Physical channel with demodulation reference signal (DMRS) based fine synchronization restrictions

Abstract

A wireless device (22) that is configured to communicate with a network node (16) is provided The wireless device (22) is configured to: receive at least one rule for performing synchronization using a demodulation reference signal, DM-RS, receive a first transmission on a physical downlink shared channel, PDSCH, that includes a first DM-RS, 5 and perform synchronization on the first DM-RS according to the at least one rule being satisfied with respect to the first transmission.

Description

[0001] PHYSICAL CHANNEL WITH DEMODULATION REFERENCE SIGNAL (DM- RS) BASED FINE SYNCHRONIZATION RESTRICTIONS

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to wireless communications, and in particular, to wireless device synchronization.

[0004] BACKGROUND

[0005] The Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile user equipments (UE), as well as communication between network nodes and between UEs. The 3GPP is also developing standards for Sixth Generation (6G) wireless communication networks.

[0006] In particular, 5G or NR supports a diverse set of use cases and a diverse set of deployment scenarios. NR uses CP-OFDM (Cyclic Prefix Orthogonal Frequency Division Multiplexing) in the downlink (i.e., from a network node, gNB, eNB, or base station, to a user equipment or UE) and both CP-OFDM and DFT-spread OFDM (DFT-S-OFDM) in the uplink (i.e., from UE to gNB). In the time domain, NR downlink and uplink physical resources are organized into equally-sized subframes of 1ms each. A subframe is further divided into multiple slots of equal duration.

[0007] The slot length depends on subcarrier spacing. For subcarrier spacing of A = 13kHz, there is only one slot per subframe and each slot always consists of 14 OFDM symbols, irrespectively of the subcarrier spacing.

[0008] Typical data scheduling in 3GPP NR is done on a per slot basis. An example is shown in FIG. 1 where the first two symbols contain physical downlink control channel (PDCCH) and the remaining 12 symbols contains physical data channel (PDCH), either a PDSCH ( physical downlink data channel) or PUSCH (physical uplink data channel).

[0009] Different subcarrier spacing values are supported in NR. The supported subcarrier spacing values (also referred to as different numerologies) are given by

[0010] A / = (15 x 2akHz where a is a non-negative integer. A = 13kHz is the basic subcarrier spacing that is also used in LTE. The slot durations at different subcarrier spacings are shown in Table 1. Table 1

[0011] In the frequency domain physical resource definition, a system bandwidth is divided into resource blocks (RBs) in which each RB corresponds to 12 contiguous subcarriers. The common RBs (CRB)are numbered starting with 0 from one end of the system bandwidth. The UE is configured with one or up to four bandwidth part (BWPs) which may be a subset of the RBs supported on a carrier. Hence, a BWP may start at a CRB larger than zero. All configured BWPs have a common reference, the CRB 0. Hence, a UE can be configured with a narrow BWP (e.g., 10 MHz) and a wide BWP (e.g., 100 MHz), but only one BWP can be active for the UE at a given point in time. The physical RB (PRB) are numbered from 0 to N-l within a BWP (but the O:th PRB may thus be the K:th CRB where K>0).

[0012] The basic NR physical time-frequency resource grid is illustrated in FIG. 2, where only one resource block (RB) within a 14-symbol slot is shown. One OFDM subcarrier during one OFDM symbol interval forms one resource element (RE).

[0013] Downlink transmissions can be dynamically scheduled, i.e., in each slot the gNB transmits downlink control information (DCI) over PDCCH about which UE data is to be transmitted to and which RBs in the current downlink slot the data is transmitted on. PDCCH is typically transmitted in the first one or two OFDM symbols in each slot in NR. The UE data are carried on PDSCH. A UE first detects and decodes PDCCH and if the decoding is successful, the UE then decodes the corresponding PDSCH based on the decoded control information in the PDCCH.

[0014] Uplink data transmission can also be dynamically scheduled using PDCCH. Similar to downlink, a UE first decodes uplink grants in PDCCH and then transmits data over PUSCH based the decoded control information in the uplink grant such as modulation order, coding rate, uplink resource allocation, etc.

[0015] QCL and TCI states

[0016] Several signals can be transmitted from the same base station antenna from different antenna ports. These signals can have the same large-scale properties, for instance, in terms of Doppler shift / spread, average delay spread, or average delay, when measured at the receiver. These antenna ports are then referred to as being quasi colocated (QCL).

[0017] The network, such as via a network node, can then signal to the UE that two antenna ports are QCL. If the UE knows that two antenna ports are QCL with respect to a certain parameter (e.g., Doppler spread), the UE can estimate that parameter based on a reference signal transmitted by one of the antenna ports and use that estimate when receiving another reference signal or physical channel the other antenna port. Typically, the first antenna port is represented by a measurement reference signal such as CSI-RS (known as source RS) and the second antenna port is a demodulation reference signal (DMRS) (known as target RS) for PDSCH or PDCCH reception.

[0018] For instance, if antenna ports A and B are QCL with respect to average delay, the UE can estimate the average delay from the signal received from antenna port A (known as the source reference signal (RS)) and assume that the signal received from antenna port B (target RS) has the same average delay. This is useful for demodulation since the UE can know beforehand the properties of the channel when trying to measure the channel utilizing the DMRS, which may help the UE in, for instance, selecting an appropriate channel estimation filter.

[0019] Information about what assumptions can be made regarding QCL is signaled to the UE from the network. In NR, four types of QCL relations between a transmitted source RS and transmitted target RS were defined:

[0020] • Type A: {Doppler shift, Doppler spread, average delay, delay spread}

[0021] • Type B: {Doppler shift, Doppler spread}

[0022] • Type C: {average delay, Doppler shift}

[0023] • Type D: {Spatial Rx parameter}

[0024] QCL type D was introduced to facilitate beam management with analog beamforming and is known as spatial QCL. There is currently no strict definition of spatial QCL, but the understanding is that if two transmitted antenna ports are spatially QCL, the UE can use the same Rx beam to receive them. This is helpful for a UE that uses analog beamforming to receive signals, since the UE needs to adjust its RX beam in some direction prior to receiving a certain signal. If the UE knows that the signal is spatially QCL with some other signal it has received earlier, then it can safely use the same RX beam to also receive this signal. Note that for beam management, the discussion, in part, has revolved around QCL Type D, but it is also necessary to convey a Type A QCL relation for the RSs to the UE, so that it can estimate all the relevant large-scale parameters.

[0025] Typically, this is achieved by configuring the UE by radio resource configuration (RRC) signaling with a CSI-RS for tracking (Tracking Reference Signal (TRS)) for time / frequency offset estimation. To be able to use any QCL reference, the UE would have to receive it with a sufficiently good SINR (e.g., SINR above a threshold). In many cases, this means that the TRS has to be transmitted in a suitable beam to a certain UE.

[0026] To introduce dynamics in beam and transmission point (TRP) selection, the UE can be configured through RRC signalling with ALTCI states, where AT is up to 128 in frequency range 2 (FR2) for the purpose of PDSCH reception and up to 8 in FR1, depending on UE capability.

