WO2018006355A1 - Transmission weight value selection method and base station - Google Patents

Abstract

Provided are a transmission weight value selection method and a base station. A base station determines a transmission weight value of each beam of a plurality of beams and estimates reference signal receiving power fed back by a terminal where a downlink control signal is transmitted to the terminal using the transmission weight value of each beam of the plurality of beams. The base station then selects a target transmission weight value from the transmission weight value according to the reference signal receiving power and determines a transmission weight value for the terminal according to the target transmission weight value. Since a transmission weight value for a terminal is determined according to reference signal receiving power, and the reference signal receiving power can reflect the quality of a downlink control channel, and therefore the selection of the transmission weight value takes the channel quality of the downlink control channel into account, it is possible to use a narrow beam to transmit a downlink control signal, and the coverage range of the control channel can be increased.

Description

Transmission weight selection method and base station Technical field

The present application relates to the field of communications, and in particular, to a method for selecting a transmission weight and a base station.

Background technique

The beamforming technique is applied in a MIMO system to improve the coverage of a cell, and since multiple antennas are used, each antenna can use a lower transmission power. FIG. 1 is a schematic diagram of communication between a base station and a terminal using beamforming. The base station sends a data signal to the terminal by using a narrow beam.

However, the beamforming technique is currently only used in the transmission of data signals, and cannot be used for the transmission of downlink control signals, that is, the downlink control signals cannot be transmitted using narrow beams.

Summary of the invention

The present application provides a method for selecting a transmission weight and a base station, and aims to solve the problem that the beamforming technology cannot be used to transmit a downlink control signal.

A first aspect of the present application provides a method for selecting a transmission weight, comprising the steps of: determining, by a base station, a transmission weight of each of a plurality of beams, and estimating that each of the plurality of beams is used In the case that the transmission weight transmits a downlink control signal to the terminal, the reference signal fed back by the terminal receives power. The base station further receives the power according to the reference signal, selects a target transmission weight from the transmission weights, and determines a transmission weight for the terminal according to the target transmission weight. Since the transmission weight for the terminal is determined according to the reference signal received power, and the reference signal received power can reflect the quality of the downlink control channel, the selection of the transmission weight takes into consideration the channel quality of the downlink control channel, so that the narrow beam transmission is used. Downlink control signals are possible, and the coverage of the control channel can be increased.

A second aspect of the present application provides a base station including a memory and a processor. The memory is used to store an application and data generated during the running of the application, and the processor is configured to execute an application in the memory to implement a function of: determining a transmission right of each of the plurality of beams a value, and, estimating, using each of the plurality of beams In the case that the transmission weight of the bundle transmits the downlink control signal to the terminal, the reference signal received by the terminal receives the power, and the target transmission weight is selected from the transmission weight according to the received power of the reference signal, and according to the The target transmission weight determines a transmission weight for the terminal.

In an implementation manner, the specific implementation manner of selecting a target transmission weight from the transmission weight according to the received power of the reference signal is: acquiring a reference signal received power set, where the reference signal receiving power set includes Receiving power of a reference signal of at least two beams sorted in a preset order, the at least two beams being a subset of the plurality of beams, and transmitting the beam corresponding to a local extremum in the set of received power signals The weight is used as the target transmission weight.

In an implementation manner, the specific implementation manner of the reference signal receiving power set is: adding reference signal receiving power that meets a preset condition among the reference signal receiving powers of the multiple beams to the reference signal receiving power set, The preset condition includes a difference from a maximum value of the reference signal received power of the multiple beams within a preset range.

In an implementation manner, the specific implementation manner of determining a transmission weight of each of the plurality of beams is: determining a transmission weight of the multiple beams according to a preset constraint, where the preset condition includes The ratio of the error generated by the terminal demodulating the downlink control signal to the downlink control signal received by the terminal is not less than a preset value; and the power of the downlink control signal received by the terminal is greater than zero. Since the preset constraint introduces the influence of the CRS into the process of determining the transmission weight, the obtained transmission weight can control the error caused by the channel vector mismatch within a range that can be received, thus making use of It is possible to transmit downlink control signals in a narrow beam.

