KR20060046676A - Preamble detection device and method and wireless relay system using same - Google Patents

Abstract

1. TECHNICAL FIELD OF THE INVENTION

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

2. The technical problem to be solved by the invention

The present invention provides a TDD scheme by detecting a preamble using only information on a TDD frame structure without information on a preamble (for example, information on a preamble pattern, a preamble symbol structure, etc.) in a TDD wireless communication system. It is an object of the present invention to provide a preamble detection device, a method and a wireless relay system using the same for enabling wireless communication equipment such as repeaters in the wireless communication to maintain time synchronization.

3. Summary of Solution to Invention

According to an aspect of the present invention, there is provided a preamble detection apparatus comprising: delay means for delaying an input signal (S (t)) of a TDD frame by a repetition period time (preferably a TDD frame length) of a preamble; Complex correlation means for obtaining a complex correlation between the time delayed signal S (tT _F ) and the input signal S (t), and output values of the complex correlation means (complex correlation value C (t)). And preamble position detecting means for detecting the position of the preamble.

4. Important uses of the invention

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

Preamble, TDD, Wireless Relay System, Time, Synchronization, Time Synchronization, Frame

Description

Apparatus and method for detecting preamble and RF repeating system using that}

1 is a structural diagram of a wireless communication frame of the TDD scheme used in the present invention;

2 is a configuration diagram of an embodiment of a preamble detection apparatus according to the present invention;

3 is an exemplary 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 configuration diagram of an embodiment of a wireless relay system using a preamble detection apparatus according to the present invention.

* Explanation of symbols for the main parts of the drawings

20: preamble detection device 21: time delay

22: complex correlator 23: preamble position detector

40: link antenna 41, 45: switching unit

42: downlink signal processor 43: frequency down converter

44: A / D converter 46: uplink signal processing unit

47: service antenna

The present invention relates to a preamble detecting apparatus and a method thereof, and a wireless relay system using the same, and more particularly, to information about a preamble (for example, a preamble pattern) in a TDD (Time Division Duplex) wireless communication system. Preamble detection using only information on the TDD frame structure without information such as a preamble symbol structure, so that wireless communication equipment such as repeaters can maintain time synchronization in TDD-based wireless communication. An apparatus and a method thereof, and a wireless relay system using the same.

In the current wireless communication market, where frequency securing is a big problem, a time division duplex (TDD) method that enables communication using a single frequency has been in the spotlight in recent years. Unlike the past, this is believed to be possible due to the development of parts and equipment that can be synchronized at the right time.

The TDD method can theoretically support the same service using timeslots smaller than the frequency division duplexing (FDD) method, and has a similar structure to the current Internet by using an asymmetrical arrangement of up / down time slots. It has the technical characteristics suitable for the transmission of the application. As a result, the TDD scheme enables a high-speed transmission rate using only half the frequency of the FDD scheme, thereby enabling a service at a relatively low cost.

Due to these characteristics, it has become a very attractive technology for wireless carriers, but it has been difficult to detect the synchronization of time slot dynamic allocation and solve the problem of time delay according to transmission distance. I was hit. However, in recent years, the market has been widened by overcoming these problems with various technologies, and as mentioned above, since downlinks can be easily combined with many current wired Internet communication systems, they are in the spotlight again.

In a typical TDD wireless communication system, a terminal acquires initial synchronization by using a preamble signal periodically transmitted from a base station (typically in a frame unit). In this case, the preamble information defined between the base station and the terminal is used.

As such, since the preamble information is defined between the base station and the terminal, the terminal can detect the location of the preamble by comparing the preamble information that is already known with the preamble signal received from the base station through the wireless link. Initial synchronization with respect to frequency and time can be obtained. It is also possible to estimate the radio channel.

However, when using a repeater in a TDD wireless communication system, the TDD repeater receives the downlink signal transmitted from the base station and retransmits it to the terminal, and receives the uplink signal transmitted from the terminal and retransmits it to the base station. As such, the TDD repeater performs a switching operation between the downlink section and the uplink section. For this purpose, the TDD repeater knows exactly the information about the downlink to uplink and downlink uplink information. Must be present

Therefore, when the TDD repeater knows the preamble information, the start position of the preamble can be detected using the preamble information already known and the preamble signal received from the base station through the radio link. And, based on the detected start position of the preamble, it is possible to know the time for switching from the downlink to the uplink and the time for switching from the uplink to the downlink by a predefined TDD frame structure.

