Patent Publication Number: US-2022225398-A1

Title: Transmission mode switching method in unlicensed controlled environments

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to U.S. Provisional Patent Application No. 63/136,652 filed on Jan. 13, 2021, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates to a transmission mode switching method, in particular to a transmission mode switching method in unlicensed spectrum control environments (UCE). 
     2. Description of the Prior Arts 
     In the fifth generation (5G) communication technology standard specifications, there are at least two transmission modes for a user equipment (UE) to transmit uplink radio signals to a next generation Node B (gNB). One of the transmission modes is the ultra-reliable and low latency communications configured grant mode (URLLC CG mode), and the other one of the transmission modes is the new radio unlicensed configured grant mode (NR-U CG mode). 
     URLLC CG mode is used in the licensed spectrum to solve the latency problem when the communication quality of the radio channel is good. The NR-U CG mode is used in the unlicensed spectrum to solve the reliability problem when the communication quality of the radio channel is bad. 
     However, the communication quality of the radio channel is constantly changing in unlicensed controlled environments (UCE). For example, unpredictable noise interference often decreases the communication quality of the radio channel. When there is no noise interference, the radio channel can maintain good communication quality. Therefore, if only a single transmission mode is used, it is easy to cause excessive latency or poor transmission reliability. 
     For example, if the UE transmits uplink radio signals to the gNB by the NR-U CG mode, when the communication quality of the radio channel is good without noise interference, the NR-U CG mode can maintain higher reliability but increase the latency. 
     If the UE transmits uplink radio signals to the gNB by the URLLC CG mode, when the communication quality of the radio channel becomes bad with noise interference, the URLLC CG mode can decrease the latency, but it can also reduce the reliability. 
     Therefore, the existing transmission method for the UE to transmit the uplink radio signals to the gNB still needs to be further improved. 
     SUMMARY 
     In view of the above problems, the present disclosure provides a transmission mode switching method in unlicensed spectrum control environments. In environments where the communication quality of the radio channel may change, a user equipment (UE) automatically switches the transmission mode of transmitting uplink radio signals to a next generation Node B (gNB) based on the communication quality of the radio channel, thereby improving spectrum usage efficiency in unlicensed spectrum control environments (UCE). 
     A transmission mode switching method in the UCE is executed by the UE, and the transmission mode switching method includes steps of: transmitting a first data to a next generation Node B (gNB); determining whether a dynamic grant signal transmitted by the gNB is received; when the dynamic grant signal is received, triggering a first trigger unit and determining whether the first trigger unit satisfies a first condition; when the first trigger unit satisfies the first condition, configuring a configured grant retransmission timer, switching to a first configured grant transmission mode, and transmitting a first retransmission data to the gNB; when the first trigger unit does not satisfy the first condition, transmitting the first retransmission data to the gNB; and when the dynamic grant signal is not received, resetting the first trigger unit. 
     When the gNB receives a data from the UE, the gNB decodes the data. When the gNB cannot successfully decode the data, the gNB generates a dynamic grant (DG) signal and sends the DG signal to the UE. Therefore, when the UE receives the DG signal, it means that the gNB cannot successfully decode the data. That is, the UE does not successfully transmit the data to the gNB. At this time, the UE triggers the first trigger unit and determines whether the first trigger unit satisfies the first condition. When the UE determines that the first trigger unit satisfies the first condition, it means that the UE fails to transmit data to the gNB many times. Therefore, the communication quality of the current radio channel is determined to be bad, which causes the UE to fail to send data to the gNB many times. Therefore, when the first trigger unit satisfies the first condition, the UE switches to the first CG transmission mode, thereby improving the reliability of data transmission by the first CG transmission mode. 
     For example, the first CG transmission mode may be an NR-U CG mode used in an unlicensed spectrum. Therefore, when the communication quality is bad, the reliability of data transmission can be improved by the first CG transmission mode. 
