WO2021108653A1

WO2021108653A1 - Using demodulation reference signal of a data transmission as a quasi-colocation reference signal source for another data transmission

Info

Publication number: WO2021108653A1
Application number: PCT/US2020/062349
Authority: WO
Inventors: Alexandros MANOLAKOS; Krishna Kiran Mukkavilli
Original assignee: Qualcomm Incorporated
Priority date: 2019-11-28
Filing date: 2020-11-25
Publication date: 2021-06-03

Abstract

Methods, systems, and devices for wireless communications are described. A base station may transmit a first grant scheduling a first downlink transmission to a user equipment (UE), the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission. The base station may transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

Description

USING DEMODULATION REFERENCE SIGNAL OF A DATA TRANSMISSION AS A QUASI-COLOCATION REFERENCE SIGNAL SOURCE FOR ANOTHER DATA

TRANSMISSION

CROSS REFERENCE

[0001] The present Application for Patent claims the benefit of Greece Provisional Patent

Application No. 20190100539 by MANOLAKOS et ah, entitled “USING DEMODULATION REFERENCE SIGNAL OF A DATA TRANSMISSION AS A QUASI COLOCATION REFERENCE SIGNAL SOURCE FOR ANOTHER DATA TRANSMISSION,” filed November 28, 2019, assigned to the assignee hereof, and expressly incorporated by reference herein.

BACKGROUND

[0002] The present disclosure relates generally to wireless communications, and more specifically to using a demodulation reference signal (DMRS) of a data transmission as a quasi-colocation (QCL) reference signal source for another data transmission.

[0003] Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple- access systems include fourth generation (4G) systems such as Long Term Evolution (LTE) systems, LTE-Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth generation (5G) systems which may be referred to as New Radio (NR) systems. These systems may employ technologies such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), or discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM). A wireless multiple-access communications system may include a number of base stations or network access nodes, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE). SUMMARY

[0004] The described techniques relate to improved methods, systems, devices, and apparatuses that support using a demodulation reference signal (DMRS) of a data transmission as a quasi-colocation (QCL) reference signal source for a subsequent data transmission. Generally, the described techniques provide for reuse of the DMRS from the first data transmission (e.g., a physical downlink shared channel (PDSCH) transmission or a physical sidelink shared channel (PSSCH)) as the QCL source for a subsequent data transmission. For example, a user equipment (UE) may receive a grant scheduling a transmission to the UE (e.g., a first grant scheduling a first transmission, such as a downlink transmission, a sidelink transmission, etc.). The grant may generally configure or otherwise identify various parameters associated with the transmission. For example, the grant may identify a reference signal to be used as a QCL source for a channel estimation during the transmission. That is, the QCL source reference signal of the transmission may be used, along with the DMRS scheduled for the transmission, for channel estimation during the transmission. Accordingly, the UE may identify a set of QCL parameters for the transmission based on the QCL source reference signal, and then identify the channel estimate for the transmission using the set of QCL parameters and the DMRS scheduled with the transmission. The UE may then receive a second grant scheduling a second transmission. In this second grant, the base station may signal for the UE to use the DMRS of the first transmission as the QCL source for the second transmission. That is, the second grant may signal for the UE to use the DMRS of the first PDSCH as the QCL source for the DMRS scheduled by the second grant. The UE may perform the channel estimation for the second transmission according to the second grant, and using the DMRS of the first transmission as the QCL source for the DMRS of the second transmission.

[0005] A method of wireless communication by a UE is described. The method may include receiving a first grant scheduling a first transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first QCL source for the first transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first transmission, identifying, based on the first reference signal, a set of QCL parameters for the first transmission, identifying the channel estimate for the first transmission based on the set of QCL parameters and the second reference signal, receiving a second grant scheduling a second transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second transmission and for the UE to determine the identified channel estimate for the second transmission, and performing a channel estimation for the second transmission based on the second reference signal, the second grant, and the third reference signal.

[0006] An apparatus for wireless communication by a UE is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to receive a first grant scheduling a first transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first QCL source for the first transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first transmission, identify, based on the first reference signal, a set of QCL parameters for the first transmission, identify the channel estimate for the first transmission based on the set of QCL parameters and the second reference signal, receive a second grant scheduling a second transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second transmission and for the UE to determine the identified channel estimate for the second transmission, and perform a channel estimation for the second transmission based on the second reference signal, the second grant, and the third reference signal.

[0007] Another apparatus for wireless communication by a UE is described. The apparatus may include means for receiving a first grant scheduling a first transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first QCL source for the first transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first transmission, identifying, based on the first reference signal, a set of QCL parameters for the first transmission, identifying the channel estimate for the first transmission based on the set of QCL parameters and the second reference signal, receiving a second grant scheduling a second transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second transmission and for the UE to determine the identified channel estimate for the second transmission, and performing a channel estimation for the second transmission based on the second reference signal, the second grant, and the third reference signal.

[0008] A non-transitory computer-readable medium storing code for wireless communication by a UE is described. The code may include instructions executable by a processor to receive a first grant scheduling a first transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first QCL source for the first transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first transmission, identify, based on the first reference signal, a set of QCL parameters for the first transmission, identify the channel estimate for the first transmission based on the set of QCL parameters and the second reference signal, receive a second grant scheduling a second transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second transmission and for the UE to determine the identified channel estimate for the second transmission, and perform a channel estimation for the second transmission based on the second reference signal, the second grant, and the third reference signal.

[0009] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying the third reference signal of the second reference signal type as the QCL source for the second transmission based on at least one of a transmission timing of the second grant, or a transmission timing of the second transmission, or a combination thereof.

[0010] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying, based on a timing indication in the second grant, the third reference signal of the second reference signal type as the QCL source for the second transmission.

[0011] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the timing indication may be based on at least one of a first grant transmission timing, or a first transmission timing, or a second grant transmission timing, or a second transmission timing, or a combination thereof.

[0012] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the timing indication may be indicated in a QCL source reference signal type identifier in a transmission configuration indicator (TCI) state or a TCI reference signal set of the second grant.

[0013] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting a UE capability message identifying a minimum supported gap between the first transmission and the second transmission that the UE supports for using the third reference signal of the second reference signal type as the QCL source for the second transmission.

[0014] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying a component carrier associated with the second transmission based on the first transmission.

[0015] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for identifying, based on the second grant, a component carrier associated with the second transmission.

[0016] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for transmitting an acknowledgement message for the first transmission, and identifying the third reference signal of the second reference signal type as the QCL source for the second transmission based on the transmission of the acknowledgement message for the first transmission.

[0017] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that a timing difference between transmission of the acknowledgement message and the second transmission may be within a threshold timing window, where using the third reference signal of the second reference signal type as the QCL source for the second transmission may be based on the timing difference.

[0018] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that there were multiple first transmissions, with each of the first transmissions associated with a different component carrier, identifying a numerical control resource set identifier associated with each first transmission, and determining to use the third reference signal of the second reference signal type as the QCL source for the second transmission based on the first transmission having a lowest numerical control resources set identifier.

[0019] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that a timing difference between the first transmission and the second transmission may have exceed a threshold, and using the third reference signal of the second reference signal type as the QCL source for the second transmission based on the timing difference exceeding the threshold.

[0020] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that a timing difference between the first transmission and the second transmission may have exceed a threshold, and using the third reference signal of the second reference signal type as the QCL source for the second transmission based on the timing difference exceeding the threshold.

[0021] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for determining that a timing difference between the first transmission and the second transmission may have exceeded a threshold, and refraining from using the third reference signal of the second reference signal type as the QCL source for the second transmission based on the timing difference exceeding the threshold.

[0022] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the first transmission occurs according to a slot- aggregation scheme including two or more slots.

[0023] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the first reference signal type includes a QCL source reference signal type identified in a TCI state or a TCI reference signal set of the first grant, and the second reference signal type includes a demodulation reference signal transmitted in conjunction with the corresponding transmission. [0024] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the first reference signal type includes at least one of a tracking reference signal, or a channel state information reference signal (CSI-RS), or a synchronization signal block (SSB), or a combination thereof.

[0025] A method of wireless communication by a base station is described. The method may include transmitting a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first QCL source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission and transmitting a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0026] An apparatus for wireless communication by a base station is described. The apparatus may include a processor, memory coupled with the processor, and instructions stored in the memory. The instructions may be executable by the processor to cause the apparatus to transmit a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first QCL source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission and transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0027] Another apparatus for wireless communication by a base station is described. The apparatus may include means for transmitting a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first QCL source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission and transmitting a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0028] A non-transitory computer-readable medium storing code for wireless communication by a base station is described. The code may include instructions executable by a processor to transmit a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first QCL source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission and transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0029] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for using the third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission may be based on at least one of a transmission timing of the second grant, or a transmission timing of the second downlink transmission, or a combination thereof.

[0030] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for configuring the second grant with a timing indication identifying the first downlink transmission from which the UE may be to use the third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0031] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the timing indication may be based on at least one of a first grant transmission timing, or a first downlink transmission timing, or a second grant transmission timing, or a second downlink transmission timing, or a combination thereof. [0032] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the timing indication may be indicated in a QCL source reference signal type identifier in a TCI state or a TCI reference signal set of the second grant.

[0033] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving a UE capability message identifying a minimum supported gap between the first downlink transmission and the second downlink transmission that the UE supports for using the third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0034] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the first downlink transmission and the second downlink transmission may be performed on a same or a different component carrier.

[0035] Some examples of the method, apparatuses, and non-transitory computer-readable medium described herein may further include operations, features, means, or instructions for receiving an acknowledgement message for the first downlink transmission, where using the third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission may be based on the receipt of the acknowledgement message for the first downlink transmission.

[0036] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, a timing difference between receipt of the acknowledgement message and the second downlink transmission may be within a threshold timing window.

[0037] In some examples of the method, apparatuses, and non-transitory computer- readable medium described herein, the first reference signal type includes a QCL source reference signal type identified in a TCI state or a TCI reference signal set of the first grant, and the second reference signal type includes a demodulation reference signal transmitted in conjunction with the corresponding downlink transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] FIG. 1 illustrates an example of a system for wireless communications that supports using a demodulation reference signal (DMRS) of a data transmission as a quasi colocation (QCL) reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0039] FIG. 2 illustrates an example of a slot configuration that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0040] FIG. 3 illustrates an example of a slot configuration that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0041] FIG. 4 illustrates an example of a slot configuration that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. [0042] FIG. 5 illustrates an example of a slot configuration that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0043] FIG. 6 illustrates an example of a slot configuration that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0044] FIG. 7 illustrates an example of a slot configuration that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0045] FIGs. 8 and 9 show block diagrams of devices that support using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0046] FIG. 10 shows a block diagram of a communications manager that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. [0047] FIG. 11 shows a diagram of a system including a device that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0048] FIGs. 12 and 13 show block diagrams of devices that support using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0049] FIG. 14 shows a block diagram of a communications manager that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0050] FIG. 15 shows a diagram of a system including a device that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

[0051] FIGs. 16 through 20 show flowcharts illustrating methods that support using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

[0052] Wireless communication systems typically use channel estimates to support wireless communications. For example, a first reference signal type (e.g., a tracking reference signal (TRS), a channel state information reference signal (CSI-RS), a synchronization signal block (SSB), etc.) may be configured as a quasi-colocation (QCL) source for a transmission (e.g., a sidelink transmission, a downlink transmission, etc.) that is used to derive large scale channel estimates for the transmission, e.g., Doppler shift, Doppler spread, average delay, delay spread, etc. A second reference signal type (e.g., a demodulation reference signal (DMRS)) may also be configured for the transmission that is used, in conjunction with the large scale channel estimates, to determine the channel estimate for the transmission. Some wireless communication systems signal the first and second reference signal types in a grant (e.g., a downlink control information (DCI) grant) scheduling the transmission. However, this approach involves substantial overhead and, perhaps more importantly, limits the configurations available for use by the base station that can then be utilized by the UE. [0053] Aspects of the disclosure are initially described in the context of a wireless communications system. The described techniques relate to improved methods, systems, devices, and apparatuses that support using a DMRS of a data transmission as a QCL reference signal source for another data transmission. Generally, the described techniques provide for reuse of the DMRS from a first data transmission (e.g., a physical downlink shared channel (PDSCH) transmission, a physical sidelink shared channel (PSSCH) transmission) as the QCL source for a subsequent data transmission. For example, a UE may receive a grant scheduling a downlink transmission to the UE (e.g., a first grant scheduling a first downlink transmission). The grant may generally configure or otherwise identify various parameters associated with the downlink transmission. For example, the grant may identify a reference signal to be used as a QCL source for a channel estimation during the downlink transmission. That is, the QCL source reference signal of the downlink transmission may be used, along with the DMRS scheduled for the downlink transmission, for channel estimation during the downlink transmission. Accordingly, the UE may identify a set of QCL parameters for the downlink transmission based on the QCL source reference signal, and then identify the channel estimate for the downlink transmission using the set of QCL parameters and the DMRS. The UE may then receive a second grant scheduling a second downlink transmission. In this second grant, the base station may signal for the UE to use the DMRS of the first downlink transmission as the QCL source for DMRS of the second downlink transmission. That is, the second grant may signal for the UE to use the DMRS of the first PDSCH as the QCL source for the DMRS scheduled by the second grant. The UE may perform the channel estimation for the second downlink transmission according to the second grant, and using the DMRS of the first downlink transmission as the QCL source for the second downlink transmission and the DMRS of the second downlink transmission.

[0054] Aspects of the disclosure are further illustrated by and described with reference to apparatus diagrams, system diagrams, and flowcharts that relate to using a DMRS of a data transmission as a QCL reference signal source for another data transmission.

[0055] FIG. 1 illustrates an example of a wireless communications system 100 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The wireless communications system 100 includes base stations 105, UEs 115, and a core network 130. In some examples, the wireless communications system 100 may be a Long Term Evolution (LTE) network, an LTE- Advanced (LTE-A) network, an LTE-A Pro network, or a New Radio (NR) network. In some cases, wireless communications system 100 may support enhanced broadband communications, ultra-reliable (e.g., mission critical) communications, low latency communications, or communications with low-cost and low-complexity devices.

[0056] Base stations 105 may wirelessly communicate with UEs 115 via one or more base station antennas. Base stations 105 described herein may include or may be referred to by those skilled in the art as a base transceiver station, a radio base station, an access point, a radio transceiver, a NodeB, an eNodeB (eNB), a next-generation NodeB or giga-NodeB (either of which may be referred to as a gNB), a Home NodeB, a Home eNodeB, or some other suitable terminology. Wireless communications system 100 may include base stations 105 of different types (e.g., macro or small cell base stations). The UEs 115 described herein may be able to communicate with various types of base stations 105 and network equipment including macro eNBs, small cell eNBs, gNBs, relay base stations, and the like.

