WO2006107136A1 - Apparatus and method for detecting preamble and rf repeating system using the same - Google Patents

Apparatus and method for detecting preamble and rf repeating system using the same Download PDF

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Publication number
WO2006107136A1
WO2006107136A1 PCT/KR2005/004540 KR2005004540W WO2006107136A1 WO 2006107136 A1 WO2006107136 A1 WO 2006107136A1 KR 2005004540 W KR2005004540 W KR 2005004540W WO 2006107136 A1 WO2006107136 A1 WO 2006107136A1
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Prior art keywords
preamble
signal
tdd frame
time
detecting
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PCT/KR2005/004540
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French (fr)
Inventor
Hae-Chul Lee
Eun-Cheul Jeong
Seong-Choon Lee
Sang-Ho Yi
Yong-Joo Tcha
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SOLID TECHNOLOGIES Inc
KT Corp
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SOLID TECHNOLOGIES Inc
KT Corp
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Priority claimed from KR1020050029617A external-priority patent/KR100902741B1/en
Application filed by SOLID TECHNOLOGIES Inc, KT Corp filed Critical SOLID TECHNOLOGIES Inc
Publication of WO2006107136A1 publication Critical patent/WO2006107136A1/en
Anticipated expiration legal-status Critical
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/14—Relay systems
    • H04B7/15—Active relay systems
    • H04B7/155—Ground-based stations

Definitions

  • the present invention relates to a preamble detecting apparatus and an RF repeating system using the same; and, more particularly, to a preamble detecting apparatus that can detect a preamble only using information on a Time Division Duplex (TDD) frame structure without preamble information including preamble pattern, preamble symbol structure and the like in an RF communication system using a TDD scheme to thereby enable RF communication equipment, e.g., a repeater, of a TDD- based RF communication to maintain time synchronization, and an RF repeating system using the same.
  • TDD Time Division Duplex
  • Time Division Duplex (TDD) scheme enables communication using a single frequency. This is possible due to the development of parts and equipments that can be accurately synchronized.
  • the TDD scheme can support the same service using a smaller number of timeslots than a Frequency Division Duplexing (FDD) scheme. Also, because the TDD scheme supports asymmetric structure, which is suitable for transmission of Internet application. Consequently, compared with the FDD scheme, the TDD scheme can transmit data at a high speed using half of the frequency, thereby providing services at a relatively low cost. These characteristics have attracted great attention from RF communication service providers. In the past, sync detection for the dynamic timeslot allocation was difficult and the problem of time delay according to transmission distance was not solved. However, in recent years, the problem is somewhat solved and the markets are expanding. As described above, because the flexibility of downlink and uplink traffic allocation in TDD scheme is compatible with the existing wired Internet communication systems having many downlink traffics, it again becomes attractive.
  • FDD Frequency Division Duplexing
  • a mobile station acquires an initial synchronization using a preamble signal transmitted from a base station periodically, generally on a frame basis. At this point, predefined preamble information is used between the base station and the mobile station.
  • the mobile can detect a preamble position by comparing the predefined preamble signal with a preamble signal received from the base station over a radio link. Also, the mobile station can acquire an initial synchronization with respect to frequency and time and estimate a radio channel condition.
  • the TDD repeater receives a downlink signal from the base station and retransmits it to the mobile terminal.
  • the TDD receiver receives an uplink signal from the mobile station and retransmits it to the base station. In this manner, the TDD repeater performs a switching operation between the downlink period and the uplink period.
  • the TDD repeater has to exactly know the time of changing from the downlink to the uplink and the time of changing form the uplink to the downlink. Therefore, when the TDD repeater knows in advance the preamble information, a starting position of the preamble can be detected using the previously known preamble information and the preamble signal received from the base station over the radio channel. Based on the detected starting position of the preamble, the time of changing from the downlink to the uplink and the time of changing from the uplink to the downlink can be known by means of the predefined TDD frame structure. However, when the TDD repeater does not know the preamble information, the starting position of the preamble cannot be detected using the method described above. Consequently, in this environment, the RF communication equipments of the RF communication system using the TDD frame structure cannot acquire the initial synchronization .
