CN103945459B - Interference elimination method based on time domain in multilayer multi-cell system - Google Patents
Interference elimination method based on time domain in multilayer multi-cell system Download PDFInfo
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Abstract
Interference elimination method based on time domain in multilayer multi-cell system, including：The reference signal that user k is sent according to different base station, estimates Reference Signal Received Power, a maximum macrocell base stations of statistics receiving power and two microcell base stations, and the result is broadcasted；The user load amount under each base station is counted, the load balancing of system is carried out, load heavier in macrocellular is transferred in microcellulor；The base station selection scheme of user is transmitted to user by macrocellular；Macrocellular carries out user's scheduling selection, and user's scheduling result is transmitted into user；User k receives the reference of serving BS according to base station selected and scheduling result, carries out channel estimation according to the signal received, obtains the channel between user k and serving BS；Channel condition information of the user according to obtained by estimation, feeds back information to its serving BS；Serving BS carries out the transmission of data.The inventive method improves the average user throughput of system in the case of load is higher.
Description
Technical field
The present invention relates to a kind of method of wireless communication field, when being based in specifically a kind of multilayer multi-cell system
The interference elimination method in domain.
Background technology
In next generation mobile communication system, the data transfer rate and cell coverage for how improving system have become industry heat
The problem of strong discussion.In order to further improve the coverage rate of system, while reducing power consumption, in lte-a system, multilayer will be discussed
The deployment of multi-cell system.It is higher in certain user's closeness in addition to needing deployment macrocell base stations in this kind of system
Region need to dispose microcell base station.In the discussion to existing system, it is the less base of transmission power to define microcell base station
Stand, they have collectively constituted the heterogeneous network of multilayer multiple cell with macrocell base stations.Herein, the concept of heterogeneous network and tradition
Concept it is different, the isomerism of base station is only embodied in the difference of transmit power in network.By dispose transmit power compared with
The user of some focuses, can be put in microcellulor and service by small base station, and this can effectively reduce the load of macrocell system, together
When improve the service quality of some Cell Edge User.The transmit power of microcell base station is small, therefore, it is possible to reduce to adjacent
The interference of community user.In addition, in the power consumption and construction cost of micro cellular system also below macrocell base stations construction.Therefore,
In mobile cellular network of future generation, deployment to microcell base station and study the developing direction as a main flow.
In existing research work, in order to reduce the user load in macro cells, the method unloaded using user
User in macro cells is changed into Micro-cell user, it is balanced and dry to discuss a variety of user loads in existing document
Disturb the method for eliminating co-design.
Found through being retrieved to existing literature, Katsunori Kikuchi and Hiroyuki Otsuka, " Proposal
of Adaptive Control CRE in Heterogeneous Networks”,IEEE International
Symposium on Personal, Indoor and Mobile Radio Communications, 2012. (in heterogeneous network
The suggestion of adaptive cell region extension control), the method using increase bias is discussed, is carried out in user base station selected
When, it is that the Reference Signal Received Power of microcell base station artificially adds one on the occasion of this mode allows user with larger
Probability accesses microcellulor, so as to expand the coverage of microcellulor in heterogeneous network, and microcell base station is more shared net
Network is loaded.
Found again through retrieval, Iana Siomina1and Di Yuan.Load Balancing in Heterogeneous
LTE:Range Optimization via Cell Offset and Load-Coupling Characterization[C]
.IEEE Communication QoS, Reliability and Modeling Symposium, 2012. (LTE heterogeneous networks
Middle balancing method of loads：Optimize with cell bias and load coupled characteristic), change the method for bias using dynamic, really
The fixed bias relevant with microcellulor, by optimizing fairness utility function, reaches the purpose loaded in equalizing system.
Found further through retrieval, Che-Sheng Chiu, Chia-Chi Huang.An Interference
Coordination Scheme for Picocell Range Expansion in Heterogeneous Network[C]
.Vehicular Technology Conference, 2012. (the interference coordination sides that microcellulor scope extends in heterogeneous network
Case), using frequency domain and the interference cancellation scheme of time domain, reduce the interference to edge customer.
