KR20040048090A - Method and apparatus for detecting peak in narrow-band interference canceling system - Google Patents

Abstract

PURPOSE: A peak value detecting method and apparatus for rejecting narrow-band interference are provided to prevent degradation of performance caused by a narrow-band interference signal received in a receiving band. CONSTITUTION: An FFT(Fast Fourier Transform) unit performs FFT on an inputted baseband signal and outputs a corresponding result(10). A power calculator calculates power levels of the FFT result and stores the FFT result in a memory(12). A peak value detector reads three consecutive power levels(N-1,N,N+1) from the memory(14) and compares the central power level(N) with the front and back power levels(N-1,N+1)(16). If the central power level(N) is greater than the front and back power levels(N-1,N+1), the peak value detector stores power level data corresponding to an index of the central power level(N) in a peak value memory(18).

Description

TECHNICAL AND APPARATUS FOR DETECTING PEAK IN NARROW-BAND INTERFERENCE CANCELING SYSTEM

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wideband mobile communication system, and more particularly, to a method and apparatus for detecting a peak in order to eliminate narrow-band interference included in a wideband received signal.

The mobile communication system provides a wireless communication service to a terminal with a given radio frequency resource. However, in practice, the performance of the mobile communication system is degraded by various interferences that may occur in a wireless environment, and in the worst case, operation may be impossible. Therefore, a technical response to such interference is needed.

In general, interference that may occur in a mobile communication system is largely divided into the same frequency interference and the near frequency interference. The same frequency interference includes interference between base stations using the same frequency, interference from other systems such as illegal radio stations, and the like. Proximity interference includes interference between base stations in the same system using adjacent frequencies and interference between adjacent systems.

The most deadly interference in the current broadband mobile communication system may be narrow-band interference from another system using the same frequency resource. Strong narrowband interference can cause system performance degradation and call dropping. In order to remove the narrowband interference, the following methods are conventionally used.

First, when the narrowband interference signal comes in, the high speed interference signal detection receiver detects it, converts the detected frequency into an intermediate frequency, and then removes the interference signal by applying a narrowband interference cancellation filter, and then removes the original frequency. Reconvert to. This method has the disadvantage that the device is heavy, large, and consumes a lot of power.

The second method uses an adaptive digital filter, which lowers the frequency of the signal input at the carrier frequency, adjusts the power gain, and quantizes the digital conversion. The interference signal is detected for this digital signal. The detected interference signal is canceled by an adaptive digital infinite length impulse response (IIR) filter. However, the second method as described above also has a problem in that system complexity increases by using an IIR filter adapted to an interference signal.

Accordingly, an object of the present invention, which was devised to solve the problems of the prior art operating as described above, is to provide a method and apparatus for preventing performance degradation caused by narrowband interference signals received in a reception band in a mobile communication system. will be.

Another object of the present invention is to provide a method and apparatus for removing a narrowband interference signal received in a reception band in a mobile communication system.

It is another object of the present invention to provide a method and apparatus for converting a received signal into a high speed digital signal having a high signal-to-noise ratio and converting it to baseband and then removing the narrowband interference signal.

It is another object of the present invention to provide a method and apparatus for detecting peak components in baseband signals to eliminate narrowband interference signals.

The method of the present invention devised to achieve the object as described above, in the method for detecting the peak value in the narrowband interference cancellation system,

Converting the input digital baseband signal into a fast Fourier transform and outputting a fast Fourier transform result including frequency components and power components, calculating power levels with respect to the fast Fourier transform result, and performing the calculation result Comparing the center power level of the three power levels with the power level before and after, and if the center power level is greater than the power level before and after, detecting the frequency component corresponding to the center power level as a peak value It is characterized by including.

An apparatus according to a first embodiment of the present invention is a device for detecting a peak value in a narrowband interference cancellation system,

A fast Fourier transformer for fast Fourier transforming an input digital baseband signal and outputting a fast Fourier transform result including frequency components and power components, and powering the fast Fourier transform result when the fast Fourier transform is completed A power calculator for calculating levels, an FFT result memory for storing the calculated power levels in order, a peak value detector for sequentially reading the stored power levels and detecting a peak value, the detected peak value and its frequency And a peak value memory for storing an index representing the component.

