Patent Publication Number: US-2019191439-A1

Title: Communication system, coordinator and interference controlling method

Description:
This application claims the benefit of Taiwan application Serial No. 106143899, filed Dec. 14, 2017, the disclosure of which is incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The disclosure relates in general to a communication system, a coordinator and an interference controlling method. 
     BACKGROUND 
     In the smart antenna technology, the best antenna can be selected from a plurality of antennas for a single base station. However, in conventional, the smart antenna technology is merely adopted for single base station, and the diversity of communication is not good. Along with the increment of the amount of the antennas, the antenna array may be very huge and cannot be used in a small base station. Moreover, the multi-base station technology is tried to be adopted to increase the spectrum efficiency. However, the interference among the base stations is not successfully solved, so the multi-base station technology cannot be adopted now. 
     SUMMARY 
     The disclosure is directed to a communication system, a coordinator and an interference controlling method. 
     According to one embodiment, an interference controlling method of a communication system is provided. The communication system is used for at least two user equipments to communicate. The interference controlling method includes the following steps. The measurement of a performance value of each of a plurality antennas electrically connected to each of a plurality of remote radio heads (RRHs) is operated for each of the user equipments by antenna sweeping. A performance table is obtained according to the performance value of each of the plurality of antennas. The performance table records an applicable relationship between each of the user equipments and the antennas or an applicable relationship between each of the user equipments and the RRHs. The RRHs are classified into at least one group. The user equipments are scheduled according to a priority information and the performance table. At least some of the user equipments using the same one of the at least one group are scheduled in different time slots to prevent from an interference. 
     According to another embodiment, a communication system is provided. The communication system includes at least two user equipments, at least two remote radio heads (RRHs) and a coordinator. Each of the RRHs is electrically connected to a plurality of antennas. The communication system is used for the user equipments to communicate. The coordinator includes a scanning unit, a storing unit and a scheduling unit. The scanning unit is used for operating measurement of a performance value of each of the antennas used for each of the user equipments by antenna sweeping, and obtaining a performance table according to the performance value of each of the plurality of antennas. The performance table records an applicable relationship between each of the user equipments and the antennas or an applicable relationship between each of the user equipments and the RRHs, and the RRHs are classified into at least one group. The storing unit is used for storing the performance table. The scheduling unit is used for scheduling the user equipments according to a priority information and the performance table. At least some of the user equipments using the same one of the at least one group are scheduled in different time slots to prevent from an interference. 
     According to an alternative embodiment, a coordinator is provided. The coordinator is used for coordinating a communication system. The communication system is used for at least two user equipments to communicate. The coordinator includes a scanning unit, a storing unit and a scheduling unit. The scanning unit is used for operating measurement of a performance value of each of a plurality of antennas electrically connected to each of a plurality of remote radio heads (RRHs) for each of the user equipments by antenna sweeping, and obtaining a performance table according to the performance value of each of the plurality of antennas. The performance table records an applicable relationship between each of the user equipments and the antennas or an applicable relationship between each of the user equipments and the RRHs. The RRHs are classified into at least one group. The storing unit is used for storing the performance table. The scheduling unit is used for scheduling the user equipments according to a priority information and the performance table. At least some of the user equipments using the same one of the at least one group are scheduled in different time slots to prevent from an interference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a communication system according to one embodiment. 
         FIGS. 2A to 2E  show several examples of grouping the RRHs in the communication system. 
         FIG. 3  shows a block diagram of a coordinator. 
         FIG. 4  shows a flowchart of an interference controlling method of the communication system according to one embodiment. 
         FIG. 5  shows a flowchart of the interference controlling method of the communication system according to another embodiment. 
     
