Wireless communication device and access node and method of operation thereof, and communication system

Abstract

The present application relates to a wireless communication device and an access node and methods of operation thereof and a communication system. A method of operating a wireless communication device, the method comprising receiving at least one downlink control message from a communication network, the at least one downlink control message indicating a frequency density of an uplink reference signal for estimating a radio channel between the wireless communication device and the communication network for coherently decoding a data signal encoding data of an uplink data transmission, the uplink reference signal and the data signal using a same precoding. The method further comprises transmitting the uplink reference signal on the radio channel using a time-frequency resource mapping set in accordance with the frequency density, the time-frequency resource mapping allocating time-frequency resource elements of a time-frequency resource grid of the radio channel to time-frequency resource elements of a plurality of time-frequency resource elements of the uplink reference signal.

Description

Technical Field

[0001] The various examples generally involve enhancing the coverage of wireless communication systems. Specifically, they involve setting time-frequency resource mappings for resource elements allocated to reference signals used for channel estimation. Background Technology

[0002] Wireless communication is widespread. A communication network can connect to multiple wireless communication devices (UEs), thus forming a communication system. Coverage is an important aspect to consider when designing a communication system. This helps ensure quality of service even for UEs located far from the access point of the communication network.

[0003] Take measures to promote enhanced coverage (CE).

[0004] For example, within the 3rd Generation Partnership Project (3GPP), there is a research project called FS_NR_CovEnh in 3GPP Release 17. The goal of this research project is to “study potential coverage enhancement solutions for specific scenarios for both FR1 and FR2.” Summary of the Invention

[0005] Therefore, advanced technologies are needed to increase the coverage of communication systems.

[0006] A method for operating a wireless communication device is provided. The method includes the steps of: receiving at least one downlink control message from a communication network, the at least one downlink control message indicating the frequency density of an uplink reference signal. The uplink reference signal is used to estimate a radio channel between the wireless communication device and the communication network. By means of the radio channel estimation, a data signal encoded for uplink data transmission can be coherently decoded. The uplink reference signal and the data signal use the same precoding. The method further includes the steps of: transmitting the uplink reference signal on the radio channel using a time-frequency resource mapping. Setting the time-frequency resource mapping according to the frequency density. Allocating time-frequency resource elements from a plurality of time-frequency resource elements of the time-frequency resource grid of the radio channel to the uplink reference signal using the time-frequency resource mapping.

[0007] For example, an uplink reference signal can be sent using another time-frequency resource mapping before using a time-frequency resource mapping to send the uplink reference signal.

[0008] It is possible to reduce the frequency density associated with a time-frequency resource map compared to another frequency density associated with another time-frequency resource map. Thus, frequency density adjustment can be achieved.

[0009] The average frequency density can be adjusted.

[0010] When the frequency density is reduced, the minimum frequency spacing between the nearest-neighbor resource components allocated to the reference signal can be increased.

[0011] When adjusting the frequency density, the type of the reference signal (e.g., characterized by the count of the antenna ports used for transmission) can remain fixed.

[0012] When adjusting the frequency density, the time-frequency resource mapping pattern can remain fixed.

[0013] Multiple adjustments to the frequency density can be performed. Multiple adjustments to the frequency density can be performed per radio frame; for example, the frequency density can be adjusted multiple times within 10 ms. The frequency density can be adjusted at least twice within 50 ms or 100 ms.

[0014] A computer program, computer program product, or computer-readable storage medium including program code is provided. The program code can be loaded and executed by control circuitry. Upon loading and execution, the at least one processor performs a method for operating a wireless communication device. The method includes the steps of: receiving at least one downlink control message from a communication network, the at least one downlink control message indicating the frequency density of an uplink reference signal. The uplink reference signal is used to estimate a radio channel between the wireless communication device and the communication network. By means of the radio channel estimation, a data signal encoded for uplink data transmission can be coherently decoded. The uplink reference signal and the data signal use the same precoding. The method further includes the steps of: transmitting the uplink reference signal on the radio channel using a time-frequency resource mapping. Setting the time-frequency resource mapping according to the frequency density. The time-frequency resource mapping allocates time-frequency resource elements from a plurality of time-frequency resource elements of the time-frequency resource grid of the radio channel to the uplink reference signal.

[0015] A wireless communication device includes control circuitry configured to receive at least one downlink control message from a communication network. The downlink control message indicates the frequency density of an uplink reference signal. The uplink reference signal is used to estimate the radio channel between the wireless communication device and the communication network to coherently decode a data signal encoded for uplink data transmission. The uplink reference signal and the data signal use the same precoding. The control circuitry is also configured to transmit the uplink reference signal on the radio channel using a time-frequency resource mapping set according to the frequency density. The time-frequency resource mapping allocates time-frequency resource elements from a plurality of time-frequency resource elements of the time-frequency resource grid of the radio channel to the uplink reference signal.

[0016] A method for operating an access node in a communication network is provided. The method includes the steps of: sending at least one downlink control message to a wireless communication device, the at least one downlink control message indicating the frequency density of an uplink reference signal. The uplink reference signal is used to estimate a radio channel between the wireless communication device and the communication network to coherently decode a data signal encoded for uplink data transmission. The uplink reference signal and the data signal use the same precoding. The method further includes the step of: receiving the uplink reference signal on the radio channel using a time-frequency resource mapping set according to the frequency density, the time-frequency resource mapping allocating time-frequency resource elements from a plurality of time-frequency resource elements of a time-frequency resource grid of the radio channel to the uplink reference signal.

[0017] A computer program, computer program product, or computer-readable storage medium including program code is provided. The program code can be loaded and executed by control circuitry. Upon loading and execution, the at least one processor performs a method for operating an access node of a communication network. The method includes the steps of: sending at least one downlink control message to a wireless communication device, the at least one downlink control message indicating the frequency density of an uplink reference signal. The uplink reference signal is used to estimate a radio channel between the wireless communication device and the communication network to coherently decode a data signal encoded for uplink data transmission. The uplink reference signal and the data signal use the same precoding. The method further includes the step of: receiving the uplink reference signal on the radio channel using a time-frequency resource mapping set according to the frequency density, the time-frequency resource mapping allocating time-frequency resource elements from a plurality of time-frequency resource elements of a time-frequency resource grid of the radio channel to the uplink reference signal.

[0018] An access node for a communication network is provided. The access node includes control circuitry. The control circuitry is configured to send at least one downlink control message to a wireless communication device, the downlink control message indicating the frequency density of an uplink reference signal. The uplink reference signal is used to estimate the radio channel between the wireless communication device and the communication network to coherently decode a data signal encoded for uplink data transmission. The uplink reference signal and the data signal use the same precoding. The control circuitry is further configured to receive the uplink reference signal on the radio channel using a time-frequency resource mapping set according to the frequency density, the time-frequency resource mapping allocating time-frequency resource elements from a plurality of time-frequency resource elements of a time-frequency resource grid that allocates the radio channel to the uplink reference signal.

[0019] A method is provided for operating a wireless communication device in a coverage enhancement mode that includes data transmission. The method includes the step of transmitting a redundant version of the data using a code rate less than 1 / 100, wherein the length of the redundant version is longer than one or more time slots, for example, at least longer than 10 time slots.

[0020] A method is provided for operating a wireless communication device in a coverage enhancement mode that includes data transmission. The method includes the steps of simultaneously transmitting multiple repetitions of a given redundant version in the time domain and offset in the frequency domain.

