Path loss estimation

Abstract

A method for use in a communication device comprises transmitting (1104), at a first transmit amplitude value and using a first symbol sequence, a first reference signal (906, 1006) to a first network node (602) along a respective signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, and transmitting (1104), at a second transmit amplitude value and using a second symbol sequence, a second reference signal (908, 1006) to the first network node (602) along the signal path, the second transmit amplitude value depending on the reference signal transmit power level and being different than the first transmit amplitude value.

Description

[0001] 42918W0 SN / NR

[0002] Path loss estimation

[0003] Technical Field

[0004] Various examples of the present disclosure generally relate to the field of determining a path loss of a signal path between a communication device and a network node. In particular, the present disclosure relates to methods for use in a communication device and a network node for determining a path loss using reference signals.

[0005] Background

[0006] In New Radio (NR) deployments, it has been identified that in certain dense macro cell configurations, uplink (UL) traffic may present a capacity bottleneck. A heterogeneous network (HetNet) deployment may alleviate some of the uplink traffic burden on a macro-cell base station (gNB) by enabling user equipment (UE) to transmit to small cells. Such small cells may be beneficial for UEs located at the cell edge, as they may allow for uplink transmissions at lower power levels, thereby reducing uplink interference. However, in scenarios where uplink traffic presents a challenge rather than downlink (DL) traffic, a conventional HetNet deployment may introduce downlink interference among transmission-reception points (TRPs) within the HetNet. A deployment scenario incorporating asymmetric downlink and uplink TRPs, in which a single transmission-reception point (sTRP) is used for downlink and multiple transmissionreception points (mTRP) are used for uplink (i.e., DL sTRP I UL mTRP), may be utilized to address such cases.

[0007] In such a deployment, an uplink-only transmission-reception point (UL-only TRP or simply UL TRP), which may be configured for uplink reception and may operate as an uplink-only cell, may be deployed within the coverage area of a macro-cell transmission-reception point (macro TRP) that supports both downlink and uplink transmissions. The coverage of the UL TRP may be at least partially overlapped with that of the macro TRP, as the UL TRP does not provide downlink signals. In such a configuration, a UE may receive downlink signals exclusively from the macro TRP, while transmitting uplink signals to the UL TRP.

[0008] In Release 19, the 3rd Generation Partnership Project (3GPP) has been working on the specification of UL-only TRPs, including mechanisms for a UE to determine the path loss (PL) associated with a UL-only TRP. Path loss is a parameter that may be used for uplink power control, which is relevant for channels such as the physical uplink shared channel (PUSCH), the physical uplink control channel (PUCCH), and the sounding reference signal (SRS). Since the macro TRP and UL TRP are geographically separated and may experience different channel conditions, their respective path loss values may differ. A UE may determine the path loss of the macro TRP using downlink reference signals based on existing specifications and may report the derived path loss value implicitly via power headroom (PHR) reporting to the macro TRP.

[0009] To facilitate the determination of UL TRP path loss, 3GPP has agreed that the macro TRP may signal a path loss offset value to the UE, where the path loss of the UL TRP may be determined as the path loss of the macro TRP minus the signaled path loss offset. However, this necessitates techniques by which the network node, such as a gNB, may determine the path loss offset associated with the UL TRP.42918W0 SN / NR

[0010] Summary

[0011] Accordingly, a need exists for techniques to improve path loss estimation, for example techniques that enable reliable path loss estimation between a UE and a UL TRP without additional or extensive need of communication overhead and resources.

[0012] An aspect relates to a method for use in a communication device. The communication device may be used in a wireless communications system, for example a cellular network.

[0013] Communication between entities in the wireless communications system, for example between the communication device and network nodes, may be a wireless radio communication. The communication device may comprise a mobile station, a user equipment (UE), a user terminal, or a mobile radio node. The network node may comprise a base station such as an eNB or gNB, an access node, or a TRP.

[0014] The method comprises transmitting, at a first transmit amplitude value and using a first symbol sequence, a first reference signal to a first network node along a respective signal path, and transmitting, at a second transmit amplitude value and using a second symbol sequence, a second reference signal to the first network node along the signal path. The first transmit amplitude value depends on a reference signal transmit power level included in a predefined set of reference signal transmit power levels. The second transmit amplitude value depends on the reference signal transmit power level and is different from the first transmit amplitude value.

[0015] This method may efficiently determine path loss by utilizing two distinct reference signals. Each signal's amplitude is adjusted according to predefined levels, allowing for accurate comparison.

[0016] It requires only a few symbol sequences - specifically one or two only - to be provided, which simplifies the implementation and reduces overhead, ensuring efficient resource utilization. The first network node, such as an uplink-only transmission-reception point (UL TRP), can easily and reliably determine the used reference signal transmit power level by analyzing the relationship between the first and second transmit amplitude values. This determination remains accurate even if the transmission was attenuated along the signal path or disturbed by noise. This approach enhances accuracy in path loss estimation, which may be used for optimizing uplink transmission parameters such as power control. The method facilitates efficient and robust communications systems, particularly in scenarios where uplink traffic management is critical, such as in heterogeneous networks (HetNet) deployments incorporating asymmetric downlink and uplink TRPs.

[0017] The method may efficiently determine path loss, especially in scenarios where the channel is unknown to the receiver. The determination can include the influence of the channel on both phase and amplitude.

[0018] According to various examples, after transmitting the first reference signal at the first transmit amplitude value using the first symbol sequence and the second reference signal at the second transmit amplitude value using the second symbol sequence, the communication device may obtain, from a second network node, information based on the path loss of the signal path.

[0019] The second network node may be a TRP capable of communicating UL and DL data with the communication device, e.g. a macro TRP, and the second network node may be in42918W0 SN / NR

[0020] communication connection with the first network node, for example via a backhaul network of the wireless communications system.

[0021] The information based on the path loss can be utilized in various ways to manage different communication scenarios effectively. For instance, the network, e.g. the first or second network node, may determine that the path loss is too large for the link between the communication device and the UL TRP to be used, in which case the UL TRP may not be used. The communication device may or may not receive an indication of this decision in the information based on the path loss. Receiving no such information may be used to implicitly indicate that the UL TRP should not be used.

[0022] Additionally, the network may inform the communication device to use another reference signal transmit power level, either a lower or higher, without explicitly indicating the actual path loss. This allows the communication device to optimize its transmission parameters based on network feedback.

[0023] Furthermore, if the path loss is within acceptable limits and no tuning is needed, the network may indicate to the communication device that it can start sending data. This ensures efficient communication by allowing data transmission to commence without unnecessary delays or adjustments.

[0024] According to various examples, the first symbol sequence is the same as the second symbol sequence. The first reference signal and the second reference signal are transmitted in different time resources. The different time resources may be different adjacent time resources, e.g. consecutive time slots. This configuration allows the use of a single symbol sequence, simplifying the system design and reducing complexity. By transmitting the reference signals at different times, the communications system can efficiently manage resource allocation while maintaining reliable channel estimation.

[0025] According to various examples, the first symbol sequence is the same as the second symbol sequence. The first reference signal and the second reference signal are transmitted in different frequency resources. This approach also enables the use of a single symbol sequence, further simplifying the system architecture. By utilizing different frequency resources for the reference signals, the communications system can enhance resource utilization and improve overall efficiency.

[0026] According to various examples, the first symbol sequence is different from the second symbol sequence. The first reference signal and the second reference signal are transmitted in the same time and frequency resource. This configuration allows both reference signals to be transmitted simultaneously at the same frequency by Code Division Multiplexing (CDM), which may improve the accuracy of identifying the reference signal transmit power level. By sharing the same time and frequency resource, the system can leverage this overlap to enhance performance and efficiency.

[0027] Additionally, the first symbol sequence may be orthogonal to the second symbol sequence. Orthogonality between the sequences ensures minimal interference and clear separation of signals, further improving the accuracy of identifying the reference signal transmit power level.42918W0 SN / NR

[0028] In various examples, at least one of the first transmit amplitude value and the second transmit amplitude value is a complex value. The first transmit amplitude value and the second transmit amplitude value differ in at least one of magnitude and phase. This may provide further options for differentiating the first and second transmit amplitude values thus further improving the accuracy of identifying the reference signal transmit power level.

[0029] In various examples, each reference signal transmit power level within of the set of reference signal transmit power levels is associated with a unique pair of respective first and second transmit amplitude values. This configuration allows for precise control over signal transmission, as each power level has a distinct amplitude pairing tailored to specific requirements.

[0030] According to various examples, these unique pairs are based on associated code vectors from a codebook. The utilization of code vectors introduces a structured approach, enhancing consistency and efficiency in managing the power levels.

[0031] In some instances, the codebook is specifically a Grassmannian codebook. This selection leverages the advantageous properties of Grassmannian codebooks, known fortheir effectiveness in optimizing signal differentiation and performance in radio communication environments, in particular in environments in which the communication channel is unknown to the receiver, i.e. in non-coherent communications.

[0032] Furthermore, according to various examples, each unique pair of amplitude values may be scaled by or normalized to the reference signal transmit power level. This scaling ensures that signals are appropriately adjusted according to the reference signal transmit power level, maintaining optimal performance for path loss determination.

[0033] According to various examples, the second transmit amplitude value differs from the first transmit amplitude value by a predetermined offset value. This fixed difference simplifies the construction of the first and second transmit amplitude values, as it provides a consistent and predictable relationship between them.

[0034] In some instances, the predetermined offset value depends on at least one of the reference signal transmit power levels. By tying the offset to specific power levels, this approach introduces flexibility in managing diverse transmission scenarios while maintaining simplicity in setup.

[0035] Furthermore, according to various examples, the predetermined offset value may depend on the smallest one of the set of reference signal transmit power levels. This may ensure that the power levels meet power constrains within the system, contributing to robust performance across all operating ranges.

[0036] According to various examples, the method further includes obtaining configuration information from the second network node. This configuration information may pertain to a request to transmit the first and second reference signals, the first symbol sequence, the second symbol sequence, the set of reference signal transmit power levels, time resources for transmitting the first and second reference signals, or frequency resources for transmitting the first and second reference signals.

[0037] This allows the network to exert control over the used resources and scheduling. By obtaining such detailed configuration information, the system can efficiently manage resource42918W0 SN / NR

[0038] allocation, ensuring optimal use of both time and frequency resources. This capability contributes to a more organized and coordinated transmission process, enhancing overall system performance.

