Patent Publication Number: US-2023145818-A1

Title: Method and system for dynamically switching transmission modes to increase reliability in unlicensed controlled environments

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the priority benefit of TW application serial No. 110141737 filed on Nov. 10, 2021, the entirety of which is hereby incorporated by reference herein and made a part of the specification. 
     BACKGROUND 
     1. Field of the Disclosure 
     The present disclosure relates to a method and a system for switching transmission modes, in particular to a method and a system for dynamically switching transmission modes to increase reliability in unlicensed spectrum control environments (UCEs). 
     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 (UCEs). 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 URLLC CG mode and 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 method and a system for dynamically switching transmission modes to increase reliability in unlicensed spectrum control environments (UCEs). In environments where the communication quality of the radio channel may change, a user equipment (UE) automatically and dynamically switches the transmission modes 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 the UCEs. 
     The system for dynamically switching transmission modes in UCEs includes a UE, and the UE executes the method for dynamically switching transmission modes in UCEs. When the UE executes the method, the UE performs a first configured grant (CG) transmission mode, and the UE executes steps of: transmitting a new data to a gNB; determining whether a dynamic grant (DG) signal transmitted by the gNB is received; when the DG signal is received, starting a CG timer, increasing a count value of a CG counter, resetting a successful transmission count value of a successful transmission counter, calculating a CG weight according to a timing value of the CG timer and the count value, and determining whether the CG weight is greater than or equal to a CG threshold; when the CG weight is greater than or equal to the CG threshold, switching from a first CG transmission mode to a second CG transmission mode; when the CG weight is smaller than the CG threshold, transmitting a retransmission data to the gNB. 
     The CG weight is calculated by the following formula: 
     
       
         
           
             
               W 
               1 
             
             = 
             a 
             1 
             × 
             t 
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             1 
             + 
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             1 
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             ; 
           
         
       
     
     
       
         
           
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     W 1  is the CG weight, α1 is a time weight, b1 is a count weight, timer_current is the timing value, timer_max is a preset maximum of waiting time, counter_current is the count value, counter_max is a maximum number of preset allowable failures, and α1 + b1 = 1. 
     The CG threshold is calculated by the following formula: 
     
       
         
           
             T 
             
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               1 
             
             = 
             M 
             A 
             X 
             
               
                 a 
                 1 
                 , 
                   
                 b 
                 1 
               
             
               
             ; 
           
         
       
     
     TH 1  is the CG threshold. 
     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 the 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 starts the CG timer and increases the count value of the CG counter. The UE further determines whether the CG weight is greater than or equal to the CG threshold. When the CG weight is greater than or equal to the CG threshold, 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, the UE switches to the second CG transmission mode, thereby improving the reliability of data transmission by the second CG transmission mode. 
     For example, the second 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 second CG transmission mode. 
     In addition, since the UE calculates the CG weight according to the timing value of the CG timer and the count value of the CG counter, the CG weight can be dynamically adjusted with time or a number of failures of transmission. In other words, the present disclosure dynamically adjusts weights of a counter and of a timer to achieve the benefit of automatically adjusting and switching the CG transmission mode according to environmental changes. 
     In summary, the present disclosure can dynamically and 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 bad, the UE switches to the second CG transmission mode. In this way, when the communication quality is bad, the second CG transmission mode can be used to improve the reliability, thereby improving spectrum usage efficiency in UCEs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic flowchart of a method for dynamically switching transmission modes to increase reliability in unlicensed spectrum control environments (UCEs) of the present disclosure. 
         FIG.  2    is a schematic block diagram of a system for dynamically switching transmission modes to increase reliability in UCEs of the present disclosure. 
         FIG.  3    is a schematic flowchart of a communication quality determination procedure of the method for dynamically switching transmission modes to increase reliability in UCEs of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG.  1    and  FIG.  2   , a method for dynamically switching transmission modes to increase reliability in unlicensed spectrum control environments (UCEs) shown in  FIG.  1    is executed by a user equipment (UE)  10  shown in  FIG.  2   . Please refer to  FIG.  1    and  FIG.  2    for the following description. 
     The method for dynamically switching transmission modes in UCEs is executed by the UE performing a first configured grant (CG) transmission mode, and includes step S 101  to step S 112 . 
     In step S 101 , the UE  10  transmits a new data to a next generation Node B (gNB)  20 . For example, the new 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 a dynamic grant (DG) signal transmitted by the gNB  20  is received. 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  according to whether the DG signal is received from the gNB  20 . 
     In step S 103 , when the DG signal is received, the UE  10  starts a CG timer  11  and increases a count value of a CG counter  12 . For example, the UE  10  starts the CG timer  11  to time a timing value of the CG timer  11  and increases the count value of the CG counter  12  by one. In the embodiment, when the UE  10  receives the DG signal at the first time, the UE  10  starts the CG timer  11  and increases the count value of the CG counter  12  by one from zero. When the UE  10  receives the DG signal at the first time, since the CG timer  11  has been started, the UE  10  does not need to start the CG timer  11 , and the UE  10  just needs to increase the count value of the CG counter  12  by one. 
     In step S 104 , the UE  10  resets a successful transmission count value of a successful transmission counter  13 . When the UE  10  receives the DG signal, the UE  10  can determine that the new data is failure transmission. Therefore, the UE  10  needs to reset the successful transmission count value of the successful transmission counter  13 . Namely, the successful transmission count value means a number of continuously successful transmissions of data transmitted from the UE  10  to the gNB  20 . 
     In step S 105 , the UE  10  calculates a CG weight according to the timing value of the CG timer  11  and the count value of the CG counter  12 , and the CG weight is calculated by the following formula: 
     