In an implementation manner, the preset condition further includes: the power of the single transmit antenna is not greater than a preset value, and the preset value is determined according to the number of transmit antennas. The goal is to have the beam overlap overlap within the coverage of the cell.

DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the description of the prior art will be briefly described below. Obviously, the drawings in the following description are only It is some embodiments of the present invention, and those skilled in the art can obtain other attachments according to these drawings without any creative work. Figure.

1 is a schematic diagram of a base station transmitting a control signal and a data signal to a terminal;

2 is a schematic structural diagram of a base station according to an embodiment of the present invention;

FIG. 3 is a flowchart of a method for selecting a transmission weight according to an embodiment of the present invention.

detailed description

In order to improve the coverage of the downlink control channel, the present application proposes that the base station uses the beamforming technology to send a downlink control signal to the terminal, that is, the base station first determines the weight set of the beam according to the CRS, and then according to the quality of the downlink control channel, the weight is determined. A plurality of weights are collectively selected to be combined into a transmission weight of the downlink control signal to use a transmission weight and transmit a downlink control signal to the terminal through multiple antennas.

2 is a schematic structural diagram of a base station shown in FIG. 1, wherein the base station includes a memory and a processor, and optionally, a transmitter, a receiver, and a modem (not shown) that are commonly provided by the base station. The memory is used to store the application and the data generated during the running of the application, and the processor is used to run the application stored in the memory to implement the process shown in FIG.

FIG. 3 is a method for selecting a transmission weight according to an embodiment of the present application, including the following steps:

S301: The base station determines, according to a preset constraint, a transmission weight of each of the multiple beams used to cover the cell.

Among them, the preset constraints include:

Constraint condition 1. The ratio of the error generated by the terminal demodulation downlink control signal to the downlink control signal received by the terminal is not less than a preset value.

Assuming that the direction angle of the control channel is θ, then H(θ) is the coefficient of the control channel. Denoting a vector consisting of the transmission weights of each of the plurality of beams covering the cell, and wcrs is the transmission weight of the CRS for covering the cell, and then the downlink control signal passes through the control channel before entering the terminal. The expression is H(θ) ^H w . If the expression of the terminal is w _crs H(θ), the expression of the downlink control signal after demodulation by the terminal is:

为H(θ)^Hw经过终端解调后的信号的 实部，表示进入终端的信号的能量，

为H(θ)^Hw经过终端解调后的信号的虚部，表示终端解调出的信号与接收到的信号H(θ)^Hw之间的误差，即终端解调下行控制信号产生的误差，此误差由终端使用CRS解调接收到的下行控制信号H(θ)^Hw的过程中出现的信道矢量失配导致。In formula (1),

The real part of the signal demodulated by H(θ) ^H w through the terminal, indicating the energy of the signal entering the terminal,

Is ^H (θ) H w imaginary-part signal through the terminal after demodulation, the demodulated signal represents the terminal and the signal H (θ) received error between ^H w, i.e., the terminal demodulates the downlink control signals generated Error, which is caused by the channel vector mismatch that occurs during the process of the terminal using the CRS to demodulate the received downlink control signal H(θ) ^H w .

Therefore, the ratio of the error generated by the terminal demodulating the downlink control signal to the downlink control signal received by the terminal can be expressed as:

其中，

为用户信道失配控制范围，单位为度，值越小越好，最大不能超过45度，实际中一般采用经验值。In this embodiment, the preset value is

among them,

For the user channel mismatch control range, the unit is degree, the smaller the value, the better, the maximum can not exceed 45 degrees, in practice, the empirical value is generally used.

That is to say, in this embodiment, the first preset constraint condition is expressed as:

It can be seen that the first constraint is determined according to the transmission weight wcrs of the CRS used to cover the cell.