[0021] It should be understood that, without departing from the scope of the invention, the features mentioned above and those to be described below can be used not only in the corresponding combinations shown, but also in other combinations or in isolation. Attached Figure Description

[0022] Figure 1 Cellular networks and UEs forming communication systems are illustrated schematically according to various examples.

[0023] Figure 2 The time-frequency resource grid of the radio link between the UE and the cellular network is illustrated schematically according to various examples.

[0024] Figure 3 The illustrations illustrate base stations of cellular networks according to various examples.

[0025] Figure 4 The UE is illustrated schematically based on various examples.

[0026] Figure 5 It is a flowchart based on various examples of methods.

[0027] Figure 6 The illustrations illustrate the dynamic adjustment of the frequency density of the reference signal according to various examples.

[0028] Figure 7 Different frequency densities of a reference signal are illustrated schematically according to various examples, which are achieved by different time-frequency resource mappings of resources allocated to the reference signal.

[0029] Figure 8 The illustrations illustrate the allocation of resources for reference signals with orthogonal polarization according to various examples.

[0030] Figure 9 It is a signaling diagram based on various examples.

[0031] Figure 10 It is a flowchart based on various examples of methods.

[0032] Figure 11 The adjustment of the frequency density of the reference signal is illustrated schematically according to various examples.

[0033] Figure 12 The adjustment of the frequency density of the reference signal is illustrated schematically according to various examples. Detailed Implementation

[0034] Some examples of this disclosure typically provide multiple circuits or other electrical devices. All references to circuits and other electrical devices, and the functions they provide, are not intended to limit them to only what is shown and described herein. While specific labels may be assigned to the various circuits or other electrical devices disclosed, such labels are not intended to limit the scope of operation of the circuits and other electrical devices. Such circuits and other electrical devices may be combined and / or separated from each other in any way based on a particular type of desired electrical implementation. It is appreciated that any circuit or other electrical device disclosed herein may include any number of microcontrollers, graphics processing units (GPUs), integrated circuits, memory devices (e.g., FLASH, random access memory (RAM)), read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variations thereof, and software that cooperates with each other to perform the operations disclosed herein. Furthermore, any one or more of the electrical devices may be configured to execute program code embodied in a non-transitory computer-readable medium, which is programmed to perform any number of the disclosed functions.

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood that the following description of the embodiments is not intended to be limiting. The scope of the present invention is not intended to be limited by the embodiments described below or by the accompanying drawings, which are merely illustrative.

[0036] The accompanying drawings are to be considered illustrative, and the elements illustrated are not necessarily shown to scale. Instead, different elements are shown such that their function and general purpose will be apparent to those skilled in the art. Any connection or linkage between functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be achieved through indirect connections or linkages. Connections between components may also be established wirelessly. Functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0037] The following describes wireless communication technology. A corresponding communication system may include one or more access nodes of a communication network, and one or more UEs (User Equipment) that can connect to the communication network via said one or more access nodes. A specific implementation of the communication network is a cellular network with multiple cells, each cell being served by one or more access points implemented as base stations (BS).

[0038] Signal communication from the UE to the cellular network is called uplink (UL) communication, while signal communication from the cellular network to the UE is called downlink (DL) communication. The techniques described in this article can be applied to both UL and DL communication.

[0039] Messages transmitted in the uplink can be called uplink messages, while messages transmitted in the downlink can be called downlink messages.

[0040] For illustrative purposes, various examples are described in the context of UL communication in a 3GPP New Radio (NR) communication system operating in frequency range 2 (FR2). However, similar techniques can be applied to other kinds and types of communication systems and / or DL ​​communication or even peer-to-peer communication (sometimes labeled as sidelink in the context of cellular networks).

[0041] This article describes various techniques for enhancing data transmission coverage in communication systems. This means, for a given data rate, increasing the distance over which transmissions can be reliably received. Conversely, it can also mean, for a given distance, increasing the maximum data rate over which transmissions can be reliably received.

[0042] Table 1 below summarizes some of the technologies for enhancing coverage:

[0043]

[0044]

[0045]

[0046] Table 1: Options for Enhanced Coverage. Technologies A, B, and C all involve RS transmission. Technologies D and E involve CE protection of transmitted data by properly configuring CE parameters.

[0047] The coverage enhancement techniques disclosed herein (particularly according to Table 1) can be applied in combination or independently. The techniques disclosed herein are applicable to the transmission of payload data and / or control data (e.g., layer 3RRC control data), and to transmission along the UL direction and / or along the DL direction. Similarly, they can be applied to a variety of frequency ranges of interest.

[0048] It has been found that UL communication in FR2 has the potential to significantly benefit from the techniques described herein in terms of increased coverage. This is for two reasons. First, according to the well-known Friis transmission equations in free space, it is concluded that path loss increases with the square of the carrier frequency. Therefore, for a given transmit power constraint, the area covered by the wireless communication system shrinks with increasing operating frequency. Second, UEs are typically battery-powered, and therefore UL communication has more limited coverage compared to DL communication (where the BS is connected to an energy grid). However, the reader should recognize that the methods disclosed herein can also be applied to DL communication, as well as sidelink or device-to-device communication. Moreover, the disclosed methods are not limited to FR2 but can also be applied to frequency bands in other frequency ranges, such as frequency range 1 (FR1).

[0049] The various techniques described in this paper rely on channel estimation of the radio channel between the cellular network and the UE. Channel estimation can facilitate coherent decoding of data signals at the receiver, for example, for Orthogonal Frequency Division Multiplexing (OFDM) modulation. Such RS is therefore also referred to as demodulation RS (DM-RS).

[0050] RS (sometimes also called pilot signal) is transmitted via a radio channel (e.g., along UL).

[0051] As a general rule, RS has a well-defined transmission shape, and therefore, the influence of the radio channel on the observed reception shape can be estimated by using the transmission shape as a baseline. For this purpose, one or more reception characteristics, such as amplitude and phase, can be determined at the receiver.

[0052] In some examples, the RS can be pre-coded. That is, spatial filters can be applied to corresponding waveforms using the amplitude and phase relationships between different antenna elements. The RS must be distinguished from the signal that encodes data (data signals) (e.g., control data and / or payload data); because the data is a priori unknown to the receiver, the transmit shape is also not well-defined or known to the receiver. The RS can be UE-specific, i.e., uniquely associated with the UE. This may be due to beamforming and can differ from non-pre-coded RS, such as the Channel Reference Signal (CRS) used in 3GPP 4G.

[0053] As a general rule, RS can be associated with payload transmission, including payload data: RS can help estimate the channel, and then coherent decoding of the data signal encoded by the transmitted data can be performed based on the channel estimate to recover the data. For this purpose, the time-frequency resource mapping from RS to the resource grid of the radio channel, which includes the time-frequency resource element (RE) grid, can allocate REs to RS across the frequency range covered by the data transmission. Specifically, the REs allocated to RS can be interspersed with REs allocated to data transmission. That is, a set of REs can be scheduled by the scheduler (i.e., a scheduling control message can indicate this set of REs), and then the UE can allocate these REs to RS or data signals by selecting REs allocated to RS from this set and REs allocated to data signals from this set. Therefore, REs different from those allocated to data signals can be allocated to RS.

[0054] The time-frequency resources allocated to the RS can be restricted to the frequencies actually used for data transmission. The RS is precoded in the same way as the data transmission, i.e., using the same spatial filters.

