CN101800578A - Method for reducing downlink multipoint cooperation implicate feedback overhead - Google Patents

Abstract

The invention discloses a method for reducing the downlink multipoint cooperation implicate feedback overhead, relating to the technical field of wireless communication. The invention mainly solves the problem of large feedback overhead in the prior art. Users only need to send feedback of CQI (Channel Quality Indication) respectively to a single link of each base station in downlink multipoint cooperation joint processing mode, and only an SNR (Signal to Noise Ratio) value of a single link needs feedback. A physical resource block is clustered on the basis, and C adjacent physical resource blocks are in one cluster. The smallest SNR on the C physical resource blocks in the cluster is taken as channel status information of the cluster, and an SNR threshold value is preset at a user side. Only when the user checks that the SNR of the cluster is larger than the preset threshold value, the feedback of the SNR of the cluster is sent to the base station side, and otherwise the channel status information of the cluster is discarded. The base station selects an appropriate TPCC structure according to the feedback SNR value to provide service for the user. The invention can greatly reduce the feedback overhead of users by selecting the appropriate SNR threshold value on the premise of little influence on system capacity.

Description

Reduce the downlink multipoint cooperation implicate feedback overhead method

Technical field

The present invention relates to wireless communication technology field, particularly a kind of method that reduces downlink multipoint cooperation implicate feedback overhead, be used for the next generation mobile communication long evolving system, the big problem of terminal feedback information amount under the multipoint cooperative framework in the solution wireless network.

Background technology

In order to satisfy the performance index of LTE-A, especially reach the performance requirement of LTE-A to Cell Edge User, the multipoint cooperative transmission technology is regarded as the raising community marginal user performance, effectively suppresses one of important technology of presence of intercell interference.

Unite in the reception scene at descending multipoint cooperative, realize cooperation transmission between a plurality of sub-districts and the user, need serving BS to obtain whole channel informations of base station, collaboration region.This feeds back to serving BS with regard to needing the user with whole channel condition informations, and by coordinating between serving BS and the cooperative base station, selects suitable transmission link.

In RAN1#57 the meeting that san francisco, usa is held, below feedback model under three kinds of multipoint cooperatives passed through by meeting:

1, explicit feedback (explicit feedback)

After the user observes channel conditions, for example: domain channel response information, this information is not carried out any processing, directly feed back to the base station, make the base station obtain channel response information completely.

2, implicit feedback (implicit feedback)

The user handles the channel information that obtains after observing channel conditions, changes into the spy

Fixed quantized values feeds back to the base station, for example CQI/PMI/RI.

3, based on the feedback of SRS

UE transmitting SRS (sounding reference signal) is given the base station, and CQI information is estimated by SRS in the base station.

Undoubtedly, explicit feedback must be brought the performance gain under the better multipoint cooperative, but, owing to whole channel response informations will be fed back to the base station, the expense of bringing to system will be very huge, therefore at present what adopt more is implicit feedback, for example channel response information is quantified as CQI/PMI/RI etc. and feeds back.Under single user situation, can finish main operation in the multipoint cooperative by implicit feedback, for example dynamic cell is selected, cooperation suppresses to disturb etc.

From the feedback data form, channel information feedback method mainly is based on the method for feedback of channel quality indication of CQI at present, and as feedback Signal to Interference plus Noise Ratio SINR, this feedback method has less feedback quantity, generally is used for random wave bundle and forms.In the CoMP down link, the base station is pilot signal transmitted at a certain time interval, the user then comes measured channel information according to these pilot frequency informations, and send the channel quality CQI information of all links to serving BS, serving BS just can carry out scheduling of resource and adaptive modulation and coding according to these CQI information.Though the CQI feedback information improves the systematic function of down link by scheduling of resource accurately and good link circuit self-adapting, it has reduced the spectrum utilization efficiency of up link as a kind of expense extraly.Therefore, effectively the compression of CQI feedback information just seems extremely important.

