CN1578294A - Method and device for detecting synchronous signal - Google Patents

Abstract

A device for detecting synchronization signals. The device for detecting a synchronization signal includes: a time information receiving unit for receiving time information from a global positioning system (GPS); and a synchronization signal detector for calculating a position of a synchronization signal of a received frame based on the time information , and thus generate a sync detection signal. Since this means for detecting the synchronization signal determines the position of the synchronization signal set in the frame and the frame structure of the OFDM signal transmitted from the transmitting end using GPS time, and thus detects the synchronization signal, it is possible to simplify the hardware for detecting the synchronization signal The realization of and the process of calculating the correlation are not necessary.

Description

Method and device for detecting synchronization signal

Technical field

The present invention relates to a receiver for receiving an Orthogonal Frequency Division Multiplexing (OFDM) carrier signal. In particular, it relates to a method and apparatus for detecting a synchronization signal from an OFDM carrier signal by using the Global Positioning System (GPS).

Background technique

An Orthogonal Frequency Division Multiplexing (OFDM) scheme is a digital modulation system proposed to increase a transmission rate per bandwidth and prevent multipath interference. According to the OFDM scheme, the entire bandwidth is divided into multiple narrowband orthogonal sub-channels, and each sub-channel is modulated by QAM (Quadrature Amplitude Modulation) to transmit data. Since the OFDM system converts data into multiple parallel data and modulates the data to multiple subcarriers, and transmits the data, the OFDM system can increase the amount of data transmission per time unit, and the receiving end is affected by multipath The effect of transmission delay is small.

In an OFDM system, transmitted data mainly includes synchronization signals and OFDM data. The synchronization signal is generally referred to as a pseudo-noise (PN) sequence. The receiving end has the same PN sequence as that from the transmitting end, and compares the PN sequences for synchronization.

FIG. 1 is a schematic diagram showing a frame structure of an OFDM signal transmitted from a transmitting end to a receiving end.

An OFDM signal includes a pseudo-noise (PN) sequence used as a synchronization signal, OFDM data (DFT3780), and a guard interval inserted between the PN sequence and OFDM data (DFT3780) for preventing interference in the OFDM data (DFT3780) (GI). An OFDM receiver (not shown) detects a PN sequence from the received OFDM signal in, and performs frequency synchronization, symbol synchronization, and channel equalization based on the detected PN sequence. Therefore, according to the conventional technique, the receiving end has a reference PN sequence having the same signal pattern as that of the synchronization signal of the received OFDM signal, calculates the correlation between the reference PN sequence and the OFDM signal, and has the correlation The maximum value of the position detection sync signal. Since the order of the synchronization signals of the OFDM signal is changed according to a predetermined rule, the reception end cannot detect the synchronization signals until a signal matching in pattern with the reference PN sequence of the reception end is generated. Therefore, if the OFDM signal transmitted from the transmitting end is a broadcast signal, the digital broadcast receiver cannot receive the broadcast signal until a predetermined time after power-on.

FIG. 2 is a conceptual block diagram of a conventional device for detecting a synchronization signal.

A conventional device for detecting a synchronization signal includes: a correlation calculator 10 , a comparison unit 20 , a counter 30 and a synchronization signal generator 40 .

The correlation calculator 10 includes a plurality (10a˜10n) of correlators each having a different position of the OFDM signal in as a starting point. The correlation calculator 10 divides the OFDM signal in into a predetermined number of parts to detect the position of the synchronous signal included in the OFDM signal in as quickly as possible, and calculates the data from a plurality of correlators (10a˜10n) at different initial points, respectively. ) for each correlation.

The comparison unit 20 generates an update signal (w_en) when a maximum value is generated in the correlation from each correlator (10a˜10n). The counter 30 counts a predetermined number of times according to the same period as the symbol period. For example, if the transmitting end transmits a digital broadcast signal in units of 3780 symbols based on a 5us period, 3780 symbols are counted in the 5us interval.