[0027] Each TCI state contains QCL information, i.e., one or two source DL RSs, each source RS associated with a QCL type. For example, a TCI state contains a pair of reference signals, each associated with a QCL type, e.g., two different CSI-RSs {CSI-RS 1, CSI-RS2} is configured in the TCI state as {qcl-Typel,qcl-Type2} = {Type A, Type D}. It indicates that the UE can derive Doppler shift, Doppler spread, average delay, delay spread from CSI-RS 1, and Spatial Rx parameter (i.e., the RX beam to use) from CSI-RS2.

[0028] Each of the states in the list of TCI states can be interpreted as a list of AL possible beams transmitted from the network or a list of AL possible TRPs used by the network to communicate with the UE. The AL TCI states can also be interpreted as a combination of one or multiple beams transmitted from one or multiple TRPs.

[0029] A first list of available TCI states is configured for PDSCH, and a second list of TCI states is configured for PDCCH. Each TCI state contains a pointer, known as TCI State ID, which points to the TCI state. The network then activates via MAC CE one TCI state for PDCCH (i.e., provides a TCI for PDCCH) and up to eight active TCI states for PDSCH. The number of active TCI states the UE support is a UE capability but the maximum is 8.

[0030] Each configured TCI state contains parameters for the quasi co-location associations between source reference signals (CSI-RS or SS / PBCH) and target reference signals (e.g., PDSCH / PDCCH DMRS ports). TCI states are also used to convey QCL information for the reception of CSI-RS.

[0031] Assume a UE is configured with 4 active TCI states (from a list of a total of 64 configured TCI states). Hence, 60 TCI states are inactive for this particular UE (but some may be active for another UE) and the UE need not be prepared to have large scale parameters estimated for those. However, the UE continuously tracks and updates the large scale parameters for the 4 active TCI states by measurements and analysis of the source RSs indicated by each TCI state. When scheduling a PDSCH to a UE, the DCI contains a pointer to one active TCI. The UE then knows which large scale parameter estimate to use when performing PDSCH DMRS channel estimation and thus PDSCH demodulation.

[0032] However, the reception of PDSCH without fine synchronization is not without issues as some reference signals used for fine synchronization are not guaranteed to be received by the UE, among other issues.

[0033] SUMMARY

[0034] The present disclosure allows the network to perform downlink shared channel transmission from any (synchronized) Transmission Reception Point (TRP) since the transmission is received without an associated periodic TRS or periodic SSB. Hence, the UE receives the transmission in a self-contained manner, i.e., by performing synchronization without using the periodic TRS.

[0035] For example, some embodiments described herein advantageously provide methods, systems, and apparatuses for user equipment synchronization based on synchronization restrictions (e.g., T>X, T<=X, as described below and herein).

[0036] For a UE receiving a PDSCH scheduled by the network (NW) and / or network node, a time T is defined as the time from the previous reception of a DM-RS with fine sync properties. In addition, a threshold time X is defined

[0037] • If T>X, then the UE can expect that the scheduled PDSCH DM-RS from the NW to the UE is restricted (e.g., in time duration, frequency bandwidth, etc.) to have fine sync properties so that the UE may perform fine synchronization using the DM-RS

[0038] « If T<=X, then the UE receives the scheduled PDSCH without any restrictions. According to one aspect of the present disclosure, a method performed by a wireless device that is configured to communicate with a network node is provided. At least one rule for performing synchronization using a demodulation reference signal, DM- RS is received. A first transmission on a physical downlink shared channel, PDSCH, that includes a first DM-RS is received. Synchronization is performed on the first DM-RS according to the at least one rule being satisfied with respect to the first transmission. According to one or more embodiments of this aspect, a time duration is compared to at least one threshold defined by the at least one rule; and the time duration corresponds to a time from receiving a previous transmission on the PDSCH to receiving the first transmission on the PDSCH.

[0039] According to one or more embodiments of this aspect, the at least one rule is based on a PDSCH rank.

[0040] According to one or more embodiments of this aspect, a PDSCH rank of 1 results in the at least one rule not being satisfied; a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity; and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

[0041] According to one or more embodiments of this aspect, the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device local oscillator.

[0042] According to one or more embodiments of this aspect, the PDSCH is scheduled according to at least one rule that is configured to control instances of fine synchronization at the wireless device.

[0043] According to one or more embodiments of this aspect, the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

[0044] According to one or more embodiments of this aspect, wireless device capability associated with the at least one rule is indicated to the network node.

[0045] According to one or more embodiments of this aspect, the wireless device is changed from a first transmission reception point, TRP, to a second TRP; the first transmission on the PDSCH being received from the second TRP; and the synchronization being a re-synchronization for receiving subsequent transmissions in a PDSCH from the second TRP.

[0046] According to one or more embodiments of this aspect, downlink control information, DCI, that indicates for the wireless device to re-synchronize is received.

[0047] According to one or more embodiments of this aspect, synchronization is performed on the first DM-RS by using additional time to acquire the synchronization, where the additional time is associated with one or both of: additional time to produce feedback signaling; and additional time to provide received data to higher layers.

[0048] According to one or more embodiments of this aspect, a second transmission is received on the PDSCH that includes second DM-RS; and synchronization is not performed on the second DM-RS as the at least one rule is not satisfied with respect to the second transmission.

[0049] According to another aspect of the present disclosure, a wireless device that is configured to communicate with a network node is provided. The wireless device is configured to: receive at least one rule for performing synchronization using a demodulation reference signal, DM-RS, receive a first transmission on a physical downlink shared channel, PDSCH, that includes a first DM-RS, and perform synchronization on the first DM-RS according to the at least one rule being satisfied with respect to the first transmission.

[0050] According to one or more embodiments of this aspect, the wireless device is further configured to compare a time duration to at least one threshold defined by the at least one rule, and the time duration corresponds to a time from receiving a previous transmission on the PDSCH to receiving the first transmission on the PDSCH.

[0051] According to one or more embodiments of this aspect, the at least one rule is based on a PDSCH rank.

[0052] According to one or more embodiments of this aspect, a PDSCH rank of 1 results in the at least one rule not being satisfied, a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity, and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

[0053] According to one or more embodiments of this aspect, the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device local oscillator.

[0054] According to one or more embodiments of this aspect, the PDSCH is scheduled according to at least one rule that is configured to control instances of fine synchronization at the wireless device.

[0055] According to one or more embodiments of this aspect, the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

[0056] According to one or more embodiments of this aspect, the wireless device is further configured to indicate, to the network node, wireless device capability associated with the at least one rule.

[0057] According to one or more embodiments of this aspect, the wireless device is changed from a first transmission reception point, TRP, to a second TRP; the first transmission on the PDSCH being received from the second TRP; and the synchronization being a re-synchronization for receiving subsequent transmissions in a PDSCH from the second TRP.

[0058] According to one or more embodiments of this aspect, the wireless device is further configured to receive downlink control information, DCI, that indicates for the wireless device to re-synchronize.

[0059] According to one or more embodiments of this aspect, the wireless device is further configured to perform synchronization on the first DM-RS by using additional time to acquire the synchronization, where the additional time is associated with one or both of: additional time to produce feedback signaling; and additional time to provide received data to higher layers.

[0060] According to one or more embodiments of this aspect, the wireless device is further configured to: receive a second transmission on the PDSCH that includes second DM-RS; and not perform synchronization on the second DM-RS as the at least one rule is not satisfied with respect to the second transmission.

