CN102573092B - Improved proportional fairness scheduling algorithm based on multiuser eigenmode transmission (MET) precoding technology - Google Patents

Abstract

The invention discloses an improved proportional fairness scheduling method based on a multiuser eigenmode transmission (MET) precoding technology in a multiuser multiple input multiple output (MU-MIMO) wireless communication system. The improved proportional fairness scheduling algorithm comprises the following steps: (1) receiving service requests of users and channel state information and then initializing average transmission rates of the users, average request rate and a service user set, by a base station; (2) updating the average request rate of each user and selecting a user of the highest priority level to constitute a first user of the service user set; (3) selecting the user of the highest priority level each time by the base station by using a greedy algorithm to constitute the service user set; and (4) after the users capable of being served by a system are selected, updating the average transmission rate of each user to a next round of user scheduling. The improved proportional fairness scheduling algorithm disclosed by the invention can be used for increasing the fairness of users with different channel conditions in the system on the basis of ensuring the superiority that the MET precoding technology can be used for obviously increasing system capacity, so that a favorable compromise is achieved between the system capacity and the user fairness.

Description

Based on multi-user features pattern precoding technique modified model proportional fair dispatching method

Technical field

The present invention relates to multi-subscriber dispatching technology and a kind of multi-user features pattern (MET) precoding technique in multiple-input and multiple-output in wireless communication technology (MIMO) communication system, more specifically, relate to a kind of modified model multiuser proportion fair scheduling method based on multi-user features pattern (MET) precoding technique.

Background technology

Multiple-input and multiple-output (MIMO) technology is one of core technology of radio communication B3G.It for mobile communication system has increased spatial degrees of freedom, provides spatial reuse gain and space diversity gain, to improve system throughput by transmitting and receiving antenna in base station and many of user side installations.

Precoding technique can solve in single point-to-multipoint communication system signal interference problem between user, it realizes the parallel transmission of multiple signals by wireless channel being treated to the method for multiple glitch-free parallel sub-channels each other, thereby obtain spatial reuse gain, improve the message transmission rate of system.

In radio communication mimo system, be subject to the restriction of number of transmit antennas, the reception antenna summation of accepting the user of service in each time slot can not be greater than number of transmit antennas, and the number of users of service is limited simultaneously, need to from all users, select the user of service, namely Mulitiple user resource scheduling problem.In multi-user MIMO system, to realize multi-user diversity, will solve multiple users by Mulitiple user resource scheduling problem and how share limited Radio Resource, improve as much as possible the spectrum efficiency of system, take into account again the service quality of each user in system simultaneously.The target of multi-subscriber dispatching is to provide a gratifying system availability (efficiently), for multimedia service provides transformable QoS service (justice).

Traditional dispatching algorithm is to utilize the fading characteristic of subscriber channel, allows the base station be that channel status is best in each time slot scheduling, provides service to obtain to several users of subscriber channel capacity maximum.Such dispatching method can make the throughput maximum of system, has but ignored the fairness between user.When a part of subscriber channel state is for a long time in poor state, when subscriber channel capacity is less, these users can cannot be served for a long time.

In order to solve the problem of user fairness, proportional fair scheduling is introduced in multi-subscriber dispatching.It is the criterion using user's channel capacity size as User Priority no longer, but the ratio of the instantaneous request rate of user and instantaneous transmission speed, that is:

$\mathrm{\μ}=\frac{R_k\left(t\right)}{T_k\left(t\right)}---\left(4\right)$

T _k(t) represent the transmission rate of user k at current time slots t.R _k(t) represent the instantaneous request rate of user k at current time slots t.Equitable proportion algorithm can improve the user's who can not get for a long time scheduling dispatching priority, thereby the fairness of user on throughput improved, and reduces the difference of average throughput between different user.

Multi-user features pattern (MET) precoding technique be a kind of based on block diagonalization Linear Precoding, in the broadcast channel of current single point-to-multipoint, multi-user features mode transfer (MET) has best performance performance in linear pre-coding system, can improve greatly the throughput of system.

Based on this, we consider proportional fair scheduling and MET precoding technique to combine, to obtain the compromise of system throughput and fairness.But this combination, in improving system fairness, lose too many throughput, can not well bring into play MET precoding technique in the superiority improving on system throughput, therefore, be necessary to provide a kind of improved multiuser proportion fair method, make it can between system throughput and fairness, obtain better compromise in the time that MET precoding technique is combined.

