KR100922729B1 - Apparatus and method for channel estimation and synchronization for OFDM/OFDMA relay system - Google Patents

Abstract

Disclosed are a channel estimation apparatus and a synchronization apparatus in a quadrature frequency division multiplexing / orthogonal frequency division multiple access relay system. The pilot signals are extracted based on the signal received by the terminal from the transmitters in the transparent relay system or the cooperative relay system, and the extracted pilot signals are transmitted based on the extracted pilot signals and preset reference pilot signals. Estimating the propagation delay between a transmitter and a terminal, estimating the propagation delay weight of the transmitter based on the estimated propagation delay, and estimating a channel between the transmitter and the terminal to receive data through a relay. Overcome channel estimation performance degradation due to It also stores the existing carrier frequency offset and timing offset for each transmitting device, identifies the transmitting device transmitting the signal when the terminal receives the signal, and stores the stored carrier frequency offset and timing offset for the identified transmitting device for that signal. By compensating, the influence of the carrier frequency offset and the timing offset between the transmitter and the terminal link is eliminated.

Multi hop relay, OFDM, synchronization, channel estimation

Description

Apparatus and method for channel estimation and synchronization for OFDM / OFDMA relay system in orthogonal frequency division multiplexing / orthogonal frequency division multiple access relay system

The present invention relates to a channel estimating apparatus and a synchronizing apparatus and a method thereof in an orthogonal frequency division multiplexing / orthogonal frequency division multiple access relay system. That is, in the OFDM / OFDMA relay system having a multi-hop relay, the channel estimation compensation device and method that can overcome the performance degradation caused when the channel estimation due to the propagation delay or the received signal is analyzed when data is transmitted through the relay; The present invention relates to a synchronization device and a method capable of compensating a carrier frequency offset and a timing offset caused by mobility of a terminal.

The present invention is derived from a study conducted as part of the IT new growth engine core technology development project of the Ministry of Information and Communication and the Korea Electronics and Telecommunications Research Institute. [Task Management Number: 2006-S-001-01, Assignment Name: Adaptation for 4th Generation Mobile Communication] Development of wireless access and transmission technology].

In general, the transmitting side of Orthogonal Frequency Division Multiplexing (OFDM) converts a symbol string input in series into a parallel unit of blocks formed of N symbols. Inverted Fast Fourier Transform (IFFT) is used to modulate each symbol into a carrier having mutual orthogonality, and then add and transmit each symbol. Accordingly, OFDM has a strong advantage in multipath channels because several symbols are transmitted and the symbol period is increased. In order to remove InterSymbol Interference (ISI), a guard interval longer than the impulse response of a channel is inserted, and a CP (Cyclic Prefix) is inserted into the guard interval to maintain orthogonality between subcarriers. .

The signal received through the channel generates a carrier frequency offset due to phase jitter, Doppler shift, and the like, and generates a symbol timing offset according to the distance between the transmitter and the receiver. The carrier frequency offset causes interference between subcarriers to change the power and phase of the signal, and the symbol timing offset generates interference between adjacent symbols and interference between adjacent channels when leaving the CP section of the orthogonal frequency division multiplexing signal. As such, when the timing between the transceivers is greatly shifted or the carrier frequency is different, interference is caused. Finally, the orthogonality between the channels cannot be maintained, thereby increasing the error rate in channel estimation and subsequent reception signal analysis. In addition, the symbol timing offset generates linear phase distortion in the frequency domain, and channel estimation performance is degraded when a conventional channel estimation method using a pilot is used.

For this reason, the carrier frequency and timing synchronization between the transceiver must be preceded at the receiving end before performing the Fast Fourier Transform (FFT). A mobile communication system using OFDM or Orthogonal Frequency Division Multiplexing Access (OFDMA) generally transmits a preamble symbol for initial synchronization at the transmitter side in front of a downlink frame. In a conventional mobile communication system, a synchronization device at a receiving end acquires a carrier frequency and symbol timing synchronization with a base station using a preamble symbol transmitted from a base station (BS).

The future mobile communication system is expected to use a high frequency band higher than the 2GHz or less band used in the current mobile communication system, so that the cell radius decreases and the shadow area increases accordingly. In addition, improving the transmission rate under limited transmit power is expected to reduce the signal-to-noise ratio (Eb / No) and degrade the system performance.

As a solution to the problems raised above, a multi hop relay system has been actively discussed. Multi-hop relay system is a type of wireless communication system for maximizing bandwidth efficiency by increasing transmission reliability or securing multiplexing gains by transmitting signals using one or more relays distributed between transmitter and receiver. to be. In a mobile communication system having a multi-hop relay, direct communication between a base station and a mobile station (MS) is possible, but terminals located at a cell boundary or in a radio shadow area are fixed relay stations (FRS) fixed at a specific location. It communicates with the base station through the relay. In the following description, multi-hop is a concept that a relay can be included in a structure in which a relay relays a signal, and thus a multi-hop relay system will be referred to simply as a relay system.

Through the relay function of the relay, not only the service area can be extended to the unserviceable area or the cell boundary but also the yield can be improved by mitigating interference between adjacent cells. In addition, the base station and the relay is wirelessly connected, and it is possible to reuse the frequency spatially by recognizing which terminal is connected to these devices, the base station is to centralize resource management for the terminals connected to the relay.

