KR100902741B1 - Apparatus and method for detecting preamble and RF repeating system using that - Google Patents

Abstract

1. Technical field to which the invention described in the claims belongs

The present invention relates to a preamble detection apparatus and method, and a radio relay system using the same.

2. Technical Challenges to be Solved by the Invention

The present invention detects a preamble using only information on a TDD frame structure without information on a preamble (e.g., preamble pattern, preamble symbol structure, etc.) in a TDD-based wireless communication system, The present invention provides a preamble detection apparatus and method, and a radio relay system using the preamble detection apparatus and method, in order to enable wireless communication equipments such as repeaters to maintain time synchronization.

3. The point of the solution of the invention

Delay means for delaying the input signal S (t) of the TDD frame by a time length corresponding to the TDD frame length, delaying the time delayed signal S (tT _F ) by the delay means, ) For detecting the position of the preamble using the complex correlation value (C (t)) obtained by the complex correlation means and the complex correlation value of the input signal S (t) And an eaves position detecting means.

4. Important Uses of the Invention

The present invention is used in a wireless communication system of TDD (Time Division Duplex) method or the like.

Preamble, TDD, Radio relay system, Time, Synchronization, Time synchronization, Frame

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preamble detection apparatus and method, and a radio relay system using the same,

1 is a diagram illustrating a TDD wireless communication frame structure used in the present invention;

2 is a block diagram of a preamble detection apparatus according to an embodiment of the present invention,

FIG. 3 is a diagram illustrating an absolute value of a complex correlator output for the TDD frame signal of FIG. 1 according to the present invention.

4 is a block diagram of a radio relay system using a preamble detection apparatus according to an embodiment of the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

20: preamble detection device 21: time delay device

22: complex correlator 23: preamble position detector

40: Link antenna 41, 45:

42: downlink signal processing unit 43: frequency down converter

44: A / D converter 46: uplink signal processor

47: Service antenna

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preamble detection apparatus and method, and a radio relay system using the same, and more particularly, to a radio relay system using a time division duplex (TDD) , Preamble symbol structure, and the like), and detects the preamble using only the information on the TDD frame structure, thereby enabling the radio communication equipments such as the repeater to maintain time synchronization in the TDD- Apparatus and method thereof, and a radio relay system using the same.

Recently, TDD (Time Division Duplex) method, which enables communication with a single frequency, is becoming more popular in the current wireless communication market where frequency securing is a big problem. This is believed to be the development of parts and equipment that can be synchronized at the right time, unlike the past.

The TDD scheme can theoretically support the same service using a smaller time slot than the Frequency Division Duplexing (FDD) scheme, and has a structure similar to the current Internet using an asymmetrical arrangement of uplink / downlink time slots, And has technical characteristics suitable for application transmission. As a result, the TDD scheme allows a high-speed transmission rate without using half the frequency as compared with the FDD scheme, thereby enabling a service at a relatively low cost.

These characteristics have made wireless telecommunication operators a very attractive technology, but in the meantime, synchronous detection of dynamic allocation of time slots is very difficult and the problem of time delay due to transmission distance can not be solved. It was. However, recently, various technologies have been used to overcome this problem and the market has been enlarged. As described above, the downlink can be easily combined with the current wired Internet communication system.

In a general TDD wireless communication system, a terminal acquires initial synchronization using a preamble signal transmitted periodically (generally, in frame units) at a base station. At this time, pre-defined preamble information is used between the base station and the mobile station.

Since the preamble information defined in advance is known between the base station and the terminal, the terminal can detect the position of the preamble by comparing the preamble information already known and the preamble signal received through the wireless link from the base station, The initial synchronization for frequency and time can be obtained. Further, the radio channel can be estimated.

However, when a repeater is used in a TDD-based wireless communication system, the TDD repeater receives the downlink signal transmitted from the base station and retransmits the signal to the terminal, receives the uplink signal transmitted from the terminal, and retransmits the signal to the base station. In this manner, the TDD repeater performs a switching operation between the downlink interval and the uplink interval. For this purpose, the TDD repeater accurately knows the time of switching from the downlink to the uplink and the time of switching from the uplink to the downlink. .

