Patent Publication Number: US-2023164748-A1

Title: Uplink signal time difference adjustment system and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwanese application no. 110143479, filed on Nov. 23, 2021. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     TECHNICAL FIELD 
     The technical field relates to an uplink signal time difference adjustment system and method. 
     BACKGROUND 
     A timing advance mechanism is stipulated based on 3GPP standards. In the standard timing advance mechanism, a base station detects time difference between the base station and a user, and a control element of a media access control layer (MAC CE) sends the time difference to a user apparatus for adjustments. However, since the time difference sent to the user apparatus for adjustments has limited granularity, high QAM modulation is subject to limitations due to insufficient SINR. 
     SUMMARY 
     One of exemplary embodiments provides an uplink signal time difference adjustment system, including a base station and multiple user apparatuses. The base station has a time slot boundary. Each user apparatus is connected to the base station via wireless communication. The base station is used for the following steps. Each first delay time of arrival of each uplink signal is detected based on the time slot boundary. Each second delay time of each uplink signal is adjusted according to multiple sampling points. Each time offset between each first delay time and each second delay time corresponding to each user apparatus is calculated. The time slot boundary is adjusted according to each time offset. 
     One of exemplary embodiments provides an uplink signal time difference adjustment method, adapted to a base station and including the following steps. Each first delay time of arrival of each uplink signal is detected based on a time slot boundary. Each second delay time of each uplink signal is adjusted according to multiple sampling points. Each time offset between each first delay time and each second delay time corresponding to each user apparatus is calculated. The time slot boundary is adjusted according to each time offset. 
     Several exemplary embodiments accompanied with figures are described in detail below to further describe the disclosure in details. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure. 
         FIG.  1    is a schematic diagram of an uplink signal time difference adjustment system according to an embodiment of the disclosure. 
         FIG.  2    is a schematic diagram of an uplink signal time difference adjustment system according to an embodiment of the disclosure. 
         FIG.  3    is a schematic diagram of an uplink signal time difference adjustment system according to an embodiment of the disclosure. 
         FIG.  4    is a schematic diagram of an uplink signal time difference adjustment system according to an embodiment of the disclosure. 
         FIG.  5    is a schematic diagram of an uplink signal time difference adjustment system according to an embodiment of the disclosure. 
         FIG.  6 A  is a schematic diagram of user apparatuses in an uplink signal time difference adjustment system according to an embodiment of the disclosure. 
         FIG.  6 B  is a schematic diagram of random grouping of user apparatuses in an uplink signal time difference adjustment system according to an embodiment of the disclosure. 
         FIG.  6 C  is a schematic diagram of effective grouping of user apparatuses in an uplink signal time difference adjustment system according to an embodiment of the disclosure. 
         FIG.  7    is a flowchart of an uplink signal time difference adjustment method according to an embodiment of the disclosure. 
         FIG.  8    is a flowchart of adjusting second delay times in the uplink signal time difference adjustment method illustrated in  FIG.  7    according to an embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION OF DISCLOSED EMBODIMENTS 
     Part of the embodiments of the disclosure will be described in detail below with accompanying drawings. For the reference numerals used in the following description, the same reference numerals appearing in different drawings will be regarded as the same or similar elements. These embodiments are only a part of the disclosure and do not disclose all possible implementations of the disclosure. 
       FIG.  1    is a schematic diagram of an uplink signal time difference adjustment system  1  according to an embodiment of the disclosure. With reference to  FIG.  1   , the uplink signal time difference adjustment system  1  includes a base station  10 , a user apparatus UE 1 , a user apparatus 
     UE 2 , and a user apparatus UE 3 , but the number of user apparatuses is not limited thereto. The base station  10  has a time slot boundary SB. Each of the user apparatuses UE 1 , UE 2 , and UE 3  is connected to the base station  10  via wireless communication. The user apparatuses UE 1 , UE 2 , and UE 3  are, for example but not limited to, electronic apparatuses that may be connected to a base station via wireless communication such as tablet computers, smart phones, or the like. 
     The distance between each of the user apparatuses UE 1 , UE 2 , UE 3  and the base station  10  is different. Therefore, downlink signals received by the user apparatuses UE 1 , UE 2 , and UE 3  from the base station  10  have different delay times ta 1 , ta 2 , and ta 3  depending on their respective distances from the base station  10 . Similarly, uplink signals UL 1 , UL 2 , and UL 3  transmitted by the user apparatuses UE 1 , UE 2 , and UE 3  to the base station  10  have different delay times ta 1 , ta 2 , and ta 3  depending on their respective distances from the base station  10  while arriving at the base station  10 . Among the above, the delay times of the downlink signals are roughly the same as the delay times of the uplink signals. 
