KR20040107566A - estimater for frequency offset of Multi-carrier transmission receiving system and a method thereof - Google Patents

Abstract

PURPOSE: A frequency offset estimator of a multi-carrier receiver and an estimating method thereof are provided to exclude interference due to a multi-path and estimate a frequency offset of a broad section by using TPS(Transition Parameter Signaling) to estimate a frequency offset. CONSTITUTION: A FFT(Fast Fourier Transform) unit(200) transforms a received signal to a frequency domain signal. A TPS(Transmission Parameter Signaling) error detector(250) is used for comparing a transmission information signal with the transformed frequency domain signal and determining a shifting state of the transmission information signal on the basis of the compared result. The received signal is a TDS-OFDM(Time Domain Synchronous-Orthogonal Frequency Division Multiplexing) signal.

Description

Estimator for frequency offset of Multi-carrier transmission receiving system and a method

The present invention relates to an apparatus and method for estimating a frequency offset of a multi-carrier receiver. More particularly, the present invention relates to a transmitter transmission scheme such as channel coding and modulation scheme embedded in a TDS-OFDM (Time Domain Synchronous-Orthogonal Frequency Division Multiplexing) signal. The present invention relates to a frequency offset estimating apparatus and a method for calculating a frequency offset by using a transmission parameter signaling (TPS) used for parameter transmission related to the present invention.

1 is a frequency domain frame structure of a TDS-OFDM. TPS inserted in each symbol set is used for parameter transmission related to a transmitter transmission scheme such as channel coding and modulation scheme. Nine TPS carriers are used for every 1248 symbol sets, and all TPS carriers in the same symbol transmit the same information bits.

However, in general, the frequency difference between the oscillator and the frequency offset occurring in the Doppler shift in the channel is one factor that degrades the reception performance of the communication system. Therefore, every communication system requires a frequency synchronization process, and the synchronization performance greatly affects the overall receiver performance.

2A is a block diagram of an apparatus for estimating a frequency frequency offset using a conventional guard interval. The frequency offset estimation apparatus of FIG. 2A includes a delay unit 10 and a phase tracker 20. The delay unit 10 receives the multi-carrier signal and transmits the delayed signal by a period of one symbol included in the multi-carrier signal. The phase tracker 20 receives the transmitted multicarrier and the delayed multicarrier to estimate the frequency offset through a predetermined process. 2b shows a multi-carrier signal frame. Referring to FIG. 2B, the multicarrier signal frame includes a synchronization signal PN, a guard interval GI, and a data symbol. The guard interval has the same signal as the predetermined section at the end of the data symbol section. The delay in the delay unit 10 is for comparing the guide interval at position a with the signal at position b. The channel estimator compares the phase of position a and the phase of position b to calculate an average frequency offset of the OFM die section.

However, the method of calculating the frequency offset using the guard interval is not accurate because the calculated frequency offset is not calculated for each symbol, and it is possible only when the range of frequency offsets that can be calculated due to the characteristics of the phase is within 2Л. Therefore, the maximum frequency offset that can be calculated is half of the frequency interval between subcarriers, and thus there is a problem that the range of the frequency offset that can be calculated is narrow. To solve this problem, a method of calculating frequency offset using synchronization has been proposed.

3A is a block diagram of an apparatus for estimating frequency offset using a synchronization signal. The frequency offset estimation apparatus of FIG. 3A includes a correlator 110, a peak detector 120, a delay unit 130, and a phase tracker 140. The correlation unit 110 receives a reference synchronization signal that is the same signal as the synchronization signal of the multicarrier signal and the multicarrier signal before transmission and obtains a correlation value. The peak detector 120 receives the correlation value and detects the position of the peak. The delay unit 130 matches the position of the peak detected by the peak detection unit 120 with the synchronization signal included in the multicarrier signal. The phase tracking unit 140 obtains a phase difference by comparing the synchronization signal of the reference synchronization signal and the signal transmitted from the delay unit 130. Since this method compares each symbol of the synchronization signal, a relatively accurate frequency offset can be obtained, and the range of the frequency offset that can be calculated is also wide.

However, in the process of calculating the frequency offset using the synchronization signal in the multipath environment illustrated in FIG. 3B, when the offset is estimated by comparing the PNs of c and f, d or e are the synchronization signals of c and PN and f. Due to the influence of the comparison process, there is a problem in that frequency offset determination performance deteriorates in a multipath environment.

