CN101702700A - Method for allocating minimum power of MIMO-OFDM multi-user system based on allelism - Google Patents

Abstract

The invention discloses a method for allocating optimal power of an MIMO-OFDM multi-user system based on power allelism of uplink power and a downlink power of a wireless channel, a user apparatus and a communication system, which are applied to the technical field of wireless transmission. A transmission terminal apparatus realizes multi-user dispatching of a downlink broadcast channel and minimizes power consumption of the transmission terminal under a restricted condition of satisfying velocity requirements of multiple users according to channel conditions of various users; the user apparatus and the transmission terminal apparatus can realize conversion of an allocation scheme of the optimal allocation of the downlink power and the allocation of the uplink by using the relation of the power allelism of the uplink and the downlink. The invention provides the power allocation method for minimizing the transmission power on the premise of satisfying the velocity requirements of various users, therefore, power overhead of the transmission terminal is reduced, and a purpose of reducing interference of inter-users and inter-cells is also achieved.

Description

MIMO-OFDM multi-user system method for allocating minimum power based on duality

Technical field

The present invention relates to a kind of multi-user system method for allocating minimum power, particularly relate to the method that minimizes transmitting power that a kind of MIMO-OFDM multi-user system satisfies the condition of each telex network speed needs.

Background technology

Use many antennas on transmitter and receiver, promptly constituted multiple-input and multiple-output (MIMO) mode, this transmission means can strengthen the reliability of wireless connections and increase the capacity of wireless communication system.In the wireless environment that reflection is enriched, for a system that has Nt transmit antennas and Nr root reception antenna, the MIMO transmission means is that relative with the reception antenna number less numerical value with number of transmit antennas is linear to the contribution that channel capacity improves.For broadband connections, OFDM (OFDM) technology is divided into the flat fading channel of one group of parallel quadrature with frequency-selective channel, has improved the system spectrum utilance greatly, and can effectively overcome the intersymbol string around (ISI).The OFDM technology combines with the MIMO technology, has become the outstanding alternative of following wide-band mobile communication system.

At present, the power division problem of MIMO-OFDM multi-user comm mainly concentrates on based on being issued to maximum capacity in certain power constraints.In theory, the multiuser downstream channel can be modeled as broadcast channel (BC), and up channel can be modeled as multiple access access channel (MAC).In BC and MAC, power control is the important way that solves near-far problem.Up to the present, in many antennas OFDM multi-user system, in the achievable rate territory,, do not solved fully based on the optimal power control strategy of expected rate.Present research mainly concentrates under the condition based on each user's power constraint, reaches the speed maximization.That is to say that former research mainly concentrates on maximum overall speed, in this case, have service opportunity that the user of better channel condition obtains and be much higher than and have the poor channel conditions user, even the user who has can not get service opportunity at all.Therefore,, be user's dispatching criterion to the maximum, will cause the extreme unjustness between the user with overall rate at real system.At this situation, the present invention considers to satisfy under each user's the rate requirement condition, minimizes transmitting power, can satisfy the system service quality thereby reach, and can reduce the consumption of transmitting power again, and can reach the effect that reduces adjacent area interference.

Summary of the invention

At the problems referred to above, main purpose of the present invention is at the deficiencies in the prior art, proposes the method that minimizes transmitting power that a kind of MIMO-OFDM multi-user system satisfies the condition of each telex network speed needs.

The present invention is by solving above-mentioned technical problem with following technical proposals: the objective of the invention is to overcome the deficiency irrationality in the present technology, provide in a kind of MIMO-OFDM multi-user comm and satisfy under the situation of each telex network demand, minimize the method for transmitting power, on the basis of optimized allocation of resources, further reduce the interference of multi-user to neighbor cell, the present invention obtains a power distribution strategies, can also be converted into the power distribution strategies of up link by the duality of up link and down link.Algorithm performance that the present invention carries is sane, and is easy to realize.The present invention is achieved by the following technical solutions, at first according to the channel condition information of each user on each subcarrier, carry out user's selection on all subcarriers, the best user of all subcarrier upper signal channel conditions will be selected, then this user concentrated deletion from candidate user.Next on the same sub-carrier at selected user place, carry out user's selection, to realize space division multiplexing emission strategy.Carry out on each subcarrier in the process of user's selection, user of every selection will be with the overall rate R on the current subcarrier ⁽ⁿ⁾With the overall rate R on the current subcarrier that does not carry out this user's selection ^(n-1)Compare, if R ⁽ⁿ⁾＜R ^(n-1), then cancel active user's selection, thereby the user on the current subcarrier is the selected user of preceding step, otherwise, carry out the next round user in the same way and select.After the user on the subcarrier selects to finish, promptly on remaining subcarrier, carry out user's selection in the same way, if all selected mistake of all users once, it is candidate user collection no user optional time, then the candidate user collection is made as all users, to the last a subcarrier obtains assigning.At last, carry out power division, thereby reach the optimization configuration of resource according to selected user's subclass and each user's power division requirement.

