CN101060505B - Joint channel estimation method and estimation device in a wireless mobile communication system - Google Patents
Joint channel estimation method and estimation device in a wireless mobile communication system Download PDFInfo
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Abstract
The disclosed combined channel estimation method uses both the active user and strong-interference user channel impulse response for estimation. This invention reduces noise power, and improves estimation precision and receiving performance.
Description
Technical field
The present invention relates to a kind of wireless communication technology, relate to combination channel estimating method and estimation unit in a kind of mobile radio system in particular.
Background technology
The performance of wireless mobile communications mainly is subjected to the restriction of wireless channel.In wireless propagation environment, the propagation path between transmitter and the receiver is very complicated, from simple line-of-sight propagation, to the landforms and the atural object that meet with various complexity.Wireless channel does not resemble the wire message way fixing and can predict, but has the randomness of height, is a kind of random time-varying channel.
Wireless signal during by wireless channel the decay of following three aspects that can be come from damage:
1. path loss (Pathloss), this be since propagation medium to propagation loss and disperse that radio wave caused;
2. shadow fading (Shadow fading), this is because hypsography, building and other barriers in the communication environments covers caused large scale decline (Large scale fading) to electric wave.This rate of fading is slower, is called slow fading again;
3. multipath fading (Multipath fading), this is the small scale decline (Small scale fading) that multipath transmisstion (Multipathtransmission) owing to mobile communication environments and Doppler frequency shift (Doppler shift) effect cause.Because its rate of fading is very fast, can be described as rapid fading again.Multipath fading is a part most characteristic in the characteristics of radio channels.
From the wireless system project angle, path loss and shadow fading mainly have influence on the covering of wireless zone, and reasonably design always can be eliminated this adverse influence.And multipath fading has a strong impact on the transmission of wireless signals quality, and is inevitable.The antenna of subscriber equipment is generally lower, and wireless signal can be subjected to stopping of groups of building or landform in transmission course, transmits will pass through many propagation paths such as direct projection, reflection, scattering and could arrive receiving terminal; And along with moving of subscriber equipment, signal amplitude, phase place and time delay on each bar propagation path change whenever and wherever possible.Receiver antenna has formed an amplitude and phase place received signal all jumpy after such multipath signal is synthesized.Receiver if can not carry out reasonable compensation at the multipath fading of wireless channel, certainly will produce mistake, thereby influence the receptivity of wireless signal when detecting transmitting according to such received signal when detection signal is adjudicated.
Simultaneously, because the multipath transmisstion and the doppler shift effect of wireless channel, wireless signal will produce time delay expansion and Doppler broadening after wireless channel transmission, be embodied in the time domain that the shared bandwidth of signal becomes greatly in the elongated and frequency domain of the duration of signal.This will cause the intersymbol interference (ISI:Inter-symbol interference) in the signal, and, therefore in a multi-user's mobile radio system, also will cause a multiple access between the different user signal the sub-district in to disturb adjacent area interference (ACI:Adjacentcell interference) between the interior different user signal of (MAI:Multiple access interference) and neighbor cell.These interference all will influence correct detection and the judgement of receiver to transmitting, and cause the receptivity of wireless signal to descend, thereby make the performance of mobile radio system impaired.
The decay infringement that above-mentioned wireless signal is subjected to during by wireless channel can be described by the channel impulse response (Channel impulse response) of wireless channel.In the third generation mobile radio system that proposes at present, the general method of emission pilot frequency sequence (Pilot) or training sequence (Midamble) that adopts makes the receiving terminal of wireless signal estimate the channel impulse response of wireless channel according to described pilot frequency sequence or training sequence, thereby in the process that detects transmitting, use described channel estimation value to compensate, reduce the error probability in transmit detection and the judgement at the characteristic of channel of wireless channel.Simultaneously, transmitting terminal at wireless signal uses direct sequence spread spectrum (DS-SS:Direct sequence-spreadspectrum) technology that signal spectrum is expanded, and use Rake to receive (Rake receive) interface differential technique at the receiving terminal of wireless signal and collect mail and number carry out despreading, utilize described spread-spectrum signal to obtain diversity gain through the multidiameter delay component that is produced behind the multipath transmisstion, make the multipath transmisstion effect of wireless channel turn bane into boon, reduce the adverse effect of intersymbol interference, thereby improve the receptivity of wireless signal input and judging process.What is more important, at the adjacent area interference between the different user signal in interference of the multiple access between the different user signal in the sub-district and the neighbor cell, in wireless signal receiver, use Multiuser Detection (Multiuser Detection) technology that transmitting of different user carried out joint-detection (Joint Detection), receiver opposing multiple access disturbs and the ability of adjacent area interference thereby improve, and improves the receptivity of multi-user radio signal.
