KR200427976Y1 - Digital communication apparatus for measuring carrier to interference and noise ratio using downlink preamble - Google Patents

Abstract

The present invention relates to a carrier signal-to-noise ratio measurement apparatus using a downlink preamble in a digital communication apparatus, and more particularly, to a plurality of cells or sectors in a digital communication apparatus using orthogonal frequency division multiplexing or orthogonal frequency division multiple access. The present invention relates to an apparatus for measuring a carrier signal-to-noise ratio using a preamble of a corresponding received signal, and using the same for handover and reverse power control. According to the present invention, the carrier signal-to-noise ratio can be easily measured using the preamble, and handover and reverse power control is performed using the measured carrier signal-to-noise ratio, so that the received carrier of the base station can be received even in a bad channel environment. By maintaining the proper signal-to-noise ratio, performance degradation can be reduced.

OFDM, OFDMA, CINR, preamble, noise and interference signals, handover, reverse power control, frequency reuse factor.

Description

DIGITAL COMMUNICATION APPARATUS FOR MEASURING CARRIER TO INTERFERENCE AND NOISE RATIO USING DOWNLINK PREAMBLE}

1 is a diagram illustrating a schematic configuration of a general OFDM transceiver.

2 is a diagram illustrating a transmission structure of a preamble according to a segment according to an embodiment of the present invention.

3 is a diagram illustrating an apparatus for measuring carrier signal to noise ratio in a plurality of cells or a plurality of sectors according to an embodiment of the present invention.

4 is a block diagram illustrating an internal configuration of a carrier signal to noise ratio measuring apparatus for performing handover determination according to an embodiment of the present invention.

5 is a block diagram illustrating an internal configuration of a carrier signal to noise ratio measuring apparatus for controlling transmission power according to an embodiment of the present invention.

6 is a block diagram illustrating an internal configuration of a carrier signal to noise ratio measuring apparatus for reporting a carrier signal to noise ratio according to an embodiment of the present invention.

7 is a block diagram illustrating an internal configuration of a signal estimator according to an embodiment of the present invention.

8 is a block diagram illustrating an internal configuration of a power calculation unit according to an embodiment of the present invention.

FIG. 9 is a block diagram illustrating an internal configuration of a power calculation unit when a frequency reuse factor is '1' according to an embodiment of the present invention.

FIG. 10 is a block diagram illustrating an internal configuration of a carrier signal to noise ratio calculator according to an embodiment of the present invention.

11 is a flowchart illustrating a method of measuring a carrier signal to noise ratio using a preamble in a plurality of cells or sectors according to the present invention.

12 is a flowchart illustrating a method of measuring a carrier signal-to-noise ratio using a preamble in a serviced cell according to the present invention.

13 is a graph illustrating a simulation result of measuring CINR using a preamble according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

401: preamble symbol acquisition unit

402: signal estimator

403: power calculation unit

404: carrier signal to noise ratio calculation unit

405: handover decision unit

The present invention relates to a carrier signal-to-noise ratio measurement apparatus using a downlink preamble in a digital communication apparatus, and more particularly, to a plurality of cells or sectors in a digital communication apparatus using orthogonal frequency division multiplexing or orthogonal frequency division multiple access. The present invention relates to an apparatus for measuring a carrier signal-to-noise ratio using a preamble of a corresponding received signal, and performing handover and reverse power control using the same.

When the signal is transmitted through the multipath channel, the received signal generates inter-symbol interference (ISI) by multipath. In order to reduce the signal distortion caused by the ISI, the period of the symbol should be larger than the delay spread of the channel. Orthogonal Frequency Division Multiplexing (OFDM) (or Orthogonal Frequency Division Multiplexing Access (OFDMA)) has been proposed as a modulation scheme that can easily compensate for distortion in such a multipath channel. . Unlike a transmission method using a single carrier, the OFDM method transmits data using a plurality of subcarriers having mutual orthogonality. That is, the OFDM method performs a serial-to-parallel conversion on the input data by the number of subcarriers used for modulation, and modulates the converted data using the corresponding subcarriers, thereby maintaining the data transmission rate while maintaining the symbol period in each subcarrier. Lengthen by. Since subcarriers having mutual orthogonality are used, bandwidth efficiency is better than that of conventional frequency division multiplexing (FDM), and symbol periods are lengthened.

The modulation and demodulation process of the transmitting and receiving end in an OFDM device is equivalent to performing an Inverse Discrete Fourier Transform (IDFT) and a Discrete Fourier Transform (DFT), which is an Inverse Fast Fourier Transform (IFFT). Transform) and Fast Fourier Transform (FFT) for efficient implementation. In addition, when a guard interval longer than the delay spread of the channel is inserted for each transmitted symbol period, orthogonality between subcarriers is maintained.

In such an OFDM device, it is important to accurately measure the channel signal quality for power control or modulation and demodulation. Carrier to Interference and Noise Ratio (CINR), an example of such channel signal quality, plays an important role in controlling power and adjusting modulation and demodulation levels according to channel quality in adaptive power control or adaptive modulation and demodulation equipment. . In this case, the CINR is defined as a value obtained by dividing the total signal power of each subcarrier by the sum of noise and interference power, and may be a measure for determining channel quality in an OFDM device.

On the other hand, in today's cell-based mobile communication environment, handover means to automatically switch the current call channel to another call channel when moving from sector to cell or moving from one cell to another. It is necessary to ensure the mobility of the terminal. For the handover or for other reasons, the base station managing each cell or sector needs to check the channel state with the terminal from time to time. In addition, the terminal itself needs to manage the channel quality with the base station so that a better channel state can be maintained.

The present invention aims to propose a new technique for measuring carrier signal-to-noise ratio more easily and accurately from a preamble of a received signal in a digital communication device, and more effectively utilizing the carrier signal-to-noise ratio in various fields such as handover. .

The present invention has been made to improve the prior art as described above, and an object of the present invention is to more easily and accurately measure a carrier signal to noise ratio by using a preamble in measuring a carrier signal to noise ratio of a received signal.

