Phase tracking reference signal transmission method based on uplink multi-codeword operation

Abstract

Methods and apparatus in a wireless network determine one or more of a number of phase tracking reference signals (PT-RSs), a time domain density of the PT-RSs, and ports associated with the PT-RSs. Control signaling for configuring a multi-codeword transmission of the at least one PT-RS is transmitted from the network entity to the UE, and the control signaling includes parameters for identifying one or more ports to be used by the UE for transmitting the PT-RS.

Description

TECHNICAL FIELD

[0001] This document generally describes methods and apparatuses operating in a wireless communication system, such as (but not limited to) those described in the 5G standard documents, referred to as 3GPP communication systems. BACKGROUND

[0002] A 5G user equipment (UE), as described in current standard documents, as an apparatus that allows a user to access network services, can be configured to transmit a phase tracking reference signal (PT-RS) associated with a physical uplink shared channel (PUSCH) to enable phase tracking and compensation for received PUSCH data for a symbol without a demodulation reference signal (DMRS). The UE can transmit the PT-RS from one port or two ports. The two PT-RS ports are multiplexed in a frequency-division multiplexing (FDM) manner. The UE can transmit the PT-RS from one port in every L symbols, where L (referred to as time-domain density) is determined based on a scheduled modulation and coding scheme (MCS). Figure 1 An example transmission block including PT-RS transmitted with a time-domain density L = 2 is shown. In this example, the PT-RS is transmitted every other symbol using the same subcarriers, except for symbols where a DMRS is transmitted using multiple subcarriers.

[0003] The UE transmits data from more than four transmission layers using two codewords. The number of layers indicates the number of columns of a precoder applied to the PUSCH transmission.

[0004] For an initial transmission, the NE can indicate an MCS for a PUSCH via downlink control information (DCI) or via radio resource control (RRC) signaling. Currently, for a dynamically granted PUSCH or a type 2 configured grant PUSCH, the NE indicates an MCS via DCI, and for a type 1 configured grant PUSCH, the NE configures an MCS via RRC signaling. In case of a retransmission, the NE can indicate the same MCS or a reserved MCS via DCI. The reserved MCS indicates an MCS higher than an MCS threshold V (e.g., V = 28 or 27, depending on other parameters shown in a table of section 5.1.3.1 of 3GPP TS 38.214). The reserved MCS indicates only a modulation order. The UE transmits a transport block (TB) as an initial transmission based on the modulation order indicated by the reserved MCS. Some features related to PT-RS are described in section 6.4.1.2 of 3GPP TS 38.211 (which defines sequence generation and resource mapping for PT-RS) and section 6.2.3 of 3GPP TS 38.214 (which describes a procedure for PT-RS transmission).

[0005] A network entity, NE, configures a UE with an MCS threshold to identify a value of a time domain density, L. The NE can be a base station, BS, but more generally it is a logically separate entity with a well-defined functionality (e.g., the functionality of a BS is to connect a UE to a core network). The presence of PT-RSs is also determined based on the scheduled MCS.

[0006] When one of the code words is disabled, as shown in Figure 2 or the code word is associated with a reserved MCS, as shown in Figure 3 it can be challenging to select the best precoder / channel / antenna port for transmission of PT-RSs and to determine the PT-RS time domain density.

[0007] Another conventional, unsolved problem is to indicate the ports for transmission of more than one (e.g., two) PT-RSs in multi-code word based operation. SUMMARY

[0008] Methods performed by a UE and a NE embody techniques for a UE to transmit one or more PT-RSs for uplink multi-code word based operation. The UE and a network entity, NE, are endpoints of a multi-code word transmission that includes one or more PT-RSs. Control signaling including parameters is communicated therebetween for configuration of the multi-code word transmission. The UE and the NE can determine a number of ports to be used by the UE for at least one PT-RS based on values and indications included in the parameters. The UE and the NE can identify ports to be used by the UE to transmit PT-RSs among ports that are alternatively used to transmit demodulation reference signals, DMRSs. The UE and the NE can also determine a time domain density and PT-RS ports for transmission of PT-RSs based on an MCS associated with a code word and by applying additional rules in case a code word initially selected for transmission of PT-RSs is disabled or its MCS is a reserved MCS. The UE then transmits data and at least one PT-RS to the NE via at least two code words in accordance with the configured multi-code word transmission and employing one or more ports identified from the parameters. BRIEF DESCRIPTION OF DRAWINGS

[0009] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more implementations and together with the description, explain these implementations.

[0010] Figure 1 An example transmission block including PT-RSs is shown.

[0011] Figure 2 A first scenario in which conventional methods fail is shown schematically.

[0012] Figure 3 A second scenario in which conventional methods fail is shown schematically.

[0013] Figure 4 is a diagram of a wireless system with an apparatus implementing PT-RS transmission for uplink multi-codeword based operation according to various embodiments.

[0014] Figure 5 is a signal diagram for PT-RS transmission for uplink multi-codeword based operation according to an embodiment.