In above-mentioned Rake reception technique and multiuser detection, the estimated value that obtains wireless channel in time, exactly is the basis that these technology are brought into play its advantage, otherwise its technique effect will be had a greatly reduced quality.At present, there has been a large amount of channel estimation methods in the prior art, but these algorithms generally design based on single user's transmission of wireless signals, when existing multiple access to disturb in the transmission course of wireless signal and during adjacent area interference, only at the significantly reduction of performance of single user's channel estimation method.Also have in some channel estimation methods and proposed to carry out channel estimating simultaneously at a plurality of users in the sub-district, this channel estimation method has considered that the multiple access between the different user signal in the sub-district disturbs, thereby can improve the channel estimating performance in the multi-user radio mobile communication system to a certain extent.But, when having stronger adjacent area interference between the different user signal in the neighbor cell, described channel estimation method at the multi-user in the sub-district can only be handled the interference from adjacent sub-district as noise, still do not have very good performance.
Thereby, how in the mobile radio system of sub-district, multi-user more than one, when existing multiple access to disturb in the transmission course of wireless signal and during adjacent area interference, obtain channel estimation value at each user in time, exactly and be to need in the prior art problem that solves.
Summary of the invention
The objective of the invention is at the above-mentioned problems in the prior art, combination channel estimating method in a kind of mobile radio system is proposed, can be in the mobile radio system of sub-district, multi-user more than one, carrying out combined channel at the interference user in the user in the sub-district and its neighbor cell simultaneously estimates, make when having multiple access interference and adjacent area interference in the transmission course of wireless signal, combination channel estimating method according to the present invention has comparatively desirable channel estimating performance, thereby improves the receptivity of multi-user radio signal.
The present invention also aims to propose the combined channel estimation unit in a kind of mobile radio system, be used for implementing according to combination channel estimating method of the present invention.
Above-mentioned goal of the invention is realized by following technical scheme: the combination channel estimating method in the mobile radio system comprises that step is as follows:
(1) at least one neighbor cell of a quilt investigation sub-district, chooses at least one active user as interference user;
(2) carry out the combined channel estimation at described interference user with by the active user in the investigation sub-district.
The method according to this invention, described step (1) comprising:
(1a) carry out multiuser channel and estimate, perhaps carry out channel estimating respectively at each active user in the described neighbor cell at the active user in the described neighbor cell;
(1b) in described active user, choose at least one user as described interference user with the strongest channel impulse response power.
The method according to this invention in described step (1), is chosen at least one apart from being investigated the nearest active user of cell base station as described interference user in described neighbor cell.
The method according to this invention, described step (1) comprising:
(1a) selected distance is investigated the active user of cell base station less than a predeterminable range in a described neighbor cell;
(1b) carry out multiuser channel and estimate, perhaps carry out channel estimating respectively at each selected active user at selected active user;
(1c) in selected active user, choose at least one user as described interference user with the strongest channel impulse response power.
The method according to this invention, described step (1) repeats every a default time T.
The method according to this invention in described step (2), is carried out the combined channel estimation based on described interference user with by the training sequence code of the active user in the investigation sub-district.
The method according to this invention, described step (2) comprising:
(2a) described interference user of structure and quilt are investigated the training sequence code matrix G of the active user in the sub-district, and wherein, the line number of described matrix G is L, and representative is used for the length of the described training sequence code received signal of channel estimating; The columns of described matrix G is W * K, represents channel impulse response length and described interference user and quilt to investigate the product of the sum of the active user in the sub-district;
(2b) according to the received signal e=Gh+n of described training sequence code, channel impulse response h is united estimation, wherein, described channel impulse response h is made up of the channel impulse response of K wireless channel, and n is the additive white Gaussian noise signal that is additional on the described received signal e.
The method according to this invention uses zero forcing algorithm channel impulse response h to be united estimation, estimated value in described step (2b)
The method according to this invention uses least-mean-square error algorithm channel impulse response h to be united estimation, estimated value in described step (2b)
Wherein, σ
2Be the power of additive white Gaussian noise signal n, I is the unit matrix on W * K rank.