[0055] RS can be customized to have small power variations in the frequency domain to allow for accurate estimation of the radio channel across the entire frequency range consumed by data transmission. For this purpose, pseudo-random sequences (e.g., Gold sequences) can be used, where the sequence can be generated across all time-frequency resources within the frequency range.

[0056] An example of RS subjected to the technology described herein is 3GPP NR DM-RS, see, for example, Dahlman, Erik, Stefan Parkvall, and Johan Skold. 5G NR: The next generation wireless access technology. Academic Press, 2018, chapter 9.11.1 DEMODULATION RSS FOR OFDM-BASEDDOWNLINK AND UPLINK.

[0057] DM-RS can be associated with data transmission on the Physical Uplink Shared Channel (PUSCH). DM-RS can also be associated with data transmission on the Physical Uplink Control Channel (PUCCH), or in DL, with data transmission on the Physical Downlink Shared Channel (PDSCH) or Physical Downlink Control Channel (PDCCH).

[0058] According to the various techniques described herein, the time-frequency mapping of the RS to the time-frequency resource grid of the radio channel can be dynamically changed or adjusted (see Table 1, Techniques A and B). This can be network-controlled, for example, using Layer 3, Layer 2, or Layer 1 control signaling. It can also be initiated by the UE.

[0059] As a general rule, various options can be used to dynamically change the time-frequency resource mapping. For example, the time interval between subsequently transmitted RSs can be adjusted. Alternatively, or additionally, the frequency interval between adjacent RSs (e.g., those located in the same transmission time slot) can be adjusted. The frequency density of RSs can be adjusted. The frequency hopping pattern defining the change in time and / or frequency position (e.g., relative to the RB) from RS timing to RS timing can be adjusted. Through such techniques, the time-frequency resource mapping can be customized. In particular, the time-domain density and / or frequency-domain density of RSs can be customized according to the coverage situation. For example, it has been found that for poor coverage situations (e.g., cell edges), different time-domain and / or frequency-domain densities of RSs may be helpful compared to good coverage situations.

[0060] In particular, the frequency density of RS can be obtained by means of the parameter pilotSeparation (expressed as Δ). P This parameter is used for adjustment; it determines the distance between two adjacent REs in the frequency domain and is assigned to the RS (i.e., it defines the frequency spacing). For example, setting Δ... P =2 (representing Rel.16NR 5G used for PUSCH transmission) corresponds to 1 / 2 of the resource element (RE) in the symbol being allocated to PUSCH DM-RS. On the other hand, by setting Δ P =24, only the 24th RE in the symbol is allocated to PUSCH DM-RS. Therefore, not all resource blocks (RBs; each RB includes multiple REs) allocated to the UE for PUSCH transmission will carry PUSCH DM-RS: the frequency density of PUSCH DM-RS will be less than the frequency density per RB. Different RBs can carry different counts of PUSCH DM-RS. Thus, by taking CE measures, a low frequency density of DM-RS can be achieved, which can help extend the coverage where freed resource blocks are used to protect data transmission.

[0061] As can be seen from the above, relying on the proposed frequency density adjustment mechanism for RS, the density of RS belongs to a continuum. RS can be evenly distributed across the covered bandwidth. At one end of the available density spectrum, data transmission of payloads or control data without associated RS can be used, i.e., so-called RS-free transmission. This corresponds to Δ... P =∞ (see Table 1, Technique B). At the other end of the spectrum, ΔP =1, and all REs in the OFDM symbol are assigned to RS.

[0062] As a general rule, one or more other configuration parameters of RS transmission can be kept constant when adjusting frequency density. For example, frequency density can be adjusted when the count of antenna ports used to transmit RS remains constant. Alternatively, or additionally, frequency density can be adjusted when the time-frequency resource mapping pattern of REs allocated to RS remains constant; that is, all frequency spacing encountered within the frequency range is adjusted equally without adding further frequency spacing. By selectively adjusting frequency density (while keeping one or more other configuration parameters of RS transmission constant), significant reconfiguration of operations at the UE and / or BS can be avoided, which facilitates rapid adjustment. Thus, changes in the channel can be tracked, especially when the UE switches from a first setting of CE parameters to a second setting of CE parameters (along with the adjustment of frequency density).

[0063] For illustration, as RS transmission begins according to the time-frequency resource mapping set according to the adjusted frequency density, the UE can switch from a first setting of CE parameters used for uplink data transmission to a second setting of CE parameters used for uplink data transmission. This means that the setting of CE parameters for data transmission can be related to the adjustment of the frequency density (or, generally, any reconfiguration of RS transmission). In short, the reconfiguration of RS transmission occurs for the purpose of CE, i.e., setting the CE parameters in a relevant manner. For example, the switching between CE parameter settings can occur simultaneously with the implementation of the adjusted frequency density; or a predetermined time offset can be considered.

[0064] Table 2 below outlines several CE parameters that can withstand the technology described herein.

[0065]

[0066]

[0067] Table 2: CE parameters can be set, for example, in a manner related to the frequency density of the adjusted RS.

[0068] According to the techniques described herein, the parameter pilotSeparation (or another parameter for RS transmission configuration) is dynamic and can be set via control signaling. For example, the parameter may be part of an L3 Radio Resource Control (RRC) information block for PUSCH-DM-RS configuration. Alternatively, it may also be set via L1 (PHY) and / or L2 (MAC) control signaling. For example, a DL control message may indicate the parameter in explicit or implicit form. For example, a signal may be used to indicate the relative change of the parameter with respect to its current value. This allows for incremental changes. The DL control message may also include an indicator indicating entries in a predetermined codebook and includes multiple candidate values ​​for the parameter. In particular, the codebook may include at least 3 entries, preferably at least 10 entries, and more preferably at least 100 entries. The codebook may be pre-configured, for example, through negotiation between the UE and BS. The codebook is synchronized between the two sides, i.e., it is known to both sides. The codebook may be fixed through standardization.

[0069] As a general rule, various triggers can be conceived to adjust the configuration parameters of RS transmission, such as frequency density. Table 3 below summarizes some of these triggering criteria.

[0070]

[0071] Table 3: Triggering criteria for adjusting RS transmission configurations (e.g., for adjusting frequency density). Combinations of one or more such triggering criteria are possible. A hierarchical structure among triggering criteria can be implemented, for example, using primary and secondary decision criteria.

[0072] For illustration, the UE can determine a current value associated with one or more of these triggering criteria outlined in Table 3, and then send a UL control message to the cellular network, the UL control message including an indicator of the requested frequency density of the RS based on the current value. The UE can also send the current value. Alternatively, the BS can also determine the current value and send a DL control message to the UE indicating the frequency density of the RS.

[0073] Figure 1 The cell NW 100 is illustrated schematically. Figure 1 The example illustrates the NW100 cellular network based on the 3GPP 5G architecture. Details of the 3GPP 5G architecture are described in 3GPP TS 23.501, version 15.3.0 (2017-09). Although... Figure 1The following description and other sections exemplify technologies within the 3GPP 5G framework for cellular NW, but similar technologies can be readily applied to other communication protocols. Examples include 3GPP LTE 4G (e.g., within the MTC or NB-IoT framework) and even non-cellular wireless systems (e.g., IEEE Wi-Fi technology).

[0074] exist Figure 1 In this scenario, UE 101 can connect to cellular NW 100. For example, UE 101 can be one of the following: cellular phone; smartphone; IoT device; MTC device; sensor; actuator; etc. UE 101 has a corresponding identifier 451, such as a user identifier.

