transceiver may be configured to receive information about a probing phase for probing the BFVs, in particular information about a start and end of the probing phase.

This provides the advantage that by using this information the processor can efficiently start the processing of the auto-correlation.

In an exemplary implementation of the UE, the transceiver may be configured to: receive a further reference signal reflected by a second network device from the set of second network devices, wherein the second network device has been identified by the base station as the one providing the strongest BFV to the UE; wherein the second network device is configured by the base station for forming a refined BFV, while any other second network device from the set of second network devices is configured by the base station to be switched off during transmission of the further reference signal; and/or estimate a channel for the refined BFV based on the further reference signal.

This provides the advantage that efficient channel estimation can be performed in the second stage by using the refined BFVs. In an exemplary implementation of the UE, the processor may be configured to: determine an index of the refined BFV which provides a highest reception energy; and/or the transceiver is configured to: transmit the index of the refined BFV which provides the highest reception energy to the base station.

According to a second aspect, the disclosure relates to a base station, BS, comprising: a transceiver, configured to: transmit a reference signal, RS; and receive, from a user equipment, UE, one or more results of an auto-correlation of the reference signal with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter; and a processor, configured to: determine a specific second network device from the set of second network devices based on the one or more results of the auto-correlation.

Such a base station can be part of a communication system in which different IRSs (also called second network elements in contrast to the BS which is the first network element) use specific repetition periods and delay shifts for forming the beamforming vectors (BFV) during a probing phase, which allow an UE to identify the IRS which reflects the strongest LOS-like BFV, simply by auto-correlating the reception signals with the delays corresponding the repetition periods and detecting the signal creating the largest peak value. The BS can receive the results and decide which of the IRS can be used for forming the strongest BFV for that UE.

In an exemplary implementation of the BS, the set of second network devices may comprise one or more second network devices, and the period of repetition for distinct second network devices is different.

This provides the advantage that each second network device can be detected based on its specific period of repetition.

In an exemplary implementation of the BS, the transceiver may be further configured to: transmit the configuration of the period of repetition to the UE. These are the periods of repetition that have been used for the different second network devices available in the communication environment.

This provides the advantage that the UE is informed about the different second network devices that are part of the communication system. The UE is not directly informed, but indirectly through the total number of different periods of repetition. Building on this, this information tells the UE how many auto-correlations it has to calculate.

In an exemplary implementation of the BS, the results of the auto-correlation may comprise at least one of:

- one or more values of auto-correlation,

- the number of delayed symbols,

- a value of auto-correlation with highest correlation value,

- a value of auto-correlation with second-highest correlation value,

- a detection threshold for the auto-correlation,

- a noise threshold for the auto-correlation.

The results of the auto-correlation can also comprise any combination of items from the above list. I.e. different combinations from the list are possible. Although a basis idea of the disclosure is to provide information on the number of delayed symbols and position of the peak value from the autocorrelation signal yielding maximum value, also more sets of tuples (delayed symbols and position) may be provided to cover more than one autocorrelation yielding highest values. Although transmitting to the BS the actual “values of the autocorrelation” may be quite complex with respect to transmission resources, the BS may derive useful information from the values of the auto-correlation.

In an exemplary implementation of the BS, the processor may be further configured to: obtain a configuration of one or more BFVs corresponding to the one or more results of the auto-correlation.

The processor may further be configured to obtain information about the second network device having formed the one or more BFVs This provides the advantage that the BS is informed about the second network devices and their respective configuration of BFVs yielding highest reception power at the UE.

In an exemplary implementation of the BS, the transceiver may be further configured to: receive an index of at least a strongest received BFV from the UE.

This provides the advantage that the BS is informed about a second network device forming the strongest BFV for that UE.

In an exemplary implementation of the BS, the one or more BFVs may be formed by one or more second network devices of the set of second network devices.

This provides the advantage that the second network devices can be used for forming BFVs that point along the line-of-sight path to the UE, thereby resulting in a better transmission quality.

In an exemplary implementation of the BS, the one or more second network devices may comprise one or more intelligent reflecting surfaces, IRS.

In an exemplary implementation of the BS, the BFVs formed by a second network device may be based on specific individual parameters of the second network device.

Transmission of the specific individual parameters enables the base station to identify the IRS of the set of IRSs providing the strongest BFV to the UE.

The specific individual parameters of an IRS define a unique signature of the IRS.

In an exemplary implementation of the BS, the specific individual parameters of a second network device may comprise a specific beam repetition period and/or a specific delay shift for the BFVs formed by the second network device. This provides the advantage that the UE can detect the specific individual parameters by auto-correlating the reflected RS signals, signal these parameters to the BS, and the BS can finally detect the originating IRS.

In an exemplary implementation of the BS, the processor may be configured to: determine the specific second network device from the set of second network devices which provides the strongest received BFV to the UE based on the one or more results of the autocorrelation fed back by the UE; and/or the transceiver is configured to: provide a configuration for forming a refined BFV at the specific second network device and/or a configuration for switching-off any other second network device of the set of second network devices.

This provides the advantage that efficient channel estimation can be performed in the second stage by using the refined BFVs.

In the alternative where more results of the auto-correlation are fed back by the UE, not only one specific second network device but also two or more specific network devices may be determined by the BS.

According to a third aspect, the disclosure relates to a second network device of a set of second network devices, the second network device comprising a controller configured to: receive a configuration from a base station, wherein the configuration comprises specific individual parameters; and form BFVs for reflecting a reference signal of the base station to a user equipment, UE, in accordance with the received configuration.

Such second network devices provide the advantage that they can improve communication efficiency, since one of the second network devices may be in line-of-sight with the UE.

In an exemplary implementation of the second network device, the second network device may comprise an intelligent reflecting surface, IRS.

In an exemplary implementation of the second network device, the specific individual parameters may comprise a specific beam repetition period and/or a specific delay shift for a BFV formed by the second network device. This provides the advantage that based on the specific beam repetition period and/or the specific delay shift, the UE can easily detect the originating IRS or second network device, respectively.

In an exemplary implementation of the second network device, the specific individual parameters may be unique for different second network devices.

This provides the advantage that by the uniqueness of each second network device, a respective second network device can be easily identified.

In an exemplary implementation of the second network device, the specific individual parameters imprint a spatial signature on reference signals reflected by the second network device, that enable a receiver to separate signals from different second network devices later on.

