KR20100000343A - Inter-cell interference cancellation method for wireless repeaters with multiple antennas - Google Patents

Abstract

PURPOSE: An adjacent cell signal interference cancellation method of a wireless repeater using the multiple antenna eliminating the signal received from the interferer station of the adjacent cell is provided to remove the signal of the neighboring base center. CONSTITUTION: An initial value q is instituted(100). The interferer station signal is presumed and removed(200). It determines whether a condition that q is 1 is fulfilled(300). The power estimation value of the noises signal is stored(400). The total number of the symbols and q value is similar is determined(600). The communicating base station transmission signal is outputted.

Description

Inter-cell interference cancellation method for wireless repeaters with multiple antennas}

The present invention relates to a wireless repeater to which multiple antennas are applied in a mobile communication system, and more particularly, to a method of removing neighboring cell signal interference in a wireless repeater using multiple antennas capable of removing a signal received from an interfering base station of a neighboring cell. It is about.

In general, a wireless repeater is a device that receives a weakened signal in the middle of a mobile communication system and amplifies, retransmits, or shapes and adjusts or reconstructs a waveform of a distorted signal, and receives a radio wave from a base station, amplifies it, and radiates it into a service area. It performs a forward link function, and performs a reverse link function that receives a radio wave in a service area, amplifies it, and transmits the radio wave to a base station.

1 illustrates such a conventional wireless repeater and its relay environment. As shown, the wireless repeater simply amplifies and transmits a signal received from a communication base station.

However, in the conventional wireless repeater, when the separation between the transmitting and receiving antennas is not good, the signal transmitted from the transmitting antenna is returned to the receiving antenna through a multipath such as a building, a vehicle, and a terrain, or an interference base station of an adjacent cell is used. A signal is also received from.

The returned interference signal is amplified not only the desired signal but also the interference signal component in the signal processing process of the wireless repeater, thereby significantly reducing the performance of the wireless repeater.

In particular, the signal received from the interfering base station of the adjacent cell has a lower impact on the system performance as the received signal-to-interference ratio in the area where the wireless repeater is installed is severely affected, and the performance of the wireless repeater is also greatly reduced. Development efforts are required.

The present invention is to solve the above-mentioned problems, an object of the present invention is to use a multi-antenna that can remove the signal received from the interfering base station of the adjacent cell from the received signal of the mobile communication wireless repeater using the multi-antenna To provide a method for canceling adjacent cell signal interference in a wireless repeater.

An object of the present invention is to output the noise signal corresponding to the noise signal through a signal processing step of estimating and removing the interference base station signal from the received signal by substituting Q transmittable symbols in the terminal transmission signal among the communication base station signal components, the noise signal It can be achieved through the method of canceling the neighboring cell signal interference of the radio repeater using the multiple antenna for outputting the terminal transmission signal of the communication base station by selecting the symbol having the smallest noise signal output value among the communication base station.

The present invention estimates the terminal transmission signal of the communication base station by substituting the transmittable symbols, thereby eliminating the signal of the neighboring base station.

Therefore, the cell coverage of the mobile communication base station can be extended by removing the interference signal, and when applied to the repeater, the repeater can be operated efficiently even in an area where the signal-to-interference ratio is low.

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

2 is a flowchart illustrating a method of canceling adjacent cell signal interference in a wireless repeater using multiple antennas according to the present invention, and FIG. 3 is a block diagram illustrating a signal processing process of the signal processing step 200 according to the present invention. Initial q value setting step 100, signal processing step 200, q value comparison step 300, storage step 400, noise signal comparison step 500, count comparison step 600, count addition step 700 ), The communication base station transmission signal selection and output step (800).

Here, it is assumed that interference signals between transmitting antennas among the signals received through the multiple reception antennas are removed in the repeater.

First, the initial q value setting step 100 is to set the q value for counting to 1 to estimate the interference base station signal.

를 출력하는 단계로서, 크게 간섭신호 추정단계와 간섭신호 제거단계 및 잡음신호 출력단계로 이루어진다.Signal processing step 200 is a symbol {Ω ₁ ,... According to the counted q value. Estimate the interfering base station signal by substituting one of, Ω _Q }, and remove the interfering base station transmission signal from the signal.

As a step of outputting, the interference signal estimating step, the interference signal removing step and the noise signal output step.

