Abstract:
The present invention proposed a method and a device for controlling propagation delay in a base station of a wireless communication system based on COMP transmission. To be specific, w hen sending downlink data to a mobile station, the base station processes part of data of one or more other unsynchronized base stations and sends the processed part of data to the mobile station at one or more specific time slots simultaneously. By applying the solution of the present invention, because data, corresponding to the length of the out-of-synchronization information, of an unsynchronized base station is sent to the mobile station at a specific time slot by a synchronized base station or other unsynchronized base stations, DL data that is sent to the mobile station by the unsynchronized base station all falls within the detection window of the mobile station, such that the resulted problem of the decreased performance of a receiver due to the propagation delay is solved.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to COMP (Coordinated Multi-Point) transmission in a wireless communication system, especially to the coherent transmission in the COMP transmission. 
       BACKGROUND OF THE INVENTION 
       [0002]    Considering the multi-path transmission of a single cell, influence on the bit error ratio performance of a receiver is unacceptable even if propagation delay between two COMP cells is less than a CP (Cyclic Prefix) length. 
         [0003]    Furthermore, the influence of propagation delay on the bit error ratio performance of a receiver ties to the transmission manner. For the same propagation delay, the bit error ratio performance of a receiver adopting non-coherent transmission is better than the bit error ratio performance of a receiver adopting coherent transmission. For the coherent transmission and the non-coherent transmission, the bit error ratio performance of a receiver when the propagation delay is less than a CP is better than the bit error ratio performance of a receiver when the propagation delay is greater than a CP. 
         [0004]    Although the DL (downlink) coherent transmission between COMP cells can obtain greater gain than non-coherent transmission. However, the performance of DL coherent transmission greatly deteriorates due to the propagation delay, and the performance of coherent transmission even becomes equivalent to that of the non-coherent transmission when the propagation delay is large. 
         [0005]      FIG. 1  shows a schematic diagram of the resulted problem of non-synchronization due to different propagation delay of three BSs (Base Station) in DL coherent transmission according to the prior art. The region between the left and right dashed lines in  FIG. 1  denotes the detection window of MS  2 ′ (mobile sta(ion). The three BSs  11 ′,  12 ′ and  13 ′ achieve GPS (Global Positioning System) synchronization and send DL data to the MS  2 ′ simultaneously. The MS  2 ′ and the BS  11 ′ achieve synchronization, that is, DL data sent by the BS  11 ′ is just detected completely within the detection window of the MS  2 ′. Because the distance from the BS  12 ′ to the MS  2 ′ is farther than the distance from the BS  11 ′ to the MS  2 ′, but the distance from the BS  13 ′ to the MS  2 ′ is nearer than the distance from the BS  11 ′ to the MS  2 ′, the MS  2 ′ can only detect part of data from the BS  12 ′ and the BS  13 ′ respectively within its detection window due to the problem of propagation delay. As shown in  FIG. 1 , part of tail data of the BS  12 ′ will fall outside of the detection window of the MS  2 ′, while part data of the BS  13 ′ will outside of the detection window of the MS  2 ′. If the length of data falling outside of the detection window of the MS  2 ′ in DL data, which the BS  12 ′ and the BS  13 ′ respectively send to the MS  2 ′, is greater than a CP, then, the receiving performance of the MS  2 ′ will greatly deteriorate. 
         [0006]    For aforesaid problem, there are two solutions in the prior art: 
         [0007]    1) adding the length of CP to tolerate greater propagation delay; 
         [0008]    2) replacing coherent transmission with non-coherent transmission. 
         [0009]    However, for the first solution, the system efficiency will greatly decrease due to the adding of the length of CP. Moreover, if the propagation delay is still greater than the length of CP, the bit error ratio performance of a receiver will still be greatly influenced. 
         [0010]    For the second solution, it means that the gain from coherent transmission is abandoned due to the fact that coherent transmission is replaced with non-coherent transmission. 
       SUMMARY OF THE INVENTION 
       [0011]    In order to solve the aforesaid disadvantages in the prior art, the present invention proposes a method and device for controlling propagation delay in a base station of a wireless communication system based on COMP transmission. To be specific, when sending downlink data to a MS, BS processes part of data of one or more other unsynchronized base stations and sends the processed part of data to the MS at one or more specific time slots simultaneously. 
         [0012]    According to the first aspect of the present invention, there is provided a method of controlling propagation delay in a base station of a wireless communication system based on COMP transmission, the method comprising the steps of: when sending downlink data to a mobile station, processing part of data of one or more other unsynchronized base stations and sending the processed part of data to the mobile station at one or more specific time slots simultaneously. 
         [0013]    According to the second aspect of the present invention, there is provided a method of assisting to control propagation delay in an unsynchronized base station of a wireless communication system based on COMP transmission, wherein when out-of-synchronization information corresponding to the unsynchronized base station is larger than 0, the method comprises the steps of: sending to a mobile station downlink data to be transmitted with head data block corresponding to the length of the out-of-synchronization information clipped. 
         [0014]    According to the third aspect of the present invention, there is provided a method of assisting to control propagation delay in an unsynchronized base station of a wireless communication system based on COMP transmission, wherein when out-of-synchronization information corresponding to the unsynchronized base station is less than 0, the method comprises the steps of: postponing transmission starting moment tOr the length of the out-of-synchronization information, and sending to a mobile station downlink data to be transmitted with tail data block corresponding to said length of the out-of-synchronization information clipped. 
         [0015]    According to the fourth aspect of the present invention, there is provided a control device for controlling propagation delay in a base station of a wireless communication system based on COMP transmission, wherein the control device is used for, when sending downlink data to a mobile station, processing part of data of one or more other unsynchronized base stations and sending the processed part of data to the mobile station at one or more specific time slots simultaneously. 
         [0016]    According to the fifth aspect of the present invention, there is provided a first assisting control device for assisting to control propagation delay in an unsynchronized base station of a wireless communication system based on COMP transmission, wherein when out-of-synchronization information corresponding to the unsynchronized base station is larger than 0, the first assisting control device comprises: a fourth sending means, for sending to a mobile station downlink data to be transmitted with head data block corresponding to the length of the out-of-synchronization information clipped. 
         [0017]    According to the fifth aspect of the present invention, there is provided a second assisting control device for assisting to control propagation delay in an unsynchronized base station of a wireless communication system based on COMP transmission, wherein when out-of-synchronization information corresponding to the unsynchronized base station is less than 0, the second assisting control device comprises: a fifth sending means, for postponing transmission starting moment for the length of the out-of-synchronization information, and sending to a mobile station downlink data to be transmitted with tail data block corresponding to said length of the out-of-synchronization information clipped. 
         [0018]    In the present invention, because data, corresponding to the length of the out-of-synchronization information, of an unsynchronized base station is sent to the mobile station at a specific time slot through a synchronized base station or other unsynchronized base stations, DL data that is sent to the mobile station by the unsynchronized base station all falls within the detection window of the mobile station, such that the resulted problem of the decreased performance of a receiver due to the propagation delay is solved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects and advantages of the present invention will become apparent. 
           [0020]      FIG. 1  shows a schematic diagram of the resulted problem of non-synchronization due to different propagation delay of three BSs in DL coherent transmission, according to the prior art; 
           [0021]      FIG. 2  shows a schematic diagram of a network of COMP transmission system based on DL coherent transmission; 
           [0022]      FIG. 3  shows a flowchart of a method of a synchronized BS processing part of data of one or more other unsynchronized BSs and sending the processed part of data to the MS at one or more specific time slots simultaneously, when sending downlink data to a MS, according to one embodiment of the present invention; 
           [0023]      FIG. 4  shows a schematic diagram of a synchronized BS processing part of data of one or more other unsynchronized BSs and sending the processed part of data to the MS at one or more specific time slots simultaneously, when sending downlink data to a MS, according to one embodiment of the present invention; 
           [0024]      FIG. 5  shows a schematic diagram of an unsynchronized BS processing part of data of one or more other unsynchronized BSs and sending the processed part of data to the MS at one or more specific time slots simultaneously, when sending downlink data to a MS, according to another embodiment of the present invention; 
           [0025]      FIG. 6  shows a schematic diagram of controlling propagation delay, according to another embodiment of the present invention; and 
           [0026]      FIG. 7  shows a block diagram of structure of a control device in a synchronized BS for processing part of data of one or more other unsynchronized BSs and sending the processed part of data to the MS at one or more specific time slots simultaneously, when sending downlink data to a MS, according to one embodiment of the present invention. 