[0075] UE 101 can be transmitted via one or more BS 112 (for simplicity, Figure 1 The diagram illustrates only a single BS 112 forming a RAN 111 connected to the core NW (CN) 115 of the cellular NW 100. A radio channel exists between the RAN 111 and the UE 101 (specifically, between one or more BSs 112 in the RAN 111 and the UE 101). This radio channel 114 can be estimated using RS. BS 112 can transmit DL RS, and UE 101 can transmit UL RS.

[0076] Radio channel 114 implements time-frequency resource grid 300, such as Figure 2 As illustrated, Orthogonal Frequency Division Multiplexing (OFDM) is typically used: here, the carrier comprises multiple subcarriers 307. The subcarriers 307 (in the frequency domain) and symbols (in the time domain) then define the time-frequency REs 309 of the time-frequency resource grid 300. Multiple REs 309 can be grouped within RBs 308. Resource scheduling for transmission can be implemented at the granularity of RBs 308. That is, scheduling control messages (e.g., DL control information (DCI) transmitted on the PDCCH) can include indicators indicating one or more RBs. Timing is further constructed using time slots 303, subframes 302 (each subframe comprising two time slots 303), and frames 301 (each frame comprising ten subframes 302).

[0077] For example, for 3GPP NR:

[0078] Time unit Duration Frame 301 10ms Subframe 302 1ms Time slot 303 0.5ms

[0079] Table 4: Time Units of Time-Frequency Resource Grid 300 in 3GPP NR. Note that the concept of a time slot differs slightly in 3GPP 4G Long Term Evolution (LTE) and 5G NR. In 5G, a time slot is the basic unit and has the same meaning as a 4G subframe. Moreover, its duration is proportional to the digital ratio. Conversely, 5G subframes and frames have fixed durations (1m and 10ms), as shown above.

[0080] Different REs 309s or RBs 308s can be assigned to different logical channels of radio channel 114. Examples include: PUCCH, PUSCH, PDSCH, and / or PUSCH.

[0081] Figure 2 The frequency range 306 used for data transmission is also illustrated. Frequency range 306 is a portion of the total bandwidth of radio channel 114, but, as a general rule, frequency range 306 may be equal to the total bandwidth.

[0082] Refer again Figure 1 CN 115 includes a User Plane (UP) 191 and a Control Plane (CP) 192. Application data is typically routed via UP 191. For this purpose, a UP Function (UPF) 121 is provided. UPF 121 enables router functionality. Payload data can pass through one or more UPF 121s. Figure 1 In this scenario, UPF 121 acts as a gateway to data NW 180 (e.g., the Internet or a local NW). Payload data can be transmitted between UE 101 and one or more servers on data NW 180.

[0083] The cellular NW 100 also includes a mobility control node, which is implemented by the Access and Mobility Management Function (AMF) 131 and the Session Management Function (SMF) 132. These entities consume and generate control data.

[0084] Cellular NW 100 also includes: Policy Control Function (PCF) 133; Application Function (AF) 134; NW Slice Selection Function (NSSF) 134; Authentication Server Function (AUSF) 136; and Unified Data Management (UDM) 137. Figure 1 The protocol reference points N1 to N22 between these nodes are also illustrated.

[0085] AMF 131 provides one or more of the following functions: connection management, sometimes referred to as registration management; NAS termination for communication between CN 115 and UE 101; connection management; reachability management; mobility management; access authentication; and connection authorization.

[0086] If the corresponding UE 101 is operating in connected mode, the SMF 132 establishes a data connection 189 for data transmission. Data connection 189 is characterized by UE subscription information hosted by the UDM 137. To track the current mode of UE 101, the AMF 131 sets UE 101 to either CM-CONNECTED or CM-IDLE. During CM-CONNECTED, a non-access stratum (NAS) connection is maintained between UE 101 and the AMF 131.

[0087] SMF 132 provides one or more of the following functions: session management including session establishment, modification, and release; bearer establishment of the UP bearer between RAN 111 and UPF 121; UPF selection and control; traffic redirection configuration; roaming functions; termination of at least some NAS messages; etc. Thus, both AMF 131 and SMF 132 implement the CP mobility management required to support mobile UEs.

[0088] Data connection 189 is established between UE 101 and RAN 111, and is established on UP 191 of CN 115 and toward DN 180. For example, a connection to the Internet or another packet data NW can be established. The payload data for data transmission can be transmitted along data connection 189. To establish data connection 189, i.e., to connect to cellular NW 100, the corresponding UE 101 can perform a random access (RACH) procedure, for example, in response to receiving a paging signal or in response to UL data initiated by a UE being buffered for transmission. This establishes at least the RAN portion of data connection 189. A server on DN 180 can host the service of transmitting payload data via data connection 189. Data connection 189 may include one or more bearers, such as dedicated bearers or default bearers. Data connection 189 can be defined at the RRC layer (e.g., typically Layer 3 in the Layer 2 OSI model).

[0089] Figure 3BS 112 is illustrated schematically. BS 112 includes control circuitry 1122, implemented, for example, by one or more processors. Control circuitry 1122 can load program code from memory 1123. BS 112 can communicate over radio channel 114 using interface 1125. When executing the loaded program code, control circuitry 1122 can perform techniques described herein, such as: configuring data transmission to or from UE 101, for example, by determining one or more CE parameters; configuring RS transmissions to or from the UE, for example, by configuring time-frequency resource mapping of REs allocated to RS; configuring RS transmissions (Table 1, Technique AC), for example, by sending one or more DL control messages to UE 101; determining the frequency density of RS; controlling interface 1125 to decode UL transmissions, for example, performing blind decoding or coherent decoding based on channel estimation determined based on the received characteristics of the received UL RS (e.g., received amplitude and / or received phase); etc.

[0090] Figure 4 UE 101 is illustrated schematically. UE 101 includes control circuitry 1012, implemented, for example, by one or more processors. Control circuitry 1012 can load program code from memory 1013. UE 101 can communicate over radio channel 114 using interface 1015. When executing the loaded program code, control circuitry 1012 can perform techniques described herein, such as: transmitting UL RS for estimating radio channel 114; monitoring DL RS; transmitting and / or receiving (transmitting) RS according to a time-frequency resource mapping set according to a frequency density that can be controlled by the network; setting the time-frequency resource mapping according to DL control messages received from cellular network 100 (e.g., according to separately indicated frequency spacing between adjacent RSs); suspending UL RS transmission, for example, in response to detecting a corresponding trigger criterion associated with UL data transmission; etc.

[0091] Figure 5 It is a flowchart based on various examples of methods. For example, Figure 5 The method can be executed by the UE, for example, by the UE's control circuitry when loading program code from the UE's local memory. The following will combine execution by UE 101. Figure 5 To illustrate the method in a specific scenario. Figure 5 The technology.

[0092] Figure 5 The optional boxes are marked with dashed lines.

[0093] In optional box 3001, the UE sends a UL control message to the cellular network. The UL control message is associated with DM-RS transmission.

[0094] DM-RS is used to estimate the radio channel between the UE and the cellular network. Based on this channel estimation, the BS of the cellular network can coherently decode the signals received from the UE. DM-RS can be associated with data transmission (e.g., payload data and / or control data (e.g., on PUSCH or PUCCH)), i.e., scattered REs allocated to data transmission, and / or using the same precoding as the data signal used to transmit data including data transmission.