In the 17th meeting of the sub-working group of LTE+, this motion of IMT-A_LTE+_09309 " CoMPImplicit CQI Feedback Options for Joint Processing " has proposed a kind of under downlink multipoint cooperation Combined Treatment pattern, only need the CQI of feedback user to each base station single link, the base station is by calculating the CQI value can draw under the TPCC different situations, thereby reduces feedback quantity.But this scheme can only reduce a spot of feedback overhead, and under and the situation that Resource Block quantity is big more at the cooperation cell number, effect is also not obvious.

Summary of the invention

The objective of the invention is to overcome the deficiency of above-mentioned prior art, on the basis of IMT-A_LTE+_09309 motion, a kind of new method that reduces downlink multipoint cooperation implicate feedback overhead is proposed, reduce feedback overhead under the situation that number of users is more and resource block number is many greatly to be implemented in, and power system capacity is not produced big influence.

For achieving the above object, technical scheme of the present invention is that the model to the MT-A_LTE+_09309 motion improves, by to the Physical Resource Block sub-clustering, bunch being the unit feedback channel information; And in the default SNR threshold value of user side, have only, just feed back this bunch channel condition information as bunch SNR during greater than user preset SNR threshold value.

The present invention is achieved as follows:

One. relational term of the present invention is explained:

The channel quality indication (channel quality indicator, CQI)

Multipoint cooperative (coordinative multiple point, CoMP)

CoMP transmission ends structure (Transmission Points Configuration for CoMP, TPCC)

Physical Resource Block (physical resource block, PRB)

The user (user equipment, UE)

Advanced LTE (long term evolution-advanced, LTE-A)

Signal to noise ratio (snr)

Signal to Interference plus Noise Ratio (SINR)

Two. realization of the present invention

Performing step of the present invention comprises as follows:

(1) user's Serving cell of living in is divided into central area and fringe region, for the user who is in fringe region, the base station is its transmission information with the form of wave beam, and each wave beam is user's service;

(2) Physical Resource Block to downlink transmission carries out sub-clustering, C adjacent Physical Resource Block is divided into one bunch, C 〉=2 record a snr value on each Physical Resource Block, and with the signal to noise ratio of the minimum that records on the Physical Resource Block of the C in each bunch state information as this bunch;

(3)) bunch being that unit measures the user and divides the channel condition information that is clipped to link between serving BS and each cooperative base station;

(4) at the default signal-noise ratio threshold value t of user side, the user judges that respectively whether the serving BS that records and each cooperative base station bunch signal to noise ratio are greater than default signal-noise ratio threshold value t, if bunch signal to noise ratio is greater than user preset signal-noise ratio threshold value t, this bunch of user feedback state information is to the transmitting terminal base station, otherwise the user does not feed back this bunch state information;

(5) the transmitting terminal base station signal to noise ratio information of returning according to user feedback, utilize following Signal to Interference plus Noise Ratio formula to calculate Signal to Interference plus Noise Ratio under the various different TPCC structure numbers:

${\mathrm{SINR}}_1=\frac{{\mathrm{SNR}}_1}{{\mathrm{SNR}}_2+{\mathrm{SNR}}_3\·\·\·\·\·\·+{\mathrm{SNR}}_L+1}$

${\mathrm{SINR}}_2=\frac{{\mathrm{SNR}}_2}{{\mathrm{SNR}}_1+{\mathrm{SNR}}_3\·\·\·\·\·\·+{\mathrm{SNR}}_L+1}$

……

……

……

${\mathrm{SINR}}_L=\frac{{\mathrm{SNR}}_L}{{\mathrm{SNR}}_1+{\mathrm{SNR}}_2\·\·\·\·\·\·+{\mathrm{SNR}}_{L-1}+1}$

${\mathrm{SINR}}_{L+1}=\frac{{\mathrm{SNR}}_1+{\mathrm{SNR}}_2}{{\mathrm{SNR}}_3\·\·\·\·\·\·+{\mathrm{SNR}}_L+1}$

