CN102647216B - Multi-point coordinated transmission method based on limiting feedback in homogeneous network system - Google Patents

Abstract

The invention provides a multi-point coordinated transmission method based on a limiting feedback in a homogeneous network system, and the method comprises the following steps of: respectively establishing base vectors for each cell to obtain a base vector aggregation; according to the base vector aggregation and a preset threshold, applying a set of candidate user selection criteria to determine user aggregation; sending feedback information with a preset value to a transmitting node by each user in the candidate user aggregation; applying a set of scheduling strategy to users sending out the feedback information, so as to select a scheduling user at the present moment from the users sending out the feedback information; giving the feedback channel information to the transmitting node by the scheduling user; and reconfiguring the channel of the scheduling user by utilizing the transmitting node according to the channel information from the feedback, and pre-coding based on the reconfigured channel, so as to send information to the scheduling user according to the result of pre-coding. According to the embodiment of the invention, the feedback efficiency of the homogeneous network is efficiently improved, and the system cost is reduced.

Description

Coordinated multi-point transmission method based on Limited Feedback in homogeneous network system

Technical field

The present invention relates to wireless communication technology field, particularly in a kind of homogeneous network the multipoint cooperative scheduling cooperative beam based on Limited Feedback be shaped, coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of coordinated multipoint transmission in local LTE-A system under Limited Feedback.

Background technology

Traditional wireless cellular network is an interference-limited system.Although multiple-input, multiple-output (MIMO:Multiple Input Multiple Output) can effectively improve power system capacity in technology Dan community, but in the cellular environment of channeling due to exist serious presence of intercell interference (ICI:Inter-cell Interference) cause systematic function decline, especially the user of cell edge is owing to suffering serious ICI cannot obtain good service.On the other hand, along with the development of the communication technology, customer service is variation day by day, and has constantly proposed new higher performance requirement.Cause the low present situation with not meeting business demand of spectrum efficiency in the face of the independent processing in each community can not effectively solve cell boarder interference, the tissues such as third generation partner program (3GPP:the 3rd Generation Partnership Project) have proposed multi-cell cooperating CoMP technology.Its principle is avoided, suppress or eliminated the co-channel interference (CCI:Co-channel Interference) from adjacent cell by the cooperative transmission between different districts, thereby effectively improves the spectrum efficiency of whole system and edge customer.

According to the information sharing degree of each cooperative node, CoMP can be divided into two kinds of transmission modes, that is: Combined Treatment (JP:Joint Processing) and cooperative scheduling/cooperative beam shaping (CS/CB:Coordinated Scheduling/Coordinated Beamforming).Under JP pattern, user is served jointly by multiple transmitting nodes (BS:Base Station), carrys out guaranteed performance advantage by improving user's received signal quality.But this mode needs sharing users data (Data), all channel condition informations (CSI:Channel State information) between each transmitting node, determine scheduling decision and transmission weight by dynamic interaction, the load-bearing burden of having brought very large overhead and backhaul, implementation complexity is larger.Under CS/CB pattern, user is only served by main transmitting node (Serving-cell), as shown in Figure 1, each transmitting node selects to disturb each other one group of less user by cooperation, by making full use of the separation property in space, the direction of each nodes coordinating transmitted signal wave beam, thus effectively avoid or reduce presence of intercell interference, improve systematic function.Under this mode, each node only needs shared portion CSI and schedule information, has reduced the burden of overhead and backhaul, is easy to realize than JP.

No matter be under JP or CS/CB pattern, the CSI that transmitting terminal obtains can greatly affect systematic function.In the time having made a start perfect channel information, multinode is can selective channel quality good and disturb each other one group of little user by cooperation, and be easy to the Linear Precoding elimination realizing or reduce between user and presence of intercell interference by ZF (ZF:Zeroforcing) or piece diagonal angle (BD:Block Diagonalization) etc., thereby improve systematic function.But in actual FDD (Frequency Division Duplex) system, uplink feedback link is that capacity is limited, each user only feeds back limited information, BS can only obtain partial channel knowledge, that is: Limited Feedback system, as shown in Figure 2, this will cause the decline of systematic function to its model.

Summary of the invention

Object of the present invention is intended at least solve one of above-mentioned technological deficiency.

For this reason, the object of the invention is to propose the coordinated multi-point transmission method based on Limited Feedback in a kind of homogeneous network system that improves homogeneous network feedback efficiency, reduction overhead.

For achieving the above object, the embodiment of the present invention has proposed the coordinated multi-point transmission method under Limited Feedback in homogeneous network system, described homogeneous network system comprises the transmitting node of multiple identical configurations, wherein the signal of each transmitting node covers Yi Ge community, each described community comprises multiple users, said method comprising the steps of: be respectively each community and set up base vector to obtain base vector set; According to described base vector set and predetermined threshold value, apply a set of candidate user choice criteria and determine candidate user set, wherein, described predetermined threshold value comprises first threshold θ ₀with Second Threshold γ ₀, described a set of candidate user choice criteria is:

$\mathrm{\&Omega;}:\left\{\begin{array}{c}\left|\cos (\&angle;(h_{l,l_k},v_l))\right|>\cos {\mathrm{\&theta;}}_0\\ \left|{g_{l,l_k}^m}^H{v}_m\right|<{\mathrm{\&gamma;}}_0,(m\&NotEqual;l)\end{array}\right.,(l=1,...,L),$