In response to the update signal (w_en) generated in the comparison unit 20, the maximum value detector 40 stores the counted value in the counter 30, and when the number of times the counted value is the same every 3780th symbol is greater than a predetermined number , a synchronous detection signal (sync) is generated. For example, if the maximum value is generated at the 1200th symbol during the counting period of the counter 30, and the maximum value is generated again at the 1200th symbol during the second counting period, a synchronization detection signal (sync) is generated at the 1200th position. The maximum value detector 40 generates a synchronous detection signal (sync) from a count value corresponding to a position at which the maximum value occurs at a specific cycle. Since the means for detecting the synchronization signal having the above structure cannot detect the position of the synchronization signal in the OFDM signal in, it takes a lot of time to detect the synchronization signal when implemented by a single correlator. In order to solve this shortcoming, the traditional device for detecting the synchronous signal divides the OFDM signal in into a predetermined number of parts to improve the detection speed of the synchronous signal, and has multiple correlators (10a~10n) to calculate from the initial point of each part Correlation. However, the above required components lead to an increase in the product cost of the receiver for the OFDM signal in, and each correlator (10a˜10n) should continuously calculate the correlation between the OFDM signal in and the reference PN sequence (R_PN sequence) Correlation. In addition, since each correlator (10a~10n) should be equipped with an adder and a multiplier, since a large number of correlators are provided in the correlation detector 10, implementation of hardware is complicated.

Contents of Invention

The present invention has been developed to solve the problems of the prior art described above. An object of the present invention is to provide an apparatus for detecting a synchronization signal using time information included in an OFDM signal, wherein implementation of hardware is simplified and production cost can be reduced.

In order to achieve the above aspects and other characteristics of the present invention, a device for detecting a synchronous signal is provided, comprising: a time information receiving unit for receiving time information from a global positioning system (GPS); and a synchronous signal detector for The position of the synchronization signal of the frame of the received OFDM signal is calculated based on the time information, and thus a synchronization detection signal is generated.

The means for detecting the synchronization signal also includes a timer synchronized with the time information from the global positioning system, and applies the periodically generated time information to the synchronization signal detector.

The sync signal detector detects a sync signal of the OFDM signal based on time information generated in the timer.

According to another aspect of the present invention, there is provided a device for detecting a synchronization signal from an OFDM signal, comprising: a time information receiving unit for receiving time information from a global positioning system (GPS); a synchronization range calculator for for calculating the position of a synchronization signal applied to a frame of a received OFDM signal based on time information; a correlator for calculating an OFDM signal including the synchronization signal and a predetermined pseudo-noise sequence set at a receiving end from the position of the synchronization signal a correlation between ; and a maximum detector for generating a sync detection signal at a point with a maximum correlation.

The means for detecting the synchronization signal also includes a timer synchronized with the time information from the global positioning system, and applies the periodically generated time information to the synchronization range calculator.

According to another aspect of the present aspect, there is provided a method for detecting a synchronization signal from an OFDM signal, comprising the steps of: receiving time information from a Global Positioning System (GPS); and calculating the received OFDM signal based on the time information The location of the sync signal in .

The method for detecting a synchronization signal from an OFDM signal further includes the steps of: generating reference time information synchronized with the received time information; and thus calculating a position of the synchronization signal based on a predetermined time unit.

According to another aspect of the present invention, there is provided a method for detecting a synchronization signal from an OFDM signal, comprising the steps of: receiving time information from a global positioning system (GPS); The position of the synchronization signal of the frame of the signal; Calculate the correlation between the OFDM signal comprising the synchronization signal and the predetermined reference pseudo-noise sequence set at the receiving end from the detected position; and generate the OFDM signal contained in the OFDM signal based on the correlation The location of the sync signal.

The method for detecting a synchronization signal from an OFDM signal further includes the steps of generating reference time information synchronized with the time information, and thus detecting a position of the synchronization signal based on a predetermined time unit.