  • an object of the present invention to provide a preamble detecting apparatus that can detect a preamble only by using information on a TDD frame structure without preamble information including preamble pattern, preamble symbol structure and the like in an RF communication system using a TDD scheme, thereby enabling RF communication equipment, e.g., a repeater, of a TDD- based RF communication to maintain time synchronization, and an RF repeating system using the same.
  • RF communication equipment e.g., a repeater
  • a preamble detecting apparatus including: a time delayer for delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length); a complex correlator for calculating a complex correlation between the time-delayed signal (S (t- TF)) and the TDD frame signal (S(t)); and a preamble position detector for detecting a preamble position using an output value (complex correlation value (C(t))) of the complex correlator.
  • a preamble detecting method comprising the steps of: a) delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length); b) calculating a complex correlation between the time-delayed signal (S(t-T F )) and the TDD frame signal (S(t)); and c) calculating an absolute value of a complex correlation value (C(t))) obtained in the step b), and detecting a preamble position using a maximum value of the absolute value.
  • an RF repeating system for setting a time of switching between a downlink and an uplink by using a preamble position detected by a preamble detecting apparatus, in which the RF repeating system detects the preamble position of the preamble signal contained in the downlink through the preamble detecting apparatus and controls switching time of switches connected to a "link antenna for RF interface with the base station" and a "service antenna for RF interface with the mobile terminal” by using the detected position of the preamble signal.
  • the RF communication system using the TDD scheme can detect the preamble using only the TDD frame structure without preamble information (e.g., preamble pattern, preamble symbol structure, etc.).
  • preamble information e.g., preamble pattern, preamble symbol structure, etc.
  • the complex correlation between the signal inputted to the preamble detecting apparatus and the delayed signal produced by delaying the input signal by the preamble period generally on a frame basis
  • the absolute value of the output value (complex correlation value) of the complex correlator is calculated. Based on the absolute value, the preamble can be detected by finding the position of the periodically repeating maximum value.
  • the present invention can enable the RF communication equipments such as the repeater to maintain the time synchronization in the TDD-based communication.
  • the RF communication equipments using the TDD scheme can maintain the time synchronization .
  • Fig. 1 illustrates an RF communication frame structure using a TDD scheme in accordance with the present invention
  • Fig. 2 is a block diagram of a preamble detecting apparatus in accordance with an embodiment of the present invention
  • Fig. 3 illustrates an absolute value of an output of a complex correlator with respect to a TDD frame signal of Fig. 1;
  • Fig. 4 is a block diagram of an RF repeating system using the preamble detecting apparatus in accordance with the present invention.
  • Fig. 1 illustrates an RF communication frame structure using a TDD scheme in accordance with the present invention.
  • reference symbols TTG, RTG, T F , T P , T DL , T UL , T TTG , and T RTG represent a transition gap between the downlink burst and the subsequent uplink burst, a transition gap between the uplink burst and the subsequent downlink burst, a TDD frame length, a preamble length, a downlink length, an uplink length, a TTG length, and a RTG length, respectively.
  • Fig. 2 is a block diagram of a preamble detecting apparatus in accordance with an embodiment of the present invention.
  • the preamble detecting apparatus detects a preamble in the TDD frame structure of Fig. 1.
  • the preamble detecting apparatus 20 includes a time delayer 21, a complex correlator 22, and a preamble position detector 23.
  • the time delayer 21 delays an external TDD frame signal S(t) by a preamble period (generally, the TDD frame length).
  • the complex correlator 22 calculates a complex correlation between the time-delayed signal S(t-T F ) and the external TDD frame signal S(t).
  • the preamble position detector 23 detects a preamble position using an output value (complex correlation value C(t)) of the complex correlator 22.
  • the preamble position can be detected using a maximum value of an output of the complex correlator 22 (an absolute value
  • the RF communication equipments such as a repeater can know a switching time between the downlink and the uplink.
  • the complex correlation between the signal S(t) inputted to the preamble detecting apparatus and the delayed signal S(t-T F ) produced by delaying the input signal S(t) by the preamble period (generally on a frame basis). Then, the absolute value
  • the output value (the complex correlation value C(t) of the complex correlator 22) can be defined as Eq. (1) below.