The content of the invention
For technical problem present in above-mentioned prior art, the present invention is provided in a kind of multilayer multi-cell system and loaded
The method that weighing apparatus and interference eliminate co-design.The present invention is according to situation about being loaded in system, the method extended using cell area
User in macrocell base stations is moved into microcell base station, and uses time domain interference elimination method, reduces microcell base station
The interference of user, particularly cell extension zone user, in the case where system load is higher, improve the average data of system
Rate.
The present invention is achieved by the following technical solutions：
Interference elimination method based on time domain in a kind of multilayer multi-cell system, comprises the following steps：
The first step, the reference signal that user k is sent according to different base station estimates Reference Signal Received Power, i.e. RSRP
(Reference Signal Receiving Power), a maximum macrocellular base of user's statistical-reference signal reception power
Stand and two maximum microcell base stations of Reference Signal Received Power, and the selection statistical result is broadcasted；
Second step, counts the user load amount under each base station, according to the RSRP value informations broadcasted in the first step, is
The load balancing of system, load heavier in macrocell base stations is transferred in microcell base station；
The base station selection scheme of user is transmitted to user by the 3rd step, macrocell base stations；
4th step, macrocell base stations carry out user's scheduling selection, and user's scheduling result is transmitted into user；
5th step, any user k receives the reference S of serving BS according to base station selected and scheduling resultk,
User k is according to the signal X receivedkChannel estimation is carried out, the channel h between user k and serving BS is obtainedk；
6th step, channel condition information of the user according to obtained by estimation, by PMI, CQI information feeds back to its serving BS；
7th step, PMI of the serving BS according to obtained by feedback, CQI information carries out the transmission of data.
Preferably, the processing method in the first step is：
To any user k in system, the reference signal that macrocell base stations and microcell base station are sent in reception system is estimated
Count the Reference Signal Received Power RSRP (Reference Signal Receiving Power) of each base station, it is assumed that macrocellular
The RSRP values that base station m is sent to user k are expressed asThe RSRP values that microcell base station n is sent to user k are expressed asUser selectsMaximum macrocell base stations andTwo maximum microcell base stations, broadcast its cell
Sequence number and RSRP values, it is as follows：
Wherein, when selecting microcell base station, two maximum microcell base stations of selection Reference Signal Received Power.
Preferably, the processing method of the load balancing in the second step is：
First, the load distribution situation in statistical system.For some cell, it includes macrocell base stations m and microcellulor
Base station n=1 ..., N, calculate the loading condition in each cell, and computational methods are as follows：
Wherein,The loading demand density of macrocell base stations m user is represented,Represent microcell base station n user
Loading demand density,The loading demand density of user being unloaded to by macrocellular in microcellulor n is represented,It is user's subscript in macrocell base stations m, Km,1It is the number of users of macrocell base stations m services
Mesh, userData be to bag rate It is user's subscript in microcell base station n, KN, 2It is
The number of users of microcell base station n services, userData be to bag rate
It is user's subscript that macrocell base stations are unloaded in microcellulor n, Kn,3It is the number of users that microcell base station n is unloaded from macrocellular
Mesh, userData be to bag rate
Then, according to the user load calculated under each base station of gained, proceed as follows：Compare macrocell base stations and micro-
Load in cellular basestationWithWherein,Can be by obtained by the mean value calculation in each microcellulor, meetingIfIllustrate overload in macrocell base stations, it is necessary to carry out user's migration, then, for grand honeybee
Nest base station m, its user is arranged according to receiving terminal Signal to Interference plus Noise Ratio ascending order, selection Signal to Interference plus Noise Ratio SINR first, i.e., minimum one
It is individual to be used as the candidate user k that moved in extended areami；
Then, it is that candidate user selects suitable microcellulor to be migrated, for candidate user, is broadcasted according to user
