CN102573092A - Improved proportional fairness scheduling algorithm based on multiuser eigenmode transmission (MET) precoding technology - Google Patents

Abstract

The invention discloses an improved proportional fairness scheduling algorithm 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 algorithm

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 the wireless communication technology (MIMO) communication system; More specifically, relate to a kind of modified model multiuser proportion fair dispatching algorithm 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 GSM has increased spatial degrees of freedom, provides spatial reuse gain and space diversity gain, to improve system throughput through transmitting and receiving antenna in base station and many of user side installations.

Precoding technique can solve single-point to signal interference problem between the user in the multipoint communication system; It realizes the parallel transmission of multiple signals through the method that wireless channel is treated to a plurality of glitch-free parallel sub-channels each other; Thereby obtain the spatial reuse gain, improve the message transmission rate of system.

In the radio communication mimo system; Receive 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 from all users, select the user of service, just the Mulitiple user resource scheduling problem.In multi-user MIMO system, to realize multi-user diversity; Will solve a plurality of users through the Mulitiple user resource scheduling problem and how share finite wireless resources; Improve the spectrum efficiency of system as much as possible, take into account each quality of services for users in the system simultaneously again.The target of multi-subscriber dispatching provides 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, lets the base station be that channel status is best in each time slot scheduling, promptly provides service to obtain to the maximum several users of subscriber channel capacity.Such dispatching method can make the throughput of system maximum, has but ignored the fairness between the user.When a part of subscriber channel state is in relatively poor state for a long time, when promptly the subscriber channel capacity was less, these users can can't obtain service for a long time.

In order to solve the problem of user fairness, the Proportional Fair algorithm is introduced in multi-subscriber dispatching.It is no longer the criterion of user's channel capacity size as User Priority, and is to use the ratio of 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) expression user k is in the transmission rate of current time slots t.R _k(t) expression user k is at the instantaneous request rate of current time slots t.The equitable proportion algorithm can improve the user's who can not get for a long time dispatching dispatching priority, thereby makes the fairness of user on throughput improve, and promptly 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 predictive coding technology; Current single-point to the broadcast channel of multiple spot in multi-user features mode transfer (MET) best performance performance is arranged in linear pre-coding system, can improve the throughput of system greatly.

Based on this, we consider Proportional Fair algorithm and MET precoding technique are combined, to obtain the compromise of system throughput and fairness.But this combination; When improving system's fairness; Lost too many throughput, can not well bring into play the MET precoding technique in the superiority that improves on the system throughput, therefore; Be necessary to provide a kind of improved multiuser proportion fair method, can between system throughput and fairness, obtain better compromise when it is combined with the MET precoding technique.

Summary of the invention

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

To achieve these goals; The invention provides a kind of follow-on multiuser proportion fair dispatching algorithm; After comprising the steps: that (1) base station receives user's services request and channel condition information, initialization user average transmission rate, average request speed and service-user collection; (2) all users are carried out the MET precoding, upgrade each user's average request speed simultaneously, and calculate each User Priority, first user who selects the 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 the MET precoding technique; Each user's channel capacity after the calculating precoding, that is user's instantaneous request rate; According to the instantaneous request rate of user, the increment after initial average transmission rate upgrades with average request rate utilizes each user's of priority computing formula update calculation dispatching priority, selects the greatest priority user to add the service-user collection; Wherein owing to each user's average request speed is only just upgraded when selecting first user; So the increment of employed average request speed all is the increment size that upgrades when selecting first user when selecting service-user at every turn; Likewise; Each user's average transmission rate only just upgrades behind all service-users having selected, so the average transmission rate of selecting service-user to use all is to have reached the maximum number of user that system can serve simultaneously in the value (4) that selected to upgrade behind all service-users last time as if the concentrated number of users of service-user at every turn, then carries out (5) and goes on foot; Otherwise, continued to repeat (3) step; (5) behind the user who has selected system to serve simultaneously, upgrade each user's average transmission rate, the average transmission rate after the 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 the said step (2), base station selected have the greatest priority user and form first user that service-user is concentrated, and employed priority computing formula 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 the epicycle scheduling user k t in the past _cAverage transmission rate in the individual time slot, R _k(t) represent the instantaneous request rate of user k at current time slots t, Be illustrated in the epicycle scheduling user k t in the past _cAverage request speed in the individual time slot, Represent in the last round of scheduling user k t in the past _cIn the individual time slot average request speed.