Types of relays include fixed relays, nomadic relays, and mobile relays, depending on mobility. The fixed relay may be used for reducing the shadow area and expanding the cell radius when the terminal receives a signal in a form fixed to a specific location such as a base station. Nomadic relays can be installed by changing the location as needed and can be used in the event venue and when the number of users increases in the short term. The mobile relay can be installed and used in trains and buses.

As another classification method of such relays, a relay relay having a compatibility with an existing mobile communication system is designed without knowing whether a relay exists from a terminal's point of view when configuring a relay system. Alternatively, a transparent mobile multihop relay is referred to, and a relay in a relay system in which a base station and a relay are cooperatively transmitted in order to increase the reliability of a received signal of a terminal is defined as a cooperative relay.

 1 is a diagram illustrating each relay according to a use in an OFDM / OFDMA relay system.

Referring to FIG. 1, a relay enhancement relay station (TE) 120 for improving data yield is located in a signal to interference plus noise ratio (SINR) region of a cell. The purpose is to improve the data yield of the terminal. The relays 120 and 130 for improving data yield only transmit data, and the link between the relay and the terminals 120 and 121 or 130 and 131 is controlled by a base station (BS) 110. do. In addition, the Coverage Extension Relay Station (CE) 140 and 150 may expand a cell area for terminals 141 and 151 outside the cell area that the base station 110 cannot be in charge of. The relays 140 and 150 for extending the cell area transmit downlink and uplink control signals with data, and the control signals between the relay and the terminals 140 and 141 or 150 and 151 are directly transmitted by the relays 140 and 150. send.

Meanwhile, the transparent relay system, which is a system including the transparent relay, must be compatible with the existing mobile communication system, so the terminal in the transparent relay system does not know whether the transparent relay exists. Therefore, in the case where the relays 120 and 130 for improving data yield are transparent relays, the terminals 121 and 131 in the relay region perform synchronization with the base station 110 but with the relays 120 and 130. The synchronization process is not performed. Therefore, when data is transmitted through the relays 120 and 130, there is a problem in that channel estimation performance is degraded due to propagation delay.

 In addition, even in a cooperative relay system including a cooperative relay rather than a transparent relay, a propagation delay of a signal transmitted through cooperative operation occurs differently according to each transmitting entity, resulting in degradation of channel estimation performance due to a propagation delay. There is this.

In addition, when a terminal moves in a transparent relay system including a transparent relay, the carrier frequency offset between the base station and the terminal link and the carrier frequency offset between the relay and the terminal link are greatly different, so that the terminal synchronizes with the base station and transmits data through the relay. If received, performance degradation occurs in channel estimation and received signal analysis when receiving data by incorrectly estimated carrier frequency offset. That is, when the carrier frequency offset tracking process is performed by the conventional mobile communication system, the carrier frequency offset of the link between the relay and the terminal cannot be estimated, resulting in performance degradation.

The technical problem to be achieved in the present invention is a channel between a transparent relay and a terminal which improves channel estimation performance deterioration due to propagation delay in an orthogonal frequency division multiplexing or an orthogonal frequency division multiple access (OFDM / OFDMA) based transparent relay system. It is to provide an apparatus for estimating.

Another technical problem to be solved by the present invention is a propagation delay in an OFDM / OFDMA type cooperative relay system including a base station and at least one cooperative relay transmitting device and a terminal receiving a signal transmitted by the transmitting device. To provide an apparatus for estimating a channel between each of the transmitting apparatus and the terminal to improve the channel estimation performance degradation due to.

Another object of the present invention is to provide a synchronization device for synchronization between a transmitting device and a terminal transmitting a signal in an OFDM / OFDMA transparent relay system.

The technical problem to be achieved in the present invention is a channel between a transparent relay and a terminal which improves channel estimation performance deterioration due to propagation delay in an orthogonal frequency division multiplexing or an orthogonal frequency division multiple access (OFDM / OFDMA) based transparent relay system. To provide a method for estimating.

Another technical problem to be solved by the present invention is a radio wave in an OFDM / OFDMA type cooperative relay system comprising a base station and at least one cooperative relay comprising a transmitting device and a terminal receiving a signal transmitted by the transmitting device. The present invention provides a method for estimating a channel between each of transmission apparatuses and a terminal for improving channel estimation performance degradation due to delay.

Another technical problem to be achieved in the present invention is to provide a synchronization method for synchronization between a transmitting device and a terminal transmitting a signal in an OFDM / OFDMA transparent relay system.

An embodiment of the apparatus for estimating a channel between a transparent relay and a terminal in an orthogonal frequency division multiplexing / orthogonal frequency division multiple access (OFDM / OFDMA) based transparent relay system according to the present invention for achieving the above technical problem For example, the pilot extraction step of extracting the pilot signals based on the fast Fourier transform frequency domain signal after the signal received by the terminal from the transparent relay is synchronized based on the signal received by the terminal from the base station; A propagation delay estimating step of estimating a propagation delay between the transparent relay and the terminal based on each of the extracted pilot signals and a reference pilot signal which is a predetermined signal value corresponding to each of the extracted pilot signals; And estimating a propagation delay weight for estimating a channel between the transparent relay and the terminal based on the estimated propagation delay.

