KR100610929B1 - Method and apparatus for acquiring synchronization in TD repeater - Google Patents

Abstract

The present invention generates the switch timing through a general frame for TDD communication received in the repeater to synchronize the switching time with the base station. To this end, the present invention can receive the signal from the base station in the repeater to obtain the switch timing by determining the frame length of the received signal. In detail, the present invention generates a Received Signal Strength Indicator (RSSI) signal from a received signal through a log amplifier, and generates the generated signal using a Schmitt trigger. By calculating the switch timing signal, the TDD switch timing synchronization acquisition procedure can be performed without the process of frame synchronization acquisition and signal demodulation. Through this, the present invention has the advantage of finding the TDD switching timing without additional signal and acquiring the frame length received from the repeater when synchronizing with the TDD repeater. In addition, the present invention has the effect of finding a sufficient switch timing because there is a guard time, such as TTG, RTG when switching between up and down links in synchronization.

TDD, Repeater, Switch Timing

Description

METHOD FOR ACQUIRING SYNCRONIZATION IN RELAY OF TIME DIVISION DUPLEXING PROCEDURE AND APPARATUS}             

1 is a schematic internal block diagram of a TDD repeater according to an embodiment of the present invention;

2 is a view showing a signal sequence in a time domain of a signal according to a wireless communication of the TDD scheme according to an embodiment of the present invention;

3 (a) to 3 (c) are views for explaining the operation of a timing signal detector according to an embodiment of the present invention;

4 is a view showing the operating characteristics of the Schmitt trigger according to an embodiment of the present invention.

5 illustrates a general frame structure for TDD communication.

The present invention relates to a relay system that can be used in wireless communication, and in particular, a relay method and apparatus for covering a partial frequency band region generated by extending a service area (coverage) or lacking electric field strength in a TDD type wireless communication system. It is about.

The wireless communication system uses a base station capable of call processing or an access point (AP) or coverage extension in mind for communication with a mobile communication terminal. Here, the repeater refers to a device capable of transmitting a signal of a base station to a remote service area in order to cover a sound range in a mobile communication network, thereby facilitating communication between a user of the mobile terminal and the base station. .

On the other hand, since the base station is considerably more expensive than the repeater, it is common to install a repeater if possible in a low traffic area, and the repeater plays a role of amplifying a signal. In this case, the type of repeater may be classified into an optical repeater, an RF repeater, a microwave repeater, and the like according to a connection method between the base station and the repeater period.

In addition, depending on the duplexing (Duplexing) method can be divided into repeaters of the frequency division duplexing (FDD), time division duplexing (TDD) method, FDD repeater is widely used in the existing mobile communication network, TDD repeater Research on it is ongoing.

However, in FDD wireless communication, a duplexer in which a band filter or the like is inserted is used to distinguish the uplink and the downlink. That is, in FDD wireless communication, uplink and downlink are allocated fixed frequencies, respectively.

On the other hand, in the TDD type communication where the base station or the AP uses the same frequency for the downlink toward the mobile communication terminal and the uplink toward the base station in the mobile communication terminal, the TDD switch is used to properly separate the uplink and the downlink. Timing is required.

In the case of an optical repeater, switch timing may be received through an additional line or signaling, but if the base station does not provide such switch timing, the uplink / downlink cannot be properly separated. In addition, repeaters used in a wireless environment have no way of receiving these switch timings separately. An optical repeater connected to a base station that does not provide switch timing should acquire the TDD switch timing only with the received signal.

Therefore, in the case of the TDD repeater, there must be a switch for selecting uplink and downlink in its structure. When the switch connects the downlink, only the downlink is connected and the uplink is disconnected so that the signal is properly amplified and transmitted to the mobile communication terminal.

As described above, in order for the TDD type repeater to operate properly, the switch connects only the downlink path in the downlink time zone in which the base station transmits radio waves toward the mobile communication terminal, and the uplink time zone in which the mobile terminal transmits radio waves in the direction of the base station. It is of utmost importance that the switch connect only the up path.

