CN102316598A - Orthogonal random beam forming (PRBF) multi-user dispatching method based on greed beam selection strategy - Google Patents

Abstract

The invention discloses an orthogonal random beam forming (PRBF) multi-user dispatching method based on a greed beam selection strategy, which comprises the following steps that: (1) each user feeds back channel sate information (CSI) to a base station; (2) the dispatching of single beam is supposed for transmitting data, and the base station selects a pair of user beam combinations for forming a dispatching scheme and calculates the system speed at the time; (3) the number of the beams to be supposed to be dispatched is increased, the base station selects a pair of user beam combinations from an undispatched user set and a beam set to be added into the original dispatching scheme, and the corresponding system speed of the updated scheme is calculated; (4) the third step is repeated until the number of the beams to be supposed to be dispatched reaches the dispatchable beam number upper limit; and (5) the base station selects the dispatching scheme most suitable for the current channel environment for realizing the data transmission according to the system speed of each scheme corresponding to the number of the beams to be dispatched. The method has the advantages that the proper beams can be dispatched in a self adaptive way in the ORBF scheme in different channel environment, users can carry out data transmission, and the system performance of the ORBF scheme is greatly improved.

Description

Greedy beam selection strategy-based ORBF multi-user scheduling method

Technical Field

The invention relates to a multi-user MIMO technology, relates to a self-adaptive transmission scheduling strategy of a MIMO BC downlink channel, and particularly relates to an ORBF multi-user scheduling method based on a greedy beam selection strategy.

Background

In a multi-user MIMO downlink system, Orthogonal Random Beamforming (ORBF) proposed by Sharif has the advantages of low computational complexity, small CSI feedback amount and the like, and thus has attracted attention of many researchers. When the number of users is more, the method has the same progressive performance as the DPC algorithm; however, when the number of users is small, the system performance of the ORBF algorithm is drastically reduced. In addition, under a high snr environment, the ORBF system is in an "interference limited" state, and the performance of the system is severely limited by the inter-beam interference. Moreover, a lot of research has proved that scheduling all beams is not necessarily the optimal transmission scheme in the ORBF transmission strategy. Therefore, in order to overcome the above-mentioned disadvantages of the ORBF, a number of researchers have proposed a multi-user scheduling strategy based on the conventional ORBF.

Nowadays, the conventional ORBF multi-user scheduling method proposed by the prior document includes a bottom-up scheduling policy, a top-down scheduling policy, and a multi-beam selection algorithm based on a lookup table, in addition to the conventional ORBF policy, which are described below.

A typical conventional ORBF scheduling policy is set forth generally below. The conventional ORBF strategy proposed by Sharif does not have adaptive user beam scheduling, so the algorithm schedules all beams for data transmission for users with the best channel environment in each transmission time slot. However, in most environments, scheduling all beams is not necessarily an optimal transmission scheme, and particularly in high signal-to-noise ratio environments, the system is in an "interference limited" state, and it is more preferable to schedule fewer beams to reduce the impact of inter-beam interference on system performance. Therefore, the conventional ORBF has a large performance penalty in many cases.

A typical bottom-up scheduling strategy is generally set forth below. When the number of the scheduling beams is 1, the algorithm allocates the user with the best performance to each beam, and the user is used as a fixed user beam combination. Then, the users selected in the first step (and their corresponding beams) are combined in all possible permutation modes in the following various scheduling beam numbers, and the performance of the users is calculated. And finally, finding the user beam combination with the highest system performance from all the combinations as the scheduling scheme of the data transmission. The algorithm can greatly improve the system performance when the actual optimal scheduling beam number is 1. However, when the actual number of beams to be scheduled is higher, the resulting scheme of the algorithm is not necessarily the optimal scheme, which may cause the algorithm to achieve less than optimal system performance even if the correct number of beams are scheduled.

