A kind of disturbance coordination method based on conflict avoidance mechanism in LTE systemTechnical field
The invention belongs to doing based on conflict avoidance mechanism in mobile communication technology field more particularly to a kind of LTE systemDisturb coordination approach.
Background technique
LTE (Long Term Evolution, long term evolution) uses OFDMA technology (Orthogonal FrequencyDivided Multiple Access, orthogonal frequency-time multiple access technology), OFDMA technology is made using the orthogonality between frequencyFor the mode for distinguishing user, the information of user is carried on mutually orthogonal different carrier waves, system is allow to accomplish frequencyMultiplexing factor is 1, i.e., it is the user in this cell that identical frequency band, which can be used, in all cells in whole system coverage areaService is provided.It, can be in object although the factors such as the offset due to carrier frequency and phase will cause the interference between subchannelReason layer is preferably minimized this interference by using advanced wireless signal Processing Algorithm.Therefore the interference very little in cell, andThe main interference of system performance is influenced from the interference of minizone.
Studying more LTE system inter-cell interference suppression technology at present has interference randomization, interference to eliminate and interfereCoordinate.
It is passively interference mitigation technology that wherein interference randomization and interference, which are eliminated, and interference coordination is a kind of activeThe construction of interference is controlled, wherein active interference suppression technology is mainly used in system transmitting terminal, and passive technology, which is mainly used in, to be connectReceiving end.See Table 1 for details for the advantage and disadvantage of three kinds of schemes.
1 three kinds of AF panel project plan comparisons of table
Herein, interference coordination technique is introduced, interference coordination technique can be divided into static interference coordination, and version static state is dryDisturb coordination, dynamic interference coordination.
In static interference coordination technology, be cured use in the rule very long-term of resource distribution, such as one day or moreIt is long,
In coordinating semi-static interference, configuration rule changes according to user distribution situation or system loading situation.?In LTE system, information needed for different base station coordinating semi-static interference technology is swapped by the X2 interface between base station.
Dynamic interference coordination technology is to be adjusted on allocating scheme in advance, Real-Time Scheduling is carried out by base station, in phaseAdjacent cell is shown in the use for coordinating resource.In dynamic interference coordination, round-trip expense is high, complicated for operation.Common interference coordination associationTune scheme mainly include the following types:
1, partial frequency multiplexing (Fractional Frequency Reuse, FFR)
For LTE system, the access way of the unique OFDMA used, so that between user in this cellIt does not interfere with each other, and then receives the stronger interference from other cells for the user of cell edge.Partial frequency multiplexingCore concept be to treat with a certain discrimination in the user of center of housing estate and cell edge, for the user of center of housing estate, due toIt is closer apart from base station distance, and channel condition is preferable, and itself is little to the interference of other cells, it is possible to be distributedIn the reuse set that frequency duplex factor as one is 1.And for the user of cell edge, serving BS distance apart from itself compared withFar, channel condition is poor, but the interference of its signal for being in identical frequency for other cells is larger, so being distributed in frequencyOn the channeling collection that rate multiplexing factor is 3, as shown in Figure 1.
Fixed frequency multiplex mode may include following two mode:
(1) 40MHz frequency spectrum is used, is divided into 4 10MHz frequency bands, the method for salary distribution, as shown in Figure 2.
Each actually available frequency spectrum of cell is 20MHz.Continuous 20MHz bandwidth can be used in two of them cell, and (f1+f2 is smallArea, f1+f3 cell), another cell can only use the 10MHz bandwidth (f1+f4 cell) of 2 separation.
(2) 20MHz frequency spectrum is used, inside is divided into 4 5MHz sub-bands, the method for salary distribution, as shown in Figure 3.
For each cell under the bandwidth of 20MHz, cell edge low signal areas actual available bandwidth is 5MHz, Intra-cellThe actually available frequency spectrum in strong signal area is 10MHz.
2, soft-frequency reuse (Soft Frequency Reuse, SFR)
Soft-frequency reuse inherits the advantages of partial frequency multiplexing, while using dynamic frequency duplex factor as one, brighterThe utilization efficiency of frequency is improved aobviously.In soft-frequency reuse, all frequency ranges are divided into two groups of subcarriers, and one group is known asMain subcarriers, another set are known as auxiliary subcarrier.Main subcarriers can use from anywhere in cell, and auxiliary subcarrier then onlyIt the heart can be used in the cell.Main subcarriers between different community are mutually orthogonal, restrained effectively interference in cell edge,And auxiliary subcarrier due to only in the cell the heart use, between each other interference it is smaller, then identical frequency can be used.