This provides the advantage that based on the signature, the respective second network device can be easily detected.

According to a fourth aspect, the disclosure relates to a correlation method, comprising: auto-correlating, by a user equipment, UE, a reference signal, RS, transmitted by a base station, BS, with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter; and transmitting one or more results of the auto-correlation by the UE to the BS.

This provides the same advantages as described above for the first aspect.

According to a fifth aspect, the disclosure relates to a method for determining a specific second network device based on auto-correlation results, the method comprising: transmitting a reference signal, RS, by a base station, BS, and receiving by the BS from a user equipment, UE, one or more results of an auto-correlation of the reference signal with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter; and determining, by the BS a specific second network device from the set of second network devices based on the one or more results of the auto-correlation.

This provides the same advantages as described above for the second aspect.

According to a sixth aspect, the disclosure relates to a computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the method according to the fourth aspect or the method according to the fifth aspect. Such a computer program product may include a nontransient readable storage medium storing program code thereon for use by a processor, the program code comprising instructions for performing the methods or the computing blocks as described hereinafter.

The computer program product may run on the components of a communication system described below with respect to Figure 10. For example, the computer program product may run on a first user device 1101 a as shown in Figure 10. Such a first user device may comprises a processing circuitry 1103a for instance, a processor 1103a, for processing and generating data, e.g. the program code described above, a transceiver 1105a, including, for instance, a transmitter, a receiver and an antenna, for exchanging data with the other components of the communication system 1100, and a non-transitory memory 1107a for storing data, e.g. the program code described above.

For example, the computer program product may run on a base station 1120 as shown in Figure 10. Such a base station 1120 may comprises a processing circuitry 1113 for instance, a processor 1113, for processing and generating data, e.g. the program code described above, a transceiver 1115, including, for instance, a transmitter, a receiver and an antenna, for exchanging data with the other components of the communication system 1100, and a non-transitory memory 1117 for storing data, e.g. the program code described above. Both memories 1107a and 1117 can include non-transitory machine-readable storage media, i.e. storage media that store code in a non-transitory way for a specific amount of time and which media can be read by the corresponding processor 1103a, 1113. Such non-transitory machine-readable storage media may be a RAM, a ROM, an EPROM or an EEPROM for example.

Using such a computer program product improves channel estimation for BFVs formed by one or more second network devices. A further aspect of the disclosure relates to a base station configuring each IRS to activate its configuration of phase shifts (which form the BFVs) with a specific repetition period and a specific delay shift, forming specific individual parameters; informing each UE on the specific individual parameters assigned in the system; transmitting reference signals (RS) for BFV probing, [Note: these RS should either be identical in every probing slot or known at the RX to enable detection of the strongest BFV at the RX by (auto-)correlation]; and triggering IRSs to start and end the probing phase [Note: the probing phase should be configurable to adjust to the number of active IRSs and number of BFVs in a first codebook (codebook 1) as described below with respect to Figure 2],

A further aspect of the disclosure relates to a UE, configured by the BS for auto-correlating the reference signals during probing phase; the UE configured for: autocorrelating the RX signal and determining the specific individual parameters of the closest IRS from detecting the maximum correlation peak; and feeding back to the BS information on the specific individual parameters, in particular the repetition period and position of the correlation peak.

A further aspect of the disclosure relates to a base station identifying the closest IRS and the corresponding BFV providing LOS-like conditions for that UE from its information feedback; and configuring the IRS accordingly for data transmission to that UE.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments of the invention will be described with respect to the following figures, in which:

Fig. 1 shows a schematic diagram illustrating an industrial loT setup for a factory of the future;

Fig. 2 shows a schematic diagram of the factory of Fig. 1 with an exemplary number of two IRSs to illustrate channel probing based on reflected beamforming;

Fig. 3a shows an example for a BFV repetition pattern for a first IRS and for a BFV repetition pattern for a second IRS;

Fig. 3b shows an example of peak locations after correlation with a delay of p=1 and of peak locations after correlation with a delay of p=2; Fig. 3c shows an exemplary BFV repetition pattern based on sequence flipping according to the disclosure;

Fig. 4 shows a schematic diagram illustrating channel estimation based on reflected beamforming according to the disclosure with an exemplary number of three BFV repetition patterns;

Fig. 5 shows a schematic diagram of BFV probing based on an exemplary set of three IRSs;

Fig. 6 shows a schematic diagram illustrating BFV repetition patterns for the BFV probing of Figure 5;

Fig. 7 shows an exemplary message sequence chart for implementing channel estimation based on reflected beamforming according to the disclosure;

Fig. 8 shows a schematic diagram illustrating a correlation method ;

Fig. 9 shows a schematic diagram illustrating a method for determining a specific second network based on auto-correlation results; and

Fig. 10 shows a schematic diagram illustrating a communication system according to the disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

In order to describe the invention in detail, the following terms, abbreviations and notations will be used:

UE User Equipment

BS Base Station

IRS Intelligent Reflecting Surface

BFV Beamforming Vector loT Internet of Things lloT Industrial loT

LOS line-of-sight

TDM time division RS reference signal

In the following detailed description, reference is made to the accompanying drawings, which form a part thereof, and in which is shown by way of illustration specific aspects in which the disclosure may be practiced. It is understood that other aspects may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

It is understood that comments made in connection with a described method may also hold true for a corresponding device or system configured to perform the method and vice versa. For example, if a specific method step is described, a corresponding device may include a unit to perform the described method step, even if such unit is not explicitly described or illustrated in the figures. Further, it is understood that the features of the various exemplary aspects described herein may be combined with each other, unless specifically noted otherwise.

The methods, devices and systems described herein may be implemented in wireless communication schemes, in particular communication schemes according to 5G or beyond. The described devices may include integrated circuits and/or passives and may be manufactured according to various technologies. For example, the circuits may be designed as logic integrated circuits, analog integrated circuits, mixed signal integrated circuits, optical circuits, memory circuits and/or integrated passives.

The devices described herein may be configured to transmit and/or receive radio signals. Radio signals may be or may include radio frequency signals radiated by a radio transmitting device (or radio transmitter or sender). However, devices described herein are not limited to transmit and/or receive radio signals, also other signals designed for transmission in deterministic communication networks may be transmitted and/or received.

