CN106031266A - Low-complexity multi-cell downlink coherent joint transmission method and device - Google Patents

Low-complexity multi-cell downlink coherent joint transmission method and device Download PDF

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CN106031266A
CN106031266A CN201480075999.4A CN201480075999A CN106031266A CN 106031266 A CN106031266 A CN 106031266A CN 201480075999 A CN201480075999 A CN 201480075999A CN 106031266 A CN106031266 A CN 106031266A
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base station
cell
user equipment
information
channel condition
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CN106031266B (en
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孙欢
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Nokia Shanghai Bell Co Ltd
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Alcatel Lucent Shanghai Bell Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L23/00—Apparatus or local circuits for systems other than those covered by groups H04L15/00 - H04L21/00
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/50—Allocation or scheduling criteria for wireless resources
    • H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria

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Abstract

Provided are a low-complexity multi-cell downlink coherent joint transmission method and device, the method comprising the steps of: conducting joint design on a precode according to the scheduling authorization information and channel status information from a first base station and a second base station to obtain a precoding matrix; the joint design of the precoding matrix of the UE takes into consideration the possible interference of the precoding matrix on downlink transmission of other user equipments (UEs) in the matrix; the scheduling authorization information is obtained by conducting independent distributed scheduling on the UEs in a cell of the base station, without considering the scheduling authorization information of the UEs in a cell neighboring the cell of the base station. The plan in the present invention decreases the calculation complexity of an original coherent joint transmission plan while maintaining the average performance gain of a cell, and is insensitive to the cluster scale, thus being easy to be implemented in practical networks.

Description

Low-complexity multi-cell downlink coherent joint transmission method and device
The method and apparatus technical field of the relevant joint transmission of the multi-cell downlink of low complex degree
The present invention is generally related to wireless communication field, more specifically, is related to the method and apparatus of the relevant joint transmission of multi-cell downlink of low complex degree.Background technology
One of key technology as LTE-A, 3GPP standardization bodies extensively study collaboration multicast communication (Co-ordinated Multi-Point:CoMP technology).In numerous CoMP schemes, the joint transmission that is concerned with scheme（ Coherent Joint Transmission:CJT the gain of maximum coordinate multipoint) is shown in cell average behavior and cell-edge performance.However, because current CJT schemes are using joint multi-cell scheduling and joint transmitting Precoding Design, its complexity is significantly increased with the increase of CoMP cluster scales, and this turns into the significant challenge for implementing CJT in systems in practice.The content of the invention
For problem above, in order to reduce the computation complexity of original CJT schemes, a kind of method and apparatus for the joint transmission that is concerned with the invention provides multi-cell downlink of low complex degree.
A kind of method for the joint transmission that is concerned with according to the first aspect of the invention there is provided multi-cell downlink of low complex degree, including the following steps performed by the central node of base station cluster：I. receive and come from the first base station in the cluster of base station and the scheduling authorization information and channel condition information of the second base station；Ii. carry out co-design to precoding to obtain pre-coding matrix according to the scheduling authorization information and the channel condition information that come from the first base station and second base station；And the precoding information of the user equipment of the first base station in the pre-coding matrix is sent to the first base station by iii., the precoding information of the user equipment of second base station in the pre-coding matrix is sent to second base station；Wherein described first base station and second base station belong to the base station cluster, and the cell of the cell of the first base station and second base station is adjacent.
According to one embodiment of present invention, the co-design is designing the user equipment The pre-coding matrix when, it is considered to the interference that the pre-coding matrix is likely to result in the downlink transfer of other user equipmenies in matrix.
According to one embodiment of present invention, in addition to the first base station business datum of the business datum of the user equipment of the second base station of institute and/or the user equipment to second base station transmission first base station is sent.
According to one embodiment of present invention, the scheduling authorization information is carried out independent distributed scheduling by the user equipment of the cell to the base station and obtained, and the independent distributed scheduling does not consider the scheduling authorization information of the user equipment of the neighbor cell of the cell of the base station.
According to one embodiment of present invention, the channel condition information includes the channel condition information of the user equipment of the neighbor cell of the channel condition information of the user equipment of the cell of the base station and the cell of the base station.
A kind of method for the joint transmission that is concerned with according to the second aspect of the invention there is provided multi-cell downlink of low complex degree, including the following steps performed by the base station in the cluster of base station：I send the scheduling authorization information of the user equipment of the cell of the base station to central node；Ii. the precoding information of the user equipment of the cell for the base station for coming from the central node is received；And iii. carries out descending joint transmission according to the precoding information and the scheduling authorization information to the business datum of the user equipment of the base station.