Therefore, when the TDD repeater knows the preamble information, it can detect the start position of the preamble using the already-known preamble information and the preamble signal received from the base station through the radio link, as described above. Then, based on the detected start position of the preamble, the time of switching from downlink to uplink and the time of switching from downlink to uplink can be known by the previously defined TDD frame structure.

However, if the TDD repeater does not know the preamble information, the start position of the preamble can not be detected in the above-described manner. Therefore, in a wireless communication system using the TDD frame structure, There is a problem that the devices are not able to acquire initial synchronization.

Therefore, in a wireless communication system using a TDD frame structure, a scheme for detecting a preamble without information on the preamble (e.g., information on a preamble pattern, a preamble symbol structure, and the like) is desperately needed.

The present invention has been proposed in order to meet the above-mentioned demand, and it is an object of the present invention to provide a TDD-based wireless communication system in which only information on a TDD frame structure without information on preamble (for example, preamble pattern, preamble symbol structure, The present invention relates to a preamble detection apparatus and method and a wireless relay system using the preamble detection apparatus and method for enabling a wireless communication apparatus such as a repeater to maintain time synchronization in a TDD wireless communication by detecting a preamble have.

Other objects and advantages of the present invention will become apparent from the following description, and it will be understood by those skilled in the art that the present invention is not limited thereto. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

The apparatus for detecting a preamble according to the present invention comprises delay means for delaying an input signal S (t) of a TDD frame by a TDD frame length, A complex correlation means for obtaining a complex correlation value between the delay signal S (tT _F ) and the input signal S (t), and a complex correlation means C (t) And preamble position detecting means for detecting the position of the eamble.

In the preamble detection method of the present invention, a delay step of delaying an input signal S (t) of a TDD frame by a TDD frame length, a delaying step of delaying the delayed signal S (tT _F ) A complex correlation step of obtaining a complex correlation value of the input signal S (t) and the input signal S (t), and a complex correlation step of obtaining an absolute value of the complex correlation value C (t) And a preamble position detecting step of detecting a position of the preamble by using the preamble position detecting step.

Meanwhile, the system of the present invention is a radio relay system for setting a time to switch (switch) between a downlink and an uplink using a position of a preamble detected by the preamble detecting apparatus, The switching time of the switching element connected to the 'link antenna for the wireless interface with the base station' and the 'service antenna for the wireless interface with the terminal' is detected using the detected position of the preamble signal And a control unit.

The present invention is for detecting a preamble without information on a preamble (for example, information on a preamble pattern, a preamble symbol structure, and the like) in a TDD-based wireless communication system. It uses only information on a TDD frame structure We want to detect the preamble.

In this case, in order to detect a preamble using only information on a TDD frame structure without preamble information, a signal obtained by delaying a signal input to the preamble detecting apparatus by a period of a preamble A complex correlation is obtained, and a preamble is detected by finding a position of a maximum value periodically repeated in the absolute value of the complex correlation.

That is, in the present invention, the position of the preamble is detected by using the complex correlation between the input signal input to the preamble detection apparatus and a predetermined internal reference signal, and thus, the wireless communication apparatuses such as repeaters in the TDD- So that time synchronization can be maintained.

The foregoing and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, in which: There will be. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a TDD wireless communication frame used in the present invention.

As shown in Figure 1, in the figure "TTG" is a region that is converted to an uplink in the downlink, "RTG" is a region that is converted to a downlink in an uplink, "T _F" is the TDD frame length, "T _P "is the preamble length," T _DL "is the length of the DL," T _UL represents a "length of the TTG interval" T _RTG "the length of the interval" is a length, in the uplink, "T _TTG, respectively.

FIG. 2 is a block diagram of a preamble detecting apparatus according to an embodiment of the present invention. FIG. 2 shows an embodiment for detecting a preamble in the TDD frame structure of FIG.

2, the preamble detecting apparatus 20 according to the present invention detects a signal S (t) of a TDD frame input from the outside by a repetition period time (generally, a TDD frame length) of the preamble (T) of the TDD frame inputted from the outside and the delayed signal S (tT _F ) delayed by the time delay 21 and a delayed signal S (t) And a preamble position detector 23 for detecting the position of the preamble using the output value (complex correlation value C (t)) of the complex correlator 22.