A synchronization procedure for such a relay to properly switch the uplink and downlink in synchronization with the base station will be described later. The repeater operating in the reception mode periodically receives a signal in the downlink period and then first acquires frame synchronization of the signal. The downlink frame is basically composed of pilot, control, and data symbols, and shapes and order of the symbols may exist in various forms. Among them, the pilot symbols are used to obtain data symbols in the most optimal state by acquiring accurate synchronization for a frame in the reception portion of the mobile communication terminal. The control symbol transmits various control data necessary for data communication.

Accordingly, conventionally, the frame synchronization is obtained by the method described above, and the information input to the downlink frame is demodulated to extract the start and end points of the frame according to the information.

As described above, in the conventional TDD repeater, a signal must be received in the downlink period in order to properly switch the uplink and downlink in synchronization with the base station to obtain frame synchronization from the signal, and demodulate the signal that has been frame-synchronized again. do. For this reason, in the conventional repeater, a circuit for synchronizing acquisition has to be complicated.

Accordingly, the present invention provides a method and apparatus for properly controlling a switch for switching an uplink / downlink for a TDD type wireless communication in a repeater.

In addition, the present invention can obtain the TDD switch timing without the process of frame synchronization acquisition and signal demodulation from the downlink signal received using an analog method rather than a digital to control the switch to switch the uplink / downlink in the repeater It provides a method and apparatus to make.

According to an aspect of the present invention, there is provided an apparatus for synchronizing in a TDD repeater, comprising: a log amplifier receiving a received signal and outputting a RSSI signal and a square wave receiving the RSSI signal; A Schmid trigger for generating a switch timing signal and outputting a switch timing signal, a TDD switch timing generator for outputting time information on downlink and uplink start points by comparing the switch timing signal from the Schmitt trigger with pre-input information; And a switch for switching to alternately connect only one direction of the uplink and downlink signals in synchronization with the base station using the output time information, and a switch controller for controlling the switch.

In addition, the present invention is a method for obtaining synchronization in a TDD repeater having the same frequency of the downlink transmitted from the base station toward the mobile communication terminal and the uplink signal transmitted from the mobile communication terminal to the base station. Outputting the RSSI signal from the signal sequence; generating a square wave by receiving the RSSI signal; outputting a switch timing signal; and synchronizing with the base station through synchronization of the timing signal extracted by using the switch timing signal; And switching to alternately connect only one direction of the downlink signal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same elements in the figures are represented by the same numerals wherever possible. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

The present invention generates the switch timing through a general frame for TDD communication received in the repeater to synchronize the switching time with the base station. To this end, the present invention can receive the signal from the base station in the repeater to obtain the switch timing by determining the frame length of the received signal. In detail, the present invention generates a Received Signal Strength Indicator (RSSI) signal from a received signal through a log amplifier, and generates the generated signal using a Schmitt trigger. By calculating the switch timing signal, the TDD switch timing synchronization acquisition procedure can be performed without the process of frame synchronization acquisition and signal demodulation.

Hereinafter, each component of the TDD repeater according to an exemplary embodiment of the present invention will be described with reference to FIG. 1 is a schematic internal block diagram of a TDD repeater according to an embodiment of the present invention.

The repeater for TDD communication according to the present invention has a structure in which a timing signal detector 115, a TDD switch timing generator 120, and a switch controller 135 shown in FIG. 1 are added to components of a conventional repeater. It should be implemented as, the switch (S / W) 140 near the transceiver 100 should perform a function of properly selecting the uplink (downlink) / downlink (downlink). In general, the signal transmitted from the base station, that is, the downlink signal, is received through the transceiver 100 and transmitted to the switch controller 135 through a processing process in each component. Then, the switch control unit 135 serves to connect the switch 140 to the up / down link in synchronization with the base station by the switch control signal generated through the processing to be described later.