[0039] A further aspect of the present disclosure relates to a method for use in a first network node. The method involves receiving a first reference signal from a communication device along a respective signal path. This first reference signal is transmitted by the communication device at a first transmit amplitude value and using a first symbol sequence. The first transmit amplitude value depends on a reference signal transmit power level included in a predefined set of reference signal transmit power levels. Additionally, the method includes receiving a second reference signal from the communication device along the same signal path. The second reference signal is transmitted at a second transmit amplitude value and uses a second symbol sequence. This second transmit amplitude value also depends on the reference signal transmit power level but differs from the first transmit amplitude value. The method further comprises determining the reference signal transmit power level based on both the first and second reference signals received. Furthermore, the path loss of the signal path is determined by using the receive power level of at least one of these reference signals and the previously determined reference signal transmit power level.

[0040] This approach requires only a few symbol sequences, i.e., one or two. The set of reference signal transmit power levels as well as the relationships between the first and second transmit amplitude values may be known to the communication device and the first network node. Thus, the first network node, which may be an UL TRP, can easily and reliably determine the used reference signal transmit power level by analyzing the relationship between the first and second transmit amplitude values. This reliability is maintained even when the transmission is affected by attenuation and noise, ensuring accurate path loss determination in challenging conditions.

[0041] According to various examples, information based on the path loss may be provided to the communication device, for example by transmitting the information via a second network node, e.g. a macro TRP.

[0042] A further aspect relates to a method for use in a second network node, such as a macro TRP. The method involves obtaining information based on a path loss of a respective signal path from a first network node, e.g. an UL TRP. In this context, the first network node receives a first reference signal and a second reference signal from a communication device along the signal path. The first reference signal is transmitted by the communication device at a first transmit amplitude value and using a first symbol sequence along the signal path. This first transmit amplitude value depends on a reference signal transmit power level included in a predefined set of reference signal transmit power levels. Similarly, the second reference signal is transmitted by the communication device at a second transmit amplitude value and using a second symbol sequence. The second transmit amplitude value also depends on the reference signal transmit power level but is different from the first transmit amplitude value. The first network node determines the reference signal transmit power level based on the first reference signal and the second reference signal. Additionally, the first network node determines the path loss of the signal path based on the receive power level of at least one of the first reference42918W0 SN / NR

[0043] signal and the second reference signal, as well as the reference signal transmit power level. The method further involves providing the information based on the path loss to the communication device.

[0044] This approach offers several advantages. For instance, only a few symbol sequences -one or two - are required to be provided. Furthermore, the first network node can easily and reliably determine the used reference signal transmit power level by considering the relation between the first and second transmit amplitude values. This determination remains robust even if the transmission was attenuated and disturbed by noise.

[0045] According to various examples, the method further comprises providing, to the communication device, configuration information regarding a request to transmit the first and second reference signals, the first symbol sequence, the second symbol sequence, the set of reference signal transmit power levels, time resources for transmitting the first and second reference signals, and / or frequency resources for transmitting the first and second reference signals.

[0046] Thus, resources, symbol sequences and the scheduling of path loss measurements may be controlled by the network, e.g. by or via the second network node.

[0047] Corresponding devices, i.e. a communication device, a first network node and a second network node, including control circuitry for executing such methods are also disclosed.

[0048] It is to be understood that the features mentioned above and those yet to be explained below may be used not only in the respective combinations indicated, but also in other combinations or in isolation without departing from the scope of the invention.

[0049] Brief description of the drawings

[0050] FIG. 1 schematically represents some aspects of a wireless communications system which may be configured to operate in accordance with various examples of the present disclosure.

[0051] FIG. 2 schematically represents some aspects of a radio access technology for a wireless communications system which may be configured to operate in accordance with various examples of the present disclosure.

[0052] FIG. 3 is a schematic diagram of an example infrastructure equipment and communication device which may be configured to operate in accordance with various examples of the present disclosure.

[0053] FIG. 4 schematically illustrates communication devices communicating with infrastructure equipment in accordance with the first type of Uplink CoMP.

[0054] FIG. 5 schematically illustrates communication devices communicating with infrastructure equipment in accordance with the second type of Uplink CoMP.

[0055] FIG. 6 schematically illustrates a wireless communications network in which a communication device performs uplink-only communication with infrastructure equipment in accordance with various examples.

[0056] FIG. 7 schematically illustrates a wireless communications network in which a communication device performs uplink-only communication with a network node in accordance with various examples.42918W0 SN / NR

[0057] FIG. 8 schematically illustrates path loss offset estimated as the difference between power of a reference signal received at an UL TRP and power of a reference signal received at a macro TRP.

[0058] FIG. 9 is a signaling diagram illustrating communication between a communication device, an UL TRP and an macro TRP according to various examples.

[0059] FIG. 10 is a signaling diagram illustrating communication between a communication device, an UL TRP and an macro TRP according to further examples.

[0060] FIG. 11 is a flowchart of a method for use in a communication device according to various examples.

[0061] FIG. 12 is a flowchart of a method for use in a network node, such as an UL TRP, according to various examples.

[0062] FIG. 13 is a flowchart of a method for use in a network node, such as a macro TRP, according to various examples.

[0063] FIG. 14 is a diagram schematically showing results of a first numerical experiment. FIG. 15 is a diagram schematically showing results of a second numerical experiment. FIG. 16 is a diagram schematically showing results of a third numerical experiment. FIG. 17 is a diagram schematically showing results of a fourth numerical experiment. Detailed Description

[0064] Some examples of the present disclosure generally provide for a plurality of circuits or other electrical devices. All references to the circuits and other electrical devices and the functionality provided by each are not intended to be limited to encompassing only what is illustrated and described herein. While particular labels may be assigned to the various circuits or other electrical devices disclosed, such labels are not intended to limit the scope of operation for the circuits and the other electrical devices. Such circuits and other electrical devices may be combined with each other and / or separated in any manner based on the particular type of electrical implementation that is desired. It is recognized that any circuit or other electrical device disclosed herein may include any number of microcontrollers, a central processing unit (CPU), a graphics processor unit (GPU), integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof), and software which co-act with one another to perform operation(s) disclosed herein. In addition, any one or more of the electrical devices may be configured to execute a program code that is embodied in a non-transitory computer readable medium programmed to perform any number of the functions as disclosed.

[0065] In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings. It is to be understood that the following description of embodiments is not to be taken in a limiting sense. The scope of the invention is not intended to be limited by the embodiments described hereinafter or by the drawings, which are taken to be illustrative only.

[0066] 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 skilled42918W0 SN / NR

[0067] 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.

[0068] Wireless communications networks may be implemented according to various radio access technologies. The following describes wireless communications networks operating in accordance with Long Term Evolution (LTE) Advanced Radio Access Technology (4G) principles and New Radio Access Technology (5G) principles, which may be relevant to implementations of determining path loss of a signal path between a communication device and a network node. However, the principles disclosed herein may be applied to any other Radio Access Technology such as 6G.

[0069] In a wireless communications network 100 operating in accordance with LTE principles, as illustrated in FIG. 1, a plurality of base stations 102 may be connected to a core network (CN) 104. Each base station 102 may provide a coverage area 106, alternatively referred to as a "cell", within which data can be communicated to and from communication devices 108. Although each base station 102 may be shown as a single entity, various functions of the base station 102 may be carried out by disparate, inter-connected elements, such as antennas, remote radio heads, amplifiers, and similar components. Collectively, one or more base stations 102 may form a radio access network.

[0070] Data may be transmitted from base stations 102 to communication devices 108 within their respective coverage areas 106 via a radio downlink (DL) 112. Uplink data may be transmitted from communication devices 108 to the base stations 102 via a radio uplink (UL) 110. The core network 104 may route data to and from the communication devices 108 via the respective base stations 102 and may provide functions such as authentication, mobility management, charging, and similar operations. The communication devices 108 may also be referred to as mobile stations, user equipment (UE), user terminals, or mobile radios. Services provided by the core network 104 may include connectivity to the Internet or to external telephony services. The core network 104 may further track the location of the communication devices 108 so that it can efficiently contact the communication devices 108 for transmitting downlink data via a radio downlink 112.

[0071] The base station 102, which is an example of network infrastructure equipment, may also be referred to as network node, transceiver station, transmission and reception point (TRP), Next Generation Node B (gNb), Evolved Node B (eNB), and similar terminology.

[0072] Different terminology may be associated with different generations of wireless communications systems for elements providing broadly comparable functionality. Various embodiments related to determining path loss may be implemented in different generations of wireless communications systems. The use of specific terminology in relation to certain example implementations may not indicate that these implementations are limited to a certain generation of network most associated with that particular terminology.

[0073] In the context of New Radio Access Technology (New RAT) in 5G, as illustrated in FIG.

[0074] 2, a wireless communications network 100 may include a plurality of transmission and reception42918W0 SN / NR

[0075] points (TRPs) 202 connected to distributed control units (DUs) 204 by a connection interface. Each TRP 202 may be arranged to transmit and receive signals via a wireless access interface within a radio frequency bandwidth available to the wireless communications network 100. Within a range for performing radio communications via the wireless access interface, each TRP 202 forms a respective cell 206 of the wireless communications network 100.

[0076] Communication devices 108 within a radio communication range provided by the cells 206 can transmit and receive signals to and from the TRPs 202 via the wireless access interface. Each DU 204 may be connected to a central unit (CU) 208, which may be referred to as a controlling node, via an interface. The CU 208 may be connected to the CN 104, which may contain all other functions required to transmit data for communicating to and from the communication devices 108. The CN 104 may be connected to other networks 210.

[0077] The elements of the wireless communications network 100 may operate similarly to corresponding elements of an LTE network. The TRPs 202 may have functionality corresponding to a base station or eNB of an LTE network. Similarly, the communication devices 108 may have functionality corresponding to communication devices known for operation with an LTE network. Operational aspects of a new RAT network may differ from those known from LTE or other mobile telecommunications standards. However, the CN components, base stations, and communication devices of a new RAT network may be functionally similar to their counterparts in an LTE wireless communications network.

[0078] In terms of broad functionality, the CN 104 connected to the new RAT telecommunications system may correspond to the CN of an LTE system. The respective central units and their associated distributed units / TRPs may provide functionality corresponding to the base stations in an LTE system or future communications system. The term "network infrastructure equipment," "infrastructure equipment," "access node", or "network node" may encompass these elements and more conventional base station type elements of wireless communications systems. Depending on the implementation, responsibility for scheduling transmissions on the radio interface between the respective distributed units and the communication devices may lie within the controlling node / central unit and / or the distributed units / TRPs.

