Communicating between network nodes via multiple cells

Abstract

A base station transmits a control indicator to a secondary cell (SCell), the control indicator indicating resources for communicating information units between the UE and the base station. The base station then communicates a first information unit in a primary cell (PCell) in accordance with the first control indicator.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to wireless communication, and more specifically to HARQ transmission of transport blocks on the same cell using PDCCH of multiple cells, and HARQ transmission of transport blocks on multiple cells using PDCCH of a cell. BACKGROUND

[0002] This background description is provided for the purpose of generally presenting the context of the disclosure. The work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that can not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the application.

[0003] In a telecommunications system, a base station can support carriers in multiple cells, which can cover the same or different (typically overlapping) geographical areas. In some cases, a base station can configure a user equipment (UE) to communicate with the base station in multiple cells simultaneously using carrier aggregation (CA). More specifically, for a UE, a base station can designate one cell as a primary cell (PCell) to operate and one or more other cells as secondary cells (SCells) to operate. When a base station operates as a master node (MN) that supports dual connectivity (DC) for a UE, and the MN configures CA for the UE, the MN similarly designates a PCell and one or more SCells. When a base station operates as a secondary node (SN) for DC, to support CA, the SN designates a primary secondary cell (PSCell) and one or more SCells.

[0004] An SCell in different operational states can be deactivated, dormant, or active. However, a PCell cannot be deactivated or dormant. A downlink carrier frequency of a cell, such as a PCell, a PSCell, or an SCell, can be within a licensed carrier band or an unlicensed carrier band, and an uplink carrier frequency of the cell can be within a licensed carrier band or an unlicensed carrier band. The downlink carrier frequency and the uplink carrier frequency can be the same carrier frequency or different carrier frequencies.

[0005] In some cases, a base station can utilize cross-carrier scheduling to provide transmission control indicators for another cell (SCell) via a channel (e.g., PDCCH) carrying control information in a PCell. However, if the base station is to configure the SCell for cross-carrier scheduling with the PCell, the UE can stop monitoring the PDCCH on the SCell when the SCell becomes dormant or deactivated, or when a related bandwidth part (BWP) on the SCell is deactivated or dormant. As a result, configuring an SCell for cross-carrier scheduling using techniques that configure a PCell for cross-carrier scheduling can result in the base station being unable to transmit data units or signaling to the UE on the PCell.

[0006] Furthermore, it is unclear whether a base station can schedule a physical downlink shared channel (PDSCH) on multiple cells using the same downlink control information (DCI), especially when the base station implements a hybrid automatic repeat request (HARQ) scheme or uses multiple-input multiple-output (MIMO) transmissions. SUMMARY

[0007] One example embodiment of these techniques is a method in a base station for communicating with a user equipment (UE) via a first cell and a second cell. The method includes sending, by the processing hardware, a first control indicator to the UE in the first cell, the first control indicator indicating resources for communicating at least a first information unit between the UE and the base station; communicating, by the processing hardware, the first information unit according to the first control indicator; and performing, by the processing hardware, at least one of (i) sending a second control indicator related to the first information unit to the UE in the second cell, or (ii) communicating, by the processing hardware, a second information unit in a different cell from the first information unit according to the first control indicator.

[0008] Another example embodiment of these techniques is a base station including processing hardware and configured to implement the above-described method.

[0009] Another example embodiment of these techniques is a method in a UE for communicating via a base station via a first cell and a second cell. The method includes receiving, by the processing hardware, a first control indicator from the base station in the first cell for communicating at least a first information unit between the UE and the base station; communicating, by the processing hardware, the first information unit according to the first control indicator; and performing, by the processing hardware, at least one of (i) receiving a second control indicator related to the first information unit from the base station in the second cell, or (ii) communicating, by the processing hardware, a second information unit in a different cell from the first information unit according to the first control indicator.

[0010] Another example embodiment of these techniques is a UE including processing hardware and configured to implement the above-described method.

[0011] Yet another example embodiment of these techniques is a method in a first network device for communicating via a second network device via a first cell and a second cell, comprising: sending, by processing hardware, a first control indicator between the first network device and the second network device in the first cell for communicating at least a first information unit between the first network device and the second network device; communicating, by the processing hardware, the first information unit according to the first control indicator; and performing, by the processing hardware, at least one of: (i) communicating a second control indicator related to the first information unit between the first network device and the second network device in the second cell, or (ii) communicating, by the processing hardware, a second information unit in a different cell than the first information unit according to the first control indicator. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1A is a block diagram of an example system in which a radio access network (RAN) and a user equipment can implement techniques of the present disclosure to schedule communications across multiple cells;

[0013] Figure 1B is a block diagram of an example protocol stack according to which a UE of Figure 1A may operate in a system of

[0014] Figure 2 is a block diagram of an example protocol stack according to which a UE of Figure 1A may operate in a system of

[0015] Figure 3A is a message diagram of an example scenario in which a base station configures a secondary cell as a scheduling cell and selects a different cell for a HARQ retransmission after a HARQ transmission on the original cell fails;

[0016] Figure 3B is a message diagram of an example scenario similar to Figure 3A but in which the UE communicates with the base station using carrier aggregation (CA) before the base station configures the secondary cell as a scheduling cell;

[0017] Figure 4A is a message diagram of an example scenario similar to Figure 3A but in which the base station operates as a secondary node (SN) and configures the scheduling cell directly over a radio interface;

[0018] Figure 4B is a message diagram of an example scenario similar to Figure 4A but in which the UE communicates with the SN using CA before the base station configures the secondary cell as a scheduling cell;

[0019] Figure 4C is a message diagram of an example scenario similar to Figure 4A , but wherein the SN provides configuration via the MN;

[0020] Figure 4D is a message diagram of an example scenario similar to Figure 4B , but wherein the SN provides configuration via the MN;

[0021] Figure 5A is a message diagram of an example scenario wherein a base station schedules HARQ transmissions of a same data unit in multiple cells via a primary cell;

[0022] Figure 5B is a message diagram of an example scenario wherein a base station schedules HARQ transmissions of a same data unit in multiple cells via a secondary cell;

[0023] Figure 5C is a message diagram of an example scenario similar to Figure 5A , but wherein the UE communicates with the SN using CA prior to the base station configuring multi-cell communication;

[0024] Figure 5D is a message diagram of an example scenario similar to Figure 5B , but wherein the UE communicates with the SN using CA prior to the base station configuring multi-cell communication;

[0025] Figure 6 is a flow diagram of an example method of transmitting or receiving a same data unit or signaling via multiple cells according to a HARQ scheme that can be implemented in a UE of Figure 1A ;

[0026] Figure 7 is a flow diagram of an example method of transmitting or receiving a same data unit via multiple cells according to a HARQ scheme that can be implemented in a base station of Figure 1A ;

[0027] Figure 8 is a flow diagram of an example method of periodically transmitting or receiving data units or signaling via multiple cells according to a HARQ scheme that can be implemented in a base station of Figure 1A ;

[0028] Figure 9 is a flow diagram of an example method of transmitting or receiving a same signaling via multiple cells according to a HARQ scheme that can be implemented in a base station of Figure 1A ;

[0029] Figure 10 is a flow diagram of an example method of transmitting or receiving a same signaling via multiple cells according to a HARQ scheme that can be implemented in a base station of Figure 1Aa flowchart of an example method for transmitting DCI in one cell with an indication that the UE should switch BWP in another cell implemented in a base station of

[0030] Figure 11 implemented in a UE of Figure 1A a flowchart of an example method for determining whether a base station should transmit DCI in the same cell as a corresponding HARQ transmission depending on whether the transmission includes data or signaling implemented in a base station of

[0031] Figure 12 implemented in a UE of Figure 1A a flowchart of an example method for processing HARQ transmissions received on multiple cells implemented in a UE of

[0032] Figure 13 implemented in a base station of Figure 1A a flowchart of an example method for processing HARQ transmissions received on multiple cells implemented in a base station of

[0033] Figure 14 implemented in a base station of Figure 1A a flowchart of an example method for selecting a cell for transmitting DCI based on whether cross-carrier scheduling is enabled for a UE implemented in a base station of

[0034] Figure 15 implemented in a base station of Figure 1A a flowchart of an example method for selecting a DCI format based on whether a base station can transmit multiple PDUs on the same cell using MIMO or multiple PDUs on different cells using the same DCI implemented in a base station of

[0035] Figure 16 implemented in a UE or base station of Figure 1A a flowchart of an example method for communicating with another network device via multiple cells implemented in a UE or base station of DETAILED DESCRIPTION

[0036] Generally, a base station of the present disclosure can dynamically switch cells that schedule transmission of data units or signaling (collectively, “information units”) in uplink or downlink directions, or schedule transmission and retransmission of the same information units via different cells using the same control information (such as DCI).

[0037] In some scenarios, the base station schedules a downlink transmission of an information unit in the PCell via the SCell. When the base station determines that the downlink transmission failed, e.g., by receiving a negative acknowledgement of the information unit according to a HARQ scheme, the base station schedules a downlink retransmission of the information in the PCell, but via the PCell in this case. In this way, even if the UE no longer monitors the SCell, the base station can ensure that the UE receives the relevant scheduling. In another example scenario, the base station uses the PCell to transmit a DCI for a downlink transmission of an information unit via the PCell, but after the transmission (retransmission) fails, the base station transmits a new DCI for the transmission of the information unit via the PCell in the SCell.

[0038] Further, in some scenarios, the base station transmits a DCI that schedules a transmission of one information unit in one cell (e.g., the PCell) and a transmission of another information unit in another cell (e.g., the SCell). Similar to the discussion above, if one of these transmissions fails, the base station can transmit a new DCI in the other cell. A UE of the present disclosure can implement corresponding techniques for receiving and / or transmitting information units.

[0039] Figure 1A An example wireless communication system 100 is depicted in which a communication device can implement the scheduling techniques of the present disclosure. The wireless communication system 100 includes a UE 102, a base station 104, a base station 106A, a base station 106B, and a core network (CN) 110. The UE 102 is initially connected to the base station 104. In some scenarios, the base station 104 can perform an SN addition procedure to configure the UE 102 to operate in DC with the base station 104 and the base station 106A. The base stations 104 and 106A operate as the MN and SN, respectively, for the UE 102.

[0040] In various configurations of the wireless communication system 100, the base station 104 can be implemented as a master eNB (MeNB) or a master gNB (MgNB), and the base station 106A or 106B can be implemented as a secondary gNB (SgNB). The UE 102 can communicate with the base station 104 and the base station 106A or 106B (106A / B) via the same RAT, such as EUTRA or NR, or different RATs. When the base station 104 is a MeNB and the base station 106A is a SgNB, the UE 102 can be in EUTRA-NR DC (EN-DC) with the MeNB and the SgNB. In some cases, the MeNB or SeNB is implemented as an ng-eNB instead of an eNB. When the base station 104 is a master ng-eNB (Mng-eNB) and the base station 106A is a SgNB, the UE 102 can be in next generation (NG) EUTRA-NR DC (NGEN-DC) with the Mng-eNB and the SgNB.

[0041] When the base station 104 is a MgNB and the base station 106A / B is a SgNB, the UE 102 can be in NR-NR DC (NR-DC) with the MgNB and the SgNB. When the base station 104 is a MgNB and the base station 106A / B is a secondary ng-eNB (Sng-eNB), the UE 102 can be in NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNB.

[0042] The base stations 104, 106A, and 106B can be connected to the same core network (CN) 110, which can be an evolved packet core (EPC) 111 or a fifth generation core (5GC) 160. The base station 104 can be implemented as an eNB that supports an S1 interface for communication with the EPC 111, as an ng-eNB that supports an NG interface for communication with the 5GC 160, or as a base station that supports an NR radio interface as well as the NG interface for communication with the 5GC 160. The base station 106A can be implemented as an EN-DC gNB (en-gNB) that has an S1 interface to the EPC 111, as an en-gNB that is not connected to the EPC 111, as a gNB that supports an NR radio interface as well as the NG interface to the 5GC 160, or as an ng-eNB that supports an EUTRA radio interface as well as the NG interface to the 5GC 160. To exchange messages directly during the scenarios discussed below, the base stations 104, 106A, and 106B can support an X2 or Xn interface.

[0043] The EPC 111 can include, among other components, a serving gateway (S-GW) 112 and a mobility management entity (MME) 114. The S-GW 112 is generally configured to transfer user plane packets related to audio calls, video calls, Internet traffic, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The 5GC 160 includes a user plane function (UPF) 162 and an access and mobility management (AMF) 164 and / or a session management function (SMF) 166. Generally, the UPF 162 is configured to transfer user plane packets related to audio calls, video calls, Internet traffic, etc., the AMF 164 is configured to manage authentication, registration, paging, and other related functions, and the SMF 166 is configured to manage PDU sessions.

[0044] As Figure 1AAs shown, base station 104 supports cell 124, base station 106A supports cell 126A, and base station 106B supports cell 126B. Cells 124 and 126A can partially overlap, as can cells 124 and 126B, such that UE 102 can communicate in DC with base station 104 (operating as a MN) and base station 106A (operating as a SN), and upon completion of an SN change, with base station 104 (operating as a MN) and SN 106B. Base station 106A can also support additional cells 125A and 127A. More specifically, when UE 102 is in DC with base station 104 and base station 106A, base station 104 operates as a MeNB, Mng-eNB, or MgNB, and base station 106A operates as a SgNB or Sng-eNB.

[0045] In general, wireless communication network 100 can include any suitable number of base stations that support NR cells and / or EUTRA cells. EPC 111 or 5GC 160 can be connected to any suitable number of base stations that support NR cells and / or EUTRA cells. Although the examples below specifically refer to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the techniques of this disclosure can also be applied to other suitable radio access and / or core network technologies, such as sixth generation (6G) radio access and / or a 6G core network or 5G NR-6G DC.

[0046] With continued reference to Figure 1A Base station 104 includes processing hardware 130, which can include one or more general-purpose processors (e.g., central processing units (CPUs)) and computer-readable memory storing machine-readable instructions executable on the general-purpose processor and / or special-purpose processing units. Processing hardware 130 in the example implementation of FIG. 1 includes a carrier aggregation (CA) controller 132 configured to manage or control CA techniques of this disclosure. For example, CA controller 132 can be configured to manage or control RRC messages and RRC configurations related to CA operations, cross-carrier scheduling, activation / deactivation of SCells, activation / deactivation of bandwidth parts (BWPs), and / or transmission of DCI to support necessary CA operations when UE 102 is connected to base station 104 in single connectivity (SC) or when base station 104 operates as a MN relative to a SN.

[0047] The base station 106A includes processing hardware 140, which can include one or more general-purpose processors (e.g., CPUs) and computer-readable memory storing machine-readable instructions executable on the general-purpose processors and / or special purpose processing units. The processing hardware 140 in the example implementation of FIG. 1 includes a CA controller 142 configured to manage or control CA techniques of the present disclosure. For example, the CA controller 142 can be configured to manage or control RRC messages and RRC configurations related to CA operations, cross-carrier scheduling, activation / deactivation of SCells, activation / deactivation of BWPs, and / or generation and transmission of DCIs to support necessary CA operations when the base station 106A operates as an SN. The base station 106B can include processing hardware similar to the processing hardware 140 of the base station 106A.

[0048] Although Figure 1A While the CA controllers 132 and 142 are shown operating in the MN and SN, respectively, the base stations can generally operate as MNs, SNs, candidate MNs, or candidate SNs in different scenarios. Thus, the MN 104, the SN 106A, and the SN 106B can implement similar sets of functionality and support both MNs and SNs.

[0049] The UE 102 includes processing hardware 150, which can include one or more general-purpose processors (e.g., CPUs) and computer-readable memory storing machine-readable instructions executable on the general-purpose processors and / or special purpose processing units. The processing hardware 150 in the example implementation of FIG. 1 includes a CA controller 152 configured to manage or control RRC messages and RRC configurations related to CA operations, cross-carrier scheduling, activation / deactivation of SCells, activation / deactivation of BWPs, and / or reception and processing of DCIs to support necessary CA operations.

[0050] In operation, the UE 102 can use radio bearers (e.g., data radio bearers (DRBs) or signaling radio bearers (SRBs)) that terminate at the MN 104 or the SN 106A at different times. When communicating on a radio bearer in the uplink (from the UE 102 to the base stations) and / or downlink (from the base stations to the UE 102) direction, the UE 102 can apply one or more security keys.

[0051] Figure 1BAn example distributed implementation of a base station, such as base station 104, 106A, or 106B is depicted. The base station in this implementation can include a centralized unit (CU) 172 and one or more distributed units (DUs) 174. The CU 172 is equipped with processing hardware that can include one or more general-purpose processors, such as CPUs and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors and / or special purpose processing units. In one example, the CU 172 is equipped with processing hardware 130. In another example, the CU 172 is equipped with processing hardware 140. The base station 106B can have the same or similar hardware as the base station 106A. The DU 174 is also equipped with processing hardware that can include one or more general-purpose processors, such as CPUs and non-transitory computer-readable memory storing machine-readable instructions executable on the one or more general-purpose processors and / or special purpose processing units. In some examples, the processing hardware in the example implementation includes a medium access control (MAC) controller configured to manage or control one or more MAC operations or processes (e.g., random access processes), and a radio link control (RLC) controller configured to manage or control one or more RLC operations or processes when the base station 104, 106A, 106B operates as a MN, SN. The processing hardware can also include a physical layer controller configured to manage or control one or more physical layer operations or processes.

[0052] Next, Figure 2 A radio protocol stack according to which the UE 102 can communicate with an eNB / ng-eNB or gNB is shown in simplified form. Each base station 104, 106A, or 106B can be an eNB / ng-eNB or gNB.

[0053] A physical layer (PHY) 202A of EUTRA provides transport channels to a EUTRA medium access control (MAC) sublayer 204A, which in turn provides logical channels to a EUTRA radio link control (RLC) sublayer 206A, and the EUTRA RLC sublayer in turn provides RLC channels to a EUTRA packet data convergence protocol (PDCP) sublayer 208 and in some cases to an NR PDCP sublayer 210. Similarly, a PHY 202B of NR provides transport channels to a NR MAC sublayer 204B, which in turn provides logical channels to a NR RLC sublayer 206B, which in turn provides RLC channels to a NR PDCP sublayer 210. In some implementations, the UE 102 supports both EUTRA and NR stacks to support handover between EUTRA and NR base stations and / or DC over EUTRA and NR interfaces. Further, as Figure 2As shown in FIG. 2, UE 102 can support layering of NR PDCP 210 over EUTRA RLC 206A.

[0054] Generally, the PDCP sublayer of a radio protocol stack provides services such as user plane data transfer, ciphering, integrity protection, etc. For example, the PDCP layer defined for the EUTRA radio interface (see 3GPP specification TS 36.323) and for NR (see 3GPP specification TS 38.323) provides for ordering of protocol data units (PDUs) in the uplink direction (from a user device, also referred to as user equipment (UE), to a base station) as well as in the downlink direction (from a base station to a UE). In addition, the PDCP sublayer provides SRBs and DRBs to the RRC sublayer. Generally, UEs and base stations can use SRBs to exchange RRC messages as well as non-access stratum (NAS) messages, and can use DRBs to transfer data on the user plane.

[0055] EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 receive packets, which can be referred to as service data units (SDUs) (e.g., from an Internet Protocol (IP) layer, layered directly or indirectly over the PDCP layer 208 or 210), and output packets, which can be referred to as protocol data units (PDUs) (e.g., to RLC layer 206A or 206B). Except where the difference between SDUs and PDUs is relevant, for simplicity the present disclosure refers to both SDUs and PDUs as “packets”

[0056] For example, on the control plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 provide SRBs to exchange radio resource control (RRC) messages. On the user plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 provide DRBs to support data exchange.

[0057] When UE 102 operates in EUTRA / NR DC (EN-DC), base station 104 operates as a MeNB and base station 106A or 106B operates as a SgNB, the network can provide UE 102 with a bearer that is MN-terminated using EUTRA PDCP 208 or a bearer that is MN-terminated using NR PDCP 210. In various scenarios, the network can also provide UE 102 with a bearer that is SN-terminated using only NR PDCP 210. The MN-terminated bearer can be a MCG bearer or a split bearer. The SN-terminated bearer can be a SCG bearer or a split bearer. The MN-terminated bearer can be an SRB (e.g., SRB1 or SRB2) or a DRB. The SN-terminated bearer can be an SRB (e.g., SRB) or a DRB.

[0058] More specifically, the UE 102 can use several types of SRBs and DRBs. When operating in DC, a cell associated with a base station operating as an MN defines a master cell group (MCG), and a cell associated with a base station operating as an SN defines a secondary cell group (SCG). So-called SRB1 resources carry RRC messages that in some cases include NAS messages on a dedicated control channel (DCCH), and SRB2 resources support RRC messages that include logged measurement information or NAS messages also on the DCCH but with lower priority than the SRB1 resources. More generally, the SRB1 and SRB2 resources allow the UE and the MN to exchange RRC messages related to the MN and embed RRC messages related to the SN, and can also be referred to as MCG SRBs. The SRB3 resources allow the UE and the SN to exchange RRC messages related to the SN, and can be referred to as an SCG SRB. Split SRBs allow the UE to exchange RRC messages directly with the MN via lower layer resources of the MN and the SN. In addition, DRBs that use only lower layer resources of the MN can be referred to as MCG DRBs, DRBs that use only lower layer resources of the SN can be referred to as SCG DRBs, and DRBs that use lower layer resources of both the MCG and the SCG can be referred to as split DRBs.

[0059] Next, reference is made to Figures 3A-4D Several example scenarios are discussed in which a base station initiates a CA operation procedure using cross-carrier scheduling configuration. Figure 3A And Figure 3B Scenarios are depicted in which a base station enables CA and cross-carrier scheduling for a UE for PUSCH or PDSCH of a PCell, and Figures 4A-4D Scenarios are depicted in which a base station enables CA and cross-carrier scheduling for a UE for PUSCH or PDSCH of a PCell, and

[0060] Although Figures 3A-4D Examples of Figure 9 Examples of

[0061] Reference is first made to Figure 3A Example scenario 300A of FIG. 3, the base station 106A operates at least cells 125A and 126A. Initially, the UE 102 communicates 302A data with the base station 106A via the PCell 125A. These communications can include uplink (UL) transmissions from the UE 102 to the base station 106A, and / or downlink (DL) transmissions from the base station 106A to the UE 102.

