Patent Publication Number: US-2023142503-A1

Title: Method and system for dynamically switching transmission modes to decrease latency in unlicensed controlled environments

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application claims the priority benefit of TW application serial No. 110141738 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 decrease latency 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 channels 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 channels is bad. 
     However, the communication quality of the radio channels is constantly changing in unlicensed controlled environments (UCEs). For example, unpredictable noise interference often decreases the communication quality of the radio channels. When there is no noise interference, the radio channels 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 and 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. 
     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 decrease latency in unlicensed spectrum control environments (UCEs). In environments where the communication quality of the radio channels 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 channels, 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 executes steps of: transmitting a new data to a gNB; determining whether the gNB successfully receives the new data; when the gNB successfully receives the new data, starting a CG timer, increasing a count value of a CG counter, resetting a failed transmission count value of a failed transmission counter, calculating a CG weight according to a timing value of the CG timer and the count value of the CG counter, 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 to a first CG transmission mode; when the CG weight is smaller than the CG threshold, transmitting a next new data to the gNB. 
     The CG weight is calculated by the following formula: 
     
       
         
           
             
               W 
               = 
               
                 
                   a 
                   × 
                   timer 
                 
                 + 
                 
                   b 
                   × 
                   counter 
                 
               
             
             ; 
           
         
       
       
         
           
             
               timer 
               = 
               
                 timer_current 
                 timer_max 
               
             
             ; 
           
         
       
       
         
           
             
               counter 
               = 
               
                 counter_current 
                 counter_max 
               
             
             ; 
           
         
       
     
     W is the CG weight, a is a time weight, b 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 success, and a+b=1. 
     The CG threshold is calculated by the following formula: 
       TH=MAX[ a,b ]; 
     TH is the CG threshold. 
     When the gNB successfully receives the new data from the UE, it means that the UE successfully transmits the new 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 successfully transmits data to the gNB many times. Therefore, the communication quality of the current radio channels is determined to be good, which causes the UE to successfully send data to the gNB many times. Therefore, the UE switches to the first CG transmission mode, thereby improving the latency of data transmission by the first CG transmission mode. 
     For example, the first CG transmission mode may be a URLLC CG mode. Therefore, when the communication quality is good, the latency of data transmission can be improved by the first 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 successful 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 modes 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 channels. When the communication quality of the radio channels is good, the UE switches to the first CG transmission mode. In this way, when the communication quality is good, the first CG transmission mode can be used to improve the latency, 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 decrease latency 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 decrease latency 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 decrease latency 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  10 , and includes step S 101  to step S 111 . 
     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 the gNB  20  successfully receives the new data. When the gNB  20  successfully receives the new data, it means that the UE  10  successfully transmits the new data to the gNB  20 . 
     In an embodiment, the UE  10  determines whether the gNB  20  successfully receives the new data is determined by determining whether an acknowledgement (ACK) signal transmitted by the gNB  20  is received. When the UE  10  receives the ACK signal transmitted by the gNB  20 , the UE  10  determines that the gNB  20  successfully receives the new data. 
     The gNB  20  will generate and transmit the ACK signal when the gNB  20  successfully receives and decodes the new data transmitted by the UE  10 . Namely, when the UE  10  can receive the ACK signal from the gNB  20 , it means that the gNB  20  successfully receives and decodes the new data. 
     In another embodiment, the UE  10  determines whether the gNB  20  successfully receives the new data by determining whether a negative-acknowledgement (NACK) signal transmitted by the gNB  20  is received. When the UE  10  receives the NACK signal transmitted by the gNB  20 , the UE  10  determines that the gNB  20  unsuccessfully receives the new data. 
     The gNB  20  will generate and transmit the NACK signal when the gNB unsuccessfully receives or decodes the new data transmitted by the UE  10 . Namely, when the UE  10  receives the NACK signal from the gNB  20 , it means that the gNB  20  unsuccessfully receives or decodes the new data. 
     In still another embodiment, whether the gNB  20  successfully receives the new data is determined by determining whether a CG retransmission timer  14  expires. When the CG retransmission timer  14  expires, the UE  10  determines that the gNB  20  unsuccessfully receives the new data. 
     The CG retransmission timer  14  is used to determine whether the UE  10  receives the ACK signal within a preset time. Namely, when the UE  10  determines that the CG retransmission timer  14  expires, it means that the UE  10  does not receive the ACK signal within the preset time, and it also means that the UE  10  does not successfully transmit the new data. 
     In step S 103 , when the gNB  20  successfully receives the new data, 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  and increases the count value of the CG counter  12  by one. In the embodiment, when the UE  10  determines that the gNB  20  successfully receives the new data 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  determines that the gNB  20  successfully receives the new data 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 failed transmission count value of a failed transmission counter  13 . When the UE  10  determines that the gNB  20  successfully receives the new data, the UE  10  can determine that the new data is successfully transmitted. Therefore, the UE  10  needs to reset the failed transmission count value of the failed transmission counter  13 . Namely, the failed transmission count value means a number of continuously failed 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 
               = 
               