[0095] UL control messages fulfill requests for DM-RS configuration, such as requests to adjust or change the DM-RS configuration. For example, they may request the addition of repeated adjustments. For instance, a UL control message may request adjustment of one or more UL DM-RS features.

[0096] For example, the one or more ULDM-RS characteristics may be selected from the group consisting of: frequency density of the DM-RS; time density of the DM-RS; frequency hopping mode; parameters of time-frequency resource mapping allocated to the REs of the DM-RS; frequency domain spacing allocated between DM-RSs of adjacent REs in the frequency domain; time domain spacing allocated between DM-RSs of adjacent REs in the time domain; count of DM-RS per RB; polarization used for the UL DM-RS; suspension of UL DM-RS transmission; etc.

[0097] The UE can determine the requested DM-RS configuration. One or more decision criteria may be considered, such as those outlined in Table 3 above.

[0098] In other examples, the configuration can be determined at the cellular network level. Reconfiguration can be triggered at the cellular network level. At least in such scenarios, execution box 3001 is unnecessary.

[0099] Next, in box 3002, DL control information is received from the communication network. The DL control message indicates the UL DM-RS configuration. For example, the DL control message may indicate the adjustment of one or more UL DM-RS characteristics (for example, as described above in conjunction with box 3001). One or more corresponding settings of the DM-RS configuration may be indicated, for example, by one or more corresponding indicators.

[0100] Then, in box 3003, DM-RS is transmitted according to the configuration indicated by the DL control message received in box 3002. For example, considering a scenario where the DL control message received in box 3002 indicates the frequency density of the UL DM-RS, then in box 3003, UL RS can be transmitted on the radio channel using a time-frequency resource mapping set according to the frequency density.

[0101] like Figure 5As illustrated, execution block 3003 can be associated with execution block 3030. Therefore, as the ULRS transmission begins in block 3003, in block 3030, there is a switching between different settings of the CE parameters for the UL data transmission associated with the DM-RS. Example CE parameters have been outlined above in Table 2.

[0102] The related execution of frame 3003 together with frame 3030 can refer to, for example, in frame 3030, executing frame 3003 when a switch in CE parameter settings is detected; or vice versa, i.e., switching the CE parameters at frame 3030 when frame 3003 begins to transmit ULRS using the configuration of frame 3002. This related execution can also refer to the UE receiving a corresponding command from the cellular network to execute frame 3003 simultaneously or at least time-aligned in frame 3030. Related execution can also refer to the setting of CE parameters in frame 3030 being determined based on the configuration of the DM-RS received in frame 3002 and used for transmission in frame 3030. For example, the UE can determine the new setting of CE parameters based on the configuration of the DM-RS (e.g., frequency density) using a predetermined correlation. This correlation “translates” the configuration of the DM-RS into the setting of the CE parameters. Table 5 below illustrates an example implementation of the correlation as a mapping table:

[0103] entry Set repeat count Frequency density A Low high B middle middle C high Low

[0104] Table 5: Example implementation of the correlation between CE parameters (here: duplicate count of redundant version retransmission) and DM-RS transmission configuration (here: frequency density).

[0105] By using this related implementation of box 3003 together with box 3030, the CE for data transmission can be facilitated through the (re)configuration of DM-RS transmission.

[0106] In box 3004, check whether DM-RS-free operation should begin. If so, in box 3005, pause DM-RS transmission.

[0107] For example, in box 3004, it can be checked whether a predetermined CE transmission mode for UL data transmission associated with DM-RS is enabled. If yes, box 3005 can be executed. This is marked as no DM-RS operation.

[0108] For illustration, a predetermined CE transmission mode can be characterized by the bit rate of the data transmitted with DM-RS, which is below a predetermined threshold. Typically, the predetermined threshold can be 1 / 100 or even less. Alternatively, the CE transmission mode can be characterized by the repetition of a given redundant version of the data. More specifically, the CE transmission mode can be characterized by a redundancy repetition count above a predetermined threshold. Typically, the predetermined threshold can be 1000 or even 5000 or more.

[0109] CE transmission mode can be characterized by combining other standards with the CE parameter definitions outlined in Table 2.

[0110] Once it is determined in box 3006 that no DM-RS operation should be stopped, the DM-RS transmission can be restarted in a further iteration of box 3003.

[0111] For example, in box 3006, it can be checked, for instance, whether a predetermined amount of time since execution 3004 has expired, based on a timer initialized during execution 3004. This amount of time can be measured in subframes or frames, for example, after at least ten subframes, etc.

[0112] In box 3006, one or more other criteria can be checked, such as whether a DL control message has been received from the cellular NW, or whether the scheduled CE transmission mode (discussed in conjunction with box 3004) has ended.

[0113] Therefore, as will be understood based on the above, Figure 5 This method helps to dynamically adjust the characteristics of ULDM-RS, especially the frequency density of ULDM-RS. Combined with... Figure 6 Details regarding this dynamic adjustment are illustrated.

[0114] Figure 6 The temporal evolution of frequency densities 401 to 404 in the DM-RS is illustrated schematically. As illustrated, different frequency densities 401 to 404 are implemented periodically. For example, the adjustment from frequency density 401 to a lower frequency density 402 is triggered by a DL control message 411 received at UE 101. Similarly, the adjustment from frequency density 402 to frequency density 403 is triggered by another DL control message 412. For example, the other DL control message 412 may indicate an incremental or relative change, i.e., the difference between frequency density 402 and frequency density 403. In contrast, DL control message 411 may indicate an entry for a specified frequency density 402 in a predetermined codebook. These are merely examples.

[0115] As a general rule, it is not required that all adjustments of frequency densities 401-402 be immediately responded to the reception of the corresponding DL control messages 411-412 (although this is a possibility). For example, a corresponding timer can be defined and initialized upon receiving DL control message 412, and adjustments from frequency densities 403 to 404 can be triggered when that time expires. Other triggering criteria for performing frequency density adjustments are conceivable, such as changes in the channel quality of radio channel 114; that is, once the channel quality meets predetermined criteria, previously configured adjustments can be performed.

[0116] As a general rule, downlink control messages can parameterize one or more triggering criteria to perform (re)configuration of ULDM-RS transmission, and the UE can then monitor whether the one or more triggering criteria are met (e.g., SINR, SNR, path loss, fading, coherence bandwidth, or any triggering criteria typically specified in Table 3).

[0117] The above has already explained aspects related to dynamically adjusting the frequency density of RS. Next, we will combine... Figure 7 The details of implementing different frequency densities of RS are discussed.

[0118] Figure 7 The illustration schematically illustrates the aspect of allocating RE 311 (selected from all available RE 309s in the time-frequency resource grid 300) to RS (DM-RS RE 311). That is, Figure 7 An example of a time-frequency resource mapping 390 from DM-RE 311 to resource grid 300 for multiple RBs 308 is illustrated. In the illustrated example, the time-frequency resource mapping 390 is defined for subframe 304 and can be repeated from the subframe. A front-loaded scenario is shown, where all DM-RS RE 311 are located in the first slot 303 of subframe 304. Another option is a back-loaded DM-RS, or a DM-RS located inside a symbol relative to the associated data allocation.

[0119] "Preload" can refer to RSs being transmitted before their auxiliary data transmission. That is, depending on the pilot type, in the first (and possibly) second symbol of the time slot or UL data allocation. Additional pilots may also appear in later symbols.