Below the inventive method is described further, comprise the steps:

1, receiving terminal obtains channel condition information, and this channel condition information can utilize certain channel estimation methods to obtain.

2 and suppose that each user feeds back to transmitting terminal with channel condition information, promptly transmitting terminal is known channel condition information accurately.

3, relatively each user begins user's selection algorithm in each channel strength above the subcarrier with this.Channel strength is with the modular representation of each user channel vector of each user on each subcarrier.Be that user k is at subcarrier N _sOn mould r _k(N _s)=h _k(N _s) h _k(N _s) ^H, concrete selection mode is:

${\mathrm{<figure-callout\; id="1"\; label="s"\; filenames="H2009101992747E0000012.png"\; state="\{\{state\}\}">s</figure-callout>}}_1=\arg \underset{\{k\&Element;T,N_s\&Element;N\}}{\max }{\mathrm{<figure-callout\; id="1"\; label="r"\; filenames="H2009101992747E0000012.png"\; state="\{\{state\}\}">r</figure-callout>}}_{1,k}\left(N_s\right)$

S wherein ₁Be first user who selects, T is a candidate user set, and N is candidate's sub-carrier number.

4, on current subcarrier, carry out next user and select user's number N of selection _uBe not more than transmitting terminal antenna number N _tThe principle of selecting is the capacity optiaml ciriterion.If R _ZfBe multi-user's speed that close-to zero beam forms, then the user of Xuan Zeing is

$s_n=\arg \underset{s_n\&Element;T}{\max }{R}_{\mathrm{zf}}(S\left(N_s\right)\&cup;\{s_n\left\}\right).$

5, on each subcarrier, carry out in user's selection next time, calculate the global rate on the current subcarrier, and with do not carry out the active user when selecting the subcarrier population size compare, if capacity has lifting, the user who then carries out next round selects, otherwise the user who stops on the current subcarrier selects.And user's selection is carried out in beginning on remaining subcarrier.

If the user on 6 all available subcarriers selects work to finish, then stop the user and select work, and the work of beginning power division.The target of power division is in order to minimize the transmitting terminal power consumption.The problem of power division can be summarized as an optimized problem, promptly

$\left\{\begin{array}{cc}\min & \underset{j=1}{\overset{K}{\mathrm{\&Sigma;}}}\underset{n=1}{\overset{N_c}{\mathrm{\&Sigma;}}}{p}_{j,n}\\ s.t.& \underset{n=1}{\overset{N_c}{\mathrm{\&Sigma;}}}{\log }_2(1+{\mathrm{<figure-callout\; id="1"\; label="d"\; filenames="H2009101992747E0000012.png"\; state="\{\{state\}\}">d</figure-callout>}}_{1,\mathrm{<figure-callout\; id="1"\; label="n\; p"\; filenames="H2009101992747E0000012.png"\; state="\{\{state\}\}">n</figure-callout>}}{p}_{}{}_{1,n})\&GreaterEqual;{\mathrm{<figure-callout\; id="1"\; label="R"\; filenames="H2009101992747E0000012.png"\; state="\{\{state\}\}">R</figure-callout>}}_1,\\ & .\\ & .\\ & .\\ & \underset{n=1}{\overset{N_c}{\mathrm{\&Sigma;}}}{\log }_2(1+d_{K,n}{p}_{K,n})\&GreaterEqual;R_K,\end{array}\right.$

Wherein, p _{J, n}Be the power on n the subcarrier that is assigned to j user, R ₁... R _KBe user 1 ..., the rate requirement of K, d _{J, n}It is the channel gain on j user's n the subcarrier.

7, by to top finding the solution of having problem most, the optimal power allocation scheme that obtains each user is

$p_{j,n}={[2^{\frac{R_j-{\mathrm{\&Sigma;}}_{n=1}^{\tilde{N}\left(j\right)}{\log }_2\left(d_{j,n}{\log }_{2}e\right)}{\tilde{N}\left(j\right)}}/\ln 2-\frac{1}{d_{j,n}}]}^{+}$

Wherein [x] ⁺For get 0 and x between maximum,

For distributing to the sub-carrier number of user j.