     The transmission mode switching method in unlicensed spectrum control environments, executed by a UE, includes steps of: transmitting a third data to a gNB; resetting and starting a configured grant retransmission timer; determining whether the configured grant retransmission timer times out; when the configured grant retransmission timer times out, resetting a second trigger unit, and transmitting a second retransmission data to the gNB; when the configured grant retransmission timer does not time out, determining whether a downlink feedback information signal transmitted by the gNB is received; when receiving the downlink feedback information signal, determining whether the downlink feedback information signal is successfully decoded; when the downlink feedback information signal is successfully decoded, determining whether the downlink feedback information signal contains an acknowledgment signal; when the downlink feedback information signal includes the acknowledgment signal, triggering the second trigger unit, and determining whether the second trigger unit satisfies a second condition; and when the second trigger unit satisfies the second condition, deconfiguring the configured grant retransmission timer, and switching to a second configured grant transmission mode. 
     When the gNB can successfully decode the data transmitted by the UE, the gNB generates a downlink feedback information (DFI) signal and sends the DFI signal to the UE. Therefore, when the UE can receive the DFI signal, it means that the gNB can successfully decode the data, that is, the UE successfully transmits the data to the gNB. At this time, the UE further decodes the DFI signal and confirms whether the DFI signal contains an ACK signal. When the DFI signal contains the ACK signal, the UE triggers the second trigger unit and determines whether the second trigger unit satisfies the second condition. And when the UE determines that the second trigger unit satisfies the second condition, it means that the UE successfully transmits data to the gNB many times. Then it can be determined that the communication quality of the current radio channel should be better, so the UE can successfully transmit data to the gNB many times. In this way, when the second trigger unit satisfies the second condition, the UE switches to the second CG transmission mode, and the latency of data transmission can be decreased by the second CG transmission mode. 
     For example, the second CG transmission mode may be a URLLC CG mode. Therefore, when the communication quality is good, the latency of data transmission can be decreased by the second CG transmission mode. 
     In summary, the present disclosure can automatically switch the current CG transmission mode based on the communication quality of the radio channel. When the communication quality of the radio channel is good, the second CG transmission mode is automatically used. And when the communication quality of the radio channel is bad, the first CG transmission mode is used automatically. In this way, when the communication quality is good, the second CG transmission mode can be used to effectively decrease latency of transmission, and when the communication quality is bad, the first CG transmission mode can be used to improve the reliability, thereby improving spectrum usage efficiency in UCE 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic flowchart of a first embodiment of the transmission mode switching method in unlicensed spectrum control environments of the present disclosure. 
         FIG. 1B  is a block diagram of a UE and a gNB. 
         FIG. 2  is a schematic flowchart of a second embodiment of the transmission mode switching method in unlicensed spectrum control environments of the present disclosure. 
         FIG. 3  is a schematic flowchart of a third embodiment of the transmission mode switching method in unlicensed spectrum control environments of the present disclosure. 
         FIG. 4  is a schematic flowchart of a fourth embodiment of the transmission mode switching method in unlicensed spectrum control environments of the present disclosure. 
         FIG. 5  is a schematic flowchart of a fifth embodiment of the transmission mode switching method in unlicensed spectrum control environments of the present disclosure. 
         FIG. 6  is a schematic flowchart of a sixth embodiment of the transmission mode switching method in unlicensed spectrum control environments of the present disclosure. 
         FIG. 7  is a schematic flowchart of a seventh embodiment of the transmission mode switching method in unlicensed spectrum control environments of the present disclosure. 
         FIG. 8A  and  FIG. 8B  are a schematic flowchart of an eighth embodiment of the transmission mode switching method in unlicensed spectrum control environments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1A  and  FIG. 1B , a transmission mode switching method in unlicensed spectrum control environments in  FIG. 1A  is executed by some or all of the components of the user equipment (UE)  10  in  FIG. 1B . 
     In a first embodiment, the transmission mode switching method in unlicensed spectrum control environments includes steps S 101  to S 108 . 
     In step S 101 , the UE  10  transmits a first data to a gNB  20 . For example, the first data may be uplink data. In the fifth generation (5G) communication technology standard specifications, the data transmitted by the UE  10  to the gNB  20  is uplink data, and the data transmitted by the gNB  20  to the user equipment  10  is downlink data. 
     In step S 102 , the UE  10  determines whether to receive a dynamic grant (DG) signal from the gNB  20 . When the gNB  20  fails to receive the data, the gNB  20  generates a DG signal and sends the DG signal to the UE  10 . Therefore, when the UE  10  receives the DG signal, it means that the gNB  20  fails to receive the data, that is, the UE  10  fails to transmit the data, such as the Listen-Before-Talk failure (LBT failure). In other words, the UE  10  can determine whether the gNB  20  successfully receives and decodes the data transmitted by the UE  10  by receiving the DG signal from the gNB  20  or not. 
