KR20100034460A - Method and apparatus for estimating channel at relay network - Google Patents

Abstract

PURPOSE: A method and an apparatus for estimating a channel in a relay network are provided to enable a terminal to use a base station transmission signal and a relay pilot signal, thereby estimating a channel between a base station and a relay and a channel between a relay and a terminal. CONSTITUTION: The first and second frequency converters(615,625) convert the first and second transmission signals of a relay into a frequency domain. The first and second pilot signal extractors(620,630) extract the first and second receiving pilot signals from the first and second transmission signals of the relay. A base station-relay channel estimator(631) estimates a channel between a relay and the base station from the first and second receiving pilot signals. A relay-terminal channel estimator(633) estimates a channel between the relay and the base station from the first and second receiving pilot signals.

Description

Method and apparatus for channel estimation in relay network {METHOD AND APPARATUS FOR ESTIMATING CHANNEL AT RELAY NETWORK}

The present invention relates to a channel estimation method and apparatus in a relay network. More specifically, the relay of the present invention transmits a base station transmission signal to a terminal simultaneously with a relay pilot signal generated in the relay, and the terminal of the present invention transmits the base station. The signal between the base station and the relay and the channel between the relay and the terminal may be estimated using the signal and the relay pilot signal, and the total channel may be estimated by multiplying the estimated channels with each other.

In the next-generation mobile communication, it is expected that a lot of communication will be performed through a relay station, rather than a base station serving all regions. By installing these relays, you can expand coverage and increase capacity. Unlike analog repeaters or digital repeaters used in conventional cellular systems, the relay system is capable of radio resource management in consideration of interference and resource conditions. As a result, a good link can be secured, thereby improving capacity, and a service can be provided to a terminal located in a shadow area, thereby improving coverage.

On the other hand, in order to accurately demodulate the signal received by the terminal, it is necessary to know the magnitude and phase characteristics of the path through which the signal transmitted from the base station passes. In order to facilitate this, when the base station transmits information, a predetermined band is allocated as a pilot signal and transmitted, and the terminal signals the pilot signal to determine the magnitude and phase characteristics of the transmission path through which the received signal has passed. Here, estimating the magnitude of the transmission path and the characteristics of the phase is called channel estimation.

In a relay network, a relay is difficult to estimate an accurate channel in the terminal because the base station retransmits the received base station transmission signal to the terminal without considering distortion of a signal that may occur when the base station transmission signal is transmitted to the relay through a wireless environment. In general, the pilot of the OFDM signal is inserted enough to solve the delay spread in consideration of the coverage. In general, the delay spread increases due to the expansion of the coverage in the relay network, thereby increasing the frequency selectivity. Accordingly, a problem arises in that it is difficult to estimate the exact channel experienced before and after the relay only with the conventionally inserted pilot signal.

The present invention has been made to solve the above problems, in the relay network, a relay generates a relay pilot signal and transmits it to the terminal along with the base station transmission signal, the terminal using the base station transmission signal and the relay pilot signal base station An object of the present invention is to provide a channel estimation method for estimating a total channel by estimating a channel between and a relay and a channel between a relay and a terminal, respectively.

The pilot signal transmission method of the relay for channel estimation in the relay network of the present invention for achieving the above object is a step of receiving a base station transmission signal, extracting the pilot included in the received base station transmission signal, the extraction Generating a first pilot signal of the relay in which the pilot is disposed at the same position in the pilot and the frequency domain; transmitting a first transmission signal of the relay obtained by adding the base station transmission signal and the first pilot signal of the relay; It is characterized by including. The method for transmitting a pilot signal of the relay may include receiving a base station transmission signal continuous to the received base station transmission signal and extracting a pilot; a relay having the same position and opposite phase in a frequency domain with the first pilot signal of the relay; Generating a second pilot signal and transmitting a second transmission signal of the relay obtained by summing the continuously received base station transmission signal and the second pilot signal of the relay.

In the method of estimating a channel in a relay network of the present invention, the relay receives a base station transmission signal, extracts a pilot, and generates a first pilot signal of a relay in which a pilot is disposed at the same position in the frequency domain with the extracted pilot. And transmitting the first transmission signal of the relay, which is the sum of the base station transmission signal and the first pilot signal of the relay, to the terminal, wherein the relay receives a base station transmission signal that is continuous to the received base station transmission signal, and extracts a pilot. And generating a second pilot signal of the relay having the same position and opposite phase in the frequency domain with the first pilot signal of the relay, summing the continuously received base station transmission signal and the second pilot signal of the relay. Transmitting a second transmission signal of one relay to the terminal; It characterized in that it comprises the step of estimating a channel for receiving the first and second transmission signals from the relay group.

