CN106850173A - A kind of multi-district pilots distribution method based on extensive MIMO - Google Patents

Abstract

The invention discloses a kind of multi-district pilots distribution method based on extensive MIMO, first using every 7 cells as a component cluster, assuming that Pilot Interference is existed only in cluster, in the absence of interference between different clusters, each user to the large scale fading coefficients β of this cell base station is asked for_11k.User in Target cell is arranged by large scale fading coefficients, it is obtained in this cell signal strength sequentially, according to signal intensity order, the user in selection target cell successively calculates the most weak user k of signal intensity in Target cell_min With the interference metric values between user in the j ' of neighbor cell.From the user that each cell selection interference metric values are minimum, such user has 7 altogether, identical pilot tone is distributed to themSteps be repeated alternatively until that all pilot tones distribute to all of user.The present invention by calculating different districts between the interference value of user carry out user grouping, alleviate the pilot pollution problem, while the user SINR in equilibrium Target cell, and algorithm complex is low.

Description

A kind of multi-district pilots distribution method based on extensive MIMO

Technical field

The invention belongs to the communications field, it is related to a kind of multi-district pilots distribution method based on extensive MIMO.

Background technology

With the development of mobile communication technology, the arrival in big data epoch makes original LTE technologies increasingly to meet User has good application prospect because of its huge potential to the demand of network, extensive MIMO in 5G radio communications.

For extensive mimo system, accurate channel estimation is most important to obtaining power system capacity higher 's.However, because coherence time is short or there is substantial amounts of user, pilot number is limited, is distributed in the user of neighbor cell not Reuse identical pilot frequency sequence with can avoiding.Led using identical by neighbor cell when subscriber channel estimation is obtained base station User's interference of frequency sequence, here it is so-called pilot pollution.Result of study shows, when the antenna number of base station tends to infinitely great When, the upward signal interference-to-noise ratio (SINR) of user is one and depends on the random of user's random site and large scale decline Amount.

In traditional extensive MIMO pilot allocation schemes, pilot tone is randomly assigned to the user of this cell for base station, by Pilot pollution produced by this just can be configured by changing base station, adjust antenna, optimizing pilot allocative decision etc. to alleviate.

There is scholar using the method for pilot tone time shift to mitigate pilot pollution, alignd by by the pilot time slot in certain cell To the data slot of neighbor cell, pilot pollution is restrained effectively under the synchronous transfer scheme of different districts, but the program is same When have also been introduced interfering for pilot tone and data.Separately there is scholar to propose a kind of pilot frequency sequence allocation strategy, its concrete thought It is the user's distribution identical pilot tone for center of housing estate, and orthogonal guide frequency is then used for Cell Edge User, so as to mitigate leads Frequency pollutes, the capacity of lifting system, but when the number of users of cell edge is relatively large, orthogonal pilot frequency sequence needed for obtaining Quantity will be a very scabrous problem.

The content of the invention

The technical problem to be solved in the present invention is that the user for making signal intensity in Target cell poor is adopted by neighbor cell The minimum interference caused with same pilot, and consider that how to process user grouping in the case of interference value identical asks Topic, the SINR of each user in equalization target cell allows each user to enjoy the service quality of equalization, without going out The poor user of existing channel conditions does not receive the signal of base station transmission, while reducing the influence of pilot pollution, reduces algorithm The problems such as complexity.Summary of the invention

To reach above-mentioned purpose, technical scheme proposed by the present invention is a kind of multi-district pilots based on extensive MIMO point Method of completing the square, specifically comprises the steps of：

First, using every 7 cells as a component cluster, the center per cluster is considered as Target cell, and note is marked as j=1, surrounding Neighbor cell is labeled as 2~7 successively, and Pilot Interference is existed only in cluster, in the absence of interference between different clusters；

2nd, for the user in Target cell, each user to the large scale fading coefficients β of this cell base station is asked for_11k, k ∈{1,2ΛK}；

3rd, the user in Target cell is arranged by large scale fading coefficients, obtains it in this cell signal strength Sequentially, if metThen represent user k₁Signal intensity ratio user k₂Greatly, marking signal intensity is minimum User is

4th, according to signal intensity order, the user in selection target cell, calculates target small according to formula formula below successively The most weak user of signal intensity in areaWith the interference metric between user in neighbor cell j ' (2≤k '≤7) Value, i.e.,

ζ_jk,j′k′Value is more big, represents if interfering for being brought when using same pilot between two users is bigger；

5th, from the user that each cell selection interference metric values are minimum：

6th, according to step 5, serial number in the user selected from each cell and Target cell User constitute one group, such user has 7 altogether, and distributes identical pilot tones to them

7th, repeat step two to six, distributes pilot tone to 7 users that each is grouped successivelyLed until all The all of user of frequency division dispensing.