The method according to this invention uses the matched filtering algorithm channel impulse response h to be united estimation, estimated value in described step (2b)
The method according to this invention, the algorithm that uses matched filtering and least mean-square error to combine in described step (2b) is united estimation to channel impulse response h, estimated value
Wherein,
Be the estimation initial value that utilizes the matched filtering algorithm to obtain,
Be the estimation median of utilizing least-mean-square error algorithm to obtain, diag (G
HG)=G
HG-diag (G
HG).
The method according to this invention comprises that also step is as follows:
(3) described channel estimation value is carried out filtering.
Combined channel estimation unit in the mobile radio system comprises:
The interference user selected cell is used for choosing at least one active user as interference user at least one neighbor cell of being investigated the sub-district;
Channel estimating unit one is used for carrying out the combined channel estimation at described interference user with by the active user in the investigation sub-district.
According to device of the present invention, described interference user selected cell comprises:
Channel estimating unit two is used for carrying out the multiuser channel estimation at the active user of a described neighbor cell, perhaps carries out channel estimating respectively at each active user in the described neighbor cell;
Comparing unit is used for choosing at least one user with the strongest channel impulse response power as described interference user at described active user.
According to device of the present invention, described interference user selected cell is chosen at least one apart from being investigated the nearest active user of cell base station as described interference user in described neighbor cell.
According to device of the present invention, described interference user selected cell comprises:
Apart from pre-selection unit, be used for being investigated the active user of cell base station less than a predeterminable range a described neighbor cell selected distance;
Channel estimating unit two is used for carrying out multiuser channel at selected active user and estimates, perhaps carries out channel estimating respectively at each selected active user;
Comparing unit is used for choosing at least one user with the strongest channel impulse response power as described interference user at selected active user.
According to device of the present invention, described interference user selected cell repeats described interference user is chosen every a default time T.
According to device of the present invention, described channel estimating unit one is carried out the combined channel estimation based on described interference user with by the training sequence code of the active user in the investigation sub-district.
According to device of the present invention, described channel estimating unit one comprises:
Training sequence code matrix generation unit is used to construct described interference user and by the training sequence code matrix G of the active user in the investigation sub-district, wherein, the line number of described matrix G is L, and representative is used for the length of the described training sequence code received signal of channel estimating; The columns of described matrix G is W * K, represents channel impulse response length and described interference user and quilt to investigate the product of the sum of the active user in the sub-district;
Signal processing unit, be used for received signal e=Gh+n according to described training sequence code, channel impulse response h is united estimation, wherein, described channel impulse response h is made up of the channel impulse response of K wireless channel, and n is the additive white Gaussian noise signal that is additional on the described received signal e.
According to device of the present invention, described signal processing unit uses zero forcing algorithm channel impulse response h to be united estimation, estimated value
According to device of the present invention, described signal processing unit uses least-mean-square error algorithm channel impulse response h to be united estimation, estimated value
Wherein, σ
2Be the power of additive white Gaussian noise signal n, I is the unit matrix on W * K rank.
According to device of the present invention, in described step (2b), use the matched filtering algorithm channel impulse response h to be united estimation, estimated value
According to device of the present invention, the algorithm that uses matched filtering and least mean-square error to combine in described step (2b) is united estimation to channel impulse response h, estimated value
Wherein,
Be the estimation initial value that utilizes the matched filtering algorithm to obtain,
Be the estimation median of utilizing least-mean-square error algorithm to obtain, diag (G
HG)=G
HG-diag (G
HG).
According to device of the present invention, also comprise: filter unit is used for described channel estimation value is carried out filtering.
Description of drawings
Below will be described in detail purpose of the present invention and characteristic in conjunction with the accompanying drawings by specific embodiment, these specific embodiments are illustrative, do not have restricted.
Fig. 1 is for using conventional channel method of estimation and the coefficient correlation of comparing with the real channel impulse response according to the estimated value of combination channel estimating method of the present invention.
Fig. 2 is for using conventional channel method of estimation and the mean error of comparing with the real channel impulse response according to the estimated value of combination channel estimating method of the present invention.
Embodiment
Core concept of the present invention is: consider in the mobile radio system, the multiple access that exists between the different user signal in sub-district disturbs, with and neighbor cell in the interference user signal to the adjacent area interference that subscriber signal was produced in the described sub-district, when doing radio channel estimation, unite and carry out at the interference user in the active user in the described sub-district and its neighbor cell, thereby in the computation complexity scope that allows, improve precision of channel estimation, strengthen the ability of channel estimating opposing multiple access interference and adjacent area interference.
