CN103873197B - The 3D MIMO Limited Feedback overhead reduction methods that spatial coherence is combined with sub-clustering - Google Patents
The 3D MIMO Limited Feedback overhead reduction methods that spatial coherence is combined with sub-clustering Download PDFInfo
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Abstract
The present invention relates to wireless communication technology field, the 3D MIMO Limited Feedback overhead reduction methods that a kind of channel space correlation is combined with sub-clustering are claimed.In 3D MIMO Limited feedback systems, base station end is usedUniform antenna array, user terminal uses linear array, and user terminal has spatial coherence and 2D antennas orthogonals channel phase characteristic altogether, horizontal peacekeeping vertical dimension is carried out feeding back optimal pre-coding matrix index based on channel（PMI）.When each vertical dimension channel has identical horizontal phase, level dimension only feeds back a PMI, sub-clustering is carried out to vertical dimension, each cluster feeds back a PMI, one overhead bit is increased respectively to horizontal peacekeeping vertical dimension PMI during feedback, corresponding vertical dimension and level dimension pre-coding matrix are found in base station, and horizontal peacekeeping vertical dimension pre-coding matrix is extended and point multiplication operation, obtain 3D pre-coding matrixes.This method can be effectively reduced feedback overhead, and complexity is low, be easier to realize.
Description
Technical field
The present invention relates to wireless communication technology field, it is related to mobile communication Long Term Evolution（LTE-Advanced) technology neck
Domain.
Background technology
, it is necessary to next generation's 4G communication systems can provide data rate higher and preferably clothes in wireless mobile communications
Business quality.Set up to improve the companies such as power system capacity and spectrum efficiency, Nuo Xi, A Lang, DOCOMO, high pass and Waduven
ARTIST4G working groups, specialize in advanced wireless interfacing (the Advanced Radio Interface of 4G systems
TechnologIes for4G SysTems, ARTIST4G), wherein, 3D multi-antenna technologies are to improve power system capacity and frequency spectrum effect
The key technology of rate, the depth for causing industry is paid attention to.3D MIMO are compared with traditional 2D MIMO, and 3D MIMO are being tieed up vertically
On increased the one-dimensional dimension for being available for and utilizing, base station end use 2D array antenna structures.So, level dimension is effectively raised
With the spectrum efficiency of vertical dimension.
In 3D MIMO Limited feedback systems, by constructing a transmitting terminal and the known horizontal peacekeeping vertical dimension of receiving terminal
Code book, receiving terminal utilizes horizontal peacekeeping vertical dimension channel condition information（CSI）, according to certain Optimality Criteria pre-designed
Optimal pre-coding matrix is selected in code book, horizontal peacekeeping vertical dimension PMI is then fed back into transmitting terminal respectively, transmitting terminal is according to connecing
The horizontal peacekeeping vertical dimension PMI for receiving, carries out certain calculation process, ultimately forms 3D pre-coding matrixes, here it is 3D MIMO systems
Limited Feedback general principle based on code book in system.
In Limited feedback systems, due to uplink feedback link limited bandwidth, and 3D MIMO increase one-dimensional in dimension vertically
The dimension for utilizing is available for, so, feedback overhead will increased than 2D MIMO, therefore, for how to efficiently reduce 3D
The feedback overhead of MIMO turn into 3D MIMO technologies can commercialization key.
The content of the invention
In view of above-mentioned technical problem, of the invention to propose that a kind of spatial coherence is limited with the 3D MIMO that sub-clustering is combined
Feedback overhead reduction method, as long as in coherence distance, sub-clustering is carried out to vertical dimension channel, so, not only can effectively reduce
Feedback overhead, and performance loss is little.
