WO2024012740A1

WO2024012740A1 - Method for facilitating channel estimation

Info

Publication number: WO2024012740A1
Application number: PCT/EP2023/060808
Authority: WO
Inventors: Kun Zhao; Fredrik RUSEK; Erik Lennart Bengtsson; José FLORDELIS
Original assignee: Sony Group Corporation; Sony Europe B.V.
Priority date: 2022-07-12
Filing date: 2023-04-25
Publication date: 2024-01-18

Abstract

A method carried out in a radio receiver, Rx, device for facilitating communication with a radio transmitter, Tx, device, the method comprising: determining (400) radio configuration for use by the Tx device to transmit a reference signal at repeated occasions over a plurality of slots; obtaining (406) information indicative at least one time location within one of said plurality of slots, associated with an autonomous disruptive operation in the Tx device; wherein the obtaining (406) enables the Rx device to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

Description

METHOD FOR FACILITATING CHANNEL ESTIMATION

Technical field

This disclosure is related to wireless communication between a receiver device and a transmitter device in a wireless system, such as between an access node of a wireless network and a wireless device. Specifically, solutions are provided for facilitating channel management in receiver device based on reference signals transmitted by the transmitter device, such as for improved channel estimation. The proposed solutions are suitable for accommodating for an actual or assumed autonomous disruptive operation in the transmitter device, which may cause phase discontinuity between reference signal transmission occasions, and particularly when communication is configured over a narrow bandwidth allocation.

Background

Various protocols and technical requirements for wireless communication have been standardized under supervision of inter alia the 3^rd Generation Partnership Project (3GPP). Improvement and further development are continuously carried out, and new or amended functions and features are thus implemented in successive releases of the technical specifications providing the framework for wireless communication.

Wireless communication may in various scenarios be carried out between a wireless network and a wireless device. The wireless network typically comprises an access network including a plurality of access nodes, which historically have been referred to as base stations. In a 5G radio access network such a base station may be referred to as a gNB. Each access node may be configured to serve one or more cells of a cellular wireless network. A variety of different types of wireless devices may be configured to communicate with the access network, and such wireless devices are generally referred to as User Equipment (UE). Communication which involves transmission from the UE and reception in the wireless network is generally referred to as Uplink (UL) communication, whereas communication which involves transmission from the wireless network and reception in the UE is generally referred to as Downlink (DL) communication. In various scenarios, the UE may be configured to communicate directly with another wireless device. This may for certain applications be referred to as sidelink communication in 3GPP specifications.

One issue that needs to be considered in wireless communication is channel estimation carried out in a radio node. One example is such channel estimation for a Physical Uplink Shared Channel (PUSCH) or a Physical Uplink Control Channel (PUCCH). Such channel estimation may be conducted in the access node, forming the radio node, based on a reference signal, or pilot signal, received from the UE. In an alternative but related scenario, channel estimation may be carried out in another wireless device acting as radio node, such as in sidelink communication.

The UE will typically be configured to communicate with the radio node, at least in UL, according to a certain radio configuration, such as on a PUSCH or PUCCH channel. In order for the radio node to accomplish channel estimation, the UE is further configured to transmit reference signals, or pilots, such as demodulation reference signals (DMRS), according to a reference signal configuration. The reference signal configuration may identify various resources of the radio configuration dedicated to reference signal transmission.

A scenario where challenges exist in the need for obtaining reference signals in the radio node to accomplish channel estimation is when a disruption in transmission from the UE occurs, or may occur, on the channel. Such disruption or discontinuity may lead to an inconsistency in the UL signals, e.g. a phase shift or an amplitude discontinuity caused by autonomous power adjustment by the UE, such as for the purpose of meeting regulatory requirements with regard to user exposure of RF signal. In 5G, this may include power adjustment made by the UE, such as by Power Management Maximum Power Reduction (P-MPR).

Summary

In view of the foregoing, solutions are presented herein for facilitating channel management in a radio receiver (Rx) device, such as an access node of a wireless network, in communication with a radio transmitter (Tx) device, such as a UE. The invention is defined by the independent claims, whereas various further advantageous features are set out in the dependent claims. According to one aspect, a method carried out in an Rx device for facilitating communication with a Tx device, the method comprising: determining radio configuration for use by the Tx device to transmit a reference signal at repeated occasions over a plurality of slots; obtaining information indicative of at least one time location within one of said plurality of slots, associated with an autonomous disruptive operation in the Tx device; wherein the obtaining enables the Rx device to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

According to another aspect, a method carried out in a Tx device is provided for facilitating communication with an Rx device, the method comprising: determining radio configuration for transmission of a reference signal by the Tx device at repeated occasions over a plurality of slots; autonomously performing a disruptive operation known to cause a phase discontinuity at a time location within one of said plurality of slots; transmitting an indication identifying said time location to the Rx device, wherein the indication enables the Rx device to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

By means of the proposed solution, improvement in channel management in the Rx device may be obtained, e.g. for channel estimation based on repeated reception of the reference signal over the determined time location. This provides the technical effect of improved basis for efficient coverage enhancement.

Brief description of the drawings

Fig. 1 schematically illustrates an implementation of a wireless communication system, in which a UE communicates with a radio node, such as an access node of wireless network or another wireless device.

Fig. 2 schematically illustrates a UE configured to communicate with the wireless network according to various embodiments.