[0062] In some scenarios, the UE 102 communicates 302A data with the base station 106A in SC. In other scenarios, the UE 102 communicates 302A data with the base station 106A operating as a MN and another base station (e.g., the base station 106B) operating as a SN in DC (to avoid clutter, the base station 106B is not shown in FIG. 3). For convenience, the base station 106A can be referred to as a MN in both SC and DC scenarios. Figure 3A

[0063] The base station 106A determines 304A at some time to configure the cell 126A as a scheduling SCell for scheduling PDSCH or PUSCH of the PCell 125A. For example, the base station 106A can make this determination based on one or more measurement results of the cell 126A received from the UE 102 or another suitable event. In response to this determination, the base station 106A sends 308A an RRC reconfiguration message including a SCell configuration and a cross-carrier scheduling configuration of the cell 126A to the UE 102. In response to the RRC reconfiguration message, the UE 102 sends 312A an RRC reconfiguration complete message to the base station 106A. In some implementations, the base station 106A can include the cross-carrier scheduling configuration in the SCell configuration. For example, the SCell configuration can be a SCellConfig information element (IE) and the cross-carrier scheduling configuration can be a CrossCarrierSchedulingConfig IE.

[0064] After receiving 308A the RRC reconfiguration message, the UE 102 in CA mode communicates 314A with the base station 106A via the PCell 125A and the SCell 126A. In accordance with the cross-carrier scheduling configuration, the base station 106A can send 316A a first DCI command (DCI1) to the UE 102 via the SCell 126A. The command can include a plurality of configuration parameters for a first hybrid automatic repeat request (HARQ) transmission of a first DL MAC PDU on the PCell 125A. The base station 106A then sends 318A the first HARQ transmission of the first DL MAC PDU on the PCell 125A in accordance with the plurality of configuration parameters. In some implementations, the base station 106A sends the DCI1 on the SCell 126A because PDCCH resources on the PCell 125A are not available for the UE 102 at the time the base station 106A sends the DCI1.

[0065] ​The plurality of configuration parameters can include a carrier indicator, a HARQ process number, a frequency domain resource assignment, a time domain resource assignment, a redundancy version (RV), a new data indicator (NDI), a modulation and coding scheme (MCS), a transmit power control (TPC) command for a physical uplink control channel (PUCCH), and / or a PUCCH resource indicator. The plurality of configuration parameters can also include additional parameters such as an identifier of a DCI format, a bandwidth part (BWP) indicator, a virtual resource block (VRB) to physical resource block (PRB) mapping, a PRB bundling size indicator, a rate matting indicator, a channel state information reference signal (CSI-RS) trigger, a downlink assignment index, a physical downlink shared channel (PDSCH) to HARQ feedback timing indicator, a number of antenna ports and layers, a transmission configuration indication, a sounding reference signal (SRS) request, and / or a demodulation reference signal (DRMS) sequence initialization.

[0066] The UE 102 receives and processes the first HARQ transmission of the first DL MAC PDU on the PCell 125A according to the plurality of configuration parameters in the DCI1. For example, the base station 106A can configure a value of the carrier indicator for the PCell 125A in the cross-carrier scheduling configuration. The base station 106A can set the carrier indicator in the DCI1 to the value of the carrier indicator for the PCell 125A. Accordingly, the UE 102 can determine to receive the first HARQ transmission of the first DL MAC PDU on the PCell 125A according to the value of the carrier indicator. The base station 106A can set the NDI in the DCI1 for the first HARQ transmission of the first DL MAC PDU to a value that indicates that the first HARQ transmission of the first DL MAC PDU is a new transmission. Accordingly, the UE 102 can determine that the first HARQ transmission of the first DL MAC PDU is a new transmission according to the value of the NDI. For example, the UE 102 can store a value of a previously received NDI associated with a HARQ process, which is identified by the HARQ process number included in the DCI1. If the value of the NDI is different (e.g., toggled) compared to the stored value of the previous NDI, the UE 102 determines that the first HARQ transmission of the first DL MAC PDU is a new HARQ transmission. Otherwise, the UE 102 determines that the first HARQ transmission of the first DL MAC PDU is a HARQ retransmission. The UE 102 can receive the first HARQ transmission on the PCell 125A within time and / or frequency resources specified by the time domain resource assignment and / or the frequency domain resource assignment included in the DCI1 command.

[0067] In some scenarios and implementations, the UE 102 successfully obtains the first DL MAC PDU from the first HARQ transmission of the first DL MAC PDU according to the DCI1. In this case, the UE 102 sends a HARQ acknowledgement (ACK) to the base station 106A on the PCell 125A to indicate successful reception of the first DL MAC PDU. For example, the UE 102 can decode the first HARQ transmission according to the DCI1 to obtain a transport block that includes the first DL MAC PDU, and the transport block passes a cyclic redundancy check (CRC) check, such that the UE 102 successfully obtains the first DL MAC PDU from the transport block.

[0068] However, in another scenario, after the UE 102 fails to obtain the first DL MAC PDU from the first HARQ transmission of the first DL MAC PDU according to the DCI1, the UE 102 sends a HARQ negative acknowledgement (NACK) to the base station 106A on the PCell 125A. For example, the UE 102 can decode the first HARQ transmission according to the DCI1 to obtain a transport block, and detect a CRC check failure of the transport block, such that the UE 102 is unable to obtain the first DL MAC PDU from the transport block. In response to the HARQ NACK, the base station 106A can send 320A a second DCI command (DCI2) on the PCell 125A for a second HARQ transmission of the first DL MAC PDU. The base station 106A can then send 322A the second HARQ transmission of the first DL MAC PDU to the UE 102 on the PCell 125A.

[0069] The UE 102 can combine the first HARQ transmission and the second HARQ transmission, and decode the combination of the first HARQ transmission and the second HARQ transmission to obtain the first DL MAC PDU. In some implementations, the base station 106A always sends a HARQ retransmission (e.g., the second HARQ transmission) of a MAC PDU on the same cell as a HARQ new transmission (e.g., the first HARQ transmission) of the MAC PDU. That is, the base station 106A refrains from performing a HARQ retransmission of a MAC PDU on a different cell than the cell on which the HARQ transmission of the MAC PDU occurred.

[0070] In one scenario, base station 106A transmits 320A DCI2 on PCell 125A because PDCCH resources on SCell 126A are not available to UE 102 at the time base station 106A transmits DCI2. In another scenario, base station 106A transmits DCI2 on PCell 125A because SCell 126A is deactivated for UE 102. In yet another scenario, base station 106A transmits DCI2 on PCell 125A because SCell 126A is in a dormant state for UE 102. In yet another scenario, base station 106A transmits DCI2 on PCell 125A because the downlink BWP on SCell 126A on which UE 102 receives PDCCH is in a dormant state for UE 102. In at least some implementations, UE 102 can not monitor PDCCH for deactivated SCell 126A, dormant SCell 126A, or a dormant downlink BWP in SCell 126A.

[0071] DCI2 can include a number of configuration parameters similar to DCI1. In one implementation, DCI2 can not include a carrier indicator. In this implementation, UE 102 can determine to receive a second HARQ transmission of the first DL MAC PDU on PCell 125A according to a default configuration. The default configuration can indicate that if UE 102 receives a DCI (e.g., DCI2) on a cell that does not include a carrier indicator and configures a HARQ transmission (e.g., the second HARQ transmission 322A), then UE 102 receives the HARQ transmission in the cell according to the DCI. In another implementation, DCI2 includes a carrier indicator. In this implementation, base station 106A can set the value of the carrier indicator to the value included in the cross-carrier scheduling configuration. Thus, UE 102 can determine from the value of the carrier indicator that it should receive the second HARQ transmission of the first DL MAC PDU on PCell 125A. The carrier indicator in DCI2 and the carrier indicator in DCI1 can have the same value or different values.

[0072] In some implementations, for the first and second HARQ transmissions of the first DL MAC PDU, DCI2 and DCI1 include the same HARQ process number (i.e., value) and the same NDI value, such that the UE 102 can determine from the HARQ process number and NDI (value) in DCI2 that the second HARQ transmission of the first DL MAC PDU is a retransmission of the first DL MAC PDU. The base station 106A can set the RV in DCI2 for the second HARQ transmission to the same or a different value than the RV in DCI1 for the first HARQ transmission. If the RV in DCI2 and the RV in DCI1 are different, the UE 102 can perform a HARQ operation (e.g., HARQ combining with incremental redundancy) to combine the first and second HARQ transmissions of the first DL MAC PDU to obtain the first DL MAC PDU. If the RV in DCI2 and the RV in DCI1 are the same, the UE 102 can perform a HARQ operation (e.g., HARQ chase combining) to combine the first and second HARQ transmissions of the first DL MAC PDU to obtain the first DL MAC PDU. If the UE 102 successfully obtains the first DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that includes the first DL MAC PDU and passes a CRC check, the UE 102 sends a HARQ ACK to the base station 106A on the PCell 125A to indicate successful reception of the first DL MAC PDU. If the UE 102 fails to obtain the first DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that fails a CRC check, the UE 102 sends a HARQ NACK to the base station 106A on the PCell 125A to indicate failure to receive the first DL MAC PDU. In response to the HARQ NACK, the base station 106A can send additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to receive a HARQ retransmission of the first DL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as DCI2. The additional DCI can include the same NDI (value) for the second HARQ transmission as DCI2 to indicate the HARQ retransmission. The additional DCI can include the same RV for the second HARQ transmission as DCI2. Alternatively, the additional DCI can include a RV for the HARQ retransmission that is different from the RV for the second HARQ transmission in DCI2. Similarly, the UE 102 can perform a HARQ operation to combine the HARQ retransmission with the first and second HARQ transmissions to obtain the first DL MAC PDU in a similar manner as described above depending on the RV in the additional DCI.

[0073] In some scenarios and implementations, the base station 106A can further configure the UE 102 to receive a first additional HARQ transmission of an additional DL MAC PDU on the PCell 125A in the DCI1. In such cases, the base station 106A can include additional configuration parameters for the first additional HARQ transmission in the DCI1. The additional configuration parameters can include specific configuration parameters for receiving and / or processing the first additional HARQ transmission. The specific configuration parameters are similar to the configuration parameters in the plurality of configuration parameters described above. The UE 102 can receive and / or process the first additional HARQ transmission on the PCell 125A according to the additional configuration parameters and some of the plurality of configuration parameters. For example, the additional configuration parameters can include MCS, NDI, and / or RV that are separate from the MCS, NDI, and / or RV of the first HARQ transmission of the first DL MAC PDU, such that the base station 106A can set different MCS, NDI, and / or RV for the first additional HARQ transmission than for the first HARQ transmission. The base station 106A can transmit the first additional HARQ transmission on the PCell 125A in the same time and frequency resources as the first HARQ transmission of the first DL MAC PDU. The UE 102 receives the first additional HARQ transmission on the PCell 125A in the same time and frequency resources as the first HARQ transmission of the first DL MAC PDU. In some implementations, the additional configuration parameters can include time domain resource assignment and / or frequency domain resource assignment that are separate from the time domain resource assignment and / or frequency domain resource assignment of the first HARQ transmission of the first DL MAC PDU. In the separate time domain resource assignment and / or frequency domain resource assignment, the base station 106A can configure different time and / or frequency resources than for the first HARQ transmission of the first DL MAC PDU. In such cases, the base station 106A can transmit the first additional HARQ transmission on the PCell 125A in the different time and / or frequency resources. The UE 102 receives the first additional HARQ transmission on the PCell 125A in the time and / or frequency resources configured by the separate time domain resource assignment and / or frequency domain resource assignment.

[0074] In other implementations, the additional configuration parameters can include a BWP indicator that is separate from the BWP indicator of the first HARQ transmission of the first DL MAC PDU. In the separate BWP indicator, the base station 106A can configure a different BWP than for the first HARQ transmission of the first DL MAC PDU. In such cases, the base station 106A can transmit the first additional HARQ transmission on the PCell 125A in the different BWP. The UE 102 receives the first additional HARQ transmission on the PCell 125A in the different BWP configured by the separate BWP indicator.

[0075] The UE 102 can receive the first additional HARQ transmission on the PCell 125A in accordance with the additional configuration parameters and some of the optional plurality of configuration parameters, if some of the configuration parameters are shared / common for the first HARQ transmission and the first additional HARQ transmission. For example, the carrier indication is shared between the first HARQ transmission and the first additional HARQ transmission. The UE 102 can determine to receive the first additional HARQ transmission of the additional DL MAC PDU on the PCell 125A in accordance with the value of the carrier indicator in the DCI1. In another example, the additional configuration parameters include an additional NDI. In one implementation, the base station 106A can set the additional NDI in the DCI1 for the first additional HARQ transmission of the first DL MAC PDU to a value indicating that the first additional HARQ transmission of the additional DL MAC PDU is a new transmission. Accordingly, the UE 102 can determine that the first additional HARQ transmission of the additional DL MAC PDU is a new transmission in accordance with the value of the additional NDI. For example, the UE 102 can store the value of the previously received NDI associated with the HARQ process, which is identified by the HARQ process number included in the DCI1. If the value of the additional NDI is different (e.g., flipped) compared to the stored value of the previous NDI, the UE 102 determines that the first additional HARQ transmission of the additional DL MAC PDU is a new HARQ transmission. Otherwise, the UE 102 determines that the first additional HARQ transmission of the additional DL MAC PDU is a HARQ retransmission. In another implementation, the base station 106A can set the additional NDI in the DCI1 for the first additional HARQ transmission of the first DL MAC PDU to a value indicating that the first additional HARQ transmission of the additional DL MAC PDU is a HARQ retransmission. Accordingly, the UE 102 can determine that the first additional HARQ transmission of the additional DL MAC PDU is a retransmission in accordance with the value of the additional NDI. For example, the UE 102 can store the value of the previously received NDI associated with the HARQ process, which is identified by the HARQ process number included in the DCI1. If the value of the additional NDI is the same (e.g., not flipped) compared to the stored value of the previous NDI, the UE 102 determines that the first additional HARQ transmission of the additional DL MAC PDU is a HARQ retransmission.

[0076] In some scenarios and implementations, the UE 102 successfully obtains the additional DL MAC PDU from the first additional HARQ transmission of the additional DL MAC PDU according to the DCI1. In this case, the UE 102 sends a HARQ ACK to the base station 106A on the PCell 125A to indicate the successful reception of the additional DL MAC PDU. For example, the UE 102 can decode the first additional HARQ transmission according to the DCI1 to obtain a transport block including the additional DL MAC PDU, and the transport block passes the CRC check, such that the UE 102 successfully obtains the additional DL MAC PDU from the transport block. If the base station 106A receives the HARQ ACK for the first DL MAC PDU and the HARQ ACK for the additional DL MAC PDU, in one implementation, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to indicate that the UE 102 is to receive an additional HARQ transmission of another DL MAC PDU on the PCell 125A. The UE 102 can receive the DL MAC PDU according to the additional DCI in a similar manner as the UE 102 receives the first DL MAC PDU according to the DCI1. The additional DCI can include the same HARQ process number as the DCI1 and other configuration parameters similar to the DCI1. The base station 106A can set the other configuration parameters to the same values as the DCI1 or different values from the DCI1.

[0077] In other scenarios and implementations, if the UE 102 fails to obtain the additional DL MAC PDU from the first additional HARQ transmission of the additional DL MAC PDU according to the DCI1, the UE 102 can transmit a HARQ NACK to the base station 106A on the PCell 125A. For example, the UE 102 can decode the first additional HARQ transmission according to the DCI1 to obtain a transport block, and fail a CRC check or parity check on the transport block such that the UE 102 is unable to obtain the additional DL MAC PDU from the transport block. In response to the HARQ NACK, the base station 106A can configure a second additional HARQ transmission of the additional DL MAC PDU in the DCI2. The base station 106A can then transmit the second additional HARQ transmission of the additional DL MAC PDU to the UE 102 on the PCell 125A. The UE 102 can receive the second additional HARQ transmission on the PCell 125A according to the common configuration parameters and the additional configuration parameters in the DCI2. The common configuration parameters are common for the UE 102 to receive the second HARQ transmission and the second additional HARQ transmission. The additional configuration parameters are specific for the UE 102 to receive and / or process the second additional HARQ transmission. The UE 102 can combine the first additional HARQ transmission and the second additional HARQ transmission, and decode the combination of the first additional HARQ transmission and the second additional HARQ transmission to obtain the additional DL MAC PDU.

[0078] For the second additional HARQ transmission, DCI2 can include additional configuration parameters similar to DCI1. For example, base station 106A can transmit the second additional HARQ transmission on PCell 125A in the same or different time and frequency resources as the second HARQ transmission of the first DL MAC PDU. In some implementations, for the first and second additional HARQ transmissions of the additional DL MAC PDU, DCI2 and DCI1 include the same HARQ process number (i.e., value) and the same additional NDI value, such that UE 102 can determine from the HARQ process number and the additional NDI (value) in DCI2 that the second additional HARQ transmission of the additional DL MAC PDU is a retransmission of the additional DL MAC PDU. Base station 106A can set the additional RV in DCI2 for the second additional HARQ transmission to the same or a different value than the additional RV in DCI1 for the first additional HARQ transmission. If the additional RV in DCI2 and the additional RV in DCI1 are different, UE 102 can perform HARQ operations with incremental redundancy to combine the first and second additional HARQ transmissions of the additional DL MAC PDU to obtain the first DL MAC PDU. If the RV in DCI2 and the RV in DCI1 are the same, UE 102 can perform HARQ operations with Chase combining to combine the first and second additional HARQ transmissions of the additional DL MAC PDU to obtain the additional DL MAC PDU.

[0079] If the UE 102 successfully obtains the additional DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that includes the additional DL MAC PDU and passes the CRC check, the UE 102 sends a HARQ ACK to the base station 106A on the PCell 125A to indicate the successful reception of the additional DL MAC PDU. If the UE 102 fails to obtain the additional DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that fails the CRC check, the UE 102 sends a HARQ NACK to the base station 106A on the PCell 125A to indicate the failure of the reception of the additional DL MAC PDU. In response to the HARQ NACK, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to receive a HARQ retransmission of the additional DL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as DCI2. The additional DCI can include the same NDI (value) as DCI2 for the second additional HARQ transmission to indicate the HARQ retransmission. The additional DCI can include the same RV as DCI2 for the second additional HARQ transmission. Alternatively, the additional DCI can include a different RV for the HARQ retransmission than the RV in DCI2 for the second additional HARQ transmission.

[0080] In some implementations, the base station 106A uses the same DCI format or different DCI formats for the DCIs (e.g., DCI1, DCI2, additional DCI, etc.). For example, the base station 106A can use an existing DCI format (e.g., DCI format 1_0, DCI format 1_1) or a new DCI format (e.g., DCI format 1_2, DCI format 1_3, etc.) for DCI1. In another example, the base station 106A can use an existing DCI format (e.g., DCI format 1_0, DCI format 1_1) or a new DCI format (e.g., DCI format 1_2, DCI format 1_3, etc.) for DCI2.

[0081] After receiving the RRC reconfiguration message, the UE 102 in CA communicates 314A with the base station 106A via the PCell 125A and the SCell 126A. According to the cross-carrier scheduling configuration, the base station 106A can transmit 324A a third DCI command (DCI3) to the UE 102 via the PCell 125A, the DCI3 including a plurality of configuration parameters for a first HARQ transmission of a second DL MAC PDU on the PCell 125A. The base station 106A then transmits 326A the first HARQ transmission of the second DL MAC PDU on the PCell 125A according to the plurality of configuration parameters. In some embodiments, the base station 106A transmits the DCI3 on the PCell 125A because PDCCH resources on the SCell 126A are not available to the UE 102 at the time instance when the base station 106A transmits the DCI3.

[0082] The DCI3 command can include the plurality of configuration parameters similar to the DCI1 command discussed above.

[0083] The UE 102 receives and processes the first HARQ transmission of the second DL MAC PDU on the PCell 125A according to the plurality of configuration parameters in the DCI3. In one embodiment, the DCI3 can not include a carrier indicator. In this embodiment, the UE 102 can determine to receive the first HARQ transmission of the second DL MAC PDU on the PCell 125A according to a default configuration. The default configuration can be that if the UE 102 receives a DCI on a cell that does not include a carrier indicator and configures a DL transmission, the UE 102 receives a HARQ transmission in the cell according to the DCI. In another embodiment, the DCI3 includes a carrier indicator. In this embodiment, the base station 106A can set a value of the carrier indicator to a value included in the cross-carrier scheduling configuration. Accordingly, the UE 102 can determine to receive the first HARQ transmission of the second DL MAC PDU on the PCell 125A according to the value of the carrier indicator.

[0084] In some implementations, the base station 106A can set the NDI in the DCI 3 for the first HARQ transmission of the second DL MAC PDU to a value that indicates that the first HARQ transmission of the second DL MAC PDU is a new transmission. Accordingly, the UE 102 can determine that the first HARQ transmission of the second DL MAC PDU is a new transmission according to the value of the new data indicator. For example, the UE 102 can store a value of a previously received NDI associated with the HARQ process, which is identified by the HARQ process number included in the DCI 3. If the value of the NDI is different (e.g., toggled) compared to the stored value of the previous NDI, the UE 102 determines that the first HARQ transmission of the second DL MAC PDU is a new transmission. In some implementations, the UE 102 can receive the first HARQ transmission on the PCell 125A in the time and / or frequency resources specified by the time domain resource assignment and / or the frequency domain resource assignment in the DCI 3 command.

[0085] In some scenarios and implementations, the UE 102 successfully obtains the second DL MAC PDU from the first HARQ transmission of the second DL MAC PDU according to the DCI 3. In this case, the UE 102 transmits a HARQ ACK to the base station 106A on the PCell 125A to indicate the successful reception of the second DL MAC PDU. For example, the UE 102 can decode the first additional HARQ transmission according to the DCI 3 to obtain a transport block that includes the second DL MAC PDU, and the transport block passes the CRC check, such that the UE 102 successfully obtains the second DL MAC PDU from the transport block.

