Method and user equipment for cross-carrier scheduling from secondary cell to primary cell

This application claims priority under 35 U.S.C. § 119 from U.S. Provisional Application No. 63/171,129, entitled “Scheduling behaviors and BD/CCE limit determination for Cross-Carrier Scheduling from SCell to PCell/PSCell,” filed on Apr. 6, 2021; U.S. Provisional Application No. 63/230,130, entitled “BD/CCE limit determination and PDCCH overbooking/dropping behaviors of USS sets for Cross-Carrier Scheduling from sSCell to P(S)Cell,” filed on Aug. 6, 2021; and U.S. Provisional Application No. 63/248,592, entitled “BD/CCE limit formula determination and PDCCH overbooking/dropping behaviors of USS/CSS sets for Cross-Carrier Scheduling from sSCell to P(S)Cell,” filed on Sep. 27, 2021, the subject matter of which is incorporated herein by reference.

The disclosed embodiments relate generally to wireless communication, and, more particularly, to method and apparatus for cross-carrier scheduling from secondary cell to primary cell.

In conventional network of 3rd generation partnership project (3GPP) 5G new radio (NR), as the number of NR devices in a network increases, there may not be enough NR physical downlink control channel (PDCCH) scheduling resources on NR primary cell (PCell) in the shared carriers. Therefore, cross-carrier scheduling (CCS) of scheduling PCell by a corresponding secondary cell (SCell) is developed. However, detail of the procedure of scheduling PCell by the corresponding SCell has not been discussed yet.

Method and user equipment (UE) are provided for scheduling for cross-carrier scheduling (CCS) from secondary cell (SCell) to primary cell (PCell). In particular, a UE can connect to a PCell and a SCell. A CCS is configured between the PCell and the SCell. According to a UE type, the UE can monitor physical downlink control channels (PDCCHs) from both the PCell and the SCell in a same slot when the UE is a first type UE, or ignore the PDCCHs from the SCell in the same slot when the UE is a second type UE.

Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.

The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.

FIG. 1 illustrates an exemplary 5G new radio network supporting scheduling for cross-carrier scheduling (CCS) from secondary cell (SCell) to primary cell (PCell) in accordance with embodiments of the current invention. The base stations of the two cells can be either co-located or non-co-located.

FIG. 2 is a simplified block diagram of the cell and the UE in accordance with embodiments of the current invention.

FIG. 3 illustrates one example of cell slot(s) in accordance with embodiments of the current invention.

FIG. 4 illustrates one example of cell slot(s) in accordance with embodiments of the current invention.

FIG. 5 illustrates one example of cell slot(s) in accordance with embodiments of the current invention.

FIG. 6 is a flow chart of a method of scheduling for CCS from SCell to PCell in accordance with embodiments of the current invention.

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

FIG. 1 illustrates an exemplary 5G new radio (NR) network 100 supporting cross-carrier scheduling (CCS) from secondary cell (SCell) to primary cell (PCell) in accordance with aspects of the current invention. The 5G NR network 100 includes a user equipment (UE) 110 communicatively connected to a PCell 121 served by base station 120 and a SCell 123 served by base station 130 . It should be noted that the PCell 121 may include general primary cell or primary cell of a secondary cell group (i.e., PSCell). In some embodiments, base station 120 of the PCell 121 and base station 130 of the SCell 123 may be either co-located or non-co-located.

The PCell 121 and the SCell 123 may provide radio access using a Radio Access Technology (RAT) (e.g., the 5G NR technology). The UE 110 may be a smart phone, a wearable device, an Internet of Things (IoT) device, and a tablet, etc. Alternatively, UE 110 may be a Notebook (NB) or Personal Computer (PC) inserted or installed with a data card which includes a modem and RF transceiver(s) to provide the functionality of wireless communication.

The PCell 121 may provide communication coverage for a geographic coverage area in which communications with the UE 110 is supported via a communication link 101 . The SCell 123 may provide communication coverage for a geographic coverage area in which communications with the UE 110 is supported via a communication link 103 . The communication links 101 and 103 shown in the 5G NR network 100 may respectively include uplink (UL) transmissions from the UE 110 to the cells 121 / 123 (e.g., on the Physical Uplink Control Channel (PUCCH) or Physical Uplink Shared Channel (PUSCH)) or downlink (DL) transmissions from the cells 121 / 123 to the UE 110 (e.g., on the Physical Downlink Control Channel (PDCCH) or Physical Downlink Shared Channel (PDSCH)). The PCell 121 and the SCell 123 may communicate with each other via a communication link 122 .