Here, the R-ML signal processing method of the R-ML signal processing step 200 is a method of finding out the signal component of the interfering base station, and combines the ML method and the linear spatial demultiplexing method (R-ML). It finds signal of communication base station by using ML method. That is, assuming that BS 1 transmits a signal modulated by a Q-ary modulation method, it is possible to obtain an estimated value of a communication base station transmission signal through Q repetitions.

Among them, the existing MLD (Maximum Likelihood Detection) has excellent performance, but it is difficult to realize due to the disadvantage that the complexity becomes very exponential depending on the number of interfering base stations and the modulation method of transmission symbols. There was this.

In the case of the linear spatial demultiplexing method such as MMSE or ZF, the performance is deteriorated compared to MLD, but it is easy to implement with low complexity.

Therefore, in the present invention, using the R-ML method combining the ML method and the linear spatial demultiplexing method, it is possible to efficiently find the communication base station signal while reducing the complexity compared to the MLD.

In addition, the signal processing step 200 of the present invention is a signal processing matrix W used in the spatial demultiplexing signal processing technique as a method for determining the signal transmitted from the interfering base station, assuming that the signal transmitted from the communication base station is Ω _q . Was used.

The spatial demultiplexing signal processing matrix W may include all existing signal processing matrices including MMSE and Zero Frocing (ZF).

Hereinafter, the signal processing step 200 of the R-ML method will be described in detail based on the R-ML method and the spatial demultiplexing technology.

First, the interference signal estimating step is a step of estimating the interference base station signal among the signals received through the multi-antenna, when the signal received through the multi-antenna in a vector form expressed by Equation 1 below.

는 N개의 기지국에서 전송된 송신신호 벡터로서, 각 원소의 평균전력은 E_s이다.Where y is a signal received from the interference signal canceller between the transmitting and receiving antennas, H is a channel,

Is a transmission signal vector transmitted from N base stations, and the average power of each element is E _s .

는 M×N 차원의 채널 행렬이 되며,

는 M×1 차원의 j번째 기지국 안테나와 단말기의 안테나 간 채널 벡터이다.Assuming an independent Rayleigh fading channel between each transmit and receive antenna,

Becomes the channel matrix in M × N dimension,

Is a channel vector between the j-th base station antenna of M × 1 dimension and the antenna of the terminal.

Therefore, each element h _ij of the channel matrix can be modeled as an iid (Independent and Identically Distributed) complex Gaussian random variable with a mean of 0 and a variance of 1.

And x ₁ of N transmission signals is a signal transmitted for the terminal, and x ₂ ,... , x _n are signal components acting as interference, and n is a receiver thermal noise component of M × 1 dimension, and an iid complex probability variable having an average of 0 and a variance of N ₀ is its element.

In order to estimate the signal of the interfering base station, the received signal of Equation 1 may be divided into a communication base station and an interfering base station signal component and expressed as Equation 2 below.

는 간섭기지국 신호로 볼 수 있다.Where h ₁ x ₁ is the communication base station signal component transmitted for the terminal,

Can be seen as an interfering base station signal.

In addition, when the communication base station signal x ₁ is a Q-ary modulated signal, candidate values {0 ₁ ,... , Ω _Q }.

로 가정하고, 수신신호 벡터 y를 활용하여 아래의 수학식 3에서와 같이 간섭기지국 신호 성분의 합으로만 이루어진 신호

을 생성할 수 있다.So x ₁

A signal consisting only of the sum of the signal components of the interfering base station as shown in Equation 3 below by using the received signal vector y.

Can be generated.

(if x₁ =Ω_q )

(if x ₁ = Ω _q )

Equation 3 is simply expressed in a matrix form as shown in Equation 4 below.

(if x₁ =Ω_q )

(if x ₁ = Ω _q )

인 행렬이고,

이다.Where H ₍₁₎ is

Matrix

to be.

A spatial demultiplexing scheme such as ZF, MMSE, etc., which is a method for detecting a transmission signal of an interfering base station using Equation 4 including only the sum of the interfering base station signal components excluding the communication base station signal component, is used.

에 곱하는 신호처리 과정을 통하여

을 추정하는 방식이다. H₍₁₎의 역행렬 W는

와 같이 구할 수 있고, 이를 활용하여 아래의 수학식 5와 같은 간섭기지국 전송신호 추정 벡터

을 얻을 수 있다.Among these spatial demultiplexing methods, ZF modifies the inverse of H ₍₁₎ .