Another object of the present invention is to enable more accurate preamble signal estimation using interpolation and averaging in estimating a preamble signal from a preamble symbol.

Another object of the present invention is to measure and compare carrier signal-to-noise ratios corresponding to a plurality of cells or a plurality of sectors, respectively, to perform a handover to ensure mobility of a user terminal.

It is still another object of the present invention to selectively extract signals of noise and interference components according to frequency reuse coefficients to measure more accurate carrier signal-to-noise ratios.

Another object of the present invention is to control the transmit power of the communication terminal to properly maintain the strength of the received signal at the base station using the measured carrier signal to noise ratio.

Another object of the present invention is to report a carrier signal-to-noise ratio measured by a communication terminal to a base station so that the base station can identify the channel state of the communication terminal and use it for scheduling.

In order to achieve the above object and solve the above-mentioned problems of the prior art, the carrier signal to noise ratio measuring apparatus according to an embodiment of the present invention corresponds to each of a plurality of cells or a plurality of sectors from a baseband frequency signal A preamble symbol obtainer for acquiring a preamble symbol, a signal estimator for estimating a preamble signal and a data signal from each preamble symbol, and a power value of the estimated data signal for each of the plurality of cells or the plurality of sectors A power calculator for calculating a power value of a noise signal from the preamble symbol and the estimated preamble signal, and for each of the plurality of cells or the plurality of sectors, a power value of the data signal and a power of the noise signal Carrier signal-to-noise ratio calculator that calculates carrier signal-to-noise ratio using values And a handover determination unit for comparing the plurality of carrier signal-to-noise ratios and determining whether a handover is performed.

In addition, the method for measuring a carrier signal-to-noise ratio using a preamble according to the present invention comprises the steps of obtaining a preamble symbol corresponding to a plurality of cells or a plurality of sectors from a baseband frequency signal, from the respective preamble symbols Estimating a preamble signal and a data signal, for each of the plurality of cells or the plurality of sectors, calculating a power value of the estimated data signal, and a power value of a noise signal from the preamble symbol and the estimated preamble signal Calculating a carrier signal-to-noise ratio using the power value of the data signal and the power value of the noise signal, for each of the plurality of cells or the plurality of sectors, and the plurality of carrier signal to Comparing the noise ratio to determine whether to perform a handover; And that is characterized.

For reference, the term "communication terminal" herein refers to a PDC (Personal Digital Cellular) phone, PCS (Personal Communication Service) phone, PHS (Personal Handyphone System) phone, CDMA-2000 (1X, 3X) phone, WCDMA (Wideband) CDMA phone, Dual Band / Dual Mode phone, Global Standard for Mobile (GSM) phone, Mobile Broadband System (MBS) phone, Digital Multimedia Broadcasting (DMB) terminal, Smart phone, OFDM Devices that may include communication functions, such as Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing), OFDMA (Orthogonal Frequency Division Multiplexing Access) communication terminals, personal digital assistants (PDAs), hand-held PCs, notebook computers, laptop computers, All types of mobile devices, including WiBro terminals, MP3 players, MD players, etc., and IMT-2000 (International Mobile Telecommunication-2000) terminals that provide international roaming services and extended mobile communications services. Handheld A portable electric and electronic device, which refers to a wireless communication device, is an orthogonal frequency division multiplexing access (OFDMA) module, a code division multiplexing access (CDMA) module, a bluetooth module, an infrared communication module (infrared data association), a wired or wireless LAN card. And a predetermined communication module such as a wireless communication device equipped with a GPS chip in order to enable location tracking through a global positioning system (GPS), and a microprocessor capable of performing a multimedia playback function may be provided. It is interpreted as a general term for a terminal capable of performing arithmetic operations.

In addition, the term "noise" (or "noise signal") used in the present invention, as well as undesired abnormal noise generated in a wireless communication environment, as well as between channels caused by overlapping signals due to overlapping frequency bands It is a concept including interference of, and is broadly interpreted as including all other signals included in the transmission and reception process in addition to the data signal to be originally transmitted. Therefore, "noise" and "noise and interference" in the present invention can be interpreted in the same sense.

Hereinafter, an apparatus for measuring a carrier signal-to-noise ratio using a downlink preamble (hereinafter, referred to as a "preamble") according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a schematic configuration of a general OFDM transceiver. As shown in the figure, a typical OFDM transceiver includes a serial / parallel converter, an FFT unit or an IFFT unit, and a frequency converter.

The serial-to-parallel converter of the transmitter converts serially input data streams into parallel data streams corresponding to the number of subcarriers, and inversely Fourier transforms each parallel data stream in an IFFT unit. In addition, the inverse Fourier transformed data is converted into serial data and transmitted through frequency conversion. The receiving side receives a signal transmitted through a wired or wireless channel and outputs data through a demodulation process, which is an inverse process of a transmitting end.

2 is a diagram illustrating a transmission structure of a preamble according to a segment according to an embodiment of the present invention. As shown in the figure, guard bands for reducing interference of adjacent frequency bands are configured on the left and right sides of the plurality of subcarriers, and a DC subcarrier, which is a null subcarrier, is configured. In addition, as shown in the figure, the preamble subcarriers within one segment are located at a predetermined interval ('3' in FIG. 2), and may be used for initial synchronization, cell search, frequency offset, and channel estimation.

3 is a diagram illustrating an apparatus for measuring carrier signal to noise ratio in a plurality of cells or a plurality of sectors according to an embodiment of the present invention.

As shown in the figure, the carrier signal-to-noise ratio measurement apparatus 302 for each of a plurality of cells or a plurality of sectors according to the present invention uses the FFT unit 301 to perform fast Fourier transform of a baseband received signal. After performing a predetermined preprocessing process to transition to the frequency domain.

The received signal transitioned to the frequency domain includes a preamble signal that can be used for initial synchronization and / or cell search, a pilot signal for channel and synchronization estimation, a data signal including actual data, a noise component, and the like. In the present invention, the carrier signal-to-noise ratio is measured using the preamble signal.