       
    
    
       [0027]    In drawings, same or similar reference signs refer to the same or similar component. 
       DETAILED DESCRIPTION OF EMBODIMENTS 
       [0028]    In COMP transmission system based on DL coherent transmission, a plurality of BSs serve one MS. Because the transmission distances from each of the plurality of BSs to the MS are different, it causes different DL propagation delay from each BS to the MS. When the MS establishes synchronization with one of the plurality of BSs, DL data that is sent to the MS by the synchronized BS will completely fall within the detection window of the MS, but part of DL data that is sent to the MS by other unsynchronized BSs will fall outside of the detection window of the MS due to the propagation delay, so that the receiving performance of the IS deteriorates. 
         [0029]    Based on this, when sending DL data to a MS, the synchronized BS may process part of data of one or more other unsynchronized BSs and send the processed part of data to the MS at one or more specific time slots simultaneously, so that DL data that is sent to the MS by one or more other unsynchronized BSs all falls within the detection window of the MS. Certainly, when sending DL data to a MS, the unsynchronized BS may also process part of data of one or more other unsynchronized BSs and send the processed part of data to the MS at one or more specific time slots simultaneously. 
         [0030]    Hereinafter, referring to the drawings, the two scenarios are described respectively. 
         [0031]      FIG. 2  shows a schematic diagram of a network of COMP transmission system based on DL coherent transmission. The BS  11 , the BS  12 , the BS  13  and the MS  2  are shown in  FIG. 2 . Wherein, the BS  11 , the BS  12  and the BS  13  achieve synchronization of GPS and send DL data to the MS  2  simultaneously. The MS  2  and the BS  11  achieve synchronization, and DL data that is sent to the MS  2  by the synchronized BS  11  completely falls within the detection window of the MS  2 . The propagation distance from the unsynchronized BS  12  to the MS  2  is greater than the propagation distance from the synchronized BS  11  to the MS  2 , and part of tail data in DL data that is sent to the MS  2  by the unsynchronized BS  12  falls outside of the detection window of the MS 2  due to propagation delay. The propagation distance from the unsynchronized BS  13  to the MS  2  is less than the propagation distance from the synchronized BS  11  to the MS  2 , part of head data in DL data that is sent to the MS  2  by the unsynchronized BS  13  falls outside of the detection window of the MS  2  due to propagation delay. 
         [0032]    It should be noted that the present invention will be descried by taking it as example that the COMP transmission system based on DL coherent transmission comprises three BSs simultaneously serving one MS, but those skilled in the art should understand that the number of BSs in the COMP transmission system based on DL coherent transmission of the present invention is not limited to three. 
         [0033]    In the COMP transmission system based on DL coherent transmission shown in  FIG. 2 , the synchronized BS  11 , the unsynchronized BS  12  and the unsynchronized BS  13  perform backhaul of data and signaling via X2 interface before the three BSs starts to send DL data to the MS  2 , therefore, any one of the three BSs knows DL data to be transmitted, channel transmission matrix H and out-of-synchronization information (namely propagation delay from other BSs to the MS  2 ) from other BSs to the MS  2 . To be specific, the synchronized BS  11  will receive backhaul information respectively from the unsynchronized BS  12  and the unsynchronized BS  13 . Wherein, backhaul information that has been received from the unsynchronized BS  12  by the synchronized BS  11  comprises DL data that is to be sent from the unsynchronized BS  12  to the MS  2 , the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2  and out-of-synchronization information of the unsynchronized BS  12  and the MS  2 , namely propagation delay from the unsynchronized BS  12  to the MS  2 ; similarly, backhaul information that has been received from the unsynchronized BS  13  by the synchronized BS  11  comprises DL data that is to be sent from the unsynchronized BS  13  to the MS  2 , the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2  and out-of-synchronization information of the unsynchronized BS  13  and the MS  2 , namely propagation delay from the unsynchronized BS  13  to the MS  2 . 
         [0034]    Accordingly, the unsynchronized BS  12  will also receive backhaul information respectively from the synchronized BS  11  and the unsynchronized BS  13 ; the unsynchronized BS  13  will also receive backhaul information respectively from the synchronized BS  11  and the unsynchronized BS  12 , which will not be described in detail for the purpose of simplicity. 
         [0035]    Hereinafter, referring to  FIG. 2 ,  FIG. 3  and  FIG. 4 , the scenario that when sending downlink data to the MS  2 , the synchronized BS  11  processes part of data of the unsynchronized BS  12  and the unsynchronized BS  13  and sends the processed part of data to the MS  2  respectively at specific time slots simultaneously is described. 
         [0036]      FIG. 3  shows a flowchart of a method of the synchronized BS  11  processing part of data of the unsynchronized BS  12  and the unsynchronized BS  13  and sending the processed part of data to the MS  2  at different time slots simultaneously, when sending DL data to the MS  2 , according to one embodiment of the present invention. 
         [0037]      FIG. 4  shows a schematic diagram of the synchronized BS  11  processing part of data of the unsynchronized BS  12  and the unsynchronized BS  13  and sending the processed part of data to the MS  2  at different time slots simultaneously, when sending DL data to the MS  2 , according to one embodiment of the present invention. 
         [0038]    In  FIG. 4 , the first row corresponds to DL data from the synchronized BS  11  that is received within the detection window of the MS  2  in the solution of the present invention. The upper portion of the second row corresponds to DL data from the unsynchronized BS  12  that is received within the detection window of the MS  2  in the solution of the prior art, the lower portion of the second row corresponds to DL data from the unsynchronized BS  12  that is received within the detection window of the MS  2  in the solution of the present invention. The upper portion of the third row corresponds to DL data from the unsynchronized BS  13  that is received within the detection window of the MS  2  in the solution of the prior art, the lower portion of the third row corresponds to DL data from the unsynchronized BS  13  that is received within the detection window of the MS  2  in the solution of the present invention. 
         [0039]    As shown in  FIG. 3 , firstly, in the step S 11 , the synchronized BS  11  respectively receives backhaul information from the unsynchronized BS  12  and the unsynchronized BS  13  via X2 interface. Wherein, backhaul message that is received from the unsynchronized BS  12  by the synchronized BS  11  comprises DL data to he transmitted from the unsynchronized BS  12  to the MS  2 , the channel transmission matrix of DL channel from the unsynchronized BS  12  to the MS  2  and out-of-synchronization information of the unsynchronized BS  12  and the MS  2 , namely propagation delay from the unsynchronized BS  12  to the MS  2 ; backhaul message that is received from the unsynchronized BS  13  by the synchronized BS  11  comprises DL data to he transmitted from the unsynchronized BS  13  to the MS  2 , the channel transmission matrix of DL channel from the unsynchronized BS  13  to the MS  2  and out-of-synchronization information of the unsynchronized BS  13  and the MS  2 , namely propagation delay from the unsynchronized BS  13  to the MS  2 . 
         [0040]    Then, in the step S 12 , the synchronized BS  11  respectively determines whether out-of-synchronization information in backhaul information from the unsynchronized BS  12  and the unsynchronized BS  13  is greater than 0. 
         [0041]    Because the MS  2  and the synchronized BS  11  achieve synchronization, out-of-synchronization information from the synchronized BS  11  to the MS  2  is considered as 0. And because the propagation distance from the unsynchronized BS  12  to the MS  2  is greater than the propagation distance from the synchronized BS  11  to the MS  2 , out-of-synchronization information corresponding to the unsynchronized BS  12  is greater than 0; and because the propagation distance from the unsynchronized BS  13  to the MS  2  is less than the propagation distance from the synchronized BS  11  to the MS  2 , out-of-synchronization information corresponding to the unsynchronized BS  13  is less than 0. 
         [0042]    Because out-of-synchronization information corresponding to the unsynchronized BS  12  is greater than 0, in the step S 13 , when sending DL data to the MS  2 , the synchronized BS  11  processes head data block corresponding to the length of the out-of-synchronization information in DL data sent by the unsynchronized BS  12  and sends the processed head data block to the MS  2  at a specific time slot simultaneously. 
         [0043]    Wherein, the specific time slot is the start time slot, lasting the length of the out-of-synchronization information, within the time slot occupied by the synchronized base station  11  for sending DL data. 
         [0044]    Accordingly, the unsynchronized BS  12  sends to the MS  2  DL data to be transmitted with the head data block corresponding to the length of the out of-synchronization information clipped. 