Wherein, described first threshold θ ₀for limiting user's the threshold value of channel direction, described Second Threshold γ ₀for the threshold value to user's interference channel intensity, described Ω is candidate user choice criteria, described in be l in l community _kindividual user's channel with l community base vector v _langle, described in

be m community to l in l community _kindividual user's interference channel

at m community base vector v _mon projection, described l and m are community No. ID; Each user in described candidate user set sends and has default big or small feedback information to transmitting node; Apply a set of scheduling strategy to the user who sends out described feedback information, to select the dispatched users of current time from the described user who sends out described feedback information; Described dispatched users is fed back described channel information to described transmitting node; And described transmitting node is reconstructed the channel of described dispatched users according to the channel information of described feedback, and channel based on described reconstruct does precoding, to send information according to described precoding result to described dispatched users.According to the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of the embodiment of the present invention, utilize the mode of hierarchical feedback, effectively utilize feedback bits to improve user's feedback efficiency, and based on feedback information multi-plot joint selection scheduling user definite launching beam, i.e. cooperative scheduling under Limited Feedback/cooperative beam is shaped, thereby to reduce the feedback overhead of system in the relatively little situation of throughput of system loss.

The aspect that the present invention is additional and advantage in the following description part provide, and part will become obviously from the following description, or recognize by practice of the present invention.

Accompanying drawing explanation

The present invention above-mentioned and/or additional aspect and advantage will become from the following description of the accompanying drawings of embodiments obviously and easily and understand, wherein:

Cooperative scheduling/cooperative beam schematic diagram of Tu1Wei Liang community;

Fig. 2 is Limited Feedback system model;

Fig. 3 is the hierarchical feedback system block diagram of the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of the embodiment of the present invention

Fig. 4 is that the candidate user of the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of the embodiment of the present invention is determined schematic diagram;

Fig. 5 is the suprasphere uniform quantization schematic diagram of the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of the embodiment of the present invention;

Fig. 6 is the homogeneous network scene schematic diagram of the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of the embodiment of the present invention;

Fig. 7 is the flow chart of the code book design of the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of one embodiment of the invention;

Fig. 8 is the sequential chart of the transfer of data of the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of one embodiment of the invention;

Fig. 9 uses the coordinated multi-point transmission method based on Limited Feedback and the performance simulation figure of ideal situation in the homogeneous network system of the embodiment of the present invention; And

Figure 10 is the flow chart of the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of the embodiment of the present invention.

Embodiment

To describe now embodiments of the invention in detail, the example of described embodiment is shown in the drawings.Although show specific embodiment, it should be understood that not mean that and limit the invention to these specific embodiments.On the contrary, present invention resides in substituting, revising and being equal in the spirit and scope of appended claim.Illustrating multiple details is for the complete understanding to theme in this paper is provided.But those of ordinary skill in the art should understand, can not implement this theme by these details.In other cases, do not describe known method, program, parts and circuit in detail, thereby avoid unnecessarily making the aspect of the present embodiment fuzzy.

Although herein may with term first, second etc. various elements are described, these elements are not limited by these terms should.These terms are only for differentiating an element and another element.For example the first order standard can be called the second order standard, and similarly, the second order standard can be called the first order standard, without departing from the scope of the invention.The first order standard and the second order standard are all order standards, but they are not identical order standards.

The term using in description of the invention is herein only used to describe the object of specific embodiment, and does not mean that limitation of the present invention.As what used in the description of the present invention and claims, singulative " " " one " and " described " mean and also comprise plural form, unless context clear pointing out in addition.Should also be understood that term as used herein "and/or" represent and comprise one or more projects of listing being associated any one and likely combine.It should also be further understood that, in the time using in specification, term " comprise " and/or specify " comprising " statement feature, operation, element and/existence of parts, but do not get rid of existence or the interpolation of one or more other features, operation, element, parts and/or their group.

As used herein, based on context, term " if " can be regarded as and refer to " when " or " ... time " " in response to determining " or " according to ... determine " or " in response to detecting ", the prerequisite of statement is real.Similarly, based on context, phrase " if determine [prerequisite of statement is real] " or " if [prerequisite of statement is real] " or " when [prerequisite of statement is real] " can be regarded as and refer to " determining ... time " " in response to determining " or " according to .... determine " " in detection ... time " or " corresponding to detection " prerequisite of stating be real.

Describe according to the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of the embodiment of the present invention below in conjunction with accompanying drawing.

Homogeneous network system comprises the transmitting node of multiple identical configurations, and wherein the signal of each transmitting node covers Yi Ge community, and each described community comprises multiple users.

Due to the feature that broadcast characteristic and the CS/CB user data of downlink transfer (transmitting node is to user's transmission information) are not shared, the user in each community can be subject to this community space division multiple access user's inter-user interference and the co-channel interference of minizone.For ease of realizing, between the transmitting node in method of the present invention, by cooperation, a user is only served in the each community of each time slot (time slot).Therefore in community, there is no inter-user interference, and the co-channel interference CCI of minizone still exists.Known through above-mentioned analysis, user's throughput not only with self channel gain about also relevant with the dispatched users of interference channel and interfered cell.Between transmitting node, only has the average spectral efficiency (ase) that could improve system by cooperative scheduling and combined optimization wave beam weight (Beamforming weight vector) or pre-coding matrix (Precoding matrix).

