CN105812039B - A kind of method for eliminating pilot pollution and device - Google Patents
A kind of method for eliminating pilot pollution and device Download PDFInfo
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- CN105812039B CN105812039B CN201610160878.0A CN201610160878A CN105812039B CN 105812039 B CN105812039 B CN 105812039B CN 201610160878 A CN201610160878 A CN 201610160878A CN 105812039 B CN105812039 B CN 105812039B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
- H04B7/0417—Feedback systems
- H04B7/0421—Feedback systems utilizing implicit feedback, e.g. steered pilot signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
- H04B7/0452—Multi-user MIMO systems
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/0413—MIMO systems
- H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
- H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
- H04B7/0697—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using spatial multiplexing
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J11/00—Orthogonal multiplex systems, e.g. using WALSH codes
- H04J11/0023—Interference mitigation or co-ordination
- H04J11/005—Interference mitigation or co-ordination of intercell interference
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L25/00—Baseband systems
- H04L25/02—Details ; arrangements for supplying electrical power along data transmission lines
- H04L25/0202—Channel estimation
- H04L25/024—Channel estimation channel estimation algorithms
Abstract
The invention discloses a kind of method for eliminating pilot pollution and devices, which comprises establishes extensive multi-input multi-output orthogonal frequency division multiplexing system model；The system parameter for obtaining system model, according to System Parameter Design set of pilot symbols, and judges whether set of pilot symbols meets complete orthogonality；If set of pilot symbols meets complete orthogonality, according to the complete orthogonality of set of pilot symbols, the estimation of time domain channel shock response is carried out, by traditional time synchronization pilot tone transmission process to completely eliminate pilot pollution.If not satisfied, the efficient channel coherence time according to channel estimation is grouped user, the user between different groups carries out time interleaving pilot transmission again, completely or partially to eliminate pilot pollution.The present invention can make base station without cooperation or the excessively high problem of complexities such as known channel second-order statistics information, also avoid the training time it is too long lead to the unpractical defect of system, while can guarantee the high accuracy requirement of channel estimation.
Description
Technical field
The present invention relates to fields of communication technology, and in particular to a kind of method for eliminating pilot pollution and device.
Background technique
Due to extensive multiple-input and multiple-output (Multiple Input Multiple Output, MIMO) orthogonal frequency division multiplexing
High spectrum effect and efficiency can be obtained with (Orthogonal Frequency Division Multiplexing, OFDM) system
Potential ability, this system are widely regarded as the candidate that development potentiality is big in 5G cellular network.However, extensive MIMO-
The performance of ofdm system is strictly dependent on the standard of channel state information (Channel State Information, CSI) estimation
True property, no matter CSI is for carrying out uplink receiving or downlink transfer.In frequency division multiplexing (Frequency Division
Duplexing, FDD) in system, obtains the number of antennas that the expense of downlink CSI is configured with base station and linearly increase, so
It is unrealistic that base station configures extensive antenna.In time division multiplexing (Time Division Duplexing, TDD) system, utilize
The reciprocity of channel, downlink CSI can be estimated by uplink training.Moreover, the expense for obtaining uplink CSI is used with mobile
The number at family linearly increases.In general, the number of mobile subscriber is much smaller than antenna for base station number.However, working as efficient channel
Coherence time (defines the time that efficient channel coherence time is pilot symbol transmitted and is that measurement is single with the OFDM symbol time
Position) it is insufficient to provide sufficient amount of orthogonal pilot frequency sequence for Target cell and neighboring community when, pilot frequency sequence will be re-used,
Worst situation is that the pilot frequency multiplexing factor is 1, i.e., all cells use identical pilot frequency sequence simultaneously, this will cause serious lead
Frequency contamination phenomenon, base station will cannot distinguish between the channel from different community at this time.
Compared with the influence of additive white Gaussian noise, pilot pollution can cause more serious damage to system accessibility
Evil.Currently, a lot of research work concentrates on the elimination or reduction of pilot pollution.In base station configured with the how small of extensive antenna
In area's MIMO-OFDM system, the influence of pilot pollution has been analyzed, this analysis is disclosed even if in extensive MIMO-OFDM
In system, pilot pollution is still had.To solve the pilot pollution problem, a kind of time interleaving pilot schemes occur therewith, the party
Case can eliminate the interference between cell using the staggeredly transmission of pilot tone in time.However, this scheme needs a center control
Device processed come manage the training of all district pilots staggeredly, guarantee the time quadrature of different community pilot transmission with this.It can be with
Find out, this scheme is a very arduous challenge.Occur later it is a kind of using the pilot tone allocation strategy to cooperate between cell,
Identical pilot frequency sequence is allocated to the user's set met certain condition.However, this cooperation channel estimation strategy needs
The second-order statistics information of all up channels known to base station.When acquisition so a large amount of second-order statistics information in base station expends very much
Between, moreover, transmitting these information needs huge loop transfer expense.Blind Channel Estimation is also suggested solution pilot pollution and asks
Topic.It is a kind of that blind Channel Estimation is carried out from received data based on the scheme of singular value decomposition, and depend on extensive MIMO system
The progressive orthogonality of system channel vector, so this scheme performance under limited antenna for base station or limited channel coherency time
Decline.Using the orthogonality of subscriber channel under extensive channel matrix, a kind of blind multi-user's decorrelation process is put forward one after another,
However only have in the case that antenna for base station is sufficiently large, the system performance that this scheme could obtain.
