CN109845164A - For distributing base station and the method for pilot frequency sequence - Google Patents
For distributing base station and the method for pilot frequency sequence Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0048—Allocation of pilot signals, i.e. of signals known to the receiver
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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
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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
- H04L25/0204—Channel estimation of multiple channels
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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
- H04L25/0224—Channel estimation using sounding signals
- H04L25/0226—Channel estimation using sounding signals sounding signals per se
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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
- H04L25/0256—Channel estimation using minimum mean square error criteria
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0058—Allocation criteria
- H04L5/006—Quality of the received signal, e.g. BER, SNR, water filling
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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
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0078—Timing of allocation
- H04L5/0082—Timing of allocation at predetermined intervals
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/0091—Signaling for the administration of the divided path
- H04L5/0096—Indication of changes in allocation
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Abstract
The present invention provides a kind of for distributing the base station (BS) 100 of pilot frequency sequence at least one user equipment (UE) 101.BS 100 is configured as the channel statistical based at least one UE 101, selects multiple pilot frequency sequences from BS 100 and at least one available pilot frequency sequence set 102 of UE 101.Then, BS 100 is configured as the index 103 of each selected pilot frequency sequence being sent at least one UE 101.The present invention also provides UE 101, it is correspondingly configured to receive the multiple indexes 103 corresponded in the pilot frequency sequence in UE 101 and the available pilot frequency sequence set 102 of BS 100 from BS 100.In addition, UE 101 is configured as the pilot frequency sequence that the selection from pilot frequency sequence set 102 corresponds to the index 103 received, and channel estimation is executed based on selected pilot frequency sequence.
Description
Technical field
The present invention relates to base station (base station, BS), user equipment (user equipment, UE) and its system,
A kind of and method for distributing pilot frequency sequence.Specifically, pilot frequency sequence is dynamically assigned to communication system emphatically by the present invention
Or one or more UE in network.Present invention is particularly suitable for multi-user (multi-user, MU) multiple-input and multiple-outputs
(multiple input multiple output, MIMO) system.
Background technique
In this MU mimo system, significant challenge first is that obtaining accurate downlink (downlink, DL) in BS
Channel state information (channel state information, CSI), prelist to be executed on identical running time-frequency resource
Code simultaneously supports multiple users.Usually, this is predefined signal (the referred to as pilot tone or instruction that channel estimation is used for by sending
Practice sequence or reference signal) it is performed.
Most of cellular systems in West Europe and the U.S. be all based on frequency division duplex (frequency-division-duplex,
FDD).In such a system, pilot frequency sequence must be sent to UE by BS.Then, UE estimates DL CSI, and is fed back to
BS.With the increase (for example, in extensive mimo system) of BS antenna amount, training expense is sharply increased, to reduce
It can be used for the resource quantity of data.
" the achievable rate of the extensive mimo system of FDD with spatial channel correlation of Z.Jiang et al.
(Achievable rates of FDD massive MIMO systems with spatial channel
Correlation) " (IEEE.Trans.Wir.Commun., volume 14, the 5th phase, the 2868-2881 pages, in May, 2015) is related to
And a kind of pilot frequency sequence design in the case of MU.In the scheme proposed, BS is configured as the space covariance square based on UE
Battle array finds the measurement mark for maximizing the sum of conditional mutual information (sum conditional mutual information, SCMI)
Quasi- sequence.However, the one of the program is greatly the disadvantage is that BS must signal when changing the set of UE in systems in practice
Whole sequence (each element of i.e. each sequence).Since the sequence found is dynamic according to the quantity and its spatial coherence of scheduled UE
The state and sequence for tempestuously changing, therefore finding in this scenario cannot be simply stored at UE.It means that in the program
Middle signal integrity sequence actually needs.Therefore, the program leads to huge expense, makes it unsuitable for having strictly
Signaling request and on different running time-frequency resources dynamic dispatching UE real system, such as LTE system.
J.Choi et al. " the downlink training technique for the extensive mimo system of FDD: open loop with memory and
Closed loop trains (Downlink training techniques for FDD massive MIMO systems:open-loop
And closed-loop training with memory) " (IEEE J.Sel.Topics Signal Process., the 8th
Volume, the 5th phase, the 802-814 pages, in October, 2014) disclose the pilot frequency sequence designed for single user situation.Due to DL pilot tone
Sequence is by user sharing, therefore the scheme proposed is not suitable for MU situation.In addition, as shown in numerical result, when being generalized to
When MU situation, the program is very undesirable.