Combined dispatching and optimization beam vector/pre-coding matrix require transmitting node end to have good channel condition information.In actual FDD system, because transmitting node cannot obtain perfect channel status (Perfect CSIT), can cause performance loss.Therefore embodiments of the invention have considered emphatically how effectively to utilize limited feedback bits for real system, improve systematic function.

Shown in Figure 10, comprise the steps: according to the coordinated multi-point transmission method based on Limited Feedback in the homogeneous network system of the embodiment of the present invention

Step S101, is respectively each community and sets up base vector to obtain base vector set.In one embodiment of the invention, in base vector set, each base vector is V _l, (l=1 ... L), wherein, described V _lbe the base vector of l community, the number that described L is community, and the mould of multiple base vectors is 1.Base vector (RV:Reference Vector) v that mould is 1 is introduced in each community _l, l=1 ..., L}.

Step S102, according to base vector set and predetermined threshold value, applies a set of candidate user choice criteria and determines candidate user set, and wherein, described predetermined threshold value comprises first threshold θ ₀with Second Threshold γ ₀, described a set of candidate user choice criteria is:

$\mathrm{\&Omega;}:\left\{\begin{array}{c}\left|\cos (\&angle;(h_{l,l_k},v_l))\right|>\cos {\mathrm{\&theta;}}_0\\ \left|{g_{l,l_k}^m}^H{v}_m\right|<{\mathrm{\&gamma;}}_0,(m\&NotEqual;l)\end{array}\right.,(l=1,...,L),$

Wherein, described first threshold θ ₀for limiting user's the threshold value of channel direction, described Second Threshold γ ₀for the threshold value to user's interference channel intensity, described Ω is candidate user choice criteria, described in

be l in l community _kindividual user's channel

with l community base vector v _langle, described in

be m community to l in l community _kindividual user's interference channel

at m community base vector v _mon projection, described l and m are community No. ID.

Particularly, take into account user self channel and interference channel the impact of SINR is passed through to set suitable threshold value (first threshold θ ₀with Second Threshold γ ₀) determine the possible candidate user set (Candidate Set) for dispatching, in one embodiment of the invention, candidate collection (candidate user set) is Γ={ Γ _l, (l=1 ..., L), Γ _lbe the candidate user set in l community, the candidate user number in candidate user set is P=card (k, k ∈ Ω), and card is the number of element in candidate user set, and described k is the user of Ω of satisfying condition.

In one embodiment of the invention, determine that candidate user set need to consider following factor, that is: one is the relation that needs self channel He Zhe community base vector of the user of scheduling.The 2nd, the interference strength that user receives.Particularly, the user who needs scheduling does computing according to self channel of estimating and interference channel and, base vector, and whether determine in this locality needs to feed back.It judges whether to need the criterion of feedback to be: the interference that subscriber channel Yu Zhe community base vector enough approaches and user receives is enough little, wherein, judge whether subscriber channel Yu Zhe community base vector enough approaches and user receives interference whether enough little be by the first threshold θ of setting ₀with Second Threshold γ ₀determine, be subject to first threshold θ ₀with Second Threshold γ ₀impact.

Step S103, the each user in candidate user set sends and has default big or small feedback information to transmitting node.The feedback quantity of the feedback information that in this example, the each user in candidate user set sends to described transmitting node is 1-bit.

Step S104, applies a set of scheduling strategy to the user who sends out described feedback information, to select the dispatched users of current time from the described user who sends out described feedback information.Particularly, scheduling strategy includes but not limited to following mode:

A: in the time of P=0, random selection scheduling user in all users in each described community; And

B: in the time of P > 0, in candidate collection Γ with the principle selection scheduling user of the historical Mean Speed user priority of minimum.

Further, the scheduling formula of scheduling strategy B is:

(l=1 ..., L), wherein,

it is k user historical average throughput in set time window in l community.

Further, in this example, also can be to described

upgrade, wherein more new formula is:

${\stackrel{\&OverBar;}{R}}_k^l(t+1)=\left\{\begin{array}{cc}(1-\frac{1}{t_c}){\stackrel{\&OverBar;}{R}}_k^l\left(t\right)+\frac{1}{t_c}{r}_k^l\left(t\right),& k={k_l}^{*}\\ (1-\frac{1}{t_c}){\stackrel{\&OverBar;}{R}}_k^l\left(t\right),& k\&NotEqual;{k_l}^{*}\end{array}\right.,$

Wherein,

for dispatched users is at the momentary rate in t moment, k _l ^*be the dispatched users in l community, t _cbe 25 time windows.

Step S105, dispatched users is fed back described channel information to described transmitting node.Dispatched users is fed back described channel information to described transmitting node, particularly: channel information is quantized channel vector

Wherein,

for user's per channel, i.e. channel direction, wherein,

and the per channel of described dispatched users

on the spherical crown of the unit's of being evenly distributed on hypersphere, C is the little code book of optimizing.More specifically,

1, be uniformly distributed characteristic, described first threshold θ according to described channel direction ₀with described dispatched users to described transmitting node number of bits of feedback n ₁, calculate the big or small N of the large code book B of described whole unit hypersphere, wherein, described large code book B={b ₁, b ₂..., b _n, described b _ifor the code word in code book B.