In space-multipath fading channel, spatial coherence is very big to the performance impact of system, influence spatial coherence
Power mainly has two factors：The size of antenna spacing and angle spread (AS).When angle spread is fixed, antenna spacing is bigger,
Correlation is smaller, and antenna spacing is smaller, then correlation is bigger.Generally, coherence distance D can be usedcBetween to weigh antenna
Correlation, coherence distance typically takes value when coefficient correlation is 0.5, and antenna spacing is less than coherence distance, then it is assumed that between antenna
Correlation, antenna spacing is more than coherence distance, then it is assumed that uncorrelated between antenna.Therefore, 3D can be improved using spatial coherence
The spectrum efficiency of mimo system.
The 3D MIMO Limited Feedback overhead reduction methods that a kind of spatial coherence is combined with sub-clustering, it mainly realizes step
It is rapid as follows：
Step 1：Base station end uses N*M aerial arrays, receiving terminal to use even linear array, and the level to 3D MIMO is tieed up respectively
Fed back with vertical dimension.Because vertical dimension channel has identical horizontal phase, therefore, level tie up channel according to signal to noise ratio most
Bigization criterion, optimal pre-coding matrix during level dimension selection maximum signal to noise ratio, records corresponding optimal pre-coding matrix
Index PMI（Level ties up PMI）；
Step 2：Vertical dimension channel is carried out into sub-clustering in coherence distance, each cluster hangs down according to minimum bit-error rate criterion
Optimal pre-coding matrix when one bit error rate of straight dimension selection is minimum, records corresponding optimal pre-coding matrix index PMI（Vertically
Dimension PMI）；
Step 3：One overhead bit is increased respectively to level dimension PMI and vertical dimension PMI, and is fed back to base station end；
Step 4：The PMI that base station end is fed back according to horizontal peacekeeping vertical dimension, recovers the horizontal optimal precoding of peacekeeping vertical dimension
Matrix, and then it is extended respectively, the matrix after extension is then used into point multiplication operation, obtain 3D pre-coding matrixes；
Vertical dimension and the level dimension of 3D MIMO use independent Limited Feedback mechanism.When PMI is fed back, it is necessary to increase
Overhead bit, is tieed up with distinguishing vertical dimension and level.Base station end according to receiving horizontal peacekeeping vertical dimension PMI, by decoding,
Corresponding horizontal peacekeeping vertical dimension pre-coding matrix is found out in codebook set, and is extended.
According to formula：Select k-th cluster of vertical dimension channel
Optimal pre-coding matrix, whereinRepresent i-th vertical dimension channel information, Ω={ w1,w2,...ws...wSRepresent code book
Set, p represents transmitting antenna general power, N0Represent noise power.Increase bit 0 before level dimension PMI, be fed back to base station
End.M vertical dimension channel is divided into cluster, bit 1 is increased before vertical dimension PMI, be fed back to base station end.When base station end is adopted
With the aerial array of 8*8, using 2 antennas, the coherence distance of base station end is 2.2 λ to receiving terminal, can be by 4 vertical dimension channels point
It is a cluster.
In traditional mimo system, precoding technique ties up direction just for level, and present invention comprehensive utilization electromagnetic wave exists
Channel information in horizontal direction and in vertical direction.So, can be lifted using the gain of horizontal peacekeeping vertical dimension simultaneously and be
System effectiveness.On vertical dimension direction, due to antenna spacing it is smaller when, between channel response have stronger correlation, therefore this
Invention proposes the 3D MIMO Limited Feedback overhead reduction methods that a kind of spatial coherence is combined with sub-clustering, in coherence distance,
Sub-clustering is carried out to vertical dimension channel, then each cluster feeds back a PMI, can so be effectively reduced feedback overhead.
Brief description of the drawings
Fig. 1 3D MIMO of the present invention are based on the limited feedback method system block diagram of code book；
Fig. 2 Limited Feedback overhead reduction method schematic diagrames of the present invention；
Base station end spatial coherence emulation under the NLOS environment of Fig. 3 present invention interior；
Fig. 4 number of bits of feedback comparison diagrams of the invention；
Fig. 5 simulation comparison diagrams of the invention.