A typical top-down scheduling strategy is generally set forth below. In direct contrast to the bottom-up algorithm, the first step of the top-down algorithm is to assume that the number of beams being scheduled is N_tAnd allocating the user with the best performance in each beam as a fixed user beam pair. The users selected in the first step (and their corresponding beams) are then combined in all possible permutations among the various possible numbers of beams in the future, and their performance is calculated. And finally, finding the user beam combination with the highest system performance from all the combinations as the scheduling scheme of the data transmission. When the current channel environment is suitable for scheduling all beams, the algorithm can achieve the optimal performance from top to bottom. However, when the number of actual scheduling beams is reduced, performance is lost because the user beam fixed allocation is not necessarily the best match for the current channel conditions.

A typical look-up table based multi-beam selection strategy is generally set forth below. The multi-beam selection algorithm based on the lookup table can store the optimal scheduling beam number under different channel environments in the base station in the form of the lookup table through the pre-simulation. In each sending time slot, the system can obtain the optimal beam number from the lookup table according to the current channel environment, and then traverse various possible user beam combinations under the beam number to find out the optimal scheduling scheme under the corresponding scheduling beam number of the system. The strategy can only give an approximate reference value of the number of the scheduling beams according to the region of the lookup table where the current channel environment is located. In a complex and variable time-varying channel environment, due to the problem of searching precision, the strategy is very easy to cause the system to schedule wrong number of beams for data transmission, and the system performance has large loss.

No matter which user scheduling strategy is adopted, the system can achieve optimal performance only under a specific channel environment, and the system can not achieve higher performance according to an optimal scheme of self-adaptive scheduling of different channel environments. Therefore, there is a need to provide an ORBF multi-user scheduling method adaptive to various channel environments to overcome the above-mentioned drawbacks.

Disclosure of Invention

The invention aims to provide a multi-user adaptive scheduling method of ORBF, which can make a base station realizing the ORBF scheduling strategy adaptively adjust users and beams to be scheduled according to different channel environments, so that the ORBF strategy can also well improve the system performance under different channel environments, and especially overcome the defect of low performance of the traditional ORBF when the number of users is low or the signal-to-noise ratio is high.

In order to achieve the above object, the present invention provides an ORBF multi-user scheduling method based on a greedy beam selection strategy, which includes the following steps: (1) each user feeds back Channel State Information (CSI) to the base station; (2) assuming that single beam transmission data is scheduled, namely when the number of the scheduled beams B is 1, a base station selects a pair of user beams from a user set and a beam set to form a scheduling scheme in a combined manner, and calculates the system rate at the moment; (3) increasing the number of beams supposed to be scheduled, selecting a pair of user beam combinations from the unscheduled user set and the beam set by the base station to add into the original scheduling scheme, and calculating the corresponding system rate under the updated scheme; (4) repeating the step (3) until the assumed number of the scheduling beams reaches the upper limit N of the number of the schedulable beams of the base station_t(ii) a (5) And according to the system rate of the scheme corresponding to each scheduling beam number, the base station selects the scheduling scheme most suitable for the current channel environment to realize data transmission.

In an embodiment of the present invention, the CSI fed back by each user is a system gain between each user and all beams

Wherein,

is the channel gain vector between the base station and the kth user,k is more than or equal to 1 and less than or equal to K, and K is the cell where the base station is locatedTotal number of users within a zone; w is a_iThe ith beamforming vector generated for the base station,

and i is more than or equal to 1 and less than or equal to N_t，N_tThe total number of beams formed for the base station antenna. In the user feedback CSI phase, each user k must send N_tValue of system gain

And the corresponding beam number i is fed back to the base station. After receiving the CSI fed back by all users, the base station can establish the KxN_tThe system gain matrix G between all users and beams of the dimension, i.e. the whole channel state information can be known. Wherein <math> <mrow> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>&Element;</mo> <mi>G</mi> <mo>,</mo> <mn>1</mn> <mo>&le;</mo> <mi>k</mi> <mo>&le;</mo> <mi>K</mi> <mo>,</mo> <mn>1</mn> <mo>&le;</mo> <mi>i</mi> <mo>&le;</mo> <msub> <mi>N</mi> <mi>t</mi> </msub> <mo>,</mo> </mrow> </math> And is