Another is not the disadvantage is that, traditional system and scheme can solve MU situation, and in MU, UE is equipped with iteration
Filter (such as Kalman filter (Kalman filter)).When UE known channel temporal correlation, iterative filter can
To help improve channel estimation quality.
Summary of the invention
In view of the above-mentioned problems and disadvantage, the present invention is directed to improve pilot frequency sequence distribution, especially in MU mimo system
In.Therefore, the purpose of the present invention is to reduce the expense as caused by the distribution, to increase the resource quantity that can be used for data.Base
In this purpose, the present invention is intended to provide a kind of solution suitable for such as LTE system.The present invention also wants to as pilot frequency sequence
Distribution provides a kind of dynamic effective solution scheme.Specifically, extensive MIMO FDD system of the demand in limited trained expense
One of effective channel estimation.Another object of the present invention is the MU for solving the UE equipped with iteration or Order Statistic Filters
Situation.
The purpose of the present invention is realized by the solution that accompanying independent claim provides.In the dependent claims
Further define Advantageous embodiments of the invention.
The first aspect of the present invention provides a kind of for distributing the base of pilot frequency sequence at least one user equipment (UE)
Stand (BS), which is configured as: the channel statistical based at least one UE, from the BS and the available pilot tone sequence of at least one UE
Multiple pilot frequency sequences are selected in column set, and the index of each selected pilot frequency sequence is sent at least one UE.
Possibly even for multiple UE, all known by the pilot frequency sequence of BS selection as BS and at least one UE by allowing
A part in the pilot frequency sequence set in road, compared with known scheme and system, the significant reduction of pilot frequency sequence signaling overheads.This
Once being because BS selects pilot frequency sequence from this collection, it only needs to send corresponding index signal at least one UE.Cause
This, the solution of first aspect is suitable for such as having the real system being strict with, such as LTE system to low signaling overheads
System.Pilot frequency sequence is found based on UE channel statistical to realize the optimal selection of sequence, this itself is one challenging
Task.Once at least one UE receives index, it is known which pilot frequency sequence BS has selected, and they can be used
In channel estimation.
According in a first aspect, BS is configured as the letter of the minimum based at least one UE in the BS of the first form of implementation
Channel estimation error maximizes the module of conditional mutual information to select pilot frequency sequence.
By the selection criteria, the optimal pilot sequence for efficient channel estimation can choose.
According to first aspect or according to the first form of implementation of first aspect, in the BS of the second form of implementation, measurement mark
Standard is designed to directly minimize channel estimation and (Channel Estimation Sum, CES) mean square error (Mean
Square Error, MSE) or weighting CES MSE, or by maximizing the sum of conditional mutual information (SCMI) come indirectly minimum
Change CES MSE.
These modules allow the optimal selection of pilot frequency sequence to carry out most effective channel estimation.
According to the second form of implementation of first aspect, in the BS of third form of implementation, BS is configured as: for from pilot tone
The possible pilot frequency sequence of each of arrangement set, which combines, determines CES MSE or SCMI, and select to generate the smallest CES MSE or
The combination of maximum SCMI is combined as desired pilot frequency sequence.
This method is particularly advantageous for small pilot frequency sequence set.
According to the second of first aspect or third form of implementation, in the BS of the 4th form of implementation, BS is configured as: being found
Optimal pilot sequence is to minimize CES MSE or maximize SCMI, and wherein the optimal pilot sequence is not only restricted to from pilot tone sequence
Column set, and it is focused to find out pilot frequency sequence from the pilot frequency sequence, which is that the son of the optimal pilot sequence is empty
Between best basis is provided.
This method is particularly advantageous for big pilot frequency sequence set.
According to any one of the second to the 4th form of implementation of first aspect, in the BS of the 5th form of implementation, in order to
Pilot frequency sequence is selected, BS is configured as: by will be seen that process is considered as linear programming problem, finding pilot frequency sequence to minimize
CES MSE maximizes SCMI.
This method is particularly advantageous for big pilot frequency sequence set.
According to first aspect or any aforementioned way of realization of first aspect, in the BS of the 6th form of implementation, if extremely
The covariance matrix of a few UE or the set of at least one UE or UE change, and BS is configured as: being reselected at least
One pilot frequency sequence, and the index of each pilot frequency sequence reselected is sent at least one UE.
Therefore, even if under varying conditions, pilot frequency sequence can also be dynamically adjusted to obtain optimum channel estimation
As a result.For example, depending on the scattering environments close to UE, the covariance matrix of at least one UE can be in several seconds or tens of seconds quantity
Grade changes.Since scheduling and network flow, the set for servicing UE may change.