[0015] Figure 6 is a flowchart illustrating UE behavior for PT-RS transmission for PUSCH with more than one codeword according to an embodiment.

[0016] Figure 7 shows NE behavior for PT-RS reception for PUSCH with more than one codeword according to an embodiment.

[0017] Figure 8 shows a scenario for PT-RS association with DMRS ports based only on enabled codewords according to an embodiment.

[0018] Figure 9 shows a scenario where PT-RS is disabled when associated with DMRS ports corresponding to disabled codewords according to an embodiment.

[0019] Figure 10 shows a scenario related to determining PT-RS time-domain density based on MCS from enabled codewords when PT-RS is associated with DMRS ports corresponding to disabled codewords according to an embodiment.

[0020] Figure 11 shows a scenario related to determining PT-RS time-domain density based on MCS from disabled codewords when PT-RS is associated with DMRS ports corresponding to disabled codewords according to an embodiment.

[0021] Figure 12 shows a scenario related to determining PT-RS time-domain density and PT-RS associated DMRS ports based on MCS for initial transmission when one of the indicated MCSs is a reserved MCS according to an embodiment.

[0022] Figure 13 shows a scenario where PT-RS associated DMRS ports and time-domain density for PT-RS ports are based on nominal MCS when one of the indicated MCSs is a reserved MCS according to an embodiment.

[0023] Figure 14Scenarios are shown in which PT-RS time-domain density is determined based on the MCS used for initial transmission when one of the indicated MCSs is a reserved MCS.

[0024] Figure 15 Scenarios are shown for determining PT-RS time-domain density based on a nominal MCS when the MCS for a codeword corresponding to a DMRS port associated with PT-RS is a reserved MCS, according to embodiments.

[0025] Figure 16 Scenarios are shown for indicating DMRS ports associated with PT-RS with limited overhead in DCI, according to embodiments.

[0026] Figure 17 is a flowchart of a method for transmitting PT-RS in multi-codeword based operation, according to embodiments. DETAILED DESCRIPTION

[0027] The methods and apparatus described in this section embody techniques related to PT-RS for uplink multi-codeword based operation. More specifically, some embodiments determine the number of PT-RS ports and antenna ports to be used for PT-RS for both initial transmission and retransmission. Some embodiments determine the time density for PT-RS ports when a codeword is disabled or associated with a reserved MCS. These embodiments of techniques for PT-RS transmission for uplink multi-codeword based operation enable transmission of PT-RS on DMRS antenna ports associated with a better precoder, which can improve the performance of PUSCH. The time-domain density determination for PT-RS according to some embodiments identifies the best PT-RS density corresponding to two (or more) codeword PUSCH, which can reduce PT-RS overhead and improve the performance of PUSCH with two codeword transmission.

[0028] Figure 4 A wireless communication system 400 is depicted that includes a UE 410 and a network entity, NE 420, which can implement various techniques related to PT-RS transmission for uplink multi-codeword based transmission according to embodiments. The NE can be a base station, BS, but more generally the term represents a wireless device with well-defined network functionality (e.g., the functionality of a BS is to connect UEs to a core network, including managing communications to and from UEs). For brevity, the UE 410 and NE 420 can include additional functionality and interfaces that are omitted from the figure. The signaling arrows 401 generally represent both uplink and downlink signals transmitted by the UE 410 and NE 420, respectively. Figure 2

[0029] ​UE 410 includes an antenna connected to a radio frequency (RF) front-end 411, and at least one RF transceiver (such as an LTE transceiver 412, a 5G NR transceiver 413, or another transceiver 414) for communicating with NE 420. The antenna and RF front-end 411 can be tuned to one or more frequency bands (e.g., subcarriers) as defined by the 3GPP LTE, 5G NR, and 6G communication standards and implemented by the corresponding transceivers. UE 410 also includes one or more precoders 415, one or more processors 416, and a computer-readable storage medium (CRM) 417. The processor 416 can be a single-core or multi-core processor, and the CRM 417 includes any suitable memory / storage device other than the propagating signal. For example, the memory / storage device may include random access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), and / or flash memory that can be used to store device data 418 and to generate the multi-codeword PT-RS 419 implementing the various technologies described in this document. Device data 418 stores instructions that can be executed by processor 416 to facilitate user plane communications, control plane signaling, and user interaction with UE 410. The generator of the multi-codeword PT-RS 419 (which can be implemented not only as software but also as hardware logic and / or circuitry) causes various steps and actions associated with PT-RS transmissions for multi-codeword-based operations.

[0030] like Figure 4 The NE 420 shown provides the functionality of a gNB (5G or 6G base station). The functionality of the NE 420 can be distributed across multiple entities (e.g., a central unit (CU), a distributed unit (DU), and a radio unit (RU)). The NE 420 includes an antenna and RF front-end 421 for communicating with the UE 410 and other NEs, as well as an RF transceiver 422 (more transceivers may exist for different technologies, as shown for the UE 410). The NE's antenna and RF front-end 421 can be tuned to one or more frequency bands (e.g., subcarriers) defined by, for example, 3GPP LTE, 5G NR, and 6G communication standards and implemented by the RF transceiver 422.