$G=\left[\begin{array}{cccc}{\left|h_1^{\mathrm{<figure-callout\; id="1"\; label="T\; w"\; filenames="HDA0000091984940000011.png"\; state="\{\{state\}\}">T</figure-callout>}}{w}_{}{}_1\right|}^2& {\left|h_1^{\mathrm{<figure-callout\; id="2"\; label="T\; w"\; filenames="HDA0000091984940000011.png"\; state="\{\{state\}\}">T</figure-callout>}}{w}_{}{}_2\right|}^2& L& {\left|h_1^T{w}_{N_t}\right|}^2\\ {\left|h_2^{\mathrm{<figure-callout\; id="1"\; label="T\; w"\; filenames="HDA0000091984940000011.png"\; state="\{\{state\}\}">T</figure-callout>}}{w}_{}{}_1\right|}^2& {\left|h_2^{\mathrm{<figure-callout\; id="2"\; label="T\; w"\; filenames="HDA0000091984940000011.png"\; state="\{\{state\}\}">T</figure-callout>}}{w}_{}{}_2\right|}^2& L& {\left|h_2^T{w}_{N_t}\right|}^2\\ L& L& O& L\\ {\left|h_{\mathrm{<figure-callout\; id="1"\; label="K\; T\; w"\; filenames="HDA0000091984940000011.png"\; state="\{\{state\}\}">K</figure-callout>}}^T{w}_{}{}_1\right|}^2& {\left|h_{\mathrm{<figure-callout\; id="2"\; label="K\; T\; w"\; filenames="HDA0000091984940000011.png"\; state="\{\{state\}\}">K</figure-callout>}}^T{w}_{}{}_2\right|}^2& L& {\left|h_K^T{w}_{N_t}\right|}^2\end{array}\right].$

In another embodiment of the present invention, the users implement error-free CSI feedback via MIMO MAC uplink channel.

In a further embodiment of the present invention, in the step (2), the base station selects the user with the best channel environment and the corresponding beamforming scheduling scheme.

In another embodiment of the present invention, in the step (2), the base station selects a user with a largest channel signal to interference plus noise ratio SINR value under a single beam.

In yet another embodiment of the present invention, the user beam pairs added in step (3) all need to be the user with the best channel environment based on the original scheduling scheme and the beam corresponding to the user with the best channel environment under the current number of scheduling beams, that is, the user with the largest SINR value of the system and the beam corresponding to the user.

In another embodiment of the present invention, the step (3) is specifically: (31) the number of the scheduling wave beams B is made to be B +1, and the set of the selected user wave beam scheduling schemes when the number of the scheduling wave beams is B-1 is made to be S; (32) the base station selects a user beam combination to be supplemented into a scheduling scheme set S from unselected user beam sets, the selected user beam combination is a scheduling scheme when the number of the scheduling beams is B-1 under the current scheduling beam number B, so that the system obtains users with SINR values larger than those when other user beam combinations are selected and corresponding beams thereof, and the supplemented scheduling scheme can enable the system to reach the highest system rate which can be reached under the current scheduling beam number on the basis of the scheduling scheme set S before the supplementation; (33) and calculating the system rate reached by the supplemented scheduling scheme under the current scheduling beam number.

In yet another embodiment of the present invention, theThe system rate is Sum-rate (Sum-rate) reached by the system under the current scheduling scheme in the multi-user MIMO environment, and then, after the steps (2), (3) and (4) are completed, the system will obtain N which is the same as the total number of beams_tAnd the sum rate corresponds to a scheduling beam number and a scheduling scheme under the beam number.

In a further embodiment of the present invention, the most suitable determination criterion of the user beam scheduling scheme for the current data transmission in step (5) is specifically: at the final N_tIn the scheduling schemes, the scheme with the maximum corresponding rate is selected as the optimal scheduling scheme of the current time slot for the base station to carry out data transmission.

Compared with the prior art, the ORBF multi-user scheduling method based on the greedy beam selection strategy can adaptively schedule proper users and beams to perform data transmission according to different channel environments, and effectively overcomes the defect that the performance of the ORBF is severely restricted when the number of users is small and the signal-to-noise ratio is high. Meanwhile, the defects that the system can obtain great performance improvement only under a specific channel environment, such as a bottom-up beam scheduling strategy, a top-down beam scheduling strategy, a lookup table-based multi-beam selection strategy and the like, are overcome. In a word, the method can greatly improve the system performance of the ORBF under different channel environments.