${\mathrm{SINR}}_{L+2}=\frac{{\mathrm{SNR}}_1+{\mathrm{SNR}}_3}{{\mathrm{SNR}}_2+{\mathrm{SNR}}_4\·\·\·\·\·\·+{\mathrm{SNR}}_L+1}$

……

……

……

${\mathrm{SINR}}_{2^L}={\mathrm{SNR}}_1+{\mathrm{SNR}}_2\·\·\·\·\·\·+{\mathrm{SNR}}_L$

Wherein L is the number of cells that can select altogether, molecule is a useful signal, represent that certain several sub-district is when the signal-noise ratio threshold value of prevariety signal to noise ratio greater than user preset in L the sub-district, denominator is an interference signal, represent that certain several sub-district is when the signal-noise ratio threshold value of prevariety signal to noise ratio less than user preset in L the sub-district, the TPCC structure always has 2 ^LIndividual numbering calculates 2 ^LIndividual Signal to Interference plus Noise Ratio value.

(6) Signal to Interference plus Noise Ratio of selection numerical value maximum in 2L Signal to Interference plus Noise Ratio

Max{SINR _j| j=1,2 ... 2 ^L, select the TPCC structure number of maximum Signal to Interference plus Noise Ratio correspondence then, be that the user provides service with the service structure under this numbering.

The present invention is owing to adopt on the basis of the independent link CQI of user feedback, adjacent Resource Block sub-clustering, with bunch as feedback unit, and at the default SNR threshold value t of user side, relatively adjudicate bunch SNR by threshold value and whether will feed back to the transmitting terminal base station, make the transmission of feedback information of having only better signal to noise ratio give the base station, greatly reduced feedback overhead; Compare with compression ratio simultaneously, less to the influence of original system throughput.Therefore the present invention is adapted at using in the real system, the hot spot region that the cooperation cell number is many and call duration time is long especially, and have availability of frequency spectrum height, the advantage that use cost is low.

Description of drawings

Fig. 1 is the flow chart of the inventive method;

Fig. 2 reduces the system model figure of feedback overhead for down link CoMP of the present invention;

The present invention and original method throughput of system ratio analogous diagram when Fig. 3 is different SNR threshold value;

The present invention and original method system feedback amount ratio analogous diagram when Fig. 4 is different SNR threshold value;

Fig. 5 equals 4 o'clock number of cells probability graphs for user's service for the SNR threshold value;

Fig. 6 equals 8 o'clock number of cells probability graphs for user's service for the SNR threshold value;

Fig. 7 equals 12 o'clock number of cells probability graphs for user's service for the SNR threshold value;

Fig. 8 equals 16 o'clock number of cells probability graphs for user's service for the SNR threshold value;

Fig. 9 equals 20 o'clock number of cells probability graphs for user's service for the SNR threshold value.

Embodiment

With reference to Fig. 1, concrete implementation step of the present invention is as follows:

Step 1, division of cells and selection CoMP sub-district.

1a) mark off central area and fringe region

It is R rice that present embodiment is selected the Serving cell radius, and the central area scope is for being 0～r rice, and the fringe region scope is r～R rice, sees Fig. 2;

1b) select the multipoint cooperative sub-district

When the user is positioned at the central area, have only serving BS to provide service for the user;

When the user is positioned at fringe region,, in L nearest sub-district of user, selecting the sub-district to provide service for the user according to link-quality owing to there is path loss.

Situation when Fig. 2 only considers that the user is positioned at fringe region.H ₀, H ₁H _L-1Be respectively c ₀, c ₁C _L-1Channel matrix to the user.