Description of drawings

The above objects and characteristics of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the accompanying drawings, in which:

1 is a schematic diagram showing an example of a frame structure of an OFDM signal transmitted from a transmitting end to a receiving end;

2 is a conceptual block diagram of a conventional device for detecting synchronization signals;

FIG. 3 is a diagram showing the overall structure of an OFDM signal;

4 is a conceptual block diagram of an apparatus for detecting a synchronization signal according to an embodiment of the present invention;

5 is a conceptual block diagram of an apparatus for detecting a synchronization signal according to another embodiment of the present invention;

6 is a flow chart of a method for detecting a synchronization signal according to an embodiment of the present invention; and

Fig. 7 is a flowchart of a method for detecting a synchronization signal according to another embodiment of the present invention.

Detailed ways

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

Referring to FIG. 3, the overall structure of the OFDM signal will be described as follows.

Generally, 255 single frames shown in FIG. 1 are collectively called a frame group, 512 frame groups are collectively called a superframe, and 478 superframes are collectively called a superframe group. The front part of the superframe of the OFDM signal having the above structure generally has time information indicating the start of the superframe group at zero point.

FIG. 4 is a conceptual block diagram of an apparatus for detecting a synchronization signal according to an embodiment of the present invention.

The device for detecting a synchronization signal includes: a GPS receiver 50 , a timer (local) 60 and a synchronization signal detector 70 .

The GPS receiver 50 receives time information in an OFDM signal in received from an artificial satellite (not shown) or from a base station (not shown) for relaying OFDM signals transmitted from an artificial satellite. As explained with reference to FIG. 3 , the transmitting end transmits a frame-structured OFDM signal at regular time intervals, and a frame transmitted at zero o'clock includes time information representing zero o'clock. The GPS receiver 50 receives this time information (for example, zero point) and uses it as reference time information for the apparatus for detecting a synchronization signal according to the present invention.

The timer (local) 60 is synchronized with the time information (for example, zero o'clock) received in the GPS receiver 50, and counts time based on the received time information until the GPS receiver 50 receives the next time at zero o'clock. Time information for zero points.

The synchronization signal detector 70 estimates the frame structure of the input OFDM signal in based on the time counted in the timer (local) 60 . Since the OFDM signal from the transmitting end transmits a synchronization signal at regular time intervals according to a predetermined rule, the synchronization signal detector 70 estimates the time corresponding to the time counted in the timer (local) 60 according to the rule agreed with the transmitting end. position of the synchronization signal, and detect the synchronization detection signal. The accuracy of the sync signal detection is determined using the accuracy of the time counted in the timer (local) 60 . Since the synchronization signal detector 70 does not need to calculate the correlation between the synchronization signal included in the OFDM signal in and the reference pseudo-noise sequence (P_N sequence) of the same pattern as the synchronization signal, it is possible to simplify the synchronization detection circuit according to the present invention. structure. Since the synchronization detection signal (sync) is generated based on time information received in the GPS receiver 50, a problem caused by a detection delay of the synchronization detection signal (sync) is avoided. For example, when applied to broadcast signal receivers, problems of the present invention such as viewing delays with power-on or channel changes are avoided.

FIG. 5 is a conceptual block diagram of an apparatus for detecting a synchronization signal according to another embodiment of the present invention.

The synchronization signal detection device includes: a GPS receiver 100 , a timer (local) 110 , a synchronization range detector 120 , a correlator 130 and a maximum value detector 140 .

The operations of the GPS receiver 100 and the timer (local) 110 are the same as those of the GPS receiver 50 and the timer 60 in FIG. 4, so it is intentionally omitted hereinafter. This embodiment solves the problem that when the receiving end with the GPS receiver 100 is far away from the artificial satellite (not shown) that transmits the OFDM signal or is far away from the base station (not shown) for relaying the OFDM signal transmitted from the artificial satellite, the GPS The problem of errors in the time received in the receiver 100 .