     In steps S 103 , S 104  and S 105 , when the UE  10  receives the DG signal, the UE  10  triggers the first trigger unit  11  (S 103 ), and determines whether the first trigger unit  11  satisfies the first condition (S 104 ). When the first trigger unit  11  satisfies the first condition, the UE  10  configures the CG retransmission timer  12  and switches to the first CG transmission mode (S 105 ). 
     In the first embodiment, referring to  FIG. 1A , in S 101 , the current CG transmission mode between the UE  10  and the gNB  20  is the URLLC CG mode. After several steps in  FIG. 1A , in S 105 , the CG transmission mode is switched to the first CG transmission mode. Wherein the first CG transmission mode is the NR-U CG mode. 
     In step S 106 , after switching to the first CG transmission mode, the UE  10  further transmits the first retransmission data to the gNB  20 . 
     As the UE  10  has received the DG signal before switching to the first CG transmission mode, when the UE  10  receives the DG signal, it means that the previously transmitted first data has not been received by the gNB  20 . Therefore, the UE  10  needs to transmit the first retransmission data to the gNB  20 , thereby retransmitting the first data to the gNB  20 . 
     In step S 107 , when the first trigger unit  11  does not meet the first condition, the UE  10  transmits the first retransmission data to the gNB  20 . 
     When the first trigger unit  11  does not satisfy the first condition, it means that the UE  10  has not failed to transmit the first data to the gNB  20  multiple times in succession. However, the UE  10  still triggers the first trigger unit  11  after receiving the DG signal and determines whether the first trigger unit  11  satisfies the first condition. Therefore, when the first trigger unit  11  does not meet the first condition, the UE  10  still needs to transmit the first retransmission data to retransmit the first data to the gNB  20 . 
     In step S 108 , when the DG signal is not received, the UE  10  resets the first trigger unit  11 . 
     Referring to  FIG. 2 , in a second embodiment, the steps S 201 , S 202 , S 205 , S 206 , and S 207  are the same as the steps S 101 , S 102 , S 105 , S 106 , and S 107  of the aforementioned first embodiment, which is not repeated here. The second embodiment is different from the first embodiment in that the first trigger unit  11  is a first configuration grant (CG) counter  111 . 
     In step S 203 , when the UE  10  triggers the first trigger unit  11 , the first count value of the first CG counter  111  is increased, such as, increasing the first count value by one. 
     In step S 204 , the UE  10  determines whether the first trigger unit  11  satisfies the first condition by determining whether the first count value of the first CG counter  111  is greater than or equal to the first threshold value. And when the first count value is greater than or equal to the first threshold value, the UE  10  determines that the first trigger unit  11  satisfies the first condition. 
     In the second embodiment, the UE  10  increases the first count value of the first CG counter  111  only when receiving the DG signal representing transmission failure. In this way, the UE  10  can determine a number of consecutive failures to transmit data to the gNB  20  according to the first count value. And when the number of consecutive failures is greater than the first threshold, it means that the UE  10  has failed to transmit data many times. Therefore, the UE  10  can determine that the current communication quality is bad, further configures the CG retransmission timer  12 , and switches to the first CG transmission mode to improve the reliability of signal transmission. 
     For example, when the first count value of the first CG counter  111  is greater than or equal to the first threshold value, it means that the UE  10  has continuously received the DG signal multiple times. That is, the number of consecutive data transmission failures is greater than or equal to the first threshold value, so the UE  10  will determine that the first condition meets the first condition, and then will switch to the first CG transmission mode. 
     In addition, the first trigger unit  11  is the first CG counter  111 , as shown in step S 208 , and then the first trigger unit  11  is reset by resetting the first count value of the first CG counter  111  to zero. 
     Referring to the second embodiment in  FIG. 2 , in step S 201 , the current CG transmission mode between the UE  10  and the gNB  20  is the URLLC CG mode. After several steps of  FIG. 2 , in step S 205 , the UE  10  switches to the first CG transmission mode, wherein the first CG transmission mode is the NR-U CG mode. 