为H(θ)^Hw经过终端解调后的信号的实部，表示进入终端的信号的能量，因此，第二个预设条件表示为：Constraint 2. The power of the downlink control signal received by the terminal is greater than zero. That is to say, it is necessary to ensure that the terminal can receive the downlink control signal. As mentioned earlier,

The real part of the signal demodulated by the terminal for H(θ) ^H w represents the energy of the signal entering the terminal. Therefore, the second preset condition is expressed as:

In addition to 1 and 2, the transmit power of the antenna may be restricted. In this embodiment, the preset constraints further include:

Constraint 3,

Where |w _i | ² is the power of a single transmit antenna, and N _A is the total number of transmit antennas.

In summary, S301 can obtain the transmission weights of multiple beams used to cover the cell by calculating the solution of the following equation:

Where f(w) is a beamforming criterion function, and the output thereof is the transmission weight of each beam when the downlink control channel is beamformed.

As shown in Figure 1, the terminal uses a Cell-Specific Reference Signal (CRS) to demodulate the downlink control signal, and the base station can only use the wide beam at the cell level to ensure coverage of all terminals in the cell. Send CRS. If a downlink control signal is sent by using a narrow beam, the downlink control signal received by the terminal does not match the beam width of the CRS, and thus the terminal may cause channel vector mismatch in the process of demodulating the downlink control signal, thereby reducing terminal demodulation. performance.

As can be seen from the above description, in this embodiment, the base station determines the transmission weights of multiple beams covering the cell according to w _crs , that is, introduces the influence of the CRS into the process of determining the transmission weight, so The transmission weight can control the error caused by the channel vector mismatch within a range that can be received, thus making it possible to transmit the downlink control signal using a narrow beam.

Optionally, in this embodiment, the number of beams, that is, the number of transmit weights, may be determined according to formula (5):

K=S×N _A , (5)

Wherein S=1, 2, . . . , where N is an integer and N≥ is integer. The goal is to have the beam overlap overlap within the coverage of the cell.

In this embodiment, after obtaining the transmission weight of each of the plurality of beams covering the cell, determining the transmission weight for a certain terminal according to the transmission weights, the specific process is as follows:

S302: The base station uses the channel coefficient of the predetermined downlink control channel to estimate the reference signal receiving power that the terminal may feed back when using the transmission weight determined in S301 to transmit the downlink control signal to the terminal. RSRP).

It should be emphasized that, in S302, the base station does not actually transmit the downlink control signal to the terminal, but uses the channel coefficient of the downlink control channel to estimate the RSRP that the terminal may feed back the downlink control signal.

S303: The base station determines a candidate weight set: adding a transmission weight of the beam with the largest RSRP (referred to as RSRPmax) (referred to as Beam _max ) to the candidate weight set, and the difference between the RSRP and the RSRP _max is within a preset range Thd _rsrp The transmit weights of the beams in _su are placed in the beam candidate set. Sort by the ID of the beam from small to large: BEAM _select = {BEAM ₀ , ..., BEAM _M }, and the RSRP corresponding to the weight in the BEAM _select is {RSRP ₀ ,...,RSRP _M }.

It should be noted that, from small to large, it is only an example of the embodiment, and other sorting methods may also be used.

S304: The base station determines the terminal transmission weight set BEAM _tx : adds Beam _max to the transmission weight set, and adds the weight corresponding to the local maximum value in {RSRP ₀ , . . . , RSRP _M } to the transmission weight set, specifically If the condition RSRP _s-1 <RSRP _s >RSRP _s+1 , s=1, 2, ... M-1 is satisfied, the BEAM _{s is} added to the set of transmission weights.

S305: The base station adds the weights in the BEAM _tx and performs normalization processing to obtain the transmission weight of the terminal.

The base station may use the foregoing determined transmission weight to transmit a downlink control signal of the narrow beam to each terminal through each of the plurality of antennas, thereby implementing the purpose of transmitting the downlink control signal by using the beamforming technology.

It can be seen that the method shown in FIG. 3 can select an appropriate transmission weight according to the channel quality of the terminal (reflected by RSRP), and use the beamforming to transmit a downlink control signal to the terminal, so that the lower transmission power can be used. The coverage of the control channel is increased, and since the determination of the weight of the beam for covering the cell is based on the beam width of the CRS, the demodulation performance of the terminal can also be guaranteed.