Since the preamble signal has a higher signal level than the data signal and the pilot signal, the signal can be easily acquired even in a bad channel environment. In the present invention, the accuracy of the preamble signal can be improved by using the carrier signal to noise ratio measurement. have.

In addition, according to the present invention, the plurality of FFT units 301 or the carrier signal-to-noise ratio measurement device 302 for each of a plurality of cells or a plurality of sectors may be divided into one FFT unit 301 or one using time division on hardware. One carrier signal-to-noise ratio measurement device 302 may be configured to share. For example, when the FFT unit 301 for transitioning the received signal into the frequency domain is configured as one, the predetermined time is divided into finely divided into a plurality of time zones, and the time zone is periodically assigned to each received signal. Time zones may be differentiated so as not to overlap each signal so as to pass through each of the FFT units. In this way, even one FFT unit 301 can easily transition the received signal for each of a plurality of cells or a plurality of sectors into the frequency domain.

The carrier signal-to-noise ratio measurement device 302 of the present invention can be installed in a digital communication device such as a communication terminal, and the digital communication device is based on at least one of the IEEE 802.16d / e standard, WiBro, and WiMAX. It may be a device.

On the other hand, the handover decision unit 303 receives and compares a carrier signal to noise ratio for each of a plurality of cells or a plurality of sectors from the plurality of carrier signal to noise ratio measuring devices 302 and compares the cells or cells having a better communication environment. Handover is performed to the sector. That is, according to the present invention, more active and efficient handover can be performed based on the carrier signal-to-noise ratio measured for each of a plurality of cells or a plurality of sectors.

4 is a block diagram illustrating an internal configuration of a carrier signal-to-noise ratio measuring device 302 performing handover according to an embodiment of the present invention.

As shown in the figure, the carrier signal to noise ratio measuring apparatus 302 includes a preamble symbol obtainer 401, a signal estimator 402, a power calculator 403, a carrier signal to noise ratio calculator 404, and A handover decision unit 405 is included.

The preamble symbol obtainer 401 obtains a preamble symbol (or preamble symbol signal) from a baseband frequency signal. As an example according to the present invention, the preamble symbol acquisition unit 401 multiplies the preamble code received from the base station by a plurality of subcarriers on a baseband frequency signal, which is an OFDM / OFDMA signal, or performs an exclusive OR operation, thereby performing a carrier OR A preamble symbol to be used for measuring the signal-to-noise ratio can be obtained.

Since the preamble symbol is previously regulated according to each channel mode, and the preamble symbol has orthogonality, only the preamble symbol can be easily extracted by multiplying the subcarrier of the received signal by a predetermined pattern of preamble sequences (codes). Can be. The preamble code is a value uniquely determined for each cell or sector and is transmitted from the base station that manages the cell or sector to the terminal.

As a specific example, when a preamble signal having a predetermined predetermined pattern is modulated using a binary phase shift keying scheme, the binary phase shift keying (BPSK) may transmit a transmission signal to a zero of a carrier wave. The preamble sequence corresponds to the complex '1' and '-1' because the phase and the π phase are transmitted in correspondence with the two phases. Therefore, if the preamble sequence is correlated with the received baseband signal, only a desired preamble symbol can be obtained.

The signal estimator 402 estimates a preamble signal and a data signal from the preamble symbol obtained by the preamble symbol acquirer 401. Since the preamble symbol obtained by the preamble symbol obtainer 401 is mixed with a signal of a preamble signal and a noise and interference component, the signal estimator 402 estimates only the preamble signal from the preamble symbol and based on the noise and interference component. We estimate the signal of. In addition, the signal estimator 402 estimates a data signal based on the preamble signal estimated value. More details regarding the operation of the signal estimator 402 will be described later with reference to FIG. 7.

The power calculator 403 calculates the power value of the data signal estimated by the signal estimator 402, and compares the preamble symbol obtained by the preamble symbol acquirer 401 and the preamble signal estimated by the signal estimator 402. Calculate the power value of the noise signal from the difference.

That is, the power calculator 403 calculates a power value by squaring the data signal and the noise signal, and calculates a power value of the data signal and a power value of the noise signal for a predetermined time with respect to a plurality of preamble symbols. By cumulative calculation, the accuracy of the carrier signal-to-noise ratio calculation can be further improved. More details regarding the operation of the power calculator 403 will be described later with reference to FIG. 8.

The carrier signal-to-noise ratio calculator 404 calculates the carrier signal-to-noise ratio using the power value of the data signal and the noise value calculated by the power calculator 403. The carrier signal-to-noise ratio is defined as the sum of the power of each subcarrier signal divided by the sum of the noise and the interference signal power. Therefore, the carrier signal-to-noise ratio calculation unit 404 divides the power value of the data signal into the power value of the noise signal. The carrier signal to noise ratio may be calculated by dividing by.

[Equation 1]

는 본 고안에서 추정된 프리앰블 신호를, p(n)은 프리앰블 신호 성분과 잡음 성분 이 섞인 프리앰블 심볼을, N은 각 단말 별 누적 파라미터를, G는 프리앰블 심볼을 이용하여 측정한 신호를 데이터 신호의 이득(gain)에 맞추기 위한 파라미터를 각각 나타낸다.Equation 1 expresses a calculation process of the carrier signal-to-noise ratio through the power calculator 403 and the carrier signal-to-noise ratio calculator 404. here,

Is a preamble signal estimated by the present invention, p (n) is a preamble symbol mixed with a preamble signal component and a noise component, N is a cumulative parameter for each terminal, and G is a signal measured using a preamble symbol. Represents a parameter for fitting to a gain.

In addition, n denotes a preamble symbol subcarrier index, and N denotes a maximum preamble subcarrier index that can be included in a downlink frame that can be determined based on power consumption. In case of multiple zones, n means a maximum value that can be included in a corresponding zone. do.

As another embodiment according to the present invention, a plurality of carrier signal-to-noise ratios corresponding to each of a plurality of cells or a plurality of sectors may be measured and used for handover.

That is, each cell or sector using the preamble code received from the baseband frequency signal corresponding to each cell or each sector from the baseband frequency signal corresponding to each of the plurality of cells or the plurality of sectors in the preamble symbol acquisition unit 401. For each preamble symbol can be obtained.