The devices and systems described herein may include processors or processing devices, memories and/or transceivers, i.e. transmitters and/or receivers. The term “processor” or “processing device” describes any device that can be utilized for processing specific tasks (or blocks or steps). A processor or processing device can be a single processor or a multicore processor or can include a set of processors or can include means for processing. A processor or processing device can process software or firmware or applications etc. The devices and systems described herein may include transceivers or transceiver devices. A transceiver is a device that is able to both transmit and receive information through a transmission medium, e.g. a radio channel. It is a combination of a transmitter and a receiver, hence the name transceiver. Transmission is usually accomplished via radio waves. By combining a receiver and transmitter in one consolidated device, a transceiver allows for greater flexibility than what either of these could provide individually.

The devices and systems described herein may include intelligent reflecting surfaces (IRSs). An IRS comprises an array of reflecting elements, each of which can independently incur some change to the incident signal. The change in general may be about the phase, amplitude, frequency, or even polarization. In most implementations the change is considered as a phase shift only to the incident signal, so that an IRS consumes no transmit power. In essence, an IRS intelligently configures the wireless environment to support the transmissions between the sender and receiver, when direct communications between them have poor qualities. Example places to put IRSs are walls, building facades, and ceilings.

Fig. 1 shows a schematic diagram illustrating an industrial loT setup for a factory of the future according to the disclosure.

A single base station (BS) 180 may be operated in a factory hall, and several IRSs 110, 120, 130, generally referred to as second network devices in this disclosure, are mounted at the ceiling or the side walls.

A controller may be used at each IRS or second network device 110, 120, 130 to configure the phase shift per reflecting element, or to switch off the IRS entirely. The controller may be connected to the BS 180 either wirelessly (through a UE device type) or by wireline. Switching the phase shift per element may be done in time domain only (time division multiplexing - TDM), as the single phase shift per element applies to the full system bandwidth. If not switched off, all installed IRSs simultaneously reflect the radio wave emitted from the BS 180 into a direction according to their elements’ configured phase shifts.

The disclosure addresses the following key questions arising in the described scenario: How to determine the LOS-like beam from the closest IRS for an UE within short time and with moderate amount of overhead; and how to distinguish beams which are reflected by different IRSs simultaneously. A basic idea is using a communication system in which different IRSs, also denoted as second network devices hereinafter, 110, 120, 130 use specific repetition periods and delay shifts for forming the beamforming vectors (BFV) during a probing phase, which allow an UE 150, 160 to identify the IRS 110, 120, 130 which reflects the strongest or qualified LOS- like BFV, simply by auto-correlating the reception signals with the delays corresponding to the periods and detecting the signal creating the largest peak value. To enable this, i.e. distinguishing such signals from the different IRSs, the base station 180 needs to configure the different IRS’s with specific repetition periods and delay shifts, and then the UE 150, 160 can report the repetition period and peak position of the strongest or qualified detected BFVs. The base station 180 can use the information reported by the UE 150, 160 to identify which IRS 110, 120, 130 provides the strongest LOS-like BFV to that UE 150, 160.

A qualified detected BFV denotes a BFV which power is large enough to enable a signal transmission with sufficient signal quality. A large enough power can be defined, for example, by a predefined power threshold, for example resulting from prior lab tests. Such power thresholds can also be derived from pre-defined auto-correlation signals.

In the following, functionality of the UEs 150, 160 and the BS 180 are described in more detail to support this basic concept of the disclosure. The UEs 150, 160 and the BS 180 may both comprise a processor 101 and a transceiver 102 as shown on bottom left side of Figure 1.

The UE 150, 160 comprises a processor 101 , configured to: auto-correlate a reference signal, RS 181 , transmitted by a base station, BS 180, with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices 110, 120, 130 with the period of repetition, and the BFV shaping the RS with a spatial filter. Examples of such BFVs are shown in Figures 2 and 5. The UE 150, 160 further comprises a transceiver 101 , configured to: transmit, to the BS 180, one or more results of the auto-correlation.

The set of second network devices 110, 120, 130 may comprise one or more second network devices, and the period of repetition for distinct second network devices may be different. The processor 101 of the UE 150, 160 may be configured to: obtain the period of repetition for auto-correlation of the RS by pre-configuration or, receive the configuration of the period of repetition from the BS.

The results of the auto-correlation may comprise at least one of:

- one or more values of auto-correlation,

- the number of delayed symbols,

- a value of auto-correlation with highest correlation value,

- a value of auto-correlation with second-highest correlation value,

- a detection threshold for the auto-correlation,

- a noise threshold for the auto-correlation.

The processor 101 of the UE 150, 160 may be configured to: estimate one or more channels of one or more BFVs, wherein the one or more BFVs are configured by the BS, or the one or more BFVs correspond to those applied for generating the one or more results of the auto-correlation.

The transceiver 102 of the UE 150, 160 may be configured to: transmit the index of at least a strongest received BFV to the BS.

The one or more BFVs may be formed by one or more second network devices 110, 120, 130.

The one or more second network devices 110, 120, 130 may comprise one or more intelligent reflecting surfaces, IRS.

The BFVs formed by a second network device 110, 120, 130 may be based on specific individual parameters of the second network device.

The specific individual parameters of a second network device 110, 120, 130 may comprise a specific beam repetition period and/or a specific delay shift for the BFVs formed by the second network device. The reference signal received by the UE 150, 160 may comprise a superposition of multiple BFVs formed by multiple second network devices at the same time.

The processor 101 of the UE 150, 160 may be configured to: determine the specific individual parameters from the autocorrelation signal with the highest correlation value by determining a delay (corresponding to the repetition period) used for generating the autocorrelation signal and/or a position of the highest correlation value of the autocorrelation signal.

The transceiver 102 of the UE 150, 160 may be configured to receive information about a probing phase for probing the BFVs, in particular information about a start and end of the probing phase.

The transceiver 102 of the UE 150, 160 may be configured to: receive a further reference signal reflected by a second network device from the set of second network devices, wherein the second network device has been identified by the base station as the one providing the strongest BFV to the UE. The second network device 110, 120, 130 may be configured by the base station 180 for forming a refined BFV, while any other second network device from the set of second network devices is configured by the base station to be switched off during transmission of the further reference signal; and/or estimate a channel for the refined BFV based on the further reference signal.