In the present invention, described active user refers to the user with the base station ongoing communication, for example, carries out the user of voice communication or data communication.
Following according to a specific embodiment of the present invention in, up link (subscriber equipment is to the base station direction) channel estimation process that will insert with Time Division-Synchronous Code Division Multiple Access in (TD-SCDMA) system is an example, describes the execution mode according to combination channel estimating method of the present invention.
As being investigated the sub-district, then the method according to this invention at first need be chosen described by the interference user in the neighbor cell of investigation sub-district in up link with a sub-district.In this step, the described base station of being investigated the sub-district can be according to the computing capability of its equipment, choose the interference user on or in described neighbor cell, these interference users can be all from a described neighbor cell, or from a plurality of described neighbor cells.When choosing interference user, described base station can be chosen according to different criterions.A kind of criterion that can adopt is the strongest channel impulse response power guidelines: described base station at first obtains the channel impulse response estimation value at each active user in the described neighbor cell; Then, in described active user, choose at least one user as described interference user with the strongest channel impulse response power.At this moment, can use any existing channel estimation methods, carry out multiuser channel at the active user in the described neighbor cell and estimate, perhaps carry out channel estimating respectively at each active user in the described neighbor cell.For example, use is carried out multiuser channel based on the Fast Channel method of estimation of Fourier transform at the active user in the described neighbor cell and estimated: because in the TD-SCDMA system, the training sequence code of the different user in sub-district is respectively the different cyclic shifts (Cyclic shift) of a basic training sequences sign indicating number (Basic midambles); Simultaneously,, therefore, can pass through the following formula 1 quick channel impulse response estimation value that obtains at each active user in the sub-district based on convolution algorithm in the time domain and the corresponding relation between the product calculation in the frequency domain,
Wherein, easy on the matrix computations,
K
mThe number of users of an interior maximum possible of time slot in the expression TD-SCDMA system; Λ represents a diagonal matrix, and its diagonal entry is respectively the basic training sequences sign indicating number
M PBehind Fourier transform everybody, i.e. λ
(l)=(DFT (
M p))
(l),
E represents the training sequence code signal vector that is used for channel estimating that receive the base station; Then, in order to suppress the harmful effect of noise to channel estimation value, can be right
Carry out thresholding filtering, be about to
In each element compare with a default threshold value respectively, the element that is lower than described predetermined threshold value will be used as noise, its value is set to 0; The element that is higher than described predetermined threshold value does not change, and is used as the channel impulse response estimation value of described active user.The another kind of criterion that can adopt is nearest criterion: described base station in described neighbor cell, choose at least one apart from its nearest active user as described interference user.Existing global positioning system (GPS) and other localization method all can be used to know the position of described active user, and and then calculate distance between described active user and described base station.In addition, the strongest channel impulse response power guidelines and nearest criterion can also be united use: described base station is its active user less than a predeterminable range D of selected distance in a described neighbor cell at first; Then, carry out multiuser channel at selected active user and estimate, perhaps carry out channel estimating respectively at each selected active user; At last, in selected active user, choose at least one user as described interference user with the strongest channel impulse response power.
Handle load in order to reduce described signal of base station, the conditions such as statistical law that can move according to the communication service statistical nature in the system or user of choosing to described interference user, carry out once every a default time T, in each default time T, can think that the selected interference user in described base station does not change.