In addition, the signal estimator 402 estimates a corresponding preamble signal and data signal from each of the plurality of preamble symbols acquired by the preamble symbol acquisition unit 401. Thereafter, the power calculator 403 calculates the power value of the data signal estimated by the signal estimator 402 corresponding to each cell or each sector, and obtains a preamble symbol and a signal obtained by the preamble symbol obtainer 401. The power value of the noise signal is calculated from the difference of the preamble signal estimated by the estimator 402.

In addition, the carrier signal-to-noise ratio calculation unit 404 uses the power value of each cell or sector-specific data signal calculated by the power calculation unit 403 and the power value of the noise signal. Calculate the noise ratio.

The carrier signal-to-noise ratio measuring device 302 according to the present invention further includes a handover determiner 405, and the handover determiner 405 includes a plurality of carrier signal-to-carrier signals measured for each of the plurality of cells or a plurality of sectors. By comparing the noise ratio, it is determined whether the handover is executed or the handover is executed.

The handover determiner 405 compares carrier signal-to-noise ratios measured for a plurality of cells or a plurality of sectors, and performs a handover to a cell or sector having a better carrier signal-to-noise ratio. By doing so, it is possible to maintain a good communication service without interruption while moving, and to perform handover for improving the communication environment more actively and efficiently.

5 is a block diagram illustrating an internal configuration of a carrier signal to noise ratio measuring apparatus for controlling transmission power according to an embodiment of the present invention.

As shown in the figure, the carrier signal to noise ratio measuring apparatus includes a preamble symbol obtainer 501, a signal estimator 502, a power calculator 503, a carrier signal to noise ratio calculator 504, and a transmit power controller. 505.

The preamble symbol obtainer 501, the signal estimator 502, the power calculator 503, and the carrier signal-to-noise ratio calculator 504 follow the configuration described in the above embodiments.

In addition, the carrier signal to noise ratio measuring apparatus according to the present embodiment further includes a transmission power control unit 505, the transmission power control unit 505 based on the carrier signal to noise ratio, the optimum adapted to the changing communication environment Generate transmit power.

In general, when the distance between the terminal and the base station is far away, the attenuation of the signal increases, and conversely, when the distance is close, the signal attenuation is small, so power control is required to minimize the effect of the signal attenuation. Therefore, the transmission power control unit 505 according to the present invention adjusts the transmission power level according to the attenuation of the signal by using the carrier signal to noise ratio as a criterion of the attenuation of the signal.

6 is a block diagram illustrating an internal configuration of a carrier signal to noise ratio measuring apparatus for reporting a carrier signal to noise ratio according to an embodiment of the present invention.

As shown in the figure, the carrier signal to noise ratio measuring apparatus includes a preamble symbol acquisition unit 601, a signal estimator 602, a power calculator 603, a carrier signal to noise ratio calculator 604, and a carrier signal to noise ratio. The noise ratio report unit 605 is included.

The preamble symbol acquirer 601, the signal estimator 602, the power calculator 603, and the carrier signal-to-noise ratio calculator 604 follow the configuration described in the embodiments of FIGS. 4 and 5.

The carrier signal-to-noise ratio reporter 605 transmits the carrier signal-to-noise ratio measured in the cell or sector currently being serviced to the base station. In addition, the base station may use the reported carrier signal-to-noise ratio to schedule radio resource elements for an efficient communication environment.

The carrier signal-to-noise ratio reporter 605 converts the carrier signal-to-noise ratio to a base station by converting the carrier signal to noise ratio in a format (eg, dB scale, mean value, and variance) required by the base station. To utilize the carrier signal-to-noise ratio.

The base station can be adaptively changed in consideration of the carrier signal-to-noise ratio received from the radio resource element (eg, modulation scheme, coding scheme, code type, and coding rate). In addition, the base station may monitor the state of the reverse channel by using the carrier signal-to-noise ratio, obtain error correction information, and compare it with a predetermined value to instruct the terminal to increase or decrease the output according to the result. In this way, the base station can adjust the power of the reverse channel of the terminal to satisfy the appropriate call quality and maximize the capacity at the same time.

7 is a block diagram illustrating an internal configuration of the signal estimator 402 according to an embodiment of the present invention. As shown in the figure, the signal estimating unit 402 includes an interpolation calculating unit 701 and an average calculating unit 702.

The interpolation operation unit 701 receives a preamble symbol and generates a predetermined virtual preamble symbol set by performing an interpolation operation in the frequency domain. According to the present invention, since the preamble symbol obtained from the preamble symbol acquisition unit 401 is insufficient for the information amount (number) or other reasons for estimating the preamble signal, the preamble symbol is used more effectively by using the preamble symbol. What is needed is a method of estimating a preamble signal.

As an example of this, the interpolation operation unit 701 increases the number of symbols by copying the preamble symbols, and generates an intermediate value between the increased preamble symbols by using a predetermined interpolation operation, thereby making a virtual preamble suitable for estimating the preamble signal. Create a symbol set.

Examples of the interpolation method may include linear interpolation, secondary interpolation, cubic spline interpolation, and interpolation using a lowpass filter. The interpolation scheme may be appropriately selected depending on the requirements and the accuracy of the apparatus.

The average calculator 702 estimates the preamble signal by performing an average operation on the virtual preamble symbol set generated by the interpolation calculator 701 in a time domain. The virtual preamble symbol set includes a signal of noise and interference components in addition to the preamble signal, and the signal of noise and interference components is a kind of white noise, and generates a random probability distribution in frequency and magnitude of occurrence. Have Accordingly, when the average operation unit 702 adds and averages each preamble symbol included in the virtual preamble symbol set in the time domain, all signals of noise and interference components are removed and only a desired preamble signal can be easily extracted. Can be.

In addition, the gain mapping unit 703 finally estimates the data signal using the preamble signal. In general, the preamble signal differs in the data signal and the transmission power according to the structure of the channel or the structure of the OFDMA / OFDM symbol. Therefore, in order to estimate the data signal from the preamble signal, the gain mapping unit 703 adjusts the gain by multiplying the estimated preamble signal by an appropriate weighting.