According to one embodiment of present invention, the scheduling authorization information is carried out independent distributed scheduling by the user equipment of the cell to the base station and obtained, and the independent distributed scheduling does not consider the scheduling authorization information of the user equipment of the neighbor cell of the cell of the base station.
According to one embodiment of present invention, also include the configuration information that the user equipment of the base station is shared with the base station of the neighbor cell of the cell of the base station in the base station cluster, the configuration information is used for the channel condition information for causing the user equipment of base station described in the base station monitors of the neighbor cell.
According to one embodiment of present invention, also include sending channel condition information to the central node, the channel condition information includes the channel condition information of the channel condition information of the user equipment of the cell of the base station and the user equipment of the cell neighbor cell of the base station. According to one embodiment of present invention, in addition to receive the base station for coming from the central node cell neighbor cell user equipment business datum to carry out descending joint transmission.
A kind of central node for the joint transmission that is concerned with according to the third aspect of the present invention there is provided multi-cell downlink for low complex degree, it includes：Receiving unit, it is used for the scheduling authorization information and channel condition information that receive the first base station and the second base station that come from the cluster of base station, wherein described first base station and second base station belong to the base station cluster, and the cell of the cell of the first base station and second base station is adjacent；Joint precoding unit, it is used to carry out co-design to precoding to obtain pre-coding matrix according to the scheduling authorization information and the channel condition information that come from the first base station and second base station；First transmitter unit, it is used to the precoding information of the user equipment of the first base station in the pre-coding matrix being sent to the first base station, and the precoding information of the user equipment of second base station in the pre-coding matrix is sent into second base station；And second transmitter unit, its be used for the first base station send second base station user equipment business datum and/or send to second base station first base station user equipment business number Ju.
According to one embodiment of present invention, the co-design is when designing the pre-coding matrix of the user equipment, it is considered to the interference that the pre-coding matrix is likely to result in the downlink transfer of other user equipmenies in matrix.
According to one embodiment of present invention, the scheduling authorization information is carried out independent distributed scheduling by the user equipment of the cell to the base station and obtained, and the independent distributed scheduling does not consider the scheduling authorization information of the user equipment of the neighbor cell of the cell of the base station.
According to one embodiment of present invention, the channel condition information includes the channel condition information of the user equipment of the neighbor cell of the channel condition information of the user equipment of the cell of the base station and the cell of the base station.
A kind of base station for the joint transmission that is concerned with according to the fourth aspect of the present invention there is provided multi-cell downlink for low complex degree, it includes：First transmitter unit, it is used for the scheduling authorization information that the user equipment of the cell of the base station is sent to central node；Shared cell, It is used for the configuration information that the user equipment of the base station is shared with the base station of the neighbor cell of the cell of the base station in the cluster of base station, the configuration information be used to causing it is described it is adjacent ' J, the channel condition information of the user equipment of base station described in the base station monitors in area, the base station of the neighbor cell of the cell of the base station and the base station belongs to the base station cluster；Second transmitter unit, it is used to send channel condition information to the central node；The channel condition information includes the channel condition information of the channel condition information of the user equipment of the cell of the base station and the user equipment of the cell neighbor cell of the base station；First receiving unit, it is used for the precoding information for receiving the user equipment of the cell for the base station for coming from the central node；Second receiving unit, it is used to receive the business datum of the user equipment of the neighbor cell of the cell for the base station for coming from the central node to carry out descending joint transmission；And the 3rd transmitter unit, it is used to carry out descending joint transmission to the business datum of the user equipment of the base station according to the precoding information and the scheduling authorization information.
According to one embodiment of present invention, the scheduling authorization information is carried out independent distributed scheduling by the user equipment of the cell to the base station and obtained, and the independent distributed scheduling does not consider the scheduling authorization information of the user equipment of the neighbor cell of the cell of the base station.
In order to reduce the computation complexity of original CJT schemes, new CJT schemes include the design of distributed scheduling and joint transmission precoder.The characteristics of this scheme is：
1. distributed scheduling is insensitive to CoMP cluster scales, and this make it that the computation complexity of proposed scheme is low and is easy to realize in real network.
2. distributed scheduling does not reduce CoMP cell average performance gain.By comparing combined dispatching and distributed scheduling, it has been found that their common ground are, although employ the PF- factors to ensure the fairness of scheduling, but still there is higher dispatching priority positioned at the user equipment of center of housing estate.In addition, the user equipment positioned at center of housing estate has high received signal to noise ratio due to it, thus it is suitable for multi-user's multiple-input and multiple-output（ Multi-User Multi-Input Multi-Output:MU-MIMO) transmit to obtain higher spatial multiplex gains.This shows that distributed scheduling and combined dispatching scheme can realize almost identical cell average behavior.