    
    
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
     DETAILED DESCRIPTION 
     Please refer to  FIG. 1 , which shows a communication system  1000  according to one embodiment. The communication system  1000  includes at least two user equipments, such as the user equipments  100 A to  100 F, at least two remote radio heads (RRHs), such as the RRHs  300 A to  300 D and a coordinator  500 . For example, each of the user equipments  100 A to  100 F may be, but not limited to, a smart phone, a laptop, a computer in vehicle, a smart TV, a robot or a smart appliance. In the present embodiment, the RRH  300 A is electrically connected to a plurality of antennas A 1  to A 5 , the RRH  300 B is electrically connected to a plurality of antennas B 1  to B 5 , the RRH  300 C is electrically connected to a plurality of antennas C 1  to C 5 , the RRH  300 D is electrically connected to a plurality of antennas D 1  to D 5 . Each of the RRHs  300 A to  300 D may adopt the smart antenna technology, that several antennas having different radiation directions can be disposed on a board or a pillar. One of the antennas A 1  to A 5 , B 1  to B 5 , C 1  to C 5 , D 1  to D 5  can be used to form several beams with different directions for the user equipments  100 A to  100 F. The dotted line in  FIG. 1  represents the beam. The antennas A 1  to A 5 , B 1  to B 5 , C 1  to C 5 , D 1  to D 5  are disposed in the inside of the RRHs  300 A to  300 D. In  FIG. 1 , antennas A 1  to A 5 , B 1  to B 5 , C 1  to C 5 , D 1  to D 5  are labeled on the beams. The coordinator  500  may be, but not limited to, a server, a processor, a chip, a circuit, a circuit board or a non-transitory computer readable media storing a plurality of program codes. 
     As shown in  FIG. 1 , the user equipments  100 A to  100 F may communicate via the RRHs  300 A to  300 D. The coordinator  500  is used for coordinating the operation of the RRHs  300 A to  300 D to prevent from the interference among the RRHs  300 A to  300 D, such that the communication efficiency of the communication system  1000  can be improved. 
     Please refer to  FIGS. 2A to 2E , which show several examples of grouping the RRHs  300 A to  300 D in the communication system  1000 . In the present embodiment, to prevent the interference among the RRHs  300 A to  300 D, several groupings may be selectively used for the RRHs  300 A to  300 D. 
     As shown in  FIG. 2A , if the user equipments  100 A to  100 F served by the RRHs  300 A to  300 D are interfered with each other, the coordinator  500  may classify the RRHs  300 A to  300 D into one group G 11 . In one time slot, the coordinator  500  selects one or more RRHs from the RRHs  300 A to  300 D in the group G 11  to serve one of the user equipments  100 A to  100 F in the group G 11 . That is to say, the user equipments  100 A to  100 F served by the RRHs  300 A to  300 D are not scheduled in one time slot to prevent from the interference. In this example, only one user equipment is scheduled in one time slot. 
     As shown in  FIG. 2B , if the user equipments  100 A,  100 B,  100 F served by the RRHs  300 A,  300 B are interfered with each other, the coordinator  500  may classify the RRHs  300 A,  300 B into a group G 21 . If the user equipments  100 C,  100 D,  100 E served by the RRHs  300 C,  300 D are interfered with each other, the coordinator  500  may classify the RRHs  300 C,  300 D into a group G 22 . In one time slot, the coordinator  500  selects one or more RRHs from the RRHs  300 A,  300 B in the group G 21  to serve one of the user equipments  100 A,  100 B,  100 F in the group G 21 , and selects one or more RRHs from the RRHs  300 C,  300 D in the group G 22  to serve one of the user equipments  100 C,  100 D,  100 E in the group G 22 . That is to say, the user equipments  100 A,  100 B,  100 F served by the RRHs  300 A,  300 B are not scheduled in one time slot to prevent from the interference, and the user equipments  100 C,  100 D,  100 E served by the RRHs  300 C,  300 D are not scheduled in one time slot to prevent from the interference. In this example, two groups G 21 , G 22  are used for communication in one time slot, so the communication efficiency is improved. 
     In the present embodiment, the RRHs are classified into at least one group; and all of the at least one group can be scheduled in one time slot. For example, as shown in  FIG. 2B , the RRHs  300 A to  300 D are classified into the group G 21  and the group G 22 . There is an interference in the group G 21 , and there is an interference in the group G 22 . There is no interference between the group G 21  and the group G 22 . In this example, the group G 21  and the group G 22  can be scheduled in one time slot. 