[0086] In other scenarios and implementations, if the UE 102 fails to obtain the second DL MAC PDU from the first HARQ transmission of the second DL MAC PDU according to the DCI3, the UE 102 can transmit a HARQ NACK to the base station 106A on the PCell 125A. For example, the UE 102 can decode the first HARQ transmission according to the DCI3 to obtain a transport block, and the CRC check of the transport block fails such that the UE 102 is unable to obtain the second DL MAC PDU from the transport block. In response to the HARQ NACK, the base station 106A can transmit 328A a fourth DCI command (DCI4) on the SCell 126A for transmitting a second HARQ transmission of the second DL MAC PDU. The base station 106A can then transmit 330A the second HARQ transmission of the second DL MAC PDU to the UE 102 on the PCell 125A. The UE 102 can combine the first HARQ transmission and the second HARQ transmission, and decode the combination of the first HARQ transmission and the second HARQ transmission to obtain the second DL MAC PDU. In some implementations, the base station 106A always transmits a HARQ retransmission (e.g., the second HARQ transmission) of a MAC PDU on the same cell as a HARQ new transmission (e.g., the first HARQ transmission) of the MAC PDU. That is, the base station 106A refrains from transmitting a HARQ retransmission of a MAC PDU on a different cell than a HARQ new transmission of the MAC PDU.

[0087] In one scenario and implementation, the base station 106A transmits the DCI4 on the SCell 126A because PDCCH resources on the PCell 125A are not available for the UE 102 at the time instance when the base station 106A transmits the DCI4.

[0088] The DCI4 can include a plurality of configuration parameters similar to the DCI3. The DCI4 includes a carrier indicator, and the base station 106A can set a value of the carrier indicator to the value included in the cross-carrier scheduling configuration. Accordingly, the UE 102 can determine to receive the second HARQ transmission of the second DL MAC PDU on the PCell 125A according to the value of the carrier indicator. If the DCI3 includes the carrier indicator, the carrier indicator in the DCI4 and the carrier indicator in the DCI 3 can have the same value or different values.

[0089] In some implementations, for the first and second HARQ transmissions of the second DL MAC PDU, DCI4 and DCI3 include the same HARQ process number (i.e., value) and the same NDI value, such that the UE 102 can determine from the HARQ process number and NDI (value) in DCI4 that the second HARQ transmission of the second DL MAC PDU is a retransmission of the second DL MAC PDU. The base station 106A can set the RV in DCI4 for the second HARQ transmission to the same or a different value as the RV in DCI3 for the first HARQ transmission. If the RV in DCI4 and the RV in DCI3 are different, the UE 102 can perform a HARQ operation (e.g., HARQ Chase Combining) to combine the first and second HARQ transmissions of the second DL MAC PDU to obtain the second DL MAC PDU. If the RV in DCI4 and the RV in DCI3 are the same, the UE 102 can perform a HARQ operation (e.g., HARQ Incremental Redundancy Combining) to combine the first and second HARQ transmissions of the second DL MAC PDU to obtain the second DL MAC PDU. If the UE 102 successfully obtains the second DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that includes the second DL MAC PDU and passes a CRC check, the UE 102 sends a HARQ ACK to the base station 106A on the PCell 125A to indicate successful reception of the second DL MAC PDU. If the UE 102 fails to obtain the second DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that fails a CRC check, the UE 102 sends a HARQ NACK to the base station 106A on the PCell 125A to indicate failure to receive the second DL MAC PDU. In response to the HARQ NACK, the base station 106A can send additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to receive a HARQ retransmission of the second DL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as DCI4. The additional DCI can include the same NDI (value) for the second HARQ transmission as DCI4 to indicate the HARQ retransmission. The additional DCI can include the same RV for the second HARQ transmission as DCI4. Alternatively, the additional DCI can include a RV for the HARQ retransmission that is different from the RV for the second HARQ transmission in DCI4. Similarly, the UE 102 can perform a HARQ operation to combine the HARQ retransmission with the first and second HARQ transmissions to obtain the second DL MAC PDU in a similar manner as described above according to the RV in the additional DCI.

[0090] In some scenarios and implementations, the base station 106A can further configure the UE 102 to receive a first additional HARQ transmission of an additional DL MAC PDU on the PCell 125A in the DCI3. In such a case, the base station 106A can include additional configuration parameters for the first additional HARQ transmission in the DCI3. The additional configuration parameters can include specific configuration parameters for receiving and / or processing the first additional HARQ transmission. The specific configuration parameters are similar to the configuration parameters in the plurality of configuration parameters described above. The UE 102 can receive and / or process the first additional HARQ transmission on the PCell 125A according to the additional configuration parameters and some of the plurality of configuration parameters. For example, the additional configuration parameters can include MCS, NDI, and / or RV that are separate from the MCS, NDI, and / or RV of the first HARQ transmission of the second DL MAC PDU, such that the base station 106A can set different MCS, NDI, and / or RV for the first additional HARQ transmission than for the first HARQ transmission. The base station 106A can transmit the first additional HARQ transmission on the PCell 125A in the same time and frequency resources as the first HARQ transmission of the second DL MAC PDU. The UE 102 receives the first additional HARQ transmission on the PCell 125A in the same time and frequency resources as the first HARQ transmission of the second DL MAC PDU. In some implementations, the additional configuration parameters can include time domain resource assignment and / or frequency domain resource assignment that are separate from the time domain resource assignment and / or frequency domain resource assignment of the first HARQ transmission of the second DL MAC PDU. In the separate time domain resource assignment and / or frequency domain resource assignment, the base station 106A can configure different time and / or frequency resources than for the first HARQ transmission of the second DL MAC PDU. In such a case, the base station 106A can transmit the first additional HARQ transmission on the PCell 125A in the different time and / or frequency resources. The UE 102 receives the first additional HARQ transmission on the PCell 125A in the time and / or frequency resources configured by the separate time domain resource assignment and / or frequency domain resource assignment.

[0091] In other implementations, the additional configuration parameters can include a BWP indicator that is separate from the BWP indicator of the first HARQ transmission of the second DL MAC PDU. In the separate BWP indicator, the base station 106A can configure a different BWP than for the first HARQ transmission of the second DL MAC PDU. In such a case, the base station 106A can transmit the first additional HARQ transmission on the PCell 125A in the different BWP. The UE 102 receives the first additional HARQ transmission on the PCell 125A in the different BWP configured by the separate BWP indicator.

[0092] The UE 102 can receive the first additional HARQ transmission on the PCell 125A in accordance with the additional configuration parameters and some of the optional plurality of configuration parameters, if some of the configuration parameters are shared / common for the first HARQ transmission and the first additional HARQ transmission. For example, if the DCI 3 includes a carrier indicator, the carrier indication is shared between the first HARQ transmission and the first additional HARQ transmission. The UE 102 can determine to receive the first additional HARQ transmission of the additional DL MAC PDU on the PCell 125A in accordance with the value of the carrier indicator in the DCI 3. In another example, the additional configuration parameters include an additional NDI. In one implementation, the base station 106A can set the additional NDI in the DCI 3 for the first additional HARQ transmission of the second DL MAC PDU to a value that indicates that the first additional HARQ transmission of the additional DL MAC PDU is a new transmission. Accordingly, the UE 102 can determine that the first additional HARQ transmission of the additional DL MAC PDU is a new transmission in accordance with the value of the additional NDI. For example, the UE 102 can store a value of a previously received NDI associated with the HARQ process, which is identified by the HARQ process number included in the DCI 3. If the value of the additional NDI is different (e.g., toggled) compared to the stored value of the previous NDI, the UE 102 determines that the first additional HARQ transmission of the additional DL MAC PDU is a new transmission. In another implementation, the base station 106A can set the additional NDI in the DCI 3 for the first additional HARQ transmission of the second DL MAC PDU to a value that indicates that the first additional HARQ transmission of the additional DL MAC PDU is a HARQ retransmission. Accordingly, the UE 102 can determine that the first additional HARQ transmission of the additional DL MAC PDU is a retransmission in accordance with the value of the additional NDI. For example, the UE 102 can store a value of a previously received NDI associated with the HARQ process, which is identified by the HARQ process number included in the DCI 3. If the value of the additional NDI is the same (e.g., not toggled) compared to the stored value of the previous NDI, the UE 102 determines that the first additional HARQ transmission of the additional DL MAC PDU is a HARQ retransmission.

[0093] In some scenarios and implementations, the UE 102 successfully obtains the additional DL MAC PDU from the first additional HARQ transmission of the additional DL MAC PDU according to the DCI3. In this case, the UE 102 sends a HARQ ACK to the base station 106A on the PCell 125A to indicate the successful reception of the additional DL MAC PDU. For example, the UE 102 can decode the first additional HARQ transmission according to the DCI3 to obtain a transport block including the additional DL MAC PDU, and the transport block passes the CRC check, such that the UE 102 successfully obtains the additional DL MAC PDU from the transport block. If the base station 106A receives the HARQ ACK for the first DL MAC PDU and the HARQ ACK for the additional DL MAC PDU from the UE 102, in one implementation, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to indicate that the UE 102 is to receive an additional HARQ transmission of another DL MAC PDU on the PCell 125A. The UE 102 can receive the DL MAC PDU according to the additional DCI in a similar manner as the UE 102 receives the first DL MAC PDU according to the DCI3. The additional DCI can include the same HARQ process number as the DCI3 and other configuration parameters similar to the DCI3. The base station 106A can set the other configuration parameters to the same values as the DCI3 or different values from the DCI3.

[0094] In other scenarios and implementations, if the UE 102 fails to obtain the additional DL MAC PDU from the first additional HARQ transmission of the additional DL MAC PDU according to the DCI3, the UE 102 can transmit a HARQ NACK to the base station 106A on the PCell 125A. For example, the UE 102 can decode the first additional HARQ transmission according to the DCI3 to obtain a transport block, and fail a CRC check or parity check on the transport block such that the UE 102 is unable to obtain the additional DL MAC PDU from the transport block. In response to the HARQ NACK, the base station 106A can configure a second additional HARQ transmission of the additional DL MAC PDU in the DCI4. The base station 106A can then transmit the second additional HARQ transmission of the additional DL MAC PDU to the UE 102 on the PCell 125A. The UE 102 can receive the second additional HARQ transmission on the PCell 125A according to the common configuration parameters and the additional configuration parameters in the DCI4. The common configuration parameters are common for the UE 102 to receive the second HARQ transmission and the second additional HARQ transmission. The additional configuration parameters are specific for the UE 102 to receive and / or process the second additional HARQ transmission. The UE 102 can combine the first additional HARQ transmission and the second additional HARQ transmission, and decode the combination of the first additional HARQ transmission and the second additional HARQ transmission to obtain the additional DL MAC PDU.

[0095] For the second additional HARQ transmission, DCI 4 can include additional configuration parameters similar to DCI 3. For example, base station 106A can transmit the second additional HARQ transmission on PCell 125A in the same or different time and frequency resources as the second HARQ transmission of the second DL MAC PDU. In some implementations, for the first and second additional HARQ transmissions of the additional DL MAC PDU, DCI 4 and DCI 3 include the same HARQ process number (i.e., value) and the same additional NDI value, such that UE 102 can determine from the HARQ process number and the additional NDI (value) in DCI 4 that the second additional HARQ transmission of the additional DL MAC PDU is a retransmission of the additional DL MAC PDU. Base station 106A can set the additional RV in DCI 4 for the second additional HARQ transmission to the same or a different value than the additional RV in DCI 3 for the first additional HARQ transmission. If the additional RV in DCI 4 and the additional RV in DCI 3 are different, UE 102 can perform HARQ operations with incremental redundancy to combine the first and second additional HARQ transmissions of the additional DL MAC PDU to obtain the second DL MAC PDU. If the RV in DCI 4 and the RV in DCI 3 are the same, UE 102 can perform HARQ operations with Chase combining to combine the first and second additional HARQ transmissions of the additional DL MAC PDU to obtain the additional DL MAC PDU.

[0096] If the UE 102 successfully obtains the additional DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that includes the additional DL MAC PDU and passes the CRC check, the UE 102 sends a HARQ ACK to the base station 106A on the PCell 125A to indicate successful reception of the additional DL MAC PDU. If the UE 102 fails to obtain the additional DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that fails the CRC check, the UE 102 sends a HARQ NACK to the base station 106A on the PCell 125A to indicate failure of reception of the additional DL MAC PDU. In response to the HARQ NACK, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to receive a HARQ retransmission of the additional DL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as the DCI 4. The additional DCI can include the same NDI (value) as the DCI 4 for the second additional HARQ transmission to indicate that the HARQ retransmission is a retransmission. The additional DCI can include the same RV as the DCI 4 for the second additional HARQ transmission. Alternatively, the additional DCI can include a different RV for the HARQ retransmission than the RV in the DCI 4 for the second additional HARQ transmission.

[0097] In some implementations, the base station 106A uses the same DCI format or different DCI formats for the DCIs (e.g., the DCI 3, the DCI 4, the additional DCI, etc.). For example, the base station 106A can use an existing DCI format (e.g., DCI format 1 0, DCI format 1 1) or a new DCI format (e.g., DCI format 1 2, DCI format 1 3, etc.) for the DCI 3. In another example, the base station 106A can use an existing DCI format (e.g., DCI format 1 0, DCI format 1 1) or a new DCI format (e.g., DCI format 1 2, DCI format 1 3, etc.) for the DCI 4.

[0098] After receiving the RRC reconfiguration message, the UE 102 in CA communicates 314A with the base station 106A via the PCell 125A and the SCell 126A. According to the cross-carrier scheduling configuration, the base station 106A can transmit 332A a fifth DCI command (DCI5) to the UE 102 via the SCell 126A, the DCI5 including a plurality of configuration parameters for a first HARQ transmission of a first UL MAC PDU on the PCell 125A. The base station 106A then generates and transmits 334A the first HARQ transmission of the first UL MAC PDU on the PCell 125A according to the plurality of configuration parameters. In some embodiments, the base station 106A transmits the DCI5 on the SCell 125A because PDCCH resources on the PCell 125A are not available for the UE 102 at the time instance when the base station 106A transmits the DCI5.

[0099] The plurality of configuration parameters can include a carrier indicator, a HARQ process number, a frequency domain resource assignment, a time domain resource assignment, a frequency hopping flag, an RV, an NDI, an MCS, a TPC command for a physical uplink shared channel (PUSCH). The plurality of configuration parameters can also include other parameters such as an identifier of a DCI format, a BWP indicator, a first DL assignment index, a second DL assignment index, an SRS resource indicator, precoding information and number of layers, antenna ports, an SRS request, a CSI request, and / or a DMRS sequence initialization.

[0100] The UE 102 generates and transmits the first HARQ transmission of the first UL MAC PDU on the PCell 125A according to the plurality of configuration parameters in the DCI5. For example, the base station 106A can configure a value of a carrier indicator for the PCell 125A in the cross-carrier scheduling configuration. The base station 106A can set the carrier indicator in the DCI5 to the value of the carrier indicator for the PCell 125A. Accordingly, the UE 102 can determine to transmit the first HARQ transmission of the first UL MAC PDU on the PCell 125A according to the value of the carrier indicator.

[0101] In some implementations, the base station 106A can set the NDI in the DCI5 for the first HARQ transmission of the first UL MAC PDU to a value that indicates that the first HARQ transmission of the first UL MAC PDU is a new transmission. Accordingly, the UE 102 can determine that the first HARQ transmission of the first UL MAC PDU is a new transmission according to the value of the new data indicator. For example, the UE 102 can store a value of a previously received NDI associated with the HARQ process, which is identified by the HARQ process number included in the DCI5. If the value of the NDI is different (e.g., toggled) compared to the stored value of the previous NDI, the UE 102 determines that the first HARQ transmission of the first UL MAC PDU is a new HARQ transmission. In some implementations, the UE 102 can transmit the first HARQ transmission on the PCell 125A in the time and / or frequency resources specified by the time domain resource assignment and / or the frequency domain resource assignment in the DCI5 command.

[0102] In some scenarios and implementations, the base station 106A successfully obtains the first UL MAC PDU from the first HARQ transmission of the first UL MAC PDU according to the DCI5. For example, the base station 106A can decode the first HARQ transmission according to the DCI5 to obtain a transport block that includes the first UL MAC PDU, and the transport block passes a CRC check, such that the base station 106A successfully obtains the first UL MAC PDU from the transport block.

[0103] In other scenarios and implementations, if the base station 106A fails to obtain the first UL MAC PDU from the first HARQ transmission of the first UL MAC PDU according to the DCI5, the base station 106A can transmit 336A a sixth DCI command (DCI6) to the UE 102 on the PCell 125A to command the UE 102 to transmit a second HARQ transmission of the first UL MAC PDU. For example, the base station 106A can decode the first HARQ transmission according to the DCI5 to obtain a transport block, and the transport block fails a CRC check, such that the base station 106A is unable to obtain the first UL MAC PDU from the transport block. In response to the DCI6, the UE 102 can then transmit 338A the second HARQ transmission of the first UL MAC PDU to the base station 106A on the PCell 125A. The base station 106A can combine the first HARQ transmission and the second HARQ transmission, and decode the combination of the first HARQ transmission and the second HARQ transmission to obtain the first UL MAC PDU.

[0104] In one scenario, the base station 106A transmits the DCI6 on the PCell 125A because the PDCCH resources on the SCell 126A are not available for the UE 102 at the time the base station 106A transmits the DCI6. In another scenario, the base station 106A transmits the DCI6 on the PCell 125A because the SCell 126A is deactivated for the UE 102. In yet another scenario, the base station 106A transmits the DCI6 on the PCell 125A because the SCell 126A is in a dormant state for the UE 102. In yet another scenario, the base station 106A transmits the DCI6 on the PCell 125A because the downlink BWP on the SCell 126A where the UE 102 receives the PDCCH is in a dormant state for the UE 102. The UE 102 can not monitor the PDCCH on the deactivated SCell 126A, the dormant SCell 126A, or the dormant downlink BWP in the SCell 126A.

[0105] The DCI6 can include a plurality of configuration parameters similar to the DCI5. In one implementation, the DCI6 can not include the carrier indicator. In this implementation, the UE 102 can determine to transmit the second HARQ transmission of the first UL MAC PDU on the PCell 125A according to a default configuration. The default configuration can be that if the UE 102 receives a DCI on a cell that does not include a carrier indicator and configures a UL transmission, the UE 102 transmits a HARQ transmission in the cell according to the DCI. In another implementation, the DCI6 includes the carrier indicator. In this implementation, the base station 106A can set the value of the carrier indicator to the value included in the cross-carrier scheduling configuration. Thus, the UE 102 can determine to transmit the second HARQ transmission of the first UL MAC PDU on the PCell 125A according to the value of the carrier indicator. The carrier indicator in the DCI6 and the carrier indicator in the DCI5 can have the same value or different values.

[0106] In some implementations, for the first and second HARQ transmissions of the first UL MAC PDU, DCI6 and DCI5 include the same HARQ process number (i.e., value) and the same NDI value, such that the UE 102 can determine from the HARQ process number and NDI (value) in DCI6 to generate the second HARQ transmission of the first UL MAC PDU as a retransmission of the first UL MAC PDU. The base station 106A can set the RV in DCI6 for the second HARQ transmission to the same or a different value as the RV in DCI5 for the first HARQ transmission. If the RV in DCI6 and the RV in DCI5 are different, the base station 106A can perform a HARQ operation (e.g., HARQ combining with incremental redundancy) to combine the first and second HARQ transmissions of the first DL MAC PDU to obtain the first DL MAC PDU. If the RV in DCI6 and the RV in DCI5 are the same, the base station 106A can perform a HARQ operation (e.g., HARQ chase combining) to combine the first and second HARQ transmissions of the first DL MAC PDU to obtain the first DL MAC PDU. In one scenario, the base station 106A successfully obtains the first DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that includes the first DL MAC PDU and passes a CRC check. After obtaining the first UL MAC PDU, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to send an additional HARQ transmission (e.g., a new HARQ transmission) of another UL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as DCI5 and other configuration parameters similar to DCI5. The base station 106A can set the other configuration parameters to the same or different values as DCI5. In another scenario, the base station 106A fails to obtain the first UL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that fails a CRC check. In response to the failure, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to send another HARQ transmission of the first UL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as DCI6. The additional DCI can include the same NDI (value) for the second HARQ transmission as DCI6 to indicate that the other HARQ transmission is a retransmission. The additional DCI can include the same RV for the second HARQ transmission as DCI6. Alternatively, the additional DCI can include a different RV for the other HARQ transmission than the RV for the second HARQ transmission in DCI6.Similarly, the base station 106A can perform HARQ operations in a similar manner as described above to combine the HARQ retransmission with the first and second HARQ transmissions according to the RV in the additional DCI to obtain a first UL MAC PDU.

[0107] In some scenarios and implementations, the base station 106A can also configure the UE 102 to transmit a first additional HARQ transmission of an additional MAC PDU on the PCell 125A in the DCI5. In this case, the base station 106A can include additional configuration parameters for the first additional HARQ transmission in the DCI5. The additional configuration parameters can include specific configuration parameters to generate and / or transmit the first additional HARQ transmission. The specific configuration parameters are similar to the configuration parameters in the plurality of configuration parameters described above. The UE 102 can generate and / or transmit the first additional HARQ transmission on the PCell 125A according to the additional configuration parameters and some of the plurality of configuration parameters. For example, the additional configuration parameters can include MCS, NDI, and / or RV for the first additional HARQ transmission that are separate from the MCS, NDI, and / or RV for the first HARQ transmission of the first UL MAC PDU, such that the base station 106A can set different MCS, NDI, and / or RV for the first additional HARQ transmission than for the first HARQ transmission. The UE 102 can transmit the first additional HARQ transmission on the PCell 125A in the same time and frequency resources as the first HARQ transmission of the first UL MAC PDU. The base station 106A receives the first additional HARQ transmission on the PCell 125A in the same time and frequency resources as the first HARQ transmission of the first UL MAC PDU. In some implementations, the additional configuration parameters can include time domain resource assignment and / or frequency domain resource assignment for the first additional HARQ transmission that are separate from the time domain resource assignment and / or frequency domain resource assignment for the first HARQ transmission of the first UL MAC PDU. In the separate time domain resource assignment and / or frequency domain resource assignment, the base station 106A can configure different time and / or frequency resources for the first additional HARQ transmission than for the first HARQ transmission of the first DL MAC PDU. In this case, the UE 102 can transmit the first additional HARQ transmission on the PCell 125A in the different time and / or frequency resources configured by the separate time domain resource assignment and / or frequency domain resource assignment. The base station 106A receives the first additional HARQ transmission on the PCell 125A in the time and / or frequency resources configured by the separate time domain resource assignment and / or frequency domain resource assignment.