In the base station transmission mode, a signal transmitted from a base station typically transmits a signal to a mobile communication terminal through a transmission medium via a switch 140. At this time, the switch control unit 135 processes the received signal according to an embodiment of the present invention to control the operation of the switch 140 so that the switch 140 is connected only in the downlink direction in synchronization with the base station. . The transmission medium may be optical, analog, RF, or the like.

In contrast, in the base station reception mode, a repeater receives a transmission signal from a mobile communication terminal through a transmission medium. In this case, as described above, the switch controller 135 controls the switch 140 so that the signal is amplified and transmitted only on the uplink. Operation for the components of such a repeater is similar to that in a conventional repeater, and a detailed description thereof is omitted.

Next, operations of the timing signal detector 115, the TDD switch timing generator 130, and the switch controller 135, which are components according to an embodiment of the present invention, in a repeater for TDD communication will be described in detail. Reference is made to FIG. 2 to describe this in detail. 2 is a diagram illustrating a signal according to a TDD wireless communication according to an embodiment of the present invention as a signal sequence in a time domain.

First, the timing signal detector 115 is a part for acquiring synchronization in a time domain without separately implementing a receiver modem in a repeater. What is important in this synchronization acquisition is a method of generating a RSSI signal from the received signal by receiving a signal according to the wireless communication of the TDD scheme. In order to generate the RSSI signal, the log amplifier 125 is implemented in the timing signal detector 115 according to an exemplary embodiment of the present invention. In addition, in another embodiment of the present invention, an integrator may be implemented instead of the log amplifier 125.

On the other hand, the signal sequence in the time domain of the transmission and reception signals in the TDD wireless communication is shown in FIG. 2 is a diagram illustrating a signal according to a TDD wireless communication according to an embodiment of the present invention as a signal sequence in a time domain.

As shown in FIG. 2, the reception signal sequence 200 is a signal sequence obtained through the reception block 105 implemented in the transceiver 100 in the repeater and appears in the base station transmission mode, and the signal transmitted from the base station is directed to the mobile communication terminal. To be delivered. Therefore, in the received signal sequence 200, a signal transmitted from the base station to the mobile communication terminal through the repeater is output only in the downlink period.

On the contrary, the transmission signal sequence 250 is obtained through the transmission block 110 implemented in the transceiver 100 in the repeater and is a signal sequence appearing in the base station reception mode. The signal received from the mobile communication terminal is transmitted to the base station. Therefore, in the transmission signal sequence 250, a signal transmitted from the mobile communication terminal to the base station through the repeater is output only in the uplink section.

In this transmission and reception signal, one frame for wireless communication in the TDD scheme is configured as follows.

1 Frame = DL (Downlink) + TTG (Tx / Rx Transition Gap) + UL (Uplink) + RTG (Rx / Tx Transition Gap)

As shown in Equation 1, one frame in the reception signal sequence 200 and the transmission signal sequence 250 is the RTG 210 section, the downlink section (DL) 220, the TTG 230, and the uplink section shown in FIG. It consists of a link section (UL) (240).

In the TDD repeater, the transceiver 100 does not interfere with each other in the same time domain. In addition, a transition gap (TG) region such as the RTG 210 and the TTG 230 is a region for preventing impulse of transmission / reception output by indicating a guard time.

Therefore, when looking at the reception signal sequence 200, it can be seen that the signal transmitted from the base station to the mobile communication terminal through the repeater is amplified only in the downlink and the signal sequence appears flat in the remaining portion. Through this, it can be estimated that the region where the signal sequence appears flat is a transition gap (TG), that is, a guard time or an uplink period.

Referring to FIG. 3 to examine the down-signal 220 section in the received signal sequence 200. 3 (a) to 3 (c) are diagrams for describing an operation of a timing signal detector according to an exemplary embodiment of the present invention, and a section in which a downlink signal is output from the received signal sequence 200 is briefly shown. .