Fig. 3 schematically illustrates an access node of the wireless network according to various embodiments. Fig. 4 illustrates different steps which may be included in various embodiments of the proposed solution in a method carried out in an Rx device, such as an access node.

Fig. 5 illustrates different steps which may be included in various embodiments of the proposed solution in a method carried out in a Tx device, such as a UE.

Fig. 6 shows a plot illustrating a simulation of channel estimation error in an Rx device due to an unknown disruptive operation by the Tx device, causing phase discontinuity between transmission occasions of a reference signal observed in the Rx device.

Fig. 7 shows a plot illustrating a corresponding simulation of channel estimation error in an Rx device due to a disruptive operation by the Tx device, causing phase discontinuity between transmission occasions of a reference signal observed in the Rx device, but where the Rx device knows time location of the disruptive operation according to the proposed solution.

Detailed description

In the following description, for purposes of explanation and not limitation, details are set forth herein related to various embodiments. However, it will be apparent to those skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. The description below further describes the single input single output (SISO) or single input multiple output (SIMO) scenario with a single transmission layer. It shall, however, be obvious to a person skilled in the art that similar approach can be applied vis-a-vis to the multiple input multiple output (MIMO) scenario, where the UE is configured with multiple simultaneous transmission layers, associated with multiple antenna configurations. In some instances, detailed descriptions of well-known devices, circuits, and methods are omitted so as not to obscure the description of the present invention with unnecessary detail. The functions of the various elements including functional blocks, including but not limited to those labeled or described as “computer”, “processor” or “controller”, may be provided through the use of hardware such as circuit hardware and/or hardware capable of executing software in the form of coded instructions stored on computer readable medium. Thus, such functions and illustrated functional blocks are to be understood as being either hardware-implemented and/or computer-implemented and are thus machine-implemented. In terms of hardware implementation, the functional blocks may include or encompass, without limitation, digital signal processor (DSP) hardware, reduced instruction set processor, hardware (e.g., digital or analog) circuitry including but not limited to application specific integrated circuit(s) (ASIC), and (where appropriate) state machines capable of performing such functions. In terms of computer implementation, a computer is generally understood to comprise one or more processors or one or more controllers, and the terms computer and processor and controller may be employed interchangeably herein. When provided by a computer or processor or controller, the functions may be provided by a single dedicated computer or processor or controller, by a single shared computer or processor or controller, or by a plurality of individual computers or processors or controllers, some of which may be shared or distributed. Moreover, use of the term “processor” or “controller” shall also be construed to refer to other hardware capable of performing such functions and/or executing software, such as the example hardware recited above.

The drawings are to be regarded as being schematic representations and elements illustrated in the drawings are not necessarily shown to scale. Rather, the various elements are represented such that their function and general purpose become apparent to a person skilled in the art. Any connection or coupling between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by an indirect connection or coupling. A coupling between components may also be established over a wireless connection. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof. The terms “receive” or “receiving” data or information shall be understood as “detecting, from a received signal”.

Fig. 1 illustrates a high-level perspective of operation of a UE 10 in a wireless network 100. The wireless network 100 may be a radio communication network 100, configured to operate under the provisions of 5G NR as specified by 3GPP, according to various embodiments outlined herein. The wireless network 100 may comprise a core network 110, which in turn may comprise a plurality of core network nodes. The core network is connected to at least one access network comprising one or more base stations or access nodes, of which one access node 120 is illustrated. The access node 120 is a radio node configured for wireless communication on a physical channel 150 with various UEs, of which only the UE 10 is shown. The core network 110 may in turn be connected to other networks 130. The UE 10 may further be configured to communicate directly with a wireless device 20, such as another UE, in device-to device (D2D) communication, e.g. on a sidelink physical channel 151.

Before discussing further details and aspects of the proposed method, functional elements for the UE 10, configured to carry out the proposed solution, will be briefly discussed.

Fig. 2 schematically illustrates an example of the UE 10 for use in a wireless network 100 as presented herein, and for carrying out various method steps as outlined.

The UE 10 comprises a radio transceiver 213 for communicating with other entities of the radio communication network 100, such as the access node 120, in different frequency bands. The transceiver 213 may thus include a receiver chain (Rx) 2131 and a transmitter chain (Tx) 2132, for communicating through at least an air interface.

The UE 10 may further comprise an antenna system 214, which may include one or more antennas, antenna ports or antenna arrays. In various examples the UE 10 is configured to operate with a single beam, wherein the antenna system 214 is configured to provide an isotropic sensitivity to transmit radio signals. In other examples, the antenna system 214 may comprise a plurality of antennas for operation of different beams in transmission and/or reception. The antenna system 214 may comprise different antenna ports, to which the Rx 2131 and the Tx 2132, respectively, may selectively be connected. For this purpose, the antenna system 214 may comprise an antenna switch.

The UE 10 further comprises logic circuitry 210 configured to communicate data and control signals, via the radio transceiver, on a physical channel 150 to the wireless communication network 100, or on a physical channel 151 to a wireless device 20.

