Many cell mimos system user dispatching method under ZF precoding strategy
Technical field
The present invention relates under a kind of ZF precoding strategy based on the extensive mimo system user scheduling method in large scale channel fading Duo community.
Background technology
In order to meet the demand of LTE communication system high data rate and high power system capacity aspect, LTE system is supported many antennas MIMO technology, comprises transmission diversity, spatial reuse, wave beam forming.In multi-user MIMO system down link, owing to disperseing on geographical position between each travelling carriage, between travelling carriage, cannot realize mutual cooperation, therefore can not utilize the receiving algorithm joint-detection in up link to go out to transmit.Now can to channel condition information CSI, be used at transmitting terminal, adopt multi-user MIMO system precoding technology to carry out preliminary treatment to transmitting, the signal that each user is received not disturbed by other users.Along with the huge increase of smart mobile phone and all kinds of mobile terminal quantity, at Future Ten, in year, the expectation of data traffic demand is by the growth that occurs 1,000 times, and how meeting power system capacity lifting demand becomes problem demanding prompt solution.As a kind of disruptive technology that can effectively resist in theory serious presence of intercell interference in global frequencies multiplex system, promote user's service speed, extensive MIMO TDD system is receiving increasing concern and further investigation.In extensive mimo system, a large amount of antennas cheaply of end, base station administration are the relatively less user's service of quantity on same running time-frequency resource, and the spectrum efficiency that only adopts simple precoding and random user scheduling strategy to obtain to attract people's attention promotes.
At present, industry is launched extensive discussions and further investigation to extensive mimo system, the dimensional energy that has scholar to utilize extensive mimo system to have correlation properties channel is concentrated characteristic, proposed multi-subscriber dispatching scheme, by the nonoverlapping user in selective channel covariance matrix subspace, reached and eliminate the object of disturbing.The extensive MIMO user's dispatching algorithm in existing many communities utilizes dimensional energy to concentrate characteristic to design, in algorithm, need to obtain user's scheduling scheme by the processes such as coding in user grouping, descending training, uplink feedback and more complicated two stages, too complicated in practical operation.And user need to carry out information feedback in this algorithm to base station, be not suitable for extensive MIMO TDD system.In addition, although extensive mimo wireless communication technology has caused international extensive concern, but correlative study work is still in the starting stage, the various researchs of extensive mimo system are all launched around infinite many these hypothesis of antenna for base station number, and this hypothesis often can not be built middle establishment at real system, closer to actual, more generally under system model, how to carry out simply and effectively the focus that user's selection and scheduling become research.
Summary of the invention
Goal of the invention: in order to overcome the deficiencies in the prior art, the invention provides under a kind of ZF precoding strategy based on the extensive mimo system user scheduling method in large scale channel fading Duo community: according to user's large scale channel fading, user complete or collected works are divided into different treating in scheduling set, and each treats that the user in scheduling set has close large scale channel fading; Within each dispatching cycle, based on poll criterion, dispatch successively all users in scheduling set that treat; The method is applicable to limited, the unlimited two kinds of parameters of antenna for base station number simultaneously and disposes lower to many communities of extensive MIMO TDD system that cooperates, can break through extensive mimo system user is dispatched to the bottleneck of all studying under infinite many these hypothesis of antenna for base station number, be convenient to can in deployment system, carry out user's scheduling operation in reality, overcome a computation complexity difficult problem simultaneously, utilize simple limited feedback quantity to realize out considerable system and rate capability.