According to first aspect or according to any aforementioned way of realization of first aspect, in the BS of the 7th form of implementation, BS
Be configured as: being dynamically selected the pilot frequency sequence, and dynamically send the index of each selected pilot frequency sequence to this at least one
A UE.
Therefore, it can need to update pilot frequency sequence according to improvement channel estimation.
According to first aspect or any aforementioned way of realization of first aspect, in the BS of the 8th form of implementation, at least
One equipped in the case where the UE of iteration or Order Statistic Filters, in order to select pilot frequency sequence, base station is configured as: each pre-
It fixes time after the period, pilot frequency sequence preferably is updated to each decline block period, and by each pilot tone periodically updated
The index of sequence is sent at least one UE.
As a result, when user uses iterative filter, the signal of pilot sequence index is periodic.Therefore, in user
In the case where using iterative filter, provide a kind of for finding the solution of pilot frequency sequence from pilot frequency sequence set.
MSE function has different structures in this Iterative filtering device, therefore cannot be from using non-iterative filter situation
The solution for the situation is simply inferred in solution.This is not solved the problems, such as in the prior art, existing skill
Art is concerned only with single user scene.
According to first aspect or according to any aforementioned way of realization of first aspect, in the BS of the 9th form of implementation, BS
It is configured as: sending the index of pilot frequency sequence at least one UE in the specific control channel of UE.
The second aspect of the present invention provides a kind of UE for communication system, which is configured as: receiving from base station BS
Corresponding to multiple indexes of pilot frequency sequence, multiple pilot frequency sequence comes from the available pilot frequency sequence set of at least one UE and BS,
Pilot frequency sequence is selected from the pilot frequency sequence set, which corresponds to received index, is based on the selected pilot tone
Sequence calculates filter, and the filter based on the calculating executes channel estimation.
Realize the advantage identical as first aspect, that is, significantly reduce signaling overheads.In addition, excellent with pilot tone is not executed
The case where changing i.e. when pilot tone is fixed (such as in LTE) is compared, and the channel estimation quality of UE obtains significant improvement.
According to second aspect, in the UE of the first form of implementation, UE is configured as: periodically receiving multiple ropes from BS
Draw, and based on the pilot frequency sequence corresponding with the index that the last one is received, calculates the iteration or Order Filtering of given iteration
Device, and channel estimation is executed based on iteration or Order Statistic Filters.
Therefore, the channel estimation of UE is modified in the case where iteration or Order Statistic Filters.
The third aspect of the present invention provides a kind of system, including at least one is according to first aspect or according to first aspect
Any form of implementation BS, and according to second aspect or at least one according to the UE of the first form of implementation of second aspect.
The system realizes the BS of first aspect and its UE and its realization of way of realization and second aspect
All advantages of form.
The fourth aspect of the present invention provides a kind of for distributing the side of pilot frequency sequence at least one user equipment (UE)
Method, this method comprises: the channel statistical based at least one UE, from base station and the available pilot frequency sequence set of at least one UE
Multiple pilot frequency sequences are selected, and send the index of each selected pilot frequency sequence at least one UE.
According to fourth aspect, in the method for the first form of implementation, this method comprises: the minimum based at least one UE
Change channel estimation errors or maximizes the module of conditional mutual information to select pilot frequency sequence.
According to fourth aspect or the first form of implementation of fourth aspect, in the method for the second form of implementation, module
It is designed to directly minimize channel estimation and (CES) mean square error (MSE), or weighting CES MSE, or passes through maximization and item
The sum of part mutual information (SCMI) minimizes CES MSE indirectly.
According to the second form of implementation of fourth aspect, in the method for third form of implementation, this method comprises: for from pilot tone
The possible pilot frequency sequence of each of arrangement set, which combines, determines CES MSE or SCMI, and selects to generate minimum CES MSE or most
The combination of big SCMI is as desired pilot frequency sequence.
According to the second of fourth aspect or third form of implementation, in the method for the 4th form of implementation, this method comprises: looking for
To optimal pilot sequence to minimize CES MSE or maximize SCMI, wherein optimal pilot sequence is not only restricted to from pilot tone sequence
Column set, and it is focused to find out pilot frequency sequence from pilot frequency sequence, which is the subspace of the optimal pilot sequence
Best basis is provided.
According to any one of the second to the 4th form of implementation of fourth aspect, in the method for the 5th form of implementation, it is
Selection pilot frequency sequence, this method comprises: find pilot frequency sequence by will be seen that process is considered as linear programming problem to minimize
CES MSE maximizes SCMI.
