CODEBOOK-BASED MULTI-BASE STATION UNITE PRE-CODING METHOD, MOBILE TERMINAL, AND BASE STATION Technical Field The present invention relates to the communication technology, and more particularly, relates to a codebook-based multi-base station unite pre-coding method, a mobile terminal, and a base station. DESCRIPTION OF THE RELATED ART In a wireless communication system, the application of pre-coding technology has become increasingly prevalent. It first pre-codes a to-be-transmitted signal based on channel information before transmitting such that the signal is more suitable to the channel, thereby improving the link quality or throughput of the user. At present, the implementation of single-base station pre-coding technology may be divided into two categories: with downlink as an example, one method is that a service base station of a mobile terminal obtains the channel information of downlink MIMO channel through a pilot signal or an uplink sounding transmitted by the mobile terminal in TDD system, and then the service base station calculates a pre-coding matrix and pre-codes the data before transmitting; the other commonly-used method is a pre-coding codebook-based method, where the mobile terminal obtains the channel information of the downlink MIMO channel through downlink pilot signal, preamble, or midambie as transmitted from the base station, and then selects an optimal pre-coding matrix index number from the pre-coding matrix codebook and feeds it back to the since base station, and the service base station pre-codes the data before transmitting. However, a user at the boarder of a cell is still subjected to strong interference from a neighboring cell, thus the pre-coding technology unite application in combination with a multi-base station cooperating technology is proposed to mitigate the inter-cell interference. In a multi-base station cooperating scenario, a plurality of base stations transmit signals to a same mobile terminal, for example, macro diversity, soft handoff, and multi-cell cooperating technology, such as network MIMO and cooperating MIMO. The pre-coding may also be applied among a plurality of base stations to further improve user performance. Hereinafter, all base stations that transmit data together to a mobile terminal are called "cooperating base stations" or "base stations," where only one thereof is a "master base station," and the other cooperating base stations are called "slave base stations." Typically, the master base station is the service base station associated with the mobile terminal. Generally, during downlink macro diversity and soft handover, the served mobile terminal is always located at the cell boarder. Two or more base stations transmit the same data to the mobile terminal at the same or different time-frequency resources. In this way, the mobile terminal realizes diversity combination reception and obtains diversity gain. If the cooperating base stations transmit data at the same time-frequency resource, the interference will be further decreased. In MIMO-enabled macro diversity handoff (MDHO) of WiMAX (IEEE 802.16e) system, all antennas of the cooperating base stations that participate in the macro diversity form an antenna array (antenna pool), and the cooperating base stations may transmit data in an MIMO manner to the mobile terminal based on a predetermined antenna selection mode. Further, any individual base station may further employ a pre-coding technology to transmit a signal to the mobile terminal in a closed-loop MIMO manner. For example, the IEEE 802.16m standard that is being formulated proposes a pre-coding codebook-based closed-loop macro diversity scheme: the mobile terminal selects the pre-coding matrix index number of each cooperating base station that transmits data to the mobile terminal and feeds this information back to the serving base station, and then the serving base station informs the corresponding cooperating base station of the pre-coding matrix index number as recommended to each cooperating base station. Thus, each cooperating base station may use its own pre-coding matrix to independently pre-code the transmitted data. It may be seen that in the case of macro diversity, an optimal pre-coding matrix is selected for each cooperating base station based on the MIMO channel from each cooperating base station to the mobile terminal, where each channel is only subjected to a closed-loop processing, while it is like an open-loop state between respective channels. Without using unite pre-coding among cooperating base stations, the space feature of the MIMO channel composed by multiple cooperating base stations and the mobile terminal (referred to as unite MIMO channel herein) cannot be fully utilized. Soft handoff is similar to the macro diversity. The network MIMO regards all antennas of all cooperating base stations as a transmit antenna array, and generates a pre-coding matrix based on all the channel state information CSI (for example, the channel response matrix) between all cooperating base stations and the mobile terminal, thereby realizing unite pre-coding among multiple base stations to eliminate the