[0061] According to another aspect of the present disclosure, a method performed by a network node that is in communication with a wireless device is provided. At least one rule for performing synchronization using a demodulation reference signal, DM-RS is transmitted to the wireless device. A physical downlink shared channel, PDSCH, is scheduled according to the at least one rule that is configured to control instances of synchronization at the wireless device using the DM-RS.

[0062] According to one or more embodiments of this aspect, the at least one rule is based on a PDSCH rank.

[0063] According to one or more embodiments of this aspect, a PDSCH rank of 1 results in the at least one rule not being satisfied, a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity, and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

[0064] According to one or more embodiments of this aspect, the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device local oscillator.

[0065] According to one or more embodiments of this aspect, the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

[0066] According to one or more embodiments of this aspect, wireless device capability is received where the wireless device capability being associated with the at least one rule. According to one or more embodiments of this aspect, the wireless device is changed from a first transmission reception point, TRP, to a second TRP, and a first transmission from the second TRP is caused on the PDSCH for re-synchronization, at the wireless device, to the second TRP.

[0067] According to one or more embodiments of this aspect, downlink control information, DCI, that indicates for the wireless device to re-synchronize is transmitted.

[0068] According to one or more embodiments of this aspect, a second transmission on the PDSCH that includes second DM-RS is transmitted where the second transmission configured to not satisfy the at least one rule.

[0069] According to another aspect of the present disclosure, a network node that is in communication with a wireless device is provided. The network node is configured to: transmit, to the wireless device, at least one rule for performing synchronization using a demodulation reference signal, DM-RS; and schedule a physical downlink shared channel, PDSCH, according to the at least one rule that is configured to control instances of synchronization at the wireless device using the DM-RS.

[0070] According to one or more embodiments of this aspect, the at least one rule is based on a PDSCH rank.

[0071] According to one or more embodiments of this aspect, a PDSCH rank of 1 results in the at least one rule not being satisfied; a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity; and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

[0072] According to one or more embodiments of this aspect, the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device local oscillator.

[0073] According to one or more embodiments of this aspect, the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

[0074] According to one or more embodiments of this aspect, the network node is further configured to receive wireless device capability, the wireless device capability being associated with the at least one rule.

[0075] According to one or more embodiments of this aspect, the network node is further configured to: change the wireless device from a first transmission reception point, TRP, to a second TRP; and cause, from the second TRP, a first transmission on the PDSCH for re-synchronization, at the wireless device, to the second TRP. According to one or more embodiments of this aspect, the network node is further configured to transmit downlink control information, DCI, that indicates for the wireless device to re-synchronize.

[0076] According to one or more embodiments of this aspect, the network node is further configured to transmit a second transmission on the PDSCH that includes second DM-RS, the second transmission configured to not satisfy the at least one rule.

[0077] BRIEF DESCRIPTION OF THE DRAWINGS

[0078] A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

[0079] FIG. 1 is a diagram of a NR time-domain structure with 15kHz subcarrier spacing;

[0080] FIG. 2 is a diagram of a NR physical resource grid;

[0081] FIG. 3 is a schematic diagram of an example network architecture illustrating a communication system according to principles disclosed herein;

[0082] FIG. 4 is a block diagram of a network node in communication with a user equipment over a wireless connection according to some embodiments of the present disclosure;

[0083] FIG. 5 is a flowchart of an example process in a network node according to some embodiments of the present disclosure;

[0084] FIG. 6 is a flowchart of another example process in a network node according to some embodiments of the present disclosure;

[0085] FIG. 7 is a flowchart of an example process in a user equipment or wireless device according to some embodiments of the present disclosure;

[0086] FIG. 8 is a flowchart of another example process in a user equipment or wireless device according to some embodiments of the present disclosure;

[0087] FIG. 9 is a block diagram illustrating a virtualization environment in which functions implemented by some embodiments may be virtualized; and

[0088] FIG. 10 is a diagram of references signals with fine sync properties according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0089] Reception of PDSCH without fine synchronization using a periodic TRS (but instead synchronization using the PDSCH DM-RS) has been proposed where an explicit indication from the network node to the UE may be used as to when to use the TRS for synchronization and when not to (enable / disable), i.e., a TRS-free state. If disabled, then the UE uses a TRS for synchronization. It assumes a 5G-NR system where TRS is always present for legacy UEs while for new (non-legacy) UEs, the TRS can be “not used” for some transmissions as this gives some flexibility on the network side to select a TRP for PDSCH transmission without the need to indicate to the UE which TRS to use for QCL.

[0090] However, this proposed solution relies on the PDSCH DM-RS always being present so that the UE can maintain fine synchronization. It may be a problem that it cannot be guaranteed that the UE receives a PDSCH DM-RS continuously to maintain synchronization. Further, this proposed solution does not address the TRP switching problem.

[0091] It is also noted that such TRS-free operation is suggested for 6G, where the benefits of such a solution to base fine synchronization on DMRS is much larger than in 5G, as there is no legacy UEs to support.

[0092] One or more embodiments of the present disclosure solve one or more issues with existing systems and / or proposals, as described herein.

[0093] Before describing in detail example embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to user equipment synchronization. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0094] As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0095] In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

[0096] In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and / or wireless connections.

[0097] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0098] The term “network node” used herein can be any kind of network node comprised in a radio network which may further comprise any of base station (BS), transmission reception point (TRP), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multi-standard radio (MSR) radio node such as MSR BS, multi-cell / multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, anode external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a user equipment (UE) such as a wireless device (WD) or a radio network node.

[0099] In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The UE herein can be any type of user equipment capable of communicating with a network node or another UE over radio signals, such as a wireless device (WD). The UE may also be a radio communication device, target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine communication (M2M), low-cost and / or low-complexity UE, a sensor equipped with UE, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device etc.

[0100] Also, in some embodiments the generic term “radio network node” is used. It can be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell / multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH).

[0101] Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and / or New Radio (NR), may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

[0102] Note further, that functions described herein as being performed by a user equipment or a network node may be distributed over a plurality of user equipments and / or network nodes. In other words, it is contemplated that the functions of the network node and user equipment described herein are not limited to performance by a single physical device and, in fact, can be distributed among several physical devices.

[0103] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0104] Some embodiments are directed to user equipment synchronization. Referring again to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 3 a schematic diagram of a communication system 10, according to an embodiment, such as a 3 GPP-type cellular network that may support standards such as LTE and / or NR (5G), which comprises an access network 12, such as a radio access network, and a core network 14. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). In some embodiments, access network 12 includes one or more Transmission Reception Points 17a- 17b (referred collectively as TRP 17) that may be part of and / or managed by network node 16. Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. A first user equipment (UE) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second UE 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of UEs 22a, 22b (collectively referred to as user equipments 22) are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding network node 16. Note that although only two UEs 22 and three network nodes 16 are shown for convenience, the communication system may include many more UEs 22 and network nodes 16.

[0105] Also, it is contemplated that a UE 22 can be in simultaneous communication and / or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a UE 22 can have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, UE 22 can be in communication with an eNB for LTE / E-UTRAN and a gNB for NR / NG-RAN.

[0106] A network node 16 (eNB or gNB) is configured to include a configuration unit 24 which is configured to perform one or more network node 16 as described herein such as those functions with respect to UE synchronization. A user equipment 22 is configured to include a sync unit 26 which is configured to perform one or more UE 22 function as described herein such as those functions with respect to UE synchronization. Example implementations, in accordance with an embodiment, of the UE 22 and network node 16 discussed in the preceding paragraphs will now be described with reference to FIG. 4.

