WO2007036139A1

WO2007036139A1 - A plurality of antennas channels multiplex method

Info

Publication number: WO2007036139A1
Application number: PCT/CN2006/002415
Authority: WO
Inventors: Changguo Sun; Shiqiang Suo
Original assignee: Shanghai Ultimate Power Communications Technology Co., Ltd.
Priority date: 2005-09-30
Filing date: 2006-09-15
Publication date: 2007-04-05
Also published as: CN1941663A; CN1941663B

Abstract

A plurality of antennas channels multiplex method which is used in a transceiver adopting a plurality of antennas units to communicate with a plurality of users, includes: at first dividing the antennas units into groups based on the predetermined rules (S1); next constructing the waiting transmission data into the transmission data steams for corresponding antennas groups according to the form of Spatial Division Multiplex (S2); and transmitting the data steams after every antennas group weights the transmission data steams bases on the beam-forming weight factor corresponding to every user (S3). Every antennas group transmits the parallel data to the different users, adopting spatial division multiplex between every antennas group, and using the beam-forming form to transmit the data among the antennas units of the antenna groups, so as to adapt to the different environment of the channels.

Description

Multi-antenna channel multiplexing method

Technical field

The present invention relates to a channel multiplexing technique for multiple antennas, and in particular to a channel multiplexing method for an antenna. Background technique

At present, for a MIMO (Multiple Input Multiple Output) system, a method of channel multiplexing using multiple antennas is classified into a spatial multiplexing method and a beamforming method.

In a wireless communication system, if both the base station and the terminal have multiple antennas, when the channel correlation is small or irrelevant, the space division multiplexing technology of the MIMO (Multiple Input Multiple Output) system can be used as the hotspot area. Providing high-speed data services, using this technology can greatly increase the rate of data transmission, but also requires a higher signal-to-noise ratio.

The so-called MIMO spatial multiplexing technology transmits multiple parallel data streams through multiple antennas at the transmitting end. Since the channel is uncorrelated or related, the channels experienced by each data stream are independent of each other, so each can pass each The channel characteristics experienced by the data stream distinguish the data content contained in the different streams. MIMO spatial multiplexing technology effectively increases data transmission rate and frequency efficiency compared to single antenna systems by transmitting different data streams in parallel on the same time and frequency resources.

In a wireless communication system, if both the base station and the terminal have multiple antennas, when the channel correlation is large, MIMO spatial multiplexing technology is used at this time, which will cause interference between the data streams. At this time, beamforming technology can be adopted. Improve system anti-interference and anti-fading performance.

The so-called beamforming technology sends the same data stream through multiple antennas at the transmitting end.

The K user signals are respectively modulated onto the Ka antenna. For each user signal, there are different weights on different antennas, and the weighted signals are transmitted in a certain shape. As shown in Figure 1, it is assumed that the transmitting end transmits the same data stream to User 1, User 2, and User 3 through 9 antennas. Since the weights of the 9 antennas are different for different users, the receiving end is separated according to the weighting signal. Out different users. Different from the spatial multiplexing technology, the channel is required to have sufficient correlation, so that the data streams weighted by different antennas can form beams in the same direction, thereby providing anti-interference and fading capability.

It can be seen from the above analysis that the two MIMO channel multiplexing methods are applicable to different environments respectively. In the environment where the scatterers are scarce, due to the large correlation of the channels, the MIMO-based W

minus 2-

The spatial multiplexing method cannot provide independent channels, so the channel cannot be multiplexed and transmitted. For the scatterer-rich environment, the beamforming method cannot effectively suppress the channel interference between different users due to the small correlation of the channels. .

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for multi-antenna channel multiplexing, which can adapt to changes in the channel environment and can be used when channel correlation is small and channel correlation is large.