According to a second aspect of the present invention, there is provided an apparatus for detecting a peak value in a narrowband interference cancellation system.

A fast Fourier transformer for fast Fourier transforming an input digital baseband signal and outputting a fast Fourier transform result including frequency components and power components, and powering the fast Fourier transform result when the fast Fourier transform is completed A power calculator for calculating levels, a comparator and an operator for comparing the power levels outputted as a result of the calculation to determine whether a peak value is detected and outputting a writable signal when it is determined that the peak value is detected; And a peak value memory for storing the detected peak value and an index representing the frequency component in response to the signal.

1 is a diagram illustrating a configuration of a system for canceling narrowband interference at baseband according to an embodiment of the present invention.

2 is a diagram illustrating a detailed configuration of the interference canceller of FIG.

3 is an example of frequency-specific power distribution of a digital baseband signal.

4 is a block diagram of a detector for detecting narrowband interference according to the first embodiment of the present invention;

5 is a flowchart showing a peak value detecting operation according to the first embodiment shown in FIG.

6 is a block diagram of a detector for detecting narrowband interference according to a second embodiment of the present invention;

7 is a flowchart illustrating a peak value detection operation according to the second embodiment shown in FIG.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The present invention described below detects a frequency component having a peak value, that is, narrowband interference by converting a baseband received signal into frequency components and comparing the power levels of the frequency components with each other.

1 is a diagram illustrating a configuration of a system for canceling narrowband interference at baseband according to an embodiment of the present invention.

Referring to FIG. 1, the first filter 102 is a band pass filter (BPF), and a signal of a desired reception band in a signal of a radio frequency (RF) band received by the antenna 101. To filter. The mixer 103 is a frequency down converter for converting a signal of the desired reception band output from the first filter 102 into a signal of an intermediate frequency (IF) band. The reason why the mixer 103 is used is that distortion may occur when the signal in the radio frequency band is converted to the baseband at once. The signal converted to the intermediate frequency band will be converted to the baseband by the Digital Down Converter (DDC) 107 described later.

The second filter 104 filters the signal down-converted by the mixer 103 more precisely. A gain controller (AGC) 105 controls the gain of the signal output from the second filter 104, and an analog to digital converter (ADC) 106 controls the gain controller (A). And the gain-controlled analog signal is converted according to the predetermined sampling frequency into digital data.

When the mobile communication system supports the reception diversity function, the reception path from the first filter 102 to the analog-to-digital converter 106 may be multiplexed. FIG. 1 illustrates a configuration of a mobile communication system that duplicates an antenna and a reception path by adopting reception diversity. However, the interference cancellation apparatus according to the embodiment of the present invention may be used in a mobile communication system that does not employ the reception diversity function.

The digital frequency converter 107 is a decimation filter that decimates samples of the converted digital data and converts them to baseband. An interference canceller 108 detects and removes a narrowband interference component from the decimated data. A modem and demodulator (MODEM) 109 decodes and demodulates the output from the interference canceller 108 to extract desired information.

Looking at the operation of removing the narrowband interference through the configuration as shown in FIG. 1 in more detail;

Since the digital signal converted by the analog-to-digital converter 106 has many sampled values for one original symbol, the digital frequency converter 107 decimates the sampled data according to a predetermined decimation ratio. Perform the simulation. The interference canceller 108 can then process fewer samples to facilitate detection of narrowband interference.

For example, in a code division multiple access (CDMA) system using data on a chip basis, the data output from the analog-to-digital converter 106 consists of 64 samples per chip. Three decimators with a decimation ratio of 2,2 are used to reduce the number of input samples to output 2 (= 64/8/2/2) samples per chip. The decimation ratios are designed according to the number of output samples of the analog / digital converter 106 and the number of input samples of the interference canceller 108.