The logic circuitry 210 may include a processing device 211, including one or multiple processors, microprocessors, data processors, co-processors, and/or some other type of component that interprets and/or executes instructions and/or data. The processing device 211 may be implemented as hardware (e.g., a microprocessor, etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an applicationspecific integrated circuit (ASIC), etc.). The processing device 211 may be configured to perform one or multiple operations based on an operating system and/or various applications or programs. The logic circuitry 210 may further include memory storage 212, which may include one or multiple memories and/or one or multiple other types of storage mediums. For example, the memory storage 212 may include a random access memory (RAM), a dynamic random access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and/or some other type of memory. The memory storage 212 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid state disk, etc.). The memory storage 212 is configured for holding computer program code, which may be executed by the processing device 211, wherein the logic circuitry 210 is configured to control the UE 10 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and/or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic circuitry 210.

Obviously, the UE 10 may include other features and elements than those shown in the drawing or described herein, such as a power supply, a casing, a user interface, sensors, etc., but these are left out for the sake of simplicity.

Fig. 3 schematically illustrates a radio node in the form of an access node 120 of the wireless network 100 as presented herein, and for carrying out the method steps as outlined. In various embodiments, the access node 120 is a radio base station for operation in the radio communication network 100, to serve one or more radio UEs, such as the UE 10.

The access node 120 may comprise a wireless transceiver 313, such as a radio transceiver for communicating with other entities of the radio communication network 100, such as the terminal 10. The transceiver 313 may thus include a radio receiver and transmitter for communicating through at least an air interface.

The access node 120 further comprises logic circuitry 310 configured to control the access node 120 to communicate with the UE 10 via the radio transceiver 313 on a physical channel 150.

The logic circuitry 310 may include a processing device 311, including one or multiple processors, microprocessors, data processors, co-processors, and/or some other type of component that interprets and/or executes instructions and/or data. Processing device 311 may be implemented as hardware (e.g., a microprocessor, etc.) or a combination of hardware and software (e.g., a system-on-chip (SoC), an application- specific integrated circuit (ASIC), etc.). The processing device 311 may be configured to perform one or multiple operations based on an operating system and/or various applications or programs.

The logic circuitry 310 may further include memory storage 312, which may include one or multiple memories and/or one or multiple other types of storage mediums. For example, memory storage 312 may include a random access memory (RAM), a dynamic random access memory (DRAM), a cache, a read only memory (ROM), a programmable read only memory (PROM), flash memory, and/or some other type of memory. Memory storage 312 may include a hard disk (e.g., a magnetic disk, an optical disk, a magneto-optic disk, a solid state disk, etc.).

The memory storage 312 is configured for holding computer program code, which may be executed by the processing device 311, wherein the logic 310 is configured to control the access node 120 to carry out any of the method steps as provided herein. Software defined by said computer program code may include an application or a program that provides a function and/or a process. The software may include device firmware, an operating system (OS), or a variety of applications that may execute in the logic 310.

The access node 120 may further comprise, or be connected to, an antenna 314, which may include an antenna array. The logic 310 may further be configured to control the radio transceiver to employ an anisotropic sensitivity profile of the antenna array to transmit radio signals in a particular transmit direction. The access node 120 may further comprise an interface 315, configured for communication with the core network 110. Obviously, the access node 120 may include other features and elements than those shown in the drawing or described herein, such as a power supply and a casing etc.

Joint channel estimation (JCE) is a mechanism which entails that a transmitter (Tx) device repeatedly transmits a reference signal over time with a constant phase, allowing a receiver (Rx) device to better process the received signals and estimate the channel. This is particularly useful for narrowband operation. In the context of this disclosure, the description will primarily be given to examples where the Rx device is an access node 120 of the wireless network 100, whereas the Tx device is the UE 10. In other words, the channel estimation is carried out by the access node. It should be noted though, that other alternative approaches are also covered by the proposed solution, such as where the Tx device is the access node 120, and where the UE 10 acts as Rx device and performs the channel estimation. Going forward, though, the description is focused on the first mentioned alternative, with the UE as the Tx device and the access node 120 as the Rx device.

JCE is discussed in Rel-17 for uplink coverage enhancement. The idea is that the UE shall transmit a known DMRS over multiple slots of a channel with a constant or slowly varying phase and amplitude (a DMRS bundling) so that the access node (gNB) can perform a JCE over those slots instead of estimating the channel slot by slot independently. In 3GPP terminology, it is the configured channel with DMRS, such as PUSCH/PUCCH, which is repeated when DMRS bundling is enabled. The effect is thus repetition of the DMRS through repeated PUSCH/PUCCH. It should be noted, though that the proposed solution is not as such bound to the specific example of DMRS.

The gain of such an operation has been well studied in 3 GPP during the Rel-17 discussion, and the condition for UE to maintain the constant phase and amplitude transmission has also been specified. One of the most critical conditions for UE to maintain the phase constant is that the transmission power should not be changed within the DMRS bundling. In this context, it may be noted that amplitude change is not as critical here since both the network and UE know how much it changes, and studies have also shown that coherent channel estimation is much more robust to amplitude change than to phase changes. Therefore, the proposed solution is presented herein with the purpose of managing phase continuity, or correspondingly for managing amplitude continuity.