In order to achieve the above technical problem, an OFDM / OFDMA type cooperative relay including a base station and at least one cooperative relay comprising a transmitting device and a terminal for receiving a signal transmitted by the transmitting device In an embodiment of the apparatus for estimating a channel between each of the transmitting apparatuses and the terminal in the system, the frequency domain is fast Fourier transformed after the signal received by the terminal is synchronized based on the signal received by the terminal from the base station A pilot extractor configured to extract pilot signals transmitted by the corresponding transmission apparatus for each transmission apparatus based on the signal; A propagation delay estimator estimating a propagation delay between each of the extracted pilot signals and a reference pilot signal that is a predetermined signal value corresponding to each of the extracted pilot signals; And a weight estimator for estimating a propagation delay weight for estimating a channel between the transmitting apparatus and the terminal for each transmitting apparatus based on the estimated propagation delay between the respective transmitting apparatus and the terminal.

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In order to achieve the above technical problem, an embodiment of a method for estimating a channel between a transparent relay and a terminal in an OFDM / OFDMA-based transparent relay system according to the present invention is provided. A pilot extraction step of extracting pilot signals based on a fast Fourier transformed frequency domain signal after the received signal is synchronized with the signal received by the terminal from a base station; A propagation delay estimating step of estimating a propagation delay between the transparent relay and the terminal based on each of the extracted pilot signals and a reference pilot signal which is a predetermined signal value corresponding to each of the extracted pilot signals; And estimating a propagation delay weight for estimating a channel between the transparent relay and the terminal based on the estimated propagation delay.

In order to achieve the above technical problem, an OFDM / OFDMA type cooperative relay system comprising a base station and at least one cooperative relay including transmission apparatuses and a terminal receiving a signal transmitted by the transmission apparatuses. According to an embodiment of the present invention, a method for estimating a channel between each of the transmitting apparatuses and the terminal includes: a fast Fourier transformed frequency domain signal after a signal received by the terminal is synchronized based on a signal received by the terminal from the base station A pilot extraction step of extracting pilot signals transmitted by the corresponding transmission apparatus for each transmission apparatus based on the? A propagation delay estimating step of estimating a propagation delay between each of the extracted pilot signals and a reference pilot signal which is a predetermined signal value corresponding to each of the extracted pilot signals; And a weight estimation step of estimating a propagation delay weight for estimating a channel between the transmitting apparatus and the terminal for each transmitting apparatus based on the estimated propagation delay between the respective transmitting apparatus and the terminal.

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According to the present invention, channel estimation is performed to overcome channel estimation performance degradation due to propagation delay in a transparent multi-hop relay system. That is, in the conventional channel estimation method, when there is a propagation delay, the performance of the entire system is degraded as the influence of the propagation delay is not eliminated in the channel estimation process, but the channel estimation method and apparatus proposed by the present invention are used. Therefore, the channel estimation performance can be improved by removing the influence on the propagation delay. In addition, the channel estimation method and apparatus proposed by the present invention has an advantage of estimating a channel by estimating propagation delay weights using a conventional pilot signal without an additional training signal.

In addition, according to the present invention, in performing the channel estimation to overcome the performance degradation due to the propagation delay in the cooperative multi-hop relay system, it is expected to improve the channel estimation performance compared to the conventional method. That is, in the conventional channel estimation method, when there is a propagation delay, the performance of the entire system is degraded as the influence of the propagation delay is not eliminated in the channel estimation process, but the channel estimation method and apparatus proposed by the present invention are used. Therefore, the channel estimation performance can be improved by removing the influence on the propagation delay.

In addition, the channel estimation method and apparatus proposed by the present invention are not limited to the case where the sum of the base station and the relay is two, and the sum of the base station and the relay has an advantage that can be applied when there are several relays.

In addition, according to the present invention, in the OFDM / OFDMA transparent relay system, performance deterioration due to the influence of the carrier frequency offset and timing that occurs when the terminal does not perform a synchronization process with the transparent relay appears. Performance improvement can be expected compared to the method. That is, the conventional system deteriorates the performance of the entire system by not removing the influence of the carrier frequency and the timing offset between the relay and the terminal link in the synchronization process, but using a synchronization method and apparatus proposed by the present invention There is an advantage in that the influence on the carrier frequency and timing offset between the relay and the terminal link can be removed.

Embodiments of the present invention and related technical contents will be described with reference to the accompanying drawings. In the drawings, the same reference numerals denote the same or similar components.

First, a channel estimation apparatus and method between a transparent relay and a terminal in an OFDM / OFDMA transparent relay system according to the present invention will be described.

FIG. 2 is a diagram illustrating locations of a base station, a relay, and a terminal in an OFDM / OFDMA relay system.

Referring to FIG. 2, a mobile station (MS) located at location 1 acquires synchronization with the base station 110 and receives data from the base station 110 or receives data from the relay RS0 for improving data yield. . The terminal located at location 2 acquires synchronization with the base station 110 and receives data from the relay RS0 for improving data yield. The terminal located at location 3 acquires synchronization with the relay RS1 for cell area extension and receives data from the relay RS1 for cell area extension.

3A illustrates a downlink frame block in an OFDM / OFDMA transparent relay system.

In FIG. 3A, the situation of FIG. 2 is assumed. MS0 receives a signal from the base station 110 to the terminal located in position 1, MS1 receives a signal from the relay (RS0) for improving the data yield to the terminal located in position 1. It is assumed that MS2 receives a signal from a relay RS0 for improving data yield to a terminal located at location 2, and MS3 receives a signal from a relay RS1 for expanding a cell area to a terminal located at location 3.

