CN104159235A - Inter-cell interference coordination method for heterogeneous wireless network - Google Patents

Abstract

The invention discloses an inter-cell interference coordination method for a heterogeneous wireless network, and belongs to a long term evolution technology in a mobile communication system in the technical field of wireless communication. According to the method, interference is reduced by finely planning all frequency resources in cells, so that the aim of improving the communication quality for users is fulfilled. The method specifically comprises the following steps: I, grading intra-cell interference; II, clustering the users based on a graph theory vertex coloring theory; and III, performing resource allocation based on spectrum efficiency. In the method, the intra-cell interference is graded, the users are clustered based on the graph theory vertex coloring theory, and the resource allocation is performed based on the spectrum efficiency, so that the number of same frequency interference sources is reduced, a part of adjacent channel interference is avoided, the overall spectrum efficiency of the users in the cells is increased, and the operation complexity is lowered.

Description

A kind of inter-cell interference coordination method of heterogeneous wireless network

Technical field

The invention belongs to wireless communication technology field, relate to the Long Term Evolution in a kind of mobile communication system, particularly a kind of inter-cell interference coordination method of heterogeneous wireless network.

Background technology

The Long Term Evolution (LTE) of UMTS (Universal Mobile Telecommunications System, universal mobile telecommunications system) is the latest developments that a series of promotion mobile communication system advance.LTE technology allows operator to use new and frequency spectrum widely, has higher data rate, lower delay and all-IP framework than 3G network.The network of only disposing macrocell is called as homogeneous network, uses identical wireless transmission standard, uses unified base station type, network topology structure rule, identical covering is provided, similar business and service is provided.The deployment of macro base station position must be passed through the network planning, thereby improves to greatest extent coverage rate and control the interference between base station.But, become increasingly difficult in the deployment of densely populated urban area macro base station, there is the problems such as " high allocating cell ", " high station ", " repeater at high proportion ".

For the place of the hotspot location to macrocell and network coverage disappearance supplements, can in macrocell (macrocell) coverage, dispose lower powered network cell and form heterogeneous network.Heterogeneous network is by macrocellular, remote radio (Remote Radio Head, RRH) and low power nodes (Low Power Node, LPN) mixed networking.Wherein, LPN comprises femto base station (PicoeNB), Home eNodeB (Femtocell) and relaying (Relay).In macrocellular net, dispose the load that low power nodes etc. has unloaded macro base station effectively, improved the covering of wireless signal to blind area, cell edge, thereby realized the lifting of community average throughput and marginal user performance, reach higher frequency spectrum resource utilization rate.

Because honeycomb relaying (Relay) technology has quite wide application prospect, the introducing of relaying technique, make the coverage expanded of cell base station (BS), be positioned at cell edge or communication blind spot region mobile terminal (UE) can by access relay station (RS) carry out double bounce even multi-hop communication to promote its communication quality.In 3GPP and WINNER (Wireless World Initiative New Radio) tissue, obtain deep research in recent years.

Bring certain performance gain although relaying technique is communication system, owing to having increased the communication link in community, need to be equipped with extra frequency resource for it, therefore introduced more interference, as shown in Figure 1.Because frequency planning is unreasonable, make to exist in adjacent bus station base station in Huo Zhe community, neighbor cell or relay station the frequency close with this website operating frequency, or this website causing based on certain factor or adjacent sites coverage are larger than former designing requirement, the interference producing all belongs to adjacent frequency and disturbs.And the carrier frequency transmitting due to other website and this website transmit, carrier frequency is identical, and the interference that receiving node is impacted is called co-channel interference.

In LTE-A communication system, there are two class co-channel interferences: the first kind is co-channel interference in community, the interference that in community, different websites use same frequency to cause receiving node.Because LTE-A system has transmission and the multiple access technology based on OFDM, therefore relatively reasonable as long as frequency resource is divided, in community, disturbing just can not be very outstanding; Equations of The Second Kind is minizone co-channel interference, and the transmitting node in neighbor cell website Yu Zhe community uses the interference that same frequency causes receiving node, and this type of disturbs as the main interference in LTE-A communication system.In order to reduce presence of intercell interference, pertinent literature has proposed the technology such as interference coordination, multi-cell cooperating.Wherein interference coordination have realization comparatively simple, can be applied to the business of various bandwidth, for disturbing the feature that suppresses to have better effects, resource multiplex and scheduling are important one of approach that realizes of interference coordination.