3. the loss that causes of the distributed scheduling to cell-edge performance is small.Joint is adjusted The Cell Edge User scheduling that schemes synthesis considers neighbor cell is spent, and distributed scheduling scheme only considered this Cell Edge User.This shows that scheduling of the distributed scheduling scheme to the Cell Edge User in cluster is suboptimum, is compared with combined dispatching scheme, and this can cause certain performance loss in cell edge, but performance loss is very small.Brief description of the drawings
After the description below with reference to the embodiment of the invention given by drawings below, the present invention is better understood with, and other objects of the present invention, details, feature and advantage will become apparent.In the accompanying drawings：
Fig. 1 shows the schematic diagram of multiple cell CoMP system model；
Fig. 2 shows the schematic diagram of the relevant joint transmission of low complex degree；
Fig. 3 shows the schematic diagram of the relevant joint Precoding Design of low complex degree；
Fig. 4 shows the flow chart of the relevant joint transmission of low complex degree；
Fig. 5 shows another flow chart of the relevant joint transmission of low complex degree；
Fig. 6 shows the schematic diagram of the relevant joint transmission performance of low complex degree in multiple cell 3GPP Casel-3D scenes；And
Fig. 7 shows the schematic diagram of relevant joint transmission ' the 1 life energy of the low complex degree in multiple cell ITU- UMI scenes；Embodiment
In the specific descriptions of following preferred embodiment, by the accompanying drawing with reference to appended by constituting a present invention part.Appended accompanying drawing, which has been illustrated by way of example, can realize specific embodiment.The embodiment of example is not intended as all embodiments of the limit according to the present invention.It is appreciated that without departing from the scope of the present invention, it is possible to use other embodiment, structural or logicality modification can also be carried out.Therefore, following specific descriptions and nonrestrictive, and the scope of the present invention is defined by the claims appended hereto.It should be noted that, although the step of describing method in the present invention in accompanying drawing with particular order, but this does not require that or implied must perform these operations according to the particular order, or the operation having to carry out shown in whole could realize desired result, on the contrary, herein Described step amidine can change execution sequence.Additionally or alternatively, it is convenient to omit some steps, multiple steps are merged into a step execution, and/or a step is decomposed into dimension execution of multiple steps.
In order to preferably describe the solution of the present invention, by the way that to CoMP system models, the joint transmission of phase thousand, low complex degree is concerned with four parts of joint transmission and system performance analysis to describe the preferred embodiments of the present invention.
CoMP system model
The concept of CoMP systems is introduced first, and original CJT (ORi-CJT) scheme is analyzed according to these concepts.On the basis of analysis ORI-CJT, the CJT schemes of performance gain are obtained with low complex degree and had.
It is contemplated that the cellular network that cell sum is L, and each cell has individual user equipment.Each base station in each cell has M antenna, and each user equipment has V antenna.HMatrix represents the link between the i-th user equipmenies and k-th cell base stations of jth-th cells, and vector representation is from k-th base stations to the transmitting precoding vectors of the i-th user equipmenies of j-th cells.J'-th cells '-user equipment received signal can use formula（1) it is expressed as (1) Wherein represent ' the transmission data vector of-cell to its Ζ-user equipment；White Gauss noise of the vector representation in intra-cell users equipment receiving terminal.One balanced device or receiver are referred to as matrix w,, it is used to compression inter-cell interference and noise（Interference
Plus Noise: IPN ) .The Signal to Interference plus Noise Ratio received（Signal and Interference phis Noise Ratio：SINR) it is represented by
Formula（2) indicate that three factors influence received SINR, first is multi-user installation interference（ Multi-User Interference:), MUI second is inter-cell interference (Inter-Cell Interference:), ICI last is receiving matrix.In time division multiplexing (Time Division Duplex:TDD) in system by using high precision channel condition information (Channel State Information:), CSI MUI can be launched precoder and effectively compress；Using the design for the cluster that cooperates, CJT schemes can be used to part ICI being converted into effective transmission channel.In a tdd system, in central node（ Central Node:CN preferable CSI and cluster scale is given in), the SNIR after reception processing can be expressed as
Si = 。 (3)
Ssidd atlCl are from formula（3) as can be seen that being continuously increased with cluster scale, efficient channel gain is dramatically increased, remaining ICI diminishes；When cluster scale for c=when, remaining ICI disappears.This shows that cluster scale is bigger, and the performance gain obtained by CJT schemes is higher.