[0031] The NE 420 includes a processor 423 and a computer-readable storage medium (CRM) 424. The processor 423 can include a single-core or multiple- core processor, and the CRM 424 includes any suitable memory / storage devices, excluding propagating signals. For example, the memory / storage devices can include random access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), and / or Flash memory. The CRM 424 stores device data 425, including network scheduling data, radio resource management data, applications, and / or an operating system, executable by the processor 423 for implementing the wireless communication 401 with the UE 410 and with other NEs.

[0032] The CRM 424 also stores a control signaling generator 426 and a multiple-codeword processor with PT-RS 427. The control signaling generator 426 of the NE causes the NE to perform various steps and actions associated with configuring a UE for multiple-codeword transmission including PT-RS. The multiple-codeword processor with PT-RS 427 processes multiple-codeword transmission including PT-RS received from the UE 410.

[0033] The NE 420 also includes an inter-base station interface 428 and a core network interface 429. The inter-base station interface 428 can be a standardized interface, such as an Xn and / or X2 interface, for exchanging user plane and control plane data with another NE (e.g., in the case of a handover). The core network interface 429 supports the exchange of user plane data and control plane information between the NE and core network functions and / or entities.

[0034] The wireless system, illustrated schematically in FIG. 5, can implement various techniques related to PT-RS transmission for uplink multiple-codeword based operation, as further described. Figure 4 The wireless system, illustrated schematically in FIG. 5, can implement various techniques related to PT-RS transmission for uplink multiple-codeword based operation, as further described. Figure 5 is a signaling diagram for PT-RS transmission and reception for PUSCH with more than one codeword (where the time flow is from top to bottom).

[0035] The UE reports 502 its capabilities related to supported PT-RS configurations for PUSCH transmission to the UE with multiple codewords. However, the signaling 502 is optional (as shown by the dashed line) as the NE can instead receive one or more capabilities from a core network (e.g., an access and mobility management function (AMF)). However, in some embodiments, the NE receives one or more capabilities from another NE (e.g., a gNB or eNB).

[0036] Based on the UE capability, the NE 420 transmits 504 RRC signaling that configures the maximum number of PT-RS ports and the codebook for PUSCH transmission. The NE can configure the PUSCH transmission based on a cyclic prefix orthogonal frequency-division multiplexing (CP-OFDM) waveform, and thus it can disable transform precoding. For configured grant PUSCH, the NE configures the uplink grant for PUSCH through RRC signaling. For dynamic grant PUSCH or type 2 configured grant PUSCH, the NE transmits 506 downlink control information (DCI) that indicates the uplink grant for PUSCH transmission, where the NE indicates the associated DMRS port for the PT-RS port. Based on the received RRC signaling and / or DCI, the UE 410 determines 508 the number of PT-RS ports, the associated DMRS port, and the time-domain density for the PT-RS ports. The UE 410 then transmits 510 the PT-RS and PUSCH based on the determined PT-RS configuration. The NE 420 determines 512 the number of PT-RS ports, the associated DMRS port, and the time-domain density for the PT-RS ports in the same manner as the UE 410.

[0037] Figure 6 The behavior of a UE for PT-RS transmission for PUSCH with more than one codeword is shown in accordance with an embodiment. Optionally (as shown by the dashed box), the UE transmits 602 UE capability regarding the supported PT-RS configuration for more than one codeword. The UE then receives 604 RRC signaling that configures the maximum number of PT-RS ports for PUSCH transmission and the codebook for PUSCH transmission and optionally configures the uplink grant for PUSCH transmission with more than one codeword. The UE can also receive 606 DCI that indicates the uplink grant for PUSCH transmission with more than one codeword and an indication of the associated DMRS port for the PT-RS (i.e., the port with the best precoder). Further, the UE determines 608 the number of PT-RS ports, the associated DMRS port, and the time-domain density for each PT-RS port.

[0038] Figure 7The behavior of the NE for PT-RS reception for PUSCH with more than one codeword is shown. Optionally (as shown by the dashed box), the NE receives 702 UE capability regarding supported PT-RS configuration for more than one codeword case. The NE then transmits 704 RRC signaling that configures the maximum number of PT-RS ports for PUSCH transmission and codebook for PUSCH transmission and optionally configures uplink grant for PUSCH transmission with more than one codeword. The NE can also transmit 706 DCI that indicates uplink grant for PUSCH transmission with more than one codeword and indication of associated DMRS ports for PT-RS. Further, the NE determines 708 the number of PT-RS ports and associated DMRS ports and time-domain density for each PT-RS port. The NE then receives 710 PUSCH and PT-RS based on the determined PT-RS configuration.