Conventionally, in order to solve this problem, a method of obtaining a final frequency offset by obtaining all frequency offsets in multiple paths has been used. However, this has a problem that the system implementation is complicated and expensive.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to effectively compensate for a wide range of frequency offsets with a small amount of calculation by using a TPS used for parameter transmission related to a transmitter transmission scheme. An apparatus and method for frequency offset estimation of a multi-carrier receiver can be provided.

1 is a frequency domain frame structure of a TDS-OFDM,

2A to 2B are block diagrams of a frequency frequency offset estimating apparatus using a conventional guard interval,

2b is a TDS-OFDM time domain frame structure according to FIG. 2a,

3A is a block diagram of an apparatus for estimating frequency offset using a synchronization signal;

3b is a TDS-OFDM time domain frame structure of a multipath environment according to FIG. 3a,

4 is a block diagram according to an embodiment of an apparatus for estimating frequency offset of a multicarrier receiver according to the present invention;

5 is a block diagram according to another embodiment of an apparatus for estimating frequency offset of a multicarrier receiver according to the present invention;

6 is a block diagram according to another embodiment of an apparatus for estimating frequency offset of a multicarrier receiver according to the present invention;

7 is a flowchart illustrating a method of operating a frequency offset estimation apparatus of a multi-carrier receiver according to FIG. 4;

8 is a flowchart illustrating a method of operating a frequency offset estimation apparatus of a multicarrier receiver according to FIG. 5;

9 is a flowchart illustrating a method of operating a frequency offset estimation apparatus of a multi-carrier receiver according to FIG. 6.

Explanation of symbols on the main parts of the drawings

200: fast Fourier transform unit 250: TPS position error detection unit

320: TPS position detector

In accordance with an aspect of the present invention, a frequency offset estimation apparatus for a multicarrier receiver includes: a fast Fourier transform unit for converting a transmitted signal into a signal in a frequency domain, and comparing a signal in the frequency domain with a transmission information signal; And a transmission information signal error detector for determining a degree of movement of the transmission information signal position. In this case, the transmitted signal is a TDS-OFDM (Time Domain Synchronous-Orthogonal Frequency Division Multiplexing) signal, and the transmission information signal is preferably TPS (Trensmission Parameter Signaling) included in the TDS-OFDM signal.

In another embodiment, the apparatus for frequency offset estimation of a multi-carrier receiver according to the present invention includes a fast Fourier transform unit for converting a transmitted signal into a signal in a frequency domain, and a current symbol and a previous symbol for a signal converted in the frequency domain. And a transmission information signal position detection unit for detecting the position of the minimum value having the smallest power difference, and a transmission information signal error detection unit for comparing the detected position and the transmission information signal position to determine the degree of movement of the transmission information signal position. The transmission information signal position detection unit may include a delay unit receiving the frequency domain signal converted by the fast Fourier transform unit and delaying the signal by one symbol length, a first power estimation unit estimating power of the delayed signal, and the high speed signal. A second power estimator for estimating the power of the signal received by the Fourier transform unit, a subtractor for calculating a difference between the power transmitted from the first power estimator and the signal transmitted from the second power estimator, and the subtractor And a section moving adder for calculating a sum in a predetermined section of the values calculated in step S, and a minimum value position detector for detecting a section in which the value calculated in the section moving adder is minimum.

In another embodiment, the transmission information signal position detector may include a delay unit configured to receive the frequency domain signal converted by the fast Fourier transform unit and delay the signal by one symbol length, and to estimate power of the delayed signal. An estimator, a second power estimator for estimating the power of the signal received by the fast Fourier transform unit, a subtraction for calculating a difference between the power transmitted from the first power estimator and the signal transmitted from the second power estimator A divider for calculating a sum of the power transmitted from the first power estimator and the signal transmitted from the second power estimator, and a divider for dividing a value calculated by the subtractor by a value calculated by the adder And a section moving adder for calculating a sum in a predetermined section of the values calculated by the divider and a section for which the value calculated by the section moving adder is minimum. It can be composed of a minimum value position detection.

Here too, the transmitted signal is a TDS-OFDM (Time Domain Synchronous-Orthogonal Frequency Division Multiplexing) signal, and the transmission information signal is preferably TPS (Trensmission Parameter Signaling) included in the TDS-OFDM signal.

In the operation method of the frequency offset estimation apparatus of a multi-carrier receiver according to the present invention, a fast Fourier transform step of converting a transmitted signal into a signal in the frequency domain and a transmission information by comparing the transmission information signal and the signal in the converted frequency domain And a transmission information signal error detecting step of determining a degree of signal position movement.