According to fourth aspect or according to any aforementioned way of realization of fourth aspect, in the method for the 6th form of implementation,
If the set of the covariance matrix of at least one UE or at least one UE or UE change, this method comprises: selecting again
At least one pilot frequency sequence is selected, and the index of each pilot frequency sequence reselected is sent at least one UE.
According to fourth aspect or according to any aforementioned way of realization in terms of first (four), in the method for the 7th form of implementation
In, this method comprises: being dynamically selected pilot frequency sequence, and the index of each selected pilot frequency sequence is dynamically sent to this at least
One UE.
According to fourth aspect or any aforementioned way of realization of fourth aspect, in the method for the 8th form of implementation, at this
At least one UE equipped with iteration or Order Statistic Filters in the case where in order to select pilot frequency sequence, this method comprises: each
After predetermined period of time, pilot frequency sequence is preferably updated to each decline block period, and send at least one UE
The index of the pilot frequency sequence each periodically updated.
According to fourth aspect or according to any aforementioned way of realization of fourth aspect, in the method for the 9th form of implementation,
This method comprises: the index of pilot frequency sequence is sent at least one UE in the specific control channel of UE.
Using fourth aspect and its method of way of realization, the above-mentioned BS about first aspect and its way of realization is realized
All advantages and effect of description.
Should be noted that all devices described in this application, element, unit and device can with software or hardware element or its
Any kind of combination is to realize.It is executed by all steps of various entities execution described in this application and by various entities
Function be intended to indicate that corresponding entity is suitable for or is configured to execute corresponding step and function.
Even if the specific function or step executed by external entity is not reflected in the description below to specific embodiment
It executes in the description of specific detailed elements of the entity of the particular step or function, it should be clear to a person skilled in the art that these
Method and function can be realized in respective software or hardware element or its any kind of combination.
Detailed description of the invention
Aforementioned aspect of the present invention and way of realization below in conjunction with being illustrated in the description of the specific embodiment of attached drawing,
In:
Fig. 1 shows the BS of embodiment according to the present invention, and also shows the UE of embodiment according to the present invention.It should
The system that the BS and UE forms embodiment according to the present invention.
Fig. 2 shows the methods of embodiment according to the present invention.
Specific embodiment
Fig. 1 shows the BS 100 and UE 101 of embodiment according to the present invention.BS 100 and UE 101 are formed together root
According to the system of the embodiment of the present invention, wherein such system also may include more than one BS 100 and/or more than one
UE 101.
BS 100 is configured as distributing to pilot frequency sequence into UE 101 or more than one UE 101.For this purpose, 100 quilt of BS
The channel statistical selection for being configured to UE 101 is multiple in BS 100 and the available pilot frequency sequence set 102 of UE 101
Pilot frequency sequence.In addition, BS 100 is configured as sending the index 103 of each selected pilot frequency sequence to UE 101.
Therefore, it is corresponding to be configured as the pilot frequency sequence received in the pilot frequency sequence set 102 from BS 100 by UE 101
Multiple indexes 103.It is configured as selecting those correspondences from pilot frequency sequence set 102 using received index 103, the UE 101
Channel estimation is executed in the pilot frequency sequence of the index received 103, and based on the pilot frequency sequence selected by these.
Fig. 2 similarly illustrates according to an embodiment of the present invention for distributing the side of pilot frequency sequence at least one UE 101
Method 200.In the first step 201 of method 200, from BS 100 and at least one available pilot frequency sequence set 102 of UE 101
The middle multiple pilot frequency sequences of selection.In the second step 201 of method 200, each selected pilot frequency sequence is sent to UE 101
Index 103.Step 201 and 202 can be executed by BS 100 as shown in Figure 1.However, individually entity (such as pilot tone letter
Number distributor, relay node, or the dedicated UE selected from the UE of communication system or network) it can also be responsible for executing these sides
Method step.
The more details of above-described embodiment have been explained below.These details are respectively suitable for the method 200 of Fig. 2, with
And the BS 100 and UE 101 of Fig. 1.
Generally, the present invention focuses on the select permeability of controlled pilot frequency sequence.In other words, as described above, it is assumed that T
Pilot frequency sequence (T represents above-mentioned number) is by preferably by BS 100 from being all known for BS 100 and at least one UE 101
Pilot frequency sequence set 102 (it is hereinafter also referred to as pilot frequency sequence set S, | S | represent the pilot frequency sequence for including in set 102
Quantity, that is, gather 102 radix) in selection.
Once BS 100 selects pilot frequency sequence, it only sends the signal of its index 103 at least one UE 101.With tradition
Method is compared, and huge expense is reduced.