     Referring to  FIG. 3 , in the third embodiment, the steps S 301 , S 302 , S 305 , S 306 , and S 307  are the same as S 101 , S 102 , S 105 , S 106 , and S 107 , so the description thereof is not be repeated here. The third embodiment is different from the first embodiment in that the first trigger unit  11  is the first CG timer  112 . 
     In step S 303 , the UE  10  triggers the first trigger unit  11  by determining whether the first CG timer  112  is started. 
     In steps S 3031 , S 304 , S 305 , when the first CG timer  112  is started, the UE  10  determines whether the first trigger unit  11  satisfies the first condition (S 304 ). When the first CG timer  112  is not started, the UE  10  starts the first CG timer  112  (S 3031 ) and then determines whether the first trigger unit  11  satisfies the first condition (S 304 ). Wherein the UE  10  determines whether the first trigger unit  11  satisfies the first condition by determining whether the first CG timer  112  times out (S 304 ), and when the first CG timer  112  times out, the UE  10  determines that the first trigger unit  11  satisfies the first condition. 
     In the third embodiment, the UE  10  determines whether the first CG timer  112  times out only when receiving a DG signal representing transmission failure. Therefore, the UE  10  confirms whether the DG signal is received continuously many times within the first time set by the first CG timer  112 . If the first CG timer  112  times out, it means that the UE  10  has continuously received the DG signal many times within the first time, which means the transmission has failed many times. Therefore, the UE  10  can determine that the current communication quality is bad, then further configures the CG retransmission timer  12  and switches to the first CG transmission mode to improve the reliability of signal transmission. 
     For example, the first CG timer  112  is a countdown timer for confirming whether the first time is reached after the first CG timer  112  is started. For example, if the UE  10  continues to receive the DG signal within the first time after the first CG timer  112  is started, the UE  10  determines that the first CG timer  112  times out when receiving the DG signal again after the first timing value. That is, the first condition is met, and then the UE  10  switches to the first CG transmission mode. 
     In addition, as the first trigger unit  11  is a first CG timer  112 , as shown in step S 308 , the UE  10  resets the first trigger unit by resetting the first time of the first CG timer  112 . 
     In the third embodiment, referring to  FIG. 3 , in step S 301 , the current CG transmission mode between the UE  10  and the gNB  20  is the URLLC CG mode. Through the operation of  FIG. 3 , in S 305 , the UE  10  switches to the first CG transmission mode, wherein the first CG transmission mode is the NR-U CG mode. 
     Referring to  FIG. 4 , in the fourth embodiment, the steps S 401 , S 402 , S 405 , S 406 , and S 407  are the same as steps S 101 , S 102 , S 105 , S 106 , and S 107 , do description thereof will not be repeated here. The fourth embodiment is different from the first embodiment in that the first trigger unit  11  is a first CG counter  111 . 
     After transmitting the first data to the gNB  20  (S 401 ), the UE  10  first resets and starts the first CG timer  112  (S 409 ), and determines whether the first CG timer  112  times out (S 410 ). If the first CG timer  112  does not time out, the UE  10  determines whether to receive the DG signal from the gNB  20  (S 402 ). If the first CG timer  112  times out, the UE  10  resets the first trigger unit  11  (S 408 ). And when the DG signal is not received, the UE  10  first determines whether the first CG timer  112  times out (S 410 ). If the first CG timer  112  times out, the UE  10  resets the first trigger unit  11  (S 408 ). 
     In addition, in the fourth embodiment, the first CG counter  111  is similar to the first CG counter  111  in the third embodiment. The difference is that when the first CG counter  111  is less than the first threshold (that is, the first trigger unit  11  does not meet the first condition), the UE  10  transmits the first retransmission data to the gNB  20 , and then further transmits the second data to the gNB  20 , resets and starts the first CG timer  112  and determines whether the first CG timer  112  times out. 
     In the fourth embodiment, as the first CG timer  112  and the first CG counter  111  are in use, when the number of consecutively received DG signals within the first time is greater than the first threshold, the UE determines that the first condition is met, and switches to the first CG transmission mode. 
     For example, after the first CG timer  112  is started, if the number of DG signals continuously received by the UE  10  is greater than or equal to the first threshold within the first time, the UE  10  determines that the first condition is met, and then switches to the first CG transmission mode. However, if the number of the DG signals is less than the first threshold value within the first time, the UE  10  determines that the first CG timer  112  times out after the first time to reset the first CG counter  111 . 