co-channel interference among multiple users. Because the unite pre-coding of this technology considers the CSI between all base stations and all mobile terminals, theoretically, the network MIMO lowers the interference caused by the time-frequency resource multiplexing to the utmost and thus the performance is the optimal. The cost of the solution to achieve the optimal performance is the extremely high complexity of the large-scale pre-coding matrix calculation. Even worse, because each base station has to exchange relevant channel information and pre-coding matrix information on the network that connects the cooperating base stations, transmission of much information causes high consumption of network resources, which makes greater burden on the network, and transmission delay of such information will deteriorate the system performance. SUMMARY OF THE INVENTION The present invention provides a novel codebook-based multi-base station unite pre-coding scheme. In this invention, multiple cooperating base stations commonly transmit signals to a mobile terminal. The mobile terminal estimates a channel matrix of a unite MIMO channel from the multiple cooperating base stations, and selects the optimal pre-coding matrix index and feeds it back to the multiple cooperating base stations from a pre-coding matrix codebook based on the unite MIMO channel matrix. Each cooperating base station selects an optimal pre-coding matrix based on the received pre-coding matrix index and using a corresponding portion of the pre-coding matrix to perform unite pre-coding on the data. Namely, the respective partial pre-coding matrixes as employed by all cooperating base stations together form a pre-coding matrix that is optimal to the mobile terminal, and the pre-coding matrix as used by each cooperating base station is a part of the optimal pre-coding matrix. Based on different methods of estimating the channel matrix of the unite MIMO channel by the mobile terminal, the cooperating base stations may also use the selected optimal pre-coding matrix to code the data. In other words, the data is pre-coded with the same pre-coding matrix as employed by all cooperating base stations. By using the codebook-based multi-base station unite pre-coding scheme according to the present invention, the user performance is improved, the complexity of implementation is low, and the demand on the network connecting base stations is very low. Further, the present invention further proposes an internal pre-coding scheme. Before performing the codebook-based multi-base station unite pre-coding, the inner pre-coding matrix for each base station is first determined, and then the mobile terminal estimates a unite equivalent channel matrix of the inner pre-coded multiple cooperating base stations and selects the optimal number from the pre-coding matrix codebook and feeds it back to multiple cooperating base stations based on the unite equivalent MIMO channel matrix. Each cooperating base station first performs unite pre-coding on the data, then uses the inner pre-coding matrix to perform inner pre-coding to the unite pre-coded data, and then transmits the data. The inner pre-coding is individually performed within each base station, which may further enhance the performance of the mobile terminal that is commonly served by the cooperating base stations. Besides, through the inner pre-coding process, the dimension of the pre-coding codebook may be decreased, the storage space for the pre-coding matrix codebook may be reduced, and the implementation complexity may be further lowered. Specifically, according to one embodiment of the present invention, there is provided a codebook-based multi-base station unite pre-coding method, the method comprising: a mobile terminal estimates channels H, from different cooperating base stations and obtaining a unite channel matrix ; the mobile terminal, based on the estimated unite channel matrix, selects an optimal unite pre-coding matrix e from the pre-coding matrix codebook; the mobile terminal feeds the index of the unite pre-coding matrix back to the cooperating base stations; the corresponding cooperating base station, based on the received unite pre-coding matrix index, selects a unite pre-coding matrix from the pre-coding matrix codebook, and performs unite pre-coding on the data using the unite pre-coding matrix before transmitting the data to the mobile terminal. According to an alternative embodiment of the present invention, the mobile terminal estimates channels Hc from different cooperating base stations and obtains the unite channel matrix means that the mobile terminal directly estimates the channels from different cooperating base stations, the result of the Hc channel estimation being the unite channel matrix According to an alternative embodiment of the present invention, the unite channel matrix c is an inner pre-coded equivalent unite channel matrix. According to an alternative embodiment of the present invention, the mobile terminal estimates channels Hc from different base stations to obtain the unite channel matrix means that the mobile terminal estimates the channels from different