KR20100089303A - Complex communication apparatus in which interference is removed - Google Patents

Abstract

PURPOSE: A multi communication device which removes a mutual interference component is provided to remove an interference of a transmitting signal of one communication method affecting a receiving signal of another communication method from a baseband signal. CONSTITUTION: A baseband converting unit(11) converts a high frequency receiving signal received from an antenna into a baseband signal. A Wiener filter(22) receives a baseband signal that a user wants to transmit by the second communication method. The Wiener filter computes an interference component which affects a high frequency signal of the first communication method transmitted from the antenna. An adder(30) subtracts the interference component calculated by the Wiener filter from the converted baseband signal by the first communication method.

Description

COMPLEX COMMUNICATION APPARATUS IN WHICH INTERFERENCE IS REMOVED}

The present invention relates to a hybrid communication device to which at least two communication methods are applied, and more particularly, to a hybrid communication device capable of eliminating or suppressing mutual interference occurring in two or more communication methods.

Recently, various technologies such as mobile TV, MP3, camera, etc. have been fused to one system, and according to the recent technology trends, various composite mobile terminals have been released to the market. A GSM (Global System for Mobile) mobile phone terminal, which is widely used in Europe, is also developing a hybrid terminal having a digital video broadcasting-handheld (DVB-H) mobile digital broadcasting receiver. However, when a plurality of communication systems are embedded together in one terminal as described above, interference between heterogeneous communication systems may be caused in circuit and frequency.

Indeed, such interference problems are occurring in GSM mobile phone terminals with a DVB-H digital broadcast receiver. When receiving the DVB-H signal, the call signal is received from the GSM antenna and received together, which acts as a large interference noise for the DVB-H receive signal, thereby greatly reducing the reception rate of the DVB-H broadcast signal. This is because the GSM transmitter and DVB-H receiver coexist in one terminal, and the GSM transmit antenna is located near the DVB-H receive antenna in the same circuit, and adjacent channel interference occurs between the DVB-H and GSM frequency bands. .

In order to prevent the reception rate of the DVB-H received signal due to the GSM transmission signal, conventionally, a method of adding a GSM signal cut filter immediately after the reception antenna at the RF terminal of the DVB-H receiver has been used. When the conventional GSM signal blocking filter is applied to a DVB-H receiver, a GSM transmission signal transmitted at a high power of about 33 dBm may cause a coupling loss and antenna loss between the DVB-H antenna and the GSM antenna. Although it is possible to attenuate the GSM signal through attenuation of the GSM signal blocking filter, etc., there is a problem in that the inflow of the GSM signal cannot be completely blocked because there is a limit to the amount that can attenuate the power of the GSM signal.

When the GSM signal blocking filter is applied, insertion loss is inevitably generated, thereby increasing the noise figure of the DVB-H receiver. Therefore, the minimum required power for DVB-H reception is increased because the noise index of the noise level is not satisfied, and the reception sensitivity is lowered because the power of the input signal is decreased. In addition, the GSM signal, which is not sufficiently blocked by the GSM signal blocking filter, is mixed with the DVB-H received signal and introduced together, and the GSM signal acts as an interference noise component, resulting in poor reception performance and deterioration in image quality.

As a result, in the hybrid handset which can use GSM and DVB-H together, the GSM band which cannot receive the DVB-H broadcast signal is limited to the area far away from the GSM band due to the GSM interference signal which is not completely eliminated. There arises a problem that all available channels cannot be used in good condition.

In addition, a method of lowering a portion of the spectrum of the GSM signal during the GSM modulation process is known as another conventional method for preventing a decrease in the reception rate of the DVB-H received signal due to the interference of the GSM transmission signal. In this conventional scheme, a conventional linear phase finite impulse response (FIR) filter is applied to a GSM transmitter, which causes a large error rate in the GSM receiver because the spectrum is deformed to transmit distorted data from the GSM transmitter. Will increase. Even when using a very precisely designed filter, there is a problem in that the delay of the filter is severe and the complexity is increased.

The present invention solves the problem of providing a hybrid communication device that eliminates mutual interference that can remove interference from a baseband signal from a transmission signal of one communication method to a received signal of another communication method in a composite communication device employing two or more communication methods. The technical problem to be made.