For example, when the preamble signal level is higher than the data signal level by a predetermined decibel, the data signal may be estimated by appropriately mapping the gain so that the preamble signal level corresponds to the data signal level.

As described above, the signal estimator 402 can extract the data signal more accurately and easily by the operations of the interpolation operator 701, the average operator 702, and the gain mapping unit 703.

8 is a block diagram illustrating an internal configuration of a power calculation unit 403 according to an embodiment of the present invention. As shown in the figure, the power calculator 403 receives the data estimate value, the preamble signal estimate value and the preamble symbol, and outputs the data signal power value and the noise signal power value.

The power calculator 403 may extract a noise signal from the difference between the preamble symbol and the estimated preamble signal. That is, since the preamble symbol includes a preamble signal and noise and interference signals, only the noise and interference signals may be extracted by subtracting the estimated preamble signal from the preamble symbol (801). In addition, the power calculator 403 calculates the data signal power value and the noise signal power value by performing a cumulative operation 803 on the data signal and the noise signal through a square operation 802 for a predetermined time.

FIG. 9 is a block diagram illustrating an internal configuration of a power calculator based on a frequency reuse factor according to an embodiment of the present invention.

The frequency reuse coefficient is a parameter used to indicate how much the frequency efficiency is, and means how many bands are allocated to one cell or one sector by dividing the entire frequency band. Used as

In the present invention, in calculating the magnitudes of the noise and interference components, different methods are applied according to the frequency reuse coefficient.

That is, when the frequency reuse coefficient is not '1', different frequency bands may be used in one cell or sector area, and thus, only the noise and interference components of the location where the preamble is transmitted in the structure of FIG. 2 need to be considered.

On the other hand, when the frequency reuse coefficient is '1', since the same frequency band may be used in one cell or sector area, the symbol values of positions where the preamble is not transmitted in the structure of FIG. It includes. Therefore, when the frequency reuse factor is '1', noise and interference components should be included in the carrier signal-to-noise ratio calculation. That is, according to the present invention, when the frequency reuse coefficient is '1', the power calculator further includes the power value of the symbols excluding the preamble symbol in the power value of the noise signal.

As shown in the figure, the selector 901 closes or opens the switch according to the frequency reuse coefficient, thereby performing an operation of adding or excluding symbol values at positions where the preamble is not transmitted as noise and interference components.

Equation 2 below is an equation for calculating a carrier signal-to-noise ratio when the frequency reuse coefficient is '1'.

[Equation 2]

는 본 고안에서 추정된 프리앰블 신호이고, p(n)은 프리앰블 신호 성분과 잡음 성분이 섞인 변조된 프리앰블 심볼(modulation DL preamble symbol)이고, p(m)은 잡음 성분이 섞인 변조되지 않은 프리앰블 심볼(un-modulation DL preamble symbol)이며, G는 프리앰블 심볼을 이용하여 측정한 신호를 데이터 신호의 이득(gain)에 맞추기 위한 파라미터를 나타낸다. 또한, n은 프리앰블 심볼 부반송파 인덱스를 나타내며, N은 전력소모를 기준으로 결정될 수 있는 다운링크 프레임 내에서 가질 수 있는 최대 프리앰블 부반송파 인덱스를, M은 누적 파라미터를 각각 나타낸다. 또한, p(m)은 좌측 보호 구간(Left Guard), 우측 보호 구간(Right Guard), 및 DC 부반송파는 제외한다.here,

Is a preamble signal estimated in the present invention, p (n) is a modulated DL preamble symbol mixed with a preamble signal component and a noise component, and p (m) is an unmodulated preamble symbol with a mixed noise component ( un-modulation DL preamble symbol), and G represents a parameter for fitting a signal measured using the preamble symbol to the gain of the data signal. In addition, n denotes a preamble symbol subcarrier index, N denotes a maximum preamble subcarrier index that can be included in a downlink frame that can be determined based on power consumption, and M denotes a cumulative parameter, respectively. In addition, p (m) excludes the left guard period, the right guard period, and the DC subcarrier.

Comparing [Equation 2] to [Equation 1], in the denominator representing the power of the noise and interference component signals, Equation 2 is the p (m) signal, which means the symbol values at the positions where the preamble is not transmitted. The power value of is further included. This means that when the frequency reuse factor is '1', the power value of the symbols except for the preamble symbol is further included in the power value of the noise signal.

As such, according to the present invention, a signal of noise and interference components may be selectively extracted according to frequency reuse coefficients, and thus a carrier signal-to-noise ratio may be measured more accurately.

10 is a block diagram illustrating an internal configuration of a carrier signal to noise ratio calculator 404 according to an embodiment of the present invention. The carrier signal-to-noise ratio represents the ratio of the carrier to the noise in the signal transmission system. In the OFDM / OFDMA device according to the present invention, the carrier-to-noise and interference ratio (CINR) can be measured as an example of the carrier signal-to-noise ratio. have. The CINR, which is generally expressed in decibels (dB), is defined as a value obtained by dividing the sum of signal powers of subcarriers by the sum of noise and interference powers. In the present invention, the power value of the data signal and the power value of the noise signal may be used.

In order to calculate the CINR, the carrier signal to noise ratio calculator 404 takes the noise signal power value as the inverse (1001) as shown in the figure and inputs it to the multiplier 1002 together with the data signal power value.

On the other hand, as another example according to the present invention, the carrier signal to noise ratio measuring apparatus for performing the handover using the preamble and the frequency reuse coefficient is a preamble symbol respectively corresponding to a plurality of cells or a plurality of sectors from the baseband frequency signal A preamble symbol obtainer for acquiring a signal, a signal estimator for estimating a preamble signal and a data signal from each preamble symbol, and a first power value of the estimated data signal for each of the plurality of cells or the plurality of sectors A power calculation unit for calculating a second power value of a noise signal from the preamble symbol and the estimated preamble signal, and for each of the plurality of cells or the plurality of sectors, the first power value and the second power A carrier signal-to-noise ratio calculation unit that calculates a carrier signal-to-noise ratio using a value, and A handover determiner configured to determine whether a handover is executed by comparing the plurality of carrier signal-to-noise ratios, and the power calculator determines a position where the preamble symbol is not transmitted according to a frequency reuse factor And determine whether to further add a third power value of the symbol of to the second power value.