Further, in step 3, it is to rise that the user in Target cell carries out arrangement by large scale fading coefficients Sequence is arranged.

In step 5, if the interference metric that the same user in same cell in two users and Target cell produces It is worth identical and minimum, then carries out following steps：

Step 51：If signal intensity is in Target cellUser it is individual small with adjacent l (l ∈ { 1,2 Λ L }) Two user k in area₁And k₂Identical least interference metric, the then sequence in step 3, selection close-up is produced to existIts big user of signal intensity ratio, is designated as below

Step 52：It is calculated with two user k in l-th cell₁And k₂The interference metric values of generation, select interference metric Be worth less user andOne group of user, then another user withAs one group.

Compared with prior art, beneficial effects of the present invention：

1, the present invention can make the poor user of signal intensity in Target cell be subject to neighbor cell using same pilot The minimum interference for causing, and consider user grouping problem how is processed in the case of interference value identical comprehensively.

2, by calculating different districts between the interference value of user carry out user grouping, alleviate the pilot pollution problem so that Different districts can be multiplexed limited pilot resources, while the user SINR in equilibrium Target cell, allow each user can The service quality of equalization is enjoyed, the signal of base station transmission is not received without the poor user of channel conditions.

Brief description of the drawings

Fig. 1 is 7 schematic diagrames of label cell system.

Co-channel interference schematic diagram between the user of Fig. 2 neighbor cells.

Fig. 3 is patent pilot tone allocation process diagram of the present invention.

Specific embodiment

Further explanation in detail is done to the present invention in conjunction with accompanying drawing.

As shown in figure 1, the figure illustrates the extensive mimo system figure of cell of label 1~7, this figure is applicable by the present invention Multi-cell system figure.

Consider L multi-user's multiple cell Massive mimo system of hexagonal cell composition, each cell is by one The base station of individual M roots antenna and the individual single-antenna subscriber compositions of K (K ＜ ＜ M).J-th k-th user of cell is to l-th cell base The channel stood can be modeled as

Wherein, g_ljkM × 1 dimensional vector that expression is made up of multipath fading coefficient, and β_ljkLarge scale fading coefficients are represented, Its distance and shadow fading and between user and base station is relevant, can be expressed as

s_ljkRepresent shadow fading, r_ljkRepresent in j-th cell that to l-th distance of base station, R is cell to k-th user Radius, α is path-loss factor.Consider that Massive mimo systems use TDD dual-modes, it is assumed that pilot tone sequence Φ=[φ₁, φ₂,Λφ_K]^T∈C^K×τ, pilot length is τ, and mutually orthogonal because pilot resources are limited two-by-two, and identical pilot group is adjacent Cell reuse.

The upward signal interference-to-noise ratio (SINR) of user is one and depends on user's random site and large scale to decline Random quantity, user k is represented by the up Signal to Interference plus Noise Ratio (SINR) of j-th cell：

Wherein,Represent and disturb incoherent noise power, and with the increase of antenna for base station number, the shadow of its value Ringing can be less and less；Represent pilot pollution, I caused by pilot frequency multiplexing_jkRepresent and used with the k in j-th cell Family is gathered using the user of same pilot, I_jk={ j ' k ':p_j′k′=p_jk}\{jk}

If Fig. 2 with regard to user between neighbor cell using the interference schematic diagram produced by identical pilot tone, the interference between user Metric is namely based on this figure to calculate.The present invention is easy to follow the trail of user's large scale fading information based on base station, makes full use of The information of user's large scale fading coefficients, by calculating different districts between the interference value of user carry out user grouping, alleviate The pilot pollution problem, while the user SINR in equilibrium Target cell, when user produces with neighbor cell user in Target cell During raw identical interference value, just consider that close-up targeted customer's herein is next, by that two that calculate it and neighbor cell The interference value size of user, judges user grouping situation, and this kind of algorithm complex is low, with certain practicality.

The present invention sorts user in Target cell by large scale fading coefficients, so as to the signal intensity for obtaining them is suitable Sequence, according to the order that interference value is minimized, selects corresponding user from each cell successively, user grouping is realized, in every group User be allocated identical pilot tone.As shown in figure 3, detailed step is as follows：

Step one：Every 7 cells are planned as a component cluster, the center per cluster is considered as Target cell, remembers marked as j=1, Surrounding neighbor cell is labeled as 2~7 successively, as shown in Figure 1.Pilot Interference is existed only in cluster, in the absence of dry between different clusters Disturb；

Step 2：For the user in Target cell, each user to the large scale fading coefficients of this cell base station is asked for β_11k, k ∈ { 1,2 Λ K }；

Step 3：Ascending order arrangement is carried out by large scale fading coefficients to the user in Target cell, so as to obtain they This cell signal strength sequentially, if that is, meetThen represent user k₁Signal intensity ratio user k₂Greatly.Mark The minimum user of signal intensity is