RSRP values and cell sequence number, the RSRP values of each microcell base station in macrocell base stations to the candidate user are arranged in descending order,
The maximum microcell base station of RSRP values is selected as the microcell base station of migration.Assuming that microcell base station n enters to elect as user's migration
Candidate's microcell base station, then according to the existing load of candidate's microcell base station, i.e.,Judged：IfWith
Family kmiIt is detachable to be downloaded in microcell base station n, otherwise, ifIllustrate in microcell base station n overload, it is impossible to again
Increase more users；And then select the microcell base station of RSRP values secondIdentical is done to compare, ifThen should
User's merger is microcell base stationExtended area user；Otherwise, the user can not be unloaded, still as macrocellular base
Stand user, when selected microcell base station n is used as user kmiUnloading microcell base station when, it is necessary to check user relative to macrocellular
The difference of the RSRP values of base station and the microcell base station that will be unloaded, if the difference is more than the threshold delta (dB) of a certain setting, explanation
The user distance macrocell base stations are nearer, if forcing to be unloaded in microcell base station, its receiving terminal Signal to Interference plus Noise Ratio will significantly
Weaken.Only when difference is less than threshold delta (dB), user's unloading can be carried out, when completing the unloading of user every time, updates every
The loading demand density in individual regionWithWork as satisfactionWhen, illustrate that the load in macrocell base stations is complete
Into the migration of user, load balancing process terminates.
Preferably, the processing method of user's scheduling in the 4th step is：
In multilayer multi-cell system, using the interference cancellation techniques of time domain, user adjusts in the different subframes of a frame
Spend algorithm different, it is assumed that in time T, almost the duration of blank subframe is TABS, meet T=TNormal+TABS, it is
User in system is divided into three parts, and Part I is the user that macrocell base stations are servicedPart II is microcellulor base
The user for the service of standingPart III is the extended area user that macrocell base stations are unloaded to microcell base stationGrand honeybee
User's dispatching algorithm difference of nest base station and microcell base station is as follows：
For macrocell base stations, in normal sub-frames, adoption rate fair algorithm scheduling macrocell userAlmost
In blank subframe, user is not dispatched, reference signal is only sent, does not send data-signal；
For microcell base station, in normal sub-frames, microcell base station user is only dispatchedIn almost blank subframe,
Adoption rate fair algorithm dispatches extended area userWith part microcell base station userIt is grand in normal sub-frames
Cellular basestation sends data-signal, can cause huge interference, therefore, can only dispatch microcell base station to the user of extended area
User；In almost blank subframe, the interference of macrocell base stations can be neglected substantially, therefore, it is possible to dispatch microcell base station
In any user, including extended area user and microcell base station user.
Preferably, the channel estimation process method of the serving BS of the user k in the 5th step is：
Wherein, M is the antenna number ρ of serving BSτIt is training sequence SkSignal to noise ratio,TτIt is serving BS
The length of the training sequence of transmitting,The signal that user k is received, N is user antenna number.IMFor M × M unit
Matrix.
Preferably, the method for the feedback in the 6th step is：
PMI use is the thought based on code book.When being fed back using PMI, base station and user terminal possess identical
Code book.Channel condition informations of the user k according to obtained by its channel estimation, finds what is most matched in the codebook according to corresponding algorithm
Code word, base station is fed back to by the corresponding index of the code word.Base station, by searching for code book, is obtained according to the codewords indexes received
Corresponding pre-coding matrix.
In LTE system, base station carries out user's selection according to CQI value and Adaptive Modulation and Coding is modulated.User's estimation is received
Signal to noise ratio is held, CQI sequence numbers are fed back according to signal to noise ratio mapping table, base station is according to CQI value look-up table, to determine modulation coding mode.
In mimo systems, the maximum number of plies that user can transmit is min (Nt,Nr).Wherein NtFor transmitting terminal antenna number,
NrFor receiving terminal antenna number.