The frequency spectrum that K.Cho etc. can use according to the number of relay is divided into some deciles, in inside, community or cell edge may produce the different subcarrier of region allocation of interference, make the frequency spectrum that uses in these regions completely orthogonal.O.Oyman etc. have discussed spectrum reuse strategy from two aspects, and in Shi Ge community, an aspect, the resource of base station and relay is completely orthogonal; That base station and multiple relay use same frequency spectrum to transmit simultaneously on the other hand.Research shows, can improve performance by multi-hop route, spectrum reuse, and it is in particular in by chance and dispatches and can bring multi-user diversity gain.In the multi-user communication of simultaneously supporting at relaying, this work provides foundation for the tradeoff design of multi-user diversity gain and interference management.Y.Shi has studied two-hop link by carrying out the method for power division maximization link throughput, although the method has been considered the disturbed condition between link, the power sum of source node and via node is retrained, and be not suitable for existing cellular network.

Summary of the invention

In view of this, the object of the present invention is to provide a kind of inter-cell interference coordination method of heterogeneous wireless network, the method is by whole frequency resources in careful planning community, first carry out a bunch division based on vertex coloring theory, then carry out resource distribution based on spectrum efficiency, disturb to reach to reduce, improve the object of user communication quality.

For achieving the above object, the invention provides following technical scheme:

An inter-cell interference coordination method for heterogeneous wireless network, comprises the following steps: step 1: the interference in community is carried out to grade classification; Step 2: user is carried out to sub-clustering based on graph theory vertex coloring theory; Step 3: carry out resource distribution based on spectrum efficiency.

Further, in step 1, the division of level of interference specifically comprises: 1) BS-RN edges of regions accesses the MS of RN, is subject to the level of interference of BS; 2) MS of the access BS in RN-RN region, is subject to the level of interference of RN; 3) the edge MS in RN-RN region, is subject to the level of interference of adjacent R N; 4) level of interference of center of housing estate MS.

Further, step 2 specifically comprises the following steps: 1) according to interference relationships figure, carry out vertex coloring; 2) finely tune according to the quantity of the quantity of sub-clustering and Resource Block RB.

Further, in step 3, specifically comprise the following steps: 1) calculate the spectrum efficiency of each bunch; 2) will bunch sort from big to small according to each bunch of spectrum efficiency; 3) resource block assignments of finding out spectrum efficiency maximum is to each bunch.

Beneficial effect of the present invention is: carry out grade classification by the interference in community, adopt and first user is carried out to sub-clustering based on graph theory vertex coloring theory, then carry out resource distribution based on spectrum efficiency, effectively reduce the number in co-channel interference source, avoid part adjacent frequency to disturb, improve user's overall spectrum efficiency in community, and reduced the complexity of computing.By dynamic distribution frequency spectrum resource, the frequency spectrum in community is allocated flexibly, improve the utilance of frequency spectrum resource.

Brief description of the drawings

In order to make object of the present invention, technical scheme and beneficial effect clearer, the invention provides following accompanying drawing and describe:

Fig. 1 is the interference scene graph of junction network;

Fig. 2 is the transmission time distribution diagram of each link;

Fig. 3 is for disturbing partition of the level schematic diagram;

Fig. 4 is user's sub-clustering flow chart;

Fig. 5 is junction network transmitting scene figure;

Fig. 6 is user's interference relationships figure.

Embodiment

Below in conjunction with accompanying drawing, the preferred embodiments of the present invention are described in detail.

Fig. 1 is the interference scene graph of junction network, the present invention, by whole frequency resources in careful planning community, first carries out a bunch division based on vertex coloring theory, then carries out resource distribution based on spectrum efficiency, disturb to reach to reduce, improve the object of user communication quality.

Specifically comprise the following steps:

Step 1, carries out initialization to system, and method is as follows:

Setting communication network model is 7 community double bounce OFDM junction network models, and setting communication environment is the LTE-A down link based on OFDMA technology;

In setting communication cell, base station is with the relay station that participates in cooperating as transmitting node, and subscriber equipment is as receiving node;

Set cell base station and relay station antenna and all adopt the directional antenna with certain argument, antenna configuration is taked 2 × 2 patterns, and setting power is fixed and meets certain ratio;

The communication mode of setting relay station is half duplex mode of communication;

Set subscriber equipment obeys and is uniformly distributed on radius of society.