       
         
           
             
               W 
               1 
             
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             a 
             1 
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             1 
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             ; 
           
         
       
     
     
       
         
           
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     W 1  is the CG weight, α1 is a time weight, b1 is a count weight, timer_current is the timing value, timer_max is a preset maximum of waiting time, counter_current is the count value, counter_max is a maximum number of preset allowable failures, and α1 + b1 = 1. For example, the preset maximum of waiting time timer_max is a maximum of the timing value of the CG timer  12 , and the maximum number of preset allowable failures counter_max is a maximum of the count value of the CG counter  12 . In this embodiment, the maximum of the timing value of the CG timer  12  is 200 milliseconds (ms), and the maximum of the count value of the CG counter  12  is  10 . 
     In step S 106 , the UE  10  further determines whether the CG weight is greater than or equal to a CG threshold. 
     The CG threshold is calculated by the following formula: 
     
       
         
           
             T 
             
               H 
               1 
             
             = 
             M 
             A 
             X 
             
               
                 a 
                 1 
                 , 
                   
                 b 
                 1 
               
             
               
             ; 
           
         
       
     
     TH 1  is the CG threshold and equals to a maximum of the time weight α1 and the count weight b1. For example, if α1 = 0.7, b1 = 0.3, since a1 &gt; b1, TH 1  = a1 = 0.7. 
     In step S 107 , when the CG weight is greater than or equal to the CG threshold, the UE  10  switches from the first CG transmission mode to a second CG transmission mode. 
     In step S 108 , when the CG weight is smaller than the CG threshold, the UE  10  transmits a retransmission data to the gNB, and further transmits a next new data to the gNB  20  (S 101 ). 
     As the UE  10  has received the DG signal, when the UE  10  receives the DG signal, it means that the previously transmitted new data has not been received by the gNB  20 . Therefore, the UE  10  needs to transmit the retransmission data to the gNB  20 , thereby retransmitting the previously transmitted new data to the gNB  20 . Then, the gNB  20  can receive and decode the retransmission data. When the UE  10  transmits the retransmission data, the UE  10  can directly transmit the next new data to the gNB  20 . 
     In the embodiment, the first CG transmission mode between the UE  10  and the gNB  20  is the URLLC CG mode. After several steps in  FIG.  1   , in S 107 , the UE  10  is switched to the second CG transmission mode. Wherein the second CG transmission mode is the NR-U CG mode. Moreover, before the UE  10  executes the method for dynamically switching transmission modes to increase reliability in UCEs, the UE  10  initializes the CG timer  11 , the CG counter  12 , and the successful transmission counter  13 . 
     In step S 109 , when the DG signal is not received, the UE  10  resets the CG counter. 
     In step S 110 , the UE  10  increases the successful transmission count value. 
     In step S 111 , the UE  10  determines whether the successful transmission count value is greater than or equal to a successful transmission threshold. 
     In step S 112 , when the successful transmission count value is greater than or equal to the successful transmission threshold, the UE  10  resets the timing value of the CG timer  11  and the successful transmission count value of the successful transmission counter  13 , and then the UE  10  transmits a next new data to the gNB  20  (S 101 ). 
     Further, when the successful transmission count value is smaller than the successful transmission threshold, the UE  10  directly transmits the next new data to the gNB (S 101 ). 
     The CG counter  12  of the UE  10  can count a number of UE failed transmission, such as UE listen before talk failures (UE LBT failures), or a number of gNB failed reception. When the UE  10  fails to transmit the new data or the gNB  20  fails to receive the new data, the UE further determines the communication quality of radio channels according to the timing value of the CG timer  11 . Namely, the UE  10  counts the number of the UE failed transmission or the number of the gNB failed reception within the preset maximum of waiting time (timer_max) according to the CG timer  11  and the CG counter  12 . 
     For example, α1 = 0.7, b1 = 0.3, TH 1  = 0.7, timer_max = 200 ms, counter_max =  10 . When the UE  10  receives the DG signal after transmitting a first new data to the gNB  20 , it means that the gNB  20  does not successfully receive the first new data. Then, the UE  10  starts the CG timer  11  and increases the counter value of the CG counter  12  by one. Since the UE  10  receives the DG signal representing the UE transmitting failure, the UE  10  resets the successful transmission count value of the successful transmission counter  13  to be zero. Then, the UE  10  calculates the CG weight according to the timing value of the CG timer  11  and the count value of the CG counter  12 . 
     Since the CG timer  11  is just started, the timing value is zero. The CG counter  12  also begins to count, and the count value is one after the count value is increased. The CG weight is calculated by the following formula: 
     