The method that load balancing and interference eliminate co-design in multilayer multi-cell system provided by the present invention, according to being
User in macrocell base stations is moved to microcell base station by situation about being loaded in system, the method extended using cell area, and
Using time domain interference elimination method, reduce the interference of microcell base station user, particularly cell extension zone user, in system
In the case that load is higher, the average data rate of system is improved.
Brief description of the drawings
By reading the detailed description made with reference to the following drawings to non-limiting example, further feature of the invention,
Objects and advantages will become more apparent upon：
Fig. 1 is user's average throughput performance comparision schematic diagram of the embodiment of the present invention.
Embodiment
With reference to specific embodiment, the present invention is described in detail.Following examples will be helpful to the technology of this area
Personnel further understand the present invention, but the invention is not limited in any way.It should be pointed out that to the ordinary skill of this area
For personnel, without departing from the inventive concept of the premise, various modifications and improvements can be made.These belong to the present invention
Protection domain.
It is each small to divide under 3 sectors, each sector using the cellular network architecture of 7 cells in the embodiment of the present invention
It is uniformly distributed 4 microcell base stations.The distribution of user is uniformly distributed 10 use using being uniformly distributed in each macrocell base stations
5 users are uniformly distributed under family, each microcell base station.Wherein, the difference of macrocell base stations and microcell base station is essentially consisted in
In its transmission power, the maximum transmission power of macrocell base stations is 46dBm, and the maximum transmission power of microcell base station is 24dBm.
The coverage of macrocell base stations is 500m, and the coverage of microcell base station is 40m.Load distribution in system uses Poisson
Distribution, that is, set the packet arrival rate of each user as λ, the size of each packet is set as 0.5Mbytes.λ numerical value
Size represents the expectation of the packet number reached each user's each second.λ size represents the weight of system load, with
λ increases, and the load of system becomes big.The channel fading model used in the present embodiment is SCM channel.
Interference elimination method based on time domain in multilayer multi-cell system provided by the present invention, comprises the following steps：
The first step, the reference signal that user k is sent according to different base station, estimation Reference Signal Received Power RSRP.User
A maximum macrocell base stations of statistical-reference signal reception power and two maximum microcellulor bases of Reference Signal Received Power
Stand, and the selection statistical result is broadcasted.
Specifically processing method is：
To any user k in system, the reference signal that macrocell base stations and microcell base station are sent in reception system is estimated
Count the Reference Signal Received Power RSRP of each base station.Assuming that the RSRP values that macrocell base stations m is sent to user k are expressed asThe RSRP values that microcell base station n is sent to user k are expressed asUser selectsMaximum grand honeybee
Nest base station andTwo maximum microcell base stations, broadcast its cell sequence number and RSRP values, as follows：
Wherein, when selecting microcell base station, two maximum microcell base stations of selection Reference Signal Received Power.
Second step, counts the user load amount under each base station, according to the RSRP value informations broadcasted in the first step, is
The load balancing of system, load heavier in macrocell base stations is transferred in microcell base station.
The processing method of load balancing is：
First, the load distribution situation in statistical system.For some cell, it includes macrocell base stations m and microcellulor
Base station n=1 ..., N, calculate the loading condition in each cell, and computational methods are as follows：
Wherein,The loading demand density of macrocell base stations m user is represented,Represent microcell base station n user
Loading demand density,Represent the loading demand density of user being unloaded to by macrocell base stations in microcell base station n.It is user's subscript in macrocell base stations m, Km,1It is the number of users of macrocell base stations m services.