cooperating base stations, respectively, obtains physical channel matrixes from each cooperating base station to the mobile terminal, and combines each physical channel matrix to obtain the unite channel matrix Hc= [H1,Λ,HK] Wherein K > 1 indicates the number of cooperating base stations serving the mobile terminal, 1 ≤i ≤ K. According to an alternative embodiment of the present invention, the mobile terminal estimates channels Hc from different base stations to obtain the unite channel matrix means that the mobile terminal estimates the channels from different cooperating base stations, respectively, to directly obtain equivalent H W7 channel matrixes ' ' from each cooperating base station to the mobile terminal, and combines each equivalent channel matrix to obtain the equivalent unite channel matrix wherein K>1 indicates the number of cooperating base stations serving the mobile terminal, 1 ≤1 ≤ K. According to an alternative embodiment of the present invention, the mobile terminal estimates the Hc channels from different base stations to obtain the unite channel matrix means that the mobile terminal estimates the channels from different cooperating base stations to obtain physical channel matrixes '; the mobile terminal receives signals from different cooperating base stations to obtain W W7 inner pre-coding matrixes • ; the mobile terminal multiplies the inner pre-coding matrixes with the estimated physical channel matrixes ' Hi respectively, to obtain equivalent channel matrixes H W from each cooperating base station after being inner pre-coded, and combines the equivalent channel matrixes from each cooperating base station to obtain the unite channel matrix Hc=[H1W1i,Λ,Hk,Wk1] Wherein K > 1 indicates the number of cooperating base stations serving the mobile terminal, 1 ≤I' ≤ K. According to an alternative embodiment of the present invention, the mobile terminal receives signals W7 from different cooperating base stations to obtain inner pre-coding matrixes ' means that the mobile W7 terminal selects inner pre-coding matrixes ' from the pre-coding matrix codebook based on the estimated physical channel matrixes According to an alternative embodiment of the present invention, the mobile terminal feeds the index of the unite pre-coding matrix to the base stations means that the mobile terminal directly feeds the index of the unite pre-coding matrix back to all cooperating base stations. According to an alternative embodiment of the present invention, the mobile terminal feeds the index of the unite pre-coding matrix back to the base stations means that the mobile terminal feeds the index of the unite pre-coding matrix back to the master base station, and the master base station transmits the index of the unite pre-coding matrix to the slave base stations. According to an alternative embodiment of the present invention, the index of the unite pre-coding matrix refers to the unite pre-coding matrix index and the inner pre-coding matrix index. According to an alternative embodiment of the present invention, further, each cooperating base station performs unite pre-coding on the data by using the unite pre-coding matrix means performing unite pre-coding on the data by using the corresponding matrix block in the unite pre-coding matrix. According to an alternative embodiment of the present invention, further, the unite pre-coded data is subjected to inner pre-coding using the inner pre-coding matrix before being transmitted to the mobile terminal. According to an embodiment of the present invention, there is provided a mobile terminal, comprising: storing means, for storing at least one pre-coding matrix codebook; channel estimating means, for estimating channels from different cooperating base stations to obtain a unite channel matrix Hc; pre-coding matrix selecting means, for selecting a unite pre-coding matrix from the pre-coding matrix codebook based on the estimated unite channel matrix; feeding back means, for feeding an index of the unite pre-coding matrix back to the cooperating base stations. According to an alternative embodiment of the present invention, the channel estimating means is for directly estimating the channels from different cooperating base stations, the result of channel estimation Hc being the unite channel matrix According to an alternative embodiment of the present invention, the unite channel matrix Hc obtained by the channel estimating means is an inner pre-coded equivalent unite channel matrix. According to an alternative embodiment of the present invention, the channel estimating means is for estimating channels from different cooperating base stations respectively to obtain physical channel matrixes Hi from each cooperating channel to the mobile terminal; further, a channel matrix combining means is comprised, which is for combining each physical channel matrix to obtain the unite channel matrix Hc=[H1,Λ,Hk] wherein K. > 1 indicates the number of cooperating base stations serving the mobile terminal, 1 ≤ z ≤ K. According to an alternative embodiment of the present invention, the channel estimating means is for estimating channels from different cooperating