The effect of receiving matrix is compressed IP N and improves effective channel gain.In order to reduce the cost and complexity of terminal, linear receiver is more favourable, and has been extensively studied.In order to meet 3GPP emulation it is assumed that it is assumed that disturbing ^ Φ using least mean-square error thousand in a user device merges (Minimum Mean Square Error- Interference Rejection Combining:MMSE-IRC) receiver, it is represented by w,7 = χ (R;7 + KJ' + Kl + ΙΣ1- Γ, (4) wherein R;J,R;Be represented by k , k
Two Ζ ^^', Fig. 1 shows a typical multiple cell CoMP system model, and a cluster is made up of three cells.The base station of each cell is connected to central node by back haul link.Using back haul link, its CSI between user equipment is collected in the base station of each cell, then sends CSI and related data to CN.After all CSI of acquisition and data message, CN carries out multi-user installation scheduling and the design of transmitting pre-encoding matrix first.Then, each base stations of the CN into cluster sends scheduling authorization information, sends the information of precoding and the data of user equipment.Relevant joint transmission
In this section, we be absorbed in given cluster scale for L, CoMP clusters relevant joint transmission.To simplify formula expression, it will be assumed that i-th user equipmenies have a unique numbering Jc in cooperation set in j-th cells, its calculation formula is=ι) κ+And ^ E { 1S2,- , Z^} .For downlink data transmission-the CoMP channels of/ζ user equipmenies can be write as
=[« .,!¾,..., ] (6)
Wherein H " represents the link between fc- party A-subscriber's equipment and cell in CoMP clusters.In following discussion and analysis, it will be assumed that all user equipmenies at every moment have data to be transmitted in Xi System.In systems in practice, these do not have the user equipment of data transfer to forgive the deletion from candidate user devices group.
A) backhaul link capacity is analyzed
In CJT schemes, its CSI associated with user equipment is shared by each cell CN cascades the descending CoMP channel condition informations of user equipment（Using the channel reciprocity of TDD system, descending channel information is obtained using up channel measurement）, and carry out multi-subscriber dispatching and other related CoMP operations using these CoMP channel condition informations.Assuming that the cluster scale of given cooperative multipoint transmission is has individual user equipment in A and each cell, the CSI of all individual user equipmenies associated with its is collected in the base station of j-th cells, and the CSI set can be expressed as
Η/'=Ι, --,. (7)
Then the base station of j-th cells quantifies these channel matrixes, and it is sent into CN by back haul link.For wide-band communication system, whole bandwidth is divided into N non-frequency-selective transmission resource block.It is in units of resource block this means base station obtains all related channels.In order to ensure CSI accuracy, each freedom/2 bit of real part and Virtual portions of a channel coefficients is quantified.If channel interaction cycle is T-(unit is subframe duration）, then the lower limit of backhaul link capacity can be expressed as
_NPRBxL]xKxMxNxbII„a
One ~ °, ^
Formula（8) represent that backhaul link capacity and cluster scale are directly proportional.In LTE TDD systems, formula（8) representative value of the parameter in is respectively（M, iV)=(8,2), NpRB=100 and T periodic=lms0
If the real part of Channel Elements and Virtual portions are quantified by 8 bits respectively, then bilHa=\e .We assume that each cell has κ=ι ο user equipmenies, then
CMlia!ll(Ll) = 256 Ll(Mbps) .This result shows that the capacity to back haul link is caused more challenges by larger cluster scale.
B scheduling unit analysis of complexity
In CJT schemes, multiple cells constitute a super cell to carry out descending multi-user transmission.Utilize formula（6) design that the CoMP CSI shown in carry out joint multiple cell multi-subscriber dispatching and transfer pre-coding is feasible.Many is used for the existing side for designing single cell transmission Case can be directly extended to super cell.The algorithm of some low complex degrees, such as multi-user features mould are transmitted（ Multi-user Eigen Mode Selection:MES) method and enhanced multi-user character modules transmission (Enhanced MES:EMES) algorithm.In MES algorithms, using the singular value decomposition of channel matrix, the maximum characteristic sub-channel of channel is obtained, and the scheduling of user equipment and the design of pre-coding matrix are participated in using these characteristic sub-channels；In EMES algorithms, main characteristic sub-channel is to carry out singular value decomposition acquisition by the projection matrix to channel, and carries out multi-subscriber dispatching and Precoding Design using it.As EMES algorithms are almost with MES complexity.If computation complexity is in units of complex operation, when number of user equipment ^ is very big, the complexity of two kinds of algorithms is about O (^M3N) 。
The result of this complicated dynamic behaviour show scheduling unit complexity and)4It is proportional.Such as definition in the 3 gpp specifications, cluster scale is 3 in CoMP scenes I, and cluster scale is 9 in scene II.Even less cluster scale, compared with single cell base station scheduling unit complexity, Ori-CJT causes computation complexity to add about 80 times.Such computation complexity serious challenge CN disposal ability.Low complex degree CJT schemes
Description more than, presence two of the CJT schemes to existing network is challenged greatly：The complexity of scheduling unit and the capacity of back haul link.In order to reduce the complexity of scheduling unit and mitigate back haul link burden, the present invention proposes a kind of CJT of low complex degree (LC-CJT) scheme.Fig. 2 shows the relevant joint transmission schematic diagram of low complex degree.In LC-CJT, each cell first in COMP clusters by the way of independent distributed scheduling；Secondly, the CSI and data of scheduled user's equipment are sent to CN;Then, CN performs connection and each base station of the Precoding Design to obtain pre-coding matrix and be separately sent to the precoding information and customer equipment data in pre-coding matrix in CoMP clusters.