In addition, the apparatus for estimating a channel of a relay network of the present invention includes a first transmission signal of a relay obtained by adding a base station transmission signal and a first pilot signal of the relay, and a second relay of the relay obtained by adding a base station transmission signal and a second pilot signal of the relay. A wireless communication unit for receiving a transmission signal from a relay, first and second frequency converters for converting the first and second transmission signals of the relay into a frequency domain, respectively, and first and second transmission signals from the first and second transmission signals of the relay, respectively. First and second pilot signal extractors for extracting a second received pilot signal, a base station-relay channel estimator for estimating a channel between a base station and a relay from the first and second received pilot signals, and the first and second received pilots A relay-terminal channel estimator for estimating a channel between the relay and the terminal from the signal, wherein the first pilot signal of the relay is The pilot is placed at the same position in the transmission signal and the frequency domain, the pilot has a first pilot signal and the position of the relay in the second pilot signal of the relay is characterized in that the same and the phases are opposed.

The relay of the present invention does not transmit the base station transmission signal transmitted from the base station to the terminal as it is, but simultaneously transmits the relay pilot signal and the base station transmission signal generated in the relay to the terminal, the terminal of the present invention the base station transmission signal and the relay The channel estimation performance in the relay network can be improved by estimating the total channel by estimating each channel between the base station and the relay and the channel between the relay and the terminal using the pilot signal.

In addition, the channel estimation method of the present invention has an advantage of not affecting the efficiency of the bandwidth because the relay pilot is superimposed on a pilot position which is conventionally used.

The terminology of an embodiment of the present invention is to be in accordance with the IEEE 802.16j standard, but this is merely to help understanding the term and is not necessarily limited thereto.

The embodiment of the present invention is also applicable to multi-hops in which a plurality of relay stations (RSs) exist, but for the sake of simplicity, two-hop, i.e., one relay For example, the case should be described. It will be readily appreciated by those skilled in the art that the uplink bandwidth request method in the two hops may be applied to the multi hops.

Hereinafter, terms used in the present invention will be defined.

The first pilot signal of the relay of the present invention is a signal that the relay generates when receiving any base station transmission signal, the second pilot signal of the relay is generated when the relay receives a base station transmission signal continuous to the base station transmission signal It is a signal. In this case, although pilots are arranged at the same position in the frequency domain, the first and second pilot signals have different phases.

The first transmission signal of the relay of the present invention is a signal transmitted to the terminal by adding any base station transmission signal and the first pilot signal of the relay, the second transmission signal of the relay is continuously received after receiving the arbitrary base station transmission signal The base station transmission signal and the second pilot signal of the relay is added to the signal transmitted to the terminal.

The first received pilot signal of the present invention is a signal from which only pilots are extracted from the first transmission signal of the relay, and the second received pilot signal is a signal from which only pilots are extracted from the second transmission signal of the relay.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that, in the drawings, the same components are denoted by the same reference symbols as possible. Further, the detailed description of well-known functions and constructions that may obscure the gist of the present invention will be omitted.

FIG. 1 is a diagram illustrating a concept in which a relay transmits a base station transmission signal to a terminal at the same time as a relay pilot signal in a relay network, and the terminal receiving the signals estimates a channel. In this case, the relay network according to the embodiment of the present invention includes a base station 110, a relay 120, and a terminal 130.

First, the base station 110 transmits a signal (hereinafter, referred to as a 'base station transmission signal') using an OFDM scheme using several subcarriers for high speed wireless data transmission. The frequency selective channel appearing in broadband transmission is then approximated as a frequency non-selective channel without intersymbol interference. Detailed description of the OFDM scheme will be apparent to those skilled in the art, and a detailed description thereof will be omitted.

The base station transmission signal is transmitted based on a symbol, and the symbol includes pilot and data. Pilots are arranged at regular intervals in the base station transmission signal to estimate the channel in a rapidly changing channel environment and used to estimate the channel. In addition, the base station 110 of the present invention simultaneously transmits the base station transmission signal to the relay 120 and the terminal 130.

The relay 120 is used to extend transmission coverage. In general, relays are classified into an amplify-and-forward scheme and a decode-and-forward scheme. In this case, post-decoding propagation is not used much at present due to problems such as increased design complexity, processing delay, and cost increase. In addition, after amplification, the propagation method is classified into a variable gain method and a fixed gain method. The variable gain method has an advantage of improving performance by compensating for a channel experienced by a transmission signal in a relay, but with complexity. Has the disadvantage of increasing. In contrast, the fixed gain method compensates only a certain gain and retransmits a transmission signal without compensating a channel, and is simple in design and can be implemented at low cost. It is assumed that the relay 120 according to the embodiment of the present invention is a relay according to a fixed gain method among the post-amplification transfer methods.

