CN102256301A - User selection method for simultaneously meeting unicast and multicast services - Google Patents

Abstract

The invention provides a user selection method for simultaneously meeting unicast and multicast services, which comprises the following steps of: (1) overlapping unicast on the original a carrier wave distributed to multicast, and establishing a user selection model; (2) ensuring that the speed of the multicast service on the carrier wave can not be reduced through block diagonalization (BD) and power control; and (3) selecting a unicast user set with largest unicast and speed. In the method provided by the invention, during multicast service transmission, the demand of a user needing the unicast service while needing the multicast service is considered simultaneously. In an OFDM (Orthogonal Frequency Division Multiplexing) system, unicast is overlapped on the subcarrier wave distributed to the multicast through BD on the premise of ensuring that the receiving property of the poorest multicast user can not be influenced. Speed maximization and no generation of new poorest link user can be ensured by selecting the optimal unicast user set and the corresponding power control scheme.

Description

User selection method for simultaneously satisfying unicast and multicast services

Technical Field

The invention belongs to the technical field of wireless communication, and particularly relates to a user selection method for simultaneously meeting unicast and multicast services.

Background

With the development of wireless networks, users have higher and higher requirements for service quality, and limited spectrum resources cannot meet the requirements of the users. Therefore, a multicast technology for transmitting the same data to a plurality of users is provided, so that the frequency spectrum can be well utilized, and the utilization efficiency of resources is improved. However, since the conditions of multiple user channel links of the multicast service are different, in order to meet the service requirements of all users, the data rate of the multicast service is often limited to the user with the worst link, so that the resources of the users with better links are not fully utilized. Meanwhile, when a plurality of users receive multicast services such as video and television programs, they also have corresponding needs for unicast services such as telephone and short message. In order to solve the problem, the situation that the user needs both multicast and unicast is considered, and the research on the simultaneous transmission of unicast and multicast services on one subcarrier has practical value.

Disclosure of Invention

The invention aims to overcome the problem that the existing multicast system is limited by the worst user of a link and the resources of good users are not fully utilized; the method maximizes the unicast rate and effectively improves the utilization rate of frequency spectrum while ensuring that the multicast rate is not reduced, thereby improving the performance of the whole system.

The purpose of the invention is realized by the following technical scheme:

the invention relates to a user selection method for simultaneously meeting unicast and multicast services, which is characterized by comprising the following steps:

1) overlaying unicast on original carrier waves allocated to multicast;

2) the multicast service rate on the carrier is ensured not to be reduced through BD and power control;

3) the unicast rate is guaranteed to be maximum by unicast user selection.

In the above technical solution, the specific operations of step 1) are as follows:

1-1), according to the result of wireless scene arrangement, scheduling multicast service and unicast service on all carriers;

1-2), in the carrier wave of the scheduling multicast, calculating the multicast rate according to the worst user performance of the link;

1-3), in a carrier wave for scheduling multicast, overlaying a unicast data stream for multicast data, and calculating the multicast rate according to the worst user performance of a multicast link at the moment:

in the above technical solution, the unicast stream is transmitted together with the multicast by superposition coding.

In the above technical solution, before superimposing unicast, the SNR of the multicast signal of the user i is:

${\mathrm{SNR}}_{m,i}^{\left(k\right)}=\frac{P_m{\left|w_{m,k}^H{h}_i^{\left(k\right)}\right|}^2}{N_0}---\left(1\right)$

after superposition, the SINR of the user i multicast signal is:

<math> <mrow> <msub> <mi>SINR</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <mo>=</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mi>m</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <mrow> <msub> <mi>P</mi> <mi>u</mi> </msub> <munder> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> </mrow> </munder> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>j</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>N</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> </math>

user j, j ∈ U_kThe unicast signal SINR is:

<math> <mrow> <msubsup> <mi>SINR</mi> <mrow> <mi>u</mi> <mo>,</mo> <mi>j</mi> </mrow> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mfrac> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>j</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>j</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mrow> <munder> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> <mo>,</mo> <mi>n</mi> <mo>&NotEqual;</mo> <mi>j</mi> </mrow> </munder> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>N</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> </math>

in the above technical solution, step 2) includes the following operations:

2-1), in the carrier wave of scheduling multicast, according to block diagonalization, making unicast data streams all be transmitted in the orthogonal subspace of the worst link user;

2-2), to prevent worse link users due to unicast interference, power control is applied to the unicast stream.