Summary of the invention

The object of this invention is to provide a kind of multi-user dispatching method, make it can between system throughput and fairness, obtain better compromise in the time that MET method for precoding is combined, can improve the channel condition fairness of the user in poor state for a long time, be unlikely to again to make system capacity loss too much.

To achieve these goals, the invention provides a kind of follow-on multiuser proportion fair scheduling method, comprise the steps: that (1) base station receives after user's service request and channel condition information, initialization user average transmission rate, average request speed and service-user collection, (2) all users are carried out to MET precoding, upgrade each user's average request speed simultaneously, and calculate each User Priority, first user who selects greatest priority user to concentrate as service-user, (3) base station utilizes greedy algorithm to carry out the selection of remaining users: in service object's set, increase a user at every turn, according to channel condition information and existing service object set, adopt MET precoding technique, each user's channel capacity after calculating precoding, that is user's instantaneous request rate, according to the instantaneous request rate of user, the increment after initial average transmission rate and average request rate upgrade, utilizes priority computing formula to upgrade the dispatching priority that calculates each user, selects greatest priority user to add service-user collection, wherein because each user's average request speed is only just upgraded in the time selecting first user, so the increment of the average request speed using in the time of each selection service-user is all the increment size upgrading while selecting first user, similarly, each user's average transmission rate only just upgrades after all service-users having selected, so the average transmission rate of selecting service-user to use is all to have selected the value (4) of upgrading after all service-users if service-user concentrates number of users to reach the maximum number of user that system can be served simultaneously in last time at every turn, carry out (5) step, otherwise, continue to repeat (3) step, (5) after the user who has selected system simultaneously to serve, upgrade each user's average transmission rate, the average transmission rate after renewal will be used for the selection of user's services set of next round as the initial value of average transmission rate.

In one embodiment of the invention, in described step (2), base station selected have greatest priority user form service-user concentrate first user, the priority computing formula using is:

$\mathrm{\μ}=\frac{R_k\left(t\right)}{\stackrel{\‾}{T_k\left(t\right)}}\·\frac{R_k\left(t\right)}{e^{-(\stackrel{\‾}{R_k\left(t\right)}-\stackrel{\‾}{R_k(t-1)})}}$

Wherein be illustrated in user k t in the past in epicycle scheduling _caverage transmission rate in individual time slot, R _k(t) represent the instantaneous request rate of user k at current time slots t, be illustrated in user k t in the past in epicycle scheduling _caverage request speed in individual time slot, represent user k t in the past in last round of scheduling _cin individual time slot average request speed.

In another embodiment of the present invention, in described step (2) medium priority computing formula in the time selecting first user, just upgrade, while selecting all the other users, all use the value after upgrading for the first time, more new formula is:

$\stackrel{\‾}{R_k(t+1)}=(1-\frac{1}{t_c})\stackrel{\‾}{R_k\left(t\right)}+\frac{1}{t_c}{R}_k\left(t\right)$

In another embodiment of the present invention, in described step (6), after the user who has selected each time all systems simultaneously to serve, user k t in the past in next round scheduling _caverage transmission rate in individual time slot need to whether dispatch state according to user upgrades as follows:

Upgrade average transmission rate R used _k(t) be while selecting last user, the channel capacity of calculating according to MET precoding.For shortcut calculation, by right with the time window upgrading is taken as the same.

In the embodiment more of the present invention, system is to know each user's instantaneous channel information, and need to utilize this information to carry out MET precoding, makes largeizationr of power system capacity.Compared with prior art, the modified model multiuser proportion fair algorithm that the present invention is based on multi-user features pattern (MET) precoding technique is by introducing instantaneous request rate and the exponential function using average request rate increment as power exponent ratio, improve channel status best with respect to self average channel condition, and there is relatively high power capacity increment user's dispatching priority, thereby increase channel status long-term poor but have with respect to self have higher capacity increment the chance that is scheduled of user, in improving system fairness, kept preferably MET precoding technique in the superiority improving in power system capacity.

By following description also by reference to the accompanying drawings, it is more clear that the present invention will become, and these accompanying drawings are used for explaining embodiments of the invention.

Brief description of the drawings

Fig. 1 is the flow chart that the present invention is based on the multiuser proportion fair method of MET.

Fig. 2 is the flow chart of speed update strategy used in the present invention.

Embodiment

With reference now to accompanying drawing, describe embodiments of the invention, in accompanying drawing, similarly element numbers represents similar element.