     Uplink signals ULd 1 , ULd 2 , and ULd 3  shown in  FIG.  1    refer to the uplink signals UL 1 , UL 2 , and UL 3  of which arrival at the base station  10  is delayed. The base station  10  respectively detects the uplink signals UL 1 , UL 2 , and UL 3  with a physical layer. With the time slot boundary SB as the benchmark, according to  FIG.  1   , the uplink signal ULd 1  is delayed by the first delay time ta 1 , the uplink signal ULd 2  is delayed by the first delay time ta 2 , and the uplink signal ULd 3  is delayed by the first delay time ta 3 . 
       FIG.  2    is a schematic diagram of the uplink signal time difference adjustment system  1  according to an embodiment of the disclosure. As shown in  FIG.  2   , the base station  10  includes a media access control layer. Due to the limited resolution of the media access control layer of the base station  10 , the physical layer of the base station  10  extracts the uplink signals ULd 1 , ULd 2 , and ULd 3  merely at multiple fixed sampling points S, and the sampling points S are related to the resolution of a control element of the media access control layer. For example, assuming that the resolution of the media access control layer of the base station  10  is 6 bits, then there are  31  sampling points on each divided half with the time slot boundary SB as a center. Therefore, the base station  10  adjusts arrival times of the uplink signals ULd 1 , ULd 2 , and ULd 3  by the control element of the media access control layer. Taking the uplink signal ULd 1  as an example, the base station  10  transmits the adjustment of the uplink signal ULd 1  required by the control element to the user apparatus UE 1  through a downlink signal (not illustrated). Next, the user apparatus UE 1  adjusts the time of transmitting an uplink signal according to the downlink signal and transmits an uplink signal UL 1 ′ to the base station  10 . Similarly, the base station  10  also adjusts the uplink signals ULd 2  and ULd 3 , and the user apparatuses UE 2  and UE 3  transmit uplink signals UL 2 ′ and UL 3 ′ to the base station  10 . According to  FIG.  2   , with the time slot boundary SB as the benchmark, the uplink signal UL 1 ′ is delayed by a second delay time ta 1 *, the uplink signal UL 2 ′ is delayed by a second delay time ta 2 *, and the uplink signal UL 3 ′ is delayed by a second delay time ta 3 *. 
       FIG.  3    is a schematic diagram of the uplink signal time difference adjustment system  1  according to an embodiment of the disclosure. As shown in  FIG.  3   , the base station  10  respectively calculates time offsets E 1 , E 2 , and E 3  between the first delay times ta 1 , ta 2 , ta 3  and the second delay times ta 1 *, ta 2 *, ta 3 * corresponding to the user apparatuses UE 1 , UE 2 , and UE 3 . 
       FIG.  4    is a schematic diagram of the uplink signal time difference adjustment system  1  according to an embodiment of the disclosure. As shown in  FIG.  4   , the base station  10  calculates a time slot boundary adjustment ta adj  according to the time offsets E 1 , E 2 , and E 3 , and adjusts the time slot boundary SB to a time slot boundary SB′ according to the time slot boundary adjustment ta adj . It should be noted that the smaller the time offsets E 1 , E 2 , and E 3 , the closer the times of the uplink signals UL 1 ′, UL 2 ′, and UL 3 ′ arriving at the base station  10  to the sampling points S. On the contrary, the greater the time offsets E 1 , E 2 , and E 3 , the farther the times of the uplink signals UL 1 ′, UL 2 ′, and UL 3 ′ arriving at the base station  10  away from the sampling points S. 
     In an embodiment, the base station  10  respectively forms an offset vector according to the time offsets E 1 , E 2 , . . . , EU corresponding to the user apparatuses UE 1 , UE 2 , . . . UEU. For example, the base station  10  forms an offset vector ta ta* according to the first delay times ta 1 , ta 2 , . . . , ta U  and the second delay times ta 1 *, ta 2 *, . . . , ta U * corresponding to the user apparatuses UE 1 , UE 2 , . . . , UEU as shown below: 
       {right arrow over (ta ta*)}=( ta   1   *   −ta   1   , ta   2   *   −ta   2   , . . . , ta   |U|   *   −ta   |U| ) 
     Among the above, U is a total number of user apparatuses. 