A) LC-CJT Solution Embodiments
Just blunt according to one embodiment of the present of invention, such as Fig. 3 is shown, it is assumed that have two cells to carry out CoMP at present, the antenna number of each base station end is M, and the number of antennas at each user equipment end is N.The cell of base station 11 and the cell of base station 21 constitute the cluster for the CoMP that a cluster scale is 2.Although in order to describe for the sake of simplicity, Fig. 3 merely illustrates two cells and every The scene of individual one user of cell, it will be apparent to those skilled in the art that it is appreciated that present invention may apply to multiple cell and the scene of multi-user.Central node in Fig. 3 can be located in any one suitable NE in Tong Xin Wang Network, or be used as an independent NE.For example, central node can be located at mobile management entity (Mobility Management Entity:MME in), it can also be located in any one base station in cluster.Fig. 4 shows a flow chart according to the present invention program.
In step S401, the user equipment 12 of the 11 pairs of cells 10 in base station in CoMP clusters carries out independent distributed scheduling and to the scheduling authorization of user equipment 12.When carrying out independent distributed scheduling in base station 11, base station 11 does not consider the schedule information of the user equipment 22 of neighbor cell 20.Same method, base station 21 carries out independent distributed scheduling to the user equipment 22 of cell 20 and to the scheduling authorization of user equipment 22.
In step S402, base station 11 sends the scheduling authorization information of user equipment 12 to central node 30, and the scheduling authorization that base station 21 sends user equipment 22 to central node 30 believes white
In step S403, respective configuration information is shared in base station 11 and base station 21, and the configuration information is used for the channel condition information H for causing the user equipment 12 of the monitoring base station 11 of base station 2112And the channel condition information H of the user equipment 22 of the monitoring base station 21 of base station 1121.In LTE systems, configuration information can be detection reference signal（SRS configuration information) also can be just other any suitable reference signals.
In step s 404, respective scheduling authorization information is shared in the base station in a small bundle of straw, etc. for silkworms to spin cocoons on group, namely base station 11 sends the scheduling authorization information of base station 11 to base station 21, and the base station of base station 21 sends the scheduling authorization information of base station 11.
In step S405, base station 11 obtains the channel condition information ^ of user equipment 12 and the channel condition information H of user equipment 22 according to configuration information and scheduling authorization information respectively21, and by H, and H21It is sent to central node 30.According to configuration information, common bluebeard takes the channel condition information H of user equipment 22 respectively for base station 2112With the channel condition information of user equipment 12
H22, and by 11,2With 1122It is sent to central node 30.
In step S406, base station 11 is to the business datum of the transmission user equipment 12 of central node 30 to central node 30, and user equipment 22 is transmitted in base station 21 to central node 30 Business datum is to central node 30.
In step S 407, central node 30 carries out co-design to obtain pre-coding matrix according to the scheduling authorization information and channel condition information that come from base station 11 and base station 21 to precoding.
First, central node synthesizes downlink channel transmission information to user equipment 12 and user equipment 22 respectively！!, Η ^Ϊ^,Ϊ^]^。
Then, following joint Precoding Design is carried out to user equipment 12：
1) the projection matrix F of the channel matrix kernel of user equipment 22 is looked for, wherein ^ can be by F ,=I-(H2H2 FF Η2Calculate；
2) projection of the channel of user equipment 12 is calculated, using projection matrix, fi can be expressed as fi^ ^F,!^；
3) Calculate the singular value decomposition of the equivalent channel of user equipment 12；
4) pre-coding matrix of user equipment 12 can be expressed as 1；= ¼(:, 1 ^), wherein
V, (:,1：K) representing matrix V, former row, if user equipment 12 has v (v≤N) individual data flow, can select
5) dimension of the precoding of user equipment 12 is 2 Μ>, may also indicate that Wherein（Tu) ^ is used for base station1The downlink data of 1 transmission user equipment 12,（τ12)Λ^ is used for the downlink service data that user equipment 12 is transmitted in base station 21.