The processor 101 of the UE 150, 160 may be configured to: determine an index of the refined BFV which provides a highest reception energy. The transceiver 102 of the UE 150, 160 may be configured to: transmit the index of the refined BFV which provides the highest reception energy to the base station 180.

The BS 180 comprises a transceiver 102, configured to: transmit a reference signal, RS; and receive, from a user equipment, UE 150, 160, one or more results of an auto-correlation of the reference signal 181 with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter.

The BS 180 comprises a processor 101 , configured to: determine a specific second network device from the set of second network devices based on the one or more results of the autocorrelation. The set of second network devices 110, 120, 130 may comprise one or more second network devices, and the period of repetition for distinct second network devices may be different.

The transceiver 102 of the BS 180 may be configured to: transmit the configuration of the period of repetition to the UE 150, 160.

The results of the auto-correlation may comprise at least one of: - one or more values of auto-correlation, - a corresponding number of delayed symbols for the one or more values of auto-correlation, - the number of delayed symbols, - corresponding positions for the one or more values of auto-correlation or for the number of delayed symbols, - a value of autocorrelation with highest correlation value, - a value of auto-correlation with second-highest correlation value, - a detection threshold for the auto-correlation, - a noise threshold for the auto-correlation.

The processor 101 of the BS 180 may be configured to: obtain a configuration of one or more BFVs corresponding to the one or more results of the auto-correlation and/or information about the second network device having formed the one or more BFVs.

The transceiver 102 of the BS 180 may be configured to: receive an index of at least a strongest received BFV from the UE.

The one or more BFVs may be formed by one or more second network devices of the set of second network devices 110, 120, 130.

The specific individual parameters of a second network device 110, 120, 130 may comprise a specific beam repetition period and/or a specific delay shift for the BFVs formed by the second network device 110, 120, 130. The processor 101 of the BS 180 may be configured to: determine the specific second network device from the set of second network devices which provides the strongest received BFV to the UE based on the one or more results of the auto-correlation fed back by the UE.

The transceiver 102 of the BS 180 may be configured to: provide a configuration for forming a refined BFV at the specific second network device 110, 120, 130 and/or a configuration for switching-off any other second network device of the set of second network devices.

Fig. 2 shows a schematic diagram of the factory of Fig. 1 with an exemplary number of two IRSs 110, 120 to illustrate channel estimation based on reflection beamforming according to the disclosure.

A set of phase shifts applied to the individual reflecting elements of an IRS (also referred to as second network device) 110, 120 forms a beamforming vector (BFV). A set of M BFVs that covers the area served by each IRS 110, 120 may be defined as codebook 1. In Figure 2, an illustration of two IRSs 110, 120 illuminating the factory area each with M=4 BFVs 111 , 112, 113, 114, 121 , 122, 123, 124 in codebook 1 is shown. Channel probing and estimation is now done in two stages. Stage 1 is about probing the BFVs of codebook 1 while Stage 2 is about BFV-based channel estimation, as detailed in the following:

Stage 1 (probing the BFVs of codebook 1) may include the following processing:

1) BS 180 may configure the IRS controller with BFVs to be switched between during probing on symbol basis.

- For IRS 1 , use repetition of BFVs with period p=1 , as exemplarily shown in Figure 3a by repetition field 301 : 1_1_2_2_3_3_4_4.

This sequence specifies the BFV repetition pattern of IRS 1 . The following sequence will have the same meaning and will not be explained again.

- For IRS 2, use repetition of BFVs with period p=2, as exemplarily shown in Figure 3a by repetition field 302: 1_3_1_3_2_4_2_4.

2) BS 180 may transmit reference signal (RS) 181 , which is reflected by the IRSs 110, 120 according to their configured BFVs.

3) UE 150 may auto- correlate received RS with its copy delayed by p symbols in timedomain and determines the maximum correlation peak;

- closest IRS can be identified via period p, generating correlation signal with maximum peak, - strongest BFV can be identified by position of correlation peak, as exemplarily shown in Figure 3b by the two correlation fields 303, 304, where first correlation field 303 includes peak locations after correlation p=1 and second correlation field 304 includes peak locations after correlation p=2. The second correlation field 304 indicates position of maximum peak 305 for IRS2 (using p=2) and BFV2 (position 5).

4) Once UE 150 detected maximum correlation peak, it may feed back p and the peak’s position to the BS.

Stage 2 (BFV-based channel estimation) may include the following processing:

For each IRS 110, 120 where feedback is available:

- Define new set of refined BFVs derived from the selected BFV (per IRS, derived from the UE‘s feedback) to obtain codebook 2.

- For estimating the refined BFVs without interference, BS 180 may configure the selected IRS with BFVs of codebook 2, while configuring any other IRS to be switched off for next RS to be sent.

- UE 150 may estimate the channel of refined BFVs based on RS, which are now solely reflected by the selected IRS.

- UE 150 may feed back the index of the best refined BFV to BS.

Fig. 3a shows an example for a BFV repetition pattern 301 for a first IRS 110 and for a BFV repetition pattern 302 for a second IRS 120.

The repetition field 301 shown in Figure 3a is: 1_1_2_2_3_3_4_4. As described above, this sequence specifies the BFV repetition pattern of IRS 1 (which is different from the signatures of other IRSs). The repetition field 301 may comprise an exemplary number of 8 slots, where first and second slots are set to 1 , third and fourth slots are set to 2, fifth and sixth slots are set to 3 and seventh and eighth slots are set to 4.

The period 1 describes here that a distance of 1 is used from first slot to second slot showing the same value 1 , from third slot to fourth slot showing the same value 2, etc.

The repetition field 302 shown in Figure 3a is: 1_3_1_3_2_4_2_4. As described above, this sequence specifies the BFV repetition pattern of IRS 1 (which is different from the signatures of other IRSs). The repetition field 302 may comprise the same exemplary number of 8 slots as the first repetition field. For the second repetition field 302, first and third slots are set to 1 , second and fourth slots are set to 3, fifth and seventh slots are set to 2 and sixth and eighth slots are set to 4. The period 2 describes here that a distance of 2 is used from first slot to third slot showing the same value 1 , from second slot to fourth slot showing the same value 3, etc.

Fig. 3b shows an example of peak locations 303 after auto-correlating pattern 301 with delay p=1 and of peak locations 304 after auto-correlating pattern 302 with delay p=2.