[0108] In other implementations, the additional configuration parameters can include a BWP indicator separate from the BWP indicator of the first HARQ transmission of the first UL MAC PDU. In the separate BWP indicator, the base station 106A can configure a different BWP than the BWP of the first HARQ transmission of the first DL MAC PDU. In this case, the UE 102 can transmit the first additional HARQ transmission on the PCell 125A in the different BWP configured by the separate BWP indicator. The base station 106A receives the first additional HARQ transmission on the PCell 125A in the different BWP configured by the separate BWP indicator.

[0109] The base station 106A can receive the first additional HARQ transmission on the PCell 125A in accordance with the additional configuration parameters and some of the optional plurality of configuration parameters, if some of the configuration parameters are shared / common for the first HARQ transmission and the first additional HARQ transmission. For example, the carrier indication is shared between the first HARQ transmission and the first additional HARQ transmission. The UE 102 can determine to receive the first additional HARQ transmission of the additional UL MAC PDU on the PCell 125A in accordance with the value of the carrier indicator in the DCI5. In another example, the additional configuration parameters include an additional NDI. In one implementation, the base station 106A can set the additional NDI in the DCI5 for the first additional HARQ transmission of the first UL MAC PDU to a value that indicates that the first additional HARQ transmission of the additional UL MAC PDU is a new transmission. Accordingly, the UE 102 can determine to generate the first additional HARQ transmission of the additional UL MAC PDU as a new transmission in accordance with the value of the additional NDI. For example, the UE 102 can store a value of a previously received NDI associated with a HARQ process, which is identified by a HARQ process number included in the DCI5. If the value of the additional NDI is different (e.g., toggled) compared to the stored value of the previous NDI, the UE 102 determines to generate the first additional HARQ transmission of the additional UL MAC PDU as a new transmission. In another implementation, the base station 106A can set the additional NDI in the DCI5 for the first additional HARQ transmission of the first UL MAC PDU to a value that indicates that the first additional HARQ transmission of the additional UL MAC PDU is a retransmission. Accordingly, the UE 102 can determine that the first additional HARQ transmission of the additional UL MAC PDU is a retransmission in accordance with the value of the additional NDI. For example, the UE 102 can store a value of a previously received NDI associated with a HARQ process, which is identified by a HARQ process number included in the DCI5. If the value of the additional NDI is the same (e.g., not toggled) compared to the stored value of the previous NDI, the UE 102 determines to generate the first additional HARQ transmission of the additional UL MAC PDU as a retransmission.

[0110] In some scenarios and implementations, the base station 106A successfully obtains the additional UL MAC PDU from the first additional HARQ transmission of the additional UL MAC PDU according to the DCI 5. For example, the base station 106A can decode the first additional HARQ transmission according to the DCI 5 to obtain a transport block including the additional UL MAC PDU, and the transport block passes a CRC check, such that the base station 106A successfully obtains the additional UL MAC PDU from the transport block. After obtaining the first UL MAC PDU and the additional UL MAC PDU, in one implementation, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to send an additional HARQ transmission of another UL MAC PDU on the PCell 125A. The UE 102 sends the additional HARQ transmission in a similar manner as the UE 102 sends the first HARQ transmission according to the DCI 5. The additional DCI can include the same HARQ process number as the DCI 5 and other configuration parameters similar to the DCI 5. The base station 106A can set the other configuration parameters to the same values as the DCI 5 or different values from the DCI 5.

[0111] In other scenarios and implementations, the base station 106A fails to obtain the additional UL MAC PDU from the first additional HARQ transmission of the additional UL MAC PDU according to the DCI 5. For example, the base station 106A can decode the first additional HARQ transmission according to the DCI 5 to obtain a transport block, and the transport block fails a CRC check or parity check, such that the base station 106A is unable to obtain the additional UL MAC PDU from the transport block. In one implementation, in response to the failure, the base station 106A can configure the UE to send a second additional HARQ transmission of the additional UL MAC PDU in a DCI 6. The UE 102 can then send the second additional HARQ transmission of the additional UL MAC PDU to the base station 106A on the PCell 125A according to the DCI 6. The base station 106A can receive the second additional HARQ transmission on the PCell 125A according to common configuration parameters and additional configuration parameters in the DCI 6. The common configuration parameters are common to the UE 102 to receive the second HARQ transmission and the second additional HARQ transmission. The additional configuration parameters are specific to the UE 102 to generate and send the second additional HARQ transmission. The base station 106A can combine and decode the first additional HARQ transmission and the second additional HARQ transmission to obtain the additional UL MAC PDU.

[0112] For the second additional HARQ transmission, DCI6 can include similar additional configuration parameters as DCI5. For example, UE 102 can transmit the second additional HARQ transmission of the additional UL MAC PDU on PCell 125A in the same or different time and frequency resources as the second HARQ transmission of the first UL MAC PDU. In some embodiments, DCI6 and DCI5 include the same HARQ process number (i.e., value) and the same additional NDI value for the first and second additional HARQ transmissions of the additional UL MAC PDU, such that UE 102 can determine from the HARQ process number and the additional NDI (value) in DCI6 that the second additional HARQ transmission of the additional UL MAC PDU is generated as a retransmission of the additional UL MAC PDU. Base station 106A can set the additional RV in DCI6 for the second additional HARQ transmission to the same or a different value as the additional RV in DCI5 for the first additional HARQ transmission. If the additional RV in DCI6 and the additional RV in DCI5 are different, base station 106A can perform HARQ operations with incremental redundancy to combine the first and second additional HARQ transmissions of the additional UL MAC PDU to obtain the first UL MAC PDU. If the RV in DCI6 and the RV in DCI5 are the same, base station 106A can perform HARQ operations with Chase combining to combine the first and second additional HARQ transmissions of the additional UL MAC PDU to obtain the additional UL MAC PDU. If base station 106A successfully obtains the additional UL MAC PDU from the HARQ operations, i.e., decodes the combination to obtain a transport block that includes the additional UL MAC PDU and passes the CRC check, in one embodiment, base station 106A can transmit an additional DCI to UE 102 on PCell 125A or SCell 126A to instruct UE 102 to transmit an additional HARQ transmission of another UL MAC PDU on PCell 125A. The additional DCI can include the same HARQ process number as DCI5 and similar other configuration parameters as DCI5. Base station 106A can set the other configuration parameters to the same or different values as DCI5.

[0113] If the base station 106A fails to obtain the additional UL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block with a CRC check failure, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to send a HARQ retransmission of the first UL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as the DCI6. The additional DCI can include the same NDI (value) for the second HARQ transmission as the DCI6 to indicate the HARQ retransmission. The additional DCI can include the same RV for the second additional HARQ transmission as the DCI6. Alternatively, the additional DCI can include a RV for the HARQ retransmission that is different from the RV for the second additional HARQ transmission in the DCI6. Similarly, the base station 106A can perform the HARQ operation to combine the HARQ retransmission with the first and second additional HARQ transmissions according to the RV in the additional DCI in a similar manner as described above.

[0114] In some implementations, the base station 106A uses the same DCI format or different DCI formats for the DCIs (e.g., DCI5, DCI6, additional DCI, etc.). For example, the base station 106A can use an existing DCI format (e.g., DCI format 0_0, DCI format 0_1) or a new DCI format (e.g., DCI format 0_2, DCI format 0_3, etc.) for the DCI5. In another example, the base station 106A can use an existing DCI format (e.g., DCI format 0_0, DCI format 0_1) or a new DCI format (e.g., DCI format 0_2, DCI format 0_3, etc.) for the DCI6.

[0115] After receiving the RRC reconfiguration message, the UE 102 in the CA communicates 314A with the base station 106A via the PCell 125A and the SCell 126A. In accordance with the cross-carrier scheduling configuration, the base station 106A can send 340A a seventh DCI command (DCI7) to the UE 102 via the PCell 125A, the DCI7 including a plurality of configuration parameters for a first HARQ transmission of a second UL MAC PDU on the PCell 125A. The base station 106A then generates and sends 342A the first HARQ transmission of the second UL MAC PDU on the PCell 125A in accordance with the plurality of configuration parameters. In some implementations, the base station 106A sends the DCI7 on the PCell 125A because PDCCH resources on the SCell 126A are not available to the UE 102 at the time the base station 106A sends the DCI7.

[0116] The plurality of configuration parameters can include a carrier indicator, a HARQ process number, a frequency domain resource assignment, a time domain resource assignment, a frequency hopping flag, an RV, an NDI, an MCS, a TPC command for a physical uplink shared channel (PUSCH). The plurality of configuration parameters can also include other parameters such as an identifier of a DCI format, a BWP indicator, a first DL assignment index, a second DL assignment index, an SRS resource indicator, precoding information and number of layers, antenna ports, an SRS request, a CSI request, and / or a DMRS sequence initialization.

[0117] The UE 102 generates and transmits the first HARQ transmission of the second UL MAC PDU on the PCell 125A according to the plurality of configuration parameters in the DCI 7. In one implementation, the DCI 7 can not include a carrier indicator. In this implementation, the UE 102 can determine to receive the first HARQ transmission of the first DL MAC PDU on the PCell 125A according to a default configuration. The default configuration can be that if the UE 102 receives a DCI on a cell that does not include a carrier indicator and configures a DL transmission, the UE 102 receives a HARQ transmission in the cell according to the DCI. In another implementation, the DCI 7 includes a carrier indicator. In this implementation, the base station 106A can configure a value of the carrier indicator for the PCell 125A in a cross-carrier scheduling configuration. The base station 106A can set the carrier indicator in the DCI 7 to the value of the carrier indicator for the PCell 125A. Accordingly, the UE 102 can determine to transmit the first HARQ transmission of the second UL MAC PDU on the PCell 125A according to the value of the carrier indicator.

[0118] In some implementations, the base station 106A can set the NDI in the DCI 7 for the first HARQ transmission of the second UL MAC PDU to a value that indicates that the first HARQ transmission of the second UL MAC PDU is a new transmission. Accordingly, the UE 102 can determine that the first HARQ transmission of the second UL MAC PDU is a new transmission according to the value of the new data indicator. For example, the UE 102 can store a value of a previously received NDI associated with a HARQ process, which is identified by the HARQ process number included in the DCI 7. If the value of the NDI is different (e.g., toggled) compared to the stored value of the previous NDI, the UE 102 determines that the first HARQ transmission of the second UL MAC PDU is a new transmission. In some implementations, the UE 102 can transmit the first HARQ transmission on the PCell 125A in the time and / or frequency resources assigned by the time domain resource assignment and / or the frequency domain resource assignment in the DCI 7.

[0119] In some scenarios and implementations, the base station 106A successfully obtains the second UL MAC PDU from the first HARQ transmission of the second UL MAC PDU according to the DCI7. For example, the base station 106A can decode the first HARQ transmission according to the DCI7 to obtain a transport block including the second UL MAC PDU, and the transport block passes the CRC check, such that the base station 106A successfully obtains the second UL MAC PDU from the transport block.

[0120] In other scenarios and implementations, if the base station 106A fails to obtain the second UL MAC PDU from the first HARQ transmission of the second UL MAC PDU according to the DCI7, the base station 106A can send 344A an eighth DCI command (DCI8) to the UE 102 on the SCell 126A to command the UE 102 to send a second HARQ transmission of the second UL MAC PDU. For example, the base station 106A can decode the first HARQ transmission according to the DCI7 to obtain a transport block, and the transport block fails the CRC check, such that the base station 106A is unable to obtain the second UL MAC PDU from the transport block. In response to the DCI8, the UE 102 can then send 346A the second HARQ transmission of the second UL MAC PDU to the base station 106A on the PCell 125A. The base station 106A can combine the first HARQ transmission and the second HARQ transmission, and decode the combination of the first HARQ transmission and the second HARQ transmission to obtain the second UL MAC PDU.

[0121] In one scenario, the base station 106A sends the DCI8 on the SCell 126A because PDCCH resources on the PCell 125A are not available for the UE 102 at the time the base station 106A sends the DCI8.

[0122] Similar to the DCI7, the DCI8 can include a plurality of configuration parameters. In one implementation, the DCI8 includes a carrier indicator. In this implementation, the base station 106A can set a value of the carrier indicator to the value included in the cross-carrier scheduling configuration. Accordingly, the UE 102 can determine to send the second HARQ transmission of the second UL MAC PDU on the PCell 125A according to the value of the carrier indicator. If the DCI7 includes the carrier indicator, the carrier indicator in the DCI8 and the carrier indicator in the DCI7 can have the same value or different values.

[0123] In some implementations, for the first and second HARQ transmissions of the second UL MAC PDU, DCI8 and DCI7 include the same HARQ process number (i.e., value) and the same NDI value, such that the UE 102 can determine from the HARQ process number and NDI (value) in DCI8 that the second HARQ transmission of the second UL MAC PDU is a retransmission of the second UL MAC PDU. The base station 106A can set the RV in DCI8 for the second HARQ transmission to the same or a different value as the RV in DCI7 for the first HARQ transmission. If the RV in DCI8 and the RV in DCI7 are different, the base station 106A can perform a HARQ operation (e.g., HARQ combining with incremental redundancy) to combine the first and second HARQ transmissions of the second UL MAC PDU to obtain the second UL MAC PDU. If the RV in DCI8 and the RV in DCI7 are the same, the base station 106A can perform a HARQ operation (e.g., HARQ chase combining) to combine the first and second HARQ transmissions of the second UL MAC PDU to obtain the second UL MAC PDU. In one scenario, the base station 106A successfully obtains the second UL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that includes the second UL MAC PDU and passes a CRC check. After obtaining the second UL MAC PDU, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to send an additional HARQ transmission (e.g., a new HARQ transmission) of another UL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as DCI7 and other configuration parameters similar to DCI7. The base station 106A can set the other configuration parameters to the same or different values as DCI7. In another scenario, the base station 106A fails to obtain the second UL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that fails a CRC check. In response to the failure, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to send another HARQ transmission of the second UL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as DCI8. The additional DCI can include the same NDI (value) for the second HARQ transmission as DCI8 to indicate that the other HARQ transmission is a retransmission. The additional DCI can include the same RV for the second HARQ transmission as DCI8. Alternatively, the additional DCI can include a different RV for the other HARQ transmission than the RV in DCI8 for the second HARQ transmission.Similarly, the base station 106A can perform HARQ operation in a similar manner as described above to combine the HARQ retransmission with the first and second additional HARQ transmissions according to the RVs in the additional DCIs to obtain a second UL MAC PDU.

[0124] In some scenarios and implementations, the base station 106A can also configure the UE 102 in the DCI7 to transmit a first additional HARQ transmission of an additional MAC PDU on the PCell 125A. In this case, the base station 106A can include additional configuration parameters for the first additional HARQ transmission in the DCI7. The additional configuration parameters can include specific configuration parameters for generating and / or transmitting the first additional HARQ transmission. The specific configuration parameters are similar to the configuration parameters in the plurality of configuration parameters described above. The UE 102 can generate and / or transmit the first additional HARQ transmission on the PCell 125A according to the additional configuration parameters and some of the plurality of configuration parameters. For example, the additional configuration parameters can include MCS, NDI, and / or RV that are separate from the MCS, NDI, and / or RV of the first HARQ transmission of the second UL MAC PDU, such that the base station 106A can set different MCS, NDI, and / or RV for the first additional HARQ transmission than for the first HARQ transmission. The UE 102 can transmit the first additional HARQ transmission on the PCell 125A in the same time and frequency resources as the first HARQ transmission of the second UL MAC PDU. The base station 106A receives the first additional HARQ transmission on the PCell 125A in the same time and frequency resources as the first HARQ transmission of the second UL MAC PDU. In some implementations, the additional configuration parameters can include time domain resource assignment and / or frequency domain resource assignment that are separate from the time domain resource assignment and / or frequency domain resource assignment of the first HARQ transmission of the second UL MAC PDU. In the separate time domain resource assignment and / or frequency domain resource assignment, the base station 106A can configure different time and / or frequency resources than for the first HARQ transmission of the first DL MAC PDU. In this case, the UE 102 can transmit the first additional HARQ transmission on the PCell 125A in the different time and / or frequency resources configured by the separate time domain resource assignment and / or frequency domain resource assignment. The base station 106A receives the first additional HARQ transmission on the PCell 125A in the time and / or frequency resources configured by the separate time domain resource assignment and / or frequency domain resource assignment.

[0125] In other implementations, the additional configuration parameters can include a BWP indicator separate from the BWP indicator of the first HARQ transmission of the second UL MAC PDU. In the separate BWP indicator, the base station 106A can configure a different BWP than the BWP of the first HARQ transmission of the first DL MAC PDU. In this case, the UE 102 can transmit the first additional HARQ transmission on the PCell 125A in the different BWP configured by the separate BWP indicator. The base station 106A receives the first additional HARQ transmission on the PCell 125A in the different BWP configured by the separate BWP indicator.

[0126] The base station 106A can receive the first additional HARQ transmission on the PCell 125A in accordance with the additional configuration parameters and some of the optional plurality of configuration parameters, if some of the configuration parameters are shared / common between the first HARQ transmission and the first additional HARQ transmission. For example, if the DCI7 includes a carrier indication, the carrier indication is shared between the first HARQ transmission and the first additional HARQ transmission. The UE 102 can determine to transmit the first additional HARQ transmission of the additional UL MAC PDU on the PCell 125A in accordance with a value of the carrier indicator in the DCI7. In another example, the additional configuration parameters include an additional NDI. In one implementation, the base station 106A can set the additional NDI in the DCI7 for the first additional HARQ transmission of the second UL MAC PDU to a value that indicates that the first additional HARQ transmission of the additional UL MAC PDU is a new transmission. Accordingly, the UE 102 can determine to generate the first additional HARQ transmission of the additional UL MAC PDU as a new transmission in accordance with the value of the additional NDI. For example, the UE 102 can store a value of a previously received NDI associated with a HARQ process, the HARQ process identified by a HARQ process number included in the DCI7. If the value of the additional NDI is different (e.g., toggled) compared to the stored value of the previous NDI, the UE 102 determines to generate the first additional HARQ transmission of the additional UL MAC PDU as a new transmission. In another implementation, the base station 106A can set the additional NDI in the DCI7 for the first additional HARQ transmission of the second UL MAC PDU to a value that indicates that the first additional HARQ transmission of the additional UL MAC PDU is a retransmission. Accordingly, the UE 102 can determine that the first additional HARQ transmission of the additional UL MAC PDU is a retransmission in accordance with the value of the additional NDI. For example, the UE 102 can store a value of a previously received NDI associated with a HARQ process, the HARQ process identified by a HARQ process number included in the DCI7. If the value of the additional NDI is the same (e.g., not toggled) compared to the stored value of the previous NDI, the UE 102 determines to generate the first additional HARQ transmission of the additional UL MAC PDU as a retransmission.

[0127] In some scenarios and implementations, the base station 106A successfully obtains the additional UL MAC PDU from the first additional HARQ transmission of the additional UL MAC PDU according to the DCI 7. For example, the base station 106A can decode the first additional HARQ transmission according to the DCI 7 to obtain a transport block including the additional UL MAC PDU, and the transport block passes a CRC check, such that the base station 106A successfully obtains the additional UL MAC PDU from the transport block. After obtaining the second UL MAC PDU and the additional UL MAC PDU, in one implementation, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to send an additional HARQ transmission (e.g., a new HARQ transmission) of another UL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as the DCI 7 and other configuration parameters similar to the DCI 7. The base station 106A can set the other configuration parameters to the same values as the DCI 7 or different values from the DCI 7.

[0128] In other scenarios and implementations, the base station 106A fails to obtain the additional UL MAC PDU from the first additional HARQ transmission of the additional UL MAC PDU according to the DCI 7. For example, the base station 106A can decode the first additional HARQ transmission according to the DCI 7 to obtain a transport block, and the transport block fails a CRC check or parity check, such that the base station 106A is unable to obtain the additional UL MAC PDU from the transport block. In one implementation, in response to the failure, the base station 106A can configure the UE to send a second additional HARQ transmission of the additional UL MAC PDU in the DCI 8. The UE 102 can then send the second additional HARQ transmission of the additional UL MAC PDU to the base station 106A on the PCell 125A according to the DCI 6. The base station 106A can receive the second additional HARQ transmission on the PCell 125A according to the common configuration parameters and the additional configuration parameters in the DCI 8. The common configuration parameters are common to the UE 102 to receive the second HARQ transmission and the second additional HARQ transmission. The additional configuration parameters are specific to the UE 102 to generate and send the second additional HARQ transmission. The base station 106A can combine and decode the first additional HARQ transmission and the second additional HARQ transmission to obtain the additional UL MAC PDU.

[0129] For the second additional HARQ transmission, DCI 8 can include similar additional configuration parameters as DCI 7. For example, UE 102 can transmit the second additional HARQ transmission on PCell 125A in the same or different time and frequency resources as the second HARQ transmission of the second UL MAC PDU. In some embodiments, DCI 8 and DCI 7 include the same HARQ process number (i.e., value) and the same additional NDI value for the first and second additional HARQ transmissions of the additional UL MAC PDU, such that UE 102 can determine from the HARQ process number and the additional NDI (value) in DCI 8 that the second additional HARQ transmission of the additional UL MAC PDU is a retransmission of the additional UL MAC PDU. Base station 106A can set the additional RV in DCI 8 for the second additional HARQ transmission to the same or a different value as the additional RV in DCI 7 for the first additional HARQ transmission. If the additional RV in DCI 8 and the additional RV in DCI 7 are different, base station 106A can perform HARQ operations with incremental redundancy to combine the first and second additional HARQ transmissions of the additional UL MAC PDU to obtain the second UL MAC PDU. If the RV in DCI 8 and the RV in DCI 7 are the same, base station 106A can perform HARQ operations with Chase combining to combine the first and second additional HARQ transmissions of the additional UL MAC PDU to obtain the additional UL MAC PDU. If base station 106A successfully obtains the additional UL MAC PDU from the HARQ operations, i.e., decodes the combination to obtain a transport block that includes the additional UL MAC PDU and passes a CRC check, in one embodiment, base station 106A can transmit an additional DCI to UE 102 on PCell 125A or SCell 126A to instruct UE 102 to transmit an additional HARQ transmission of another UL MAC PDU on PCell 125A. UE 102 transmits the additional HARQ transmission in a similar manner as UE 102 transmits the first HARQ transmission according to DCI 7. The additional DCI can include the same HARQ process number as DCI 7 and similar other configuration parameters as DCI 7. Base station 106A can set the other configuration parameters to the same or different values as DCI 7.