2, described transmitting node and dispatched users obtain the little code book C according to described spherical crown according to the base vector of corresponding community and large code book B.

3. searching optimum code word according to described little code book C quantizes the channel direction of described dispatched users.Transmitting node transmitting node

Step S106, transmitting node is reconstructed the channel of described dispatched users according to the channel information of described feedback, and channel based on described reconstruct does precoding, to send information according to precoding result to described dispatched users.Particularly, transmitting node is searched corresponding code word according to the index of the described little code book C of described dispatched users feedback in described little code book C, with according to the channel of dispatched users described in described code word reconstruct.

According to the above embodiments, the thinking that channel is reconstructed is: have compared with perfect channel information with making a start, this Limited Feedback can affect the performance of system to a certain extent.The performance loss causing in order to reduce Limited Feedback, code book design (corresponding above-mentioned steps S105) becomes the key of improving systematic function.Definite scheme (corresponding above-mentioned steps S102) of the candidate user of the embodiment of the present invention, direction based on candidate user channel h in such criterion (candidate user choice criteria) be restricted and user self channel h and interference channel g between separate feature, can obtain as drawn a conclusion:

User's per channel vector

on a spherical crown of the unit's of being evenly distributed on hypersphere.The base vector of this spherical crown You Gai community and thresholding (predetermined threshold value) determine jointly.According to the number of bits of feedback n1 of this equally distributed conclusion, system and threshold value θ ₀, by calculating as follows the codebook size N that quantizes whole hypersphere:

Wherein, D1 and D0 represent respectively the surface area of spherical crown and whole ball.The size of D1 and spheroid dimension and threshold value θ ₀relevant, D0 is relevant with spheroid dimension.Therefore the large codebook size of whole hypersphere is: | B|=N, the little codebook size that spherical crown is corresponding is

large code book is denoted as B={b ₁, b ₂..., b _n, can generate by off-line, and in each transmitting node and shared among users.Jointly determined by large code book B He Gai community base vector for the little code book C of each community, that is: in B with this benchmark inner product maximum before

individual code word forms C.

Community transmitting node and dispatched users obtain little code book C according to this community base vector and large code book B.The code book C of the dispatched users of having chosen based on optimizing finds optimum code word to quantize channel direction, and the index in C (channel information) feeds back to transmitting node by this code word, transmitting node finds corresponding code word according to the index of feedback in C, thus reconstruct subscriber channel.

Thus, the code book design of embodiments of the invention based on above-mentioned, has taken into full account the distribution characteristics that is quantized channel, and has completed the quantification of channel direction CDI with larger code book and less feedback overhead.

For the method for the embodiment of the present invention is had to clearer understanding, below with object lesson, method set forth in the present invention is explained in detail.

[embodiment 1]

The scene description of system:

The present embodiment relates to the cooperative scheduling cooperative beam shaping scheme under Limited Feedback in many communities, multi-user's homogeneous network system, and homogeneous network system as shown in Figure 6.Whole system is made up of an eNB and multiple high power RRH (Remote Radio Head), and these RRH are connected with center eNB by optical fiber.So-called homogeneous network refers to here, and RRHYu center eNB has identical transmitting power, antenna configuration and coverage.Be from the different of traditional homogeneous network, the radio-frequency maser that these RRH just pull out from center eNB, it only has transmission-receiving function and does not possess signal handling capacity, that is to say after these RRH receive the information of user feedback and need to pass to center eNB by optical fiber link, center eNB is equivalent to a master controller and makes scheduling decision, then completes transfer of data by each transmitting node.Therefore in whole system, large feedback overhead (referring to the feedback quantity of the up-link wireless link from user to each transmitting node) also can cause the load-bearing of backhaul to be born simultaneously, is not easy in practice to realize.Therefore, embodiments of the invention are for actual multiple sectors at same network forming network, new hierarchical feedback scheme (method of user feedback channel information) has been proposed, effectively utilize the performance loss that limited feedback bits causes to reduce Limited Feedback, complete the transmission of user data, promoted feedback efficiency and elevator system communication performance.

This homogeneous network is made up of L community, and the even random distribution in each community has K single antenna user.This L community forms a cooperation set (CS:Coordinated Set), shares each other CSI, and dynamic interaction is made scheduling decision and completed transfer of data.ENB and RRH all dispose N _troot antenna, and have identical transmitting power P _t.A user is only dispatched by the each time slot of cooperation (time slot) in each community.Therefore in community, there is no inter-user interference, the co-channel interference CCI of minizone still exists.Now l in the l community _kindividual user's reception signal is as follows:

$y_{{l,l}_k}={h_{l{,l}_k}}^H{x}_l+\underset{m\&NotEqual;l}{\mathrm{\&Sigma;}}{g_{{l,l}_k}^m}^H{x}_m+n_l$

$={h_{{l,l}_k}}^H{w}_{l_k}^l{s}_{l_k}^l+\underset{m\&NotEqual;l}{\mathrm{\&Sigma;}}{g_{{l,l}_k}^m}^H{w}_{m_k}^m{s}_{m_k}^m+n_l$ l＝{1，...，L}(2)

Wherein,

represent l community Dao Zhe community l _kindividual user's channel gain,

represent that m community is to l in l community _kindividual user's interference channel gain.

with

represent respectively the wave beam weight vector initial data of dispatched users in l community, weight

transmitting of l transmitting node.N _l～C _n(0, σ ²) be the additive white Gaussian noise that dispatched users receives.