[0039] In the above signaling diagram (i.e., the behavior of the UE and the NE), the RRC signaling can be a RRC reconfiguration message from the NE to the UE or a system information block (SIB), where the SIB can be an existing SIB (e.g., SIB1) or a new SIB (e.g., SIBJ, where J is an integer greater than 21) transmitted by the NE.

[0040] In some embodiments, the UE and the NE determine (as in 608 and 708, respectively) the number of PT-RS ports for PUSCH transmission with more than four ports based on at least one of: the maximum number of PT-RS ports configured by the RRC signaling, the precoder indicated by the uplink grant, and the PUSCH ports sharing a common PT-RS port.

[0041] The UE can report UE capability indicating whether the UE supports more than one PT-RS port (e.g., two PT-RS ports) and the PUSCH ports sharing a common PT-RS port. In some other implementations, the PUSCH ports sharing a common PT-RS port are predefined. In one example, PUSCH ports 1000, 1001, 1004, and 1005 can share one PT-RS port and PUSCH ports 1002, 1003, 1006, and 1007 can share another PT-RS port. In another example, PUSCH ports 1000, 1002, 1004, and 1006 can share one PT-RS port and PUSCH ports 1001, 1003, 1005, and 1007 can share another PT-RS port.

[0042] In some embodiments, if the maximum number of PT-RS ports is 1, the UE can transmit PT-RS from only one port; otherwise, the UE determines the number of PT-RS ports based on the indicated precoder. If the indicated precoder is a full-coherent precoder (i.e., a precoder that requires antenna combining for all PUSCH ports), the UE transmits PUSCH from one port; otherwise, the UE determines the number of PT-RS ports based on the non-zero-power (NZP) PUSCH ports indicated by the precoder and the PUSCH ports that share a common PT-RS port. If all NZP PUSCH ports share a common PT-RS port, the UE transmits PT-RS from one port; otherwise, the UE transmits PT-RS from more than one port.

[0043] In some other embodiments, the UE determines the number of PT-RS ports based only on the configured maximum number of PT-RS ports. If the maximum number of PT-RS ports is X, the UE transmits PT-RS from X ports.

[0044] In some other embodiments, for more than 4-port transmission (e.g., 8-port PUSCH or PUSCH associated with 8-port SRS), only one-port PT-RS is used. Thus, the NE can avoid configuring the maximum number of PT-RS ports to be greater than 1. Alternatively, if the configured maximum number of PT-RS ports is greater than 1 and the PUSCH is for more than 4-port transmission, the NE and UE can determine the number of PT-RS ports to be 1.

[0045] In some embodiments, if one of the codewords for the PUSCH is disabled, the NE and / or UE determines the associated DMRS ports for the PT-RS ports based only on the DMRS ports associated with the enabled (scheduled) codeword(s). The NE and / or UE can then determine the time-domain density for the PT-RS based on the MCS for the enabled codeword(s).

[0046] The associated DMRS ports can be selected from the DMRS ports associated with the enabled codeword(s), where the DMRS ports associated with the enabled codeword(s) are indicated in the scheduling DCI. Figure 8A scenario 800 is shown for a case where PT-RS is associated with DMRS ports based on only the enabled codewords. Ports 850, 852, 854, and 856 are related to a first codeword configured for an initial transmission with MCS = 20. Ports 860, 862, 864, and 866 are related to a second codeword that is disabled as indicated by MCS = 26 and RV = 1 (where RV stands for redundancy version). In this scenario, the NE and / or UE determines 808 the PT-RS associated DMRS port from the DMRS ports 850 to 856 and determines the PT-RS time-domain density based on the MCS of the first codeword (MCS = 20).

[0047] In other embodiments, if one of the codewords for the PUSCH is disabled and the NE and / or UE determines that the associated DMRS port for the PT-RS port is one of the DMRS ports associated with the disabled codeword, the NE and / or UE determines that the PT-RS is not present. Thus, the UE refrains from transmitting the PT-RS for the PUSCH. The UE can transmit PUSCH data in the resource elements reserved / allocated for the PT-RS. Alternatively, the UE can transmit the PT-RS with a default time-domain density (e.g., L = 1), where the default time-domain density can be predefined, configured by the NE via RRC signaling, or reported by the UE via UE capability. Figure 9 A scenario 900 is shown where the PT-RS is disabled when associated with the DMRS ports corresponding to the disabled codeword. The scenario 900 has the same setup as the scenario 800 (where the second codeword is disabled), but, here, the NE and / or UE determines 908 not to transmit the PT-RS and instead transmits PUSCH data using the resource elements reserved for the PT-RS.

[0048] In other embodiments, if one of the codewords for the PUSCH is disabled and the NE and / or UE determines that the associated DMRS port for the PT-RS port is one of the DMRS ports associated with the disabled codeword, the NE and / or UE determines that the PT-RS is still associated with the disabled codeword and determines the time-domain density for the PT-RS based on the MCS for the enabled codeword. Alternatively, the NE and / or UE still determines the time-domain density for the PT-RS based on the MCS for the codeword corresponding to the associated DMRS port. Figure 10A scenario 1000 related to determining PT-RS time-domain density based on MCS from the enabled codeword in case PT-RS is associated with DMRS ports corresponding to the disabled codeword is shown. The scenario 1000 has the same settings as scenarios 800 and 900 (where the second codeword is disabled), but here, the NE and / or UE determines 1008 the PT-RS associated port DMRS from the DMRS ports 1060, 1062, 1064, and 1066 of the disabled codeword and determines the time-domain density for PT-RS based on the MCS of the first codeword (MCS = 20).