         [0045]    For example, if the out-of-synchronization information of the unsynchronized BS  12  and the MS  2  is 0.1 μs. then when sending DL data to the MS  2 , the synchronized BS  11  processes head data block corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  12  and sends the processed head data block to the MS  2  at the start time slot of the length of 0.1 μs for sending DL data simultaneously. 
         [0046]    Accordingly, the unsynchronized BS  12  sends to the MS  2  DL data to be transmitted with the head data block corresponding to the length of 0.1 μs clipped. 
         [0047]    It may be seen from  FIG. 4  that the upper portion of the second row corresponds to DL data from the unsynchronized BS  12  that is received within the detection window of the MS  2  in the solution of the prior art, because of propagation delay such as 0.1 μs between the unsynchronized BS  12  and the MS  2 , data block (shown as “         ” in  FIG. 4 ) with the length of 0.1 μs falls outside of the detection window of the MS  2  in the solution of the prior art. After using the solution of the present invention, because head data block (shown as “         ” in  FIG. 4 ) corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  12  is sent by the synchronized BS  11  instead of the unsynchronized BS  12  at the start time slot of the length of 0.1 μs for sending DL data simultaneously when the synchronized BS  11  sending DL data, and DL data that is sent to the MS  2  by the unsynchronized BS  12  is the DL data with head data block corresponding to the length of 0.1 μs clipped. Therefore, it may be seen from the solution of the present invention of the lower portion of the second row that DL data (namely DL data with head data block corresponding to the length of 0.1 μs clipped) that is received from the unsynchronized BS  12  by the MS  2  falls within the detection window of the MS  2  completely. And the head data block sent by the synchronized BS  11  instead of the unsynchronized BS  12  falls within the detection window of the MS  2 , the head data block being denoted by “         ” corresponding to the first row in  FIG. 4 . 
         [0048]    Furthermore, the aforesaid processing is multiplying the head data block to be transmitted by the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2  and the precoding matrix of the unsynchronized BS  12 , as well as the inverse matrix of the channel transmission matrix of the DL channel from the synchronized BS  11  to the MS  2  and the inverse matrix of the precoding matrix of the synchronized BS  11 . To be specific, assuming that DL data to be transmitted of the unsynchronized BS  12  is S 2 , wherein the head data block sent by the synchronized BS  11  instead of the unsynchronized BS  12  is S 21 , the remaining data block is S 22 , wherein S 2 =S 21 +S 22 . 
         [0049]    Before sending to the MS  2  the head data block S 21  of the unsynchronized BS  12 , the synchronized BS  11  firstly processes the head data block S 21 , that is, the head data block S 21  is transformed into F 1   −1 H 1   −1 H 2 F 2 S 21 , wherein, F 1   −1  is the inverse matrix of the prccoding matrix of the synchronized BS  11 , H 1   −1  is the inverse matrix of the channel transmission matrix of the DL channel from the synchronized BS  11  to the MS  2 , H 2  is the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2 , and F 2  is the precoding matrix of the unsynchronized BS  12 . 
         [0050]    Because the synchronized BS  11  sends the processed head data block F 1   −1 H 1   −1 H 2 F 2 S 21  to the MS  2 , and the unsynchronized BS  12  sends to the MS  2  the remaining data S 22  with the head data block clipped, for the MS  2 , the received data of the MS  2  is y 2 =H 1 F 1 F 1   −1 H 1   −1 H 2 F 2 S 21 +H 2 F 2 S 22 =H 2 F 2 S 2 , that is, all of DL data belonging to the unsynchronized BS  12 . 
         [0051]    Here, it is to be noted that, if the transmission manner of transmission diversity is used between BS and MS, then the synchronized BS  11  may send the processed head data block of the unsynchronized BS  12  by using the antenna for sending its own DL data but if the transmission manner of space multiplexing is used between BS and MS, the synchronized BS  11  should use extra transmitting antenna to transmit the processed head data block of the unsynchronized BS  12 . 
         [0052]    Similarly, Because out-of-synchronization information corresponding to the unsynchronized BS  13  is less than 0, in the step S 14 , when sending DL data to the MS  2 , the synchronized BS  11  processes tail data block corresponding to the length of the out-of-synchronization information in DL data sent by the unsynchronized BS  13  and sends the processed tail data block to the MS  2  at a specific time slot simultaneously. 
         [0053]    Wherein, the specific time slot is the final time slot, lasting the length of the out-of-synchronization information, within the time slot occupied by the synchronized base station  11  for sending DL signal. 
         [0054]    Accordingly, the unsynchronized BS  13  postpones the transmission starting moment for the length of the out-of-synchronization information and then sends to the MS  2  DL data to bc transmitted with the tail data block corresponding to the length of the out-of-synchronization information clipped. 
         [0055]    For example, if the out-of-synchronization information of the unsynchronized BS  13  and the MS  2  is −0.1 μs, then when sending DL data to the MS  2 , the synchronized BS  11  processes tail data block corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  13  and sends the processed tail data block to the MS  2  at the final time slot of the length of 0.1 μs for sending DL data simultaneously. 
         [0056]    Accordingly, the unsynchronized BS  13  postpones the transmission starting moment for the length of 0.1 μs and then sends to the MS  2  DL data to be transmitted with the tail data block corresponding to the length of 0.1 μs clipped. 
         [0057]    It may be seen from  FIG. 4  that the upper portion of the third row corresponds to DL data from the unsynchronized BS  13  that is received within the detection window of the MS  2  in the solution of thc prior art, because of propagation delay such as −0.1 μs between the unsynchronized BS  13  and the MS  2 , data block (shown as “         ” in  FIG. 4 ) with the length of 0.1 μs falls outside of the detection window of the MS  2  in the solution of the prior art. After using the solution of the present invention, because tail data block (shown as “         ” in  FIG. 4 ) corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  13  is sent by the synchronized BS  11  instead of the unsynchronized BS  13  at the final time slot of the length of 0.1 μs for sending DL data simultaneously when the synchronized BS  11  sends DL data, and the unsynchronized BS  13  postpones the transmission starting moment for the length of 0.1 μs and then sends to the MS  2  DL data to be transmitted with tail data block corresponding to the length of 0.1 μps clipped. Therefore, it can be seen from the solution of the present invention of the lower portion of the third row that DL data (namely DL data with tail data block corresponding to the length of 0.1 μs clipped) that is received from the unsynchronized BS  13  by the MS  2  falls within the detection window of the MS  2  completely. And the tail data block sent by the synchronized BS  11  instead of the unsynchronized BS  13  falls within the detection window of the MS  2 , the tail data block being denoted by “         ” corresponding to the first row in  FIG. 4 . 
         [0058]    Furthermore, the aforesaid processing is multiplying the tail data block to be transmitted by the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2  and the precoding matrix of the unsynchronized BS  13 , as well as the inverse matrix of the channel transmission matrix of the DL channel from the synchronized BS  11  to the MS  2  and the inverse matrix of the precoding matrix of the synchronized BS  11 . 
         [0059]    To be specific, assuming that DL data to be transmitted of the unsynchronized BS  13  is S 3 , wherein the tail data block sent by the synchronized BS  11  instead of the unsynchronized BS  13  is S 31 , the remaining data block is S 32 , wherein S 3 =S 31 +S 32 . 
         [0060]    Before sending to the MS  2  the tail data block S 31  of the unsynchronized BS  13 , the synchronized BS  11  firstly processes the tail data block S 31 , that is, the tail data block S 31  is transformed into F 1   −1 H 1   −1 H 3 F 3 S 31 , wherein, F 1   −1  is the inverse matrix of the precoding matrix of the synchronized BS  11 , H 1   −1  is the inverse matrix of the channel transmission matrix of the DL channel from the synchronized BS  11  to the MS  2 , H 3  is the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2 , F 3  is the precoding matrix of the unsynchronized BS  13 . 
         [0061]    Because the synchronized BS  11  sends the processed tail data block F 1   −1 H 1   −1 H 3 F 3 S 31  to the MS  2 , and the unsynchronized BS  13  sends to the MS  2  the ming data S 32  with the tail data block clipped, for the MS  2 , the received data of the MS  2  is y 3 =H 1 F 1 F 1   −1 H 1   −1 H 3 F 3 S 31 +H 3 F 3 S 32 =H 3 F 3 S 3 , that is, all of DL data belonging to the unsynchronized BS  13 . 