In this case, the transmitted signal is a TDS-OFDM (Time Domain Synchronous-Orthogonal Frequency Division Multiplexing) signal, and the transmission information signal is preferably TPS (Trensmission Parameter Signaling) included in the TDS-OFDM signal.

According to another aspect of the present invention, there is provided a method of estimating a frequency offset of a multicarrier receiver, comprising: a fast Fourier transform step of converting a transmitted signal into a signal in a frequency domain; And a transmission information signal position detection step of detecting a position of the minimum value having the smallest power difference, and a transmission information signal error detection step of determining a degree of movement of the transmission information signal position by comparing the detected position with the transmission information signal position.

The first method of the transmission information signal position detection step includes a delay step of receiving the frequency domain signal converted in the fast Fourier transform step and delaying the signal by one symbol length, and a first power estimation step of estimating power of the delayed signal. A second power estimating step of estimating the power of the signal received in the fast Fourier transform step, calculating a difference between the power transmitted in the first power estimating step and the signal transmitted in the second power estimating step, Calculating a sum in a predetermined section of the calculated values in the step of calculating a difference, and detecting a minimum value position detecting a section in which the calculated sum is minimum.

Another method of the transmission information signal position detection step may include: a delay step of receiving the frequency domain signal converted in the fast Fourier transform step and delaying the signal by one symbol length; first power estimating power of the delayed signal; An estimating step, a second power estimating step of estimating the power of the signal received in the fast Fourier transform step, calculating a difference between the power transmitted in the first power estimating step and the signal transmitted in the second power estimating step Calculating a sum of the power transmitted in the first power estimation step and the signal transmitted in the second power estimation step, dividing the calculated difference by the calculated sum, and calculating the ratio of the sum and the difference; Calculating a sum in a predetermined section of the ratio values and detecting a minimum value position for detecting a section in which the sum of the predetermined sections is minimum Steps.

Herein, the transmitted signal is a TDS-OFDM signal and the transmission information signal is TPS (Trendmission Parameter Signaling) included in the TDS-OFDM signal.

Hereinafter, with reference to the drawings will be described the present invention in more detail.

4 is a block diagram according to an embodiment of a frequency offset estimating apparatus according to the present invention. Referring to the drawings, the frequency offset estimating apparatus is composed of a fast Fourier transform unit 200 and a TPS position error detector 250. The offset estimator of FIG. 4 may be used when both the magnitude and position of the TPS signal are known, and the fast Fourier transform unit 200 receives the signal and converts the signal into a frequency domain. The TPS position error detector 250 estimates the frequency offset by comparing the TPS signal with the converted signal in the frequency domain and detecting the changed TPS position. Since the TPS signal includes a position and a value, it is easy to determine the degree of change of the TPS signal including the frequency offset.

5 is a block diagram according to this embodiment of an offset estimation apparatus according to the present invention. 5 is a case where the position information of the TPS is known, but the size of the TPS is not known, the fast Fourier calculating unit 300, the TPS position detecting unit 320, and the TPS position error detecting unit 350 are included. The fast Fourier transform unit 300 receives the time domain signal and converts it into the frequency domain. The TPS position detector 320 receives the signal converted into the frequency domain from the fast Fourier transform unit and detects the position of the TPS. In detail, the TPS position detector 320 includes a first power estimator 321, a delay unit 322, a second power estimator 323, a subtractor 324, an interval shift adder 328, and a minimum value position detector. 329. The first power calculator 321 calculates power of a signal calculated by Fast Fourier. In general, TPS uses error-resistant properties such as BPSK and QPSK, while user data uses high bit rate properties such as 16QAM and 64QAM for band band effects. However, the TPS has a characteristic that its power is constant. The delay unit 322 delays and outputs the fast Fourier operation signal by one symbol period. The second power estimator 323 estimates the power of the delayed signal. The subtraction unit 324 calculates the difference between the two signals. The section moving adder 328 calculates the sum of the sections while moving by a predetermined section to increase the accuracy. The minimum value position detector 329 detects a section where the result of the section moving adder is minimum and estimates the TPS location. The TPS position error detector 350 estimates a frequency offset by comparing a known TPS position with a position of the TPS detected by the minimum value position detector 329.