The invention will become more apparent from the following description when taken in conjunction with the accompanying drawings, which illustrate embodiments of the invention.

Drawings

Fig. 1 is a flowchart of an ORBF multi-user scheduling method based on a greedy beam selection strategy according to the present invention.

Fig. 2 is a typical multi-user MIMO BC downlink broadcast channel environment in which the greedy beam selection strategy-based ORBF multi-user scheduling method shown in fig. 1 is located.

Fig. 3 is a schematic diagram of feedback channel state information of each user in the ORBF multi-user scheduling method based on the greedy beam selection strategy shown in fig. 1.

Fig. 4a to 4d are screening pairing processes performed on users and beams by a greedy algorithm in the greedy beam selection strategy based ORBF multi-user scheduling method shown in fig. 1.

Fig. 5 is a schematic diagram of data transmission performed after scheduling users and beams by a greedy algorithm in the ORBF multi-user scheduling method based on the greedy beam selection policy shown in fig. 1.

Detailed Description

Embodiments of the present invention will now be described with reference to the drawings, wherein like element numerals represent like elements.

The ORBF multi-user scheduling method based on the greedy wave beam selection strategy is realized based on a typical multi-user MIMO downlink channel environment: in a MIMO BC downlink broadcast channel, a cell base station BS is configured with N_tA cell is provided with K single-antenna users; the channels between the beams formed by the antennas and the users are mutually independent Rayleigh fading channels; each user terminal can obtain complete CSI and can utilize the MIMO MAC uplink channel to feed back the CSI at low speed without errors.

Before describing the greedy beam selection strategy-based ORBF multi-user scheduling method of the present embodiment, the following concepts involved in the method are explained:

signal to interference plus noise ratio (SINR): the ratio of the signal power received by the terminal in the multi-use MIMO downlink system to the noise power and the interference power is disclosed. In the ORBF scheduling policy, if the information required by the kth user is transmitted by the beam i, the received signal of the user is:

<math> <mrow> <msub> <mi>r</mi> <mi>k</mi> </msub> <mo>=</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>W</mi> <mi>B</mi> </msub> <msub> <mi>s</mi> <mi>B</mi> </msub> <mo>+</mo> <msub> <mi>n</mi> <mi>k</mi> </msub> <mo>=</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>W</mi> <mi>i</mi> </msub> <msub> <mi>S</mi> <mi>i</mi> </msub> <mo>+</mo> <munder> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <mi>B</mi> <mo>,</mo> <mi>j</mi> <mo>&NotEqual;</mo> <mi>i</mi> </mrow> </munder> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <mi>j</mi> </msub> <msub> <mi>s</mi> <mi>j</mi> </msub> <mo>+</mo> <msub> <mi>n</mi> <mi>k</mi> </msub> </mrow> </math>

wherein,is the channel gain matrix between the base station and the kth user,

b is the current scheduling beam subset of the base station, and B ═ card (B) is the corresponding scheduling beam number; w_BA sub-matrix of a random beamforming matrix generated for the base station with respect to the scheduling beam subset B, and w_i∈W_B，i∈B；s_BA subset of transmission data sets for the base station to transmit with respect to the subset of scheduling beams B, and s_i∈s_B，i∈B；n_kIs the additive white gaussian noise experienced by the channel between the base station and the kth user. At this time, if the total transmission power of the base station is E

And the base station transmit power is equally distributed to each number of transmissionsOn the corresponding beam, the transmission power obtained by each beam is P/B. It follows that the average signal-to-noise ratio of the transmission system is P ═ P/σ². Therefore, we can obtain the SINR between k and i beams as:

<math> <mrow> <msub> <mi>SINR</mi> <mrow> <mi>k</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>=</mo> <mfrac> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mrow> <mi>B</mi> <mo>/</mo> <mi>&rho;</mi> <mo>+</mo> <msub> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <mi>B</mi> <mo>,</mo> <mi>j</mi> <mo>&NotEqual;</mo> <mi>i</mi> </mrow> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <mi>j</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> </mfrac> </mrow> </math>

and rate (Sum-rate): the sum of the transmission rates of all channels in the system, and the maximum value of the sum rate, is called the system sum capacity. So when the base station schedules N_tWhen the B beams in the beams are used for data transmission and the power P is evenly distributed to each beam used for transmission, the speed expression is as follows:

<math> <mrow> <mi>R</mi> <mrow> <mo>(</mo> <mi>B</mi> <mo>)</mo> </mrow> <mo>&cong;</mo> <munder> <mi>&Sigma;</mi> <mrow> <mi>i</mi> <mo>&Element;</mo> <mi>B</mi> </mrow> </munder> <msub> <mi>log</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <munder> <mi>max</mi> <mrow> <mn>1</mn> <mo>&le;</mo> <mi>k</mi> <mo>&le;</mo> <mi>K</mi> </mrow> </munder> <msub> <mi>SINR</mi> <mrow> <mi>k</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>B</mi> <mo>)</mo> </mrow> <mo>)</mo> </mrow> </mrow> </math>

wherein,

the maximum SINR value for the scheduled beam i among the K users.

The following specifically describes the flow of the ORBF multi-user scheduling method based on the greedy beam selection strategy in this embodiment. In connection with fig. 1, 3, 4a-4d, 5, it is assumed that the base station BS forms a total of N_t4 beams A, B, C, D, and K8 single antenna users a, b, c, d, e, f, g, h in the cell, the method comprises the following steps:

in step S1, the base station BS lets all N formed by the antennas_tEach beam broadcasts training symbols to all K users in a cell by utilizing a MIMO BC downlink channel, and each user K calculates the system gain of each beam i after receiving broadcast signals

In the CSI feedback stage of users, each user k utilizes MIMOMAC feedback channel to send each N_tGain of individual system

And feeding back the corresponding beam number i to the base station BS (as shown in FIG. 3), the base station BS establishing a system gain matrix G between all current users and beams according to the CSI fed back by all the users, and initializing a current set K of alternative users₁K, the current alternative set of beams B₁＝{1，..，N_tGet the scheduling scheme selected

(see FIG. 3, K)₁＝{k_a，k_b，k_c，k_d，k_e，k_f，k_g，k_h}，B₁＝{i_A，i_B，i_C，i_D})；

Step S2, let the number of scheduling beams B be 1, the base station BS selects the selectable user set K according to the system gain matrix G₁Set of beams B₁Selects a pair of user beam combination (k) with best channel environment under the condition of single beam data transmission₁，i₁) The user beam combination meets the requirements:

<math> <mrow> <mrow> <mo>(</mo> <msub> <mi>k</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>i</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> <mo>=</mo> <msub> <mrow> <mi>arg</mi> <mi> </mi> <mi>max</mi> </mrow> <mrow> <mo>(</mo> <mi>k</mi> <mo>,</mo> <mi>i</mi> <mo>)</mo> </mrow> </msub> <mi>&rho;</mi> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>,</mo> <mo>&ForAll;</mo> <mrow> <mo>(</mo> <mi>k</mi> <mo>,</mo> <mi>i</mi> <mo>)</mo> </mrow> <mo>&Element;</mo> <msub> <mi>K</mi> <mn>1</mn> </msub> <mo>&times;</mo> <msub> <mi>B</mi> <mn>1</mn> </msub> </mrow> </math>

wherein (k)₁，i₁) For the number corresponding to the user beam combination, ρ is the system average signal-to-noise ratio, and (k) is calculated₁，i₁) Adding to scheduling scheme S, making S { (k)₁，i₁) (see fig. 4a, S { (k) } (see fig. 4 a)_e，i_B)})；

Step S3, calculating the system and rate when scheduling single beam at this time, and when scheduling ORBF S:

<math> <mrow> <msub> <mi>R</mi> <mn>1</mn> </msub> <mo>=</mo> <mi>&Theta;</mi> <mrow> <mo>(</mo> <mi>&rho;</mi> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <msub> <mi>k</mi> <mn>1</mn> </msub> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <msub> <mi>i</mi> <mn>1</mn> </msub> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>)</mo> </mrow> </mrow> </math>

wherein, Θ (x) is log₂(1+x)