In correlation field 303, peak locations are regularly distributed after each second slot.

In correlation field 304, peak locations may be regularly distributed within 2 successive slots after 2 non-peak slots. A maximum peak 305 can be determined in slot 5 as an example.

Fig. 3c shows an exemplary BFV repetition pattern 311 , 312 based on sequence flipping 313 according to the disclosure.

For supporting more IRSs, sequence flipping can be applied as shown in Figure 3c. A first repetition pattern 311 that is 1_3_1_3_2_4_2_4 as an example, can be flipped 313 to obtain a second repetition pattern 312, that is 4_2_4_2_3_1_3_1 as an example.

An example for supporting more IRS by applying the sequence flipping sample shown in Figure 3c is detailed in Figure 4.

Fig. 4 shows a schematic diagram illustrating channel probing based on reflected beamforming according to the disclosure with an exemplary number of three BFV repetition patterns. In particular, Figure 4 illustrates the method to generate the BFV repetition patterns based on the specific individual parameters for each IRS.

Figure 4 shows on the left side the two sets of different BFV repetition patterns 401 and 402. Each of the sets 401 , 402 consists of three BFV repetition patterns, as given by the three rows in Fig. 4. The set 403 shown below in Fig. 4 is identical to the first set 401 of BFV repetition patterns. The three BFV repetition patterns of the first set 401 are applied to IRS0, IRS1 and IRS2. Each row is generated by a period p from the example set {1 , 2, 4}.

The second set of patterns 402 may be shifted 411 by max(p)-1 slots, e.g. 3 slots with respect to the first set of patterns 401 , following from max(p) = 4 in Fig. 4. The three BFV repetition patterns of the second set 402 are applied to IRS3, IRS4 and IRS5. The third set of patterns 403 may be shifted 411 by 2*max(p) slots, e.g. 8 slots with respect to the first set of patterns 401. The three BFV repetition patterns of the third set 402 are applied to IRS6, IRS7 and IRS8. Thus, it can be concluded that this generation scheme supports up to 9 IRS for simultaneous probing.

Figure 4 shows on the right side the peak locations 410 after auto-correlation with the corresponding delay p. For the first set of patterns 401 a first set of peak locations 421 results. For the second set of patterns 402 a second set of peak locations 422 results. It can be seen that for a given p, peak locations of the second set of peak locations 422 mainly occur where the first set of peak locations 421 has no peaks (see the arrows on right side of Fig. 4). It can be further seen that for a given p, peak locations of the third set of peak locations 423 mainly occur where the second set of peak locations 422 has no peaks (see the arrows on right side of Fig. 4).

The method for generating the BFV patterns based on the specific individual parameters for each IRS may comprise the following steps:

1) Repeat BFV repetition patterns and flip sequences of BFV indices, see Figure 3c for example;

2) Shift by maximum repetition period used in the set of repetition patterns minus 1 to the right 411 : max(p) - 1 ;

(i) leading zero symbols mean the corresponding IRS will be switched off during that time;

(ii) auto-correlation will create peaks at different positions compared to first set 401 of repetition patterns, enabling identification of IRS;

3) For adding another set, use 1^st set of patterns 401 shifted by 2*max(p) 412, yielding time orthogonality with 1^st set 401 .

The main novelty in this solution is the probing of BFVs reflected from many different IRSs 110, 120 at the same time, where the IRS providing the best (LOS-like) BFV and the best BFV itself can be identified by the beam repetition period p and the peak’s position, as configured by the base station 180.

For the probing, rather coarse BFVs should be used to allow identifying the main direction, and hence a 2^nd stage (as described above) may be needed for refinement of the selected BFV. This 2^nd stage will be like a beam sweep around the coarse BFV selected at the 1^st stage. The specialty for the 2^nd stage is that all other IRS’s will be switched off during sweeping. The number of BFVs in the 2^nd stage can be chosen arbitrarily, but it should be rather small to keep the overhead limited.

The attractiveness of the parallel probing of BFVs from different IRSs in the 1^st stage lies in the overhead saving, which becomes the more prominent the more IRSs are installed in parallel. This can be illustrated by the following example:

Example:

1) There are N=6 IRSs in total, and B=4 BFVs shall be probed in the 1^st stage for each IRS.

2) If this is done conventionally by probing each BFV in a separate time slot, N*B = 24 time slots are needed.

3) For probing the BFVs in parallel using the BFV patterns illustrated in Figure 4, only 11 time slots are needed for probing all BFVs reflected by the N=6 IRSs

4) The relative overhead amounts to 11/24 < 0.5, hence the overhead saving is > 50%.

This calculation of the relative overhead can be generalized for arbitrary B and N by the formula:

As can be seen, only for N=2 there is no saving, while in all other cases there is, with a saving > 50% for N = {6, 9, 12, ...}.

Fig. 5 shows a schematic diagram of BFV probing 500 according to the disclosure based on an exemplary set of three IRSs. Shown are three exemplary IRS or second network devices, respectively and their functionality during a BFV probing phase.

IRS0 140 may include a controller 145 and a reflecting surface forming an exemplary number of four beamforming vectors, BFVs 141 , 142, 143, 144. IRS1 110 may include a controller 115 and a reflecting surface forming an exemplary number of four BFVs 111 , 112, 113, 114. IRS2 may include a controller 125 and a reflecting surface forming an exemplary number of four BFVs 121 , 122, 123, 124. User Equipment 150 may receive BFVs formed by reflecting surfaces.

According to an example, the particular design of the BFV sequences within the BFV repetition patterns for BFV probing is described below. The problem for BFV probing at stage 1 (i.e. IRS1 110) is that BFVs from neighbor IRS2 120 may cause high interference in the auto-correlation product of RS from probed IRS1 if those BFVs are directed towards the UE 150.

Requirements for neighboring IRSs are therefore that repetition patterns may be chosen such that BFVs from neighbor IRS2 120 being involved in the auto-correlation of RS from probed IRS1 110 may either:

(1) point into a different direction than the BFV from IRS1 110 to be probed; or

(2) form a pair of non-adjacent BFVs at IRS2 120.

A solution to that problem is given in the following:

A) An exemplary number of 4 BFVs is given per IRS, that means 8 symbols for BFV probing.