     In the fourth embodiment, referring to  FIG. 4 , in step S 401 , the current CG transmission mode between the UE  10  and the gNB  20  is the URLLC CG mode, and through the operation in  FIG. 4 , it is switched to the first CG transmission mode, wherein the first CG transmission mode is the NR-U CG mode. 
     Referring to  FIG. 5 , in the fifth embodiment, the transmission mode switching method in unlicensed spectrum control environments includes steps S 501  to S 512 . 
     In step S 501 , the UE  10  transmits the third data to the gNB  20 . For example, the third data transmitted by the UE  10  is uplink data. 
     In step S 502 , the UE  10  resets and starts the CG retransmission timer  12 . In the first CG transmission mode, the UE  10  confirms whether to retransmit data to the gNB  20  through the CG retransmission timer  12 . Therefore, in the first CG transmission mode, the UE  10  needs to reset and start the CG retransmission timer  12 . 
     In step S 503 , the UE  10  determines whether the CG retransmission timer  12  times out. 
     In step S 504 , if the CG retransmission timer  12  times out, the UE  10  resets the second trigger unit  13 . 
     In step S 505 , the UE  10  transmits the second retransmission data to the gNB  20 . 
     For example, if the CG retransmission timer  12  times out, it means that the UE  10  successfully receives the reception confirmation signal from the gNB  20  within the retransmission time of the CG retransmission timer  12 . Therefore, if the CG retransmission timer  12  times out, the UE  10  resets the second trigger unit  13  and transmits the second retransmission data to retransmit the third data to the gNB  20 . That is to say, if the CG retransmission timer  12  times out, it means that the gNB  20  fails to receive data. That is, the UE  10  fails to transmit data, such as the transmission mechanism of listening before speaking (LBT failure). The UE  10  can determine whether the gNB  20  successfully receives and decodes the data transmitted by the UE  10  by determining whether the CG retransmission timer  12  times out. 
     In step S 506 , when the CG retransmission timer  12  does not time out, the UE  10  determines whether the downlink feedback information (DFI) signal transmitted by the gNB  20  is received. 
     In step S 507 , when the UE  10  receives the DFI signal, the UE  10  determines whether the DFI signal is successfully decoded. However, when the UE  10  does not receive the DFI signal, the UE  10  determines whether the CG retransmission timer  12  times out (S 503 ). 
     In step S 508 , when the UE  10  successfully decodes the DFI signal, the UE  10  determines whether the DFI signal includes an acknowledgement (ACK) signal. When the UE  10  fails to decode the DFI signal, the UE  10  determines whether the CG retransmission timer  12  times out (S 503 ). 
     In step S 509 , when the DFI signal includes an ACK signal, the UE  10  starts the second trigger unit  13 . However, when the DFI signal does not include the ACK signal, the UE  10  resets the second trigger unit  13  (S 504 ), and transmits the second retransmission data to the gNB  20  (S 505 ). 
     In steps S 510 , S 511 , S 512 , the UE  10  determines whether the second trigger unit  13  satisfies the second condition (S 510 ). When the second trigger unit  13  meets the second condition, the UE  10  de-configures the CG retransmission timer  12  and switches to the second CG transmission mode (S 511 ). But when the second trigger unit  13  does not meet the second condition, the UE  10  further transmits the fourth data to the gNB  20  (S 512 ), resets and starts the CG retransmission timer  12  (S 502 ), and then determines whether the CG retransmission timer  12  times out (S 503 ). 
     Further, in the fifth embodiment, S 513  and S 514  are further included. 
     In steps S 513  and S 514 , the UE  10  determines whether the CG retransmission timer  12  is configured. When the CG retransmission timer  12  is configured, the UE  10  transmits the third data to the gNB  20  (S 501 ), and resets and starts the CG retransmission timer  12  (S 502 ), and then determines whether the CG retransmission timer  12  times out. However, when the CG retransmission timer  12  is not configured, the UE  10  executes the second CG transmission mode. 
     In the fifth embodiment, referring to  FIG. 5 , in S 501 , the current CG transmission mode between the UE  10  and the gNB  20  is the NR-U CG mode. Through the operation of  FIG. 5 , in S 511 , the second CG transmission mode is switched, wherein the second CG transmission mode is the URLLC CG mode. 