[0049] Figure 11 A scenario 1100 related to determining PT-RS time-domain density based on MCS from the disabled codeword in case PT-RS is associated with DMRS ports corresponding to the disabled codeword is shown. The scenario 1100 is also a scenario where the second codeword is disabled, but here, the NE and / or UE determines 1108 the PT-RS associated port DMRS from the DMRS ports 1160, 1162, 1164, and 1166 of the disabled codeword and determines the time-domain density for PT-RS based on the MCS of the second codeword (MCS = 26).

[0050] In other embodiments, the UE can report a UE capability indicating whether it supports transmission of PT-RS associated with DMRS ports corresponding to the disabled codeword. If the UE does not support transmission of PT-RS associated with DMRS ports corresponding to the disabled codeword, the UE refrains from transmitting PT-RS when the codeword is disabled. If the UE receives an indication / configuration from the NE to transmit PT-RS associated with DMRS ports corresponding to the disabled codeword, the UE can ignore or discard the indication / configuration. Alternatively, the NE can refrain from indicating PT-RS ports associated with DMRS ports corresponding to the disabled codeword if the UE does not support transmission of PT-RS associated with DMRS ports corresponding to the disabled codeword.

[0051] In some embodiments, if one of the MCSs indicated in the scheduling DCI is a reserved MCS, the NE and / or UE determines the PT-RS time-domain density and the associated DMRS port for the PT-RS port based on the previously indicated MCS for the initial transmission of the codeword and the reserved MCS in the scheduling DCI and the other indicated MCSs for transmission in the scheduling DCI. For the initial transmission, the network entity refrains from indicating the reserved MCS. Figure 12Scenarios related to determining PT-RS time-domain density and PT-RS associated DMRS ports based on the MCS used for initial transmission when one of the indicated MCSs is a reserved MCS are shown. In Figure 12 In scenario 1200 shown in FIG. 12, the initial transmission MCS of codeword 2, not the retransmission MCS of codeword 2, is used for comparison with the initial transmission MCS of codeword 1. Unlike scenarios 800, 900, 1000, and 1100, in this scenario, the second codeword is not disabled, but retransmitted after the initial transmission of MCS = 6 as indicated by MCS = 29. In this scenario, the NE and / or UE determines 1208 the PT-RS associated DMRS ports from DMRS ports 1250 to 1256 and determines the PT-RS time-domain density based on the MCS of the first codeword (MCS = 20).

[0052] In other embodiments, if one of the indicated MCSs is a reserved MCS, the NE and / or UE determines the associated DMRS ports for PT-RS ports and the time-domain density for PT-RS based on a nominal MCS and other indicated MCSs used for the current transmission. One example of selecting / determining the nominal MCS is based on the computed average spectral efficiency (SE) for each layer of the corresponding codeword and the MCS table. The maximum MCS in the MCS table corresponding to a smaller SE than the computed SE is selected as the nominal MCS. Alternatively, the minimum MCS in the MCS table corresponding to a higher SE than the computed SE is selected. The SE can be computed as follows: where B indicates the transport block (TB) size for the codeword; is the number of layers for the codeword; is the number of resource elements scheduled for PUSCH; is the overhead for DMRS and other signals.

[0053] In some other implementations, the network and UE can determine the associated DMRS ports based on the SE from all MCSs. In some implementations, for the indicated MCSs other than the reserved MCS, the UE selects the SE based on the MCS table. In some other implementations, the UE computes the actual SE based on the equation above.

[0054] Figure 13 Scenario 1300 is shown in which the PT-RS associated DMRS ports and the time-domain density for PT-RS ports are based on a nominal MCS when one of the indicated MCSs is a reserved MCS. Although from the perspective of the network, the nominal MCS is selected based on the SE from all indicated MCSs, from the perspective of the UE, the nominal MCS is selected based on the SE from the indicated MCSs other than the reserved MCS. Figure 12The same setup begins, but in this scenario, the nominal MCS is used, rather than the retransmission MCS of the second codeword, for comparison with the initial transmission MCS of the first codeword. That is, the NE and / or UE determines 1308 the DMRS port associated with PT-RS from ports 1350, 1352, 1354, and 1356, and determines the time-domain density for PT-RS based on the MCS of the first codeword (MCS = 20).