11 is a flowchart illustrating a method of measuring carrier signal-to-noise ratios corresponding to a plurality of cells or a plurality of sectors, respectively, using a preamble according to the present invention.

In step S1101, a preamble symbol corresponding to a plurality of cells or a plurality of sectors is obtained from the baseband frequency signal.

As an example according to the present invention, in this step, a predetermined preamble code received from a base station is multiplied by a plurality of subcarriers on a baseband frequency signal, which is an OFDM / OFDMA signal, or performed an exclusive OR operation, thereby performing a carrier signal-to-noise ratio. It is possible to obtain a preamble symbol to be used to measure.

Since the preamble symbol is previously regulated according to each channel mode, and the preamble symbol has orthogonality, only the preamble symbol can be easily extracted by multiplying the subcarrier of the received signal by a predetermined pattern of preamble sequences (codes). Can be.

In step S1102, a preamble signal and a data signal are estimated from the respective preamble symbols. Since the preamble symbol obtained in step S1101 is a mixture of a preamble signal, a signal of noise and an interference component, in this step, the preamble signal is estimated from the preamble symbol.

According to the present invention, step S1102 may be performed to generate a virtual preamble symbol set by performing an interpolation operation on the preamble symbol in a frequency domain, and to perform an average operation on the virtual preamble symbol set in a time domain. Estimating the preamble signal.

Since the preamble symbol obtained from step S1101 is generally insufficient in information quantity (number) or other reasons for estimating the preamble signal, a method of more effectively estimating the preamble signal using the preamble symbol. Is required.

In the generating of the virtual preamble symbol set, the preamble symbol is received, the preamble symbol is copied, the number of symbols is increased, and an intermediate value between the extended preamble symbols is generated by using a predetermined interpolation operation. Generate a virtual preamble symbol set suitable for estimating.

Examples of the interpolation method may include linear interpolation, secondary interpolation, cubic spline interpolation, and interpolation using a lowpass filter, and the like. May be appropriately selected depending on the requirements and accuracy of the device.

In the estimating of the preamble signal, the virtual preamble symbol set is averaged in a time domain to estimate the preamble signal. The virtual preamble symbol set includes a signal of noise and interference components in addition to the preamble signal, and the signal of noise and interference components is a kind of white noise, and generates a random probability distribution in frequency and magnitude of occurrence. Have Accordingly, in this step, when each preamble symbol included in the virtual preamble symbol set is added and averaged in the time domain, all signals of noise and interference components are suppressed and only a desired preamble signal can be easily extracted.

In addition, in this step, in order to finally estimate the data signal using the preamble signal, the gain is adjusted by multiplying the preamble signal estimate by an appropriate weighting. For example, when the preamble signal level is higher than the data signal level by a predetermined decibel, the data signal may be estimated by appropriately mapping the gain so that the preamble signal level corresponds to the data signal level.

In operation S1103, the estimated data signal, the preamble signal, and the preamble symbol are received to calculate a data signal power value and a noise signal power value. That is, in this step, for each of a plurality of cells or a plurality of sectors, a power value of the data signal estimated in step S1102 is calculated, and a noise signal is obtained from the estimated preamble signal and the preamble symbol obtained in step S1101. Calculate the power value of.

Since the preamble symbol includes a preamble signal and noise and interference signals, only the noise and interference signals may be extracted by subtracting the estimated preamble signal from the preamble symbol. In addition, in the present step, the data signal power value and the noise signal power value are calculated by performing an accumulation operation for a predetermined time through the squared operation on the extracted data signal and the noise signal.

In addition, in this step, according to the frequency reuse coefficient, which is a parameter indicating how many cells the entire frequency band is divided into, that is, how much the frequency efficiency is, the symbol values at positions where the preamble is not transmitted are added as noise and interference components, Or may be excluded.

That is, when the frequency reuse factor is '3', different frequency bands may be used in each cell region, and thus, only the noise and interference components of the location where the preamble is transmitted in the structure of FIG. 2 need to be considered.

On the other hand, when the frequency reuse coefficient is '1', since the same frequency band may be used in all regions, symbol values at positions where the preamble is not transmitted in the structure of FIG. 2 also include noise and interference components. Therefore, when the frequency reuse coefficient is '1', the noise and interference components should be included in the carrier signal to noise ratio calculation. That is, according to the present invention, when the frequency reuse coefficient is '1', the power calculator further includes the power value of the symbols excluding the preamble symbol in the power value of the noise signal.

In step S1104, a carrier signal-to-noise ratio is calculated for each of the plurality of cells or the plurality of sectors by using the power value of the data signal and the power value of the noise signal calculated in step S1103. That is, since the carrier signal-to-noise ratio is defined as a value obtained by dividing the total of each subcarrier signal power by the total of noise and interference signal power, in this step, the power value of the data signal is divided by the power value of the noise signal, The signal-to-noise ratio can be calculated.

In step S1105, a handover execution is determined by comparing a plurality of carrier signal-to-noise ratios measured for each of a plurality of cells or a plurality of sectors in step S1104.

That is, in this step, the carrier signal-to-noise ratio measured for each of a plurality of cells or a plurality of sectors is compared to perform handover to a cell or sector having a better carrier signal-to-noise ratio. By doing so, it is possible to maintain a good communication service without interruption while moving, and to perform handover for improving the communication environment more actively and efficiently.

12 is a flowchart illustrating a method of measuring a carrier signal-to-noise ratio using a preamble in a serviced cell according to another embodiment of the present invention.