Due to 11^=0, therefore pre-coding matrix τ is utilized, when being the transmission downlink service data of user equipment 12, effectively inhibit influence of the downlink service data of user equipment 12 to user equipment 22.The pre-coding matrix of user equipment 22 can be designed with similar method.
In step S40S, central node 30 will (Tg^ be sent to base station 11, by (T12)WxiBase station 21 is sent to, while the downlink service data of user equipment 12 is sent to base station 21 by central node 30.Similarly, central node30 by (T2) ^ is sent to base station21, by (T22)WittBase station 11 is sent to, while central node 30 sends out the downlink service data of user equipment 22 Give base station 11.
It is user equipment 12 and the transmission downlink service data of user equipment 22 after obtaining the pre-coding matrix and downlink service data of respective user equipment in base station 11 and base station 21.
Fig. 5 shows another flow chart of the relevant joint transmission of low complex degree.Fig. 5 step Sudden S501 to S503 are identical with Fig. 4 step S401 to S403, will not be repeated here.In step S504, share the scheduling authorization information of base station in cluster in base station of the central node 30 into cluster, namely central node 30 sends the scheduling authorization information of base station 21 to base station 11, central node 30 sends the scheduling authorization information of base station 11 to base station 12.Can also be central node 30 simultaneously to base station 11 and the broadcast base station 11 of base station 21 and base station 21 scheduling authorization information.Fig. 5 step S505 to S508 and Fig. 4 step S405 to S408 are identical, will not be repeated here.
B LC-CJT backhaul link capacities are analyzed
Because each base station only sends the CSI of scheduled user equipment, the capacity requirement to system backhaul link is reduced.If we assume that each cell selection user equipment, wherein=!,-, ζ, backhaul link capacity shared CSI can be calculated as follows
cLcCJT(the U J of 1 Shang 0 of-≡ 3
Definition¼=, the ratio between LC-CJT and ORI-CJT can be expressed as：
Cf'c—rjr― n
0 (11)
Under normal conditions,μι <κ.In LTE versions 11, for their transmission mode 9 (TM9) and 10 (TM10),；, representative value is 4.This result shows, is compared with ORI-CJT, and requirements of the LC-CJT to backhaul link capacity is reduced a lot.
C) scheduling unit analysis of complexity
In LC- CJT, because each cell independently carries out distributed multi-user scheduling, In the absence of the challenge to CN disposal abilities.Compare combined dispatching and distributed scheduling, it has been found that its common ground is, although the equitable proportion factor（The PF- factors）The fairness of scheduling is for ensuring that, the user equipment positioned at center of housing estate still has higher scheduled priority.This sunset is foretold, and the user equipment positioned at center of housing estate has high received signal to noise ratio due to it（SNR), it is suitable for multi-user's multiple-input and multiple-output（MU-MIMO) transmit to obtain higher spatial multiplex gains.This shows that distributed scheduling scheme and combined dispatching scheme can realize almost identical cell average gain.However, combined dispatching scheme considers the scheduling of Cell Edge User equipment in global scope, and distributed scheduling scheme only considered the scheduling of the edge customer equipment of this cell.This shows that the scheduling that distributed scheduling scheme obtains user equipment for the cell edge in cluster is suboptimum, is compared with combined dispatching scheme, and this can cause certain performance loss in cell edge.All these analysis results have obtained the checking of system emulation.