Present embodiment hypothesis base-station transmitting-power all equates, then the signal that receives of user is:

y＝H ₀P ₀s+H ₁P ₁s+H ₂P ₂s……+H _L-1P _L-1s+n

H _i(i=0,1 ... L-1) be Rayleigh channel, transmitting terminal antenna and receiving terminal number of antennas are N _t* N _r=4 * 2, to H _iSingular value decomposition gets H _i=u _iDv _i, u _iAnd v _iBe orthogonal matrix, d is H _iEigenmatrix, s is a transmission information, n is an additive white Gaussian noise, P _i(i=0,1 ... L-1) be pre-coding matrix on the i bar link, its size is v _iFirst column element.

Step 2, sub-clustering and Computational Physics Resource Block state information.

2a) set always total K the Physical Resource Block of line link, obtain the state information on each Physical Resource Block:

$\mathrm{SNR}\left(k\right)=\frac{{\left|\right|H_k{P}_k\left|\right|}^{2}E}{N}$

K=1,2,3 ..., K; H _kBe Rayleigh channel; P _kPre-coding matrix when transmitting k Physical Resource Block; E is a transmitted power; N is an additive white Gaussian noise power;

2b) Physical Resource Block to downlink transmission carries out sub-clustering, and C adjacent Physical Resource Block is divided into one bunch, always is divided into M=(K/C) ₊Individual bunch, () ₊Expression is got whole, and m bunch corresponding to (k, k+1 ... k+C-1) this C Physical Resource Block, the size of bunch state information SNR (m) are min (SNR (k), SNR (k+1) ... SNR (k+C-1)), m=1,2 ..., M.

Present embodiment adopts K Resource Block to pass data, after the sub-clustering, K Resource Block is divided into M=(K/C) ₊Individual bunch.

$\mathrm{SNR}\left(m\right)=\min (\mathrm{SNR}\left(k\right),\mathrm{SNR}(k+1),\·\·\·\·\·\·\mathrm{SNR}(k+C-1))$

$=\min (\frac{{\left|\right|H_k{P}_k\left|\right|}^{2}E}{N},\frac{{\left|\right|H_{k+1}{P}_{k+1}\left|\right|}^{2}E}{N},\·\·\·\·\·\·\frac{{\left|\right|H_{k+C-1}{P}_{k+C-1}\left|\right|}^{2}E}{N})$

SNR (m) represents bunch channel condition information, m=1, and 2 ..., (K/C) ₊State information on Physical Resource Block of SNR (k) expression, k=1,2,3 ..., K; H _kBe Rayleigh channel; P _kPre-coding matrix when transmitting k Physical Resource Block; E is a transmitted power; N is an additive white Gaussian noise power.

Step 3 is bunch being that unit measures the user and divides the channel condition information that is clipped to link between serving BS and each cooperative base station.

I bar link m bunch channel condition information is:

${\mathrm{SNR}}_i\left(m\right)=\min ({\mathrm{SNR}}_i\left(k\right),{\mathrm{SNR}}_i(k+1),\·\·\·\·\·\·{\mathrm{SNR}}_i(k+C-1))$

$=\min (\frac{{\left|\right|H_k{P}_k\left|\right|}^{2}E}{N},\frac{{\left|\right|H_{k+1}{P}_{k+1}\left|\right|}^{2}E}{N},\·\·\·\·\·\·\frac{{\left|\right|H_{k+C-1}{P}_{k+C-1}\left|\right|}^{2}E}{N})$

It may be the CoMP sub-district of user's service that present embodiment is selected from L nearest sub-district conduct of user, i=1, and 2 ... L.

SNR ₁(m)＝min(SNR ₁(k)，SNR ₁(k+1)，……SNR ₁(k+C-1))

SNR ₂(m)＝min(SNR ₂(k)，SNR ₂(k+1)，……SNR ₂(k+C-1))

……

……

……

SNR _L(m)＝min(SNR _L(k)，SNR _L(k+1)，……SNR _L(k+C-1))

SNR ₁(m) be Serving cell bunch signal to noise ratio; SNR ₂(m), SNR ₃(m) ... SNR _L(m) be respectively each cooperation cell bunch signal to noise ratio.