[0079] Each TRP 202 may be surrounded by a coverage area or "cell" 206 within which a communication device 108 may exchange signaling with the CU 208 via one of the distributed units / TRPs associated with the coverage area. Each coverage area 206 may be generated or provided by the TRP 202 associated with that coverage area 206. Each TRP 202 may provide or generate its associated coverage area 206 under the control of the DU 204 and / or CU 208. Alternatively stated, each coverage area 206 may be provided by infrastructure equipment of the wireless communications network 100.

[0080] FIG. 3 illustrates a more detailed view. A TRP 202 may comprise a wireless transmitter (TX) 302, a wireless receiver (RX) 304, and a controller, control circuitry or controlling processor 306 which may operate to control the wireless transmitter 302 and the wireless receiver 304 to transmit and receive radio signals to one or more communication devices 108 within the coverage area 206 formed by the TRP 202. A communication device 108 may include a corresponding wireless transmitter (TX) 310, wireless receiver (RX) 312, and controller or42918W0 SN / NR

[0081] control circuitry 314 configured to control the transmitter 310 and receiver 312 to transmit signals representing uplink data to the wireless communications network 100 via the wireless access interface formed by the TRP 202 and to receive downlink data as signals transmitted by the transmitter 302 and received by the receiver 312.

[0082] The transmitters 302, 310 and receivers 304, 312 may include radio frequency filters and amplifiers as well as signal processing components and devices to transmit and receive radio signals in accordance with, for example, the 5G / NR standard. The controllers 306, 314 may be microprocessors, CPUs, or dedicated chipsets configured to carry out instructions stored on a computer-readable medium, such as a non-volatile memory. Processing steps may be carried out by a microprocessor in conjunction with a random access memory, operating according to instructions stored on a computer-readable medium.

[0083] The TRP 202 may also include a network interface (NW IF) 308 which connects to the DU via a physical interface, providing a communication link for data and signaling traffic from the TRP 202 via the DU 204 and the CU 208 to the core network 104. The interface between the DU 204 and the CU 208 is known as the F1 interface, which can be a physical or logical interface. The F1 interface may operate in accordance with specifications 3GPP TS 38.470 and 3GPP TS 38.473, and may be formed from a fiber optic or other wired or wireless high bandwidth connection. The connection from the TRP 202 to the DU 204 may be via fiber optic. The connection between the TRP 202 and the core network 104 can be generally referred to as a backhaul, which comprises the interface from the network interface 308 of the TRP 202 to the DU 204 and the F1 interface from the DU 204 to the CU 208.

[0084] 3GPP specifications may allow complete flexibility of physical deployment of the network components. For example, a TRP 202 and DU 204 may be deployed in the same location or in different locations. Similarly, a CU 208 and a DU 204 may be deployed in the same location or different locations, and a TRP 202, DU 204, and CU 208 may be deployed in the same location or separately in two or three different locations.

[0085] In the context of determining path loss of a signal path between a communication device 108 and a network node such as the TRP 202, the described network architectures provide the framework within which reference signals may be transmitted and received to facilitate path loss calculations. The communication device 108 may correspond to the communication devices or UEs described above, while the network node 202 may correspond to the base stations 102, TRPs 202, or other elements of the network infrastructure equipment described herein.

[0086] The coverage areas 206 in wireless networks may be symmetric or asymmetric. A symmetric coverage area refers to an area where a communication device 108 can both perform uplink transmissions to and receive downlink transmissions from infrastructure equipment. However, in real deployments, asymmetric coverage areas may also be common, where the downlink coverage area and uplink coverage area do not cover the exact same geographical area.

[0087] Asymmetric coverage may result from differences in transmission power capabilities between infrastructure equipment and communication devices. Infrastructure equipment typically has higher transmission power compared to communication devices, which often leads to larger downlink coverage areas than uplink coverage areas. This asymmetry creates42918W0 SN / NR

[0088] scenarios where a communication device 108 may be able to receive downlink transmissions but unable to establish uplink transmissions because it is located within the downlink coverage area but outside the uplink coverage area.

[0089] The asymmetric coverage may introduce several technical challenges. First, downlink path loss and uplink path loss may differ, potentially requiring different power control methods for uplink and downlink transmissions. Second, uplink and downlink propagation delays may be different, which can affect timing advance mechanisms. Third, channel reciprocity between uplink and downlink channels may not be maintained.

[0090] In dense deployment scenarios, where many communication devices are located close to infrastructure equipment, some of these challenges may be mitigated due to the lower path loss resulting from shorter distances between communication devices and network equipment. The lower path loss may allow for wider bandwidth utilization in uplink transmissions through carrier aggregation while maintaining relatively high power spectral density. However, dense deployments introduce other challenges, such as the need for extensive cell planning to coordinate inter-cell interference and avoid communications collisions.

[0091] One approach to addressing inter-cell interference in dense deployments is Uplink Coordinated Multipoint Operation (CoMP). In Long Term Evolution (LTE) networks, there are two types of Uplink CoMP: coordination between coverage areas and multiple receptions at neighboring coverage areas.

[0092] The first type of Uplink CoMP, coordination between coverage areas, is illustrated in FIG. 4. In the first type of Uplink CoMP, the infrastructure equipment coordinates the transmission of uplink grants to communication devices to prevent collisions. When a first TRP 402 sends an uplink grant to a first User Equipment (UE) 404, a second TRP 406 refrains from sending an uplink grant to a second UE 408, and vice versa. This coordination may be implemented through time scheduling, frequency scheduling, or space multiplexing.

[0093] The second type of Uplink CoMP, multiple receptions at neighboring coverage areas, is illustrated in FIG. 5. In the second type of Uplink CoMP, a communication device 500 transmits uplink data to a first TRP 502 according to an uplink grant, and the same uplink data is received by multiple TRPs 504, 506 connected to the same Distributed Unit (DU) and / or Central Unit (CU). The DU and / or CU can combine the uplink data from all TRPs 502, 504, 506 to improve reception quality. This approach requires short fronthaul delay between TRPs 502, 504, 506 and the DU / CU for effective signal combination.

[0094] While Uplink CoMP can help reduce interference in dense deployments, it may not be easily applied to New Radio (NR) networks, which utilize beamforming for directional transmissions between communication devices and infrastructure equipment.

[0095] To improve uplink coverage in dense deployments, uplink-only access points may be deployed. These access points can be implemented using techniques such as Carrier Aggregation, Dual Connectivity, or Supplementary Uplink. Generally, an uplink-only access point may be configured to provide downlink coverage also, but the downlink coverage functionality of the uplink-only access point may not be used or enabled in the specific scenario, e.g. due to resource or power restrictions.42918W0 SN / NR

[0096] Here, an uplink-only access point, such as a TRP, is referred to as uplink-only TRP, uplink-dedicated TRP, UL-only TRP or simply UL TRP.

[0097] In Carrier Aggregation (CA), communication between devices and infrastructure equipment occur over multiple component carriers. These communication typically involves a Primary Carrier (PCell) and a Secondary Carrier (SCell). The primary carrier manages both user plane data and control plane signaling and remains continuously active. The secondary carrier only handles user plane data and may be activated or deactivated based on data traffic requirements. Carrier Aggregation is configured by the Media Access Control (MAC) layer, requiring the primary and secondary carriers to be controlled by the same scheduler. This approach allows for deploying a primary carrier in one location for both uplink and downlink transmissions, while a secondary carrier may be deployed elsewhere for uplink-only transmissions.

[0098] Dual Connectivity (DC) similarly enables a communication device to connect simultaneously to two different infrastructure equipment, such as two base stations. One base station serves as the Master Cell Group (MCG), and the other serves as the Secondary Cell Group (SCG). The device may communicate with the MCG using one carrier frequency and with the SCG using another carrier frequency. Dual Connectivity is managed by a common Packet Data Convergence Protocol (PDCP) layer entity, but each connection has its own Radio Link Control (RLC), MAC, and Physical (PHY) layer entities. This approach offers greater flexibility, as the communications links can operate independently, and may be used for base stations in the same or different wireless networks.

[0099] While Carrier Aggregation and Dual Connectivity can improve uplink coverage, they increase hardware complexity for communication devices. The devices require multiple transmitters and receivers, and supporting various carrier combinations may be challenging.

[0100] Supplementary Uplink (SUL) represents an alternative approach with potentially lower device complexity. In SUL, a communication device is configured with two separate uplink carriers: a conventional uplink carrier and a supplementary uplink carrier. The communication device cannot transmit on both carriers simultaneously. The supplementary uplink carrier is reserved for uplink transmissions only, with its frequency and bandwidth determined by the network operator's frequency planning. The supplementary uplink carrier typically has a narrower bandwidth but operates at a lower frequency than the conventional uplink carrier. The lower frequency reduces path loss and improves coverage, although the narrower bandwidth limits data capacity.

[0101] In a basic SUL configuration, the conventional and supplementary uplink carriers may be co-located at the same site, meaning the same TRP, DU, and CU manage both carriers. The TRP provides separate coverage areas for conventional downlink transmissions, conventional uplink transmissions, and supplementary uplink transmissions. The supplementary uplink coverage area is typically larger than the conventional uplink coverage area due to the lower path loss associated with the lower frequency.

[0102] For use cases involving heavy uplink traffic, such as video uploading, the basic SUL configuration may be insufficient due to the limited bandwidth of the supplementary uplink carrier. Using a higher frequency for the supplementary carrier can increase bandwidth but also42918W0 SN / NR

[0103] increases path loss and reduces coverage. To address this, multiple TRPs may be deployed as uplink-only access points to extend the supplementary uplink coverage area.

[0104] In such deployments, a communication device located outside the conventional uplink coverage area but within a supplementary uplink coverage area can still perform uplink transmissions through the supplementary uplink TRP. However, this approach introduces new challenges, particularly in NR networks, where uplink and downlink path loss may differ significantly.

[0105] In wireless communications networks, a path through which signals propagate between a communication device and a network node may experience signal attenuation, commonly referred to as path loss. Determining this path loss accurately can be essential for efficient power control and network performance optimization.

[0106] In symmetric coverage scenarios, network nodes, such as base stations or TRPs, may provide both uplink and downlink coverage to communication devices. In these scenarios, uplink path loss may be determined by measuring downlink reference signals transmitted from the network node to the communication device. For instance, a communication device may measure cell specific reference signals (CRS), channel state information reference signals (CSI-RS), or synchronization signal blocks (SS-Blocks) transmitted by the network node in the downlink direction. The communication device may then use these measurements to estimate the path loss in the uplink direction, e.g. based on reciprocity.