[0107] The communication system 10 includes a network node 16 provided in a communication system 10 and including hardware 28 enabling it to communicate with the UE 22. The hardware 28 may include a radio interface 30 for setting up and maintaining at least a wireless connection 32 with a UE 22 located in a coverage area 18 served by the network node 16. The radio interface 30 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 30 includes an array of antennas 34 to radiate and receive signal(s) carrying electromagnetic waves.

[0108] In the embodiment shown, the hardware 28 of the network node 16 further includes processing circuitry 36. The processing circuitry 36 may include a processor 38 and a memory 40. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 36 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 38 may be configured to access (e.g., write to and / or read from) the memory 40, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0109] Thus, the network node 16 further has software 42 stored internally in, for example, memory 40, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node 16 via an external connection. The software 42 may be executable by the processing circuitry 36. The processing circuitry 36 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by network node 16. Processor 38 corresponds to one or more processors 38 for performing network node 16 functions described herein. The memory 40 is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 42 may include instructions that, when executed by the processor 38 and / or processing circuitry 36, causes the processor 38 and / or processing circuitry 36 to perform the processes described herein with respect to network node 16. For example, processing circuitry 36 of the network node 16 may include configuration unit 24 which is configured to perform one or more network node 16 functions as described herein such as those functions with respect to UE synchronization.

[0110] The communication system 10 further includes the UE 22 already referred to. The UE 22 may have hardware 44 that may include a radio interface 46 configured to set up and maintain a wireless connection 32 with a network node 16 serving a coverage area 18 in which the UE 22 is currently located. The radio interface 46 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 46 includes an array of antennas 48 to radiate and receive signal(s) carrying electromagnetic waves.

[0111] The hardware 44 of the UE 22 further includes processing circuitry 50. The processing circuitry 50 may include a processor 52 and memory 54. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 50 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 52 may be configured to access (e.g., write to and / or read from) memory 54, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0112] Thus, the UE 22 may further comprise software 56, which is stored in, for example, memory 54 at the UE 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the UE 22. The software 56 may be executable by the processing circuitry 50. The software 56 may include a client application 58. The client application 58 may be operable to provide a service to a human or non-human user via the UE 22.

[0113] The processing circuitry 50 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by UE 22. The processor 52 corresponds to one or more processors 52 for performing UE 22 functions described herein. The UE 22 includes memory 54 that is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 56 and / or the client application 58 may include instructions that, when executed by the processor 52 and / or processing circuitry 50, causes the processor 52 and / or processing circuitry 50 to perform the processes described herein with respect to UE 22. For example, the processing circuitry 50 of the user equipment 22 may include sync unit 26 which is configured to perform one or more UE 22 functions as described herein such as those functions with respect to UE synchronization.

[0114] In some embodiments, the inner workings of the network node 16 and UE 22 may be as shown in FIG. 4 and independently, the surrounding network topology may be that of FIG. 3.

[0115] The wireless connection 32 between the UE 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and / or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc. In some embodiments, a measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve.

[0116] Although FIGS. 3 and 4 show various “units” such as configuration unit 24 and sync unit 26 as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

[0117] FIG. 5 is a flowchart of an example process in a network node 16 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the configuration unit 24), processor 38, and / or radio interface 30. Network node 16 is configured to determine (Block SI 00) a time duration from a timing of a previous physical downlink shared channel, PDSCH, transmission that was configured to be usable for performing synchronization to a timing of a scheduled PDSCH transmission where the synchronization is associated with predefined synchronization properties, as described herein. Network node 16 is configured to determine (Block SI 02), based on the time duration, whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization, as described herein. Network node 16 is configured to transmit (Block SI 04) the scheduled PDSCH transmission that is based on the determination whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization, as described herein. According to one or more embodiments, the determining whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization comprises: comparing the time duration to a threshold; when the time duration is greater than the threshold, the scheduled PDSCH transmission being configured with a a demodulation reference signal, DM-RS, that is usable for performing the synchronization; and when the time duration is less than the threshold, the scheduled PDSCH transmission is not configured to be usable for performing the synchronization.

[0118] According to one or more embodiments, the predefined synchronization properties are fine sync properties for performing fine synchronization that is different from coarse synchronization.

[0119] According to one or more embodiments, the fine sync properties comprise at least one of: predefined reference signal, RS, bandwidth, predefined RS timing spacing, predefined time duration, and predefined periodicity.

[0120] FIG. 6 is a flowchart of another example process in a network node 16 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the configuration unit 24), processor 38, and / or radio interface 30. Network node 16 is configured to transmit (Block S106), to the wireless device 22, at least one rule for performing synchronization using a demodulation reference signal, DM-RS, as described herein. Network node 16 is configured to schedule (Block S108) a physical downlink shared channel, PDSCH, according to the at least one rule that is configured to control instances of synchronization at the wireless device 22 using the DM-RS, as described herein.

[0121] According to one or more embodiments, the at least one rule is based on a PDSCH rank.

[0122] According to one or more embodiments, a PDSCH rank of 1 results in the at least one rule not being satisfied; a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity; and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

[0123] According to one or more embodiments, the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device local oscillator.

[0124] According to one or more embodiments, the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth. According to one or more embodiments, the network node 16 is further configured to receive wireless device capability, the wireless device capability being associated with the at least one rule.

[0125] According to one or more embodiments, the network node 16 is further configured to: change the wireless device 22 from a first transmission reception point, TRP 17, to a second TRP 17; and cause, from the second TRP 17, a first transmission on the PDSCH for re-synchronization, at the wireless device 22, to the second TRP 17.

[0126] According to one or more embodiments, the network node 16 is further configured to transmit downlink control information, DCI, that indicates for the wireless device 22 to re-synchronize.

[0127] According to one or more embodiments, the network node 16 is further configured to transmit a second transmission on the PDSCH that includes second DM-RS, the second transmission configured to not satisfy the at least one rule.

[0128] FIG. 7 is a flowchart of an example process in a user equipment 22 (e.g., wireless device 22) according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of user equipment 22 such as by one or more of processing circuitry 50 (including the sync unit 26), processor 52, and / or radio interface 46. User equipment 22 is configured to receive (Block SI 10) a physical downlink shared channel, PDSCH, transmission, as described herein. UE 22 is configured to determine (Block SI 12), based at least on a timing when the PDSCH transmission was received, whether the PDSCH transmission is for use in performing synchronization associated with predefined synchronization properties, as described herein. UE 22 is configured to, in response to determining the PDSCH transmission is for use in performing the synchronization, acquire (Block SI 14) synchronization using a demodulation reference signal, DM-RS, in the PDSCH transmission, as described herein.

[0129] According to one or more embodiments, the UE 22 is further configured to determine, based at least on a timing when the PDSCH transmission was received, that the PDSCH transmission is not for use in performing the synchronization associated with the predefined synchronization properties.

[0130] According to one or more embodiments, the determining whether the PDSCH transmission is for use in performing the synchronization comprises: determining a time duration from receiving a previous PDSCH transmission that was used for performing the synchronization to the receiving of the PDSCH transmission; and comparing the time duration to a threshold. According to one or more embodiments, when the time duration is greater than the threshold, the PDSCH transmission is determined to be for use in performing the synchronization.