[0057] Each base station 105 may be associated with a particular geographic coverage area 110 in which communications with various UEs 115 is supported. Each base station 105 may provide communication coverage for a respective geographic coverage area 110 via communication links 125, and communication links 125 between a base station 105 and a UE 115 may utilize one or more carriers. Communication links 125 shown in wireless communications system 100 may include uplink transmissions from a UE 115 to a base station 105, or downlink transmissions from a base station 105 to a UE 115. Downlink transmissions may also be called forward link transmissions while uplink transmissions may also be called reverse link transmissions.

[0058] The geographic coverage area 110 for a base station 105 may be divided into sectors making up a portion of the geographic coverage area 110, and each sector may be associated with a cell. For example, each base station 105 may provide communication coverage for a macro cell, a small cell, a hot spot, or other types of cells, or various combinations thereof. In some examples, a base station 105 may be movable and therefore provide communication coverage for a moving geographic coverage area 110. In some examples, different geographic coverage areas 110 associated with different technologies may overlap, and overlapping geographic coverage areas 110 associated with different technologies may be supported by the same base station 105 or by different base stations 105. The wireless communications system 100 may include, for example, a heterogeneous LTE/LTE-A/LTE-A Pro or NR network in which different types of base stations 105 provide coverage for various geographic coverage areas 110.

[0059] The term “cell” refers to a logical communication entity used for communication with a base station 105 (e.g., over a carrier), and may be associated with an identifier for distinguishing neighboring cells (e.g., a physical cell identifier (PCID), a virtual cell identifier (VCID)) operating via the same or a different carrier. In some examples, a carrier may support multiple cells, and different cells may be configured according to different protocol types (e.g., machine-type communication (MTC), narrowband Internet-of-Things (NB-IoT), enhanced mobile broadband (eMBB), or others) that may provide access for different types of devices. In some cases, the term “cell” may refer to a portion of a geographic coverage area 110 (e.g., a sector) over which the logical entity operates.

[0060] UEs 115 may be dispersed throughout the wireless communications system 100, and each UE 115 may be stationary or mobile. A UE 115 may also be referred to as a mobile device, a wireless device, a remote device, a handheld device, or a subscriber device, or some other suitable terminology, where the “device” may also be referred to as a unit, a station, a terminal, or a client. A UE 115 may also be a personal electronic device such as a cellular phone, a personal digital assistant (PDA), a tablet computer, a laptop computer, or a personal computer. In some examples, a UE 115 may also refer to a wireless local loop (WLL) station, an Internet of Things (IoT) device, an Internet of Everything (IoE) device, or an MTC device, or the like, which may be implemented in various articles such as appliances, vehicles, meters, or the like.

[0061] Some UEs 115, such as MTC or IoT devices, may be low cost or low complexity devices, and may provide for automated communication between machines (e.g., via Machine-to-Machine (M2M) communication). M2M communication or MTC may refer to data communication technologies that allow devices to communicate with one another or a base station 105 without human intervention. In some examples, M2M communication or MTC may include communications from devices that integrate sensors or meters to measure or capture information and relay that information to a central server or application program that can make use of the information or present the information to humans interacting with the program or application. Some UEs 115 may be designed to collect information or enable automated behavior of machines. Examples of applications for MTC devices include smart metering, inventory monitoring, water level monitoring, equipment monitoring, healthcare monitoring, wildlife monitoring, weather and geological event monitoring, fleet management and tracking, remote security sensing, physical access control, and transaction-based business charging.

[0062] Some UEs 115 may be configured to employ operating modes that reduce power consumption, such as half-duplex communications (e.g., a mode that supports one-way communication via transmission or reception, but not transmission and reception simultaneously). In some examples half-duplex communications may be performed at a reduced peak rate. Other power conservation techniques for UEs 115 include entering a power saving “deep sleep” mode when not engaging in active communications, or operating over a limited bandwidth (e.g., according to narrowband communications). In some cases, UEs 115 may be designed to support critical functions (e.g., mission critical functions), and a wireless communications system 100 may be configured to provide ultra-reliable communications for these functions.

[0063] In some cases, a UE 115 may also be able to communicate directly with other UEs 115 (e.g., using a peer-to-peer (P2P) or device-to-device (D2D) protocol). One or more of a group of UEs 115 utilizing D2D communications may be within the geographic coverage area 110 of a base station 105. Other UEs 115 in such a group may be outside the geographic coverage area 110 of a base station 105, or be otherwise unable to receive transmissions from a base station 105. In some cases, groups of UEs 115 communicating via D2D communications may utilize a one-to-many (1:M) system in which each UE 115 transmits to every other UE 115 in the group. In some cases, a base station 105 facilitates the scheduling of resources for D2D communications. In other cases, D2D communications are carried out between UEs 115 without the involvement of a base station 105.

[0064] Base stations 105 may communicate with the core network 130 and with one another. For example, base stations 105 may interface with the core network 130 through backhaul links 132 (e.g., via an SI, N2, N3, or other interface). Base stations 105 may communicate with one another over backhaul links 134 (e.g., via an X2, Xn, or other interface) either directly (e.g., directly between base stations 105) or indirectly (e.g., via core network 130). [0065] The core network 130 may provide user authentication, access authorization, tracking, Internet Protocol (IP) connectivity, and other access, routing, or mobility functions. The core network 130 may be an evolved packet core (EPC), which may include at least one mobility management entity (MME), at least one serving gateway (S-GW), and at least one Packet Data Network (PDN) gateway (P-GW). The MME may manage non-access stratum (e.g., control plane) functions such as mobility, authentication, and bearer management for UEs 115 served by base stations 105 associated with the EPC. User IP packets may be transferred through the S-GW, which itself may be connected to the P-GW. The P-GW may provide IP address allocation as well as other functions. The P-GW may be connected to the network operators IP services. The operators IP services may include access to the Internet, Intranet(s), an IP Multimedia Subsystem (IMS), or a Packet-Switched (PS) Streaming Service.

[0066] At least some of the network devices, such as a base station 105, may include subcomponents such as an access network entity, which may be an example of an access node controller (ANC). Each access network entity may communicate with UEs 115 through a number of other access network transmission entities, which may be referred to as a radio head, a smart radio head, or a transmission/reception point (TRP). In some configurations, various functions of each access network entity or base station 105 may be distributed across various network devices (e.g., radio heads and access network controllers) or consolidated into a single network device (e.g., a base station 105).

[0067] Wireless communications system 100 may operate using one or more frequency bands, typically in the range of 300 megahertz (MHz) to 300 gigahertz (GHz). Generally, the region from 300 MHz to 3 GHz is known as the ultra-high frequency (UHF) region or decimeter band, since the wavelengths range from approximately one decimeter to one meter in length. UHF waves may be blocked or redirected by buildings and environmental features. However, the waves may penetrate structures sufficiently for a macro cell to provide service to UEs 115 located indoors. Transmission of UHF waves may be associated with smaller antennas and shorter range (e.g., less than 100 km) compared to transmission using the smaller frequencies and longer waves of the high frequency (HF) or very high frequency (VHF) portion of the spectrum below 300 MHz. [0068] Wireless communications system 100 may also operate in a super high frequency (SHF) region using frequency bands from 3 GHz to 30 GHz, also known as the centimeter band. The SHF region includes bands such as the 5 GHz industrial, scientific, and medical (ISM) bands, which may be used opportunistically by devices that may be capable of tolerating interference from other users.

[0069] Wireless communications system 100 may also operate in an extremely high frequency (EHF) region of the spectrum (e.g., from 30 GHz to 300 GHz), also known as the millimeter band. In some examples, wireless communications system 100 may support millimeter wave (mmW) communications between UEs 115 and base stations 105, and EHF antennas of the respective devices may be even smaller and more closely spaced than UHF antennas. In some cases, this may facilitate use of antenna arrays within a UE 115. However, the propagation of EHF transmissions may be subject to even greater atmospheric attenuation and shorter range than SHF or UHF transmissions. Techniques disclosed herein may be employed across transmissions that use one or more different frequency regions, and designated use of bands across these frequency regions may differ by country or regulating body.

[0070] In some cases, wireless communications system 100 may utilize both licensed and unlicensed radio frequency spectrum bands. For example, wireless communications system 100 may employ License Assisted Access (LAA), LTE-Unlicensed (LTE-U) radio access technology, or NR technology in an unlicensed band such as the 5 GHz ISM band. When operating in unlicensed radio frequency spectrum bands, wireless devices such as base stations 105 and UEs 115 may employ listen-before-talk (LBT) procedures to ensure a frequency channel is clear before transmitting data. In some cases, operations in unlicensed bands may be based on a carrier aggregation configuration in conjunction with component carriers operating in a licensed band (e.g., LAA). Operations in unlicensed spectrum may include downlink transmissions, uplink transmissions, peer-to-peer transmissions, or a combination of these. Duplexing in unlicensed spectrum may be based on frequency division duplexing (FDD), time division duplexing (TDD), or a combination of both.

[0071] In some examples, base station 105 or UE 115 may be equipped with multiple antennas, which may be used to employ techniques such as transmit diversity, receive diversity, multiple-input multiple-output (MIMO) communications, or beamforming. For example, wireless communications system 100 may use a transmission scheme between a transmitting device (e.g., a base station 105) and a receiving device (e.g., a UE 115), where the transmitting device is equipped with multiple antennas and the receiving device is equipped with one or more antennas. MIMO communications may employ multipath signal propagation to increase the spectral efficiency by transmitting or receiving multiple signals via different spatial layers, which may be referred to as spatial multiplexing. The multiple signals may, for example, be transmitted by the transmitting device via different antennas or different combinations of antennas. Likewise, the multiple signals may be received by the receiving device via different antennas or different combinations of antennas. Each of the multiple signals may be referred to as a separate spatial stream, and may carry bits associated with the same data stream (e.g., the same codeword) or different data streams. Different spatial layers may be associated with different antenna ports used for channel measurement and reporting. MIMO techniques include single-user MIMO (SU-MIMO) where multiple spatial layers are transmitted to the same receiving device, and multiple-user MIMO (MU- MIMO) where multiple spatial layers are transmitted to multiple devices.

[0072] Beamforming, which may also be referred to as spatial filtering, directional transmission, or directional reception, is a signal processing technique that may be used at a transmitting device or a receiving device (e.g., a base station 105 or a UE 115) to shape or steer an antenna beam (e.g., a transmit beam or receive beam) along a spatial path between the transmitting device and the receiving device. Beamforming may be achieved by combining the signals communicated via antenna elements of an antenna array such that signals propagating at particular orientations with respect to an antenna array experience constructive interference while others experience destructive interference. The adjustment of signals communicated via the antenna elements may include a transmitting device or a receiving device applying certain amplitude and phase offsets to signals carried via each of the antenna elements associated with the device. The adjustments associated with each of the antenna elements may be defined by a beamforming weight set associated with a particular orientation (e.g., with respect to the antenna array of the transmitting device or receiving device, or with respect to some other orientation).

[0073] In one example, a base station 105 may use multiple antennas or antenna arrays to conduct beamforming operations for directional communications with a UE 115. For instance, some signals (e.g. synchronization signals, reference signals, beam selection signals, or other control signals) may be transmitted by a base station 105 multiple times in different directions, which may include a signal being transmitted according to different beamforming weight sets associated with different directions of transmission. Transmissions in different beam directions may be used to identify (e.g., by the base station 105 or a receiving device, such as a UE 115) a beam direction for subsequent transmission and/or reception by the base station 105.

[0074] Some signals, such as data signals associated with a particular receiving device, may be transmitted by a base station 105 in a single beam direction (e.g., a direction associated with the receiving device, such as a UE 115). In some examples, the beam direction associated with transmissions along a single beam direction may be determined based at least in in part on a signal that was transmitted in different beam directions. For example, a UE 115 may receive one or more of the signals transmitted by the base station 105 in different directions, and the UE 115 may report to the base station 105 an indication of the signal it received with a highest signal quality, or an otherwise acceptable signal quality. Although these techniques are described with reference to signals transmitted in one or more directions by a base station 105, a UE 115 may employ similar techniques for transmitting signals multiple times in different directions (e.g., for identifying a beam direction for subsequent transmission or reception by the UE 115), or transmitting a signal in a single direction (e.g., for transmitting data to a receiving device).

[0075] A receiving device (e.g., a UE 115, which may be an example of a mmW receiving device) may try multiple receive beams when receiving various signals from the base station 105, such as synchronization signals, reference signals, beam selection signals, or other control signals. For example, a receiving device may try multiple receive directions by receiving via different antenna subarrays, by processing received signals according to different antenna subarrays, by receiving according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, or by processing received signals according to different receive beamforming weight sets applied to signals received at a plurality of antenna elements of an antenna array, any of which may be referred to as “listening” according to different receive beams or receive directions. In some examples a receiving device may use a single receive beam to receive along a single beam direction (e.g., when receiving a data signal). The single receive beam may be aligned in a beam direction determined based at least in part on listening according to different receive beam directions (e.g., a beam direction determined to have a highest signal strength, highest signal-to-noise ratio, or otherwise acceptable signal quality based at least in part on listening according to multiple beam directions).

[0076] In some cases, the antennas of a base station 105 or UE 115 may be located within one or more antenna arrays, which may support MIMO operations, or transmit or receive beamforming. For example, one or more base station antennas or antenna arrays may be co located at an antenna assembly, such as an antenna tower. In some cases, antennas or antenna arrays associated with a base station 105 may be located in diverse geographic locations. A base station 105 may have an antenna array with a number of rows and columns of antenna ports that the base station 105 may use to support beamforming of communications with a UE 115. Likewise, a UE 115 may have one or more antenna arrays that may support various MIMO or beamforming operations.

[0077] In some cases, wireless communications system 100 may be a packet-based network that operate according to a layered protocol stack. In the user plane, communications at the bearer or Packet Data Convergence Protocol (PDCP) layer may be IP -based. A Radio Link Control (RLC) layer may perform packet segmentation and reassembly to communicate over logical channels. A Medium Access Control (MAC) layer may perform priority handling and multiplexing of logical channels into transport channels. The MAC layer may also use hybrid automatic repeat request (HARQ) to provide retransmission at the MAC layer to improve link efficiency. In the control plane, the Radio Resource Control (RRC) protocol layer may provide establishment, configuration, and maintenance of an RRC connection between a UE 115 and a base station 105 or core network 130 supporting radio bearers for user plane data. At the Physical layer, transport channels may be mapped to physical channels.