In another embodiment of the present invention;

in said step (2) the medium priority computing formula just upgrades when selecting first user; When 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 the said step (6), behind the user who has selected all systems to serve simultaneously each time, user k t in the past in the next round scheduling _cAverage transmission rate in the individual time slot

Need whether dispatch state according to the user upgrades by following formula:

Upgrade the used R of average transmission rate _k(t) be when selecting last user, according to the channel capacity of MET precoding calculating.Be shortcut calculation, will be taken as the same with the time window that

upgrades .

In the embodiment more of the present invention, each user's instantaneous channel information can be known by system, and need utilize this information to carry out the MET precoding, makes bigizationner 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 through the instantaneous request rate of introducing with the ratio of average request rate increment as the exponential function

of power exponent; It is best with respect to self average channel condition to improve channel status; And has relative higher capacity increment user's a dispatching priority; Thereby increase channel status long-term relatively poor but have with respect to self have the higher capacity increment the chance that is scheduled of user, when improving system's fairness, kept the MET precoding technique in the superiority that improves on the power system capacity preferably.

Through following description and combine accompanying drawing, it is more clear that the present invention will become, and these accompanying drawings are used to explain embodiments of the invention.

Description of 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 used speed update strategy among the present invention.

Embodiment

With reference now to accompanying drawing, describe embodiments of the invention, the similar elements label is represented similar elements in the accompanying drawing.

Before setting forth the modified model Proportional Fair algorithm of present embodiment based on multi-user features pattern (MET) precoding technique, the following notion that relates in the said method of explanation earlier:

The service-user collection: for system at a time the set formed of the user that will serve, user wherein is exactly the user who has obtained scheduling.The process of user's scheduling is exactly a process from the interpolation user to service-user that concentrate.

Dispatching priority: for weighing the amount of the degree of priority of user in scheduling.Dispatching priority is high more, and the probability that the user obtains dispatching in once dispatching is just high more.In actual the enforcement, all be 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, only being made at current it seems is best choice.In the method, greedy algorithm is used to the user and selects, and only selects to make the current service user to concentrate the maximum user of dispatching priority of users sum when selecting the user at every turn.

Channel matrix: for coefficient is the matrix of the fading coefficients between reception antenna and the transmitting antenna.If the 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 is this user's a reception antenna number; For a plurality of users, channel matrix is for vertically to connect each user's channel matrix, and the reception antenna number is that all users' reception antenna is counted sum.

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

Specify the flow process of present embodiment below based on the modified model equitable proportion algorithm of multi-user features model selection precoding technique.In conjunction with Fig. 2, described modified model equitable proportion method may further comprise the steps:

Step S1, the user sends services request to the base station, feeds back to the base station to the channel condition information of self simultaneously, and the base station can access each user's channel matrix according to the channel condition information of feedback;

Step S2; Initialization average transmission rate and average request rate; Both initial values can be taken as 1; That is: these two initial values of

are used for the service-user scheduling of the first round; In follow-up service user scheduling, then be utilized in the value selecting to upgrade in each all user procedures of service as initial value.

Step S3, initialization service-user collection makes that the service-user collection is an empty set;

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

Step S5; The instantaneous request rate that utilization obtains; Upgrade all users' average request speed; also can obtain the increment of average request speed thus, and the value after the renewal will be as the initial value of the average request speed in the scheduling of next round service-user;

Step S6 is calculated each user's priority by formula .Be selected into the service-user collection to user, promptly confirmed first user that service-user is concentrated with limit priority;

Then, according to greedy selection algorithm, begin to prepare never in the user that service-user is concentrated, to select the user to join service-user and concentrate.Following step is exactly a tentative process, promptly each user to be selected is added service-user exploratoryly and concentrates and to go, and investigates the quality of each scheme, selects best scheme at last, thereby confirms that the back adds the user that service-user is concentrated.Explanation for ease is the example explanation with the 2nd user who selects service-user to concentrate;