Referring to FIG. 3A, P, FCH, and MAP are all transmitted from the base station 110 or the relay RS1 for cell area extension, and are respectively preambles for initial synchronization, frame control headers that are control signals, Indicates MAP information. BS tx is a downlink frame transmitted from the base station 110, RS0 tx is a downlink frame transmitted by the relay (RS0) for improving data yield, RS1 tx is a downlink transmitted by the relay (RS1) for cell area expansion Represents a frame. BS-> MS / RS represents a frame period transmitted by the base station 110, and RS-> MS represents a frame period transmitted by the relays RS0 and RS1.

의 전파 지연이 발생하고, 기지국(110)과 동기를 획득하는 구간은

의 전파지연이 발생하게 되어, 데이터 수율 향상을 위한 릴레이(RS0)로부터 데이터를 수신함으로 인한

의 전파지연이 발생하게 된다. MS2의 경우에서도 마찬가지로 전파지연이 발생하게 된다.Since MS0 receives a signal from the base station 110, the MS0 performs a synchronization process with the base station 110 through a preamble transmitted by the base station 110. In addition, MS2 performs a process of synchronizing with the relay RS1 for cell area extension through a preamble transmitted by the relay RS1 for cell area extension. However, MS1 receives a signal from the relay RS0 for improving data yield, but does not acquire synchronization with the relay RS0. That is, the data signal received from the relay RS0

The propagation delay of the interval occurs, and the interval for obtaining synchronization with the base station 110

Propagation delay occurs, and due to receiving data from the relay (RS0)

A propagation delay of. In the case of MS2, propagation delay occurs in the same manner.

FIG. 3B is a diagram illustrating the effect of propagation delay caused by a transparent relay on channel estimation in an OFDM / OFDMA transparent relay system.

의 전파지연이 주파수 영역에서 위상회전으로 나타나 채널 보상시 성능이 열화된다.Referring to FIG. 3B, a symbol timing estimate for the base station 110 is estimated with respect to the signal received by the terminal, the CP is removed from the estimated length by a CP, and a Fast Fourier Transform (FFT) is performed. As a result, interference between adjacent symbols does not occur. nevertheless

The propagation delay of P is shown as phase rotation in the frequency domain, resulting in deterioration of performance during channel compensation.

Similar to the problem of propagation delay, the performance degradation due to the carrier frequency offset is also shown in the case of MS1 receiving a signal from RS0 but not synchronizing with RS0 and acquiring synchronization with the base station 110. In the case of MS0 receiving a signal from the base station 110 transmitting the preamble for initial synchronization and MS3 receiving a signal from RS1 transmitting the preamble for the initial synchronization, the carrier frequency offset does not appear. As described above, the terminal receiving a signal from the transparent relay for improving data yield in the transparent relay system may have a performance that may be degraded due to the influence of the carrier frequency offset.

FIG. 3C illustrates an uplink frame block for symbol timing analysis in an OFDM / OFDMA transparent relay system.

Referring to FIG. 3C, it can be seen that a propagation delay occurs in a transparent relay system including a transparent relay for improving data yield. The MS0 located at location 1 and receiving data from the base station 110 receives a signal transmitted from the base station 110 continuously from the preamble symbol to the last downlink symbol. Since both MS1 located at position 1 and receiving data from RS0 and MS2 located at position 2 and receiving data from RS0 are in synchronization with the base station 110, the relay is delayed from the start position of the symbols acquired by MS1 and MS2. Receive data from That is, although MS0 receives signals transmitted from the base station 110 continuously during the entire downlink period, additional symbol timing offsets are not generated due to propagation delays. However, MS1 and MS2 use the preamble symbols of the base station 110 to correct the signal. Even if synchronization is obtained, since the actual data receives a signal transmitted from the relay RS0, a symbol timing offset is additionally generated due to the propagation delay. If there is an additional symbol timing offset, phase distortion occurs in the frequency domain, which makes it impossible to estimate a perfect channel using the conventional channel estimation method, thereby degrading the performance of the entire system.

Channel estimation apparatus and method according to the present invention described in Figures 4 to 5 in a transparent relay system including a base station, a transparent relay, the terminal is synchronized with the base station, the data signal from the transparent relay It can be applied in the receiving situation.

4A is a diagram illustrating a first embodiment of a channel estimating device between a transparent relay and a terminal in an OFDM / OFDMA transparent relay system according to the present invention.

4B is a diagram illustrating a second embodiment of an apparatus for estimating a channel between a transparent relay and a terminal in an OFDM / OFDMA transparent relay system according to the present invention.

5A is a flowchart illustrating an embodiment of a channel estimation method between a transparent relay and a terminal in an OFDM / OFDMA transparent relay system according to the present invention.

Each step in FIG. 5A as well as in FIG. 5 may be performed by each component in FIG. 4A as well as in FIG. 4. Hereinafter, FIGS. 4 and 5 will be described together. The overlapping components of FIGS. 4A and 4B will be described together.

Referring to FIG. 4A, a channel estimator between a transparent relay and a terminal according to the present invention includes a pilot extractor 410, a pilot storage 420, a propagation delay estimator 430, a weight estimator 440, The channel estimator 450 and the channel compensator 460 are included.