[0131] According to one or more embodiments, when the time duration is less than the threshold, the PDSCH transmission is determined to not be for use in performing the synchronization.

[0132] According to one or more embodiments, the the predefined synchronization properties are fine sync properties for performing fine synchronization that is different from coarse synchronization.

[0133] According to one or more embodiments, the fine sync properties comprise at least one of: predefined reference signal, RS, bandwidth, predefined RS timing spacing, predefined time duration, and predefined periodicity.

[0134] FIG. 8 is a flowchart of another example process in a user equipment 22 (e.g., wireless device 22) according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of user equipment 22 such as by one or more of processing circuitry 50 (including the sync unit 26), processor 52, and / or radio interface 46. Wireless device 22 is configured to receive (Bloc SI 16) at least one rule for performing synchronization using a demodulation reference signal, DM-RS, as described herein. Wireless device 22 is configured to receive (Block S 118) a first transmission on a physical downlink shared channel, PDSCH, that includes a first DM-RS, as described herein. Wireless device 22 is configured to perform (Block S120) synchronization on the first DM-RS according to the at least one rule being satisfied with respect to the first transmission, as described herein.

[0135] According to one or more embodiments, the wireless device 22 is further configured to compare a time duration to at least one threshold defined by the at least one rule; and the time duration corresponds to a time from receiving a previous transmission on the PDSCH to receiving the first transmission on the PDSCH.

[0136] According to one or more embodiments, the at least one rule is based on a PDSCH rank.

[0137] According to one or more embodiments, a PDSCH rank of 1 results in the at least one rule not being satisfied, a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity, and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity. According to one or more embodiments, the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device local oscillator.

[0138] According to one or more embodiments, the PDSCH is scheduled according to at least one rule that is configured to control instances of fine synchronization at the wireless device 22.

[0139] According to one or more embodiments, the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

[0140] According to one or more embodiments, the wireless device 22 is further configured to indicate, to the network node 16, wireless device capability associated with the at least one rule.

[0141] According to one or more embodiments, the wireless device 22 is changed from a first transmission reception point, TRP 17, to a second TRP 17; the first transmission on the PDSCH being received from the second TRP 17; and the synchronization being a resynchronization for receiving subsequent transmissions in a PDSCH from the second TRP 17.

[0142] According to one or more embodiments, the wireless device 22 is further configured to receive downlink control information, DCI, that indicates for the wireless device 22 to re-synchronize.

[0143] According to one or more embodiments, the wireless device 22 is further configured to perform synchronization on the first DM-RS by using additional time to acquire the synchronization, where the additional time is associated with one or both of: additional time to produce feedback signaling; and additional time to provide received data to higher layers.

[0144] According to one or more embodiments, the wireless device 22 is further configured to: receive a second transmission on the PDSCH that includes second DM-RS; and not perform synchronization on the second DM-RS as the at least one rule is not satisfied with respect to the second transmission.

[0145] For example, in some embodiments, the telecommunication system 10 includes one or more Open-RAN (ORAN) network nodes 16. An ORAN network node 16 is a node in the telecommunication system 10 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in the telecommunication system 10, including one or more network nodes 16 in the access network 12 and / or core network nodes 14.

[0146] Examples of an ORAN network node 16 include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU-CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near- real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adjective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an 0-2 interface defined by the O- RAN Alliance or comparable technologies. The network nodes 16 facilitate direct or indirect connection of user equipment (UE), such as by connecting UEs 22a, 22b, 22c, and 22d (one or more of which may be generally referred to as UEs 22) to the core network 14 over one or more wireless connections.

[0147] FIG. 9 is a block diagram illustrating a virtualization environment 94 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in one or more virtual environments 94 hosted by one or more of hardware nodes, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 94 includes components defined by the O-RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an 0-2 interface.

[0148] Applications 96 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 94 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0149] Hardware 98 includes processing circuitry, memory that stores software and / or instructions executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 100 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 102a and 102b (one or more of which may be generally referred to as VMs 102), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. The virtualization layer 100 may present a virtual operating platform that appears like networking hardware to the VMs 102.

[0150] The VMs 102 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 100. Different embodiments of the instance of a virtual appliance 96 may be implemented on one or more of VMs 102, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0151] In the context of NFV, a VM 102 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of the VMs 102, and that part of hardware 98 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 102 on top of the hardware 98 and corresponds to the application 96.

[0152] Hardware 98 may be implemented in a standalone network node with generic or specific components. Hardware 98 may implement some functions via virtualization. Alternatively, hardware 98 may be part of a larger cluster of hardware (e.g., such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration 104, which, among others, oversees lifecycle management of applications 96. In some embodiments, hardware 98 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 106 which may alternatively be used for communication between hardware nodes and radio units.

[0153] Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for UE synchronization using, for example the PDSCH DM-RS having fine sync properties.

[0154] One or more UE 22 (e.g., wireless device 22) functions described below may be performed by one or more of processing circuitry 50, processor 52, sync unit 26, radio interface 46, etc. One or more network node 16 functions described below may be performed by one or more of processing circuitry 36, processor 38, configuration unit 24, radio interface 30, etc.

[0155] In 3GPP 5G networks, a UE 22 can obtain coarse synchronization using the SSB, and a fine synchronization using TRS. The TRS is designed with a certain bandwidth and time duration to allow for such fine synchronization properties. Fine synchronization is necessary to receive multiple MIMO layers (spatial multiplexing) and / or higher order modulation (e.g., 64QAM).

[0156] In general, an example of a reference signal designed to have such properties (i.e., fine sync properties) is shown in FIG. 10. This RS is defined by the following parameters (with 3GPP NR parameters in parentheses for 30 kHz subcarrier spacing (SCS)):

[0157] • RS Bandwidth B (NR TRS @30 kHz SCS can use 52 RB = 18,72 MHz);

[0158] • RS time spacing A (NR TRS @30 kHz SCS use 4 OFDM symbols = 143 us);

[0159] • Time duration S (NR TRS @30 kHz SCS use 1 ms); and

[0160] • Periodicity P (NR TRS periodicity 20,40,80,.. ms).

[0161] There are discussions in 6G development to not have a TRS, since using TRS has several drawbacks, examples of which include that: • It is a periodic RS and thus prevents the NW power amplifiers from going to sleep to save energy when there is no traffic in the cell (same issue as with CRS in LTE);

[0162] • It causes interference to neighboring cells; and

[0163] • Each transmission point (TRP 17) requires a unique TRS and when the NW decides to switch transmission to another TRP 17, it must indicate that to the UE 22 (using the QCL indication framework). In 6G, it is envisioned that the number of TRPs 17 increase significantly compared to 5G (i.e., distributed MIMO (D- MIMO)). This will create a large overhead of QCL signaling such as when TRP 17 switching occurs.

[0164] Therefore, a TRS -less design is preferable, and the UE 22 may instead perform synchronization on the DMRS that is associated with the PDSCH where such DMRS must therefore have “fine sync properties”, i.e., predefined synchronization properties, as described above. After such DMRS has been received, it is expected that the UE 22 has acquired fine synch / sync and the subsequent PDSCH transmissions in the following OFDM symbols need not have the fine sync properties (i.e., predefined synchronization properties for performing fine synchronization) for some time for which it is expected that the acquired fine sync is valid.