The feature of not sharing according to the user data of CS/CB, l _kindividual user's data

only provided by its Serving-cell, so in (2) formula, the right Section 1 is user l _kdesired signal, Section 2 is the co-channel interference from other communities.This user's reception Signal to Interference plus Noise Ratio (SINR:Signal-to-interference-plus-noise ratio) is as follows:

${\mathrm{SINR}}_{l_k}^l=\frac{P_t{\left|{h_{{l,l}_k}}^H{w}_{l_k}^l\right|}^2}{1+P_t\underset{m\&NotEqual;l}{\mathrm{\&Sigma;}}{\left|{g_{{l,l}_k}^m}^H{w}_{m_k}^m\right|}^2}---\left(3\right)$

Hierarchical feedback method to the embodiment of the present invention (method of user feedback channel information, corresponding above-mentioned steps S105) is further explained below, the specific implementation process of hierarchical feedback method in the present embodiment, and its system block diagram is as shown in Figure 3.

In order to reduce the complexity of multiple minizones cooperation and the feedback quantity of system, first introduce the base vector v that a random mould producing is 1 in each community _l, l=1 ..., and L}, subscript l represents cell id.By setting suitable threshold value (predetermined threshold value), utilize criterion Ω to determine possible dispatched users set Γ={ Γ _l, (l=1 ..., L).Therefore only have the user feedback 1-bit in set Γ need to be scheduled with notice transmitting node at first step feedback stage, now, other users are not to transmitting node feedback information.The Ω criterion of determining candidate user is as follows:

$\mathrm{\&Omega;}:\left\{\begin{array}{c}\left|\cos (\&angle;(h_{l,l_k},v_l))\right|>\cos {\mathrm{\&theta;}}_0\\ \left|{g_{l,l_k}^m}^H{v}_m\right|<{\mathrm{\&gamma;}}_0,(m\&NotEqual;l)\end{array}\right.,(l=1,...,L)---\left(4\right)$

Formula 4 represents that user self channel Yu Zhe community base vector is the most enough and approaches and the enough little user of projection on the benchmark of interfered cell is only the candidate user that may be scheduled from the interference channel of other communities.The space of candidate collection is illustrated as shown in Figure 4.Determine realization that the method for candidate user is approximate and disturbed and evade, effectively suppressed presence of intercell interference.Make relatively to simplify for the code book design of subscriber channel simultaneously.

Thresholding θ ₀(first threshold) and γ ₀(Second Threshold) limited respectively the direction of subscriber channel and approximate interference strength.By above-mentioned two thresholdings are set, greatly reduce the scope of feedback.Although only have certain customers' feedback information to become possible dispatched users, the scope that user selects is diminished, reduce multi-user diversity gain, in fact, the user only in multi-user system with good instantaneous channel status just has an opportunity to be scheduled, those users that mourn in silence (there is no the user to transmitting node feedback information) do not meet the requirement of Ω, illustrate and there is no good SINR, even if therefore all users participate in feedback, the possibility that these users are scheduled is still very little, therefore thresholding is set dwindles feedback scope and can't make the performance of the multi-user diversity of system be subject to large impact.。And the candidate user that meets Ω is only fed back 1-bit to service transmitting node, and the feedback quantity that greatly reduces system takes full advantage of the performance of selecting multi-user diversity (SMUD) to guarantee system simultaneously.Regulate threshold parameter θ ₀and γ ₀, can limit on the one hand the size of candidate collection, the feedback quantity of control system, can guarantee the performance of system on the other hand indirectly.

The transmitting node of each community is received after the 1-bit information of user feedback, is made as the scheduling decision of (5) formula.Make P=card{k, k ∈ Ω } represent to meet in whole system user's number of candidate's condition Ω.

Dispatching principle A:

P=0 represents not have in system user to meet the restriction of Ω, i.e. Γ=Φ, and now each community random selection scheduling user in all users, to reduce the wasting of resources.

Dispatching principle B:

In the time of P > 0, in candidate collection Γ, according to the principle selection scheduling user of the historical Mean Speed user priority of minimum, take into account the fairness between user guaranteeing systematic function when.