Step 2, available frequency spectrum resource in planning community, method is as follows:

The running time-frequency resource of system is divided into time-frequency grid, and is referred to as Resource Block (RB, Resource Block).A Resource Block takies a time slot in time domain, on frequency domain, is made up of 12 subcarriers, and establishing its number is N.

In LTE, TTI is the time span of a subframe of transmission, is set to 1ms, is the minimum scheduling interval of system.Owing to carrying out Inter-Cell Interference Coordination and need to measure the state of channel, in order to reduce overhead, the time interval of carrying out interference coordination can comprise multiple TTI conventionally.

In the time interval of interference coordination, the transmission time of each link distributes as shown in Figure 2.In slot1, BS sends information to RN, and in slot2, BS and RN send information to user separately respectively.Time distribution coefficient α, 1-α represent respectively the time ratio that slot1, slot2 are shared.

Signal interference ratio when BS uses RB n to send information to RN k in Slot1 can be described as:

${\mathrm{SINR}}_{\mathrm{kn}}=\frac{P_{l.k}{g}_{l,k}}{N_0{W}_n+{\mathrm{\Σ}}_{l^{\′},l^{\′}\≠l}{P}_{l^{\′},k^{\′}}{g}_{l^{\′},k}}$

Wherein g _l,krepresent the channel fading between RN k and BSl, P _l,krepresent the through-put power of BSl to RNk.N ₀for thermal noise density, W _nbeing fixed constant, is a bandwidth that Resource Block takies, and total bandwidth is expressed as W=Σ _nw _n. represent the interference from neighbor cell.

In Slot2, because BS and RN can not communicate with certain user simultaneously, therefore need to determine user's ownership.User's set of communicating by letter with RN k with BS respectively in the l of community is designated as respectively to U and V _k(k=1 ... K).

Therefore when, the BS of community l uses RB n to send information to MSm, signal interference ratio can be described as:

${\mathrm{SINR}}_{\mathrm{mn}}^B=\frac{P_{l,m}^B{g}_{l,m}^B}{N_0{W}_n+{\mathrm{\Σ}}_{l^{\′}=1}^L{\mathrm{\Σ}}_{m^{\′}\≠m,B^{\′}\∈Q}{P}_{l^{\′},m^{\′}}^{B^{\′}}{g}_{l^{\′},m^{\′}}^{B^{\′}}}$

The R of community l _kwhile using RBn to send information to MSm, signal interference ratio can be described as:

${\mathrm{SINR}}_{\mathrm{mn}}^{R_k}=\frac{P_{l,m}^{{\text{R}}_k}{g}_{l,m}^{R_k}}{N_0{W}_n+{\mathrm{\Σ}}_{l^{\′}=1}^L{\mathrm{\Σ}}_{m^{\′}\≠m,{R_k}^{\′}\∈Q}{P}_{l^{\′},m^{\′}}^{{R_k}^{\′}}{g}_{l^{\′},m}^{{R_k}^{\′}}}$

Step 3, carries out a bunch division based on vertex coloring theory, and method is as follows:

1, other division of interference level, judges whether to be interfered as shown in Figure 3, need to decide according to user's ownership and present position, and division principle is as follows:

(1), for the user in center of housing estate, think noiseless;

(2) if interference source is BS, in the MS of BS-RN edges of regions access RN, be subject to the interference of BS, interference rank is f _b.

(3) if when interference source is adjacent R N, the MS of the access BS in RN-RN region, is subject to the interference of RN, disturbs rank to be defined as f _r.

(4) if when interference source is adjacent R N, in the edge in RN-RN region MS, be subject to the interference of adjacent R N, disturb rank to be defined as f _r.

(5) be greater than the power of RN due to the power of BS, so define f _b> f _r.

(6) if 2 MS of same BS or RN use same RB simultaneously, be defined as conflict, use f _crepresent.

(7), according to disturbed condition, draw user's interference relationships figure.

2, user is carried out to sub-clustering, as shown in Figure 4, concrete steps are as follows:

(1) adopt the vertex coloring theory of graph theory, user's interference figure is carried out painted, make the summit with line there is different colors, have and disturb or the user of conflict can not use identical frequency spectrum.The quantity that the number of colours using in whole color is bunch.

