Method and Apparatus for Controlling Co-channel Interference In a Wireless Communication System

Field Of The Invention

[0001] The present invention relates to a wireless communication system, more particularly, to a wireless communication system based on collaborative MIMO (Co-MIMO).

Background Of The Invention

[0002] The next generation wireless communication systems aim for higher targets such as higher spectrum efficiency, better coverage and higher peak data rate, etc. However, these requirements have brought a great challenge, that is, inter-cell interference (ICI), which has become a severe obstacle to the performance improvement of wireless communication systems, especially for cell-edge users. In order to overcome ICI, many technologies have been proposed, but Co-MIMO has become one of the most promising technologies due to its capability to improve the cell-edge throughput and average sector throughput at the same time.

[0003] The basic idea of Co-MIMO is to perform joint MIMO transmission among multiple base stations (BS) and multiple mobile stations (MS).Each BS performs multi-user precoding to control co-channel interference (CCI). In order to perform effective precoding, each BS needs to know the channel state information (CSI) of the MSs that it serves.

[0004] In the Time Division Duplex (TDD) mode, the channel response information of the uplink and downlink is symmetric. Therefore, each base station can obtain the uplink channel responses from the MS to each BS according to the uplink from the MS and calculate the downlink information from each BS to the MS and the corresponding respective downlink precoding matrixes according to the uplink channel responses.

[0005] However, in the Frequency Division Duplex (FDD) mode, the frequency difference of carriers between the uplink and the downlink is generally greater than the coherent bandwidth of the channel, therefore the channel fading of the uplink and downlink is not related to each other, resulting in that each BS cannot determine its downlink channel information according to the uplink channel fading. Thus, each BS cannot determine corresponding respective downlink precoding matrixes. In a single BS MIMO system, the problem is solved through the codebook feedback. That is, a preset codebook is shared between the BS and the MS. The MS estimates the downlink channel according to the reference signal such as the downlink pilot signal and etc, and then selects a suitable codeword from the codebook as the precoding matrix and feedbacks the index of the codeword to the BS. The BS performs precoding by using the feedback of the MS. Since the working flowchart and mechanism of the single BS MIMO and Co-MIMO system are very different, it is very difficult to spread the present single BS precoding technology based on the codebook feedback directly to the Co-MIMO system. Nowadays, there is no effective methods which are capable to solve this problem in the prior art.

Detailed Description Of The Invention

[0006] In order to solve the drawbacks described above in the prior art, the present invention provides a method and an apparatus of controlling co-channel interference in a base station of a wireless communication system based on collaborative MIMO and the corresponding method and apparatus of assisting a serving base station to control co-channel interference in a mobile station of a wireless communication system based on collaborative MIMO.

[0007] According to the first aspect of the present invention, a method of controlling co-channel interference in a base station of a wireless communication system based on collaborative MIMO is provided, wherein the method comprises the steps of: a. sending a downlink reference signal to a served mobile station and at least one coordinating mobile station; b. receiving precoding information corresponding to a downlink signal from the base station to the served mobile station from the served mobile station; c. sending the received precoding information to at least one serving base station of the at least one coordinating mobile station; d. receiving at least one precoding information corresponding to at least one downlink signal from the base station to the at least one coordinating mobile station respectively forwarded by at least one serving base station of the at least one coordinating mobile stations from the at least one coordinating mobile station; e. precoding a downlink signal from the base station to the served mobile station based on the precoding information corresponding to a downlink signal from the base station to the served mobile station, and precoding the at least one downlink signal from the base station to the at least one coordinating mobile stations respectively based on the at least one precoding information corresponding to the at least one downlink signal from the base station to the at least one coordinating mobile stations; wherein, after step b and before step e, the method comprises the steps of: m. receiving at least one precoding information corresponding to at least one precoding information of at least one downlink signal from the at least one serving base stations to the at least one coordinating mobile stations respectively forwarded by at least one serving base station of the at least one coordinating mobile station from the at least one coordinating mobile station; n. sending the received at least one precoding information to the served mobile station; o. receiving at least one precoding information corresponding to at least one downlink signal from at least one serving base station of the at least one coordinating mobile station to the served mobile station; p. sending the received at least one precoding information to at least one serving base station of the at least one coordinating mobile station respectively.

[0008] According to the second aspect of the present invention, a method of assisting a serving base station to control co-channel interference in a mobile station of a wireless communication system based on collaborative MIMO is provided, wherein the method comprises the steps of: A. receiving a downlink reference signal from a serving base station and at least one downlink reference signal from at least one coordinating base station; B. according to the received downlink reference signal from the serving base station, estimating a channel transmission matrix of a downlink channel from the serving base station to the mobile station, and according to the received at least one downlink reference signal from the at least one coordinating base stations, estimating at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base stations to the mobile station respectively; C. according to the estimated channel transmission matrix of a downlink channel from the serving base station to the mobile station, selecting a precoding vector corresponding to a downlink signal from the serving base station to the mobile station from a shared codebook; D. sending precoding information corresponding to a downlink signal from the serving base station to the mobile station to the serving base station; E. receiving at least one precoding information corresponding to at least one downlink signal from the at least one coordinating base station to at least one served mobile station of the at least one coordinating base station forwarded by the at least one coordinating base station and the serving base station from the at least one served mobile station from the at least one coordinating base station; F. based on the received at least one precoding information and the estimated at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base station to the mobile station, selecting at least one precoding vector corresponding to at least one downlink signal from at least one coordinating base stations to the mobile station from the shared codebook respectively; wherein the precoding vector corresponding to a downlink signal from each coordinating base station to the mobile station is orthogonal with the precoding vector corresponding to a downlink signal from the coordinating base station to the served mobile station of the coordinating base station; G. sending at least one precoding information corresponding to at least one downlink signal from the at least one coordinating base station to the mobile station to the serving base station.