8, for the duality relation of uplink and downlink, can obtain by up and descending duality relation.If p _i ^MAnd p _i ^BBe respectively the power of user i in uplink and downlink, total number of users is K, h _iAnd v _iThe channel gain and the wave beam that are respectively user i form vector, then

$p_i^B=p_i^{\mathrm{<figure-callout\; id="1"\; label="M"\; filenames="H2009101992747E0000012.png"\; state="\{\{state\}\}">M</figure-callout>}}\frac{1}{1+{\mathrm{\&Sigma;}}_{j=i+1}^K{p}_j^M{\left|h_j{v}_1\right|}^2}$

$p_i^M=p_i^{\mathrm{<figure-callout\; id="1"\; label="B"\; filenames="H2009101992747E0000012.png"\; state="\{\{state\}\}">B</figure-callout>}}\frac{1+p_{i+1}^M{\left|h_{i+1}{v}_i\right|}^2}{1+{\mathrm{\&Sigma;}}_{j=1}^{i-1}{p}_j^B{\left|h_i{v}_j\right|}^2}$

Positive progressive effect of the present invention is: the present invention is based on the user and select to obtain optimized resource allocation policy with power division.With respect to traditional user choosing method, the present invention has better fairness, thereby makes system have better fairness, and the present invention has simultaneously drawn the optimum power distribution method theoretically, thereby makes the transmitting power minimum.Be highly suitable for the situation that transmitter and receiver is radio node.Simultaneously because the use of duality.Can make each user use lowest power, thereby reduce energy consumption, and can further reduce co-channel interference adjacent sub-district.Have higher utility, can for the third generation (3G), super three generations (B3G), the 4th generation (4G) cellular mobile communication and the pre-coding scheme of Digital Television, wireless lan (wlan), wireless wide area network systems such as (WWAN) important theory foundation and concrete implementation method are provided.

Description of drawings

Fig. 1 has the MIMO-OFDM multi-user system schematic diagram that the user selects;

Fig. 2 is the schematic diagram that the user on each subcarrier distributes;

Fig. 3 is an algorithm flow chart of the present invention;

Fig. 4 is the tactful desired power simulation curve of the various emissions figure that has the multi-user system of 4 transmitting antennas;

Fig. 5 is the tactful desired power of various emissions (not considering fairness) the simulation curve figure that has the multi-user system of 4 transmitting antennas;

Fig. 6 has the simulation curve figure that user that fairness considers selects number of times;

Fig. 7 be multi-user diversity influence simulation curve figure;

Fig. 8 be transmitting antenna influence simulation curve figure.

Embodiment

Provide preferred embodiment of the present invention below in conjunction with accompanying drawing, to describe technical scheme of the present invention in detail.

(1) has the structure of the MIMO-OFDM multi-user system that the user selects

The structure that has a MIMO-OFDM system that the user selects as shown in Figure 1, the present invention adopts the MIMO-OFDM system of receiving for 42 that the user selects that has, and adopts the QPSK modulation system.Channel condition information obtains at receiving terminal, and the present invention does not relate to concrete obtain manner.And suppose each user feedback to transmitter channel condition information separately, transmitting terminal is finished the user according to the channel condition information of feedback and is selected and power division.For the influence of full test the present invention, adopt multipath Rayleigh channel model to carry out system-level performance simulation to systematic function.The channel multi-path number of multipath Rayleigh channel model is 3, and its normalized power, delay parameter are [1 1/exp (1) 1/exp (2)], and wherein exp (α) represents α power of the truth of a matter of natural logrithm.

(2) distribution of MIMO-OFDM multi-user system between subcarrier

In the present invention, carry out user's selection in user's peacekeeping subcarrier dimension.Shown in Figure 2 is to adopt user the distribution pattern on each subcarrier of the mode of space division multiplexing as the emission strategy of transmitter, obtains corresponding user's selection mode simultaneously.At first on a subcarrier, carry out user's selection, the mode of the mode (SDMA) by adopting space division multiplexing, each subcarrier can be the several users service simultaneously, promptly each subcarrier can be selected several users.On remaining subcarrier, carry out user's selection then with same principle.When number of subcarriers was big, the user who has can obtain repeatedly choice, made choice impartial more like this, thereby made system possess better fairness.