[0055] In other embodiments, if one of the indicated MCSs is a reserved MCS, the NE and / or UE determines the DMRS port associated with PT-RS based on the codeword with the reserved MCS, and determines the time-domain density for the PT-RS port based on the indicated MCS for the same codeword in the initial transmission. For the initial transmission, the network entity avoids indicating the reserved MCS. Figure 14 A scenario 1400 is shown in which the PT-RS time-domain density is determined based on the MCS for the initial transmission when one of the indicated MCSs is a reserved MCS. The scenario 1400 has the same setup and MCS values as scenarios 1200 and 1300. Here, the NE and UE determine 1408 the DMRS port associated with PT-RS from ports 1450, 1452, 1454, and 1456, and determine the time-domain density for PT-RS based on the initial MCS (MCS = 20).

[0056] In other embodiments, if one of the indicated MCSs is a reserved MCS, the NE and / or UE determines the DMRS port associated with PT-RS based on the codeword with the reserved MCS, and determines the time-domain density for the PT-RS port based on the indicated MCS for the same codeword in the initial transmission. For the initial transmission, the network entity avoids indicating the reserved MCS. Figure 15 A scenario 1500 is shown for determining the PT-RS time-domain density based on the nominal MCS when the MCS for the codeword corresponding to the DMRS port associated with PT-RS is a reserved MCS. The scenario 1500 has similar setup and MCS values as scenarios 1200, 1300, and 1400, but still the second codeword for retransmission has the nominal transmission MCS = 6. Here, the NE and UE determine 1508 the DMRS port associated with PT-RS from ports 1550, 1552, 1554, and 1556, and determine the time-domain density for PT-RS based on the nominal MCS (MCS = 6).

[0057] In some embodiments, if one of the indicated MCSs is a reserved MCS, the NE and / or the UE determines that the PT-RS is not present. Thus, if the MCS for the codeword corresponding to the DMRS port associated with the PT-RS is a reserved MCS, the UE refrains from transmitting the PT-RS for the PUSCH. The UE can transmit PUSCH data in the resource elements reserved / allocated for the PT-RS. Alternatively, if one of the indicated MCSs is a reserved MCS, the NE and / or the UE determines that the PT-RS is based on a default time-domain density, where the default time-domain density can be predefined or configured by the network entity via RRC signaling or reported by the UE via UE capability.

[0058] In other embodiments, the UE reports the UE capability indicating whether the UE supports transmitting the PT-RS associated with the DMRS port corresponding to the codeword with the reserved MCS. If the UE does not support transmitting the PT-RS using the port corresponding to the codeword with the reserved MCS, the UE refrains from transmitting the PT-RS. The UE receiving an indication / configuration from the NE to transmit the PT-RS associated with the DMRS port corresponding to the codeword with the reserved MCS ignores or discards the indication / configuration. Alternatively, if the UE does not support transmitting the PT-RS using the port corresponding to the codeword with the reserved MCS, the NE refrains from indicating the reserved MCS when the PT-RS is present or configured in the active bandwidth part.

[0059] In some embodiments, if the maximum number of PT-RS ports is greater than 1 (e.g., 2), the bitwidth of the DCI field indicating the PT-RS association with the DMRS port is based on the bitwidth for the 1-port PT-RS case. Then for 2-port PT-RS, the network entity can indicate one of the DMRS ports in the subset of DMRS ports sharing the first PT-RS port and the second PT-RS port, respectively. For example, for 1-port PT-RS, 2 bits are reserved / used for the PT-RS association with the DMRS port. The NE can indicate one of the four DMRS ports associated with one codeword. For 2-port PT-RS, the NE can indicate one of the 2 DMRS ports in the 4 DMRS ports sharing the first PT-RS port via the first bit and another one of the 2 DMRS ports in the 4 DMRS ports sharing the first PT-RS port via the second bit. Figure 16 A scenario 1600 for indicating PT-RS associated DMRS ports with limited overhead in DCI is shown. In this scenario, DMRS ports 1650 and 1652 and 1660 and 1662 are candidate DMRS ports for PT-RS port 0 and PT-RS port 1, respectively.

[0060] In some embodiments, a subset of DMRS ports (e.g., the first K DMRS ports among the DMRS ports sharing the common PT-RS port) can be predefined. In some other embodiments, the subset of DMRS ports can be determined based on the scheduled MCS for the DMRS ports associated with the codeword (e.g., the K DMRS ports are the first K DMRS ports associated with the codeword with the higher MCS). If the MCS of the codewords are the same, the first K DMRS ports are selected. In some other embodiments, the NE configures the subset of DMRS ports via RRC signaling or MAC CE. For example, the network entity configures whether the subset of DMRS ports are the first two DMRS ports or the last two DMRS ports or any combination of the two DMRS ports. In some other embodiments, the NE indicates the subset of DMRS ports via DCI. For example, in the DCI, the network entity can indicate whether the candidate associated DMRS ports are the first two DMRS ports or the last two DMRS ports or any combination of the two DMRS ports by some reserved fields (e.g., DMRS antenna ports).