There is following benefit to the CN scheduling authorization information for transmitting scheduled user equipment：First, for CN disposal ability, CN needs number of user equipment to be processed to substantially reduce；The second is iterative calculation when can avoid carrying out multi-subscriber dispatching using greedy algorithm；3rd is that CN need not consider the order of user equipment when designing pre-coding matrix.Thus, such as formula（11) the ratio ratio of the computation complexity of ORI-CJT and LC- CJT in be more than ' Λ：.System performance analysis
In order to preferably prove the advantage of the present invention, the present invention is compared by system emulation
ORI-CJT and LC-CJT performance.In order to clearly illustrate the performance gain of two kinds of CoMP schemes, the performance of single cell is used as datum line.In single cell (Single Cell:SC), in ORI-CJT and LC- CJT schemes, using the dispatching user facility algorithm based on eMES.The gain of all CoMP schemes is relatively to be based on showing that a typical CoMP scene is carried out in Fig. 1.Main simulation parameter is set as listed by table 1, and the relevant descending simulation parameter settings of TDD are consistent with specified in 3GPP for this.In order to liberally compare LC-CJT and ORI-CJT schemes, to statistic property（By cumulative distribution function（CDF) show）Compared with system average behavior.System average behavior includes cell spectrum efficiency（It is expressed as " cell AVG "；) [bit/frequency/cell] and 5 % user equipment spectrum efficiency（It is expressed as " small Area edge "）The average behavior of [bit/hertz/user equipment].The system emulation parameter setting of table 1
Fig. 6 shows the schematic diagram of the relevant joint transmission performance of low complex degree in multiple cell 3GPP Casel-3D scenes.Curve as shown in Figure 6 shows the descending CoMP transmission System meters property of SC, LC-CJT and ORI-CJT scheme in 3GPP easel 3D scenes
! 5 Can contrast.These curves show, compared with the SC of non-coordinated multipoint transmission, and LC- CJT schemes can obtain huge CoMP gains, and LC-CJT schemes and ORI-CJT scheme performance gap very littles.The average behavior of three schemes is as listed in table 2.In table 2, it will be seen that LC- CJT schemes can obtain the performance gain of the cell average performance gain more than 35 % and 30 more than % cell edge.However, compared with ORI-CJT schemes, due to next Optimized Operation, the performance gain of LC-CJT schemes about 8 % cell edge.Performance comparision of the table 2 in 3GPP Casel-3D scenes
In order to verify robustness of the LC-CJT schemes under other transmitting scenes, the present invention is in the scene that the UMI of International Telecommunication Association is transmitted, and to SC, LC-CJT and ORI-CJT schemes are compared.Fig. 7 shows the schematic diagram of the relevant joint transmission performance of low complex degree in the scene of the UMI transmission of the International Telecommunication Association of multiple cell.Curve as shown in Fig. 7 shows that LC-CJT can obtain the performance gain bigger than SC scheme in the scene that the UMI of International Telecommunication Association is transmitted, and the multipoint cooperative gain inequality between LC-CJT and ORI-CJT is away from very little.Average behavior in these three schemes is as listed in table 3.Compared with SC, LC-CJT can achieve over the performance gain of 40 % cell average performance gain and 35 more than % cell edge, but between LC-CJT and ORI-CJT about 9 % cell-edge performance gain inequality away fromβ
Performance comparision of the table 3 in International Telecommunication Association's UMI transmitting scenes
The present invention of ORI-CJT 5.1856 0.2093 39.63% 46.57% 0.8174 proposes the low complex degree CJT schemes for CoMP downlink transfers.Under several cooperative multipoint transmission scenes, scheme proposed by the invention obtains good performance gain, relative to single cell scenario, realizes the cell average performance gain more than 35 % and 30 more than % cell-edge performance gain.Compared with ORI-CJT, the cost of LC-CJT schemes is the performance loss of 10 % or so cell edge.But LC-CJT schemes can neatly be implemented due to its low complex degree in real network, can improve the performance of whole system.
It is obvious to a person skilled in the art that the invention is not restricted to the details of above-mentioned one exemplary embodiment, and without departing from the spirit or essential characteristics of the present invention, the present invention can be realized in other specific forms.Therefore, from the point of view of anyway, embodiment all should be regarded as exemplary, and be nonrestrictive.In addition, it will be evident that " an including " word is not excluded for other elements and step, and wording " one " is not excluded for plural number.The multiple element stated in device claim can also be realized by an element.The first, the second grade word is used for representing title, and is not offered as any specific order.
The above description of the present invention is used to enable any those of ordinary skill of this area to realize or using the present invention.To those skilled in the art, various modifications of the invention will be apparent from, and general principle defined herein can also be applied to other deformations in the case of without deviating from the spirit and scope of the disclosed invention.Therefore, the present invention is not limited to example as described herein and design, but consistent with the widest scope of principle disclosed herein and novel features.

Claims (1)

  1. Claims
    A kind of method of joint transmission 1. multi-cell downlink of low complex degree is concerned with, including the following steps performed by the central node of base station cluster：
    1. reception comes from the first base station in the base station cluster and the scheduling authorization information and channel condition information of the second base station；
    Ii. carry out co-design to precoding to obtain pre-coding matrix according to the scheduling authorization information and the channel condition information that come from the first base station and second base station；And
    Iii. the precoding information of the user equipment of the first base station in the pre-coding matrix is sent to the first base station, the precoding information of the user equipment of second base station in the pre-coding matrix is sent to second base station；
    Wherein described first base station and second base station belong to the base station cluster, and the cell of the cell of the first base station and second base station is adjacent.
    2. according to the method described in claim 1, wherein the co-design is when designing the pre-coding matrix of the user equipment, it is considered to the interference that the pre-coding matrix is likely to result in the downlink transfer of other user equipmenies in matrix.
    3. according to the method described in claim 1, in addition to the first base station send the business datum of the user equipment of second base station and/or the business datum of the user equipment of the first base station is sent to second base station.