In step S1201, a preamble symbol is obtained from a baseband frequency signal in a cell or sector currently being serviced. In this step, a predetermined preamble code received from the base station is multiplied by a plurality of subcarriers on a baseband frequency signal, which is an OFDM / OFDMA signal, or by performing an exclusive OR operation (XOR), to measure a carrier signal to noise ratio. A preamble symbol can be obtained.

In step S1202, the preamble signal and the data signal are estimated from the preamble symbol. Since the preamble symbol obtained in step S1201 is a mixture of a preamble signal and a signal of noise and interference components, only a preamble signal is estimated in the preamble symbol.

According to the present invention, step S1202 may be performed to generate a virtual preamble symbol set by performing an interpolation operation on the preamble symbol in a frequency domain and to perform an average operation on the virtual preamble symbol set in a time domain. Estimating the preamble signal.

In the generating of the virtual preamble symbol set, the preamble symbol is input, the number of symbols is increased by copying the preamble symbols, and an intermediate value between the extended preamble symbols is generated using a predetermined interpolation operation to estimate the preamble signal. Generate a virtual preamble symbol set suitable for the following.

In the estimating of the preamble signal, the virtual preamble symbol set is averaged in a time domain to estimate the preamble signal. The virtual preamble symbol set includes a signal of noise and interference components in addition to the preamble signal, and the signal of noise and interference components is a kind of white noise, and generates a random probability distribution in frequency and magnitude of occurrence. Have Therefore, in this step, when each preamble symbol included in the virtual preamble symbol set is added and averaged in the time domain, all signals of noise and interference components are suppressed and only a desired preamble signal can be easily extracted. have.

In addition, in this step, in order to finally estimate the data signal using the preamble signal, the gain is adjusted by multiplying the preamble signal estimate by an appropriate weighting.

In operation S1203, the estimated data signal, the preamble signal, and the preamble symbol are received to calculate a data signal power value and a noise signal power value. That is, in this step, the power value of the data signal estimated in step S1202 is calculated, and the power value of the noise signal is calculated from the estimated preamble signal and the preamble symbol obtained in step S1201.

In addition, in this step, according to the frequency reuse coefficient, which is a parameter indicating how many cells are allocated to the entire frequency band, that is, how much the frequency efficiency is, the symbol values at the positions where the preamble is not transmitted are added as noise and interference components. Or may be excluded.

In step S1204, the carrier signal to noise ratio is calculated using the power value of the data signal and the noise value of the data signal calculated in step S1203. That is, since the carrier signal-to-noise ratio is defined as a value obtained by dividing the total of each subcarrier signal power by the total of noise and interference signal power, in this step, the power value of the data signal is divided by the power value of the noise signal, The signal-to-noise ratio can be calculated.

In step S1205, efficient transmission power is generated according to the carrier signal to noise ratio measured from steps S1201 to S1204. In general, when the distance between the terminal and the base station is far away, the attenuation of the signal increases, and conversely, when the distance is close, the signal attenuation is small, so power control is required to minimize the effect of the signal attenuation. Therefore, in this step, the transmission power level is efficiently adjusted according to the attenuation of the signal by using the carrier signal to noise ratio as a criterion for the attenuation of the signal.

In step S1206, the carrier signal-to-noise ratio measured from steps S1201 to S1204 is reported on the uplink to the base station associated with the cell or sector currently being served. In addition, the base station may use the reported carrier signal-to-noise ratio to schedule radio resource elements for an efficient communication environment.

In this step, the carrier signal to noise ratio is converted and reported to the base station in a format (eg, dB scale, mean value, and variance) required by the base station, thereby utilizing the carrier signal to noise ratio. To help. In addition, the base station may adaptively change the radio signal element (eg, modulation scheme, coding scheme, code type, coding rate, etc.) in consideration of the carrier signal-to-noise ratio received.

So far, a method of measuring a carrier signal-to-noise ratio using the preamble according to the present invention has been described, and the above-mentioned details of the embodiments of FIGS. 1 to 10 can be applied to the present embodiment as it is. The contents will be omitted.

The method for measuring a carrier signal-to-noise ratio using the preamble according to the present invention can be implemented in the form of program instructions that can be executed by various computer means and recorded in a computer-readable medium. The computer readable medium may include program instructions, data files, data structures, etc. alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the present invention, or may be known and available to those skilled in computer software. Examples of computer-readable recording media include magnetic media such as hard disks, floppy disks, and magnetic tape, optical media such as CD-ROMs, DVDs, and magnetic disks, such as floppy disks. Magneto-optical media, and hardware devices specifically configured to store and execute program instructions, such as ROM, RAM, flash memory, and the like. The medium may be a transmission medium such as an optical or metal wire, a waveguide, or the like including a carrier wave for transmitting a signal specifying a program command, a data structure, or the like. Examples of program instructions include not only machine code generated by a compiler, but also high-level language code that can be executed by a computer using an interpreter or the like. The hardware device described above may be configured to operate as one or more software modules to perform the operations of the present invention, and vice versa.

13 is a graph illustrating a simulation result of measuring CINR using a preamble according to an embodiment of the present invention.

In this simulation, when the frequency reuse factor is '3', the UE is moving at a speed of 3km / h in Pedestrian-A among AWGN (Additive White Gaussian Noise) and channel models of the International Telecommunication Union Radiocommunication Sector (ITU-R). Each experiment was conducted in the situation. In addition, the FFT size applied in the simulation is 1024, and averaged about 3000 measurement results.

Meanwhile, 'Target CINR' shown on the graph represents a target CINR value, and 'Est. CINR 'represents a measurement result by applying a CINR measurement algorithm using a preamble according to the present invention. In addition, ‘Est. Error "means" Target CINR "and" Est. A value representing the difference from CINR ', which indicates a measurement error of the CINR measurement algorithm according to the present invention. In addition, the horizontal axis represents Eb / No (ratio of signal power and noise power per data bit) [dB], and the vertical axis represents actual measured value and error value. Therefore, a graph in the form of a straight line in which the values of the horizontal axis and the vertical axis coincide with each other to have an error of '0' or a constant value of the error will be most preferable.