Summary of the invention
The complexities such as cooperation or known channel second-order statistics information are needed since current pilot pollution results in base station
Excessively high problem and training time is too long to lead to the unpractical defect of system, while needing to guarantee the high accuracy of channel estimation
Problem, the present invention propose a kind of method for eliminating pilot pollution and device.
In a first aspect, the present invention proposes a kind of method for eliminating pilot pollution, comprising:
Establish extensive multi-I/O OFDM MIMO-OFDM system model；
The system parameter for obtaining the MIMO-OFDM system model, according to the System Parameter Design set of pilot symbols, and
Judge whether the set of pilot symbols meets complete orthogonality；
If the set of pilot symbols meets complete orthogonality, according to the complete orthogonality of the set of pilot symbols, pass through biography
The time synchronization pilot tone transmission process of system carries out the estimation of time domain channel shock response, to completely eliminate pilot pollution.
Preferably, further includes:
If the set of pilot symbols is unsatisfactory for complete orthogonality, according to the partial orthogonality of the set of pilot symbols, obtain
Optimal user grouping and optimal user packet count；
The pilot tone that processing obtains every group of user in optimal user grouping is mutually orthogonal；
When the efficient channel coherence time of channel estimation being more than or equal to the optimal user packet count, by different groups of use
By time interleaving pilot transmission information between family, to completely eliminate pilot pollution.
Preferably, further includes:
When the efficient channel coherence time of the channel estimation being less than the optimal user packet count, actual user is obtained
Grouping and actual user's packet count, actual user's packet count are equal to efficient channel coherence time length, user in every group
Pilot tone cannot be completely mutually orthogonal；
By time interleaving pilot transmission information between the user that different actual users are grouped, to partially remove pilot tone dirt
Dye.
It is preferably, described to establish extensive multi-I/O OFDM MIMO-OFDM system model, comprising:
According to time division duplex protocol, the MIMO-OFDM system model is established.
Preferably, the system parameter include: cell number L, user's number U, subcarrier number N in each cell and
Distinguishable multipath number K.
Preferably, described according to the System Parameter Design set of pilot symbols, and judge whether the set of pilot symbols is full
The complete orthogonality of foot, comprising:
When sub-carrier resources abundance, i.e. KLU≤N, the set of pilot symbols meets complete orthogonality；
When sub-carrier resources are inadequate, i.e. when KLU > N, the set of pilot symbols meets partial orthogonality.
Second aspect, the present invention also propose a kind of pilot frequency pollution eliminating device, comprising:
Model building module, for establishing extensive multi-I/O OFDM MIMO-OFDM system model；
Orthogonality judgment module is joined for obtaining the system parameter of the MIMO-OFDM system model according to the system
Number design set of pilot symbols, and judge whether the set of pilot symbols meets complete orthogonality；
First pollution cancellation module, if for judging that the set of pilot symbols meets complete orthogonality, according to the pilot tone
The complete orthogonality of glossary of symbols carries out the estimation of time domain channel shock response by traditional time synchronization pilot tone transmission process,
To completely eliminate pilot pollution.
Preferably, further includes:
Optimal user grouping obtains module, for when the set of pilot symbols is unsatisfactory for complete orthogonality, according to described
The partial orthogonality of set of pilot symbols obtains optimal user grouping and optimal user packet count；
Pilot tone processing module, for handle obtain optimal user be grouped in every group of user pilot tone it is mutually orthogonal；
Second abatement of pollution module is more than or equal to the optimal user for the efficient channel coherence time when channel estimation
When packet count, time interleaving pilot transmission information will be passed through between different groups of user, to completely eliminate pilot pollution.
Preferably, further includes:
Actual user, which is grouped, obtains module, is less than the optimal user for the efficient channel coherence time when channel estimation
When packet count, actual user's grouping and actual user's packet count are obtained, actual user's packet count is relevant equal to efficient channel
Time span, the pilot tone of user cannot be completely mutually orthogonal in every group；
Transmission process module is believed by time interleaving pilot transmission between the user for being grouped different actual users
Breath, to partially remove pilot pollution.
Preferably, the orthogonality judgment module is used for:
When sub-carrier resources abundance, i.e. KLU≤N, the set of pilot symbols meets complete orthogonality；
When sub-carrier resources are inadequate, i.e. when KLU > N, the set of pilot symbols meets partial orthogonality；
Wherein, system parameter includes cell number L, user's number U, subcarrier number N in each cell and distinguishable
Multipath number K.
As shown from the above technical solution, the present invention is by establishing MIMO-OFDM system model, according to the system of the model
Parameter designing set of pilot symbols, when the set of pilot symbols meets complete orthogonality, according to the set of pilot symbols completely just
The property handed over is carried out the estimation of time domain channel shock response by traditional time synchronization pilot tone transmission process, can completely eliminate and lead
Frequency pollutes, if not satisfied, the efficient channel coherence time according to channel estimation is grouped user, the user between different groups
Time interleaving pilot transmission is carried out again, can completely or partially eliminate pilot pollution.So that base station is not necessarily to cooperation or known
The excessively high problem of the complexities such as channel second-order statistics information, also avoid the training time it is too long cause system it is unpractical lack
It falls into, while can guarantee the high accuracy requirement of channel estimation.
Detailed description of the invention
In order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, to embodiment or will show below
There is attached drawing needed in technical description to be briefly described, it should be apparent that, the accompanying drawings in the following description is only this
Some embodiments of invention for those of ordinary skill in the art without creative efforts, can be with
Other attached drawings are obtained according to these figures.