(3) embodiment

Present embodiment is based on above-mentioned multipath Rayleigh channel model.Suppose that at first channel status is quasi-static, promptly channel status is constant in the transmission course of a packet.The data bit of present case is through sign map and QPSK modulation.Suppose that then each user feeds back to transmitting terminal with channel condition information in receiving terminal known channel state information, the transmitting terminal then channel information by each user of feeding back carries out that the user selects and power optimization designs.Each chooses user's signal by after the precoding, and signal is loaded into the emission of 4 transmit antennas, and the signal of emission is the superposed signal of a plurality of subscriber signals, through multipath Rayleigh channel, is received by each user's single receive antenna at receiving terminal.Because the user's who selects channel is in accurate quadrature in the space, therefore, each user's precoding vector also has accurate orthogonality relation, therefore, through after the effect of channel, the influence of interference signal will be very little, so wave beam forms the effect that multi-user interference is eliminated that reached.The received signal of reception antenna is carried out the OFDM demodulation respectively simultaneously.Receiving terminal extracts precoding vectors according to precoding codebook sequence number feedback bits information equally from code book, the restituted signal weighting is merged.Combined signal is finally deciphered the acquisition data symbol according to maximum-likelihood criterion, obtains data bit through the QPSK demodulation.

MIMO-OFDM system under the multipath Rayleigh channel model shown in Figure 1, number of transmit antennas is 4, each user's reception antenna number is 1.The sub-carrier number of each OFDM symbol is 64, and the Cyclic Prefix number is 16.Rate0 among Fig. 3 is the random number that produces from 0.01 to 0.16, with representative of consumer speed at random.Suppose that the total number of users in the experiment is 80.Fig. 4 shows, compares with traditional TDMA access way, adopts dirty paper code (DPC) technology, and ZF dirty paper code (ZFDPC) technology and close-to zero beam formation technology only need power seldom.Theoretically, DPC is an optimal case, it also is the minimum a kind of launch scenario of required power, ZFDPC is a kind of launch scenario of suboptimum, and desired power also seldom still need be carried out dirty paper code owing to these two kinds of schemes, has very high complexity, also there is not a kind of scheme to realize dirty paper code in practice at present, and the performance of the very approaching dirty paper sign indicating number of the performance of ZFBF, and save a large amount of transmitting powers than present TDMA access way.Therefore, the present invention has higher utility.

Figure 5 shows that the simulation curve of the power demand of the various launch scenarios under the situation of not considering fairness, wherein the sub-carrier number that is configured to of OFDM is 64, and Cyclic Prefix is 16.Rate0 is the random number that produces from 0.01 to 0.16, with the speed at random of representative of consumer.Compare with Fig. 4, TDMA, DPC, the power that ZF-DPC and ZFBF consumed is littler than the power that consideration fairness shown in Figure 4 is consumed, but the cost of paying is exactly the reduction of fairness.Therefore having one between fairness and the power consumption trades off.

Figure 6 shows that the analogous diagram that fairness is considered.Here, sub-carrier number is 1024, and the Cyclic Prefix number is 256.Considering has 100 users, and as we can see from the figure, each user's selection frequency is very approximate, and illustrative system has fairness preferably.

Figure 7 shows that the effect of multi-user diversity.Here, produce at random each user's the speed from 0.0156 to 0.25.Be without loss of generality, number of users is 64 multiple, and the sub-carrier number of OFDM symbol is 64, and Cyclic Prefix is 16.Fig. 7 demonstrates when number of users is big, and the power that the user needs will further reduce.This be because, along with increasing of number of users, transmitter can be selected orthogonality user's subclass preferably with higher probability, thus the performance of elevator system.

Figure 8 shows that the influence of transmitting terminal antenna amount.Here, the sub-carrier number of each OFDM symbol is 64, and the Cyclic Prefix number is 16.Each user's speed at random is the random number that produces from 1 to 8, and the hypothesis number of users is 64.As can be seen from Figure 8, along with the increase of antenna number, the required power of launch scenario will further reduce in each, but when the emission world greater than 4 the time, the decline of power demand is not obvious.Therefore can reach a conclusion, the antenna number of transmitter does not need very big.

From above diagram as can be seen, the present invention has fairness preferably, compares with the TDMA access way of using at present simultaneously, and the energy that is consumed will reduce greatly, and very near theoretic optimal performance.Consider that the close-to zero beam among the present invention forms the low complex degree of (ZFBF) technology, make that the present invention is easy to realize having higher actual application value in practice.

More than show and described basic principle of the present invention and principal character and advantage of the present invention.The technical staff of the industry should understand; the present invention is not restricted to the described embodiments; that describes in the foregoing description and the specification just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications; these changes and improvements all fall in the claimed scope of the invention, and the claimed scope of the present invention is defined by appending claims and equivalent thereof.