     As shown in  FIG. 2C , if the user equipments  100 A to  100 F served by the RRHs  300 A to  300 D are not interfered with each other, the coordinator  500  may classify the RRHs  300 A to  300 D into four groups G 31  to G 34 . In the one time slot, the coordinator  500  selects the RRH  300 A in the group G 31  to serve the user equipment  100 A in the group G 31 , selects the RRH  300 B in the group G 32  to serve one of the user equipments  100 B,  100 C in the group G 32 , selects the RRH  300 C in the group G 33  to serve one of the user equipments  100 D,  100 E in the group G 33 , and selects the RRH  300 D in the group G 34  to serve the user equipment  100 F in the group G 34 . In this example, four groups G 31  to G 34  are used for communication in one time slot, so the communication efficiency is improved. 
     In the present embodiment, the RRHs are classified into at least one group; and all of the at least one group can be scheduled in one time slot. For example, as shown in  FIG. 2C , the RRHs  300 A to  300 D are classified into the group G 31 , the group G 32 , the group G 33  and the group G 34 . There is an interference in the group G 31 , there is an interference in the group G 32 , there is an interference in the group G 33 , and there is an interference in the group G 34 . There is no interference among the group G 31 , the group G 32 , the group G 33  and the group G 34 . In this example, the group G 31 , the group G 32 , the group G 33  and the group G 34  can be scheduled in one time slot. 
     As shown in  FIG. 2D , if the user equipments  100 A,  100 B,  100 F served by the RRHs  300 A,  300 D are interfered with each other, the coordinator  500  may classify the RRHs  300 A,  300 D into a group G 41 . If the user equipments  100 C,  100 D,  100 E served by the RRHs  300 B,  300 D are interfered with each other, the coordinator  500  may classify the RRHs  300 B,  300 D into a group G 42 . In one time slot, the coordinator  500  selects one or more RRHs from the RRHs  300 A,  300 D in the group G 41  to serve one of the user equipments  100 A,  100 B,  100 F in the group G 41 , and selects one or more RRHs from the RRHs  300 B,  300 C in the group G 42  to serve one of the user equipments  100 C,  100 D,  100 E in the group G 42 . That is to say, the user equipments  100 A,  100 B,  100 F served by the RRHs  300 A,  300 D are not scheduled in one time slot to prevent from the interference, and the user equipments  100 C,  100 D,  100 E served by the RRHs  300 B,  300 C are not scheduled in one time slot to prevent from the interference. In this example, two groups G 41 , G 42  are used for communication in one time slot, so the communication efficiency is improved. 
     In the present embodiment, the RRHs are classified into at least one group, and all of the at least one group can be scheduled in one time slot. For example, as shown in  FIG. 2D , the RRHs  300 A to  300 D are classified into the group G 41  and the group G 42 . There is an interference in the group G 41 , and there is an interference in the group G 42 . There is no interference between the group G 41  and the group G 42 . In this example, the group G 41  and the group G 42  can be scheduled in one time slot. 
     As shown in  FIG. 2E , if the user equipments  100 B,  100 C,  100 D,  100 E served by the RRHs  300 B,  300 C are interfered with each other, the coordinator  500  may classify the RRHs  300 B,  300 C into a group G 52 . If the user equipments  100 A,  100 F served by the RRHs  300 A,  300 D are not interfered with the user equipments in the group G 52 , the coordinator  500  may classify the RRHs  300 A,  300 D into two groups G 51 , G 53  respectively. In the one time slot, the coordinator  500  selects the RRH  300 A in the group G 51  to serve the user equipment  100 A in the group G 541 , selects one or more RRHs from the RRHs  300 B,  300 C in the group G 52  to serve one of the user equipments  100 B,  100 C,  100 D,  100 E in the group G 52 , and selects the RRH  300 D in the group G 53  to serve the user equipment  100 F in the group G 53 . That is to say, the user equipments  100 B,  100 C,  100 D,  100 E served by the RRHs  300 B,  300 C are not scheduled in one time slot to prevent from the interference. In this example, three groups G 51  to G 53  are used for communication in one time slot, so the communication efficiency is improved. 
     In the present embodiment, the RRHs are classified into at least one group, and all of the at least one group can be scheduled in one time slot. For example, as shown in  FIG. 2E , the RRHs  300 A to  300 D are classified into the group G 51 , the group G 52  and the group G 53 . There is an interference in the group G 51 , there is an interference in the group G 52 , and there is an interference in the group G 53 . There is no interference among the group G 51 , the group G 52  and the group G 53 . In this example, all of the group G 51 , the group G 52  and the group G 53  can be scheduled in one time slot, so the communication efficiency is improved. 