Fig. 1 is a kind of flow diagram for method for eliminating pilot pollution that one embodiment of the invention provides；
Fig. 2 is frequency domain channel transmission function normalized mean squared errors that one embodiment of the invention provides and other methods
Comparison diagram；
Fig. 3 is the comparison diagram of uplinks and rate that one embodiment of the invention provides and other methods；
Fig. 4 is the comparison diagram of downlinks and rate that one embodiment of the invention provides and other methods；
Fig. 5 is the comparison diagram of downlinks and rate that one embodiment of the invention provides and other methods；
Fig. 6 is a kind of pilot frequency pollution eliminating device that one embodiment of the invention provides.
Specific embodiment
With reference to the accompanying drawing, the specific embodiment of invention is further described.Following embodiment is only used for more clear
Illustrate to Chu technical solution of the present invention, and not intended to limit the protection scope of the present invention.
Fig. 1 shows a kind of flow diagram of method for eliminating pilot pollution of one embodiment of the invention offer, comprising:
S1, extensive multi-I/O OFDM MIMO-OFDM system model is established；
S2, the system parameter for obtaining the MIMO-OFDM system model, according to the System Parameter Design frequency pilot sign
Collection, and judge whether the set of pilot symbols meets complete orthogonality；
If S3, the set of pilot symbols meet complete orthogonality, according to the complete orthogonality of the set of pilot symbols, pass through
Traditional time synchronization pilot tone transmission process carries out the estimation of time domain channel shock response, to completely eliminate pilot pollution.
The present embodiment is by establishing MIMO-OFDM system model, according to the System Parameter Design frequency pilot sign of the model
Collection, when the set of pilot symbols meets complete orthogonality, according to the complete orthogonality of the set of pilot symbols, by it is traditional when
Between synchronizing pilot transmission process carry out time domain channel shock response estimation, pilot pollution can be completely eliminated so that base station without
It need to cooperate or the excessively high problems of complexities such as known channel second-order statistics information, also avoiding the training time too long leads to system
Unpractical defect, while can guarantee the high accuracy requirement of channel estimation.
Optinal plan as the present embodiment, further includes:
If S4, the set of pilot symbols are unsatisfactory for complete orthogonality, according to the partial orthogonality of the set of pilot symbols, obtain
Take optimal user grouping and optimal user packet count；
The pilot tone that S5, processing obtain every group of user in optimal user grouping is mutually orthogonal；
S6, when the efficient channel coherence time of channel estimation be more than or equal to the optimal user packet count when, by different groups
User between by time interleaving pilot transmission information, to completely eliminate pilot pollution.
Further, further includes:
S7, when the efficient channel coherence time of the channel estimation being less than the optimal user packet count, obtain practical
User grouping and actual user's packet count, actual user's packet count are equal to efficient channel coherence time length, use in every group
The pilot tone at family cannot be completely mutually orthogonal；
By time interleaving pilot transmission information between S8, the user for being grouped different actual users, led with partially removing
Frequency pollutes.
Further, further includes:
S9, frequency domain channel transmission function is obtained by the time domain channel shock response estimated by Fast Fourier Transform (FFT).
Specifically, step S1 includes:
According to time division duplex protocol, the MIMO-OFDM system model is established.
Further, the system parameter includes: cell number L, user's number U, subcarrier number N in each cell
With distinguishable multipath number K.
Further, step S2 includes:
According to the signal that all subcarriers and single target BS antenna receive, judge whether the set of pilot symbols is full
The complete orthogonality of foot.
Multiple cell extensive multi-input multi-output orthogonal frequency division multiplexing system model is based on time division duplex protocol, and system
Analysis is based on all subcarriers of consideration, the signal that single target BS antenna receives.The prior art is to the pilot pollution problem
Analysis is based on consideration single sub-carrier, the signal that all target BS antennas receive.In the uplink training stage, each user is passed
Defeated length is the pilot frequency sequence of M, so having even if carrying out the Conventional temporal synchronizing pilot transmission process there are serious pilot pollution
Effect channel coherency time has to be larger than or is equal to M, wherein M is more than or equal to U；However the analysis of the present embodiment is then based on considering
All subcarriers, the signal that single target BS antenna receives, in order to accurately be estimated under limited pilot resources
CSI, is all users design set of pilot symbols in all cells first with system parameter, this set of pilot symbols is used for time domain
The estimation of channel impulse response, subsequent analysis system parameter, judges whether set of pilot symbols meets complete orthogonality.
Further, step S2 includes:
When sub-carrier resources abundance, i.e. KLU≤N, the set of pilot symbols meets complete orthogonality；
When sub-carrier resources are inadequate, i.e. when KLU > N, the set of pilot symbols meets partial orthogonality
It is described when sub-carrier resources are sufficient, i.e. when KLU≤N, using the complete orthogonality of set of pilot symbols, by traditional
The estimation that time synchronization pilot tone transmission process carries out time domain channel shock response can completely eliminate pilot pollution, and only need one
A efficient channel coherence time.
It is described when sub-carrier resources are inadequate, i.e. when KLU > N, it was demonstrated that there is optimal user groupings, are accorded with using pilot tone
Number collection partial orthogonality make the pilot tone of user in every group mutually orthogonal, the user between different groups carries out time interleaving again and leads
It keeps pouring in defeated.It is greater than or equal to optimal user packet count when efficient channel coherence time, pilot pollution can be completely eliminated, at this time
Required efficient channel coherence time is equal to optimal user packet count；Even if efficient channel coherence time is less than optimal user point
Group number, pilot pollution can also be reduced by big degree, and user grouping number is equal to efficient channel coherence time at this time.