Specific embodiment
In 3D mimo system Limited Feedback schemes, the horizontal optimal precoding index of each self feed back of peacekeeping vertical dimension, base station
The index according to feedback is held, from codebook set Ω={ w1,w2,...ws...wSIn find corresponding optimal pre-coding matrix,
By extension and dot product, 3D pre-coding matrixes are obtained, so can effectively reduce overhead.
Fig. 1 show the limited feedback method system block diagram that 3D MIMO proposed by the present invention are based on code book.Assuming that base station end
Using N*M array antennas, wherein N represents the line number of aerial array, and M represents the columns of aerial array, and receiving terminal antenna number is Nr,
The data flow of input maps by QPSK modulation and layer, is divided into L parallel subflow x, for convenience of calculation, it will be assumed that L=
1.Then L parallel subflow is matched on base station end array antenna and is sent by precoding.Output signal can table
It is shown as：
Wherein GZFSqueeze theorem matrix is represented, p represents transmitting antenna general power, and H represents 3D channel matrixes, W3DRepresent phase
The 3D pre-coding matrixes answered, x represents parallel data flow, n0It is zero to obey average, and variance is N0Additive white Gaussian noise.
Receiving terminal carries out estimating to obtain channel information H to channel：
Further, H is decomposed, obtains j-th level dimension channel information：
With i-th vertical dimension channel information：
After receiving terminal receives signal, using squeeze theorem algorithm, the corresponding squeeze theorem matrix of a linear transformation is：
Corresponding received signal to noise ratio is represented by：
In Limited feedback systems, include S code word { w in codebook set Ω altogether1,w2,...ws...wS, receiving terminal
Criterion is maximized using signal to noise ratio according to horizontal Vc SI optimal pre-coding matrix is chosen in codebook set, according to vertical dimension
CSI utilizes minimum bit-error rate criterion, and each cluster chooses optimal pre-coding matrix from codebook set, then horizontal peacekeeping is hung down
The PMI of straight dimension is extensive by feeding back to base station end, the PMI that base station end is fed back according to horizontal peacekeeping vertical dimension after additional overhead bit
The flat optimal pre-coding matrix of peacekeeping vertical dimension of rehydration, and then it is extended respectively, then the matrix after extension is used a little
Multiplication, obtains 3D pre-coding matrixes W3D。
Limited Feedback overhead reduction method schematic diagram proposed by the present invention is illustrated in figure 2, it is comprised the following steps that：
(1) according to horizontal Vc SI, in codebook set Ω={ w1,w2,...ws...wSIn search to meet signal to noise ratio maximum
The optimal pre-coding matrix w for changingh,
WhereinRepresent the individual level dimension channel information of jth (j=1,2...N).
(2) sub-clustering is carried out to vertical dimension channel according to spatial coherence, in coherence distance, channel has compared with strong correlation
Property, therefore, according to spatial coherence, m vertical dimension channel is divided into cluster, m values are bigger, then the expense fed back is smaller, but generation
Valency is systemic loss of energy, and m values are smaller, then systematic function is better, but cost is that feedback overhead increases, thus sub-clustering when
Wait, to be compromised therebetween.
(3) optimal pre-coding matrix is chosen to k-th cluster of vertical dimension channel according to minimum bit-error rate criterion：
Wherein,Represent i-th vertical dimension channel information, Ω={ w1,w2,...ws...wSRepresent codebook set, p tables
Show transmitting antenna general power, N0Noise power is represented, m is vertical dimension channel number in every family.
(4) overhead bit is increased respectively to level dimension PMI and vertical dimension PMI, and is fed back to base station end, such as
Increase bit 0 before level dimension PMI, bit 1 is increased before vertical dimension PMI.