[0107] FIG. 6 illustrates an asymmetric coverage scenario. In asymmetric coverage scenarios, a communication device 108 may be located in an area where it can transmit uplink (UL) signals to a network node 602, but cannot receive downlink signals from the same network node 602. Such network nodes 602 may be referred to as uplink-only network nodes or uplink-only TRPs 602. These UL TRPs 602 may provide uplink-only coverage areas 604 that may or may not overlap with conventional uplink coverage areas 608 provided by conventional TRPs 606 providing uplink and downlink coverage. The conventional TRP 606 typically covers a larger areas 608, 610 than the UL TRP 602, i.e., the conventional TRP 606 may cover at least in the DL direction a macro cell 610. Therefore, in the following, the conventional TRP 606 will also referred to as macro TRP 606.

[0108] When a communication device 108 is located within an uplink-only coverage area 604 and outside the conventional uplink coverage area 608, the communication device 108 can perform uplink (UL) transmissions with the UL TRP 602 but cannot perform uplink transmissions with the macro TRP 606. The central unit 208 may manage the control plane signaling to and from the macro TRP 606 and the UL TRP 602. For example, the central unit 208 may be configured to control Radio Resource Control (RRC) signaling. The distributed unit 204 may be configured to control baseband processing and scheduling for the macro TRP 606 and the UL TRP 602.

[0109] As previously explained, in conventional networks, the uplink path loss may be determined by measuring a downlink signal from a TRP to a communication device. However, in asymmetric coverage scenarios, the communication device 108 does not have downlink coverage from the UL TRP 602. As such, no downlink signals from the UL TRP 602 to the42918W0 SN / NR

[0110] communication device 108 can be used to determine the uplink path loss for the signal path from the communication device 108 to the UL TRP 602.

[0111] Attempting to calculate an uplink path loss based on an uplink signal, rather than a downlink signal, may provide additional challenges. For example, there may be generally no stable uplink signal from the communication device 108 to the UL TRP 602 which can be reliably measured to determine the uplink path loss. In other words, there may be no uplink signaling analogous to synchronization signal block (SS-Block) signaling or a channel state information reference signal (CSI-RS) that could be used to determine an uplink path loss. Potential candidate signaling such as demodulation reference signals (DMRS) or sounding reference signals (SRS) are typically transmitted by communication devices at varying power levels, and there is no conventional mechanism for a communication device to inform infrastructure equipment of the transmission power that was used, which is needed in order to calculate the uplink path loss.

[0112] In a first approach, a macro TRP 606, e.g. a base station, with downlink coverage to a communication device 108 may transmit configuration information for a sounding reference signal (SRS) to be transmitted by the communication device 108. The configuration information for the SRS may specify that the communication device 108 is to transmit SRS signaling with a constant transmission power over a predetermined uplink measurement period. A value of the constant transmission power may be configured also by the macro TRP 606 or may be selected by the communication device 108. The communication device 108 may transmit the SRS with the constant transmission power over the predetermined uplink measurement period. The UL TRP 602 may measure the received signal power of the SRS transmission and may report the received signal power to the macro TRP 606. The transmission power of the SRS transmission as used by the communication device 108 may be reported by the communication device 108 to the macro TRP 606 (e.g. via the UL TRP 602 in a power headroom measurement report). The macro TRP 606 may then calculate the uplink path loss as the difference between the transmission power of the SRS transmission and the received signal power of the SRS transmission measured by the UL TRP 602. The macro TRP 606 may transmit the calculated uplink path loss to the communication device 108, which may use the uplink path loss to control its transmission power for subsequent transmissions.

[0113] In a second approach, the path loss is calculated in the communication device 108. As in the first approach, the macro TRP 606 with downlink coverage to the communication device 108 may transmit configuration information for the SRS and the communication device 108 may transmit SRS accordingly. The received signal power of the SRS transmission measured by the UL TRP 602 may be reported to the communication device 108 via the macro TRP 606. The communication device 108 may then calculate the uplink path loss as the difference between the transmission power of its own SRS transmission and the received signal power reported by the macro TRP 606.

[0114] Both approaches may involve the macro TRP 606 transmitting configuration information for the SRS to be transmitted by the communication device 108. The configuration information for the SRS may specify that the communication device is to transmit SRS signaling with a constant transmission power over a predetermined uplink measurement period. The42918W0 SN / NR

[0115] configuration information may in some cases specify the transmission power for the SRS transmissions, or in other cases the macro TRP 606 may separately broadcast a predetermined transmission power at which communication devices 108 are to transmit the SRS transmissions.

[0116] The macro TRP 606 may also transmit to the communication device 108 a message activating an uplink path loss measurement process for the communication device 108, which may initiate the transmission of SRS signaling and power headroom measurements, as well as begin an uplink measurement period. The uplink measurement period may be defined as the time between the activation of SRS measurement and deactivation of the SRS measurement. Alternatively, the uplink measurement period may be defined by a timer value commencing from the SRS measurement activation, where the timer value may be provided with the SRS measurement activation or via RRC signaling, or the timer value may be a pre-defined timer.

[0117] Within the uplink measurement period, the communication device 108 may generate and transmit SRS signaling to the UL TRP 602. The UL TRP 602 may then measure the received signal power of the SRS. Multiple SRS transmissions may be sent by the communication device 108 within the uplink measurement period and the UL TRP 602 may measure the received signal power of each of these SRS transmissions. In alternative arrangements, the communication device 108 may send only a single SRS transmission.

[0118] The approaches described above require the communication device 108 to transmit the SRS transmissions at a constant transmission power within the uplink measurement period.

[0119] Generally, a communication device may need to know the path loss of the signal path to the macro TRP 606 as well as the path loss to the UL TRP 602 because path loss values are used for determining the power control of the UL channels such as PUSCH, PUCCH and SRS towards the macro TRP 606 or UL TRP 602. Obviously, the path loss values for the macro TRP 606 and UL TRP 602 will be different due to their geographical location and channel conditions. Note that the communication device 108 may derive the macro TRP 606 DL path loss value from DL reference signals (i.e., based on legacy specification). The communication device 108 may report the DL path loss value implicitly via "power head room (PHR)" reporting to the macro TRP 606.

[0120] The macro TRP 606 may signal a path loss relating to the UL TRP 602 as a direct path loss value as described above, or the macro TRP 606 may signal the path loss relating to the UL TRP 602 as a path loss offset value to the communication device 108. Hence, after receiving the path loss offset value, the communication device 108 can estimate the UL TRP 602 path loss as the difference between the DL path loss of the path from the macro TRP 606 and the path loss offset.

[0121] A further approach for estimating the path loss value of the UL TRP 602 is to use a single shot uplink SRS transmission on the same resource to both the macro TRP 606 and the UL TRP 602. As shown in FIG. 7, since both macro TRP 606 and UL TRP 602 can receive the same single SRS signal on the same resource, these TRPs 602, 606 can exchange information of the received power of the SRS through backhaul. As illustrated in FIG. 8, the path loss offset 802 may be estimated as the difference between the power 804 of the SRS received at the UL TRP 602 and the power 806 of the SRS received at the macro TRP 606. This calculated path loss offset 802 may be signaled to the communication device 108 so that the communication42918W0 SN / NR

[0122] device 108 can determine the final path loss value for the UL path between the communication device 108 and UL TRP 602. However, in an environment such as Frequency Range 2 (FR2), it may be difficult for the SRS to reach both macro TRP 606 and UL TRP 602 using the same Tx beam and resource, because the signal may not be transmitted in different directions or may not be transmitted in both directions uniformly due to beamforming. Accuracy of the path loss offset calculation may be adversely affected.

[0123] Therefore, a further approach may use an SRS transmission only toward UL TRP 602. The SRS transmission may optionally beamformed. The SRS transmission may include an indication of the transmission power through a selected SRS sequence.

[0124] For example, in New Radio (NR) and 5G, SRS may be based on Zadoff-Chu (ZC) sequences. A length of the sequence may be equal to the number of subcarriers in one physical resource block (PRB). By creating a cyclic shift of the same base sequence, a total of 12 sequences may be further generated from a single PRB of 12 subcarriers. Based on these 12 cyclic shifts, a one-to-one mapping between an uplink SRS power (SRS transmission power) and the cyclic shifts of the SRS sequences may be predefined. Table 1 below provides an example of such a mapping:

[0125] Power level UL SRS power Corresponding cyclic shift of

[0126] the SRS sequence

[0127] 1 1 dBm 0

[0128] 2 2 dBm 1

[0129] 3 3 dBm 2

[0130] 4 4 dBm 3

[0131] 5 6 dBm 4

[0132] 6 8 dBm 5

[0133] 7 10 dBm 6

[0134] 8 12 dBm 7

[0135] 9 14 dBm 8

[0136] 10 16 dBm 9

[0137] 11 18 dBm 10

[0138]

[0139] 12 20 dBm 11

[0140] Table 1: Example of one-to-one mapping between UL SRS power and cyclic shift of SRS

[0141] Using mappings such as those shown in Table 1, a communication device 108 may select a transmission power for the SRS (for example based on a location of the communication device 108) from the predefined list of transmission powers and then generate the SRS sequence based on the corresponding cyclic shift index.

[0142] The UL TRP 602 may then blindly determine the path loss value based on the SRS power level through the selected SRS sequence. This method does not need UL SRS transmission to be received on both macro TRP 606 and UL TRP 602, i.e., the SRS transmission may be only toward UL TRP 602 with beamforming. When receiving the SRS42918W0 SN / NR

[0143] transmission, the UL TRP 602 may determine which cyclic shift the communication device 108 has used for its SRS transmission by correlating different cyclic shifts of the base sequence of length 12, where the cyclic shift with the highest output peak is determined to be the cyclic shift used by the communication device 108 for its uplink SRS transmission. The UL TRP 602 is therefore able to determine the UL SRS transmission power using the mappings between the cyclic shifts and the transmission powers (e.g. from the Table 1 above).

[0144] Similarly as in the approach previously described above, a path loss offset may be calculated based on the macro TRP path loss and the UL TRP path loss of the SRS. This calculated path loss offset may be signaled to the communication device 108 via the macro TRP 606.

[0145] In more detail, assuming that there are P possible SRS power levels available and denoting these by p1,p2, - > PP- For example, P = 12 and the power values pkmay correspond to those defined in the Table 1 above.

[0146] P different symbol sequences such as different SRS sequences may be defined, each one at least of length P. In practice and for simplicity and clarity, in the following a length of P is assumed. These P different SRS sequences may be, in practice, cyclic shifts of a Zadoff-Chu sequence, i.e. versions of a same base sequence with different cyclic shifts. However, a set of arbitrary length-P sequences

[0147]

[0148] ..., <pPmay be used with the only constraint that they need to be mutually orthogonal, i.e., <pk<p{= 0,k r f. Cyclic shifts of any Zadoff-Chu sequence satisfy this property.