         [0062]    Here, it is to he noted that, if the transmission manner of transmission diversity is used between BS and MS, the synchronized BS  11  may send the processed tail data block of the unsynchronized BS  13  by using the antenna for sending its own DL data; but if the transmission manner of space multiplexing is used between BS and MS, the synchronized BS  11  should use extra transmitting antenna to transmit the processed tail data block of the unsynchronized BS  13 . 
         [0063]    Hereinbefore, the scenario that when sending downlink data to the MS  2 , the synchronized BS  11  processes part of data of the unsynchronized BS  12  and the unsynchronized BS  13  and sends the processed part of data to the MS  2  respectively at specific time slots simultaneously is described. 
         [0064]    Hereinafter, referring to  FIG. 2  and  FIG. 5 , the scenarios that when sending DL data to the MS  2 , the unsynchronized BS  12  processes part of data of the unsynchronized BS  13  and sends the processed part of data of the unsynchronized BS  13  to the MS  2  at specific time slots simultaneously, and when sending DL data to the MS  2 , the synchronized BS  13  processes part of data of the unsynchronized BS  12  and sends the processed part of data of the unsynchronized BS  12  to the MS  2  at specific ime slots simultaneously are described. 
         [0065]      FIG. 5  shows a schematic diagram of the unsynchronized BS  12  processing part of data of the unsynchronized BS  13  and sending the processed part of data of the unsynchronized BS  13  to the MS  2  at specific time slots simultaneously when sending DL data to the MS  2 , and the synchronized BS  13  processing part of data of the unsynchronized BS  12  and sending the processed part of data of the unsynchronized BS  12  to the MS  2  at specific time slots simultaneously when sending DL data to the MS  2 . 
         [0066]    In  FIG. 5 , the first row corresponds to DL data from the synchronized BS  11  that is received within the detection window of the MS  2  in the solution of the present invention. The upper portion of the second row corresponds to DL data from the unsynchronized BS  12  that is received within the detection window of the MS  2  in the solution of the prior art, the lower portion of the second row corresponds to DL data from the unsynchronized BS  12  that is received within the detection window of the MS  2  in the solution of the present invention. The upper portion of the third row corresponds to DL data from the unsynchronized BS  13  that is received within the detection window of the MS  2  in the solution of the prior art, the lower portion of the third row corresponds to DL data from the unsynchronized BS  13  that is received within the detection window of the MS  2  in the solution of the present invention. 
         [0067]    For the unsynchronized BS  12 , firstly, the unsynchronized BS  12  receives backhaul information from the unsynchronized BS  13  via X2 interface. Wherein, backhaul message that is received from the unsynchronized BS  13  by the unsynchronized BS  12  comprises DL data to be transmitted from the unsynchronized BS  13  to the MS  2 , the channel transmission matrix of DL channel from the unsynchronized BS  13  to the MS  2  and out-of-synchronization information of the unsynchronized BS  13  and the MS  2 , namely propagation delay from the unsynchronized BS  13  to the MS  2 . 
         [0068]    Then, the unsynchronized BS  12  determines whether out-of-synchronization information in backhaul information from the unsynchronized BS  13  is greater than 0. 
         [0069]    Because the propagation distance from the unsynchronized BS  13  to the MS  2  is less than the propagation distance from the synchronized BS  11  to the MS  2 , out-of-synchronization information corresponding to the unsynchronized BS  13  is less than 0. 
         [0070]    Because out-of-synchronization information corresponding to the unsynchronized BS  13  is less than 0, when sending DL data to the MS  2 , the unsynchronized BS  12  processes tail data block corresponding to the length of the out-of-synchronization information in DL data sent by the unsynchronized BS  13  and sends the processed tail data block to the MS  2  at a specific time slot simultaneously. 
         [0071]    Wherein, the specific time slot is the final time slot, lasting the length of the out-of-synchronization information, within the time slot occupied by the synchronized BS  12  for sending DL data. 
         [0072]    Accordingly, the unsynchronized BS  13  postpones the transmission starting moment for the length of the out-of-synchronization information and sends to the MS  2  DL data to be transmitted with the tail data block corresponding to the length of the out-of-synchronization information clipped. 
         [0073]    For example, if the out-of-synchronization information of the unsynchronized BS  13  and the MS  2  is −0.1 μs, then when sending DL data to the MS  2 , the unsynchronized BS  12  processes tail data block corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  13  and sends the processed tail data block to the MS  2  at the final time slot of the length of 0.1 μs for sending DL data simultaneously. 
         [0074]    Accordingly, the unsynchronized BS  13  postpones the transmission starting moment for the length of 0.1 μs and then sends to the MS  2  DL data to be transmitted with the tail data block corresponding to the length of 0.1 μs clipped. 
         [0075]    It may be seen from  FIG. 5  that the upper portion of the third row corresponds to DL data from the unsynchronized BS  13  that received within the detection window of the MS  2  in the solution of the prior art, because of propagation delay such as −0.1 μs between the unsynchronized BS  13  and the MS  2 , data block (shown as “         ” in  FIG. 5 ) with the length of 0.1 μs falls outside of the detection window of the MS  2  in the solution of the prior art. Aller using the solution of the present invention, because tail data block (shown as “         ” in  FIG. 5 ) corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  13  is sent by the unsynchronized BS  12  instead of the unsynchronized BS  13  at the tinal time slot of the length of 0.1 μs for sending DL data simultaneously when the synchronized BS  12  sends DL data, and the unsynchronized BS  13  postpones the transmission starting moment for the length of 0.1 μs and then sends to the MS  2  DL data to he transmitted with tail data block corresponding to the length of 0.1 μs clipped. Therefore, it may be seen from the solution of the present invention of the lower portion of the third row that DL data (namely DL data with tail data block corresponding to the length of 0.1 μs clipped) that is received from the unsynchronized BS  13  by the MS  2  falls within detection window of the MS  2  completely. And the tail data block sent by the unsynchronized BS  12  instead of the unsynchronized BS  13  falls within the detection window of the MS  2 , the tail data block being denoted by “         ” corresponding to the lower portion of the second row in  FIG. 5 . 
         [0076]    Furthermore, the aforesaid processing is that the unsynchronized BS  12  multiplies the tail data block to be transmitted by the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2  and the precoding matrix of the unsynchronized BS  13 , as well as the inverse matrix of the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2  and the inverse matrix of the precoding matrix of the unsynchronized BS  12 . 
         [0077]    To be specific, assuming that DL data to be transmitted of the unsynchronized BS  13  is S 3 , wherein the tail data block sent by the unsynchronized BS  12  instead of the unsynchronized BS  13  is S 31 , the remaining data block is S 32 , wherein S 3 =S 31 +S 32 . 
         [0078]    Before sending to the MS  2  the tail data block S 31  of the unsynchronized BS  13 , the unsynchronized BS  12  firstly processes the tail data block S 31 , that is, the tail data block S 31  is transformed into F 2   −1 H 2   −1 H 3 F 3 S 31 , wherein, F 2   −1  is the inverse matrix of the precoding matrix of the unsynchronized BS  12 , H 2   −1  is the inverse matrix of the channel transmission matrix of the DL channel from the unsynchronized 
         [0079]    BS  12  to the MS  2 , H 3  is the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2 , F 3  is the precoding matrix of the unsynchronized BS  13 . 
         [0080]    Because the unsynchronized BS  12  sends the processed tail data block F 2   −1 H 2   −1 H 3 F 3 S 31  to the MS  2 , and the unsynchronized BS  13  sends to the MS  2  the remaining data S 32  with the tail data block clipped, for the MS  2 , the received data of the MS  2  is y 3 =H 2 F 2 F 2   −1 H 2   −1 H 3 F 3 S 31 +H 3 F 3 S 32 =H 3 F 3 S 3 , that is, all of DL data belonging to the unsynchronized BS  13 . 
         [0081]    Here, it is to be noted, if the transmission manner of transmission diversity is used between BS and MS, the unsynchronized BS  12  may send the processed tail data block of the unsynchronized BS  13  by using the antenna for sending its own DL data; but if the transmission manner of space multiplexing is used between BS and MS, the unsynchronized BS  12  should use extra transmitting antenna to transmit the processed tail data block of the unsynchronized BS  13 . 