Typically, the UE 10 behaves the way it is configured, either by the wireless network 100 or by specification. Nevertheless, UE behavior may in various circumstances comprise autonomous disruptive operations, and which may also cause phase discontinuity between occasions of reference signal transmission. In this context, autonomous thus refers to the UE 10 (as Tx device) determines to perform the disruptive operation, and/or when the disruptive operation takes place, without the access node (the Rx device) having knowledge thereof. The disruptive operation may thus not be configured or foreseeable by the wireless network. An example of such an operation is an unconfigured power adjustment. A reason for avoiding power change is that is requires an adjustment of PA (Power Amplifier) amplification in the UE, which usually changes the PA's output phase. Therefore, 3GPP has agreed that the network should not configure the UE with different power levels within a DMRS bundle. However, this agreement only resolves the possible power change due to closed-loop power control, but it does not prevent the autonomous power adjustment from the UE side. One outstanding issue is that the UE may need to autonomously adjust its output power through P-MPR to meet the exposure limitations, for example, SAR or power density change due to the user movement. The UE needs to prioritize such a power adjustment since it is related to regulatory requirements, and this will typically break the phase continuity through the DMRS bundling. Meanwhile, the existing P-MPR reporting mechanism is only on the MAC (Medium Access Control) layer under power headroom reporting (PHR), which is too slow compared to the physical layer phase changing. Therefore, a solution is needed to resolve the issue of channel estimation using reference signals which may be sent at different occasions with phase discontinuity. To resolve the issue mentioned above, a straightforward solution is that UE shall indicate to the network that the power has changed within the bundling, identifying that there is no guarantee of the phase continuity for the DMRS bundling. Responsive to such an indication, the network would not perform JCE over this DMRS bundling. However, such an approach may lead to a total loss of JCE gain.

In contrast, the proposed solution provides a more beneficial approach. According to one example, the Tx device is the UE 10, and the Rx device is the access node 120, which will predominantly be the example discussed. As noted, though, in alternative embodiments the access node 120 may act as the Tx device while the UE 10 acts as the Rx device.

In broad terms, according to a first aspect, the proposed solution entails that the Tx device indicates to the Rx device the time location where an autonomous disruptive operation or event has taken place in the Tx device. According to second aspect, the Tx device may be configured, by the network or by specification, with one or more predetermined time locations at which it may selectively perform a disruptive operation. Based on one or more of these aspects, the Rx device can optimize its JCE accordingly, while still making use of reference signals received both before and after said time location. In this context, the time location may be a symbol position. The result is a better channel estimation than what had been obtained if the Rx device had assumed a constant phase.

Fig. 4 shows a flow chart of an example of a method according to the proposed solution, carried out by an Rx device. The Rx device comprises a radio transceiver and logic circuitry for controlling the Rx device to facilitate communication with a Tx device, by execution of the method in the logic circuitry.

In various examples, the Rx device is the access node 120 to which the UE 10, acting as the Tx device, is camped on in connected mode.

In step 400, the Rx device determines radio configuration for use by the Tx device to transmit a reference signal at repeated occasions over a plurality of slots. In this context, a known reference signal is transmitted at repeated times over said slots. In some scenarios it may be transmission of the actual configured channel (e.g. PUSCH/PUCCH) that is repeated, which contains both reference signals and data. Content in the repetition is not exactly the same, but rather similar in the sense that at least a part, or majority of the content in two repetitions is equal. Where the Rx device is an access node 121, this step may comprise configuring resources in time and frequency domain, which channel to use, number of repetitions (transmission occasions), etc. Alternatively, where the Rx device is the UE 10, this step may comprise obtaining the radio configuration from the access node 120, acting as the Tx device.

In optional step 402, the Rx device may transmit the radio configuration to the Tx device, which may include providing information to the Tx device so as to enable the Tx device to obtain the radio configuration. This step is preferably included where the Rx device is the access node 120, which then configures the UE 10 to transmit the reference signals, e.g. by Radio Resource Control (RRC) scheduling.

In this context, the reference signal may be a DMRS, wherein the radio node 120 may provide configuration of radio resources for DMRS bundling. The purpose is typically to configure the Tx device, e.g. the UE 10, to transmit the same DMRS in multiple time slots, for reception and use in the Rx device, e.g. the radio node 120, for coverage enhancement. The Rx device is in this context enabled to perform JCE based on the DMRS in multiple time slots to improve the accuracy of channel estimation. JCE is as such a known procedure and is therefore not described in detail in this disclosure. Nevertheless, one example of how JCE can be improved based on the time location of the assumed disruptive operation will be described with reference to Figs 6 and 7 below.

In step 404, which may be included in various embodiments, the Rx device receives, from the Tx device, an indication of performance of an autonomous disruptive operation by the Tx device. In step 406, the Rx device obtains information indicative of at least one time location within one of said plurality of slots, such as a symbol, associated with an autonomous disruptive operation in the Tx device.

Where step 404 is included, the obtainment of the information indicative of the time location may comprise determining the time location based on the indication. As such, the indication may explicitly identify the time location. As an alternative, the time location may be determined based on a radio resource used by the UE 10 for transmitting the indication, such as the used time domain resource.