As a means for solving the above technical problem, the present invention,

A baseband converter for converting a high frequency reception signal of a first communication method received from an antenna into a baseband;

Wiener for receiving a baseband signal to be transmitted by a second communication method and calculating an interference component of the high-frequency signal transmitted by the second communication method to the high-frequency signal of the first communication method received from the antenna. filter; And

Provided is a composite communication device with mutual interference elimination including a summer for subtracting the interference component calculated by the Wiener filter from the received signal of the first communication scheme converted to the baseband.

Preferably, the first communication method may be Digital Video Broadcasting-Handheld (DVB-H), and the second communication method may be Global System for Mobile (GSM).

Preferably, the Wiener filter calculates an interference component by Equation 1 below, and the weight vector of Equation 1 below may be determined by Equation 2 below.

[Equation 1]

[Equation 2]

In Equation 1 and Equation 2, n _k represents an interference component caused by the transmission signal of the second communication method included in the received signal of the first communication method, W represents a weight vector, and X _k represents the second. Represents a baseband signal to be transmitted in a communication method, W _opt represents an optimal weight vector to be applied to Equation 1 above, and P = E [y _k X _k ] and R = E [X _k X _k ^T ] Where y _k denotes a high frequency reception signal of the first communication scheme received from the antenna, and E [.] Denotes an operation symbol representing an average value.

An embodiment of the present invention includes a fast Fourier transform unit for converting the baseband signal to be transmitted in the second communication method into a frequency domain; A mixer which combines the frequencies of the bands used in the first communication scheme from the baseband signals to be transmitted of the second communication scheme converted into the frequency domain to remove frequency band components of the first communication scheme; And an inverse fast Fourier transform unit for converting the signal from which the frequency band component of the first communication scheme is removed by the mixer into a time domain. In this case, the signal converted into the time domain by the inverse fast Fourier transform unit may be modulated by a predetermined modulator to generate a transmission signal of the second communication method.

In one embodiment of the present invention, the baseband conversion unit, the carrier removal unit for removing a carrier component from the high frequency reception signal of the first communication method received from the antenna and the baseband by digitally sampling the received signal from which the carrier is removed It may include an ADC sampling unit for generating a band signal.

According to the present invention, by removing the interference component by using the baseband signal, there is an effect that can effectively remove the interference component generated in the received signal by the transmission signal of another communication method while using a simple configuration.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiment of this invention is provided in order to demonstrate this invention more completely to the person skilled in the art to which this invention belongs. Therefore, it should be noted that the shape and size of the components shown in the drawings may be exaggerated for more clear explanation.

1 is a block diagram of a composite communication device in which mutual interference is eliminated according to an embodiment of the present invention.

As shown in FIG. 1, a hybrid communication apparatus in which mutual interference is eliminated according to an embodiment of the present invention includes a baseband converter configured to convert a high frequency received signal of a first communication method received from an antenna 10 into a baseband. (11) and receiving a baseband signal to be transmitted by the second communication method, and calculating an interference component that the high-frequency signal transmitted by the second communication method has to the high-frequency signal of the first communication method received from the antenna. A Wiener filter 22 and a summer 30 for subtracting the interference component calculated by the Wiener filter from the received signal of the first communication method converted into the baseband.

The baseband converter 11 removes a carrier component from the high frequency received signal of the first communication method and generates a baseband signal through digital sampling. The baseband converter 11 digitally samples the carrier remover 111 for removing a carrier component from the high frequency received signal of the first communication method received from the antenna 10 and the received signal from which the carrier has been removed. It may include an ADC sampling unit 112 for generating the baseband signal.

The signal y _k received from the antenna 10 and input to the baseband converter 11 is another antenna 20 in the second communication method to the original signal s _k to be received in the first communication method. It can be understood as a signal containing the interference component (n _k ) by the signal transmitted in the). The present invention is characterized by finding the interference component (n _k ) using the baseband transmission signal of the second communication method and removing the interference component.