Pilot frequency sequence can be selected based on different modules, for example, the module of CES MSE is minimized, or
Some other modules of CES MSE are minimized indirectly, and for example, SCMI maximizes the module of design.Based on these degree
Different methods can be used to select pilot frequency sequence in amount standard.
First method is brute force solution.For example, BS 100 can traverse the institute obtained from pilot frequency sequence set S
Possible pilot frequency sequence combination, and can choose the combination for minimizing CES MSE or maximizing SCMI.When not too many group
When conjunction, for example, when size (i.e. | S | the value) hour of set 102, this method is especially feasible.
Second method is carried out in two steps.In the first step, it preferably finds and minimizes CES MSE or maximize SCMI's
Pilot frequency sequence and these pilot frequency sequences are not only restricted to from set S (that is, finding optimal pilot sequence).In second step, find
From those of set S pilot frequency sequence, those pilot frequency sequences are the optimal pilot sequence by finding in the first step
Subspace provides optimal basis.This method is preferred for large-sized set 102.
The third method is based on linear programming.That is, CES MSE is minimized or SCMI maximization problems can be used as
Linear programming problem is suggested, to find desired pilot frequency sequence from set S.
Any one of these methods all return to selected pilot frequency sequence { s1,s2,…,sT}.Then by these pilot tones
103 { the i of index of sequence1,…,iTIt is sent at least one UE 101.Note that each pilot frequency sequence can use ceil (log2(|
S |)) a bit is as index, and wherein ceil (x) indicates the smallest positive integral for being greater than or equal to x.Once at least one UE 101 connects
Index 103 is received, it is known that the selection of BS 100 and which pilot frequency sequence used, and they can be used for its and respective estimated
It counts filter (for example, MMSE filter).In fact, index 103 can be in the specific control channel of UE (for example, in LTE
PDCCH it is sent on).
Preferably, BS 100 can reselect pilot frequency sequence, and at least one UE 101 into its cell is sent
The index 103 of the pilot frequency sequence reselected.Whenever at least one covariance matrix for the UE 101 that at least one is serviced is aobvious
It writes and changes, or when changing the one group of UE 101 serviced, it is preferable that the execution of BS 100 reselects.
Depending on the scattering environments close to UE 101, the covariance matrix of the UE 101 serviced was by the several seconds to tens of seconds
The order of magnitude changes, and due to scheduling and network flow, the one group of UE 101 serviced changes.Due to these factors, sequence index
103 signaling is preferably dynamic.
Pilot sequence index { the i in common control channel must be specified1,…,iTDynamic signaling, therefore channel estimation
It is specific.Note that the distribution of pilot frequency sequence (for example, cell specific reference signal) is quiet in DL in the system of such as LTE
State/predefined.
Note that the space covariance matrix of at least one UE 101 of BS 100 assumed that.
Next, the solution for above-mentioned second method provides Exemplary mathematical description.
Specifically, consider the system of BS 100 and K with the M antenna UE 101 with single antenna.The letter of UE k
Road byIt indicates, and there is zero-mean and space covariance matrix Rk.BS 100 is within the duration of T time slot
Pilot frequency sequence is sent, that is, sends T pilot frequency sequence.Pilot frequency sequence in first of time slot isPilot frequency sequence is collected in
MatrixIn.K-th of UE 101 receives the pilot frequency sequence sent by channel:
yk=SHhk+nk
Wherein nkIt is with power σ2K-th of UE 101 additional noise.K-th of UE 101 executes MMSE estimation, and shape
At channel estimation:
CES MSE is a function of S, it is indicated are as follows:
MSE (S)=Σktr(Rk-RkS(SHRkS+σ2IT)-1SHRk) (1)
The wherein mark of tr () representing matrix.Set S known to given BS 100 and at least one UE 101 1, the collection
Closing S includes N > T sequence, i.e. S={ v1,…,vN, selection minimizes the T pilot frequency sequence of MSE (S) from S.In second of side
The selection is carried out in two steps in method.The first step is to find a unconfined solution for the selection, i.e., one not necessarily
Solution { a in S1,…,aT}.That is, the pilot frequency sequence selected in the first step does not need to be included in pilot frequency sequence collection
It closes in S.Then, second step finds the solution { a closest to the first step from set S1,…,aTT pilot frequency sequence.