Where step 404 is not included, the information indicative of said at least one time location may be obtained based on a predetermined rule. In such an embodiment, the Rx device may as such not be informed whether any disruptive event has indeed occurred. Rather, the Rx device is enabled to process received reference signals of the plurality of slots based on the assumption that a disruptive event that causes phase discontinuity may have taken place at said time location. According to some examples, one or more time locations may be predetermined for use by the Tx device for selectively performing the disruptive operation. In such an embodiment, the Tx device may thus be preconfigured, either by the radio network, or by standard specification, to use certain radio resources for autonomously performing the disruptive operation, such as executing a power backoff. According to some examples, the time location of the radio resources for autonomously performing the disruptive operation may be determined dependent on a certain frequency band, sub-carrier spacing, or other data defining circumstances for the context of the data communication between the Tx device and the Rx device. In this context, the information indicative of the time location may comprise the determined 400 radio configuration. The radio resources for use by the Tx device for selectively performing the disruptive operation may be configured with a predetermined interval so as to be frequent enough to meet e.g. exposure requirements, such as timing requirements for executing a power backoff by P-MPR or similar.

By means of the proposed solution, the Rx device is enabled to process 408 repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

This may involve performing JCE based on the repeated reception of the reference signal over said plurality of slots, taking the assumed phase discontinuity in said time location into account. In this context, the Rx device may be enabled to perform JCE from the repeated reception of the reference signal spanning over said time location, i.e. based on reception of the reference signal before and after said time location.

Fig. 5 shows a flow chart of various examples of a method according to the proposed solution, carried out by a Tx device, such as the UE 10. The Tx device comprises a radio transceiver and logic circuitry for controlling the Tx device to facilitate communication with an Rx device, by execution of the method in the logic circuitry.

In step 500, the Tx device, e.g. the UE 10, determines radio configuration for transmission of a reference signal by the Tx device at repeated occasions over a plurality of slots, e.g. for DMRS bundling. The radio configuration may be received from the Rx device, e.g. radio node 120, or from another radio node of the wireless network 100. Alternatively, the radio configuration may be predetermined by standard specification, e.g. predetermined given a certain frequency band, sub-carrier spacing, or other data defining circumstances for the context of the data communication between the Tx device and the Rx device. Step 500 corresponds to steps 400-402 of Fig. 4.

Step 501, which may optionally be included, provides that the Tx device obtains information indicative of at least one time location within one of said plurality of slots, usable for an autonomous disruptive operation in the Tx device. With reference to the discussion provided in relation to step 404, the information indicative of said at least one time location may obtained based on a predetermined rule. According to some examples, one or more time locations may be predetermined for use by the Tx device for selectively performing the disruptive operation. In such an embodiment, the Tx device may thus be preconfigured, either by the radio network, or by standard specification, to use certain radio resources for autonomously performing the disruptive operation, such as executing a power backoff. According to some examples, the time location of the radio resources for autonomously performing the disruptive operation may be determined dependent on a certain frequency band, sub-carrier spacing, or other data defining circumstances for the context of the data communication between the Tx device and the Rx device. In this context, the information indicative of the time location may comprise the determined 400 radio configuration. The radio resources for use by the Tx device for selectively performing the disruptive operation may be configured with a predetermined interval so as to be frequent enough to meet e.g. exposure requirements, such as timing requirements for executing a power backoff by P-MPR or similar.

In step 502, the Tx device autonomously performs a disruptive operation known to cause a phase discontinuity at a time location within one of said plurality of slots. Such an operation may e.g. be autonomous, i.e. non-scheduled or non-ordered, power adjustment of the transmit power at said time location between successive reference signal transmission occasions. This may e.g. be caused by P-MPR or a corresponding process, for meeting exposure requirements.

Where step 501 is included, the Rx device may as such not be informed whether any disruptive event has indeed occurred. However, the Tx device is configured to carry out the disruptive operation at one of said at least one time location within one of said plurality of slots. The Rx device is thereby enabled to process received reference signals of the plurality of slots based on the assumption that a disruptive event that causes phase discontinuity may have taken place at said time location. Specifically, if a disruptive operation has indeed occurred, the Rx device according to this embodiment is preconfigured to know/assume that it occurred at a time location that is already known.

In step 504, the Tx device may transmit an indication of said time location to the Rx device, wherein the Rx device is enabled to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location. The indication thus identifies, to the Rx device, that the disruptive operation or event has taken place, and when. The indication may either indicate that the operation has caused phase discontinuity between reference signal transmissions, or only that the Rx device shall assume that the disruptive operation caused phase discontinuity. This corresponds to step 404 of Fig. 4.

Step 504 may in some embodiments be included instead of step 501. In such embodiments, the Rx device has as such not obtained any prior information indicative of the time location. Instead, the indication provides for the obtainment in the Rx device of the information indicative of the time location.

Step 501 may in some embodiments be included instead of step 504. In such embodiments. In such an embodiment, the Rx device is configured to assume that each of said at least one time location within one of said plurality of slots, usable for an autonomous disruptive operation in the Tx device, may have caused a phase discontinuity. In such an embodiment, the proposed solution may comprise a method carried out in a Tx device for facilitating communication with an Rx device, the method comprising: determining 500 radio configuration for transmission of a reference signal by the Tx device at repeated occasions over a plurality of slots; obtaining 501 information indicative of at least one time location within one of said plurality of slots, usable for an autonomous disruptive operation in the tx device; autonomously performing 502 a disruptive operation known to cause a phase discontinuity at one of said at least one time location within one of said plurality of slots, wherein the Rx device is enabled to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