[0149] For example, the communication device 108 may be triggered, for example by a network node such as the macro TRP 606, to perform a path loss measurement for the signal path between the communication device 108 and a nearby UL TRP 602. The communication device 108 may determine an appropriate power level for an SRS transmission, for example based on a geographic location of the communication device 108 within the network. The number of available power levels may be 12, i.e. P = 12, as in the Table 1 above.

[0150] As an example, if the communication device 108 uses SRS power level k, then the transmitted signal from the communication device may be expressed as s = p^(pk, i.e. the signal s is transmitted at amplitude ^fp^ and using symbol sequence <>k. That is, the communication device 108 transmits a specific SRS sequence depending on its power level, and there is a one-to-one mapping between power levels and SRS sequences.

[0151] Therefore, this approach is referred to here as one-of-P-SRS-approach.

[0152] The signal y received at the UL TRP 602 may be defined as

[0153] y

[0154]

[0155] = sh + n = h / p^<pk+ n

[0156] where h represents the channel and n is complex Gaussian (white) noise with variance Noper entry. The task of the UL TRP 602 is to estimate the path loss, i.e., | h |2, in the absence of knowledge of k.

[0157] The maximum likelihood (ML) estimator performs a joint estimate over / c, h, i.e., it solves42918W0 SN / NR

[0158] (k, h) = argmaxp(y| / c, h~)

[0159]

[0160] where p(y\k, h.) is the conditional probability of receiving y given k,h. This simplifies to

[0161] (

[0162] vk, h

[0163] 7) = arg axp(y| / c, h)

[0164] k,h ( 2 '

[0165] - 7 «V -0

[0166] 2

[0167] = argmm||y-h7^0fe||

[0168] = arg min \h\2pk- 2Re{hy / p^yii<pk}

[0169]

[0170] This optimization may be solved in a straightforward manner, producing the result:

[0171] rr-j |yH0fc°P‘l

[0172] |h| =. -

[0173]

[0174] VPfc°Pt

[0175] where kopt= arg max |yHfe|.

[0176] k

[0177] The one-of-P-SRS-approach allows for path loss estimation despite the fact that the actually used SRS power level of the communication device 108 is unknown or communicated. The complexity on the UL TRP 602 side is low (a set of P correlators). However, it requires that P SRS sequences are reserved, although only a single one is actually used. This may add a significant overhead to the overall communications system.

[0178] Exemplary embodiments of the present invention are described below. These embodiments may require a smaller number of different symbol sequences. It should be noted that the present description refers in many places to SRS sequences. However, the SRS sequence is only one example of a symbol sequence, and any other type of symbol sequence may be used instead, such as DM RS sequences.

[0179] The following approach requires two time instances for transmitting SRS and a single SRS sequence <p. These two instances may be adjacent in time.

[0180] Therefore, this approach is referred to here as single-SRS-approach.

[0181] During a first time instance, the communication device 108 transmits a first signal S-L = p^(p resulting in a first received signal y = h^fp^tp + n±at the UL TRP 602. The first signalsi = pipP has a first amplitude value ^fp^ and the single SRS sequence <p. During a second time instant, the communication device 108 transmits a second signal s2= qk(p, which produces a second received signal y2= hqk< / ) + n2at the UL TRP 602. The second signal s2= qkcp has a second amplitude value qkand the single SRS sequence <p. Again, twelve power values Pi,p2< -P12 may be defined. The values pkand qkare pre-determined and fully known to the UL TRP 602 (but the value k is, of course, not). For example, pke {1,2,3,4,6,8,10,12,14,16,18,20} (dBm).42918W0 SN / NR

[0182] The definition of qkwill be described in more detail below. Here, it is to be noted that the values of qkmay be positive or negative. Based on the signals y1,y2an ML estimator may be set up:

[0183] (k, h) = argrnaxp(y1,y2| / c, / i)

[0184]

[0185] = argmaxpCy- / c, h)p(y2\k, h)

[0186] k,h

[0187] 2 \ 71 - \ / M'| | / 1172 - |- \ = arg max exp k,h - - Pl - - J =arg™nIbi_MM’II + 11^2 - ^fc^ll2=arg™nl^l2(. Pk + Qfc) - 2Re{ / rA / Kyi10 +

[0188]

[0189] hqky^(p}

[0190] This optimization may be solved, producing the result

[0191] _ IpfcoptyH^ + qfcopty^0|

[0192]

[0193] (pkopt + Qfcopt)

[0194] where

[0195] ,ODtIVKy^ + qfcy^l k2

[0196] = arg max - - - 7- -

[0197]

[0198] k(pk+ qk2)

[0199] FIG. 9 is a signaling diagram illustrating communication between the communication device 108, the UL TRP 602 and the macro TRP 606. The macro TRP 606 may transmit configuration information 902 to the communication device 108. The configuration information 902 may comprise, for example, a request to transmit the first and second reference signals, a request for performing a path loss measurement, a symbol sequence <> to be used by the communication device 108 for the reference signal, a set of reference signal transmission power levels that may be used by the communication device 108 for determining the first transmit amplitude value, a definition for determining the second transmit amplitude value based on the first transmit amplitude value, and time and / or frequency resources for transmitting the first and second reference signals. Transmission of the configuration information 902 or parts thereof may be optional and at least some of the configuration information may be predefined in the network.

[0200] In box 904, the communication device 108 obtains the transmit power levels for transmitting the first and second reference signals. For example, the communication device 108 may determine a first transmit amplitude value, e.g. √p_k, based on a reference signal transmission power level pkincluded in a predefined set of reference signal transmission power levels, for example one of the power levels p₁...p12as discussed above and listed in Table 1. The communication device 108 may select one of the power levels based on its geographic42918W0 SN / NR

[0201] position with respect to the UL TRP 602. In other examples, the communication device 108 may select different reference signal transmission power levels in different attempts for obtaining the path loss, for example in an iterative procedure. In some examples, the communication device 108 may use the reference signal transmission power level as indicated in the configuration 902. Based on the first transmit amplitude value ^fp^, the communication device 108 may determine a second transmit amplitude value qk. Details regarding determination of the first and second transmit amplitude values p^, qkwill be described in more detail below.

[0202] A first reference signal 906, i.e. S-L = p^(p, and a second reference signal 908, i.e. s2= qk<p, are transmitted subsequently from the communication device 108 to the UL TRP 602.

[0203] In box 910, the UL TRP 602 determines the reference signal transmission power level pkthat was a used for the transmission of the first and second reference signals 906, 908. As described above, the UL TRP 602 may determine the value k based on the received first and second reference signals 906, 908, and may use the predefined set of reference signal transmission power levels for determining the reference signal transmission power level pk.

[0204] In box 912, the UL TRP 602 may determine the path loss of the uplink path between the communication device 108 and the UL TRP 602. For example, the UL TRP 602 may determine the difference between the determined reference signal transmission power level pkand the power level of the received first reference signal as the path loss.

[0205] The UL TRP 602 may generate information based on the determined path loss and may transmit this information to the macro TRP 606 (signaling 914), and the macro TRP 606 may forward the information which is based on the path loss to the communication device 108 (signaling 916).

[0206] In box 918, the communication device 108 may use the received path loss to control transmission power of subsequent uplink transmissions.

[0207] The complexity at the UL TRP 602 may be small. In particular, complexity at the UL TRP 602 may be comparable to the complexity at the UL TRP 602 of the one-of-P-SRS-approach that requires to reserve the P SRS sequences, e.g. 12 SRS sequences. However, the number of SRS sequences to be reserved in the single-SRS-approach is reduced to one.

[0208] In the previous example, two SRS transmissions are used at different time instances, both of which are based on the same sequence <p.

[0209] In a further approach, two different SRS sequences and <p2may be used at the same time instance. These two different SRS sequences may be, in practice, cyclic shifts of a Zadoff-Chu sequence, i.e. versions of a same base sequence with different cyclic shifts. However, two arbitrary sequences fa and <p2may be used with the only constraint that they need to be mutually orthogonal, e.g.,

[0210]

[0211] <p2= 0. Cyclic shifts of any Zadoff-Chu sequence satisfy this property.

[0212] Therefore, this approach is referred to here as two-SRS-approach.

[0213] During a single time instance, the communication device 108 transmits a reference signal s

[0214]

[0215] = + Qfc 2. which results in the signal y = h. p^fa + hqk<p2+ n received at the UL TRP 602.

[0216] Due to the orthogonality of the SRS sequences fa and <p2, reference signal s may be considered as two reference signals and transmitted at the same time. fa and qk42918W0 SN / NR

[0217] are transmitted with different amplitudes, i.e. a first amplitude value √p̄k and a second amplitude value qk. Thus, it is clear that this is mathematically equivalent to the single-SRS-approach. Instead of time multiplexing, code multiplexing is used here. The estimator structure remains the same, and may be expressed by

[0218] |√p_k^opt y^H φ₁ + q_k^opt y^H φ₂|

[0219]

[0220] (pkopt + Qfcopt)

[0221] where

[0222] |√p_k y^H φ₁ + q_k y^H φ₂|²

[0223] kopt= arg max

[0224]

[0225] (Pfc + Qk)

[0226] FIG. 10 is a signaling diagram illustrating corresponding communication between the communication device 108, the UL TRP 602 and the macro TRP 606. The macro TRP 606 may transmit configuration information 1002 to the communication device 108. The configuration information 1002 may comprise, for example, a request to transmit the reference signal s, a request for performing a path loss measurement, symbol sequences φ₁ and φ₂ to be used by the communication device 108, a set of reference signal transmission power levels that may be used by the communication device 108 for determining the first transmit amplitude value, a definition for determining the second transmit amplitude value based on the first transmit amplitude value, and a time and frequency resource for transmitting the reference signal s. Transmission of the configuration information 1002 or parts thereof may be optional and at least some of the configuration information may be predefined in the network.

[0227] In box 1004, the communication device 108 obtains the first and second transmit power levels for composing reference signal s. For example, the communication device 108 may determine the first transmit amplitude value, e.g. √p_k, based on a reference signal transmission power level pkincluded in a predefined set of reference signal transmission power levels, for example one of the power levels p₁...p12as discussed above and listed in Table 1. The communication device 108 may select one of the power levels based on its geographic position with respect to the UL TRP 602. In other examples, the communication device 108 may select different reference signal transmission power levels in different attempts for obtaining the path loss, for example in an iterative procedure. Based on the first transmit amplitude value √p_k, the communication device 108 may determine the second transmit amplitude value qk. Details regarding determination of the first and second transmit amplitude values √p_k, qkwill be described in more detail below.