[0009] According to the third aspect of the present invention, a control apparatus of controlling co-channel interference in a base station of a wireless communication system based on collaborative MIMO is provided, wherein the apparatus comprises: a first sending means, for sending a downlink reference signal to a served mobile station and at least one coordinating mobile station; a first receiving means, for receiving precoding information corresponding to a downlink signal from the base station to the served mobile station from the served mobile station; a second sending means, for sending the received precoding information to at least one serving base station of the at least one coordinating mobile station; a second receiving means, for receiving at least one precoding information corresponding to at least one downlink signal from the base station to the at least one coordinating mobile station respectively forwarded by at least one serving base station of the at least one coordinating mobile stations from the at least one coordinating mobile station; a first precoding means, for precoding a downlink signal from the base station to the served mobile station based on the precoding information corresponding to a downlink signal from the base station to the served mobile station, and precoding the at least one downlink signal from the base station to the at least one coordinating mobile stations respectively based on the at least one precoding information corresponding to the at least one downlink signal from the base station to the at least one coordinating mobile stations; wherein, the control apparatus further includes: a third receiving means, for receiving at least one precoding information corresponding to at least one precoding information of at least one downlink signal from the at least one serving base stations to the at least one coordinating mobile stations respectively forwarded by at least one serving base station of the at least one coordinating mobile station from the at least one coordinating mobile station; a third sending means, for sending the received at least one precoding information to the served mobile station; a sixth receiving means, for receiving at least one precoding information corresponding to at least one downlink signal from at least one serving base station of the at least one coordinating mobile station to the served mobile station; a seventh receiving means, for sending the received at least one precoding information to at least one serving base station of the at least one coordinating mobile station respectively.

[0010] According to the fourth aspect of the present invention, an assist control apparatus of assisting a serving base station to control co-channel interference in a mobile station of a wireless communication system based on collaborative MIMO is provided, wherein the assist control apparatus comprises: a fourth receiving means, for receiving a downlink reference signal from a serving base station and at least one downlink reference signal from at least one coordinating base station; an estimating means, for according to the received downlink reference signal from the serving base station, estimating a channel transmission matrix of a downlink channel from the serving base station to the mobile station, and according to the received at least one downlink reference signal from the at least one coordinating base stations, estimating at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base stations to the mobile station respectively; a first selecting means, for according to the estimated channel transmission matrix of a downlink channel from the serving base station to the mobile station, selecting a precoding vector corresponding to a downlink signal from the serving base station to the mobile station from a shared codebook; a fourth sending means, for sending precoding information corresponding to a downlink signal from the serving base station to the mobile station to the serving base station; a fifth receiving means, for receiving at least one precoding information corresponding to at least one downlink signal from the at least one coordinating base station to at least one served mobile station of the at least one coordinating base station forwarded by the at least one coordinating base station and the serving base station from the at least one served mobile station from the at least one coordinating base station; a second selecting means, for based on the received at least one precoding information and the estimated at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base station to the mobile station, selecting at least one precoding vector corresponding to at least one downlink signal from at least one coordinating base stations to the mobile station from the shared codebook respectively; wherein the precoding vector corresponding to a downlink signal from each coordinating base station to the mobile station is orthogonal with the precoding vector corresponding to a downlink signal from the coordinating base station to the served mobile station of the coordinating base station; a fifth sending means, for sending at least one precoding information corresponding to at least one downlink signal from the at least one coordinating base station to the mobile station to the serving base station.

[0011] Since the feedback mechanism based on the codebook is employed in the Co-MIMO system in the present invention to enable the BS to obtain the precoding information, the present invention can be used to both TDD mode and FDD mode. Moreover, since the precoding vectors selected by different MSs for the same BS are always orthogonal, multi-user co-channel interference can be reduced.

Description of Drawings

[0012] With reference to the following description to the non-limited embodiments of the figures, other features, aims and advantages will be more apparent.

[0013] FIG.1 shows a network schematic diagram of a wireless communication system based on the Co-MIMO according to a detailed embodiment of the present invention;

[0014] FIG.2 shows a flowchart of the method of controlling the co-channel interference in a wireless communication system based on the Co-MIMO according to a detailed embodiment of the present invention;

[0015] FIG.3 shows a block diagram of a control apparatus in a BS of a wireless communication system based on the Co-MIMO for controlling the co-channel interference according to a detailed embodiment of the present invention; and

[0016] FIG4 shows a block diagram of an assist control apparatus in a MS of a wireless communication system based on the Co-MIMO for controlling the co-channel interference according to a detailed embodiment of the present invention;

[0017] Wherein, through different figures above, same or similar reference numerals refer to corresponding features or functions.

Detailed description of embodiments

[0018] With reference to the figures, the present invention will be described in detail in the following.

[0019] FIG.l shows a network schematic diagram of a wireless communication system based on the Co-MIMO according to a detailed embodiment of the present invention.

[0020] The wireless communication system shown in FIG.1 includes MS la, MS lb, BS 2a and BS 2b. It should be noted that the technical solution of the present invention will be described later by using an example in which a wireless communication system includes 2 BSs and 2 MSs, but those skilled in the art shall be appreciated that the wireless communication system of the present invention is not limited to 2 BSs and 2 MSs.

[0021] Moreover, without loss of generality, the present invention will be described later by using an example, in which both MS la and MS lb include two receiving antennas, and both BS 2a and BS 2b include four transmitting antennas. It should be noted that in the specific application, BS 2a and BS 2b may include any number of transmitting antennas, MS la and MS lb may include any number of receiving antennas, which will be understood by those skilled in the art and will not be described in detail here. But it should be noted that, in order to ensure MS la and MS lb to restore the date stream received from BS 2a and BS 2b accurately, the number of the receiving antennas of MS la must be greater than or equal to the stream number of the data streams that are received from BS 2a and BS 2b by MS la. Similarly, the number of the receiving antennas of MS lb must be greater than or equal to the stream number of the data streams that are received from BS 2a and BS 2b by MS lb.

[0022] In the wireless communication system based on Co-MIMO shown in FIG.1, it is assumed that, BS 2a sends one data stream to MS la and MS lb respectively, and similarly, BS 2b also sends one data stream to MS la and MS lb respectively.

[0023] For BS 2a, MS la is the served MS of BS 2a, and MS lb is the coordinating MS of BS 2a. For BS 2b, MS lb is the served MS of BS 2b, and MS la is the coordinating MS of BS 2b.

[0024] For MS la, BS 2a is the serving BS of MS la, and BS 2b is the coordinating BS of MS la. For MS lb, BS 2b is the serving BS of MS lb, and BS 2a is the coordinating BS of MS lb.

[0025] FIG.2 shows a flowchart of a method of controlling the co-channel interference in a wireless communication system based on the Co-MIMO according to a detailed embodiment of the present invention.

[0026] Referring to FIG.2 and in conjunction with FIG.1, the technical solution of the present invention will be described in detail. The description for FIG. 1 above will also be taken as a reference here.

[0027] Firstly, in step S1, BS 2a sends a downlink reference signal to MS la and MS lb. The downlink reference signal can be a public pilot signal, or a training sequence.