  • Eq. (1) is expressed in a digital signal form, the result can be defined as Eq. (2) below.
  • N F is an integer closest to T F xf s
  • N P is an integer closest to T P xf s
  • the absolute value I C ( t ) I of the output value (complex correlation value C(t)) of the complex correlator 22 has the characteristics of Fig. 3.
  • Fig. 3 illustrates an example of the absolute value
  • the preamble position can be found using the maximum value of the absolute value
  • the RF communication equipments can know the information on the time of switching between the downlink and the uplink (that is, the time of switching from the downlink to the uplink and the time of switching from the uplink to the downlink) by using the detected preamble period.
  • the time from t PE i-T P to t PE i+T DL -T P is the downlink period (the downlink length T DL in Fig. 1)
  • the time from t PE i+T DL -T P +T TTG to t PE i+T DL -T P +T TTG +T UL is the uplink period (the uplink length T UL in Fig. 1). This is repeated every frame period (the TDD frame length T F in Fig. 1).
  • the time of switching from the downlink to the uplink is set between t PE i+T DL -T P and t PE i+T DL -T P +T TTG
  • the time of switching from the uplink to the downlink is set between t PE i+T DL -T P +T TT G+TuL and t PE i+T DL -T P +T TT G+T UL +T RTG .
  • Fig. 4 is a block diagram of the RF repeating system using the preamble detecting apparatus in accordance with an embodiment of the present invention.
  • the RF repeating system detects the position of the preamble signal contained in the downlink through the preamble detecting apparatus 20 of Fig. 2, and controls switching time of the switches 41 and 42 connected to a "link antenna for RF interface with the base station" and a "service antenna for RF interface with the mobile terminal" by using the detected position of the preamble signal.
  • the RF repeating system using the preamble detecting apparatus includes a link antenna 40, a downlink signal processor 42, an uplink signal processor 43, switches 41 and 45, a frequency down- converter 43, an analog/digital (A/D) converter 44, a preamble detecting apparatus 20, and a service antenna 47.
  • the link antenna 40 transmits/receives RF signals between the base station and the RF repeating system.
  • the downlink signal processor 42 performs a downlink process on the RF signal, which is received from the base station, through a low noise amplifier (LNA), a gain controller, and a linear power amplifier.
  • LNA low noise amplifier
  • the uplink signal processor 43 performs an uplink processing on the RF signal, which is received from the mobile station, through a low noise amplifier, a gain controller, and a linear power amplifier.
  • the switches 41 and 45 switch the downlink and the uplink path.
  • the frequency down- converter 43 down-converts analog signal that is low- noise-amplified at the downlink signal processor 42.
  • the A/D converter 44 converts the analog signal from the frequency down-converter 43 into digital signal.
  • the preamble detecting apparatus 20 receives the digital signal from the A/D converter 44 to detect the position of the preamble signal contained in the downlink, and controls the switching time (that is, the time of switching from the downlink to the uplink and the time of switching from the uplink to the downlink) of the switches 41 and 45 connected to the link antenna 40 and the service antenna 47 by using the detected position of the preamble signal.
  • the service antenna 47 transmits/receives RF signals between the mobile terminal and the RF repeating system.
  • the RF repeating system using the preamble detecting apparatus in accordance with the present invention can enable the RF communication equipments such as the repeater to maintain the time synchronization in the TDD-based communication.

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  • Computer Networks & Wireless Communication (AREA)
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Abstract

A preamble detecting apparatus includes: a time delayer for delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length); a complex correlator for calculating a complex correlation between the time-delayed signal (S(t-TF)) and the TDD frame signal (S(t)); and a preamble position detector for detecting a preamble position using an output value (complex correlation value (C(t))) of the complex correlator.

