Abstract:
A base station (BS), a subordinated station (SS) and the transmission methods thereof for use in a multi-input multi-output (MIMO) network are provided. The BS stores resource allocation information about the MIMO network and an SS list, and generate a super frame according to the resource allocation information and the SS list. The super frame comprises a pilot pattern which comprises a plurality of pilots and data. The BS and SS both considers the pilot pattern as an identifier of the SS. When there are communications occurred between the BS and the SS, the BS/SS will confirm whether the pilot pattern of the super frame matches the identifier of the SS to reduce interference from other stations in the MIMO network.

Description:
[0001]    This application is a continuation-in-part application of application Ser. No. 12/435,792 filed on May 5, 2009, which application claims the benefit of priority based on U.S. Ser. No. 61/050,351 filed May 5, 2008, the disclosures of which are incorporated herein by reference in their entirety. This application also claims the benefit of priority based on U.S. Ser. No. 61/078,666 filed on Jul. 7, 2008, the disclosure of which are incorporated herein by reference in their entirety. 
     
    
     CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0002]    Not applicable. 
       BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to a base station, a subordinated station and transmission methods thereof. More specifically, the present invention relates to a base station, a subordinated station and transmission methods thereof complying with an IEEE 802.16m standard. 
         [0005]    2. Descriptions of the Related Art 
         [0006]    With continuous advancement in science and technology, people are imposing ever higher requirements on communications. Nowadays, more and more importance is being attached to convenience of communications in addition to requirements on quality of communications. Wireless communications are advantageous in that they provide higher mobility by obviating the need of physical communication network wiring. Therefore, wireless-communication-enabled products such as mobile phones, notebook computers and the like are more and more popular in recent years and have become the mainstream products in the consumer electronics market. 
         [0007]    In the conventional wireless networks, there are four kinds of interference types in transmission: data transition in time division duplex (TDD), data transition in frequency division duplex (FDD), the interference in central zone edge, and the interference in cell zone edge. 
         [0008]    Particularly, please refer to  FIG. 1A , which is a schematic view of a transmission cell  1   a  in the conventional wireless network. The transmission cell  1   a  comprises a plurality of central zones  100 ,  104 ,  108 , a plurality of cell edge zones  102 ,  106 ,  110 , a base station (BS)  111   a , a plurality of subordinated station (SS)  103 ,  105 ,  107 ,  109 ,  111 ,  113 ,  115 ,  117  corresponding to the BS  101   a . First, the interference of the data transition in TDD is described. In the different central zones, if down link (DL) and up link (UL) between the BS  101   a  and the SSs are operated at the same time, the different SSs may have interference in the data transmission. 
         [0009]    The interference of the data transition in FDD occurs in this situation that if the different SSs operate at the same frequency, the SS may receive another SS&#39;s signal and get interference. The interference in central zone edge means that if the SS is positioned in the edge of the central zone, it may receive the two kinds of signals from the two different central zones, and one of the signals received by the SS is the interference. For example, the SS  117  may receive the two kinds of signals from the central zones  100  and  104 , and one of the signals received by the SS  117  is the interference. Similarly, the SSs  109  and  113  may meet the same interference as the SS  117 , and will not be described again. 
         [0010]    The interference in cell zone edge means that if the SS is positioned in cell zone edge and the BS&#39;s signal power is lower, it may receive another BS&#39;s signal to make interference. For example, the SS  107  is positioned in the edge of the cell zone and the BS&#39;s  101   a  signal power is lower, the SS  107  may receive another BS&#39;s signal to make interference. Similarly, the SSs  111  and  115  may meet the same interference as the SS  107 , and will not be described again. 