In the following description, a first communication method will be described using Digital Video Broadcasting-Handheld (DVB-H) as an example, and a second communication method will be described using a Global System for Mobile (GSM) as an example. DVB-H communicates over a frequency band of 470-862 MHz, and GSM uses a frequency band of 880-915 MHz for transmission of the terminal and 925-960 MHz for reception. As described above, since the upper frequency channel of the DVB-H and the transmission channel of the GSM are very close to each other, the GSM transmission signal interferes with the reception signal of the DVB-H in one composite terminal capable of using both the DVB-H and GSM methods. It is likely to cause it. Therefore, the present invention can be remarkably effective when applied to a hybrid terminal employing both DVB-H and GSM schemes.

The Wiener filter 22 is an optimum filter designed to minimize the mean square error between a filter output and a smooth or predicted desired output for a normal input which is generally mixed with a signal and noise. In the present invention, the Wiener filter 22 receives the baseband GSM transmission signal X _k from the transmission unit 21 of the second communication method and uses the DVB-H based on the baseband transmission signal X _k as a reference. The interference component n _k included in the received signal is calculated. The output of the Wiener filter 22 may be determined by determining a weight for minimizing the mean square error of the signal component that does not include the interference originally intended to be received in the DVB-H method.

The summer 30 subtracts the interference component calculation signal calculated by the Wiener filter 22 from the DVB-H received signal converted to the baseband, thereby eliminating the interference of the DVB-H received signal (s _k). )

On the other hand, the present invention, when the transmission of the second communication method is received in the first communication method while minimizing the distortion of the transmission signal of the second communication method by removing the frequency band of the first communication method from the transmission signal of the second communication method in advance. Provides a configuration that can suppress the interference that may occur in advance. That is, the GSM transmitter 21, which is the transmitter of the second communication method shown in FIG. 1, may have a technical configuration of removing the frequency band of the first communication method DVB-H from the baseband signal to be transmitted in advance. This technical configuration is shown in FIG.

Referring to FIG. 2, an embodiment of the present invention includes a fast Fourier transform unit 211 for converting a baseband signal to be transmitted in the second communication scheme into a frequency domain, and the second transformed into the frequency domain. By the mixer 212 and the mixer 212 to remove the frequency band component of the first communication method by combining the frequency of the band used for the first communication method in the baseband signal to be transmitted in the communication method The apparatus may further include an inverse fast Fourier transform unit 213 for converting a signal from which a frequency band component of one communication method is removed to a time domain. These components may be included in the transmission unit 21 of FIG. 1. The signal converted into the time domain by the inverse fast Fourier transform unit 213 may be modulated by a modulation method adopted by the second communication method, and then may be transmitted through an antenna (20 in FIG. 1) on a carrier signal.

Hereinafter, with reference to the accompanying drawings will be described in more detail the operation and effect of the embodiments of the present invention having the configuration as described above.

First, as shown in FIG. 1, a high frequency reception signal of DVB-H, which is a first communication method, is received through an antenna 10. It is to be understood that this received signal y _k includes the original received signal s _k desirably desired to be received in the first communication method and the interference signal component n _k generated by the transmitted signal of the second communication method. Can be. The present invention does not immediately remove an interference component from a DVB-H high frequency received signal, and converts a signal including interference to a baseband and then removes the interference component from the received signal converted to the baseband. To this end, the received DVB-H high frequency signal is a carrier component of the high frequency is removed from the carrier removing unit 111 in the baseband converter 11, the ADC sampling unit 112 is a preset analog signal from which the carrier component is removed It can be digitally sampled at a sampling rate and converted to a digital baseband signal.

Meanwhile, the transmitter 21 of the second communication method GSM may transmit a transmission signal through the antenna 20 while the DVB-H signal is received. The GSM signal transmitted while receiving the DVB-H signal interferes with the DVB-H reception. At this time, the baseband component (X _k ) of the signal transmitted from the GSM transmitter 21 to the antenna is input to the Wiener filter 22, and the Wiener filter 22 receives the base received from the GSM transmitter 21. The interference component of the GSM transmission signal is calculated by applying a weight to the GSM transmission signal of the band as a reference signal. The Wiener filter 22 calculates a weight (optimized weight) for minimizing the mean square error of the signal component not including the interference originally intended to be received by the DVB-H method, and calculates the interference component that is closest to the actual interference component. . The optimized weight may be determined as a value for minimizing the mean square error of signal components that do not include interference originally intended to be received in the DVB-H scheme. The process of determining the optimized weight can be described using a formula as follows.