[0028] Secondly, in step S2, MS la receives the downlink reference signal from BS 2a; in step S2\ MS lb receives the downlink reference signal from BS 2a.

[0029] It should be noted that, there is no necessary order between step S2 and S2[0030] Then, in step S3, MS la estimates channel transmission matrix Ha,a of the downlink channel from BS 2a to MS la according to the downlink reference signal received from BS 2a; in step S3', MS lb estimates channel transmission matrix Hb,a of the downlink channel from BS 2a to MS lb according to the downlink reference signal received from BS 2a.

[0031] It should be noted that, there is no necessary order between step S3 and S3'.

[0032] After MS la estimates the channel transmission matrix Haa of the downlink channel from BS 2a to MS la, in step S4, according to the estimated channel transmission matrix Ha>a, MS la selects a precoding vector va>a corresponding to the downlink signal from BS 2a to MS la from a shared codebook.

[0033] Further, selecting a precoding vector vaa from a shared codebook by MS la is based on the following formula:

[0034] Wherein, C represents codebook, the above formula represents that any column of vector c in the codebook C is traversed. The column of vector c which makes \HbJ)c\2 reach the maximum value is the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la.

[0035] It should be noted, that MS la only needs to select a column of vector which meets the above formula from the shared codebook as the precoding vector for the data stream, since in the description the technical solution is described by using an example in which BS 2a sends one data stream to MS la. But those skilled in the art shall be appreciated that, if BS 2a sends a plurality of data streams to MS la, MS la must select a plurality of columns of vectors which meet the formula above from the shared codebook as the precoding vectors for the plurality of data streams.

[0036] Further, the shared codebook is shared among MS la, MS lb, BS 2a and BS 2b. Still further, the codebook may be a DFT codebook, 3GPP LTE codebook, IEEE802.16e codebook, or other types of codebooks, which is intelligible for those skilled in the art and will not be described in detail here.

[0037] Typically, the codebook consists of a plurality of precoding matrixes; each matrix consists of a plurality of columns of vectors. Preferably, each column of precoding vectors in the same precoding matrix is orthogonal with each other.

[0038] Further, the number of rows of a precoding matrix is equal to the number of the BS transmitting antennas. The number of columns of a precoding matrix is equal to the maximum data stream number that can be sent by a BS. In the embodiment, since it is assumed that BS 2a and BS 2b include 4 transmitting antennas respectively and the maximum data stream number that can be sent by a BS is 4, a precoding matrix in the shared codebook is a 4x4 matrix.

[0039] After MS la selects the precoding vector va, a corresponding to the downlink signal from BS 2a to MS la from the shared codebook, in step S5, MS la sends to BS 2a the precoding information corresponding to the downlink signal from BS 2a to MS la.

[0040] It should be noted that, MS la can send to BS 2a the precoding vector va, a corresponding to the downlink signal from BS 2a to MS la directly. Preferably, MS la can send to BS 2a the index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la.

[0041] In the following, the example, in which MS la sends to BS 2a the index of the precoding vector va, a corresponding to the downlink signal from BS 2a to MS la, will be described.

[0042] Next, in step S6, BS 2a receives from MS la the index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la. Then, in step S7, BS 2a sends to BS 2b the received index of the precoding va, a corresponding to the downlink signal from BS 2a to MS la.

[0043] Above is described from the view point of BS 2a, but it is intelligible to those skilled in the art, BS 2b also interacts with MS lb and MS la, while BS 2a interacts with MS la and MS lb.

[0044] More specifically, firstly, BS 2b sends a downlink reference signal to MS lb and MS la. The downlink reference signal can be a public pilot signal, or a training sequence.

[0045] Secondly, MS lb receives the downlink reference signal from BS 2b; in step S2' MS la receives the downlink reference signal from BS 2b.

[0046] Similarly, there is no necessary order between the step of MS lb receiving the downlink reference signal from BS 2b and the step of MS la receiving the downlink reference signal from BS 2b.

[0047] Then, MS lb estimates channel transmission matrix Hb,b of the downlink channel from BS 2b to MS lb according to the downlink reference signal received from BS 2b; MS la estimates channel transmission matrix Ha, b of the downlink channel from BS 2b to MS la according to the downlink reference signal received from BS 2b.

[0048] Next, according to the estimated channel transmission matrix Hbb, MS lb selects a precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb from a shared codebook.

[0049] Further, selecting a precoding vector vb>b from a shared codebook by MS lb is based on the following formula:

[0050] Wherein, C represents codebook, the above formula represents that any column of vector c in the codebook C is traversed. The column of vector c which makes \HbJ)c\2 reach the maximum value is the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb.

[0051] Then, MS lb sends to BS 2b the precoding information corresponding to the downlink signal from BS 2b to MS lb.

[0052] It should be noted that, MS lb can send to BS 2b the precoding vector Vb,b corresponding to the downlink signal from BS 2b to MS lb directly. Preferably, MS lb can send to BS 2b the index of the precoding vector vbb corresponding to the downlink signal from BS 2b to MS lb.

[0053] In the following, the example, in which MS lb sends to BS 2b the index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb, will be described.

[0054] After BS 2b receives from MS lb the index of the precoding vector Vb,b corresponding to the downlink signal from BS 2b to MS lb, it sends the index of the precoding vector Vb.b to BS 2a.

[0055] In step S7', BS 2a receives the index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb forwarded by BS 2b from MS lb. Then, in step S8, BS 2a sends the received index of the precoding vector vb,b to MS la.

[0056] It should be noted that, there is no order between step S7 and step S7' above.

[0057] Next, in step S9, MS la receives the index of the precoding vector vb, b corresponding to the downlink signal from BS 2b to MS lb forwarded by BS 2a, then, in step S10, based on the received index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb and the estimated channel transmission matrix Hab of the downlink channel from BS 2b to MS la, MS la selects the precoding vector va,a corresponding to the downlink signal from BS 2b to MS la from the shared codebook.

[0058] More specifically, firstly according to the received index of the precoding vector vb, b corresponding to the downlink signal from BS 2b to MS lb, MS la searches the corresponding precoding vector vb,b from the shared codebook. Then according to the precoding vector vb)b corresponding to the downlink signal from BS 2b to MS lb and the estimated channel transmission matrix Ha,b of the downlink channel from BS 2b to MS la, MS la selects the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the codebook.

[0059] Wherein, the selected precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the shared codebook should be orthogonal with the selected precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb.