     In different time slots, the RRHs are classified by different ways according to the status of the user equipments  100 A to  100 F. For clearly illustrating the classifying of the RRHs  300 A to  300 D, the elements of the coordinator  500  and the operation thereof are illustrated as below. 
     Please refer to  FIG. 3 , which shows a block diagram of the coordinator  500 . The coordinator  500  includes a scanning unit  510 , a storing unit  520  and a scheduling unit  530 . The scanning unit  510  is used for obtaining the information of the antennas A 1  to A 5 , B 1  to B 5 , C 1  to C 5 , D 1  to D 5  by antenna sweeping. For example, the scanning unit  510  may be a chip, a circuit, a circuit board or a non-transitory computer readable media storing a plurality of program codes. The storing unit  520  is used for storing information. For example, the storing unit  520  may be a memory, a hard disk or a cloud data center. The scheduling unit  530  is used for scheduling the communication. For example, the scheduling unit  530  may be a chip, a circuit, a circuit board or a non-transitory computer readable media storing a plurality of program codes. The operation of those elements is illustrated as below via a flowchart. 
     Please refer to  FIG. 4 , which shows a flowchart of an interference controlling method of the communication system  1000  according to one embodiment. In step S 110 , the scanning unit  510  operates the measurement of a performance value of each of the antennas A 1  to A 5 , B 1  to B 5 , C 1  to C 5 , D 1  to D 5  electrically connected to the RRHs  300 A to  300 D used for each of the user equipments  100 A to  100 F by antenna sweeping. 
     In step S 120 , the scanning unit  510  creates a performance table TB 1  according to the performance values. The performance table TB 1  records an applicable relationship between each of the user equipments  100 A to  100 F and the antennas A 1  to A 5 , B 1  to B 5 , C 1  to C 5 , D 1  to D 5  and/or an applicable relationship between each of the user equipments  100 A to  100 F and the RRHs  300 A to  300 D. The RRHs  300 A to  300 D are classified into at least one group. 
     In step S 130 , the scheduling unit  530  schedules the user equipments  100 A to  100 F according to a priority information PR and the performance table TB 1 , such that at least some of the user equipments  100 A to  100 F using the same one of the at least one group are scheduled in different time slots to prevent from the interference. 
     Please refer to  FIG. 5 , which shows a flowchart of the interference controlling method of the communication system  1000  according to another embodiment. In detail, the interference controlling method of the communication system  1000  may include more detail steps. In step S 100 , a user equipment pool (UE pool) is created. The user equipment pool records the user equipments  100 A to  100 F. 
     In the S 110 , the scanning unit  510  operates the measurement of the performance value of each of the antennas A 1  to A 5 , B 1  to B 5 , C 1  to C 5 , D 1  to D 5  electrically connected to the RRHs  300 A to  300 D used for each of the user equipments  100 A to  100 F in the equipment pool by antenna sweeping. The scanning unit  510  may obtain the measurements via Channel Quality Indicator (CQI), Signal-to-Noise Ratio (SNR), Signal-to-Interference-plus-Noise Ratio (SINR), Received Signal Strength Indicator (RSSI), Reference Signal Received Quality (RSRQ), Reference Signal Received Power (RSRP), or Throughput. 
     In one embodiment, the scanning unit  510  may operate the measurement of part of the RRHs  300 A to  300 D for part of the user equipments  100 A to  100 F during the idle time. Or, in another embodiment, the scanning unit  510  may update the measurement only if the RRHs  300 A to  300 D change. Or, the scanning unit  510  may update the measurement only if the user equipments  100 A to  100 F change. 
     In step S 120 , the scanning unit  510  creates the performance table TB 1  according to the performance values. The performance table TB 1  records the applicable relationship between each of the user equipments  100 A to  100 F and the antennas A 1  to A 5 , B 1  to B 5 , C 1  to C 05 , D 1  to D 5  and/or the applicable relationship between each of the user equipments  100 A to  100 F and the RRHs  300 A to  300 D. The performance table TB 1  is stored in the storing unit  520 . For example, an example of the performance table TB 1  is illustrated as table I. The applicable relationship can be determined by determining whether the performance index is larger than a threshold. If the performance index of one antenna is larger than the threshold, then it is deemed that this antenna is applicable for this user equipment; if the performance index of one antenna is not larger than the threshold, then it is deemed that this antenna is not applicable for this user equipment. In table I, if one antenna is applicable for the user equipment, it is labeled “V”; if one antenna is not applicable for the user equipment, it is not labeled. 
     