                 
                   a 
                   × 
                   timer 
                 
                 + 
                 
                   b 
                   × 
                   counter 
                 
               
             
             ; 
           
         
       
       
         
           
             
               timer 
               = 
               
                 timer_current 
                 timer_max 
               
             
             ; 
           
         
       
       
         
           
             counter 
             = 
             
               
                 counter_current 
                 counter_max 
               
               . 
             
           
         
       
     
     W is the CG weight, a is a time weight, b 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 success, and a+b=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 success 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 ten. 
     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: 
       TH=MAX[ a,b ]; 
     TH is the CG threshold and equals to a maximum of the time weight a and the count weight b. For example, if a=0.7, b=0.3, since a&gt;b, TH=a=0.7. 
     In step S 107 , when the CG weight is greater than or equal to the CG threshold, the UE  10  switches to the first CG transmission mode. 
     When the CG weight is smaller than the CG threshold, the UE  10  transmits a next new data to the gNB  20  (S 101 ). 
     In the embodiment, a CG transmission mode between the UE  10  and the gNB  20  executed in the step S 101  is the NR-U CG mode. After several steps in  FIG.  1   , in S 107 , the UE  10  is switched to the first CG transmission mode, wherein the first CG transmission mode is the URLLC CG mode. 
     In step S 108 , when the gNB  20  unsuccessfully receives the new data, the UE  10  resets the CG counter  12 . 
     In step S 109 , the UE  10  increases the failed transmission count value. 
     In step S 110 , the UE  10  determines whether the failed transmission count value is greater than or equal to a failed transmission threshold. 
     In step S 111 , when the failed transmission count value is greater than or equal to the failed transmission threshold, the UE  10  resets the timing value of the CG timer  11  and the failed transmission count value of the failed transmission counter  13 , and then the UE  10  transmits a next new data to the gNB  20  (S 101 ). 
     Further, when the failed transmission count value is smaller than the failed 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 successful transmissions, or a number of gNB successful receptions. When the UE  10  successfully transmits the new data or the gNB  20  successfully receives the new data, the UE  10  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 successful transmissions or the number of the gNB successful receptions within the preset maximum of waiting time (timer_max) according to the CG timer  11  and the CG counter  12 . 
     For example, a1=0.7, b1=0.3, TH 1 =0.7, timer_max=200 ms, counter_max=10. When the UE  10  determines that the gNB  20  successfully receives the new data after the UE  10  transmits a first new data to the gNB  20 , the UE  10  starts the CG timer  11 , and increases the counter value of the CG counter  12  by one. Since the UE  10  determines that the gNB  20  successfully receives the new data, the UE  10  resets the failed transmission count value of the failed 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  just begins to start timing, the timing value is zero. The CG counter  12  also begins to count, and the count value becomes one after the count value is increased. The CG weight is calculated by the following formula: 
     
       
         
           
             
               W 
               = 
               
                 
                   
                     a 
                     × 
                     timer 
                   
                   + 
                   
                     b 
                     × 
                     counter 
                   
                 
                 = 
                 
                   
                     
                       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 a second new data to the gNB  20 . 
     If the UE  10  determines that the gNB  20  unsuccessfully receives the new data 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 failed transmission count value of the failed transmission counter  13  by one. Then, the UE  10  determines whether the failed transmission count value is greater than or equal to the failed transmission threshold. 
     The failed transmission counter  13  is increased by one when the UE  10  determines that the gNB  20  unsuccessfully receives the new data. When the UE  10  determines that the gNB  20  successfully receives the new data, the UE  10  will reset the failed transmission count value of the failed transmission counter  13 . Therefore, when the gNB  20  has unsuccessfully received the multiple new data continuously, the failed transmission count value of the failed transmission counter  13  will be continuously accumulated. Namely, when the failed transmission count value of the failed transmission counter  13  is greater than the failed transmission threshold, it means that the gNB  20  has continuously and unsuccessfully received the multiple new data transmitted by the UE  10 . Therefore, the UE  10  can determine the communication quality of the radio channels is bad, the UE  10  does not need to switch to the first CG transmission mode, and the UE  10  needs to maintain the current CG transmission mode for maintaining high reliability communications. The UE  10  further resets the CG timer  11  and the failed transmission counter  13  for avoiding switching to the first CG transmission mode. 
     However, after the UE  10  transmits the second new data to the gNB  20 , if the UE  10  determines that the gNB  20  successfully receives the new data, 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 
               = 
               