Description

APPARATUS AND METHOD FOR DETECTING PREAMBLE AND RF REPEATING SYSTEM USING THE SAME
Description Technical Field
The present invention relates to a preamble detecting apparatus and an RF repeating system using the same; and, more particularly, to a preamble detecting apparatus that can detect a preamble only using information on a Time Division Duplex (TDD) frame structure without preamble information including preamble pattern, preamble symbol structure and the like in an RF communication system using a TDD scheme to thereby enable RF communication equipment, e.g., a repeater, of a TDD- based RF communication to maintain time synchronization, and an RF repeating system using the same.
Background Art
Since frequency spectrum is an extremely limited resource, how to use frequency spectrum becomes an important issue in the radio frequency (RF) communication markets. Recently, a Time Division Duplex (TDD) scheme enables communication using a single frequency. This is possible due to the development of parts and equipments that can be accurately synchronized.
The TDD scheme can support the same service using a smaller number of timeslots than a Frequency Division Duplexing (FDD) scheme. Also, because the TDD scheme supports asymmetric structure, which is suitable for transmission of Internet application. Consequently, compared with the FDD scheme, the TDD scheme can transmit data at a high speed using half of the frequency, thereby providing services at a relatively low cost. These characteristics have attracted great attention from RF communication service providers. In the past, sync detection for the dynamic timeslot allocation was difficult and the problem of time delay according to transmission distance was not solved. However, in recent years, the problem is somewhat solved and the markets are expanding. As described above, because the flexibility of downlink and uplink traffic allocation in TDD scheme is compatible with the existing wired Internet communication systems having many downlink traffics, it again becomes attractive.
In the general RF communication system using the TDD scheme, a mobile station acquires an initial synchronization using a preamble signal transmitted from a base station periodically, generally on a frame basis. At this point, predefined preamble information is used between the base station and the mobile station.
Because the base station and the mobile station have the predefined preamble information, the mobile can detect a preamble position by comparing the predefined preamble signal with a preamble signal received from the base station over a radio link. Also, the mobile station can acquire an initial synchronization with respect to frequency and time and estimate a radio channel condition. When the TDD-based communication system uses a repeater, the TDD repeater receives a downlink signal from the base station and retransmits it to the mobile terminal. The TDD receiver receives an uplink signal from the mobile station and retransmits it to the base station. In this manner, the TDD repeater performs a switching operation between the downlink period and the uplink period. For this purpose, the TDD repeater has to exactly know the time of changing from the downlink to the uplink and the time of changing form the uplink to the downlink. Therefore, when the TDD repeater knows in advance the preamble information, a starting position of the preamble can be detected using the previously known preamble information and the preamble signal received from the base station over the radio channel. Based on the detected starting position of the preamble, the time of changing from the downlink to the uplink and the time of changing from the uplink to the downlink can be known by means of the predefined TDD frame structure. However, when the TDD repeater does not know the preamble information, the starting position of the preamble cannot be detected using the method described above. Consequently, in this environment, the RF communication equipments of the RF communication system using the TDD frame structure cannot acquire the initial synchronization .
Therefore, in the RF communication system using the TDD frame structure, there is an increasing demand for a system that can detect the preamble without preamble information, e.g., preamble pattern, preamble symbol structure and the like.
Disclosure Technical Problem
It is, therefore, an object of the present invention to provide a preamble detecting apparatus that can detect a preamble only by using information on a TDD frame structure without preamble information including preamble pattern, preamble symbol structure and the like in an RF communication system using a TDD scheme, thereby enabling RF communication equipment, e.g., a repeater, of a TDD- based RF communication to maintain time synchronization, and an RF repeating system using the same. Other objects and advantages of the present invention can be understood more fully through the embodiments of the present invention. Also, the objects and advantages of the present invention can be easily implemented by means of the following claims and combination thereof.
Technical Solution
In accordance with one aspect of the present invention, there is provided a preamble detecting apparatus including: a time delayer for delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length); a complex correlator for calculating a complex correlation between the time-delayed signal (S (t- TF)) and the TDD frame signal (S(t)); and a preamble position detector for detecting a preamble position using an output value (complex correlation value (C(t))) of the complex correlator.