As shown in FIG. 1, the DVB-H received signal y _k , which is a first communication method received through the antenna 10, has a second communication to the DVB-H original signal s _{k that} does not include an interference component. The interference component n _k by the GSM received signal, which is a scheme, may be included as shown in Equation 3 below.

[Equation 3]

Accordingly, the original received signal s _k of DVB-H in Equation 3 can be obtained by removing the interference component n _k from the signal y _k received from the antenna 10 as shown in Equation 4 below. In this case, the interference component n _k is obtained by summing the product of the weight (w (i)) with the baseband signal X _k used for transmission of the second communication scheme GSM for a predetermined interval, as shown in Equation 4 below. The matrix may be expressed in the form of a matrix product of the transpose W ^T of the matrix W representing the weight and the matrix X _k representing the reference signal.

[Equation 4]

The Wiener filter 22 obtains the mean square error (J) of the DVB-H original signal represented by Equation 4 as shown in Equation 5 below, and differentiates the value with respect to the weight W to give as shown in Equation 6 below. W with the determined derivative value 0 is determined as a weight that minimizes the mean square error, that is, an optimal weight value.

[Equation 5]

[Equation 6]

In Equations 5 and 6, E [·] is an operator representing an average value, σ represents a variance of y _k , and a relationship of P = E [y _k X _k ] and R = E [X _k X _k ^T ] Is established.

The weight (W) value that makes Equation 6 equal to 0, that is, the optimal weight value is determined as in Equation 2 below, and when Equation 2 is applied to the weight value in Equation 1 below, the received signal of GSM as the second communication method The interference component n _k can be calculated.

[Equation 2]

[Equation 1]

The interference component calculated as described above may be subtracted from the baseband-converted signal of the antenna reception signal by the adder 30 to output the DVB-H reception signal s _k from which interference originally intended to be received is excluded.

The composite communication device according to the embodiment of the present invention constructed and operated as described above can be proved through various simulations.

3 and 4 illustrate a DVB-H received signal including an interference component and a DVB-H received signal including an interference component by applying both a first communication method DVB-H and a second communication method GSM, together with the present invention shown in FIG. Fig. 1 is a constellation diagram showing the distribution of DVB-H received signals in the composite communication device to which the configuration according to the embodiment of the present invention is applied.

3 and 4, the green dot is a DVB-H received signal transmitted without the GSM interference signal, and the black dot is a DVB-H received signal distorted due to the GSM interference signal. In addition, the blue dot can obtain the DVB-H received signal when the configuration according to the embodiment of the present invention shown in FIG. 1 is applied.

3 and 4, when the configuration according to the embodiment of the present invention is applied, the distribution of the blue dot is improved to be very similar to the distribution of the green dot which is the DVB-H signal received without the interference signal. You can check it.

FIG. 5 is a diagram illustrating a comparison of a signal-to-interference noise ratio between a conventional composite communication device and a composite communication device according to an embodiment of the present invention shown in FIG. 1.

As shown in FIG. 5, in the conventional hybrid communication device of the present invention illustrated in FIG. 1, the DVB-H received signal has a symbol error rate at a Signal to Interference Noise Ratio (SINR) = -30 dB. It can be seen that the significant decrease from 3x10 ^-1 to 4x10 ^-3 . In another aspect, when applied based on a point having a symbol error rate of 10 ⁻¹ , an SINR per bit is improved by about 27 dB.

6 and 7 illustrate a GSM power spectrum of a hybrid communication device and a conventional hybrid communication device employing a GSM transmitter structure that pre-suppresses a DVB-H band frequency during GSM transmission according to an embodiment of the present invention shown in FIG. 2. And an error rate in GSM reception, respectively.