[0165] The following describes example UE 22 behaviour to acquire fine sync using DMRS:

[0166] For a 5G-NR UE 22 or a 6G UE 22 receiving a PDSCH scheduled by the NW or network node 16, the associated RS (e.g., the PDSCH DM-RS) is under some conditions (described below) intended to be used for fine synchronization, and in addition, a time T is defined as the time from the previous reception of a DMRS with fine sync properties. In addition, a threshold time X is configured to the UE 22 by the NW and / or indicated by the UE 22 to the NW as a UE capability, or specified in 3GPP specifications (or a combination of these methods).

[0167] • If T>X, then the scheduled UE 22 can expect that the scheduled PDSCH DMRS from the NW to the UE 22 is restricted to have fine sync properties so that the UE 22 can perform fine synchronization. Hence, the NW is obliged to provide the UE 22 with a DM-RS with such properties (e.g., fine sync properties).

[0168] • If T<=X, then the UE 22 receives the scheduled PDSCH without any restrictions since it is assumed that the UE 22 has already acquired fine sync. For example, the scheduled PDSCH may not have fine sync properties. o For instance, the UE 22 can be scheduled with a small bandwidth <B and a small time duration <S (e.g., 1 PRB and 2 OFDM symbols)

[0169] Some additional example embodiments

[0170] Resynchronization (before the time X)

[0171] A resynchronization may be necessary, for example, when the NW, e.g., via one or more network nodes 16, has performed a TRP 17 switch, meaning that the TRP 17 that is transmitting PDSCH to the UE 22 changes from a first to a second TRP 17.

[0172] Alternatively, the beam / MIMO precoder used to transmit the PDSCH DMRS has changed significantly from a first beam / MIMO precoder to a second beam / MIMO precoder so that the NW determines that a resynchronization is necessary.

[0173] The NW provides a DMRS with fine sync properties transmitted using the second TRP 17 / beam / precoder so that the UE 22 can re-synchronize to receive subsequent PDSCHs from the second TRP 17 / beam / precoder.

[0174] In one embodiment, one or more of the following rules apply:

[0175] • A scheduled PDSCH DMRS has fine sync properties (even at a time t shorter than X from the previous reception of a PDSCH DMRS with fine sync properties), and the UE 22 always resynchronizes using that PDSCH DMRS. The timer t is reset to zero to start a new period P.

[0176] • The PDSCH DMRS does not have fine sync properties, the UE receives the scheduled PDSCH without any restrictions since it is assumed that the UE has already acquired fine sync.

[0177] In one alternative embodiment, the DCI that schedules the PDSCH contains a resynchronization indication (e.g., a DCI field to indicate whether UE 22 should resynchronize)

[0178] • If set (the NW has switched the TRP 17 / beam / MIMO precoder), the PDSCH DMRS has fine sync properties (even at a time t shorter than X from the previous reception of a PDSCH DMRS with fine sync properties) and the UE 22 resynchronizes using that PDSCH DMRS. The timer t is reset to zero to start a new period P.

[0179] • If not set (the NW has not switched the TRP 17 / beam / MIMO precoder), and the PDSCH DMRS does not have fine sync properties, then the UE 22 receives the scheduled PDSCH without any restrictions since it is assumed that the UE 22 has already acquired fine sync • If not set (the NW has not switched the TRP 17 / beam / MIMO precoder), and the PDSCH DMRS does have fine sync properties (even at a time t shorter than X from the previous reception of a PDSCH DMRS with fine sync properties), then the UE 22 receives the scheduled PDSCH and it may or may not use the PDSCH DMRS to re-synchronize. The timer t is not reset to zero to start a new period P.

[0180] Requirements for X, the maximum time between fine sync DMRS

[0181] In a more detailed embodiment, the threshold X depends on additional conditions such as the modulation and coding scheme, and / or the number of PDSCH MIMO layers. For example, a table can be defined as shown in Table 2 below.

[0182] Table 2

[0183] This example implies that if rank=l PDSCH is scheduled, the time X is infinite, meaning that there is no need for DMRS with fine sync properties at all. For rank 2 and 3, the UE 22 requires a DMRS with fine sync properties every 40 ms and for rank above 3, it requires such a DMRS at least every 10 ms.

[0184] The value(s) of X depends on UE implementation and may be reported from the UE 22 to the network node 16 using UE capability signaling.

[0185] Requirements for S, the time duration of the fine sync DMRS

[0186] In a more detailed embodiment, the time S depends on the relative frequency stability between NW and UE local oscillators and the UE speed. Different values of S can be supported in specifications and indicated from UE 22 to network as a UE 22 capability and from the NW, e.g., via network node 16 to UE 22 using higher layer configuration. The value of S (as well as the other parameters B, Delta) are configured from the NW to the UE 22. The value of S may also depend on the subcarrier spacing (SCS).

[0187] Delay in estimating fine sync

[0188] In some embodiments, may the UE 22 require additional time to acquire fine sync from provided DMRS. The additional time may, in some embodiments, be visible in relaxed processing requirements, e.g., expressed as the time to produce feedback signaling to the network regarding decoding result (HARQ feedback) or delivering received data to higher layers. In other embodiments, the UE 22 may only receive a transmission requiring fine sync Y symbols after receiving the first DMRS fulfilling the bandwidth requirement.

[0189] Update fine sync configuration based on UE measurement

[0190] In some embodiments, UE 22 can optionally report the actual configurations that is enough for fine synchronization measurements based on a current channel property. The UE 22 reported configuration can include explicit B and S values, or it can be relative to the current system configured B and S values, for example, if UE 22 reports x and y, then x*B and y*S will be sufficient for fine sync measurement.

[0191] T>X

[0192] When T>X, if scheduled DMRS bandwidth and duration is sufficient for fine sync measurement, UE 22 can use it to perform fine sync.

[0193] If the scheduled DMRS bandwidth and duration are not sufficient for fine sync measurement, UE 22 can report to the NW such as via network node 16.

[0194] Accordingly, one or more embodiments described herein provide a signaling and / or a criteria that determines whether a UE 22 may use or may not use a TRS to assist demodulation of a physical downlink channel.

[0195] For a UE 22 receiving a PDSCH scheduled by the NW, e.g., network node 16, a time T is defined as the time from the previous reception of a DM-RS with fine sync properties. In addition, a threshold time X is defined where:

[0196] • If T>X, then the UE 22 can expect that the scheduled PDSCH DM-RS from the NW to the UE 22 is restricted (e.g., in time duration, frequency bandwidth, etc.) to have fine sync properties so that the UE 22 may perform fine synchronization using the DM-RS.

[0197] • If T<=X, then the UE 22 receives the scheduled PDSCH without any restrictions (e.g., the scheduled PDSCH does not have fine synch / sync properties). Accordingly, one or more embodiments described herein provide one or more of the following advantages. One or more embodiments described herein provide more flexibility for the network and deployment as it allows the network to perform PDSCH transmission from any (synchronized) TRP 17 since the PDSCH is received without an associated periodic TRS or periodic SSB. The UE 22 hence receives the PDSCH in a self- contained manner, i.e., by performing synchronization without using the periodic TRS, e.g., by using the PDSCH DM-RS. One or more embodiments enable the NW, e.g., the network nodes 16, to operate a carrier without configuring periodic TRS or with reduced periodic TRS periodicity hence reducing energy consumption of the network, especially at low load.