Scheduling strategy B during below to P > 0 describes:

This scheduling strategy is the variant of equitable proportion (PF:Proportional fair) scheduling strategy.Owing to there is no concrete user channel quality information in first step feedback, therefore cannot obtain user's instantaneous channel status, therefore traditional PF is deformed into:

${k_l}^{*}=\arg \underset{k\&Element;{\mathrm{\&Gamma;}}_l}{\max }\frac{1}{{\stackrel{\&OverBar;}{R}}_k^l\left(t\right)},(l=1,...,L)---\left(6\right)$

, the scheduler of l community by t time slot allocation to user k _l ^*dispatch.Wherein,

be k the user in l community at time window t _cinterior historical average throughput.Γ _lrepresent the candidate user set of l community.

upgrade in the following manner:

${\stackrel{\&OverBar;}{R}}_k^l(t+1)=\left\{\begin{array}{cc}(1-\frac{1}{t_c}){\stackrel{\&OverBar;}{R}}_k^l\left(t\right)+\frac{1}{t_c}{r}_k^l\left(t\right),& k={k_l}^{*}\\ (1-\frac{1}{t_c}){\stackrel{\&OverBar;}{R}}_k^l\left(t\right),& k\&NotEqual;{k_l}^{*}\end{array}\right.---\left(7\right)$

Wherein

the momentary rate of dispatched users in the t moment.

According to above-mentioned scheduling strategy, determine the dispatched users S set of system at each time slot _t={ k _l ^*, l=1 ..., L}, k _l ^*it is the dispatched users of l community.Transmitting node is determined scheduling S set _tafter, activate its feedback quantization channel of these user notifications that will dispatch.Therefore, S set in second step feedback _tin user in code book C separately, select optimum quantization code word according to (8), and the index of its optimum code word is sent to transmitting node by the channel of Limited Feedback.

$\hat{h}=Q\left(\tilde{h}\right)=\arg \underset{c_i\&Element;C}{\max }\left|{\tilde{h}}^H{c}_i\right|---\left(8\right)$

Transmitting node finds corresponding code word reconstruct subscriber channel after receiving the index of feedback in code book.Then, the channel of transmitting node based on reconstruct does wave beam and completes transfer of data.

The present invention has introduced base vector in the deterministic process Zhong Duige community of candidate user, and by threshold constraints has been set two aspects: first subscriber channel needs Yu Zhe community benchmark very approaching, and it two requires approximate interference strength enough little.Due to the independence of subscriber channel h and interference channel g, make the distribution of interference channel g not affect the distribution of subscriber channel h.Obtain thus normalized subscriber channel

on a spherical crown of unit hypersphere, obey and be uniformly distributed, this spherical crown is determined jointly by reference vector v and the thresholding of community.Based on equally distributed characteristic, in the present invention, determine according to the size of limited number of bits of feedback and spherical crown the codebook size N that quantizes whole suprasphere, and by simulating N electronics at N _tmutual repulsion process on dimension unit hypersphere, finally obtains N _tthe code book B of dimension unit hypersphere uniform quantization.

The uniform quantization of suprasphere is illustrated as shown in Figure 5.Its principle is as follows:

The principle of mutually repelling according to physics moderate, same sex electric charge generates code book.Optimization aim is now that N electronics is evenly distributed in to N as far as possible _ton the unit hypersphere of dimension, i.e. the Coulomb potential of minimization system, makes this N electronics on unit ball, reach poised state, and now under poised state, the coordinate of each electronics is our required code word.

Fig. 7 shows the flow chart of code book design, and the concrete steps of this algorithm are as follows:

Step S701: maximum iteration time Nmax is set.

Step S702: wait electric charge electron distributions to N by N _ton dimension unit hypersphere, according to the Coulomb potential of formula 9 computing systems.

Step S703: fix an electronics, calculate the suffered Coulomb force of each electronics according to formula 10.

Step S704: the position in next moment of calculating each electronics under the effect of Coulomb force.

Step S705: recalculate system Coulomb potential, iterations adds 1.

Step S706: if Coulomb potential E declines, upgrade the position of an electronics, return to step S704 otherwise adjust step-length.

Step S707: if system iterative number of times is less than Nmax, return to step S703, otherwise iteration stops.

Wherein, formula (9) and formula (10) are as follows:

$E=\underset{i=1}{\overset{N-1}{\mathrm{\&Sigma;}}}\underset{j=i+1}{\overset{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="HDA0000152788000000011.png,HDA0000152788000000041.png"\; state="\{\{state\}\}">N</figure-callout>}}{\mathrm{\&Sigma;}}}\frac{1}{|x_i-x_j|}---\left(9\right)$

$F_i=\underset{j=1,j\&NotEqual;i}{\overset{N-1}{\mathrm{\&Sigma;}}}\underset{i=1}{\overset{N}{\mathrm{\&Sigma;}}}\frac{x_i-x_j}{{|x_i-x_j|}^3}---\left(10\right)$

Wherein, E is Coulomb potential, x _ibe the coordinate of i electronics, x _jbe the coordinate of j electronics, F _ibe i the Coulomb force that electronics is suffered.

Thus, while finally reaching poised state, the position vector of each electronics is exactly the each code word vector in code book B.

The code book B Shi Ge community obtaining by said method and user know altogether, and its size learns according to formula 1 | B|=N.The little codebook size that spherical crown is corresponding is the little code book C for spherical crown part is tried to achieve based on large code book B after generating base vector in each community.That is: in B with this benchmark inner product maximum before individual code word forms C.

In one embodiment of the invention, the specific implementation flow process of method of the present invention is as follows:

Thresholding θ is set ₀and γ ₀.

According to the number of bits of feedback of system requirements and θ ₀determine the big or small N of large code book according to (1) formula.

Flow scheme design size according to Fig. 7 is the code book B of N.