In order to solve the above technical problem, the present invention provides a multi-antenna channel multiplexing method for a transceiver that uses one or more antenna units to communicate with a plurality of remote users, including the steps:

1) grouping the antenna elements according to a predetermined rule;

2) constituting the transmit data stream of the corresponding antenna group according to the spatial multiplexing manner of the data to be transmitted;

3) Each antenna group performs weighting processing on the transmitted data stream according to its corresponding weighting coefficient of each user, and then transmits.

Preferably, the predetermined rule is that the number of antenna units included in each antenna group is greater than or equal to the number of groups of antenna groups.

The antenna elements in the antenna group are adjacently arranged.

Further,

Each antenna unit in each antenna group performs channel estimation on each of the users multiplexed with the channel by using the received data;

Obtaining a weighting coefficient for each user of each antenna group according to the channel estimation result.

The shaping weight coefficient is obtained according to the receiving power of the user corresponding to the antenna group and the receiving power of the user corresponding to the other antenna group.

Further, before the step of acquiring the shaping right coefficients of each antenna group for each user according to the channel estimation result, the method further includes acquiring a spatial covariance matrix of each antenna group with respect to each user, and the covariance matrix is calculated according to the following formula: : where R ( "i ," ^{2 )} is the spatial covariance matrix of the antenna group 77 ₇ to the user, and the dimension is

( ^M '"' ^M " H ( ^nl ' ^{n2 )} is the matrix of the channel estimation result for the antenna group to the user. Wherein, the shaping weight coefficient is obtained according to the following formula:

_W "R(",") _W

w =argmax

W ' where w ( ⁿ ) is the matrix of the shape weight coefficients of the user n, representing the conjugate transposed matrix, which is a unit matrix of dimensions (M„, M„), and λ is a scale factor. In addition, a Schmidt orthogonalization matrix of each antenna group with respect to each user is obtained, and the shaping weight coefficient is obtained according to the Schmidt orthogonalization matrix and the channel estimation.

Compared with the prior art, the beneficial effects of the present invention are: The present invention groups the antennas according to the number of users multiplexing the channels, and discloses a method for obtaining the shaping weight coefficients between the antenna elements of the antenna group, each The antenna group transmits parallel data to different users, spatial multiplexing between the antenna groups, and beamforming between the antenna elements of the antenna group. When the channel correlation is high, due to the internal antenna groups Each antenna unit performs beamforming to separate channels between different users, so that the parallel data transmitted by the antenna group can still distinguish different users, and is not limited to environmental changes; meanwhile, when the scatterers are rich At the same time, due to the sufficient spacing between the antenna groups, the independence between the antenna groups can be ensured, and the data can be transmitted by spatial multiplexing.

Further, since the present invention divides the adjacent antenna elements into one antenna group when grouping the antenna elements, the requirement that the space multiplexing between the antenna groups is greater than half a wavelength is ensured.

In addition, since the present invention includes a plurality of antenna elements in each antenna group, it is suitable for the expansion of the existing smart antenna system.

DRAWINGS

1 is a relationship diagram between a beam forming technology antenna unit and a user in the prior art.

2 is a flow chart of a method of channel multiplexing according to the present invention;

3 is a diagram showing relationship between an antenna unit and a user in a beamforming technique in a specific embodiment; and FIG. 4 is an explanatory view of an antenna unit in a specific embodiment.

detailed description Since the fading between each pair of transmit and receive antennas in a MIMO system is independent, one MIMO channel can be viewed as multiple parallel subchannels, providing for the transmission of parallel data streams. If different data streams are transmitted on these parallel subchannels, it is called spatial multiplexing. The spatial multiplexing technique divides the data stream into a plurality of sub-data streams, and simultaneously transmits the sub-data streams to different mobile stations through different antenna units. Therefore, the capacity of the MIMO channel is linearly increased with the number of subchannels. Multiple antennas are used simultaneously at the transmitter and receiver, and MIMO can greatly increase the capacity of the channel in a rich scatterer environment.