[0130] If the base station 106A fails to obtain the additional UL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block with a CRC check failure, the base station 106A can send an additional DCI to the UE 102 on the PCell 125A or the SCell 126A to instruct the UE 102 to send a HARQ retransmission of the second UL MAC PDU on the PCell 125A. The additional DCI can include the same HARQ process number as the DCI 8. The additional DCI can include the same NDI (value) for the second HARQ transmission as the DCI 8 to indicate the HARQ retransmission. The additional DCI can include the same RV for the second additional HARQ transmission as the DCI 8. Alternatively, the additional DCI can include a different RV for the HARQ retransmission than the RV for the second additional HARQ transmission in the DCI 8. Similarly, the base station 106A can perform the HARQ operation to combine the HARQ retransmission with the first and second additional HARQ transmissions to obtain an additional UL MAC PDU according to the RV in the additional DCI in a similar manner as described above.

[0131] In some implementations, the base station 106A uses the same DCI format or different DCI formats for the DCIs (e.g., the DCI 7, the DCI 8, the additional DCI, etc.). For example, the base station 106A can use an existing DCI format (e.g., DCI format 0_0, DCI format 0_1) or a new DCI format (e.g., DCI format 0_2, DCI format 0_3, etc.) for the DCI 7. In another example, the base station 106A can use an existing DCI format (e.g., DCI format 0_0, DCI format 0_1) or a new DCI format (e.g., DCI format 0_2, DCI format 0_3, etc.) for the DCI 8.

[0132] In some implementations, the base station 106A can receive a UE capability IE (e.g., a UE-NR-Capability IE or a UE-MRDC-Capability IE) from the UE 102, another base station (e.g., the base station 104), or the core network 110 (e.g., the AMF 164). The UE capability IE includes UE capabilities of the UE 102 indicating support for different protocol functions or features, mobility, and measurements for different protocol layers. In one implementation, the UE capability IE further includes a cross-carrier scheduling capability indicating that the UE 102 supports cross-carrier scheduling on a SCell for a PCell. In another implementation, the UE capability IE further includes a cross-carrier scheduling capability indicating that the UE 102 supports cross-carrier scheduling on a SCell for a PCell and on a SCell for a PSCell. In yet another implementation, the UE capability IE further includes a cross-carrier scheduling capability indicating that the UE 102 supports cross-carrier scheduling on a SCell for a PCell and a cross-carrier scheduling capability indicating that the UE 102 supports cross-carrier scheduling on a SCell for a PSCell.

[0133] In the above implementations, the UE capability IE can or can not include a cross-carrier scheduling capability indicating that the UE 102 supports cross-carrier scheduling on one SCell for another SCell. For example, the UE capability IE can or can not include a crossCarrierScheduling-SameSCS IE indicating that the UE 102 supports cross-carrier scheduling on one SCell for another SCell. In another example, the UE capability IE can or can not include a crossCarrierScheduling-OtherSCS IE indicating that the UE 102 supports cross-carrier scheduling on one SCell for another SCell.

[0134] In some implementations, the base station 106A can send a UECapabilityEnquiry message to the UE and receive the UE capability IE from the UE 102 in a UECapabilitylnformation message in response to the UECapabilityEnquiry message. In other implementations, the base station 106A can receive an Initial Context Setup message including the UE capability IE from the core network 110 (e.g., AMF 164). In other implementations, the base station 106A can receive a Handover Request message or Retrieve UE Context Response message including the UE capability IE from another base station (e.g., base station 104).

[0135] In some implementations, the base station 106A generates a PDCP PDU including the RRC reconfiguration message 308A, an RLC PDU including the PDCP PDU, and a MAC PDU including the RLC PDU. The base station 106A generates one or more HARQ transmissions of the MAC PDU and one or more DCI commands (DCI) for the HARQ transmissions. The base station 106A can transmit the DCI and the HARQ transmissions to the UE 102 on the PCell 125A. The UE 102 can receive the HARQ transmissions according to the DCI, obtain the MAC PDU from the HARQ transmissions, extract the RLC PDU from the MAC PDU, extract the PDCP PDU from the RLC PDU, and then extract the RRC reconfiguration message from the PDCP PDU.

[0136] In some implementations, the UE 102 generates a PDCP PDU including the RRC reconfiguration complete message 312A, an RLC PDU including the PDCP PDU, and a MAC PDU including the RLC PDU. The UE 102 can receive one or more DCI commands (DCI) for UL transmissions from the base station 106A on the PCell 125A and use the DCI to generate one or more HARQ transmissions of the MAC PDU. The UE 102 can transmit the HARQ transmissions to the base station 106A on the PCell 125A. The base station 106A can receive the HARQ transmissions according to the DCI, obtain the MAC PDU from the HARQ transmissions, extract the RLC PDU from the MAC PDU, extract the PDCP PDU from the RLC PDU, and then extract the RRC reconfiguration complete message from the PDCP PDU.

[0137] In some implementations, if the base station 106A is a gNB, the RRC reconfiguration and RRC reconfiguration complete messages are RRCReconfiguration and RRCReconfigurationComplete messages, respectively.

[0138] Reference is now made to Figure 3B , which is generally similar to Figure 3A scenario 300A, but here, the UE 102 initially communicates with the base station 106A using CA before the base station 106A provides the UE 102 with cross-carrier scheduling configuration. The differences between the scenarios of Figure 3A and Figure 3B are considered below. Similar events are labeled with the same reference number, with a different letter appended to the reference number, in order to more clearly distinguish between the scenarios.

[0139] The UE 102 initially communicates 303B data with the base station 106A via the PCell 125A and via the SCell 126A. Similar to the communications of event 302A discussed above, these communications can include UL and / or DL transmissions. Similar to event 304A, after the base station 106A determines 304B to configure the cell 126A as a scheduling SCell for scheduling PDSCH or PUSCH of the PCell 125A, the base station 106A sends 309B an RRC reconfiguration message including cross-carrier scheduling configuration for the cell 126A to the UE 102. The base station 106A can send 309B the message in the PCell 126A.

[0140] Figures 4A-4D Several scenarios are shown in which the UE 102 operates in DC with the base stations 104 and 106B. In these scenarios, the base station 104 operates as the MN and the base station 106A operates as the SN. Thus, the cells 125A and 126A operate as the PSCell and SCell, respectively. The differences between the scenarios of Figure 3A , Figure 3B and Figures 4A-4D are considered below. Similar events are labeled with the same reference number, with a different letter appended to the reference number, in order to more clearly distinguish between the scenarios.

[0141] Reference is first made to scenario 400A of Figure 4A , the UE 102 communicates 402A data in DC with the base station 106A in the PSCell 125A. This event is similar to event 402A, but here the UE 102 also communicates with the MN 104 and the base station 106A operates as the SN. In this scenario, SRB3 is available to the UE 102 and the SN 106A to directly exchange control messages via the radio interface, and the SN 106A accordingly sends 408A an RRC reconfiguration message including SCell configuration and cross-carrier scheduling configuration for the cell 126A to the UE 102.

[0142] In Figure 4BIn scenario 400B, similar to scenario 300B above, before base station 106A provides cross-carrier scheduling configuration to UE 102, UE 102 initially communicates with base station 106A using CA 403B. SN 106A sends an RRC reconfiguration message including cross-carrier scheduling configuration via SRB3 on cell 126A.

[0143] Figure 4C The scenario 400C is similar to Figure 4A In scenario 400A, UE 102 also communicates 402C data with base station 106A in PSCell 125A and DC. However, SRB3 is not available for UE 102 and SN 106A to directly exchange control messages via the radio interface. As a result, SN 106A sends a 452C RRC reconfiguration message to MN 104, which includes the SCell configuration and cross-carrier scheduling configuration of cell 126A, and MN 104 then forwards the 456C RRC reconfiguration message to UE 102 via the radio interface (e.g., SRB1).

[0144] exist Figure 4D In scenario 400D, similar to scenario 400B described above, UE 102 initially communicates with base station 106A using CA 402D before base station 106A provides cross-carrier scheduling configuration to UE 102. Similar to scenario 400C, base station 106A cannot directly send RRC reconfiguration messages via the radio interface. Therefore, SN 106A sends an RRC reconfiguration message 453D, which includes the cross-carrier scheduling configuration of cell 126A, to MN 104, and MN 104 then forwards the RRC reconfiguration message 457D to UE 102 via the radio interface (e.g., SRB1).

[0145] Next, we will present several example scenarios of a base station initiating a CA operation process with multi-cell scheduling. Figures 5A-5D This describes a scenario where the base station enables CA and multi-cell scheduling for the UE and the base station's PCell PUSCH or PDSCH. In the following description, the terms "DCI" and "DCI command" are used interchangeably.

[0146] First refer to Figure 5A In scenario 500A, base station 106A is the serving base station for operating cells 125A and 126A. Initially, UE 102 communicates 502A data (e.g., uplink (UL) data PDUs and / or downlink (DL) data PDUs) with base station 106A via PCell 125A. In some scenarios, UE 102 communicates 502A data with base station 106A in the SC, or in the DC as... Figure 5AThe base station 106A, which is not shown in FIG. 5, communicates 502A data with the base station 106B operating the MN and the SN (e.g., the base station 106B).

[0147] The base station 106A determines 504A at some time that it should configure the cell 126A as an SCell for PDSCH and / or PUSCH of the PCell 125A and enable multi-cell scheduling with single DCI on the PCell 125A. For example, the base station 106A can make this determination based on one or more measurement results of the cell 126A received from the UE 102 or another suitable event. In response to the determination, the base station 106A sends 508A an RRC reconfiguration message to the UE 102, the RRC reconfiguration message including an SCell configuration and a multi-cell scheduling configuration for the PCell 125A. In response to the RRC reconfiguration message, the UE 102 sends 512A an RRC reconfiguration complete message to the base station 106A. In some implementations, the base station 106A can include the multi-cell scheduling configuration in the SCell configuration to enable multi-cell scheduling on the PCell 125A. For example, the SCell configuration can be an SCellConfig information element (IE).

[0148] After receiving the RRC reconfiguration message, the UE 102 in CA communicates 514A with the base station 106A via the PCell 125A and the SCell 126A. The UE 102 enables multi-cell scheduling according to / responsive to the multi-cell scheduling configuration. According to the multi-cell scheduling configuration, the base station 106A can send 516A a first DCI command (DCI1) to the UE 102 via the PCell 125A, the first DCI command (DCI1) including a plurality of configuration parameters for a first HARQ transmission of a first DL MAC PDU on the PCell 125A and a first HARQ transmission of a second DL MAC PDU on the SCell 126A. Then, according to the plurality of configuration parameters, the base station 106A sends 518A the first HARQ transmission of the first DL MAC PDU to the UE 102 on the PCell 125A and sends 520A the first HARQ transmission of the second DL MAC PDU to the UE 102 on the SCell 126A. According to the plurality of configuration parameters in the DCI1, the UE 102 receives and processes the first HARQ transmission 518A on the PCell 125A and receives and processes the first HARQ transmission 520A on the SCell 126A.

[0149] In some implementations, the plurality of configuration parameters can include a first set and a second set of parameters respectively configuring the first HARQ transmission 518A and the first HARQ transmission 520A. Each of the two sets can include some or all of the parameters such as a carrier indicator, a HARQ process number, a frequency domain resource assignment, a time domain resource assignment, an RV, an NDI, an MCS, a TPC command for PUCCH, and / or a PUCCH resource indicator. Each of the two sets can also include some or all of the other parameters such as an identifier of a DCI format, a BWP indicator, a VRB-to-PRB mapping, a PRB bundling size indicator, a rate matching indicator, a CSI-RS trigger, a downlink assignment index, a PDSCH-to-HARQ feedback timing indicator, a number of antenna ports and layers, a transmission configuration indication, an SRS request, and / or a DRMS sequence initialization. If each of the two sets includes some parameters, the remaining parameters can be common to both the first HARQ transmission 518A and the first HARQ transmission 520A.

[0150] In different implementations, the first set can or can not include a carrier indicator, and the second set can or can not include a carrier indicator. In one implementation, the first set can include a first carrier indicator indicating that the first HARQ transmission 518A is on the PCell 125A, and the second set can include a second carrier indicator indicating that the first HARQ transmission 520A is on the SCell 126A. The UE 102 can determine to receive the first HARQ transmission 518A on the PCell 125A according to the first carrier indicator, and to receive the first HARQ transmission 520A on the SCell 126A according to the second carrier indicator. In one implementation, the base station 106A can configure the first carrier indicator (value) and the second carrier indicator (value) in a multi-cell configuration. The multi-cell configuration can configure the first carrier indicator (value) and the second carrier indicator (value) respectively associated with the PCell 125A and the SCell 126A.

[0151] In another implementation, the first set can not include the carrier indicator, and the second set can include the carrier indicator indicating the first HARQ transmission 520A on the SCell 126A. In this implementation, the UE 102 can determine to receive the first HARQ transmission 518A on the PCell 125A according to a default configuration. The default configuration can be that if the UE 102 receives a DCI (e.g., DCI1) on a cell (e.g., PCell 125A) that does not include a carrier indicator of a HARQ transmission (e.g., first HARQ transmission 518A) and configures a DL transmission, the UE 102 receives the HARQ transmission (e.g., first HARQ transmission 518A) in the cell (e.g., PCell 125A) according to the DCI. The UE 102 can determine to receive the first HARQ transmission 518A on the SCell 126A according to the carrier indicator. In one implementation, the base station 106A can configure the carrier indicator associated with the SCell 126A in the multi-cell configuration. In yet another implementation, neither the first set nor the second set includes the carrier indicator. The UE 102 can determine to receive the first HARQ transmission 518A on the PCell 125A and the first HARQ transmission 520A on the SCell 126A according to a format of the DCI1 or a specific field in the DCI1. For example, the format of the DCI1 or the specific field is specially designed to indicate the UE 102 to receive the HARQ transmission on the two cells (e.g., PCell 125A and SCell 126A) configured by the RRC reconfiguration message.

[0152] In other implementations, the plurality of configuration parameters can include a single set of parameters configuring both the first HARQ transmission 518A and the first HARQ transmission 520A. That is, the base station 106A uses each of the single set of parameters to transmit both the first HARQ transmission 518A and the first HARQ transmission 520A. There is no duplicated parameter field in the DCI1. The single set of parameters can include the HARQ process number, the frequency domain resource assignment, the time domain resource assignment, the RV, the NDI, the MCS, the TPC command for PUCCH, and / or the PUCCH resource indicator. Other parameters such as the identifier of the DCI format, the BWP indicator, the VRB-to-PRB mapping, the PRB bundling size indicator, the rate matching indicator, the CSI-RS trigger, the downlink assignment index, the PDSCH-to-HARQ feedback timing indicator, the number of antenna ports and layers, the transmission configuration indication, the SRS request, and / or the DMRS sequence initialization can also be included in the single set.

[0153] In some implementations, the first set includes a first NDI and a first HARQ process number, and the second set includes a second NDI and a second HARQ process number. In one implementation, the base station 106A can set the first NDI to a first value that indicates that the first HARQ transmission 518A is a new transmission. Accordingly, the UE 102 can determine from the first value that the first HARQ transmission 518A is a new transmission. In response to the determination, the UE 102 can flush a soft buffer associated with the first HARQ process number to store the first HARQ transmission 518A. Similarly, the base station 106A can set the second NDI to a second value that indicates that the first HARQ transmission 520A is a new transmission. Accordingly, the UE 102 can determine from the second value that the first HARQ transmission 520A is a new transmission. In response to the determination, the UE 102 can flush a soft buffer associated with the (first) HARQ process number to store the first HARQ transmission 520A. The first and second values can be the same or different.

[0154] In another implementation, the base station 106A can set the first NDI to a third value that indicates that the first HARQ transmission 518A is a retransmission. Accordingly, the UE 102 can determine from the third value that the first HARQ transmission 518A is a retransmission. In response to the determination, the UE 102 does not flush a soft buffer associated with the (first) HARQ process number. The UE 102 stores the first HARQ transmission 518A in the soft buffer. Similarly, the base station 106A can set the second NDI to a fourth value that indicates that the first HARQ transmission 520A is a retransmission. Accordingly, the UE 102 can determine from the fourth value that the first HARQ transmission 520A is a HARQ retransmission. In response to the determination, the UE 102 does not flush a soft buffer associated with the (second) HARQ process number. The UE 102 stores the first HARQ transmission 520A in the soft buffer. The third and fourth values can be the same or different. For example, the UE 102 can store a value of a previously received NDI associated with a HARQ process identified by the first HARQ process number. If the first or third value is different (e.g., flipped) compared to the stored value of the previous NDI, the UE 102 determines that the first HARQ transmission 518A is a new HARQ transmission. Similarly, the UE 102 can store a value of a previously received NDI associated with a HARQ process identified by the second HARQ process number. If the second or fourth value is different (e.g., flipped) compared to the stored value of the previous NDI, the UE 102 determines that the first HARQ transmission 520A is a HARQ new transmission. The first and second HARQ process numbers can be the same or different.

[0155] In other implementations, the base station 106A can use a single NDI for both the first HARQ transmission 518A and the first HARQ transmission 520A, and the UE 102 can use the single NDI to determine whether both the first HARQ transmission 518A and the first HARQ transmission 520A are new transmissions or retransmissions in a similar manner as described above.

[0156] In some implementations, the first set includes a first MCS and the second set includes a second MCS. The first MCS and the second MCS can be set to the same value or different values. The UE 102 decodes the first HARQ transmission 518A according to the first MCS and decodes the first HARQ transmission 520A according to the second MCS. In some implementations, the base station 106A can determine the first MCS according to at least one first channel state information (CSI) and / or at least one first SRS received from the UE 102 on the PCell 125A. Similarly, the base station 106A can determine the second MCS according to at least one second CSI received from the UE 102 on the PCell 125A and / or according to at least one second SRS received from the UE 102 on the SCell 126A. In one implementation, the UE 102 can obtain the at least one first CSI according to at least one first signal detected / received on the PCell 125A and transmit the at least one first CSI to the base station 106A on the PCell 125A. Similarly, the UE 102 can obtain the at least one second CSI according to at least one second signal detected / received on the SCell 126A and transmit the at least one second CSI to the base station 106A on the PCell 125A. The at least one first or second signal can include synchronization signals, such as a primary synchronization signal, a secondary synchronization signal, and / or a synchronization signal block, and / or include reference signals, such as a CSI reference signal (CSI-RS). In other implementations, the base station 106A can include a single MCS in the DCI1 for both the first HARQ transmission 518A and the first HARQ transmission 520A, and the UE 102 can use the single MCS to decode the first HARQ transmission 518A and the first HARQ transmission 520A in a similar manner as described above. In one implementation, the base station 106A can determine the single MCS value according to the at least one first CSI or SRS or the at least one second CSI or SRS. In another implementation, the base station 106A can determine the single MCS value according to the at least one first CSI or SRS and the at least one second CSI or SRS.

[0157] In some implementations, the first set includes a first RV and the second set includes a second RV. The first and second RVs can be set to the same value or different values. The UE 102 decodes the first HARQ transmission 518A according to the first RV and the first HARQ transmission 520A according to the second RV. In some implementations, if the first HARQ transmission 518A is a new transmission, the base station 106A can set the first RV value to 0. Similarly, if the first HARQ transmission 520A is a new transmission, the base station 106A can set the second RV value to 0. In other implementations, if the first HARQ transmission 518A is a retransmission, the base station 106A can set the first RV value to 2, 3, or 1. Similarly, if the first HARQ transmission 520A is a retransmission, the base station 106A can set the second RV value to 2, 3, or 1. In other implementations, the base station 106A can include a single RV in the DCI1 for both the first HARQ transmission 518A and the first HARQ transmission 520A, and the UE 102 can use the single RV to decode the first HARQ transmission 518A and the first HARQ transmission 520A in a similar manner as described above.

[0158] In some implementations, the first set can include a first time domain resource assignment and / or a first frequency domain resource assignment that assigns first time and / or frequency resources on the PCell 125A, and the second set can include a second time domain resource assignment and / or a second frequency domain resource assignment that assigns second time and / or frequency resources on the SCell 126A. In such implementations, the base station 106A can transmit the first HARQ transmission 518A on the PCell 125A and the first HARQ transmission 520A on the SCell 126A on the first time and / or frequency resources and the second time and / or frequency resources, respectively. In other implementations, the base station 106A can include a single time domain resource assignment and / or a single frequency domain resource assignment in the DCI1 for both the first HARQ transmission 518A and the first HARQ transmission 520A, and the UE 102 can use the single time domain resource assignment and / or the single frequency domain resource assignment to receive the first HARQ transmission 518A on the PCell 125A and the first HARQ transmission 520A on the SCell 126A in a similar manner as described above.

[0159] In some implementations, the first set can include a first BWP indicator indicating a first BWP on the PCell 125A, and the second set can include a second BWP indicator indicating a second BWP on the SCell 126A. The first and second BWP indicators can be set to the same value or different values. The base station 106A can transmit the HARQ transmission 518A on the first BWP and the HARQ transmission 520A on the second BWP. The UE 102 can receive the HARQ transmission 518A on the first BWP according to the first BWP indicator and the HARQ transmission 520A on the second BWP according to the second BWP indicator. In other implementations, the base station 106A can use a single BWP indicator to indicate the first BWP on the PCell 125A and the second BWP on the SCell 126A, and include the single BWP indicator in the DCI1 for both the first HARQ transmission 518A and the first HARQ transmission 520A. The base station 106A can transmit the HARQ transmission 518A on the first BWP and the HARQ transmission 520A on the second BWP. The UE 102 can use the single BWP indicator to receive the first HARQ transmission 518A on the first BWP and the first HARQ transmission 520A on the second BWP.

[0160] In some scenarios and implementations, the UE 102 successfully obtains the first DL MAC PDU from the first HARQ transmission 518A according to the DCI1. In this case, the UE 102 transmits a HARQ ACK to the base station 106A on the PCell 125A to indicate the successful reception of the first DL MAC PDU. For example, the UE 102 can decode the first HARQ transmission 518A according to the DCI1 to obtain a transport block including the first DL MAC PDU, and the transport block passes the CRC check, such that the UE 102 successfully obtains the first DL MAC PDU from the transport block.