B) Select a repetition period for each IRS, e.g. for 3 IRSs, select p = {1 , 2, 4}, for example. Any integer period can be selected in general, such as p = {1 ,2,3}; however, p = 2ⁿ allows for regular pattern structures and eases pattern design.

C) Degrees of freedom are (i) the order of repetition patterns (where a pattern is defined by the repetition period p) along the IRS's, e.g. p = {2,1 ,4}; and (ii) the order of beam indices (sequence) used inside a pattern, e.g. BFV = {1 ,3,2,4}.

D) The particular repetition patterns for neighboring IRSs may be constructed from the above requirements. In the example of Figure 5, where 3 IRS's 140, 110, 120 may be installed along a wall/ceiling (IRS0, IRS1 , IRS2): a first repetition pattern 601 can be 1_3_1_3_2_4_2_4 with a period p=2; a second repetition pattern 602 can be 1_1_3_3_2_2_4_4 with a period p=1 ; and a third repetition pattern 603 can be 1_3_2_4_1_3_2_4 with a period p=4 as exemplarily shown in Figure 6.

In slots 3 and 4 as indicated by block 604 in Figure 6, IRS1 110 forms BFV3 113 and IRS2 120 forms BFV2 122 and BFV4 124.

Fig. 6 shows a schematic diagram illustrating BFV repetition patterns 600 for the BFV probing 500 of Figure 5. A first repetition pattern 601 is 1_3_1_3_2_4_2_4 with a period p=2; a second repetition pattern 602 is 1_1_3_3_2_2_4_4 with a period p=1 ; and a third repetition pattern 603 is 1_3_2_4_1_3_2_4 with a period p=4 as exemplarily shown in Figure 6.

In slots 3 and 4 as indicated by block 604, IRS1 110 forms BFV3 113 and IRS2 120 forms BFV2 122 and BFV4 124. That means, when auto-correlating BFV3 from IRS1 with period p=1 , BFV2 and BFV4 (which are transmitted simultaneously from IRS2 in slot 3 and 4) will get involved in this auto-correlation. However, since they point into different directions and they are non-adjacent beams, their contribution to the auto-correlation will have low power and thus be negligible, allowing the UE to reliably detect BFV3 from IRS1 .

Fig. 7 shows an exemplary message sequence chart 700 for implementing channel estimation based on reflected beamforming according to the disclosure. The communication environment corresponds to the environment shown in Figure 1 . For simplification reasons, only two IRS 110, 120 or second network devices, respectively and only one UE 150 are illustrated.

The message sequence chart 700, illustrates the information exchange between BS 180, UE 150 and the controllers 115, 125 of two IRSs 110, 120 for implementing the concept of the disclosure. A prerequisite for reliable operation is the proper synchronization between the BS 180 and the controllers 115, 125 of the IRSs 110, 120 to enable the IRSs 110, 120 to switch the BFVs synchronous with the symbol clock at the BS 180. The necessary signaling is described in the following:

Stage 1 : Probing the BFVs of codebook 1 , 700a

Codebook 1 is defined 731 by BS 180 for each IRS 110, 120.

1) The BS 180 may configure 701 , 702 each IRS 110, 120 with the BFVs of codebook 1 (may be different or equal for distinct IRSs) and its individual repetition pattern for the RS transmission phase by providing this information to each IRS’s controller (S01), which sets up the IRS accordingly.

2) The BS 180 may inform 703 the UE 150 on the periods for auto-correlation of the RS (i.e., the repetition patterns the existing IRSs 110, 120 have been configured with) and triggers the UE 150 to initiate the BFV measurement (S02).

3) The BS 180 may transmit 704a, 705a the RS to the IRSs (S03) 110, 120, which reflect 704b, 705b those using their individual BFV configuration (codebook 1 + repetition pattern), and the UE 150 determines 721 the specific individual parameters of the IRS providing the strongest LOS-like BFV using the auto-correlation method described above.

4) The UE 150 may feed back 706 to the BS 180 the specific individual parameters obtained from the auto-correlation signal yielding highest overall correlation value (S04), enabling the BS 180 to identify the IRS providing the strongest LOS-like BFV. The UE 150 may also provide feedback for more than one IRS; in that case, UE 150 feeds back 706 several sets of specific individual parameters.

Stage 2: BFV-based channel estimation, 700b

Codebook 2a is defined 732 by BS 180 for first selected IRS, e.g. IRS1 110.

1) The BS 180 may configure 707 IRS1 110 with the BFVs of codebook 2 (which is defined 732, 733 individually for any IRS based on the feedback from stage 1 , e.g. codebook 2a for IRS1 and codebook 2b for IRS2) through its controller 115 (S05) and advices 708 the controller 125 of IRS2 120 to switch off IRS2 during the next phase of RS transmission (S06).

2) The BS 180 may transmit 709a the RS to IRS1 110 (S07), which reflects 709b those using its BFV configuration (codebook 2a), and the UE 150 estimates 722 the channel for each reflected BFV.

3) The UE 150 may feed back 710 to the BS 180 the index of the strongest received BFV from IRS1 110 (S08).

These steps 1-3 may be repeated for any other IRS, if feedback for more than one IRS is available from stage 1 , and if more than one IRS shall be used for transmitting data between BS 180 and UE 150.

In the example of Figure 7, an exemplary number of two IRSs 110, 120 is used. Hence the message sequence chart continues:

Codebook 2b is defined 733 by BS 180 for second selected IRS, e.g. IRS2 120.

1) The BS 180 may configure 711 IRS2 120 with the BFVs of codebook 2b through its controller 125 (S05) and advices 712 the controller 115 of IRS1 110 to switch off IRS1 during the next phase of RS transmission (S06). 2) The BS 180 may transmit 713a the RS to IRS2 120 (S07), which reflects 713b those using its BFV configuration (codebook 2b), and the UE 150 may estimate 723 the channel for each reflected BFV.

3) The UE 150 may feed back 714 to the BS 180 the index of the strongest received BFV from IRS2 120 (S08).

Fig. 8 shows a schematic diagram illustrating a correlation method 800 according to the disclosure.

The method 800 comprises: auto-correlating 801 , by a user equipment, UE, a reference signal, RS, transmitted by a base station, BS, with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter, e.g. according to the functionality of the UE as described above with respect to Figures 1 to 7.

