KR101043939B1 - Method for combining signals using channel state information and noise power in communication systems using multiple receiving antennas - Google Patents

Abstract

The present invention relates to a method of combining signals received by each antenna in a communication system using multiple reception antennas. The present invention uses only information including various types of channel state information passed through signals received by each antenna. The present invention relates to a method for improving receiver sensitivity performance by using noise power in addition to the signal combining method of. Accordingly, by combining the received signals so that the signal-to-noise ratio is maximized according to the situation of the antenna by using the noise power when combining the received signals, it is possible to obtain better reception performance in various channel situations. The greater the difference in noise-ratio performance, the greater the gain that can be achieved over conventional maximum ratio combining.

Multiple Receive Antenna, Signal-to-Noise Ratio, Noise Power, Automatic Gain Control Channel Status Information, Maximum Ratio Receiver Combining (MRRC)

Description

Signal combination method using channel state information and noise power in a communication system using multiple receiving antennas

The present invention relates to a method of combining signals received at each antenna in a communication system using multiple receive antennas.

FIG. 1 is a conventional diagram illustrating a maximum ratio combining method of combining received signals using two receiving antennas.

In this case, since the maximum ratio combining method only needs to add the channel-compensated data for each antenna 10 through the channel estimator 20 as shown in FIG. 1, almost no additional calculation is required even when using a single antenna. In addition, performance is widely used because it can maximize the signal-to-noise ratio after combining as described above, so that good performance can be expected.

However, the conventional maximum ratio combining method in FIG. 1 requires the assumption that the average signal-to-noise ratio of the signal received by each antenna 10 is the same. In other words, the method of FIG. 1 causes errors in accuracy since the average signal-to-noise ratios of the signals received by each antenna 10 are different from each other and further away from the maximum signal-to-noise ratio that can be obtained after combining.

In general, when using the multiple receiving antenna 10, even if using the same antenna, RF and modem chip, the signal-to-noise ratio of the signals received in a specific time interval in the channel conditions that vary independently for each antenna 10 with time Cannot always be the same. In particular, the shorter the time interval for calculating the signal-to-noise ratio, the more severe the difference appears.

In addition, when the antenna 10 is inadvertently located in the sound region of the signal or in a space where the signal is very weak, or conversely, when the reception sensitivity of the specific antenna is very good, according to the existing maximum ratio combining method, Since we only add signals at the same ratio, we can no longer expect the maximum signal-to-noise ratio performance.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and a data signal combining method for adaptively obtaining a maximum signal-to-noise ratio according to a situation by using a signal-to-noise ratio of a signal received by each antenna. The main purpose is to provide.

It is still another object of the present invention to provide a signal combining method using noise power in addition to channel information for each antenna, in particular, a situation in which an unintentionally specific antenna is located in a shaded region or vice versa. To provide a data signal combining method that can obtain a receiver sensitivity performance gain superior to the conventional combining method.

The signal combining method of the communication system of the present invention for solving the above-described conventional problems and to achieve the technical problem according to the present invention, is used in a signal combining device consisting of a plurality of receiving antennas, each receiver, a coupling processor and a decoder In a signal combining method of a communication system using multiple reception antennas, in the process of combining the received data for each of the receiving antennas, combining the signals by using additional information according to channel state information and noise power and weight (α). ) To maximize the signal-to-noise ratio after combining.

delete

In addition, in applying the weight α, the noise power is estimated and accumulated in the noise power of each antenna for a predetermined time interval, and used in the process of combining the corresponding signals.

In addition, the weight α is characterized by using a method of multiplying and combining a predetermined weight before signal combining as shown in Equation 3 below.

&Quot; (3) "

In this case, the average signal-to-noise ratio to which the weight α is applied is calculated and calculated as shown in Equation 5 below, and a partial differential is taken with respect to α to obtain a weight value that maximizes the average signal-to-noise ratio.

<Equation 5>

(P _N1 and P _N2 mean the average power of N ₁ and N ₂ , respectively.)

Further, in the process of combining the received data for each of the receiving antennas, the effects of gain and noise amplification generated in the analog processing of the received signal may be canceled through digital processing.

In addition, in the data combining process from the receiving antenna, additional information other than channel state information or channel-compensated received signal for combining at every predetermined time may be used for the combining process.