Through signal processing to multiply by

It is a way of estimating. The inverse W of H ₍₁₎ is

Can be obtained as follows, and using this, an interference base station transmission signal estimation vector as shown in Equation 5 below.

Can be obtained.

The MMSE method, which is another method of the spatial demultiplexing technique, is a method of utilizing the noise power value N ₀ for the W matrix, and is generated as shown in Equation 6 below.

와 같은 신호처리 과정을 통하여 간섭기지국 전송신호 추정 백터

을 얻을 수 있다.Like ZF

Transmission signal estimation vector of interfering base station through signal processing

Can be obtained.

은 열잡음 신호 Wn 을 포함하고 있으므로 이러한 Wn은 슬라이싱(Slicing) 과정을 통해 제거할 수 있으며, 이를 통해 간섭기지국 전송신호만을 추정할 수 있다.Then, the interference base station transmission signal obtained through the interference signal estimation step

Since Wn includes a thermal noise signal Wn, this Wn can be removed through a slicing process, thereby estimating only an interfering base station transmission signal.

The slicing process is a technique of estimating a symbol having a minimum distance from a received symbol as a transmission symbol, as shown in FIG. 3, to effectively remove a noise signal in an AWGN environment. That's how it is.

를 이용하여 아래의 수학식 7과 같이 신호처리를 하였다.The interference signal removing step is a step of removing the signal of the interference base station estimated by the interference signal estimating step. For this purpose, in the present invention, the transmission signal of the interference base station from which the noise signal Wn is removed is removed.

Signal processing was performed using Equation 7 below.

는 간섭기지국 신호성분의 합인

에서 간섭기지국의 전송 신호 성분

가 제거된 순수한 잡음신호가 된다.therefore

Is the sum of the signal components of the interfering base station

Signal component of the interfering base station in

Becomes a pure noise signal with removed.

의 Frobenius norm 값인

을 출력하게 된다.The noise signal outputting step is a step of outputting a noise signal obtained through the interference signal removing step.

Frobenius norm value of

Will print

의 경우에는 비교 대상이 없으므로 다음 단계로 진행하게 된다. 그리고 반복된 카운팅에 따라 다른

등이 출력되는 경우에는 이를 비교하여 그 중 최저값인 다음 단계에서 저장하게 된다.The q-value comparison step 300 is a comparison step that satisfies the condition of q = 1, and when q = 1, the first value is output.

In case of, there is no comparison target, so it proceeds to the next step. And depending on the repeated counting

If the lamp is output, it is compared and stored in the next step, which is the lowest value among them.

의 파워 추정값을 γ을 저장하고, 이때의 심볼

의 q값을

에 저장하는 단계로서, 이를 통해 최소값의 잡음신호

와, 이때의 q값을 갱신 및 추정하게 된다.The storage step 400 is a noise signal output through the signal processing step 200

The power estimate of γ is stored, and the symbol at this time

The value of q

To store the noise signal in the minimum value

And q value at this time is updated and estimated.

과 상기한 저장단계(400)의 γ을 비교하게 된다.The noise signal comparing step 500 is performed when the condition q = 1 is not satisfied through the q value comparing step 300. When the count value q is 2, 3, 4 ... Each noise signal

And γ of the storage step 400 is compared.

인 조건을 만족하는 경우에는 γ값을 새로운

으로 갱신하고, 싱가한 조건을 만족하지 못하는 경우에는 저장단계(400) 이후로 넘어가게 되며, 이러한 과정을 통해 γ에는 가장 작은

값이 저장되고,

에는 가장 작은

값에 대한 심볼

의 q값이 저장된다.Thus γ>

If the condition is

If it is updated to, and does not satisfy the simple condition, the process proceeds after the storage step 400, through this process the smallest in γ

The value is stored,

The smallest

Symbol for a value

The q value of is stored.

The count comparison step 600 determines whether the count value q is equal to the total number Q of all symbols. For example, when the total number of symbols is 16, the count comparison step 600 determines whether the count value q = 16 is satisfied. .