[0161] In some scenarios and implementations, the UE 102 successfully obtains the second DL MAC PDU from the first HARQ transmission 520A according to the DCI1. In this case, the UE 102 transmits a HARQ ACK to the base station 106A on the PCell 125A to indicate the successful reception of the second DL MAC PDU. For example, the UE 102 can decode the first HARQ transmission 520A according to the DCI1 to obtain a transport block including the second DL MAC PDU, and the transport block passes the CRC check, such that the UE 102 successfully obtains the second DL MAC PDU from the transport block.

[0162] In other scenarios and implementations, if the UE 102 fails to obtain the second DL MAC PDU from the first HARQ transmission 520A according to the DCI1, the UE 102 can send a HARQ NACK to the base station 106A on the PCell 125A. For example, the UE 102 can decode the first HARQ transmission 520A according to the DCI1 to obtain a transport block, and fail a CRC check on the transport block, such that the UE 102 cannot obtain the second DL MAC PDU from the transport block. In response to the HARQ NACK, the base station 106A can send 524A a second DCI command (DCI2) on the SCell 126A for a second HARQ transmission of the second DL MAC PDU on the SCell 126A. The base station 106A can then send 526A the second HARQ transmission of the second DL MAC PDU to the UE 102 on the SCell 126A. The UE 102 can combine the first HARQ transmission 520A and the second HARQ transmission, and decode the combination of the first HARQ transmission and the second HARQ transmission to obtain the second DL MAC PDU. The base station 106A can determine to perform the events 524A and 526A because the UE 102 does not support cross-carrier scheduling, or the base station 106A does not enable cross-carrier scheduling for the UE 102. If the base station 106A enables cross-carrier scheduling for the UE 102, the base station 106A can send a DCI command on the SCell 126A for a second HARQ transmission of the second DL MAC PDU on the PCell 125A in a similar manner as described for the events 328A and 330A.

[0163] DCI2 can include a plurality of configuration parameters for UE 102 to receive the second HARQ transmission 526A. The plurality of configuration parameters can include a carrier indicator, a HARQ process number, a frequency domain resource assignment, a time domain resource assignment, an RV, an NDI, an MCS, a TPC command for PUCCH, and / or a PUCCH resource indicator. The plurality of configuration parameters can also include other parameters such as an identifier of a DCI format, a BWP indicator, a VRB-to-PRB mapping, a PRB bundling size indicator, a rate matching indicator, a CSI-RS trigger, a downlink assignment index, a PDSCH-to-HARQ feedback timing indicator, a number of antenna ports and layers, a transmission configuration indication, an SRS request, and / or a DMRS sequence initialization. In one implementation, if the base station 106A does not enable cross-carrier scheduling for the UE 102, the DCI2 can not include the carrier indicator. In this implementation, the UE 102 can determine to receive the second HARQ transmission of the second DL MAC PDU on the SCell 125A according to the DCI2 because the UE 102 does not support cross-carrier scheduling or the base station 106A does not enable cross-carrier scheduling for the UE 102. In another implementation, if the base station 106A enables multi-cell scheduling for the UE 102, the DCI2 includes the carrier indicator. In this implementation, the base station 106A can set a value of the carrier indicator to a value included in the multi-cell scheduling configuration. Accordingly, the UE 102 can determine to receive the second HARQ transmission 526A on the SCell 126A according to the value of the carrier indicator. The carrier indicator in the DCI2 and the carrier indicator in the DCI1 can have the same value or different values.

[0164] In some implementations, for the first HARQ transmission 520A and the second HARQ transmission 526A, the DCI2 and the DCI1 include the same HARQ process number (i.e., value) and the same NDI value, such that the UE 102 can determine from the HARQ process number and the NDI (value) in the DCI2 that the second HARQ transmission 526A is a HARQ retransmission. The base station 106A can set the RV in the DCI2 of the second HARQ transmission 526A to the same or a different value as the RV in the DCI1 of the first HARQ transmission 520A. If the RV in the DCI2 and the RV in the DCI1 are different, the UE 102 can perform a HARQ operation (e.g., HARQ combining with incremental redundancy) to combine the first HARQ transmission 520A and the second HARQ transmission 526A to obtain the second DL MAC PDU. If the RV in the DCI2 and the RV in the DCI1 are the same, the UE 102 can perform a HARQ operation (e.g., HARQ chase combining) to combine the first HARQ transmission 520A and the second HARQ transmission 526A to obtain the second DL MAC PDU.

[0165] If the UE 102 successfully obtains the second DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block comprising the first DL MAC PDU and passing the CRC check, the UE 102 sends a HARQ ACK on the PCell 125A to the base station 106A to indicate the successful reception of the second DL MAC PDU. If the UE 102 fails to obtain the second DL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block failing the CRC check, the UE 102 sends a HARQ NACK on the PCell 125A to the base station 106A to indicate the failed reception of the second DL MAC PDU. In response to the HARQ NACK, the base station 106A can send an additional DCI to the UE 102 on the SCell 126A to instruct the UE 102 to receive a HARQ retransmission of the second DL MAC PDU on the SCell 126A. The additional DCI can include the same HARQ process number as DCI2. The additional DCI can include the same NDI (value) for the second HARQ transmission 526A as DCI2 to indicate the HARQ retransmission. The additional DCI can include the same RV for the second HARQ transmission 526A as DCI2. Alternatively, the additional DCI can include a different RV for the HARQ retransmission than the RV for the second HARQ transmission in DCI2. Similarly, the UE 102 can perform the HARQ operation to combine the HARQ retransmission with the first HARQ transmission 520A and the second HARQ transmission 526A to obtain the second DL MAC PDU according to the RV in the additional DCI in a similar manner as described above.

[0166] In some scenarios and implementations, the base station 106A can also configure the UE 102 to receive a first additional HARQ transmission of a first additional DL MAC PDU on the PCell 125A in DCI1 in a similar manner as described above for DCI1 in Figure 3A The base station 106A can include additional configuration parameters for the first additional HARQ transmission in DCI1, and the UE 102 can receive the first additional HARQ transmission on the PCell 125A according to DCI1. If the base station 106A receives a HARQ NACK for the first additional HARQ transmission from the UE 102, the base station 106A can also configure the UE 102 to receive a second additional HARQ transmission of the first additional DL MAC PDU on the PCell 125A in a fifth DCI command (DCI5) in a similar manner as described above for DCI2 in Figure 3A The base station 106A can include additional configuration parameters for the first additional HARQ transmission in DCI1, and the UE 102 can receive the first additional HARQ transmission on the PCell 125A according to DCI1. If the base station 106A receives a HARQ NACK for the first additional HARQ transmission from the UE 102, the base station 106A can also configure the UE 102 to receive a second additional HARQ transmission of the first additional DL MAC PDU on the PCell 125A in a fifth DCI command (DCI5) in a similar manner as described above for DCI2 in

[0167] In some scenarios and implementations, the base station 106A can also configure the UE 102 in the DCI1 to receive a first additional HARQ transmission of a second additional DL MAC PDU on the SCell 126A in a similar manner as described for the DCI3 in Figure 3A The base station 106A can include additional configuration parameters for the first additional HARQ transmission in the DCI1, and the UE 102 can receive the first additional HARQ transmission on the SCell 126A according to the DCI1. If the base station 106A receives a HARQ NACK for the first additional HARQ transmission from the UE 102, the base station 106A can also configure the UE 102 in the DCI2 to receive a second additional HARQ transmission of the second additional DL MAC PDU on the SCell 126A in a similar manner as described for the DCI2 in Figure 3A The descriptions of the DCI2 320A and the second HARQ transmission 322A on the PCell 125A can apply to the DCI1 and the second additional HARQ transmission of the second additional DL MAC PDU on the SCell 126A.

[0168] In some implementations, the base station 106A uses the same DCI format or different DCI formats for the DCIs (e.g., DCI1, DCI2, additional DCIs, etc.). For example, the base station 106A can use an existing DCI format (e.g., DCI format 1 0, DCI format 1 1) or a new DCI format (e.g., DCI format 1 2, DCI format 1 3, etc.) for the DCI1. In another example, the base station 106A can use an existing DCI format (e.g., DCI format 1 0, DCI format 1 1) or a new DCI format (e.g., DCI format 1 2, DCI format 1 3, etc.) for the DCI2.

[0169] After receiving the RRC reconfiguration message, the UE 102 in CA communicates 514A with the base station 106A via the PCell 125A and the SCell 126A. The UE 102 enables multi-cell scheduling according to / in response to the multi-cell scheduling configuration. According to the multi-cell scheduling configuration, the base station 106A can transmit 528A a third DCI command (DCI3) to the UE 102 via the PCell 125A, the third DCI command (DCI3) including a plurality of configuration parameters for a first HARQ transmission of a first DL MAC PDU on the PCell 125A and a first HARQ transmission of a second DL MAC PDU on the SCell 126A. Then, according to the plurality of configuration parameters, the UE 102 transmits 530A the first HARQ transmission of the first DL MAC PDU to the base station 106A on the PCell 125A and transmits 532A the first HARQ transmission of the second DL MAC PDU to the base station 106A on the SCell 126A. According to the plurality of configuration parameters in the DCI3, the base station 106A receives and processes the first HARQ transmission 530A on the PCell 125A and receives and processes the first HARQ transmission 532A on the SCell 126A.

[0170] In some embodiments, the plurality of configuration parameters can include a first set of parameters and a second set of parameters respectively configuring the first HARQ transmission 530A and the first HARQ transmission 532A. Each of the two sets can include some or all of the parameters such as carrier indicator, HARQ process number, frequency domain resource assignment, time domain resource assignment, frequency hopping flag, RV, NDI, MCS, TPC command for PUSCH. Each of the two sets can also include some or all of the other parameters such as identifier of DCI format, BWP indicator, first DL assignment index, second DL assignment index, SRS resource indicator, precoding information and number of layers, antenna port, SRS request, CSI request, and / or DMRS sequence initialization. If each of the two sets includes some parameters, the remaining parameters can be common parameters for both the first HARQ transmission 530A and the first HARQ transmission 532A.

[0171] In different embodiments, the first set can or can not include a carrier indicator, and the second set can or can not include a carrier indicator. In one embodiment, the first set can include a first carrier indicator indicating the first HARQ transmission 530A on the PCell 125A, and the second set can include a second carrier indicator indicating the first HARQ transmission 532A on the SCell 126A. The UE 102 can determine to transmit the first HARQ transmission 530A on the PCell 125A according to the first carrier indicator, and transmit the first HARQ transmission 532A on the SCell 126A according to the second carrier indicator. In one embodiment, the base station 106A can configure the first carrier indicator (value) and the second carrier indicator (value) in a multi-cell configuration. The multi-cell configuration can configure the first carrier indicator (value) and the second carrier indicator (value) associated with the PCell 125A and the SCell 126A, respectively.

[0172] In another embodiment, the first set can not include a carrier indicator, and the second set can include a carrier indicator indicating the first HARQ transmission 532A on the SCell 126A. In this embodiment, the UE 102 can determine to transmit the first HARQ transmission 530A on the PCell 125A according to a default configuration. The default configuration can be that if the UE 102 receives a DCI (e.g., DCI3) configuring a UL transmission without a carrier indicator of a HARQ transmission (e.g., the first HARQ transmission 530A) on a cell (e.g., the PCell 125A), the UE 102 transmits the HARQ transmission (e.g., the first HARQ transmission 530A) on the cell (e.g., the PCell 125A) according to the DCI. The UE 102 can determine to transmit the first HARQ transmission 530A on the SCell 126A according to the carrier indicator. In one embodiment, the base station 106A can configure the carrier indicator associated with the SCell 126A in a multi-cell configuration. In yet another embodiment, neither the first set nor the second set includes a carrier indicator. The UE 102 can determine to transmit the first HARQ transmission 530A on the PCell 125A and the first HARQ transmission 532A on the SCell 126A according to a format of the DCI3 or a specific field in the DCI3. For example, the format of the DCI3 or the specific field is specially designed to indicate the UE 102 to transmit a HARQ transmission on two cells (e.g., the PCell 125A and the SCell 126A) configured by an RRC reconfiguration message.

[0173] In other implementations, the plurality of configuration parameters can include a single set of parameters that configures both the first HARQ transmission 530A and the first HARQ transmission 532A. That is, the base station 106A uses each of the single set of parameters to transmit the first HARQ transmission 530A and the first HARQ transmission 532A. There are no duplicated parameter fields in the DCI 3. The single set of parameters can include a carrier indicator, a HARQ process number, a frequency domain resource assignment, a time domain resource assignment, a frequency hopping flag, an RV, an NDI, an MCS, a TPC command for a physical uplink shared channel (PUCCH). Other parameters such as an identifier of a DCI format, a BWP indicator, a first DL assignment index, a second DL assignment index, an SRS resource indicator, precoding information and number of layers, antenna ports, an SRS request, a CSI request, and / or a DMRS sequence initialization can also be included in the single set.

[0174] In some implementations, the first set includes a first NDI and a first HARQ process number, and the second set includes a second NDI and a second HARQ process number. In one implementation, the base station 106A can set the first NDI to a first value that indicates that the first HARQ transmission 530A is a new HARQ transmission. Accordingly, the UE 102 can determine from the first value that the first HARQ transmission 530A is a new HARQ transmission. For example, the UE 102 can store a value of a previously received NDI associated with a HARQ process identified by the first HARQ process number. The base station 106A can flush a soft buffer associated with the (first) HARQ process number and store the first HARQ transmission 530A due to the new HARQ transmission. Similarly, the base station 106A can set the second NDI to a second value that indicates that the first HARQ transmission 532A is a new HARQ transmission. Accordingly, the UE 102 can determine from the second value that the first HARQ transmission 532A is a new HARQ transmission. The base station 106A can flush a soft buffer associated with the (second) HARQ process number and store the first HARQ transmission 532A due to the new HARQ transmission. The first and second values can be the same or different.

[0175] In another implementation, the base station 106A can set the first NDI to a third value that indicates that the first HARQ transmission 530A is a HARQ retransmission. Accordingly, the UE 102 can determine from the third value that the first HARQ transmission 530A is a HARQ retransmission. Due to the retransmission, the base station 106A does not flush the soft buffer associated with the (first) HARQ process number and stores the first HARQ transmission 530A. Similarly, the base station 106A can set the second NDI to a fourth value that indicates that the first HARQ transmission 532A is a HARQ retransmission. Accordingly, the UE 102 can determine from the fourth value that the first HARQ transmission 532A is a HARQ retransmission. Due to the retransmission, the base station 106A does not flush the soft buffer associated with the (second) HARQ process number and stores the first HARQ transmission 532A. The third and fourth values can be the same or different. For example, the UE 102 can store a value of a previously received NDI associated with the HARQ process identified by the first HARQ process number. If the first or third value is different (e.g., flipped) compared to the stored value of the previous NDI, the UE 102 determines that the first HARQ transmission 530A is a new HARQ transmission. Otherwise, the UE 102 determines that the first HARQ transmission 530A is a HARQ retransmission. Similarly, the UE 102 can store a value of a previously received NDI associated with the HARQ process identified by the second HARQ process number. If the second or fourth value is different (e.g., flipped) compared to the stored value of the previous NDI, the UE 102 determines that the first HARQ transmission 532A is a new HARQ transmission. Otherwise, the UE 102 determines that the first HARQ transmission 532A is a HARQ retransmission. The first and second HARQ process numbers can be the same or different.

[0176] In other implementations, the base station 106A can use a single NDI for both the first HARQ transmission 530A and the first HARQ transmission 532A, and the UE 102 can use the single NDI to determine whether both the first HARQ transmission 530A and the first HARQ transmission 532A are new transmissions or retransmissions in a similar manner as described above.

[0177] In some implementations, the first set includes a first MCS and the second set includes a second MCS. The first and second MCSs can be set to the same value or different values. The UE 102 generates the first HARQ transmission 530A according to the first MCS and the first HARQ transmission 532A according to the second MCS. In some implementations, the base station 106A can determine the first MCS according to at least one first channel state information (CSI) and / or at least one first SRS received from the UE 102 on the PCell 125A. Similarly, the base station 106A can determine the second MCS according to at least one second CSI received from the UE 102 on the PCell 125A and / or according to at least one second SRS received from the UE 102 on the SCell 126A. In one implementation, the UE 102 can obtain the at least one first CSI according to at least one first signal detected / received on the PCell 125A and transmit the at least one first CSI to the base station 106A on the PCell 125A. Similarly, the UE 102 can obtain the at least one second CSI according to at least one second signal detected / received on the SCell 126A and transmit the at least one second CSI to the base station 106A on the PCell 125A. The at least one first or second signal can include synchronization signals, such as a primary synchronization signal, a secondary synchronization signal, and / or a synchronization signal block, and / or a reference signal, such as a CSI reference signal (CSI-RS). In other implementations, the base station 106A can include a single MCS in the DCI 3 for both the first HARQ transmission 530A and the first HARQ transmission 532A, and the UE 102 can use the single MCS to decode the first HARQ transmission 530A and the first HARQ transmission 532A in a similar manner as described above. In one implementation, the base station 106A can determine the single MCS value according to the at least one first CSI or SRS or the at least one second CSI or SRS. In another implementation, the base station 106A can determine the single MCS value according to the at least one first CSI or SRS and the at least one second CSI or SRS.

[0178] In some implementations, the first set includes a first RV and the second set includes a second RV. The first and second RVs can be set to the same value or different values. The UE 102 generates the first HARQ transmission 530A according to the first RV and the first HARQ transmission 532A according to the second RV. In some implementations, the base station 106A can set the first RV value to 0 if the first HARQ transmission 530A is a new HARQ transmission. Similarly, the base station 106A can set the second RV value to 0 if the first HARQ transmission 532A is a new HARQ transmission. In other implementations, the base station 106A can set the first RV value to 2, 3, or 1 if the first HARQ transmission 530A is a retransmission. Similarly, the base station 106A can set the second RV value to 2, 3, or 1 if the first HARQ transmission 532A is a retransmission. In other implementations, the base station 106A can include a single RV in the DCI 3 for both the first HARQ transmission 530A and the first HARQ transmission 532A, and the UE 102 can use the single RV to generate the first HARQ transmission 530A and the first HARQ transmission 532A in a similar manner as described above.

[0179] In some implementations, the first set can include a first time domain resource assignment and / or a first frequency domain resource assignment that assigns first time and / or frequency resources on the PCell 125A, and the second set can include a second time domain resource assignment and / or a second frequency domain resource assignment that assigns second time and / or frequency resources on the SCell 126A. In such implementations, the base station 106A can transmit the first HARQ transmission 530A on the PCell 125A and the first HARQ transmission 532A on the SCell 126A on the first time and / or frequency resources and the second time and / or frequency resources, respectively. In other implementations, the base station 106A can include a single time domain resource assignment and / or a single frequency domain resource assignment in the DCI 1 for both the first HARQ transmission 530A and the first HARQ transmission 532A, and the UE 102 can use the single time domain resource assignment and / or the single frequency domain resource assignment to transmit the first HARQ transmission 530A on the PCell 125A and the first HARQ transmission 532A on the SCell 126A in a similar manner as described above.

[0180] In some implementations, the first set can include a first BWP indicator indicating a first BWP on the PCell 125A, and the second set can include a second BWP indicator indicating a second BWP on the SCell 126A. The first and second BWP indicators can be set to the same value or different values. The UE 102 can transmit the HARQ transmission 530A on the first BWP according to the first BWP indicator. The UE 102 can transmit the HARQ transmission 532A on the second BWP according to the second BWP indicator. The base station 106A can receive the HARQ transmission 530A on the first BWP according to the first BWP indicator, and receive the HARQ transmission 532A on the second BWP according to the second BWP indicator. In other implementations, the UE 102 can use a single BWP indicator to indicate the first BWP on the PCell 125A and the second BWP on the SCell 126A, and include the single BWP indicator in the DCI1 of both the first HARQ transmission 530A and the first HARQ transmission 532A. The UE 102 can transmit the first HARQ transmission 530A on the first BWP using the single BWP indicator, and transmit the first HARQ transmission 532A. The base station 106A can receive the HARQ transmission 530A on the first BWP according to the first BWP indicator, and receive the HARQ transmission 532A on the second BWP according to the second BWP indicator.

[0181] In some scenarios and implementations, the UE 102 successfully obtains the first UL MAC PDU from the first HARQ transmission 530A according to the DCI3. In this case, the UE 102 transmits a HARQ ACK to the base station 106A on the PCell 125A to indicate the successful reception of the first UL MAC PDU. For example, the UE 102 can decode the first HARQ transmission 530A according to the DCI3 to obtain a transport block including the first UL MAC PDU, and the transport block passes the CRC check, such that the UE 102 successfully obtains the first UL MAC PDU from the transport block.

[0182] In some scenarios and implementations, the base station 106A successfully obtains the first UL MAC PDU from the first HARQ transmission 530A and the second UL MAC PDU from the first HARQ transmission 532A according to the DCI3. In this case, the base station 106A can send a DCI command to the UE 102 to schedule the UE 102 to transmit a HARQ transmission of the UL MAC PDU in a similar manner as described for the DCI3 and the first HARQ transmissions 324A and 326A. The DCI command can not include a carrier indicator. For example, the base station 106A can decode the first HARQ transmissions 530A and 532A according to the DCI3 to obtain transport blocks including the first UL MAC PDU and the second UL MAC PDU, respectively, and the transport blocks pass the CRC check, such that the base station 106A successfully obtains the first and second UL MAC PDU from the transport blocks.

[0183] In other scenarios and implementations, the base station 106A fails to obtain the second UL MAC PDU from the first HARQ transmission 532A according to the DCI3. For example, the base station 106A can decode the first HARQ transmission 532A according to the DCI3 to obtain a transport block and fail the CRC check for the transport block, such that the base station 106A is unable to obtain the second UL MAC PDU from the transport block. In response to the failure, the base station 106A can send 534A a fourth DCI command (DCI4) on the SCell 126A for a second HARQ transmission of the second UL MAC PDU on the SCell 126A. The UE 102 can then send 536A the second HARQ transmission of the second UL MAC PDU to the base station 106A on the SCell 126A. The base station 106A can combine the first HARQ transmission 532A and the second HARQ transmission 536A and decode the combination of the first HARQ transmission and the second HARQ transmission to obtain the second UL MAC PDU. The base station 106A can determine to perform the events 534A and 536A because the UE 102 does not support cross-carrier scheduling or the base station 106A does not enable cross-carrier scheduling for the UE 102. If the base station 106A enables cross-carrier scheduling for the UE 102, the base station 106A can send a DCI command on the SCell 126A for a second HARQ transmission of the second UL MAC PDU on the PCell 125A in a similar manner as described for the events 344A and 346A.