As described above, the present invention may vary in the amount of gain obtained according to a communication system using multiple receive antennas, but it is generally applicable to all systems in that the signal-to-noise ratio is maximized after combining. .

In terms of performance, the gain can be expected because the coupling weight is adaptively determined by identifying the situation of each antenna in a general channel condition that changes over time. In addition, when the average signal-to-noise ratio between antennas is changed by unintentional factors, the larger the difference, the greater the amount of gain that can be obtained by the method of the present patent.

Hereinafter, a preferred embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram showing an example of two antennas in the method proposed in the present invention, and FIG. 3 is a block diagram showing an example of a signal combining process in the case of two antennas in the method proposed in the present invention. It is also.

In the conventional maximum ratio combining method, when the conditions that are difficult to obtain the maximum signal-to-noise ratio are considered, it may be considered that the strength of the signal received by each antenna is different.

In this case, even though the signal is received by the same antenna, the channel changes independently for each antenna, and the strength of the channel also varies in a short time period. However, inside the RF chip, noise is generated by temperature-sensitive devices and set to an appropriate reference signal level by an automatic gain control device.

As a result, the signal power at the output of the analog-to-digital converter (ADC) is similarly adjusted for each antenna, but the amount of added noise is different. In this case, using the existing maximum ratio combining method is beyond the assumption that the average signal-to-noise ratio of each antenna is equal in the combining period, and thus performance degradation can be expected.

In the present invention, the signal power of each antenna is similar in the above situation, but in addition to the channel state information in order to adaptively obtain the maximum signal-to-noise ratio under various conditions by using the difference in the noise power. We suggest how to use.

In the description of the embodiments of the present invention, the description is based on the assumption that there are two antennas for better understanding of the description. However, the present invention can be applied regardless of the number of antennas.

As shown in FIG. 2, a signal combining apparatus using channel state information and noise power in a communication system using multiple reception antennas includes a plurality of antennas 100, their respective receivers 110 and 120, and channel compensation data ( R ₁ , R ₂ ) and noise power (P _N1 , P _N2 ) using a combined processor 200 and decoder 300 to perform a received signal combining operation process. In this case, since the information amount of noise power (P _N1 , P _N2 ) is relatively small compared to the information amount of channel compensated data channel compensation data (R ₁ , R ₂ ), the internal connection for coupling is implemented. Almost no burden

Hereinafter, a signal combining method using a plurality of equations used in the received signal combining method according to the present invention will be described.

First, assuming that the channel estimator 20 is perfect in FIG. 1, a signal combined by the maximum ratio combining method may be expressed by Equation 1 as follows.

&Quot; (1) &quot;

In this case, the weight of the signal is maximized according to the average power of the channel through which the signal passes, thereby maximizing the signal-to-noise ratio after combining. In this case, this method is effective if the average power of N ₁ and N ₂ is the same.

However, suppose that the average power of N ₁ and N ₂ in Equation 1 is not the same, and in extreme cases, when N ₁ is very large compared to N ₂ , Equation 2 below The configuration can be predicted that the performance will be better as N ₁ disappears from the final equation.

<Equation 2>

In addition, the present invention proposes a method of combining by multiplying a predetermined weight before combining as shown in Equation 3 to obtain good performance even when the average power of N ₁ and N ₂ is different or the same as above. do. Here, the weight means the relative ratio of each antenna that maximizes the signal-to-noise ratio after combining.

&Quot; (3) &quot;

Subsequently, when Equation 3 is developed and the signal component and the noise component are separated, it can be expressed as Equation 4.

<Equation 4>

The average signal-to-noise ratio after combining from Equation 4 can be expressed as Equation 5 below.

<Equation 5>

Here, P _N1 and P _N2 mean average power of N ₁ and N ₂ , respectively.

In the above Equation 5, a partial derivative with respect to α is obtained in order to obtain an α value that maximizes the average signal-to-noise ratio. At this time, the value of α which makes the partial derivative value '0' becomes the value which maximizes the average signal-to-noise ratio, and the expansion process is obtained as in Equation (7).

&Quot; (6) &quot;

<Equation 7>

Accordingly, in order to maximize the signal-to-noise ratio after the combination by multiplying the weights in advance when combining the channel compensated data from each antenna 100, the noise power P _N1 , which is added to each antenna 100 as shown in equation (7). P _N2 ) only need information about.