    4. according to the method described in claim 1, wherein described scheduling authorization information is carried out independent distributed scheduling by the user equipment of the cell to the base station and obtained, and the independent distributed scheduling does not consider the scheduling authorization information of the user equipment of the neighbor cell of the cell of the base station.
    5. according to the method described in claim 1, wherein the channel condition information includes the channel condition information of the user equipment of the neighbor cell of the channel condition information of the user equipment of the cell of the base station and the cell of the base station.
    A kind of method of joint transmission 6. multi-cell downlink of low complex degree is concerned with, including the following steps performed by the base station in the cluster of base station： I. the scheduling authorization information of the user equipment of the cell of the base station is sent to central node；
    Ii. the precoding information of the user equipment of the cell for the base station for coming from the central node is received；And
    Iii. descending joint transmission is carried out to the business datum of the user equipment of the base station according to the precoding information and the scheduling authorization information.
    7. method according to claim 6, wherein described scheduling authorization information is carried out independent distributed scheduling by the user equipment of the cell to the base station and obtained, and the independent distributed scheduling does not consider the scheduling authorization information of the user equipment of the neighbor cell of the cell of the base station.
    8. method according to claim 6, also include the configuration information that the user equipment of the cell of the base station is shared with the base station of the neighbor cell of the cell of the base station in the base station cluster, the configuration information is used for the channel condition information for causing the user equipment of the cell of base station described in the base station monitors of the neighbor cell.
    9. method according to claim 6, also include sending channel condition information to the central node, the channel condition information includes the channel condition information of the user equipment of the neighbor cell of the channel condition information of the user equipment of the cell of the base station and the cell of the base station.
    10. method according to claim 6, in addition to reception come from the business datum of the user equipment of the neighbor cell of the cell of the base station of the central node to carry out descending joint transmission.
    The central node of joint transmission 11. a kind of multi-cell downlink for low complex degree is concerned with, it includes：
    Receiving unit, it is used for the scheduling authorization information and channel condition information that receive the first base station and the second base station that come from the cluster of base station, wherein described first base station and second base station belong to the base station cluster, and the cell of the cell of the first base station and second base station is adjacent；
    Joint precoding unit, it is used to carry out co-design to precoding according to the scheduling authorization information and the channel condition information that come from the first base station and second base station To obtain pre-coding matrix；
    First transmitter unit, it is used to the precoding information of the user equipment of the first base station in the pre-coding matrix being sent to the first base station, and the precoding information of the user equipment of second base station in the pre-coding matrix is sent into second base station；And
    Second transmitter unit, it is used for the business datum that the user equipment of the first base station is sent to the business datum of the user equipment of first base station transmission second base station and/or to second base station.
    12. central node according to claim 11, wherein the co-design is when designing the pre-coding matrix of the user equipment, it is considered to the interference that the pre-coding matrix is likely to result in the downlink transfer of other user equipmenies in matrix.
    13. central node according to claim 11, wherein described scheduling authorization information is carried out independent distributed scheduling by the user equipment of the cell to the base station and obtained, and the independent distributed scheduling does not consider the scheduling authorization information of the user equipment of the neighbor cell of the cell of the base station.
    14. central node according to claim 11, wherein the channel condition information includes the channel condition information of the user equipment of the neighbor cell of the channel condition information of the user equipment of the cell of the base station and the cell of the base station.
    The base station of joint transmission 15. a kind of multi-cell downlink for low complex degree is concerned with, it includes：
    First transmitter unit, it is used for the scheduling authorization information that the user equipment of the cell of the base station is sent to central node；
    Shared cell, it is used for the configuration information that the user equipment of the base station is shared with the base station of the neighbor cell of the cell of the base station in the cluster of base station, the configuration information is used to cause the channel shape of the user equipment of base station described in the base station monitors of the neighbor cell to know information, and the base station of the neighbor cell of the cell of the base station and the base station belongs to the base station cluster；
    Second transmitter unit, it is used to send channel condition information to the central node, and the channel condition information includes the channel status letter of the user equipment of the cell of the base station The channel condition information of the user equipment of the neighbor cell of the cell of breath and the base station；First receiving unit, it is used for the precoding information for receiving the user equipment of the cell for the base station for coming from the central node；
    Second receiving unit, it is used to receive the business datum of the user equipment of the neighbor cell of the cell for the base station for coming from the central node to carry out descending joint transmission；And
    3rd transmitter unit, it is used to carry out descending joint transmission to the business datum of the user equipment of the base station according to the precoding information and the scheduling authorization information.
    16. base station according to claim 15, wherein described scheduling authorization information is carried out independent distributed scheduling by the user equipment of the cell to the base station and obtained, and the independent distributed scheduling does not consider the scheduling authorization information of the user equipment of the neighbor cell of the cell of the base station.
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