     Referring to  FIG. 6 , in the sixth embodiment, steps S 601  to S 608  are the same as steps S 501  to S 508  of the foregoing fifth embodiment, so the description thereof is not be repeated here. The difference between the sixth embodiment and the fifth embodiment is that the second trigger unit  13  is a second CG counter  131 . 
     In step S 609 , when the UE  10  triggers the second trigger unit  13 , the second count value of the second CG counter  131  is increased, for example, increasing the second count value by one. 
     And as shown in steps S 610 , S 611 , and S 612 , the UE  10  determines whether the second trigger unit  13  satisfies the second condition by determining whether the second count value of the second CG counter  131  is greater than or equal to the first two thresholds (S 610 ). And when the second count value is greater than or equal to the second threshold value, the UE  10  determines that the second trigger unit  13  satisfies the second condition, de-configures the CG retransmission timer  12 , and switches to the second CG transmission mode (S 611 ). However, when the second count value is less than the second threshold value, the UE  10  determines that the second trigger unit  13  does not meet the second condition, and the UE  10  further transmits the fourth data to the gNB  20  (S 612 ), and resets and starts the CG retransmission timer  12  (S 602 ), and then determines whether the CG retransmission timer  12  times out (S 603 ). 
     In the sixth embodiment, the UE  10  successfully receives and decodes the DFI signal and determines that the DFI signal has an ACK signal, and the second count value of the second CG counter  131  is increased. Therefore, the UE  10  can confirm the number of ACK signals successfully received from the gNB  20  according to the second count value. And when the number of consecutively successfully received ACK signals is greater than the second threshold, it means that the gNB  20  successfully receives the data transmitted by the UE  10  many times. The UE  10  can determine that the current communication quality is better, and further deconfigures the CG retransmission timer  12 , and switches to the second CG transmission mode to decrease transmission latency. 
     For example, when the second count value of the second CG counter  131  is greater than or equal to the second threshold value, it means that the UE  10  has continuously received the ACK signal multiple times, that is, the number of successful data transmissions is greater than or equal to the second threshold value, so the UE  10  determines that the second condition is met, and then switches to the second CG transmission mode. 
     In the sixth embodiment, referring to  FIG. 6 , in step S 601 , the current CG transmission mode between the UE  10  and the gNB  20  is the NR-U mode. Through the operation of  FIG. 6 , in step S 611 , the CG transmission mode is switched, wherein the second CG transmission mode is the URLLC CG mode. 
     Referring to  FIG. 7 , in the seventh embodiment, the steps S 701  to S 708  are the same as steps S 501  to S 508  in the fifth embodiment, so the description thereof is not be repeated here. The difference between the seventh embodiment and the fifth embodiment is that the second trigger unit  13  is a second CG timer  132 . 
     In step S 709 , when the UE  10  triggers the second trigger unit  13 , it is determined whether the second CG timer  132  is started. 
     As shown in steps S 7091 , S 710 , and S 711 , when the second CG timer  132  starts, the UE  10  determines whether the second trigger unit  13  satisfies the second condition (S 710 ). When the CG timer  132  is not started, the UE  10  first starts the second CG timer  132  (S 7091 ), and then determines whether the second trigger unit  13  meets the second condition (S 710 ). And the UE  10  determines whether the second trigger unit  13  satisfies the second condition by determining whether the second CG timer  132  expires (S 710 ). If the second CG timer  132  times out, the UE  10  determines that the second trigger unit  13  satisfies the second condition. 
     In the seventh embodiment, the UE  10  starts and determines whether the second CG timer  132  times out only when confirming that the DFI signal has an ACK signal. Therefore, the UE  10  determines whether the ACK signal is received continuously multiple times within the second timing value set by the second CG timer  132 . When the second CG timer  132  times out, it means that the UE  10  continuously receives the ACK signal multiple times within the second timing value. That is, the data has been successfully transmitted to the gNB  20  multiple times. Then the UE  10  can determine the current communication quality is better, then deconfigures the CG retransmission timer  12 , and switches to the second CG transmission mode to decrease latency of signal transmission. 
