CN104113496A - Method of carrying out channel estimation by using sequential pilot sequence - Google Patents

Method of carrying out channel estimation by using sequential pilot sequence Download PDF

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Publication number
CN104113496A
CN104113496A CN201410275875.2A CN201410275875A CN104113496A CN 104113496 A CN104113496 A CN 104113496A CN 201410275875 A CN201410275875 A CN 201410275875A CN 104113496 A CN104113496 A CN 104113496A
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user
base station
channel
pilot tone
send
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屈代明
孔德莹
江涛
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Huazhong University of Science and Technology
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Huazhong University of Science and Technology
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Abstract

The invention provides a method of carrying out channel estimation by using a sequential pilot sequence. In the method, users adopt sequential pilot sending modes, that is, different users send pilots in an interleaving mode in different time slots. In one certain time slot, a base station only needs to estimate one user channel, and later the base station forms a beam for the user. In the next time slot, the base station estimates the channel of another user. Thus, the method can effectively solve the problems that in the traditional channel estimation method, Complex orthogonal design needs to be carried out on the pilot sequence, the length of the needed pilot sequence can be prominently reduced, and throughput of the system is enhanced.

Description

A kind of method of utilizing sequential pilot frequency sequence to carry out channel estimating
Technical field
The invention belongs to extensive technical field of multi-antenna wireless communication, more specifically, relate to a kind of method of utilizing sequential pilot frequency sequence to carry out channel estimating.
Background technology
Extensive multiple-input and multiple-output (Massive Multiple-Input Multiple-Output, Massive MIMO) proposition of technology makes the availability of frequency spectrum reach unprecedented level, in this transmission plan, base station end has the low power antenna of enormous amount, and number of antennas is considerably beyond the single antenna number of users of dispatching simultaneously.Extensive MIMO technology can make wireless communication system reach very high throughput.In traditional channel estimation methods, user sends pilot frequency sequence simultaneously, and base station is carried out channel estimating at synchronization to all users.Conventional method need to design complicated orthogonal pilot frequency sequence, and the design dependency of pilot frequency sequence is in user's number.
Summary of the invention
For above defect or the Improvement requirement of prior art, the present invention proposes the method that the sequential transmission pilot tone of a kind of multi-user is carried out channel estimating and data communication.Can complicated pilot tone orthogonal sequence, estimate user's channel in the case of not carrying out, and loss system performance hardly.
For achieving the above object, the invention provides a kind of method of utilizing sequential pilot frequency sequence to carry out channel estimating, comprising:
Step 1, the user of the K in community sends pilot tone in sequential mode to base station: the user of the K in community is simultaneously to base station transmitted signal on same channel, and base station adopts extensive MIMO technology simultaneously for this K user provides data transport service; A described K user sends pilot tone sequentially to base station, on a time point, only have a user to send pilot tone to base station, and other K-1 users send upstream data simultaneously to base station;
Step 2, channel estimating is carried out in base station under sequential pilot tone send mode: base station on a channel simultaneously for K user provides service; On certain time point, only there is user k to send pilot tone to base station, all the other K-1 with send per family upstream data to base station, and all the other K-1 user's channel obtains in transmission pilot tone before and channel estimation phase; Base station is estimated the channel of user k after receiving the signal of K user's transmission.
In one embodiment of the invention, in described step 2, base station is estimated the channel of user k after receiving the signal that K user send, and is specially and adopts sciagraphy to carry out channel estimating:
Calculate the then channel g to user k with Y' kcarry out direct estimation;
Wherein: Y' be Y with the space of the column vector spatial vertical of opening on component, for Y exists the column vector space of opening on projection, for the projection matrix in the column vector space of opening, for having estimated the channel matrix that other K-1 user's who obtains channel forms, g in base station ithe channel vector of user i to N × 1 dimension of base station, the estimated value of the channel of user i, i=1.....K, y is that base station receives that the signal matrix Y that K user sends carries out the vector obtaining after vectorization operator, the number of antennas that N is base station.
In one embodiment of the invention, in described step 2, base station is estimated the channel of user k after receiving the signal that K user send, and is specially and adopts linear minimum mean-squared error method to carry out channel estimating, estimates that the subscriber channel obtaining is:
Wherein: s kthe pilot frequency sequence that the length sending for user is L, p dfor user sends the power of data, σ 2for the power of white Gaussian noise, for having estimated the channel matrix that other K-1 user's who obtains channel forms in base station, channel g ksecond moment, I n × Nthe unit matrix of N × N dimension, I l × Lbe the unit matrix of L × L dimension, y is that base station receives that the signal matrix Y that K user sends carries out the vector obtaining after vectorization operator, the number of antennas that N is base station.
In one embodiment of the invention, described sequential pilot tone send mode is the sequential pilot tone send mode of grouping, be specially: user is divided into groups, user does not on the same group send pilot tone in different time slots, need meet K × L≤T, the group number that wherein K is user, every group of slot length that is used for sending pilot tone is L symbol period, be T the correlation time of channel; The user of same group uses simple orthogonal guide frequency to send pilot tone in same time slot, the pilot frequency sequence that the user i in same group and k send { s j i , j = 0,1 , . . . , L - 1 } With { s k i , j = 0,1 , . . . , L - 1 } Meet orthogonality relation Σ j = 0 L - 1 s j i ( s j k ) * = 0 , The length that wherein L is pilot frequency sequence.
In one embodiment of the invention, the sequential pilot tone send mode of user grouping in described sequential pilot tone send mode Wei Duo community, be specially: the user of neighbor cell is divided into groups, the each group of multiple users that comprise from different districts, user does not on the same group send pilot tone in different time slots, user on the same group sends pilot tone at identical time slot, and user's on the same group pilot frequency sequence is mutually orthogonal.
In general, the above technical scheme of conceiving by the present invention compared with prior art, the present invention can effectively solve pilot frequency sequence in traditional channel estimating way and must carry out the problem of complicated orthogonal design, and can significantly reduce the length of required pilot frequency sequence, and throughput that can elevator system.Have and be presented as:
1. solve the complicated orthogonal design problem in pilot design
In the prior art, user sends pilot tone simultaneously to base station, and for user's channel is carried out to good estimation, the pilot frequency sequence that each user sends need keep orthogonal, therefore need in the time of design pilot tone, need to carry out complicated orthogonal design.Technical scheme of the present invention does not need each user's pilot tone to carry out orthogonal design.
2. reduce each user's pilot length
Existing technology is not less than user's number in order to ensure each user's the length of the needed pilot tone of orthogonality of pilot frequency sequence, thereby pilot length can increase along with the increase of number of users.And pilot length in technical scheme of the present invention can be very short, and can not increase along with the increase of number of users.
3. improve the throughput of system
Although the data-signal that the pilot signal that user sends and other users send does not exist orthogonality, in extensive mimo system, base station still can obtain user's good estimation channel.Technical scheme of the present invention has reduced the length of pilot tone, obtain increase for the running time-frequency resource that sends data-signal, therefore improved the utilance of running time-frequency resource, and used this scheme, can support more user, can have a certain upgrade to the throughput of system.
Brief description of the drawings
Fig. 1 is pilot frequency sequence send mode schematic diagram sequential in the present invention.
Embodiment
In order to make object of the present invention, technical scheme and advantage clearer, below in conjunction with drawings and Examples, the present invention is further elaborated.Should be appreciated that specific embodiment described herein, only in order to explain the present invention, is not intended to limit the present invention.In addition,, in each execution mode of described the present invention, involved technical characterictic just can combine mutually as long as do not form each other conflict.
As shown in Figure 1, in the extensive MIMO communication system that the present invention proposes, the method that the sequential transmission pilot tone of multi-user is carried out channel estimating and data communication is as follows:
Multiple users in community are upper simultaneously to base station transmitted signal at same channel (frequency), and base station adopts extensive MIMO technology simultaneously for these multiple users provide data transport service.Multiple users send pilot tone sequentially to base station, on a time point, only have a user to send pilot tone to base station, and other users can send upstream data simultaneously to base station.
Suppose that there is N root antenna base station, on a channel simultaneously for K user provides service.On certain time point, only there is user k to send pilot tone to base station, all the other K-1 with send per family upstream data to base station, and all the other K-1 user's channel obtains in transmission pilot tone before and channel estimation phase.Base station can be used sciagraphy, LMMSE (linear minimum mean-squared error) method in the time that the channel of user k is estimated, to suppress the interference causing from K-1 user's data-signal after receiving the signal of K user's transmission.