6 is a block diagram according to another embodiment of an offset estimating apparatus according to the present invention. The configuration is the same as that shown in FIG. 3B but further includes an adder 425 and a divider 426 in the TPS position detector. This is to prevent an error in the case where the signals transmitted from the first power estimator 421 and the second power estimator 423 are both small values among the general data. The adder 425 receives signals received from the first power estimator and the second power estimator, and calculates a sum thereof. The divider 426 divides the signal output from the subtractor 424 by the signal output from the adder. Considering the characteristic that the TPS signal generally has the same large power value as the general data signal, the values calculated for the TPS have a smaller value, and the other signals have a larger value, so the more accurate TPS position detection is possible. The value calculated by the divider 426 is transmitted to the section movement adder 428, and the following apparatus is the same as FIG.

7 is a flowchart illustrating an operation of the frequency offset estimating apparatus according to FIG. 4. Referring to FIG. 7, the fast Fourier calculating unit 200 receives a TDS OPM signal in a time domain and converts the signal into a frequency domain (S500), and converts the signal into a frequency domain signal converted by the TPS position error detector 250. Comparing the size of the known TPS and detecting the position, and comparing the position of the known TPS and the detected position to estimate the frequency offset (S550). The TPS signal includes size and location information.

8 is a flowchart illustrating an operation of the frequency offset estimating apparatus according to FIG. 5. Referring to FIG. 7, the fast Fourier calculating unit 300 receives a TDS OPM signal in a time domain and converts the signal into a frequency domain (S600), and receives a signal converted into a frequency domain and detects a position of the TPS. In operation S650, the frequency offset is estimated by comparing the detected TPS position information with the detected position information (S650). In detail, in operation S620, first power that is power of a signal in a frequency domain received in operation S600 is estimated (S621). The signal received in step S600 is delayed by one symbol period (S622), and the second power which is the power of the delayed signal is estimated (S623). The difference between the first power and the second power is calculated (S624), and the sum thereof is obtained while moving by the predetermined interval with respect to the calculated value (S638). The position having the smallest value among the sums obtained in step S628 is sensed (S629). This is because the estimated power is almost the same because all TPSs are composed of the same signal, so when comparing the current signal with the previous signal, the general data is largely different between the two signals, but the difference is almost zero at the position of the TPS. Im using it. The frequency offset is calculated by comparing the detected position with the known TPS position in step S629 to find the degree of change of the TPS in the transmitted signal. Although the position of the TPS is promised during the transmission and reception period, the power can be changed, so it is suitable for the receiver that does not know the size.

9 is a flowchart illustrating an operation of the frequency offset estimating apparatus according to FIG. 6. The method for estimating the frequency offset according to FIG. 9 is similar in configuration to the method for estimating the frequency offset according to FIG. 8. However, in calculating the position of the TPS by calculating the difference between the previous signal and the current signal, if the power of the general signal existing at the same position of both signals is small, the difference is calculated to be close to 0, which may cause an error in detecting the TPS position. The following steps were further configured to solve the problem. Referring to FIG. 9, the method is the same as the step S624 or lower of FIG. 8, and then, a step of calculating a power sum that is the sum of the first power and the second power (S725) and the power difference by dividing the power difference by the power sum. Add step S726 to obtain. This makes the power ratio of two smaller values of the general signal larger and the power ratio of the TPS small. The following method is the same as step S728 of FIG. 7.

By the above method, the range of compensable frequency offsets can be extended by a simple apparatus and method, and accurate frequency offset estimation is possible even in the presence of multipath frequency fading.

As described above, according to the present invention, by using the TPS used for parameter transmission related to the transmitter transmission scheme in the frequency domain when estimating the frequency offset, it is possible to eliminate the interference due to multipath, and the frequency of the wider section than the conventional one. The offset can be calculated.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims (12)