         [0011]    Moreover, please refer to  FIG. 1B , which is a schematic view illustrating the transmission cell  1   a  and a transmission cell  1   b  in the conventional wireless network. As shown in  FIG. 1B , the SS  111  is within the signal coverage between the transmission cell  1   a  and the transmission cell  1   b . Specifically, the SS  111  is in a cell zone edge of the transmission cell  1   a  and the transmission cell  1   b , and is communicating with the BS  101   a  of the transmission cell  1   a  and a BS  101   b  of the transmission cell  1   b  at the same time, which often occurs in a handover procedure. However, the SS  111  may receive signals from the BS  101   a  and the BS  101   b  meantime, and the interference occurs in cell zone edge accordingly to effect the communication quality. 
         [0012]    In summary, the aforementioned interference affects the quality of communications between the BS and the SS in the wireless network seriously. How to reduce the interference in the wireless network efficiently is still an objective for the industry to endeavor. 
       SUMMARY OF THE INVENTION 
       [0013]    The primary objective of the present invention is to provide a base station (BS) for use in a multi-input multi-output (MIMO) network. The MIMO network includes another BS and a subordinated station (SS). The SS is within a signal coverage between the BS and the another BS. The another BS communicates with the SS by at least one first pilot structure in a first super frame. The BS comprises a transceiver, a storage module and a generation module. The transceiver is configured to receive the first super frame. The storage module is configured to store pilot structure information. The generation module is configured to select at least one second pilot structure of a second super frame according to the pilot structure information and the at least one first pilot structure of the first super frame to generate the second super frame with the at least one second pilot structure. The at least one second pilot structure is orthogonal to the at least one first pilot structure. The transceiver of the BS may communicates with the SS by the second super frame with the at least one second pilot structure to avoid a transmission interference between the BS and the another BS. 
         [0014]    Another objective of the present invention is to provide a transmission method for use in a BS of an MIMO network. The BS comprises a transceiver, a storage module and a generation module. The storage module stores pilot structure information. The MIMO network system includes another BS and an SS. The SS is within a signal coverage between the BS and the another BS. The another BS communicates with the SS by at least one first pilot structure in a first super frame. The transmission method comprises the following steps: enabling the transceiver to receive the first super frame; enabling the generation module to select at least one second pilot structure of a second super frame with according to the pilot structure information and the at least one first pilot structure of the first super frame to generate the second super frame with the at least one second pilot structure; and enabling the transceiver to communicate with the SS by the second super frame with the at least one second pilot structure to avoid a transmission interference between the BS and the another BS. 
         [0015]    The present invention uses different pilot structures, which are orthogonal to each other, in the BSs to transmit the data to the SS. These two different BSs may communicate with an SS in different frequency/channel by using the different pilot structures orthogonal to each other. The transmission interference, which occurs when the SS is communicating with the different BSs at the same time, may be reduced effectively. Thereby, the defects of the conventional technique may be overcome effectively, and the quality of communications may be enhanced obviously. 
         [0016]    The detailed technology and preferred embodiments implemented for the subject invention are described in the following paragraphs accompanying the appended drawings for people skilled in this field to well appreciate the features of the claimed invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1   a  illustrates a transmission cell  1   a  in the conventional wireless network; 
           [0018]      FIG. 1   b  illustrates the transmission cell  1   a  and a transmission cell  1   b  in the conventional wireless network; 
           [0019]      FIG. 2  illustrates a first embodiment of the present invention; 
           [0020]      FIG. 3  illustrates the super frame of the first embodiment; 
           [0021]      FIG. 4A  illustrates a configuration of the pilot pattern of the first embodiment; 
           [0022]      FIGS. 4B-4I  illustrate variations of the configuration of the pilot pattern of the first embodiment; 
           [0023]      FIG. 5A  illustrates another configuration of the pilot pattern of the first embodiment; 
           [0024]      FIGS. 5B-5D  illustrate variations of the another configuration of the pilot pattern of the first embodiment; 
           [0025]      FIGS. 6A-6B  illustrate a second embodiment of the present invention; 
           [0026]      FIG. 7  illustrates a third embodiment of the present invention; 
           [0027]      FIG. 8  illustrates the pilot structures of the first embodiment; and 
           [0028]      FIG. 9  illustrates a fourth embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0029]    In the following description, the present invention will be explained with reference to embodiments thereof. However, these embodiments are not intended to limit the present invention to any specific environment, applications or particular implementations described in these embodiments. Therefore, descriptions of these embodiments are only intended to illustrate rather than to limit the present invention. It should be appreciated that, in the following embodiments and the attached drawings, elements not related directly to the present invention are omitted from illustration; and dimensional relationships among individual elements in the attached drawings are illustrated only for ease of understanding, but not to limit the actual scale. 