When the relay 120 receives the base station transmission signal from the base station 110, the relay 120 extracts a pilot from the base station transmission signal. In addition, the relay 120 generates a relay pilot signal in which a pilot is disposed at the same position as the extracted pilot position in the frequency domain of each subcarrier (hereinafter, the same applies). In this case, the relay pilot signal generated by the relay 120 has pilot only and the data region is zero.

In this case, the relay 120 generates a + P _add signal (hereinafter referred to as a 'first pilot signal of a relay') upon receiving a base station transmission signal, and _adds the arbitrary base station transmission signal and the first pilot signal of the relay. To the terminal.

After receiving the base station transmission signal, the relay 120 generates a -P _add signal (hereinafter referred to as 'relay second pilot signal') when receiving a continuous base station transmission signal, and receives the received base station transmission signal and the relay. The second pilot signal of the sum and transmits to the terminal. In this case, if there is no change in the channel between two consecutive symbols, when the two consecutive reception signals are summed at the terminal 130, the second pilot signal of the first and the relay becomes 0, and the effect is eliminated.

The terminal 130 receives the first transmission signal of the relay and the second transmission signal of the relay transmitted from the relay 120 and estimates a channel using the channel estimation apparatus according to the embodiment of the present invention.

The terminal 130 of the present invention estimates a channel between the base station 110 and the relay 120 and a channel between the relay 120 and the terminal 130, and then obtains a channel of the data region through interpolation based on the channel. In the present invention, since the channel between the base station 110 and the relay 120 and the channel between the relay 120 and the terminal 130 do not have a large delay spread, each channel can be estimated more accurately with a given number of pilots.

2 is a diagram illustrating a concept in which the relay 120 generates a relay pilot signal and transmits the relay pilot signal to the terminal 130 simultaneously with the base station transmission signal.

3A is a diagram illustrating a structure of a base station transmission signal transmitted from a base station in a frequency band, and FIG. 3B is a diagram showing a structure of a first pilot signal of a relay generated in a relay in a frequency band, FIG. 3C is a diagram illustrating a structure of a second pilot signal of a relay generated in a relay in a frequency band, and FIG. 3D shows a relay pilot signal having a different phase from a base station transmission signal continuously received. It is a figure which shows an example.

First, the relay 120 sequentially receives base station transmission signals continuously transmitted from the base station and extracts a pilot 210. In this case, the structure of any base station transmission signal transmitted from the base station is as shown in A of FIG.

As shown in FIG. 3A, pilots are arranged at a predetermined period in any base station transmission signal. The actual data is placed between the pilot and the pilot.

The relay 120 does not directly retransmit the received base station transmission signal to the terminal 130, but stores the received base station transmission signal in a memory (220). This is to temporarily wait while a relay pilot signal is generated, which is added with the received base station transmission signal.

The relay 120 storing any received base station transmission signal in the memory generates a first pilot signal of the relay. In addition, the relay 120 generates a second pilot signal of the relay upon receiving the continuous base station transmission signal after receiving the arbitrary base station transmission signal. In this case, the first pilot signal of the relay and the second pilot signal of the relay have pilots in the same position in the frequency domain, but the phases are opposite to each other.

Examples of the first pilot signal and the second pilot signal generated in this case are shown in B and C of FIG. 3. As described above, the relay pilot signal alternately generates the first pilot signal of the relay and the second pilot signal of the relay which are out of phase with each other. FIG. 3C is a diagram showing a second pilot signal of the relay whose phase is opposite to the first pilot signal of the relay.

As shown in B and C of FIG. 3, the pilot pilot is arranged only at the same position as the pilot arranged in the base station transmission signal, and the data area is zero.

3D illustrates a method of generating relay pilot signals having different phases when receiving base station transmission signals continuously. As can be seen in FIG. 3D, the relay 120 generates a relay pilot signal having a positive phase when an arbitrary base station transmit signal is received. The relay 120 generates a relay pilot signal having a negative phase when receiving a continuous base station transmission signal after receiving the base station transmission signal. The relay 120 repeats the above process and alternately generates relay pilot signals having different phases.

The relay 120 converts the generated relay pilot signal to the time domain after generating the relay pilot signal (240). This is because in the OFDM system, although the signal processing is performed in the frequency domain, the actual signal is transmitted and received in the time domain which is an analog signal.

In addition, the relay 120 generates a cyclic prefix (CP) and inserts the CP into a relay pilot signal converted into a time domain in order to prevent the destruction of orthogonality caused by the delay of a subcarrier used in OFDM.