     In addition, the base station  10  also forms a weight matrix w according to weights w 1 , . . . , w |U|  corresponding to the user apparatuses UE 1 , UEU as shown below: 
     
       
         
           
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                     0 
                   
                   
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     Among the above, those skilled in the art may set the corresponding weights wi, according to the importance of the user apparatuses UE 1 , UEU. For example, in an uplink signal, if the signaling radio bearer (SRB) requirement is greater than the data radio bearer (DRB), a weight may be set according to SRB/DRB or according to a signal demodulation mode. 
     After gaining the offset vector {right arrow over (ta ta*)} and the weight matrix w, the base station  10  obtains the minimum value according to a product of the offset vector ta ta* and the weight matrix w by a vector norm. The vector norm is a method of converting a vector into a scalar. The base station  10  obtains the minimum value (scalar) from the product of the offset vector ta ta and the weight matrix w by the vector norm, such as min∥w·{right arrow over (ta ta*)}∥ p . With min∥w·{right arrow over (ta ta*)}∥ p  as the time slot boundary adjustment ta adj , the time slot boundary SB is adjusted to the time slot boundary SB&#39; according to the time slot boundary adjustment ta adj.    
       FIG.  5    is a schematic diagram of the uplink signal time difference adjustment system  1  according to an embodiment of the disclosure. As shown in  FIG.  5   , taking the uplink signal 
     ULd 3  as an example, the base station  10  transmits the adjustment of the uplink signal ULd 3  required by the control element to the user apparatus UE 3  through a downlink signal (not illustrated) according to the sampling points S. Next, the user apparatus UE 3  adjusts the time of transmitting the uplink signal UL 3 ′ to the base station  10  according to the downlink signal, and the base station  10  detects the second delay time ta 3 *of arrival of the uplink signal UL 3 ′. The base station  10  calculates the time offset E 3  between the first delay time ta 3  and the second delay time ta 3 * corresponding to the user apparatus UE 3 . According to  FIG.  5   , since the time slot boundary SB of the base station  10  has been adjusted to the time slot boundary SB&#39;, with the time slot boundary SB′ as the benchmark, the time offset E 3  between the first delay time ta 3  and the second delay time ta 3 * corresponding to the user apparatus UE 3  has been eliminated, which means the uplink signal UL 3 ′ of the user apparatus UE 3  may be extracted by the physical layer of the base station  10  as soon as arriving at the base station  10 . 
     However, since the time slot boundary SB of the base station  10  has been adjusted to the time slot boundary SB′, with the time slot boundary SB′ as the benchmark, the second delay time ta 1 * of the uplink signal UL 1 ′ and the second delay time ta 2 * of the uplink signal UL 2 ′ are also be changed, such that the time offsets E 1  and E 2  between the first delay times ta 1 , ta 2  and the second delay time ta 1 *, ta 2 * corresponding to the user apparatuses UE 1  and UE 2  are changed accordingly. With reference to  FIG.  4    and  FIG.  5    together, after the time slot boundary SB of the base station  10  is adjusted to the time slot boundary SB′, the time offset E 2  is also reduced, which means the time of the uplink signal UL 2 ′ arriving at the base station  10  is closer to the sampling points S. 
     However, the time offset E 1  has increased, which means the time of the uplink signal UL 1 ′ arriving at the base station  10  is farther from the sampling points S. 
     During the communication between the base station  10  and the user apparatuses through the uplink signals and the downlink signals, the base station  10  continues the adjustment according to the uplink signal of each user apparatus. Therefore, the base station keeps adjusting the time slot boundary SB to reduce uplink time deviation of all user apparatuses. 
     In an embodiment, without violating QoS principles, the media access control layer of the base station  10  may group the user apparatuses.  FIG.  6 A  is a schematic diagram of user apparatuses in the uplink signal time difference adjustment system  1  according to an embodiment of the disclosure. As shown in  FIG.  6 A , the base station  10  detects uplink signals UL 1 , UL 2 , UL 3 , and UL 4  of user apparatuses UE 1 , UE 2 , UE 3 , and UE 4  by the physical layer. According to  FIG.  6 A , with the time slot boundary SB as the benchmark, the uplink signal ULd 1  is delayed by the first delay time ta 1 , the uplink signal ULd 2  is delayed by the first delay time ta 2 , the uplink signal ULd 3  is delayed by the first delay time ta 3 , and the uplink signal ULd 4  is delayed by a first delay time ta 4 . 