[0184] The DCI 4 can include a plurality of configuration parameters for the UE 102 to transmit the second HARQ transmission 536A. The plurality of configuration parameters can include a carrier indicator, a HARQ process number, a frequency domain resource assignment, a time domain resource assignment, a frequency hopping flag, an RV, an NDI, an MCS, a TPC command for PUSCH. The plurality of configuration parameters can also include some or all of other parameters such as an identifier of a DCI format, a BWP indicator, a first DL assignment index, a second DL assignment index, an SRS resource indicator, precoding information and number of layers, antenna ports, an SRS request, a CSI request, and / or a DMRS sequence initialization. In one implementation, if the base station 106A does not enable cross-carrier scheduling for the UE 102, the DCI 4 can not include the carrier indicator. In this implementation, the UE 102 can determine to transmit the second HARQ transmission of the second UL MAC PDU on the SCell 126A according to the DCI 4 because the UE 102 does not support cross-carrier scheduling or the base station 106A does not enable cross-carrier scheduling for the UE 102. In another implementation, if the base station 106A enables multi-cell scheduling for the UE 102, the DCI 4 includes the carrier indicator. In this implementation, the base station 106A can set the value of the carrier indicator to the value included in the multi-cell scheduling configuration. Accordingly, the UE 102 can determine to transmit the second HARQ transmission 536A on the SCell 126A according to the value of the carrier indicator. The carrier indicator in the DCI 4 and the carrier indicator in the DCI 3 can have the same value or different values.

[0185] In some implementations, the DCI 4 and the DCI 3 include the same HARQ process number (i.e., value) and the same NDI value for the first HARQ transmission 532A and the second HARQ transmission 536A, such that the UE 102 can determine from the HARQ process number and the NDI (value) in the DCI 4 that the second HARQ transmission 536A is a HARQ retransmission. The base station 106A can set the RV in the DCI 4 for the second HARQ transmission 536A to the same or different value as the RV in the DCI 3 for the first HARQ transmission 532A. The UE 102 generates the second HARQ transmission 536A according to the RV in the DCI 4. If the RV in the DCI 4 and the RV in the DCI 3 are different, the base station 106A can perform a HARQ operation (e.g., HARQ combining with incremental redundancy) to combine the first HARQ transmission 532A and the second HARQ transmission 536A to obtain the second UL MAC PDU. If the RV in the DCI 4 and the RV in the DCI 3 are the same, the base station 106A can perform a HARQ operation (e.g., HARQ chase combining) to combine the first HARQ transmission 532A and the second HARQ transmission 536A to obtain the second UL MAC PDU.

[0186] If the base station 106A successfully obtains the second UL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that includes the first UL MAC PDU and passes the CRC check, the base station 106A can send a DCI command to the UE 102 to schedule the UE 102 to send a HARQ transmission of the UL MAC PDU in a manner similar to that described for DCI1 and the first HARQ transmissions 518A and 520A. If the base station 106A fails to obtain the second UL MAC PDU from the HARQ operation, i.e., decodes the combination to obtain a transport block that fails the CRC check, the base station 106A can send an additional DCI to the UE 102 on the SCell 126A to instruct the UE 102 to send a HARQ retransmission of the second UL MAC PDU on the SCell 126A. The additional DCI can include the same HARQ process number as DCI4. The additional DCI can include the same NDI (value) for the second HARQ transmission 536A as DCI4 to indicate the HARQ retransmission. The additional DCI can include the same RV for the second HARQ transmission 536A as DCI4. Alternatively, the additional DCI can include a different RV for the HARQ retransmission than the RV for the second HARQ transmission 536A in DCI4. Similarly, the base station 106A can perform the HARQ operation to combine the HARQ retransmission with the first HARQ transmission 532A and the second HARQ transmission 536A according to the RV in the additional DCI to obtain the second UL MAC PDU in a manner similar to that described above.

[0187] In some scenarios and implementations, the base station 106A can also configure the UE 102 in DCI3 to send a first additional HARQ transmission of a first additional UL MAC PDU on the PCell 125A in a manner similar to that described for DCI5 in Figure 3A The base station 106A can include additional configuration parameters for the first additional HARQ transmission on the PCell 125A in DCI1, and the UE 102 can send the first additional HARQ transmission on the PCell 125A according to DCI3. If the base station 106A fails to obtain the first additional UL MAC PDU from the first additional HARQ transmission, the base station 106A can send a DCI command on the PCell 125A to instruct the UE 102 to send a second HARQ transmission of the first additional UL MAC PDU to the base station 106A on the PCell 125A. The description of DCI6 336A and the second HARQ transmission 338A on the PCell 125A can apply to a DCI command and a second additional HARQ transmission of a second additional UL MAC PDU on the SCell 126A.

[0188] In some scenarios and implementations, the base station 106A can also configure the UE 102 to transmit a first additional HARQ transmission of the second additional UL MAC PDU on the SCell 126A in DCI3 in a similar manner as described for DCI5 in Figure 3A The base station 106A can include additional configuration parameters for the first additional HARQ transmission in DCI3 on the SCell 126A, and the UE 102 can transmit the first additional HARQ transmission on the SCell 126A according to DCI3. The description of DCI5332A and the first HARQ transmission 334A on the PCell 125A can apply to DCI3 and the second additional HARQ transmission of the second additional UL MAC PDU on the SCell 126A. If the base station 106A fails to obtain the second additional UL MAC PDU from the first additional HARQ transmission, the base station 106A can configure the UE 102 to transmit a HARQ retransmission of the first additional UL MAC PDU on the PCell 125A and a HARQ retransmission of the second additional UL MAC PDU on the SCell 126A in a DCI command in a similar manner as described for DCI3 528A. The UE 102 can transmit the HARQ retransmission of the first additional UL MAC PDU on the PCell 125A and the HARQ retransmission of the second additional UL MAC PDU on the SCell 126A to the base station 106A in a similar manner as described for the first HARQ transmission 518A and the first HARQ transmission 520A. Figure 3A The base station 106A can configure the UE 102 to transmit a second additional HARQ transmission of the second additional UL MAC PDU on the PCell 125A in DCI4 in a similar manner as described for DCI6 in

[0189] If the base station 106A fails to obtain the first and second additional UL MAC PDUs from the first and second additional HARQ transmissions, respectively, the base station 106A can configure the UE 102 to transmit a HARQ retransmission of the first additional UL MAC PDU on the PCell 125A and a HARQ retransmission of the second additional UL MAC PDU on the SCell 126A in a DCI command in a similar manner as described for DCI3 528A. The UE 102 can transmit the HARQ retransmission of the first additional UL MAC PDU on the PCell 125A and the HARQ retransmission of the second additional UL MAC PDU on the SCell 126A to the base station 106A in a similar manner as described for the first HARQ transmission 518A and the first HARQ transmission 520A.

[0190] In some implementations, base station 106A uses the same DCI format or a different DCI format for DCI (e.g., DCI3, DCI4, additional DCI, etc.). For example, base station 106A may use an existing DCI format (e.g., DCI format 1_0, DCI format 1_1) or a new DCI format (e.g., DCI format 1_2, DCI format 1_3, etc.) for DCI3. In another example, base station 106A may use an existing DCI format (e.g., DCI format 1_0, DCI format 1_1) or a new DCI format (e.g., DCI format 1_2, DCI format 1_3, etc.) for DCI4.

[0191] In some scenarios, UE 102 in CA can be located in PCell 125A, SCell 126A, and SCell 127A ( Figure 5A (Not shown in the diagram) communicates with base station 106A. In one embodiment, base station 106A may enable multi-cell scheduling only for PCell 125A and SCell 126A, and not just for SCell 127A, as described above. In this embodiment, base station 106A may send a single DCI (e.g., DCI1) to UE 102, which indicates (i.e., schedules) two HARQ transmissions on PCell 125A and SCell 126A respectively in the manner described above. In order to schedule HARQ transmissions on SCell 127A, base station 106A can only send the DCI for HARQ transmissions on SCell 127A, unless base station 106A enables cross-carrier scheduling on the cell (i.e., PCell 125A or SCell 126A) to schedule HARQ transmissions for UE 102 on SCell 127A. In another implementation, in addition to enabling multi-cell scheduling using a single DCI on PCell 125A, base station 106A can also enable multi-cell scheduling on SCell 126A for both PCell 125A and SCell 126A (see [link to implementation]). Figure 5B In another implementation, base station 106A can use a single DCI on SCell 126A to enable multi-cell scheduling to schedule HARQ transmissions on SCell 127A.

[0192] In some implementations, the base station 106A can receive a UE capability IE (e.g., a UE-NR-Capability IE or a UE-MRDC-Capability IE) from the UE 102, another base station (e.g., the base station 104), or the core network 110 (e.g., the AMF 164) as described above. The UE capability IE includes UE capabilities of the UE 102, which indicate support for different protocol functions or features, mobility, and measurements for different protocol layers. The UE capability IE also includes a multi-cell scheduling capability, which indicates that the UE 102 supports multi-cell scheduling with single DCI. In one implementation, the UE 102 can indicate in the UE capability IE that it supports multi-cell scheduling with single DCI for specific CA band combinations. For example, in the UE capability IE, the UE 102 can indicate support for multi-cell scheduling with single DCI for at least one first CA band combination and indicate no support for multi-cell scheduling with single DCI for at least one second CA band combination. If the base station 106A configures CA for the UE 102 on a CA band combination of the at least one first CA band combination, the base station 106A can determine to enable multi-cell scheduling with single DCI for the UE 102. For example, the carrier frequency of the PCell 125A and the carrier frequency of the SCell 126A comply with the CA band combination. If the base station 106A configures CA for the UE 102 on a CA band combination of the at least one second CA band combination, the base station 106A can determine to not enable multi-cell scheduling with single DCI for the UE 102.

[0193] In another implementation, the UE 102 can indicate in the UE capability IE that it supports multi-cell scheduling with single DCI regardless of specific CA band combinations. In other words, if the UE 102 includes the multi-cell scheduling capability in the UE capability IE, the UE 102 supports multi-cell scheduling with single DCI for all CA band combinations for the RAT (e.g., NR) supported by the UE.

[0194] In some implementations, the base station 106A generates a PDCP PDU that includes the RRC reconfiguration message 308A, an RLC PDU that includes the PDCP PDU, and a MAC PDU that includes the RLC PDU. The base station 106A generates one or more HARQ transmissions of the MAC PDU and one or more DCI commands (DCI) for the HARQ transmissions. The base station 106A can transmit the DCI and the HARQ transmissions to the UE 102 on the PCell 125A. The UE 102 can receive the HARQ transmissions according to the DCI, obtain the MAC PDU from the HARQ transmissions, extract the RLC PDU from the MAC PDU, extract the PDCP PDU from the RLC PDU, and then extract the RRC reconfiguration message from the PDCP PDU.

[0195] In some implementations, the UE 102 generates a PDCP PDU that includes the RRC reconfiguration complete message 312A, an RLC PDU that includes the PDCP PDU, and a MAC PDU that includes the RLC PDU. The UE 102 can receive one or more DCI commands (DCI) for UL transmissions from the base station 106A on the PCell 125A and use the DCI to generate one or more HARQ transmissions of the MAC PDU. The UE 102 can transmit the HARQ transmissions to the base station 106A on the PCell 125A. The base station 106A can receive the HARQ transmissions according to the DCI, obtain the MAC PDU from the HARQ transmissions, extract the RLC PDU from the MAC PDU, extract the PDCP PDU from the RLC PDU, and then extract the RRC reconfiguration complete message from the PDCP PDU.

[0196] In some implementations, if the base station 106A is a gNB, the RRC reconfiguration and RRC reconfiguration complete messages are RRCReconfiguration and RRCReconfigurationComplete messages, respectively.

[0197] Reference is now made to Figure 5B Scenario 500B is generally similar to Figure 5A Scenario 500A, but here the base station 106A schedules the HARQ transmissions via a secondary cell instead of a primary cell as described in Scenario 500A. The differences between Figure 5A and Figure 5B are considered below. Like events are labeled with the same reference number, with a different letter appended to the reference number to more clearly distinguish between the scenarios.

[0198] According to the multi-cell scheduling configuration, the base station 106A transmits 517B, to the UE 102 via the SCell 126A, a first DCI order (DCI1) including multiple configuration parameters for a first HARQ transmission of a first DL MAC PDU on the PCell 125A and a first HARQ transmission of a second DL MAC PDU on the SCell 126A. Similar to events 518A and 520A, the base station 106A then transmits 518B, 520B, and then transmits the first and second DL MAC PDUs. In response to a HARQ NACK for the first DL MAC PDU, the base station 106A can transmit 524A a second DCI order (DCI2) on the PCell 125A for performing a second HARQ transmission of the second DL MAC PDU on the PCell 125A.

[0199] In the uplink direction, the base station 106A transmits 529B, to the UE 102 via the SCell 126A, a first DCI order (DCI1) including multiple configuration parameters for a first HARQ transmission of a first UL MAC PDU on the PCell 125A and a first HARQ transmission of a second UL MAC PDU on the SCell 126A. Similar to events 530A and 532A, the base station 106A then transmits 530B, 532B the first and second UL MAC PDUs. If the base station fails to receive the first UL MAC PDU, the base station 106A can transmit 535B a second DCI order (DCI2) on the PCell 125A for performing a second HARQ transmission of the second UL MAC PDU on the PCell 125A.

[0200] Figure 5C Scenario 500C is generally similar to Figure 5A Scenario 500A, but here the UE communicates 503C with the base station using CA before the base station configures the secondary cell as a scheduling cell. The differences between Figure 5A and Figure 5C are considered below. Similar events are labeled with the same reference number, with a different letter appended to the reference number to more clearly distinguish between the scenarios.

[0201] UE 102 initially communicates 503C data with base station 106A via PCell 125A and SCell 126A. Like the communications of event 502A discussed above, these communications can include UL and / or DL transmissions. After base station 106A determines 504C to configure cell 126A for multi-cell scheduling, base station 106A sends 509C an RRC reconfiguration message to UE 102 that includes a multi-cell scheduling configuration for cell 126A. Base station 106A can send 309C this message in SCell 126A.

[0202] Figure 5D Scenario 500D is generally similar to Figure 5B Scenario 500B, but here the UE communicates 503D with the base station using CA before the base station configures the secondary cell as a scheduling cell. The differences between Figure 5B and 5D are considered below. Similar events are labeled with the same reference number, with different letters appended to the reference number to more clearly distinguish between scenarios.

[0203] UE 102 initially communicates 503D data with base station 106A via PCell 125A and SCell 126A. After base station 106A determines 505D that it should configure cell 126A for multi-cell scheduling, base station 106A sends 509D an RRC reconfiguration message to UE 102 that includes a multi-cell scheduling configuration for cell 126A. Base station 106A can send 509D this message in SCell 126A. As in Figure 5B Scenario 500C, base station 106A sends 517D a CII message in SCell 126A.

[0204] Several example methods that can be implemented in a base station, a UE, or both are discussed next. For clarity, the examples below are discussed with specific reference to UE 102 and base station 106A. These methods can be implemented using processing hardware, such as one or more processors executing instructions stored on a non-transitory computer-readable medium.

[0205] First referring to Figure 6 , UE 102 (or another suitable UE) can implement example method 600 to transmit or receive the same data unit or signaling via multiple cells according to a HARQ scheme. At block 602, UE 102 communicates with a base station in a first cell and a second cell. At block 604, UE 102 enables multi-cell scheduling for the first and second cells, which can include cross-carrier scheduling. UE 102 can enable multi-cell scheduling on a secondary cell when the first cell is a primary cell and the second cell is a secondary cell.

[0206] At block 606, the UE 102 can receive a first DCI command on the first cell. Then, at block 608, the UE 102 can communicate a first HARQ transmission on the second cell in accordance with the first DCI command. The communication can include transmitting or receiving an information unit that can include data or signaling. The first HARQ transmission can occur within a first time instance (e.g., a slot).

[0207] At block 610, the UE 102 can receive a second DCI command on the second cell. Then, at block 612, the UE 102 can communicate a second HARQ transmission of the same information unit on the second cell in accordance with the second DCI command. The second HARQ transmission can occur within a second time instance (e.g., a slot).

[0208] Figure 7 An example method 700 is shown that a base station 106A can implement to transmit or receive the same data unit via multiple cells in accordance with a HARQ scheme. At block 702, the base station 106A communicates with a UE in a first cell and a second cell. At block 704, the base station enables multi-cell scheduling for the first and second cells, which can include cross-carrier scheduling. When the first cell is a primary cell and the second cell is a secondary cell, the base station 106A can enable multi-cell scheduling on the secondary cell.

[0209] At block 706, the base station 106A can transmit a first DCI command on the first cell. Then, at block 708, the base station 106A can communicate a first HARQ transmission on the second cell in accordance with the first DCI command. The communication can include transmitting or receiving a data unit. The first HARQ transmission can occur within a first time instance (e.g., a slot).

[0210] At block 710, the base station 106A can transmit a second DCI command on the second cell. Then, at block 712, the base station 106A can communicate a second HARQ transmission of the same data unit on the second cell in accordance with the second DCI command. The second HARQ transmission can occur within a second time instance (e.g., a slot).

[0211] Reference is now made to Figure 8 The base station 106A can implement an example method 800 to periodically transmit or receive a data unit or signaling via multiple cells in accordance with a HARQ scheme. For example, the base station 106A can implement the method 800 to support semi-persistent scheduling. At block 802, the base station 106A communicates with a UE in a first cell and a second cell. At block 804, the base station 106A enables multi-cell scheduling for the first and second cells, which can include cross-carrier scheduling. When the first cell is a primary cell and the second cell is a secondary cell, the base station 106A can enable multi-cell scheduling on the secondary cell.

[0212] At block 806, the base station 106A transmits a first DCI command on the first cell. However, unlike the first DCI of the above-described method, the first DCI at block 806 includes a configured grant that the UE 102 and the base station 106A can use for periodic transmissions.

[0213] At block 808, the base station 106A can periodically communicate a first HARQ transmission of the signaling on the second cell in accordance with the first DCI command. The communicating can include a transmission or reception of information units, which can include data or signaling.

[0214] At block 810, the base station 106A can transmit a second DCI command on the second cell. Unlike the second DCI of the above-described method, the second DCI at block 810 includes a command to release the configured grant. Thus, at block 812, the base station 106A stops the periodic communication of the HARQ transmission on the second cell in accordance with the second DCI.

[0215] Figure 9 An example method 900 is shown that a base station 106A can implement to transmit or receive the same signaling via multiple cells in accordance with a HARQ scheme. At block 902, the base station 106A communicates with a UE in a first cell and a second cell. At block 904, the base station enables multi-cell scheduling for the first and second cells, which can include cross-carrier scheduling. When the first cell is a primary cell and the second cell is a secondary cell, the base station 106A can enable multi-cell scheduling on the secondary cell.

[0216] At block 906, the base station 106A can transmit a first DCI command on the first cell. Then, at block 908, the base station 106A can receive a first HARQ transmission of the signaling, such as CSI or SRS, on, for example, the second cell in accordance with the first DCI command. The first HARQ transmission can occur within a first time instance (e.g., slot).

[0217] At block 910, the base station 106A can transmit a second DCI command on the second cell. Then, at block 912, the base station 106A can receive a second HARQ transmission of the signaling on the second cell in accordance with the second DCI command. The second HARQ transmission can occur within the first time instance (e.g., slot).

[0218] Figure 10An example method 1000 is shown that a base station 106A can implement to transmit DCI in one cell with an indication that a UE should switch BWPs in another cell. At block 1002, the base station 106A communicates with a UE in a first cell and a second cell. At block 1004, the base station enables multi-cell scheduling for the first and second cells, which can include cross-carrier scheduling. When the first cell is a primary cell and the second cell is a secondary cell, the base station 106A can enable multi-cell scheduling on the secondary cell.

[0219] At block 1006, the base station 106A can transmit a first DCI command to the UE on the first cell. The first DCI can include an indication that the UE 102 should switch from a first BWP on the second cell to a second BWP. For example, the base station 106A can determine that a certain BWP of the secondary cell is now in a dormant state and the UE 102 can no longer monitor that BWP.

[0220] At block 1008, the base station 106A can communicate with the UE 102 on the second BWP of the second cell in accordance with the first DCI. The communication can include receiving or transmitting information units, which can include data or signaling.

[0221] Next, at block 1010, the base station 106A can transmit a second DCI command to the UE on the second cell. The second DCI can include an indication that the UE 102 should switch from the second BWP on the second cell to a third BWP. Next, at block 1012, the base station 106A can communicate with the UE 102 on the third BWP of the second cell in accordance with the second DCI.

[0222] Referring now to Figure 11 , the base station 106A can implement an example method 1100 to determine whether the base station should transmit DCI in the same cell as the corresponding HARQ transmission depending on whether the transmission includes data or signaling and transmit the DCI command accordingly.

[0223] At block 1102, the base station 106A communicates with a UE in a first cell and a second cell. At block 1104, the base station enables multi-cell scheduling for the first and second cells, which can include cross-carrier scheduling. When the first cell is a primary cell and the second cell is a secondary cell, the base station 106A can enable multi-cell scheduling on the secondary cell.

[0224] At block 1106, the base station 106A can determine that a DCI command is available for transmission to the UE 102. The base station 106A can also determine that the DCI command can be sent on a primary cell or a secondary cell. At block 1108, the base station 106A determines whether the DCI command schedules a transmission of data (e.g., a PDU) or a non-data transmission (e.g., signaling such as SRS or CSI). When the base station 106A determines that the DCI command schedules data, flow proceeds to block 1110; otherwise, flow proceeds to block 1112.

[0225] At block 1110, the base station 106A sends the DCI command to the UE 102 on the first cell. Thus, when the DCI command schedules a transmission on the second cell, the base station 106A configures cross-carrier scheduling for the data units at block 1110. On the other hand, at block 1112, the base station 106A sends the DCI command to the UE 102 on the second cell. When the DCI command schedules a transmission on the second cell, the base station 106A thus configures same-carrier scheduling for the non-data transmission at block 1110.