UserData be to bag rate It is user's subscript in microcell base station n, Kn,2It is
The number of users of microcell base station n services.UserData be to bag rate
It is user's subscript that macrocell base stations are unloaded in microcell base station n, Kn,3It is that microcell base station n is unloaded from macrocell base stations
Number of users.UserData be to bag rate
Then, according to the user load calculated under each base station of gained, proceed as follows：Compare macrocell base stations and micro-
Load in cellular basestationWithWherein,Can be by obtained by the mean value calculation in each microcell base station, meetingIfIllustrate overload in macrocell base stations, it is necessary to carry out user's migration.Then, for grand honeybee
Nest base station m, its user is arranged according to receiving terminal Signal to Interference plus Noise Ratio ascending order, selection Signal to Interference plus Noise Ratio SINR first, i.e., minimum one
It is individual to be used as the candidate user k that moved in extended areami。
Then, it is that candidate user selects suitable microcell base station to be migrated.For candidate user, broadcasted according to user
RSRP values and cell sequence number, the RSRP values of each microcell base station in macrocell base stations to the candidate user are arranged in descending order
Row, select the maximum microcell base station of RSRP values as the microcell base station of migration.Moved assuming that microcell base station n enters to elect user as
Candidate's microcell base station of shifting, then according to the existing load of candidate's microcell base station, i.e.,Judged：If
User kmiIt is detachable to be downloaded in microcell base station n, otherwise, ifIllustrate in microcell base station n overload, no
More users can be further added by；And then select the microcell base station of RSRP values secondIdentical is done to compare, ifThen
It is microcell base station by user's mergerExtended area user；Otherwise, the user can not be unloaded, still as grand honeybee
Nest base station user.When selected microcell base station n is used as user kmiUnloading microcell base station when, it is necessary to check user relative to grand
The difference of the RSRP values of cellular basestation and the microcell base station that will be unloaded, if the difference is more than the threshold delta (dB) of a certain setting,
Illustrate that the user distance macrocell base stations are nearer, if forcing to be unloaded in microcell base station, its receiving terminal Signal to Interference plus Noise Ratio will
Weaken significantly.Only when difference is less than threshold delta (dB), user's unloading can be carried out.In the present embodiment, the thresholding is set
Value meets δ (dB)=9dB.When completing the unloading of user every time, the loading demand density in each region is updated WithWork as satisfactionWhen, illustrate that the load in macrocell base stations has completed the migration of user, load balancing process knot
Beam.
The base station selection scheme of user is transmitted to user by the 3rd step, macrocell base stations.
4th step, macrocell base stations carry out user's scheduling selection, and user's scheduling result is transmitted into user.
User scheduling processing method be：
In multilayer multi-cell system, using the interference cancellation techniques of time domain, user adjusts in the different subframes of a frame
Spend algorithm different.Assuming that in time T, almost the duration of blank subframe is TABS, meet T=TNormal+TABS.
In the present embodiment, it is determined that a fixed almost blank subframe ratio, i.e., select several in 10 subframes of a data frame
The number of blank subframe is 3, i.e., almost blank subframe ratio is 3/10.User in system is divided into three parts, the
The user that a part services for macrocell base stationsPart II is the user that microcell base station is servicedPart III is
Macrocell base stations are unloaded to the extended area user of microcell base stationThe user of macrocell base stations and microcell base station adjusts
Spend algorithm difference as follows：
For macrocell base stations, in normal sub-frames, adoption rate fair algorithm scheduling macrocell userAlmost
In blank subframe, user is not dispatched, reference signal is only sent, does not send data-signal.
For microcell base station, in normal sub-frames, microcell base station user is only dispatchedIn almost blank subframe,
Adoption rate fair algorithm dispatches extended area userWith part microcell base station userIt is grand in normal sub-frames
Cellular basestation sends data-signal, can cause huge interference, therefore, can only dispatch microcell base station to the user of extended area
User；In almost blank subframe, the interference of macrocell base stations can be neglected substantially, therefore, it is possible to dispatch microcell base station
In any user, including extended area user and microcell base station user.