base stations to directly obtain the equivalent channel H W7 matrixes from each cooperating base station to the mobile terminal; further, a channel matrix combining means is comprised, which is for combining each equivalent channel matrix to obtain the equivalent unite channel matrix Hc=[H1W1I,Λ,HkWKl] wherein A > 1 indicates the number of cooperating base stations serving the mobile terminal, 1 ≤i≤K According to an alternative embodiment of the present invention, the channel estimating means is for estimating the channels from different cooperating base stations to obtain the physical channel matrixes from each cooperating base station; further, a matrix multiplying operation means is comprised, W7 which is for multiplying the physical channel matrixes with the inner pre-coding matrixes from each cooperating base station, respectively, to obtain inner pre-coded equivalent channel matrixes H W7 further, a channel matrix combining means is further comprised, which is for combining each equivalent channel matrix to obtain the equivalent unite channel matrix wherein K>1 indicates the number of cooperating base stations serving the mobile terminal, 1 1 indicates the number of cooperating base stations serving the mobile terminal, 1 ≤i≤K According to an alternative embodiment of the present invention, the mobile terminal estimates channels Hc from different base stations to obtain the unite channel matrix means that the mobile terminal estimates the channels from different cooperating base stations, respectively, to directly obtain equivalent H W7 channel matrixes 11 from each cooperating base station to the mobile terminal, combines each equivalent channel matrix to obtain an equivalent unite channel matrix wherein K >1indicates the number of cooperating base stations serving the mobile terminal, 1 1 indicates the number of cooperating base stations serving the mobile terminal, 1 2 J dimension from the pre-coding matrix codebook; at step S355, the index of the unite pre-coding matrix and all inner pre-coding matrix indexes are sent to respective cooperating base stations. Fig. 4a and Fig. 4b illustrate a schematic block diagram of the structure of a base station according to an embodiment of the present invention, respectively. Fig. 5a and Fig. 5b illustrate a schematic block diagram of the structure of a mobile terminal according to an embodiment of the present invention, respectively. Wherein, the base station of Fig. 4a corresponds to the mobile terminal of Fig. 5a; and Fig. 4a and Fig. 5a correspond to Fig. 2a and Fig. 3a, respectively; the base station of Fig. 4b corresponds to the mobile terminal of Fig. 5b; and Fig. 4b and Fig. 5b correspond to Fig. 2e and Fig. 3e, respectively. Specifically, in the embodiment of the present invention, the base station 400 is for performing unite pre-coding on the data and sending the data. The base station 400 may comprise receiving means 401, storage means 402, unite pre-coding matrix selecting means 403, unite pre-coding means 404, and sending means 405. Specifically, the receiving means 401 may be configured to receive a unite pre-coding matrix index; storage means 402 is configured to store at least one pre-coding codebook; the unite pre-coding matrix selecting means 403 is configured to select a unite pre-coding matrix from the codebook in the storage means 402 based on the unite pre-coding matrix index as outputted by the receiving means 401, and output the unite pre-coding matrix to the unite pre-coding means 404; the unite pre-coding means 404 performs unite pre-coding on the data before outputting it to the sending means 405, and then the sending means 405 sends the data out; additionally, the sending means 405 is further configured to send a pilot signal before sending the data. Correspondingly, the mobile terminal 500 is configured to select a unite pre-coding matrix based on the unite channel estimation and feed back the unite pre-coding matrix index. The mobile terminal 500 may comprise receiving means 501, channel estimating means 502, storage means 503, unite pre-coding matrix selecting means 504, and feeding back means 505. Specifically, the receiving means 501 is configured to receive pilot signals; the channel estimating means 502 is configured to perform channel estimation on the pilot signals inputted by the receiving means 501, and after obtaining the unite channel, output it to the unite pre-coding matrix selecting means 504; the storage means 503 is configured to store at least one pre-coding codebook; the unite pre-coding matrix selecting means 504 selects an optimal unite pre-coding matrix from the codebook in the storage means 503 based on the unite channel, and outputs the index of the matrix to the feeding back means 505 that performs feedback. According to the embodiments and examples of the present invention, the base station 400 and mobile terminal 500 may make various changes. Fig. 4b (base station 410) and Fig. 5b (mobile terminal 510) are only one change thereof, respectively, which will be described in detail. Those skilled in the art may simply and intuitively obtain other changes of the base station and the mobile