[0198] One or more embodiments enable the UE to implement TRS-free operation with without excessive cost of expensive local oscillators (that can maintain phase drift limited for a longer time), thereby lowering the cost of UEs 22.

[0199] Some Examples

[0200] Example Al. A method implemented in a user equipment, UE 22, that is configured to communicate with a network node 16, the method comprising: receiving a physical downlink shared channel, PDSCH, transmission; determining, based at least on a timing when the PDSCH transmission was received, whether the PDSCH transmission is for use in performing synchronization associated with predefined synchronization properties; and in response to determining the PDSCH transmission is for use in performing the synchronization, acquiring synchronization using a demodulation reference signal, DM- RS, in the PDSCH transmission.

[0201] Example A2. The method of Example Al, further comprising determining, based at least on a timing when the PDSCH transmission was received, that the PDSCH transmission is not for use in performing the synchronization associated with the predefined synchronization properties.

[0202] Example A3. The method of any one of Examples A1-A2, wherein the determining whether the PDSCH transmission is for use in performing the synchronization comprises: determining a time duration from receiving a previous PDSCH transmission that was used for performing the synchronization to the receiving of the PDSCH transmission; and comparing the time duration to a threshold.

[0203] Example A4. The method of Example A3, wherein, when the time duration is greater than the threshold, the PDSCH transmission is determined to be for use in performing the synchronization.

[0204] Example A5. The method of Example A3, wherein, when the time duration is less than the threshold, the PDSCH transmission is determined to not be for use in performing the synchronization. Example A6. The method of any one of Examples A1-A5, wherein the the predefined synchronization properties are fine sync properties for performing fine synchronization that is different from coarse synchronization.

[0205] Example A7. The method of Example A6, wherein the fine sync properties comprise at least one of: predefined reference signal, RS, bandwidth; predefined RS timing spacing; predefined time duration; and predefined periodicity.

[0206] Example Bl . A user equipment, UE 22, that is configured to communicate with a network node 16, the UE 22 configured to, and / or comprising a radio interface 46 and / or processing circuitry 50 configured to: receive a physical downlink shared channel, PDSCH, transmission; determine, based at least on a timing when the PDSCH transmission was received, whether the PDSCH transmission is for use in performing synchronization associated with predefined synchronization properties; and in response to determining the PDSCH transmission is for use in performing the synchronization, acquire synchronization using a demodulation reference signal, DM-RS, in the PDSCH transmission.

[0207] Example B2. The UE 22 of Example Bl, wherein the UE 22 is further configured to determine, based at least on a timing when the PDSCH transmission was received, that the PDSCH transmission is not for use in performing the synchronization associated with the predefined synchronization properties.

[0208] Example B3. The UE 22 of any one of Examples B1-B2, wherein the determining whether the PDSCH transmission is for use in performing the synchronization comprises: determining a time duration from receiving a previous PDSCH transmission that was used for performing the synchronization to the receiving of the PDSCH transmission; and comparing the time duration to a threshold.

[0209] Example B4. The UE 22 of Example B3, wherein, when the time duration is greater than the threshold, the PDSCH transmission is determined to be for use in performing the synchronization. Example B5. The UE 22 of Example B3, wherein, when the time duration is less than the threshold, the PDSCH transmission is determined to not be for use in performing the synchronization.

[0210] Example B6. The UE 22 of any one of Examples B1-B5, wherein the the predefined synchronization properties are fine sync properties for performing fine synchronization that is different from coarse synchronization.

[0211] Example B7. The UE 22 of Example B6, wherein the fine sync properties comprise at least one of: predefined reference signal, RS, bandwidth; predefined RS timing spacing; predefined time duration; and predefined periodicity.

[0212] Example Cl . A method implemented in a network node 16 that is configured to communicate with a user equipment 22, the method comprising: determining a time duration from a timing of a previous physical downlink shared channel, PDSCH, transmission that was configured to be usable for performing synchronization to a timing of a scheduled PDSCH transmission, the synchronization being associated with predefined synchronization properties; determining, based on the time duration, whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization; and transmitting the scheduled PDSCH transmission that is based on the determination whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization.

[0213] Example C2. The method of Example Cl, wherein the determining whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization comprises: comparing the time duration to a threshold; when the time duration is greater than the threshold, the scheduled PDSCH transmission being configured with a demodulation reference signal, DM-RS, that is usable for performing the synchronization; and when the time duration is less than the threshold, the scheduled PDSCH transmission is not configured to be usable for performing the synchronization. Example C3. The method of any one of Examples C1-C2, wherein the the predefined synchronization properties are fine sync properties for performing fine synchronization that is different from coarse synchronization.

[0214] Example C4. The method of Example C3, wherein the fine sync properties comprise at least one of: predefined reference signal, RS, bandwidth; predefined RS timing spacing; predefined time duration; and predefined periodicity.

[0215] Example DI. A network node 16 configured to communicate with a user equipment, UE 22, the network node 16 configured to, and / or comprising a radio interface 30 and / or comprising processing circuitry 36 configured to: determine a time duration from a timing of a previous physical downlink shared channel, PDSCH, transmission that was configured to be usable for performing synchronization to a timing of a scheduled PDSCH transmission, the synchronization being associated with predefined synchronization properties; determine, based on the time duration, whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization; and cause transmission the scheduled PDSCH transmission that is based on the determination whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization.

[0216] Example D2. The network node 16 of Example DI, wherein the determining whether to configure the scheduled PDSCH transmission to be usable for performing the synchronization comprises: comparing the time duration to a threshold; when the time duration is greater than the threshold, the scheduled PDSCH transmission being configured with a a demodulation reference signal, DM-RS, that is usable for performing the synchronization; and when the time duration is less than the threshold, the scheduled PDSCH transmission is not configured to be usable for performing the synchronization.

[0217] Example D3. The network node 16 of any one of Examples D1-D2, wherein the the predefined synchronization properties are fine sync properties for performing fine synchronization that is different from coarse synchronization. Example D4. The network node 16 of Example D3, wherein the fine sync properties comprise at least one of: predefined reference signal, RS, bandwidth; predefined RS timing spacing; predefined time duration; and predefined periodicity.

[0218] As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and / or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and / or functionality described herein may be performed by, and / or associated to, a corresponding module, which may be implemented in software and / or firmware and / or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that can be executed by a computer. Any suitable tangible computer readable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

[0219] Some embodiments are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0220] These computer program instructions may also be stored in a computer readable memory or storage medium that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0221] The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0222] It is to be understood that the functions / acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

[0223] Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java® or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0224] Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments can be combined in any way and / or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

[0225] It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

CLAIMS:

1. A method performed by a wireless device (22) that is configured to communicate with a network node (16), the method comprising: receiving (SI 16) at least one rule for performing synchronization using a demodulation reference signal, DM-RS; receiving (S 118) a first transmission on a physical downlink shared channel, PDSCH, that includes a first DM-RS; and performing (S120) synchronization on the first DM-RS according to the at least one rule being satisfied with respect to the first transmission.

