KR20200093349A - Method and Apparatus for Transceiver Filter Design for Minimizing the Self-Interference of FBMC - Google Patents

Abstract

A method of designing a transmission and reception filter which minimizes the inherent interference of a filter bank multi carrier (FBMC) system is presented. According to the present invention, a transmission and reception filter design method for minimizing inherent interference of an FBMC system comprises the steps of: representing a quadrature amplitude modulation-FBMC (QAM-FBMC) system as a matrix in order to model a signal interference of the QAM-FBMC system; designing a reception coupling filter according to minimum mean squared error (MMSE) conditions which minimize the power of signal interference; and designing a transmission pulse forming filter according to the designed reception coupling filter.

Description

Method and Apparatus for Transceiver Filter Design for Minimizing the Self-Interference of FBMC}

The present invention relates to a method and apparatus for designing a transmission/reception filter that minimizes inherent interference of a filter bank multi-carrier system.

CP-OFDM can be easily applied in many applications such as LTE and WiFi, and has the advantage of being able to easily introduce complex signal processing such as MIMO technology.

However, CP-OFDM has high out-of-band emission characteristics in the frequency domain due to the symbol of the square wave, and therefore, the frequency limiting characteristics are poor, and thus, a significant number of guard bands are allocated in LTE, thereby deteriorating bandwidth efficiency. I am wearing. Moreover, since CP is used to prevent orthogonal loss by the ISI of the OFDM system, loss is also forced on the time axis. This property of CP-OFDM does not satisfy the flexibility required in the next generation wireless communication environment. Particularly, in an asynchronous environment such as NB-IoT, loss of orthogonality is unavoidable from the viewpoint of OFDM, which lacks time and frequency localization characteristics. Accordingly, a new waveform technology has been proposed that can simultaneously satisfy time and frequency localization characteristics and orthogonality.

OQAM-FBMC is a selected candidate for the new waveform technology. FBMC can satisfy various scenarios by applying filters per subcarrier to improve frequency limiting characteristics and enable flexible waveform design. OQAM-FBMC, which has been proposed as a strong topic after the PHYDYAS project, applies OQAM modulation to achieve orthogonality in the real axis and is the same as OFDM in terms of performance. Orthogonality in such a real axis damages the orthogonality by violating the residual interference of the imaginary part when striking a real complex channel or applying a MIMO technique. Therefore, in OQAM-FBMC, an additional complex transmission/reception structure is needed to deal with such interference.

In order to solve the interference problem of OQAM-FBMC, a QAM-FBMC technique has been proposed. In a recent study, a QAM-FBMC filter design is proposed that can satisfy the general Nyquist condition as much as possible through global optimization of filter coefficients. In this filter design, the filter orthogonality and the frequency reduction ratio for frequency limiting characteristics are in a trade-off relationship with each other, and it is impossible to satisfy them at the same time. In addition, higher filter orthogonality was achieved by applying different filter bases to multiple filter bank systems. The QAM-FBMC system through such a filter design guarantees a certain degree of orthogonality and high frequency limiting characteristics, but since the filter does not have perfect orthogonality, a performance limitation exists due to the remaining interference components.

The filter design for the existing QAM-FBMC system uses a matched filter that determines the prototype filter of the transmit filter and the receive filter identically. This prototype filter was designed through a global optimization technique to maximize the self-signal-to-interference ratio (Self-SIR) of the transmit and receive filters.

Technical problem to be achieved by the present invention, when the prototype filter of the transmission pulse forming filter and the prototype filter of the receiving coupling filter do not use the same, MMSE (Minimum Mean-Squared-Error) that minimizes the interference power of the signal It is to provide a method and apparatus for designing a transmission/reception filter that minimizes intrinsic interference of a filter bank multi-carrier system capable of designing a reception coupling filter in the manner of) and representing the reception coupling filter as a transmission pulse forming filter.

In one aspect, the method of designing a transmission/reception filter that minimizes the inherent interference of the filter bank multi-carrier system proposed by the present invention is a QAM-FBMC to model signal interference of a Quadrature Amplitude Modulation-Filter Bank Multi Carrier (QAM-FBMC) system. It includes the steps of representing the system as a matrix, designing a receive coupling filter according to a MMSE (Minimum Mean Squared Error) condition that minimizes the power of signal interference, and designing a transmission pulse forming filter according to the designed receive coupling filter.