         [0030]    A first embodiment of the present invention is shown in  FIG. 2 , which is a schematic view of an MIMO network  2 . The MIMO network  2  comprises a BS  21  and an SS  23 . The SS  23  is within a signal coverage of the BS  21 . It should be noted that, in this embodiment, the MIMO network  2  just comprises the BS  21  and the SS  23  for description convenience. In other embodiment, the MIMO network  2  may further comprise other BSs and SSs, the operations and functions thereof are similar to those of the BS  21  and the SS  23 . Peoples skilled in the art can understand easily according to the description in this embodiment. 
         [0031]    First, the downlink (DL) transmission between the BS  21  and the SS  23  is described. The BS  21  comprises a storage module  211 , a generation module  213  and a transceiver  215 . The storage module  211  is configured to store resource allocation information  210  about the MIMO network  2  and an SS list  212 . The resource allocation information  210  is used to records how the resource of the MIMO network  2  allocates currently. The SS list  212  is used to record the basic information, such as the identifier (ID), of all SSs (including the SS  23 ) in the MIMO network  2 . 
         [0032]    To transmitting DL data to the SS  23 , the generation module  213  of the BS  21  is configured to generate a super frame  214  corresponding to the SS  23  according to the resource allocation information  210  and the SS list  212 . The super frame  214  being generated by the generation module  213  comprises an interference-reducing (IR) zone. The IR zone comprises a pilot pattern. 
         [0033]    For more details, please refer to  FIG. 3 , which is a schematic view of the super frame  214 . In  FIG. 3 , FH represents “Frame Header”, F 0 -F 3  represent “Frames  0 - 3 ” respectively, SFM represents “Sub-Frame Map”, DLSF 0 -DLSF 4  represent “DownLink Sub-Frames  0 - 4 ” respectively, IRR represents “Interference Reducing Request” and ULSF 5 -ULSF 7  represent “UpLink Sub-Frames  5 - 7 ” respectively. The super frame  214  further comprises switch points  214   a  and  214   b . In the following description, only differences from the conventional techniques will be described, and the portions of the super frame  214  identical with those of the conventional techniques are omitted from description herein and understood by peoples skilled in the art easily. 
         [0034]    To reducing or avoiding interference of the data transmission, the present invention provides the IR zone (i.e. frame F 1 ) in the super frame  214 . The IR zone of the super frame  214  comprises a pilot pattern  216  which is arranged as an identifier of the SS  23 . The pilot pattern comprises a plurality of pilots and data, where each pilot comprises mitigation information, the functions of which will be described later. The configuration of the pilot pattern may be presented as shown in  FIG. 4A . In  FIG. 4A , the horizontal axis represents “symbol”, the vertical axis represents “subcarrier”, the gray grid represents a pilot and the white grid represents data. In this embodiment, since each of the BS  21  and the SS  23  uses two antennas to communicate, the configuration of the pilot pattern will be simplified as shown in  FIGS. 4B-4I  which just illustrates the pilot parts of  FIG. 4A . 