In the network 100 , CCS from the SCell 123 to the PCell is configured. In particular, when CCS from the SCell 123 to the PCell 121 is configured, some PDCCHs of the PCell 121 may be re-allocated to the SCell 123 . In other words, these allocated PDCCHs on the SCell 123 may impose control to the PCell 121 .

FIG. 2 is a simplified block diagram of the PCell 121 /SCell 123 (the PCell 121 or the SCell 123 ) and the UE 110 in accordance with embodiments of the present invention. For the PCell 121 /SCell 123 , an antenna 197 transmits and receives radio signal. A radio frequency (RF) transceiver module 196 , coupled with the antenna, receives RF signals from the antenna, converts them to baseband signals and sends them to processor 193 . RF transceiver 196 also converts received baseband signals from the processor 193 , converts them to RF signals, and sends out to antenna 197 . Processor 193 processes the received baseband signals and invokes different functional modules and circuits to perform features in the PCell 121 /SCell 123 . Memory 192 stores program instructions and data 190 to control the operations of the PCell 121 /SCell 123 .

Similarly, for the UE 110 , antenna 177 transmits and receives RF signals. RF transceiver module 176 , coupled with the antenna, receives RF signals from the antenna, converts them to baseband signals and sends them to processor 173 . The RF transceiver 176 also converts received baseband signals from the processor 173 , converts them to RF signals, and sends out to antenna 177 . Processor 173 processes the received baseband signals and invokes different functional modules and circuits to perform features in the UE 110 . Memory 172 stores program instructions and data 170 to control the operations of the UE 110 .

The PCell 121 /SCell 123 and the UE 110 also include several functional modules and circuits that can be implemented and configured to perform embodiments of the present invention. In the example of FIG. 2 , the PCell 121 /SCell 123 includes a set of control functional modules and circuit 180 . Scheduling circuit 182 handles CCS from the SCell 123 to the PCell 121 and associated network parameters for the UE 110 . Configuration and control circuit 181 provides different parameters to configure and control the UE 110 . The UE 110 includes a set of control functional modules and circuit 160 . Scheduling circuit 162 handles CCS from the SCell 123 to the PCell 121 and associated network parameters. Configuration and control circuit 161 handles configuration and control parameters from the PCell 121 /SCell 123 .

Note that the different functional modules and circuits can be implemented and configured by software, firmware, hardware, and any combination thereof. The function modules and circuits, when executed by the processors 193 and 173 (e.g., via executing program codes 190 and 170 ), allow the PCell 121 /SCell 123 and the UE 110 to perform embodiments of the present invention.

In some embodiments, the UE 110 may: (1) monitor PDCCHs from both the PCell 121 and the SCell 123 in a same slot when the UE 110 is a first type UE (e.g., an advanced UE supporting CCS from SCell to PCell); or (2) ignore the PDCCHs from the SCell 123 in the same slot when the UE 110 is a second type UE (e.g., a legacy UE that does not support CCS from SCell to PCell).

FIG. 3 illustrates one example of cell slot(s) in accordance with one novel aspect. In this example, sub-carrier spacing (SCS) of the PCell 121 is 15 kHz, SCS of the SCell 123 is 30 kHz and the UE 110 is the second type UE. Because the UE 110 is the second type UE (e.g., a legacy UE), the UE 110 may not expect to monitor PDCCHs from both the PCell 121 and the SCell 123 in the same slot for scheduling PDSCHs of the PCell 121 . Therefore, the UE 110 only monitors the PDCCHs for self-scheduling from the PCell 121 and ignores the PDCCH for CCS from the SCell 123 in the same slot (i.e., the slot # 0 ).

In some embodiments, at least one common search space (CSS) set (e.g., Type 0/0A/1/2 CSS set) on the PCell 121 may be configured to overlap with at least one UE specific search space (USS) set, which is for scheduling the PCell 121 , on the SCell 123 . The UE 110 may drop the at least on USS set, which is for scheduling the PCell 121 , on the SCell 123 .