2. The method of Claim 1, further comprising comparing a time duration to at least one threshold defined by the at least one rule; and the time duration corresponds to a time from receiving a previous transmission on the PDSCH to receiving the first transmission on the PDSCH.

3. The method of any one of Claims 1-2, wherein the at least one rule is based on a PDSCH rank.

4. The method of Claim 3, wherein: a PDSCH rank of 1 results in the at least one rule not being satisfied; a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity; and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

5. The method of any one of Claims 1-4, wherein the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device (22) local oscillator.

6. The method of any one of Claims 1-5, wherein the PDSCH is scheduled according to at least one rule that is configured to control instances of fine synchronization at the wireless device (22).

7. The method of Claim 6, wherein the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

8. The method of any one of Claims 1-7, further comprising indicating, to the network node (16), wireless device (22) capability associated with the at least one rule.

9. The method of any one of Claims 1-8, wherein the wireless device (22) is changed from a first transmission reception point, TRP (17), to a second TRP (17); the first transmission on the PDSCH being received from the second TRP (17); and the synchronization being a re-synchronization for receiving subsequent transmissions in a PDSCH from the second TRP (17).

10. The method of Claim 9, further comprising receiving downlink control information, DCI, that indicates for the wireless device (22) to re-synchronize.

11. The method of any one of Claims 1-10, further comprising performing synchronization on the first DM-RS by using additional time to acquire the synchronization, the additional time being associated with one or both of: additional time to produce feedback signaling; and additional time to provide received data to higher layers.

12. The method of any one of Claims 1-11, further comprising: receiving a second transmission on the PDSCH that includes second DM-RS; not performing synchronization on the second DM-RS as the at least one rule is not satisfied with respect to the second transmission.

13. A wireless device (22) that is configured to communicate with a network node (16), the wireless device (22) is configured to: receive at least one rule for performing synchronization using a demodulation reference signal, DM-RS; receive a first transmission on a physical downlink shared channel, PDSCH, that includes a first DM-RS; and perform synchronization on the first DM-RS according to the at least one rule being satisfied with respect to the first transmission.

14. The wireless device (22) of Claim 13, wherein the wireless device (22) is further configured to compare a time duration to at least one threshold defined by the at least one rule; and the time duration corresponds to a time from receiving a previous transmission on the PDSCH to receiving the first transmission on the PDSCH.

15. The wireless device (22) of any one of Claims 13-14, wherein the at least one rule is based on a PDSCH rank.

16. The wireless device (22) of Claim 15, wherein: a PDSCH rank of 1 results in the at least one rule not being satisfied; a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity; and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

17. The wireless device (22) of any one of Claims 13-16, wherein the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device (22) local oscillator.

18. The wireless device (22) of any one of Claims 13-17, wherein the PDSCH is scheduled according to at least one rule that is configured to control instances of fine synchronization at the wireless device (22).

19. The wireless device (22) of Claim 18, wherein the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

20. The wireless device (22) of any one of Claims 13-19, wherein the wireless device (22) is further configured to indicate, to the network node (16), wireless device (22) capability associated with the at least one rule.

21. The wireless device (22) of any one of Claims 13-20, wherein the wireless device (22) is changed from a first transmission reception point, TRP (17), to a second TRP (17); the first transmission on the PDSCH being received from the second TRP (17); and the synchronization being a re-synchronization for receiving subsequent transmissions in a PDSCH from the second TRP (17).

22. The wireless device (22) of Claim 21, wherein the wireless device (22) is further configured to receive downlink control information, DCI, that indicates for the wireless device (22) to re-synchronize.

23. The wireless device (22) of any one of Claims 13-22, wherein the wireless device (22) is further configured to perform synchronization on the first DM-RS by using additional time to acquire the synchronization, the additional time being associated with one or both of: additional time to produce feedback signaling; and additional time to provide received data to higher layers.

24. The wireless device (22) of any one of Claims 13-23, wherein the wireless device (22) is further configured to: receive a second transmission on the PDSCH that includes second DM-RS; and not perform synchronization on the second DM-RS as the at least one rule is not satisfied with respect to the second transmission.

25. A method performed by a network node (16) that is in communication with a wireless device (22), the method comprising: transmitting (SI 06), to the wireless device (22), at least one rule for performing synchronization using a demodulation reference signal, DM-RS; and scheduling (SI 08) a physical downlink shared channel, PDSCH, according to the at least one rule that is configured to control instances of synchronization at the wireless device (22) using the DM-RS.

26. The method of Claim 25, wherein the at least one rule is based on aPDSCH rank.

27. The method of Claim 26, wherein: a PDSCH rank of 1 results in the at least one rule not being satisfied; a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity; and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

28. The method of any one of Claims 25-27, wherein the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device (22) local oscillator.

29. The method of Claim 28, wherein the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

30. The method of any one of Claims 25-29, further comprising receiving wireless device (22) capability, the wireless device (22) capability being associated with the at least one rule.

31. The method of any one of Claims 25-30, further comprising: changing the wireless device (22) from a first transmission reception point, TRP (17), to a second TRP (17); and causing, from the second TRP (17), a first transmission on the PDSCH for resynchronization, at the wireless device (22), to the second TRP (17).

32. The method of Claim 31, further comprising transmitting downlink control information, DCI, that indicates for the wireless device (22) to re-synchronize.

33. The method of any one of Claims 25-32, further comprising transmitting a second transmission on the PDSCH that includes second DM-RS, the second transmission configured to not satisfy the at least one rule.

34. A network node (16) that is in communication with a wireless device (22), the network node (16) configured to: transmit, to the wireless device (22), at least one rule for performing synchronization using a demodulation reference signal, DM-RS; and schedule a physical downlink shared channel, PDSCH, according to the at least one rule that is configured to control instances of synchronization at the wireless device (22) using the DM-RS.

35. The network node (16) of Claim 34, wherein the at least one rule is based on a PDSCH rank.

36. The network node (16) of Claim 35, wherein: a PDSCH rank of 1 results in the at least one rule not being satisfied; a PDSCH rank of 2 or 3 results in the at least one rule being satisfied with a first time periodicity; and a PDSCH rank of 4 or greater results in the at least one rule being satisfied with a second periodicity.

37. The network node (16) of any one of Claims 34-36, wherein the at least one rule is based on a frequency stability between at least one network local oscillator and at least one wireless device (22) local oscillator.

38. The network node (16) of Claim 37, wherein the at least one rule is associated with one or more of a time duration, a time spacing, a periodicity and a frequency bandwidth.

39. The network node (16) of any one of Claims 34-38, wherein the network node (16) is further configured to receive wireless device (22) capability, the wireless device (22) capability being associated with the at least one rule.

40. The network node (16) of any one of Claims 34-39, wherein the network node (16) is further configured to:change the wireless device (22) from a first transmission reception point, TRP (17), to a second TRP (17); and cause, from the second TRP (17), a first transmission on the PDSCH for resynchronization, at the wireless device (22), to the second TRP (17).

41. The network node (16) of Claim 40, wherein the network node (16) is further configured to transmit downlink control information, DCI, that indicates for the wireless device (22) to re-synchronize.

42. The network node (16) of any one of Claims 34-41, wherein the network node (16) is further configured to transmit a second transmission on the PDSCH that includes second DM-RS, the second transmission configured to not satisfy the at least one rule.

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