In order to model the signal interference of the QAM-FBMC system, the step of representing the QAM-FBMC system as a matrix is QAM- using the stacked vector representation of the transmitted signal and the stacked vector representation of the received signal to model the signal interference of the QAM-FBMC system. The FBMC system is represented by a matrix.

The step of designing the receive coupling filter according to the MMSE (Minimum Mean Squared Error) condition that minimizes the power of signal interference uses the prototype filter of the transmission pulse shaping filter and the prototype filter of the receive coupling filter not identically, and the signal interference After designing the receiving coupling filter in the MMSE method that minimizes the power of, the receiving coupling filter is represented by the expression of the transmission pulse forming filter.

The step of designing the transmit pulse shaping filter according to the designed receive combine filter is through a global optimization technique to maximize the self-signal to interference ratio (Self-SIR) of the receive combine filter and the transmit pulse shaping filter. Design.

In another aspect, the transmission/reception filter for minimizing the inherent interference of the filter bank multi-carrier system proposed in the present invention is a QAM-FBMC to model signal interference of a QAM-FBMC (Quadrature Amplitude Modulation-Filter Bank Multi Carrier) system. It includes a modeling unit representing the system as a matrix, a receive coupling filter designed according to a MMSE (Minimum Mean Squared Error) condition that minimizes the power of signal interference, and a transmission pulse forming filter designed according to the designed receive coupling filter.

To model the signal interference of the QAM-FBMC system, the modeling unit represents the QAM-FBMC system as a matrix by using the stacked vector representation of the transmitted signal and the stacked vector representation of the received signal.

The receive coupling filter uses the prototype filter of the transmit pulse shaping filter and the prototype filter of the receive coupling filter, and designs the receive coupling filter in an MMSE method that minimizes the power of signal interference. It is represented by the formula of the transmission pulse forming filter.

The transmit pulse shaping filter is designed through a global optimization technique to maximize the self-signal to interference ratio (Self-SIR) of the receive combining filter and the transmit pulse shaping filter.

According to embodiments of the present invention, a filter is designed using global optimization techniques and constraints by considering the relational expressions of the transmit and receive filters, and a higher self-SIR and a higher self-SIR than the matched filter using the same transmit and receive filters It may show more improved BER performance.

1 is a flowchart illustrating a method for designing a transmission/reception filter that minimizes inherent interference in a filter bank multi-carrier system according to an embodiment of the present invention.
2 is a diagram showing a QAM-FBMC transmission structure according to an embodiment of the present invention.
3 is a view showing the configuration of a transmission and reception filter to minimize the inherent interference of the filter bank multi-carrier system according to an embodiment of the present invention.
4 is a graph showing a simulation result of a transmission/reception filter that minimizes inherent interference in a filter bank multi-carrier system according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart illustrating a method for designing a transmission/reception filter that minimizes inherent interference in a filter bank multi-carrier system according to an embodiment of the present invention.

The proposed method of designing a transmission/reception filter to minimize the inherent interference of the filter bank multi-carrier system is a step of representing a QAM-FBMC system as a matrix to model signal interference of a QAM-FBMC (Quadrature Amplitude Modulation-Filter Bank Multi Carrier) system (110) ), a step 120 of designing a reception coupling filter according to a minimum mean squared error (MMSE) condition that minimizes the power of signal interference, and a step 130 of designing a transmission pulse forming filter according to the designed reception coupling filter (130). .

In step 110, the QAM-FBMC system is represented by a matrix to model signal interference of the QAM-FBMC system. To model the signal interference of the QAM-FBMC system, the QAM-FBMC system is represented by a matrix using the stacked vector representation of the transmitted signal and the stacked vector representation of the received signal. Instead of using the same existing transmit and receive prototype filters in the QAM-FBMC system according to an embodiment of the present invention, a method of using transmit and receive prototype filters differently is used.

In step 120, a receive coupling filter is designed according to MMSE conditions that minimize the power of signal interference. After using the prototype filter of the transmit pulse forming filter and the prototype filter of the receive coupling filter, and designing the receive coupling filter in an MMSE method that minimizes the power of signal interference, the receive coupling filter is used to transmit the pulse forming filter. It is expressed as

In step 130, a transmit pulse shaping filter is designed according to the designed receive combining filter. In order to maximize the intrinsic signal-to-interference ratio of the receive coupling filter and the transmit pulse forming filter, filter coefficients are determined through a global optimization technique and a transmit pulse forming filter is designed. Hereinafter, a method of designing a transmission/reception filter that minimizes inherent interference of a filter bank multi-carrier system will be described in more detail.