FIG. 4 illustrates one example of cell slot(s) in accordance with one novel aspect. In this example, SCS of the PCell 121 is 15 kHz, SCS of the SCell 123 is 30 kHz and the UE 110 is the first type UE. Because the UE 110 is the first type UE (e.g., an advanced UE supporting CCS from SCell to PCell), the UE 110 may monitor PDCCHs from both the PCell 121 and the SCell 123 in the same slot for scheduling PDSCHs of the PCell 121 . Therefore, the UE 110 monitors the PDCCHs for self-scheduling from the PCell 121 and monitors the PDCCH for CCS from the SCell 123 in the same slot (i.e., the slot # 0 ).

More specifically, on the PCell 121 , the UE 110 monitors at most α×X number of PDCCH blind detection candidates per PCell slot. On the SCell 123 , the UE 110 monitors at most β×X number of PDCCH blind detection candidates per PCell slot.

In some embodiments, α+β=1. In some embodiments, α, β or both may be configured in a radio resource control (RRC) configuration transmitted from the PCell 121 to the UE 110 . For example, α can be configured between 0 and 1.

In some embodiments, X may be min(M PDCCH max,slot,μ , M PDCCH total,slot,μ ) while μ is the SCS (e.g., 15 kHz) of the PCell 121 . M PDCCH max,slot,μ is the maximum number of monitored PDCCH candidates per slot on the PCell 121 . M PDCCH total,slot,μ may be └N cells cap ×M PDCCH max,slot,μ ×N cells DL,μ /Σ j=0 3 N cells DL,j ┘ while N cells cap is a number of cell that the UE 110 is capable of connecting to, and N cells DL,j is a number of DL cell with an SCS j that the UE 110 is configured.

In some embodiments, the α×X number of PDCCH blind detection candidates on the PCell 121 may be configured for an overbooking procedure of PDCCH. In particular, the maximum number of PDCCH blind detection candidates used for overbooking procedure may not exceed α×X.

In some embodiments, at most α×X number of PDCCH blind detection candidates may be monitored. For example, for CCS from the SCell 123 to PCell 121 , a number M S uss of counted PDCCH candidates for monitoring for USS set S uss may be at most α×X.

FIG. 5 illustrates one example of cell slot(s) in accordance with one novel aspect. In this example, SCS of the PCell 121 is 15 kHz, SCS of the SCell 123 is 30 kHz and the UE 110 is the first type UE. Because the UE 110 is the first type UE (e.g., an advanced UE supporting CCS from SCell to PCell), the UE 110 may monitor PDCCHs from both the PCell 121 and the SCell 123 in the same slot for the PCell 121 . Therefore, the UE 110 monitors the PDCCHs for self-scheduling from the PCell 121 and monitors the PDCCH for CCS from the SCell 123 in the same slot (i.e., the slot # 0 ). In these embodiments, the UE 110 monitors the PDCCHs for self-scheduling from the SCell 123 .

More specifically, on the PCell 121 , the UE 110 monitors at most α×X number of PDCCH blind detection candidates per PCell slot. On the SCell 123 , the UE 110 monitors: (1) at most Y number of PDCCH blind detection candidates per SCell slot; and (2) at most β×X number of PDCCH blind detection candidates per PCell slot. In some embodiments, α+β=1.

In some embodiments, X may be min (M PDCCH max,slot,μ , M PDCCH total,slot,μ ) while μ is the SCS (e.g., 15 kHz) of the PCell 121 . M PDCCH max,slot,μ is the maximum number of monitored PDCCH candidates per slot on the PCell 121 . M PDCCH total,slot,μ may be └N cells cap ×M PDCCH max,slot,μ ×N cells DL,μ /Σ j=0 3 N cells DL,j ┘ while N cells cap is a number of cell that the UE 110 is capable of connecting to, and N cells DL,j is a number of DL cell with an SCS j that the UE 110 is configured.

In some embodiments, Y is min(M PDCCH max,slot,μ1 , M PDCCH total,slot,μ1 ) or M PDCCH max,slot,μ1 while μ1 is the SCS (e.g., 30 kHz) of the SCell 123 . M PDCCH max,slot,μ1 is maximum number of monitored PDCCH candidates per slot on the SCell 123 . M PDCCH total,slot,μ1 may be └N cells cap ×M PDCCH max,slot,μ1 ×N cells DL,μ1 /Σ j=0 3 N cells DL,j ┘ while N cells cap is a number of cell that the UE 110 is capable of connecting to, and N cells DL,j is a number of DL cell with an SCS j that the UE 110 is configured.