The core idea of the present invention is to group each antenna unit, each antenna group transmits a different data stream to a corresponding mobile station, and realizes spatial multiplexing of the antenna group; at the same time, each antenna unit of each antenna group transmits the same data stream. Beamforming.

The traditional beamforming technology is that all antenna units send the same data stream to different users, and different users are separated at the receiving end by different shaping coefficient of different users, in order to enable the antenna to use spatial multiplexing technology. When the beamforming technique is used, the beamforming method provided by the present invention firstly groups the antenna elements according to a predetermined rule, and adopts a specific process of beamforming of the antenna groups for each antenna group. It is well known that beamforming of a plurality of antenna elements requires obtaining a shaping weight coefficient. The method for acquiring beamforming coefficients provided by the present invention firstly performs channel selection for each user multiplexed with each channel in each antenna group. Estimating; then obtaining a weighting coefficient based on the channel estimate. Different from the prior art, the present invention modulates a user signal corresponding to each antenna group to each antenna unit of the antenna group, and performs weighting on each antenna group according to the weighting coefficient of each antenna group, and then transmits the data to the corresponding user. Antenna units, rather than all antenna groups, send the same data stream to different users.

The above channel estimation can be obtained according to the following formula:

— L ⁿ ”, where H ( ^nl ' ^{n2 )} is the channel estimation matrix of the antenna group pair user “ ₂ ; the dimension of the channel estimation matrix is (Κ, ), and W is a channel sampled in units of chip periods The number of impulse response taps, Μ _η1 is the number of antenna elements included in the antenna group, and h ⁽ '"'" ²⁾ represents the channel estimation matrix of the mth antenna in the antenna group n1 to the user π2, and the dimension is (W, l ), 1 < η Μ _η1 .

In order to simplify the design difficulty, the present invention obtains a method commonly used by those skilled in the art through channel estimation. The spatial covariance matrix of each antenna group with respect to each user, the shape weight coefficient is obtained by the spatial covariance matrix and the channel estimation. The covariance matrix is calculated according to the following formula:

("l,"2) _ _g ^, |jj(»l >» ₂ ) ^// Jj(»I .3⁄4) where R( "' , ⁿ²⁾ is the antenna group corresponding to the user's spatial covariance matrix, dimension The number is ( ^Μ ', ^Μ "' ), (·)" indicates the conjugate transposed matrix.

The shaping weight coefficient is obtained according to the received power of the user corresponding to the antenna group and the received power of the user corresponding to the other antenna group. The present invention provides a specific implementation method that is implemented according to the following formula:

Where w ( ^{n )} is the matrix of the weighting coefficient of user n, (·) is the conjugate transposed matrix, and is the unit matrix of dimension (Μ„,Μ„), which is the scale factor.

In addition, the method of obtaining the shaping weight coefficient can also realize the shaping coefficient of the interference suppression by the Schmidt orthogonalization method and the 酉 transformation method, and obtain the weighting coefficient of the interference suppression in the Schmidt orthogonalization method. The Schmitt orthogonalization matrix of each antenna group relative to each user is orthogonally transformed to form a weight coefficient orthogonal to other interference channels and in the same direction as the desired channel. In addition to the above method, interference suppression beamforming can also be achieved by estimating the direction of arrival of the desired user and the interfering user.