The relay 120 adds the base station transmission signal and the relay pilot signal received from the base station (260), and amplifies the summed signal by a relay power gain for amplifying the signal (270). The relay 120 transmits the sum of the base station transmission signal and the relay pilot signal to the terminal 130 (280).

4 is a block diagram showing the internal structure of a relay 120 according to an embodiment of the present invention. The relay 120 includes a wireless communication unit 410, a memory 420, and a control unit 430, and the control unit 430 includes a relay pilot signal generator 430A, a time domain converter 430B, and a CP generator. 430C, the signal summing unit 430D may be included.

5A to 5C are diagrams illustrating structures of generation stages of the relay pilot signal. In this case, it should be noted that FIGS. 5A to 5C are merely conceptual views of the structure of the relay pilot signal. Hereinafter, with reference to FIGS. 4 and 5a to 5c.

The wireless communication unit 410 may include an RF transmitter for upconverting and amplifying a frequency of a transmitted signal, and an RF receiver for low noise amplifying and downconverting a received signal. The wireless communication unit 210 according to an embodiment of the present invention receives the base station transmission signal transmitted from the base station and transmits it to the control unit 430. In addition, the wireless communication unit receives the sum signal of the base station transmission signal and the relay pilot signal output from the control unit and transmits to the terminal 130.

The memory 420 temporarily stores the base station transmission signal transmitted from the base station 110 while the relay pilot signal is generated.

The controller 430 controls the overall operation of the relay 120. When the base station transmission signal is received from the wireless communication unit 410, the controller 430 controls to temporarily store the received base station transmission signal in the memory 420 until the relay pilot signal is generated. The controller 430 according to the embodiment of the present invention may include a relay pilot signal generator 430A, a time domain converter 430B, a CP generator 430C, and a signal adder 430D.

The relay pilot signal generator 430A generates a relay pilot signal in which a pilot is disposed at the same position as the pilot position of the base station transmission signal. The data area is filled with zeros so that the relay pilot signal does not have actual data. In this case, the relay pilot signal generation unit 430A according to the embodiment of the present invention generates a first pilot signal of the relay when receiving any base station transmission signal, and continuously generates a second pilot signal of the relay when receiving the base station transmission signal. do.

In this case, the structure of the first pilot signal of the relay generated is shown in FIG. 5A. Hereinafter, only a process of generating and converting a first pilot signal of a relay will be described, but referring to this process, a process of generating and converting a second pilot signal of a relay having a phase opposite to that of the first pilot signal of the relay is obvious to those skilled in the art. something to do. As shown in FIG. 5A, the pilot of the first pilot signal of the relay is disposed at the same position as the pilot position of the base station transmission signal and the data area is zero.

The time domain converter 430B converts the pilot signal generated by the relay pilot signal generator 430A into the time domain. In this case, the time domain transformer 430B may be implemented by an inverse fast fourier transform (IFFT) that converts a signal that is a digital signal but is a frequency domain into a time domain.

5B illustrates a structure in which the first pilot signal of the relay in the frequency domain generated by the relay pilot signal generator 430A is converted into the time domain. As shown in FIG. 5B, the relay pilot signal in the frequency domain is converted into the relay pilot signal in the time domain in the x1 to x2 time period by the IFFT of the time domain converter.

The CP generator 430C generates a CP for preventing the destruction of orthogonality that may be caused by the delay of the OFDM subcarrier, and inserts the CP into the first pilot signal of the relay in the time domain. In other words, the OFDM symbol period is the sum of the effective symbol period and the guard interval to which the actual data is transmitted, and the orthogonality is prevented by copying and inserting the signal CP of the last interval from the valid symbol interval in the guard period.

5C is a diagram illustrating a structure of a first pilot signal of a final relay in which CP is generated and inserted into a first pilot signal of a relay in a time domain. As illustrated in FIG. 5C, the CP is inserted into the guard period of the first pilot signal of the relay converted into the time domain by the time domain converter 430B.

The signal summing unit 430D adds the base station transmission signal stored in the memory 420 and the relay pilot signal generated in the relay. In this case, the signal summing unit 430D may be implemented as a simple adder, and the two signals are summed and output to the wireless communication unit 410. Then, the summed relay transmission signal is amplified by the relay power gain and then transmitted to the terminal 130.

6 is a diagram illustrating an internal structure of a channel estimating apparatus of a terminal 130 according to an embodiment of the present invention. As shown in FIG. 6, the apparatus for estimating a channel of a terminal includes a wireless communication unit 605, a memory 610, first and second frequency converters 615 and 625, and first and second pilot signal extractors 620 and 630. And a base station-relay channel estimator 631, a relay-terminal channel estimator 633, interpolators 660 and 665, and a multiplier 670. In this case, the base station-relay channel estimator includes adders 635, first and third dividers 640 and 655, and the relay-terminal channel estimator includes a subtractor 645 and a second divider 650. .