terminal based on the basic concept and the above embodiments, which will not be detailed one by one herein. In Fig. 4b, besides implementing the basic configuration function of the base station 400, the base station 410 is further configured to perform inner pre-coding matrix selection and inner code the pilot signal/ data. The base station 410 may comprise receiving means 401, storage means 402, unite pre-coding matrix selecting means 403, unite pre-coding means 404, and sending means 405, and further, it may further comprise inner pre-coding matrix selecting means 411 and inner pre-coding means 412. Specifically, the receiving means 401 is configured to receive the unite pre-coding matrix index and is further configured to receive the uplink sounding signal and estimate the downlink MIMO physical channel from the base station to the mobile terminal; the inner pre-coding selecting means 411 is configured to select an optimal inner pre-coding matrix based on the downlink physical channel estimation; storage means 402 is configured to store at least one pre-coding codebook; the unite pre-coding matrix selecting means 403 is configured to select a unite pre-coding matrix from the codebook in the storage means 402 based on the unite pre-coding matrix index from the receiving means 401, and further, the unite pre-coding matrix selecting means further selects a matrix block corresponding to the present base station from the selected unite pre-coding matrix as the unite pre-coding matrix of the present base station, and then outputs the unite pre-coding matrix of the present base station to the unite pre-coding means 404; the unite pre-coding means 404 performs unite pre-coding on the data, outputs the data to the inner pre-coding means 412; the inner pre-coding means 412 is configured to perform inner pre-coding on the pilot signal based on the inner pre-coding matrix as outputted from the inner pre-coding selecting means 411 and then output it to the sending means 405; the inner pre-coding means 412 is further configured to perform inner pre-coding on the unite pre-coded data from the unite pre-coding means 404 based on the inner pre-coding matrix outputted from the inner pre-coding selecting means 411, and output the inner pre-coded data to the sending means 405; the sending means 405 is configured to send the inner pre-coded pilot signal and data from the inner pre-coding means. Correspondingly, the mobile terminal 510 is configured to obtain a unite equivalent channel based on the channel estimation and inner pre-coding matrix and select a unite pre-coding matrix, and then feed back the unite pre-coding matrix index. The mobile terminal 510 may comprise receiving means 501, channel estimating means 502, storage means 503, unite pre-coding matrix selecting means 504, and feeding back means 505. Further, it further comprises inner pre-coding matrix selecting means 511, matrix multiplying operation means 512, and channel matrix combining means 513. Specifically, the receiving means 501 is configured to receive the pilot signals and inner pre-coding matrix indexes; the channel estimating means 502 is configured to perform channel estimation on the pilot signals inputted from the receiving means, respectively, to obtain the estimated physical channels 1 t and 2 and output them to the matrix multiplying operation means 512; the storage means 503 is configured to store at least one codebook; the inner pre-coding matrix selecting means 511 is configured W1 W' to select corresponding inner pre-coding matrixes 1 and 2 from the codebook in the storage means 503, respectively, based on the inner pre-coding matrix indexes outputted from the receiving means 501, and output the inner pre-coding matrixes to the matrix multiplying operation means 512; the matrix multiplying operation means 512 is configured to perform matrix multiplying operation to the inputted inner pre-coding matrixes and estimated physical channels, respectively, to obtain the equivalent channel estimates and H2W2 and then output the equivalent channel estimates to the channel matrix combining means 513; the channel matrix combining means 513 is configured to perform matrix H W1 H W 1 combination on the equivalent channel estimates 11 and 22 to obtain the unite equivalent H =\H W1 H W11 channel c L 11 ' 22 J, and then output it to the unite pre-coding matrix selecting means 504; the unite pre-coding matrix selecting means 504 selects the optimal unite pre-coding matrix from the codebook in the storage means 503 based on the unite equivalent channel, and outputs the index of the matrix to the feeding back means 505, and the feeding back means 505 feeds back the index. In the above embodiments, the codebook for selecting a unite pre-coding matrix and the codebook for selecting an inner pre-coding matrix may be identical or different. Hereinafter, the required dimension of the codebook in the present invention will be analyzed: in the present invention, in an embodiment without the inner pre-coding process, in case that a unite channel is H = H + H obtained by summing the estimated physical channels, in other words, c 1 2, the dimension