The method 800 may further comprise transmitting 802 one or more results of the autocorrelation by the UE to the BS, e.g. according to the functionality of the UE as described above with respect to Figures 1 to 7.

This provides the same advantages as the UE described above.

Fig. 9 shows a schematic diagram illustrating a method 900 for determining a specific second network device based on auto-correlation results.

The method 900 comprises: transmitting 901 a reference signal, RS, by a base station, BS, and receiving by the BS from a user equipment, UE, one or more results of an autocorrelation of the reference signal with its copy delayed by a number of symbols in timedomain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter, e.g. according to the functionality of the BS 180 as described above with respect to Figures 1 to 7.

The method 900 may further comprise: determining 902, by the BS a specific second network device from the set of second network devices based on the one or more results of the auto-correlation, e.g. according to the functionality of the BS 180 as described above with respect to Figures 1 to 7.

This provides the same advantages as the BS described above.

Fig. 10 shows a schematic diagram illustrating a communication system 1100 according to the disclosure.

The communication system 1100, includes a first user device 1101a or UE, respectively, according to an embodiment, a plurality of neighboring user devices 1101 b, c of the first user device 1101a and a base station 1120.

In the embodiment shown in figure 10, the first user device 1101a and one of the neighboring user devices 1101c are, by way of example, portable devices, in particular smartphones 1101a,c, while another neighboring user device is, by way of example, a laptop computer 1101 b.

The first user device 1101a, and the neighboring user devices 1101 b,c may be configured to communicate with the base station 1120, for instance, via Uu channel. The base station 1120 can use the second network devices 1120a, 1120b, e.g. implemented as IRS as described above, to enable communication to the first user device 1101a (shown in Figure 10) or to enable communication to the neighboring user devices 1101 b,c of the first user device 1101a (not shown in Figure 10). The first user device 1101a, and the neighboring user devices 1101 b,c may also be configured to communicate with each other by sidelink channel without the base station 1120 (this communication is not shown in Figure 10).

As can be taken from figure 10, the first user device 1101a may comprise a processing circuitry 1103a for instance, a processor 1103a, for processing and generating data, a transceiver 1105a, including, for instance, an transmitter, a receiver and an antenna, for exchanging data with the other components of the communication system 1100, and a non- transitory memory 1107a for storing data.

The processor 1103a of the first user device 1101 a may be implemented in hardware and/or software. The hardware may comprise digital circuitry, or both analog and digital circuitry. Digital circuitry may comprise components such as application-specific integrated circuits (ASICs), field-programmable arrays (FPGAs), digital signal processors (DSPs), or general- purpose processors. The non-transitory memory 1107a may store data as well as executable program code which, when executed by the processor 1103a, causes the first user device 1101a to perform the functions, operations and methods described in this disclosure.

In an embodiment, the neighboring user devices 1101 b, c of the first user device 1101a may have a similar architecture as the first user device 101a, i.e. may comprise a processor for processing and generating data, a transceiver for exchanging data with the other components of the communication system 1100 as well as a memory for storing data.

Likewise, as illustrated in figure 10, the base station 1120 may comprise a processor 1113 for processing and generating data, a transceiver 1115 for exchanging data with the other components of the communication system 1100 as well as a non-transitory memory 1117 for storing data.

As described above, the processor 1103a of the first user device 1101a may be configured to: auto-correlate a reference signal, transmitted by the base station 1120, with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector (BFV), wherein the BFV is formed by one from a set of second network devices 1120a, 1120b with the period of repetition, and the BFV shaping the RS with a spatial filter. The transceiver 1105a of the first user device 1101a may be configured to: transmit, to the BS 1120, one or more results of the auto-correlation.

As described above, the transceiver 1115 of the base station 1120 may be configured to transmit a reference signal, RS; and receive, from a user equipment 1101a, 1101 b, 1101c, one or more results of an auto-correlation of the reference signal with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices 1120a. 1120b with the period of repetition, and the BFV shaping the RS with a spatial filter. The processor 1113 of the base station 1120 may be configured to: determine a specific second network device from the set of second network devices 1120a, 1120b based on the one or more results of the auto-correlation.

The present disclosure also supports a computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the performing and computing steps described herein, in particular the methods and procedures described above. Such a computer program product may include a readable non-transitory storage medium storing program code thereon for use by a computer. The program code may perform the processing and computing steps described herein, in particular the methods and procedures described above.

The solution presented in this disclosure may be applied for industrial loT communication, the required signaling can be defined in corresponding standard documents.

The most important signaling information is the UE feedback containing information on the specific individual parameters, in particular repetition period and position of the correlation peak, allowing to identify the closest IRS and its BFV yielding LOS-like conditions. This information can be decoded from the signaling messages.

While a particular feature or aspect of the disclosure may have been disclosed with respect to only one of several implementations, such feature or aspect may be combined with one or more other features or aspects of the other implementations as may be desired and advantageous for any given or particular application. Furthermore, to the extent that the terms "include", "have", "with", or other variants thereof are used in either the detailed description or the claims, such terms are intended to be inclusive in a manner similar to the term "comprise". Also, the terms "exemplary", "for example" and "e.g." are merely meant as an example, rather than the best or optimal. The terms “coupled” and “connected”, along with derivatives may have been used. It should be understood that these terms may have been used to indicate that two elements cooperate or interact with each other regardless whether they are in direct physical or electrical contact, or they are not in direct contact with each other.

Although specific aspects have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific aspects shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific aspects discussed herein.

Although the elements in the following claims are recited in a particular sequence with corresponding labeling, unless the claim recitations otherwise imply a particular sequence for implementing some or all of those elements, those elements are not necessarily intended to be limited to being implemented in that particular sequence. Many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the above teachings. Of course, those skilled in the art readily recognize that there are numerous applications of the invention beyond those described herein. While the present invention has been described with reference to one or more particular embodiments, those skilled in the art recognize that many changes may be made thereto without departing from the scope of the present invention. It is therefore to be understood that within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described herein.

Claims

CLAIMS:

1. A user equipment, UE (150, 160), comprising: a processor (101), configured to: auto-correlate a reference signal, RS (181), transmitted by a base station, BS (180), with its copy delayed by a number of symbols in time-domain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV (111 , 112, 113, 114), wherein the BFV is formed by one from a set of second network devices (110, 120, 130) with the period of repetition, and the BFV shaping the RS with a spatial filter; and a transceiver (101), configured to: transmit, to the BS (180), one or more results of the auto-correlation.