However, if the TDD repeater does not know the preamble information, since the start position of the preamble cannot be detected in the above-described manner, wireless communication in a wireless communication system using the TDD frame structure in a situation in which the information on the preamble is not known. The problem arises that the equipment fails to acquire initial synchronization.

Accordingly, in a wireless communication system using a TDD frame structure, a method for detecting a preamble without using information on the preamble (for example, information on a preamble pattern, a preamble symbol structure, etc.) is urgently needed.

The present invention has been proposed to meet the above requirements, and in a TDD wireless communication system, only information on a TDD frame structure without information on a preamble (for example, information on a preamble pattern, a preamble symbol structure, etc.) is provided. The purpose of the present invention is to provide a preamble detecting apparatus, a method, and a wireless relay system using the same, by which preambles are detected, so that wireless communication equipment such as repeaters can maintain time synchronization in TDD wireless communication. have.

Other objects and advantages of the present invention can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. Also, it will be readily appreciated that the objects and advantages of the present invention may be realized by the means and combinations thereof indicated in the claims.

The apparatus of the present invention for achieving the above object, in the preamble detection device, time-delaying the input signal (S (t)) of the TDD frame by the repetition period time (preferably TDD frame length) of the preamble A complex correlation means for obtaining a complex correlation between the delayed signal S (tT _F ) delayed by the delay means and the input signal S (t), and an output value (complex) of the complex correlation means. And a preamble position detecting means for detecting the position of the preamble using the correlation value C (t)).

On the other hand, the method of the present invention, in the preamble detection method, the delay step of delaying the input signal (S (t)) of the TDD frame by the repetition period time (preferably TDD frame length) of the preamble; A complex correlation step of obtaining a complex correlation between a time delayed delay signal S (tT _F ) and the input signal S (t), and an absolute value of the complex correlation value C (t) obtained through the complex correlation step. And a preamble position detecting step of detecting the position of the preamble using the maximum value of the absolute value.

On the other hand, the system of the present invention, in the wireless relay system for setting the time to be switched (switched) between the downlink and the uplink by using the position of the preamble detected by the preamble detection device, included in the downlink Detects the position of the preamble signal, and uses the position of the detected preamble signal to determine the switching time of the switching element connected to the 'link antenna for air interface with the base station' and 'service antenna for air interface with the terminal'. It is characterized by controlling.

The present invention is to detect the preamble without the information on the preamble (for example, information on the preamble pattern, preamble symbol structure, etc.) in the TDD wireless communication system, by using only the information on the TDD frame structure We want to detect the preamble.

In this case, in order to detect the preamble using only the information on the TDD frame structure without the preamble information, the present invention provides a signal obtained by delaying a signal input to the preamble detection apparatus by a period (generally, frame) of the preamble. The preamble is detected by finding the complex correlation and finding the position of the maximum value that is periodically repeated in the absolute value of the complex correlation.

That is, in the present invention, by detecting the position of the preamble by using a complex correlation between an input signal input to the preamble detection device and a predetermined internal reference signal, wireless communication equipment such as a repeater in a TDD wireless communication system is detected. Keep time synchronized.

The above objects, features and advantages will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, whereby those skilled in the art may easily implement the technical idea of the present invention. There will be. In addition, in describing the present invention, when it is determined that the detailed description of the known technology related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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

As shown in FIG. 1, in the figure, "TTG" is a period for switching from downlink to uplink, "RTG" is a period for switching from uplink to downlink, "T _F " is a TDD frame length, "T _P "" Indicates the preamble length, "T _DL " indicates the length of the downlink, "T _UL " indicates the length of the uplink, the length of the "T _TTG " TTG interval, and the length of the "T _RTG " interval, respectively.

FIG. 2 is a diagram illustrating an embodiment of a preamble detection apparatus according to the present invention, and illustrates an embodiment for detecting a preamble in the TDD frame structure of FIG.