In the frequency offset estimation apparatus of a multi-carrier receiver, A fast Fourier transform unit for converting the transmitted signal into a signal in a frequency domain; And And a transmission information signal error detector for comparing a transmission information signal with a signal in the converted frequency domain to determine a degree of position shift of the transmission information signal. The method of claim 1, The transmitted signal is a Time Domain Synchronous-Orthogonal Frequency Division Multiplexing (TDS-OFDM) signal, and the transmission information signal is a TPS (Trensmission Parameter Signaling) included in the TDS-OFDM signal. Estimation device. In the frequency offset estimation apparatus of a multi-carrier receiver, A fast Fourier transform unit for converting the transmitted signal into a signal in a frequency domain; A transmission information signal position detector for detecting a position of a minimum value having a smallest power difference between a current symbol and a previous symbol with respect to the signal converted into the frequency domain; And And a transmission information signal error detection unit comparing the detected position with the transmission information signal position to determine a degree of movement of the transmission information signal position. The method of claim 3, wherein the transmission information signal position detection unit, A delay unit receiving the frequency domain signal converted by the fast Fourier transform unit and delaying the signal by one symbol length; A first power estimator for estimating power of the delayed signal; A second power estimating unit estimating power of a signal received by the fast Fourier transform unit; A subtractor configured to calculate a difference between the power transmitted from the first power estimate and the signal transmitted from the second power estimate; An interval moving adder configured to calculate a sum in a predetermined section of the values calculated by the subtractor; and And a minimum value position detector for detecting a section having a minimum value calculated by the section movement adder. The method of claim 3, wherein the transmission information signal position detection unit, A delay unit receiving the frequency domain signal converted by the fast Fourier transform unit and delaying the signal by one symbol length; A first power estimator for estimating power of the delayed signal; A second power estimating unit estimating power of a signal received by the fast Fourier transform unit; A subtractor configured to calculate a difference between the power transmitted from the first power estimate and the signal transmitted from the second power estimate; An adder for calculating a sum of the power transmitted from the first power estimator and the signal transmitted from the second power estimator; A divider dividing a value calculated by the subtractor by a value calculated by the adder; A section moving adder configured to calculate a sum in a predetermined section of the values calculated by the divider; And And a minimum value position detector for detecting a section having a minimum value calculated by the section movement adder. The method of claim 3, wherein The transmitted signal is a Time Domain Synchronous-Orthogonal Frequency Division Multiplexing (TDS-OFDM) signal, and the transmission information signal is a TPS (Trensmission Parameter Signaling) included in the TDS-OFDM signal. Estimation device. In the frequency offset estimation method of a multi-carrier receiver, A fast Fourier transform step of converting the transmitted signal into a signal in a frequency domain; And And a transmission information signal error detecting step of comparing a transmission information signal with a signal in the converted frequency domain to determine a degree of position shift of the transmission information signal. The method of claim 7, wherein The transmitted signal is a Time Domain Synchronous-Orthogonal Frequency Division Multiplexing (TDS-OFDM) signal, and the transmission information signal is a TPS (Trensmission Parameter Signaling) included in the TDS-OFDM signal. Estimation method. In the frequency offset estimation method of a multi-carrier receiver, A fast Fourier transform step of converting the transmitted signal into a signal in a frequency domain; A transmission information signal position detection step of detecting a position of a minimum value having a smallest power difference between a current symbol and a previous symbol with respect to the signal converted into the frequency domain; And And a transmission information signal error detecting step of comparing the detected position with the transmission information signal position to determine a degree of movement of the transmission information signal position. 10. The method of claim 9, wherein the transmitting information signal position detecting step comprises: A delay step of delaying the signal by a symbol length that receives the frequency domain signal converted in the fast Fourier transform step; A first power estimating step of estimating power of the delayed signal; A second power estimating step of estimating the power of the signal received in the fast Fourier transform step; Calculating a difference between the power transmitted in the first power estimation step and the signal transmitted in the second power estimation step; Calculating a sum in a predetermined section of the values calculated in the calculating of the difference; and And a minimum value position detection step of detecting a section in which the calculated sum is the minimum. The method of claim 9, wherein the transmitting information signal position detecting step comprises: A delay step of receiving the frequency domain signal converted in the fast Fourier transform step and delaying the signal by one symbol length; A first power estimating step of estimating power of the delayed signal; A second power estimating step of estimating the power of the signal received in the fast Fourier transform step; Calculating a difference between the power transmitted in the first power estimation step and the signal transmitted in the second power estimation step; Calculating a sum of the power transmitted in the first power estimation step and the signal transmitted in the second power estimation step; Calculating a ratio between the sum and the difference by dividing the calculated difference by the calculated sum; Calculating a sum in a predetermined interval of the calculated ratio values; And And a minimum value position detecting step of detecting a section in which the sum of the predetermined intervals is the minimum. The method of claim 9, The transmitted signal is a Time Domain Synchronous-Orthogonal Frequency Division Multiplexing (TDS-OFDM) signal, and the transmission information signal is a TPS (Trensmission Parameter Signaling) included in the TDS-OFDM signal. Estimation method.