Step 4：

According to signal intensity order, the user in selection target cell successively, in calculating Target cell first according to formula (3) The most weak user of signal intensityWith the interference metric values between user in neighbor cell j ' (2≤k '≤7), such as Shown in Fig. 2, i.e.,

ζ_jk,j′k′Value is more big, represents if interfering for being brought when using same pilot between two users is bigger；

Step 5：

From the user that each cell selection interference metric values are minimum：

If two users are identical simultaneously with the interference metric values that the same user in Target cell produces in same cell And it is minimum, then carry out following steps：

Step 51：If signal intensity is in Target cellUser it is individual small with adjacent l (l ∈ { 1,2 Λ L }) Two user k in area₁And k₂Identical least interference metric, the then sequence in step 3, selection close-up is produced to existIts big user of signal intensity ratio, is designated as below

Step 52：It is calculated with two user k in l-th cell₁And k₂The interference metric values of generation, select interference metric Be worth less user andOne group of user, then another user withAs one group；

Step 6：Serial number in the user selected from each cell according to step 5 and Target cellUser constitute one group, such user has 7 altogether, and distributes identical pilot tones to them

Step 7：Repeat step 2-6, distributes pilot tone to 7 users that each is grouped successivelyUntil all Pilot tone distributes to all of user.

Claims (3)

1. a kind of multi-district pilots distribution method based on extensive MIMO, it is characterised in that comprise the steps of：

First, using every 7 cells as a component cluster, the center per cluster is considered as Target cell, and note is marked as j=1, and surrounding is adjacent Cell is labeled as 2~7 successively, and Pilot Interference is existed only in cluster, in the absence of interference between different clusters；

2nd, for the user in Target cell, each user to the large scale fading coefficients β of this cell base station is asked for_11k, k ∈ {1,2ΛK}；

3rd, the user in Target cell is arranged by large scale fading coefficients, obtains it in this cell signal strength sequentially, If metThen represent user k₁Signal intensity ratio user k₂Greatly, the minimum user of marking signal intensity is

4th, according to signal intensity order, the user in selection target cell successively, in calculating Target cell according to formula formula below The most weak user of signal intensityWith the interference metric values between user in neighbor cell j ' (2≤k '≤7), i.e.,

${\mathrm{\ζ}}_{jk,j^{\′}{k}^{\′}}={\mathrm{\β}}_{{\mathrm{jj}}^{\′}{k}^{\′}}^2/{\mathrm{\β}}_{jjk}^2+{\mathrm{\β}}_{j^{\′}jk}^2/{\mathrm{\β}}_{j^{\′}{j}^{\′}{k}^{\′}}^2$

ζ_jk,j′k′Value is more big, represents if interfering for being brought when using same pilot between two users is bigger；

5th, from the user that each cell selection interference metric values are minimum：

$\begin{array}{cc}{k}_{j^{\′}}^{\′}=\arg \underset{k^{\′}\∈\{1,2,\mathrm{...},K\}\backslash k_{\min }}{\underset{j^{\′}\∈\{2,3,\mathrm{...},7\},}{\min }}{\mathrm{\ζ}}_{j^{\′}{k}^{\′},1k_{\min }}={\mathrm{\β}}_{1j^{\′}{k}^{\′}}^2/{\mathrm{\β}}_{11k_{\min }}^2+{\mathrm{\β}}_{j^{\′}1k_{\min }}^2/{\mathrm{\β}}_{j^{\′}{j}^{\′}{k}^{\′}}^2& j^{\′}\∈\{2,3,\mathrm{...},7\}\end{array};$

6th, according to step 5, serial number in the user selected from each cell and Target cell User constitute one group, such user has 7 altogether, and distributes identical pilot tones to them

7th, repeat step two to six, distributes pilot tone to 7 users that each is grouped successivelyUntil all pilot tones point The all of user of dispensing.

2. the multi-district pilots distribution method based on extensive MIMO according to claim 1, it is characterised in that step 3 Described in the user in Target cell by large scale fading coefficients carry out arrangement be do ascending order arrange.

3. the multi-district pilots distribution method based on extensive MIMO according to claim 1, it is characterised in that step 5 In if in same cell two users and the same user in Target cell produce interference metric values are identical and minimum, Then carry out following steps：

Step 51：If signal intensity is in Target cellUser with adjacent l (l ∈ { 1,2 Λ L }) individual cell Two user k₁And k₂Identical least interference metric, the then sequence in step 3, selection close-up is produced to existAfterwards Face signal intensity ratio its big user, is designated as

Step 52：It is calculated with two user k in l-th cell₁And k₂The interference metric values of generation, selection interference metric values compared with Small user andOne group of user, then another user withAs one group.