When the beamforming method of the above multi-antenna is applied to the spatial multiplexing technology, the present invention provides a channel multiplexing method, which is applied to a transceiver that uses one or more antenna units to communicate with a plurality of remote users. As shown in FIG. 2, the antenna units are first grouped according to a predetermined rule, and the antenna groups are required to correspond to one user respectively (S1); then the data to be transmitted is spatially multiplexed to form a corresponding antenna group. The data stream (S2); and each antenna group performs weighting processing on the transmitted data stream according to its corresponding weighting coefficient of each user (S3). Different from the prior art, the data stream that is channel-multiplexed by the present invention is a data stream that is weighted by beamforming, and does not need to change the original receiving mode when receiving at the receiving end, and is difficult to design. The method for obtaining the shape weight coefficient is the same as above, and will not be described again. The predetermined rule for grouping antenna groups according to the present invention is that each antenna group is required to include more than or equal to the number of antenna groups in order to utilize the beamforming algorithm. Since the spacing between antenna groups for spatial multiplexing requires at least half a wavelength, in order to achieve the object, the present invention divides adjacently arranged antenna elements into one antenna group. In this embodiment, the number of users multiplexing a certain channel is such that the number of antenna units required by the base station is M ≥ N ² . The M antenna elements are divided into N antenna groups, which are called antenna sub-arrays. Each antenna group contains at least two antenna elements, and the antenna elements in the group are adjacently arranged to beamform the antennas in the group.

To obtain channel estimates for each of the N users multiplexing the channel, it is first necessary to obtain a channel impulse response on each antenna unit.

Suppose that the number of antenna elements of the ^nth , ^{n = l} , ^L , ^ antenna sub-array is the antenna element is ^L , the user "," = 1, L, N, which is at the "^ 1, L 'Μ" antenna The channel impulse response on the cell is denoted by ^h — ^ ^{j /} 3⁄4 ' ^L ”. The number of response taps for the channel impulse.

The method for channel estimation of all antenna units in an antenna sub-array for N users sharing the same channel is:

Taking any antenna sub-array "^ ^{= 1} as an example, any user other than the user nl corresponding to the antenna sub-array

The channel estimation matrix of Ύ is shown by the formula ( _{L 1} ), and the dimension is (Κ' ), wherein the antenna element included in the antenna sub-array is '_|; H "L ^h , ^L ' ^h ” ( 1.1)

Calculate the spatial covariance matrix of the antenna sub-array "I-to-user" ² as shown in the formula (1.2), and the dimension is ",);

Where (·)" indicates a conjugate transpose operation.

Each antenna sub-array corresponds to a user sharing the same channel to perform shaped reception or shaped transmission data. The criterion for shaping is to suppress interference of other users sharing the same channel. To achieve this purpose, the shaping coefficient is as follows. Obtained:

For the antenna subarray "," ^{= 1} ' ^L , ^, receive/transmit its corresponding user" signal, then the receive/transmit shaping weight coefficient is

w

w ^w R("'"V

The meaning of the formula (1.3) is to make ^v "1"' ^≠ "the largest w is the optimal solution, the unit of the dimension is ( ^M "' ^M "), A is the scale factor, and the role of the unit matrix is The main lobe direction is not deviated from the desired user direction. It is well known that this problem makes a generalized eigenvalue problem.

According to the above-obtained shaping system, beamforming can be performed on the antenna elements in the respective antenna sub-arrays.

When channel multiplexing is performed on a plurality of antenna sub-arrays, each antenna unit in each antenna sub-array is weighted according to a respective shaping weight coefficient w and transmitted to each corresponding user.

Taking the number of multiplexed users of one channel as 3, as shown in FIG. 3, the antenna unit is divided into three antenna sub-groups, and each antenna group is called an antenna sub-array, that is, the antenna sub-array shown in the figure. 1. The antenna sub-array 2 and the antenna sub-array 3, and each antenna sub-array includes three antenna units for beamforming each user, for example, three antenna units 11 of the antenna sub-array 1.