Step 4, user preset SNR threshold value and judgement.

User side is preset SNR threshold value t; Bunch channel condition information SNR of every the link that records as the user _iDuring (m) greater than threshold value t, then feed back the SNR of this bunch _i(m) to the base station, promptly the base station receives feedback states information SNR _i={ SNR _i(m) | SNR _i(m)＞t}; Otherwise, if bunch SNR that the user records _i(m), then abandon the channel information of this bunch less than threshold value t.

Step 5, the base station is according to the SNR of single link _iCalculate the SINR under the corresponding TPCC structure _j

5a) the SINR of calculating single link _j

${\mathrm{<figure-callout\; id="1"\; label="SINR"\; filenames="H201010013573XE00021.png,H201010013573XE00031.png"\; state="\{\{state\}\}">SINR</figure-callout>}}_1=\frac{{\mathrm{<figure-callout\; id="1"\; label="SNR"\; filenames="H201010013573XE00021.png,H201010013573XE00031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_1}{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_2+{\mathrm{<figure-callout\; id="3"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_3\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L+1}$

${\mathrm{<figure-callout\; id="2"\; label="SINR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SINR</figure-callout>}}_2=\frac{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_2}{{\mathrm{<figure-callout\; id="1"\; label="SNR"\; filenames="H201010013573XE00021.png,H201010013573XE00031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_1+{\mathrm{<figure-callout\; id="3"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_3\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L+1}$

……

……

……

${\mathrm{SINR}}_L=\frac{{\mathrm{<figure-callout\; id="1"\; label="SNR\; L\; SNR"\; filenames="H201010013573XE00021.png,H201010013573XE00031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_L}{{\mathrm{SNR}}_{}}$

SINR ₁It is the Signal to Interference plus Noise Ratio that the user arrives Serving cell; SINR ₂SINR _LIt is respectively the Signal to Interference plus Noise Ratio that the user arrives each cooperation cell;

5b) calculate SINR under all the other corresponding TPCC structures _j

${\mathrm{SINR}}_{L+1}=\frac{{\mathrm{<figure-callout\; id="1"\; label="SNR"\; filenames="H201010013573XE00021.png,H201010013573XE00031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_2}{{\mathrm{<figure-callout\; id="3"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_3\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L+1}$

${\mathrm{SINR}}_{L+2}=\frac{{\mathrm{<figure-callout\; id="1"\; label="SNR"\; filenames="H201010013573XE00021.png,H201010013573XE00031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_1+{\mathrm{<figure-callout\; id="3"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_3}{{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_2+{\mathrm{<figure-callout\; id="4"\; label="SNR"\; filenames="H201010013573XE00031.png,H201010013573XE00032.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_4\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L+1}$

……

……

……

${\mathrm{SINR}}_{2^L}={\mathrm{<figure-callout\; id="1"\; label="SNR"\; filenames="H201010013573XE00021.png,H201010013573XE00031.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_1+{\mathrm{<figure-callout\; id="2"\; label="SNR"\; filenames="H201010013573XE00041.png,H201010013573XE00042.png"\; state="\{\{state\}\}">SNR</figure-callout>}}_2\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L$

SNR _i＝{SNR _i(m)|SNR _i(m)＞t}，i＝1，2……L；

Step 6 is selected maximum Signal to Interference plus Noise Ratio, provides service with the structure under the corresponding TPCC numbering for the user.

Present embodiment SINR _j(j=1,2 ..., 2 ^L) corresponding TPCC structure such as table 1,

The TPCC structure number	The CoMP transmission ends
		??1	??C0
??2	??C1
		??3	??C2
??……	??……
		??L	??CL-1
??L+1	??C0?and?C1
		??L+2	??C0?and?C2
??……	??……
		??2 L	??C0，C1……CL-1

Table 1

The Signal to Interference plus Noise Ratio that has calculated according to above-mentioned steps is 2 ^LSelect the Signal to Interference plus Noise Ratio max{SINR of numerical value maximum in the individual Signal to Interference plus Noise Ratio _j| j=1,2 ... 2 ^L, select TPCC structure number corresponding under this maximum Signal to Interference plus Noise Ratio then, the service structure under numbering with this is that the user provides service.