(5) PMI that base station end is fed back according to horizontal peacekeeping vertical dimension, recovers the horizontal optimal precoding square of peacekeeping vertical dimension
Battle array, and then it is extended respectively：Wh=[wh;wh;...wh](N*M)*L.Wherein, whExpression level ties up pre-coding matrix.Vertically
Dimension pre-coding matrix can be extended to following form according to the channel information number included in cluster, be wrapped in vertical dimension pre-coding matrix
Pre-coding matrix number containing each race equal with vertical dimension channel number m in every family.I.e.：
As m=2：
As m=4：
Wherein, WvVertical dimension pre-coding matrix is represented,The 1st pre-coding matrix of cluster of vertical dimension is represented,Represent and hang down
The 2nd pre-coding matrix of cluster is directly tieed up,The M/2 pre-coding matrix of cluster of vertical dimension is represented,Represent vertical dimension M/
4 pre-coding matrixes of cluster, L is the subflow number of input data.
(5) by extension after the horizontal optimal pre-coding matrix of peacekeeping vertical dimension use point multiplication operation, obtain 3D precoding squares
Battle array：W3D=Wh.*Wv
Fig. 3 show spatial coherence emulation under NLOS environment indoors of the invention.For ease of analysis antenna spacing to sky
Between correlation influence, angle spread is set to definite value, i.e., AS=5 ° in the present invention, and the day of base station end and receiving terminal is assumed during emulation
Line spacing is all 0.5 λ, and base station end uses 2 reception antennas using the aerial array of 8*8 in receiving terminal.Base station end is not on the same day
Normalization spatial coherence between line is expressed as：
Wherein, ρ representation spaces correlation, Δ d represents the vertical dimension antenna spacing of base station end, Δ dnRepresent the water of base station end
Flat dimension antenna spacing, Δ duThe antenna spacing of receiving terminal is represented, τ represents the time delay between different antennae,WithPoint
Not Biao Shi two channel responses of antenna of receiving terminal, σ represents the standard deviation of channel response.By figure it will be seen that base station end
Coherence distance be about 2.2 λ.Therefore, it can 4 vertical dimension channels to be divided into a cluster, i.e., it is optimal to take m≤4.
Fig. 4 show number of bits of feedback comparison diagram of the invention, wherein feedback frame number is 100.As can be seen from Figure, relevant
In distance, feedback overhead when taking m=4 and during m=2 is all fewer than the feedback overhead of vertical dimension ideal feedback a lot, meanwhile, m=4
When feedback overhead again than m=2 when it is few, so, in coherence distance, m values are bigger, feedback overhead just it is smaller.
Fig. 5 show simulation comparison diagram of the invention.As seen from the figure, m values are smaller, and bit error rate performance is got over
Close to vertical dimension ideal unity feedback.As m=4, the slightly inferior properties of the bit error rate are when m=2 but figure 4, it can be seen that corresponding
Feedback overhead but significantly declines, although performance is lost.In for practical application, because uplink feedback link bandwidth has
Limit, so this performance loss is worth.The present invention proposes the 3D MIMO that a kind of channel space correlation is combined with sub-clustering
Limited Feedback overhead reduction method, the method can be effectively reduced feedback overhead, and complexity is low, be easier to realize.
Claims (6)
1. the 3D MIMO Limited Feedback overhead reduction methods that a kind of spatial coherence is combined with sub-clustering, it is characterised in that including
Step：Base station end uses N*M aerial arrays, receiving terminal to use even linear array, and the horizontal peacekeeping vertical dimension to 3D MIMO is entered respectively
Row feedback；Level when selection signal to noise ratio is maximum ties up optimal pre-coding matrix, records corresponding level dimension PMI；Relevant
In distance, vertical dimension channel is carried out into sub-clustering, optimal pre-coding matrix is selected according to minimum bit-error rate criterion in each cluster,
Record corresponding vertical dimension PMI；One overhead bit is increased respectively to level dimension PMI and vertical dimension PMI, and is fed back to base
Stand end；Base station end recovers the horizontal optimal pre-coding matrix of peacekeeping vertical dimension, respectively according to the horizontal peacekeeping vertical dimension PMI of feedback
Point multiplication operation is carried out after being extended to it, 3D pre-coding matrixes are obtained.