12, 13 is used for beamforming the data stream of the user 1. When the channel multiplexing is performed, the antenna elements 11, 12, and 13 of the antenna sub-array 1 transmit the data stream of the user 1 to the user 1 according to the beamforming coefficient, and the antenna elements 21 and 22 of the antenna sub-array 2 are also transmitted. 23, the user 2 data stream is weighted according to the beamforming coefficient and transmitted to the user 2; the antenna unit 31, 32, 33 of the antenna sub-array 3 weights the data stream of the user 3 according to the beamforming coefficient and transmits the data to the user. 3. Described above is the case where multiple spatial channels are multiplexed to different users. For the case where multiple spatial channels are multiplexed to the same user (for example, user 1), the data stream segment of user 1 is first allocated to different antennas. Groups, the transmission data streams constituting the antenna group, and then each antenna group obtains the transmission weighting coefficients of the respective groups to the user 1. At this time, there is no interference with the user, and the interference term in the denominator in equation (1.3) is 0. According to the data stream transmitted in the above manner, due to the sufficient spacing between the antenna sub-arrays, the antenna sub-arrays are independent of each other. Therefore, when the channel correlation is small, spatial multiplexing between the antenna sub-arrays is adopted. Technology, and when the channel correlation is large, since the antenna elements in each antenna sub-array are beam-shaped, it is still possible to distinguish each user when the spatial multiplexing technique is used at this time. Figure 4 shows the day when the channel correlation is large. The anisotropic pattern of each antenna element in the line sub-array 1, 2, 3, and the like. The figure is obtained in the case of direct direct current and no angular spread. It is well known that the signals between the antennas are completely correlated at this time, and the MIMO channel multiplexing method in the prior art cannot be realized. The terminal is also unable to demodulate different data streams transmitted on multiple antennas. When using the present invention, it can be seen from the figure that the shaped beams of each antenna group form a main lobe in the user direction served by the antenna group, while in the other antenna groups, although the example of FIG. 3 is only one for each antenna group. It is clear to the user, but those skilled in the art should be aware that there may be multiple users in each antenna group, and the multiple users use the code division multiple access method for spreading, so that different users can be used. The spreading code distinguishes the data streams of different users, and the principle is the same as that of the conventional code division multiple access communication system using beamforming, and is not repeated here. The user here can also be understood as multiple data streams sent from the same user terminal.

The above description is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can also make several improvements and retouchings without departing from the principles of the present invention. It is considered as the scope of protection of the present invention.

Claims

Rights request

A multi-antenna channel multiplexing method for a transceiver that uses a plurality of antenna units to communicate with one or more users at a remote end, comprising the steps of:

1) grouping the antenna elements according to a predetermined rule;

2. The method of multi-antenna channel multiplexing according to claim 1, wherein: the number of antenna elements included in each antenna group is greater than or equal to the number of groups of antenna groups.

3. The method of multi-antenna channel multiplexing according to claim 2, wherein: the antenna elements in the antenna group are adjacently arranged.

The multi-antenna channel multiplexing method according to claim 3, wherein each antenna unit in each antenna group performs channel estimation on each of the users multiplexed with the channel by using the received data;

The multi-antenna channel multiplexing method according to claim 4, wherein: the shaping weight coefficient is obtained by a received power of a user corresponding to the antenna group and a received power of a user corresponding to another antenna group.

The multi-antenna channel multiplexing method according to claim 5, further comprising: acquiring each antenna group before the step of acquiring the shaping right coefficients of each antenna group for each user according to the channel estimation result Relative to each user's spatial covariance matrix, the covariance matrix is calculated according to the following formula: where R ( "' , " ² ) is the spatial covariance matrix of the antenna group to the user, and the dimension is '". ) _? ^(nl ' ⁿ²⁾ is the channel estimation result matrix of the antenna group to the user.

7. The method of multi-antenna channel multiplexing according to claim 6, wherein the shaping weight coefficient is obtained according to the following formula:

Where w ⁽ⁿ ) is the matrix of the weighting coefficient of user n, indicating the conjugate transposed matrix, and (M„) is the unit matrix of dimension (M„, M„), which is the scale factor.

The multi-antenna channel multiplexing method according to claim 3, wherein a Schmidt orthogonalization matrix of each antenna group with respect to each user is obtained, according to the Schmidt orthogonalization matrix and the The channel estimation obtains the shape weight coefficient.