2 is a diagram showing a QAM-FBMC transmission structure according to an embodiment of the present invention.

In order to model the interference system of QAM-FBMC, it is necessary to express the QAM-FBMC system as a matrix.

First, a process of representing a stacked matrix representation of a transmission signal will be described.

번째 시간 도메인 송신 신호 벡터

를 표현하면,

로 나타낼 수 있고, 여기서

는 데이터 심볼 벡터(data symbol vector)(Mx1),

는 주파수 도메인 필터 계수 행렬(frequency domain filter coefficient matrix)(NxM),

는 N-포인트 DFT 행렬(N-point DFT matrix)(NxN),

는 확장된 FFT 사이즈(extended FFT size), L은 오버랩핑 팩터를 나타낸다.

First time domain transmission signal vector

If you express

Can be represented as, where

Is the data symbol vector (Mx1),

Is a frequency domain filter coefficient matrix (NxM),

Is the N-point DFT matrix (NxN),

Is an extended FFT size, and L is an overlapping factor.

번째 중첩된 송신 신호를 정리하면 다음과 같다. When considering the overlap + sum

The first superimposed transmission signal is as follows.

는 오버랩-합(Overlap-and-sum) 구조에 의해

번째 송신 신호에 중첩되는 심볼의 데이터를 횡으로 쌓은 벡터이고,

와 같이 나타낼 수 있다. here,

Is an overlap-and-sum structure.

Is a vector of horizontally stacked data of a symbol overlapping the first transmission signal,

Can be represented as

는 각 데이터 값에 대한 송신 펄스 형성 필터이고,

와 같이 나타낼 수 있다.

Is a transmit pulse shaping filter for each data value,

Can be represented as

이고,

는 업샘플링-주파수 도메인(upsampled-frequency domain) QAM-FBMC 필터링 행렬(filtering matrix)이다.

이고,

은 프로토타입의 업샘플링 주파수 도메인 계수이고,

는

의 k번째 요소,

는 시간-도메인 필터링 행렬이고, 다음과 같이 나타낼 수 있다:

ego,

Is an upsampled-frequency domain QAM-FBMC filtering matrix.

ego,

Is the upsampling frequency domain coefficient of the prototype,

The

The kth element of,

Is a time-domain filtering matrix, and can be expressed as:

의 컴포넌트

를 정리하면 다음과 같다: In the definition above

Components of

The following is the summary:

는

을 m번째 콜룸 벡터로 가진

행렬,

는

을 n 번째 요소로 가진

행렬,

는 주파수 도메인 프로토타입 필터

의 시간 도메인 신호(

의 n 번째 요소)를 나타낸다. here,

The

With as the mth collum vector

procession,

The

With n as the element

procession,

Filter frequency domain prototype

Time domain signal(

(Nth element).

Next, a process of representing the stacked vector representation of the received signal will be described.

번째 수신 신호

는 다음과 같다: Channel

Second received signal

Is as follows:

는 시간-도메인 컨볼루션 행렬(time-domain convolution matrix)(circular convolution, Toeplitz matrix)

이고,

는 AWGN 벡터이다. here,

Is a time-domain convolution matrix (circular convolution, Toeplitz matrix)

ego,

Is the AWGN vector.

를 거친

번째 수신 심볼

는 다음과 같다: Receive combined filter

Rough

First received symbol

Is as follows:

는

는 설계 대상인 심볼 들에 대한 수신 결합 필터이다. here,

The

Is a receive combining filter for symbols to be designed.

를 생략하여 표기하면 다음과 같고, The MMSE condition of the receive coupling filter first considers additive noise. Symbol index

If omitted, it is as follows,

The development process is as follows:

를 각 컴포넌트 별로 분리하면 다음과 같이 나타낼 수 있고, Squared error

If is separated for each component, it can be expressed as follows,

If you put it together and organize it,

으로 SVD에 의해 분해될 수 있으므로, 다음과 같이 나타낼 수 있다: Matrix A is

Can be decomposed by SVD, so it can be expressed as:

를 최소화 하기 위해서는, non-negative 인 첫 텀(term)을 줄이는 것이 최선이므로, 첫 텀을 제로로 설정하면,

To minimize, it is best to reduce the non-negative first term, so if you set the first term to zero,

And consequently

이고,

ego,

가 항등 행렬(identity matrix)일 때를 가정하면(AWGN Only), channel

Assuming that is an identity matrix (AWGN Only),

이 된다.