In accordance with another aspect of the present invention, there is provided a preamble detecting method comprising the steps of: a) delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length); b) calculating a complex correlation between the time-delayed signal (S(t-TF)) and the TDD frame signal (S(t)); and c) calculating an absolute value of a complex correlation value (C(t))) obtained in the step b), and detecting a preamble position using a maximum value of the absolute value.
In accordance with yet another aspect of the present invention, there is provided an RF repeating system for setting a time of switching between a downlink and an uplink by using a preamble position detected by a preamble detecting apparatus, in which the RF repeating system detects the preamble position of the preamble signal contained in the downlink through the preamble detecting apparatus and controls switching time of switches connected to a "link antenna for RF interface with the base station" and a "service antenna for RF interface with the mobile terminal" by using the detected position of the preamble signal.
The RF communication system using the TDD scheme can detect the preamble using only the TDD frame structure without preamble information (e.g., preamble pattern, preamble symbol structure, etc.). To achieve the above object, the complex correlation between the signal inputted to the preamble detecting apparatus and the delayed signal produced by delaying the input signal by the preamble period (generally on a frame basis), and then the absolute value of the output value (complex correlation value) of the complex correlator is calculated. Based on the absolute value, the preamble can be detected by finding the position of the periodically repeating maximum value.
By detecting the preamble position using the complex correlation between the input signal of the preamble detecting apparatus and the predetermined internal reference signal, the present invention can enable the RF communication equipments such as the repeater to maintain the time synchronization in the TDD-based communication.
Advantageous Effects
In the TDD-based RF communication, it is possible to know the time of switching from the downlink to the uplink and the time of switching from the uplink to the downlink by detecting the preamble position using only information on the TDD frame structure without preamble information (e.g., preamble pattern, preamble symbol structure, etc.). Therefore, even when there is no preamble information, the RF communication equipments using the TDD scheme can maintain the time synchronization .
Description of Drawings
The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which: Fig. 1 illustrates an RF communication frame structure using a TDD scheme in accordance with the present invention;
Fig. 2 is a block diagram of a preamble detecting apparatus in accordance with an embodiment of the present invention;
Fig. 3 illustrates an absolute value of an output of a complex correlator with respect to a TDD frame signal of Fig. 1; and
Fig. 4 is a block diagram of an RF repeating system using the preamble detecting apparatus in accordance with the present invention.
Best Mode for the Invention
Other objects and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, which is set forth hereinafter.
Fig. 1 illustrates an RF communication frame structure using a TDD scheme in accordance with the present invention.
In Fig. 1, reference symbols TTG, RTG, TF, TP, TDL, TUL, TTTG, and TRTG represent a transition gap between the downlink burst and the subsequent uplink burst, a transition gap between the uplink burst and the subsequent downlink burst, a TDD frame length, a preamble length, a downlink length, an uplink length, a TTG length, and a RTG length, respectively.
Fig. 2 is a block diagram of a preamble detecting apparatus in accordance with an embodiment of the present invention. The preamble detecting apparatus detects a preamble in the TDD frame structure of Fig. 1.
Referring to Fig. 2, the preamble detecting apparatus 20 includes a time delayer 21, a complex correlator 22, and a preamble position detector 23. The time delayer 21 delays an external TDD frame signal S(t) by a preamble period (generally, the TDD frame length). The complex correlator 22 calculates a complex correlation between the time-delayed signal S(t-TF) and the external TDD frame signal S(t). The preamble position detector 23 detects a preamble position using an output value (complex correlation value C(t)) of the complex correlator 22.
The preamble position can be detected using a maximum value of an output of the complex correlator 22 (an absolute value |C(t)| of the complex correlation value C(t)). Using the preamble position, the RF communication equipments such as a repeater can know a switching time between the downlink and the uplink. An operation of the preamble detecting apparatus 20 in accordance with the present invention will be described below in detail.
In a method for detecting the preamble using only information on the TDD frame structure without preamble information, the complex correlation between the signal S(t) inputted to the preamble detecting apparatus and the delayed signal S(t-TF) produced by delaying the input signal S(t) by the preamble period (generally on a frame basis). Then, the absolute value |C(t)| of the output value (complex correlation value C(t)) of the complex correlator 22 is calculated. Based on the absolute value |C(t)|, the preamble can be detected by finding the position of the periodically repeating maximum value.