As shown in FIG. 2, the preamble detection apparatus 20 according to the present invention uses a signal S (t) of a TDD frame input from the outside by the repetition period time (generally, TDD frame length) of the preamble. A complex correlation between the time delay 21 for delaying, the delayed signal S (tT _F ) delayed through the time delay 21 and the signal S (t) of the TDD frame input from the outside And a preamble position detector 23 for detecting the position of the preamble by using the complex correlator 22 for obtaining the? And 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 complex correlator 22 output (complex correlation value C (t)). Using this, it is possible to know information on the time that wireless communication equipment such as a repeater should switch between the downlink and the uplink.

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

According to the present invention, a method of detecting a preamble using only information on a TDD frame structure without information on a preamble includes: a signal S (t) input to a preamble detection device, using a period of a preamble (generally, a frame). A complex correlation is obtained with the signal S (tT _F ) which is time-delayed by a unit, and an absolute value is taken into the complex correlator 22 output value (complex correlation value C (t)) (| C (t) |), Based on this, the preamble can be detected by finding the position of the maximum value that is periodically repeated.

Therefore, in the TDD frame structure as shown in FIG. 1, when the preamble detection device 20 as shown in FIG. 2 is used, an output value (complex correlation value C (t)) of the complex correlator 22 is expressed by an equation. It can be defined as [Equation 1] below.

If Equation 1 is expressed in the form of a digital signal, it can be defined as Equation 2 below.

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

1 and 2, when the signal S (t) of the TDD frame has an additional white Gaussian noise (AWGN) signal characteristic or a band limited additional white Gaussian noise (Band-Limited AWGN) characteristic, the complex correlator 22 If the absolute value is taken into the output value (complex correlation value C (t)) of (| C (t) |), it will have the characteristic similar to FIG. 3 mentioned later. In general, signals such as Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), and the combination of these signals have band limited additional white Gaussian noise characteristics. Accordingly, FIG. 3 shows an example in which an absolute value (| C (t) |) is taken as an output value (complex correlation value C (t)) of the complex correlator 22 for the TDD frame signal of FIG.

As shown in FIG. 3, the absolute value (| C (t) |) of the complex correlator 22 output (complex correlation value C (t)) is determined by a preamble signal that is periodically repeated. Has the maximum value in the part. Therefore, the position of the preamble can be found by using the maximum value according to the absolute value | C (t) | of the complex correlator 22 output (complex correlation value C (t)) repeated in the preamble period. In this way, the function of detecting the position of the preamble using the output of the complex correlator 22 (complex correlation value C (t)) 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 (ie, downlink to uplink in the downlink) is used by the radio communication equipment such as a repeater to switch (switch) between the downlink and the uplink. Time to be switched to, downlink to 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 _P to t _PE1 + T _DL -T _P downlink interval (downlink length T _DL in FIG. 1), and t _PE1 + _TDL -T _P + T _TTG to t _PE1 + T _DL -T _P + T _TTG It can be seen that the uplink period (uplink length T _UL in FIG. 1) until + T _UL time. This is repeated in units of frame periods (TDD frame length T _F of FIG. 1). Therefore, the time for switching from the downlink to the uplink in the wireless communication equipment may be set between t _PE1 + T _DL -T _P and t _PE1 + T _DL -T _P + T _TTG . The switching time is set between t _PE1 + T _DL- T _P + T _TTG + T _UL and t _PE1 + T _DL- T _P + T _TTG + T _UL + T _RTG .

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

4 is a configuration diagram of a wireless relay system using a preamble detection apparatus according to the present invention, and the position of the preamble signal included in the downlink through the preamble detection apparatus 20 having the configuration of FIG. To control the switching time of the switching elements 41 and 45 connected to the 'link antenna for air interface with the base station' and the 'service antenna for air interface with the terminal' using the detected position of the preamble signal. Shows the configuration.