The wireless communication unit 605 may include an RF transmitter for upconverting and amplifying a frequency of a transmitted signal, and an RF receiver for low noise amplifying and downconverting a received signal. The wireless communication unit 605 receives the base station transmission signal and the relay pilot signal transmitted from the relay 120 and transmits the received signal to the memory 610. In this case, the wireless communication unit 605 receives the first transmission signal of the relay and the second transmission signal of the relay from the relay 120.

The memory 610 receives the first transmission signal of the relay and the second transmission signal of the relay from the wireless communication unit 605. In this case, the memory 610 transmits the first transmission signal of the relay to the first frequency converter 615 and the second transmission signal of the relay to the second frequency converter 625, respectively.

The first frequency converter 615 and the second frequency converter 625 receive the first transmission signal of the relay and the second transmission signal of the relay from the memory 610, respectively. The first transmission signal of the relay in the time domain and the second transmission signal of the relay are converted into a signal in the frequency domain by fast fourier transform (FFT). The first frequency converter 615 and the second frequency converter 625 transfer the signals converted into the frequency domain to the first and second pilot signal extractors 620 and 630, respectively.

The first pilot signal extractor 620 and the second pilot signal extractor 630 are the first transmission signal of the relay in the frequency domain received from the first frequency converter 615 and the second frequency converter 625 and the second of the relay. It receives the transmission signal and extracts only the pilot signal.

In this case, the pilot signal extracted from the first transmission signal of the relay (hereinafter, 'first received pilot signal') is represented by Equation 1 below.

[Equation 1]

Y1 (k) = H _sr (k) * G * H _rd (k) * P (k) + G * H _rd (k) * P _add (k)

Where H _sr (k) is the channel between relays in the base station, G is the relay power gain, H _rd (k) is the channel between terminals in the relay, P (k) is the pilot of the base station transmission signal, and P _add (k) is the relay pilot. It means the pilot of the signal. Where k is the k-th subcarrier.

In addition, when the pilot signal extracted from the second transmission signal of the relay (hereinafter referred to as a 'second received pilot signal') is expressed by Equation 2 below.

[Equation 2]

Y2 (k) = H _sr (k) * G * H _rd (k) * P (k)-G * H _rd (k) * P _add (k)

Where H _sr (k) is the channel between relays in the base station, G is the relay power gain, H _rd (k) is the channel between terminals in the relay, P (k) is the pilot of the base station transmission signal, and P _add (k) is the relay pilot. It means the pilot of the signal. Likewise, k means the k th subcarrier.

As can be seen in Equations 1 and 2, the sign of the relay pilot signal added by the relay 120 is expressed as '+' in the first received pilot signal and '-' in the second received pilot signal. It is expressed because the phase of the first pilot signal of the relay and the second pilot signal of the relay is reversed.

The first pilot signal extractor 620 and the second pilot signal extractor 630 extract pilot signals from the first transmission signal of the relay and the second transmission signal of the relay, respectively, and then extract the pilot signals from the base station-relay channel estimator 631. The relay outputs to the channel estimator 633.

The channel estimating apparatus of the present invention first estimates the entire channel between the base station and the terminal by the base station-relay channel estimator 631 (first process), and then relays and the terminal estimated by the relay-terminal channel estimating unit 633. The channel between the base station and the relay is estimated (third process) using the channel (second process). In this case, the first process and the second process may be performed independently. Hereinafter, the above process will be described sequentially.

<Estimate of total channel between base station and terminal (first process)>

The adder 635 of the base station-relay channel estimator 631 receives the first received pilot signal and the second received pilot signal extracted from the first pilot signal extractor 620 and the second pilot signal extractor 630. Add. In this case, the output signal is shown in Equation 3 below.

&Quot; (3) &quot;

Y1 (k) + Y2 (k) = 2 * H _sr (k) * G * H _rd (k) * P (k)

The adder 635 which adds the first received pilot signal and the second received pilot signal outputs the result to the first divider 640.

The first divider 640 receives the sum of the first received pilot signal and the second received pilot signal output from the adder 635, P (k), which is a pilot of the base station transmission signal, G, which is a relay power gain, and adds. Divide by 2 each due to. The terminal 130 already knows the values of P (k) and G, and in this case, the output signal is as shown in Equation 4 below.

[Equation 4]

[Y1 (k) + Y2 (k)] / [2 * P (k) * G] = [2 * H _sr (k) * G * H _rd (k) * P (k)] / [2 * P (k) * G]

= H _sr (k) * H _rd (k)

That is, the result of the division result of the first divider 640 is a channel between the base station 110 and the terminal 130. Hereinafter, this value is called A. The first divider 640 outputs the value to the third divider 655.