The present embodiment does not need to carry out cooperating between base station or the complexities such as known channel second-order statistics information are excessively high
Operation；Simultaneously because in systems in practice, optimal user packet count is always less than L, so the present embodiment only needs very short effective letter
Road coherence time, i.e. uplink training time can completely eliminate or reduce pilot pollution to degree greatly, to improve pilot tone
The feasibility of abatement of pollution method in practical applications.
In order to which method for eliminating pilot pollution provided in this embodiment is described in more detail, citing is introduced in detail below:
A1, the extensive MIMO-OFDM system model of multiple cell is established；
The system model of foundation specifically:
Consider a cellular network being made of L hexagonal cell, cell number is denoted as l=1,2 ..., L.It is each small
U single-antenna subscriber is distributed in area, each cell base station configures the array being made of Q root antenna, and base-station antenna array is uniform
Linear array, it is assumed that Q > > U, system are used TDD agreement, all base stations and user's synchronization and be multiplexed based on cell frequency.
All users in all cells transmit an OFDM frequency pilot sign to respective target BS simultaneously.It is used in cell l
The pilot tone symbol of family u is denoted asWherein N is subcarrier number, and each
Pilot tonePower be 1.For on subcarrier n, in cell l in user u and cell l' between antenna for base station q
Uplink frequency domain channel transmission function.Yl',q[n] is on subcarrier n, and the signal that antenna for base station q is received in cell l' can
To indicate are as follows:
Wherein:
1≤l'≤L；
1≤q≤Q；
prFor the average transmission power of user；
For up channel frequency domain additive white Gaussian noise.
Consider N number of subcarrier, 1≤n≤N, (1) formula becomes:
Wherein:
Y l',q∈CN×1By Yl',q[n], 1≤n≤N are constituted；
By1≤n≤N is constituted；
Wl',q ∈CN×1By Wl',q[n], 1≤n≤N are constituted.
It can be expressed as:
Wherein:
F∈CN×KFor fast Fourier transform matrix；
For the line n kth column element of F；
1≤n≤N, 1≤k≤K and K≤N.
For channel impulse response vector, expression are as follows:
Wherein:
Spacing of the D between antenna；
λ is subcarrier wavelength；
The arrival direction angle of path k between antenna for base station q in user u in cell l and cell l'.
The complex value tap definition of kth paths are as follows:
Wherein:
For the phase in path, obey [0,2 π) on be uniformly distributed；
Including path loss and shadow fading and1≤k≤K, 1≤q≤Q.
According to (3) formula, (2) formula can be rewritten are as follows:
A2, set of pilot symbols is designed for all users in all cells using system parameter；
The set of pilot symbols of design specifically:
Wherein:
I is the index of LU user；
1≤u≤U, 1≤l≤L.
Specifically, i-th of element that frequency pilot sign is concentrated is based on reference signalIt generates:
P [i]=Φ [i] P [1], 1≤i≤LU (8)
Wherein:
A3, analysis system parameter, judge whether the set of pilot symbols meets complete orthogonality；
Judge whether set of pilot symbols meets the condition of complete orthogonality are as follows:That is KLU≤N.Specific card
Bright process is as follows:
The set of pilot symbols of design is substituted into (6) formula, available:
It is givenIt needs to prove:
Set matrix T=(P [i1]F)H(P[i2] F), 1≤i1,i2≤ LU, the then kth of matrix T1Row kth2Column element are as follows:
Set integer t=k1-k2, obtain | t |≤K-1.Equation (12) can be written as:
Assuming that i1> i2With t ≡ N+t as t≤0, obtain
In order to guarantee δ (t- (i1-i2) ζ)=0, i.e. t ≠ (i1-i2) ζ, the inequality in (16) formula must not have intersection, institute
With K-1 < (i1-i2) ζ < N-K+1.In other words,
If limiting the range of ζ are as follows:
This obvious range meets formula (15), then for all i1> i2Available T=0K×K.Correspondingly for all
I1< i2It can lead to the same conclusion.So whenWhen,So that T=0K×K.Due to i=(u-1) L
+ l, i1≠i2With l1≠l2∪u1≠u2It is of equal value.
I is considered now1=i2, it is equivalent to l1=l2∩u1=u2.If l1=l2∩u1=u2If t=k1-k2≠ 0, it shows
SoIf (i1=i2)∩(k1=k2), it is clear thatSo when ζ meets condition (16), for i1
=i2,
By the above process it may be concluded that working asWhen, the complete orthogonality of the set of pilot symbols of (12) formula
Met, it is clear that whenWhen this conclusion equally set up.
A4, if satisfied, using the set of pilot symbols complete orthogonality, be transmitted across by traditional time synchronization pilot tone
The estimation of Cheng Jinhang time domain channel shock response can completely eliminate pilot pollution；
As KLU≤N, pilot pollution is completely eliminated pilot pollution specific steps are as follows:
Wherein:
Time domain channel shock response vector estimation between antenna for base station q in user u to cell l' in cell l'
Value.