In the above technical solution, the purpose of keeping the worst user rate of the multicast link unchanged is achieved through the BD, and then it is ensured that no other worse users are generated through power control, so that the multicast rate is kept unchanged, and unicast data streams can be superimposed.

In the above technical solution, the step 3) includes the following operations:

3-1), traversing all possible unicast user sets, calculating unicast rates under various unicast user sets according to the step 2), and selecting a unicast set with the highest unicast rate;

3-2) and a suboptimal user set selection strategy, according to the step 2), firstly selecting a user with the maximum rate, then selecting the next user on the basis of the selection of the user, if the rate is increased, continuing the selection, otherwise, finishing the user selection.

The invention has the following beneficial effects: according to the method, firstly, the problem that unicast data streams cannot influence the performance of the original worst multicast user is solved through block diagonalization, then, the problem that the user with the performance worse than the original worst multicast user cannot be generated is guaranteed through power control, and finally, the problem that the unicast data rate is maximized on the premise that the multicast data rate is not reduced is guaranteed through user selection; meanwhile, a suboptimal user selection method with lower complexity is provided.

Drawings

FIG. 1 is a diagram of a system model of the present invention;

FIG. 2 is a block diagram of a transmitter when unicast and multicast are superimposed;

FIG. 3 is a block diagram of a receiver when unicast and multicast are superimposed;

FIG. 4 is a flow chart of the method of the present invention.

Detailed Description

The invention is described in further detail below with reference to the figures and the examples of embodiments.

The core idea of the invention is that in the carrier wave allocated to multicast, because the multicast is limited by the worst user of the link, the resource of the good user of the link is not fully utilized, therefore, the invention proposes to send the multicast and the unicast by superposition coding on the premise of ensuring that the multicast rate is not influenced. In order to achieve the purpose of not influencing the multicast rate, firstly, Block Diagonalization (BD) is used to solve the problem that the unicast data stream does not influence the performance of the original worst multicast user, then power control is used to ensure that the user with the performance worse than that of the original worst multicast user is not generated, and finally, a user selection strategy is used to ensure that the unicast data rate is maximized on the premise of not reducing the multicast data rate. Meanwhile, a suboptimal user selection strategy with lower complexity is provided.

The invention relates to a user selection method for simultaneously meeting unicast and multicast services, which comprises the following steps:

1) the method includes the following specific steps of overlaying unicast on original carriers allocated to multicast:

1-1), the OFDM system of the invention is under a cell scene, the Base Station (BS, Base Station) of the cell has N antennas, the cell has M Mobile Stations (MS) with single antenna, and M > N, total K carriers can be used for transmitting data. Each MS requires both unicast and multicast traffic. Thus, a total of M unicast streams and one multicast stream are available for transmission. But unicast streams cannot all be used for transmission and therefore a user needs to be selected for transmission, as shown in fig. 1. A total of K sub-carriers are used to transmit data when the minimum SNR of all users on the K carrier is greater than the threshold SNR_thIf so, K is greater than or equal to 1 and less than or equal to K, the kth subcarrier is used for transmitting multicast service, otherwise, unicast service is transmitted, as shown in fig. 4. And the multicast transmission power is P on each subcarrier for transmitting the multicast_mUnicast transmission power is P_u. Let h_iA downlink channel vector, h, representing user i_iEach element in (1) is independently identically distributed and follows a complex gaussian distribution with a mean of 0 and a variance of 1. We assume that the BS knows the channel state information of all users and that the channel does not change for the length of one frame.

Assuming that the k-th subcarrier is allocated to multicast, the channel vector for user i on the k-th subcarrier is

Firstly, a unicast user set U is selected_kSatisfy 1 ≦ U_kLess than or equal to M, wherein, U_kAnd | represents the number of users in the user set. Let the multicast signal be x, U_{For k with}The unicast signal of the user is y_j，j∈U_kAnd has E | x-²]＝E[|y_j|²]＝1，j∈U_k. For multicast traffic, each antenna sends the same signal, i.e. the multicast transmission vector is

The wave beam forming vector of the unicast signal of the jth user is w_j，k，j∈U_kAll of w_j，kBeamforming vector w forming unicast_u，k. As shown in fig. 2, the multicast and beamformed unicast signals are transmitted in a superposition so that the ith user receives as