[0060] Since each column of the precoding vectors in each precoding matrix in the shared codebook is orthogonal with each other, preferably, according to the estimated channel transmission matrix Ha,b of the downlink channel from BS 2b to MS la, MS la selects the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the precoding matrix where the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb is located.

[0061] Further, selecting a precoding vector va,b from a shared codebook by MS la is based on the following formula:

[0062] Wherein, C represents codebook, c represents the conjugate transposed matrix of c. The above formula represents that any column of precoding vector in the precoding matrix, where the precoding vector vb,b is located, in the codebook C, is traversed. The column of vector c which makes \HaJbc\ reach the maximum value is the precoding vector va>b corresponding to the downlink signal from BS 2b to MS la.

[0063] After MS la selects the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the shared codebook, in step S1 1, MS la sends the index of the selected precoding vector va,b to BS 2a.

[0064] Of course, MS la can also send the precoding vector va,b to BS 2a directly.

[0065] In step S1 2, BS 2a receives from MS la the index of the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la and sends it to BS 2b.

[0066] In the meantime when MS 1 a selects the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the shared codebook, MS lb also selects the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb from the shared codebook.

[0067] More specifically, in step S7 above, after BS 2a sends to BS 2b the received index of the precoding va, a corresponding to the downlink signal from BS 2a to MS la, BS 2b receives the index of the precoding vector va, a corresponding to the downlink signal from BS 2a to MS la forwarded by BS 2a from MS la and sends the index of the precoding vector va,a to MS lb.

[0068] After MS lb receives the index of the precoding vector va,a, based on the index of the precoding vector va, a and the estimated channel transmission matrix Hb,a of the downlink channel from BS 2a to MS lb, MS lb selects the precoding vector Vb,a corresponding to the downlink signal from BS 2a to MS lb from the shared codebook.

[0069] More specifically, firstly according to the received index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la, MS lb searches the corresponding precoding vector vaa from the shared codebook. Then according to the precoding vector va>a corresponding to the downlink signal from BS 2a to MS la and the estimated channel transmission matrix Hb,a of the downlink channel from BS 2a to MS lb, MS la selects the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb from the codebook.

[0070] Wherein, the selected precoding vector Vb,a corresponding to the downlink signal from BS 2a to MS lb from the shared codebook should be orthogonal with the selected precoding vector va,a corresponding to the downlink signal from BS 2a to MS la.

[0071] Since each column of the precoding vectors in each precoding matrix in the shared codebook is orthogonal with each other, preferably, according to the estimated channel transmission matrix Hb,a of the downlink channel from BS 2a to MS lb, MS lb selects the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb from the precoding matrix where the precoding vector va, a corresponding to the downlink signal from BS 2a to MS la is located.

[0072] Further, selecting a precoding vector Vb, a from a shared codebook by MS lb is based on the following formula:

[0073] Wherein, C represents codebook, c' represents the conjugate transposed matrix of c. The above formula represents that any column of precoding vector in the precoding matrix, where the precoding vector va>a is located, in the codebook C, is traversed. The column of vector c which makes \Hb ac\ reach the maximum value is the precoding vector vb, a corresponding to the downlink signal from BS 2a to MS lb.

[0074] After MS lb selects the precoding vector Vb,a corresponding to the downlink signal from BS 2a to MS lb from the shared codebook, MS lb sends the index of the selected precoding vector vb, a to BS 2b.

[0075] Of course, MS lb can also send the precoding vector vb,a to BS 2b directly.

[0076] After BS 2b receives from MS lb the index of the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb, BS 2b sends it to BS 2a.

[0077] In step S1 3, BS 2a receives the index of the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb forwarded by BS 2b from MS lb.

[0078] Next, in step S1 4, based on the received index of the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb and the index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la, BS 2a precodes the downlink signals sent to MS la and MS lb respectively.

[0079] More specifically, firstly, according to the received index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la, BS 2a searches the corresponding precoding vector va,a from the shared codebook, and according to the received index of the precoding vector Vb, a corresponding to the downlink signal from BS 2a to MS lb, BS 2a searches the corresponding precoding vector vb,a from the shared codebook.

[0080] Then, according to the searched precoding vector vM, BS 2a precodes the downlink signal which is sent by BS 2a to MS la, and according to the searched precoding vector vb)a, BS 2a precodes the downlink signal which is sent by BS 2a to MS lb.

[0081] At last, BS 2a sends the precoded downlink signals to MS la and MS lb respectively.

[0082] Similarly, after BS 2b receives the index of the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la forwarded by BS 2a from MS la, based on the received index of the precoding vector Vb, a corresponding to the downlink signal from BS 2a to MS lb and the index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb, BS 2b precodes the downlink signals sent to MS lb and MS la respectively.

[0083] More specifically, firstly, according to the received index of the precoding vector vbjb corresponding to the downlink signal from BS 2b to MS lb, BS 2b searches the corresponding precoding vector vbjb from the shared codebook, and according to the received index of the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la, BS 2b searches the corresponding precoding vector va,b from the shared codebook.

[0084] Then, according to the searched precoding vector vb,b, BS 2b precodes the downlink signal which is sent by BS 2b to MS lb, and according to the searched precoding vector va,b, BS 2b precodes the downlink signal which is sent by BS 2b to MS 1 a.

[0085] At last, BS 2b sends the precoded downlink signals to MS lb and MS 1 a respectively.

[0086] The technical solution of the present invention is described above from the view point of the method. In the following, the technical solution of the present invention will be described from the view point of the apparatus module.

[0087] FIG.3 shows a block diagram of a control apparatus in a BS of a wireless communication system based on the Co-MIMO for controlling the co-channel interference according to a detailed embodiment of the present invention. The control apparatus 20 in FIG.3 includes a first sending means 201, a first receiving means 202, a second sending means 203, a third receiving means 204, a third sending means 205, a sixth receiving means 206, a seventh sending means 207, a second receiving means 208 and a first precoding means 209.

[0088] FIG.4 shows a block diagram of an assist control apparatus in a MS of a wireless communication system based on the Co-MIMO for controlling the co-channel interference according to a detailed embodiment of the present invention. The assist control apparatus 10 in FIG.4 includes a fourth receiving means 101, an estimating means 102, a first selecting means 103, a fourth sending means 104, a fifth receiving means 105, a second selecting means 106 and a fifth sending means 107.

[0089] Hereinafter, referring to FIG.3 and FIG.4 and in conjunction with FIG. 1, the technical solution of the present invention will be described in detail. The description for FIG. 1 above will also be taken as a reference here.