(2) graph of a relation is expressed as to G=(U, E), wherein U={u ₁, u ₂..., u _mthe set of node that user forms, E exists between the collection representation node of limit to disturb or conflict.Bunch the set that forms of sequence number be labeled as H, need to distribute different Resource Block due to different bunches, number needs therefore bunch is less than the quantity of Resource Block.

(3) known resource number of blocks is N, and that supposes to mark off in the l of community bunch has Φ=X, in the time of X > N, need to make it meet X=N to bunch finely tuning of dividing.According to disturbing rank, by the same cluster that is placed on lower phase mutual interference.

3, the resource based on spectrum efficiency is distributed, and concrete steps are as follows:

(1) calculate the spectrum efficiency C (i) of each bunch,

$C\left(i\right)=\underset{n\∈N}{\mathrm{\Σ}}(\underset{m\∈Y_i^{\′}\∩U}{\mathrm{\Σ}}\log (1+\mathrm{\λ}*{\mathrm{SINR}}_{\mathrm{mn}}^B)+\underset{k}{\mathrm{\Σ}}\underset{m\∈Y_i^{\′}\∩V_k}{\mathrm{\Σ}}\log (1+\mathrm{\λ}*{\mathrm{SINR}}_{\mathrm{mn}}^{R_k}))$

in formula, λ is error rate threshold values.

(2) will bunch sort from big to small according to each bunch of spectrum efficiency C (i), obtain order Y={Y _j.

(3) find out Resource Block n _j, make

$n_j=\arg \underset{n\∈N}{\max }(\underset{m\∈Y_i\∩U}{\mathrm{\Σ}}\log (1+\mathrm{\λ}*{\mathrm{SINR}}_{\mathrm{mn}}^B)+\underset{k}{\mathrm{\Σ}}\underset{m\∈Y_i\∩V_k}{\mathrm{\Σ}}\log (1+\mathrm{\λ}*{\mathrm{SINR}}_{\mathrm{mn}}^{R_k}))$

(4) by Resource Block n _jdistribute to a bunch Y _i

(5) if unappropriated Resource Block non-NULL goes to step 3.

Resource in conjunction with slot2 and slot1 is distributed, and the throughput that can obtain system is:

$T=\underset{l=1}{\overset{L}{\mathrm{\Σ}}}\underset{i=1}{\overset{X}{\mathrm{\Σ}}}(\underset{m,n\∈\{U\∩Y_i,N_i\}}{\mathrm{\Σ}}(1-\mathrm{\α})C_{\mathrm{1,2}}^B+\underset{k=1}{\overset{K}{\mathrm{\Σ}}}\min (\underset{m,n\∈\{V_k\∩Y_i,N_i\}}{\mathrm{\Σ}}(1-\mathrm{\α})C_{\mathrm{1,2}}^{R_k},\underset{n\∈N}{\mathrm{\Σ}}{\mathrm{\αC}}_{l,1}))$

C in formula _{l, 1}=γ W _nlog (1+ λ * SINR _kn) be expressed as access BS RN _khighest achievable rate,

$C_{l,2}^B=\mathrm{\γ}{W}_n\log (1+\mathrm{\λ}*{\mathrm{SINR}}_{\mathrm{mn}}^B)$ Represent the highest achievable rate of the MS m of access BS,

$C_{l,2}^{R_k}=\mathrm{\γ}{W}_n\log (1+\mathrm{\λ}*{\mathrm{SINR}}_{\mathrm{mn}}^{R_k})$ The highest achievable rate of the MS m of access RN,

γ is that RBn is distributed to RN in the l of community by 0 or 1,1 expression _k(or BS) and MSm connect and compose link.

Specifically, in the present embodiment:

Step 1, system is carried out to initialization, for 7 community double bounce OFDM junction network models, setting communication cell radius is R, each community is divided 3 sectors altogether, and base station is positioned at center of housing estate, along the symmetrical relay station of regular hexagon diagonal of cellular cell, distance between all relay stations and cell base station is L, and temporarily chooses L=2R/3.

Half-duplex characteristic based on wireless relay network, considers that BS-RN link communicates at slot1 in the time that user selects to access relay station, and RN-MS and BS-MS link communicate at slot2.