If channel matrix is G=[g 1g 2... g k], wherein g ithe channel vector of user i to N × 1 dimension of base station.Suppose that pilot length is L.The signal matrix that user sends is X=[x 1x 2... x k] t, wherein x i=[x i, 1x i, 2... x i,L] tbe the burst that i user sends in L symbol period, x k=s k=[s i, 1s i, 2... s i,L] tthe pilot frequency sequence that k user sends to base station. the signal matrix that receive base station is Y=GX+W, and W is the zero-mean white Gaussian noise in channel.Before the channel of user k is estimated, other K-1 user's channel estimated, the channel matrix of these channels compositions is the matrix that other K-1 user's real channel forms is the data matrix that this K-1 user sends is illustrate the implementation method of sciagraphy and LMMSE method below.
Sciagraphy: in the time that a certain user is carried out to channel estimating, adopt base station is received to signal projects to the method for estimating on the vertical space of known users channel space. the projection matrix in the column vector space of opening be therefore Y exists the space of being opened on be projected as therefore y with the space of the spatial vertical of being opened on component be then with Y', the channel of user k is carried out to direct estimation.
LMMSE method: known observation vector y=Vec (Y), uses LMMSE method to unknown parameter g kthe formula of estimating is wherein Vec () is vectorization operator.Suppose known channel g ksecond moment C g k g k = E { ( g k - E { g k } ) ( g k - E { g k } ) H } = E { g k g k H } = R g k g k By E{g k}=0, E{y}=0, substitution obtains g ^ k = E { g k } + C g k y C yy - 1 ( y - E { y } ) = C g k y C yy - 1 y .
By calculating:
Make w=Vec (W),
Wherein, for the long-pending computing of Kronecker, p dfor user sends the power of data, σ 2for the power of white Gaussian noise.
Thereby
g ^ k = R g k g k ( s k ⊗ I N × N ) H ( ( s k ⊗ I N × N ) R g k g k ( s k ⊗ I N × N ) H + p d ( I L × L ⊗ G · k ) ( I L × L ⊗ G · k ) H + σ 2 I NL × NL ) - 1 y .
Due in practice, base station cannot know channel matrix therefore use estimated value replace.Thereby,
In one embodiment of the invention, described sequential pilot tone send mode is the sequential pilot tone send mode of grouping, is specially: user is divided into groups, and user does not on the same group send pilot tone in different time slots.If user is divided into K group, every group of slot length that is used for sending pilot tone is L symbol period, and be T the correlation time of channel, needs to meet K × L≤T.The user of same group uses simple orthogonal guide frequency to send pilot tone in same time slot, the pilot frequency sequence that the user i in same group and k send { s j i , j = 0,1 , . . . , L - 1 } With { s k i , j = 0,1 , . . . , L - 1 } Meet orthogonality relation Σ j = 0 L - 1 s j i ( s j k ) * = 0 , The length that wherein L is pilot frequency sequence.
In another embodiment of the present invention, the sequential pilot tone send mode of user grouping in described sequential pilot tone send mode Wei Duo community, be specially: the user of neighbor cell is divided into groups, the each group of multiple users that comprise from different districts, user does not on the same group send pilot tone in different time slots, user on the same group sends pilot tone at identical time slot, and user's on the same group pilot frequency sequence is mutually orthogonal.
Be sent as example explanation the inventive method with the sequential pilot tone of multiple users in same community below, specific as follows.
Embodiment:
This specific embodiment be, in community, there are 10 users upper simultaneously to the base station transmitted signal that has 128 antennas at same channel (frequency), base station adopts extensive MIMO technology simultaneously for these multiple users provide data transport service, and the pilot length of supposing each user is L=1.
On certain time point, only have user k (k=1,2 ..., 10) and send pilot tone to base station, all the other 9 use send upstream data per family to base station, and all the other 9 users' channel obtains in transmission pilot tone before and channel estimation phase.After base station receives the signal of these 10 users' transmissions, can use sciagraphy, LMMSE (linear minimum mean-squared error) method in the time that the channel of user k is estimated, to suppress the interference causing from other 9 users' data-signal, the channel of user k is estimated.Suppose that the signal vector that base station receives is Y, the channel matrix that known user's channel vector forms is
Sciagraphy: in the time that user k is carried out to channel estimating, adopt base station is received to signal projects to the method for estimating on the vertical space of known users channel space.Y with the space of the spatial vertical of being opened on component be recycling Y' carries out channel estimating to user k.
LMMSE method:
Wherein σ 2the power of channel white Gaussian noise, s kthe pilot frequency sequence that the length sending for user is L, p dfor user sends the power of data, channel g ksecond moment.
Those skilled in the art will readily understand; the foregoing is only preferred embodiment of the present invention; not in order to limit the present invention, all any amendments of doing within the spirit and principles in the present invention, be equal to and replace and improvement etc., within all should being included in protection scope of the present invention.