[0120] Other REs not allocated to the DM-RS can be allocated to data transmission. For example, all remaining REs in subframe 304 can be allocated to data transmission, or at least 80% or at least 50%. Some REs can be allocated to other RSs, etc. RB 308, which includes at least one DM-RS RE 311, may also not include any other signals, such as OFDM uplinks used for DFT extension.

[0121] As a general rule, allocation can be relative to a reference subcarrier that acts as the baseline. The reference subcarrier can be network-configured. This will be used for absolute allocation in DM-RS RE 311. (e.g.) Figure 7 The exemplified RBA, DM-RS RE 311, essentially extends across the entire frequency range of data transmission 306.

[0122] exist Figure 7 In the examples, different frequency spacings 321 to 323 are illustrated for different frequency densities 401-403 (for example, see the parameter Δ discussed above). P ).like Figure 7 As illustrated, for the lower frequency densities 401 to 403, the frequency spacing 321 to 323 increases.

[0123] As a general rule, and as Figure 7 As illustrated, the frequency spacing can be approximately constant across the entire frequency range 306. For example, the variation can be less than 80% or less than 20%.

[0124] exist Figure 7 In the examples, frequency density 401 is 2 per RB 308, frequency density 402 is 0.5 per RB 308, and frequency density 403 is two-thirds per RB 308 (excluding RB 308 of the second time slot of subframe 304, which is not typically used for DM-RS transmission). These are just examples.

[0125] For the time-frequency resource mapping 390 that implements frequency density 402 and frequency density 403, some RBs 308 do not include REs 309 allocated to DM-RS, while other RBs 308 include one or two REs 311 (again, only those time slots carrying any DM-RS are considered), that is, different RBs 308 of the first time slot include different counts of DM-RS.

[0126] Figure 8 An aspect of allocating RE 312 and RE 313 (selected from all available RE 309s in the time-frequency resource grid 300) to RS (DM-RS RE 312 and DM-RS RE 313) is illustrated schematically.

[0127] In the illustrative example, DM-RS RE 312 is assigned to the DM-RS with 0° polarization, and DM-RS RE 313 is assigned to the DM-RS with 90° polarization (defined relative to each other, i.e., orthogonal). It will be appreciated that the frequency domain density of the two subgroups of the demodulation reference signal (i.e., 0° and 90° polarization) is the same, i.e., one-third per RB 308. This is just an example. As a general rule, the frequency domain density can be different for the two subgroups, for example, to track the dominant polarization of radio channel 114. As a general rule, the frequency density of the two subgroups can be configured separately (see...). Figure 5 (See box 3002). Typically, polarization does not need to be exactly at 90° and 0° along the absolute direction. It can be appreciated that any two independent polarizations (such as any two orthogonal polarizations) will apply equally.

[0128] Figure 9 This is a signaling diagram of the communication between UE 101 and BS 112.

[0129] In optional box 5001, UE 101 determines the requested frequency density of DM-RS 31 repeatedly transmitted by UE 101 to BS 112 (for clarity, Figure 9 In the diagram, the arrow indicating DM-RS 31 is not directly connected to BS 112; however, BS 112 attempts to receive these DM-RS 31 signals.

[0130] This determination can be based on at least one of the following: the coherence bandwidth of radio channel 114, the reception quality of the signal received on radio channel 114, or the coverage enhancement parameters used for UL data transmission (see Table 2).

[0131] Then, optionally, at 5002, UL control message 4001 is sent to BS 112. UL control message 4001 indicates the requested frequency density of DM-RS 31.

[0132] Therefore, boxes 5001 and 5002 correspond to Figure 5 Box 3001.

[0133] In box 5003, BS 112 determines the frequency density to be used for DM-RS 31. This may be based on at least one of the following: the coherence bandwidth of radio channel 114, the reception quality of the signal transmitted on radio channel 114, the CE parameters used for UL data transmission (see Table 2), or (where applicable) UL control message 4001.

[0134] In box 5003, BS 112 can also determine the settings of the CE parameters (see Table 2) to switch to payload data transmission 4012 when using the most recently determined frequency density. The frequency density can be determined based on the determined settings, and vice versa.

[0135] In block 5004, BS 112 sends a DL control message 4002 indicating the frequency density of DM-RS 31 as determined in block 5003. Therefore, DL control message 4002 can implement one of the DL control messages 411 and 412 discussed above.

[0136] For illustration, DL control message 4002 can be an L2 or L1 control message. This facilitates rapid adjustment of frequency density without requiring a complete reconfiguration of the DM-RS transmission (e.g., on L3).

[0137] As a general rule, DL control message 4002 can be sent multiple times within a frame, for example, once per subframe. This allows for dynamic adjustment of the frequency spacing over short timescales, thus providing flexibility in tracking the status of radio channel 114. Fixed resource allocations, for example, available on the PDCCH, can exist to adjust the frequency spacing (or another configuration parameter for DM-RS transmission).

[0138] 5004 therefore corresponds to Figure 5 Box 3002.

[0139] DL control message 4002 (or another DL control message) Figure 9 (not shown in the text) can also indicate any specific setting of the CE parameters.

[0140] like Figure 9 As illustrated, upon receiving DL control message 4001, frequency density 402 is implemented after frequency density 401 (see [link]). Figure 5 (Frame 3003).

[0141] At 5005, BS 112 sends UL scheduling permission 4011 to UE 101. The UL scheduling permission, for example, indicates a set of REs 309 in the time-frequency resource grid 300 by indicating one or more RBs 308. UE 101 can then select from the indicated set of REs time-frequency REs 311 to RE 313 to allocate to DM-RS 31, and other time-frequency REs to allocate to payload signals encoding payload data for payload data transmission 4012 performed at 5006, 5007, and 5008. This selection can be based on a time-frequency resource map 390, which is set according to the frequency density indicated by DL control message 4002.

[0142] Payload data transmission 4012 can be configured according to the CE parameters most recently determined in 5003 as described above in some examples (see above). Figure 5 (frame 3030).

[0143] At 5009, BS 112 determines that DM-RS-free operation should begin, and at 5010, BS 112 sends the corresponding control message 4003 to notify UE 101 (see [link]). Figure 5 (box 3004). Therefore, zero frequency density 409 is enabled and DM-RS 31 is not transmitted (i.e., Δ P =∞). The BS 112 performs blind decoding of the data signal encoded by the payload data 4012 transmitted in 5011 and 5012.

[0144] In box 5013 (see also) Figure 5 (Box 3006) Determines to stop DM-RS operation, and resends DM-RS 31 when sending the corresponding DL control message 4004 to enable DM-RS.

[0145] Figure 10 It is a flowchart based on various examples of methods. For example, Figure 10 The method can be executed by the BS. For example, Figure 10 The method can be implemented by the control circuit 1122 of the BS 112 of the cellular network 100.

[0146] exist Figure 10 The dashed line in the middle represents the selectable box.

[0147] In optional box 3101, a UL control message indicating the requested adjustment used for transmitting DM-RS configuration is received from the UE. Box 3101 corresponds to box 3001.

[0148] In box 3102, one or more control messages sent in the DL are used to determine the configuration of the DM-RS, which is then provided to the UE. Box 3102 corresponds to box 3002.

[0149] Then, in box 3103, DM-RS is received according to the configuration provided in box 3102. Box 3103 can be associated with box 3130, where the CE parameter settings are switched. The relevant details have been explained above in conjunction with boxes 3003 and 3030.