[0226] Referring now to Figure 12 The UE 102 can implement the method 1200 to process HARQ transmissions received on multiple cells according to the same DCI. The method 1200 begins at block 1202, where the UE 102 communicates with the base station 106A in a first cell and a second cell. At block 1204, the UE 102 enables multi-cell scheduling with a single DCI.

[0227] At block 1206, the UE 102 receives a first DCI command on the first cell. Then, at block 1208, the UE 102 receives or transmits multiple HARQ transmissions on the first and second cells according to the first DCI.

[0228] In some cases, when the HARQ communication is a downlink transmission, at block 1210, the UE 102 can transmit a HARQ negative acknowledgement on the second cell for a HARQ transmission of the HARQ transmissions. The UE 102 can then receive a second DCI command on the second cell (block 1212) and receive a HARQ retransmission on the second cell according to the second DCI command (block 1214). When the HARQ communication is an uplink transmission, the UE 102 is not configured to receive a HARQ negative acknowledgement and can treat the second DCI command as an implicit indication of a failure of the first HARQ transmission. At block 1216, the UE 102 can decode a combination of the HARQ transmission and the HARQ retransmission to obtain a data unit or signaling when the HARQ transmission is a downlink transmission.

[0229] The base station 106A can implement Figure 13Method 1300 illustrates a method 1300 for receiving HARQ transmissions on multiple cells as a function of a same DCI. Method 1300 begins at block 1302, where base station 106A communicates with UE 102 in a first cell and a second cell. At block 1304, base station 106A enables multi-cell scheduling with a single DCI.

[0230] At block 1306, base station 106A transmits a first DCI command to UE 102 on the first cell. Then, at block 1308, base station 106A receives or transmits multiple HARQ transmissions on the first and second cells as a function of the first DCI.

[0231] In some cases, when the HARQ communications are downlink transmissions, at block 1310, base station 106A can receive a HARQ negative acknowledgement on the second cell for one of the HARQ transmissions. Base station 106A can then transmit a second DCI command on the second cell (block 1312) and transmit a HARQ retransmission on the second cell as a function of the second DCI command (block 1314). When the HARQ communications are uplink transmissions, base station 106A is not configured to transmit a HARQ negative acknowledgement and can transmit the second DCI command as an implicit indication of a first HARQ transmission failure. At block 1316, when the HARQ transmissions are uplink transmissions, the base station can decode a combination of the HARQ transmission and the HARQ retransmission to obtain a data unit or signaling.

[0232] Figure 14 An example method 1400 for selecting a cell for transmitting a DCI based on whether cross-carrier scheduling is enabled for a UE is shown, which can be implemented in base station 106A. More specifically, when UE 102 supports multi-cell scheduling that does not necessarily include cross-carrier scheduling, base station 106A can implement the method.

[0233] Method 1400 begins at block 1402, where base station 106A communicates with UE 102 in a first cell and a second cell. At block 1404, base station 106A enables multi-cell scheduling with a single DCI. Next, at block 1406, base station 106A transmits a first DCI command to UE 102 on the first cell. At block 1408, the base station transmits multiple information units on the first and second cells using a HARQ scheme and as a function of the first DCI command.

[0234] At block 1410, base station 106A receives a negative acknowledgement from UE 102 of a HARQ transmission that occurred on the second cell. Base station 106A can then generate a second DCI command in response to the HARQ negative acknowledgement (block 1412).

[0235] At block 1414, the base station 106A determines whether cross-carrier scheduling is enabled for the UE. When cross-carrier scheduling is enabled, flow proceeds to block 1416, where the base station 106A transmits a second DCI command to the UE 102 on the first cell. When cross-carrier scheduling is not enabled, flow proceeds to block 1418, where the base station 106A transmits the second DCI command to the UE 102 on the second cell. In either case, the second DCI command schedules a HARQ retransmission on the second cell. Accordingly, at block 1420, the base station 106A performs the HARQ retransmission on the second cell in accordance with the second DCI command.

[0236] Figure 15 is a flowchart of an example method 1500 that the base station 106A can implement to select a format for a DCI based on whether the base station 106A can transmit multiple PDUs on the same cell using MIMO or can transmit multiple PDUs on different cells using the same DCI.

[0237] Method 1500 begins at block 1502, where the base station 106A communicates with the UE 102 in a first cell and a second cell. At block 1504, the base station 106A enables multi-cell scheduling with a single DCI. At block 1506, the base station 106A determines whether it should transmit multiple PDUs to the UE on a single cell or multiple cells. The base station 106A can determine, for example, whether transmissions should occur on the same cell using MIMO techniques or should occur in multiple cells using multi-cell scheduling with a single DCI.

[0238] When the base station 106A selects to use a single cell, flow proceeds to block 1508, where the base station 106A generates a first DCI command for multiple HARQ transmissions of multiple PDUs using a certain (first) DCI format. More specifically, the first DCI format can specify that the base station 106A will transmit the multiple PDUs using MIMO. At block 1510, the base station 106A transmits the first DCI command on the first cell or the second cell. At block 1512, the base station 106A performs the multiple HARQ transmissions to the UE on the single cell in accordance with the first DCI command.

[0239] On the other hand, when the base station 106A selects to use multiple cells at block 1506, flow proceeds to block 1514, where the base station 106A generates a second DCI command for multiple HARQ transmissions of multiple PDUs using another (second) DCI format. More specifically, the second DCI format can specify that the base station 106A is to transmit the multiple PDUs on multiple cells. At block 1516, the base station 106A transmits the second DCI command on the first cell or the second cell. At block 1518, the base station 106A performs the multiple HARQ transmissions to the UE on the multiple cells according to the second DCI command.

[0240] For further clarity, Figure 16 An example method 1600 for communicating with another network device via multiple cells is shown, which can be implemented in the UE 102 or the base station 106A of Figure 1A or more generally, in a suitable UE or a suitable base station. At block 1602, the network device transmits a first control indicator, such as a DCI, between the first network device and the second network device in a first cell, such as for communicating at least a first information unit (e.g., a PDU or signaling) between the first network device and the second network device. See, e.g., the DCI1, DCI3, DCI5, or DCI7 of Figure 3A and Figure 3B the DCI1, DCI3, DCI5, or DCI7 of Figures 4A-4D the DCI1, DCI3, DCI5, or DCI7 of Figures 5A-5D the DCI1 or DCI3 of Figure 6 block 606 of Figure 7 block 706 of Figure 8 block 806 of Figure 9 block 906 of Figure 10 block 1006 of

[0241] At block 1604, the network device communicates the first information unit according to the first control indicator (e.g., Figure 3A the events 318A, 326A, 334A, and 342A of Figure 4A the events 418A, 426A, 434A, and 442A of Figure 5A the events 516A or 530A of

[0242] The network device then performs at least one of blocks 1606 and 1608.

[0243] At block 1606, the network device transmits a second control indicator related to the first information unit between the first network device and the second network device in a second cell. For example, the second control indicator can be for a retransmission of the first information unit (e.g., Figure 3A and Figure 3BDCI2, DCI4, DCI6, or DCI8 of the DCI2, DCI4, DCI6, or DCI8; Figures 4A-4D DCI2, DCI4, DCI6, or DCI8 of the DCI2, DCI4, DCI6, or DCI8); or stop periodic transmission (e.g., Figure 8 of block 808).

[0244] At block 1608, the network device communicates a second information unit (e.g., Figure 5A of event 520A or 532A).

[0245] The following description can apply to the above description.

[0246] A user device (e.g., UE 102) in which techniques of this disclosure can be implemented can be any suitable device capable of wireless communication, such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, another personal media device, a wearable device such as a smartwatch, a wireless hotspot, a femtocell, or a broadband router. Further, in some cases, a user device can be embedded in an electronic system, such as an audio head unit (audio head unit) or an advanced driver assistance system (ADAS) of a vehicle. Further, a user device can operate as an Internet of Things (IoT) device or a mobile internet device (MID). Depending on the type, a user device can include one or more general-purpose processors, computer-readable memory, a user interface, one or more network interfaces, one or more sensors, and the like.

[0247] Certain embodiments are described in this disclosure as including logic or a number of components or modules. Modules can be software modules (e.g., code, or machine-readable instructions stored on non-transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit capable of performing certain operations and can be configured or arranged in a certain manner. A hardware module can include dedicated circuitry or logic that is permanently configured to perform certain operations (e.g., as a special-purpose processor, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.). A hardware module can also include programmable logic or circuitry (e.g., as encompassed in a general- purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry, or in temporarily configured circuitry (e.g., configured by software) can be driven by cost and time considerations.

[0248] When implemented in software, the techniques can be provided as part of an operating system, a library used by multiple applications, a particular software application, etc. The software can be executed by one or more general-purpose processors or one or more special-purpose processors.

[0249] In reading the present disclosure, those skilled in the art will understand that, by virtue of the principles disclosed herein, additional and alternative structures and functional designs for handling mobility between base stations are contemplated. Accordingly, although a particular embodiment and applications have been shown and described, it is understood that the disclosed embodiment is not limited to the precise construction and components disclosed herein. Various modifications, changes and variations which will be apparent to those skilled in the art can be made in the arrangement, operation and details of the methods and apparatus disclosed herein without departing from the spirit and scope defined in the following claims.

[0250] The following list of examples reflects various embodiments that are explicitly contemplated by the present disclosure.

[0251] Example 1. A method in a base station for communicating via a user equipment (UE) via a first cell and a second cell, the method comprising: sending, by processing hardware, a first control indicator to the UE in the first cell, the first control indicator indicating resources for communicating at least a first information unit between the UE and the base station; communicating, by the processing hardware, the first information unit in accordance with the first control indicator; and performing, by the processing hardware, at least one of: (i) sending a second control indicator to the UE in the second cell related to the first information unit, or (ii) communicating, by the processing hardware, a second information unit in accordance with the first control indicator and in a different cell than the first information unit.

[0252] Example 2. The method of example 1, wherein the first control indicator schedules communication of the first information unit in the second cell.

[0253] Example 3. The method of example 1, wherein the first control indicator schedules communication of the first information unit in the first cell.

[0254] Example 4. The method of any of the preceding examples, wherein performing comprises option (i); the method further comprising: in response to determining, by the processing hardware, that communication of the first information unit failed, re-communicating the first information unit in accordance with the second control indicator.

[0255] Example 5. The method of example 4, wherein the communication of the first information unit comprises sending the first information unit to the UE; and the determining comprises receiving a negative acknowledgement from the UE of the sending.

[0256] Example 6. The method of example 4, wherein: the communication of the first information unit comprises receiving a transmission of the first information unit from the UE; and the determining comprises failing to obtain the first information unit from the transmission.

[0257] Example 7. The method of any of the preceding examples, wherein the communication of the first information unit is in compliance with a hybrid automatic repeat request (HARQ) protocol.

[0258] Example 8. The method of any of the preceding examples, wherein the base station operates as a secondary node (SN) to support dual connectivity at the UE.

[0259] Example 9. The method of example 8, further comprising transmitting, to the UE, a cross-carrier scheduling configuration and / or a multi-cell configuration directly via a radio interface prior to transmitting the first control indicator.

[0260] Example 10. The method of example 8, further comprising transmitting, to the UE, a cross-carrier scheduling configuration and / or a multi-cell configuration via a master node (MN) prior to transmitting the first control indicator.

[0261] Example 11. The method of example 1, wherein the communicating the first information unit comprises periodically communicating information in the second cell.

[0262] Example 12. The method of example 11, wherein the first control indicator comprises a configured grant.

[0263] Example 13. The method of example 12, wherein the second control indicator comprises a command to release the configured grant.

[0264] Example 14. The method of example 1, wherein the first cell is a primary cell; the second cell is a secondary cell; and the first control indicator schedules the communication of the first information unit in the primary cell and the communication of the second information unit in the secondary cell.

[0265] Example 15. The method of example 14, further comprising determining, by the processing hardware, that the communication of the second information unit failed; and transmitting, by the processing hardware to the UE in the second cell, a new control indicator for the communication of the second information unit again in the secondary cell.

[0266] Example 16. The method of example 1, wherein: the first cell is a secondary cell; the second cell is a primary cell; and the first control indicator schedules the communication of the first information unit in the primary cell and the communication of the second information unit in the secondary cell.

[0267] Example 17. The method of example 16, further comprising determining, by the processing hardware, that the communication of the first information unit failed; and transmitting, by the processing hardware to the UE in the second cell, a new control indicator for the communication of the first information unit again in the primary cell.

[0268] Example 18. The method of any of the preceding examples, further comprising transmitting (i) a cross-carrier scheduling configuration and / or a multi-cell configuration and (ii) a secondary cell configuration to the UE in a primary cell prior to transmitting the first control indicator, wherein one of the first cell and the second cell is the primary cell and the other of the first cell and the second cell is the secondary cell.

[0269] Example 19. The method of any of examples 1-17, further comprising transmitting a cross-carrier scheduling configuration and / or a multi-cell configuration to the UE in a secondary cell prior to transmitting the first control indicator, wherein one of the first cell and the second cell is the primary cell and the other of the first cell and the second cell is the secondary cell.

[0270] Example 20. The method of any of the preceding examples, wherein the information unit comprises a protocol data unit (PDU).

[0271] Example 21. The method of any of examples 1-19, wherein the information unit comprises signaling data.

[0272] Example 22. The method of example 21, wherein the signaling data comprises channel state information (CSI) or a sounding reference signal (SRS).

[0273] Example 23. The method of any of the preceding examples, wherein the control indicator is in accordance with a downlink control indicator (DCI) format.

[0274] Example 24. The method of any of examples 1-19, further comprising determining whether the first control indicator and the first unit should be transmitted in the same or different cells based on whether the first information unit comprises data or signaling.

[0275] Example 25. The method of any of the preceding examples, wherein the first control indicator indicates that the UE is to switch from a first bandwidth part (BWP) to a second BWP of the second cell for communicating the first information.

[0276] Example 26. The method of example 1, further comprising communicating a third information unit in the same cell as the first information unit at the same time as the first information unit in accordance with the control indicator.

[0277] Example 27. The method of example 25, wherein communicating the first information unit and the third information unit comprises using a multiple-input multiple-output (MIMO) scheme.

[0278] Example 28. The method of example 1, further comprising: in a first instance, selecting a first format of the control indicator in response to determining that the control indicator schedules transmission of the first information unit in only the first cell or the second cell; and in a second instance, selecting a second format of the control indicator in response to determining that the control indicator schedules transmission of the first information unit and a third information unit in the first cell or the second cell.

[0279] Example 29. A base station comprising processing hardware and configured to implement any of the preceding examples.

[0280] Example 30. A method in a user equipment for communicating via a base station via a first cell and a second cell, the method comprising: receiving, by the processing hardware, a first control indicator from the base station in the first cell for communicating at least a first information unit between the UE and the base station; communicating, by the processing hardware, the first information unit in accordance with the first control indicator; and performing, by the processing hardware, at least one of (i) receiving a second control indicator from the base station in the second cell related to the first information unit, or (ii) communicating, by the processing hardware, a second information unit in accordance with the first control indicator and in a different cell than the first information unit.

[0281] Example 31. The method of example 30, wherein the first control indicator schedules communication of the first information unit in the second cell.

[0282] Example 32. The method of example 30, wherein the first control indicator schedules communication of the first information unit in the first cell.

[0283] Example 33. The method of any of examples 30-32, further comprising re-communicating the first information unit in accordance with the second control indicator in response to determining, by the processing hardware, that communication of the first information unit failed.

[0284] Example 34. The method of example 33, wherein the communication of the first information unit comprises transmitting the first information unit to the base station; and the determining comprises receiving the second control indicator from the base station.

[0285] Example 35. The method of example 33, wherein the communication of the first information unit comprises receiving transmission of the first information unit from the base station; and the determining comprises failing to obtain the first information unit from the transmission; the method further comprising transmitting a negative acknowledgement of the first information unit to the base station.

[0286] Example 36. The method of any of examples 30-35, wherein the communication of the first information unit is in accordance with a hybrid automatic repeat request (HARQ) protocol.

[0287] Example 37. The method of example 30, further comprising: prior to receiving the first control indicator, receiving, directly via a radio interface, the cross-carrier scheduling configuration and / or the multi-cell configuration from the base station operating as a secondary node (SN).

[0288] Example 38. The method of example 30, further comprising, prior to receiving the first control indicator, receiving, via a master node (MN), the cross-carrier scheduling configuration and / or the multi-cell configuration from the base station operating as a SN.

[0289] Example 39. The method of example 30, wherein communicating the first information unit comprises periodically receiving the first information unit in the second cell.

[0290] Example 40. The method of example 39, wherein the first control indicator comprises a configured grant.

[0291] Example 41. The method of example 39, wherein the second control indicator comprises a command to release the configured grant.

[0292] Example 42. The method of example 30, wherein: the first cell is a master cell; the second cell is a secondary cell; and the first control indicator schedules communication of the first information unit in the master cell and communication of the second information unit in the secondary cell.

[0293] Example 43. The method of example 42, further comprising: determining, by the processing hardware, that the communication of the second information unit failed; receiving, by the processing hardware, a new control indicator from the base station in the second cell for communicating the second information unit again in the secondary cell.

[0294] Example 44. The method of example 30, wherein: the first cell is a secondary cell; the second cell is a master cell; and the first control indicator schedules communication of the first information unit in the master cell and communication of the second information unit in the secondary cell.

[0295] Example 45. The method of example 44, further comprising: determining, by the processing hardware, that the communication of the first information unit failed; receiving, by the processing hardware, a new control indicator from the base station in the second cell for communicating the first information unit again in the master cell.

[0296] Example 46. The method of any of examples 30-44, further comprising: prior to receiving the first control indicator, receiving, in the master cell from the base station, (i) the cross-carrier scheduling configuration and / or the multi-cell configuration and (ii) a secondary cell configuration, wherein one of the first cell and the second cell is the master cell and the other of the first cell and the second cell is the secondary cell.

[0297] Example 47. The method of any of Examples 30-44, further comprising: prior to receiving the first control indicator, receiving a cross-carrier scheduling configuration and / or a multi-cell configuration from the base station in the secondary cell, wherein one of the first cell and the second cell is a primary cell and the other of the first cell and the second cell is a secondary cell.

[0298] Example 49. The method of any of Examples 30-47, wherein the information unit comprises a PDU.

[0299] Example 50. The method of any of Examples 30-47, wherein the information unit comprises signaling data.

[0300] Example 51. The method of any of Example 50, wherein the signaling data comprises CSI or SRS.

[0301] Example 52. The method of any of Examples 30-50, wherein the control indicator is in accordance with a DCI format.

[0302] Example 53. The method of any of Examples 30-51, wherein the first control indicator indicates that the UE is to switch from a first bandwidth part (BWP) to a second BWP of the second cell for communicating the first information.

[0303] Example 54. The method of Example 30, further comprising communicating a third information unit in the same cell as the first information unit at the same time according to the control indicator.

[0304] Example 55. The method of Example 53, wherein communicating the first information unit and the third information unit comprises using a MIMO scheme.

[0305] Example 56. A UE comprising processing hardware and configured to implement any of Examples 30-54.

Claims

1. A method in a base station of communicating with a user equipment (UE) via a primary cell (PCell) and a secondary cell (SCell), the method comprising: sending, by the base station, a control indicator to the UE in the SCell, the control indicator indicating resources for communicating a protocol data unit (PDU) from the UE to the base station on a physical uplink shared channel (PUSCH) in the PCell; and receiving, by the base station, the PDU in the PCell in accordance with the control indicator. The sending also uses a physical downlink control channel (PDCCH) of the SCell.

2. The method of claim 1, wherein, 3. The method of claim 1 or 2, the method further comprising: determining, by the base station, a failure of the communication of the PDU; and in response to the determining, sending, to the UE in the PCell, a new control indicator for re-communicating the PDU in the PCell. The communication of the PDU is in accordance with a hybrid automatic repeat request (HARQ) protocol.

5. The method of claim 1 or 2, further comprising:

4. The method of claim 1 or 2, wherein, communicating, by the base station, a second PDU in the SCell in accordance with the control indicator.

6. The method of claim 1 or 2, further comprising: sending, to the UE in the PCell, a cross-carrier scheduling configuration and / or a multi-cell configuration prior to sending the control indicator.

7. The method of claim 1 or 2, wherein: the base station operates as a secondary node (SN) to support dual connectivity at the UE; the method further comprises: sending, to the UE, a cross-carrier scheduling configuration and / or a multi-cell configuration directly via a radio interface or via a master node (MN) prior to sending the control indicator.

8. The method of claim 1 or 2, further comprising: in response to determining that the PDU includes data, determining that the control indicator and the PDU should be sent in different cells. The control indicator indicates that the UE is to switch from a first bandwidth part (BWP) of the PCell to a second BWP for communicating the PDU.

10. A method in a user equipment (UE) of communicating with a base station via a primary cell (PCell) and a secondary cell (SCell), the method comprising:

9. The method of claim 1 or 2, wherein, receiving, by the UE, a control indicator from the base station in the SCell, the control indicator indicating resources for sending a protocol data unit (PDU) from the UE to the base station on a physical uplink shared channel (PUSCH) in the PCell; and communicating, by the UE, the PDU in the PCell in accordance with the control indicator.

11. The method of claim 10, further comprising: receiving, by the UE and in the PCell, a new control indicator indicating resources for communicating the PDU; and in response to determining, by the UE, a failure of the communication of the PDU in accordance with the control indicator, re-communicating the PDU in the PCell in accordance with the new control indicator.

12. The method of claim 10 or 11, further comprising: communicating, by the UE, a second PDU in the SCell in accordance with the control indicator.

13. The method of claim 10 or 11, further comprising: ​ ​ ​ ​ receiving, from the base station, a cross-carrier scheduling configuration and / or a multi-cell configuration in the PCell prior to receiving the control indicator.

14. The method of claim 10 or 11, wherein, the control indicator indicates that the UE is to switch from a first bandwidth part (BWP) of the PCell to a second BWP for communicating the PDU.

15. An apparatus comprising processing hardware configured to implement any of the methods of claims 1-9.

16. A user equipment (UE) comprising processing hardware configured to implement any of the methods of claims 10-14.

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