Step S4, the base station BS sets the number of scheduling beams B to B +1, and makes the optional user set K_B＝K_B-1-{k_B-1H, optional set of beams B_B＝B_B-1-{i_B-1In which k is_B-1For adding scheduling schemes so that the number of scheduled beams becomes B-1User, i_B-1The method comprises the steps of adding the scheduling beam number into a scheduling scheme to enable the scheduling beam number to be changed into a beam of B-1;

in step S5, the BS selects the user set K according to the user set K obtained in step S4_BAnd beam set B_BCarrying out various combination pairing on the unselected users and the wave beams;

step S6, the BS selects the user with best channel environment and the corresponding beam to form the user beam combination (k) under the current scheduling beam number according to the various combination pairs obtained in step S5_B，i_B) The user beam combination meets the requirements:

$(k_B,i_B)=$

<math> <mrow> <msub> <mrow> <mi>arg</mi> <mi></mi> <mi>max</mi> </mrow> <mrow> <mo>(</mo> <mi>k</mi> <mo>,</mo> <mi>i</mi> <mo>)</mo> </mrow> </msub> <mfenced open='{' close='}'> <mtable> <mtr> <mtd> <mi>&Theta;</mi> <mrow> <mo>(</mo> <mfrac> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mrow> <mi>B</mi> <mo>/</mo> <mi>&rho;</mi> <mo>+</mo> <msubsup> <mi>&Sigma;</mi> <mrow> <mi>s</mi> <mo>=</mo> <mn>1</mn> </mrow> <mrow> <mi>B</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <msub> <mi>i</mi> <mi>s</mi> </msub> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> </mfrac> <mo>)</mo> </mrow> </mtd> </mtr> <mtr> <mtd> <mo>+</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>p</mi> <mo>=</mo> <mn>1</mn> </mrow> <mrow> <mi>B</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <mi>&Theta;</mi> <mrow> <mo>(</mo> <mfrac> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <msub> <mi>k</mi> <mi>p</mi> </msub> <mi>T</mi> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mrow> <mi>B</mi> <mo>/</mo> <mi>&rho;</mi> <mo>+</mo> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <msub> <mi>k</mi> <mi>p</mi> </msub> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msubsup> <mi>&Sigma;</mi> <mrow> <mi>s</mi> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mi>s</mi> <mo>&NotEqual;</mo> <mi>p</mi> </mrow> <mrow> <mi>B</mi> <mo>-</mo> <mn>1</mn> </mrow> </msubsup> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <msub> <mi>k</mi> <mi>p</mi> </msub> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <msub> <mi>i</mi> <mi>s</mi> </msub> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> </mfrac> <mo>)</mo> </mrow> </mtd> </mtr> </mtable> </mfenced> <mo>,</mo> </mrow> </math>

<math> <mrow> <mo>&ForAll;</mo> <mrow> <mo>(</mo> <mi>k</mi> <mo>,</mo> <mi>i</mi> <mo>)</mo> </mrow> <mo>&Element;</mo> <msub> <mi>K</mi> <mi>B</mi> </msub> <mo>&times;</mo> <msub> <mi>B</mi> <mi>B</mi> </msub> </mrow> </math>

wherein (k)_B，i_B) For the number corresponding to the user beam combination, Θ (x) is log₂(1+ x), the user beam combination (k)_B，i_B) Is in the current selectable user beam set K_B、B_BIn the method, the system can obtain the user beam combination with the SINR value which is larger than that when other user beam combinations are selected under the current scheduling beam number on the basis of the original scheduling scheme S, namely the system can reach the highest system speed which can be reached under the current scheduling beam number, and the combination (k) is combined_B，i_B) Added to the scheduling scheme S, i.e. S ═ S + { (k)_B，i_B)}；

Step S7, calculating the system and rate when the current scheduling beam number B, the ORBF schedules S:

<math> <mrow> <msub> <mi>R</mi> <mi>B</mi> </msub> <mo>=</mo> <munderover> <mi>&Sigma;</mi> <mrow> <mi>p</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>B</mi> </munderover> <mi>&Theta;</mi> <mrow> <mo>(</mo> <mfrac> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <msub> <mi>k</mi> <mi>p</mi> </msub> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <msub> <mi>i</mi> <mi>p</mi> </msub> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mrow> <mi>B</mi> <mo>/</mo> <mi>&rho;</mi> <mo>+</mo> <msubsup> <mi>&Sigma;</mi> <mrow> <mi>s</mi> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mi>s</mi> <mo>&NotEqual;</mo> <mi>p</mi> </mrow> <mi>B</mi> </msubsup> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <msub> <mi>k</mi> <mi>p</mi> </msub> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <msub> <mi>i</mi> <mi>s</mi> </msub> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> </mfrac> <mo>)</mo> </mrow> </mrow> </math>

wherein, Θ (x) is log₂(1+x)；

Step S8, judging whether the number B of the dispatching wave beams is less than the total number N of the antennas_tWhether B satisfies B < N_tIf yes, go to step S4 (as in FIGS. 4b-4d), if no, continue the next step;

step S9, the BS finally obtains N_tSelecting corresponding system and rate R from various scheduling schemes_B，1≤B≤N_tOne scheme S with the largest value_end，S_endThe following requirements are met:

B^*＝argmax_BR_B，1≤B≤N_t

$S_{\mathrm{end}}=\{({\mathrm{<figure-callout\; id="1"\; label="k"\; filenames="HDA0000091984940000011.png"\; state="\{\{state\}\}">k</figure-callout>}}_1,i_1),...,(k_{B^{*}},i_{B^{*}})\}$

wherein, B^*For the number of scheduling beams, S, corresponding to the rate maximization scheme_endFront B corresponding to S^*The final scheduling scheme is composed of user wave beam combinations, and the base station BS schedules the wave beam number B according to the final scheduling^*And scheduling scheme S_endThe adaptive scheduling of the current time slot is realized (as shown in figure 5), and the current system and rate are

Finishing;

it can be seen from the above that, the ORBF multi-user scheduling method based on the greedy beam selection strategy of this embodiment can adaptively schedule appropriate users and beams for data transmission according to different channel environments, the selection scheduling process is continuously evolved on the existing scheduling scheme, the existing scheduling scheme can be utilized to the maximum extent, and the need of re-screening and pairing all user beams when the number of scheduled beams is increased is avoided. By the method, the defect that the system performance is severely restricted when the ORBF is small in number of users and high in signal-to-noise ratio is effectively overcome. Meanwhile, the defect that the system can obtain great performance improvement only under a specific channel environment due to a bottom-up beam scheduling strategy, a top-down beam scheduling strategy, a lookup table-based multi-beam selection strategy and the like is overcome, and the system can obtain great performance improvement under different signal-to-noise ratio environments when the ORBF scheme is implemented.

The present invention has been described in connection with the preferred embodiments, but the present invention is not limited to the embodiments disclosed above, and is intended to cover various modifications, equivalent combinations, which are made in accordance with the spirit of the present invention.

Claims (9)

1. An ORBF multi-user scheduling method based on a greedy beam selection strategy comprises the following steps:

(1) each user feeds back Channel State Information (CSI) of each user to the base station;

(2) assuming that single beam transmission data is scheduled, namely when the number of the scheduled beams B is 1, a base station selects a pair of user beams from a user set and a beam set to form a scheduling scheme in a combined manner, and calculates the system rate at the moment;

(3) increasing the number of beams supposed to be scheduled, selecting a pair of user beam combinations from the unscheduled user set and the beam set by the base station to add into the original scheduling scheme, and calculating the corresponding system rate under the updated scheme;

(4) repeating the step (3) until the assumed number of the scheduling beams reaches the upper limit N of the number of the schedulable beams of the base station_t；

(5) And according to the system rate of the scheme corresponding to each scheduling beam number, the base station selects the scheduling scheme most suitable for the current channel environment to realize data transmission.