Determined after the described interference user that next the method according to this invention, need carry out the combined channel estimation at selected interference user and the active user of being investigated in the sub-district.Represent selected interference user and investigated the sum of the active user in the sub-district with K, based on selected interference user with investigated the training sequence code of the active user in the sub-district
In this step, at first, can construct training sequence code matrix G, G=[G
(1), G
(2)..., G
(K)]; For each described interference user or active user, G
(k)The form that can have following formula 2,
Wherein, L represents to be used for the length of the training sequence code received signal of channel estimating, L≤N, and W represents channel impulse response length; Then, the described training sequence code received signal that is used for channel estimating then can be expressed as the form of following formula 3,
E=Gh+n expression formula 3
Wherein, h=[(h
(1))
T, (h
(2))
T..., (h
(K))
T]
TExpression is at a described K user's uplink channel impulse response,
K=1 ..., K; The length that n represents to be attached on the received signal vector e is the additive white Gaussian noise signal vector of L.At last, described base station is united estimation according to received signal vector e to channel impulse response h.At this moment, ZF (Zero forcing) or least mean-square error (Minimum mean square error) scheduling algorithm all can be used to h is united estimation.For example, when using zero forcing algorithm, estimated value
For a kind of nothing to h is estimated partially.Easy for matrix computations can add the training sequence code of being investigated the non-active user in the sub-district when the described training sequence code matrix G of structure, make described matrix G become a square formation, thereby with above-mentioned computational short cut be
In aforementioned calculation, main amount of calculation comes from matrix inversion operation.For this reason, in the specific implementation, can use the LU decomposition method to reduce the complexity of calculating.Concrete grammar is: at first, matrix being carried out LU decompose, is the product of a lower triangular matrix and a upper triangular matrix with described matrix notation; When being a square formation as G, it is decomposed into G=LU, L is a lower triangular matrix, U is a upper triangular matrix; Then, can obtain described estimated value by the calculating of carrying out in the following formula 4
Wherein, " " the left division operation of representing matrix; For lower triangular matrix L, left division operation can utilize forward direction displacement (Forwardsubstitution) algorithm to finish, and for upper triangular matrix U, left division operation can utilize backward-substitition (Backwardsubstitution) algorithm to finish.And for example, when using least-mean-square error algorithm, estimated value
Wherein, σ
2Be the power of additive white Gaussian noise signal n, I is the unit matrix on W * K rank, for the least mean-square error to h is estimated.For another example, when using the matched filtering algorithm, estimated value
Because in the TD-SCDMA system
Then described estimated value can be reduced to
In addition, also matched filtering algorithm and least-mean-square error algorithm can be combined, at this moment, at first utilize the matched filtering algorithm to obtain estimating initial value
Then, utilize least-mean-square error algorithm to obtain estimating median, and can carry out noise reduction process to it, for example carry out thresholding filtering, the estimation median after noise reduction process is designated as
At last, according to
With
Obtain estimated value
Wherein, diag (G
HG)=G
HG-diag (G
HG).
Owing to can carry out once every a default time T choosing of described interference user, in each default time T, think that the selected interference user in described base station does not change.Accordingly, in each default time T, do not changed if investigate the active user of sub-district, to G yet
HG or G
HG+ σ
2The calculating that I inverts can only be carried out once; Simultaneously, the computing of matrix inversion can be divided a plurality of subframes finish in described time T, with the amount of calculation load that alleviates base station equipment and avoid the peak value of amount of calculation to occur a time.The approximate calculation method that also can adopt other directly not invert in the realization.
Above-mentioned in order to implement according to combination channel estimating method of the present invention, combined channel estimation unit according to the present invention will comprise the interference user selected cell, be used for choosing at least one active user as interference user at least one neighbor cell of being investigated the sub-district; And channel estimating unit one, be used for carrying out the combined channel estimation at selected interference user with by the active user in the investigation sub-district.
Choose criterion according to described different interference user, described interference user selected cell can correspondingly comprise: channel estimating unit two, be used for carrying out the multiuser channel estimation, perhaps carry out channel estimating respectively at each active user in the described neighbor cell at the active user of a described neighbor cell; And comparing unit, be used for choosing at least one user as described interference user with the strongest channel impulse response power at described active user.Or comprise:, be used for being investigated the active user of cell base station less than described predeterminable range D a described neighbor cell selected distance apart from pre-selection unit; Channel estimating unit two is used for carrying out multiuser channel at selected active user and estimates, perhaps carries out channel estimating respectively at each selected active user; And comparing unit, be used for choosing at least one user as described interference user with the strongest channel impulse response power at selected active user.
In order to carry out the combined channel estimation at selected interference user with by the active user in the investigation sub-district, described channel estimating unit one can correspondingly comprise: training sequence code matrix generation unit is used to construct described training sequence code matrix G; And signal processing unit, be used for received signal e=Gh+n according to described training sequence code, channel impulse response h is united estimation, wherein, ZF, least mean-square error or matched filtering scheduling algorithm all can be used to h is united estimation.Above-mentioned according to the specific embodiment of the present invention in, drawing described channel estimation value
After, can use existing filtering method that it is carried out filtering, with the described channel estimation value of further raising
Precision.Accordingly, above-mentionedly then can further comprise filter unit, be used for described channel estimation value is carried out filtering according to channel estimating apparatus of the present invention.