As shown in the figure, both the experimental results in the AWGN condition (reference numeral 1301) and the experimental results in the situation where the terminal is moving at a speed of 3 km / h in Pedestrian-A (reference symbol 1302) are 'Est . Since the value of Error 'is small and nearly constant close to' 0 ', it can be seen that the algorithm of the present invention shows excellent simulation results in measuring the carrier signal-to-noise ratio.

In the present invention as described above has been described by the specific embodiments, such as specific components and limited embodiments and drawings, but this is provided to help a more general understanding of the present invention, the present invention is not limited to the above embodiment. For those skilled in the art to which the present invention pertains, various modifications and variations are possible.

Accordingly, the spirit of the present invention should not be limited to the described embodiments, and all of the equivalents and equivalents of the claims, as well as the following claims, will fall within the scope of the present invention. .

According to the present invention, the carrier signal-to-noise ratio can be measured more easily and accurately by using the preamble in measuring the carrier signal-to-noise ratio of the received signal.

In addition, according to the present invention, it is possible to efficiently estimate the preamble signal from the preamble symbol by using interpolation and averaging.

In addition, according to the present invention, by performing a handover between cells or sectors by measuring and comparing carrier signal-to-noise ratios corresponding to a plurality of cells or a plurality of sectors, it is possible to maintain a good communication service without interruption even during movement.

In addition, according to the present invention, it is possible to selectively extract the signal of the noise and interference components according to the frequency reuse coefficient, thereby measuring the carrier signal-to-noise ratio more accurately.

In addition, according to the present invention, by controlling the transmission power of the communication terminal using the carrier signal to noise ratio in the base station, it is possible to appropriately adjust the strength of the signal received from the communication terminal.

In addition, according to the present invention, it is possible to further improve the communication quality by generating an optimal transmission power adapted to the changing communication environment using the measured carrier signal-to-noise ratio.

In addition, according to the present invention, by reporting the carrier signal to noise ratio measured in the communication terminal, it is possible to control the base station to check the channel state of the communication terminal to properly respond to the channel quality degradation.

Claims (12)

A preamble symbol obtaining unit obtaining a preamble symbol corresponding to each of a plurality of cells or a plurality of sectors from the baseband frequency signal; A signal estimator for estimating a preamble signal and a data signal from each preamble symbol; A power calculator configured to calculate a power value of the estimated data signal for each of the plurality of cells or the plurality of sectors, and calculate a power value of a noise signal from the preamble symbol and the estimated preamble signal; A carrier signal-to-noise ratio calculator for calculating a carrier signal-to-noise ratio using the power value of the data signal and the power value of the noise signal for each of the plurality of cells or the plurality of sectors; And A handover decision unit which determines whether a handover is executed by comparing the plurality of carrier signal-to-noise ratios. Digital communication device comprising a. A preamble symbol obtainer obtaining a preamble symbol from a baseband frequency signal; A signal estimator for estimating a preamble signal and a data signal from the preamble symbol; A power calculator configured to calculate a power value of a noise signal from the preamble symbol and the estimated preamble signal, and calculate a power value of the estimated data signal; A carrier signal-to-noise ratio calculator which calculates a carrier signal-to-noise ratio using the power value of the data signal and the power value of the noise signal; And A transmit power control unit that generates transmit power in accordance with the carrier signal to noise ratio Digital communication device comprising a. A preamble symbol obtainer obtaining a preamble symbol from a baseband frequency signal; A signal estimator for estimating a preamble signal and a data signal from the preamble symbol; A power calculator configured to calculate a power value of a noise signal from the preamble symbol and the estimated preamble signal, and calculate a power value of the estimated data signal; A carrier signal-to-noise ratio calculator which calculates a carrier signal-to-noise ratio using the power value of the data signal and the power value of the noise signal; And Carrier signal to noise ratio report unit for transmitting the carrier signal to noise ratio to the base station Digital communication device comprising a. The method of claim 1, And the preamble signal obtaining unit obtains a preamble symbol corresponding to each of the plurality of cells or the plurality of sectors using time division from one fast Fourier transform device. The method according to any one of claims 1 to 3, The baseband frequency signal is an orthogonal frequency division multiplexing (OFDM) signal or an orthogonal frequency division multiplexing access (OFDMA) signal. The method according to any one of claims 1 to 3, The signal estimating unit An interpolation calculator configured to generate a virtual preamble symbol set by performing an interpolation operation on the preamble signal in a frequency domain; And An average operation unit estimating the preamble signal by performing an average operation on the virtual preamble symbol set in a time domain Digital communication device comprising a. The method according to any one of claims 1 to 3, The signal estimator adjusts the gain of the estimated preamble signal to estimate the data signal. Digital communication device comprising a. The method of claim 1, When the frequency reuse factor is '1', the power calculation unit further includes a power value of a symbol at a position where the preamble symbol is not transmitted, in the power value of the noise signal. . The method of claim 3, And the base station adjusts the reported carrier signal to noise ratio using the carrier signal to noise ratio. The method of claim 9, And wherein the radio resource element comprises at least one of a modulation scheme, a coding scheme, a code type, and a coding rate. The method according to any one of claims 1 to 3, The device is a digital communication device, characterized in that the device based on at least one of the IEEE 802.16d / e standard, WiBro, and WiMAX. A preamble symbol obtaining unit obtaining a preamble symbol corresponding to each of a plurality of cells or a plurality of sectors from the baseband frequency signal; A signal estimator for estimating a preamble signal and a data signal from each preamble symbol; A power calculator configured to calculate a first power value of the estimated data signal for each of the plurality of cells or the plurality of sectors, and calculate a second power value of the noise signal from the preamble symbol and the estimated preamble signal ; A carrier signal-to-noise ratio calculator for calculating a carrier signal-to-noise ratio using the first power value and the second power value for each of the plurality of cells or the plurality of sectors; And A handover determination unit configured to compare the plurality of carrier signal-to-noise ratios and determine whether handover is performed between the plurality of cells or the plurality of sectors, And the power calculator determines whether to further add a third power value of a symbol at a position at which the preamble symbol is untransmitted to the second power value according to a frequency reuse factor. .

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