of Hc js MxN in case that a unite channel is obtained through combining the estimated physical H — r H H1 H channels, in other words, c L " 2 J, the dimension of c is x ^ ; while in the embodiment with an inner pre-coding process, in case that a unite channel is obtained through summing the estimated JJ -HW'+HW1 H MxR1 physical channels, in other words, e 11 2 2 , the dimension of c is R1 = R1 2; in case that a unite channel is obtained through combining the estimated physical channels, in otherwords, = dimension of He Mx[R(+R>] R(+R1 through the inner pre-coding process, the dimension of the pre-coding codebook may be decreased, the pre-coding matrix codebook storage space may be reduced, and the implementation complexity may be further lowered. Additionally, the system may adapt the amount of data flow based on the settings when sending the data flow; in this case, the ranks of the pre-coding matrixes, which comprise the unite pre-coding matrix and the inner pre-coding matrix, must also be adapted, then when sending the pre-coding matrix indexes, the mobile terminal and cooperating base stations must also send the ranks of respectively pre-coding matrixes; when selecting a pre-coding matrix in the codebook, the selection must also be made in conjunction with the rank of the pre-coding matrix. This rank adaptation part has many embodiments in the prior art and thus will not be detailed in the embodiments of the present invention. However, those skilled in the art may simply and intuitively implement the present invention with rank adaptation based on the above depiction; with or without the rank adaptation, it is a variation within the technical scope of the present invention and should not be understood as the limitation to the present invention. The codebook-based multi-base station unite pre-coding scheme according to the present invention considers the channel condition between all base stations and the mobile terminal; it mitigates the interference caused by time-frequency resource multiplexing and enhances the user performance; moreover, the inner pre-coding is used to further enhance the performance of the mobile terminal commonly served by the cooperating base stations. Besides, through the inner pre-coding process, the dimension of the pre-coding codebook may be decreased, the storage space for the pre-coding matrix codebook may be reduced, and the implementation complexity may be further lowered. The present invention may be implemented by hardware, software, firmware, and their combination. The skilled in the art should know that the present invention may also be embodied in a computer program product set on a signal carrying medium usable for any suitable data processing system. Such signal bearing medium may be a transmission medium or a recordable medium for computer-readable information, including a magnetic medium, an optical medium, or other suitable medium. Examples of recordable mediums include: a magnetic disk or floppy disk in a hard disk driver, an optical disk for a CD driver, a magnetic tape, and other medium that can be contemplated by the skilled in the art. The skilled in the art should understand that any communication apparatus with an appropriate programming apparatus can implement steps of the method of the present invention as embodied in the program product. It is to be understood from the foregoing description that modifications and alterations may be made to the respective embodiments of the present invention without departing from the spirit of the present invention. The description in the present specification is intended to be illustrative and not limiting. The scope of the present invention is limited by the appended claims only. WE CLAIM: 1. A codebook-based multi-base station unite pre-coding method, comprising: the mobile terminal estimates channels from different cooperating base stations to obtain a unite channel matrix Hc the mobile terminal, based on the estimated unite channel matrix, selects an optimal unite pre-coding matrix c from a pre-coding matrix codebook; the mobile terminal feeds an index of the unite pre-coding matrix back to the cooperating base stations; the corresponding cooperating base station, based on the received index of the unite pre-coding matrix, selects a unite pre-coding matrix from the pre-coding matrix codebook, and performs unite pre-coding on data using the unite pre-coding matrix before sending the data to the mobile terminal. 2. The method according to claim 1, wherein the mobile terminal estimates channels from different cooperating base stations to obtain the unite channel matrix c means the mobile terminal directly estimates the channels from different cooperating base stations, the result of the channel estimation being the unite channel matrix Hc Hc 3. The method according to claim 2, wherein the unite channel matrix is an inner pre-coded equivalent unite channel matrix. 