4B, in addition to the above components, the channel estimation apparatus between the transparent relay and the terminal according to the present invention includes a synchronizer 404, a CP remover 405, a fast Fourier transform unit 406, and a demodulator 407. ) May be further included. The RF receiver 401 may further include an analog-digital converter (A / D) 402, a controller 403, and the like.

The RF receiver 401 receives a time domain signal from a transparent relay through a receive antenna. The received time domain signal is digitized by the analog-to-digital converter 402. The digitized signal is synchronized by the synchronization unit 404 on the basis of a signal received by the RF receiver 401 from the base station, that is, a preamble transmitted by the base station, and the synchronized signal is transmitted by the CP remover 405. The CP is removed and converted by the fast Fourier transform unit 406 into a frequency domain signal. The frequency domain signal is input to the pilot extractor 410 and the channel compensator 460.

The pilot signal is described for the description of the pilot storage 420 and the pilot extractor 410. The pilot signal includes time synchronization acquisition, frequency synchronization acquisition, cell search, i.e., base station classification, channel estimation, and channel quality information measurement. This is the signal used for.

In particular, in order to estimate a channel for a time-varying channel in an OFDM / OFDMA relay system, a transmitter transmits a pilot signal known to a receiver to a pilot subcarrier allocated to some subcarriers in a symbol. The receiving side then performs channel estimation on the subcarriers through which data is actually transmitted by interpolation using pilots.

The pilot signal known to the receiver, that is, the terminal, is stored in the pilot storage unit 420 as a reference pilot signal (S510).

The pilot extractor 410 is a transparent relay included in the frequency domain signal based on previously known information on which subcarriers are transmitted on which subcarriers in which order symbols, that is, known pilot positions. Extract the pilot signals received by the terminal from (S520).

The propagation delay estimator 430 estimates a propagation delay between the transparent relay and the terminal based on each of the pilot signals extracted in this manner and a reference pilot signal corresponding thereto (S530). The reference pilot signal stored at 420 may be used.

The weight estimator 440 estimates the propagation delay weight based on the propagation delay between the transparent relay estimated by the propagation delay estimator 430 and the terminal (S540). The propagation delay weight is a frequency received by the terminal. It can be expressed as a channel transfer function that corrects the effect of the estimated propagation delay on the region signal.

The channel estimator 450 estimates each of the pilot signals extracted by the pilot extractor 410, the reference pilot signal of the pilot storage unit 420 corresponding to each of the extracted pilot signals, and the weight estimator 440. The channel between the transparent relay and the terminal is estimated using the received propagation delay weight (S550).

The channel compensator 460 performs channel compensation on the signal received by the terminal based on the channel between the transparent relay estimated by the channel estimator 450 and the terminal (S560).

4C is a diagram illustrating an embodiment of a propagation delay estimator 430 among components of a channel estimating apparatus between a transparent relay and a terminal according to the present invention.

5B is a flowchart illustrating an embodiment of a propagation delay estimating step S50 of the configuration step of the channel estimation method between the transparent relay and the terminal according to the present invention.

Referring to FIG. 4C, the propagation delay estimator 430 includes a complex multiplier 431, a conjugate complex number converter 432, an exponential function generator 433, an accumulator 434, an absolute value calculator 435, A maximum value search section 436.

번째 심볼의 파일럿 위치 p에서 주파수 영역 신호로부터 추출된 파일럿 신호인 Y_l(p)와 공액복소수 변환부(432)에 의해 그 추출된 파일럿 신호 Y_l(p)에 대응하는 기준 파일럿 신호를 공액 복소수 변환한 R_l ^*(p)와 지수함수 생성부(433)에 의해 파일럿 위치 p에 기초하여 생성한 지수함수

에 비례하는 제1 복소값

을 생성한다.(S531) 여기서 n은 시간 영역 샘플, N은 고속푸리에변환의 사이즈이다.The complex multiplier 431 is driven by the pilot extractor 410.

Conjugate complex number Y _l (p), which is a pilot signal extracted from the frequency domain signal at the pilot position p of the first symbol, and a reference pilot signal corresponding to the extracted pilot signal Y _l (p) by the conjugate complex conversion unit 432. Exponential function generated based on the pilot position p by the converted R _l ^* (p) and exponential function generator 433

First complex value proportional to

Where n is a time-domain sample and N is the size of the fast Fourier transform.

을 추출된 파일럿 신호들에 대하여 누산하여 제2 복소값

을 생성한다.(S532) 여기서 S_p는 파일럿 위치 p의 집합을 의미한다.Accumulation processing unit 434 is the first complex value

Is a second complex value accumulated over the extracted pilot signals.

(S532) where S _p means a set of pilot positions p.

을 생성한다.(S533)The absolute value calculator 435 is an absolute value of the second complex value.

(S533)

을 탐색하여 트랜스패런트 릴레이와 단말 간의 전파지연을 추정한다.(S534)The maximum value search section 436 is a time domain sample that maximizes the absolute value of the second complex value.

The propagation delay between the transparent relay and the terminal is estimated by searching for (S534).

4D is a diagram illustrating an embodiment of a weight estimator 440 among components of a channel estimating apparatus between a transparent relay and a terminal according to the present invention.

5C is a flowchart illustrating an embodiment of a weight estimating step S540 among the steps of configuring a channel estimation method between a transparent relay and a terminal according to the present invention.