2. The UE (150, 160) according to claim 1 , wherein the set of second network devices comprises one or more second network devices, and the period of repetition for distinct second network devices (110, 120, 130) is different.

3. The UE (150, 160) according to claim 1 or 2, the processor is further configured to: obtain the period of repetition for auto-correlation of the RS by pre-configuration or, receive the configuration of the period of repetition from the BS (180).

4. The UE (150, 160) according to anyone of the claims 1 to 3, wherein the results of the auto-correlation comprises at least one of:

- one or more values of auto-correlation,

- the number of delayed symbols,

- a value of auto-correlation with highest correlation value,

35 - a value of auto-correlation with second-highest correlation value,

- a detection threshold for the auto-correlation,

- a noise threshold for the auto-correlation.

5. The UE (150, 160) according to anyone of the claims 1 to 4, the processor is further configured to: estimate one or more channels of one or more BFVs, wherein the one or more BFVs are configured by the BS (180), or the one or more BFVs correspond to those applied for generating the one or more results of the auto-correlation.

6. The UE (150, 160) according to claim 5, the transceiver (102) is further configured to: transmit the index of at least a strongest received BFV to the BS.

7. The UE (150, 160) according to claim 5 or 6, wherein the one or more BFVs are formed by one or more second network devices (110, 120, 130).

8. The UE (150, 160) according to claim 7, wherein the one or more second network devices (110, 120, 130) comprise one or more intelligent reflecting surfaces, IRS.

9. The UE (150, 160) according to claim 7 or 8, wherein the BFVs formed by a second network device (110, 120, 130) are based on specific individual parameters of the second network device (110, 120, 130).

10. The UE (150, 160) according to claim 9, wherein the specific individual parameters of a second network device (110, 120, 130) comprise a specific beam repetition period and/or a specific delay shift for the BFVs formed by the second network device (110, 120, 130).

11. The UE (150, 160) according to one of claims 9 to 10, wherein the reference signal received by the UE (150, 160) comprises a superposition of multiple BFVs formed by multiple second network devices (110, 120, 130) at the same time.

12. The UE (150, 160) according to one of claims 9 to 11 , wherein the processor (101) is configured to:

36 determine the specific individual parameters from the autocorrelation signal with the highest correlation value by determining an autocorrelation period used for generating the autocorrelation signal and/or a position of the highest correlation value of the autocorrelation signal.

13. The UE (150, 160) according to one of the preceding claims, wherein the transceiver is configured to receive information about a probing phase for probing the BFVs, in particular information about a start and end of the probing phase.

14. The UE (150, 160) according to one of the preceding claims, wherein the transceiver is configured to: receive a further reference signal reflected by a second network device (110, 120, 130) from the set of second network devices, wherein the second network device has been identified by the base station as the one providing the strongest BFV to the UE (150, 160); wherein the second network device (110, 120, 130) is configured by the base station (180) for forming a refined BFV, while any other second network device from the set of second network devices is configured by the base station to be switched off during transmission of the further reference signal; and/or estimate a channel for the refined BFV based on the further reference signal.

15. The UE (150, 160) according to claim 14, wherein the processor is configured to: determine an index of the refined BFV which provides a highest reception energy; and/or wherein the transceiver is configured to: transmit the index of the refined BFV which provides the highest reception energy to the base station.

16. A base station, BS (180), comprising: a transceiver (102), configured to: transmit a reference signal, RS; and receive, from a user equipment, UE (150, 160), one or more results of an autocorrelation of the reference signal with its copy delayed by a number of symbols in timedomain, wherein the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter; and a processor (101), configured to: determine a specific second network device from the set of second network devices based on the one or more results of the auto-correlation.

17. The BS (180) according to claim 16, wherein the set of second network devices comprises one or more second network devices, and the period of repetition for distinct second network devices is different.

18. The BS (180) according to claim 17 or 18, the transceiver is further configured to: transmit the configuration of the period of repetition to the UE.

19. The BS (180) according to anyone of the claims 16 to 18, wherein the results of the auto-correlation comprises at least one of:

- one or more values of auto-correlation,

- the number of delayed symbols,

- a value of auto-correlation with highest correlation value,

- a value of auto-correlation with second-highest correlation value,

- a detection threshold for the auto-correlation,

- a noise threshold for the auto-correlation.

20. The BS (180) according to anyone of the claims 16 to 19, the processor is further configured to: obtain a configuration of one or more BFVs corresponding to the one or more results of the auto-correlation and/or information about the second network device having formed the one or more BFVs.

21 . The BS (180) according to claim 20, the transceiver is further configured to: receive an index of at least a strongest received BFV from the UE.

22. The BS (180) according to claim 20 or 21 , wherein the one or more BFVs are formed by one or more second network devices of the set of second network devices.

23. The BS (180) according to claim 22, wherein the one or more second network devices comprise one or more intelligent reflecting surfaces, IRS.

24. The BS (180) according to claim 22 or 23, wherein the BFVs formed by a second network device are based on specific individual parameters of the second network device.

25. The BS (180) according to claim 24, wherein the specific individual parameters of a second network device comprise a specific beam repetition period and/or a specific delay shift for the BFVs formed by the second network device.

26. The BS (180) according to one of claims 16 to 25, wherein the processor is configured to: determine the specific second network device from the set of second network devices which provides the strongest received BFV to the UE based on the one or more results of the auto-correlation fed back by the UE; and/or wherein the transceiver is configured to: provide a configuration for forming a refined BFV at the specific second network device and/or a configuration for switching-off any other second network device of the set of second network devices (110, 120, 130).

27. A correlation method (800), comprising: auto-correlating (801), by a user equipment, UE, a reference signal, RS, transmitted by a base station, BS, with its copy delayed by a number of symbols in time-domain, wherein 39 the number of symbols corresponds to a period of repetition of a beamforming vector, BFV, wherein the BFV is formed by one from a set of second network devices with the period of repetition, and the BFV shaping the RS with a spatial filter; and transmitting (802) one or more results of the auto-correlation by the UE to the BS.

28. A computer program product including computer executable code or computer executable instructions that, when executed, causes at least one computer to execute the method according to claim 27.

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