     The base station  10  adjusts the uplink signals ULd 1 , ULd 2 , ULd 3 , and ULd 4 , and then the user apparatuses UE 1 , UE 2 , UE 3 , and UE 4  transmit the uplink signals UL 1 ′, UL 2 ′, UL 3 ′, UL 4 ′ to the base station  10 . With the time slot boundary SB as the benchmark, the uplink signal UL 1 ′ is delayed by the second delay time ta 1 *, the uplink signal UL 2 ′ is delayed by the second delay time ta 2 *, the uplink signal UL 3 ′ is delayed by the second delay time ta 3 *, and the uplink signal UL 4 ′ is delayed by a second delay time ta 4 *. The base station  10  respectively calculates time offsets E 1 , E 2 , E 3 , and E 4  between the first delay times ta 1 , ta 2 , ta 3 , ta 4  and the second delay time ta 1 *, ta 2 *, ta 3 *, ta 4 * corresponding to the user apparatuses UE 1 , UE 2 , UE 3 , and UE 4 . 
     In an embodiment, the media access control layer of the base station  10  may group the user apparatuses UE 1 , UE 2 , UE 3 , and UE 4  according to the time offsets E 1 , E 2 , E 3 , and E 4 .  FIG.  6 B  is a schematic diagram of random grouping of the user apparatuses in the uplink signal time difference adjustment system  1  according to an embodiment of the disclosure. As shown in  FIG.  6 B , it is assumed that the media access control layer of the base station  10  randomly groups the user apparatus UE 1  and the user apparatus UE 2  into a user apparatus group UEG. In the user apparatus group UEG, the base station  10  calculates the time slot boundary adjustment ta adj  according to the time offset E 1  of the user apparatus UE 1  and the time offset E 2  of the user apparatus UE 2 , and adjusts the time slot boundary SB to the time slot boundary SB′ according to the time slot boundary adjustment ta adj . 
     Furthermore, in the user apparatus group UEG, with the time slot boundary SB′ as the benchmark, the second delay time ta 1 * of the uplink signal UL 1 ′ and the second delay time ta 2 * of the uplink signal UL 2 ′ are changed as well, causing the time offsets E 1  and E 2  between the first delay time ta 1 , ta 2  and the second delay time ta 1 *, ta 2 * corresponding to the user apparatuses UE 1  and UE 2  to be changed accordingly. With reference to  FIG.  6 A  and  FIG.  6 B  together, in the user apparatus group UEG, after the time slot boundary SB of the base station  10  is adjusted to the time slot boundary SB′, the time offset E 1  becomes greater than that before grouping, and the time offset E 2  becomes smaller than that before grouping. Even if the time slot boundary SB of the base station  10  is adjusted to the time slot boundary SB′, this random grouping makes no difference in the distances between the times of the uplink signals UL 1 ′, UL 2 ′ arriving at the base station  10  and the sampling points S in the user apparatus group UEG, compared to those before grouping. 
     In view of this, a better grouping method may shorten the sampling period of the physical layer of the base station  10 . For example, assuming that the resolution of the media access control layer of the base station  10  is 6 bits, then there are  31  sampling points on each divided half with the time slot boundary SB as a center. The time offsets E 1 , E 2 , . . . , EU between the first delay times ta 1 , ta 2 , . . . , ta U  and the second delay times ta 1 *, ta 2 *, . . . , ta U * corresponding to the user apparatuses UE 1 , UE 2 , UEU are relative to the time slot boundary SB. If the  31  sampling points on one half of the time slot boundary SB is divided into 10 time slots, and user apparatuses having time offsets in the same time slot are grouped into the same user apparatus group, then the time offsets corresponding to the user apparatuses in each user apparatus group are close to each other. 
     According to  FIG.  6 A , the time offset E 1  corresponding to the user apparatus UE 1  is relatively close to the time offset E 3  corresponding to the user apparatus UE 3 , while the time offset E 2  corresponding to the user apparatus UE 2  is relatively close to the time offset E 4  corresponding to the user apparatus UE 4 . Therefore, the media access control layer of the base station  10  may conduct grouping according to the time offsets of the user apparatuses. 
       FIG.  6 C  is a schematic diagram of effective grouping of user apparatuses in an uplink signal time difference adjustment system according to an embodiment of the disclosure. As shown in  FIG.  6 C , the media access control layer of the base station  10  groups the user apparatus 
     UE 1  and the user apparatus UE 3  into a user apparatus group UEGa, and groups the user apparatus UE 2  and the user apparatus UE 4  into a user apparatus group UEGb. 