Referring to FIG. 4D, the weight estimator 440 includes a delta function generator 442 and a delay unit 441.

를 생성하고, 생성된 시간 영역의 델타함수에 전파지연 추정부(430)에서 추정된 전파지연만큼 지연부(441)에 의하여 시간지연시켜서

를 생성한다.(S541) 그리고 가중치 추정부(440)는 이 시간지연된 시간 영역의 델타함수에 대한 고속푸리에변환을 고속푸리에변환부(406)에 요청하고, 이 고속푸리에변환이 이루어진 값을 전파지연 가중치로 추정하게 된다.(S542) The weight estimator 440 is a delta function in the time domain by the delta function generator 442.

Is generated and time-delayed by the delay unit 441 by the propagation delay estimated by the propagation delay estimator 430 in the generated delta function.

(S541) and the weight estimator 440 requests the fast Fourier transform 406 for the delta function of the time delayed time domain to the fast Fourier transform 406, and propagates the value of the fast Fourier transform. It is estimated by the weight (S542).

Here, the fast Fourier transform is a basic technique in the OFDM technique. The weight estimator 440 does not necessarily request the fast Fourier transform unit 406 to obtain the fast Fourier transform value, and performs fast Fourier transform or other fast Fourier transforms within itself. The fast Fourier transform value may be obtained from a component or the like.

4E is a diagram illustrating an embodiment of a channel estimator 450 among components of a channel estimating apparatus between a transparent relay and a terminal according to the present invention.

5D is a flowchart illustrating an embodiment of a channel estimating step S550 among the steps of configuring a channel estimation method between a transparent relay and a terminal according to the present invention.

 Referring to FIG. 4E, the channel estimator 450 includes a phase distortion remover 451, an interpolator 452, and a channel estimation determiner 453.

The phase distortion removing unit 451 includes a conjugate complex conversion unit 451a, a complex multiplication unit 451b, and a complex division unit 451c.

를 구한다.(S551)The phase distortion remover 451 obtains the extracted pilot signal Y _l (p) from the pilot extractor 410. This is an input of the complex multiplication unit 451b. In addition, the phase distortion remover 451 obtains the propagation delay weight W (p) at the pilot position p of the extracted pilot signal Y _l (p) using the propagation delay weight estimated by the weight estimator 440. This W (p) is input to the conjugate complex conversion unit 451a to perform conjugate complex number conversion. W ^* (p), which has been subjected to the conjugate complex conversion, and the extracted pilot signal Y _l (p) of the pilot extractor 410, are input to the complex multiplier 451b, and are positive values at the complex multiplier 451b. Is multiplied. The complex division unit 451c obtains the reference pilot signal R _l (p) at the pilot position p stored in the pilot storage unit 420, and divides Y _l (p) W ^* (p) by R _l (p). Phase Distortion Cancellation channel that eliminates phase distortion due to propagation delay between the transparent relay and the terminal at each pilot position p

(S551)

를 구한다.(S552) 보간은 선형보간을 활용할 수 있다.The interpolator 452 is interpolated by performing interpolation on the frequency domain of the frequency domain signal based on the phase distortion removing channel.

(S552) Interpolation may use linear interpolation.

와 가중치 추정부(440)에 의하여 추정된 전파지연 가중치 W(k)를 곱하여 이루어질 수 있다. 이 곱해진 값은 채널 보상부(460)에 전달된다.The channel estimation determiner 453 estimates a channel between the transparent relay and the terminal based on the interpolated channel and the propagation delay weight (S553).

And the propagation delay weight W (k) estimated by the weight estimator 440. This multiplied value is transmitted to the channel compensator 460.

Next, an operation of a channel estimating device between a transparent relay and a terminal in an OFDM / OFDMA transparent relay system will be described with reference to FIGS. 4 and 5 based on the equation.

In the transparent relay system, a signal of the l- th OFDM symbol transmitted from a transmitting end, that is, a base station or a subject transmitting a signal such as a relay is represented as follows.

Here, x _l (n) and X _l (k) is a k-th frequency domain signals of the n-th time domain sample time-domain signal, the l-th OFDM symbol in the l-th OFDM symbol, respectively, N is the size of the fast Fourier transform Indicates.

When the OFDM symbol transmitted from the transmitting antenna passes through the channel and there is a carrier frequency offset, a symbol timing offset, and a propagation delay, the signal transmitted by the relay and received by the terminal is expressed as follows.

Here, y _l (n) is the received signal of the n th sample of the l- th OFDM symbol, H (k) is the frequency response of the channel between the transparent relay and the terminal, that is, the channel transfer function, ε is normalization between the base station and the terminal The normalized carrier frequency offset (normalized CFO), δ is a normalized symbol timing offset (STO) between the base station and the terminal, δ _R represents a normalized propagation delay between the relay and the terminal.

The signal of the carrier frequency synchronization and the symbol timing synchronization with the base station using the conventional method using the synchronization unit 404 shown in FIG. 4b is expressed as follows.

Equation 3 is expressed as a frequency domain signal by performing a fast Fourier transform.

As shown in Equation 4, even if the received frequency domain signal having the propagation delay is synchronized with the base station by the estimated carrier frequency offset and the estimated symbol timing offset, the influence on the propagation delay by the relay remains. It can be seen that. Therefore, it is necessary to accurately estimate the offset due to the propagation delay. The propagation delay estimation process is as follows.