(1) basic model SFR
Under 20MHz bandwidth, it is divided into 3 6.67MHz frequency bands as Main subcarriers, it is each for 3 adjacent cell edgesUse one；Each center of housing estate region 2/3 frequency spectrum other using this cell simultaneously, the method for salary distribution, as shown in figures 4 a and 4b.
In this manner, center of housing estate uses 2/3 usable spectrum, and cell edge uses 1/3 usable spectrum.
(2) enhanced SFR
Although soft-frequency reuse all there has been the inhibition of cell edge disturbed condition and the flexible allocation of subcarrierCertain consideration, but its mutually orthogonal Main subcarriers for distributing to different community still can bring a degree of resource waveTake, especially when the portfolio of cell edge is larger, the frequency duplex factor as one between cell can be brought to increase, the availability of frequency spectrumThe consequences such as decline.The soft-frequency reuse scheme of enhancing inherits the thought of traditional soft-frequency reuse, and carries out on its basisIt improves, essentially consists in the problem of improving the possible wasting of resources in portfolio variation.
Under 20MHz frequency spectrum, 3 frequency bands are divided into as Main subcarriers, while 20MHz frequency band only exists as auxiliary subcarrierCenter of housing estate uses, as shown in figure 5 a and 5b.
Not only the occupied bandwidth of f2, f3, f4 are adjusted according to the portfolio dynamic of each cell edge region, big according to portfolioSmall, each center of housing estate region usable spectrum also can reach as 20MHz.
Modified SFR uses dynamic configuration mode, it is to be understood that the load information of peripheral cell, therefore need to be (small with ICICSection interference coordination) technology is used cooperatively, it can be only achieved good effect.
It sees on the whole, current interference coordination technique can more efficiently inhibit cell to see interference, the middle body of systemIt can be improved to a certain extent.Substantially cell is shown in that interference coordination technique is a kind of scheduling strategy, it means that rightDownlink and the scheduler of uplink carry out certain limitation, to effectively inhibit inter-cell interference.But eitherFFR or SFR.It is all only to take appropriate measures and carried out simply to it in the angle of the resources such as frequency or powerDistribution, and how to solve the interference problem of the user in cell edge region and how to carry out reasonable efficient resource distributionIn problem, there is no further investigate, it is therefore desirable to suitable interference dispatching technique is effectively combined with dispatching algorithm, with intoThe performance of one step lifting system.
Summary of the invention
Disturbance coordination method based on conflict avoidance mechanism in the one of the application proposition is reducing LTE inter-cell interferenceMeanwhile lifting system throughput performance, reduce system implementation complexity.
The present invention includes the following steps:
Step 1, according to user at a distance from base station, user is divided into Cell Edge User and Cell Center User；
Step 2, for Cell Edge User, the down channel of the user is determined with the presence or absence of interference, if it does, Xiang JiStation reports information, allows base station to terminate to user's downlink data transmission, and execute step 3, does not otherwise deal with；
Step 3, after base station receives the termination downlink data transmission message of reporting of user, random back T for a period of time4, soDownlink transfer is carried out to user with identical frequency resource again afterwards, if the down channel signal-to-noise ratio SINR of user's measurement at this time becomesChange amount B is less than threshold value M1, then follow the steps 5；
If the down channel signal-to-noise ratio SINR variable quantity B of user's measurement at this time is greater than threshold value M1, then base station carries out secondIt is secondary to keep out of the way, random back T for a period of time again4, downlink transfer is then carried out to user with identical frequency resource again, if thisWhen user measurement down channel signal-to-noise ratio SINR variable quantity B be less than threshold value M1, then follow the steps 5；
If the down channel signal-to-noise ratio SINR variable quantity B of user's measurement at this time is greater than threshold value M1, then base station carries out thirdIt is secondary to keep out of the way, random back T for a period of time again4, downlink transfer is then carried out to user with identical frequency resource again, if thisWhen user measurement down channel signal-to-noise ratio SINR variable quantity B be less than threshold value M1, then follow the steps 5；
If the down channel signal-to-noise ratio SINR variable quantity B of user's measurement is greater than threshold value M after keeping out of the way three times1, then holdRow step 4；
Step 4, base station is that user changes downlink channel transmission frequency resource, uses not used frequency in system bandwidth of operationRate resource carries out downlink data transmission to it, returns to step 1；
Step 5, this downlink transfer success terminates the operation to the user if the user data transmission all terminates,Otherwise 1 is returned to step.