[0228] The thus composed reference signal s 1006 is transmitted from the communication device 108 to the UL TRP 602.

[0229] In box 1010, the UL TRP 602 determines the reference signal transmission power level pkthat was a used for composing the reference signal s 1006. As described above, the UL TRP 602 may determine the value k based on the received reference signal s 1006, and may use the predefined set of reference signal transmission power levels for determining the reference signal transmission power level pk.42918W0 SN / NR

[0230] In box 1012, the UL TRP 602 may determine the path loss of the uplink path between the communication device 108 and the UL TRP 602. For example, the UL TRP 602 may determine the difference between the reference signal transmission power level pkand the power level of the SRS sequences of the received reference signal s as the path loss.

[0231] The UL TRP 602 may deduct information based on the determined path loss and may transmit the information to the macro TRP 606 (signaling 1014), and the macro TRP 606 may forward the information which is based on the path loss to the communication device 108 (signaling 1016).

[0232] In box 1018, the communication device 108 may use the received path loss to control transmission power of subsequent uplink transmissions.

[0233] Again, the complexity at the UL TRP 602 may be small. In particular, complexity at the UL TRP 602 may be comparable to the complexity at the UL TRP 602 of the one-of-P-SRS-approach that requires to reserve the P SRS sequences, e.g. 12 SRS sequences. However, the number of SRS sequences to be reserved is reduced to two.

[0234] Generally, any set of values of pkand qkmay be applied that are feasible within the transmission power constraints of the communication device.

[0235] In some examples, based on numerical experiments, it has been found that pkand qkmay defined such that the differences √p_k - qkare constant for all k, i.e., qk= √p_k + α for a constant α. In numerical experiments, which will be discussed below in more detail, a may be determined by

[0236] α = -2√p₁

[0237] which maximizes |α| under constraint that |qk|2≤ min pk.

[0238] k

[0239] In some further examples, the pairs pkand qkmay be defined based on Grassmannian codebooks. The pairs pkand qkmay be determined as follows.

[0240] If the communication device 108 transmits according to the single-SRS-approach, amplitude ak1may be used during the first SRS transmission, i.e. s₁ = ak1φ, and ak2may be used during the second first SRS transmission, i.e. s2= ak2φ. If the communication device 108 transmits according to the two-SRS-approach, amplitude ak1may be used in connection with the sequence φ₁, and ak2may be used in connection with the sequence φ₂, i.e. s = ak1φ₁ + ak2φ₂. A vector ckmay be defined as ck= [ak1ak2] and may be constrained to power pk, i.e., ckckH= pk. I.e., the amplitude pair ak1ak2may be scaled by or normalized to the power pk. The chordal distance is defined as

[0241] 1

[0242] dch(ck, cℓ) = 1 / √2 ||ckHck- cℓHcℓ||

[0243]

[0244] Then, a codebook maximally spread over the Grassmannian manifold may be constructed by (e.g., numerically) solving42918W0 SN / NR

[0245] {ckopt} = max min dch(ck / √pk, such that ckckH= pk

[0246] The solution to this problem is known for selected values of P, see e.g. the publication R. -A. Pitaval, H. -L. Maattanen, K. Schober, O. Tirkkonen and R. Wichman, " Beamforming Codebooks for Two Transmit Antenna Systems Based on Optimum Grassmannian Packings, " in IEEE Transactions on Information Theory, vol. 57, no. 10, pp. 6591-6602, Oct. 2011, doi: 10.1109 / TIT.2011.2165820. In 3GPP contexts, the value P = 12 is of particular interest as it corresponds to a typical length of an SRS in the frequency domain. For P = 12, the solution to the above optimization is a regular icosahedron and the solution is

[0247] kk / VK} p+ i r P+ i r P+ P- P- P- P- P- G p-J > L-r 2p-J > L-? 4 p-J > L-? 6 p-J > L-? 8 p-J k 0 f 2 f 4 f 6 > 8

[0248] P+J k P+J k P+J k p+J k P+

[0249] where ρ+= √((5+√5) / 10), ρ-= √((5-√5) / 10), ζ = ejπ / 5

[0250]

[0251] r+\ 10r\ 10 ' ’

[0252] The approaches above described, such as the single-SRS-approach and the two-SRS-approach, may be implemented by the following methods for the communication device, the UL TRP and the macro TRP.

[0253] FIG. 11 is a flowchart of a method 1100 for use in a communication device, such as the communication device 108.

[0254] The method 1100 of FIG. 11 can be executed by a communication device, e.g. a user equipment, a mobile terminal, or an Internet of Things (loT) device, operated in a communications network, e.g. a cellular network. For example, the method can be executed by a control circuitry of the communication device. For instance, the method can be executed by a processor upon loading and executing program code that is stored in a memory. For example, the method of FIG. 11 may be executed by a communication device that is located in an access network or a core network of the cellular network.

[0255] In optional step 1102, the communication device 108 may obtain configuration information from the network, for example from the macro TRP 606, cf. the description of signaling 902 and 1002 above.

[0256] In step 1104, the communication device transmits a first reference signal and a second reference signal to the UL TRP 602. The first reference signal may be transmitted at a first transmit amplitude value and using a first symbol sequence. The first transmit amplitude value depends on a reference signal transmission power level included in a predefined set of reference signal transmission power levels. The second reference signal may be transmitted at a second transmit amplitude value and using a second symbol sequence. The second transmit amplitude value depends on the reference signal transmission power level and is different than the first transmit amplitude value.42918W0 SN / NR

[0257] In some examples, the first symbol sequence may be the same as the second symbol sequence. In this case, the first reference signal and the second reference signal may be transmitted in different time resources, i.e., at different time instances, cf. signaling 906 and 908. As an alternative or in addition, in this case, the first reference signal and the second reference signal may be transmitted in different frequency resources, e.g., in different frequency resource blocks (RB).

[0258] In some examples, the first symbol sequence and the second symbol sequence may be different. In this case, the first reference signal and the second reference signal may be transmitted in the same time and frequency resource, cf. signaling 1006. The first and second reference signals may include orthogonal sequences thus providing a code multiplexing.

[0259] In some examples, the first and second transmit amplitude values may be complex values defined based on a Grassmannian codebook. They may differ in magnitude and / or phase. In some other examples, the first and second transmit amplitude values may differ by a predetermined offset value.

[0260] Each pair of first and second transmit amplitude values may be uniquely assigned to one of the reference signal transmission power levels such that the UL TRP 602 that receives the first and second reference signals can determine the reference signal transmission power level based on the combination of the first and second transmit amplitude values even if the first and second reference signals are attenuated along the signal path between the communication device 108 and the UL TRP 602 and noise is added along the signal path.

[0261] Thus, the UL TRP 602 can determine the path loss along the signal path based on the actually received signal power level of the first and / or second reference signals and the reference signal transmission power level derived from the combination of the first and second transmit amplitude values. In some examples, the UL TRP 602 may provide the actually received signal power level of the first and / or second reference signals and the reference signal transmission power level to another network node, for example the macro TRP, which determines the path loss.

[0262] Information based on the path loss may be provided to the communication device 108, e.g. by the UL TRP 602 via the macro TRP 606 or by any other network node.

[0263] In optional step 1106, the communication device 108 obtains information based on the path loss, e.g. from the UL TRP 602 via the macro TRP 606, from the macro TRP 606 itself or from any other network node. In some examples, the information may directly indicate the determined path loss. In further examples, the UL TRP 602, the macro TRP 606 or any other network node may determine that the path loss is too large for the link between the communication device 108 and the UL TRP 602. In this case, the UL TRP 602 would not be used and the communication device 108 may receive in the information a corresponding indication, or the communication device 108 may not receive any information and may consequently not use the UL TRP 602. In some examples, the UL TRP 602, the macro TRP 606 or any other network node may use the information to inform the communication device 108 to lower or increase the reference signal transmit power level, but does not indicate the actually determined path loss. In some further examples, the information may indicate to the communication device 108 that it can start sending data, for example with the reference signal42918W0 SN / NR

[0264] transmit power level used for transmitting the first and second reference signals, meaning that the path loss was acceptable and no power level tunings are needed.

[0265] The communication device 108 may use the obtained information for future transmission configuration. For example, the communication device 108 may select an increased or decreased reference signal transmit power level and may again transmit corresponding first and second reference signals for further path loss estimation. In some examples, the communication device 108 may control its output power for subsequent transmissions, for example payload data transmissions, in step 1108.

[0266] The above method 1100 may be repeated according to a predefined or configured schedule, in response to a trigger from the network, or upon detecting that uplink communication to the UL TRP 602 has failed or exhibits increased error rates.

[0267] FIG. 12 is a flowchart of a method 1200 for use in a network node, such as the UL TRP 602.

[0268] The method 1200 of FIG. 12 can be executed by a node of a cellular network. For example, the method can be executed by a control circuitry of the node of the cellular network. For instance, the method can be executed by a processor upon loading and executing program code that is stored in a memory. For example, the method of FIG. 12 may be executed by a node that is located in an access network

[0269] In step 1202, the UL TRP 602 receives a first reference signal and a second reference signal from the communication device 108, corresponding to step 1104 of the method 1100 described above. The first reference signal may be transmitted at a first transmit amplitude value and the second reference signal may be transmitted at a second transmit amplitude value. As described above, each pair of first and second transmit amplitude values may be uniquely assigned to one of the reference signal transmission power levels such that the UL TRP 602 can determine in step 1204 the reference signal transmission power level based on the combination of the first and second transmit amplitude values without being explicitly informed about which reference signal transmission power level was selected and used by the communication device 108.

[0270] Thus, the UL TRP 602 can determine in step 1206 the path loss along the signal path based on the actually received signal power level of the first and / or second reference signals and the reference signal transmission power level derived from the combination of the first and second transmit amplitude values. For determining the path loss, in some examples the UL TRP 602 may provide the actually received signal power level of the first and / or second reference signals and the reference signal transmission power level to another network node, for example the macro TRP, which then determines the path loss based thereon.

[0271] Anyhow, in optional step 1208 information based on the path loss may be provided to the communication device 108, e.g. by the UL TRP 602 via the macro TRP 606 or by any other network node.