[0090] Firstly, the first sending means 201 in the control apparatus 20 in BS 2a sends a downlink reference signal to MS la and MS lb. The downlink reference signal can be a public pilot signal, or a training sequence.

[0091] Secondly, the fourth receiving means 101 in the assist control apparatus 10 in MS la receives the downlink reference signal from BS 2a;

the fourth receiving means 101 in the assist control apparatus 10 in MS lb receives the downlink reference signal from BS 2a.

[0092] Then, the estimating means 102 in the assist control apparatus 10 in MS la estimates channel transmission matrix Ha, a of the downlink channel from BS 2a to MS la according to the downlink reference signal received from BS 2a; the estimating means 102 in the assist control apparatus 10 in MS lb estimates channel transmission matrix Hb,a of the downlink channel from BS 2a to MS lb according to the downlink reference signal received from BS 2a.

[0093] After the estimating means 102 in the assist control apparatus 10 in MS la estimates the channel transmission matrix Ha, a of the downlink channel from BS 2a to MS la, according to the estimated channel transmission matrix Ha,a, the first selecting means 103 in the assist control apparatus 10 in MS la selects a precoding vector va,a corresponding to the downlink signal from BS 2a to MS la from a shared codebook.

[0094] Further, selecting a precoding vector va,a from a shared codebook by the selecting means 103 in the assist control apparatus 10 in MS la is based on the following formula:

[0095] Wherein, C represents codebook, the above formula represents that any column of vector c in the codebook C is traversed. The column of vector c which makes \HbJbc\ reach the maximum value is the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la.

[0096] It should be noted, that MS la only needs to select a column of vector which meets the above formula from the shared codebook as the precoding vector for the data stream, since in the description the technical solution is described by using an example in which BS 2a sends one data stream to MS la. But those skilled in the art shall be appreciated that, if BS 2a sends a plurality of data streams to MS la, MS la must select a plurality of columns of vectors which meet the formula above from the shared codebook as the precoding vectors for the plurality of data streams.

[0097] Further, the shared codebook is shared among MS la, MS lb, BS 2a and BS 2b. Still further, the codebook may be a DFT codebook, 3GPP LTE codebook, IEEE802.16e codebook, or other types of codebooks, which is intelligible for those skilled in the art and will not be described in detail here.

[0098] Typically, the codebook consists of a plurality of precoding matrixes; each matrix consists of a plurality of columns of vectors. Preferably, each column of precoding vectors in the same precoding matrix is orthogonal with each other.

[0099] Further, the number of rows of a precoding matrix is equal to the number of the BS transmitting antennas. The number of columns of a precoding matrix is equal to the maximum data stream number that can be sent by a BS. In the embodiment, since it is assumed that BS 2a and BS 2b include 4 transmitting antennas respectively and the maximum data stream number that can be sent by a BS is 4, a precoding matrix in the shared codebook is a 4x4 matrix.

[00100] After the first selecting means 103 in the assist control apparatus 10 in MS la selects the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la from the shared codebook, the fourth sending means 104 in the assist control apparatus 10 in MS la sends to BS 2a the precoding information corresponding to the downlink signal from BS 2a to MS la.

[00101] It should be noted that, the fourth sending means 104 in the assist control apparatus 10 in MS la can send to BS 2a the precoding vector va,b corresponding to the downlink signal from BS 2a to MS la directly. Preferably, the fourth sending means 104 in the assist control apparatus 10 in MS la can send to BS 2a the index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la.

[00102] Further, the determining means in the fourth sending means 104 firstly determines the index of the precoding vector va,a according to the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la. Then, the sixth sending means in the fourth sending means 104 sends to BS 2a the determined index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la.

[00103] In the following, the example, in which the fourth sending means 104 in the assist control apparatus 10 in MS la sends to BS 2a the index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la, will be described.

[00104] Next, the first receiving means 202 in the control apparatus 20 in BS 2a receives from MS la the index of the precoding vector va, a corresponding to the downlink signal from BS 2a to MS la. Then, the second sending means 203 in the control apparatus 20 in BS 2a sends to BS 2b the received index of the precoding va,a corresponding to the downlink signal from BS 2a to MS la.

[00105] Above is described from the view point of BS 2a, but it is intelligible to those skilled in the art, BS 2b also interacts with MS lb and MS la, while BS 2a interacts with MS la and MS lb.

[00106] More specifically, firstly, the first sending means 201 in the control apparatus 20 in BS 2b sends a downlink reference signal to MS lb and MS 1 a. The downlink reference signal can be a public pilot signal, or a training sequence.

[00107] Secondly, the fourth receiving means 101 in the assist control apparatus 10 in MS lb receives the downlink reference signal from BS 2b; the fourth receiving means 101 in the assist control apparatus 10 in MS la receives the downlink reference signal from BS 2b.

[00108] Then, the estimating means 102 in the assist control apparatus 10 in MS lb estimates channel transmission matrix Hb,b of the downlink channel from BS 2b to MS lb according to the downlink reference signal received from BS 2b; the estimating means 102 in the assist control apparatus 10 in MS la estimates channel transmission matrix Hab of the downlink channel from BS 2b to MS la according to the downlink reference signal received from BS 2b.

[00109] Next, according to the estimated channel transmission matrix Hb,b, the first selecting means 103 in the assist control apparatus 10 in MS lb selects a precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb from a shared codebook.

[00110] Further, selecting a precoding vector vb,b from a shared codebook by the first selecting means 103 in the assist control apparatus 10 in MS lb is based on the following formula:

[00111] Wherein, C represents codebook, the above formula represents that any column of vector c in the codebook C is traversed. The column of vector c which makes \Hbbc\2 reach the maximum value is the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb.

[00112] Then, the fourth sending means 104 in the assist control apparatus 10 in MS lb sends to BS 2b the precoding information corresponding to the downlink signal from BS 2b to MS lb.

[00113] It should be noted that, the fourth sending means 104 in the assist control apparatus 10 in MS lb can send to BS 2b the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb directly. Preferably, the fourth sending means 104 in the assist control apparatus 10 in MS lb can send to BS 2b the index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb.

[00114] Further, the determining means in the fourth sending means 104 firstly determines the index of the precoding vector vb,b according to the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb. Then, the sixth sending means in the fourth sending means 104 sends to BS 2b the determined index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb.

[00115] In the following, the example, in which the fourth sending means 104 in the assist apparatus means 10 in MS lb sends to BS 2b the index of the precoding vector vb, b corresponding to the downlink signal from BS 2b to MS lb, will be described.