The accuracy of channel estimating can be assessed by defining two parameters: coefficient correlation and mean error.Wherein, coefficient correlation is calculated the correlation of normalized channel impulse response estimation value and real channel impulse response, and it is 1 good more that the result approaches more.The phase relation numerical representation is shown in following expression formula 5:
The mean difference of mould value between mean error calculating channel impulse response estimated value and the real channel impulse response, this value is more little, illustrates that the accuracy of channel estimating is high more.The expression of mean error is shown in following expression formula 6:
Suppose describedly to be investigated the sub-district 4 active users are arranged, 4 interference user are respectively from the described different neighbor cells of being investigated the sub-district, and 8 users' average power equates.Under the condition of different additive white Gaussian noise power, will use conventional channel method of estimation (based on the Fast Channel method of estimation of Fourier transform) respectively and compare according to the estimated value and the real channel impulse response of combination channel estimating method of the present invention.The coefficient correlation and the mean error of the estimated value of two kinds of channel estimation methods and real channel impulse response have been shown under different user average transmit power and the white noise power ratio condition among Fig. 1 and Fig. 2 respectively.The result shows: combination channel estimating method according to the present invention has higher coefficient correlation and littler mean error.Therefore, when having multiple access interference and adjacent area interference in the transmission course of wireless signal, than traditional channel estimation methods, combination channel estimating method according to the present invention has higher accuracy.
Owing to be subject to the computing capability of existing subscriber equipment, can in uplink channel estimation, implement by base station equipment according to combination channel estimating method of the present invention.But,, when subscriber equipment has enough computing capabilitys,, can in Downlink channel estimation, implement by subscriber equipment equally according to combination channel estimating method of the present invention based on identical technical conceive along with the development of technology.Simultaneously, combination channel estimating method according to the present invention has more than to be limited to based on training sequence code and carries out, in a mobile communication system of not using training sequence code sequence or pilot frequency sequence, according to thought of the present invention, in specific implementation process of the present invention, carry out simple change, can finish the combined channel estimation procedure based on the decision-feedback information that sends data.Described relevant user information according to neighbor cell in the combination channel estimating method of the present invention can obtain by base station controller.And those skilled in the art should be not difficult to find out, and is suitable equally in the mobile radio system that uses multi-antenna technology or multi-transceiver technology according to combination channel estimating method of the present invention and combined channel estimation unit.
Claims (20)
1. the combination channel estimating method in the mobile radio system is characterized in that comprising that step is as follows:
(1) at least one neighbor cell of a quilt investigation sub-district, chooses at least one active user as interference user;
(2) described interference user of structure and quilt are investigated the training sequence code matrix G of the active user in the sub-district, and according to described interference user with by the received signal e=Gh+n of the training sequence code of the active user in the investigation sub-district, channel impulse response h is united estimation, wherein, the line number of described matrix G is L, and representative is used for the described interference user of channel estimating and is investigated the length of the training sequence code received signal of the active user in the sub-district; The columns of described matrix G is W * K, represent channel impulse response length and described interference user and quilt to investigate the product of the sum of the active user in the sub-district, described channel impulse response h is made up of the channel impulse response of K wireless channel, n is the additive white Gaussian noise signal that is additional on the described received signal e, K is described interference user and the sum of being investigated the active user in the sub-district, and W is a channel impulse response length.
2. channel estimation methods according to claim 1 is characterized in that described step (1) comprising:
(1a) carry out multiuser channel and estimate, perhaps carry out channel estimating respectively at each active user in the described neighbor cell at the active user in the described neighbor cell;
(1b) in described active user, choose at least one user as described interference user with the strongest channel impulse response power.
3. channel estimation methods according to claim 1 is characterized in that in described step (1), chooses at least one apart from being investigated the nearest active user of cell base station as described interference user in described neighbor cell.
4. channel estimation methods according to claim 1 is characterized in that described step (1) comprising:
(1a) selected distance is investigated the active user of cell base station less than a predeterminable range in a described neighbor cell;
(1b) carry out multiuser channel and estimate, perhaps carry out channel estimating respectively at each selected active user at selected active user;
(1c) in selected active user, choose at least one user as described interference user with the strongest channel impulse response power.