First, the log amplifier 125 receives a signal received as shown in FIG. 3 (a) through the transceiver 100 and outputs a signal as shown in FIG. 3 (b). Referring to a), it can be seen that the horizontal axis is defined as the time axis and the downlink signal is amplified and output only in the downlink period. At this time, the period in one frame composed of the RTG section, the downlink section DL, the TTG, and the uplink section UL in the received signal sequence 200 shown in FIG. The downlink time at which the signal is output is T2. As shown in FIG. 3A, a frame having a period T1 repeatedly appears in the reception signal sequence 200.

As such, when a signal having an output as shown in FIG. 3A is received by the transceiver 100 through the transmission medium, the received signal is input to the log amplifier 125. Accordingly, the log amplifier 125 outputs the RSSI signal as shown in FIG. 3 (b) by using the received signal. At this time, the period and downlink time of one frame shown in FIG. 3 (a) are the same as T1 and T2 in FIGS. 3 (b) and 3 (c).

Then, the RSSI signal output from the log amplifier 125 is used as an input signal of the Schmitt trigger 120. The Schmitt trigger 120 receives the RSSI signal and receives a square wave of a shape as shown in FIG. The signal is output. The Schmitt trigger 120 receives the RSSI signal and generates a square wave signal that becomes a reference signal of the TDD switch timing generator 130.

Here, comparing FIG. 3 (a) and FIG. 3 (c), as shown in FIG. 3 (a), one frame start point is A point, but the frame start point in FIG. 3 (c) has the same downlink time. Is point B which has been misaligned from point A by a predetermined time. The reason for this error is related to the log amplifier 125, the error time of which is at most 1usec or less.

Here, the error time of less than or equal to 1usec is much smaller than the TTG time of the TTG section following the downlink section, that is, the guard time of 120usec or more, so the error time does not affect the operation of the system.

Here, since the downlink time is determined according to the general frame structure of the entire TDD system, the uplink starting point can be found by using information pre-programmed by the TDD switch timing generation unit 130 and transmitted to the switch control unit 135. To control the switch 140.

On the other hand, the reason for implementing the Schmitt trigger 120 in the timing signal detector 115 in the embodiment of the present invention is that it is possible to prevent errors due to noise that may occur when the square wave output. Typically, the Schmitt trigger circuit is used for detecting voltage levels, shaping waveforms, and the like. Further, in another embodiment of the present invention, a square wave generator may be applied instead of the Schmitt trigger.

This operation in the Schmitt trigger 120 will be described with reference to FIG. 4 is a view showing the operating characteristics of the Schmitt trigger according to an embodiment of the present invention.

4 shows a basic waveform output from the Schmitt trigger 120. In FIG. 4, reference numeral 400 denotes a high trigger voltage (UPT), and reference numeral 410 denotes a low trigger voltage (LTP).

The Schmitt trigger 120 operates sensitively according to the input voltage value, operates at a low trigger voltage, and the trigger signal is equal to a slowly changing AC voltage. The input waveform is a sine-like waveform that changes slowly, and the output is a square wave that forms two high and low logic states: 1 or 0 value.

Referring to FIG. 4, the level of the high trigger voltage 400 in the section where the output changes from 0 to 1, that is, the C and the low trigger voltage 410 in the section where the output changes from 1 to 0, that is, the D section. You can see that the levels of) are different. In addition, since the level of the high trigger voltage 400 is greater than the level of the low trigger level 410, even if a high level of noise occurs in the input voltage, the output transition from 0 to 1 can be solved. That is, it is possible to prevent an incorrect switch timing error signal caused by a high level of noise in the input voltage.

Meanwhile, to describe a general frame structure determined for TDD communication, reference is made to FIG. 5. 5 is a diagram illustrating a general frame structure for TDD communication.