2. method according to claim 1, it is characterised in that in level dimension, according to formula：In codebook set Ω={ w1,w2,...ws...wSIn search to meet signal to noise ratio maximized
Optimal pre-coding matrix wh, wherein,Represent the individual level dimension channel information of jth (j=1,2...N).
3. method according to claim 1, it is characterised in that optimal precoding square is selected according to minimum bit-error rate criterion
Battle array is specially：According to formula：K-th of selection vertical dimension channel
The optimal pre-coding matrix of cluster；Wherein,I-th vertical dimension channel information is represented, p represents transmitting antenna general power, N0Represent
Noise power, m is vertical dimension channel number, Ω={ w in every cluster1,w2,...ws...wSRepresent codebook set.
4. method according to claim 1, it is characterised in that level dimension PMI and vertical dimension PMI is increased respectively one it is auxiliary
Bit is helped to be specially：Increase bit 0 before level dimension PMI, m vertical dimension channel is divided into cluster, increase before vertical dimension PMI
Bit 1.
5. method according to claim 1, it is characterised in that enter to the horizontal optimal pre-coding matrix of peacekeeping vertical dimension respectively
Row extension is specifically included：According to formula Wh=[wh；wh；...wh](N*M)*LOptimal pre-coding matrix is tieed up to level to be extended, its
In, whExpression level ties up pre-coding matrix；Vertical dimension pre-coding matrix is：As m=2：As m=4：
Wherein, L represents parallel substreams number；WvVertical dimension pre-coding matrix is represented,Represent the 1st precoding square of cluster of vertical dimension
Battle array,The 2nd pre-coding matrix of cluster of vertical dimension is represented,The M/2 pre-coding matrix of cluster of vertical dimension is represented,Table
Show the M/4 pre-coding matrix of cluster of vertical dimension, m is vertical dimension channel number in every cluster.
6. method according to claim 3, it is characterised in that when base station end is using the aerial array of 8*8, receiving terminal is used
4 vertical dimension channels when the coherence distance of base station end is 2.2 λ, are divided into a cluster by 2 antennas.
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| CN104243008B (en) * | 2014-09-29 | 2018-03-06 | 中国联合网络通信集团有限公司 | A kind of method and apparatus of Limited Feedback information |
| CN107078778B (en) * | 2014-11-06 | 2021-01-15 | 上海诺基亚贝尔股份有限公司 | Method, device and system for transmitting antenna port configuration information |
| CN106470061B (en) * | 2015-08-14 | 2019-09-17 | 电信科学技术研究院 | Feedback method, device and the terminal of information |
| WO2017054192A1 (en) * | 2015-09-30 | 2017-04-06 | 华为技术有限公司 | Communication method and apparatus based on codebook feedback |
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| CN102412885A (en) * | 2011-11-25 | 2012-04-11 | 西安电子科技大学 | Three-dimensional wave beam forming method in long term evolution (LET) |
| CN103152140A (en) * | 2013-03-05 | 2013-06-12 | 东南大学 | Limiting feedback method of three-dimensional multi-user MIMO (multiple input multiple output) based on direct-product code books |
| WO2013144361A1 (en) * | 2012-03-30 | 2013-10-03 | Nokia Siemens Networks Oy | Feedback methodology for per-user elevation mimo |
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| CN102412885A (en) * | 2011-11-25 | 2012-04-11 | 西安电子科技大学 | Three-dimensional wave beam forming method in long term evolution (LET) |
| WO2013144361A1 (en) * | 2012-03-30 | 2013-10-03 | Nokia Siemens Networks Oy | Feedback methodology for per-user elevation mimo |
| CN103152140A (en) * | 2013-03-05 | 2013-06-12 | 东南大学 | Limiting feedback method of three-dimensional multi-user MIMO (multiple input multiple output) based on direct-product code books |
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