     For example, the second CG timer  132  is a countdown timer for confirming whether to reach the second timing value after the second timer is started. For example, after the second CG timer  132  is started, if the UE  10  continually receives the ACK signal within the second timing value, when receiving the ACK signal again after the second timing value, the UE  10  determines that the second CG timer  132  times out and the second condition is met, and then switches to the second CG transmission mode. 
     In the seventh embodiment, referring to  FIG. 7 , in step S 701 , the current CG transmission mode between the UE  10  and the gNB  20  is the NR-U CG mode. Through the operation of  FIG. 7 , in step S 711 , it is switched to the second CG transmission mode, wherein the second CG transmission mode is the URLLC CG mode. 
     Referring to  FIG. 8A  and  FIG. 8B , in the eighth embodiment, steps S 801  to S 808  are the same as steps S 501  to S 508  in the fifth embodiment, so the description thereof is not repeated here. The difference between the eighth embodiment and the fifth embodiment is that the second trigger unit  13  is a second CG counter  131 . 
     And as shown in steps S 812 , S 813 , S 814 , and S 815 , when the UE  10  transmits the third data to the gNB  20  (S 801 ), the UE  10  first resets and starts the second CG timer  132  (S 813 ), resets and starts the CG retransmission timer  12  (S 802 ), and the further determines whether the second CG timer  132  times out (S 814 ). If the second CG timer  132  does not time out, the UE  10  determines whether the CG retransmission timer  12  times out (S 803 ). However, if the second CG timer  132  times out, the UE  10  resets the second CG counter  131  (S 815 ). 
     In addition, in the eighth embodiment, the operation of the second CG counter  131  is similar to that of the second CG counter  131  in the sixth embodiment. The difference is that when the second CG counter  131  is less than the second threshold, that is, when the second trigger unit  13  does not meet the second condition, the UE  10  resets and starts the second CG timer  132  (S 813 ) after transmitting the fourth data to the gNB  20  (S 812 ), and then resets and starts the CG retransmission timer  12  (S 802 ). 
     For example, the CG retransmission timer  12  and the second CG timer  132  are both countdown timers, and the CG retransmission timer  12  is used to confirm whether to reach the retransmission time after the CG retransmission timer  12  is started. And the second CG timer  132  is used to confirm whether to reach the second time after the second timer is started. 
     For example, after the second CG timer  132  is started, if the number of ACK signals continuously received by the UE  10  within the second time is greater than or equal to the second threshold, the UE  10  determines that the second condition is met, and then switches to the second CG transmission mode. However, if the number of ACK signals consecutively received within the second time is less than the second threshold value, the UE  10  determines that the second CG timer  132  times out after the second time expires to reset the second counter. And if the second CG timer  132  does not expire, the UE  10  still needs to confirm whether to receive the ACK signal within the retransmission time of the CG retransmission timer  12  (S 806  to S 808 ). If the ACK signal cannot be confirmed within the retransmission time, the UE  10  determines that the CG retransmission timer  12  times out, resets the second CG counter  131 , and transmits the second retransmission data to the gNB  20 . 
     In the eighth embodiment, referring to  FIG. 8 , in step S 801 , the current CG transmission mode between the UE  10  and the gNB  20  is the NR-U CG mode. Through the operation of  FIG. 8 , in step S 811 , the second CG transmission mode is switched, wherein the second CG transmission mode is the URLLC CG mode. 
     In summary, the transmission mode switching method in unlicensed spectrum control environments of the present disclosure switches to the first CG transmission mode (for example, the NR-U CG mode), as shown in any one of the first to fourth embodiments. And it switches to the second CG transmission mode (for example, URLLC CG mode), as shown in any one of the fifth to eighth embodiments. The present disclosure can automatically switch the current CG transmission mode according to the communication quality of the radio channel. When the communication quality of the radio channel is good, the second CG transmission mode is automatically switched, and when the communication quality of the radio channel is poor, the second CG transmission mode is automatically switched. In this way, when the communication quality is good, the second CG transmission mode can effectively decrease latency, and when the communication quality is poor, the first CG transmission mode can improve the reliability. Therefore, the present disclosure dynamically evaluates the channel state to automatically switch to the best transmission mode, thereby improving the spectrum usage efficiency in the unlicensed spectrum control environments. 
     Even though numerous characteristics and advantages of the present disclosure have been set forth in the foregoing description, together with details of the structure and features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.