         [0082]    Similarly, for the unsynchronized BS  13 , firstly, the unsynchronized BS  13  receives backhaul information from the unsynchronized BS  12  via X2 interface. Wherein, backhaul information that is received from the unsynchronized BS  12  by the unsynchronized BS  13  comprises DL data to be transmitted from the unsynchronized BS  12  to the MS  2 , the channel transmission matrix of DL channel from the unsynchronized BS  12  to the MS  2  and out-of-synchronization information of the unsynchronized BS  12  and the MS  2 , namely propagation delay from the unsynchronized BS  12  to the MS  2 . 
         [0083]    Then, the unsynchronized BS  13  determines whether out-of-synchronization information in backhaul information from the unsynchronized BS  12  is greater than 0. 
         [0084]    Because the propagation distance from the unsynchronized BS  12  to the MS  2  is greater than the propagation distance from the synchronized BS  11  to the MS  2 , out-of-synchronization information corresponding to the unsynchronized BS  12  is greater than 0. 
         [0085]    Because out-of-synchronization information corresponding to the unsynchronized BS  12  is greater than 0, when sending DL data to the MS  2 , the unsynchronized BS  13  processes head data block corresponding to the length of the out-of-synchronization information in DL data sent by the unsynchronized BS  12  and sends the processed head data block to the MS  2  at a specific time slot simultaneously. 
         [0086]    Wherein, the specific time slot is the start time slot, lasting the length of the out-of-synchronization information, within the time slot occupied by the synchronized base station  13  for sending DL signal. 
         [0087]    Accordingly, the unsynchronized BS  12  sends to the MS  2  DL data to be transmitted with the head data block corresponding to the length of the out-of-synchronization information clipped. 
         [0088]    For example, if the out-of-synchronization information of the unsynchronized BS  12  and the MS  2  is 0.1 μs, then when sending DL data to the MS  2 , the unsynchronized BS  13  processes head data block corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  12  and sends the processed head data block to the MS  2  at the start time slot of the length of 0.1 μs for sending DL data simultaneously. 
         [0089]    Accordingly, the unsynchronized BS  12  sends to the MS  2  DL data to be transmitted with the head data block corresponding to the length of 0.1 μs clipped. 
         [0090]    It may he seen from  FIG. 5  that the upper portion of the second corresponds to DL data from the unsynchronized BS  12  that is received within the detection window of the MS  2  in the solution of the prior art, because of propagation delay such as 0.1 μs between the unsynchronized BS  12  and the MS  2 , data block (shown as “         ” in  FIG. 5 ) with the length of 0.1 μs falls outside of the detection window of the MS  2  in the solution of the prior art. After using the solution of the present invention, because head data block (shown as “         ” in  FIG. 5 ) corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  12  is sent by the unsynchronized BS  13  instead of the unsynchronized BS  12  at the start time slot of the length of 0.1 μs for sending DL data simultaneously when the unsynchronized BS  13  sends DL data, and DL data that is sent to the MS  2  by the unsynchronized BS  12  is the DL data with head data block corresponding to the length of 0.1 μs clipped. Therefore, it may be seen from the solution of the present invention of the lower portion of the second row that DL data (namely DL data with head data block corresponding to the length of 0.1 μs clipped) that is received from the unsynchronized BS  12  by the MS  2  falls within the detection window of the MS  2  completely. And the head data block sent by the unsynchronized BS  13  instead of the unsynchronized BS  12  falls within the detection window of the MS  2 , the head data block being denoted by “         ” corresponding to the lower portion of the third row in  FIG. 5 . 
         [0091]    Furthermore, the aforesaid processing is that the unsynchronized BS  13  multiplies the head data block to be transmitted by the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2  and the precoding matrix of the unsynchronized BS  12 , as well as the inverse matrix of the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2  and the inverse matrix of the precoding matrix of the unsynchronized BS  13 . 
         [0092]    To be specific, assuming that DL data to be transmitted of the unsynchronized BS  12  is S 2 , wherein the head data block sent by the unsynchronized BS  13  instead of the unsynchronized BS  12  is S 21 , the remaining data block is S 22 , wherein S 2 =S 21 +S 22 . 
         [0093]    Before sending to the MS  2  the head data block S 21  of the unsynchronized BS  12 , the unsynchronized BS  13  firstly processes the head data block S 21 , that is, the head data block S 21  stormed into F 3   −1 H 3   −1 H 2 F 2 S 21 , wherein, F 3   −1  is the inverse matrix of the precoding matrix of the unsynchronized BS  13 , H 3   −1  is the inverse matrix of the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2 , H 2  is the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2 , F 2  is the precoding matrix of the unsynchronized BS  12 . 
         [0094]    Because the unsynchronized BS  13  sends the processed head data block F 3   −1 H 3   −1 H 2 F 2 S 21  to the MS  2 , and the unsynchronized BS  12  sends to the MS  2  the remaining data S 22  with the head data block clipped, for the MS  2 , the received data of the MS  2  is y 2 =H 3 F 3 F 3   −1 H 3   −1 H 2 F 2 S 21 +H 2 F 2 S 22 =H 2 F 2 S 2 , that is, all of DL data belonging to the unsynchronized BS  12 . 
         [0095]    Here, it is to he noted that, if the transmission manner of transmission diversity is used between BS and MS, the unsynchronized BS  13  may send the processed head data block of the unsynchronized BS  12  by using the antenna for sending its own DL data but if the transmission manner of space multiplexing is used between BS and MS, the unsynchronized BS  13  should use extra transmitting antenna to transmit the processed head data block of the unsynchronized BS  12 . 
         [0096]    In a variation shown in  FIG. 6 , an unsynchronized BS  14  is included, and the propagation distance from the unsynchronized BS  14  to the MS  2  is greater than the propagation distance from the unsynchronized BS  12  to the MS  2 . 
         [0097]    Assuming that out-of-synchronization information corresponding to the unsynchronized BS  12  is 0.1 μs and out-of-synchronization information corresponding to the unsynchronized BS  14  is 0.2 μs. it may be known from the aforesaid description of the solution of the present invention that the head data block corresponding to the length of 0.2 μs in DL data to be transmitted of the unsynchronized BS  14  may be sent to the MS  2  at a specific time slot by the synchronized BS  11  simultaneously when the synchronized BS  11  sends DL data, and may also be sent to the MS  2  at a specific time slot by the unsynchronized BS  13  simultaneously when the unsynchronized BS  13  sends DL data. 
         [0098]    Certainly, those skilled in the art may understand that the latter 0.1 μs data block (shown as “         ” in  FIG. 6 ) in the head data block corresponding to the length of 0.2 μs may be sent to the MS  2  by the unsynchronized BS  12  at the start time slot of the length of 0.1 μs for sending DL data simultaneously when the unsynchronized BS  12  sends DL data, and the former 0.1 μs data block (shown as “         ” in  FIG. 6 ) in the head data block corresponding to the length of 0.2 μs may be sent to the MS  2  by the synchronized BS  11  or the unsynchronized BS  13  at the start time slot of the length of 0.1 μs for sending DL data simultaneously when the synchronized BS  11  or the unsynchronized BS  13  sends DL data. 
         [0099]    Hereinbefore, the solution of the present invention is described from the aspect of method; hereinafter the solution of the present invention will be further described from the aspect of device module. 
         [0100]    Hereinafter, referring to  FIG. 2 ,  FIG. 4  and  FIG. 7 , the scenario that when sending downlink data to the MS  2 , a control device  100  in the synchronized BS  11  processes part of data of the unsynchronized BS  12  and the unsynchronized BS  13  and sends the processed part of data to the MS  2  respectively at specific time slots simultaneously is described. Thc descriptions for  FIG. 2  and  FIG. 4  in the preceding context are taken as reference together. 
         [0101]      FIG. 7  shows a block diagram of structure of a control device  100  in the synchronized BS  11  for processing part of data of the unsynchronized BS  12  and the unsynchronized BS  13  and sending the processed part of data to the MS  2  at different time slots simultaneously. when sending downlink data to the MS  2 , according to one embodiment of the present invention. 