5th step, any user k receives the reference S of serving BS according to base station selected and scheduling resultk,
User k is according to the signal X receivedkChannel estimation is carried out, the channel h between user k and serving BS is obtainedk。
The channel estimation process method of user k serving BS is：
Wherein, M is the antenna number ρ of serving BSτIt is training sequence SkSignal to noise ratio,TτIt is serving BS
The length of the training sequence of transmitting,The signal that user k is received.N is user antenna number.IMFor M × M unit
Matrix.
6th step, channel condition information of the user according to obtained by estimation, by PMI, CQI information feeds back to its serving BS.
The method of feedback is：
PMI use is the thought based on code book.When being fed back using PMI, base station and user terminal possess identical
Code book.Channel condition informations of the user k according to obtained by its channel estimation, finds what is most matched in the codebook according to corresponding algorithm
Code word, base station is fed back to by the corresponding index of the code word.Base station, by searching for code book, is obtained according to the codewords indexes received
Corresponding pre-coding matrix.
In LTE system, base station carries out user's selection according to CQI value and Adaptive Modulation and Coding is modulated.CQI feedback needs to adopt
Use 4bits feedback overheads.User estimates receiving terminal signal to noise ratio, feeds back CQI sequence numbers according to signal to noise ratio mapping table, base station is according to CQI
It is worth look-up table 1, to determine modulation coding mode.
In mimo systems, the maximum number of plies that user can transmit is min (Nt,Nr).Wherein NtFor transmitting terminal antenna number,
NrFor receiving terminal antenna number.
7th step, PMI of the serving BS according to obtained by feedback, CQI information carries out the transmission of data.
Table 1AMC mapping tables
Fig. 1 is to illustrate user data to bag rate λ in user's average throughput performance comparision schematic diagram of the present embodiment, figure
Respectively 0.1~0.8 user's average throughput.The load balancing scheme that is proposed in this patent and not is compared in the present embodiment
Do the comparison of load balancing scheme.By useful to macrocellular average user throughput, microcellulor average user throughput and institute
The comparison of the average throughput at family, is illustrated in the case where system is in high capacity, is disappeared using load balancing and time domain interference
The method removed can effectively improve the average user throughput of system.By comparing, as λ >=0.2, i.e., when in system
Load when reaching to a certain degree, either macrocellular or microcellulor, using set forth herein the elimination of the interference based on time domain
Scheme (ABS marked in figure) have higher user's average throughput than basic method all the time.Thus whole system
In the average throughput of all users also have larger gain.As λ=0.1, i.e., when the load in system is smaller, it can be found that
Using the scheme of ABS interference cancellation techniques than basic scheme, the average throughput of macrocell user is reduced on the contrary, but micro- honeybee
The average throughput of nest user increases, and the average throughput of all users also has gain in system.There is this phenomenon
Reason is, when system load is smaller, in macrocellular, influences the system resource of one of two factors of user's throughput and turns into
Principal element, when carrying out interference using ABS and eliminating, macrocell base stations not service user in the subframe of part, thus waste portion
Divide time resource, reduce the average throughput of macrocell user.But when system load than it is larger when, influence user throughput
Another factor interference becomes principal element, thus employs the scheme of ABS system with higher user's average throughput.This
It can also draw, the deployment of microcell base station, the use of interference elimination method have preferable in the case where system load is larger
Performance.Meanwhile, user's throughput performance under different loads is in by analogue system, it can be found that when the load of system reaches
To a certain extent, i.e. during λ >=0.6, the average user throughput of system enters a saturation state.
The specific embodiment of the present invention is described above.It is to be appreciated that the invention is not limited in above-mentioned
Particular implementation, those skilled in the art can make various deformations or amendments within the scope of the claims, this not shadow
Ring the substantive content of the present invention.