[0078] In some cases, UEs 115 and base stations 105 may support retransmissions of data to increase the likelihood that data is received successfully. HARQ feedback is one technique of increasing the likelihood that data is received correctly over a communication link 125. HARQ may include a combination of error detection (e.g., using a cyclic redundancy check (CRC)), forward error correction (FEC), and retransmission (e.g., automatic repeat request (ARQ)). HARQ may improve throughput at the MAC layer in poor radio conditions (e.g., signal-to-noise conditions). In some cases, a wireless device may support same-slot HARQ feedback, where the device may provide HARQ feedback in a specific slot for data received in a previous symbol in the slot. In other cases, the device may provide HARQ feedback in a subsequent slot, or according to some other time interval.

[0079] Time intervals in LTE or NR may be expressed in multiples of a basic time unit, which may, for example, refer to a sampling period of T_s = 1/30,720,000 seconds. Time intervals of a communications resource may be organized according to radio frames each having a duration of 10 milliseconds (ms), where the frame period may be expressed as Tf = 307,200 Ts. The radio frames may be identified by a system frame number (SFN) ranging from 0 to 1023. Each frame may include 10 subframes numbered from 0 to 9, and each subframe may have a duration of 1 ms. A subframe may be further divided into 2 slots each having a duration of 0.5 ms, and each slot may contain 6 or 7 modulation symbol periods (e.g., depending on the length of the cyclic prefix prepended to each symbol period). Excluding the cyclic prefix, each symbol period may contain 2048 sampling periods. In some cases, a subframe may be the smallest scheduling unit of the wireless communications system 100, and may be referred to as a transmission time interval (TTI). In other cases, a smallest scheduling unit of the wireless communications system 100 may be shorter than a subframe or may be dynamically selected (e.g., in bursts of shortened TTIs (sTTIs) or in selected component carriers using sTTIs).

[0080] In some wireless communications systems, a slot may further be divided into multiple mini-slots containing one or more symbols. In some instances, a symbol of a mini slot or a mini-slot may be the smallest unit of scheduling. Each symbol may vary in duration depending on the subcarrier spacing or frequency band of operation, for example. Further, some wireless communications systems may implement slot aggregation in which multiple slots or mini-slots are aggregated together and used for communication between a UE 115 and abase station 105.

[0081] The term “carrier” refers to a set of radio frequency spectrum resources having a defined physical layer structure for supporting communications over a communication link 125. For example, a carrier of a communication link 125 may include a portion of a radio frequency spectrum band that is operated according to physical layer channels for a given radio access technology. Each physical layer channel may carry user data, control information, or other signaling. A carrier may be associated with a pre-defmed frequency channel (e.g., an evolved universal mobile telecommunication system terrestrial radio access (E-UTRA) absolute radio frequency channel number (EARFCN)), and may be positioned according to a channel raster for discovery by UEs 115. Carriers may be downlink or uplink (e.g., in an FDD mode), or be configured to carry downlink and uplink communications (e.g., in a TDD mode). In some examples, signal waveforms transmitted over a carrier may be made up of multiple sub-carriers (e.g., using multi-carrier modulation (MCM) techniques such as orthogonal frequency division multiplexing (OFDM) or discrete Fourier transform spread OFDM (DFT-S-OFDM)).

[0082] The organizational structure of the carriers may be different for different radio access technologies (e.g., LTE, LTE-A, LTE-A Pro, NR). For example, communications over a carrier may be organized according to TTIs or slots, each of which may include user data as well as control information or signaling to support decoding the user data. A carrier may also include dedicated acquisition signaling (e.g., synchronization signals or system information, etc.) and control signaling that coordinates operation for the carrier. In some examples (e.g., in a carrier aggregation configuration), a carrier may also have acquisition signaling or control signaling that coordinates operations for other carriers.

[0083] Physical channels may be multiplexed on a carrier according to various techniques. A physical control channel and a physical data channel may be multiplexed on a downlink carrier, for example, using time division multiplexing (TDM) techniques, frequency division multiplexing (FDM) techniques, or hybrid TDM-FDM techniques. In some examples, control information transmitted in a physical control channel may be distributed between different control regions in a cascaded manner (e.g., between a common control region or common search space and one or more UE-specific control regions or UE- specific search spaces).

[0084] A carrier may be associated with a particular bandwidth of the radio frequency spectrum, and in some examples the carrier bandwidth may be referred to as a “system bandwidth” of the carrier or the wireless communications system 100. For example, the carrier bandwidth may be one of a number of predetermined bandwidths for carriers of a particular radio access technology (e.g., 1.4, 3, 5, 10, 15, 20, 40, or 80 MHz). In some examples, each served UE 115 may be configured for operating over portions or all of the carrier bandwidth. In other examples, some UEs 115 may be configured for operation using a narrowband protocol type that is associated with a predefined portion or range (e.g., set of subcarriers or RBs) within a carrier (e.g., “in-band” deployment of a narrowband protocol type).

[0085] In a system employing MCM techniques, a resource element may consist of one symbol period (e.g., a duration of one modulation symbol) and one subcarrier, where the symbol period and subcarrier spacing are inversely related. The number of bits carried by each resource element may depend on the modulation scheme (e.g., the order of the modulation scheme). Thus, the more resource elements that a UE 115 receives and the higher the order of the modulation scheme, the higher the data rate may be for the UE 115. In MIMO systems, a wireless communications resource may refer to a combination of a radio frequency spectrum resource, a time resource, and a spatial resource (e.g., spatial layers), and the use of multiple spatial layers may further increase the data rate for communications with a UE 115.

[0086] Devices of the wireless communications system 100 (e.g., base stations 105 or UEs 115) may have a hardware configuration that supports communications over a particular carrier bandwidth, or may be configurable to support communications over one of a set of carrier bandwidths. In some examples, the wireless communications system 100 may include base stations 105 and/or UEs 115 that support simultaneous communications via carriers associated with more than one different carrier bandwidth.

[0087] Wireless communications system 100 may support communication with a UE 115 on multiple cells or carriers, a feature which may be referred to as carrier aggregation or multi-carrier operation. A UE 115 may be configured with multiple downlink component carriers and one or more uplink component carriers according to a carrier aggregation configuration. Carrier aggregation may be used with both FDD and TDD component carriers.

[0088] In some cases, wireless communications system 100 may utilize enhanced component carriers (eCCs). An eCC may be characterized by one or more features including wider carrier or frequency channel bandwidth, shorter symbol duration, shorter TTI duration, or modified control channel configuration. In some cases, an eCC may be associated with a carrier aggregation configuration or a dual connectivity configuration (e.g., when multiple serving cells have a suboptimal or non-ideal backhaul link). An eCC may also be configured for use in unlicensed spectrum or shared spectrum (e.g., where more than one operator is allowed to use the spectrum). An eCC characterized by wide carrier bandwidth may include one or more segments that may be utilized by UEs 115 that are not capable of monitoring the whole carrier bandwidth or are otherwise configured to use a limited carrier bandwidth (e.g., to conserve power).

[0089] In some cases, an eCC may utilize a different symbol duration than other component carriers, which may include use of a reduced symbol duration as compared with symbol durations of the other component carriers. A shorter symbol duration may be associated with increased spacing between adjacent subcarriers. A device, such as a UE 115 or base station 105, utilizing eCCs may transmit wideband signals (e.g., according to frequency channel or carrier bandwidths of 20, 40, 60, 80 MHz, etc.) at reduced symbol durations (e.g., 16.67 microseconds). A TTI in eCC may consist of one or multiple symbol periods. In some cases, the TTI duration (that is, the number of symbol periods in a TTI) may be variable.

[0090] Wireless communications system 100 may be an NR system that may utilize any combination of licensed, shared, and unlicensed spectrum bands, among others. The flexibility of eCC symbol duration and subcarrier spacing may allow for the use of eCC across multiple spectrums. In some examples, NR shared spectrum may increase spectrum utilization and spectral efficiency, specifically through dynamic vertical (e.g., across the frequency domain) and horizontal (e.g., across the time domain) sharing of resources.

[0091] A UE 115 may receive a first grant scheduling a first transmission to the UE 115, the first grant identifying a first reference signal of a first reference signal type for the UE 115 to use as a first QCL source for the first transmission and a second reference signal of a second reference signal type for the UE 115 to use to perform a channel estimation for the first transmission. The UE 115 may identify, based at least in part on the first reference signal, a set of QCL parameters for the first transmission. The UE 115 may identify the channel estimate for the first transmission based at least in part on the set of QCL parameters and the second reference signal. The UE 115 may receive a second grant scheduling a second transmission to the UE 115, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second transmission and for the UE 115 to determine the identified channel estimate for the second transmission. The UE 115 may perform a channel estimation for the second transmission based at least in part on the second reference signal, the second grant, and the third reference signal.

[0092] A base station 105 may transmit a first grant scheduling a first downlink transmission to a UE 115, the first grant identifying a first reference signal of a first reference signal type for the UE 115 to use as a first QCL source for the first downlink transmission and a second reference signal of a second reference signal type for the UE 115 to use to perform a channel estimation for the first downlink transmission. The base station 105 may transmit a second grant scheduling a second downlink transmission to the UE 115, the second grant identifying a third reference signal of the second reference signal type as the QCL source for the second downlink transmission and for the UE 115 to determine the identified channel estimate for the second downlink transmission.

[0093] FIG. 2 illustrates an example of a slot configuration 200 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. In some examples, slot configuration 200 may implement aspects of wireless communication system 100. Aspects of slot configuration 200 may be implemented by a base station and/or a UE, which may be examples of the corresponding devices described herein.

[0094] Slot configuration 200 may include a plurality of slots 205, with slots 205-a, 205- b, 205-c, 205-d, and 205-e being shown by way of example only. It is to be understood that slot configuration 200 may include fewer or more slots 205 than the five slots 205 illustrated in FIG. 2. Slots 205 may be contiguous or non-contiguous slots 205, e.g., in the time domain. In the example illustrated in slot configuration 200, each slot 205 may be associated with one or more physical channel transmissions 210. As illustrated, the transmissions 210 may be referred to as PyxCH transmissions, e.g., where y = (S)idelink or (D)ownlink and x =

(S)hared or (C)ontrol. That is, the transmissions 210 may be examples of PDSCH downlink transmissions, physical downlink control channel (PDCCH) transmissions, physical sidelink control channel (PSCCH) transmissions, physical sidelink shared channel (PSSCH) transmissions, or any combination thereof. Generally, each transmission 210 may have one or more associated reference signals 215. Each transmission 210 may be scheduled by a grant, such as a DCI grant that configures the reference signals 215 for the downlink transmission. [0095] Reference signals 215 are typically used for channel performance estimations. However, different reference signal types may be used for different purposes. In one example, a first reference signal type of a first reference signal 215 may be used or otherwise designated as a QCL source for a transmission 210. The QCL source is generally the reference signal used by the UE to determine a set of QCL parameters corresponding to the large scale properties of the channel. Examples of the set of QCL parameters may correspond to the Doppler shift, the Doppler spread, the average delay, the delay spread, and the like, for the channel used for the transmission 210. In some examples, the reference signal type of a reference signal 215 may correspond to or otherwise be based on the set of QCL parameters. For instance, reference signal 215-a may be a reference signal Type-A, and the UE may determine the set of QCL parameters according to the reference signal Type-A. A second reference signal (e.g., a DMRS) may also be identified in the grant scheduling the downlink transmission.

[0096] Generally, the reference signals 215 may be configured in a grant, such as a DCI grant that schedules the transmission 210. For example, the grant may include a transmission configuration indicator (TCI) state or TCI reference signal set that includes an information element, bit(s), field(s), etc., that identifies the reference signals 215 being used for the transmission 210. In some wireless communication systems, the TCI state or TCI reference signal indicated in the grant identifies a first reference signal of a first reference signal type that serves as a QCL source reference signal for the downlink transmission. Examples of the first reference signal type include, but are not limited to, a TRS, a CSI-RS, an SSB, etc. For example, the TCI may use 0 bit if higher layer parameter tci-PresentlnDCI is not enabled or three (or more) bits if the higher layer parameter is enabled.

[0097] The UE uses the first reference signal of the first reference signal type to measure, derive, or otherwise identify the set of QCL parameters for the transmission 210. For example, the UE may identify the set of QCL parameters based on the type of the reference signal. The grant may also be configured to identify a second reference signal of a second reference signal type for the UE to use for performing channel estimation for the transmission 210. Examples of the second reference signal of the second reference signal type include, but are not limited to, a DMRS, a CRI-RS, an SSB, and the like. [0098] The UE would then use the set of QCL parameters derived from the first reference signal (e.g., TRS) along with the second reference signal (e.g., the DMRS) to measure, determine, or otherwise identify the channel estimate for the transmission 210. The channel estimate is used by the UE to receive and decode the transmission 210.

[0099] This example is illustrated in slot configuration 200 where a first grant schedules the transmission 210-a and identifies the first reference signal of the first reference signal type as the QCL source for the transmission 210-a and the second reference signal of the second reference signal type (e.g., a DMRS) for the UE to use to perform the channel estimation for the transmission 210-a. For example, the UE may use the first reference signal (e.g. the TRS) to identify the set of QCL parameters and then use the set of QCL parameters and the second reference signal (e.g., the DMRS) to identify the channel estimate for the transmission 210-a scheduled by the grant.

[0100] In some wireless communication systems, this approach is utilized for each grant scheduling a transmission 210. However, this approach uses considerable overhead and limits the available configurations that can be used. Moreover, this approach may be unnecessary in some situations. For example, the large scale properties of the channel (e.g., the set of QCL parameters) may not change enough between successive grants and/or slots to justify the UE having to recalculate the set of QCL parameters for each transmission 210. For example, low UE mobility may indicate that the large scale properties of the channel do not change enough between successive grants. In this situation, the techniques discussed above may be unnecessary and/or wasteful.

[0101] Accordingly, aspects of the described techniques support the UE receiving a second grant scheduling a second downlink transmission (e.g., transmission 210-b) to the UE. The second grant may carry or otherwise convey information identifying a third reference signal of the second reference signal type (e.g., a DMRS of the first transmission 210-a) that the UE is to use as the QCL source for the second transmission 210-b. In one example, the first reference signal 215 of the first reference signal type may be a TRS, the second reference signal of the second reference signal type may be the DMRS scheduled by the first grant, and the third reference signal of the second reference signal type may be the DMRS of the first transmission 210-a. Accordingly, the base station may configure the UE to use the TRS of the channel, e.g., a PDSCH, as the QCL source of the DMRS of the first PDSCH (e.g., the reference signal 215-a in the first transmission 210-a), and to use the DMRS of the first PDSCH as the QCL source of the DMRS of the second PDSCH. The UE may perform the channel estimation for the second downlink transmission according to the second grant and using the second reference signal and the third reference signal.