[00116] After the first receiving means 202 in the control apparatus 20 in BS 2b receives from MS lb the index of the precoding vector vb, b corresponding to the downlink signal from BS 2b to MS lb, the second sending means 203 in the control apparatus 20 in BS 2b sends the index of the precoding vector vb,b to BS 2a.

[00117] The third receiving means 204 in the control apparatus 20 in BS 2a receives the index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb forwarded by BS 2b from MS lb. Then, the third sending means 205 in the control apparatus 20 in BS 2a sends the received index of the precoding vector vb,b to MS la.

[00118] Next, the fifth receiving means 105 in the assist control apparatus 10 in MS la receives the index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb forwarded by BS 2a, then, based on the received index of the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb and the estimated channel transmission matrix Ha,b of the downlink channel from BS 2b to MS la, the second selecting means 106 in the assist control apparatus 10 in MS la selects the precoding vector va>b corresponding to the downlink signal from BS 2b to MS la from the shared codebook.

[00119] More specifically, firstly according to the received index of the precoding vector vbb corresponding to the downlink signal from BS 2b to MS lb, the second searching means in the second selecting means 106 in MS la searches the corresponding precoding vector vb,b from the shared codebook. Then according to the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb and the estimated channel transmission matrix Ha,b of the downlink channel from BS 2b to MS la, the third selecting means in the second selecting means 106 selects the precoding vector va, b corresponding to the downlink signal from BS 2b to MS la from the codebook.

[00120] Wherein, the selected precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the shared codebook should be orthogonal with the selected precoding vector vb, b corresponding to the downlink signal from BS 2b to MS lb.

[00121] Since each column of the precoding vectors in each precoding matrix in the shared codebook is orthogonal with each other, preferably, according to the estimated channel transmission matrix Ha,b of the downlink channel from BS 2b to MS la, the second selecting means 106 in the assist control means 10 in MS la selects the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the precoding matrix where the precoding vector vb,b corresponding to the downlink signal from BS 2b to MS lb is located.

[00122] Further, selecting a precoding vector va,b from a shared codebook by the second selecting means 106 in the assist control apparatus 10 in MS la is based on the following formula:

va)A=argmax|/v|2
ceC

[00123] Wherein, C represents codebook, c' represents the conjugate transposed matrix of c. The above formula represents that any column of precoding vector in the precoding matrix, where the precoding vector vb, b is located, in the codebook C, is traversed. The column of vector c which makes \Habc\ reach the maximum value is the precoding vector va, b corresponding to the downlink signal from BS 2b to MS la.

[00124] After the second selecting means 106 in the assist control
apparatus 10 in MS la selects the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the shared codebook, the fifth sending means 107 in the assist control apparatus 10 in MS la sends the index of the selected precoding vector va,b to BS 2a.

[00125] Of course, the fifth sending means 107 in the assist control apparatus 10 in MS la can also send the precoding vector va, b to BS 2a directly.

[00126] The sixth receiving means 206 in the control apparatus 20 in BS 2a receives from MS la the index of the precoding vector va, b corresponding to the downlink signal from BS 2b to MS la and the seventh sending means 207 in the control apparatus 20 in BS 2a sends it to BS 2b.

[00127] In the meantime when MS la selects the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la from the shared codebook, MS lb also selects the precoding vector vb, a corresponding to the downlink signal from BS 2a to MS lb from the shared codebook.

[00128] More specifically, after the second sending means 203 in the control apparatus 20 in BS 2a sends to BS 2b the received index of the precoding va,a corresponding to the downlink signal from BS 2a to MS la, the third receiving means 204 in the control apparatus 20 in BS 2b receives the index of the precoding vector va>a corresponding to the downlink signal from BS 2a to MS la forwarded by BS 2a from MS la and the third sending means 205 in the control apparatus 20 sends the index of the precoding vector va,a to MS lb.

[00129] After the fifth receiving means 105 in the assist control apparatus 10 in MS lb receives the index of the precoding vector va>a, based on the index of the precoding vector va,,a and the estimated channel transmission matrix Hb,a of the downlink channel from BS 2a to MS lb, the second selecting means 106 in the assist control apparatus 10 in MS lb selects the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb from the shared codebook.

[00130] More specifically, firstly according to the received index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la, the second searching means in the second selecting means 106 in MS lb searches the corresponding precoding vector va,a from the shared codebook. Then according to the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la and the estimated channel transmission matrix Hb,a of the downlink channel from BS 2a to MS lb, the third selecting means in the second selecting means 106 selects the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb from the codebook.

[00131] Wherein, the selected precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb from the shared codebook should be orthogonal with the selected precoding vector va,a corresponding to the downlink signal from BS 2a to MS la.
[00132] Since each column of the precoding vectors in each precoding matrix in the shared codebook is orthogonal with each other, preferably, according to the estimated channel transmission matrix Hb,a of the downlink channel from BS 2a to MS lb, the second selecting means 106 in the assist control apparatus 10 in MS lb selects the precoding vector vb>a corresponding to the downlink signal from BS 2a to MS lb from the precoding matrix where the precoding vector va>a corresponding to the downlink signal from BS 2a to MS la is located.

[00133] Further, selecting a precoding vector vb>a from a shared codebook by the second means 106 in the assist control apparatus 10 in MS lb is based on the following formula:

vM = argmaxKacf
ceC

[00134] Wherein, C represents codebook, c' represents the conjugate transposed matrix of c. The above formula represents that any column of precoding vector in the precoding matrix, where the precoding vector va,a is located, in the codebook C, is traversed. The column of vector c which makes \Hbac\ reach the maximum value is the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb.

[00135] After the second selecting means 106 in the assist control apparatus 10 in MS lb selects the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb from the shared codebook, the fifth sending means 107 in the assist control apparatus 10 in MS lb sends the index of the selected precoding vector vb,a to BS 2b.

[00136] Of course, the fifth sending means 107 in the assist control apparatus 10 in MS lb can also send the precoding vector vb,a to BS 2b directly.

[00137] After the sixth receiving means 206 in the control apparatus 20 in BS 2b receives from MS lb the index of the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb, the seventh sending means 207 in the control apparatus 20 in BS 2b sends it to BS 2a.

[00138] The second receiving means 208 in the control apparatus 20 in BS 2a receives the index of the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb forwarded by BS 2b from MS lb.

[00139] Next, based on the received index of the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb and the index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la, the first precoding means 209 in the control apparatus 20 in BS 2a precodes the downlink signals sent to MS la and MS lb respectively.