<math> <mrow> <msub> <mi>r</mi> <mrow> <mi>i</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>=</mo> <msqrt> <msub> <mi>P</mi> <mi>m</mi> </msub> </msqrt> <msubsup> <mi>w</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mi>x</mi> <mo>+</mo> <msqrt> <msub> <mi>P</mi> <mi>u</mi> </msub> </msqrt> <munder> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> </mrow> </munder> <msubsup> <mi>w</mi> <mrow> <mi>j</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <msub> <mi>y</mi> <mi>i</mi> </msub> <mo>+</mo> <msub> <mi>n</mi> <mrow> <mi>i</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>,</mo> <msub> <mi>n</mi> <mrow> <mi>i</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <mo>&Element;</mo> <mi>CN</mi> <mrow> <mo>(</mo> <mn>0</mn> <mo>,</mo> <msub> <mi>N</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <mo>.</mo> </mrow> </math>

Wherein n is_i，kRepresenting the white Gaussian noise, N, of the ith user on the kth subcarrier₀Refers to the power spectral density of the noise.

At the receiving end, all users directly decode the multicast data, and the user j belongs to the U_kAlso the received data r_j，kAfter subtracting the multicast data, the unicast data is decoded as shown in fig. 3.

1-2), before superimposing the unicast, the SNR of the multicast signal of the user i on the kth subcarrier is:

${\mathrm{SNR}}_{m,i}^{\left(k\right)}=\frac{P_m{\left|w_{m,k}^H{h}_i^{\left(k\right)}\right|}^2}{N_0}---\left(1\right)$

1-3), after superposition, the SINR of the user i multicast signal on the kth subcarrier is:

<math> <mrow> <msubsup> <mi>SINR</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>i</mi> </mrow> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mi>m</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <mrow> <msub> <mi>P</mi> <mi>u</mi> </msub> <munder> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> </mrow> </munder> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>j</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>N</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> </math>

user j, j ∈ U_kThe SINR of the unicast signal on the kth subcarrier is:

<math> <mrow> <msubsup> <mi>SINR</mi> <mrow> <mi>u</mi> <mo>,</mo> <mi>j</mi> </mrow> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mfrac> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>j</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>j</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mrow> <munder> <mi>&Sigma;</mi> <mrow> <mi>n</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> <mo>,</mo> <mi>n</mi> <mo>&NotEqual;</mo> <mi>j</mi> </mrow> </munder> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>N</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow> </math>

the invention aims to improve the unicast performance on the basis of ensuring that the multicast rate is not reduced, and the multicast rate on the k sub-carrier is $R_m^{\left(k\right)}=\log (1+\underset{i}{\min }\{{\mathrm{SNR}}_{m,i}^{\left(k\right)}\left\}\right),i=\mathrm{1,2},...,M,$ That is, the multicast rate is only related to the worst link user, so as to ensure that the multicast service is not affected as long as the SNR of the worst link user is not changed after superimposing the unicast.

In summary, the following optimization models are proposed: by means of user selection, power control and beam forming design, the sum of the unicast data rate is maximized on the premise of ensuring the multicast rate to be unchanged.

$\underset{U_k,P_u,w_{j,k}}{\max }{R}_u^{\left(k\right)}$

$s.t.:\underset{i}{\min }{\mathrm{SINR}}_{m,i}^{\left(k\right)}=\underset{i}{\min }{\mathrm{SNR}}_{m,i}^{\left(k\right)},i=\mathrm{1,2},...,M$ (4)

<math> <mrow> <msubsup> <mi>R</mi> <mi>u</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msub> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> </mrow> </msub> <msub> <mi>log</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <msubsup> <mi>SINR</mi> <mrow> <mi>u</mi> <mo>,</mo> <mi>j</mi> </mrow> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>)</mo> </mrow> <mo>,</mo> <mi>k</mi> <mo>=</mo> <mn>1,2</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>K</mi> </mrow> </math>

j∈U_k

The first condition of equation (4) indicates that the unicast signal has no influence on the worst user of the multicast channel, that is, after the unicast signal is superimposed, the performance of the worst user of the multicast channel does not change. The second condition refers to the unicast total rate on the kth subcarrier.