Claims (6)

1. MIMO-OFDM multi-user system method for allocating minimum power based on duality, it is characterized in that: described method comprises the steps:

A, according to channel condition, transmitting end equipment selects to have on each subcarrier a user of optimal channel conditions;

B, transmitting end equipment carry out user's selection on the subcarrier at selected user place, the standard of selection is maximum channel capacity or subscriber equipment associating speed;

C, transmitting end equipment are after the user of current subcarrier selects to finish, selected user is concentrated deletion in selectable user, and the user who carries out next round selects, promptly the best new user of selective channel condition in remaining subcarrier and remaining user continues to select other users then on the subcarrier of selected user place;

D, all assign, carry out optimized power then and distribute, the rate requirement of each subscriber equipment is met up to all available subcarriers;

E, descending power allocation scheme are converted into the power allocation scheme of up link by the power duality relation.

2. the MIMO-OFDM multi-user system method for allocating minimum power based on duality according to claim 1, it is characterized in that: the transmitting end equipment described in the described steps A is selected a best user of all subcarrier upper signal channel conditions according to channel condition, here, the quality of channel condition is based on the size of channel vector mould;

What use among the step B is close-to zero beam formation (ZFBF) technology that has lower complexity, can reach the performance of approaching optimum capacity;

Described in the step C after the finishing scheduling on first subcarrier, the user that selected is concentrated deletion from selectable user, be to consider for system's fairness;

The optimized power of carrying out described in the step D is distributed, each user's rate requirement is met, and is that the system resource allocation problem is converted into optimization problem, passes through water-filling, try to achieve each user's power division optimal solution, and guarantee that each user's rate requirement is met;

The optimal power allocation scheme about up link described in the step e can be obtained by the up link of MIMO multi-user system and the duality of down link.

3. the MIMO-OFDM multi-user system method for allocating minimum power based on duality according to claim 1 and 2, it is characterized in that: the user who selects each subcarrier upper signal channel condition optimum described in the described steps A according to channel condition information, with the starting point of selecting as the user, wherein channel condition information is that subscriber equipment obtains by channel estimation technique, and the concrete selection mode of transmitting end equipment is:

$s_1=\arg \underset{\{k\&Element;T,N_s\&Element;N\}}{\max }{r}_{1,k}\left(N_s\right)$

S wherein ₁Be first user who selects, N _sSubcarrier number, r _{1, k}(N _s)=h _k(N _s) h _k(N _s) ^HBe channel N _sThe mould value of the channel vector of the user k on the subcarrier.

4. the MIMO-OFDM multi-user system method for allocating minimum power based on duality according to claim 1 and 2, it is characterized in that: on initial selected subcarrier, carry out user's selection among the described step B, further comprise: on previous user's basis, transmitting end equipment is selected a user from remaining user's set, the user who has selected with the front forms user's collection, calculate associating speed then, transmitting end equipment selects that user of associating speed maximum as user to be selected, then with current this associating speed R ⁽ⁿ⁾Do not select the associating speed R of user's subclass of this user ^(n-1)Compare, if R ⁽ⁿ⁾＞R ^(n-1), then the user of current selection is effective, and carries out the user search of next round, if R ⁽ⁿ⁾≤ R ^(n-1), then the user of current search is considered to invalid, and transmitting end equipment terminates in the user search above the current subcarrier then, and the user search of beginning on next subcarrier.

5. the MIMO-OFDM multi-user system method for allocating minimum power based on duality according to claim 1 and 2, it is characterized in that: described in the described step C after user search on the subcarrier finishes, with the user search on the next subcarrier of beginning, further comprise: transmitting end equipment is selected the user in the subcarrier outside the subcarrier that carried out user's selection, mainly show the user who on remaining subcarrier, selects a channel condition optimum, on this subcarrier, carry out user's selection then, thereby realize space division multiplexing.

6. the MIMO-OFDM multi-user system method for allocating minimum power based on duality according to claim 1 and 2, it is characterized in that: the rate requirement that makes each subscriber equipment among the described step D is met, be to consider after user's selection course finishes generally to be assigned a plurality of users on each subcarrier, and the user who has may appear on several subcarriers, transmitting end equipment carries out combined optimization to a plurality of subcarriers and a plurality of users' power, thereby realize the optimum allocation of resource, the power optimization algorithm that transmitting end equipment carries out is a water-filling algorithm.

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