When the preamble detecting apparatus 20 of Fig. 2 is used in the TDD frame structure of Fig. 1, the output value (the complex correlation value C(t) of the complex correlator 22) can be defined as Eq. (1) below.
Figure imgf000009_0001
If Eq. (1) is expressed in a digital signal form, the result can be defined as Eq. (2) below.
Figure imgf000009_0002
In Eq. (2), when the digital signal is sampled at a frequency fs, NF is an integer closest to TFxfs, and NP is an integer closest to TPxfs. In Eqs. (1) and (2), when the TDD frame signal S(t) has signal characteristics of Additive White Gaussian Noise (AWGN) or Band-limited AWGN, the absolute value I C ( t ) I of the output value (complex correlation value C(t)) of the complex correlator 22 has the characteristics of Fig. 3. Generally, Code Division Multiple Access (CDMA) signal, Orthogonal Frequency Division Multiple (OFDM) signal, Orthogonal Frequency- Division Multiple Access (OFDMA) signal and combination thereof have the Band-limited AWGN characteristics. Accordingly, Fig. 3 illustrates an example of the absolute value |C(t)| of the output value (complex correlation value (C(t)) of the complex correlator 22 with respect to the TDD frame signal of Fig. 1.
As illustrated in Fig. 3, the absolute value |C(t) | of the output value (complex correlation value C(t)) of the complex correlator 22 has the maximum value at an ending position of the preamble period due to the periodically repeating preamble signal. Therefore, the preamble position can be found using the maximum value of the absolute value |C(t)| of the output value (complex correlation value C(t)) of the complex correlator 22, which is repeated every preamble period. This function of detecting the preamble position is carried out by the preamble position detector 23. If the preamble position detector 23 detects the preamble position, the RF communication equipments can know the information on the time of switching between the downlink and the uplink (that is, the time of switching from the downlink to the uplink and the time of switching from the uplink to the downlink) by using the detected preamble period.
That is, as illustrated in Fig. 3, when the absolute value |C(t)| of the output (complex correlation value C(t)) of the complex correlator 22 has the maximum value at tpEi, the time from tPEi-TP to tPEi+TDL-TP is the downlink period (the downlink length TDL in Fig. 1), and the time from tPEi+TDL-TP+TTTG to tPEi+TDL-TP+TTTG+TUL is the uplink period (the uplink length TUL in Fig. 1). This is repeated every frame period (the TDD frame length TF in Fig. 1). Accordingly, in the RF communication equipments, "the time of switching from the downlink to the uplink" is set between tPEi+TDL-TP and tPEi+TDL-TP+TTTG, and "the time of switching from the uplink to the downlink" is set between tPEi+TDL-TP+TTTG+TuL and tPEi+TDL-TP+TTTG+TUL+TRTG. An operation of an RF repeating system using the above-described preamble detecting apparatus in accordance with the present invention will be described below in detail.
Fig. 4 is a block diagram of the RF repeating system using the preamble detecting apparatus in accordance with an embodiment of the present invention. The RF repeating system detects the position of the preamble signal contained in the downlink through the preamble detecting apparatus 20 of Fig. 2, and controls switching time of the switches 41 and 42 connected to a "link antenna for RF interface with the base station" and a "service antenna for RF interface with the mobile terminal" by using the detected position of the preamble signal.
More specifically, the RF repeating system using the preamble detecting apparatus includes a link antenna 40, a downlink signal processor 42, an uplink signal processor 43, switches 41 and 45, a frequency down- converter 43, an analog/digital (A/D) converter 44, a preamble detecting apparatus 20, and a service antenna 47. The link antenna 40 transmits/receives RF signals between the base station and the RF repeating system. The downlink signal processor 42 performs a downlink process on the RF signal, which is received from the base station, through a low noise amplifier (LNA), a gain controller, and a linear power amplifier. The uplink signal processor 43 performs an uplink processing on the RF signal, which is received from the mobile station, through a low noise amplifier, a gain controller, and a linear power amplifier. The switches 41 and 45 switch the downlink and the uplink path. The frequency down- converter 43 down-converts analog signal that is low- noise-amplified at the downlink signal processor 42. The A/D converter 44 converts the analog signal from the frequency down-converter 43 into digital signal. The preamble detecting apparatus 20 receives the digital signal from the A/D converter 44 to detect the position of the preamble signal contained in the downlink, and controls the switching time (that is, the time of switching from the downlink to the uplink and the time of switching from the uplink to the downlink) of the switches 41 and 45 connected to the link antenna 40 and the service antenna 47 by using the detected position of the preamble signal. The service antenna 47 transmits/receives RF signals between the mobile terminal and the RF repeating system.