       
         
           
             
               W 
               1 
             
             = 
             a 
             1 
             × 
             t 
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             m 
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             r 
             1 
             + 
             b 
             1 
             × 
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             t 
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             r 
             1 
             = 
             0.7 
             × 
             
               0 
               
                 200 
               
             
             + 
             0.3 
             × 
             
               1 
               
                 10 
               
             
             = 
             0.03 
           
         
       
     
     Since 0.03 &lt; 0.7, the CG weight is smaller than the CG threshold. Therefore, the UE  10  transmits retransmission data to the gNB  20 , and then the UE  10  further transmits a second new data the gNB  20 . 
     If the UE  10  does not receive the DG signal after the UE  10  transmits the second new data to the gNB  20 , the UE  10  resets the count value of the CG counter  12  to be zero, and increases the successful transmission count value of the successful transmission counter  13  by one. Then the UE  10  determines whether the successful transmission count value is greater than or equal to the successful transmission threshold. 
     The successful transmission counter  13  is increased by one when the UE  10  does not receive the DG signal. When the UE  10  receives the DG signal, the UE  10  will reset the successful transmission count value of the successful transmission counter  13 . Therefore, when the UE  10  continuously transmits multiple new data without receiving the DG signal, it means that the gNB  20  has successfully received the multiple new data continuously, and the successful transmission count value of the successful transmission counter  13  will be continuously accumulated. Namely, when the successful transmission count value of the successful transmission counter  13  is greater than the successful transmission threshold, it means that the gNB  20  has continuously and successfully received and decoded the multiple new data transmitted by the UE  10 . Therefore, the UE  10  can determine the communication quality of the radio channels is good, the UE  10  does not need to switch to the second CG transmission mode, and the UE  10  needs to maintain the first CG transmission mode for maintaining low latency communications. The UE  10  further resets the CG timer  11  and the successful transmission counter  13  for avoiding switching to the second CG transmission mode. 
     However, if the UE  10  receives the DG signal after the UE  10  transmits the second new data to the gNB  20 , the UE  10  further increases the count value of the CG counter  12  by one, and calculates the CG weight again. At this time, since the CG timer  11  has been started, the timing value of the CG timer  11  is not zero. For example, the timing value of the CG timer  11  is 10 ms, and the count value of the CG counter  12  is two. The CG weight is calculated by the following formula: 
     
       
         
           
             
               W 
               1 
             
             = 
             a 
             1 
             × 
             t 
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             m 
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             r 
             1 
             + 
             b 
             1 
             × 
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             1 
             = 
             0.7 
             × 
             
               
                 10 
               
               
                 200 
               
             
             + 
             0.3 
             × 
             
               2 
               
                 10 
               
             
             = 
             0.095 
           
         
       