A5, if not satisfied, prove there is optimal user grouping, the partial orthogonality using the set of pilot symbols makes
The pilot tone for obtaining user in every group is mutually orthogonal, and the user between different groups carries out time interleaving pilot transmission again.Work as efficient channel
Coherence time is greater than or equal to optimal user packet count, and pilot pollution can be completely eliminated, even if efficient channel coherence time
Less than optimal user packet count, pilot pollution can also be reduced by big degree；
Optimal user grouping is existing to prove detailed process are as follows:
Given system parameter, i.e. cell number L, the user number U in each cell, subcarrier number N, distinguishable multipath
Number K.Definition:
In the multiple cell MIMO-OFDM system being multiplexed based on cell frequency, user's number U in each cell is usually not
Can be very big, however distinguishable multipath number K is usually very big in wireless propagation environment abundant, so it is easily verified that f is one
The integer of very little, nuIt is bigger than f, it obtains:
2≤f < L and nu> f (19)
For example, table 1 gives a typical system parameter, formula (19) is set up.
Table 1
It is givenConsider formula (13) again to determine that optimal user is grouped.
Still in i1> i2With t ≡ N+t under conditions of t≤0, obtain
In order to guarantee δ (t- (i1-i2) ζ)=0, i.e. t ≠ (i1-i2) ζ,It must satisfyIn other words,
It obtains simultaneously:
Therefore, as a pair of of user index i1, i2Meet formula (22), then distributes to this pilot tone sign matrix to user
It could be mutually orthogonal.
Due to i1With i2Minimal difference be f, we naturally enough consider LU user to be divided into f group.Specifically,
Index is that the user of 1, f+1,2f+1 ... is divided into first group；The user that index is 2, f+2,2f+2 ... is divided into second group etc.
Deng.Due toEvery group of number of users is nuOr nu+ 1 depends on remainder
1) R=0:The user index collection of groupFor
User's number in every group is nu.Due to for anyAnd i1> i2, meet condition (22), so point
The pilot tone sign matrix of every group of user of dispensing is mutually orthogonal.Thus prove that LU user is divided into f group is optimal use
Family grouping, as shown in table 2, the number of users in every group are nu。
Table 2
2) R ≠ 0: remainder R ∈ 1,2 ..., f-1 }.All users are divided into f group, User's rope of group
Draw collectionFor
TheNumber of users in group is
Therefore, the number of users in every group is nuOr nu+1.See Table 3 for details for this grouping.
Table 3
ForI.e.Number of users in every group is nu.Moreover, for any
And i1> i2, meet condition (22), so distributing to the n of every group of useruA pilot tone sign matrix is mutually orthogonal.
However, forI.e.Number of users in every group is nu+1.At this point, groupIn mutually just
The pilot tone sign matrix number of friendship is nuOr nu+1。
2.1) R ≠ 0 andFor anyAnd i1> i2, whenWhen, meet condition (22), at this point, groupIn mutually orthogonal pilot tone sign matrix number be nu+1.Therefore,
The grouping scheme of table 3 is optimal user grouping, and it is mutually orthogonal for distributing to the pilot tone sign matrix of every group of user.
2.2) R ≠ 0 andFor anyAnd i1> i2, when
When, in addition to groupIn first userWith the last one userCondition (22) are unsatisfactory for, i.e.,Any other a pair of user meets (22).In this case, LU user should
It is divided into f+1 group, number of users is less than or equal to n in every groupu.Therefore, the f+1 group optimal user grouping scheme of design must protect
It is mutually orthogonal that card, which distributes to the pilot tone sign matrix of every group of user,.The building base of f+1 group optimal user grouping scheme
In table 3, the specific steps are as follows:
Step 0: R user (n is extracted from the R group of table 3u(R-1)) f+R ..., (nu- 1) f+R, nuF+R constructs f
+ 1 group.Obviously, there is R user in f+1 group, be less than nu, and the pilot tone sign matrix of this R user is mutually orthogonal
's.Remaining n in table 3uF user is grouped as follows again；
Step 1: in (nu(R-1)) f+R column in, the element of R+1 row to f row is all moved up a line, this
When make the position of f row idle；
Step 2: in next column, the element of the 1st row to R-1 row all being moved up a line, at this time the member of the 1st row
Element is moved into the idle f row of previous column, while the element of R+1 row to f row is all moved up a line and makes the
The position of f-1 row and f row is idle；
Continue to repeat step as above, until reaching step R, so that n-thuIn f+R column, the element of the 1st row to R-1 row is complete
Portion moves up R-1 row, that is, has filled up previous column and left unused f- (R-2) row to get off to f row.This f+1 group optimal group side
See Table 4 for details for case.
Table 4
Obviously, in table 4, forGroup, the number of users in every group are nu, need to prove for appointing
MeaningAnd i1> i2, meet condition (22).
Notice in the table 3 that original all users are divided into f group, the user index in every group with f sequentially, however it is right
In each column, user index with 1 sequentially.Moreover, for user index i any pair of in each group1> i2, available
i1-i2≥f。
Analytical procedure 1 arrives step R, it is clear that forAny pair of user index i in each group1> i2, can be with
Obtain i1-i2≥f.Moreover, the indexed sequential of any group of user is incremented by table 4, so, it is only necessary to check first user's rope
Draw with whether the difference of the index of the last one user is less than or equal toForMaximum difference is
(nu- 1) f+R-2, forMaximum difference is (nu-1)f+R-1.Obviously,So condition (22) is met, table 4 is optimal user grouping.