Channel Estimation Between Relay and Terminal (Second Step)

Independently of the operation of the base station-relay channel estimator 631, the relay-terminal channel estimator 633 estimates a channel between the relay and the terminal by using the first and second received pilot signals. Hereinafter, this will be described in detail.

The subtractor 645 of the relay-terminal channel estimator 633 receives the first received pilot signal and the second received pilot signal from the first pilot signal extractor 620 and the second pilot signal extractor 630, respectively. The second received pilot signal is subtracted from the received pilot signal. In this case, the output signal is as shown in Equation 5 below.

[Equation 5]

Y1 (k) -Y2 (k) = 2 * G * H _rd (k) * P _add (k)

The subtractor 645 subtracting the first received pilot signal and the second received pilot signal outputs the result to the second divider 650.

The second divider 650 may subtract the first and second received pilot signals output from the subtractor 645 to P _add (k), which is a pilot of the relay, G, which is a relay power gain, and 2 due to addition. Divide by each. In this case, the output signal is shown in Equation 6 below.

&Quot; (6) &quot;

[Y1 (k) -Y2 (k)] / [2 * P _add (k) * G] = [2 * G * H _rd (k) * P _add (k)] / [2 * P _add (k) * G]

= H _rd (k)

That is, the result of the division result of the second divider 650 is a channel H _rd (k) between the relay 120 and the terminal 130. Since the relay 120 simultaneously transmits a relay pilot signal having a different phase from a base station transmission signal, the terminal 130 receiving the same may estimate a channel between the relay 120 and the terminal 130. Hereinafter, this value is referred to as B. The second divider 650 outputs the value to the third divider 655 and the second interpolator 655.

Channel estimation between base station and relay (3rd step)

The base station-relay channel estimator 631 estimates a channel between the base station and the relay by using the entire channel between the base station and the terminal estimated in the first step and the channel between the relay and the terminal estimated in the second step.

The third divider 655 of the base station-relay channel estimator 631 receives A (ie, H _sr (k) * H _rd (k)) from the first divider 640, and the second divider 655. A / B is performed by receiving B (ie, H _rd (k)) from 650. This may be expressed as Equation 7 below.

[Equation 7]

A / B = [H _sr (k) * H _rd (k)] / H _rd (k) = H _sr (k)

That is, the result output through the third divider 655 is a channel between the base station 110 and the relay 120. The third divider 655 transfers the output value to the first interpolator 660.

<Channel Estimation in the Data Area>

According to an embodiment of the present invention, a channel estimating apparatus estimates a channel between a base station 110 and a relay 120 and a channel between a relay 120 and a terminal 130 and interpolates a channel of a data area using the same. interpolation). If the delay spread is large, the channel estimation error becomes large when the interpolation method is performed based on the entire channels acquired according to the conventional method. In the embodiment of the present invention, the channel between the base station 110 and the relay 120 and the relay ( The channels between 120 and the terminal 130 are separately obtained and each interpolation method is performed.

The first interpolator 660 obtains a data area channel between the base station and the relay through interpolation using a channel between the base station 110 and the relay 120 output from the third divider 655. . The first interpolator 660 transfers the output value to the multiplier 670.

The second interpolator 665 obtains a data area channel between the relay and the terminal through interpolation using a channel between the relay 120 and the terminal 130 output from the second divider 650. The second interpolator 665 transfers the output value to the multiplier 670.

The multiplier 670 receives the values output from the first interpolator 660 and the second interpolator 665 and multiplies each other. Then, the channel of the data area from the base station 110 to the terminal 130 can be estimated.

FIG. 7 illustrates that the relay 120 generates a relay pilot signal having a different phase and transmits the signal to the terminal 130 along with a base station transmission signal, and the terminal 130 estimates the channel. This is a flow chart showing the process.

First, when the relay 120 receives any base station transmission signal transmitted from the base station in step S705, the relay 120 extracts a pilot from any base station transmission signal received in step S710. In operation S715, the relay 120 generates a first pilot signal of a relay in which a pilot is disposed at the same position in the frequency domain as the extracted pilot. The relay 120 adds the received base station transmission signal and the first pilot signal of the generated relay in step S720 (first transmission signal of the relay), and transmits it to the terminal 130 in step S725. .