     
     Since 0.095 &lt; 0.7, the CG weight is still smaller than the CG threshold. Therefore, the UE  10  transmits retransmission data to the gNB  20 , and then the UE  10  further transmits a third new data the gNB  20 . 
     After a while, the UE  10  has not continuously and successfully received the multiple new data. The successful transmission count value of the successful transmission counter  13  is not greater than the successful transmission threshold, the timing value of the CG timer  11  would not be reset, and it means that the CG timer  11  does not stop timing. When the UE  10  receives the DG signal, the UE  10  calculates the CG weight again. For example, the timing value of the CG timer  11  is 180 ms, and the count value of the CG counter  12  is three. The CG weight is calculated by the following formula: 
     
       
         
           
             
               W 
               1 
             
             = 
             a 
             1 
             × 
             t 
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             m 
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             r 
             1 
             + 
             b 
             1 
             × 
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             t 
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             r 
             1 
             = 
             0.7 
             × 
             
               
                 180 
               
               
                 200 
               
             
             + 
             0.3 
             × 
             
               3 
               
                 10 
               
             
             = 
             0.72 
           
         
       
     
     Since 0.72 ≥ 0.7, the CG weight is greater than the CG threshold. Therefore, the UE  10  switches to the second CG transmission mode. 
     Moreover, the multiple new data transmitted by the UE  10  may partially be received and decoded by the gNB  20 . If times of the gNB  20  continuously and successfully receiving and decoding the multiple new data is not greater than the successful transmission threshold, the UE  10  resets the CG counter  12  but does not reset the CG timer  11 . Even if the count value of the CG counter  12  is reset, the CG timer  11  does not stop timing. When the timing value of the CG timer  11  (timer_current ) reaches the preset maximum of waiting time (timer_max), the CG weight is calculated by the following formula: 
     
       
         
           
             
               W 
               1 
             
             = 
             a 
             1 
             × 
             t 
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             m 
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             r 
             1 
             + 
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             1 
             × 
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             r 
             1 
             = 
             0.7 
             × 
             
               
                 200 
               
               
                 200 
               
             
             + 
             0.3 
             × 
             
               0 
               
                 10 
               
             
             = 
             0.7 
           
         
       
     
     Since 0.7 ≥ 0.7, the CG weight is greater than the CG threshold. Therefore, the UE  10  switches to the second CG transmission mode. Namely, even if the count value of the CG counter  12  is reset, the UE  10  can switch to the second CG transmission mode when the timing value of the CG timer  11  reaches the preset maximum of waiting time. 
     With reference to  FIG.  3   , the method for dynamically switching transmission modes in UCEs further includes step S 301  to step S 306 . 
     In steps S 301 , the UE  10  respectively sets the time weight α1 and the count weight b1 to an initial value and presets a previous communication quality parameter. 
     In step S 302 , the UE  10  executes a communication quality determination procedure to generate a current communication quality parameter. 
     In step S 303 , the UE  10  determines whether communication quality is reduced according to the previous communication quality parameter and the current communication quality parameter for adjusting the time weight α1 and the count weight b1. In the embodiment, a sum of the time weight α1 and the count weight b1 is 1. 
     In step S 304 , when the communication quality is reduced, the UE  10  increases the time weight α1 and reduces the count weight b1. 
     In step S 305 , the UE  10  updates the previous communication quality parameter to be the current communication quality parameter. 
     In step S 306 , when the communication quality is not reduced, the UE  10  maintains the time weight α1 and the count weight b1, and updates the previous communication quality parameter to be the current communication quality parameter (S 305 ). 
     The UE  10  can determine the communication quality of the radio channels becoming better or worse according to the communication quality determination procedure. Then, the UE  10  can dynamically adjust the time weight α1 and the count weight b1 according to the communication quality. Namely, the CG weight is calculated corresponding to the communication quality. When the communication quality is changed, the time weight α1 and the count weight b1 are correspondingly changed. Further, the UE  10  can calculate the CG weight only based on the time weight α1 or the count weight b1. Namely, the UE  10  can set the time weight α1 to be one, and set the count weight b1 to be zero. Or the UE can set the time weight α1 to be zero, and set the count weight b1 to be one. 
     For example, the initial value of the time weight α1 is 0.5, and the initial value of the count weight b1 is 0.5. Namely, α1 = 0.5, b1 = 0.5, TH 1  = 0.5, timer_max = 200 ms, counter_max = 10. Further, the timing value of the CG timer  11  is 100 ms, and the count value of the CG counter  12  is three. When the UE  10  receives the DG signal from the gNB  20 , the UE  10  calculates the CG weight according to the following formula: 
     