It is greater than or equal to optimal user packet count when efficient channel coherence time, all users divide according to table 3 or table 4
Group, difference, which is organized, carries out the transmission of time interleaving pilot tone between user.Due to user in every group pilot tone sign matrix mutually just
It hands over, pilot pollution can be completely eliminated；It is less than optimal user packet count, the at this time grouping of user when efficient channel coherence time
Number size is equal to efficient channel coherence time, and see Table 5 for details for grouping situation.At this point, in every group user pilot tone sign matrix
Cannot be completely mutually orthogonal, there are partial contaminations, but pilot pollution can be reduced in the case by big degree.
Table 5
A6, frequency domain channel transmission function is obtained by the time domain channel shock response estimated by Fast Fourier Transform (FFT).
So far pilot pollution elimination/reduction work in the extensive MIMO-OFDM system of multiple cell is completed.
The present embodiment proposes pilot pollution in a kind of extensive MIMO-OFDM system of multiple cell and eliminates or minishing method,
It does not need to carry out the excessively high operations of complexities such as cooperation or known channel second-order statistics information between base station；Work as sub-carrier resources
When sufficient, time domain channel estimation is carried out using the set of pilot symbols of design, even if efficient channel is relevant in worst case
Between be 1, all users in all cells, which carry out time synchronization pilot transmission pilot pollution, to be completely eliminated.Work as subcarrier
When resource is inadequate, all users in all cells can be divided into the optimal user group of number very little, the pilot tone in every group
Glossary of symbols is mutually orthogonal.Use when efficient channel coherence time being more than or equal to optimal user packet count, between different groups
Family carries out time interleaving pilot transmission, and pilot pollution can be completely eliminated.Even if efficient channel coherence time is less than most optimal sorting
Group number, the group number that user is divided at this time are equal to the size of efficient channel coherence time, and the user between different groups carries out the time
Staggered pilot transmission, pilot pollution can be reduced by big degree.
The ratio of scheme is eliminated/reduced to user grouping scheme and other existing pilot pollutions that the present embodiment is presented below
Compared with so that the advantage and feature of the present embodiment are more obvious.
The system configuration parameter of the present embodiment is shown in Table 6.
Table 6
The signal-to-noise ratio (Signal-to-Noise Ratio, SNR) of system is defined as Es/N0, EsFor the energy of each symbol,For the power of AWGN.AllFor independent identically distributed Gaussian random variable, mean value isVariance is σAoA=90o.
Obviously, N < KLU in this system, obtains
Due to
This situation meets R ≠ 0,Optimal user is grouped into 4 the method for table, and organizing number at this time is f+1
=4.If effective channel coherency time r >=f+1=4,4 groups of optimal user uplink training programs can completely eliminate pilot tone dirt
Dye.If r=3,3 groups of user uplink training programs can big degree reduction pilot pollution.Even if worst situation r=1,1 group of use
Family, that is, uplink synchronization training program also can be realized the reduction of pilot pollution.
Firstly, verifying the validity of the present embodiment with NMSE, NMSE is defined are as follows:
Wherein:
For the frequency domain transfer function estimated value between antenna for base station q in user u to cell l in cell l.
Fig. 2 gives under the conditions of different uplink training signal-to-noise ratio (Signal-to-Noise Ratio, SNR), this reality
Apply the method for example and frequency domain channel transmission function normalized mean squared error (the Normalized Mean Square of other methods
Error, NMSE) comparison diagram；Under the conditions of different signal-to-noise ratio, 4 groups of user packet methods based on the present embodiment are based on this reality
Apply 3 groups of user packet methods of example, 2 groups of user packet methods based on the present embodiment, 1 group of user grouping based on the present embodiment
Method, document " the Successive pilot based on Conventional temporal synchronizing pilot sending method and based on Vu et al.
contamination elimination in multiantenna multicell networks,”IEEE Wireless
Commun.Let., the NMSE comparison diagram of vol.3, no.6, pp.617-620, Dec.2014.；As can be seen from Figure, if there is
Channel coherency time r >=f+1=4 is imitated, optimal 4 groups of user packet methods based on the present embodiment can completely eliminate pilot pollution.
If effective channel coherency time r=3,3 groups of user packet methods degree can reduce pilot pollution greatly, at this time the floor effect of NMSE
Should be worth is 4 × 10-5.If effective channel coherency time r=2, the NMSE floor effect value that 2 groups of user packet methods reach are
0.01.Even if worst situation efficient channel coherence time r=1, the attainable NMSE floor effect value of 1 group of user packet method
It is 0.05.Conventional temporal synchronizing pilot sending method can realize when efficient channel coherence time r >=8, at this time
The NMSE floor effect value reached is higher, is 0.1.The scheme of two kinds of elimination pilot pollutions is proposed in the document of Vu et al., and all
It is required that efficient channel coherence time r >=64.Second of performance better method is simulated in Fig. 2, it can be seen that this scheme can
Pilot pollution and no floor effect are completely eliminated, but performance is 2dB poorer than 4 groups of optimal user group technologies of the present embodiment, it is former
Because being the signal cancellation Product management model noise of this scheme.