Technical scheme: for achieving the above object, the technical solution used in the present invention is:
Under a kind of ZF precoding strategy based on the extensive mimo system user scheduling method in large scale channel fading Duo community, in this mimo system, there are a plurality of communities, the center base station of each community all disposes extensive evenly line style aerial array, and each community is transmitted alternately in time reverse-link pilot frequency and carried out channel estimating; For same community, some single antenna users accept base station service on same running time-frequency resource, and by user, according to certain rule grouping, different user groups is called within different dispatching cycles; Base station adopts ZF precoding strategy, and the similitude based on large scale channel fading is divided into groups to user, and concrete dispatching method comprises the steps:
(1), to a plurality of communities, obtain the local large scale channel fading factor of all users in each community;
(2) each community independently, each community side by side carries out user grouping according to following process: in Jiang Zhe community, the most close user of the local large scale channel fading factor assigns in same user organizes, number of users in each user's group is identical, and grouping information and each user's the local out to out channel fading factor is fed back to base station;
(3) each community independently, each community side by side carries out poll according to following process: based on polling dispatching criterion, within a dispatching cycle, in all user's groups in Zhe community, base station, user's group of random selection communicates, and the user that base station notice is scheduled organizes and prepares to receive data; In each polling cycle, all user's groups in this community have and are only once scheduled;
(4) base station carries out being transferred to the user who is scheduled after ZF precoding to data.
In described step (2), divide into groups according to local large scale channel fading factor pair user independently in each community, and each user's group has identical number of users; For j community, all user's set expressions are
, number of users is expressed as
will according to rule of classification
be divided into
individual user organizes set κ
jn,
each user organizes set κ
jnin have K user; When the user in j community divides into groups, first right
in all users' local large scale channel fading factor-beta
jkjsort, by minimum or the maximum local large scale channel fading factor, start continuous grouping, by the most close K of the local large scale channel fading factor
individual user assigns in same user organizes, and finally obtains
individually treat scheduling set; β wherein
jkjrepresent k user in j community and the large scale channel fading factor between this cell-site antenna.
In described step (3), in order to embody better fairness between user, base station adopts polling dispatching criterion, and each polling cycle comprises
individual dispatching cycle; Within any one dispatching cycle, all users that have and only have a user to organize in set are dispatched simultaneously, and in other dispatching cycles in this polling cycle, this user organizes set and will can again not be scheduled; In a polling cycle, owning in this community
individual use has completed once scheduling per family; In the dispatching cycle of a polling cycle, the dispatching sequence that user organizes set is arbitrarily, and base station is organized set to user and selected at random.
Each community is transmitted alternately in time reverse-link pilot frequency and is carried out channel estimating, be specially: pilot frequency sequence is all known signals of base station and user, receive after the pilot signal that user sends base station, estimate the channel coefficients between current time base station and user, answer transmission coefficient, base station utilizes the multiple transmission coefficient estimating to carry out ZF precoding to improve systematic function to forward link data; The set L={1 that time-interleaved transmission plan forms all communities in mimo system, 2 ..., L} is divided into Γ mutually disjoint set A
1, A
2..., A
Γ, then removing in each relevant cycle of reverse link data transmission, have and only have one set Zhong community carry out reverse link pilot transmission, and all the other set in all communities all in the forward link data transmission stage.
The form that be expressed as multiple transmission coefficient between user and the base station multiple rapid fading factor and the large scale channel fading factor multiply each other, wherein k user in l community and the large scale channel fading factor representation between j cell-site antenna are β
jkl; β
jklthe slow fading coefficient that represents geonetrical attenuation and shadow fading, because frequency, antenna for base station are all constants, so β
jklwithin each coherence time, remain unchanged, without renewal; And the multiple rapid fading factor to be standard circulate again Gaussian random variable, even be also change at random within the relevant cycle.
The large scale channel fading factor
r wherein
jklrepresent that k user in l community is to the distance of j cell base station, γ is damped expoential, z
jkllognormal stochastic variable, i.e. a 10log
10(z
jkl) obey zero-mean, standard deviation is σ
shadowgaussian Profile, according to the poor σ of the various criterion of system scene
shadowspan also different.
β
jkland r
jklindex be inverse ratio, because each user is less than this user to the distance of other cell base stations to the distance of home base stations, so β
jkj>> β
jkl, i.e. local large scale fading factor β
jkjtherefore in performance, play major decision effect, so in the methods of the invention, as long as obtain each all user's in community the local large scale channel fading factor, can carry out user grouping, also each community independently, each community side by side carries out user grouping.