The synchronization range detector 120 estimates the approximate position of the synchronization signal in the OFDM signal in and the synchronization signal located at the estimated position based on time information supplied from the timer (local) 110 having time information synchronized with the GPS receiver 100 signal mode. Since the order of the pattern of the synchronization signal of the OFDM signal in gradually changes according to a predetermined rule, the pattern of the synchronization signal can be traced back at the time received based on the time information at the first zero o'clock. The synchronization range calculator 120 can obtain the frame and frame group in the received OFDM signal in according to the time counted by the timer (local) 110 based on the time information (zero time) received by the GPS receiver 100 . The signal pattern of the reference pseudo-noise sequence (R_PN sequence) prepared at the receiving end does not change, while the synchronization signal included in the OFDM signal in does. Accordingly, the synchronization range calculator 120 operates the correlator 130 at a position in a frame including a synchronization signal having the same signal pattern as the reference pseudo-noise sequence (R_PN sequence).

The correlator 130 calculates the correlation between the OFDM signal in received from the time point set in the synchronization range detector 120 and the reference pseudo-noise sequence (R_PN sequence). The correlator 130 uses only a single correlator 130, contrary to the conventional situation where the received OFDM signal in is divided into predetermined parts for fast detection of the synchronization signal. Therefore, hardware implementation is simplified and the calculation process of the correlation is unnecessary.

The maximum value detector 140 generates a synchronization detection signal (sync) at a time point at which the maximum value of the correlation between the OFDM signal in and the reference pseudo-noise sequence (R_PN sequence) is generated. At this time, the maximum value detector 140 determines whether the maximum value is repeated a predetermined number of times, such as three times, at regular time intervals to prevent a maximum value detection error caused by multipath fading or external noise, and if so, generates a synchronous detection signal (sync).

FIG. 6 is a flowchart outlining a method for detecting a synchronization signal according to an embodiment of the present invention.

The GPS receiver 100 receives time information included in the OFDM signal in from an artificial satellite (not shown) or from a base station (not shown) for relaying the OFDM signal transmitted from the artificial satellite (S210). Time information is included at the leading end of a superframe group that is periodically transmitted at intervals of 24 hours. The GPS receiver 100 synchronizes the timer (local) 60 built in the receiving end (S220). Therefore, the time of the timer (local) 60 set at the receiving end is synchronized with the OFDM signal in transmitted from the artificial satellite or the base station. The receiving end estimates the position of the synchronization signal in the OFDM signal in with reference to the time counted in the timer (local) 110 synchronized with the GPS time, and generates a synchronization detection signal at the estimated position (S230). This method for detecting synchronization signals does not require the process of computing a single correlation to detect synchronization signals.

FIG. 7 is a flowchart showing a method for detecting a synchronization signal according to another embodiment of the present invention.

This embodiment is applied in the case where the receiving end is placed far away from an artificial satellite (not shown) transmitting an OFDM signal in or away from a base station (not shown) for relaying an OFDM signal in propagated from an artificial satellite, An error occurred in the GPS time received by the receiver.

The GPS receiver 100 receives time information in an OFDM signal in received from a satellite (not shown) or from a base station for relaying the OFDM signal in from the satellite (S310). Time information is included at the leading end of a superframe group that is periodically transmitted at 24-hour intervals. Next, the GPS receiver 100 synchronizes the timer (local) 110 built in the receiving end (S320). Therefore, the time of the timer (local) 110 set in the receiving end is synchronized with the OFDM signal in transmitted from the artificial satellite or the base station.

The approximate position and pattern of the synchronization signal in the OFDM signal input based on the GPS time or the time counted by the timer (local) 110 are calculated (S330). Since the OFDM signal transmits a frame at every regular time interval based on the zero point, and the pattern of the synchronization signal included in the frame changes according to a predetermined order, it is possible to calculate the time of the OFDM signal from the transmitting end through exact time information. Frame information and a pattern of synchronization signals included in the frame information.