Fig. 3 gives system configuration uplink and trains SNR consistent with uplink SNR, in different uplink SNR conditions
Under, 4 groups of user packet methods based on the present embodiment, 3 groups of user packet methods based on the present embodiment, based on the present embodiment
2 groups of user packet methods, 1 group of user packet method based on the present embodiment are based on Conventional temporal synchronizing pilot sending method, base
In the document of Vu et al. and the uplink based on perfect channel estimation and rate comparison figure；As can be seen from Figure, the result of Fig. 3 with
Fig. 2 is consistent, i.e., better NMSE performance can obtain higher uplink and rate.1 group of user based on the present embodiment point
Group method only needs r=1 efficient channel coherence time, than being higher by with rate capability for Conventional temporal synchronizing pilot sending method
5bits/s/Hz, and Conventional temporal synchronizing pilot sending method needs r >=8 efficient channel coherence time.The text of Vu et al.
Offer acquisition reachable uplink is reachable and rate is close to 4 groups of user packet methods based on the present embodiment, however the document of Vu et al.
It is r >=64 that method, which needs effective channel coherency time, and the present embodiment only needs r >=f+1=4.
Fig. 4 gives system configuration uplink training SNR=20dB, and each base station carries out downlink based on the channel that uplink is estimated
Force zero precoding transmissions, the method for the present embodiment and the downlink and rate of other methods under the conditions of different downlink transfer SNR
Comparison diagram；System configuration uplink training SNR is Es/N0=20dB, each base station carry out downlink based on the channel that uplink is estimated and compel
Zero precoding transmissions, under the conditions of different downlink transfer SNR, 4 groups of user packet methods based on the present embodiment are based on this implementation
3 groups of user packet methods, the 2 groups of user packet methods based on the present embodiment, 1 group of user grouping side based on the present embodiment of example
Method, based on Conventional temporal synchronizing pilot sending method, the document based on Vu et al. and downlink and speed based on perfect channel estimation
Rate comparison diagram；As can be seen from Figure, the literature method of 4 groups of user packet methods based on the present embodiment and Vu et al. are close to complete
Beautiful CSI circle.1 group of user packet method based on the present embodiment only needs r=1 efficient channel coherence time, compares Conventional temporal
Synchronizing pilot sending method is higher by 5bits/s/Hz with rate capability.
Fig. 5 gives system configuration uplink training SNR=20dB, and downlink transfer SNR=20dB, each base station is based on uplink
The channel of estimation carries out downlink force zero precoding transmissions, under the conditions of different base station antenna number Q, the present embodiment method and its other party
The downlink of method and the comparison diagram of rate；System configuration uplink training SNR is Es/N0=20dB, downlink transfer signal-to-noise ratio are Es/N0
=20dB, each base station carries out downlink force zero precoding transmissions based on the channel that uplink is estimated, in different base station antenna number Q condition
Under, 4 groups of user packet methods based on the present embodiment, 3 groups of user packet methods based on the present embodiment, based on the present embodiment
2 groups of user packet methods, 1 group of user packet method based on the present embodiment are based on Conventional temporal synchronizing pilot sending method, base
In the document of Vu et al. and the downlink based on perfect channel estimation and rate comparison figure；As can be seen from Figure, with desired one
Sample, increasing antenna for base station number can improve that downlink is reachable and rate, 4 groups of user packet methods and Vu based on the present embodiment et al.
Literature method close to perfection CSI circle.1 group of user packet method based on the present embodiment only needs r=1 efficient channel relevant
It is time, more preferable with rate capability than Conventional temporal synchronizing pilot sending method.
Fig. 6 shows a kind of structural schematic diagram of pilot frequency pollution eliminating device of one embodiment of the invention offer, comprising:
Model building module 61, for establishing extensive multi-I/O OFDM MIMO-OFDM system mould
Type；
Orthogonality judgment module 62, for obtaining the system parameter of the MIMO-OFDM system model, according to the system
Parameter designing set of pilot symbols, and judge whether the set of pilot symbols meets complete orthogonality；
First pollution cancellation module 63, if being led for judging that the set of pilot symbols meets complete orthogonality according to described
The complete orthogonality of frequency symbol collection carries out estimating for time domain channel shock response by traditional time synchronization pilot tone transmission process
Meter, to completely eliminate pilot pollution.
The present embodiment is by establishing MIMO-OFDM system model, according to the System Parameter Design frequency pilot sign of the model
Collection, when the set of pilot symbols meets complete orthogonality, according to the complete orthogonality of the set of pilot symbols, by it is traditional when
Between synchronizing pilot transmission process carry out time domain channel shock response estimation, pilot pollution can be completely eliminated so that base station without
It need to cooperate or the excessively high problems of complexities such as known channel second-order statistics information, also avoiding the training time too long leads to system
Unpractical defect, while meeting the high accuracy requirement to channel estimation.
Optinal plan as the present embodiment, further includes:
User grouping number obtains module 64, for obtaining optimal when the set of pilot symbols is unsatisfactory for complete orthogonality
User grouping and optimal user packet count；
Pilot tone processing module 65, for handle obtain optimal user be grouped in every group of user pilot tone it is mutually orthogonal；
Second abatement of pollution module 66 is more than or equal to the optimal use for the efficient channel coherence time when channel estimation
When the packet count of family, time interleaving pilot transmission information will be passed through between different groups of user, to completely eliminate pilot pollution；
Further, further includes:
Actual user, which is grouped, obtains module 67, is less than the optimal use for the efficient channel coherence time when channel estimation
When the packet count of family, actual user's grouping and actual user's packet count are obtained, actual user's packet count is equal to efficient channel phase
Time span is done, the pilot tone of user cannot be completely mutually orthogonal in every group；
Transmission process module 68 is believed by time interleaving pilot transmission between the user for being grouped different actual users
Breath, to partially remove pilot pollution.