Next a kind of sequence optimisation method is described.Cost function MSE (S) is non-convex in S, and for its minimum
Change the solution that closed form is not present.Therefore, on the contrary, naturally enough considering iterative technique, such as descending method.In addition, locating
When managing matrix variables, research cost function is each entry depending on its matrix parameter, is still only dependent upon matrix parameter column
The subspace opened is useful.Latter situation leads to the reduction of problem space, and exists for handling these problems
The efficient algorithm based on gradient.In fact, generating shirtsleeve operation:
MSE (S)=MSE (S Q) (2)
WhereinIt is unitary matrice (i.e. Q QH=QHQ=IT).Therefore, MSE cost function is for single rotation
Constant, and be the function of the subspace of S column.By this important research with force Orthonormality constraints in conjunction with SHS=IT
The solution for minimizing MSE (S) is generated, which can be used the acquisition of the iteration steepest descent method in Grassmann manifold.
Iteration steepest is lowered back in matrix Sopt=[a1,…,aT] in collect sequence a1,…,aT.In order to be looked for from S
To closest to { a1,…,aTT pilot frequency sequence sd1,…,sdT, it should be noted that SoptCES MSE be not SoptEach
Purpose function, but the function of the subspace of its column, or, in other words, Range Representation is ran (Sopt).Therefore, it builds
View is selected as ran (Sopt) the T pilot frequency sequence on best basis is provided.This is the inspiration by traditional match tracing technology, and
It is that by the summary of this technology of Subspace Matching.
For the thought dedicated for finding the best vector in subspace in each step, which includes ran
(Sopt) and the intersection of the orthogonal complement code of subspace opened of the vector that has been selected.In other words, it is attempted in each step
Remnants (residue) subspace that the vector that " covering " had not been selected previously is covered.This step is completed, needs to define some amount
Value.Allow PoptAs ran (Sopt) on orthogonal projector, content is as follows:
Popt=Sopt(Sopt HSopt)-1Sopt H.
In addition, the pilot frequency sequence selected after t step is stacked on matrix St=[sd1,…,sdt] in.Then, in ran (St)
Orthogonal complement code on projection operator indicate are as follows:
Pcomp,t=I-St(St HSt)-1St H
Finally, projection operator is in ran (Sopt) and ran (St) orthogonal complement code intersection on can be used as PoptAnd Pcomp,t
Function calculate:
WhereinIndicate Moore-Penrose (Moore-Penrose) pseudoinverse.Needed for following exemplary algorithm can be used for finding
Sequence.
Initialization:
Pintersect,0=Popt；
Step t=1 to T
sdt=arg maxs∈S-T||Pintersect,t-1s||2
T←{T,sdt}
St=[St-1,sdt]
According to StCalculate Pcomp,t
According to Pcomp,tAnd PoptCalculate Pintersect,t
Terminate
It should be noted that SCMI can be used instead of S when running above-mentioned algorithmoptMaximization (is expressed as without constrained solution
Scmi), because CMI function is also constant for the single rotation of its matrix parameter.Then it needs to use Pcmi=Scmi
(Scmi HScmi)-1Scmi HInstead of Popt.Rest part carries out in a similar manner.
Next, the combination of description and iterative filtering.Iteration/Order Filtering (such as Kalman filtering) is applied in UE 101
In the case where, pilot frequency sequence preferably is selected on the basis of declining block time slot by BS 100, to minimize MSE.To this
Prerequisite is to know the space-time End-user relevance of BS 100.Here, single order Gauss Markov (Gauss-Markov) process
Suitable for being described as follows the temporal correlation of the channel of k-th of UE 101:
hk[1]=Rk 1/2g1, g1With independent NC (0,1) element, (NC (0,1) indicates circle symmetrical Gaussian variable, mean value
It is zero, variance 1)
hk[n]=η hk[n-1]+sqrt(1–η2)Rk 1/2gn,n>1
Wherein hk[n] is the channel of UE k in n-th of decline block, and η is time correlation coefficient, gnIt is to have and all n > 1
hk[n -1] and g1The vector of incoherent independent NC (0,1) element.The channel of UE k has space association side at all decline blocks
Poor Rk。
In this case, the Kalman filter that k-th of user uses at n-th of decline block can be write as
Kk[n]=Mk[n/n-1]S[n](S[n]HMk[n/n-1]S[n]+σ2I)-1
Wherein MkWhat the minimum prediction MSE matrix of [n/n-1] and S [n] expression and BS 100 were used at n-th of decline block leads
Frequency sequence.Mk[n/n-1] is indicated are as follows:
Mk[n/n-1]=η2Mk[n-1/n-1]+(1-η2)Rk
This is the minimum MSE matrix M of (n-1) a decline blockkThe function of [n-1/n-1]:
Mk[n-1/n-1]=(I-Kk[n-1]S[n-1]H)Mk[n-1/n-2].