The transmitting power of base station, fixed cells and relay station also determines that its ratio is 0.6, and in community, the transmitting antenna of base station and each relay station is the directional antenna with certain argument.In community, subscriber equipment and base station spacing are obeyed and are uniformly distributed.

Step 2, to cell scenario, figure analyzes.The transmitting scene of the present embodiment Wei Liang community, as shown in Figure 5.This scene graph is analyzed as follows:

(1) for being thought of as noiseless situation in Cell Center User MS4, MS5, MS6.But MS4 and MS5, MS1 and MS6 use identical RB simultaneously, can produce conflict.

(2) community, left side, the user MS1 of connection BS1, due to the edge in RN1, is therefore subject to the interference from RN1.

(3) community, right side, connects the edge customer MS3 of RN2 by the interference being subject to from BS2.

(4) simultaneously due to the existence of RN, the user in RN intra-zone is by the interference being subject to from adjacent cell.In the time that MS2 and MS3 are assigned to same frequency resources, the inside of MS2 in RN region, will be subject to the interference of RN2, and MS3 is due to the edge in RN2, and away from RN1, the interference that is therefore subject to RN1 is ignored.

(5) set up user's interference relationships figure, as shown in Figure 6.

Step 3, carries out sub-clustering to user, and taking Fig. 4 as example, detailed process is as follows:

According to the interference/conflict number sequence existing, make u ₁, u ₂, u ₃, u ₄, u ₅, u ₆correspond respectively to MS3, MS4, MS5, MS2, MS1, MS6;

Make Φ (u)=x represent that MS u is divided in bunch x, carries out a bunch distribution according to vertex coloring theory.

(1)Φ(u _i)＝1,i＝1；

(2) if i > 6 stops.

(3) otherwise, make H (u _i+1)={ Φ (u _j) | j≤i, u _i+1next to u _j, and to establish x be minimum positive integer, is designated as Φ (u _i)=x;

(4) make i=i+1, turn (3).

According to a bunch assigning process, user node can be divided into 3 bunches, is respectively { MS1, MS3}, { MS4, MS2}, { MS5, MS6}.

Step 4, carries out resource distribution based on spectrum efficiency, and detailed process is as follows:

(1) calculate the spectrum efficiency C (i) of each bunch;

(2) will bunch sort from big to small according to each bunch of spectrum efficiency C (i), obtain order Y={Y _i;

(3) find out and make a bunch Y _ithe RBn of spectrum efficiency maximum _j, and distribute to a bunch Y _i;

(4) make i=i+1, j=j+1, and turn (3);

To step 4, can complete LTE-A relay resource assigning process by above step 1.

Finally explanation is, above preferred embodiment is only unrestricted in order to technical scheme of the present invention to be described, although the present invention is described in detail by above preferred embodiment, but those skilled in the art are to be understood that, can make various changes to it in the form and details, and not depart from the claims in the present invention book limited range.

Claims (4)

1. an inter-cell interference coordination method for heterogeneous wireless network, is characterized in that: comprise the following steps:

Step 1: the interference in community is carried out to grade classification;

Step 2: user is carried out to sub-clustering based on graph theory vertex coloring theory;

Step 3: carry out resource distribution based on spectrum efficiency.

2. the inter-cell interference coordination method of a kind of heterogeneous wireless network according to claim 1, is characterized in that: in step 1, the division of level of interference specifically comprises: 1) BS-RN edges of regions accesses the MS of RN, is subject to the level of interference of BS; 2) MS of the access BS in RN-RN region, is subject to the level of interference of RN; 3) the edge MS in RN-RN region, is subject to the level of interference of adjacent R N; 4) level of interference of center of housing estate MS.

3. the inter-cell interference coordination method of a kind of heterogeneous wireless network according to claim 2, is characterized in that: step 2 specifically comprises the following steps: 1) according to interference relationships figure, carry out vertex coloring; 2) finely tune according to the quantity of the quantity of sub-clustering and Resource Block RB.

4. the inter-cell interference coordination method of a kind of heterogeneous wireless network according to claim 3, is characterized in that: in step 3, specifically comprise the following steps: 1) calculate the spectrum efficiency of each bunch; 2) will bunch sort from big to small according to each bunch of spectrum efficiency; 3) resource block assignments of finding out spectrum efficiency maximum is to each bunch.