[0061] In some embodiments, if the maximum number of PT-RS ports is greater than 1 (e.g., 2), the bit-width of the DCI field for indicating the PT-RS association with the DMRS ports is based on the bit-width of the number of PT-RS ports with the highest bit-width, e.g., 2-port PT-RS case, e.g., 4 bits. Then for 2-port PT-RS, the network entity can indicate one of the DMRS ports sharing the common PT-RS port.

[0062] In some embodiments, for 1-port PT-RS, a subset of bits (e.g., the first two bits) are used for PT-RS association with the DMRS ports, which indicates one of the DMRS ports is associated with the codeword, and the other two bits are reserved. In some other embodiments, for one PT-RS port, a subset of bits (e.g., the first three bits) are used for PT-RS association with the DMRS ports, which indicates one of the DMRS ports among all the DMRS ports, and the remaining one bit is reserved. In some other implementations, for 1-port PT-RS, a subset of bits (e.g., the first 2 bits) can be used for PT-RS association with the DMRS ports, which indicates one of the DMRS ports associated with the codeword, while another subset of bits (e.g., 1 bit) can be used to indicate the codeword index for the candidate DMRS port, and the other bits (e.g., 1 bit) are reserved.

[0063] In other embodiments, the bit-width of the DCI field used to indicate the association of PT-RS with DMRS port is determined based on whether it is one-port PT-RS case or two-port PT-RS case. For example, if it is one-port PT-RS case, the bit-width of the DCI field used to indicate the association of PT-RS with DMRS port is 2, and if it is two-port PT-RS case, the bit-width of the DCI field used to indicate the association of PT-RS with DMRS port is 4.

[0064] In other embodiments, the amount of DCI fields used to indicate the association of PT-RS with DMRS port in the scheduling DCI is determined based on whether it is one-port PT-RS case or two-port PT-RS case. For example, if it is one-port PT-RS case, the scheduling DCI carries one DCI field with 2 bit-width used to indicate the association of PT-RS with DMRS port; if it is two-port PT-RS case, the scheduling DCI carries two DCI fields, each of which indicates the association of PT-RS with DMRS port and has 2 bit-width.

[0065] Figure 17 A flowchart of a method 1700 performed by a wireless device (NE or UE) participating in multi-codeword transmission including PT-RS. The method 1700 includes transmitting 1704 control signaling for configuring multi-codeword transmission of at least one phase tracking reference signal, PT-RS, the control signaling providing parameters for identifying one or more ports to be used by a user equipment, UE, for the PT-RS. The method 1700 further includes transmitting 1710 data and at least one PT-RS via at least two codewords in accordance with the configured multi-codeword transmission and employing the one or more ports identified in accordance with the parameters.

[0066] If the wireless device performing the method 1700 is a UE, then transmitting the control signaling includes receiving the control signaling, and transmitting the data and the at least one PT-RS includes transmitting the data and the at least one PT-RS via the at least two codewords. If the wireless device is a network device, then transmitting the control signaling includes transmitting the control signaling, and transmitting the data and the at least one PT-RS includes receiving the data and the at least one PT-RS.

[0067] The method 1700 can further include determining a number of PT-RS ports to be used by the UE for the at least one PT-RS based on at least one of a maximum number of PT-RS ports included in the parameter, a precoder indicated by the uplink grant for the multi-codeword transmission, or an indication of data ports sharing a common PT-RS. The number of PT-RS ports to be used by the UE for the at least one PT-RS can be equal to the maximum number of PT-RS ports. If the maximum number of PT-RS ports is greater than one, the determining can include selecting the number of PT-RS ports based on at least one of the precoder or the indication of data ports sharing a common PT-RS. If the maximum number of PT-RS ports is greater than one, the parameter can include a subset indication of port combination candidates for one or more ports to be used by the UE to transmit the PT-RS.

[0068] The method 1700 can further include identifying one or more ports to be used by the UE for the PT-RS among ports used to transmit a demodulation reference signal, DMRS, in other symbols instead. Alternatively or additionally, the method 1700 can further include determining a time-domain density for transmission of the PT-RS based on a modulation and coding scheme, MCS, associated with a codeword among at least two codewords available for transmission of the at least one PT-RS, wherein the codeword is associated with a highest MCS if the highest MCS is a non-reserved MCS and the codeword among the at least two codewords is enabled. If the codeword is disabled, the UE can: (1) refrain from transmitting the at least one PT-RS, (2) the one or more ports to be used by the UE for the PT-RS are related to the disabled codeword and the time-domain density has a default value, or (3) the one or more ports to be used by the UE for the PT-RS are related to the disabled codeword and the determination of the time-domain density is based on an MCS associated with an enabled codeword among the at least two codewords. If the highest MCS is a reserved MCS, the determination of the time-domain density and the identification of the one or more ports to be used by the UE for the PT-RS can be based on another MCS value computed or configured.

[0069] The method 1700 can further include communicating a UE capability for uplink PT-RS included in the multi-codeword transmission, and then the control signaling is based on the UE capability for the uplink PT-RS included in the multi-codeword transmission.