4. The method according to claim 1, wherein the mobile terminal estimates channels from different cooperating base stations to obtain the unite channel matrix Hc means: the mobile terminal estimates the channels from different cooperating base stations, respectively, to obtain physical channel matrixes Hi from each cooperating base station to the mobile terminal, and combines each physical channel matrix to obtain the unite channel matrix Hc=[H1,^,Hk] , wherein K > I indicates the number of cooperating base stations serving the mobile terminal, 1 ≤i≤k. 5. The method according to claim 1, wherein the mobile terminal estimates channels from different cooperating base stations to obtain the unite channel matrix c means: the mobile terminal estimates the channels from different cooperating base stations, H W respectively, to directly obtain equivalent channel matrixes from each cooperating base station to the mobile terminal, and combines each equivalent channel matrix to obtain an equivalent unite channel matrix, Hc=[H1W1I,,HK,WK1] , wherein K>1 indicates the number of cooperating base stations serving the mobile terminal, 1≤1≤K 6. The method according to claim 1, wherein the mobile terminal estimates channels from different cooperating base stations to obtain the unite channel matrix c means: the mobile terminal estimates channels from different cooperating base stations to obtain physical channel matrixes 'Hi the mobile terminal receives signals from different cooperating base stations to obtain inner W7 pre-coding matrixes 1 ; the mobile terminal multiplies the inner pre-coding matrixes ' with the estimated physical H H W channel matrixes ' , respectively, to obtain equivalent channel matrixes of cooperating base stations after being inner pre-coded, and combines the equivalent channel matrix from each cooperating base station to obtain the unite channel matrix -[H,1,W1I ,Λ,Hk,Wj,] Wherein K>1 indicates the number of cooperating base stations serving the mobile terminal, liK 7. The method according to claim 6, wherein the mobile terminal receives signals from different cooperating base stations to obtain inner pre-coding matrixes ' means that the W; mobile terminal selects the inner pre-coding matrixes 1 from a pre-coding matrix W1i codebook based on the estimated physical channel matrixes 8. The method according to any one of claims 1-7, wherein the mobile terminal feeds the index of the unite pre-coding matrix back to the base stations means that the mobile terminal directly feeds the index of the unite pre-coding matrix back to all cooperating base stations. 9. The method according to any one of claims 1-7, wherein the mobile terminal feeds the index of the unite pre-coding matrix back to the base stations means that the mobile terminal feeds the index of the unite pre-coding matrix index to the master base station, and the master base station transmits the index of the unite pre-coding matrix to the slave base stations. 10. The method according to claim 8 or 9, wherein the index of the unite pre-coding matrix means an unite pre-coding matrix index and inner pre-coding matrix indexes. 11. The method according to any one of claims 1-10, wherein further, that each cooperating base station performs unite pre-coding on data by using the unite pre-coding matrix means performing unite pre-coding on the data by using a corresponding matrix block in the unite pre-coding matrix. 12. A mobile terminal comprising: storage means, for storing at least one pre-coding matrix codebook; channel estimating means, for estimating channels from different cooperating base stations to obtain a unite channel matrix pre-coding matrix selecting means, for selecting a unite pre-coding matrix from the pre-coding matrix codebook based on the estimated unite channel matrix; feeding back means, for feeding an index of the unite pre-coding matrix back to the cooperating base stations. 13. A base station, comprising: storage means, for storing at least one pre-coding matrix codebook; receiving means, for receiving a signal that comprises information regarding at least one pre-coding matrix index; unite pre-coding matrix selecting means, for selecting an optimal unite pre-coding matrix from a pre-coding matrix codebook based on the unite pre-coding matrix index; unite pre-coding means, for performing unite pre-coding on data using a pre-coding matrix; sending means, for sending a pilot signal and unite pre-coded data. 14. A codebook-based multi-base station unite pre-coding matrix selection method, comprising: the mobile terminal estimates channels from different cooperating base stations to obtain a unite channel matrix Hc the mobile terminal, based on the estimated unite channel matrix, selectes an optimal unite re-coding matrix c from the pre-coding matrix codebook; the mobile terminal feeds an index of the unite pre-coding matrix back to the cooperating base stations; 15. A codebook-based base station pre-coding method, comprising: the base station sends a pilot signal; the base station receives a signal that comprises information regarding at least one unite pre-coding matrix index; the base station selects an optimal unite pre-coding matrix from a pre-coding matrix codebook based on the unite pre-coding matrix index; the base station performs unite pre-coding on data using the unite pre-coding matrix; the base station sends the unite pre-coded data.