5. according to the arbitrary described channel estimation methods of claim 1 to 4, it is characterized in that described step (1) repeats every a default time T.
6. channel estimation methods according to claim 1 is characterized in that using in described step (2) zero forcing algorithm channel impulse response h to be united estimation, estimated value
7. channel estimation methods according to claim 1 is characterized in that using in described step (2) least-mean-square error algorithm channel impulse response h to be united estimation, estimated value
Wherein, σ
2Be the power of additive white Gaussian noise signal n, I is the unit matrix on W * K rank.
8. channel estimation methods according to claim 1 is characterized in that using in described step (2) the matched filtering algorithm channel impulse response h to be united estimation, estimated value
9. channel estimation methods according to claim 1 is characterized in that in described step (2) algorithm that uses matched filtering and least mean-square error to combine unites estimation to channel impulse response h, estimated value
Wherein,
Be the estimation initial value that utilizes the matched filtering algorithm to obtain,
Be the estimation median of utilizing least-mean-square error algorithm to obtain,
10. channel estimation methods according to claim 1, it is as follows to it is characterized in that also comprising step:
(3) described associating estimated channel estimated value is carried out filtering.
11. the combined channel estimation unit in the mobile radio system is characterized in that comprising: interference user selected cell and channel estimating unit one, described channel estimating unit one comprises training sequence code matrix generation unit and signal processing unit,
Described interference user selected cell is used for choosing at least one active user as interference user at least one neighbor cell of being investigated the sub-district;
Described training sequence code matrix generation unit, be used to construct the training sequence code matrix G of the active user in described interference user and the quilt investigation sub-district, wherein, the line number of described matrix G is L, and representative is used for the described interference user of channel estimating and is investigated the length of the training sequence code received signal of the active user in the sub-district; The columns of described matrix G is W * K, represents channel impulse response length and described interference user and quilt to investigate the product of the sum of the active user in the sub-district;
Signal processing unit, be used for according to described interference user with by the received signal e=Gh+n of the training sequence code of the active user in the investigation sub-district, channel impulse response h is united estimation, wherein, described channel impulse response h is made up of the channel impulse response of K wireless channel, and n is the additive white Gaussian noise signal that is additional on the described received signal e.
12. channel estimating apparatus according to claim 11 is characterized in that described interference user selected cell comprises:
Channel estimating unit two is used for carrying out the multiuser channel estimation at the active user of a described neighbor cell, perhaps carries out channel estimating respectively at each active user in the described neighbor cell;
Comparing unit is used for choosing at least one user with the strongest channel impulse response power as described interference user at described active user.
13. channel estimating apparatus according to claim 11 is characterized in that described interference user selected cell chooses at least one apart from being investigated the nearest active user of cell base station as described interference user in described neighbor cell.
14. channel estimating apparatus according to claim 11 is characterized in that described interference user selected cell comprises:
Apart from pre-selection unit, be used for being investigated the active user of cell base station less than a predeterminable range a described neighbor cell selected distance;
Channel estimating unit two is used for carrying out multiuser channel at selected active user and estimates, perhaps carries out channel estimating respectively at each selected active user;
Comparing unit is used for choosing at least one user with the strongest channel impulse response power as described interference user at selected active user.
15., it is characterized in that described interference user selected cell repeats described interference user is chosen every a default time T according to the arbitrary described channel estimating apparatus of claim 11 to 14.
16. channel estimating apparatus according to claim 11 is characterized in that described signal processing unit uses zero forcing algorithm channel impulse response h to be united estimation, estimated value
17. channel estimating apparatus according to claim 11 is characterized in that described signal processing unit uses least-mean-square error algorithm channel impulse response h to be united estimation, estimated value
Wherein, σ
2Be the power of additive white Gaussian noise signal n, I is the unit matrix on W * K rank.
18. channel estimating apparatus according to claim 11 is characterized in that described signal processing unit uses the matched filtering algorithm channel impulse response h to be united estimation, estimated value
19. channel estimating apparatus according to claim 11 is characterized in that the algorithm that described signal processing unit uses matched filtering and least mean-square error to combine unites estimation to channel impulse response h, estimated value
Wherein,
Be the estimation initial value that utilizes the matched filtering algorithm to obtain,
Be the estimation median of utilizing least-mean-square error algorithm to obtain,
20. channel estimating apparatus according to claim 11 is characterized in that also comprising:
Filter unit is used for described associating estimated channel estimated value is carried out filtering.
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