Before setting forth the modified model proportional fair scheduling of the present embodiment based on multi-user features pattern (MET) precoding technique, the following concept relating in described method is first described:

Service-user collection: the set that the user that at a time will serve for system forms, user is wherein exactly the user who has obtained scheduling.The process of user's scheduling is exactly one and concentrates the process of adding user to service-user.

Dispatching priority: for weighing the amount of the degree of priority of user in scheduling.Dispatching priority is higher, and the probability that user obtains scheduling in once dispatching is just higher.In actual enforcement, be all to select to have the user of high dispatching priority at every turn.

Greedy algorithm: be a kind of method for solving of problem, do not pursue globally optimal solution, being only made at current it seems is best selection.In the method, greedy algorithm is used to user and selects, and only selects to make current service user to concentrate the user of dispatching priority of users sum maximum when selecting user at every turn.

Channel matrix: for coefficient is the matrix of the fading coefficients between reception antenna and transmitting antenna.If reception antenna number is N, number of transmit antennas is M, and channel matrix is exactly the complex matrix of N × M so.For unique user, the reception antenna number that reception antenna number is this user; For multiple users, channel matrix is that each user's channel matrix is longitudinally connected, and the reception antenna that reception antenna number is all users is counted sum.

MET precoding technique: be a kind of precoding technique of block diagonalization, MET has three parts, (1) block diagonalization based on linear predictive coding (BD) technology, (2) are the selection of user and feature stream thoroughly, and (3) are for the power division to selected feature stream.In MET, block diagonalization technology greatly reduces transmitting precoding and receiving terminal complexity.Current in the broadcast channel of single point-to-multipoint multi-user features mode transfer (MET) in linear pre-coding system, have the performance of best performance.

Illustrate the flow process of the modified model equitable proportion method of the present embodiment based on multi-user features model selection precoding technique below.In conjunction with Fig. 2, described modified model equitable proportion method comprises the following steps:

Step S1, user sends service request to base station, and the while, base station, according to the channel condition information of feedback, can obtain each user's channel matrix the information feedback of self to base station;

Step S2, initialization average transmission rate and average request rate, both initial values can be taken as 1, that is: these two initial values, for the service-user scheduling of the first round, in follow-up service user scheduling, utilize the value of upgrading in all user procedures of the each service of selection as initial value.

Step S3, initialization service-user collection, makes service-user integrate as empty set;

Step S4, each user, by each user's channel matrix, according to adopted MET method for precoding, is calculated in the channel capacity not having under disturbed condition in base station.The result obtaining is as each user's instantaneous request rate R _k(t);

Step S5, utilizes the instantaneous request rate obtaining, and upgrades all users' average request speed, and can obtain thus the increment of average request speed, the value after renewal is using the initial value of the average request speed in the scheduling of next round service-user;

Step S6, by formula calculate each user's priority.The user with limit priority is selected into service-user collection, has determined first user that service-user is concentrated;

Then, according to greedy selection algorithm, never start to prepare to select user to join service-user and concentrate in the concentrated user of service-user.Following step is exactly a tentative process, each user to be selected is added service-user to concentrate exploratoryly and goes, and investigates the quality of each scheme, finally selects best scheme, thereby adds the concentrated user of service-user after determining.For convenience of description, to select the 2nd concentrated user of service-user as example explanation;

Step S7, try by each user to be selected join service-user concentrate go.After adding, count the user that original user and Xin add in, service-user is concentrated and is now had 2 users, utilizes these two users' channel matrix in conjunction with MET precoding technique, recalculates the channel capacity that obtains each user;

Step S8, calculation services user concentrates each user's channel capacity, and using this new result as instantaneous request rate R _k(t);

Step S9, the average request rate increment of upgrading according to the new instantaneous request rate obtaining in step S8 with while selecting user for the first time and initial average transmission rate, calculate each exploratory user's who adds priority;

Step S10 selects the user of priority maximum to join service-user and concentrates from all exploratory users that add, and has determined second user who is selected in set;

Step S11, judges whether the concentrated number of users of service-user has reached the maximum number of user that system can be served simultaneously.If do not reached, get back to step S7, now, be no longer to concentrate and add the 2nd user to service-user, but add the 3rd user, the like.If reached, continue step S12;

Step S12, user is the exploratory instantaneous request rate that adds service-user collection to obtain the last time, whether dispatches state upgrade average transmission rate according to user the initial value of the average transmission rate of dispatching as next round service-user collection.