In the multi-user case, it can be seen that summing to MSE of all users at n-th of decline block indicates are as follows:
MSE [n]=Σktr(Mk[n/n-1]–Mk[n/n-1]S[n](S[n]HMk[n/n-1]S[n]+σ2I)-1S[n]HMk
[n/n-1]) (3)
Due to recurrence/sequential organization of Kalman filter, the MSE of difference decline block may be different.In addition, given
Decline block selection pilot frequency sequence not only influences the MSE of given block, but also influences the MSE of all subsequent blocks.For example, the selection of S [n]
Influence Kk[n], therefore influence Mk[n/n], Mk[n+1/n], Kk[n+1], MSE [n+1] etc..Minimize the S's [n] of MSE [n]
Given selection for subsequent block n+1, n+2 ... in MSE may be suboptimum.If not reluctant, this
It was found that so as to find global optimal pilot sequence very challenging.
Therefore, the method that the present invention follows is similar to S.Noh et al. " for channel estimation in extensive mimo system
Pilot beam mode designs (Pilot beam pattern design for channel estimation in massive
MIMO systems) " (IEEE J.Sel.Topics Signal Process., volume 8, the 5th phase, the 787-801 pages, 2014
Year October) described in method, and pilot frequency sequence is designed in a manner of serious hope.I.e., it is assumed that S [l] is fixed, change for l < n
Amount S [n] is optimised for minimizing MSE [n].In this case, MSE [n] is only the function of S [n].In addition, observing above
Formula (3), once the space covariance R of user kkMSE matrix M is predicted by minimumk[n/n-1] substitution, so that it may find that it is similar
In formula (1).Therefore, above-mentioned conclusion is also applied for this, and the pilot frequency sequence of user's Kalman filtering is designed and is given above
Description it is similar, it may be assumed that
First, it is assumed that S [l] be for l < n it is fixed, can pass through in Grassmann manifold execute iteration steepest decline
Method come obtain minimize MSE [n] without constrained solution S [n].
Secondly, in order to find solution from the S of approximate S [n] set, the P in second algorithmoptBy Popt[n]=S [n] (S
[n]HS[n])-1S[n]HSubstitution.
Compared with above-mentioned no Kalman filter, pilot frequency sequence here is additionally the function (decline block index) of time
And it is designed to each decline block.
Assuming that updating pilot frequency sequence for each decline block, this may cause bigger expense.However, one is simply replaced
It is to update pilot frequency sequence and send their index 103 in each pth decline block for scheme, wherein p is equal to such as 2 or 5.In full
Shown in word, which is only slightly increased in estimation MSE, and is still substantially better than randomly selected pilot tone sequence
Column.New pilot tone, which is sent, in each time slot whether indexes 103 signals beneficial to the data volume for depending on to be sent by substitution.As one
A simply example, it is assumed that Kalman filtering can reduce required T to realize the given MSE from T=8 to T=6.In addition, allowing
K=8 user receives 16-QAM symbol.Then, there are additional (8-6) * K*4 bit=64 to send data bit, but is used for
The expense for sending 103 signal of pilot sequence index is 6*6=36 bit (assuming that one group of 64 sequence).When final result is each
64-36=28 additional data bits of gap.Therefore, it is still beneficial that the pilot tone of each time slot, which indexes 103 signals,.
It is worth noting that, for the present invention, it is assumed that when BS 100 is equipped with M antenna, covariance matrix R1,…,Rk
It is space covariance matrix, and system model is using specific frequency subband as target.Alternatively, when BS 100 is equipped with individual antenna
When, system model can be using M subband as target.It that case, covariance corresponds to frequency covariance.Finally, it assists
Variance can correspond to Combined Frequency-spatial coherence (multiple BS antennas and multiple sub-band system models).The present invention is suitable for
These any combinations.
It is otherwise noted that in the present invention, lead code pilot frequency format is assumed to be simple form.The present invention is also suitable
For the scattered pilot format with small MSE function adaptability.
Finally, for the sake of simplicity, current invention assumes that decline block models in channel multiple time slots are kept constant.So
And to those skilled in the art, when decline block is not applicable, i.e., when a channel changes, for example, (claiming in LTE in time slot
For symbol time slot) on the basis of, the present invention is obviously equally applicable.
The present invention has combined relevant embodiment to be described as example and realization.However, by attached drawing, originally
The research of disclosure and independent claims, it will be appreciated by those skilled in the art that with other modifications are realized, and can be real
Trample invention claimed.In claims and specification, word " comprising " is not excluded for other elements or step, and
And indefinite article "a" or "an" be not excluded for it is multiple.If what discrete component or other units may be implemented to record in claim
The function of dry entity or project.The fact that describe certain measures in mutually different dependent claims is not offered as these and arranges
The combination applied cannot be used in advantageous embodiment.