[00140] More specifically, firstly, according to the received index of the precoding vector va,a corresponding to the downlink signal from BS 2a to MS la, the first searching means in the first precoding means 209 in BS 2a searches the corresponding precoding vector va,a from the shared codebook, and according to the received index of the precoding vector vb,a corresponding to the downlink signal from BS 2a to MS lb, BS 2a searches the corresponding precoding vector Vb,a from the shared codebook.

[00141] Then, according to the searched precoding vector va,a, the second precoding means in the first precoding means 209 in BS 2a precodes the downlink signal which is sent by BS 2a to MS la, and according to the searched precoding vector vb,a, the second precoding means in the first precoding means 209 in BS 2a precodes the downlink signal which is sent by BS 2a to MS lb.

[00142] At last, BS 2a sends the precoded downlink signals to MS la and MS lb respectively.

[00143] Similarly, after the second receiving means 208 in the control apparatus 20 in BS 2b receives the index of the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la forwarded by BS 2a from MS la, based on the received index of the precoding vector vb, a corresponding to the downlink signal from BS 2a to MS lb and the index of the precoding vector vb, b corresponding to the downlink signal from BS 2b to MS lb, the first precoding means 209 in the control apparatus 20 in BS 2b precodes the downlink signals sent to MS lb and MS la respectively.

[00144] More specifically, firstly, according to the received index of the precoding vector vb, b corresponding to the downlink signal from BS 2b to MS lb, the first searching means in the precoding means 209 in BS 2b searches the corresponding precoding vector Vb,b from the shared codebook, and according to the received index of the precoding vector va,b corresponding to the downlink signal from BS 2b to MS la, BS 2b searches the corresponding precoding vector va>b from the shared codebook.

[00145] Then, according to the searched precoding vector vb,b, the second precoding means in the first precoding means 209 in BS 2b precodes the downlink signal which is sent by BS 2b to MS lb, and according to the searched precoding vector va,b, the second precoding means in the first precoding means 209 in BS 2b precodes the downlink signal which is sent by BS 2b to MS la.

[00146] At last, BS 2b sends the precoded downlink signals to MS lb and MS la respectively.

[00147] The concrete embodiments of the present invention have been described above. It is understandable, that the present invention is not limited to the specific embodiments mentioned above. Those skilled in the art may perform various variation or modification in the protection scope of the claims.

CLAIMS

1. A method of controlling co-channel interference in a base station of a wireless communication system based on collaborative MIMO, wherein the method comprises the steps of:

a. sending a downlink reference signal to a served mobile station and at least one coordinating mobile station;

b. receiving precoding information corresponding to a downlink signal from the base station to the served mobile station from the served mobile station;

c. sending the received precoding information to at least one serving base station of the at least one coordinating mobile station;

d. receiving at least one precoding information corresponding to at least one downlink signal from the base station to the at least one coordinating mobile station respectively forwarded by at least one serving base station of the at least one coordinating mobile stations from the at least one coordinating mobile station;

e. precoding a downlink signal from the base station to the served mobile station based on the precoding information corresponding to a downlink signal from the base station to the served mobile station, and precoding the at least one downlink signal from the base station to the at least one coordinating mobile stations respectively based on the at least one precoding information corresponding to the at least one downlink signal from the base station to the at least one coordinating mobile stations;

wherein, after step b and before step e, the method comprises the steps of:

m. receiving at least one precoding information corresponding to at least one precoding information of at least one downlink signal from the at least one serving base stations to the at least one coordinating mobile stations respectively forwarded by at least one serving base station of the at least one coordinating mobile station from the at least one coordinating mobile station;

n. sending the received at least one precoding information to the served mobile station;

o. receiving at least one precoding information corresponding to at least one downlink signal from at least one serving base station of the at least one coordinating mobile station to the served mobile station;
p. sending the received at least one precoding information to at least one serving base station of the at least one coordinating mobile station respectively.

2. A method according to claim 1, wherein the precoding information is a precoding vector or an index of a precoding vector.

3. A method according to claim 2, wherein when the precoding information is an index of a precoding vector, the step e further comprises the steps of:

el. according to the received index of a precoding vector corresponding to a downlink signal from the base station to the served mobile station, searching corresponding precoding vector from a shared codebook, and according to the received index of at least one precoding vector corresponding to at least one downlink signal from the base station to the at least one coordinating mobile stations, searching corresponding at least one precoding vector from the shared codebook;

e2. according to the searched precoding vector corresponding to a downlink signal from the base station to the served mobile station, precoding a downlink signal from the base station to the served mobile station, and according to the searched at least one precoding vector corresponding to at least one downlink signal from the base station to the at least one coordinating mobile station, precoding at least one downlink signal from the base station to the at least one coordinating mobile station.

4. A method of assisting a serving base station to control co-channel interference in a mobile station of a wireless communication system based on collaborative MIMO, wherein the method comprises the steps of:

A. receiving a downlink reference signal from a serving base station and at least one downlink reference signal from at least one coordinating base station;

B. according to the received downlink reference signal from the serving base station, estimating a channel transmission matrix of a downlink channel from the serving base station to the mobile station, and according to the received at least one downlink reference signal from the at least one coordinating base stations, estimating at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base station to the mobile station respectively;

C. according to the estimated channel transmission matrix of a downlink channel from the serving base station to the mobile station, selecting a precoding vector corresponding to a downlink signal from the serving base station to the mobile station from a shared codebook;

D. sending precoding information corresponding to a downlink signal from the serving base station to the mobile station to the serving base station;

E. receiving at least one precoding information corresponding to at least one downlink signal from the at least one coordinating base station to at least one served mobile station of the at least one coordinating base station forwarded by the at least one coordinating base station and the serving base station from the at least one served mobile station from the at least one coordinating base station;

F. based on the received at least one precoding information and the estimated at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base station to the mobile station, selecting at least one precoding vector corresponding to at least one downlink signal from at least one coordinating base stations to the mobile station from the shared codebook respectively; wherein the precoding vector corresponding to a downlink signal from each coordinating base station to the mobile station is orthogonal with the precoding vector corresponding to a downlink signal from the coordinating base station to the served mobile station of the coordinating base station;

G. sending at least one precoding information corresponding to at least one downlink signal from the at least one coordinating base station to the mobile station to the serving base station.

5. A method according to claim 4, wherein the precoding information is a precoding vector or an index of a precoding vector.

6. A method according to claim 5, wherein the precoding information is an index of a precoding vector, the step D further comprises the steps of:

Dl. according to the selected precoding vector corresponding to a downlink signal from the serving base station to the mobile station, determining an index of the precoding vector;

D2. sending the determined index of the precoding vector corresponding to a downlink signal from the serving base station to the mobile station to the serving base station.