[0102] More particularly, the base station may transmit a first grant to the UE during slot 205-a that schedules a first transmission 210-a for the UE. The first grant may identify the first reference signal of the first reference signal type as the QCL source for the first transmission 210-a and a second reference signal of the second reference signal type for the UE to use to perform channel estimation for the first transmission 210-a. The UE may use the first reference signal as the QCL source to identify the set of QCL parameters and then use the QCL parameters and the second reference signal to perform channel estimation during the first transmission 210-a. The UE may receive and decode the first transmission 210-a from the base station during slot 205-a based, at least in some aspects, on the channel estimation.

[0103] During slot 205-b, the UE may receive a second grant from the base station scheduling a second transmission 210-b for the UE. The second grant may identify the third reference signal of the second reference signal type (e.g., the DMRS of the first transmission 210-a) as the QCL source for the second transmission 210-b. The UE may, according to the second grant, use the DMRS from the first transmission 210-a and the DMRS scheduled with the second downlink transmission to perform channel estimation for the second transmission 210-b. The UE may receive and decode the second transmission 210-b from the base station during slot 205-b based, at least in some aspects, on the channel estimation.

[0104] In some aspects, these techniques may be extended for more than two slots. For example, in slot 205-c, the UE may receive a third grant from the base station scheduling a third transmission 210-c for the UE. The third grant may identify the third reference signal of the second reference signal type (e.g., the DMRS of the first transmission 210-a and/or the DMRS of the second transmission 210-b) as the QCL source for the third transmission 210-c. The UE may, according to the third grant, use the DMRS from the first transmission 210-a and/or from the second transmission 210-b along with the DMRS scheduled with the third transmission 210-c to perform channel estimation for the third transmission 210-c. The UE may receive and decode the third transmission 210-c from the base station during slot 205-c based, at least in some aspects, on the channel estimation. [0105] Similarly, during slot 205-d, the UE may receive a fourth grant from the base station scheduling a fourth transmission 210-d for the UE. The fourth grant may identify the third reference signal of the second reference signal type (e.g., the DMRS of the first transmission 210-a, the second transmission 210-b, and/or the third transmission 210-c) as the QCL source for the fourth transmission 210-d. The UE may, according to the fourth grant, use the DMRS from the previous transmission 210 and the DMRS scheduled with the fourth transmission 210-d to perform channel estimation for the fourth transmission 210-d. The UE may receive and decode the fourth transmission 210-d from the base station during slot 205-d based, at least in some aspects, on the channel estimation.

[0106] Although the discussion above describes second, third, and fourth grants being received from the base station and scheduling respective downlink transmissions 210, it is to be understood that in some examples the second (or subsequent) grant may indicate for the UE to use the third reference signal of the second reference signal type as the QCL source for X subsequent slot(s)/downlink transmission(s). In another example, the indication to use the third reference signal of the second reference signal type as the QCL source for the scheduled downlink transmission may be based on a variance of measured channel parameters. For example, the base station/UE may use these techniques until a measured channel estimation is more than X percent different from a previous channel estimation. Additionally, although the examples herein are described in the context of downlink transmissions from a base station to a UE, it is to be understood that such techniques may be applied generally to any type of data transmissions between any type of wireless devices (e.g., sidelink transmissions, etc.)

[0107] In some aspects, the described techniques may be implemented for a certain time period. The time period may be any time period in which the large scale channel properties (e.g., the set of QCL parameters) are expected to remain within a defined range. The time period may be based on UE mobility, past channel performance, and the like.

[0108] In some aspects, the time period may be based on a maximum number of X “QCL chains” that is supported by the wireless communication system in which the DMRS of the first transmission 210 can be used as the QCL source for the DMRS of the second transmission 210. A QCL chain may generally refer to the number of slots in which the DMRS of the previous transmission 210 can be used as the QCL source for the DMRS of the current transmission 210. In the example illustrated in FIG. 2, there are four QCL chains extending from slot 205-a through 205-d. In some aspects, the DMRS of the transmission 210 cannot be used as the QCL source for the DMRS of a subsequent transmission 210 if they are not within X slots of each other. In the situation where discontinuous reception (DRX) is configured, the DMRS of the first transmission 210 cannot be used as the QCL source for the DMRS of the subsequent transmission 210 if they are not in the same active time. After the maximum number of QCL chains is reached, subsequent grants may again identify the first reference signal of the first reference signal type and the second reference signal of the second reference signal type for the UE to use for channel estimation during the corresponding transmission 210.

[0109] Accordingly, during slot 205-e, the base station may transmit a fifth grant to the UE that schedules a fifth transmission 210-e for the UE. The fifth grant may identify the first reference signal of the first reference signal type as the QCL source for the fifth transmission 210-e and a second reference signal of the second reference signal type for the UE to use to perform channel estimation for the fifth transmission 210-e. The UE may use the first reference signal as the QCL source to identify the set of QCL parameters and then use the QCL parameters and the second reference signal to perform channel estimation during the fifth transmission 210-e. The UE may receive and decode the fifth transmission 210-e from the base station during slot 205-e based, at least in some aspects, on the channel estimation.

[0110] Accordingly, aspects of the described techniques support using the DMRS of another channel (e.g., a PDSCH) as a QCL source for the DMRS of a channel (e.g., a PDSCH). Additional QCL types may be supported whenever such a QCL source is allowed. The reason is that the DMRS of the previous PDSCH is UE-specifically precoded, so the similarity between the two channels is expected to be much higher than using a CSI-RS. Example of additional QCL relations include, but are not limited to: Power Delay profile (and not just Delay spread, or average delay); Doppler profile (and not just Doppler spread, or Doppler shift); strong or weak DMRS bundling; and the like.

[0111] In some aspects, DMRS bundling may be supported in accordance with the described techniques. For example, the receiver (e.g., UE) may assume that the same precoder is used across data channels of different scheduling units. The DMRS is coherently transmitted over different time instances, and at the receiver, the DMRS over different time instances can be coherently filtered to enhance the accuracy of channel estimation. This spread may be across mini-slots, across slots 205, and/or across a slot and a mini-slot.

[0112] FIG. 3 illustrates an example of a slot configuration 300 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. In some examples, slot configuration 300 may implement aspects of wireless communication system 100 and/or slot configuration 200. Aspects of slot configuration 300 may be implemented by a base station and/or a UE, which may be examples of the corresponding devices described herein.

[0113] Slot configuration 300 may include a plurality of slots 305, with slots 305-a, 305- b, 305-c, and 305-d being shown by way of example only. It is to be understood that slot configuration 300 may include fewer or more slots 305 than the four slots 305 illustrated in FIG. 3. Slots 305 may be contiguous or non-contiguous slots, e.g., in the time domain. In the example illustrated in slot configuration 300, slots 305 may be associated with one or more grants 310 scheduling corresponding downlink transmissions 315, e.g., PDCCH and/or PDSCH downlink transmissions. As illustrated, the downlink transmissions 315 may be referred to as PyxCH transmissions, e.g., where y = (S)idelink or (D)ownlink and x =

(S)hared or (C)ontrol. That is, the transmissions 315 may be examples of PDSCH downlink transmissions, physical downlink control channel (PDCCH) transmissions, physical sidelink control channel (PSCCH) transmissions, physical sidelink shared channel (PSSCH) transmissions, or any combination thereof. Generally, each downlink transmission 315 may have one or more associated reference signals. Each downlink transmission 315 may be scheduled by a grant 310, such as a DCI grant that configures the reference signals for the downlink transmission 315.

[0114] As discussed above, aspects of the described techniques support a UE using the DMRS (e.g., a third reference signal of a second reference signal type) from an earlier downlink transmission as the QCL source for a subsequent downlink transmission. For example, a base station may transmit a grant 310-a during slot 305-a to a UE scheduling a downlink transmission 315-a to the UE. The grant 310-a may carry or otherwise convey information identifying a first reference signal of a first reference signal type (e.g. a TRS type A, type D, etc.) as the QCL source for the downlink transmission 315-a and a second reference signal of a second reference signal type (e.g., a DMRS scheduled with the downlink transmission 315-a) for the UE to use to perform channel estimation for the downlink transmission 315-a. The UE may use the first reference signal to identify the QCL parameters and then use the QCL parameters and the second reference signal to identify or otherwise perform the channel estimate for the downlink transmission 315-a.

[0115] During slot 305-b, the base station may transmit a grant 310-b to the UE scheduling a downlink transmission 315-b to the UE. The grant 310-b may carry or otherwise convey information identifying a first reference signal of a first reference signal type (e.g. a TRS type A, type D, etc.) as the QCL source for the downlink transmission 315-b and a second reference signal of a second reference signal type (e.g., a DMRS scheduled with the downlink transmission 315-b) for the UE to use to perform channel estimation for the downlink transmission 315-b. The UE may use the first reference signal to identify the QCL parameters and then use the QCL parameters and the second reference signal to identify or otherwise perform the channel estimate for the downlink transmission 315-b.

[0116] During slot 305-c, the base station may transmit a grant 310-c to the UE scheduling a downlink transmission 315-c to the UE. The grant 310-c may carry or otherwise convey information identifying a third reference signal of the second reference signal type (e.g. the DMRS from an earlier downlink transmission 315) as the QCL source for the downlink transmission 315-c and for the UE to perform channel estimation for the downlink transmission 315-c. The UE may use the third reference signal of the second reference signal type to identify the QCL parameters and then use the QCL parameters and the DMRS scheduled for the downlink transmission 315-c to identify or otherwise perform the channel estimate for the downlink transmission 315-c.

[0117] That is, the DMRS of the previous downlink transmission 315 may be used as the QCL source for the DMRS of the downlink transmission 315-c. The downlink grant 310-c (e.g., DCI 2) may signal (e.g., in the TCI state) or otherwise indicate that the “DMRS of a PDSCH” is used as the QCL source for the DMRS scheduled with the downlink transmission 315-c. However, this raises the question of which DMRS of the previous downlink transmission 315 is to be used as the QCL source for the DMRS of the downlink transmission 315-c, e.g., the DMRS of downlink transmission 315-a and/or the DMRS of downlink transmission 315-b. [0118] In one example, the third reference signal of the second reference signal type being used as the QCL source for the downlink transmission 315-c (e.g., the second downlink transmission in this example) may be based on a transmission timing. For example, the transmission timing of the grant 310-c and/or the transmission timing of the downlink transmission 315-c may be used as the timing reference. That is, some examples may include an assumption that the downlink transmission 315 (e.g., PDSCH) is the one that starts, overlaps, or ends X symbols or slots before the start of the transmission of the grant 310-c and/or the start of the downlink transmission 315-c.

[0119] For example, the UE may transmit or otherwise convey an indication of the UE capability configuration supported by the UE, which may include information identifying the UE’s capability with respect to a minimum gap needed between transmission of the first grant (e.g., grants 310-a or 310-b) and identifying to use the third reference signal of the second reference signal type as a QCL source for downlink transmission 315-c. That is, the UE may transmit the UE capability message to the base station that carries or otherwise conveys information identifying the minimum supported gap between the first downlink transmission 315 and the second downlink transmission 315-c the UE supports.

[0120] In the example where carrier aggregation (CA) is adopted for one or more of the downlink transmissions 315, one option may include the downlink transmission 315-c (e.g., the PDSCH) being associated with the same component carrier (CC) or may be associated with a different CC. Accordingly, the UE may identify the CC associated with the downlink transmission 315-c based on the previous downlink transmission 315 (e.g., based on the CC used for the previous downlink transmission 315) and/or based on the grant 310-c.

[0121] Another example may include the grant 310-c carrying or conveying a timing indication. For example, the timing indication may provide information for the UE to use to identify which DMRS of the previous downlink transmission 315 to use as a QCL source for downlink transmission 315-c. The timing indication may be carried or otherwise conveyed in a TCI state, a TCI reference signal set, and the like, for the grant 310-c. Accordingly, there may be X symbol(s)/slot(s) configured in the TCI state, which enables the base station to pick which DMRS from a downlink transmission 315 (e.g., downlink transmission 315-a or downlink transmission 315-b) is to be used as the QCL source for the downlink transmission 315-c. The timing indication may be an absolute timing indication (e.g., indicating for the UE to use the DMRS of downlink transmission 315-b) and/or a relative timing indication (e.g., based on the timing associated with a previous transmission). For example, the timing indication may be relative to the grant 310 and/or downlink transmission 315 corresponding to the first grant and first downlink transmission (e.g., grants 310-a or 310-b corresponding to downlink transmissions 315-a or downlink transmission 315-b, respectively) and/or corresponding to the second grant and second downlink transmission (e.g., grant 310-c corresponding to downlink transmission 315-c). Again, in some examples, a CC index may also be included or otherwise conveyed in the TCI state configuration of grant 310-c.

[0122] In the example illustrated in FIG. 3, the UE may use, based on the grant 310-c, the DMRS of downlink transmission 315-b as the QCL source for the DMRS of downlink transmission 315-c. Accordingly, the UE may perform channel estimation for the downlink transmission 315-c and receive and decode downlink transmission 310-c based on the channel estimate.

[0123] FIG. 4 illustrates an example of a slot configuration 400 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. In some examples, slot configuration 400 may implement aspects of wireless communication system 100 and/or slot configurations 200 and/or 300. Aspects of slot configuration 400 may be implemented by a base station and/or a UE, which may be examples of the corresponding devices described herein.

[0124] Slot configuration 400 may include a plurality of slots 405, with slots 405-a, 405- b, 405-c, and 405-d being shown by way of example only. It is to be understood that slot configuration 400 may include fewer or more slots 405 than the four slots 405 illustrated in FIG. 4. Slots 405 may be contiguous or non-contiguous slots, e.g., in the time domain. In the example illustrated in slot configuration 400, slots 405 may be associated with one or more grants 410 scheduling corresponding downlink transmissions 415, e.g., PDCCH and/or PDSCH downlink transmissions. As illustrated, the transmissions 415 may be referred to as PyxCH transmissions, e.g., where y = (S)idelink or (D)ownlink and x = (S)hared or (C)ontrol. That is, the transmissions 415 may be examples of PDSCH downlink transmissions, physical downlink control channel (PDCCH) transmissions, physical sidelink control channel (PSCCH) transmissions, physical sidelink shared channel (PSSCH) transmissions, or any combination thereof. Generally, each downlink transmission 415 may have one or more associated reference signals. Each downlink transmission 415 may be scheduled by a grant 410, such as a DCI grant that configures the reference signals for the downlink transmission 415.