ZF precoding refers to ZF precoding, the object of zero forcing algorithm is to eliminate interchannel interference, precoding algorithm based on Zero Forcing is mostly the characteristic of utilizing channel matrix or channel correlation matrix itself, thereby channel matrix is done and decomposed the impact that channel is eliminated in distortion completely.The process of described ZF precoding is: before formal transmission data, each user in each user's group can be to home base stations pilot signal transmitted, and pilot frequency sequence is all known signals of base station and user, when receive after pilot signal base station, utilize the pilot signal receiving to do ZF precoding, concrete way is: suppose that the pilot signal that receive l base station is
this base station is by inciting somebody to action
be multiplied by pilot frequency sequence
conjugate transpose obtain the channel estimation value between k user of community, Yu Qi place, l base station
by a treated K user's channel estimating vector representation, be Y
l=[y
1l, y
2l..., y
kl], the ZF precoding way of base station l is to make pre-coding matrix W
lfor following form:
base station carries out sending to user after ZF precoding to data.
Beneficial effect: based on the extensive mimo system user scheduling method in large scale channel fading Duo community, with respect to prior art, there is following advantage under ZF precoding strategy provided by the invention:
1, the large scale channel fading coefficient based on user is dispatched, only utilize the feedback information of large scale channel fading coefficient and minute quantity just can complete whole scheduling step, effectively reduce computation complexity, and solved the loss that extensive mimo system information feedback is brought;
2, can in the TDD system of arranging limited foundation station antenna, improve effectively simply fairness between user rate and user, it is all based on infinite many these restrictions of antenna for base station number to the research of extensive MIMO that algorithm has been broken through existing, the limited system of antenna for base station number can be built middle establishment actual, be more rational system model, the algorithm therefore obtaining has more theoretical significance and actual application value;
3, not only can in the limited extensive MIMO TDD system of antenna for base station number, set up, also be applicable to the infinite scene of antenna for base station number; In addition, if do not adopt, alternately do not transmit pilot schemes in system, during each community associated transmission pilot tone, can apply above-mentioned simple algorithm yet and obtain good systematic function, so this algorithm has general applicability to corresponding precoding policy system.
Accompanying drawing explanation
Fig. 1 is application scenarios schematic diagram of the present invention; 1-st cell represents the 1st community, and l-th cell represents l community, and j-th cell represents j community, and L-th cell represents L community;
Fig. 2 is the inventive method flow chart.
Embodiment
Below in conjunction with accompanying drawing, the present invention is further described.
As shown in Figure 1, in the extensive mimo system in Duo community, each center of housing estate has an even aerial array of line style, in j community, has
individual single antenna user is evenly randomly dispersed in community, and each community is transmitted alternately in time reverse-link pilot frequency and carried out channel estimating; Under TDD transmission mode, for same community, some single antenna users accept base station service on same running time-frequency resource, and by user, according to certain rule grouping, different user groups is called within different dispatching cycles; Base station adopts ZF precoding strategy, and the similitude based on large scale channel fading is divided into groups to user, and concrete dispatching method comprises the steps:
(1), to a plurality of communities, obtain the local large scale channel fading factor of all users in each community;
(2) each community independently, each community side by side carries out user grouping according to following process: in Jiang Zhe community, the most close user of the local large scale channel fading factor assigns in same user organizes, number of users in each user's group is identical, and grouping information and each user's the local out to out channel fading factor is fed back to base station;
(3) each community independently, each community side by side carries out poll according to following process: based on polling dispatching criterion, within a dispatching cycle, in all user's groups in Zhe community, base station, user's group of random selection communicates, and the user that base station notice is scheduled organizes and prepares to receive data; In each polling cycle, all user's groups in this community have and are only once scheduled;
(4) base station carries out being transferred to the user who is scheduled after ZF precoding to data.