In yet another alternative embodiment, step 504 is included in addition to step 501. In such an embodiment, the Rx device and the Tx device may both have obtained 406, 501 information indicative of the at least one time location usable by the Tx device for autonomously carrying out a disruptive operation that may cause phase discontinuity. Both the Rx device and the Tx device are thus be preconfigured according to a predetermined rule to identify such time locations. However, if and when the Tx device carries out such a disruptive operation, the Tx device further transmits 504 an indication of the time location associated with the disruptive operation to the Rx device. In such an embodiment, the proposed solution may comprise a method carried out in a Tx device for facilitating communication with an Rx device, the method comprising: determining 500 radio configuration for transmission of a reference signal by the Tx device at repeated occasions over a plurality of slots; obtaining 501 information indicative of at least one time location within one of said plurality of slots, usable for an autonomous disruptive operation in the tx device; autonomously performing 502 a disruptive operation known to cause a phase discontinuity at one of said at least one time location within one of said plurality of slots; and transmitting 504 an indication of said time location to the Rx device, wherein the Rx device is enabled to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location. By means of the proposed solution, the radio node 120 is enabled to perform JCE using repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity in said time location as identified by said information and/or said indication.

Assumption of phase discontinuity may thus be based on an indication of a power adjustment, which provides knowledge of the actual existence of the disruptive operation, e.g. a backoff power adjustment, having taken place, and the associated time location. This provides the benefit of detailed timing information usable by the Rx device, such as the radio node 120, for adaptation of JCE determination, and only when a power adjustment has taken place. Alternatively, assumption of phase discontinuity may be based on knowledge of the preconfigured resources selectively usable for such a disruptive operation when needed, without actually knowing whether or not the Tx device has actually performed any such disruptive operation. In other words, no indication is transmitted from the Tx device. This may deteriorate JCE determination over the plurality of time slots, but will enable the radio node to determine JCE in any event of autonomous power adjustment without requiring radio resources for allowing the UE to provide any indication.

Predominantly two approaches may alternatively be taken in different embodiments of the proposed solution, with reference to transmitting 504 the indication from the Tx device, e.g. the UE 10, and receiving it in the Rx device, e.g. the radio node 120.

In a first approach, the indication is comprised in a data block, such as a transport block (TB), transmitted by the Tx device in one or more slots over said time location. The indication may be incorporated as a part of a codeword during TB K, transmitted over at least the slot encompassing the indicated time location. Alternatively, the indication may be multiplexed with the reference signal. Transmitting the indication during the slot comprising the indication allows the Rx, e.g. the access node 120, to carry out the processing 408 to initially make a first decoding of the codeword with assumption that there is no change, i.e. no phase discontinuity. The encoding of the indication may be robust so that it is decodable even with high Channel State Information (CSI) error. After having decoded the indication, the processing 408 by the Rx device may comprise making a new decoding of the TB, now with improved CSI estimation. In a second approach, the indication is transmitted in a separate transmission adjacent to (i.e., after) the slot comprising the time location, or even after the bundled transmission. The indication may be comprised in a transport block transmitted by the Tx device after said time location, or be multiplexed with the reference signal or another, e.g., over a control channel.

The two approaches have slightly different impacts. In particular, it seems important to consider the TB-size in comparison to the bundle-time. According to some examples, the Rx device buffers the signal within one TB, and the DMRS observations for some time before a current TB. In this sense, DMRS observations made both prior to, during, and potentially after, reception of a TB may be usable for estimating the channel.

For the first approach, if a disruptive operation, e.g. P-MPR, occurs during TB number K, then the indication arrives within TB K.

For the second approach, if the indication reaches the Rx device during TB K+l, then the performance of TB K is as if the indication never arrives. While, for TB K+l, K+2,... the performance improves.

This consideration is based on the assumption that it is most likely that TB K has already been decoded and the underlying Rx signal has been erased from memory. Thus, it is too late for the current TB. If the cyclic redundancy check (CRC) fails, meaning that there is an error, only LLRs (log likelihood ratio parameter for decoding) of TB K are saved, not the original signal. It is in this context not possible to improve these LLRs based on a better channel estimate. In an example where the underlying received Rx signal is indeed saved, then also TB K can be corrected but require additional Rx device capacity in terms of memory.

In order to illustrate the technical effect that is achieved by the proposed solution, Fig. 6 shows a plot of a simulation of the channel estimation error of 100 pilot symbols for DMRS, without knowledge in the Rx device that a phase discontinuity occurs at symbol (time location) 51. Fig. 7 shows the corresponding plot, but where the Rx device makes the channel estimation based on assumed phase discontinuity at symbol 51, based on the proposed solution.

100 pilot symbols with a correlation coefficient in the channel of .98 between two consecutive pilots are used here. It is assumed that the Rx device has knowledge of the power and phase level during pilots 1-50, but unknown power and phase level during pilots 51-100 due to the change of P-MPR (the disruptive operation to autonomously adjust the power occurs at pilot 51). The power and phase during pilots 51-100 is random according to uniform power in (0.7, 1.3) times the old one, and a totally random phase.

The plots show the channel estimation error for an SNR (signal-to-noise ratio) of 10 dB. The curve in Fig. 7 is the normalized channel estimation error (i.e., it assumed that each channel tap has unit power) if the Rx device knows/assumes that there will be a change in power/phase in pilot number 51. The curve in Fig. 6 is the CSI error if the Rx does not know this. It may be noted that the bumps in the beginning and the end of the respective curve are just edge effects as there are no “past” pilots at pilot 1 and no future pilots at pilot 100, so the error is a little higher. As can be seen from the difference between the curves in Figs 6 and 7, the gain of the proposed solution is indicated by the shown obtainable improvement in channel estimation error.