The GPS receiver 100 calculates a correlation at a frame point having the same signal pattern as a reference pseudonoise sequence (R_PN sequence) at the receiving end according to information counted by the GPS time or the timer (local) 110 (S340). Since the correlation calculation starts at a point close to the synchronization signal, it can be calculated more efficiently than the traditional method of continuously detecting the correlation between all input OFDM signals in and all input reference pseudo-noise sequences (R_PN sequences). out correlation.

The GPS receiver 100 determines whether the position having the maximum value in the correlation is repeated more than a predetermined number of times (S350). If the maximum value is repeated at the same position more than a predetermined number of times (for example, three times), the GPS receiver 100 generates a synchronization detection signal (sync). Therefore, the method for detecting a synchronization signal according to the present invention does not require a process of detecting a correlation, and when applied to hardware, can be constructed with a very simple circuit.

As described above, in some exemplary embodiments of the present invention, the position of the synchronization signal included in the frame and the frame structure of the received OFDM signal are estimated using GPS time, and then the synchronization signal is detected accordingly. As a result, hardware implementation can be simplified, and the process of calculating the correlation is unnecessary.

The advantages, objects and characteristics of additional embodiments of the present invention are set forth in part and will be disclosed in part to persons having ordinary skill in the art, or can be learned from practice of the present invention. The objects and advantages of the embodiments of the invention may be realized and attained as particularly pointed out in the appended claims.

Claims (9)

1, a kind of device that is used to detect synchronizing signal comprises:

The temporal information receiving element is used for from global positioning system (GPS) receiving time information; With

Synchronized signal detector is used for calculating based on temporal information the position of the synchronizing signal of the frame that receives, and therefore produces synchronous detection signal.

2, the device that is used to detect synchronizing signal as claimed in claim 1, also comprise with from the synchronous timer of the temporal information of global positioning system, the temporal information with the generation of preset time gap periods wherein is applied to synchronized signal detector.

3, the device that is used to detect synchronizing signal as claimed in claim 2, wherein, synchronized signal detector detects the synchronizing signal of ofdm signal based on the temporal information that produces in timer.

4, a kind of device that is used to detect synchronizing signal comprises:

The temporal information receiving element is used for from global positioning system (GPS) receiving time information;

The locking range calculator is used for calculating based on temporal information the position of the synchronizing signal of the frame that is applied to the ofdm signal that receives;

Correlator is used for comprising from the position calculation of synchronizing signal the ofdm signal and the correlation between the predetermined pseudo noise sequence that receiving terminal is provided with of synchronizing signal; With

Maximum value detector is used for producing synchronous detection signal at the point with maximum correlation.

5, the device that is used to detect synchronizing signal as claimed in claim 4, also comprise with from the synchronous timer of the temporal information of global positioning system, the temporal information with the generation of preset time gap periods wherein is applied to synchronized signal detector.

6, a kind of method that is used for detecting from ofdm signal synchronizing signal comprises step:

From global positioning system (GPS) receiving time information; With

Calculate the position of the synchronizing signal of the ofdm signal that receives based on temporal information.

7, the method that is used to detect synchronizing signal as claimed in claim 6 also comprises step: the reference time information that the temporal information that produces and receive is synchronous, and the position of therefore calculating synchronizing signal based on preset time unit.

8, a kind of method that is used to detect synchronizing signal comprises step:

From global positioning system (GPS) receiving time information;

Calculate the position of the synchronizing signal of the frame that is applied to the ofdm signal that receives based on temporal information;

The ofdm signal and the correlation between the predetermined reference pseudo noise sequence that receiving terminal is provided with that comprise synchronizing signal from detected position calculation; With

Be created in the position of the synchronizing signal that comprises in the ofdm signal based on this correlation.

9, the method that is used to detect synchronizing signal as claimed in claim 8, wherein, the step that detects synchronizing signal position produces and the synchronous reference time information of temporal information, and therefore detects the position of synchronizing signal based on preset time unit.

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