In described step (2), divide into groups according to local large scale channel fading factor pair user independently in each community, and each user's group has identical number of users; For j community, all user's set expressions are
, number of users is expressed as
will according to rule of classification
be divided into
individual user organizes set κ
jn,
each user organizes set κ
jnin have K user; When the user in j community divides into groups, first right
in all users' local large scale channel fading factor-beta
jkjsort, by minimum or the maximum local large scale channel fading factor, start continuous grouping, by the most close K of the local large scale channel fading factor
individual user assigns in same user organizes, and finally obtains
individually treat scheduling set; β wherein
jkjrepresent k user in j community and the large scale channel fading factor between this cell-site antenna.
In described step (3), in order to embody better fairness between user, base station adopts polling dispatching criterion, and each polling cycle comprises
individual dispatching cycle; Within any one dispatching cycle, all users that have and only have a user to organize in set are dispatched simultaneously, and in other dispatching cycles in this polling cycle, this user organizes set and will can again not be scheduled; In a polling cycle, owning in this community
individual use has completed once scheduling per family; In the dispatching cycle of a polling cycle, the dispatching sequence that user organizes set is arbitrarily, and base station is organized set to user and selected at random.
Each community is transmitted alternately in time reverse-link pilot frequency and is carried out channel estimating, be specially: pilot frequency sequence is all known signals of base station and user, receive after the pilot signal that user sends base station, estimate the channel coefficients between current time base station and user, answer transmission coefficient, base station utilizes the multiple transmission coefficient estimating to carry out ZF precoding to improve systematic function to forward link data; The set L={1 that time-interleaved transmission plan forms all communities in mimo system, 2 ..., L} is divided into Γ mutually disjoint set A
1, A
2..., A
Γ, then removing in each relevant cycle of reverse link data transmission, have and only have one set Zhong community carry out reverse link pilot transmission, and all the other set in all communities all in the forward link data transmission stage.
The form that be expressed as multiple transmission coefficient between user and the base station multiple rapid fading factor and the large scale channel fading factor multiply each other, wherein k user in l community and the large scale channel fading factor representation between j cell-site antenna are β
jkl; β
jklthe slow fading coefficient that represents geonetrical attenuation and shadow fading, because frequency, antenna for base station are all constants, so β
jklwithin each coherence time, remain unchanged, without renewal; And the multiple rapid fading factor to be standard circulate again Gaussian random variable, even be also change at random within the relevant cycle.
The large scale channel fading factor
r wherein
jklrepresent that k user in l community is to the distance of j cell base station, γ is damped expoential, z
jkllognormal stochastic variable, i.e. a 10log
10(z
jkl) obey zero-mean, standard deviation is σ
shadowgaussian Profile, according to the poor σ of the various criterion of system scene
shadowspan also different.
β
jkland r
jklindex be inverse ratio, because each user is less than this user to the distance of other cell base stations to the distance of home base stations, so β
jkj>> β
jkl, i.e. local large scale fading factor β
jkjtherefore in performance, play major decision effect, so in the methods of the invention, as long as obtain each all user's in community the local large scale channel fading factor, can carry out user grouping, also each community independently, each community side by side carries out user grouping.
ZF precoding refers to ZF precoding, the object of zero forcing algorithm is to eliminate interchannel interference, precoding algorithm based on Zero Forcing is mostly the characteristic of utilizing channel matrix or channel correlation matrix itself, thereby channel matrix is done and decomposed the impact that channel is eliminated in distortion completely.The process of described ZF precoding is: before formal transmission data, each user in each user's group can be to home base stations pilot signal transmitted, and pilot frequency sequence is all known signals of base station and user, when receive after pilot signal base station, utilize the pilot signal receiving to do ZF precoding, concrete way is: suppose that the pilot signal that receive l base station is
this base station is by inciting somebody to action
be multiplied by pilot frequency sequence
conjugate transpose obtain the channel estimation value between k user of community, Yu Qi place, l base station
by a treated K user's channel estimating vector representation, be Y
l=[y
1l, y
2l..., y
kl], the ZF precoding way of base station l is to make pre-coding matrix W
lfor following form:
base station carries out sending to user after ZF precoding to data.
The above is only the preferred embodiment of the present invention; be noted that for those skilled in the art; under the premise without departing from the principles of the invention, can also make some improvements and modifications, these improvements and modifications also should be considered as protection scope of the present invention.