       
         
           
             
               W 
               1 
             
             = 
             a 
             1 
             × 
             t 
             i 
             m 
             e 
             r 
             1 
             + 
             b 
             1 
             × 
             c 
             o 
             u 
             n 
             t 
             e 
             r 
             1 
             = 
             0.5 
             × 
             
               
                 100 
               
               
                 200 
               
             
             + 
             0.5 
             × 
             
               3 
               
                 10 
               
             
             = 
             0.4 
           
         
       
     
     Since 0.4 &lt; 0.7, the CG weight is smaller than the CG threshold. Therefore, the UE  10  transmits retransmission data to the gNB  20 , and then the UE  10  further transmits a third new data the gNB  20 . 
     After a while, the UE  10  executes a communication quality determination procedure to determine whether the communication quality of the radio channels is reduced. When the communication quality of the radio channels is reduced, the UE  10  increases the time weight α1, reduces the count weight b1, and further updates the CG threshold. 
     For example, after the UE  10  increases the time weight α1 and reduces the count weight b1, the time weight α1 is 0.7, the count weight b1 is 0.3, and the CG threshold TH 1  is 0.7. Further, timer_max = 200 ms, counter_max = 10. At this time, the timing value of the CG timer  11  is 180 ms, and the count value of the CG counter  12  is three. When the UE  10  receives the DG signal from the gNB  20 , the UE  10  calculates the CG weight according to the following formula: 
     
       
         
           
             
               W 
               1 
             
             = 
             a 
             1 
             × 
             t 
             i 
             m 
             e 
             r 
             1 
             + 
             b 
             1 
             × 
             c 
             o 
             u 
             n 
             t 
             e 
             r 
             1 
             = 
             0.7 
             × 
             
               
                 180 
               
               
                 200 
               
             
             + 
             0.3 
             × 
             
               3 
               
                 10 
               
             
             = 
             0.72 
           
         
       
     
     Since 0.72 ≥ 0.7, the CG weight is greater than the CG threshold. Therefore, the UE  10  switches to the second CG transmission mode. 
     When the communication quality is reduced, it means that the communication quality is easy to change. Therefore, the UE  10  increases the time weight α1 and reduces the count weight b1. Thereby, the influence of the timing value of the CG timer  11  can be increased by increasing the time weight α1 when the UE  10  calculates the CG weight. 
     In the embodiment, the communication quality determination procedure is executed periodically. 
     In another embodiment, the communication quality determination procedure is executed when the UE  10  switches to the second CG transmission mode. 
     In addition, the UE  10  can also execute the communication quality determination procedure in real time according to the communication quality for updating the time weight α1, the count weight b1, and the CG threshold TH 1  in real time. 
     The UE  10  can determine whether the communication quality is reduced by measuring the signal strength of communication signals. For example, the previous communication quality parameter is a strength value of a first communication signal received at the beginning. The current communication quality parameter is a strength value of a communication signal received when the communication quality determination procedure is executed. If the previous communication quality parameter is greater than or equal to the current communication quality parameter, it means that the signal strength of the communication signals is reduced, so that the UE  10  can determine that the communication quality is reduced. 
     Furthermore, the UE  10  may also measure an error rate, a failure rate, or a retransmission rate of transmitting the new data to the gNB  20  to determine whether the communication quality is reduced. For example, when the error rate, the failure rate, or the retransmission rate becomes higher, the UE  10  determines that the communication quality is reduced. 
     Moreover, the UE  10  can determine whether the communication quality is reduced by measuring thedelay time of transmitting the new data to the gNB  20 . For example, when the delay time becomes longer, the UE  10  determines that the communication quality is reduced. 
     Alternatively, the UE  10  can determine whether the communication quality is reduced by measuring a switching frequency of switching the CG transmission modes. For example, when the switching frequency becomes higher, the UE  10  determines that the communication quality is reduced. 
     In summary, the UE  10  can count the number of UE failed transmission, such as UE LBT failures, or a number of gNB failed reception by the CG counter  12 . 
     Thereby, the communication quality of the radio channels can be determined, the UE  10  can increase reliability by switching to the second CG transmission mode for improving a utilization rate of resources and getting better performance. 
     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 disclosure, 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 disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.