In these embodiments, M PDCCH total,slot,μ may be scaled by applying a first weight and M PDCCH total,slot,μ1 may be scaled by applying a second weight. The sum of the first weight and the second weight may be 1. For example, the first weight is 1 and the second weight is 0.

It should be noted that M PDCCH max,slot,μ or M PDCCH max,slot,μ1 mentioned above may be defined as the below table of the 3GPP specification:

In some embodiments, some downlink control information (DCI) of PDCCH should be transmitted between the UE 110 and the PCell 121 . Specifically, DCI format 2_5 (used for integrated access and backhaul control) or DCI format 2_6 (wake-up signal which is used outside active time) needs to be transmitted from the PCell 121 to the UE 110 . The UE may receive/monitor DCI format 2_5 or DCI format 2_6 from the PCell 121 only.

FIG. 6 is a flow chart of a method of scheduling for CCS from SCell to PCell from UE perspective in a 5G/NR network in accordance with one novel aspect. In step 601 , a UE connects to a PCell and a SCell. CCS is configured between the PCell and the SCell. In step 602 , the UE monitors PDCCHs from both the PCell and the SCell in a same slot when the UE is a first type UE, or ignores the PDCCHs from the SCell in the same slot when the UE is a second type UE. In some embodiments, the first type UE may be an advanced UE supporting CCS from SCell to PCell, and the second type UE may be a legacy UE.

In some embodiments, when the UE is the second type UE and at least one CSS set on the PCell is configured to overlap with at least one USS set, which is for scheduling the PCell, on the SCell, the step 602 may further include dropping the at least on USS set, which is for scheduling the PCell, on the SCell.

In some embodiments, when the UE is the first type UE, the step 602 may further include: (1) monitoring at most α×X number of PDCCH blind detection candidates per PCell slot on the PCell; and (2) monitoring at most β×X number of PDCCH blind detection candidates per PCell slot on the SCell.

In some embodiments, α+β=1. In some embodiments, α, β or both may be configured in an RRC configuration transmitted from the PCell 121 to the UE 110 . For example, α can be configured between 0 and 1.

In some embodiments, X may be min (M PDCCH max,slot,μ , M PDCCH total,slot,μ ) while μ is the SCS (e.g., 15 kHz) of the PCell. M PDCCH max,slot,μ is the maximum number of monitored PDCCH candidates per slot on the PCell. M PDCCH total,slot,μ may be └N cells cap ×M PDCCH max,slot,μ ×N cells DL,μ /Σ j=0 3 N cells DL,j ┘ while N cells cap is a number of cell that the UE is capable of connecting to, and N cells DL,j is a number of DL cell with an SCS j that the UE is configured.

In some embodiments, the α×X number of PDCCH blind detection candidates on the PCell may be configured for an overbooking procedure of PDCCH. In particular, the maximum number of PDCCH blind detection candidates used for overbooking procedure may not exceed α×X.

In some embodiments, at most α×X number of PDCCH blind detection candidates may be monitored. For example, for CCS from the SCell to PCell, a number M S uss of counted PDCCH candidates for monitoring for USS set S uss may be at most α×X.

In some embodiments, when the UE is the first type UE, the step 602 may further include: monitor at most Y number of PDCCH blind detection candidates per SCell slot on the SCell.

In some embodiments, Y is min(M PDCCH max,slot,μ1 , N PDCCH total,slot,μ1 ) or M PDCCH max,slot,μ1 while μ1 is the SCS (e.g., 30 kHz) of the SCell. M PDCCH max,slot,μ1 is maximum number of monitored PDCCH candidates per slot on the SCell. M PDCCH total,slot,μ1 may be └N cells cap ×M PDCCH max,slot,μ1 ×N cells DL,μ1 /Σ j=0 3 N cells DL,j ┘ while N cells cap is a number of cell that the UE is capable of connecting to, and N cells DL,j is a number of DL cell with an SCS j that the UE is configured.

In these embodiments, M PDCCH total,slot,μ may be scaled by applying a first weight and M PDCCH total,slot,μ1 may be scaled by applying a second weight. The sum of the first weight and the second weight may be 1. For example, the first weight is 1 and the second weight is 0.

Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.