It becomes.

Next, a transmission filter is designed.

)가 최대화 되어야 하며, 다음의 제한 조건들이 추가된 최적화 문제로 정의된다: The transmit filter is basically self-SIR(

) Must be maximized, and the following constraints are defined as added optimization problems:

는 설계 타겟 주파수 영역 프로토타입 필터

의 시간 영역 신호이다(

의 n 번째 요소). here,

Design target frequency domain prototype filter

Is the time domain signal (

Of the nth element).

In the prior art, the receiving filter was used as a matched filter, and the overall filter was defined as follows:

However, in the present invention, since the reception filter is different, the definition of self-SIR is different:

이다. The filter was designed through a global optimization technique, and examples of filter coefficients designed according to embodiments are shown in the table below. At this time, the tolerance parameter (torelance)

to be.

3 is a view showing the configuration of a transmission and reception filter to minimize the inherent interference of the filter bank multi-carrier system according to an embodiment of the present invention.

The transmission/reception filter 300 for minimizing the inherent interference of the filter bank multi-carrier system includes a modeling unit 310, a reception combining filter 320, and a transmission pulse forming filter 330. The modeling unit 310, the reception combining filter 320, and the transmission pulse forming filter 330 may be configured to perform the steps 110 to 130 of FIG. 1.

The modeling unit 310 represents a QAM-FBMC system as a matrix to model signal interference of a QAM-FBMC (Quadrature Amplitude Modulation-Filter Bank Multi Carrier) system. To model the signal interference of the QAM-FBMC system, the QAM-FBMC system is represented by a matrix using the stacked vector representation of the transmitted signal and the stacked vector representation of the received signal. Instead of using the same existing transmit and receive prototype filters in the QAM-FBMC system according to an embodiment of the present invention, a method of using transmit and receive prototype filters differently is used.

The reception combining filter 320 is designed according to a minimum mean squared error (MMSE) condition that minimizes the power of signal interference. After using the prototype filter of the transmit pulse forming filter and the prototype filter of the receive coupling filter, and designing the receive coupling filter in an MMSE method that minimizes the power of signal interference, the receive coupling filter is used to transmit the pulse forming filter. It is expressed as

The transmit pulse shaping filter 330 is designed according to the designed receive combining filter. In order to maximize the intrinsic signal-to-interference ratio of the receive coupling filter and the transmit pulse forming filter, filter coefficients are determined through a global optimization technique and a transmit pulse forming filter is designed.

4 is a graph showing a simulation result of a transmission/reception filter that minimizes inherent interference in a filter bank multi-carrier system according to an embodiment of the present invention.

), TYPE N00, N03, N06을 이용하고, 수신 필터는 아래와 같은 정합 필터가 아닌 MMSE 필터를 사용한다: In the simulation environment, the transmission filter is TYPE D(

), TYPE N00, N03, N06, and the receiving filter uses the MMSE filter, not the following matching filter:

AWGN channel is used, and the number of carriers M = 64. The overlapping factor L = 4, and QPSK modulation is used.

When the prototype filter of the transmission pulse forming filter and the prototype filter of the reception coupling filter are not used identically, the reception coupling filter is implemented in a manner of minimum mean-squared-error (MMSE) that minimizes the interference power of the signal. By designing and using a transmit/receive filter that minimizes intrinsic interference of a filter bank multi-carrier system capable of representing a receive-coupling filter in the form of a transmit pulse forming filter, the transmit filter and the receive filter are identically used as shown in FIG. It can show higher self-SIR and better BER performance than the matched filter.

The device described above may be implemented with hardware components, software components, and/or combinations of hardware components and software components. For example, the devices and components described in the embodiments include, for example, processors, controllers, arithmetic logic units (ALUs), digital signal processors (micro signal processors), microcomputers, field programmable arrays (FPAs), It may be implemented using one or more general purpose computers or special purpose computers, such as a programmable logic unit (PLU), microprocessor, or any other device capable of executing and responding to instructions. The processing device may run an operating system (OS) and one or more software applications running on the operating system. In addition, the processing device may access, store, manipulate, process, and generate data in response to the execution of the software. For convenience of understanding, a processing device may be described as one being used, but a person having ordinary skill in the art, the processing device may include a plurality of processing elements and/or a plurality of types of processing elements. It can be seen that may include. For example, the processing device may include a plurality of processors or a processor and a controller. In addition, other processing configurations, such as parallel processors, are possible.