In more detail, the wireless relay system using the preamble detection apparatus according to the present invention includes a link antenna 40 for exchanging radio signals between the base station and the wireless relay system, a low noise amplifier for receiving radio signals received from the base station, The downlink signal processor 42 for performing downlink signal processing through the gain regulator and the linear power amplifier, and the uplink signal processing through the low noise amplifier, the gain regulator, and the linear power amplifier for the wireless signal received from the terminal. The uplink signal processor 43, the switching units 41 and 45 for downlink and uplink switching, and the downlink signal processor 42 for frequency downconverting the low noise amplified analog signal. The digital downconverter 43 and the analog signal transmitted through the frequency downconverter 43 are digitally A / D converter 44 for converting the signal to a digital signal, and the converted digital signal through the A / D converter 44 detects the position of the preamble signal included in the downlink, and 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 (that is, the downlink to uplink and downlink to the uplink) A preamble detection device 20 for controlling, and a service antenna 47 for transmitting and receiving a radio signal between the terminal and the wireless relay system.

As described above, the wireless relay system using the preamble detection apparatus according to the present invention detects the position of the preamble by using a complex correlation between an input signal transmitted to the preamble detection apparatus and a predetermined internal reference signal. In the TDD wireless communication, wireless communication equipment such as a repeater can maintain time synchronization.

The present invention described above is capable of various substitutions, modifications, and changes without departing from the technical spirit of the present invention for those skilled in the art to which the present invention pertains. It is not limited by the drawings.

As described above, the present invention detects the location of the preamble using only the TDD frame structure information without information on the preamble (for example, information on the preamble pattern, the preamble symbol structure, etc.) in the TDD wireless communication. By doing so, the time for switching from downlink to uplink and the time for switching from uplink to downlink (switching) can be known, so that TDD-type wireless communication devices maintain time synchronization even when there is no information on preamble. It has the effect of making it possible.

Claims (9)

In the preamble detection device, Delay means for delaying the input signal (S (t)) of the TDD frame by the repetition period time (preferably the TDD frame length) of the preamble; Complex correlation means for obtaining a complex correlation between the delayed signal S (tT _F ) delayed through the delay means and the input signal S (t); And Preamble position detecting means for detecting the position of the preamble using the output value (complex correlation value C (t)) of the complex correlation means Preamble detection device comprising a. The method of claim 1, The preamble position detecting means, And a function of setting a time for switching (switching) between a downlink and an uplink using the detected position of the preamble. The method of claim 1, The preamble position detecting means, And taking an absolute value into an output value (complex correlation value C (t)) of the complex correlation means, and detecting a portion where the preamble section ends using the maximum value of the absolute value. The method according to any one of claims 1 to 3, The output signal C (t) of the complex correlation means is If Equation 1 is expressed below and Equation 1 is expressed in the form of a digital signal, it is represented by Equation 2 below. When the digital signal is sampled at a frequency of fs, N _F is And an integer closest to the T _F * fs value, and N _P represents an integer closest to the T _P * fs value. [Equation 1]

[Equation 2]

In the preamble detection method, A delay step of time-delaying the input signal (S (t)) of the TDD frame by the repetition period time (preferably the TDD frame length) of the preamble; A complex correlation step of obtaining a complex correlation between the time delayed delay signal S (tT _F ) and the input signal S (t); And A preamble position detection step of taking an absolute value to the complex correlation value C (t) obtained through the complex correlation step and detecting the position of the preamble using the maximum value of the absolute value. Preamble detection method comprising a. The method of claim 5, wherein The preamble position detection step, And setting a time for switching (switching) between a downlink and an uplink using the detected position of the preamble. The method according to claim 5 or 6, The absolute value is The preamble detection method having a maximum value at a portion where the preamble section ends, according to a characteristic of a preamble signal that is periodically repeated. In the wireless relay system for setting the time to be switched (switched) between the downlink and the uplink using the position of the preamble detected by the preamble detection device of claim 1 or 2, The switching element connected to the 'link antenna for air interface with the base station' and 'service antenna for air interface with the terminal' by detecting the position of the preamble signal included in the downlink and using the detected position of the preamble signal. Wireless relay system, characterized in that for controlling the switching time of. The method of claim 8, Detecting the position of the preamble, The input signal (S (t)) of the TDD frame is delayed by the repetition period time (preferably the TDD frame length) of the preamble, and the time delayed delay signal S (tT _F ) and the input signal S ( After obtaining the complex correlation of t)), take the absolute value of the complex correlation value C (t), and detect the position of the preamble using the maximum value of the absolute value, but use the detected position of the preamble. Wireless relay system, characterized in that for setting the time to switch (switch) between the downlink and uplink.

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