In addition, when the noise power (P _N1 , P _N2 ) from each antenna 100 is the same, the weight α value to be multiplied to all the antennas are the same to obtain the same result as the conventional maximum ratio combining method. If the equation above is extended for the case of M antennas, i The weight multiplied by the first antenna may be expressed by Equation 8.

<Equation 8>

In the method of the present invention described above, an example of two receiving antennas is shown in FIG. As shown in the figure, in order to apply the signal combining method of the present invention to the existing maximum ratio combining method, only noise power information P _N1 and P _{N2 for} each antenna 100 is added once per predetermined time interval. in need.

Since this is a relatively small amount of information compared to the channel compensated data (R _1. R ₂ ) used in the conventional combining method, it is hardly a burden to implement the internal connection for combining.

Meanwhile, in the process of combining the received data of the antenna 100, it is preferable to cancel the effects of gain and noise amplification generated in the analog processing of the received signal through digital processing.

FIG. 3 is a diagram illustrating an exemplary embodiment of the combined processor 200 of FIG. 2. As shown, it can be seen that a multiplier 210 and a simple normalizer 220 are simply implemented to combine the received data using the noise powers P _N1 and P _N2 .

However, in actual implementation, it can be implemented in various ways similarly.

As described above, in implementing a signal combining method using channel state information and noise power in a communication system using multiple reception antennas of the present invention using multiple equations, good performance can be expected by maximizing the signal-to-noise ratio after combining. To help.

That is, the present invention can expect better performance than the conventional coupling method by allowing the signal-to-noise ratio of the combined signal to be maximized while periodically adapting to the situation in a channel situation that changes over time. In particular, when the antenna is inadvertently located in the shadowed area or vice versa, where the signal is strongly received, a superior performance gain can be obtained over the conventional coupling method.

In the present specification and drawings, preferred embodiments of the present invention have been disclosed, and although specific terms are used, these are merely used in a general sense for easily describing the technical content of the present invention, and are intended to limit the scope of the present invention. It is not.

That is, it will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention may be implemented in addition to the embodiments disclosed herein.

Therefore, the scope of the present invention is shown in the claims below. For example, the invention described so far has been described by limiting the number of receiving antennas to two in order to easily describe the embodiments, but it is not limited thereto, and it can be understood that the present invention may be modified according to the number of antennas and various usage environments. Should.

<Equation 7 development process>

1 is a block diagram illustrating a commonly known maximum ratio combining method.

Figure 2 is a block diagram showing an example of the case of two antennas in the method proposed in the present invention

Figure 3 is a block diagram showing an example of the implementation of the signal combining process in the case of two antennas of the method proposed in the present invention

<Description of Symbols for Main Parts of Drawings>

100: receiving antenna 110, 120: receiver

200: combined processor 210: multiplier

220: normalizer 300: decoder

Claims (7)

In the signal combining method of a communication system using a multiple receiving antenna used in a signal combining device consisting of a plurality of receiving antennas, each receiver, a coupling processor and a decoder, In the process of combining the received data for each of the receiving antennas, combining the signals using channel state information and additional information according to noise power and adding the weights with a weight α to maximize the signal-to-noise ratio after the combining. A signal combining method of a communication system comprising the step of giving. delete The method of claim 1,  The signal combining method of the communication system, characterized in that in the process of combining the corresponding signal by accumulating the noise power for a predetermined time interval in applying the weight (α). The method according to claim 1 or 3, The weight (α) is a signal combining method of the communication system, characterized in that using a method of multiplying and combining a predetermined weight before the signal combination as shown in equation (3). &Quot; (3) &quot;

The method of claim 4, wherein The average signal-to-noise ratio to which the weight α is applied is calculated and calculated as shown in Equation 5 below, and a partial differential is taken with respect to α to obtain a weight value that maximizes the average signal-to-noise ratio. Joining method. <Equation 5>

(P _N1 and P _N2 mean the average power of N ₁ and N ₂ , respectively.) The method of claim 5, And in the combining of the received data for each of the receiving antennas, canceling the effects of gain and noise amplification generated in the analog processing of the received signal through digital processing. The method of claim 6, In the data combining process from the receiving antenna, additional information in addition to the channel state information or the channel-compensated receiving signal for combining every predetermined time is transmitted to the noise power information for each receiving antenna and used in the combining process. Joining method.

Images