         [0102]    As shown in  FIG. 7 , firstly, a first receiving means  1001  in control device  100  in the synchronized BS  11  respectively receives backhaul information from the unsynchronized BS  12  and the unsynchronized BS  13  via X2 interface. Wherein, backhaul message that is received from the unsynchronized BS  12  by the first receiving means  1001  comprises DL data to be transmitted from the unsynchronized BS  12  to the MS  2 , the channel transmission matrix of DL channel from the unsynchronized BS  12  to the MS  2  and out-of-synchronization information of the unsynchronized BS  12  and the MS  2 , namely propagation delay from the unsynchronized BS  12  to the MS  2 ; backhaul message that is received from the unsynchronized BS  13  by the first receiving means  1001  comprises DL data to be transmitted from the unsynchronized BS  13  to the MS  2 , the channel transmission matrix of DL channel from the unsynchronized BS  13  to the MS  2  and out-of-synchronization information of the unsynchronized BS  13  and the MS  2 , namely propagation delay from the unsynchronized BS  13  to the MS  2 . 
         [0103]    Then, a first determining means  1002  in the control device  100  in the synchronized BS  11  respectively determines whether out-of-synchronization information in backhaul information from the unsynchronized BS  12  and the unsynchronized BS  13  is greater than 0. 
         [0104]    Because the MS  2  and the synchronized BS  11  achieve synchronization, out-of-synchronization information from the synchronized BS  11  to the MS  2  is considered as 0. And because the propagation distance from the unsynchronized BS  12  to the MS  2  is greater than the propagation distance from the synchronized BS  11  to the MS  2 , out-of-synchronization information corresponding to the unsynchronized BS  12  is greater than 0; and because the propagation distance from the unsynchronized BS  13  to the MS  2  is less than the propagation distance from the synchronized BS  11  to the MS  2 , out-of-synchronization information corresponding to the unsynchronized BS  13  is less than 0. 
         [0105]    Because out-of-synchronization information corresponding to the unsynchronized BS  12  is greater than 0, when sending DL data to the MS  2 , a first sending means  1003  in the control device  100  in the synchronized BS  11  processes head data block corresponding to the length of the out-of-synchronization information in DL data sent by the unsynchronized BS  12  and sends the processed head data block to the MS  2  at a specific time slot simultaneously. 
         [0106]    Wherein, the specific time slot is the start time slot, lasting the length of the out-of-synchronization information, within the time slot occupied by the first sending means  1003  in the synchronized base station  11  for sending DL data. 
         [0107]    Accordingly, a fourth sending means in a first assisting control device in the unsynchronized BS  12  sends to the MS  2  DL data to be transmitted with the head data block corresponding to the length of the out-of-synchronization information clipped. 
         [0108]    For example, if the out-of-synchronization information of the unsynchronized BS  12  and the MS  2  is 0.1 μs, then when sending DL data to the MS  2 , the first sending means  1003  in the synchronized BS  11  processes head data block corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  12  and sends the processed head data block to the MS  2  at the start time slot of the length of 0.1 μs for sending DL data simultaneously. 
         [0109]    Accordingly, the fourth sending means in the first assisting control device in the unsynchronized BS  12  sends to the MS  2  DL data to be transmitted with the head data block corresponding to the length of 0.1 μs clipped. 
         [0110]    It may be seen from  FIG. 4  that the upper portion of the second row corresponds to DL data from the unsynchronized BS  12  that is received within the detection window of the MS  2  in the solution of the prior art, because of propagation delay such as 0.1 μs between the unsynchronized BS  12  and the MS  2 , data block (shown as “         ” in  FIG. 4 ) with the length of 0.1 μs as falls outside of the detection window of the MS  2  in the solution of the prior art. After using the solution of the present invention, because head data block (shown as “         ” in  FIG. 4 ) corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  12  is sent by the first sending means  1003  in the synchronized BS  11  instead of the unsynchronized BS  12  at the start time slot of the length of 0.1 μs for sending DL data simultaneously when the synchronized BS  11  sends DL data, and DL data that is sent to the MS  2  by the fourth sending means in the first assisting control device in the unsynchronized BS  12  is the DL data with head data block corresponding to the length of 0.1 μs clipped. Therefore, it may be seen from the solution of the present invention of the lower portion of the second row that DL data (namely DL data with head data block corresponding to the length of 0.1 μs clipped) that is received from the unsynchronized BS  12  by the MS  2  falls within the detection window of the MS  2  completely. And the head data block sent by the first sending means  1003  in the synchronized BS  11  instead of the unsynchronized BS  12  falls within the detection window of the MS  2 , the head data block being denoted by “         ” corresponding to the first row in  FIG. 4 . 
         [0111]    Furthermore, the aforesaid processing is multiplying the head data block to be transmitted by the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2  and the precoding matrix of the unsynchronized BS  12 , as well as the inverse matrix of the channel transmission matrix of the DL channel from the synchronized BS  11  to the MS  2  and the inverse matrix of the precoding matrix of the synchronized BS  11 . 
         [0112]    To be specific, assuming that DL data to bc transmitted of the unsynchronized BS  12  is S 2 , wherein the head data block sent by the first sending means  1003  in the synchronized BS  11  instead of the unsynchronized BS  12  is S 21 , the remaining data block is S 22 , wherein S 2 =S 21 +S 22 . 
         [0113]    Before sending to the MS  2  the head data block S 21  of the unsynchronized BS  12 , the first sending means  1003  in the synchronized BS  11  firstly processes the head data block S 21  , that is, the head data block S 21  is transformed into F 1   −1 H 1   −1 H 2 F 2 S 21 , wherein, F 1   −1  is the inverse matrix of the precoding matrix of the synchronized BS  11 , f, H 1   −1  is the inverse matrix of the channel transmission matrix of the DL channel from the synchronized BS  11  to the MS  2 , H 2  is the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2 , and F 2  is the precoding matrix of the unsynchronized BS  12 . 
         [0114]    Because the first sending means  1003  in the synchronized BS  11  sends the processed head data block F 1   −1 H 1   −1 H 2 F 2 S 21  to the MS  2 , and the fourth sending means in a first assisting control device in the unsynchronized BS  12  sends to the MS  2  the remaining data S 22  with the head data block clipped, for the MS  2 , the received data of the MS  2  is y 2 =H 1 F 1 F 1   −1 H 1   −1 H 2 F 2 S 21 +H 2 F 2 S 22 =H 2 F 2 S 2 , that is, all of DL data belonging to the unsynchronized BS  12 . 
         [0115]    Here, it is to be noted that, if the transmission manner of transmission diversity is used between BS and MS, then the synchronized BS  11  may send the processed head data block of the unsynchronized BS  12  by using the antenna for sending its own DL data; but if the transmission manner of space multiplexing is used between BS and MS, the synchronized BS  11  should use extra transmitting antenna to transmit the processed head data block of the unsynchronized BS  12 . 
         [0116]    Similarly, Because out-of-synchronization information corresponding to the unsynchronized BS  13  is less than 0, when sending DL data to the MS  2 , the first sending means  1003  in the control device  100  in the synchronized BS  11  processes tail data block corresponding to the length of the out-of-synchronization information in DL data sent by the unsynchronized BS  13  and sends the processed tail data block to the MS  2  at a specific time slot simultaneously. 
         [0117]    Wherein, the specific time slot is the final time slot, lasting the length of the out-of-synchronization information, within the time slot occupied by the first sending means  1003  in the synchronized base station  11  for sending DL signal. 
         [0118]    Accordingly, a fifth sending means in a second assisting control device in the unsynchronized BS  13  postpones the transmission starting moment for the length of the out-of-synchronization information and then sends to the MS  2  DL data to be transmitted with the tail data block corresponding Co the length of the out-of-synchronization information clipped. 
         [0119]    For example, if the out-of-synchronization information of the unsynchronized BS  13  and the MS  2  is −0.1 μs, then when sending DL data to the MS  2 , the first sending means  1003  in the synchronized BS  11  processes tail data block corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  13  and sends the processed tail data block to the MS  2  at the final time slot of the length of 0.1 μs for sending DL data simultaneously. 
         [0120]    Accordingly, the fifth sending means in the second assisting control device in the unsynchronized BS  13  postpones the transmission starting moment for the length of 0.1 μus and then sends to the MS  2  DL data to be transmitted with the tail data block corresponding to the length of 0.1 μs clipped. 