7. A method according to claim 5 or 6, wherein the precoding information is an index of a precoding vector, the step F further comprises the steps of:

Fl. according to the received index of at least one precoding vector corresponding to at least one downlink signal from the at least one coordinating base station to at least one served mobile station of the at least one coordinating base station, searching corresponding at least one precoding vector from the shared codebook;

F2. according to the searched at least one precoding vector and the estimated at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base station to the mobile station, selecting at least one precoding vector corresponding to at least one downlink signal from at least one coordinating base station to the mobile station from the shared codebook respectively; wherein the precoding vector corresponding to a downlink signal from each coordinating base station to the mobile station is orthogonal with the precoding vector corresponding to a downlink signal from the coordinating base station to the served mobile station of the coordinating base station.

8. A control apparatus of controlling co-channel interference in a base station of a wireless communication system based on collaborative MIMO, wherein the apparatus comprises:

a first sending means, for sending a downlink reference signal to a served mobile station and at least one coordinating mobile station;

a first receiving means, for receiving precoding information corresponding to a downlink signal from the base station to the served mobile station from the served mobile station;

a second sending means, for sending the received precoding information to at least one serving base station of the at least one coordinating mobile station;

a second receiving means, for receiving at least one precoding information corresponding to at least one downlink signal from the base station to the at least one coordinating mobile station respectively forwarded by at least one serving base station of the at least one coordinating mobile stations from the at least one coordinating mobile station;

a first precoding means, for precoding a downlink signal from the base station to the served mobile station based on the precoding information corresponding to a downlink signal from the base station to the served mobile station, and precoding the at least one downlink signal from the base station to the at least one coordinating mobile stations respectively based on the at least one precoding information corresponding to the at least one downlink signal from the base station to the at least one coordinating mobile station;

wherein, the control apparatus further includes:

a third receiving means, for receiving at least one precoding information corresponding to at least one precoding information of at least one downlink signal from the at least one serving base stations to the at least one coordinating mobile stations respectively forwarded by at least one serving base station of the at least one coordinating mobile station from the at least one coordinating mobile station;

a third sending means, for sending the received at least one precoding information to the served mobile station;

a sixth receiving means, for receiving at least one precoding information corresponding to at least one downlink signal from at least one serving base station of the at least one coordinating mobile station to the served mobile station;

a seventh receiving means, for sending the received at least one precoding information to at least one serving base station of the at least one coordinating mobile station respectively.

9. A control apparatus according to claim 8, wherein the precoding information is a precoding vector or an index of a precoding vector.

10. A control apparatus according to claim 9, wherein when the precoding information is an index of a precoding vector, the first precoding means includes:

a first searching means, for according to the received index of a precoding vector corresponding to a downlink signal from the base station to the served mobile station, searching corresponding precoding vector from a shared codebook, and according to the received index of at least one precoding vector corresponding to at least one downlink signal from the base station to the at least one coordinating mobile stations, searching corresponding at least one precoding vector from the shared codebook;

a second precoding means, for according to the searched precoding vector corresponding to a downlink signal from the base station to the served mobile station, precoding a downlink signal from the base station to the served mobile station, and according to the searched at least one precoding vector corresponding to at least one downlink signal from the base station to the at least one coordinating mobile station, precoding at least one downlink signal from the base station to the at least one coordinating mobile station.

11. An assist control apparatus of assisting a serving base station to control co-channel interference in a mobile station of a wireless communication system based on collaborative MIMO, wherein the assist control apparatus comprises:

a fourth receiving means, for receiving a downlink reference signal from a serving base station and at least one downlink reference signal from at least one coordinating base station;

an estimating means, for according to the received downlink reference signal from the serving base station, estimating a channel transmission matrix of a downlink channel from the serving base station to the mobile station, and according to the received at least one downlink reference signal from the at least one coordinating base stations, estimating at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base stations to the mobile station respectively;

a first selecting means, for according to the estimated channel transmission matrix of a downlink channel from the serving base station to the mobile station, selecting a precoding vector corresponding to a downlink signal from the serving base station to the mobile station from a shared codebook;

a fourth sending means, for sending precoding information corresponding to a downlink signal from the serving base station to the mobile station to the serving base station;

a fifth receiving means, for receiving at least one precoding information corresponding to at least one downlink signal from the at least one coordinating base station to at least one served mobile station of the at least one coordinating base station forwarded by the at least one coordinating base station and the serving base station from the at least one served mobile station from the at least one coordinating base station;

a second selecting means, for based on the received at least one precoding information and the estimated at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base station to the mobile station, selecting at least one precoding vector corresponding to at least one downlink signal from at least one coordinating base stations to the mobile station from the shared codebook respectively;

wherein the precoding vector corresponding to a downlink signal from each coordinating base station to the mobile station is orthogonal with the precoding vector corresponding to a downlink signal from the coordinating base station to the served mobile station of the coordinating base station;

a fifth sending means, for sending at least one precoding information corresponding to at least one downlink signal from the at least one coordinating base station to the mobile station to the serving base station.

12. An assist control apparatus according to claim 11, wherein the precoding information is a precoding vector or an index of a precoding vector.

13. An assist control apparatus according to claim 12, wherein the precoding information is an index of a precoding vector, the fourth sending means further includes:

a determining means, for according to the selected precoding vector corresponding to a downlink signal from the serving base station to the mobile station, determining an index of the precoding vector;

a sixth sending means, for sending the determined index of the precoding vector corresponding to a downlink signal from the serving base station to the mobile station to the serving base station.

14. An assist control apparatus according to claim 12 or 13, wherein the precoding information is an index of a precoding vector, the second selecting means further includes:

a second searching means, for according to the received index of at least one precoding vector corresponding to at least one downlink signal from the at least one coordinating base station to at least one served mobile station of the at least one coordinating base station, searching corresponding at least one precoding vector from the shared codebook;

a third selecting means, for according to the searched at least one precoding vector and the estimated at least one channel transmission matrix of at least one downlink channel from the at least one coordinating base station to the mobile station, selecting at least one precoding vector corresponding to at least one downlink signal from at least one coordinating base station to the mobile station from the shared codebook respectively; wherein the precoding vector corresponding to a downlink signal from each coordinating base station to the mobile station is orthogonal with the precoding vector corresponding to a downlink signal from the coordinating base station to the served mobile station of the coordinating base station.