Claims (14)
1. one kind is for distributing the base station (BS) (100) of pilot frequency sequence, the BS at least one user equipment (UE) (101)
(100) it is configured as:
It is available from the BS (100) and at least one described UE (101) based on the channel statistical of at least one UE (101)
Pilot frequency sequence set (102) in the multiple pilot frequency sequences of selection, and
The index (101) of each selected pilot frequency sequence is sent at least one described UE (101).
2. BS (100) according to claim 1, the BS (100) is configured as:
The module for minimizing channel estimation errors or maximizing conditional mutual information based at least one UE (101)
To select the pilot frequency sequence.
3. BS (100) according to claim 1 or 2, in which:
Module is designed to directly minimize channel estimation and (CES) mean square error (MSE), or weighting CES MSE, or
CES MSE is minimized indirectly by maximizing the sum of conditional mutual information (SCMI).
4. BS (100) according to claim 3, wherein in order to select the pilot frequency sequence, the BS (100) is configured
Are as follows:
CES MSE or SCMI are determined to combine from the possible pilot frequency sequence of each of the pilot frequency sequence set (102), and
Select the combination for generating minimum CES MSE or maximum SCMI as desired pilot frequency sequence.
5. BS (100) according to claim 3 or 4, wherein in order to select the pilot frequency sequence, the BS (100) is matched
It is set to:
Optimal pilot sequence is found to minimize CES MSE or maximize SCMI, the optimal pilot sequence is not only restricted to come from
The set (102) of the pilot frequency sequence, and
The pilot frequency sequence is found from the pilot frequency sequence set (102), the pilot frequency sequence is the optimal pilot sequence
The subspace opened provides best basis.
6. BS (100) according to any one of claim 3 to 5, wherein in order to select the pilot frequency sequence, the BS
(100) it is configured as:
By will be seen that process is considered as linear programming problem, pilot frequency sequence is found to minimize CES MSE or maximize SCMI.
7. BS (100) according to any one of claim 1 to 6, is configured as, if at least one described UE (101)
Covariance matrix or the set of described at least one UE (101) or UE (101) change:
At least one described pilot frequency sequence is reselected, and the index (103) of each pilot frequency sequence reselected is sent to
At least one described UE (101).
8. BS (100) according to any one of claim 1 to 7, is configured as:
Pilot frequency sequence described in dynamic select, and the index (103) of each selected pilot frequency sequence is dynamically sent to institute
State at least one UE (101).
9. BS (100) according to any one of claim 1 to 8, wherein at least one described UE (101) equipped with
In the case where iteration or Order Statistic Filters, in order to select the pilot frequency sequence, the BS (100) is configured as:
After each predefined time cycle, the pilot frequency sequence preferably is updated to each decline block period, and
And
The index (103) of the pilot frequency sequence each periodically updated is sent at least one described UE (101).
10. BS (100) according to any one of claim 1 to 9, is configured as:
The index (103) of pilot frequency sequence is sent at least one described UE (101) in the specific control channel of UE.
11. a kind of user equipment (UE) (101) for communication system, the UE (101) are configured as:
It is received from base station (BS) (100) and comes from least one UE (101) and the available pilot frequency sequence set of the BS (100)
(102) the corresponding multiple indexes (103) of pilot frequency sequence in,
From the selection pilot frequency sequence in the pilot frequency sequence set (102), the pilot frequency sequence corresponds to the received rope
Draw (103),
Filter is calculated according to the selected pilot frequency sequence, and
Channel estimation is executed based on the calculated filter.
12. UE (101) according to claim 11, is configured as:
Multiple indexes (103) periodically are received from the BS (100), and
Based on the last one received iteration or Order Filtering for indexing (103) corresponding described pilot frequency sequence and calculating given iteration
Device, and
Channel estimation is executed based on the iteration or Order Statistic Filters.
13. a kind of system, including at least one base station (BS) (100) according to any one of claim 1 to 10 and extremely
A few user equipment (UE) (101) according to claim 11 or 12.
14. one kind is for distributing the method (200) of pilot frequency sequence, the method packet at least one user equipment (UE) (101)
It includes:
It is available from base station (100) and at least one described UE (101) based on the channel statistical of at least one UE (101)
(201) multiple described pilot frequency sequences are selected in the set (102) of pilot frequency sequence, and
The index (103) of (202) each selected pilot frequency sequence is sent at least one described UE (101).
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