번째 심볼에서의 기설정된 주파수 위치인 파일럿 위치, S_p는 파일럿 위치 p들의 집합,

은 추정된 전파 지연, n은 시간 영역 샘플, Y_l(p)는 파일럿 위치 p에서의 파일럿 추출부(410)에 의하여 추출된 파일럿 신호, R^* _l(p)는 파일럿 위치 p에서의 파일럿 저장부(420)의 기준 파일럿 신호의 공액 복소수 변환 신호, N은 고속푸리에변환의 사이즈이다.The propagation delay between the transparent relay and the terminal is estimated by Equation 5, in which p is a frequency domain signal.

A pilot position, S _p, is a set of pilot positions p,

Is an estimated propagation delay, n is a time domain sample, Y _l (p) is a pilot signal extracted by the pilot extractor 410 at pilot position p, and R ^* _l (p) is a pilot storage at pilot position p The conjugate complex conversion signal, N, of the reference pilot signal of the section 420 is the size of the fast Fourier transform.

은 전파지연에 해당하는 위치에서 시작하는 채널 임펄스 응답의 형태를 갖는다. 채널 임펄스 응답이 지수함 수적으로 감소하는 형태라 가정할 때 전파지연은 상기 수학식 5과 같이 절대값 연산부(435)의 출력을 최대로 하는 시간 영역 샘플 위치를 구함으로써 추정할 수 있다. 이 때 정확한 전파지연을 추정하기 위해서는 정수배 반송파 주파수 옵셋이 발생하지 않아야 하기 때문에, 도 4b의 동기화부(404)를 통과한 신호를 이용하여 추정한다.When Y ₁ (p) and R ₁ (p) are the same signal, the output of the absolute value calculator 435 of FIG.

Has a form of channel impulse response starting at a position corresponding to propagation delay. Assuming that the channel impulse response decreases exponentially, propagation delay can be estimated by obtaining a time-domain sample position that maximizes the output of the absolute value calculator 435 as shown in Equation 5 above. In this case, since an integer carrier frequency offset should not occur in order to estimate an accurate propagation delay, it is estimated using a signal passed through the synchronization unit 404 of FIG. 4B.

The propagation delay estimated from Equation 5 is input to the weight estimator 440, and a process for estimating the propagation delay weight using the estimated propagation delay is as follows.

Here, δ (n) denotes a delta function, and W (k) denotes a propagation delay weight estimated by the weight estimator 440 at a frequency position, that is, a position k on a frequency domain of a subcarrier transmitting a received signal. The propagation delay weight is a value for channel estimation between the transparent relay and the terminal. Equation 6 is the same as taking the fast Fourier transform with the delta function time delayed by the propagation delay.

The channel estimator 450 removes the phase distortion due to the propagation delay from the received frequency domain signal, estimates the channel, and then performs interpolation to estimate the channel value for all subcarriers. Finally, the estimated channel is phase-distorted to equal the channel of the actual received signal. The process of removing the phase distortion due to the propagation delay from the received frequency domain signal is as follows.

는 각각 파일럿 위치 p 에서 전파지연에 의한 위상 왜곡을 제거한 후의 추정된 채널인 위상 왜곡 제거 채널, 파일럿 위치 p에서 단말이 수신한 주파수 영역 신호, 파일럿 위치 p에서 가중치 추정부(440)에 의해 추정된 전파지연 가중치의 공액 복소수 변환 성분을 나타낸다. here,

Are respectively estimated by the phase distortion elimination channel after removing the phase distortion due to the propagation delay at the pilot position p, the frequency domain signal received by the terminal at the pilot position p, and estimated by the weight estimator 440 at the pilot position p. It represents the conjugate complex conversion component of the propagation delay weight.

The process of estimating channel values for all subcarriers from Equation 7 is as follows.

는 전 부반송파의 추정된 채널을 나타낸다. here,

Denotes an estimated channel of all subcarriers.

에 전 파지연에 의한 위상 왜곡을 보상하는 과정은 다음과 같다.Finally, to estimate the channel experienced by the actual received signal

The process of compensating for phase distortion due to propagation delay is as follows.

는 실제 수신된 주파수 영역 신호가 경험한 채널의 추정치를 나타낸다. here,

Represents an estimate of the channel experienced by the actual received frequency domain signal.

Substituting Equation 9 into Equation 4 gives:

로 양변을 나눔으로써, X_l(k)를 알아낼 수 있다. 따라서 채널 보상부(460)에서는 채널 추정부(450)에 의해 추정된 채널

를 통하여 단말이 수신한 주파수 영역 신호인 Y_l(k)에 대하여 채널 보상을 수행하여 송신한 신호인 X_l(k)를 추정할 수 있다.In Equation 10

By dividing both sides by, we can find X _l (k). Accordingly, the channel compensator 460 estimates the channel estimated by the channel estimator 450.

By performing channel compensation on Y _l (k), which is a frequency domain signal received by the terminal, it is possible to estimate X _l (k), which is a transmitted signal.

Next, a channel estimation apparatus and method between each transmitting apparatus and a terminal in an OFDM / OFDMA interoperable relay system according to the present invention will be described.