         [0035]    For example,  FIG. 4B  illustrates eight possible pilot patterns, each of which has six pilot structures. Since the each of the BS  21  and the SS  23  uses two antennas to communicate, each pilot structure has two pilots ( FIG. 4B  shows them in nonwhite grid). Each pilot pattern in  FIG. 4B  can be considered as an identifier of the SS  23 . In other words, the pilot patterns in  FIG. 4B  can be identifiers of eight SSs respectively. Similarly, each of the pilot patterns in  FIGS. 4B-4I  can be an identifier of an SS. 
         [0036]    Please refer to  FIG. 5A , which shows another configuration of the pilot pattern. In  FIG. 5A , the horizontal axis represents “symbol”, the vertical axis represents “subcarrier”, the gray grid represents a pilot and the white grid represents data. The configuration of the pilot pattern will also be simplified as shown in  FIGS. 5B-5D  which just illustrates the pilot parts of  FIG. 5A . Similarly, each of the pilot patterns in  FIGS. 5B-5D  can be an identifier of an SS. 
         [0037]    After the generation module  213  of the BS  21  generates the super frame  214 , the transceiver  215  configured to transmit the DL data to the SS  23  by the super frame  214  so that the SS  23  may receive the DL data after confirming the pilot pattern of the super frame  214  matches the identifier of the SS  23 . Particularly, the SS  23  comprises a transceiver  231  and a confirmation module  233 . The transceiver  231  of the SS  23  is configured to receive the pilot pattern  216  of the super frame  214 . Then the confirmation module  233  is configured to confirm whether the pilot pattern  216  of the super frame  214  matches the identifier of the SS  23  and then generate a confirmation result  230 . 
         [0038]    If the confirmation result  230  indicates the pilot pattern  216  of the super frame  214  matches the identifier of the SS  23 , the transceiver  231  is further configured to receive the DL data according to the confirmation result  230 . In addition, since each of pilots in the pilot pattern  216  comprises the mitigation information, the transceiver  231  is further configured to overcome a transmission interference of the DL data according to the mitigation information after receiving the DL data. 
         [0039]    Now the uplink (UL) transmission between the BS  21  and the SS  23  is described. The transceiver  231  of the SS  23  is further configured to transmit a UL data to the BS  21  by the super frame  214 . Similar to the DL transmission between the BS  21  and the SS  23 , the transceiver  215  of the BS  21  is configured to receive the pilot pattern  216  of the super frame  214  and confirm whether the pilot pattern  216  of the super frame  214  matches the ID of the SS  23 . If so, the transceiver  215  of the BS  21  will receive the UL data and further overcome the transmission interference of the UL data according to the mitigation information after receiving the UL data. 
         [0040]    A second embodiment of the present invention is shown in  FIGS. 6A-6B , which is a flow chart of a transmission method for use in the MIMO network  2  of the first embodiment. First, step  300  is executed to generate a super frame corresponding to the SS  23  according to the resource allocation information and the SS list. The super frame comprises a pilot pattern being arranged as an identifier of the SS  23 . Step  301  is executed to generate an IR zone in the super frame, where the IR zone comprises the pilot pattern. Step  302  is executed to transmit DL data to the SS  23  by the super frame. 
         [0041]    Then step  303  is executed to receive the pilot pattern of the super frame. Step  304  is executed to confirm whether the pilot pattern of the super frame matches the identifier of the SS  23  and generates a confirmation result. If the confirmation result is negative, step  305  is executed to stop receiving the DL data. If the confirmation result is positive, step  306  is executed to receive the DL data according to the confirmation result. Since the pilot pattern comprises a plurality of pilots, each of which comprises mitigation information, step  307  is executed to overcome a transmission interference of the DL data according to the mitigation information after receiving the DL data. 
         [0042]    Step  308  is executed to transmitting a UL data to the BS  21  by the super frame. Step  309  is executed to receive the UL data after confirming the pilot pattern of the super frame matches the identifier of the SS  23 . Finally, step  310  is executed to overcome a transmission interference of the UL data according to the mitigation information after receiving the UL data. 