Effect of the present invention can further specify by following emulation:

1. simulated conditions: make up the downlink multipoint cooperation model, comprise a serving BS and two cooperative base station, consider power system capacity and feedback quantity size when the user is in fringe region, simulation parameter is chosen as shown in table 2:

Parameter	Value
		The transmitting antenna number	??4
The reception antenna number	??2
		Number of cells	??3
Each bunch comprises the physics resource block number	??4
		The Physical Resource Block total number	??1024
Bandwidth	??10MHz

Parameter	Value
		The code book number	??4
Transmitted power on each Physical Resource Block	??50mw
		Noise power	??75mw
Each community user number	??20
		Channel	Rayleigh channel
The SNR threshold value	??4/8/12/16/20
		Radius of society	??500m
Fringe region	??300-500m
		Shadow fading	??8dB
Path loss	??30.18+26log(d)km

Table 2

2. emulation content

2a) find the solution prior art systems capacity C apacity and feedback quantity R

When in the prior art, adopting not sub-clustering and not default threshold schemes: suppose always to have K Physical Resource Block, bandwidth is B, and then power system capacity is:

$\mathrm{Capacity}=\underset{k=1}{\overset{K}{\mathrm{\&Sigma;}}}{B\log }_2(1+\max \left({\mathrm{SINR}}_j\left(k\right)\right))$

Adopt wave beam to transmit information for the user, suppose that all feedback quantities quantize with 8bit, during unity feedback, the feedback quantity size is:

R＝KUb

K represents the Physical Resource Block number, and U represents number of users, b=(log ₂K) ++ (log ₂N) ₊The required bit number of+8 each Resource Block of expression, () ₊Expression is got whole, and N represents the precoding codebook number.

2b) ask power system capacity Capacity of the present invention and feedback quantity R '

The power system capacity that the present invention reduces the downlink multipoint cooperation implicate feedback overhead method is:

${\mathrm{Capacity}}^{\&prime;}=\underset{m=1}{\overset{M}{\mathrm{\&Sigma;}}}{B\log }_2(1+\max \left({\mathrm{SINR}}_j\left(m\right)\right))$

M=(K/C) ₊, SINR _j(m) Signal to Interference plus Noise Ratio for calculating under bunch signal to noise ratio after the sub-clustering.

Here, if bunch SNR＜t of current area does not then adopt this sub-district to be user's service, owing to may exist this link better to user's the link-quality that other are in current region, so the signal of this link is used as interference.

The present invention reduces the feedback quantity size of downlink multipoint cooperation implicate feedback overhead method:

R′＝pMUb′

M=(K/C) ₊, U represents number of users, b '=(log ₂M) ₊+ (log ₂N) ₊+ 8, p is bunch a feedback probability, and size be that minimum signal to noise ratio is greater than the probability of threshold value t on C Resource Block in this bunch, and according to the threshold value difference of user preset, the size that probability is fed back in each sub-district is difference also, and specifically numerical value is as shown in table 3:

	C0 feeds back probability	C1 feeds back probability	C2 feeds back probability
				During t=4	??1	??0.9949	??0.9950
During t=8	??1	??0.8531	??0.8544
				During t=12	??1	??0.5067	??0.5059
During t=16	??0.9999	??0.2094	??0.2080
				During t=20	??0.9995	??0.0651	??0.0662

Table 3

3. simulation result

As shown in Figure 3, along with the increase of SNR threshold value, the present invention compares original technological system capacity and can descend to some extent, and this is because the SNR threshold value is high more, and the probability that ropy channel information is dropped is big more, and the total capacity of system just descends to some extent.