FIG. 2 is a diagram illustrating a detailed configuration of the interference canceller 108 of FIG. 1 and illustrates a configuration for removing narrowband interference included in a digital conversion signal at baseband according to an embodiment of the present invention. .

Referring to FIG. 2, the interference canceller 108 is configured to detect a narrowband interference signal from the digital baseband signal from the digital frequency converter 107 and remove the detected narrowband interference signal. It consists of the filter part 111. That is, the detector 110 analyzes the power distribution for each frequency of the digital baseband signal, and detects the presence or absence of a narrowband interference signal and provides the center frequencies to the filter unit 111. Then, the filter unit 111 removes a narrowband interference signal included in the digital baseband signal by applying a band cancellation filter according to the detected center frequencies.

FIG. 3 illustrates an example of power distribution for each frequency of a digital baseband signal, and as shown in FIG. 3, frequency components represented in a frequency domain each have a predetermined power level. Signals of a CDMA communication system using spread spectrum technology have a relatively uniform level for each frequency. Accordingly, signals of frequency components having a relatively high power level compared to other frequencies, that is, peak values A, B, and C, may be determined as narrowband interference. To this end, the detector 108 detects a peak value of the input digital baseband signal and determines it as narrowband interference.

A first embodiment of the configuration of the detector 108 for detecting narrowband interference according to the present invention is shown in FIG. The first embodiment shown in FIG. 4 stores power distribution for each frequency analyzed through a Fast Fourier Transform (FFT) in a memory, reads them sequentially, and compares three adjacent data with each other. Find it.

Referring to FIG. 4, the fast Fourier transformer (FFT) 200 performs a fast Fourier transform (FFT) on a digital baseband signal to analyze power distribution for each frequency. The signals used in the fast Fourier transformer 200 will be described below.

W_Addr is a write address for writing input data for fast Fourier transform in the fast Fourier transformer 200 into an internal memory, and DIN is input data written to the W_Addr. FFO Go is a signal instructing to start fast Fourier transform and FFT Done is a signal indicating that the fast Fourier transform is completed in the fast Fourier transformer 200. R_Addr is a read address for reading the fast Fourier transform result from the internal memory of the fast Fourier transformer 200, and the FFT result is the fast Fourier transform result output according to the R_Addr.

The fast Fourier transformer 200 receives a digital baseband signal during a predetermined time interval and performs a fast Fourier transform to output a fast Fourier transform result (FFT result). The FFT result is to include frequency components and power components of the digital baseband signal. A power calculator (Pwr Cal) 202 then calculates a power level for each of the frequency components of the FFT result. The calculated power levels are stored in the corresponding memory area of the FFT result memory 204 in accordance with the R_Addr.

Peak detector 206 reads three consecutive data (i.e. power levels) from the FFT result memory 204 and compares the center power level with the power levels before and after, respectively. If the value is greater than the levels, it is determined as a peak value. Referring to FIG. 3, it can be seen that the narrowband interference has a larger power level than the front and rear frequency components. Thus, the determined peak value is considered narrowband interference. The data determined as the peak value and its index are stored in a peak memory 208. Here, the index is information indicating the position of the frequency component determined as the peak value in the FFT result, and the index indicates the center frequency corresponding to the peak value.

When detection of the peak value is completed with respect to the result of the Fourier transform by the fast Fourier transform unit 200, as described above, the filter unit 111 illustrated in FIG. 2 corresponds to the address of the detected peak value. The center frequency is determined and the band frequency filtering is performed on the center frequency component.

5 is a flowchart illustrating a peak value detection operation according to the first embodiment shown in FIG. 4.

Referring to FIG. 5, in step 10, the fast Fourier transformer 200 converts a digital baseband signal input for a predetermined time period and outputs a conversion result by performing fast Fourier transform. Herein, the fast Fourier transform result includes frequency components and power components. In step 12 the power calculator 202 calculates the power levels of the fast Fourier change result and stores them in frequency order in the FFT result memory 204.