The software may include a computer program, code, instruction, or a combination of one or more of these, and configure the processing device to operate as desired, or process independently or collectively You can command the device. Software and/or data may be interpreted by a processing device or to provide instructions or data to a processing device, of any type of machine, component, physical device, virtual equipment, computer storage medium or device. Can be embodied in The software may be distributed on networked computer systems, and stored or executed in a distributed manner. Software and data may be stored in one or more computer-readable recording media.

The method according to the embodiment may be implemented in the form of program instructions that can be executed through various computer means and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, or the like alone or in combination. The program instructions recorded on the medium may be specially designed and constructed for the embodiments or may be known and usable by those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tapes, optical media such as CD-ROMs, DVDs, and magnetic media such as floptical disks. -Hardware devices specifically configured to store and execute program instructions such as magneto-optical media, and ROM, RAM, flash memory, and the like. Examples of program instructions include high-level language code that can be executed by a computer using an interpreter, etc., as well as machine language codes produced by a compiler.

As described above, although the embodiments have been described by a limited embodiment and drawings, those skilled in the art can make various modifications and variations from the above description. For example, the described techniques are performed in a different order than the described method, and/or the components of the described system, structure, device, circuit, etc. are combined or combined in a different form from the described method, or other components Alternatively, even if replaced or substituted by equivalents, appropriate results can be achieved.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (8)

Representing a QAM-FBMC system as a matrix to model signal interference of a QAM-FBMC (Quadrature Amplitude Modulation-Filter Bank Multi Carrier) system;
Designing a reception combining filter according to a minimum mean squared error (MMSE) condition that minimizes the power of signal interference; And
Designing a transmit pulse shaping filter according to the designed receive coupling filter
A transmission and reception filter design method comprising a. According to claim 1,
In order to model the signal interference of the QAM-FBMC system, the step of representing the QAM-FBMC system as a matrix is:
To model the signal interference of the QAM-FBMC system, the QAM-FBMC system is represented as a matrix using the stacked vector representation of the transmitted signal and the stacked vector representation of the received signal.
Transceiver filter design method. According to claim 1,
The step of designing a reception coupling filter according to a MMSE (Minimum Mean Squared Error) condition that minimizes the power of signal interference is:
After using the prototype filter of the transmit pulse forming filter and the prototype filter of the receive coupling filter, and designing the receive coupling filter in an MMSE method that minimizes the power of signal interference, the receive coupling filter is used as the transmission pulse forming filter Indicative of
Transceiver filter design method. According to claim 1,
The step of designing a transmission pulse shaping filter according to the designed receive coupling filter,
Designed through global optimization techniques to maximize the Self-Signal to Interference Ratio (Self-SIR) of receive-coupling filters and transmit pulse-forming filters
Transceiver filter design method. A modeling unit representing a QAM-FBMC system as a matrix to model signal interference of a QAM-FBMC (Quadrature Amplitude Modulation-Filter Bank Multi Carrier) system;
A receive coupling filter designed according to a MMSE (Minimum Mean Squared Error) condition to minimize the power of signal interference; And
Transmit pulse shaping filter designed according to the designed receive coupling filter
Sending and receiving filter comprising a. According to claim 1,
Modeling Department,
To model the signal interference of the QAM-FBMC system, the QAM-FBMC system is represented as a matrix using the stacked vector representation of the transmitted signal and the stacked vector representation of the received signal.
Send and receive filters. According to claim 1,
The receiving combination filter,
After using the prototype filter of the transmit pulse forming filter and the prototype filter of the receive coupling filter, and designing the receive coupling filter in an MMSE method that minimizes the power of signal interference, the receive coupling filter is used as the transmission pulse forming filter Indicative of
Send and receive filters. According to claim 1,
The transmission pulse forming filter,
Designed through global optimization techniques to maximize the Self-Signal to Interference Ratio (Self-SIR) of the receive-coupled filter and the transmit pulse-forming filter.
Send and receive filters.

Images