At this time, the position of the preamble can be detected using the maximum value according to the absolute value (| C (t) |) of the output (complex correlation value C (t)) of the complex correlator 22. With this, it is possible to know information on the time required for the wireless communication devices such as repeaters to switch between the downlink and the uplink.

The operation of the preamble detecting apparatus 20 according to the present invention having the above-described configuration will be described in detail as follows.

A method of detecting a preamble using only information on a TDD frame structure without information on a preamble according to the present invention is a method of detecting a preamble signal S (t) (T)) obtained by obtaining a complex correlation with a signal (S (tT _F )) delayed by a predetermined amount (a unit of the complex correlator 22) Based on this, the preamble can be detected by locating the maximum value repeated periodically.

Therefore, when the preamble detection apparatus 20 shown in FIG. 2 is used in the TDD frame structure as shown in FIG. 1, the output value (complex correlation value C (t)) of the complex correlator 22 is expressed by a mathematical expression Can be defined as the following Equation (1).

Equation (1) can be expressed in the form of a digital signal as follows: " (2) "

In Equation (2), if the digital signal is sampled at a frequency of fs, N _F is an integer closest to the value of T _F * fs, and N _P is an integer closest to the value of T _P * fs.

1 and 2, when the signal S (t) of the TDD frame has the characteristics of the additive white Gaussian noise (AWGN) signal or the band limited additive white Gaussian noise (Band-Limited AWGN) (| C (t) |) is taken as the absolute value of the output value (complex correlation value C Generally, signals such as Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple (OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), and the like are combined with each other to have band-limited additional white Gaussian noise characteristics. Therefore, FIG. 3 shows an example in which the absolute value | C (t) | is taken as the output value (complex correlation value C (t)) of the complex correlator 22 with respect to the TDD frame signal of FIG.

3, the absolute value | C (t) |) of the output of the complex correlator 22 (complex correlation value C (t)) by the preamble signal, which is normally periodically repeated, The maximum value is obtained. Therefore, the position of the preamble can be found by using the maximum value according to the absolute value | C (t) |) of the output of the complex correlator 22 repeated in the preamble period (the complex correlation value C (t)). Thus, the function of detecting the position of the preamble using the output (complex correlation value C (t)) of the complex correlator 22 is performed by the preamble position detector 23. [

When the position of the preamble is detected by the preamble position detector 23, information on the time required for the wireless communication devices such as the repeater to switch between the downlink and the uplink (i.e., The time to switch from the uplink to the downlink).

That is, as shown in FIG. 3, at t _PE1 complex correlator 22 outputs the absolute value of the (complex correlation value C (t)) (| C (t) |) when the given maximum value, _PE1 t -T in _{PE1 P} t + T _DL -T _P to a time (T length _DL in the downlink in Fig. 1) DL duration, t _PE1 + _TDL -T _P + T _TTG in _{t PE1 + T DL -T P +} T TTG It can be seen that uplink time (uplink length T _UL in FIG. 1) up to + T _UL time. This is repeated in units of a frame period (TDD frame length T _{F in} Fig. 1). Therefore, in the wireless communication equipment, it is necessary to set the 'time for switching from the downlink to the uplink' between t _PE1 + T _DL -T _P to t _PE1 + T _DL -T _P + T _TTG , The switching time is set to be between t _PE1 + T _DL -T _P + T _TG + T _UL and t _PE1 + T _DL -T _P + T T _TG + T _UL + T _RTG .

The operation of the radio relay system using the preamble detection apparatus according to the present invention having the above-described configuration will be described in detail as follows.

FIG. 4 is a block diagram of a radio relay system using a preamble detecting apparatus according to an embodiment of the present invention. Referring to FIG. 4, a preamble detecting apparatus 20 having the configuration shown in FIG. 2 detects a preamble signal included in a downlink The switching time of the switching elements 41 and 45 connected to the 'link antenna for the wireless interface with the base station' and the service antenna for the wireless interface with the terminal is controlled using the detected position of the preamble signal Lt; / RTI >