2) The method ensures that the multicast service rate on the carrier is not reduced through BD and power control, and comprises the following specific steps:

since equation (4) is a multivariable optimization problem, the multiple variables are separated, i.e., the design of beamforming, power control and user selection are solved separately. Firstly, the design of a beam forming vector and power control when a user determines are researched; and secondly, determining U by an exhaustive method and a low-complexity suboptimal algorithm respectively. Since only the problem on a single carrier is considered, "k" is ignored below for ease of writing.

2-1), solving by BD does not affect the link worst user performance, i.e., w_uIs determined

To ensure that the multicast rate is not affected, it is ensured that the worst users of the link are not interfered by unicast. The BD is adopted to solve the problem, and the beamforming vector for the unicast is obtained from the orthogonal subspace of the channel of the worst link user, so that the unicast data beam can be ensured to be concentrated in the direction of other users, and the worst user is not influenced a little.

Due to interference between unicast data and BD for selected unicast users, BD is performed for users with U and users with worst link to obtain beamforming vector w_u. Thus, since the MSs are all single antennas and the BS has N antennas in common, U_kThe number of elements (c) should not exceed N-1.

The original multicast worst user can not be influenced by the beamforming vector obtained by the BD and the worst user, but the reception situation of other users is influenced, and in order to ensure that the multicast minimum SINR after unicast superposition is as large as the minimum SNR before unicast superposition, it is required to ensure that a new link worst user is not generated, and this problem can be solved by controlling the power of unicast.

2-2), by power control ensuring that no worse link users, i.e. P, are generated_uIs determined

Unicast power control strategy: unicast power control strategies are introduced because unicast interference may result in a change of the worst multicast receiving user.

In order to ensure that the unicast data has no influence on the multicast transmission rate, the power of the unicast data after the BD is controlled, and the distributed power P is_uThe following conditions need to be satisfied:

(1) the interference caused by overlaying unicast does not influence the multicast transmission rate, namely the minimum SINR of multicast;

(2) the power needs to be as large as possible;

(3) the power cannot exceed a certain upper limit, and is marked as P_max。

Therefore, to ensure that no worst users of the new link are born, the unicast power must be sufficient

<math> <mrow> <munder> <mi>min</mi> <mi>i</mi> </munder> <mo>{</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mi>m</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mi>m</mi> <mi>H</mi> </msubsup> <msub> <mi>h</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <mrow> <msub> <mi>P</mi> <mrow> <mi>u</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <munder> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <mi>U</mi> </mrow> </munder> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mi>j</mi> <mi>H</mi> </msubsup> <msub> <mi>h</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>N</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>}</mo> <mo>=</mo> <munder> <mi>min</mi> <mi>i</mi> </munder> <mo>{</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mi>m</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mi>m</mi> <mi>H</mi> </msubsup> <msub> <mi>h</mi> <mi>i</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>}</mo> <mo>=</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mi>m</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mi>m</mi> <mi>H</mi> </msubsup> <msub> <mi>h</mi> <mi>min</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> </mrow> </math>

Solve to obtain P_u，iAnd because unicast power cannot exceed P_maxThe total power allocated to unicast traffic is therefore P_u＝min{P_u，i，P_max}。

The model is then simplified to the following equation:

$\underset{U}{\max }{R}_u$

$s.t.:\underset{i}{\min }{\mathrm{SINR}}_{m,i}=\underset{i}{\min }{\mathrm{SNR}}_{m,i},k=\mathrm{1,2},...,K$

|U|≤N-1 (5)

<math> <mrow> <msub> <mi>R</mi> <mi>u</mi> </msub> <mo>=</mo> <msub> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <mi>U</mi> </mrow> </msub> <msub> <mi>log</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <mfrac> <mrow> <msub> <mi>p</mi> <mi>j</mi> </msub> <msup> <mrow> <mo>|</mo> <msub> <mi>w</mi> <mi>j</mi> </msub> <msub> <mi>h</mi> <mi>j</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>)</mo> </mrow> </mrow> </math>

3) the method ensures the maximum unicast rate through unicast user selection, and comprises the following specific steps:

in the above equation (5), there is only one variable of U. First, the principle of U selection is defined:

(1) the interference of the signal of the selected unicast user to the multicast signal needs to be concentrated at the multicast user with good link condition as much as possible, namely, the user with the worst link is not influenced, so that the user with the worst link cannot be selected;

(2) and the unicast users in the U require low mutual channel correlation, namely, the unicast sum rate after the BD is ensured to be maximum.