[0272] The information based on the path loss may directly indicate the determined path loss, an indication that the path loss is too large for the link to be used, information to lower or increase the reference signal transmit power level, or an indication for the communication42918W0 SN / NR

[0273] device 108 to start sending data, for example with the reference signal transmit power level used for transmitting the first and second reference signals.

[0274] FIG. 13 is a flowchart of a method 1300 for use in a network node, such as the macro TRP 606.

[0275] The method 1300 of FIG. 13 can be executed by a node of a cellular network. For example, the method can be executed by a control circuitry of the node of the cellular network. For instance, the method can be executed by a processor upon loading and executing program code that is stored in a memory. For example, the method of FIG. 13 may be executed by a node that is located in an access network or a core network of the cellular network. The node may be a management node.

[0276] In optional step 1302, the macro TRP 606 may provide configuration information to the communication device 108, cf. the description of signaling 902 and 1002 above.

[0277] As described above in connection with method 1100 and method 1200, the UL TRP 602 may determine information which is based on a path loss of the signal path between the communication device 108 and the UL TRP 602. In step 1304, the macro TRP 606 may obtain the information from the UL TRP 602. For example, the information may directly indicate the path loss determined by the UL TRP 602. Additionally or as an alternative, the information may indicate the reference signal transmission power level used by the communication device 108 and determined based on the first and second reference signals by the UL TRP 602, and the actually received power level of the first and / or second reference signal as received at the UL TRP 602. In this case, the macro TRP 606 may determine the path loss based on the provided information.

[0278] In step 1306, the macro TRP 606 may provide the information based on the path loss to the communication device 108. For example, the information may directly indicate the determined path loss, an indication that the path loss is too large for the link to be used, information to lower or increase the reference signal transmit power level, or an indication for the communication device 108 to start sending data, for example with the reference signal transmit power level used for transmitting the first and second reference signals.

[0279] From numerical experiments the following results may be achieved.

[0280] In view of the above discussed approaches, in particular the one-of-P-SRS-approach, the single-SRS-approach and the two-SRS-approach, the numerical experiments may be based on the assumption that? = 12 and pke {1,2,3,4,6,8,10,12,14,16,18,20} (dBm). The SNR may be defined as

[0281] pk|h|2

[0282] SNR = —2

[0283] / Vo

[0284] and the root mean square (rms) error may be defined as

[0285] rms = E|log10|h|2- log10|ĥ|2|242918W0 SN / NR

[0286] It is to be noted that the single-SRS-approach and the two-SRS-approach provide essentially the same results in these numerical experiments. The single-SRS-approach and the two-SRS-approach are referred to together as the single / two-SRS-approach in the following.

[0287] In a first numerical experiment k = 3 is selected, i.e. the communication device is using a reference signal transmit power level of 3 dBm. Furthermore, in the first numerical experiment |h|2= -40 dB and a is constant, e.g. α = -2√p₁. A comparison of the estimation errors for the one-of-P-SRS-approach with the single / two-SRS-approach is shown in FIG. 14. The rms error as a function of the SNR is shown for the one-of-P-SRS-approach as graph 1402 and for the single / two-SRS-approach as graph 1404.

[0288] In a second numerical experiment k = 6, i.e., the communication device is using a reference signal transmit power level of 8 dBm. Furthermore, in the second numerical experiment | / i|2= -45 dB and a is constant, e.g. α = -2√p₁. This results in the same received power at the UL TRP as in the first numerical experiment. However, the estimation results differ. A comparison of the estimation errors for the one-of-P-SRS-approach with the single / two-SRS-approach is shown in FIG. 15. The rms error as a function of the SNR is shown for the one-of-P-SRS-approach as graph 1502 and for the single / two-SRS-approach as graph 1504.

[0289] In a third numerical experiment k = 12, i.e., the communication device is using a reference signal transmit power level of 20 dBm. Furthermore, in the third numerical experiment | h |2= -57 dB and a is constant, e.g. α = -2√p₁. This results in the same received power at the UL TRP as in the first and second numerical experiments. A comparison of the estimation errors for the one-of-P-SRS-approach with the single / two -SRS-approach is shown in FIG. 16. The rms error as a function of the SNR is shown for the one-of-P-SRS-approach as graph 1602 and for the single / two-SRS-approach as graph 1604.

[0290] From these three numerical experiments, it may be concluded that the single / two-SRS-approach is superior to the one-of-P-SRS-approach for low signal power levels, while the one-of-P-SRS-approach is superior at large power levels. However, this is a result of the construction of a and by changing this construction the operational point of the single / two-SRS-approach can be adapted.

[0291] For example, the pairs (√p_k, q_k) may be based on Grassmannian codebooks as discussed above. Such construction may improve the single / two-SRS-approach. Results of a corresponding fourth numerical experiment are shown in FIG. 17.

[0292] Note that in FIG. 17 the x-axis is not using the previous normalization with pk. Here, h represents the channel and No the noise variance. The channel is assumed to have |h|2= -40dB. For a reference signal transmit power level of 3 dBm, the rms error as a function of the SNR is shown for the one-of-P-SRS-approach as graph 1702 and for the single / two-SRS-approach as graph 1752. For a reference signal transmit power level of 8 dBm, the rms error as a function of the SNR is shown for the one-of-P-SRS-approach as graph 1704 and for the single / two-SRS-approach as graph 1754. For a reference signal transmit power level of 14 dBm, the rms error as a function of the SNR is shown for the one-of-P-SRS-approach as graph 1706 and for the single / two-SRS-approach as graph 1756. For a reference signal transmit power level of 20 dBm, the rms error as a function of the SNR is shown for the one-of-P-SRS-approach as graph 1708 and for the single / two-SRS-approach as graph 1758.42918W0 SN / NR

[0293] It may be concluded from FIG. 17 that the single / two-SRS-approach is almost as efficient as the one-of-P-SRS-approach despite the fact that the single / two-SRS-approach uses much less SRS resources. In particular, for small rms errors, which are of practical interest, the performance of the single / two-SRS-approach and the one-of-P-SRS-approach coincides.

[0294] Summarizing, at least the following EXAMPLES have been disclosed:

[0295] EXAMPLE 1: A method for use in a communication device, the method comprising: transmitting (1104), at a first transmit amplitude value and using a first symbol sequence, a first reference signal (906, 1006) to a first network node (602) along a respective signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, and

[0296] transmitting (1104), at a second transmit amplitude value and using a second symbol sequence, a second reference signal (908, 1006) to the first network node (602) along the signal path, the second transmit amplitude value depending on the reference signal transmit power level and being different than the first transmit amplitude value.

[0297] EXAMPLE 2: The method of EXAMPLE 1, further comprising:

[0298] upon transmitting (1104) the first reference signal (906, 1006) and the second reference signal (908, 1006), obtaining (1106), from a second network node (606), information based on a path loss (916, 1016) of the signal path.

[0299] EXAMPLE 3: The method of EXAMPLE 1 or EXAMPLE 2, wherein the first symbol sequence is the same as the second symbol sequence, wherein the first reference signal (906) and the second reference signal (908) are transmitted in different time resources.

[0300] EXAMPLE 4: The method of any one of the preceding EXAMPLES, wherein the first symbol sequence is the same as the second symbol sequence, wherein the first reference signal (906) and the second reference signal (908) are transmitted in different frequency resources.

[0301] EXAMPLE 5: The method of EXAMPLE 1 or EXAMPLE 2, wherein the first symbol sequence is different than the second symbol sequence, wherein the first reference signal (1006) and the second reference signal (1006) are transmitted in a same time and frequency resource.

[0302] EXAMPLE 6: The method of EXAMPLE 5, wherein the first symbol sequence is orthogonal to the second symbol sequence.

[0303] EXAMPLE 7: The method of any one of the preceding EXAMPLES, wherein at least one of the first transmit amplitude value and the second transmit amplitude value is a complex value, wherein the first transmit amplitude value and the second transmit amplitude value differ in at least one of magnitude and phase.

[0304] EXAMPLE 8: The method of any one of the preceding EXAMPLES, wherein each reference signal transmit power level of the set of reference signal transmit power levels is associated with a unique pair of a respective first transmit amplitude value and a respective second transmit amplitude value.

[0305] EXAMPLE 9: The method of EXAMPLE 8, wherein each of the unique pairs is based on an associated code vector of a codebook.42918W0 SN / NR

[0306] EXAMPLE 10: The method of EXAMPLE 9, wherein the codebook is a Grassmannian codebook.

[0307] EXAMPLE 11: The method of EXAMPLE 9 or EXAMPLE 10, wherein each of the unique pairs is scaled by the reference signal transmit power level.

[0308] EXAMPLE 12: The method of any one the preceding EXAMPLES, wherein the second transmit amplitude value differs from the first transmit amplitude value by a predetermined offset value.

[0309] EXAMPLE 13: The method of EXAMPLE 12, wherein the predetermined offset value depends on at least one of the set of reference signal transmit power levels.

[0310] EXAMPLE 14: The method of EXAMPLE 12 or EXAMPLE 13, wherein the predetermined offset value depends on a smallest one of the set of reference signal transmit power levels.

[0311] EXAMPLE 15: The method of any one the preceding EXAMPLES, further comprising: obtaining (1102), from the second network node (606), configuration information (902, 1002) regarding at least one of:

[0312] a request to transmit the first and second reference signals (906, 908, 1006), the first symbol sequence,

[0313] the second symbol sequence,

[0314] the set of reference signal transmit power levels,

[0315] time resources for transmitting the first and second reference signals (906, 908, 1006), and

[0316] frequency resources for transmitting the first and second reference signals (906, 908, 1006).

[0317] EXAMPLE 16: A method for use in a first network node, the method comprising: receiving (1202) a first reference signal (906, 1006) from a communication device (108) along a respective signal path, wherein the first reference signal (906, 1006) is transmitted by the communication device (108) at a first transmit amplitude value and using a first symbol sequence, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels,

[0318] receiving (1202) a second reference signal (908, 1006) from the communication device (108) along the signal path, wherein the second reference signal (908, 1006) is transmitted by the communication device (108) at a second transmit amplitude value and a using second symbol sequence, the second transmit amplitude value depending on the reference signal transmit power level and being different from the first transmit amplitude value, determining (1204) the reference signal transmit power level based on the first reference signal (906, 1006) and the second reference signal (908, 1006), and

[0319] determining (1206) a path loss of the signal path based on a receive power level of at least one of the first reference signal (906, 1006) and the second reference signal (908, 1006) and the reference signal transmit power level.

[0320] EXAMPLE 17: The method of EXAMPLE 16, further comprising:

[0321] providing (1208) information based on the path loss (914, 916, 1014, 1016) to the communication device (108) via a second network node (606).