The peak value detector 206 reads the three successive power levels N-1, N, N + 1 in the FFT result memory 204 in step 14 and the three power levels in step 16. Among them, the center power level N is compared with the power levels N-1 and N + 1 before and after, respectively. As a result of the comparison, if the center power level N is not greater than the N-1 and N + 1, the process returns to step 14, and the next three power levels N, N + 1 and N + 2 are read and compared. Repeat the operation. On the other hand, if the center power level N is greater than the N-1 and N + 1, the peak detector 206 stores the index of N and the corresponding power level data in the peak memory 208 in step 18. do. Then, narrowband interference can be eliminated by removing frequency components exceeding a predetermined power level according to the data read from the peak value memory 208.

A second embodiment of the configuration of the detector 108 for detecting the narrowband interference according to the present invention is shown in FIG. In the first embodiment illustrated in FIG. 6, a peak value is immediately detected from hardware fast Fourier transform (FFT) results using hardware elements to be described later, and an address and data corresponding to the detected peak value are stored. This second embodiment requires hardware arithmetic elements compared to the first embodiment, but can reduce the number of memories required.

Referring to FIG. 6, the fast Fourier transform (FFT) 300 performs a fast Fourier transform (FFT) on a digital baseband signal to analyze power distribution for each frequency. The signals used in the fast Fourier transformer 300 will be described below.

W_Addr is a write address for writing input data for fast Fourier transform in the fast Fourier transformer 300 into an internal memory, and DIN is input data written to the W_Addr. FFT Go is a signal instructing to start fast Fourier transform and FFT Done is a signal indicating that the fast Fourier transform is completed in the fast Fourier transformer 300. R_Addr is a read address for reading the fast Fourier transform result from the internal memory of the fast Fourier transformer 300, and FFT Result_D is the fast Fourier transform result output according to the R_Addr.

The fast Fourier transformer 300 receives a digital baseband signal for a predetermined time interval, performs fast Fourier transform, and outputs a fast Fourier transform result (FFT result). The FFT result is to include frequency components and corresponding power components of the digital baseband signal. Pwr Cal 302 then calculates a power level for each of the frequency components of the FFT result. D denoted in the power calculator 302 block means that the power level for the fast Fourier transform result is delayed by one clock. The calculated power levels are provided to a Compare & And Block 308.

Blocks 312 and 316 denoted by D in the comparison and operation block 308 are delayers that perform one clock delay, respectively. The power level calculated in the power calculator 302 is delayed by one clock by the first delayer 312 and again by one clock by the second delayer 316. These delayers 312 and 316 are for comparing three successive power levels, respectively. In this case, the center power level N is the output of the first delayer 312 and the front and rear power levels N-1, N + 1 are the output of the second delayer 316 and the first delayer 312, respectively. Is the input of.

The first comparator 310 outputs '1' when the output of the first delayer 312 is large compared with the input of the first delayer 312 and the output of the first delayer 312. . In addition, the second comparator 314 compares the output of the first delayer 312 and the output of the second delayer 316 and outputs '1' when the input of the first delayer 312 is large. do. The AND gate 318 outputs '1' when the outputs of the first and second comparators 310 and 314 are both '1'. The output of the AND gate 318 is provided to the peak value memory 306 as a write enable signal.

Meanwhile, R_Addr indicating an address corresponding to the FFT result output from the fast Fourier transformer 300 is input to the third delay unit 304 and delayed by 2 clocks. This takes into account the delay caused by the first calculator 312 of the power calculator 302 and the comparison and operation block 308. The peak value memory 306 stores an address input from the third delay unit 304 and corresponding power level data when a writable signal is generated from the AND gate 318. The power level data is provided from the power calculator 332. The address stored in the peak value memory 208 is an index indicating the position of the frequency component determined as the peak value in the FFT result, and the index indicates the center frequency corresponding to the peak value.

7 is a flowchart illustrating a peak value detection operation according to the second embodiment shown in FIG. 6.

Referring to FIG. 7, in step 20, the fast Fourier transformer 300 converts a digital baseband signal input for a predetermined time period and outputs a conversion result by performing fast Fourier transform. Herein, the fast Fourier transform result includes frequency components and power components. In step 12, the power calculator 302 calculates power levels of the fast Fourier change result and outputs them in frequency order.