2. The ORBF multi-user scheduling method based on greedy beam selection strategy of claim 1, wherein the CSI fed back by each user is a system gain between each user and all beams of a base station

Wherein,

is the channel gain vector between the base station and the kth user,

k is more than or equal to 1 and less than or equal to K, K is the total number of users in the cell where the base station is located, w_iThe ith beamforming vector generated for the base station,

and i is more than or equal to 1 and less than or equal to N_t，N_tThe total number of beams formed for the base station antenna,

then, during the CSI feedback phase, each user k must apply Nt system gain values

And its corresponding beam number i are fed back to the base station,

then, after receiving CSI fed back by all users, the base station may establish kxn_tThe system gain matrix G between all users and beams of the dimension, so that the whole channel state information can be obtained, wherein <math> <mrow> <msup> <mrow> <mo>|</mo> <msubsup> <mi>h</mi> <mi>k</mi> <mi>T</mi> </msubsup> <msub> <mi>w</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>&Element;</mo> <mi>G</mi> <mo>,</mo> <mn>1</mn> <mo>&le;</mo> <mi>k</mi> <mo>&le;</mo> <mi>K</mi> <mo>,</mo> <mn>1</mn> <mo>&le;</mo> <mi>i</mi> <mo>&le;</mo> <msub> <mi>N</mi> <mi>t</mi> </msub> <mo>,</mo> </mrow> </math> And is

$G=\left[\begin{array}{cccc}{\left|h_1^T{w}_1\right|}^2& {\left|h_1^T{w}_2\right|}^2& L& {\left|h_1^T{w}_{N_t}\right|}^2\\ {\left|h_2^T{w}_1\right|}^2& {\left|h_2^T{w}_2\right|}^2& L& {\left|h_2^T{w}_{N_t}\right|}^2\\ L& L& O& L\\ {\left|h_K^T{w}_1\right|}^2& {\left|h_K^T{w}_2\right|}^2& L& {\left|h_K^T{w}_{N_t}\right|}^2\end{array}\right].$

3. The ORBF multi-user scheduling method based on the greedy beam selection strategy of claim 2, wherein each user implements error-free CSI feedback through a MIMO MAC uplink channel.

4. The ORBF multi-user scheduling method based on greedy beam selection strategy as claimed in claim 1, wherein in the step (2), the base station selects the user with the best channel environment and the corresponding beam forming scheduling scheme.

5. The ORBF multi-user scheduling method based on greedy beam selection strategy as claimed in claim 1, wherein in step (2), the base station selects the user with the largest channel signal to interference plus noise ratio (SINR) value under a single beam.

6. The ORBF multi-user scheduling method based on greedy beam selection strategy as claimed in one of claims 4 and 5, wherein the user beam pairs added in step (3) all have to be the user with the best channel environment based on the original scheduling scheme and its corresponding beam, i.e. the user with the largest system SINR value and its corresponding beam, at the current number of scheduling beams.

7. The ORBF multi-user scheduling method based on greedy beam selection strategy according to one of claims 1-5, wherein the step (3) is specifically as follows:

(31) the number of the scheduling wave beams B is made to be B +1, and the set of the selected user wave beam scheduling schemes when the number of the scheduling wave beams is B-1 is made to be S;

(32) the base station selects a user beam combination to be supplemented into a scheduling scheme set S from unselected user beam sets, the selected user beam combination is a scheduling scheme when the number of the scheduling beams is B-1 under the current scheduling beam number B, so that the system obtains users with SINR values larger than those when other user beam combinations are selected and corresponding beams thereof, and the supplemented scheduling scheme can enable the system to reach the highest system rate which can be reached under the current scheduling beam number on the basis of the scheduling scheme set S before the supplementation;

(33) and calculating the system rate reached by the supplemented scheduling scheme under the current scheduling beam number.

8. The ORBF multi-user scheduling method based on greedy beam selection strategy according to claim 7, wherein the system rate is Sum rate (Sum-rate) achieved by the system under the current scheduling scheme in the multi-user MIMO environment,

then, after the steps (2), (3) and (4) are completed, the system will obtain N equal to the total number of beams_tAnd the sum rate corresponds to a scheduling beam number and a scheduling scheme under the beam number.

9. The ORBF multi-user scheduling method based on greedy beam selection strategy as claimed in claim 8, wherein the decision of the user beam scheduling scheme most suitable for the current data transmission in the step (5) is based on:

at the final N_tIn the scheduling schemes, the scheme with the maximum corresponding rate is selected as the optimal scheduling scheme of the current time slot for the base station to carry out data transmission.

Images