         [0121]    It may be seen from  FIG. 4  that the upper portion of the third row corresponds to DL data from the unsynchronized BS  13  that is received within the detection window of the MS  2  in the solution of the prior art, because of propagation delay such as −0.1 μus between the unsynchronized BS  13  and the MS  2 , data block (shown as “         ” in  FIG. 4 ) with the length of 0.1 μs falls outside of the detection window of the MS  2  in the solution of the prior art. After using the solution of the present invention, because tail data block (shown as “         ” in  FIG. 4 ) corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  13  is sent by the first sending means  1003  in the synchronized BS  11  instead of the unsynehronized BS  13  at the final time slot of the length of 0.1 μs for sending DL data simultaneously when the synchronized BS  11  sends DL data, and the fifth sending means in the second assisting control device in the unsynchronized BS  13  postpones the transmission starting moment for the length of 0.1 μs and then sends to the MS  2  DL data to be transmitted with tail data block corresponding to the length of 0.1 μs clipped. Therefore, it can be seen from the solution of the present invention of the lower portion of the third row that DL data (namely DL data with tail data Flock corresponding to the length of 0.1 μs clipped) that is received from the unsynchronized BS  13  by the MS  2  falls within the detection window of the MS  2  completely. And the tail data block sent by the first sending means  1003  in the synchronized BS  11  instead of the unsynchronized BS  13  falls within the detection window of the MS  2 , the tail data block being denoted by “         ” corresponding to the first row in  FIG. 4 . 
         [0122]    Furthermore, the aforesaid processing is multiplying the tail data block to he transmitted by the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2  and the precoding matrix of the unsynchronized BS  13 , as well as the inverse matrix of the channel transmission matrix of the DL channel from the synchronized BS  11  to the MS  2  and the inverse matrix of the precoding matrix of the synchronized BS  11 . 
         [0123]    To be specific, assuming that DL data to be transmitted of the unsynchronized BS  13  is S 3 , wherein the tail data block sent by the first sending means  1003  in the synchronized BS  11  instead of the unsynchronized BS  13  is S 31 , the remaining data block is S 32 , wherein S 3 =S 31 +S 32 . 
         [0124]    Before sending to the MS  2  the tail data block S 31  of the unsynchronized BS  13 , the first sending means  1003  in the synchronized BS  11  firstly processes the tail data block S 31 , that is, the tail data block S 31  is transformed into F 1   −1 H 1   −1 H 3 F 3 S 31 , wherein, F 1   −1  is the inverse matrix of the precoding matrix of the synchronized BS  11 , H 1   −1  is the inverse matrix of the channel transmission matrix of the DL channel the synchronized BS  11  to the MS  2 , H 3  is the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2 , F 3  is the precoding matrix of the unsynchronized BS  13 . 
         [0125]    Because the first sending means  1003  in the synchronized BS  11  sends the processed tail data block F 1   −1 H 1   −1 H 3 F 3 S 31  to the MS  2 , and the fifth sending means in the second assisting control device in the unsynchronized BS  13  sends to the MS  2  the remaining data S 32  with the tail data block clipped, for the MS  2 , the received data of the MS  2  is y 3 =H 1 F 1 F 1   −1 H 1   −1 H 3 F 3 S 31 +H 3 F 3 S 32 =H 3 F 3 S 3 , that is, all of DL data belonging to the unsynchronized BS  13 . 
         [0126]    Here, it is to be noted that, if the transmission manner of transmission diversity is used between BS and MS, the synchronized BS  11  may send the processed tail data block of the unsynchronized BS  13  by using the antenna for sending its own DL data; but if the transmission manner of space multiplexing is used between BS and MS, the synchronized BS  11  should use extra transmitting antenna to transmit the processed tail data block of the unsynchronized BS  13 . 
         [0127]    Hereinbefore, the scenario that when sending downlink data to the MS  2 , the control device  100  in the synchronized BS  11  processes part of data of the unsynchronized BS  12  and the unsynchronized BS  13  and sends the processed part of data to the MS  2  respectively at specific time slots simultaneously is described. 
         [0128]    Hereinafter, referring to  FIG. 2  and  FIG. 5 , the scenarios that when sending DL data to the MS  2 , the unsynchronized BS  12  processes part of data of the unsynchronized BS  13  and sends the processed part of data of the unsynchronized BS  13  to the MS  2  at specific time slots simultaneously, and when sending DL data to the MS  2 , the synchronized BS  13  processes part of data of the unsynchronized BS  12  and sends the processed part of data of the unsynchronized BS  12  to the MS  2  at specific time slots simultaneously are described. 
         [0129]    The descriptions for  FIG. 2  and  FIG. 5  in the preceding contexts are taken as reference together. 
         [0130]    For the unsynchronized BS  12 , firstly, a second receiving means in a control device in the unsynchronized BS  12  receives backhaul information from the unsynchronized BS  13  via X2 interface. Wherein, backhaul message that is received from the unsynchronized BS  13  by the second receiving means in the control device in the unsynchronized BS  12  comprises DL data to be transmitted from the unsynchronized BS  13  to the MS  2 , the channel transmission matrix of DL channel from the unsynchronized BS  13  to the MS  2  and out-of-synchronization information of the unsynchronized BS  13  and the MS  2 , namely propagation delay from the unsynchronized BS  13  to the MS  2 . 
         [0131]    Then, a second determining means in the control device in the unsynchronized BS  12  determines whether out-of-synchronization information in backhaul information from the unsynchronized BS  13  is greater than 0. 
         [0132]    Because the propagation distance from the unsynchronized BS  13  to the MS  2  is less than the propagation distance from the synchronized BS  11  to the MS  2 , out-of-synchronization information corresponding to the unsynchronized BS  13  is less than 0. 
         [0133]    Because out-of-synchronization information corresponding to the unsynchronized BS  13  is less than 0, when sending DL data to the MS  2 , a second sending means in the control device in the unsynchronized BS  12  processes tail data block corresponding to the length of the out-of-synchronization information in DL data sent by the unsynchronized BS  13  and sends the processed tail data block to the MS  2  at a specific time slot simultaneously. 
         [0134]    Wherein, the specific time slot is the final time slot, lasting the length of the out-of-synchronization information, within the time slot occupied by the second sending means in the control device in the synchronized BS  12  for sending DL data. 
         [0135]    Accordingly, the fifth sending means in the second assisting control device in the unsynchronized BS  13  postpones the transmission starting moment for the length of the out-of-synchronization information and sends to the MS  2  DL data to be transmitted with the tail data block corresponding to the length of the out-of-synchronization information clipped. 
         [0136]    For example, if the out-of-synchronization information of the unsynchronized BS  13  and the MS  2  is −0.1 μs, then when sending DL data to the MS  2 , the second sending means in the control device in the unsynchronized BS  12  processes tail data block corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  13  and sends the processed tail data block to the MS  2  at the final time slot of the length of 0.1 μs for sending DL data simultaneously. 
         [0137]    Accordingly, the fifth sending means in the second assisting control device in the unsynchronized BS  13  postpones the transmission starting moment for the length of 0.1 μs and then sends to the MS  2  DL data to be transmitted with the tail data block corresponding to the length of 0.1 μs clipped. 
         [0138]    It may he seen from  FIG. 5  that the upper portion of the third row corresponds to DL data from the unsynchronized BS  13  that received within the detection window of the MS  2  in the solution of the prior art, because of propagation delay such as −0.1 μs between the unsynchronized BS  13  and the MS  2 , data block (shown as “         ” in  FIG. 5 ) with the length of 0.1 μs falls outside of the detection window of the MS  2  in the solution of the prior art. After using the solution of the present invention, because tail data block (shown as “         ” in  FIG. 5 ) corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  13  is sent by the second sending means in the control device in the unsynchronized BS  12  instead of the unsynchronized BS  13  at the final time slot of the length of 0.1 μs for sending DL data simultaneously when the synchronized BS  12  sends DL data, and the fifth sending means in the second assisting control device in the unsynchronized BS  13  postpones the transmission starting moment for the length of 0.1 μs and then sends to the MS  2  DL data to be transmitted with tail data block corresponding to the length of 0.1 μs clipped. Therefore, it may be seen from the solution of the present invention of the lower portion of the third row that DL data (namely DL data with tail data block corresponding to the length of 0.1 μs clipped) that is received from the unsynchronized BS  13  by the MS  2  falls within detection window of the MS  2  completely. And the tail data block sent by the second sending means in the control device in the unsynchronized BS  12  instead of the unsynchronized BS  13  falls within the detection window of the MS  2 , the tail data block being denoted by “         ” corresponding to the lower portion of the second row in  FIG. 5 . 
         [0139]    Furthermore, the aforesaid processing is that the second sending means in the control device in the unsynchronized BS  12  multiplies the tail data block to be transmitted by the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2  and the precoding matrix of the unsynchronized BS  13 , as well as the inverse matrix of the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2  and the inverse matrix of the precoding matrix of the unsynchronized BS  12 . 