The delays 312 and 316 of the compare and operation block 308 in step 24 temporarily generate three consecutive power levels N-1, N and N + 1, and in step 26 the comparators 310 and 314. ) Compares the center power level N of the three power levels with the power levels N-1 and N + 1 before and after respectively. As a result of the comparison, if the center power level N is not greater than the N-1 and N + 1, the process returns to step 24 to read and compare the next three consecutive power levels N, N + 1 and N + 2. Repeat the operation. On the other hand, if the center power level N is greater than the N-1 and N + 1, the AND gate 318 generates a writable signal in step 28 so that the address and data of the N are the peak value memory 306. Are stored in. Then, narrowband interference can be removed by removing frequency components exceeding a predetermined power level according to the data read from the peak memory 306.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible 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 not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention can quickly and accurately detect peak values that are considered narrowband interference signals in a narrowband interference cancellation system. In particular, the second embodiment of the present invention has the effect of improving the performance of the narrowband interference cancellation system by minimizing the peak value more quickly and simplifying the implementation and reducing the cost by minimizing the memory usage.

Claims (9)

In the method for detecting the peak value in a narrowband interference cancellation system, Outputting a fast Fourier transform result of fast Fourier transforming an input digital baseband signal and including frequency components and power components, Calculating power levels for the frequency components using the fast Fourier transform result; Comparing the first power level among the power levels consecutive in frequency order with the second power levels before and after the calculation result; And detecting the frequency component corresponding to the first power level as a peak value when the first power level is greater than the second power levels before and after the first power level. 2. The method of claim 1 including detecting the first power level with the detected frequency component. In the method for detecting the peak value in a narrowband interference cancellation system, Outputting a fast Fourier transform result of fast Fourier transforming an input digital baseband signal and including frequency components and power components, Calculating power levels for the frequency components using the fast Fourier transform result; Comparing the center power level with the power levels before and after each of the three power levels consecutive in frequency order as a result of the calculation; And detecting the center power level and a corresponding frequency component as a peak value when the center power level is greater than the front and rear power levels. An apparatus for detecting a peak value in a narrowband interference cancellation system, A fast Fourier transformer for fast Fourier transforming the input digital baseband signal and outputting a fast Fourier transform including frequency components and power components; A power calculator for calculating power levels for the frequency components using the fast Fourier transform result when the fast Fourier transform is completed; An FFT result memory for storing the calculated power levels in frequency order; And a peak value detector configured to sequentially read the stored power levels to detect a peak value. 5. The peak detector according to claim 4, wherein the peak detector reads three consecutive power levels among the stored power levels in order, and if the center power level of the three power levels is greater than the preceding and subsequent power levels, Detecting a power level and a corresponding frequency component as a peak value. 5. The apparatus of claim 4, further comprising a peak value memory for storing indices representing power levels and frequency components corresponding to peak values detected by said peak value detector. An apparatus for detecting a peak value in a narrowband interference cancellation system, A fast Fourier transformer for fast Fourier transforming the input digital baseband signal and outputting a fast Fourier transform including frequency components and power components; A power calculator for calculating power levels for the frequency components using the fast Fourier transform result when the fast Fourier transform is completed; A comparison and calculator that compares the power levels output in frequency order with each other to determine whether a peak value is detected, and outputs a writable signal when the peak value is detected; And a peak value memory configured to store an index representing a power level and a frequency component corresponding to the detected peak value in response to the writable signal. The method of claim 7, wherein the comparison and calculator is, A first delay unit delaying the power level output by the calculation result by one clock; A second delay unit delaying the output of the first delay unit by one clock; A first comparator comparing the input and the output of the first delayer and outputting 1 when the output is greater than the input; A second comparator comparing the input and the output of the second delayer and outputting 1 when the output is larger than the input; And an AND gate for outputting the outputs of the first comparator and the second comparator to the writable signal. The apparatus of claim 8, wherein the power calculator outputs the calculated power levels by delaying the calculated power levels by one clock.