       
         
           
               
               
             
               
                 TABLE I 
               
             
            
               
                   
               
               
                 remote 
                 user equipment 
               
               
                 radio 
                 (priority information) 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 head 
                   
                 100A 
                 100B 
                 100C 
                 100D 
                 100E 
                 100F 
               
               
                 (RRH) 
                 antenna 
                 (1) 
                 (4) 
                 (6) 
                 (2) 
                 (3) 
                 (5) 
               
               
                   
               
               
                 300A 
                 A1 
                 V 
                   
                   
                   
                   
                   
               
               
                   
                 A2 
                   
                   
                   
                 V 
               
               
                   
                 A3 
                   
                   
                 V 
               
               
                   
                 A4 
                 V 
                 V 
               
               
                   
                 A5 
                   
                 V 
               
               
                 300B 
                 B1 
                   
                   
                 V 
                 V 
               
               
                   
                 B2 
                   
                   
                   
                 V 
               
               
                   
                 B3 
                 V 
                   
                 V 
               
               
                   
                 B4 
                   
                 V 
               
               
                   
                 B5 
               
               
                 300C 
                 C1 
               
               
                   
                 C2 
                   
                   
                 V 
               
               
                   
                 C3 
                   
                   
                   
                 V 
                 V 
               
               
                   
                 C4 
                   
                   
                   
                   
                   
                 V 
               
               
                   
                 C5 
                   
                   
                   
                   
                 V 
               
               
                 300D 
                 D1 
               
               
                   
                 D2 
                   
                   
                 V 
                 V 
               
               
                   
                 D3 
                   
                   
                 V 
                   
                 V 
                 V 
               
               
                   
                 D4 
               
               
                   
                 D5 
               
            
           
           
               
               
               
               
            
               
                 group 
                 group G21: 
                 group G11: RRHs 
                 group G22: RRH 
               
               
                   
                 RRHs 300A, 
                 300A to 300D 
                 300C, 300D 
               
               
                   
                 300B 
               
               
                   
               
            
           
         
       
     