Each community generates base vector v separately _l, 1=1 ..., L}.

Transmitting node downlink broadcast v _l, l=1 ..., L}, and generate each community little code book C separately in both sides.

User's side is calculated:

$\left\{\begin{array}{c}\mathrm{\&theta;}=\&angle;(h_{{l,l}_k},v_l)\\ \mathrm{\&gamma;}=\left|{g_{{l,l}_k}^m}^H{v}_m\right|\end{array}\right.,$ And the user who meets Ω condition is added to candidate user collection Γ.

User feedback 1-bit in Γ gives service transmitting node, completes first step feedback.

Each transmitting node is determined the S set of dispatched users according to the scheduling strategy of (5) formula _t.

S _tin user select optimum code word based on the little code book C of community separately according to (8), and feed back the index of this code word, complete second step feedback.

Transmitting node (transmitting terminal), according to the feedback information reconstruct subscriber channel receiving, does beam forming based on this, completes transfer of data.As shown in Figure 8, be the sequential chart of transfer of data according to an embodiment of the invention.

According to the above embodiments, its simulation result is as follows:

In order to verify the performance of Limited Feedback cooperative scheduling cooperative beam shaping Algorithm of proposition, take system average spectral efficiency (ase) as measurement index, carry out Computer Simulation checking.In emulation, consider the homogeneous network of 3 community compositions.Partial simulation parameter is as shown in the table:

Scene layout	The homogeneous network of 3 cell cooperatives
		Distance between sites	500m
Each node number of transmit antennas	4
		User antenna number	1
Number of users	Be uniformly distributed 10 user/communities
		Channel quantitative	2 bits or 4 bits
Noise spectral density	-174dbm/HZ
		Business model	Full load

Table 1

As shown in Figure 9, be the simulation figure of the power system capacity V.S. transmitting node transmitting power of method of the present invention and ideal situation under Limited Feedback.As shown in Figure 9, no matter be ideally or under Limited Feedback, system and capacity all increase with the increase of transmitting node transmitting power.Because system when the high transmit power is interference-limited, therefore compare low power section at high power region capacity with the trend of the rising of power mild.In the time of ideal situation, the volumetric properties of system is best, due to the perfect channel information cooperative scheduling of transmitting node utilization and further eliminated presence of intercell interference by spatial beams, has therefore obtained best performance, and this is consistent with notional result.In figure, also can see that the systematic function that Limited Feedback causes declines, and performance loss degree is relevant with feedback quantity.Performance in the time of system 4 bit feedback is better than 2 bit feedback.Although Limited Feedback has caused hydraulic performance decline, the performance loss degree that in the present invention, the method for embodiment causes is also little, substantially can obtain most of performance gain ideally.This algorithm has reduced feedback quantity and the implementation complexity of system significantly on the other hand, has also taken into account the fairness between user simultaneously.

Any process of otherwise describing in flow chart or at this or method are described and can be understood to, represent to comprise that one or more is for realizing module, fragment or the part of code of executable instruction of step of specific logical function or process, and the scope of the preferred embodiment of the present invention comprises other realization, wherein can be not according to order shown or that discuss, comprise according to related function by the mode of basic while or by contrary order, carry out function, this should be understood by embodiments of the invention person of ordinary skill in the field.

The logic and/or the step that in flow chart, represent or otherwise describe at this, for example, can be considered to the sequencing list of the executable instruction for realizing logic function, may be embodied in any computer-readable medium, use for instruction execution system, device or equipment (as computer based system, comprise that the system of processor or other can and carry out the system of instruction from instruction execution system, device or equipment instruction fetch), or use in conjunction with these instruction execution systems, device or equipment.With regard to this specification, " computer-readable medium " can be anyly can comprise, device that storage, communication, propagation or transmission procedure use for instruction execution system, device or equipment or in conjunction with these instruction execution systems, device or equipment.The example more specifically (non-exhaustive list) of computer-readable medium comprises following: the electrical connection section (electronic installation) with one or more wirings, portable computer diskette box (magnetic device), random access memory (RAM), read-only memory (ROM), the erasable read-only memory (EPROM or flash memory) of editing, fiber device, and portable optic disk read-only memory (CDROM).In addition, computer-readable medium can be even paper or other the suitable medium that can print described program thereon, because can be for example by paper or other media be carried out to optical scanner, then edit, decipher or process in electronics mode and obtain described program with other suitable methods if desired, be then stored in computer storage.

Should be appreciated that each several part of the present invention can realize with hardware, software, firmware or their combination.In the above-described embodiment, multiple steps or method can realize with being stored in software or the firmware carried out in memory and by suitable instruction execution system.For example, if realized with hardware, the same in another embodiment, can realize by any one in following technology well known in the art or their combination: there is the discrete logic for data-signal being realized to the logic gates of logic function, there is the application-specific integrated circuit (ASIC) of suitable combinational logic gate circuit, programmable gate array (PGA), field programmable gate array (FPGA) etc.

Those skilled in the art are appreciated that realizing all or part of step that above-described embodiment method carries is can carry out the hardware that instruction is relevant by program to complete, described program can be stored in a kind of computer-readable recording medium, this program, in the time carrying out, comprises step of embodiment of the method one or a combination set of.