[0125] As discussed above, aspects of the described techniques support a UE using the DMRS (e.g., a third reference signal of a second reference signal type) from an earlier downlink transmission 415 as the QCL source for a subsequent downlink transmission 415. For example, a base station may transmit a grant 410-a during slot 405-a to a UE scheduling a downlink transmission 415-a to the UE. The grant 410-a may carry or otherwise convey information identifying a first reference signal of a first reference signal type (e.g. a TRS type A, type D, etc.) as the QCL source for the downlink transmission 415-a and a second reference signal of a second reference signal type (e.g., a DMRS scheduled with the downlink transmission 415-a) for the UE to use to perform channel estimation for the downlink transmission 415-a. The UE may use the first reference signal to identify the QCL parameters and then use the QCL parameters and the second reference signal to identify or otherwise perform the channel estimate for the downlink transmission 415-a.

[0126] In some aspects, the grant 410-a may also configure HARQ information for the downlink transmission 415-a. For example, the grant 410-a may identify resources for the UE to use the transmit feedback information (e.g., acknowledgment/negative-acknowledgment (ACK/NACK) information) to the base station indicating whether the UE successfully received and decoded downlink transmission 415-a. Accordingly, during slot 405-b the UE may transmit an ACK/NACK message for the downlink transmission 415-a (e.g., the first downlink transmission in this scenario).

[0127] In some aspects, transmission of the ACK/NACK message may be used in conjunction with aspects of the described techniques. For example, in the situation where the HARQ codebook is dynamic (e.g., pdsch-HARQ-ACK-Codebook=dynamic), aspects of the described techniques may use the latest downlink transmission 415 (e.g., PDSCH transmission) whose HARQ-ACK information has been transmitted by the UE. For example, the UE may receive the grant 410-a which contains a slot 405 offset in which the UE is to report HARQ-ACK message. Then, the second downlink transmission (e.g., downlink transmission 415-d) that is configured to use the DMRS of downlink transmission 415-a as the QCL source for the DMRS of downlink transmission 415-d can only be X symbols or slots after the last symbol of the PHY channel carrying the HARQ-ACK information.

[0128] For example, the UE may determine its monitoring occasions for PDCCH with DCI format 1 0 or DCI format 1 1 for scheduling PDSCH receptions or SPS PDSCH release on an active downlink bandwidth part (BWP) of a serving cell C, for which the UE transmits HARQ-ACK information in a same physical uplink control channel (PUCCH) in slot n based on: (1) PDSCH-to-HARQ_feedback timing values for PUCCH transmission with HARQ- ACK information in slot n in response to PDSCH receptions or SPS PDSCH release and/or (2) slot offsets Ko provided by time domain resource assignment field in DCI format 1 0 or DCI format 1 1 for scheduling PDSCH receptions or SPS PDSCH release and by pdsch- AggregationF actor, when provided.

[0129] In another example, in the situation where the HARQ codebook is semi-static (e.g., pdsch-HARQ-ACK-Codebook=semi-static), aspects of the described techniques use the latest downlink transmission 415 (e.g., PDSCH transmission) whose HARQ-ACK information has been transmitted by the UE and has been ACK’d. For example, the UE may be configured with some occasions to transmit ACK/NACK. If no PDSCH is received, the UE transmits NACK information in the acknowledgment message. If the UE has successfully received and decoded the DCI, and received the PDSCH scheduled by the DCI, the UE transmits ACK information in the acknowledgment message. Accordingly, the second downlink transmission (e.g., downlink transmission 415-d in this example) can be signaled with the DMRS of downlink transmission 415-a to be used as the QCL source if at least X symbols or slots have passed from the PHY channel containing the ACK of downlink transmission 415-a.

[0130] That is, if the UE is configured with semi-static HARQ, the UE may report HARQ-ACK information for the corresponding PDSCH reception or SPS PDSCH release in a HARQ-ACK codebook that the UE transmits in a slot 405 indicated by a value of a PDSCH-to-HARQ_feedback timing indicator field and a corresponding DCI format 1 0 or DCI format 1 1. The UE reports NACK value(s) for HARQ-ACK information bit(s) in a HARQ-ACK codebook that the UE transmits in a slot 405 not indicated by value of that PDSCH-to-HARQ_feedback timing indicator field and a corresponding DCI format 1 0 or DCI format 1 1. [0131] Accordingly, the UE may transmit the ACK/NACK information (e.g., depending on the configured HARQ codebook) in an acknowledgment message 420-b for the downlink transmission 415-a. Based on the UE transmitting the acknowledgment message 420-b, the base station may know that the UE can support using the DMRS of the downlink transmissions 415-a as the QCL source for the DMRS of downlink transmission 415-d.

[0132] The UE may determine that the timing difference between transmission of the acknowledgment message and the downlink transmission 415-d is within a threshold timing window, which may support the UE re-using the DMRS of the downlink transmission 415-a as the QCL source for the DMRS of downlink transmission 415-d.

[0133] In the intervening slot 405-c, the base station may transmit a grant 410-c to the UE scheduling a downlink transmission 415-c for the UE. The grant 410-c may also identify resources for the UEs to use to transmit an acknowledgment message 420-e during a later slot 405.

[0134] FIG. 5 illustrates an example of a slot configuration 500 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. In some examples, slot configuration 500 may implement aspects of wireless communication system 100 and/or slot configurations 200, 300 and/or 400. Aspects of slot configuration 500 may be implemented by a base station and/or a UE, which may be examples of the corresponding devices described herein.

[0135] Slot configuration 500 may include a plurality of slots 505, with slots 505-a, 505- b, 505-c, and 505-d being shown by way of example only. It is to be understood that slot configuration 500 may include fewer or more slots 505 than the four slots 505 illustrated in FIG. 5. Slots 505 may be contiguous or non-contiguous slots, e.g., in the time domain. In the example illustrated in slot configuration 500, slots 505 may be associated with one or more grants 510 scheduling corresponding downlink transmissions 515, e.g., PDCCH and/or PDSCH downlink transmissions. As illustrated, the transmissions 515 may be referred to as PyxCH transmissions, e.g., where y = (S)idelink or (D)ownlink and x = (S)hared or (C)ontrol. That is, the transmissions 515 may be examples of PDSCH downlink transmissions, physical downlink control channel (PDCCH) transmissions, physical sidelink control channel (PSCCH) transmissions, physical sidelink shared channel (PSSCH) transmissions, or any combination thereof. Generally, each downlink transmission 515 may have one or more associated reference signals. Each downlink transmission 515 may be scheduled by a grant 510, such as a DCI grant that configures the reference signals for the downlink transmission 515.

[0136] As discussed above, aspects of the described techniques support a UE using the DMRS (e.g., a third reference signal of a second reference signal type) from an earlier downlink transmission 515 as the QCL source for a subsequent downlink transmission 515. For example, a base station may transmit a grant 510-a during slot 505-a to a UE scheduling a downlink transmission 515-a to the UE. The grant 510-a may carry or otherwise convey information identifying a first reference signal of a first reference signal type (e.g. a TRS type A, type D, etc.) as the QCL source for the downlink transmission 515-a and a second reference signal of a second reference signal type (e.g., a DMRS scheduled with the downlink transmission 515-a) for the UE to use to perform channel estimation for the downlink transmission 515-a. The UE may use the first reference signal to identify the QCL parameters and then use the QCL parameters and the second reference signal to identify or otherwise perform the channel estimate for the downlink transmission 515-a. In some aspects, the grant 510-a may also identify resources for the UE to use to transmit an acknowledgment message to the base station indicating whether the UE successfully received and decoded the corresponding downlink transmission 515-a. Accordingly and during slot 505-b, the UE may transmit the acknowledgment message 520-b to the base station.

[0137] In the intervening slot 505-c, the base station may transmit a grant 510-c to the UE scheduling a downlink transmission 515-c to the UE. The grant 510-c may configure the resources for the corresponding downlink transmission 515-c as well as configure one or more reference signals for the UE to use during the downlink transmission 515-c, e.g., for channel estimation.

[0138] During slot 505-d, the base station may transmit a grant 510-d (e.g., a second grant in this example) scheduling downlink transmission 515-d to the UE. As discussed above, the second grant (e.g., grant 510-d) may carry or convey information identifying the third reference signal of the second reference signal type (e.g., the DMRS of the downlink transmission 515-a) for the UE to use as the QCL for the DMRS of the downlink transmission 515-d. For example, the UE may use the DMRS of the downlink transmission 515-a as the QCL source for the DMRS when performing channel estimation during the downlink transmission 515-d.

[0139] In the example illustrated in FIG. 5, there may be a multiple instances of the first downlink transmission (e.g., downlink transmission 515-a), with each instance of the first downlink transmission being associated with a different CC. Accordingly, this raises the question of which instance of the downlink transmission 515-a is the UE to use as the QCL source for the DMRS of the downlink transmission 515-d. In one example, the UE may determine the numerical control resource set identifier (e.g., the control resource set ID) to determine which instance of the downlink transmission 515-a to use. For example, the UE may determine to use the third reference signal of the second reference signal type as the QCL source for the second downlink transmission 515-d based on the instance of the first downlink transmission having the lowest numerical control resource set identifier.

[0140] Accordingly, the UE may determine to use the DMRS of the first downlink transmission 515-a as the QCL source for the DMRS of downlink transmission 515-d based on the instance of the downlink transmission 515-a having the lowest control resource set identifier.

[0141] FIG. 6 illustrates an example of a slot configuration 600 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. In some examples, slot configuration 600 may implement aspects of wireless communication system 100 and/or slot configurations 200, 300400 and/or 500. Aspects of slot configuration 600 may be implemented by a base station and/or a UE, which may be examples of the corresponding devices described herein.

[0142] Slot configuration 600 may include a plurality of slots 605, with slots 605-a, 605- b, 605-c, 605-d, and 605-e being shown by way of example only. It is to be understood that slot configuration 600 may include fewer or more slots 605 than the five slots 605 illustrated in FIG. 6. Slots 605 may be contiguous or non-contiguous slots, e.g., in the time domain. In the example illustrated in slot configuration 600, slots 605 may be associated with one or more grants scheduling corresponding downlink transmissions 610, e.g., PDCCH and/or PDSCH downlink transmissions. As illustrated, the transmissions 610 may be referred to as PyxCH transmissions, e.g., where y = (S)idelink or (D)ownlink and x = (S)hared or (C)ontrol. That is, the transmissions 610 may be examples of PDSCH downlink transmissions, physical downlink control channel (PDCCH) transmissions, physical sidelink control channel (PSCCH) transmissions, physical sidelink shared channel (PSSCH) transmissions, or any combination thereof. Generally, each downlink transmission 610 may have one or more associated reference signals 615. Each downlink transmission 610 may be scheduled by a grant, such as a DCI grant that configures the reference signals 615 for the downlink transmission 610.

[0143] As discussed above, aspects of the described techniques support a UE using the DMRS (e.g., a third reference signal of a second reference signal type) from an earlier downlink transmission 610 as the QCL source for a subsequent downlink transmission 610. For example, a base station may transmit a grant during slot 605-a to a UE scheduling a downlink transmission 610-a to the UE. The grant may carry or otherwise convey information identifying a first reference signal of a first reference signal type (e.g. a TRS type A, type B, etc.) as the QCL source for the downlink transmission 610-a. In some examples, the reference signal type may be based on the set of QCL parameters to be determined by the UE. The grant may also carry or otherwise convey a second reference signal of a second reference signal type (e.g., a DMRS scheduled with the downlink transmission 610-a) for the UE to use to perform channel estimation for the downlink transmission 610-a. The UE may use the first reference signal to identify the QCL parameters and then use the QCL parameters and the second reference signal to identify or otherwise perform the channel estimate for the downlink transmission 610-a.

[0144] During slot 605-b, the base station may transmit a second grant to the UE scheduling a second downlink transmission 610-b. In some aspects, the second grant may identify a third reference signal of the second reference signal type (e.g., the DMRS of downlink transmission 610-a) to use as the QCL source for the DMRS of the second downlink transmission 610-b. Accordingly, the UE may use the DMRS of the first downlink transmission 610-a as the QCL source for the DMRS of the second downlink transmission 610-b. The UE may perform channel estimation for the second downlink transmission 610-b in accordance with the second grant, the DMRS scheduled with the second downlink transmission 610-b, and the DMRS of the first downlink transmission 610-a (e.g., which was used to identify QCL parameters for the second downlink transmission 605-b). In another example, the second grant may indicate for the UE to use the DMRS of the first downlink transmission 610-a as the QCL source for the DMRS of the downlink transmission 610-b. [0145] During slot 605-c, the base station may transmit a third grant to the UE scheduling a third downlink transmission 610-c. In some aspects, the third grant may identify a third reference signal of the second reference signal type (e.g., the DMRS of downlink transmission 610-a and/or the DMRS of downlink transmission 610-b) to use as the QCL source for the DMRS of the third downlink transmission 610-c. Accordingly, the UE may use the DMRS of the first downlink transmission 610-a and/or the DMRS of the second downlink transmission 610-b as the QCL source for the DMRS of the third downlink transmission 610- c. The UE may perform channel estimation for the third downlink transmission 610-c in accordance with the third grant, the DMRS scheduled with the third downlink transmission 610-c, and the DMRS of the previous downlink transmission 610 (e.g., which was used to identify QCL parameters for the third downlink transmission 605-c). In another example, the third grant may indicate for the UE to use the DMRS of the first downlink transmission 610-a as the QCL source for the DMRS of the downlink transmission 610-c.

[0146] However, in some examples, during slot 605-d, the timeline may not be satisfied. For example, the UE may determine that the timing difference between the first downlink transmission (e.g., downlink transmission 610-a and/or downlink transmission 610-c) and the fourth downlink transmission 610-d has exceeded a threshold. In some examples, the UE may use the third reference signal of the second reference signal type as the QCL source for the fourth downlink transmission 610-d based on the timing difference exceeding the threshold. For example, the UE may determine to use the CSI-RS of the DMRS of the PDSCH in the single QCL chain (e.g., the UE may determine to use the DMRS of the first downlink transmission 610-a as the QCL source for the DMRS of the downlink transmission 610-d). In another example, the UE may assume the PDSCH DMRS and a SS/PBCH block to be QCL with respect to Doppler shift, Doppler spread, average delay, delay spread, and/or, when applicable, spatial received parameters. Accordingly, the UE may use the DMRS of the first downlink transmission 610-a as a QCL source for the DMRS of downlink transmission 610- d.

[0147] During slot 605-e, base station may transmit a fifth grant to the UE scheduling a fifth downlink transmission 610-e. The fifth grant may identify the first reference signal of the first reference signal type to use as a QCL source for the downlink transmission 610-e and a second reference signal of the second reference signal type to use for performing channel estimation for the downlink transmission 610-e. [0148] FIG. 7 illustrates an example of a slot configuration 700 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. In some examples, slot configuration 700 may implement aspects of wireless communication system 100 and/or slot configurations 200, 300400 500 and/or 600. Aspects of slot configuration 700 may be implemented by a base station and/or a UE, which may be examples of the corresponding devices described herein.