Step 1 of the present invention includes the following steps:
Step 1-1, according to the following formula calculate user to base station distance L:
Wherein, (a, b) is the position coordinates of base station, and (c, d) is the position coordinates of user；
(threshold value M can be set to the 1/10 of coverage radius of cell, or with system simulative optimization by step 1-2, given threshold MObtain or operator's sets itself, value range suggestion be the 1/10~1/5 of coverage radius of cell), when user arrives base stationWhen distance L is less than or equal to M, determine that user is Cell Center User, otherwise determines that user is Cell Edge User；
Step 1-3, when user location changes, position coordinates become (c1, d1), set lag time T1, work as warpCross lag time T1(T1Can be set to the other values of 5s or operator's sets itself, value range suggestion is 5~10s) after,User location coordinate becomes (c2, d2), user is calculated in lag time T1The changing value D of the position of interior user:
If in lag time T1Interior, changing value D is consistently less than the 1/10 of base station section covering radius, or less than by transportingWhen seeking other numerical value that quotient voluntarily determines according to network coverage situation, value range suggestion is the 1/ of base station section covering radius10~1/5, then determine that the subdistrict position attribute (Cell Center User or Cell Edge User) of the user is constant.
Step 2 of the present invention includes the following steps:
Step 2-1 counts Cell Edge User U in a period of time T2Interior descending transmission channel signal and interference plus noiseThan the average value of SINR (Signal to Interference plus Noise Ratio, Signal to Interference plus Noise Ratio) valueSINR1；
Step 2-2, when Cell Edge User U descending transmission channel Signal to Interference plus Noise Ratio SINR value changes,Become SINR2, variable quantity B is calculated by following formula:
B=SINR1—SINR2；
Step 2-3, when in T3In time, the value of B, which is consistently greater than, is equal to threshold value N1, N1Value can take 3dB, or be greater thanWhen equal to other numerical value voluntarily determined by operator according to network coverage situation (it is recommended that its value range is 3-6dB), determineThere is interference in the down channel of the user, reporting of user base station allows base station to terminate the downlink data transmission to it, and executes step3, otherwise do not deal with.
In step 3 of the present invention, back off time T is calculated by following formula4:
T4=RAND () * CW*N,
Wherein RAND () is random number functions, for generating the random number between 0~1；CW is to keep out of the way window (value of CW canTo be determined as 0.5s, or by operator numerical value is voluntarily determined according to network coverage situation, it is proposed that value range is 0~1s), NFor the number kept out of the way, N is 1 when keeping out of the way for the first time, and N is 2 when keeping out of the way for the second time, and N is 3 when keeping out of the way for the third time.Maximum keeps out of the way numberIt can voluntarily be determined by operator according to network coverage situation.
Since LTE system uses identical networking mode, the interference in system is mainly derived from the interference that cell is shown in, especiallyIt is the user of cell edge, is easy the interference by other Cell Edge User.Therefore in this context, for being located at baseStand sector covering central area user, resource scheduling algorithm is without modification.And it is located at the user of cell edge, when progress downlinkWhen data receiver, by the interference of other Cell Edge User, and interference strength is more than a certain range, then notifies base station, at randomDownlink transmission is carried out again after keeping out of the way the regular hour, if after continuous several times random-backoff time, under the user of edge cellRow channel disturbance is still serious, then base station will dispatch other frequency resources (subcarrier) and be scheduled to this edge customer, with ruleKeep away interference.
The utility model has the advantages that
The present invention has following technological merit:
1, interference differentiation and avoidance are dynamically carried out
This programme can be according to the real-time condition of channel, the case where dynamic discriminant is interfered, to reduce minizone co-channel interferenceInfluence to user, meanwhile, a possibility that taking corresponding avoidance mechanism, reduce interference next time, improve the handling capacity of network.