         [0043]    In addition to the steps shown in  FIGS. 6A and 6B , this embodiment can also execute all the operations and functions of the above embodiments. Those of ordinary skill in the art will readily know how to execute the corresponding operations and functions in this embodiment by considering those in the first embodiment; therefore, a detailed description will be omitted here. 
         [0044]    The method described above may be embodied in a computer readable medium storing the previously described computer program to execute the above steps. The computer readable medium may be a soft disk, a hard disk, a compact disk, a mobile disk, a magnetic tape, a database accessible via a network, or any storage medium that is known to those skilled in the art to have similar functions. 
         [0045]    A third embodiment of the present invention is shown in  FIG. 7 , which is a schematic view of an MIMO network  7 . The MIMO network  7  comprises a BS (i.e. the BS  71  in  FIG. 7 ), another BS (i.e. BS  72  in  FIG. 7 ) and a SS  73 . The BS  71  comprises a storage module  711 , a generation module  713  and a transceiver  715 . The storage module  711  is configured to store pilot structure information  714  recording the information about the pilot structures of the BS  71  and the BS  72 . The SS  73  is within a signal coverage between the BS  71  and the BS  72 . 
         [0046]    For the convenience of following description, it is assumed that the SS  73  is communicating with the BS  71  and the BS  72  at the same time for a handover procedure. In other embodiments, the SS  73  may communicate with BSs  71 ,  72  at the same time in different procedures. People skilled in the art may understand it according to the description in this embodiment. 
         [0047]    Based on the above assumption, the SS  73  is handovering from the BS  72  to the BS  71 . Before starting the handover procedure, the BS  72  is communicating with the SS  73  by at least one first pilot structure in a first super frame  724 . After starting the handover procedure, the SS  73  has to communicate with the BS  71  and the BS  72  simultaneously. In order to avoid the transmission interference while the SS  73  is communicating with the BS  71  and the BS  72 , the transceiver  715  of the BS  71  is configured to receive the first super frame  724  to know the at least one first pilot structure. 
         [0048]    The generation module  713  is configure to select at least one second pilot structure of a second super frame  714  according to the pilot structure information  712  and the at least one first pilot structure of the first super frame  724  to generate the second super frame  714  with the at least one second pilot structure, wherein the at least one second pilot structure is orthogonal to the at least one first pilot structure. After generating the second super frame  714 , the transceiver  715  of the BS  71  may communicates with the SS  73  by the second super frame  714  avoid a transmission interference between the BS  71  and the BS  72 . 
         [0049]    More particularly, please refer to  FIG. 8  together. As described in aforementioned embodiments, the first super frame  724  may comprise a pilot pattern like the one shown in  FIG. 4A . The pilot pattern comprised in the first super frame  724  may be divided into three sub-channels  751 - 753  in frequency. Each of sub-channels  751 - 753  may comprise a first pilot structure, i.e. first pilot structure  7241 , first pilot structure  7242  and first pilot structure  7243 . Each first pilot structure may comprise a plurality of pilots (such as the gray grids and the stripe grids of  FIG. 8 ), each of which comprises mitigation information so that the SS  73  may overcome the transmission interference according to the mitigation information. Similar to the first super frame  724 , the second super frame  714  comprises second pilot structures  7141 - 7143 . 
         [0050]    In addition, as shown in  FIG. 8 , the second pilot structure  7141  is orthogonal to the first pilot structure  7241  to avoid the transmission interference. The pilot structure information  712  of the storage module  711  is to record the corresponding relation of the first pilot structures  7241 - 7243  and the second pilot structures  7141 - 7143  as shown in  FIG. 8 . Hence, after the transceiver  715  receives the first super frame  724 , the generation module  713  may know the at least one first pilot structure of the first super frame  724  is like the first pilot structure  7241 , and then select the at least one second pilot structure of the second super frame  714 , which is like the second pilot structure  7141 , according to the pilot structure information  712  and the first pilot structure  7241 . 