[0149] Slot configuration 700 may include a plurality of slots 705, with slots 705-a, 705- b, 705-c, 705-d, and 705-e being shown by way of example only. It is to be understood that slot configuration 700 may include fewer or more slots 705 than the five slots 705 illustrated in FIG. 7. Slots 705 may be contiguous or non-contiguous slots, e.g., in the time domain. In the example illustrated in slot configuration 700, slots 705 may be associated with one or more grants scheduling corresponding downlink transmissions 710, e.g., PDCCH and/or PDSCH downlink transmissions. As illustrated, the transmissions 710 may be referred to as PyxCH transmissions, e.g., where y = (S)idelink or (D)ownlink and x = (S)hared or (C)ontrol. That is, the transmissions 710 may be examples of PDSCH downlink transmissions, physical downlink control channel (PDCCH) transmissions, physical sidelink control channel (PSCCH) transmissions, physical sidelink shared channel (PSSCH) transmissions, or any combination thereof. Generally, each downlink transmission 710 may have one or more associated reference signals 715. Each downlink transmission 710 may be scheduled by a grant, such as a DCI grant that configures the reference signals 715 for the downlink transmission 710.

[0150] As discussed above, aspects of the described techniques support a UE using the DMRS (e.g., a third reference signal of a second reference signal type) from an earlier downlink transmission 710 as the QCL source for a subsequent downlink transmission 710. For example, a base station may transmit a grant during slot 705-a to a UE scheduling a downlink transmission 710-a to the UE. The grant may carry or otherwise convey information identifying a first reference signal of a first reference signal type (e.g. a TRS type A, type B, etc.) as the QCL source for the downlink transmission 710-a and a second reference signal of a second reference signal type (e.g., a DMRS scheduled with the downlink transmission 710-a) for the UE to use to perform channel estimation for the downlink transmission 710-a. The UE may use the first reference signal to identify the QCL parameters and then use the QCL parameters and the second reference signal to identify or otherwise perform the channel estimate for the downlink transmission 710-a.

[0151] However, in some aspects, slot aggregation techniques may be implemented within the wireless communication system. For example, slots 705-a and 705-b may be aggregated according to a slot aggregation scheme into a single slot. For example, the grant provided in slot 705-a scheduling the downlink transmission 710-a and identifying the corresponding reference signals 715 may also schedule the downlink transmission 710-b during slot 705-b.

[0152] During slot 705-c, the base station may transmit a second grant to the UE scheduling a second downlink transmission 710-c. In some aspects, the second grant may identify a third reference signal of the second reference signal type to use as the QCL source for the DMRS of the second downlink transmission 710-c. However, this raises the question of which previous downlink transmission 710 that the UE is to use the DMRS from as the QCL source for the DMRS of downlink transmission 710-c. In some aspects, the UE may determine that, based on the slot aggregation scheme implemented during slot 705-a and 705- b, that both slots 705-a and 705-b are considered one slot, and therefore the UE may utilize the DMRS of the downlink transmission 710-a and/or 710-b as the QCL source for the DMRS of downlink transmission 710-c.

[0153] Accordingly, the UE may use the DMRS of the first downlink transmission 710-a and/or 710-b as the QCL source for the DMRS of the downlink transmission 710-c (e.g., the second downlink transmission in this example). The UE may perform channel estimation for the downlink transmission 710-c in accordance with the second grant, the DMRS scheduled with the downlink transmission 710-c, and the DMRS of the downlink transmission 710-a and/or 710-b.

[0154] During slot 705-d, the base station may transmit a third grant to the UE scheduling a third downlink transmission 710-d. In some aspects, the third grant may identify a third reference signal of the second reference signal type (e.g., the DMRS of downlink transmission 710-c) to use as the QCL source for the DMRS of the third downlink transmission 710-d. Accordingly, the UE may use the DMRS of the second downlink transmission 710-c as the QCL source for the DMRS of the third downlink transmission 710- d. The UE may perform channel estimation for the third downlink transmission 710-d in accordance with the third grant, the DMRS scheduled with the third downlink transmission 710-d, and the DMRS of the second downlink transmission 710-c (e.g., which was used to identify QCL parameters for the third downlink transmission 705-d). ). In another example, the third grant may indicate for the UE to use the DMRS of the first downlink transmission 710-a and/or 710-b as the QCL source for the DMRS of the downlink transmission 710-d.

[0155] During slot 705-e, base station may transmit a fifth grant to the UE scheduling a fifth downlink transmission 710-e. The fifth grant may identify the first reference signal of the first reference signal type to use as a QCL source for the downlink transmission 710-e and a second reference signal of the second reference signal type to use for performing channel estimation for the downlink transmission 710-e.

[0156] FIG. 8 shows a block diagram 800 of a device 805 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The device 805 may be an example of aspects of a UE 115 as described herein. The device 805 may include a receiver 810, a communications manager 815, and a transmitter 820. The device 805 may also include one or more processors, memory coupled with the one or more processors, and instructions stored in the memory that are executable by the one or more processors to enable the one or more processors to perform the reference signal features discussed herein. Each of these components may be in communication with each other (e.g., via one or more buses).

[0157] The receiver 810 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to using a DMRS of a data transmission as a QCL reference signal source for another data transmission, etc.). Information may be passed on to other components of the device 805. The receiver 810 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The receiver 810 may utilize a single antenna or a set of antennas.

[0158] The communications manager 815 may receive a first grant scheduling a first downlink transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission, and receive a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. The communications manager 815 may also identify, based on the first reference signal, a set of quasi-colocation parameters for the first downlink transmission, identify the channel estimate for the first downlink transmission based on the set of quasi-colocation parameters and the second reference signal, and perform a channel estimation for the second downlink transmission based on the second reference signal, the second grant, and the third reference signal. The communications manager 815 may be an example of aspects of the communications manager 1110 described herein.

[0159] The communications manager 815, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 815, or its sub-components may be executed by a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

[0160] By including or configuring the communications manager 815 in accordance with examples as described herein, the device 805 (e.g., a processor controlling or otherwise coupled to the receiver 810, the transmitter 820, the communications manager 815, or a combination thereof) may support techniques for reduced processing and more efficient utilization of communication resources. For example, by using a DMRS of a data transmission as a QCL reference signal source for another transmission, the communications manager 815 may avoid receiving a reference signal for each received data transmission, and may thus receive and process fewer overall transmissions.

[0161] The communications manager 815, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the communications manager 815, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communications manager 815, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

[0162] The transmitter 820 may transmit signals generated by other components of the device 805. In some examples, the transmitter 820 may be collocated with a receiver 810 in a transceiver module. For example, the transmitter 820 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The transmitter 820 may utilize a single antenna or a set of antennas.

[0163] FIG. 9 shows a block diagram 900 of a device 905 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The device 905 may be an example of aspects of a device 805, or a UE 115 as described herein. The device 905 may include a receiver 910, a communications manager 915, and a transmitter 935. The device 905 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

[0164] The receiver 910 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to using a DMRS of a data transmission as a QCL reference signal source for another data transmission, etc.). Information may be passed on to other components of the device 905. The receiver 910 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The receiver 910 may utilize a single antenna or a set of antennas.

[0165] The communications manager 915 may be an example of aspects of the communications manager 815 as described herein. The communications manager 915 may include a grant manager 920, a QCL parameter manager 925, and a channel estimate manager 930. The communications manager 915 may be an example of aspects of the communications manager 1110 described herein.

[0166] The grant manager 920 may receive a first grant scheduling a first downlink transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission and receive a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0167] The QCL parameter manager 925 may identify, based on the first reference signal, a set of quasi-colocation parameters for the first downlink transmission.

[0168] The channel estimate manager 930 may identify the channel estimate for the first downlink transmission based on the set of quasi-colocation parameters and the second reference signal and perform a channel estimation for the second downlink transmission based on the second reference signal, the second grant, and the third reference signal.

[0169] The transmitter 935 may transmit signals generated by other components of the device 905. In some examples, the transmitter 935 may be collocated with a receiver 910 in a transceiver module. For example, the transmitter 935 may be an example of aspects of the transceiver 1120 described with reference to FIG. 11. The transmitter 935 may utilize a single antenna or a set of antennas.

[0170] In some cases, the grant manager 920, QCL parameter manager 925, and channel estimate manager 930 may each be or be at least a part of a processor (e.g., a transceiver processor, or a radio processor, or a transmitter processor, or a receiver processor). The processor may be coupled with memory and execute instructions stored in the memory that enable the processor to perform or facilitate the features of the grant manager 920, QCL parameter manager 925, and channel estimate manager 930 discussed herein. A transceiver processor may be collocated with and/or communicate with (e.g., direct the operations of) a transceiver of the device. A radio processor may be collocated with and/or communicate with (e.g., direct the operations of) a radio (e.g., an NR radio, an LTE radio, a Wi-Fi radio) of the device. A transmitter processor may be collocated with and/or communicate with (e.g., direct the operations of) a transmitter of the device. A receiver processor may be collocated with and/or communicate with (e.g., direct the operations of) a receiver of the device. [0171] FIG. 10 shows a block diagram 1000 of a communications manager 1005 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The communications manager 1005 may be an example of aspects of a communications manager 815, a communications manager 915, or a communications manager 1110 described herein. The communications manager 1005 may include a grant manager 1010, a QCL parameter manager 1015, a channel estimate manager 1020, a timing manager 1025, a capability configuration manager 1030, a CC manager 1035, an ACK/NACK manager 1040, and a CORESET manager 1045. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

[0172] The grant manager 1010 may receive a first grant scheduling a first downlink transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission.

[0173] In some examples, the grant manager 1010 may receive a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. In some cases, the first downlink transmission occurs according to a slot-aggregation scheme including two or more slots. In some cases, the first reference signal type includes a quasi-colocation source reference signal type identified in a TCI state or a TCI reference signal set of the first grant.

[0174] The QCL parameter manager 1015 may identify, based on the first reference signal, a set of quasi-colocation parameters for the first downlink transmission.

[0175] The channel estimate manager 1020 may identify the channel estimate for the first downlink transmission based on the set of quasi-colocation parameters and the second reference signal. In some examples, the channel estimate manager 1020 may perform a channel estimation for the second downlink transmission based on the second reference signal, the second grant, and the third reference signal. [0176] The timing manager 1025 may identify the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission based on at least one of a transmission timing of the second grant, or a transmission timing of the second downlink transmission, or a combination thereof. In some examples, the timing manager 1025 may identify, based on a timing indication in the second grant, the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission. In some examples, the timing manager 1025 may determine that a timing difference between the first downlink transmission and the second downlink transmission has not exceeded a threshold.

[0177] In some examples, the timing manager 1025 may use the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission based on the timing difference not exceeding the threshold. In some examples, the timing manager 1025 may determine that a timing difference between the first downlink transmission and the second downlink transmission has exceeded a threshold. In some examples, the timing manager 1025 may refrain from using the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission based on the timing difference exceeding the threshold.

[0178] In some cases, the timing indication is based on at least one of a first grant transmission timing, or a first downlink transmission timing, or a second grant transmission timing, or a second downlink transmission timing, or a combination thereof. In some cases, the timing indication is indicated in a quasi-colocation source reference signal type identifier in a TCI state or a TCI reference signal set of the second grant.

[0179] The capability configuration manager 1030 may transmit a UE capability message identifying a minimum supported gap between the first downlink transmission and the second downlink transmission that the UE supports for using the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission.

[0180] The CC manager 1035 may identify a component carrier associated with the second downlink transmission based on the first downlink transmission. In some examples, the CC manager 1035 may identify, based on the second grant, a component carrier associated with the second downlink transmission. [0181] The ACK/NACK manager 1040 may transmit an acknowledgement message for the first downlink transmission. In some examples, the ACK/NACK manager 1040 may identify the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission based on the transmission of the acknowledgement message for the first downlink transmission. In some examples, the ACK/NACK manager 1040 may determine that a timing difference between transmission of the acknowledgement message and the second downlink transmission is within a threshold timing window, where using the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission is based on the timing difference.

[0182] The CORESET manager 1045 may determine that there were multiple first downlink transmissions, with each of the first downlink transmissions associated with a different component carrier. In some examples, the CORESET manager 1045 may identify a numerical control resource set identifier associated with each first downlink transmission. In some examples, the CORESET manager 1045 may determine to use the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission based on the first downlink transmission having a lowest numerical control resources set identifier.

[0183] In some cases, the grant manager 1010, QCL parameter manager 1015, channel estimate manager 1020, timing manager 1025, capability configuration manager 1030, CC manager 1035, ACK/NACK manager 1040, and CORESET manager 1045 may each be or be at least a part of a processor (e.g., a transceiver processor, or a radio processor, or a transmitter processor, or a receiver processor). The processor may be coupled with memory and execute instructions stored in the memory that enable the processor to perform or facilitate the features of the grant manager 1010, QCL parameter manager 1015, channel estimate manager 1020, timing manager 1025, capability configuration manager 1030, CC manager 1035, ACK/NACK manager 1040, and CORESET manager 1045 discussed herein.

[0184] FIG. 11 shows a diagram of a system 1100 including a device 1105 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The device 1105 may be an example of or include the components of device 805, device 905, or a UE 115 as described herein. The device 1105 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 1110, an I/O controller 1115, a transceiver 1120, an antenna 1125, memory 1130, and a processor 1140. These components may be in electronic communication via one or more buses (e.g., bus 1145).

[0185] The communications manager 1110 may receive a first grant scheduling a first downlink transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission, and receive a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. The communications manager 1110 may also identify, based on the first reference signal, a set of quasi-colocation parameters for the first downlink transmission, identify the channel estimate for the first downlink transmission based on the set of quasi-colocation parameters and the second reference signal, and perform a channel estimation for the second downlink transmission based on the second reference signal, the second grant, and the third reference signal.

[0186] By including or configuring the communications manager 1110 in accordance with examples as described herein, the device 1105 may support techniques for reduced power consumption and reduced latency. For example, by using a DMRS of a data transmission as a QCL reference signal source for another transmission, the device 805 may avoid receiving a reference signal for each received data transmission. The device 805 may thus process fewer overall transmissions and, accordingly, may experience reduced power consumption and reduced latency.

[0187] The I/O controller 1115 may manage input and output signals for the device 1105. The I/O controller 1115 may also manage peripherals not integrated into the device 1105. In some cases, the I/O controller 1115 may represent a physical connection or port to an external peripheral. In some cases, the I/O controller 1115 may utilize an operating system such as iOS®, ANDROID®, MS-DOS®, MS-WINDOWS®, OS/2®, UNIX®, LINUX®, or another known operating system. In other cases, the I/O controller 1115 may represent or interact with a modem, a keyboard, a mouse, a touchscreen, or a similar device. In some cases, the I/O controller 1115 may be implemented as part of a processor. In some cases, a user may interact with the device 1105 via the I/O controller 1115 or via hardware components controlled by the I/O controller 1115.