As described above, the RF repeating system using the preamble detecting apparatus in accordance with the present invention can enable the RF communication equipments such as the repeater to maintain the time synchronization in the TDD-based communication.
While the present invention has been described with respect to certain preferred embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.

Claims

What is claimed is:
1. A preamble detecting apparatus comprising: a time delayer for delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length) ; a complex correlator for calculating a complex correlation between the time-delayed signal (S(t-TF)) and the TDD frame signal (S(t)); and a preamble position detector for detecting a preamble position using an output value (complex correlation value (C(t))) of the complex correlator.
2. The preamble detecting apparatus as recited in claim 1, wherein the preamble position detector further includes a function of setting a time of switching between a downlink and an uplink by using the detected preamble position.
3. The preamble detecting apparatus as recited in claim 1, wherein the preamble position detector calculates an absolute value of the output value (complex correlation value ((C(t))) of the complex correlator and detects an ending position of the preamble period by using the maximum value of the absolute value.
4. The preamble detecting apparatus as recited in claim 1, wherein the output value ((C(t)) of the complex correlator is expressed as Eq. (1):
Figure imgf000013_0001
when Eq. (1) is expressed in a digital signal form, the result is expressed as Eq. (2):
C(n)=£ιS(n-k)-S'(n-NF-k) Eq. (2)
Jt=O
when the digital signal is sampled at a frequency fs, NF is an integer closest to TFxfs, and NP is an integer closest to TpXf5.
5. A preamble detecting method comprising the steps of: a) delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length); b) calculating a complex correlation between the time-delayed signal (S(t-TF)) and the TDD frame signal
( S ( t ) ) ; and c) calculating an absolute value of a complex correlation value (C(t))) obtained in the step b), and detecting a preamble position using a maximum value of the absolute value.
6. The preamble detecting method as recited in claim 5, wherein the step c) of detecting the preamble position further includes the step of setting a time of switching between a downlink and an uplink by using the detected preamble position.
7. The preamble detecting method as recited in claim 5, wherein the absolute value has a maximum value at an ending position of the preamble period according to characteristics of a periodically repeating preamble signal.
8. An RF repeating system for setting a time of switching between a downlink and an uplink by using a preamble position detected by a preamble detecting apparatus, the preamble detecting apparatus comprising: a time delayer for delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length) ; a complex correlator for calculating a complex correlation between the time-delayed signal (S(t-TF)) and the TDD frame signal (S(t)); and a preamble position detector for detecting a preamble position using an output value (complex correlation value (C(t))) of the complex correlator, wherein the RF repeating system detects the preamble position of the preamble signal contained in the downlink through the preamble detecting apparatus and controls switching time of switches connected to a "link antenna for RF interface with the base station" and a "service antenna for RF interface with the mobile terminal" by using the detected position of the preamble signal.
9. The RF repeating system as recited in claim 8, wherein the process of detecting the preamble position includes: delaying a TDD frame signal (S(t)) by a preamble period (preferably, a TDD frame length); calculating a complex correlation between the time- delayed signal (S(t-TF)) and the TDD frame signal (S(t)); and calculating an absolute value of the complex correlation value (C(t))), and detecting the preamble position using a maximum value of the absolute value; and setting a time of switching between a downlink and an uplink by using the detected preamble position.
PCT/KR2005/004540 2005-04-08 2005-12-26 Apparatus and method for detecting preamble and rf repeating system using the same Ceased WO2006107136A1 (en)

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