     One of the user equipments may use one of the antennas. Or, one of the user equipments may use more than one of the antennas. As shown in table I, the user equipment  100 A uses the antennas A 1 , A 4  connected to the RRH  300 A and the antenna B 3  connected to the RRH  300 B. The user equipment  100 B uses the antennas A 4 , A 5  connected to the RRH  300 A and the antenna B 4  connected to the RRH  300 B. According to the applicable relationship that the user equipment  100 A and the user equipment  100 B use the RRHs  300 A,  300 B only, the user equipments  100 A,  100 B and the RRHs  300 A,  300 B are grouped as the group G 21 . 
     The user equipment  1000  uses the antenna A 3  connected to the RRH  300 A, the antennas B 2 , B 3  connected to the RRH  300 B, the antenna C 2  of the RRH  300 C and the antennas D 2 , D 3  connected to the RRH  300 D. The user equipment  100 D uses the antenna A 2  of the RRH  300 A, the antennas B 1 , B 2  connected to the RRH  300 B, the antenna C 3  connected to the RRH  300 C, and the antenna D 2  connected to the RRH  300 D. According to the applicable relationship that both of the user equipment  100 C and the user equipment  100 D use the RRH  300 A to  300 D, the user equipments  100 C,  100 D and the RRHs  300 A to  300 D are grouped as the group G 11 . 
     The user equipment  100 E uses the antennas C 3 , C 5  connected to the RRH  300 C and the antenna D 3  connected to the RRH  300 D. The user equipment  100 F uses the antenna C 4  connected to the RRH  300 C and the antenna D 4  connected to the RRH  300 D. According to the applicable relationship that both of the user equipment  100 E and the user equipment  100 F use the RRHs  300 C to  300 D only, the user equipments  100 E,  100 F and the RRHs  300 C to  300 D are grouped as the group G 22 . That is to say, in the  8120 , the RRHs  300 A to  300 D are classified into at least one group. 
     In step S 130 , the scheduling unit  530  schedules the user equipments  100 A to  100 F according to the priority information PR and the performance table TB 1 , such that at least some of the user equipments  100 A to  100 F using the same one of the at least one group are scheduled in different time slots to prevent from the interference. 
     For example, according to the priority information PR, the user equipments  100 A to  100 F may be arranged as “the user equipment  100 A, the user equipment  100 D, the user equipment  100 E, the user equipment  100 B, the user equipment  100 F and the user equipment  100 C.” The step S 130  includes steps S 131  to S 133 . In step S 131 , the scheduling unit  530  first schedules the user equipment having the highest priority information PR. As shown in table II, the scheduling unit  530  schedules the user equipment  300 A having the highest priority information PR to use the RRHs  300 A,  300 B in the first time slot. 
     
       
         
           
               
               
               
               
               
             
               
                   
                 TABLE II 
               
               
                   
                   
               
               
                   
                   
                   
                   
                 Fourth 
               
               
                   
                 First time 
                 Second time 
                 Third time 
                 time 
               
               
                   
                 slot 
                 slot 
                 slot 
                 slot 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 group 
                 G21 
                 G22 
                 G11 
                 G21 
                 G22 
                 G11 
               
               
                 RRH 
                 300A, 
                 300C, 
                 300A to 
                 300A, 
                 300C, 
                 300A to 
               
               
                   
                 300B 
                 300D 
                 300D 
                 300B 
                 300D 
                 300D 
               
               
                 Antenna 
                 A1, A4, 
                 C3, C5, 
                 A2, B1, B2, 
                 A4, A5, 
                 C4, D4 
                 A3, B1, 
               
               
                   
                 B3 
                 D3 
                 C3, D2 
                 B4 
                   
                 B3, C2, 
               
               
                   
                   
                   
                   
                   
                   
                 D2, D3 
               
               
                 user 
                 100A 
                 100E 
                 100D 
                 100B 
                 100F 
                 100C 
               
               
                 equipment 
               
               
                   
               
            
           
         
       
     