[0188] The transceiver 1120 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1120 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1120 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

[0189] In some cases, the wireless device may include a single antenna 1125. However, in some cases the device may have more than one antenna 1125, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

[0190] The memory 1130 may include RAM and ROM. The memory 1130 may store computer-readable, computer-executable code 1135 including instructions that, when executed, cause the processor to perform various functions described herein. In some cases, the memory 1130 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices.

[0191] The processor 1140 may include an intelligent hardware device (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 1140 may be configured to operate a memory array using a memory controller. In other cases, a memory controller may be integrated into the processor 1140. The processor 1140 may be configured to execute computer-readable instructions stored in a memory (e.g., the memory 1130) to cause the device 1105 to perform various functions (e.g., functions or tasks supporting using a DMRS of a data transmission as a QCL reference signal source for another data transmission).

[0192] The code 1135 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1135 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1135 may not be directly executable by the processor 1140 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

[0193] FIG. 12 shows a block diagram 1200 of a device 1205 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The device 1205 may be an example of aspects of a base station 105 as described herein. The device 1205 may include a receiver 1210, a communications manager 1215, and a transmitter 1220. The device 1205 may also include one or more processors, memory coupled with the one or more processors, and instructions stored in the memory that are executable by the one or more processors to enable the one or more processors to perform the reference signal features discussed herein. Each of these components may be in communication with one another (e.g., via one or more buses).

[0194] The receiver 1210 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to using a DMRS of a data transmission as a QCL reference signal source for another data transmission, etc.). Information may be passed on to other components of the device 1205. The receiver 1210 may be an example of aspects of the transceiver 1520 described with reference to FIG. 15. The receiver 1210 may utilize a single antenna or a set of antennas.

[0195] The communications manager 1215 may transmit a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission and transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. The communications manager 1215 may be an example of aspects of the communications manager 1510 described herein. [0196] The communications manager 1215, or its sub-components, may be implemented in hardware, code (e.g., software or firmware) executed by a processor, or any combination thereof. If implemented in code executed by a processor, the functions of the communications manager 1215, or its sub-components may be executed by a general-purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described in the present disclosure.

[0197] The communications manager 1215, or its sub-components, may be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations by one or more physical components. In some examples, the communications manager 1215, or its sub-components, may be a separate and distinct component in accordance with various aspects of the present disclosure. In some examples, the communications manager 1215, or its sub-components, may be combined with one or more other hardware components, including but not limited to an input/output (I/O) component, a transceiver, a network server, another computing device, one or more other components described in the present disclosure, or a combination thereof in accordance with various aspects of the present disclosure.

[0198] By including or configuring the communications manager 1215 in accordance with examples as described herein, the device 1205 (e.g., a processor controlling or otherwise coupled to the receiver 1210, the transmitter 1220, the communications manager 1215, or a combination thereof) may support techniques for more efficient use of communication resources. For example, the device 1205 may transmit fewer indications of reference signals, which may enable the device 1205 to use resources previously used for such indications for other transmissions.

[0199] The transmitter 1220 may transmit signals generated by other components of the device 1205. In some examples, the transmitter 1220 may be collocated with a receiver 1210 in a transceiver module. For example, the transmitter 1220 may be an example of aspects of the transceiver 1520 described with reference to FIG. 15. The transmitter 1220 may utilize a single antenna or a set of antennas.

[0200] FIG. 13 shows a block diagram 1300 of a device 1305 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The device 1305 may be an example of aspects of a device 1205, or a base station 105 as described herein. The device 1305 may include a receiver 1310, a communications manager 1315, and a transmitter 1330. The device 1305 may also include a processor. Each of these components may be in communication with one another (e.g., via one or more buses).

[0201] The receiver 1310 may receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to using a DMRS of a data transmission as a QCL reference signal source for another data transmission, etc.). Information may be passed on to other components of the device 1305. The receiver 1310 may be an example of aspects of the transceiver 1520 described with reference to FIG. 15. The receiver 1310 may utilize a single antenna or a set of antennas.

[0202] The communications manager 1315 may be an example of aspects of the communications manager 1215 as described herein. The communications manager 1315 may include a first grant manager 1320 and a second grant manager 1325. The communications manager 1315 may be an example of aspects of the communications manager 1510 described herein.

[0203] The first grant manager 1320 may transmit a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission.

[0204] The second grant manager 1325 may transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0205] The transmitter 1330 may transmit signals generated by other components of the device 1305. In some examples, the transmitter 1330 may be collocated with a receiver 1310 in a transceiver module. For example, the transmitter 1330 may be an example of aspects of the transceiver 1520 described with reference to FIG. 15. The transmitter 1330 may utilize a single antenna or a set of antennas.

[0206] In some cases, the first grant manager 1320 and the second grant manager 1325 may each be or be at least a part of a processor (e.g., a transceiver processor, or a radio processor, or a transmitter processor, or a receiver processor). The processor may be coupled with memory and execute instructions stored in the memory that enable the processor to perform or facilitate the features of the first grant manager 1320 and the second grant manager 1325 discussed herein. A transceiver processor may be collocated with and/or communicate with (e.g., direct the operations of) a transceiver of the device. A radio processor may be collocated with and/or communicate with (e.g., direct the operations of) a radio (e.g., an NR radio, an LTE radio, a Wi-Fi radio) of the device. A transmitter processor may be collocated with and/or communicate with (e.g., direct the operations of) a transmitter of the device. A receiver processor may be collocated with and/or communicate with (e.g., direct the operations of) a receiver of the device.

[0207] FIG. 14 shows a block diagram 1400 of a communications manager 1405 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The communications manager 1405 may be an example of aspects of a communications manager 1215, a communications manager 1315, or a communications manager 1510 described herein. The communications manager 1405 may include a first grant manager 1410, a second grant manager 1415, a timing manager 1420, a timing indication manager 1425, a capability configuration manager 1430, a grant manager 1435, and an ACK/NACK manager 1440. Each of these modules may communicate, directly or indirectly, with one another (e.g., via one or more buses).

[0208] The first grant manager 1410 may transmit a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission.

[0209] The second grant manager 1415 may transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0210] The timing manager 1420 may use the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission is based on at least one of a transmission timing of the second grant, or a transmission timing of the second downlink transmission, or a combination thereof.

[0211] The timing indication manager 1425 may configure the second grant with a timing indication identifying the first downlink transmission from which the UE is to use the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0212] In some cases, the timing indication is based on at least one of a first grant transmission timing, or a first downlink transmission timing, or a second grant transmission timing, or a second downlink transmission timing, or a combination thereof. In some cases, the timing indication is indicated in a quasi-colocation source reference signal type identifier in a TCI state or a TCI reference signal set of the second grant.

[0213] The capability configuration manager 1430 may receive a UE capability message identifying a minimum supported gap between the first downlink transmission and the second downlink transmission that the UE supports for using the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0214] The grant manager 1435 may control, monitor, or otherwise manage aspects of the first downlink transmission and the second downlink transmission being performed on a same or a different component carrier. In some cases, the first reference signal type includes a quasi-colocation source reference signal type identified in a TCI state or a TCI reference signal set of the first grant. In some cases, the second reference signal type includes a demodulation reference signal transmitted in conjunction with the corresponding downlink transmission. [0215] The ACK/NACK manager 1440 may receive an acknowledgement message for the first downlink transmission, where using the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission is based on the receipt of the acknowledgement message for the first downlink transmission. In some cases, a timing difference between receipt of the acknowledgement message and the second downlink transmission is within a threshold timing window.

[0216] In some cases, the first grant manager 1410, second grant manager 1415, timing manager 1420, timing indication manager 1425, capability configuration manager 1430, grant manager 1435, and ACK/NACK manager 1440 may each be or be at least a part of a processor (e.g., a transceiver processor, or a radio processor, or a transmitter processor, or a receiver processor). The processor may be coupled with memory and execute instructions stored in the memory that enable the processor to perform or facilitate the features of first grant manager 1410, second grant manager 1415, timing manager 1420, timing indication manager 1425, capability configuration manager 1430, grant manager 1435, and ACK/NACK manager 1440 discussed herein.

[0217] FIG. 15 shows a diagram of a system 1500 including a device 1505 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The device 1505 may be an example of or include the components of device 1205, device 1305, or a base station 105 as described herein. The device 1505 may include components for bi-directional voice and data communications including components for transmitting and receiving communications, including a communications manager 1510, a network communications manager 1515, a transceiver 1520, an antenna 1525, memory 1530, a processor 1540, and an inter-station communications manager 1545. These components may be in electronic communication via one or more buses (e.g., bus 1550).

[0218] The communications manager 1510 may transmit a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission and transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

[0219] By including or configuring the communications manager 1510 in accordance with examples as described herein, the device 1505 may reduce overhead and increase communications efficiency. For example, the device 1505 may avoid signaling a first and second reference signal in a grant for each transmission. Using a first reference signal of a first data transmission as a QCL source for another data transmission may therefore reduce signaling overhead and may enable the device 1505 to communicate more efficiently.

[0220] The network communications manager 1515 may manage communications with the core network (e.g., via one or more wired backhaul links). For example, the network communications manager 1515 may manage the transfer of data communications for client devices, such as one or more UEs 115.

[0221] The transceiver 1520 may communicate bi-directionally, via one or more antennas, wired, or wireless links as described above. For example, the transceiver 1520 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1520 may also include a modem to modulate the packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

[0222] In some cases, the wireless device may include a single antenna 1525. However, in some cases the device may have more than one antenna 1525, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

[0223] The memory 1530 may include RAM, ROM, or a combination thereof. The memory 1530 may store computer-readable code 1535 including instructions that, when executed by a processor (e.g., the processor 1540) cause the device to perform various functions described herein. In some cases, the memory 1530 may contain, among other things, a BIOS which may control basic hardware or software operation such as the interaction with peripheral components or devices. [0224] The processor 1540 may include an intelligent hardware device (e.g., a general- purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, a discrete gate or transistor logic component, a discrete hardware component, or any combination thereof). In some cases, the processor 1540 may be configured to operate a memory array using a memory controller. In some cases, a memory controller may be integrated into processor 1540. The processor 1540 may be configured to execute computer- readable instructions stored in a memory (e.g., the memory 1530) to cause the device 1505 to perform various functions (e.g., functions or tasks supporting using a DMRS of a data transmission as a QCL reference signal source for another data transmission).

[0225] The inter-station communications manager 1545 may manage communications with other base station 105, and may include a controller or scheduler for controlling communications with UEs 115 in cooperation with other base stations 105. For example, the inter-station communications manager 1545 may coordinate scheduling for transmissions to UEs 115 for various interference mitigation techniques such as beamforming or joint transmission. In some examples, the inter-station communications manager 1545 may provide an X2 interface within an LTE/LTE-A wireless communication network technology to provide communication between base stations 105.

[0226] The code 1535 may include instructions to implement aspects of the present disclosure, including instructions to support wireless communications. The code 1535 may be stored in a non-transitory computer-readable medium such as system memory or other type of memory. In some cases, the code 1535 may not be directly executable by the processor 1540 but may cause a computer (e.g., when compiled and executed) to perform functions described herein.

[0227] FIG. 16 shows a flowchart illustrating a method 1600 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The operations of method 1600 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1600 may be performed by a communications manager as described with reference to FIGs. 8 through 11. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special- purpose hardware.

[0228] At 1605, the UE may receive a first grant scheduling a first downlink transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission. The operations of 1605 may be performed according to the methods described herein. In some examples, aspects of the operations of 1605 may be performed by a grant manager as described with reference to FIGs. 8 through 11.

[0229] At 1610, the UE may identify, based on the first reference signal, a set of quasi colocation parameters for the first downlink transmission. The operations of 1610 may be performed according to the methods described herein. In some examples, aspects of the operations of 1610 may be performed by a QCL parameter manager as described with reference to FIGs. 8 through 11.

[0230] At 1615, the UE may identify the channel estimate for the first downlink transmission based on the set of quasi-colocation parameters and the second reference signal. The operations of 1615 may be performed according to the methods described herein. In some examples, aspects of the operations of 1615 may be performed by a channel estimate manager as described with reference to FIGs. 8 through 11.

[0231] At 1620, the UE may receive a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. The operations of 1620 may be performed according to the methods described herein. In some examples, aspects of the operations of 1620 may be performed by a grant manager as described with reference to FIGs. 8 through 11.

[0232] At 1625, the UE may perform a channel estimation for the second downlink transmission based on the second reference signal, the second grant, and the third reference signal. The operations of 1625 may be performed according to the methods described herein. In some examples, aspects of the operations of 1625 may be performed by a channel estimate manager as described with reference to FIGs. 8 through 11.

[0233] FIG. 17 shows a flowchart illustrating a method 1700 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The operations of method 1700 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1700 may be performed by a communications manager as described with reference to FIGs. 8 through 11. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special- purpose hardware.

[0234] At 1705, the UE may receive a first grant scheduling a first downlink transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission. The operations of 1705 may be performed according to the methods described herein. In some examples, aspects of the operations of 1705 may be performed by a grant manager as described with reference to FIGs. 8 through 11.

[0235] At 1710, the UE may identify, based on the first reference signal, a set of quasi colocation parameters for the first downlink transmission. The operations of 1710 may be performed according to the methods described herein. In some examples, aspects of the operations of 1710 may be performed by a QCL parameter manager as described with reference to FIGs. 8 through 11.

[0236] At 1715, the UE may identify the channel estimate for the first downlink transmission based on the set of quasi-colocation parameters and the second reference signal. The operations of 1715 may be performed according to the methods described herein. In some examples, aspects of the operations of 1715 may be performed by a channel estimate manager as described with reference to FIGs. 8 through 11.

[0237] At 1720, the UE may receive a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. The operations of 1720 may be performed according to the methods described herein. In some examples, aspects of the operations of 1720 may be performed by a grant manager as described with reference to FIGs. 8 through 11.

[0238] At 1725, the UE may identify the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission based on at least one of a transmission timing of the second grant, or a transmission timing of the second downlink transmission, or a combination thereof. The operations of 1725 may be performed according to the methods described herein. In some examples, aspects of the operations of 1725 may be performed by a timing manager as described with reference to FIGs. 8 through 11

[0239] At 1730, the UE may perform a channel estimation for the second downlink transmission based on the second reference signal, the second grant, and the third reference signal. The operations of 1730 may be performed according to the methods described herein. In some examples, aspects of the operations of 1730 may be performed by a channel estimate manager as described with reference to FIGs. 8 through 11.