In Fig. 6, the black solid line represents the spectrum of the DVB-H signal, the solid blue line represents the original GSM signal spectrum, the green solid line represents the GSM signal spectrum when filtering in a typical high frequency band is applied, and the red solid line represents FIG. 2 shows the GSM signal spectrum when the GSM transmitter structure according to the present invention shown in FIG. 2 is applied. As shown in FIG. 6, when the transmitter structure of the GSM communication, which is the second communication method shown in FIG. 2, is applied, GSM is suppressed by suppressing the DVB-H band frequency, which is the first communication method, in a baseband state. The interference that the signal has on the DVB-H signal can be greatly reduced.

In FIG. 7, the solid blue line represents the bit error rate of the original GSM signal, the solid green line represents the bit error rate of the GSM signal when filtering in a typical high frequency band is applied, and the solid red line represents the present invention shown in FIG. The bit error rate of the GSM signal when the GSM transmitter structure is applied is shown. As shown in FIG. 7, in the case of using the conventional high frequency filtering method, an error rate of GSM reception is increased due to distortion of transmission data, while data distortion of GSM reception is applied by applying a GSM transmission technique as shown in FIG. 2. You can see that does not appear.

Through the simulation results as described above, it can be confirmed that the GSM transmission data can be transmitted without distortion and the effect of reducing the effect of the GSM transmission signal as interference noise on the DVB-H band.

In the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the following claims and their equivalents.

1 is a block diagram of a composite communication device in which mutual interference is eliminated according to an embodiment of the present invention.

2 is a block diagram illustrating a part of a GSM transmitter for pre-suppressing the DVB-H band frequency during GSM transmission according to an embodiment of the present invention.

3 and 4 illustrate a DVB-H received signal without interference components, a DVB-H received signal including interference components by a GSM-type received signal, and one embodiment of the present invention shown in FIG. This is a constellation diagram showing the distribution of DVB-H received signals in the composite communication device to which the above configuration is applied.

FIG. 5 is a diagram illustrating a comparison of a signal-to-interference noise ratio between a conventional composite communication device and a composite communication device according to an embodiment of the present invention shown in FIG. 1.

6 and 7 illustrate a GSM power spectrum of a hybrid communication device and a conventional hybrid communication device employing a GSM transmitter structure that pre-suppresses a DVB-H band frequency during GSM transmission according to an embodiment of the present invention shown in FIG. 2. And an error rate in GSM reception, respectively.

* Description of the symbols for the main parts of the drawings *

10, 20: antenna 11: baseband converter

111: carrier removing unit 112: ADC sampling unit

21: GSM transmitter 22: Wiener filter

30: summer

Claims (5)

A baseband converter for converting a high frequency reception signal of a first communication method received from an antenna into a baseband; Wiener filter for receiving a baseband signal to be transmitted in a second communication method, and calculating an interference component of the high-frequency signal transmitted in the second communication method to the high-frequency signal of the first communication method received from the antenna. ; And And a summer for subtracting the interference component calculated by the Wiener filter from the received signal of the first communication scheme converted into the baseband. The method of claim 1, And the first communication method is DVB-H, and the second communication method is GSM. The method of claim 1, The Wiener filter calculates an interference component by Equation 1 below, and the weight vector of Equation 1 is determined by Equation 2 below. [Equation 1]

[Equation 2]

In Equations 1 and 2, n _k : interference component, W: weight vector, X _k : baseband signal to be transmitted by the second communication scheme, W _opt : optimal weight vector, P = E [y _k X _k ], R = E [X _k X _k ^T ], y _k : high frequency reception signal of the first communication method received from the antenna, E [.]: Average value) The method of claim 1, A fast Fourier transform unit for converting the baseband signal to be transmitted in the second communication scheme into a frequency domain; A mixer which combines the frequencies of the bands used in the first communication scheme from the baseband signals to be transmitted of the second communication scheme converted into the frequency domain to remove frequency band components of the first communication scheme; And And an inverse fast Fourier transform unit for converting the signal from which the frequency band component of the first communication scheme is removed by the mixer into a time domain. And generating a transmission signal of a second communication method by modulating the signal converted into the time domain by the inverse fast Fourier transform unit. The method of claim 1, wherein the baseband conversion unit, A carrier removal unit for removing a carrier component from the high frequency reception signal of the first communication method received from the antenna; And And an ADC sampling unit configured to digitally sample the received signal from which the carrier has been removed to generate the baseband signal.

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