         [0051]    Herein, the transceiver  715  of the BS  71  may communicates with the SS  73  by the second super frame  714  with the at least one second pilot structure (i.e. second pilot structure  7141 ) to avoid the transmission interference between the BS  71  and the BS  73 . In addition, the generation module  713  is further configured to generate an interference-reducing (IR) zone in the second super frame  714 , and the IR zone comprises the at least one second pilot structure. The IR zone is explained in aforementioned embodiments and not described again. 
         [0052]    A fourth embodiment of the present invention is shown in  FIGS. 9A-9B , which is a flow chart of a transmission method for use in a BS of a MIMO network, such as the BS  71  of the MIMO network  7  in the third embodiment. The BS comprises a transceiver, a storage module and a generation module. The storage module stores pilot structure information. The MIMO network system includes another BS and an SS. The SS is within a signal coverage between the BS and the another BS. The another BS communicates with the SS by at least one first pilot structure in a first super frame. 
         [0053]    The transmission method of this embodiment comprises the following steps. First, step  901  is executed to enable the transceiver to receive the first super frame. Step  902  is executed to enable the generation module to generate the second super frame. Step  903  is executed to enable the generation module to generate an IR zone in the second super frame. Step  904  is executed to enable the generation module to generate the at least one second pilot structure in the IR zone of the second super frame. 
         [0054]    The steps  902 - 904  may be considered as a step of enabling the generation module to select at least one second pilot structure of a second super frame according to the pilot structure information and the at least one first pilot structure of the first super frame to generate the second super frame with the at least one second pilot structure. Finally, step  905  is executed to enable the transceiver to communicate with the SS by the second super frame with the at least one second pilot structure to avoid a transmission interference between the BS and the another BS. In addition, the at least one second pilot structure comprises a plurality of pilots, each of which comprises mitigation information so that the SS may further overcome the transmission interference according to the mitigation information. 
         [0055]    In addition to the steps shown in  FIG. 9 , this embodiment can also execute all the operations and functions of the third embodiment. Those of ordinary skill in the art will readily know how to execute the corresponding operations and functions in this embodiment by considering those in the third embodiment; therefore, a detailed description will be omitted here. 
         [0056]    The method described above may be embodied in a computer readable medium storing the previously described computer program to execute the above steps. The computer readable medium may be a soft disk, a hard disk, a compact disk, a mobile disk, a magnetic tape, a database accessible via a network, or any storage medium that is known to those skilled in the art to have similar functions. 
         [0057]    The present invention arranges a pilot pattern, which comprises a plurality of pilots, of the super frame as an identifier of an SS. No matter data transition in the TDD, FDD, the central zone edge or the cell zone edge, the BS and the SS will confirm whether the pilot pattern of the super frame matches the identifier of the SS which the BS/SS attempts to communicate with. If the confirmation result is positive, the communication will be proceeded. If the confirmation result is negative, the communication will be terminated. By confirming the pilot pattern, interference of transmission in the MIMO network will be reduced effectively, and the quality of communications will be enhanced effectively. 
         [0058]    Furthermore, the present invention uses different pilot structures, which are orthogonal to each other, in the BSs to transmit the data to the SS. These two different BSs may communicate with an SS in different frequency/channel by using the different pilot structures orthogonal to each other. The transmission interference, which occurs when the SS is communicating with the different BSs at the same time, may be reduced effectively. Thereby, the defects of the conventional technique may be overcome effectively, and the quality of communications may be enhanced obviously. 
         [0059]    The above disclosure is related to the detailed technical contents and inventive features thereof. People skilled in this field may proceed with a variety of modifications and replacements based on the disclosures and suggestions of the invention as described without departing from the characteristics thereof. Nevertheless, although such modifications and replacements are not fully disclosed in the above descriptions, they have substantially been covered in the following claims as appended.