2, network O&M is convenient
This programme realizes that simply the letter that each base station only needs to collect, monitor this cell inward flange user shines than SINR feelingsCondition does not need to cooperate between base station, does not need to modify any parameter under the networks change conditions such as newly-increased base station, resettlement base station,Network O&M is very convenient.
3, implementation complexity is low
Compared with enhanced SFR needs more base station Coordination Treatments, this programme pertains only to the adjustment of the scheduling of resource in this cell,The cooperation of other cells is not needed, therefore this programme implementation complexity is lower, it is less to the change of network.
Detailed description of the invention
The present invention is done with reference to the accompanying drawings and detailed description and is further illustrated, it is of the invention above-mentioned orOtherwise advantage will become apparent.
Fig. 1 is partial frequency multiplexing schematic diagram.
Fig. 2 is partial frequency multiplexing division mode (1).
Fig. 3 is partial frequency multiplexing division mode (2).
Fig. 4 a and Fig. 4 b are basic model soft-frequency reuse schematic diagram.
Fig. 5 a and Fig. 5 b are enhanced soft-frequency reuse schematic diagram.
Fig. 6 is flow chart of the present invention.
Specific embodiment
The present invention will be further described with reference to the accompanying drawings and embodiments.
As shown in fig. 6, the invention discloses the disturbance coordination method based on conflict avoidance mechanism in a kind of LTE system, packetInclude following steps:
Step 1, according to user at a distance from base station, user is divided into Cell Edge User and Cell Center User；
Step 2, for Cell Edge User, the down channel of the user is determined with the presence or absence of interference, if it does, Xiang JiStation reports information, allows base station to terminate to user's downlink data transmission, and execute step 3, does not otherwise deal with；
Step 3, after base station receives the termination downlink data transmission message of reporting of user, random back T for a period of time4, soDownlink transfer is carried out to user with identical frequency resource again afterwards, if the down channel signal-to-noise ratio SINR of user's measurement at this time becomesChange amount B is less than threshold value M1, then follow the steps 5；
If the down channel signal-to-noise ratio SINR variable quantity B of user's measurement at this time is greater than threshold value M1, then base station carries out secondIt is secondary to keep out of the way, random back T for a period of time again4, downlink transfer is then carried out to user with identical frequency resource again, if thisWhen user measurement down channel signal-to-noise ratio SINR variable quantity B be less than threshold value M1, then follow the steps 5；
If the down channel signal-to-noise ratio SINR variable quantity B of user's measurement at this time is greater than threshold value M1, then base station carries out thirdIt is secondary to keep out of the way, random back T for a period of time again4, downlink transfer is then carried out to user with identical frequency resource again, if thisWhen user measurement down channel signal-to-noise ratio SINR variable quantity B be less than threshold value M1, then follow the steps 5；
If the down channel signal-to-noise ratio SINR variable quantity B of user's measurement is greater than threshold value M after keeping out of the way three times1, then holdRow step 4；
Step 4, base station is that user changes downlink channel transmission frequency resource, uses not used frequency in system bandwidth of operationRate resource carries out downlink data transmission to it, returns to step 1；
Step 5, this downlink transfer success executes step 6, otherwise returns if the user data transmission all terminatesExecute step 1；
Step 6, terminate.
Step 1 of the present invention includes the following steps:
Step 1-1, according to the following formula calculate user to base station distance L:
Wherein, (a, b) is the position coordinates of base station, and (c, d) is the position coordinates of user；
Step 1-2, given threshold M (threshold value M can be set to the 1/10 of coverage radius of cell, or with system simulative optimizationObtain or operator's sets itself, value range suggestion be the 1/10~1/5 of coverage radius of cell), when user arrives base stationWhen distance L is less than or equal to M, determine that user is Cell Center User, otherwise determines that user is Cell Edge User；
Step 1-3, when user location changes, position coordinates become (c1, d1), set lag time T1, work as warpCross lag time T1(T1Can be set to the other values of 5s or operator's sets itself, value range suggestion is 5~10s) after,User location coordinate becomes (c2, d2), user is calculated in lag time T1The changing value D of the position of interior user:
If in lag time T1Interior, changing value D is consistently less than the 1/10 of base station section covering radius, or less than by transportingSeek quotient according to network coverage situation voluntarily determine other numerical value when (its value range suggestion be coverage radius of cell 1/10~1/5), then determine that the subdistrict position attribute (Cell Center User or Cell Edge User) of the user is constant.