As shown in Figure 4, along with the increase of SNR threshold value, the present invention compares original technology feedback quantity to be had significantly and reduces, and this is because the SNR threshold value is high more, needs the channel condition information of feedback few more, and feedback quantity decreases.

During difference signal to noise ratio snr threshold value, be the number of cells probability difference of user's service.Because Serving cell is for user's path attenuation minimum, service quality is good, so no matter adopt which SNR threshold value, Serving cell almost is always the user service is provided, promptly be exactly to have at least a sub-district to be user's service, do not have substantially that not have the sub-district be the situation that the user serves.

As shown in Figure 5, during SNR=4, the SNR of three channels almost all greater than default SNR threshold value, does not have the channel information that is dropped substantially, and three cell cooperatives provide service for the user.

As shown in Figure 6, during SNR=8, two cooperation cell increase less than the probability of threshold value to some extent to user's SNR, and cooperation cell has the sub-fraction channel information to be dropped, and the situation of two sub-districts of Serving cell and cooperation cell for user's service occur.

As shown in Figure 7, during SNR=12, almost a link will be dropped in two cooperation cell, and two sub-districts are the probability maximums of user's service, and sub-district is respectively about 1/4 for the probability that the user serves for user's service and three sub-districts.

As shown in Figure 8, during SNR=16, a sub-district is mainly Serving cell for the probability maximum that the user serves.Two sub-districts comprise that Serving cell and a cooperation cell account for about 1/3 for the probability that the user serves, and the probability minimum of three cell cooperatives is almost nil.

As shown in Figure 9, during SNR=20, mainly rely on Serving cell to provide service for the user, cooperation cell seldom can participate in into the service for the user.

Simulation result shows, the present invention compares with original technology, because Physical Resource Block is carried out sub-clustering, and in the default suitable SNR threshold value of user side, can make in that power system capacity is influenced under the little situation, significantly reduce feedback overhead, be particularly suitable for the multipoint cooperative edge customer and use, and along with the raising of later network complexity and the increase of subscriber traffic, its performance will outclass original technical scheme.

Claims (6)

1. one kind reduces the downlink multipoint cooperation implicate feedback overhead method, comprises the steps:

(1) user's Serving cell of living in is divided into central area and fringe region, for the user who is in fringe region, the base station is its transmission information with the form of wave beam, and each wave beam is user's service;

(2) to the Physical Resource Block of downlink transmission in order from first physical resource BOB(beginning of block), C Physical Resource Block is divided into one bunch, C 〉=2, be divided up to all Physical Resource Block that will transmit, if last bunch Physical Resource Block number deficiency C, then these Resource Block are divided into one bunch, record a snr value SNR on each Physical Resource Block, and with the signal to noise ratio min{SNR} of the minimum that records in each bunch channel condition information as this bunch;

(3) bunch being that unit measures the user and divides the channel condition information that is clipped to link between serving BS and each cooperative base station;

(4) at the default signal-noise ratio threshold value t of user side, the user judges that respectively whether the serving BS that records and each cooperative base station bunch signal to noise ratio are greater than default signal-noise ratio threshold value t, if bunch signal to noise ratio is greater than user preset signal-noise ratio threshold value t, the user feeds back to the transmitting terminal base station with this bunch state information, otherwise the user does not feed back this bunch state information;

(5) the transmitting terminal base station signal to noise ratio information of returning according to user feedback, utilize following Signal to Interference plus Noise Ratio formula to calculate Signal to Interference plus Noise Ratio under the various different TPCC structure numbers:

${\mathrm{SINR}}_1=\frac{{\mathrm{SNR}}_1}{{\mathrm{SNR}}_2+{\mathrm{SNR}}_3\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L+1}$

${\mathrm{SINR}}_2=\frac{{\mathrm{SNR}}_2}{{\mathrm{SNR}}_1+{\mathrm{SNR}}_3\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L+1}$