The following describes one example of processing repeated reception of the reference signal in step 408, according to an example benefitting from the proposed solution, which was used to obtain the simulation results of Figs 6 and 7. The proposed solution relates to facilitating communication between an Rx device and a Tx device, such as an access node 120 and a UE 10, by providing conditions for obtaining improved channel estimation based on pilot, or reference signal (e.g. DMRS) transmissions where a disruptive operation in the Tx device may cause an abrupt change in phase during the pilot transmission (e.g. caused by a transmit power change). According to the proposed solution, the Rx device is aware of the position, i.e. time location, where the change occurs, but not the new phase (and power) values.

There are many possible setups, and the following provides details of, arguably, the simplest possible embodiment setup. However, to the person skilled in the art, it should be clear how tailoring to another setup is done.

A sequence of channel observations y_k of the form y_k = h_kA_k + n_k, k = 0 ... K — 1 is considered, where n_k is zero-mean, circularly symmetric complex Gaussian noise with sample variance N_o, h_k is wide-sense stationary complex Gaussian channel coefficients (to be estimated) with covariance E = 7 , and A_k are pilot

symbols. Note that the sequence h_k and time-indices k are defined only at the observation instances. In practical systems there are many channels to be estimated between the channel observations, but it will be clear to the person skilled in the art how those should be estimated based on the material provided next. The setup of the proposed solution is that it is known to the Rx device that A_k = 1, 0 ≤ k ≤ L and that A_k = A, L + l ≤ k ≤ K — 1. The value of L is known to the Rx device, due to our invention, but the value A is not.

The estimation problem is, consequently, to estimate the value A and the channel coefficients h_k, k = 0 ... K — 1. At our disposal is the entire sequence y_k. In many practical scenarios, the coefficient h_k must be estimated no later than at index k + T_max, but here we assume the entire block. Note that further refinements can be obtained if the Rx device utilizes channel observations from previous data blocks (e.g. TBs), but we do not include that into our exposition.

We solve the estimation problem by maximum-likelihood estimation of A, followed by a maximum-a-posteriori (MAP) estimation of h_k, k = 0 ... K — 1.

The likelihood function p A) is:

where the notation denotes the column vector

= [y₀ y_x ...y_K_^ ]^T ■ To

estimate A, we should, thus, solve:

Removing all multiplicative factors not related to A, we can express the likelihood function as:

where D(A) = diag([l_L+1 A1_K-L-1J), 1_M is a row vector of M ones, diag(-) is a diagonal matrix with its argument along the main diagonal, and R is the covariance matrix of the channel vector h = [h₀, ... , h_K_₁]^T . Assuming that the channel coefficients are zero-mean, we have R = E [h/i^H], and the (i,j) element of R is rj__t. Re{-} extracts the real part of the argument.

Let Z(A) = This matrix has eigenvalue decomposition

Z(A) = Q(A)2(A)Q^H(A). Make the variable substitution = Q^H Since Q^H (A) is

unitary, the associated Jacobian is unity. With that, we have:

This integral can be simplified into:

where is the fcth diagonal element of matrix 2(A), and [-]_fc is the fcth

element of a vector. These integrals are all of the same form, and has trivial solutions, namely:

Altogether, we have reached a form of the likelihood p that is easy to

evaluate. Using a simple numerical search, we can therefore solve:

We can now regard A as the true value of A and estimate h_k. We can do this in many ways, out of which MMSE and MAP stand out as the most reasonable. The MAP estimator, which is well known in the literature, is given by:

Without the proposed solution, it would be unknown to the Rx device that a phase and power change have occurred, which implies that the channel estimate reads:

To evaluate efficiency with the proposed solution, we can compare the estimation error made using the proposed solution, which is shown in Fig. 7, to

the corresponding error without the proposed solution, which is

shown in Fig. 6.

As can be seen in the simulation plot of Fig. 6, the error caused by phase discontinuity remains for some time (i.e. for some indices, with reference to Figs 6 and 7) if the PMPR change is left untreated. This impacts TB K+l, K+2,... If it is known at TB K+l that there is a change at TB K, and provided that DMRS signals are stored, then this error can be almost eliminated already at TB K+l.

Various features and functions of different embodiment of the proposed solution are presented herein. Except where clearly contradictory, these features and functions can be combined in any way.

Claims

1. A method carried out in a radio receiver, Rx, device for facilitating communication with a radio transmitter, Tx, device, the method comprising: determining (400) radio configuration for use by the Tx device to transmit a reference signal at repeated occasions over a plurality of slots; determining (406) at least one time location within one of said plurality of slots, associated with an autonomous disruptive operation in the Tx device; wherein the Rx device is enabled to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

2. The method of claim 1, wherein said disruptive operation comprises an adjustment of transmit power of the Tx device.

3. The method of claim 1 or 2, wherein said disruptive operation comprises a transmit power backoff to meet a regulatory requirement in the Tx device.

4. The method of any preceding claim, wherein the Rx device is enabled to perform Joint Channel Estimation, JCE, from the repeated reception of the reference signal.