Step 2 of the present invention includes the following steps:
Step 2-1 counts Cell Edge User U in a period of time T2Interior descending transmission channel signal and interference plus noiseThan the average value of SINR (Signal to Interference plus Noise Ratio, Signal to Interference plus Noise Ratio) valueSINR1；
Step 2-2, when Cell Edge User U descending transmission channel Signal to Interference plus Noise Ratio SINR value changes,Become SINR2, variable quantity B is calculated by following formula:
B=SINR1—SINR2；
Step 2-3, when in T3In time, the value of B, which is consistently greater than, is equal to threshold value N1, N1Value can take 3dB, or be greater thanWhen equal to other numerical value voluntarily determined by operator according to network coverage situation (it is recommended that its value range is 3-6dB), determineThere is interference in the down channel of the user, reporting of user base station allows base station to terminate the downlink data transmission to it, and executes step3, otherwise do not deal with.
In step 3 of the present invention, back off time T is calculated by following formula4:
T4=RAND () * CW*N,
Wherein RAND () is random number functions, for generating the random number between 0~1；CW is to keep out of the way window, and N is to keep out of the wayNumber, when keeping out of the way for the first time N be 1, when keeping out of the way for the second time N be 2, when keeping out of the way for the third time N be 3.Maximum keeps out of the way number can be byOperator voluntarily determines according to network coverage situation.
Embodiment
Assuming that certain all base station of operator's LTE network use three sector mode networkings, using the 1/2 of coverage radius of cell asThresholding is determined according to formula (1) with for for center of housing estate zone user or fringe region user.The tentative setting of other parameters is such asUnder: SINR1For -3dB；M is 3dB；CW is 0.5s；N is 3.
Scheme operational process is as follows:
Step 1: when initial launch, user U is calculated at a distance from base station.If distance is greater than the 1/2 of coverage radius of cell,Then determine that this user for Cell Edge User, executes step 2；If distance is less than the 1/2 of coverage radius of cell, this use is determinedFamily is Cell Center User, thens follow the steps 1.
Step 2: when the down channel signal-to-noise ratio SINR of user U is in T3In time, SINR2Average value is -1dB, variable quantity B=SINR1-SINR2=-3- (- 1)=- 2, at this time B < M, then it is assumed that the downlink of user U is noiseless, return step 2；If when usingThe down channel signal-to-noise ratio SINR of family U is in T3In time, SINR2Average value is -7dB, variable quantity B=SINR1-SINR2=-3-(- 7)=4, at this time B > M, then it is assumed that the down channel serious interference of user U, Xiang Jizhan reporting message allow it to terminate to its downlinkData transmission, and execute step 3.
Step 3: after base station receives the termination downlink transfer message that user U is reported, random back T for a period of time4=RANDThen () * CW*N=0.43*0.5*1=0.215s carries out downlink transfer to user U with identical frequency resource again.If thisWhen user U measurement down channel SINR variable quantity B < M, then follow the steps 5；If B > M, 3 are thened follow the steps, carries out secondary move backIt keeps away.If after keeping out of the way three times, B > M thens follow the steps 4.
Step 4: base station is that user U changes downlink channel transmission frequency resource, using not used in system bandwidth of operationFrequency resource carries out downlink data transmission to it, executes step 1.
Step 5: downlink transfer success executes step 6, otherwise returns and execute if the user data transmission all terminatesStep 1；
Step 6, terminate.
The present invention provides the disturbance coordination methods based on conflict avoidance mechanism in a kind of LTE system, implement the skillThere are many method and approach of art scheme, the above is only a preferred embodiment of the present invention, it is noted that this technology is ledFor the those of ordinary skill in domain, various improvements and modifications may be made without departing from the principle of the present invention, theseImprovements and modifications also should be regarded as protection scope of the present invention.The available prior art of each component part being not known in the present embodimentIt is realized.