Claims (8)
1. the interference elimination method based on time domain in a kind of multilayer multi-cell system, it is characterised in that comprise the following steps：
The first step, the reference signal that user k is sent according to different base station estimates Reference Signal Received Power, i.e. RSRP, Yong Hutong
A maximum macrocell base stations of Reference Signal Received Power and two maximum microcell base stations of Reference Signal Received Power are counted,
And broadcast the statistical result；
Second step, counts the user load amount under each base station, according to the RSRP value informations broadcasted in the first step, carries out system
Load balancing, load heavier in macrocell base stations is transferred in microcell base station；
The base station selection scheme of user is transmitted to user by the 3rd step, macrocell base stations；
4th step, macrocell base stations are in normal sub-frames, adoption rate fair algorithm scheduling macrocell user；In almost blank
Frame in, does not dispatch user, only sends reference signal, does not send data-signal, and microcell base station in normal sub-frames, is only dispatched
Microcellulor user；In almost blank subframe, adoption rate fair algorithm scheduling extended area user and part microcell base station
User；
5th step, any user k receives the reference S of serving BS according to base station selected and scheduling resultk, user k
According to the signal X receivedkChannel estimation is carried out, the channel h between user k and serving BS is obtainedk；
6th step, channel condition information of the user according to obtained by estimation, by PMI, CQI information feeds back to its serving BS；
7th step, PMI of the serving BS according to obtained by feedback, CQI information carries out the transmission of data.
2. the interference elimination method based on time domain in multilayer multi-cell system according to claim 1, it is characterised in that institute
Stating the specific method of the first step is：
To any user k in system, the reference signal that macrocell base stations and microcell base station are sent in reception system, estimation is each
The Reference Signal Received Power RSRP of individual base station, it is assumed that the RSRP values that macrocell base stations m is sent to user k are expressed as
The RSRP values that microcell base station n is sent to user k are expressed asUser selectsMaximum macrocell base stations andTwo maximum microcell base stations, broadcast its cell sequence number and RSRP values, as follows：
Wherein, when selecting microcell base station, two maximum microcell base stations of selection Reference Signal Received Power.
3. the interference elimination method based on time domain in multilayer multi-cell system according to claim 1, it is characterised in that institute
Stating the processing method of the load balancing in second step is：
First, the load distribution situation in statistical system, for some cell, it includes macrocell base stations m and microcell base station
N=1, L, N, calculate the loading condition in each cell, and computational methods are as follows：
Wherein, TNormalRepresent common subframe time, T in a frameABSThe almost blank subframe time is represented,Represent macrocell base stations
The loading demand density of m user,The loading demand density of microcell base station n user is represented,Represent by macrocellular
Base station is unloaded to the loading demand density of the user in microcell base station n,It is macrocell base stations
User's subscript in m, Km,1It is the number of users of macrocell base stations m services, userData be to bag rate It is user's subscript in microcell base station n, Kn,2It is the number of users of microcell base station n services,
UserData be to bag rate It is that macrocell base stations are unloaded to microcellulor base
The user's subscript stood in n, Kn,3It is the number of users that microcell base station n is unloaded from macrocell base stations, userData arrive
Bag rate is
Then, according to the user load calculated under each base station of gained, proceed as follows：Compare macrocell base stations and microcellulor
Load in base stationWithWherein,Can be by obtained by the mean value calculation in each microcell base station, meetingIfIllustrate overload in macrocell base stations, it is necessary to carry out user's migration, then, for grand honeybee
Nest base station m, its user is arranged according to receiving terminal Signal to Interference plus Noise Ratio ascending order, selection Signal to Interference plus Noise Ratio SINR first, i.e., minimum one
It is individual to be used as the candidate user k that moved in extended areami；
Then, it is that candidate user selects suitable microcell base station to be migrated, for candidate user, is broadcasted according to user
RSRP values and cell sequence number, the RSRP values of each microcell base station in macrocell base stations to the candidate user are arranged in descending order,
The maximum microcell base station of RSRP values is selected as the microcell base station of migration, it is assumed that microcell base station n enters to elect as user's migration
Candidate's microcell base station, then according to the existing load of candidate's microcell base station, i.e.,Judged：IfUser
kmiIt is detachable to be downloaded in microcell base station n, otherwise, ifIllustrate in microcell base station n overload, it is impossible to increase again
Plus more users；And then select the microcell base station of RSRP values secondIdentical is done to compare, ifThen this is used
Family merger is microcell base stationExtended area user；Otherwise, the user can not be unloaded, still as macrocell base stations
User, when selected microcell base station n is used as user kmiUnloading microcell base station when, it is necessary to check user relative to macrocellular base
The difference stood with the RSRP values for the microcell base station that will be unloaded, if the difference is more than the threshold delta (dB) of a certain setting, explanation
The user distance macrocell base stations are nearer, if forcing to be unloaded in microcell base station, its receiving terminal Signal to Interference plus Noise Ratio will significantly
Weaken, only when difference is less than threshold delta (dB), user's unloading can be carried out, when completing the unloading of user every time, update every
The loading demand density in individual regionWithWork as satisfactionWhen, illustrate that the load in macrocell base stations is complete
Into the migration of user, load balancing process terminates.