     In the user apparatus group UEGa, the base station  10  calculates a time slot boundary adjustment ta adja  according to the time offset E 1  of the user apparatus UE 1  and the time offset E 3  of the user apparatus UE 3 , and adjusts the time slot boundary SB to a time slot boundary SBa according to the time slot boundary adjustment ta adja . In this way, in the user apparatus group UEGa, with the time slot boundary SBa as the benchmark, the second delay time ta 1 * of the uplink signal UL 1 ′ and the second delay time ta 3 * of the uplink signal UL 3 ′ are also changed, causing the time offsets E 1  and E 3  between the first delay times ta 1 , ta 3  and the second delay times ta 1 *, ta 3 * corresponding to the user apparatuses UE 1  and UE 3  to be changed accordingly. With reference to  FIG.  6 A and  6 C  together, in the user apparatus group UEGa, after the time slot boundary SB of the base station  10  is adjusted to the time slot boundary SBa, although there is no significant change in the time offset E 3 , the time offset E 1  is significantly reduced. This means in the user apparatus group UEGa, the times of the uplink signals UL 1 ′ and UL 3 ′ arriving at the base station  10  are close to the sampling points S, which may reduce sampling errors of the physical layer of the base station  10 . 
     Similarly, in the user apparatus group UEGb, the base station  10  calculates a time slot boundary adjustment ta adjb  according to the time offset E 2  of the user apparatus UE 2  and the time offset E 4  of the user apparatus UE 4 , and adjusts the time slot boundary SB to a time slot boundary SBb according to the time slot boundary adjustment ta adjb . In this way, in the user apparatus group UEGb, with the time slot boundary SBb as the benchmark, the second delay time ta 2 * of the uplink signal UL 2 ′ and the second delay time ta 4 * of the uplink signal UL 4 ′ are also changed, causing the time offsets E 2  and E 4  between the first delay times ta 2 , ta 4  and the second delay times ta 2 *, ta 4 * corresponding to the user apparatuses UE 2  and UE 4  to be changed accordingly. With reference to  FIG.  6 A  and  FIG.  6 C  together, in the user apparatus group UEGb, after the time slot boundary SB of the base station  10  is adjusted to the time slot boundary SBb, both the time offsets 
     E 2  and E 4  are significantly reduced. This means in the user apparatus group UEGb, the times of the uplink signals UL 2 ′ and UL 4 ′ arriving at the base station  10  are close to the sampling points S, which may reduce sampling errors of the physical layer of the base station  10 . 
       FIG.  7    is a flowchart of an uplink signal time difference adjustment method  7  shown in an embodiment of the disclosure. As shown in  FIG.  7   , in step S 710 , a base station detects each first delay time of arrival of each uplink signal based on a time slot boundary. In step S 720 , each second delay time of each uplink signal is adjusted according to multiple sampling points. In step  5730 , each time offset between each first delay time and each second delay time corresponding to each user apparatus is calculated. In step S 740 , the time slot boundary is adjusted according to each time offset. 
     In an embodiment, the base station further includes a physical layer and a media access control layer. The sampling points S are related to the resolution of a control element of the media access control layer. The media access control layer notifies the physical layer to adjust the time slot boundary according to each time offset. 
       FIG.  8    is a flowchart of adjusting the second delay times in step  5720  in the uplink signal time difference adjustment method illustrated in  FIG.  7    according to an embodiment of the disclosure. As shown in  FIG.  8   , in step S 721 , each downlink signal is transmitted to each user apparatus according to the sampling points. In step S 722 , each user apparatus adjusts the time of arrival of each uplink signal at the base station according to each downlink signal. In step S 723 , the base station detects each second delay time of arrival of each uplink signal. 
     In an embodiment, the uplink signal time difference adjustment method further includes grouping each user apparatus into multiple user apparatus groups according to each time offset corresponding to each user apparatus. In each user apparatus group, the time slot boundary relative to each user apparatus group is adjusted according to each time offset of each user apparatus in each user apparatus group. 
     In an embodiment, the uplink signal time difference adjustment method further includes forming an offset vector according to each time offset corresponding to each user apparatus, setting a weight corresponding to each user apparatus to form a weight matrix, obtaining the minimum value from a product of the offset vector and the weight matrix by a vector norm, and adjusting the time slot boundary according to the minimum value. 
     In summary, the uplink signal time difference adjustment system and method provided in the disclosure may enable the base station to modulate uplink signals without being limited by the resolution of the media access control layer of the base station. The time slot boundary is adjusted according to the difference between the original delay time and the delay time adjusted by the control element of the media access control layer corresponding to each user apparatus, thereby reducing the time difference of the uplink signals between the base station and the user apparatuses and improving the performance of the base station in modulating the uplink signals. 
     In addition, through the timing fine-tuning mechanism of the base station, the granularity problem of the user apparatuses is fixed to improve the SINR of the base station system. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.