Therefore, if q = Q, all symbols {Ω ₁ ,... Since the estimation work for, Ω _Q } is completed, proceed to the next step. If q ≠ Q is not satisfied, all symbols {Ω ₁ ,... Since the estimation operation for, Ω _Q } is not completed, the count addition step 700, which is a next step, is performed.

The count adding step 700 is a step of adding a q value indicating a count, such as q ++, and through the signal processing step 200, a symbol {Ω ₂ ,. In this step, the estimation work for, Ω _Q } is continued.

값과 이에 대한

를 통해 이에 해당하는

값을 교신기지국 전송신호

값으로 선택하고, 교신기지국 전송신호

를 출력하는 단계이다.When the communication base station transmit signal selection and output step 800 satisfies the count comparison step 600 described above, the noise signal stored through the storage step 400 is stored.

Value and that

Equivalent through

Value Communication signal to the base station

Value is selected and the communication signal of the communication base station

The step of outputting.

라는 가정이 맞고, 상기한 신호처리 행렬 W를 사용하여 얻은

의 추정값

가 정확하다면,

이 되며, R-ML의 출력값

는 최소가 되고, 교신기지국 전송신호 추정 값

은

를 만족한다고 볼 수 있다.That is, the signal transmitted from the communication base station

Is assumed and obtained using the signal processing matrix W described above.

Estimate of

If is correct

Output value of R-ML

Is the minimum, and the estimated signal of the communication base station

silver

It can be seen that satisfactory.

값으로

를 선택하고, 이때

는 ML 방식을 사용하여 아래의 수학식 8과 같이 구하게 된다.Therefore, communication base station transmission signal

By value

, Where

Is calculated using Equation 8 below using the ML method.

일 경우에는

는 아래의 수학식 9와 같이 신호성분으로 추정되는 에러 파라미터

이 추가된 것으로 볼 수 있다.Meanwhile,

If

Is an error parameter estimated as a signal component as shown in Equation 9 below.

This can be seen as added.

이 되며, R-ML의 출력값

인 관계가 성립된다.therefore

Output value of R-ML

Relationship is established.

일 경우에는

이 되므로 상기한 카운트 가산단계(700)를 통해 카운트 q값을 달리하여 심볼 {Ω ₂ ,…,Ω _Q } 중 다른 하나의 값을 연속적으로 대입하고, 이를 통해

를 얻을 때까지 상기한 R-ML 신호처리단계(200)를 연속 수행하게 된다.therefore

If

Since the count q is changed through the count addition step 700, the symbol { Ω ₂ ,. , Ω _Q }, the value of the other one in succession

The R-ML signal processing step 200 is continuously performed until.

6 is a graph illustrating signal detection performance of a wireless repeater using multiple antennas according to the present invention. In order to obtain an estimated value of a communication signal of a communication base station, an existing MLD and MMSE and an R-ML type BER (Bit) of the present invention. Error Rate) This is a simulation result comparing performance.

 As shown, M = 2 and N = 3 were used as parameters for the simulation, and the BPSK modulation method was used for the transmission signal of the communication base station. It can be seen that the signal processing performance of the R-ML method of the present invention is deteriorated than ML but superior to MMSE.

In addition, in terms of complexity, the ML method requires Q ^N iterations and the MMSE requires one operation to obtain the inverse of the M × N matrix, whereas the R-ML method of the present invention uses Q iterations and M × One operation is needed to find the inverse of the (N-1) matrix.

Therefore, the present invention having the signal processing step 200 of the R-ML method reduces the complexity ratio by about Q ^{N −1} compared to the conventional ML method, and requires an additional iteration complexity of Q times compared to the existing MMSE method. It will be.

1 is a schematic diagram showing a typical wireless repeater and its relay environment.

2 is a flowchart illustrating a method for canceling adjacent cell signal interference in a wireless repeater according to the present invention.

Figure 3 is a block diagram showing a signal processing procedure of the signal processing step according to the present invention.

4 is a graph showing signal detection performance of a wireless repeater using multiple antennas according to the present invention.