[0070] Embodiments in this section are described with reference to the drawings. Like reference numerals in different drawings identify the same or similar elements. The detailed description set forth below in connection with the appended drawings is a description of exemplary embodiments and is not intended to represent the only embodiments contemplated. The embodiments are not limited to the described configurations but are applicable to other arrangements.

[0071] Reference throughout this section to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” or “in an embodiment” in various places throughout the specification are not necessarily all referring to the same embodiment. Further, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments.

[0072] The numerical adjectives “first,” “second,” and “third,” etc. mean quantities can refer to the same or different quantities. The terms “first,” “second,” and “third,” etc. are used herein merely to distinguish one element from another element, without necessarily implying a sequence or order to those elements. Unless specifically stated otherwise, a reference to a single (e.g., “a” or “an”) should be interpreted as including a plurality (i.e., “one or more”).

[0073] Although features and elements are described herein in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. Methods or flow charts can be implemented in a computer program, software, or firmware tangibly embodied in a computer-readable storage medium for execution by a specifically programmed computer or processor.

Claims

1. A method (1700) performed by a wireless device (410, 420), the method comprising: transmitting (1704, 304, 306, 404, 406, 504, 506) control signaling for configuring a multi-codeword data transmission with at least one phase tracking reference signal, PT-RS, the control signaling providing a parameter for identifying one or more ports to be used by a user equipment, UE, for the PT-RS; and transmitting (1710, 310, 410) data and the at least one PT-RS via at least two codewords in accordance with the configured multi-codeword transmission and employing the one or more ports identified in accordance with the parameter.

2. The method of claim 1, wherein, The data is transmitted on a physical uplink shared channel, PUSCH.

3. The method of any one of claims 1 or 2, further comprising: determining a number of PT-RS ports to be used by the UE for the at least one PT-RS based on at least one of a maximum number of PT-RS ports included in the parameter, a precoder indicated by an uplink grant for the multi-codeword transmission, or an indication of data ports sharing a common PT-RS.

4. The method of claim 3, wherein, The number of PT-RS ports to be used by the UE for the at least one PT-RS is equal to the maximum number of PT-RS ports.

5. The method of claim 3, wherein, If the maximum number of PT-RS ports is greater than one, the determining comprises selecting the number of PT-RS ports based on at least one of the precoder or the indication of the data ports sharing the common PT-RS.

6. The method of claim 3, wherein, If the maximum number of PT-RS ports is greater than one, the parameter comprises a subset indication of port combination candidates for the one or more ports to be used by the UE for transmitting the PT-RS.

7. The method of any one of claims 1 to 6, further comprising: identifying the one or more ports to be used by the UE for the PT-RS among ports that are alternatively used for transmitting a demodulation reference signal, DMRS, the PT-RS being transmitted with a precoder used for the DMRS.

8. The method of any one of claims 1 to 7, further comprising: determining a time domain density for transmitting the PT-RS based on a modulation and coding scheme, MCS, associated with a codeword among the at least two codewords that can be used for transmitting the at least one PT-RS, wherein the codeword is associated with a highest MCS if the highest MCS is a non-reserved MCS and the codeword among the at least two codewords is enabled.

9. The method of claim 8, wherein, If the codeword is disabled, the UE refrains from transmitting the at least one PT-RS.

10. The method of claim 8, wherein, If the codeword is disabled, the one or more ports to be used by the UE for the PT-RS are related to the disabled codeword and the time domain density has a default value.

11. The method of claim 8, wherein, If the code word is disabled, the one or more ports to be used by the UE for the PT-RS are related to the disabled code word, and the determination of the time domain density is based on the MCS associated with an enabled code word among the at least two code words.

12. The method of claim 8, wherein, If the highest MCS is a reserved MCS, the determination of the time domain density and the identification of the one or more ports to be used by the UE for the PT-RS are based on a previous MCS of the code word.

13. The method of claim 8, wherein, If the highest MCS is a reserved MCS, the determination of the time domain density and the identification of the one or more ports to be used by the UE for the PT-RS are based on another calculated or configured MCS value.

14. The method of any of claims 1-13, further comprising: transmitting a UE capability for uplink PT-RSs included in the multi-code word transmission, wherein the control signaling is based on the UE capability for uplink PT-RSs included in the multi-code word transmission.

15. The method of any one of claims 1 to 14, wherein, The wireless device is the UE, the transmitting the control signaling comprises receiving the control signaling, and the transmitting the data and the at least one PT-RS comprises transmitting the data and the at least one PT-RS via the at least two code words.

16. The method of any one of claims 1 to 14, wherein, The wireless device is a network device, the transmitting the control signaling comprises transmitting the control signaling, and the transmitting the data and the at least one PT-RS comprises receiving the data and the at least one PT-RS.

17. A wireless communication device (110, 120) comprising a transceiver (112, 113, 114, 122), a processor (115, 123), and a computer-readable storage medium (117, 124) storing executable instructions (119, 126, 127) for the processor to use the wireless transceiver to perform any of the methods recited in claims 1-16.

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