[0240] FIG. 18 shows a flowchart illustrating a method 1800 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The operations of method 1800 may be implemented by a UE 115 or its components as described herein. For example, the operations of method 1800 may be performed by a communications manager as described with reference to FIGs. 8 through 11. In some examples, a UE may execute a set of instructions to control the functional elements of the UE to perform the functions described below. Additionally or alternatively, a UE may perform aspects of the functions described below using special- purpose hardware.

[0241] At 1805, the UE may transmit a UE capability message identifying a minimum supported gap between the first downlink transmission and the second downlink transmission that the UE supports for using the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission. The operations of 1805 may be performed according to the methods described herein. In some examples, aspects of the operations of 1805 may be performed by a capability configuration manager as described with reference to FIGs. 8 through 11.

[0242] At 1810, the UE may receive a first grant scheduling a first downlink transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission. The operations of 1810 may be performed according to the methods described herein. In some examples, aspects of the operations of 1810 may be performed by a grant manager as described with reference to FIGs. 8 through 11.

[0243] At 1815, the UE may identify, based on the first reference signal, a set of quasi colocation parameters for the first downlink transmission. The operations of 1815 may be performed according to the methods described herein. In some examples, aspects of the operations of 1815 may be performed by a QCL parameter manager as described with reference to FIGs. 8 through 11.

[0244] At 1820, the UE may identify the channel estimate for the first downlink transmission based on the set of quasi-colocation parameters and the second reference signal. The operations of 1820 may be performed according to the methods described herein. In some examples, aspects of the operations of 1820 may be performed by a channel estimate manager as described with reference to FIGs. 8 through 11.

[0245] At 1825, the UE may receive a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. The operations of 1825 may be performed according to the methods described herein. In some examples, aspects of the operations of 1825 may be performed by a grant manager as described with reference to FIGs. 8 through 11.

[0246] At 1830, the UE may perform a channel estimation for the second downlink transmission based on the second reference signal, the second grant, and the third reference signal. The operations of 1830 may be performed according to the methods described herein. In some examples, aspects of the operations of 1830 may be performed by a channel estimate manager as described with reference to FIGs. 8 through 11.

[0247] FIG. 19 shows a flowchart illustrating a method 1900 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The operations of method 1900 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 1900 may be performed by a communications manager as described with reference to FIGs. 12 through 15. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

[0248] At 1905, the base station may transmit a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission. The operations of 1905 may be performed according to the methods described herein. In some examples, aspects of the operations of 1905 may be performed by a first grant manager as described with reference to FIGs. 12 through 15.

[0249] At 1910, the base station may transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. The operations of 1910 may be performed according to the methods described herein. In some examples, aspects of the operations of 1910 may be performed by a second grant manager as described with reference to FIGs. 12 through 15.

[0250] FIG. 20 shows a flowchart illustrating a method 2000 that supports using a DMRS of a data transmission as a QCL reference signal source for another data transmission in accordance with aspects of the present disclosure. The operations of method 2000 may be implemented by a base station 105 or its components as described herein. For example, the operations of method 2000 may be performed by a communications manager as described with reference to FIGs. 12 through 15. In some examples, a base station may execute a set of instructions to control the functional elements of the base station to perform the functions described below. Additionally or alternatively, a base station may perform aspects of the functions described below using special-purpose hardware.

[0251] At 2005, the base station may transmit a first grant scheduling a first downlink transmission to a UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission. The operations of 2005 may be performed according to the methods described herein. In some examples, aspects of the operations of 2005 may be performed by a first grant manager as described with reference to FIGs. 12 through 15.

[0252] At 2010, the base station may receive an acknowledgement message for the first downlink transmission, where using the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission is based on the receipt of the acknowledgement message for the first downlink transmission. The operations of 2010 may be performed according to the methods described herein. In some examples, aspects of the operations of 2010 may be performed by an ACK/NACK manager as described with reference to FIGs. 12 through 15.

[0253] At 2015, the base station may transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission. The operations of 2015 may be performed according to the methods described herein. In some examples, aspects of the operations of 2015 may be performed by a second grant manager as described with reference to FIGs. 12 through 15.

[0254] It should be noted that the methods described herein describe possible implementations, and that the operations and the steps may be rearranged or otherwise modified and that other implementations are possible. Further, aspects from two or more of the methods may be combined. [0255] Techniques described herein may be used for various wireless communications systems such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and other systems. A CDMA system may implement a radio technology such as CDMA2000, Universal Terrestrial Radio Access (UTRA), etc. CDMA2000 covers IS-2000, IS-95, and IS- 856 standards. IS-2000 Releases may be commonly referred to as CDMA2000 IX, IX, etc. IS-856 (TIA-856) is commonly referred to as CDMA2000 lxEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes Wideband CDMA (WCDMA) and other variants of CDMA. A TDMA system may implement a radio technology such as Global System for Mobile Communications (GSM).

[0256] An OFDMA system may implement a radio technology such as Ultra Mobile Broadband (UMB), Evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunications System (UMTS). LTE, LTE-A, and LTE-A Pro are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A, LTE-A Pro, NR, and GSM are described in documents from the organization named “3rd Generation Partnership Project” (3GPP). CDMA2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). The techniques described herein may be used for the systems and radio technologies mentioned herein as well as other systems and radio technologies. While aspects of an LTE, LTE-A, LTE-A Pro, or NR system may be described for purposes of example, and LTE, LTE-A, LTE-A Pro, or NR terminology may be used in much of the description, the techniques described herein are applicable beyond LTE, LTE-A, LTE-A Pro, or NR applications.

[0257] A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. A small cell may be associated with a lower-powered base station, as compared with a macro cell, and a small cell may operate in the same or different (e.g., licensed, unlicensed, etc.) frequency bands as macro cells. Small cells may include pico cells, femto cells, and micro cells according to various examples. A pico cell, for example, may cover a small geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femto cell may also cover a small geographic area (e.g., a home) and may provide restricted access by UEs having an association with the femto cell (e.g., UEs in a closed subscriber group (CSG), UEs for users in the home, and the like). An eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, a pico eNB, a femto eNB, or a home eNB. An eNB may support one or multiple (e.g., two, three, four, and the like) cells, and may also support communications using one or multiple component carriers.

[0258] The wireless communications systems described herein may support synchronous or asynchronous operation. For synchronous operation, the base stations may have similar frame timing, and transmissions from different base stations may be approximately aligned in time. For asynchronous operation, the base stations may have different frame timing, and transmissions from different base stations may not be aligned in time. The techniques described herein may be used for either synchronous or asynchronous operations.

[0259] Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

[0260] The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

[0261] The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and appended claims. For example, due to the nature of software, functions described herein can be implemented using software executed by a processor, hardware, firmware, hardwiring, or combinations of any of these. Features implementing functions may also be physically located at various positions, including being distributed such that portions of functions are implemented at different physical locations.

[0262] Computer-readable media includes both non-transitory computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A non-transitory storage medium may be any available medium that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media may include random- access memory (RAM), read-only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory, compact disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include CD, laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

[0263] As used herein, including in the claims, “or” as used in a list of items (e.g., a list of items prefaced by a phrase such as “at least one of’ or “one or more of’) indicates an inclusive list such that, for example, a list of at least one of A, B, or C means A or B or C or AB or AC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase “based on” shall not be construed as a reference to a closed set of conditions. For example, an exemplary step that is described as “based on condition A” may be based on both a condition A and a condition B without departing from the scope of the present disclosure. In other words, as used herein, the phrase “based on” shall be construed in the same manner as the phrase “based at least in part on.”

[0264] In the appended figures, similar components or features may have the same reference label. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If just the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label, or other subsequent reference label.

[0265] The description set forth herein, in connection with the appended drawings, describes example configurations and does not represent all the examples that may be implemented or that are within the scope of the claims. The term “exemplary” used herein means “serving as an example, instance, or illustration,” and not “preferred” or “advantageous over other examples.” The detailed description includes specific details for the purpose of providing an understanding of the described techniques. These techniques, however, may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

[0266] The description herein is provided to enable a person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not limited to the examples and designs described herein, but is to be accorded the broadest scope consistent with the principles and novel features disclosed herein.

Claims

CLAIMS What is claimed is:

1. A method for wireless communication by a user equipment (UE), comprising: receiving a first grant scheduling a first transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission; identifying, based at least in part on the first reference signal, a set of quasi colocation parameters for the first downlink transmission; identifying the channel estimate for the first transmission based at least in part on the set of quasi-colocation parameters and the second reference signal; receiving a second grant scheduling a second transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second transmission and for the UE to determine the identified channel estimate for the second transmission; and performing a channel estimation for the second transmission based at least in part on the second reference signal, the second grant, and the third reference signal.

2. The method of claim 1, further comprising: identifying the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission based on at least one of a transmission timing of the second grant, or a transmission timing of the second transmission, or a combination thereof.

3. The method of claim 1, further comprising: identifying, based at least in part on a timing indication in the second grant, the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission.

4. The method of claim 3, wherein the timing indication is based on at least one of a first grant transmission timing, or a first transmission timing, or a second grant transmission timing, or a second transmission timing, or a combination thereof.

5. The method of claim 3, wherein the timing indication is indicated in a quasi-colocation source reference signal type identifier in a transmission configuration indicator (TCI) state or a TCI reference signal set of the second grant.

6. The method of claim 1, further comprising: transmitting a UE capability message identifying a minimum supported gap between the first transmission and the second transmission that the UE supports for using the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission.

7. The method of claim 1, further comprising: identifying a component carrier associated with the second transmission based at least in part on the first transmission.

8. The method of claim 1, further comprising: identifying, based at least in part on the second grant, a component carrier associated with the second transmission.

9. The method of claim 1, further comprising: transmitting an acknowledgement message for the first transmission; and identifying the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission based at least in part on the transmission of the acknowledgement message for the first transmission.

10. The method of claim 9, further comprising: determining that a timing difference between transmission of the acknowledgement message and the second transmission is within a threshold timing window, wherein using the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission is based at least in part on the timing difference.

11. The method of claim 1, further comprising: determining that there were multiple first transmissions, with each of the first transmissions associated with a different component carrier; identifying a numerical control resource set identifier associated with each first transmission; and determining to use the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission based at least in part on the first transmission having a lowest numerical control resources set identifier.

12. The method of claim 1, further comprising: determining that a timing difference between the first transmission and the second transmission has exceeded a threshold; and using the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission based at least in part on the timing difference exceeding the threshold.

13. The method of claim 1, further comprising: determining that a timing difference between the first transmission and the second transmission has not exceeded a threshold; and using the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission based at least in part on the timing difference not exceeding the threshold.

14. The method of claim 1, further comprising: determining that a timing difference between the first transmission and the second transmission has exceeded a threshold; and refraining from using the third reference signal of the second reference signal type as the quasi-colocation source for the second transmission based at least in part on the timing difference exceeding the threshold.

15. The method of claim 1, wherein the first transmission occurs according to a slot-aggregation scheme comprising two or more slots.

16. The method of claim 1, wherein: the first reference signal type comprises a quasi-colocation source reference signal type identified in a transmission configuration indicator (TCI) state or a TCI reference signal set of the first grant; and the second reference signal type comprises a demodulation reference signal transmitted in conjunction with the corresponding transmission.

17. The method of claim 1, wherein: the first reference signal type comprises at least one of a tracking reference signal, or a channel state information reference signal (CSI-RS), or a synchronization signal block (SSB), or a combination thereof.

18. A method for wireless communication by a base station, comprising: transmitting a first grant scheduling a first downlink transmission to a user equipment (UE), the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission; and transmitting a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission.

19. The method of claim 18, further comprising: identifying the third reference signal of the second reference signal type as the quasi-colocation source for the UE to determine the identified channel estimate for the second downlink transmission.

20. The method of claim 18, wherein: using the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission is based on at least one of a transmission timing of the second grant, or a transmission timing of the second downlink transmission, or a combination thereof.

21. The method of claim 18, further comprising: configuring the second grant with a timing indication identifying the first downlink transmission from which the UE is to use the third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

22. The method of claim 20, wherein the timing indication is based on at least one of a first grant transmission timing, or a first downlink transmission timing, or a second grant transmission timing, or a second downlink transmission timing, or a combination thereof.

23. The method of claim 20, wherein the timing indication is indicated in a quasi-colocation source reference signal type identifier in a transmission configuration indicator (TCI) state or a TCI reference signal set of the second grant.

24. The method of claim 18, further comprising: receiving a UE capability message identifying a minimum supported gap between the first downlink transmission and the second downlink transmission that the UE supports for using the third reference signal of the second reference signal type as the quasi colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.

25. The method of claim 18, wherein the first downlink transmission and the second downlink transmission are performed on a same or a different component carrier.

26. The method of claim 18, further comprising: receiving an acknowledgement message for the first downlink transmission, wherein using the third reference signal of the second reference signal type as the quasi colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission is based at least in part on the receipt of the acknowledgement message for the first downlink transmission.

27. The method of claim 25, wherein a timing difference between receipt of the acknowledgement message and the second downlink transmission is within a threshold timing window.

28. The method of claim 18, wherein: the first reference signal type comprises a quasi-colocation source reference signal type identified in a transmission configuration indicator (TCI) state or a TCI reference signal set of the first grant; and the second reference signal type comprises a demodulation reference signal transmitted in conjunction with the corresponding downlink transmission.

29. An apparatus for wireless communication by a user equipment (UE), comprising: a processor, memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to: receive a first grant scheduling a first transmission to the UE, the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first transmission; identify, based at least in part on the first reference signal, a set of quasi-colocation parameters for the first transmission; identify the channel estimate for the first transmission based at least in part on the set of quasi-colocation parameters and the second reference signal; receive a second grant scheduling a second transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second transmission and for the UE to determine the identified channel estimate for the second transmission; and perform a channel estimation for the second transmission based at least in part on the second reference signal, the second grant, and the third reference signal.

30. An apparatus for wireless communication by a base station, comprising: a processor, memory coupled with the processor; and instructions stored in the memory and executable by the processor to cause the apparatus to: transmit a first grant scheduling a first downlink transmission to a user equipment (UE), the first grant identifying a first reference signal of a first reference signal type for the UE to use as a first quasi-colocation source for the first downlink transmission and a second reference signal of a second reference signal type for the UE to use to perform a channel estimation for the first downlink transmission; and transmit a second grant scheduling a second downlink transmission to the UE, the second grant identifying a third reference signal of the second reference signal type as the quasi-colocation source for the second downlink transmission and for the UE to determine the identified channel estimate for the second downlink transmission.