     In step S 132 , the scheduling unit  530  schedules another user equipment according to the priority information PR without any interference. As shown in table I, there is an interference between the user equipment  100 D having the second highest priority information PR and the user equipment  100 A for using the RRHs  300 A,  300 B, so the scheduling unit  530  tries to schedule the user equipment  100 E having the third priority information PR. Therefore, the scheduling unit  530  schedules the user equipment  100 E in the first time slot to use the RRHs  300 C,  300 D. 
     In step S 133 , the scheduling unit  530  removes the scheduled user equipments  100 A,  100 E from the user equipment pool. 
     In step S 140 , the scheduling unit  530  determines whether the user equipment pool is empty. If the user equipment pool is not empty, then the process returns to steps S 131  to S 133 , until the user equipment pool is empty. As shown in table II, after scheduling the first time slot, the user equipments  100 B,  100 C,  100 D,  100 F may be arranged as the user equipment  100 D, the user equipment  100 B, the user equipment  100 F, the user equipment  100 C″ according to the priority information PR. 
     Then, the scheduling unit  530  schedules the user equipment  100 D having the highest priority information PR in the second time slot to use the RRHs  300 A to  3000 . 
     The RRHs  300 A to  300 D are used in the second time slot, so other user equipments  100 B,  100 F,  100 C cannot be scheduled in the second time slot. 
     After scheduling the second time slot, the user equipments  100 B,  100 C,  100 F may be arranged as “the user equipment  100 B, the user equipment  100 F, the user equipment  100 C” according to the priority information PR. Then, the scheduling unit  530  schedules the user equipment  100 B having the highest priority information PR in the third time slot to use the RRHs  300 A,  300 B. There is no interference between the user equipment  100 F having the second priority information to use the RRHs  300 C,  300 D and the user equipment  100 B to use the RRHs  300 A,  300 B, so the scheduling unit  530  can schedules the user equipment  100 F in the third time slot to use the RRHs  300 C,  300 D. 
     After scheduling the third time slot, the user equipment  100 C is arranged according to the priority information PR. Then, the scheduling unit  530  schedules the user equipment  100 C having the highest priority information in the fourth time slot to use the RRHs  300 A to  300 D. 
     Base on above, the grouping in  FIG. 2B  is adopted in the first time slot, and the user equipments  100 A,  100 E scheduled in the first time use all of the groups G 21 , G 22  in  FIG. 2B . The grouping in  FIG. 2A  is adopted in the second time slot, and the user equipment  100 D scheduled in the second time use the group G 11  in  FIG. 2A . The grouping in  FIG. 2B  is adopted in the third time slot, and the user equipments  100 B,  100 F scheduled in the third time use all of the groups G 21 , G 22  in  FIG. 2B . The grouping in  FIG. 2A  is adopted in the fourth time slot, and the user equipment  100 C scheduled in the fourth time use the group G 11  in  FIG. 2A . In first to fourth time slots, the RRHs  300 A to  300 D are classified by different ways, such as  FIGS. 2A to 2E . 
     According to the embodiments, at least some of the user equipments  100 A to  100 F using the same one of the at least one group are scheduled in different time slots to prevent from the interference. For example, the user equipments  300 A to  300 D using the group G 11  are scheduled in the first time slot, the second time slot, the fourth time slot and the third time slot respectively. The user equipments  300 A,  300 B using the group G 21  are scheduled in the first time slot and the third time slot. The user equipments  300 A,  300 B using the group G 22  are scheduled in the fourth time slot and the second time slot. 
     Besides, some of the user equipments  100 A to  100 F scheduled in the same time slot belong to different groups, to prevent from the interference. For example, the user equipments  100 A,  100 E scheduled in the first time slot belong to the different groups G 21 , G 22 . The user equipment  100 D scheduled in the second time slot belongs to the group G 11 . The user equipments  100 B,  100 F scheduled in the third time slot belong to the different groups G 21 , G 22 . The user equipment  100 C scheduled in the fourth time slot belongs to the group G 11 . 
     In other words, some of the user equipments  100 A to  100 F which are interfered with each are scheduled in different time slots. For example, the antenna A 4  is applicable for the user equipment  100 A and the user equipment  100 B, so the user equipment  100 A and the user equipment  100 B cannot be scheduled in one time slot; the antenna B 1  is applicable for the user equipment  100 C and the user equipment  100 D, so the user equipment  100 C and the user equipment  100 D cannot be scheduled in one time slot. On the other hand, there is no common antenna applicable for both of the user equipment  100 A and the user equipment  100 E, so the user equipment  100 A and the user equipment  100 E can be scheduled. There is no common antenna applicable for both of the user equipment  100 B and the user equipment  100 F, so the user equipment  100 B and the user equipment  100 F can be scheduled. 
     In the first time slot (the third time slot), the amount of the scheduled user equipments  100 A,  100 E ( 100 B,  100 F) is more than one. In the second time slot (the fourth time slot), the amount of the user equipment  100 D ( 100 C) is one. That is to say, in different time slots, the amounts of the scheduled user equipments are different. Besides, other kinds of grouping may be adopted in other time slots, and it depended on the status at that time slot. 
     According to the embodiments, the communication system  1000  may use one or more groups in one time slot, such that the spectrum efficiency can be improved. And, the communication system  1000  may adopt the grouping technology to prevent from the interference among the RRHs  300 A to  300 D. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed embodiments. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.