In addition, the each functional unit in each embodiment of the present invention can be integrated in a processing module, can be also that the independent physics of unit exists, and also can be integrated in a module two or more unit.Above-mentioned integrated module both can adopt the form of hardware to realize, and also can adopt the form of software function module to realize.If described integrated module realizes and during as production marketing independently or use, also can be stored in a computer read/write memory medium using the form of software function module.

The above-mentioned storage medium of mentioning can be read-only memory, disk or CD etc.

In the description of this specification, the description of reference term " embodiment ", " some embodiment ", " example ", " concrete example " or " some examples " etc. means to be contained at least one embodiment of the present invention or example in conjunction with specific features, structure, material or the feature of this embodiment or example description.In this manual, the schematic statement of above-mentioned term is not necessarily referred to identical embodiment or example.And specific features, structure, material or the feature of description can be with suitable mode combination in any one or more embodiment or example.

Although illustrated and described embodiments of the invention, for the ordinary skill in the art, be appreciated that without departing from the principles and spirit of the present invention and can carry out multiple variation, modification, replacement and modification to these embodiment, scope of the present invention is by claims and be equal to and limit.

Claims (10)

1. the coordinated multi-point transmission method based on Limited Feedback in a homogeneous network system, it is characterized in that, described homogeneous network system comprises the transmitting node of multiple identical configurations, wherein the signal of each transmitting node covers Yi Ge community, each described community comprises multiple users, said method comprising the steps of:

Be respectively each community and set up base vector to obtain base vector set;

According to described base vector set and predetermined threshold value, apply a set of candidate user choice criteria and determine candidate user set, wherein, described predetermined threshold value comprises first threshold θ ₀with Second Threshold γ ₀, described a set of candidate user choice criteria is:

(l=1,...,L)，

Wherein, described first threshold θ ₀for limiting user's the threshold value of channel direction, described Second Threshold γ ₀for the threshold value to user's interference channel intensity, described Ω is candidate user choice criteria, described in

be l in l community _kindividual user's channel

with l community base vector v _langle, described in

be m community to l in l community _kindividual user's interference channel

at m community base vector v _mon projection, described l and m are community No. ID;

Each user in described candidate user set sends and has default big or small feedback information to transmitting node;

Apply a set of scheduling strategy to the user who sends out described feedback information, to select the dispatched users of current time from the described user who sends out described feedback information;

Described dispatched users is to described transmitting node feedback channel information; And

Described transmitting node is reconstructed the channel of described dispatched users according to the channel information of described feedback, and channel based on described reconstruct does precoding, to send information according to described precoding result to described dispatched users.

2. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 1, is characterized in that, in described base vector set, each base vector is V _l, (l=1 ... L), wherein, the base vector that described Vl is l community, the number that described L is community, and the mould of multiple base vectors is 1.

3. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 1, is characterized in that, the feedback quantity of the feedback information that the each user in described candidate user set sends to described transmitting node is 1-bit.

4. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 1, is characterized in that, described candidate collection is Γ={ Γ _l, (l=1 ..., L), described Γ _lbe the candidate user set in l community, the candidate user number in described candidate user set is P=card (k, k ∈ Ω), and wherein, described card is the number of element in candidate user set, and described k is the user of Ω of satisfying condition.

5. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 4, is characterized in that, described a set of scheduling strategy is:

A: in the time of P=0, random selection scheduling user in all users in each described community; And

B: in the time of P>0, in candidate collection Γ with the principle selection scheduling user of the historical Mean Speed user priority of minimum.

6. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 5, is characterized in that, the scheduling formula of described scheduling strategy B is: (l=1 ..., L), wherein,

it is k user historical average throughput in set time window in l community.

7. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 6, is characterized in that, also comprises described

upgrade, wherein more new formula is:

Wherein, for dispatched users is at the momentary rate in t moment, k _l ^*be the dispatched users in l community, t _cfor time window.

8. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 1, is characterized in that, described dispatched users is fed back described channel information to described transmitting node, and wherein, described channel information is quantized channel vector wherein,

Wherein, for user's per channel, i.e. channel direction, wherein,

and the per channel of described dispatched users on the spherical crown of the unit's of being evenly distributed on hypersphere, C is the little code book of optimizing, and H is complex-conjugate transpose.

9. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 8, is characterized in that, further comprises:

Be uniformly distributed characteristic, described first threshold θ according to described channel direction ₀with described dispatched users to described transmitting node number of bits of feedback n ₁, calculate the big or small N of the large code book B of described whole unit hypersphere, wherein, described large code book B={b ₁, b ₂..., b _n, described b _ifor the code word in code book B;

Described transmitting node and dispatched users obtain the little code book C according to described spherical crown according to the base vector of corresponding community and large code book B;

Searching optimum code word according to described little code book C quantizes the channel direction of described dispatched users.

10. the coordinated multi-point transmission method based on Limited Feedback in homogeneous network system according to claim 9, is characterized in that, described transmitting node is reconstructed the channel of described dispatched users according to the channel information of described feedback, further comprises:

Described transmitting node is searched corresponding code word according to the index of the described little code book C of described dispatched users feedback in described little code book C, with according to the channel of dispatched users described in described code word reconstruct.

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