The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on differences from other embodiments, and the same or similar parts of the respective embodiments may be referred to each other.

Claims (12)

A method for selecting a transmission weight, comprising: Determining a transmission weight of each of the plurality of beams; Estimating, in a case where a downlink control signal is transmitted to a terminal by using a transmission weight of each of the plurality of beams, the reference signal received by the terminal receives power; Selecting a target transmission weight from the transmission weights according to the reference signal received power; A transmission weight for the terminal is determined according to the target transmission weight. The method according to claim 1, wherein said selecting a target transmission weight from said transmission weights according to said reference signal received power comprises: Obtaining a reference signal received power set, where the reference signal received power set includes reference signal received power of at least two beams sorted in a preset order, the at least two beams being a subset of the multiple beams; The transmission weight of the beam corresponding to the local extremum in the reference signal received power set is used as the target transmission weight. The method according to claim 2, wherein the acquiring the reference signal receiving power set comprises: Adding reference signal received power that satisfies a preset condition among reference signal received powers of the plurality of beams to the reference signal received power set, wherein the preset condition is included in a reference signal received power of the multiple beams The difference between the maximum values is within the preset range. The method according to any one of claims 1 to 3, wherein the determining the transmission weight of each of the plurality of beams comprises: Determining transmission weights of the multiple beams according to preset constraints, where the preset conditions include: And the ratio of the error generated by the terminal demodulating the downlink control signal to the downlink control signal received by the terminal is not less than a preset value; and The power of the downlink control signal received by the terminal is greater than zero. The method according to claim 4, wherein the preset condition further comprises: The power of a single transmitting antenna is not greater than a preset value, and the preset value is determined according to the number of transmitting antennas. The method according to any one of claims 1 to 5, wherein the number of the plurality of beams is K = S × N _A , wherein S = 1, 2, ..., N, where N is Integer and N≥1. A base station, comprising: a memory for storing an application and data generated during the running of the application; a processor, configured to execute an application in the memory to implement a function of: determining a transmission weight of each of the plurality of beams, and estimating an emission of each of the plurality of beams When the weight is transmitted to the terminal, the reference signal received by the terminal, according to the received power of the reference signal, selects a target transmission weight from the transmission weight, and according to the target transmission right The value determines the transmission weight for the terminal. The base station according to claim 7, wherein the processor is configured to receive power according to the reference signal, and selecting a target transmission weight from the transmission weights includes: The processor is specifically configured to: acquire a reference signal received power set, where the reference signal received power set includes reference signal received power of at least two beams that are sorted according to a preset order, where the at least two beams are the multiple And a subset of the beams, and the transmission weight of the beam corresponding to the local extremum in the reference signal receiving power set is used as the target transmission weight. The base station according to claim 8, wherein the acquiring, by the processor, the reference signal received power set comprises: The processor is specifically configured to add a reference signal received power that meets a preset condition among reference signal received powers of the multiple beams to the reference signal received power set, where the preset condition includes The difference between the maximum values of the reference signal received powers of the multiple beams is within a preset range. The base station according to any one of claims 7 to 9, wherein the processor is configured to determine a transmission weight of each of the plurality of beams, including: The processor is specifically configured to determine, according to a preset constraint, a transmission weight of the multiple beams, where the preset condition includes: an error generated by the terminal demodulating the downlink control signal and the terminal receiving The ratio of the downlink control signal to the received value is not less than a preset value; and the power of the downlink control signal received by the terminal is greater than zero. The base station according to claim 10, wherein said processor is configured to Determining constraints to determine the transmission weights of the plurality of beams includes: The processor is specifically configured to determine, according to a preset constraint, a transmission weight of the multiple beams, where the preset condition further includes: a power of the single transmitting antenna is not greater than a preset value, and the preset value is Determined according to the number of transmitting antennas. The base station according to any one of claims 7 to 11, wherein the processor is further configured to: Determining the number of the plurality of beams is K=S×N _A , where S=1, 2, . . . , where N is an integer and N≥1.

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