As described above, the input signal is subjected to a corresponding process so as to be divided into an uplink 510, a downlink 530, and a guard time 520, as shown in FIG. 5. The log amplifier 125 and the Schmitt trigger 120 may be used to obtain a switch timing signal for controlling the switch so that the switch may be alternately synchronized with the up / down link.

First, when the base station transmits the uplink data 510 shown in FIG. 5 to the repeater and passes a predetermined guard time 520, the base station operates in a reception mode and demodulates the received signals. It is performed to go through the process corresponding to 540 to 580 continuously. Here, the guard time is a time required for the base station to switch from the transmission mode to the reception mode, and refers to RTG, TTG, etc. constituting one frame, the base station and the repeater by using the guard time to synchronize the transmission and reception mode to the mobile terminal Allow communication between them.

However, since no information can be transmitted or received during the guard time, the radio resources are inefficiently used. Therefore, if the repeater is not correctly synchronized with the base station in the middle, the effect of reducing the guard time occurs, so that the coverage is reduced by that, and therefore, accurate synchronization between the base station and the relay period is important. Therefore, according to the embodiment of the present invention, an appropriate switch timing may be found by correcting an error occurring in the log amplifier by the TDD switch timing generator.

On the other hand, when the switch timing signal is received from the timing signal detector 115, the TDD switch timing generator 130 transmits the information on the start point of the downlink and the start point of the uplink to the switch controller 135 using the previously input information. Output That is, the TDD switch timing generator 130 compares the switch timing signal from the Schmitt trigger 120 with pre-input information and outputs time information regarding downlink and uplink start points. As such, the switch timing synchronization acquisition procedure is performed through the timing signal synchronization extracted by using the switch timing signal from the timing signal detection unit 115 without the process of frame synchronization acquisition and signal demodulation.

According to the control signal output from the TDD switch timing generator 130 through the above process, that is, time information, the switch controller 135 controls the switch 140 to match the corresponding link signal with the corresponding path. In other words, based on the time information extracted through the TDD switch timing generator 130, the switch controller 135 generates a switch control command in the repeater to control the switch 140.

Through the above-described process, the repeater alternates the up / down link in synchronization with the base station and the mobile communication terminal in the previously promised form, and performs the switching of the transmission / reception mode during the guard time.

As described above, according to the present invention, when the TDD repeater acquires synchronization, the TDD switching timing can be found without an additional signal, and the frame length received by the repeater can be determined. In addition, the present invention has the effect of finding a sufficient switch timing because there is a guard time, such as TTG, RTG when switching between up and down links in synchronization.

Claims (4)

In the apparatus for obtaining synchronization in a TDD repeater, A timing signal detector comprising a log amplifier receiving a received signal and outputting a RSSI signal and a Schmitt trigger receiving the RSSI signal to generate a square wave to output a switch timing signal; A TDD switch timing generation unit for comparing the switch timing signal from the Schmitt trigger of the timing signal detection unit with pre-input information and outputting time information on downlink and uplink starting points; A switch configured to alternately connect only one direction of an uplink and a downlink signal in synchronization with a base station by using the output time information; And a switch controller for controlling the switch. The method of claim 1, wherein the TDD switch timing generator And outputting time information on downlink and uplink starting points from a square wave output from the timing signal detector. A method of obtaining synchronization in a TDD repeater having the same frequency of a downlink transmitted from a base station to a mobile communication terminal and an uplink signal transmitted from a mobile communication terminal to a base station, the method comprising: Outputting the RSSI signal from the received signal sequence on the time domain; Receiving the RSSI signal and generating a square wave to output a switch timing signal; And switching to alternately connect only one direction of an uplink and a downlink signal in synchronization with a base station through timing signal synchronization extracted by using the switch timing signal. The method of claim 3, wherein the outputting of the switch timing signal comprises: A method for preventing a switch timing error signal from occurring due to a high level of noise in an input voltage.

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