In step S730, the relay 120 receives a base station transmission signal that is continuously transmitted to any base station transmission signal of step S705. The relay 120 then extracts the pilot from the base station transmission signal received continuously in step S735. In operation S740, the relay 120 generates the first pilot signal of the relay in which the pilot having the same position in the frequency domain but the pilot of which the phase is opposite to the pilot of the first pilot signal of the relay is disposed. . In addition, the relay 120 adds the base station transmission signal continuously received in step S745 and the second pilot signal of the generated relay (second transmission signal of the relay), and transmits it to the terminal 130 in step S750. .

The steps S705 to S750 merely illustrate an example of a process in which a relay generates a relay pilot signal having a different phase and transmits the same to a terminal, but is not necessarily limited to the order. For example, steps S705 to S725 and steps S730 to S750 may be performed independently of each other according to a reception time point of any base station transmission signal and a continuous base station transmission signal.

The terminal 130 converts the relay transmission signal received in step S755 into the frequency domain using the FFT. The terminal 130 extracts a pilot signal from the relay transmission signal in step S760 and estimates a channel in step S765 using the extracted pilot signal.

8 is a flowchart illustrating a process of estimating a channel using a channel estimating apparatus when the terminal 130 receives the first and second transmission signals of the relay from the relay 120 according to an exemplary embodiment of the present invention.

First, the terminal 130 sequentially receives the first and second transmission signals of the relay from the relay 120 in step S805. In operation S810, the terminal 130 converts the first and second transmission signals of the received relay from the time domain to the frequency domain, and then, in step S815, the terminal 130 receives the first received pilot signal from the first transmission signal of the relay. Extract and extract the second received pilot signal from the second transmitted signal of the relay.

The terminal 130 estimates the total channel by estimating the channel between the base station 110 and the relay 120 and the channel between the relay 120 and the terminal 130 using the channel estimating apparatus of the present invention in step S820 and below. To control a series of processes.

If the channel is estimated between the relay 120 and the terminal 130, the channel estimating apparatus subtracts the second received pilot signal from the first received pilot signal in step S825. In operation S830, the channel estimating apparatus estimates the channel between the relay 120 and the terminal 130 by dividing the subtracted result by the set value (2 * G * P _add ). In this case, since the description of the characters has been described above, a detailed description thereof will be omitted.

If the terminal 130 determines that the channel between the relay 120 and the terminal 130 is not estimated at step S820, the terminal 130 determines whether to estimate the channel between the base station 110 and the relay 120 at step S840. If estimating a channel between the base station 110 and the relay 120, the channel estimating apparatus adds the first received pilot signal and the second received pilot signal in step S845. In operation S850, the channel estimating apparatus estimates the channel between the base station 110 and the terminal 130 by dividing the added result by the set value (2 * G * P). Thereafter, when the channel estimating apparatus divides the channel between the base station 110 and the terminal 130 obtained in step S850 by the channel between the relay 120 and the terminal 130 obtained in step S830 in step S855, the base station 110. ) And a channel between the relay 120 can be obtained.

The channel estimator obtaining the channel between the base station 110 and the relay 120 and the channel between the relay 120 and the terminal 130 estimates a data channel by performing interpolation for each of the channels in step S835.

When the channel estimating apparatus multiplies each channel subjected to the interpolation using a multiplier in operation S860, the entire channel including the channel of the data region between the base station 110 and the terminal 130 may be estimated.

The embodiments of the present invention disclosed in the present specification and drawings are merely illustrative of specific embodiments of the present invention and are not intended to limit the scope of the present invention in order to facilitate understanding of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention can be carried out in addition to the embodiments disclosed herein.

1 is a diagram illustrating a concept in which, in a relay network, a relay transmits a base station transmission signal to a terminal at the same time as a relay pilot signal and the terminal receiving the signals estimates a channel.

2 is a diagram illustrating a concept in which the relay 120 generates a relay pilot signal and transmits the same to the terminal 130 at the same time as the base station transmission signal.

3A is a diagram showing the structure of a base station transmission signal transmitted from a base station in a frequency band.

3B is a diagram showing the structure of a first pilot signal of a relay generated in a relay in a frequency band.

3C is a diagram showing the structure of a second pilot signal of a relay generated in a relay in a frequency band;

3D is a diagram illustrating a method of generating a relay pilot signal having a different phase when receiving a base station transmission signal continuously;

4 is a block diagram showing the internal structure of a relay 120 according to an embodiment of the present invention.

5A to 5C are diagrams illustrating structures for each generation stage of a relay pilot signal.

6 is a diagram illustrating an internal structure of a channel estimating apparatus of a terminal 130 according to an embodiment of the present invention.

FIG. 7 illustrates that the relay 120 generates a relay pilot signal having a different phase and transmits the signal to the terminal 130 along with the base station transmission signal, and the terminal 130 estimates the channel. Flowchart representing the process.