Claims (12)

The corresponding noise signal is output through the signal processing step 200 of substituting Q transmittable symbols into the terminal transmission signal among the communication base station signal components, and estimating and removing the interference base station signal from the received signal. Selecting a symbol having a small noise signal output value as a terminal transmission signal of a communication base station, and outputting a terminal transmission signal of a communication base station from which an interference base station signal is removed, eliminating interference of adjacent cell signals of a wireless repeater using multiple antennas Way. The method of claim 1, An initial q value setting step (100) of setting 1 as the count q value in order to substitute Q transmittable symbols in the terminal transmission signal among the communication base station signal components; Q transmittable symbols {Ω ₁ ,... A signal processing step (200) of substituting a symbol? _Q corresponding to the count q value among the? _Q } to estimate and remove the interference base station signal from the received signal and to output a corresponding noise signal; a q value comparing step 300 for comparing whether the condition of q = 1; Noise signal output through the signal processing step 200

Is stored in γ, and {Ω ₁ ,... _Q value of the symbol Ω _q corresponding to the q value counted among

A storage step of storing and updating the data; If the q = 1 condition is not satisfied through the q value comparing step 300, the noise signal according to the signal processing of the symbol Ω _q

And γ of the storage step 400 to compare γ>

If the condition is

A noise signal comparison step 500 for updating to and continuing after the storage step 400 if the condition is not satisfied; A count comparison step 600 for determining whether the count value q is equal to the total number of substituted symbols Q; A count addition step 700 of adding the q value, which is a count value, to return to the signal processing step 200; The noise signal stored through the storing step 400 after the count adding step 700

Corresponding to a value

To obtain the corresponding

Value Communication signal to the base station

Value of communication base station

Selecting and outputting the communication base station transmission signal outputting step 800 Adjacent cell signal interference cancellation method of a wireless repeater using multiple antennas, characterized in that made. According to claim 1 or 2, wherein the signal processing step 200 is a wireless repeater using a multi-antenna characterized in that the signal processing is performed through the R-ML signal processing method combined with the ML method and the linear spatial demultiplexing method. Adjacent cell signal interference cancellation The method of claim 2, wherein the signal processing method Of the received signal component symbols to the base station communication signal x ₁ {Ω _1, ... A signal consisting of the sum of the signal components of the interfering base station by substituting one of, Ω _Q }

To estimate the transmission signal of the interfering base station and to estimate the transmission signal of the interfering base station through spatial demultiplexing.

Estimate the transmitted signal of the interfering base station

Interference Base Transmitted Signal Estimated by Eliminating the Thermal Noise Signal Wn

An interference signal estimating step of obtaining; Interference base station signal component for q

And the estimated interfering base station transmission signal

Noise signal for q through

An interference signal removing step of obtaining; Noise Signal Obtained by the Interference Signal Elimination Step

For

Noise signal output stage to output Adjacent cell signal interference cancellation method of a wireless repeater using multiple antennas, characterized in that made. 5. A signal according to claim 4, wherein the signal consists of the sum of the interfering base station signal components.

Adjacent cell signal interference cancellation method of a wireless repeater using multiple antennas, characterized in that generated by the following equation. [Equation]

(if x ₁ = Ω _q ) 5. The method of claim 4, wherein the interference base station transmission signal estimation vector

The spatial inverse multiplexing scheme for obtaining the neighboring cell signal interference cancellation method of a wireless repeater using multiple antennas, characterized in that the spatial inverse multiplexing scheme of the ZF method using the inverse [formula] below. [Equation]

5. The method of claim 4, wherein the interference base station transmission signal estimation vector

The spatial demultiplexing method for obtaining the neighbor cell signal interference cancellation method of a wireless repeater using multiple antennas, characterized in that the spatial inverse multiplexing method of the MMSE method using the inverse [formula] below. [Equation]

5. The interference base station transmission signal estimation vector.

Thermal noise signal of Wn Adjacent cell signal interference cancellation method for a wireless repeater using multiple antennas, characterized in that the removal by slicing. The method of claim 4, wherein the noise signal

Adjacent cell signal interference cancellation method of a wireless repeater using multiple antennas, characterized in that obtained by the following equation. [Equation]

The method of claim 2, wherein

The neighbor cell signal interference cancellation method of a wireless repeater using multiple antennas, characterized in that obtained by using the ML method as shown in [Formula] below. [Equation]

The method of claim 2 or 4, wherein the noise signal

silver

Adjacent cell signal interference cancellation method of a wireless repeater using multiple antennas, characterized in that the Frobenius norm value of. The method of claim 1, wherein the received signal is a signal from which a feedback interference signal between transmitting and receiving antennas is removed.

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