5. The method of any preceding claim, wherein determining a time location comprises receiving (404), from the Tx device, an indication of performance of the disruptive operation at said time location.

6. The method of claim 5, wherein said indication is comprised in a transport block transmitted by the Tx device over said time location.

7. The method of claim 5, wherein said indication is comprised in a transport block transmitted by the Tx device after said time location.

8. The method of claim 6 or 7, wherein said indication is incorporated in a codeword of said transport block.

9. The method of any of claims 5-8, wherein said indication is multiplexed with the reference signal at one of said a transmission occasions.

10. The method of claim 5, wherein said indication is received after said plurality of slots.

11. The method of any of claims 5-10, wherein said indication is received on a data channel.

12. The method of any of claims 5-10, wherein said indication is received on a control channel.

13. The method of any of claims 1-4, wherein said at least one slot is predetermined for use by the Tx device for selectively performing the disruptive operation.

14. The method of any preceding claim, comprising: configuring (402) the Tx device to transmit the reference signal according to the radio configuration.

15. The method of any preceding claim, wherein the Rx device is an access node (120) of a wireless network (100), and the Tx device is a User Equipment, UE (10).

16. The method of any of claims 1-13, wherein the Tx device is an access node (120) of a wireless network (100), and the Rx device is a User Equipment, UE (10).

17. A radio receiver, Rx, device (120) configured for communicating with a radio transmitter, Tx, device (10), said Rx device comprising: a radio transceiver (313); and logic circuitry (310) for controlling the Rx device to facilitate communication with the Tx device, wherein the logic circuitry is configured to: determine radio configuration for use by the Tx device to transmit a reference signal at repeated occasions over a plurality of slots; determine at least one time location within one of said plurality of slots, associated with an autonomous disruptive operation in the Tx device; wherein the Rx device is enabled to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

18. The Rx device of claim 17, wherein the logic circuitry is further configured to operate in accordance with any of claims 2-16 to facilitate communication with the Tx device.

19. A method carried out in a radio transmitter, Tx, device for facilitating communication with a radio receiver, Rx, device, the method comprising: determining (500) radio configuration for transmission of a reference signal by the Tx device at repeated occasions over a plurality of slots; autonomously performing (502) a disruptive operation known to cause a phase discontinuity at a time location within one of said plurality of slots; transmitting (504) an indication of said time location to the Rx device, wherein the Rx device is enabled to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

20. A method carried out in a radio transmitter, Tx, device for facilitating communication with a radio receiver, Rx, device, the method comprising: determining (500) radio configuration for transmission of a reference signal by the Tx device at repeated occasions over a plurality of slots; obtaining (501) information indicative of at least one time location within one of said plurality of slots, usable for an autonomous disruptive operation in the tx device; autonomously performing (502) a disruptive operation known to cause a phase discontinuity at one of said at least one time location within one of said plurality of slots, wherein the Rx device is enabled to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

21. The method of claim 20, further comprising: transmitting (504) an indication of said one time location to the Rx device.

22. The method of any of claims 19-21, wherein said disruptive operation comprises an adjustment of transmit power of the Tx device.

23. The method of any of claims 19-22, wherein said disruptive operation comprises a transmit power backoff to meet a regulatory requirement in the Tx device.

24. The method of any of claims 19-23, wherein the Rx device is enabled to perform Joint Channel Estimation, JCE, from the repeated reception of the reference signal.

25. The method of any of claims 19-24, wherein said indication, when transmitted, is comprised in a transport block transmitted by the Tx device over said time location.

26. The method of any of claims 19-24, wherein said indication, when transmitted, is comprised in a transport block transmitted by the Tx device after said time location.

27. The method of claim 25 or 26, wherein said indication is incorporated in a codeword of said transport block.

28. The method of any of claims 25-27, wherein said indication, when transmitted, is multiplexed with the reference signal at one of said a transmission occasions.

29. The method of any of claims 19-24, wherein said indication, when transmitted, is transmitted after said plurality of slots.

30. The method of any of claims 19-29, wherein said indication, , when transmitted, is transmitted on a data channel.

31. The method of any of claims 19-29, wherein said indication, when transmitted, is transmitted on a control channel.

32. The method of any of claims 19-31, wherein the radio configuration is received (500) from the Rx device.

33. The method of any of claims 19-32, wherein the Tx device is a User Equipment, UE (10), and the Rx device is an access node (120) of a wireless network (100).

34. The method of any of claims 19-32, wherein the Tx device is an access node (120) of a wireless network (100), and the Rx device is a User Equipment, UE (10).

35. A radio transmitter, Tx, device (10) configured for communicating with a radio, receiver, Rx, device (120), said Tx device comprising: a radio transceiver (213); and logic circuitry (210) for controlling the Tx device to facilitate communication with the Rx device, wherein the logic circuitry is configured to: determine radio configuration for transmission of a reference signal by the radio transceiver at repeated occasions over a plurality of slots; autonomously perform a disruptive operation known to cause a phase discontinuity at a time location within one of said plurality of slots; transmit an indication of said time location to the Rx device, wherein the Rx device is enabled to perform processing of repeated reception of the reference signal over said plurality of slots, based on assumed phase discontinuity at said time location.

36. The Tx device of claim 35, wherein the logic circuitry is further configured to operate in accordance with any of claims 20-34 to facilitate communication with the Rx device.