The radio relay system using the preamble detection apparatus according to the present invention includes a link antenna 40 for transmitting and receiving a radio signal between a base station and a radio relay system, A downlink signal processing unit 42 for performing downlink signal processing through a gain controller and a linear power amplifier, and a downlink signal processing unit 42 for performing uplink signal processing through a low noise amplifier, a gain controller, and a linear power amplifier, And a downlink signal processor 42 for downconverting the low noise amplified analog signal in the downlink signal processor 42. The uplink signal processor 43 includes an uplink signal processor 43, Frequency down-converter 43 and the frequency down-converter 43 to the digital down- D converter 44 for receiving the digital signal converted by the A / D converter 44, detects the position of the preamble signal included in the downlink, and outputs the position of the detected preamble signal The switching time of the switching units 41 and 45 connected to the link antenna 40 and the service antenna 47 (i.e., the switching time from the downlink to the uplink, the time from the uplink to the downlink) And a service antenna 47 for transmitting and receiving a radio signal between the terminal and the radio relay system.

As described above, the radio relay system using the preamble detecting apparatus according to the present invention detects the position of the preamble by using the complex correlation between the input signal transmitted to the preamble detecting apparatus and a predetermined internal reference signal , And wireless communication devices such as repeaters can maintain time synchronization in TDD-based wireless communication.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. The present invention is not limited to the drawings.

The present invention as described above detects the position of a preamble using only the TDD frame structure information without information on the preamble (e.g., preamble pattern, preamble symbol structure, etc.) in the TDD radio communication Thus, it is possible to know the time for switching from the downlink to the uplink and the time for switching (switching) from the uplink to the downlink, so that even when there is no information on the preamble, the TDD- There is an effect to be able to do.

Claims (9)

A preamble detection apparatus comprising: Delay means for time delaying the input signal (S (t)) of the TDD frame by the TDD frame length; A complex correlation means for obtaining a complex correlation value between the delayed signal S (tT _F ) delayed by the delay means and the input signal S (t); And And a preamble position detection means for detecting a position of the preamble using the complex correlation value C (t) obtained by the complex correlation means The preamble detection apparatus comprising: The method according to claim 1, Wherein the preamble position detecting means comprises: Further comprising a function of setting a time to switch (switch) between the downlink and the uplink using the detected position of the preamble. The method according to claim 1, Wherein the preamble position detecting means comprises: Wherein the absolute value is taken as the absolute value of the complex correlation value (C (t)) obtained by the complex correlation means, and a portion where the preamble interval ends is detected using the absolute value of the absolute value. 4. The method according to any one of claims 1 to 3, The output signal (C (t)) of the complex correlation means, To a is represented by Equation 1, when being expressed by Equation 2 below is expressed by Equation 1 in the form of digital signal, the digital signal is sampled at a frequency fs, N _F is Is an integer closest to a value of T _F * fs, and N _P is an integer closest to a value of T _P * f s. [Equation 1]

&Quot; (2) "

In the preamble detection method, A delaying step of delaying the input signal S (t) of the TDD frame by the TDD frame length; A complex correlation step of obtaining a complex correlation value of the delayed delayed signal S (tT _F ) and the input signal S (t); And A preamble position detecting step of taking an absolute value of the complex correlation value C (t) obtained through the complex correlation step and detecting a position of the preamble using the absolute value of the absolute value; And detecting the preamble. 6. The method of claim 5, Wherein the preamble position detecting step comprises: Further comprising the step of setting a time for switching (switching) between the downlink and the uplink using the detected position of the preamble. The method according to claim 5 or 6, The absolute value may be an absolute value, Wherein the preamble has a maximum value at the end of the preamble period according to characteristics of the periodic repeated preamble signal. A radio relay system for setting a time for switching (switching) between a downlink and an uplink using a position of a preamble detected by the preamble detecting apparatus of claim 1 or 2, A link antenna for a radio interface with a base station and a switching antenna connected to a service antenna for a radio interface between the base station and the mobile station by detecting the position of the preamble signal included in the downlink and using the detected position of the preamble signal, And the switching time of the wireless relay system is controlled. 9. The method of claim 8, Wherein the step of detecting the position of the preamble comprises: A delayed time delayed signal S (tT _F ) and a time delayed input signal S (t) are generated by delaying the input signal S (t) of the TDD frame by the repetition period time (preferably TDD frame length) (t)). Then, the absolute value is taken as the complex correlation value C (t), the position of the preamble is detected using the maximum value of the absolute value, and the position of the detected preamble is used And sets a time to switch (switch) between the downlink and the uplink.

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