4. the interference elimination method based on time domain in multilayer multi-cell system according to claim 1, it is characterised in that institute
Stating the processing method of the scheduling of the user in the 4th step is：
In multilayer multi-cell system, using the interference cancellation techniques of time domain, user's scheduling is calculated in the different subframes of a frame
Method is different, it is assumed that in time T, and almost the duration of blank subframe is TABS, meet T=TNormal+TABS, in system
User be divided into three parts, Part I is the user that macrocell base stations are servicedPart II takes for microcell base station
The user of businessPart III is the extended area user that macrocell base stations are unloaded to microcell base stationMacrocell base stations
User's dispatching algorithm difference with microcell base station is as follows：
For macrocell base stations, in normal sub-frames, adoption rate fair algorithm scheduling macrocell userIn almost blank
In subframe, user is not dispatched, reference signal is only sent, does not send data-signal；
For microcell base station, in normal sub-frames, microcellulor user is only dispatchedIn almost blank subframe, adoption rate
Fair algorithm dispatches extended area userWith part microcell base station userIn normal sub-frames, macrocell base stations hair
Data-signal is sent, can cause huge interference, therefore, microcell base station user can only be dispatched to the user of extended area；Several
In blank subframe, the interference of macrocell base stations can be neglected substantially, therefore, it is possible to dispatch any use in microcell base station
Family, including extended area user and microcell base station user.
5. the interference elimination method based on time domain in multilayer multi-cell system according to claim 1, it is characterised in that institute
Stating the channel estimation process method of the serving BS of the user k in the 5th step is：
Wherein, M is the antenna number of serving BS, ρτIt is training sequence SkSignal to noise ratio,TτIt is serving BS transmitting
Training sequence length,The signal that user k is received, N is user antenna number, IMFor M × M unit matrix.
6. the interference elimination method based on time domain in multilayer multi-cell system according to claim 3, it is characterised in that institute
Progress user's transition condition is stated when judging, the door of the difference of the RSRP values of macrocell base stations and the RSRP values of candidate's microcell base station
Limit value is set to need to check user relative to macrocell base stations and the difference of the RSRP values for the microcell base station that will be unloaded, if
The difference is more than the threshold delta (dB) of setting, illustrates that the user distance macrocell base stations are nearer, if forcing to be unloaded to micro- honeybee
In nest base station, its receiving terminal Signal to Interference plus Noise Ratio will weaken significantly, only when difference is less than threshold delta (dB), can carry out user
Unloading.
7. the interference elimination method based on time domain in multilayer multi-cell system according to claim 6, it is characterised in that institute
State threshold delta (dB)=9dB.
8. the interference elimination method based on time domain in multilayer multi-cell system according to claim 4, it is characterised in that
Almost during the setting of blank subframe ratio, 3 conducts almost blank subframe in 10 data bursts of selection.
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