Claims (5)

1. utilize sequential pilot frequency sequence to carry out a method for channel estimating, it is characterized in that, described method comprises:
Step 1, the user of the K in community sends pilot tone in sequential mode to base station: the user of the K in community is simultaneously to base station transmitted signal on same channel, and base station adopts extensive MIMO technology simultaneously for this K user provides data transport service; A described K user sends pilot tone sequentially to base station, on a time point, only have a user to send pilot tone to base station, and other K-1 users send upstream data simultaneously to base station;
Step 2, channel estimating is carried out in base station under sequential pilot tone send mode: base station on a channel simultaneously for K user provides service; On certain time point, only there is user k to send pilot tone to base station, all the other K-1 with send per family upstream data to base station, and all the other K-1 user's channel obtains in transmission pilot tone before and channel estimation phase; Base station is estimated the channel of user k after receiving the signal of K user's transmission.
2. the method for claim 1, is characterized in that, in described step 2, base station is estimated the channel of user k after receiving the signal that K user send, and is specially and adopts sciagraphy to carry out channel estimating:
Calculate the then channel g to user k with Y' kcarry out direct estimation;
Wherein: Y' be Y with the space of the column vector spatial vertical of opening on component, for Y exists the column vector space of opening on projection, for the projection matrix in the column vector space of opening, for having estimated the channel matrix that other K-1 user's who obtains channel forms, g in base station ithe channel vector of user i to N × 1 dimension of base station, the estimated value of the channel of user i, i=1.....K, y is that base station receives that the signal matrix Y that K user sends carries out the vector obtaining after vectorization operator, the number of antennas that N is base station.
3. the method for claim 1, is characterized in that, described base station receives the signal of K user's transmission to be estimated the channel of user k afterwards, is specially and adopts linear minimum mean-squared error method to carry out channel estimating:
Estimate that the subscriber channel obtaining is
Wherein: s kthe pilot frequency sequence that the length sending for user is L, p dfor user sends the power of data, σ 2for the power of white Gaussian noise, for having estimated the channel matrix that other K-1 user's who obtains channel forms in base station, channel g ksecond moment, I n × Nthe unit matrix of N × N dimension, I l × Lbe the unit matrix of L × L dimension, y is that base station receives that the signal matrix Y that K user sends carries out the vector obtaining after vectorization operator, the number of antennas that N is base station, represent Kronecker product calculation.
4. the method as described in claims 1 to 3 any one, it is characterized in that, described sequential pilot tone send mode is the sequential pilot tone send mode of grouping, be specially: user is divided into groups, user does not on the same group send pilot tone in different time slots, need meet K × L≤T, the group number that wherein K is user, every group of slot length that is used for sending pilot tone is L symbol period, and be T the correlation time of channel; The user of same group uses simple orthogonal guide frequency to send pilot tone in same time slot, the pilot frequency sequence that the user i in same group and k send with meet orthogonality relation the length that wherein L is pilot frequency sequence.
5. the method as described in claims 1 to 3 any one, it is characterized in that, the sequential pilot tone send mode of user grouping in described sequential pilot tone send mode Wei Duo community, be specially: the user of neighbor cell is divided into groups, the each group of multiple users that comprise from different districts, user does not on the same group send pilot tone in different time slots, and user on the same group sends pilot tone at identical time slot, and user's on the same group pilot frequency sequence is mutually orthogonal.
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Application publication date: 20141022