                 
                   
                     a 
                     × 
                     timer 
                   
                   + 
                   
                     b 
                     × 
                     counter 
                   
                 
                 = 
                 
                   
                     
                       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 a third new data to the gNB  20 . 
     After a while, the gNB  20  has not continuously and unsuccessfully received the multiple new data. The failed transmission count value of the failed transmission counter  13  is not greater than the failed 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  determines that the gNB  20  successfully receives the new data, 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 
               = 
               
                 
                   
                     a 
                     × 
                     timer 
                   
                   + 
                   
                     b 
                     × 
                     counter 
                   
                 
                 = 
                 
                   
                     
                       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 first CG transmission mode. 
     Moreover, the gNB  20  may partially unsuccessfully receive the multiple new data. If a number of the gNB  20  continuously and unsuccessfully receiving the multiple new data is not greater than the failed 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  will 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 
               = 
               
                 
                   
                     a 
                     × 
                     timer 
                   
                   + 
                   
                     b 
                     × 
                     counter 
                   
                 
                 = 
                 
                   
                     
                       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 first CG transmission mode. Namely, even if the count value of the CG counter  12  is reset, the UE  10  can switch to the first 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 a and the count weight b 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 increased according to the previous communication quality parameter and the current communication quality parameter for adjusting the time weight a and the count weight b. In the embodiment, a sum of the time weight a and the count weight b is 1. 
     In step S 304 , when the communication quality is increased, the UE  10  increases the time weight a and reduces the count weight b. 
     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 increased, the UE  10  maintains the time weight a and the count weight b, and updates the previous communication quality parameter to be the current communication quality parameter. 
     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 a and the count weight b 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 a and the count weight b are correspondingly changed. Further, the UE  10  can calculate the CG weight only based on the time weight a or the count weight b. Namely, the UE  10  can set the time weight a to be one, and set the count weight b to be zero. Or the UE can set the time weight a to be zero, and set the count weight b to be one. 
     For example, the initial value of the time weight a is 0.5, and the initial value of the count weight b is 0.5. Namely, a=0.5, b=0.5, TH=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  determines that the gNB  20  successfully receives the new data, the UE  10  calculates the CG weight according to the following formula: 
     
       
         
           
             W 
             = 
             
               
                 
                   a 
                   × 
                   timer 
                 
                 + 
                 
                   b 
                   × 
                   counter 
                 
               
               = 
               
                 
                   
                     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 a next new data to 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 increased. When the communication quality of the radio channels is increased, the UE  10  increases the time weight a, reduces the count weight b, and further updates the CG threshold. 
     For example, after the UE  10  increases the time weight a and reduces the count weight b, the time weight a is 0.7, the count weight b is 0.3, and the CG threshold TH 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  determines that the gNB  20  successfully receives the new data, the UE  10  calculates the CG weight according to the following formula: 
     
       
         
           
             W 
             = 
             
               
                 
                   a 
                   × 
                   timer 
                 
                 + 
                 
                   b 
                   × 
                   counter 
                 
               
               = 
               
                 
                   
                     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 first CG transmission mode. 
     When the communication quality is increased, it means that the communication quality is stable. Therefore, the UE  10  increases the time weight a, and reduces the count weight b. Thereby, the influence of the timing value of the CG timer  11  can be increased by increasing the time weight a 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 first 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 a, the count weight b, and the CG threshold TH in real time. 
     The UE  10  can determine whether the communication quality is increased 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 smaller than or equal to the current communication quality parameter, it means that the signal strength of the communication signals is increased, so that the UE  10  can determine that the communication quality is increased. 
     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 increased. For example, when the error rate, the failure rate, or the retransmission rate is uncreased, the UE  10  determines that the communication quality is increased. 
     Moreover, the UE  10  can determine whether the communication quality is increased by measuring the delay time of transmitting the new data to the gNB  20 . For example, when the delay time becomes shorter, the UE  10  determines that the communication quality is increased. 
     Alternatively, the UE  10  can determine whether the communication quality is increased by measuring a switching frequency of switching the CG transmission modes. For example, when the switching frequency becomes lower, the UE  10  determines that the communication quality is increased. 
     In summary, the UE  10  can count the number of UE successful transmissions, or a number of gNB successful receptions by the CG counter  12 . Thereby, the communication quality of the radio channels can be determined, the UE  10  can decrease latency by switching to the first 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.