3-1), because the number of users in U is not more than N-1 as soon as the number of users is M, the optimal result can be obtained only by traversing all possible user sets. The traversal algorithm is as follows:

step 1: firstly, finding a worst link user i on a k-th subcarrier, and enabling Ω to be {1, 2., M } \ i and U to be phi;

step 2: enumerating all possible U from Ω, L in total,

is marked as U^(l)，l＝1，2，...，L；

And step 3: performing BD on each U, and distributing power;

and 4, step 4: calculate the rate of each U <math> <mrow> <msubsup> <mi>R</mi> <mi>u</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msub> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msup> <mi>U</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msup> </mrow> </msub> <msub> <mi>log</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <mfrac> <mrow> <msub> <mi>p</mi> <mi>j</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mi>j</mi> <mi>H</mi> </msubsup> <msub> <mi>h</mi> <mi>j</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>)</mo> </mrow> <mo>;</mo> </mrow> </math>

And 5: the optimal U serial number is obtained, <math> <mrow> <msub> <mi>l</mi> <mi>opt</mi> </msub> <mo>=</mo> <munder> <mrow> <mi>arg</mi> <mi>max</mi> </mrow> <mrow> <mn>1</mn> <mo>&le;</mo> <mi>l</mi> <mo>&le;</mo> <mi>L</mi> </mrow> </munder> <msubsup> <mi>R</mi> <mi>u</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msubsup> <mo>.</mo> </mrow> </math>

3-2), because the traversal algorithm has high complexity, a suboptimal selection algorithm for reducing the complexity is provided as follows:

step 1: firstly, finding a worst link user i on a k-th subcarrier, and enabling Ω to be {1, 2., M } \ i and U to be phi;

step 2: after each user in Ω makes BD together with user i, power control is performed, and a user pi (1) with the largest rate is selected, so that Ω ═ Ω \ pi (1), U ═ U + { pi (1) }, and t ═ 1;

and step 3: iteration: if t > N-1, the algorithm ends. Otherwise, the users in omega search for BD respectively corresponding to the users i, pi (1),.. and pi (t-1), then power control is carried out, pi (t) with the maximum sum rate of pi (1),. and pi (t-1) is selected, <math> <mrow> <msubsup> <mi>R</mi> <mi>u</mi> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msub> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msup> <mi>U</mi> <mrow> <mo>(</mo> <mi>l</mi> <mo>)</mo> </mrow> </msup> </mrow> </msub> <msub> <mi>log</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <mfrac> <mrow> <msub> <mi>p</mi> <mi>j</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mi>j</mi> <mi>H</mi> </msubsup> <msub> <mi>h</mi> <mi>j</mi> </msub> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>)</mo> </mrow> </mrow> </math> is a sum rate, wherein

If it is

The algorithm ends. Otherwise, Ω - { pi (t) }, U + { pi (t) }.

The above solution can yield three parameters: beamforming vector w_uUnicast power P_uAnd a unicast service user set U, the general flow chart is shown in fig. 4.

Claims (5)

1. A user selection method for meeting unicast and multicast services at the same time is used for a cell, the cell comprises a base station with N antennas, M mobile stations with single antenna, M is more than N, and K carriers are used for transmitting data; the method is characterized in that:

1) overlaying unicast on original carrier waves distributed to multicast to establish a user selection model;

2) ensuring that the multicast traffic rate on the carrier is not reduced by block diagonalization and power control;

3) and selecting the unicast user set with the highest unicast and highest rate.

2. The method of claim 1, wherein the specific method in step 1) is as follows:

1-1) calculating SNR of multicast signals of a user i on a k-th subcarrier before superposition of unicast, wherein the calculation formula is as follows:

${\mathrm{SNR}}_{m,i}^{\left(k\right)}=\frac{P_m{\left|w_{m,k}^H{h}_i^{\left(k\right)}\right|}^2}{N_0}---\left(1\right)$

wherein, P_mRefers to the power of the multicast on a single subcarrier,

refers to the beamforming vector multicast on the k sub-carrier, which indicates that each antenna transmits the same signal,

representing the channel coefficient, N, of the ith user on the kth subcarrier₀Refers to the noise power spectral density;

1-2) calculating the SINR of the user i multicast signal on the kth subcarrier after superposition, wherein the calculation formula is as follows:

<math> <mrow> <msubsup> <mi>SINR</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>i</mi> </mrow> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mi>m</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <mrow> <msub> <mi>P</mi> <mi>u</mi> </msub> <munder> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> </mrow> </munder> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>j</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>N</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow> </math>

wherein, P_uRefers to the power, w, of unicast on a single subcarrier_j，kRefers to the unicast signal beamforming vector, U, of the jth user on the kth subcarrier_kThe unicast user set selected on the kth subcarrier is referred to;

1-3) rate of superimposing multicast before unicast is $R_m^{\left(k\right)}=\log (1+\underset{i}{\min }\{{\mathrm{SNR}}_{m,i}^{\left(k\right)}\left\}\right),i=\mathrm{1,2},...,M;$

The multicast rate after superposition is equal to the multicast rate before superposition, and the model is as follows:

$\underset{U_k,P_u,w_{j,k}}{\max }{R}_u^{\left(k\right)}$

$s.t.:\underset{i}{\min }{\mathrm{SINR}}_{m,i}^{\left(k\right)}=\underset{i}{\min }{\mathrm{SNR}}_{m,i}^{\left(k\right)},i=\mathrm{1,2},...,M$ (3)

<math> <mrow> <msubsup> <mi>R</mi> <mi>u</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>=</mo> <msub> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> </mrow> </msub> <msub> <mi>log</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mn>1</mn> <mo>+</mo> <msubsup> <mi>SINR</mi> <mrow> <mi>u</mi> <mo>,</mo> <mi>j</mi> </mrow> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>)</mo> </mrow> <mo>,</mo> <mi>k</mi> <mo>=</mo> <mn>1,2</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>K</mi> </mrow> </math>

j∈U_k

wherein,

indicating U on the k sub-carrier_kThe total rate of unicast users.

3. The method for selecting the user to satisfy both the unicast and the multicast services according to claim 1, wherein the step 2) comprises the following steps:

2-1) sending unicast streams on orthogonal subspaces of worst users of the link by block diagonalization to ensure that the unicast streams do not influence the performance of the worst users of the link;

2-2) controlling unicast power to ensure that unicast interference can not cause that the multicast generates worse users after unicast superposition than worst users before unicast superposition;

unicast power P_uMust not exceed P_u，i，P_u，iSatisfy the requirement of

<math> <mrow> <munder> <mi>min</mi> <mi>i</mi> </munder> <mo>{</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi> </mrow> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <mrow> <msub> <mi>P</mi> <mrow> <mi>u</mi> <mo>,</mo> <mi>i</mi> </mrow> </msub> <munder> <mi>&Sigma;</mi> <mrow> <mi>j</mi> <mo>&Element;</mo> <msub> <mi>U</mi> <mi>k</mi> </msub> </mrow> </munder> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>j</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msub> <mi>N</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>}</mo> <mo>=</mo> <munder> <mi>min</mi> <mi>i</mi> </munder> <mo>{</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mi>m</mi> </msub> <msup> <mrow> <mo>|</mo> <msubsup> <mi>w</mi> <mrow> <mi>m</mi> <mo>,</mo> <mi>k</mi> </mrow> <mi>H</mi> </msubsup> <msubsup> <mi>h</mi> <mi>i</mi> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> </msubsup> <mo>|</mo> </mrow> <mn>2</mn> </msup> </mrow> <msub> <mi>N</mi> <mn>0</mn> </msub> </mfrac> <mo>}</mo> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow> </math>

Unicast power cannot exceed P_maxTotal power allocated to unicast traffic is P_u＝min{P_u，i，P_maxIn which P is_maxRepresenting the maximum power that can be allocated by unicast on a single carrier.

4. The method for selecting the user to satisfy both the unicast and the multicast services according to claim 1, wherein the specific steps of step 3) are as follows:

and traversing all possible unicast user sets, calculating unicast rates under various unicast user sets according to the step 2), and selecting the unicast user set with the highest unicast and rate.

5. The method for selecting users to satisfy both unicast and multicast services according to claim 1, namely selecting an optimal unicast user set, wherein the specific steps of step 3) are as follows:

according to step 2), firstly selecting a user with the maximum rate, then selecting the next user on the basis of the selection of the user, if the rate is increased, continuing the selection, otherwise, the user selection is ended.

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