……

……

……

${\mathrm{SINR}}_L=\frac{{\mathrm{SNR}}_L}{{\mathrm{SNR}}_1+{\mathrm{SNR}}_2\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_{L-1}+1}$

${\mathrm{SINR}}_{L+1}=\frac{{\mathrm{SNR}}_1+{\mathrm{SNR}}_2}{{\mathrm{SNR}}_3\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L+1}$

${\mathrm{SINR}}_{L+2}=\frac{{\mathrm{SNR}}_1+{\mathrm{SNR}}_3}{{\mathrm{SNR}}_2+{\mathrm{SNR}}_4\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L+1}$

……

……

……

${\mathrm{SINR}}_{2^L}={\mathrm{SNR}}_1+{\mathrm{SNR}}_2\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;\&CenterDot;+{\mathrm{SNR}}_L$

Wherein L is the number of cells that can select altogether, molecule is a useful signal, represent that certain several sub-district is when the signal-noise ratio threshold value of prevariety signal to noise ratio greater than user preset in L the sub-district, denominator is an interference signal, represent that certain several sub-district is when the signal-noise ratio threshold value of prevariety signal to noise ratio less than user preset in L the sub-district, the TPCC structure always has 2 ^LIndividual numbering calculates 2 ^LIndividual Signal to Interference plus Noise Ratio value.

(6) 2 ^LSelect the Signal to Interference plus Noise Ratio max{SINR of numerical value maximum in the individual Signal to Interference plus Noise Ratio _j| j=1,2 ... 2 ^L, select the TPCC structure number of maximum Signal to Interference plus Noise Ratio correspondence then, be that the user provides service with the service structure under this numbering.

2. the downlink multipoint cooperation implicate feedback overhead method that reduces according to claim 1, wherein described central area of step (1) and fringe region, be that the residing Serving cell radius of setting user is a R rice, with the base station is that the center is divided into the central area with 0～r radius, r～R radius is divided into fringe region, R＞r.

3. the downlink multipoint cooperation implicate feedback overhead method that reduces according to claim 1, wherein described each wave beam of step (1) is user's service, be meant that the base station is the pilot frequency information that will send to the user, on a wave beam, transmit, and each wave beam only exclusive be that a user is transmitted pilot signal.

4. the downlink multipoint cooperation implicate feedback overhead method that reduces according to claim 1, wherein the described signal to noise ratio with the minimum that records on the Physical Resource Block of the C in each bunch of step (2) is as the channel condition information of this bunch, be for bunch in each Physical Resource Block k, according to the signal to noise ratio formula $\mathrm{SNR}\left(k\right)=\frac{{\left|\right|H_k{P}_k\left|\right|}^{2}E}{N}$ Obtain a snr value, C Physical Resource Block can be obtained C snr value, again in the snr value that C obtains with the signal to noise ratio of minimum channel condition information, wherein H as this bunch _kBe Rayleigh channel, P _kPre-coding matrix when transmitting k Physical Resource Block, E are to be the transmitted power that each Physical Resource Block distributes, and N is an additive white Gaussian noise.

5. the downlink multipoint cooperation implicate feedback overhead method that reduces according to claim 1, wherein step (3) is described bunch being that unit measures the user and divides the channel condition information that is clipped to link between serving BS and each cooperative base station, be for each bunch m, the user will measure the SNR of each base station to user's single link _i(m), i=1,2 ... L, i represent i sub-district, comprise a serving BS, L-1 cooperative base station, SNR ₁(m) be the Serving cell signal to noise ratio, SNR ₂(m), SNR ₃(m) ... SNR _L(m) be respectively each cooperation cell signal to noise ratio.

6. the downlink multipoint cooperation implicate feedback overhead method that reduces according to claim 1, wherein step (4) is described at the default signal-noise ratio threshold value t of user side, be that the service quality that the number of users that can hold according to user's environment of living in, Serving cell and user will satisfy is provided with 4≤t≤20.

Images