Specifically, the model building module 61 is used to establish the MIMO-OFDM system mould according to time division duplex protocol
Type.
Further, the orthogonality judgment module 62 is used to be received according to all subcarriers and single target BS antenna
The signal arrived, judges whether the set of pilot symbols meets complete orthogonality.
Further, the system parameter includes cell number L, user's number U, subcarrier number N in each cell
With distinguishable multipath number K.
Further, the orthogonality judgment module 62 is used for:
When sub-carrier resources abundance, i.e. KLU≤N, the set of pilot symbols meets complete orthogonality；
When sub-carrier resources are inadequate, i.e. when KLU > N, the set of pilot symbols meets partial orthogonality.
In specification of the invention, numerous specific details are set forth.It is to be appreciated, however, that the embodiment of the present invention can be with
It practices without these specific details.In some instances, well known method, structure and skill is not been shown in detail
Art, so as not to obscure the understanding of this specification.
Claims (10)
1. a kind of method for eliminating pilot pollution characterized by comprising
Establish extensive multi-I/O OFDM MIMO-OFDM system model；
The system parameter for obtaining the MIMO-OFDM system model according to the System Parameter Design set of pilot symbols, and judges
Whether the set of pilot symbols meets complete orthogonality；
If the set of pilot symbols meets complete orthogonality, according to the complete orthogonality of the set of pilot symbols, in all cells
All users the estimation of time domain channel shock response is carried out by the pilot tone transmission process of traditional time synchronization, to disappear completely
Except pilot pollution.
2. the method according to claim 1, wherein further include:
If the set of pilot symbols is unsatisfactory for complete orthogonality, according to the partial orthogonality of the set of pilot symbols, obtain optimal
User grouping and optimal user packet count；
The pilot tone that processing obtains every group of user in optimal user grouping is mutually orthogonal；
When the efficient channel coherence time of channel estimation be more than or equal to the optimal user packet count when, by different groups of user it
Between by the pilot transmission information of time interleaving, to completely eliminate pilot pollution.
3. according to the method described in claim 2, it is characterized by further comprising:
When the efficient channel coherence time of the channel estimation being less than the optimal user packet count, actual user's grouping is obtained
With actual user's packet count, actual user's packet count is equal to efficient channel coherence time length, the pilot tone of user in every group
It cannot be completely mutually orthogonal；
By the pilot transmission information of time interleaving between the user that different actual users are grouped, to partially remove pilot tone dirt
Dye.
4. according to the method described in claim 3, it is characterized in that, described to establish extensive multi-input multi-output orthogonal frequency division multiple
With MIMO-OFDM system model, comprising:
According to time division duplex protocol, the MIMO-OFDM system model is established.
5. according to the method described in claim 4, it is characterized in that, the system parameter includes: cell number L, each cell
Interior user's number U, subcarrier number N and distinguishable multipath number K.
6. according to the method described in claim 5, it is characterized in that, described according to the System Parameter Design set of pilot symbols,
And judge whether the set of pilot symbols meets complete orthogonality, comprising:
When sub-carrier resources abundance, i.e. KLU≤N, the set of pilot symbols meets complete orthogonality；
When sub-carrier resources are inadequate, i.e. when KLU > N, the set of pilot symbols meets partial orthogonality.
7. a kind of pilot frequency pollution eliminating device characterized by comprising
Model building module, for establishing extensive multi-I/O OFDM MIMO-OFDM system model；
Orthogonality judgment module is set for obtaining the system parameter of the MIMO-OFDM system model according to the system parameter
Set of pilot symbols is counted, and judges whether the set of pilot symbols meets complete orthogonality；
First pollution cancellation module, if for judging that the set of pilot symbols meets complete orthogonality, according to the frequency pilot sign
The complete orthogonality of collection, the pilot tone transmission process progress time domain letter that all users in all cells pass through traditional time synchronization
The estimation of road shock response, to completely eliminate pilot pollution.
8. device according to claim 7, which is characterized in that further include:
Optimal user grouping obtains module, for when the set of pilot symbols is unsatisfactory for complete orthogonality, according to the pilot tone
The partial orthogonality of glossary of symbols obtains optimal user grouping and optimal user packet count；
Pilot tone processing module, for handle obtain optimal user be grouped in every group of user pilot tone it is mutually orthogonal；
Second abatement of pollution module is grouped for the efficient channel coherence time when channel estimation more than or equal to the optimal user
When number, by the pilot transmission information between different groups of user by time interleaving, to completely eliminate pilot pollution.
9. device according to claim 8, which is characterized in that further include:
Actual user, which is grouped, obtains module, is grouped for the efficient channel coherence time when channel estimation less than the optimal user
When number, actual user's grouping and actual user's packet count are obtained, actual user's packet count is equal to efficient channel coherence time
Length, the pilot tone of user cannot be completely mutually orthogonal in every group；
Transmission process module, by the pilot transmission information of time interleaving between the user for being grouped different actual users,
To partially remove pilot pollution.
10. device according to claim 9, which is characterized in that the orthogonality judgment module is used for:
When sub-carrier resources abundance, i.e. KLU≤N, the set of pilot symbols meets complete orthogonality；
When sub-carrier resources are inadequate, i.e. when KLU > N, the set of pilot symbols meets partial orthogonality；
Wherein, system parameter includes cell number L, user's number U, subcarrier number N and distinguishable multipath in each cell
Number K.
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