         [0140]    To be specific, assuming that DL data to be transmitted of the unsynchronized BS  13  is S 3 , wherein the tail data block sent by the second sending means in the control device in the unsynchronized BS  12  instead of the unsynchronized BS  13  is S 31 , the remaining data block is S 32 , wherein S 3 =S 31 +S 32 . 
         [0141]    Before sending to the MS  2  the tail data block S 31  of the unsynchronized BS  13 , the second sending means in the control device in the unsynchronized. BS  12  firstly processes the tail data block S 31 , that is, the tail data block S 31  is transformed into F 2   −1 H 2   −1 H 3 F 3 S 31 , wherein, F 2   −1  is the inverse matrix of the precoding matrix of the unsynchronized BS  12 , H 2   −1  is the inverse matrix of the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2 , H 3  is the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2 , F 3  is the precoding matrix of the unsynchronized BS  13 . 
         [0142]    Because the second sending means in the control device in the unsynchronized BS  12  sends the processed tail data block F 2   −1 H 2   −1 H 3 F 3 S 31  to the MS  2 , and the fifth sending means in the second assisting control device in the unsynchronized BS  13  sends to the MS  2  the remaining data S 32  with the tail data block clipped, for the MS  2 , the received data of the MS  2  is y 3 =H 2 F 2 F 2   −1 H 2   −1 H 3 F 3 S 31 +H 3 F 3 S 32 =H 3 F 3 S 3 , that is, all of DL data belonging to the unsynchronized BS  13 . 
         [0143]    Here, it is to be noted, if the transmission manner of transmission diversity is used between BS and MS, the unsynchronized BS  12  may send the processed tail data block of the unsynchronized BS  13  by using the antenna for sending its own DL data; but if the transmission manner of space multiplexing is used between BS and MS, the unsynchronized BS  12  should use extra transmitting antenna to transmit the processed tail data block of the unsynchronized BS  13 . 
         [0144]    Similarly, for the unsynchronized BS  13 , firstly, a third receiving means in the control device in the unsynchronized BS  13  receives backhaul information from the unsynchronized BS  12  via X2 interface. Wherein, backhaul information that is received from the unsynchronized BS  12  by the third receiving means in the control device in the unsynchronized BS  13  comprises DL data to be transmitted from the unsynchronized BS  12  to the MS  2 , the channel transmission matrix of DL channel from the unsynchronized BS  12  to the MS  2  and out-of-synchronization information of the unsynchronized BS  12  and the MS  2 , namely propagation delay from the unsynchronized BS  12  to the MS  2 . 
         [0145]    Then, a third determining means in the control device M the unsynchronized BS  3  determines whether out-of-synchronization information in backhaul information from the unsynchronized BS  12  is greater than 0. 
         [0146]    Because the propagation distance from the unsynchronized BS  12  to the MS  2  is greater than the propagation distance from the synchronized BS  11  to the MS  2 , out-of-synchronization information corresponding to the unsynchronized BS  12  is greater than 0. 
         [0147]    Because out-of-synchronization information corresponding to the unsynchronized BS  12  is greater than 0, when sending DL data to the MS  2 , a third sending means in the control device in the unsynchronized BS  13  processes head data block corresponding to the length of the out-or-synchronization information in DL data sent by the unsynchronized BS  12  and sends the processed head data block to the MS  2  at a specific time slot simultaneously. 
         [0148]    Wherein, the specific time slot is the start time slot, lasting the length of the out-of-synchronization information, within the time slot occupied by the third sending means in the control device in the synchronized base station  13  for sending DL signal. 
         [0149]    Accordingly, the fourth sending means in the first assisting control device in the unsynchronized BS  12  sends to the MS  2  DL data to be transmitted with the head data block corresponding to the length of the out-of-synchronization information clipped. 
         [0150]    For example, if the out-of-synchronization information of the unsynchronized BS  12  and the MS  2  is 0.1 μs, then when sending DL data to the MS  2 , the third sending means in the control device in the unsynchronized BS  13  processes head data block corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  12  and sends the processed head data block to the MS  2  at the start time slot of the length of 0.1 μs for sending DL data simultaneously. 
         [0151]    Accordingly, the fourth sending means in the first assisting control device in the unsynchronized BS  12  sends to the MS  2  DL data to be transmitted with the head data block corresponding to the length of 0.1 μs clipped. 
         [0152]    It may be seen from  FIG. 5  that the upper portion of the second row corresponds to DL data from the unsynchronized BS  12  that is received within the detection window of the MS  2  in the solution of the prior art, because of propagation delay such as 0.1 μs between the unsynchronized BS  12  and the MS  2 , data block (shown as “         ” in  FIG. 5 ) with the length of 0.1 μs falls outside of the detection window of the MS  2  in the solution of the prior art. After using the solution of the present invention, because head data block (shown as “         ” in  FIG. 5 ) corresponding to the length of 0.1 μs in DL data sent by the unsynchronized BS  12  is sent by the third sending means in the control device in the unsynchronized BS  13  instead of the unsynchronized BS  12  at the start time slot of the length of 0.1 μs for sending DL data simultaneously when the unsynchronized BS  13  sends DL data, and DL data that is sent to the MS  2  by the fourth sending means in the first assisting control device in the unsynchronized BS  12  is the DL data with head data block corresponding to the length of 0.1 μs clipped. Therefore, it may be seen from the solution of the present invention of the lower portion of the second row that DL data (namely DL data with head data block corresponding to the length of 0.1 μs clipped) that is received from the unsynchronized BS  12  by the MS  2  falls within the detection window of the MS  2  completely. And the head data block sent by the third sending means in the control device in the unsynchronized BS  13  instead of the unsynchronized BS  12  falls within the detection window of the MS  2 , the head data block being denoted by “         ” corresponding to the lower portion of the third row in  FIG. 5 . 
         [0153]    Furthermore, the aforesaid processing is that the third sending means in the control device in the unsynchronized BS  13  multiplies the head data block to be transmitted by the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2  and the precoding matrix of the unsynchronized BS  12 , as well as the inverse matrix of the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2  and the inverse matrix of the precoding matrix of the unsynchronized BS  13 . 
         [0154]    To be specific, assuming that DL data to be transmitted of the unsynchronized BS  12  is S 2 , wherein the head data block sent by the third sending means in the control device in the unsynchronized BS  13  instead of the unsynchronized BS  12  is S 21 , the remaining data block is S 22 , wherein S 2 =S 21 +S 22 . 
         [0155]    Before sending to the MS  2  the head data block S 21  of the unsynchronized BS  12 , the third sending means in the control device in the unsynchronized BS  13  firstly processes the head data block S 21 , that is, the head data block S 21  is transformed into F 3   −1 H 3   −1 H 2 F 2 S 21 , wherein, F 3   −1  is the inverse matrix of the precoding matrix of the unsynchronized BS  13 , H 3   −1  is the inverse matrix of the channel transmission matrix of the DL channel from the unsynchronized BS  13  to the MS  2 , H 2  is the channel transmission matrix of the DL channel from the unsynchronized BS  12  to the MS  2 , F 2  is the precoding matrix of the unsynchronized BS  12 . 
         [0156]    Because the third sending means in the control device in the unsynchronized BS  13  sends the processed head data block F 3   −1 H 3   −1 H 2 F 2 S 21  to the MS  2 , and the fourth sending means in the first assisting control device in the unsynchronized BS  12  sends to the MS  2  the remaining data S 22  with the head data block clipped, for the MS  2 , the received data of the MS  2  is y 2 =H 3 F 3 F 3   −1 H 3   −1 H 2 F 2 S 21 +H 2 F 2 S 22 =H 2 F 2 S 2 , that is, all of DL data belonging to the unsynchronized BS  12 . 
         [0157]    Here, it is to be noted that, if the transmission manner of transmission diversity is used between BS and MS, the unsynchronized BS  13  may send the processed head data block of the unsynchronized BS  12  by using the antenna for sending its own DL data; but if the transmission manner of space multiplexing is used between BS and MS, the unsynchronized BS  13  should use extra transmitting antenna to transmit the processed head data block of the unsynchronized BS  12 . 
         [0158]    The detailed embodiments of the present invention are described hereinbefore, it needs to be understood that the present invention is not limited to the aforesaid specific embodiments, those skilled in the art may make all kinds of variation or modification within the scope of the appended claims.