Step S7 tries that each user to be selected is joined service-user and concentrates and to go.After the adding, count original user and initiate user in, service-user concentrates have 2 users this moment, utilizes these two users' channel matrix to combine the MET precoding technique, recomputates the channel capacity that obtains each user;

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

Step S9, average request rate increment of upgrading when for the first time selecting the user according to the new instantaneous request rate that obtains among the step S8 and initial average transmission rate calculate the user's of each exploratory adding priority;

Step S10 selects the maximum user of priority to join service-user from the user of all exploratory addings and concentrates, and has promptly confirmed to be selected into second user in the set;

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

Step S12; Use the resulting instantaneous request rate of user's exploratory the last time adding service-user collection, whether dispatch state according to the user and upgrade the initial value of average transmission rate as the average transmission rate of next round service-user collection scheduling.

Invention has been described more than to combine most preferred embodiment, but the present invention is not limited to the embodiment of above announcement, and should contain various modification, equivalent combinations of carrying out according to essence of the present invention.

Claims (9)

1. based on multi-user features pattern precoding technique modified model Proportional Fair algorithm, comprise the steps:

(1) after the base station receives user's services 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 constitutes first user of service-user collection;

(3) base station utilizes greedy algorithm to select the user with greatest priority to add the service-user collection at every turn;

(4) behind the user who has selected system to serve simultaneously, the average transmission rate that upgrades each user is used for next round user scheduling.

2. as claimed in claim 1 based on multi-user features pattern precoding technique modified model Proportional Fair algorithm, it is characterized in that: the user who selects the greatest priority user to concentrate as service-user, employed priority computing formula is:

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

(1)

Wherein Be illustrated in the epicycle scheduling user k t in the past _cAverage transmission rate in the individual time slot, R _k(t) represent the instantaneous request rate of user k in current time slots,

Be illustrated in the epicycle scheduling user k t in the past _cAverage request speed in the individual time slot,

Represent in the last round of scheduling user k t in the past _cIn the individual time slot average request speed.

3. as claimed in claim 2 based on multi-user features pattern precoding technique modified model Proportional Fair algorithm; Its characteristic also is: behind all users that selected system to serve simultaneously each time, the formula of whether dispatching state renewal average transmission rate according to the user is:

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

4. as claimed in claim 2 based on multi-user features pattern precoding technique modified model Proportional Fair algorithm, its characteristic also is: Be illustrated in the epicycle scheduling user k t in the past _cAverage request speed in the individual time slot, it just upgrades when selecting first user, when 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 the used R of average request speed _k(t) be when selecting first user, each user's who calculates according to the MET precoding channel capacity.

5. as claimed in claim 4 based on multi-user features pattern precoding technique modified model Proportional Fair algorithm, its characteristic also is: will be taken as the same with the time window that

upgrades to

.

6. as claimed in claim 2 based on multi-user features pattern precoding technique modified model Proportional Fair algorithm; Its characteristic also is; Each user's instantaneous channel information can be known by system, and need utilize this information to carry out the MET precoding, makes bigizationner of power system capacity.

7. as claimed in claim 2 it is characterized in that: described channel capacity is according to channel matrix based on multi-user features pattern precoding technique modified model Proportional Fair algorithm, calculates with reference to the method for precoding that is adopted.

8. as claimed in claim 2 based on multi-user features pattern precoding technique modified model Proportional Fair algorithm; Its characteristic also is; Also comprise: for the relatively poor user of channel condition; When channel condition is in himself peak value, can obtain selecting down heap(ed) capacity user's the higher scheduling probability of dispatching algorithm than simple MET precoding technique, can well improve the fairness of system.

9. as claimed in claim 2 based on multi-user features pattern precoding technique modified model Proportional Fair algorithm; Its characteristic also is; Also comprise: when the relatively poor user of selective channel condition, it is bigger to have a probability that the user of larger capacity increment obtains dispatching, and can guarantee like this when improving system's fairness; Be unlikely to lose too big power system capacity, can the superiority of better utilization MET precoding technique on the raising power system capacity.

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