In conjunction with most preferred embodiment, invention has been described above, but the present invention is not limited to the embodiment of above announcement, and should contain the various amendments of carrying out according to essence of the present invention, equivalent combinations.

Claims (6)

1. based on multi-user features pattern MET precoding technique modified model proportional fair dispatching method, comprise the steps:

(1) base station receives after user's service request and channel condition information, initialization user average transmission rate, average request speed and service-user collection;

(2) upgrade each user's average request speed, and the user who selects to have greatest priority forms first user of service-user collection; Select greatest priority user as the concentrated user of service-user, the priority computing formula using is:

$\mathrm{\μ}=\frac{R_k\left(t\right)}{T_k\left(t\right)}\·\frac{R_k\left(t\right)}{e^{-(\stackrel{\‾}{R_k\left(t\right)}-\stackrel{\‾}{R_k(t-1)})}}---\left(1\right)$

Wherein be illustrated in user k t in the past in epicycle scheduling _caverage transmission rate in individual time slot, R _k(t) represent the instantaneous request rate of user k in current time slots, be illustrated in user k t in the past in epicycle scheduling _caverage request speed in individual time slot, represent user k t in the past in last round of scheduling _caverage request speed in individual time slot;

After all users that selected each time system simultaneously to serve, whether dispatch state according to user and upgrade average transmission rate formula be:

Upgrade average transmission rate R used _k(t) be while selecting last user, the channel capacity of calculating according to MET precoding;

be illustrated in user k t in the past in epicycle scheduling _caverage request speed in individual time slot, it just upgrades in the time selecting first user, while selecting all the other users, all uses the value after upgrading for the first time, and more new formula is:

$\stackrel{\‾}{R_k(t+1)}=(1-\frac{1}{t_c})\stackrel{\‾}{R_k\left(t\right)}+\frac{1}{t_c}{R}_k\left(t\right)---\left(3\right)$

Upgrade average request speed R used _k(t) be while selecting first user, the each user's who calculates according to MET precoding channel capacity;

(3) user that base station utilizes the each selection of greedy algorithm to have greatest priority adds service-user collection; Concrete steps are: step S7, try by each user to be selected join service-user concentrate go; After adding, count the user that original user and Xin add in, service-user is concentrated and is now had 2 users, utilizes these two users' channel matrix in conjunction with MET precoding technique, recalculates the channel capacity that obtains each user; Step S8, calculation services user concentrates each user's channel capacity, and using this new result as instantaneous request rate R _k(t); Step S9, the average request rate increment of upgrading according to the new instantaneous request rate obtaining in step S8 with while selecting user for the first time and initial average transmission rate, calculate each exploratory user's who adds priority; Step S10 selects the user of priority maximum to join service-user and concentrates from all exploratory users that add, and has determined second user who is selected in set; Step S11, judges whether the concentrated number of users of service-user has reached the maximum number of user that system can be served simultaneously; If do not reached, get back to step S7, now, be no longer to concentrate and add the 2nd user to service-user, but add the 3rd user, the like;

(4), after the user who has selected system simultaneously to serve, upgrade each user's average transmission rate and dispatch for next round user.

2. as claimed in claim 1 based on multi-user features pattern MET precoding technique modified model proportional fair dispatching method, be further characterized in that: by right with the time window upgrading is taken as the same.

3. as claimed in claim 1 based on multi-user features pattern MET precoding technique modified model proportional fair dispatching method, be further characterized in that, system is to know each user's instantaneous channel information, and need to utilize this information to carry out MET precoding, makes largeizationr of power system capacity.

4. as claimed in claim 1ly it is characterized in that: described channel capacity is according to channel matrix based on multi-user features pattern MET precoding technique modified model proportional fair dispatching method, calculate with reference to the method for precoding adopting.

5. as claimed in claim 1 based on multi-user features pattern MET precoding technique modified model proportional fair dispatching method, be further characterized in that, also comprise: for the poor user of channel condition, at channel condition during in himself peak value, can obtain, than the higher scheduling probability of dispatching algorithm of selecting heap(ed) capacity user under simple MET precoding technique, can well improving the fairness of system.

6. as claimed in claim 1 based on multi-user features pattern MET precoding technique modified model proportional fair dispatching method, be further characterized in that, also comprise: in the time of the poor user of selective channel condition, it is larger that the user with larger capacity increment obtains the probability of scheduling, can ensure like this in improving system fairness, be unlikely to the power system capacity that loss is too large, can better utilize MET precoding technique in the superiority improving in power system capacity.