[0150] In box 3104, check whether to suspend DM-RS transmission, as explained above in conjunction with box 3004. If yes, in box 3105, BS blind decoding includes the data signal of the data being transmitted, because there is no DM-RS transmitted by the UE.

[0151] The determination in box 3104 can be based on the enabling of the CE transmission mode used for data transmission, as explained above in conjunction with box 3004.

[0152] Then, in box 3106, it can be determined that the DM-RS transmission is reconnected.

[0153] Next, we will combine Figure 11 and Figure 12 This will explain the details regarding adjusting the frequency density of RS.

[0154] Figure 11 The illustrations illustrate various aspects of changing the frequency density of RS by altering the frequency spacing between adjacent RS 31. Figure 11 This is a histogram illustrating the various frequency spacings across a frequency range of 306 for RS 31. (Example:) Figure 11 The complete bar in the diagram illustrates only a single (relatively small) frequency spacing 371 (here, the size of frequency spacing 371 is the size of RB 308), meaning that all RS 31 are uniformly distributed across frequency range 306. There are no clusters of RS 31 with small frequency spacings in the frequency domain. It can be said that the spectral frequency spacing has only a single contribution. The histogram of this frequency spacing defines the pattern of the time-frequency resource mapping 390, as... Figure 11 exemplified at the bottom of .

[0155] Frequency density adjustment is achieved by uniformly scaling the frequency spacing 371 across the frequency range 306 to the frequency spacing 372. The mode of the time-frequency resource map 390 is preserved because no new contributions are added to the spectrum, so all that is observed is a shift of a single, unique contribution.

[0156] Therefore, as a general rule, frequency density adjustment can be achieved by changing one or more frequency spacings between adjacent RS 31 without changing the count of frequency spacings across frequency range 306. The pattern of time-frequency resource mapping 390 can remain unaffected by frequency density adjustment. This simplifies adjustment, thereby allowing for reduced adjustment complexity; consequently, adjustment can be performed quickly, for example, multiple times within a frame. This enables accurate tracking of radio channel 114.

[0157] Figure 12 Different scenarios are illustrated. Here, the frequency spacing count is altered by forming clusters of tightly packed RSs with a spacing of 374, introducing a new contribution to the frequency spacing spectrum. The mode of the time-frequency resource mapping 390 is changed by adjustment. Furthermore, the average frequency density is reduced (from 1 per RB 308 to 0.5 per RB 308).

[0158] For example, 3GPP NR Type 1 and Type 2 DM-RS are characterized by variations in the time-frequency resource mapping (RTRP) pattern 390. See Dahlman, Erik, Stefan Parkvall, and Johan Skold. 5G NR: The next generation wireless access technology. Academic Press, 2018; FIG. 9.18 vs. FIG. 9.19. For Type 1, a new cluster of RS is introduced. The switch between DM-RS Type 1 and Type 2 is relatively complex and slow (typically requiring RRC reconfiguration), and thus limited in its applicability to tracking changes on the radio channel and adjusting the frequency density of DM-RS transmissions or other parameters along with changes in CE parameter settings, as explained above.

[0159] As a general rule, one or more configuration parameters for RS transmission can be changed by specifying a new type (e.g., type 3DM-RS). Changes can also be specified for type 1 or type 2 DM-RS in 3GPP NR.

[0160] In summary, at least the following examples have been described above:

[0161] Example 1: A method for controlling the density of RS used for demodulation-associated payload data transmission in UL and / or DL, the method comprising the steps of: signaling a BS (optionally) from a UE to request a desired density of pilot signals; and signaling a UE from the BS to configure the density of RS (in the frequency domain).

[0162] Example 2: According to the method of Example 1, wherein the density depends on one or more of the following factors: (in this specification, this is implemented, i.e., transparent)

[0163] a. Coherent bandwidth of the radio channel estimated by the UE and / or BS in the DL and / or in the UL (can be zero, i.e., no DM RS required);

[0164] b. Signal-to-noise ratio (SNR) or signal-to-interference-to-noise ratio (SINR) estimated by the BS or UE in the DL and / or in the UL;

[0165] c. The desired or actual bit rate of associated payload data transmission in the DL and / or UL.

[0166] Example 3: Following the method of any of the preceding examples, where the RS is divided into two groups, each using a different transmit polarization, so that the associated data transmission can track the polarization of the radio channel. Example 3 can be implemented in one of the following ways:

[0167] a. By using feedback signaling indicating the observed polarization of the transmitted RS. In the example (note that steps i. and v. are typically performed simultaneously):

[0168] i. The UE sends a PUSCH DM-RS to the BS.

[0169] ii.BS estimates the polarization of the received PUSCH DM-RS (per correlation bandwidth, which depends on the DM RS density in the frequency domain).

[0170] iii. The BS uses a signal to inform the UE of the estimated optimal polarization direction.

[0171] iv. The UE aligns subsequent PUSCH data transmissions based on the polarization feedback from the BS.

[0172] v.UE sends more PUSCH DM-RS to BS, etc.

[0173] b. In contrast to the above scenarios, RS is transmitted in the opposite direction. For example, the UE can use a properly designed PDSCH DM-RS (or CSI-RS) to estimate the appropriate polarization for PUSCH transmission and associated PUSH DM-RS transmission. In this case, a feedback channel is not required.

[0174] Example 4: Ultra-low code rates for reliable data transmission of payload data and / or control data (e.g., Layer 3 RRC control data). For example, code rates below 1 / 100 can be signaled to a UE located at the cell edge. Transmissions with ultra-low code rates can span multiple time slots.

[0175] Example 5: Blind decoding of payload data transmission, i.e., without associated RS. For example, blind decoding can be signaled for the transmission of payload data and / or control data with extremely low bit rates. (No DM RS)

[0176] Example 6: Repeated payload data transmission in the frequency domain using the same or different redundant versions. The associated RS can be sent in all repetitions, in some repetitions, or not in any repetitions.

[0177] In addition, at least the following examples have been described above.

[0178] Although the invention has been shown and described with reference to specific preferred embodiments, equivalents and modifications will occur to those skilled in the art upon reading and understanding this specification. The invention includes all such equivalents and modifications and is limited only by the scope of the appended claims.

[0179] For illustration, various scenarios have already been discussed above in the context of UL RS being transmitted from the UE to the communication network. Similar techniques can be easily applied to DL RS. For example, the frequency density of the DL RS can be signaled to the UE, and then the UE can monitor the DL RS using a time-frequency resource mapping set according to the frequency mapping.

[0180] For further illustration, various scenarios have been discussed in the context of the logic used to determine frequency density (or another configuration for RS transmission) residing at the network. In other scenarios, this logic may reside at the UE.

[0181] For further illustration, various examples have been described in conjunction with DM-RS, but similar techniques can be implemented using other kinds and types of RS.

[0182] To illustrate further, although various examples of adjusting the frequency density of the reference signal have been described, in other scenarios, other configuration parameters of the reference signal transmission configuration can be adjusted, such as frequency spacing (to keep the average frequency density constant), polarization used, etc.

Claims

1. A method for operating a wireless communication device, the method comprising the following steps: - Receive at least one downlink control message from a communication network, the downlink control message indicating the frequency density of an uplink reference signal used to estimate the radio channel between the wireless communication device and the communication network, to coherently decode data signals encoded for uplink data transmission, the uplink reference signal and the data signal using the same precoding. - Using a time-frequency resource mapping set according to the frequency density, the uplink reference signal is transmitted on the radio channel, and the time-frequency resource mapping allocates time-frequency resource elements from a plurality of time-frequency resource elements of the time-frequency resource grid of the radio channel to the uplink reference signal; as well as - When the predetermined coverage enhancement transmission mode for the uplink data transmission is enabled, the transmission of the uplink reference signal is suspended.