[0322] EXAMPLE 18: A method for use in a second network node, the method comprising:42918W0 SN / NR

[0323] obtaining (1304) information based on a path loss (914, 1014) of a respective signal path from a first network node (602), wherein the first network node (602) receives a first reference signal (906, 1006) and a second reference signal (908, 1006) from a communication device (108) along the signal path, wherein the first reference signal (906, 1006) is transmitted by the communication device (108) at a first transmit amplitude value and using a first symbol sequence along the signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, wherein the second reference signal (908, 1006) is transmitted by the communication device (108) at a second transmit amplitude value and using a second symbol sequence, the second transmit amplitude value depending on the reference signal transmit power level and being different from the first transmit amplitude value, wherein the first network node (602) determines the reference signal transmit power level based on the first reference signal (906, 1006) and the second reference signal (908, 1006), wherein the first network node (602) determines the path loss of the signal path based on a receive power level of at least one of the first reference signal (906, 1006) and the second reference signal (908, 1006) and the reference signal transmit power level, and

[0324] providing (1306) the information based on the path loss (916, 1016) to the communication device (108).

[0325] EXAMPLE 19: The method of EXAMPLE 18, further comprising:

[0326] providing (1302), to the communication device (108), configuration information (902, 1002) regarding at least one of:

[0327] a request to transmit the first and second reference signals (906, 908, 1006), the first symbol sequence,

[0328] the second symbol sequence,

[0329] the set of reference signal transmit power levels,

[0330] time resources for transmitting the first and second reference signals (906, 908, 1006), and

[0331] frequency resources for transmitting the first and second reference signals (906, 908, 1006).

[0332] EXAMPLE 20: A communication device comprising control circuitry (314) configured to: transmit (1104), at a first transmit amplitude value and using a first symbol sequence, a first reference signal (906, 1006) to a first network node (602) along a respective signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, and

[0333] transmit (1104), at a second transmit amplitude value and using a second symbol sequence, a second reference signal (908, 1006) to the first network node (602) along the signal path, the second transmit amplitude value depending on the reference signal transmit power level and being different than the first transmit amplitude value.

[0334] EXAMPLE 21: The communication device of EXAMPLE 20, wherein the control circuitry (314) is configured to execute the method (1100) of any one of EXAMPLES 1 to 15.

[0335] EXAMPLE 22: A first network node comprising control circuitry (306) configured to:42918W0 SN / NR

[0336] receive (1202) a first reference signal (906, 1006) from a communication device (108) along a respective signal path, wherein the first reference signal (906, 1006) is transmitted by the communication device (108) at a first transmit amplitude value and using a first symbol sequence, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels,

[0337] receive (1202) a second reference signal (908, 1006) from the communication device (108) along the signal path, wherein the second reference signal (908, 1006) is transmitted by the communication device (108) at a second transmit amplitude value and a using second symbol sequence, the second transmit amplitude value depending on the reference signal transmit power level and being different from the first transmit amplitude value,

[0338] determine (1204) the reference signal transmit power level based on the first reference signal (906, 1006) and the second reference signal (908, 1006), and

[0339] determine (1206) a path loss of the signal path based on a receive power level of at least one of the first reference signal (906, 1006) and the second reference signal (908, 1006) and the reference signal transmit power level.

[0340] EXAMPLE 23: The first network node of EXAMPLE 22, wherein the control circuitry (306) is configured to execute the method (1200) of EXAMPLE 17.

[0341] EXAMPLE 24: A second network node comprising control circuitry (306) configured to: obtain (1304) information based on a path loss (914, 1014) of a respective signal path from the first network node (602), wherein the first network node (602) receives a first reference signal (906, 1006) and a second reference signal (908, 1006) from a communication device (108) along the signal path, wherein the first reference signal (906, 1006) is transmitted by the communication device (108) at a first transmit amplitude value and using a first symbol sequence along the signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, wherein the second reference signal (908, 1006) is transmitted by the communication device (108) at a second transmit amplitude value and using a second symbol sequence, the second transmit amplitude value depending on the reference signal transmit power level and being different from the first transmit amplitude value, wherein the first network node (602) determines the reference signal transmit power level based on the first reference signal (906, 1006) and the second reference signal (908, 1006), wherein the first network node (602) determines the path loss of the signal path based on a receive power level of at least one of the first reference signal (906, 1006) and the second reference signal (908, 1006) and the reference signal transmit power level, and

[0342] provide (1306) the information based on the path loss (916, 1016) to the communication device (108).

[0343] EXAMPLE 25: The second network node of EXAMPLE 24, wherein the control circuitry (306) is configured to execute the method (1300) of EXAMPLE 19.

Claims

42918W0 SN / NRClaims1. A method for use in a communication device, the method comprising:transmitting, at a first transmit amplitude value and using a first symbol sequence, a first reference signal to a first network node along a respective signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, andtransmitting, at a second transmit amplitude value and using a second symbol sequence, a second reference signal to the first network node along the signal path, the second transmit amplitude value depending on the reference signal transmit power level and being different than the first transmit amplitude value.

2. The method of claim 1, further comprising:upon transmitting the first reference signal and the second reference signal, obtaining, from a second network node, information based on a path loss of the signal path.

3. The method of claim 1, wherein the first symbol sequence is the same as the second symbol sequence, wherein the first reference signal and the second reference signal are transmitted in different time resources.

4. The method of claim 1, wherein the first symbol sequence is the same as the second symbol sequence, wherein the first reference signal and the second reference signal are transmitted in different frequency resources.

5. The method of claim 1, wherein the first symbol sequence is different than the second symbol sequence, wherein the first reference signal and the second reference signal are transmitted in a same time and frequency resource.

6. The method of claim 5, wherein the first symbol sequence is orthogonal to the second symbol sequence.

7. The method of claim 1, wherein at least one of the first transmit amplitude value and the second transmit amplitude value is a complex value, wherein the first transmit amplitude value and the second transmit amplitude value differ in at least one of magnitude and phase.

8. The method of claim 1, wherein each reference signal transmit power level of the set of reference signal transmit power levels is associated with a unique pair of a respective first transmit amplitude value and a respective second transmit amplitude value.

9. The method of claim 8, wherein each of the unique pairs is based on an associated code vector of a codebook.

10. The method of claim 9, wherein the codebook is a Grassmannian codebook.

11. The method of claim 9, wherein each of the unique pairs is scaled by the reference signal transmit power level.

12. The method of claim 1, wherein the second transmit amplitude value differs from the first transmit amplitude value by a predetermined offset value.

13. The method of claim 1, further comprising:obtaining, from the second network node, configuration information regarding at least one of:a request to transmit the first and second reference signals,the first symbol sequence,42918W0 SN / NRthe second symbol sequence,the set of reference signal transmit power levels,time resources for transmitting the first and second reference signals, and frequency resources for transmitting the first and second reference signals.

14. A method for use in a first network node, the method comprising:receiving a first reference signal from a communication device along a respective signal path, wherein the first reference signal is transmitted by the communication device at a first transmit amplitude value and using a first symbol sequence, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels,receiving a second reference signal from the communication device along the signal path, wherein the second reference signal is transmitted by the communication device at a second transmit amplitude value and a using second symbol sequence, the second transmit amplitude value depending on the reference signal transmit power level and being different from the first transmit amplitude value,determining the reference signal transmit power level based on the first reference signal and the second reference signal, anddetermining a path loss of the signal path based on a receive power level of at least one of the first reference signal and the second reference signal and the reference signal transmit power level.

15. The method of claim 14, further comprising:providing information based on the path loss to the communication device via a second network node.

16. A method for use in a second network node, the method comprising:obtaining information based on a path loss of a respective signal path from a first network node, wherein the first network node receives a first reference signal and a second reference signal from a communication device along the signal path, wherein the first reference signal is transmitted by the communication device at a first transmit amplitude value and using a first symbol sequence along the signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, wherein the second reference signal is transmitted by the communication device at a second transmit amplitude value and using a second symbol sequence, the second transmit amplitude value depending on the reference signal transmit power level and being different from the first transmit amplitude value, wherein the first network node determines the reference signal transmit power level based on the first reference signal and the second reference signal, wherein the first network node determines the path loss of the signal path based on a receive power level of at least one of the first reference signal and the second reference signal and the reference signal transmit power level, andproviding the information based on the path loss to the communication device.

17. The method of claim 16, further comprising:providing, to the communication device, configuration information regarding at least one of:42918W0 SN / NRa request to transmit the first and second reference signals,the first symbol sequence,the second symbol sequence,the set of reference signal transmit power levels,time resources for transmitting the first and second reference signals, and frequency resources for transmitting the first and second reference signals.

18. A communication device comprising control circuitry configured to:transmit, at a first transmit amplitude value and using a first symbol sequence, a first reference signal to a first network node along a respective signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, andtransmit, at a second transmit amplitude value and using a second symbol sequence, a second reference signal to the first network node along the signal path, the second transmit amplitude value depending on the reference signal transmit power level and being different than the first transmit amplitude value.

19. A first network node comprising control circuitry configured to:receive a first reference signal from a communication device along a respective signal path, wherein the first reference signal is transmitted by the communication device at a first transmit amplitude value and using a first symbol sequence, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels,receive a second reference signal from the communication device along the signal path, wherein the second reference signal is transmitted by the communication device at a second transmit amplitude value and a using second symbol sequence, the second transmit amplitude value depending on the reference signal transmit power level and being different from the first transmit amplitude value,determine the reference signal transmit power level based on the first reference signal and the second reference signal, anddetermine a path loss of the signal path based on a receive power level of at least one of the first reference signal and the second reference signal and the reference signal transmit power level.

20. A second network node comprising control circuitry configured to:obtain information based on a path loss of a respective signal path from the first network node, wherein the first network node receives a first reference signal and a second reference signal from a communication device along the signal path, wherein the first reference signal is transmitted by the communication device at a first transmit amplitude value and using a first symbol sequence along the signal path, the first transmit amplitude value depending on a reference signal transmit power level included in a predefined set of reference signal transmit power levels, wherein the second reference signal is transmitted by the communication device at a second transmit amplitude value and using a second symbol sequence, the second transmit amplitude value depending on the reference signal transmit power level and being different from the first transmit amplitude value, wherein the first network node determines thereference signal transmit power level based on the first reference signal and the second reference signal, wherein the first network node determines the path loss of the signal path based on a receive power level of at least one of the first reference signal and the second reference signal and the reference signal transmit power level, and- provide the information based on the path loss to the communication device.

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