8 is a flowchart illustrating a process of estimating a channel using a channel estimating apparatus when a terminal 130 receives a first transmission signal of a first and a relay from a relay 120 according to an embodiment of the present invention.

Claims (16)

A method for transmitting a pilot signal of a relay for channel estimation in a relay network, the method comprising: Receiving a base station transmission signal and extracting a pilot included in the received base station transmission signal; Generating a first pilot signal of a relay having a pilot disposed at the same position in the frequency domain with the extracted pilot; And transmitting the first transmission signal of the relay obtained by adding the base station transmission signal and the first pilot signal of the relay. The method of claim 1, Extracting a pilot by receiving a base station transmission signal consecutive to the received base station transmission signal; Generating a second pilot signal of the relay having the same position and opposite phase in the frequency domain with the first pilot signal of the relay; And And transmitting the second transmission signal of the relay obtained by adding up the continuously received base station transmission signal and the second pilot signal of the relay. In the channel estimation method in a relay network, Receiving, by the relay, a base station transmission signal, extracting a pilot, and generating a first pilot signal of the relay in which the pilot is disposed at the same position in the frequency domain with the extracted pilot; Transmitting a first transmission signal of a relay obtained by adding the base station transmission signal and the first pilot signal of the relay to a terminal; The relay receives a base station transmission signal consecutive to the received base station transmission signal, extracts a pilot, and generates a second pilot signal of the relay having the same position and opposite phase in the frequency domain with the first pilot signal of the relay. Process of doing; Transmitting a second transmission signal of the relay obtained by adding the continuously received base station transmission signal and the second pilot signal of the relay to the terminal; And And estimating a channel by the terminal receiving the first and second transmission signals of the relay. The method of claim 3, wherein the channel estimation process Converting the first and second transmission signals of the relay into a frequency domain, respectively; Extracting a first received pilot signal from the first transmitted signal of the relay and extracting a second received pilot signal from the second transmitted signal of the relay; Estimating a channel between a relay and a terminal and a channel between a base station and a terminal from the first and second received pilot signals; And And estimating a channel between the base station and the relay by dividing a channel between the base station and the terminal into a channel between the relay and the terminal. The method of claim 4, wherein And estimating a channel between the relay and the terminal by subtracting the second received pilot signal from the first received pilot signal and dividing by a set value. The method of claim 5, The set value is a channel estimation method in a relay network, characterized in that twice the product of the relay power gain and the relay pilot signal. The method of claim 6, And estimating a channel between the base station and the terminal by adding the second received pilot signal from the first received pilot signal and dividing the set value by a predetermined value. The method of claim 7, wherein And the set value is twice the product of the relay power gain and the base station pilot signal. The method of claim 4, wherein Interpolating a channel between the base station and the relay and a channel between the relay and the terminal; And And estimating an entire channel between the base station and the terminal by multiplying the interpolation result. The method of claim 3, The relay is a channel estimation method in a relay network, characterized in that the post-amplification transmission method using a fixed gain. In the channel estimation apparatus of a relay network, A wireless communication unit configured to receive from the relay a first transmission signal of the relay obtained by adding the base station transmission signal and the first pilot signal of the relay and a second transmission signal of the relay obtained by adding the base station transmission signal and the second pilot signal of the relay; First and second frequency converters for converting the first and second transmission signals of the relay into a frequency domain, respectively; First and second pilot signal extractors for extracting first and second received pilot signals from first and second transmitted signals of the relay, respectively; A base station-relay channel estimator for estimating a channel between a base station and a relay from the first and second received pilot signals; And A relay-terminal channel estimator for estimating a channel between the relay and the terminal from the first and second received pilot signals, The pilot of the first pilot signal of the relay is located in the same position in the frequency domain and the base station transmission signal, the pilot of the second pilot signal of the relay is the same position and the opposite phase of the first pilot signal of the relay Channel estimation device of the relay network, characterized in that. The method of claim 11, wherein the base station-relay channel estimator, An adder for adding and outputting the first and second received pilot signals; A first divider for dividing and outputting the added value by a set value; And a third divider for dividing and outputting the value output from the first divider into channels between the relay and the terminal. The method of claim 12, And the set value is twice the relay power gain and the base station pilot signal. The method of claim 12, wherein the relay terminal terminal estimation unit, A subtractor which subtracts and outputs the second received pilot signal from the first received pilot signal; And And a second divider dividing the subtracted output value by a set value. The method of claim 14, And the set value is twice the product of the relay power gain and the relay pilot signal. The method of claim 11, A first interpolator for interpolating and outputting a channel between the base station and the relay; A second interpolator for interpolating and outputting a channel between the relay and the terminal; And And a multiplier for multiplying output values of the first and second interpolators with each other.

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