2. The method according to claim 1, in, Using scheduling control messages that include indicators pointing to one or more resource blocks, additional time-frequency resource elements from the plurality of time-frequency resource elements of the time-frequency resource grid are allocated to the data signal. Each resource block includes multiple time-frequency resource elements of the time-frequency resource grid. The time-frequency resource elements allocated to the uplink reference signal are different from the additional time-frequency resource elements. The frequency density is no greater than the frequency density of one per resource block.

3. The method according to claim 1 or 2, in, Using scheduling control messages that include indicators pointing to one or more resource blocks, further time-frequency resource elements from the plurality of time-frequency resource elements of the time-frequency resource grid are allocated to the data signal, each resource block comprising the plurality of time-frequency resource elements of the time-frequency resource grid. Specifically, the time-frequency resource mapping assigns different counts of the time-frequency resource elements to the uplink reference signal for adjacent resource blocks.

4. The method according to claim 1, further comprising the following steps: - As the transmission of the uplink reference signal begins according to the time-frequency resource mapping set according to the frequency density, the first setting of the coverage enhancement parameters used for the uplink data transmission is switched to a second setting of the coverage enhancement parameters used for the uplink data transmission.

5. The method according to claim 4, in, The coverage enhancement parameters include the transmission power of the data signal.

6. The method according to claim 4 or 5, in, The coverage enhancement parameters include at least one of the redundancy count of the data in the time domain and / or frequency domain of the uplink data transmission, and the bit rate of the data in the uplink data transmission.

7. The method according to claim 6, wherein, The second setting of the bit rate is less than 1 / 100.

8. The method according to claim 6, wherein, The length of a given redundant version of the data transmitted using the second setting of the bit rate in the uplink data transmission is longer than at least two time slots.

9. The method according to claim 4 or 5, in, The second setting of the coverage enhancement parameters is determined based on a predetermined correlation between multiple frequency densities and multiple settings of the coverage enhancement parameters, or The at least one downlink control message indicates the second setting of the coverage enhancement parameter used for the uplink data transmission.

10. The method according to claim 1, further comprising the following step: in, Assign some other time-frequency resource elements from the plurality of time-frequency resource elements of the time-frequency resource grid to the data signal. The method further includes the following steps: - Receive from the communication network a scheduling control message indicating a set of time-frequency resource elements, and - Select the time-frequency resource element and the other time-frequency resource elements from the set of time-frequency resource elements.

11. The method according to claim 1, further comprising the following step: - Send at least one uplink control message to the communication network, the at least one uplink control message indicating the requested frequency density of the uplink reference signal.

12. The method according to claim 11, further comprising the following step: The requested frequency density is determined based on at least one of the following: the coherence bandwidth of the radio channel, the reception quality of the uplink and / or downlink signals transmitted on the radio channel, and the coverage enhancement parameters used for the uplink data transmission.

13. The method according to claim 1, in, The uplink reference signal includes a first uplink reference signal with a first polarization and a second uplink reference signal with a second polarization, wherein the first polarization and the second polarization are orthogonal. The at least one downlink control message indicates at least one of the first frequency density of the first uplink reference signal and the second frequency density of the second uplink reference signal.

14. The method according to claim 1, in, At least one of the at least one downlink control messages indicates the relative change in the frequency density of the uplink reference signal.

15. The method according to claim 1, in, At least one of the at least one downlink control messages indicates the frequency density by selecting from a predetermined codebook, which includes at least three entries.

16. The method according to claim 1, in, The predetermined coverage enhancement transmission mode is characterized by the data having a bit rate below a predetermined threshold.

17. The method according to claim 16, wherein, The predetermined threshold is 1 / 100.

18. The method according to claim 16, wherein, The length of a given redundant version of the data transmitted using the second setting of the bit rate in the uplink data transmission is longer than at least two time slots.

19. The method according to claim 1 or 16, in, The predetermined coverage enhancement transmission mode is characterized by the count of repetitions of a given redundant version of the data exceeding a predetermined threshold, wherein the repetitions of the given redundant version are in the time domain and / or frequency domain.

20. A method for operating an access node of a communication network, the method comprising the following steps: - Send at least one downlink control message to the wireless communication device, the downlink control message indicating the frequency density of an uplink reference signal used to estimate the radio channel between the wireless communication device and the communication network, to coherently decode data signals encoded for uplink data transmission, the uplink reference signal and the data signal using the same precoding. - Using a time-frequency resource mapping set according to the frequency density, the uplink reference signal is received on the radio channel, wherein the time-frequency resource mapping allocates time-frequency resource elements from a plurality of time-frequency resource elements of the time-frequency resource grid of the radio channel to the uplink reference signal. The frequency density is determined based on at least one of the coherent bandwidth of the radio channel, the reception quality of the uplink signal and / or downlink signal transmitted on the radio channel, the coverage enhancement parameters used for the uplink data transmission, and the uplink control message received from the wireless communication device, wherein the uplink control message indicates a requested frequency density of the uplink reference signal.

21. The method according to claim 20, - The settings of the coverage enhancement parameters used for the uplink data transmission are determined in a manner related to the determined frequency density.

22. A wireless communication device, the wireless communication device comprising a control circuit, the control circuit being configured to: - Receive at least one downlink control message from a communication network, the downlink control message indicating the frequency density of an uplink reference signal used to estimate the radio channel between the wireless communication device and the communication network, to coherently decode data signals encoded for uplink data transmission, the uplink reference signal and the data signal using the same precoding. - Using a time-frequency resource mapping set according to the frequency density, the uplink reference signal is transmitted on the radio channel, the time-frequency resource mapping allocating time-frequency resource elements from a plurality of time-frequency resource elements of the radio channel's time-frequency resource grid to the uplink reference signal; and - When the predetermined coverage enhancement transmission mode for the uplink data transmission is enabled, the transmission of the uplink reference signal is suspended.

23. The wireless communication device according to claim 22, wherein, The control circuit is configured to perform the method according to any one of claims 1 to 19.

24. An access node for a communication network, the access node comprising control circuitry configured to: - Send at least one downlink control message to the wireless communication device, the downlink control message indicating the frequency density of an uplink reference signal used to estimate the radio channel between the wireless communication device and the communication network, to coherently decode data signals encoded for uplink data transmission, the uplink reference signal and the data signal using the same precoding. - Using a time-frequency resource mapping set according to the frequency density, the uplink reference signal is received on the radio channel, the time-frequency resource mapping allocating time-frequency resource elements from a plurality of time-frequency resource elements of the radio channel's time-frequency resource grid to the uplink reference signal, and The frequency density is determined based on at least one of the coherent bandwidth of the radio channel, the reception quality of the uplink signal and / or downlink signal transmitted on the radio channel, the coverage enhancement parameters used for the uplink data transmission, and the uplink control message received from the wireless communication device, wherein the uplink control message indicates a requested frequency density of the uplink reference signal.

25. The access node according to claim 24, wherein, The control circuit is configured to perform the method according to any one of claims 20 to 21.

26. A communication system, the communication system comprising: The wireless communication device according to claim 22 or 23, and the access node according to claim 24 or 25.

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