Diversity gain can be obtained in the cooperative multi-hop relay system in which the base station and the relay transmit cooperatively to increase the reliability of the received signal. In the cooperative multi-hop system, since the terminal recognizes the relay, the path selection in the terminal may be considered together using the preamble transmitted from the base station and the relay. However, since the propagation delay and the frequency offset of the signal received from the base station and the signal received from the relay are different, there is a problem that accurate carrier synchronization and timing synchronization are difficult.

FIG. 6A illustrates a downlink frame block for symbol timing analysis according to a position of a terminal in an OFDM / OFDMA type cooperative relay system.

FIG. 6B is a diagram illustrating generation of a symbol timing offset according to propagation delay in an OFDM / OFDMA system cooperative relay system.

6 assumes a case where a terminal is located between a base station and a relay and receives a cooperative space-time block code (STBC) signal from the base station and the relay.

Referring to FIG. 6A, since the terminal is in synchronization with the base station, propagation delay occurs between the signal received from the base station and the signal received from the relay.

Referring to FIG. 6B, a symbol timing offset is additionally generated due to the generated propagation delay.

Since the terminal receiving the cooperative STBC signal from the two relays is also in synchronization with the base station, the signal timing offset occurs additionally due to the propagation delay of both signals received from the two relays. In this case, when the channel estimation is performed using the pilot signal, the higher the order of the modulation scheme due to the performance deterioration due to the channel estimation, the lower the performance of the entire system will be.

The apparatus and method for channel estimation according to the present invention described with reference to FIG. 7 to FIG. 9 in a cooperative relay system including a base station, at least one cooperative relay, and a terminal are used to transmit signals transmitted by a transmitting device such as a base station or a relay. This can be applied in the receiving situation.

FIG. 7A is a diagram illustrating a first embodiment of a channel estimating device between a transmitting device and a terminal in an OFDM / OFDMA cooperative relay system according to the present invention.

8A is a diagram illustrating a first embodiment of a channel estimating apparatus between each transmitting apparatus and a terminal in an OFDM / OFDMA interoperable relay system according to the present invention.

9A is a flowchart illustrating an embodiment of a channel estimating method between each transmitting apparatus and a terminal in an OFDM / OFDMA cooperative relay system according to the present invention.

Each step in FIG. 9 as well as in FIG. 9 may be performed by each component in FIG. 7A as well as in FIG. 7. Hereinafter, FIGS. 7 and 9 will be described together. The overlapping portions of FIGS. 7 and 8 will be described together. 8 assumes a case in which a terminal receives a signal from a base station and a relay 1 or a relay 1 and a relay 2.

Referring to FIG. 7A, a channel estimating device between a transmitter and a terminal according to the present invention includes a pilot extractor 710, a pilot storage 720, a propagation delay estimator 730, a weight estimator 740, and a channel adder. The government 750 and the decoder 760 are included.

Referring to FIG. 8A, a channel estimating device between each transmitting apparatus and a terminal according to the present invention may include first and second pilot extractors 811 and 812 corresponding to the pilot extractor 710 of FIG. 7A, and pilots of FIG. 7A. The first and second pilot storage units 821 and 822 corresponding to the storage unit 710, the propagation delay estimator 830 corresponding to the propagation delay estimator 730 of FIG. 7A, and the weight estimator of FIG. 7A ( First and second weight estimators 841 and 842 corresponding to 740 and first and second channel estimators 851 and 852 corresponding to the channel estimator 750 of FIG. 7A. In addition to this, a synchronization unit 804, a CP removal unit 805, a fast Fourier transform unit 806 and a demodulator 807 and the like. The RF receiver 801 further includes an analog-digital converter (A / D) 802, a controller 803, and the like. In the following description, corresponding components of FIGS. 7A and 8A will be described with reference to FIG. 7.

The RF receiver 801 receives a time domain signal from each transmitting apparatus such as a base station or a relay through a receiving antenna. The received time domain signal is digitized by the analog-to-digital converter 802. The digitized signal is synchronized by the synchronization unit 804 based on a signal received by the RF receiver 801 from the base station, that is, by a preamble transmitted by the base station, and the synchronized signal is transmitted by the CP remover 805. The CP is removed and converted into a frequency domain signal by the fast Fourier transform unit 806. The frequency domain signal is input to the pilot extractors 810, 811, and 812 and the channel compensators 860, 861, and 862.

The pilot storage unit 720 stores pilot signals for each transmitting apparatus known to the terminal as reference pilot signals (S910).

The pilot extractor 710 uses the previously known information on which subcarriers are transmitted on which symbols in which sequence for each transmitting apparatus, that is, by using the pilot positions previously known for each transmitting apparatus, and received by the terminal. The pilot signals of each transmitting apparatus included in the frequency domain signal are extracted (S920).

The propagation delay estimator 730 estimates a propagation delay between the transmitter and the terminal that transmitted the extracted pilot signal based on each of the extracted pilot signals and the reference pilot signal corresponding thereto (S930). May use a reference pilot signal stored in the pilot storage 720.

The weight estimating unit 740 estimates the propagation delay weight of each transmitting apparatus based on the propagation delay between each transmitting apparatus and the terminal estimated by the propagating delay estimating unit 730. (S940) Here, the propagating delay of each transmitting apparatus. The weight may be expressed as a channel transfer function that corrects the effect of the estimated propagation delay on the frequency domain signal received by the terminal.

The channel estimator 750 is a reference pilot signal of the pilot storage unit 720 corresponding to each of the pilot signals extracted by the pilot extractor 710 and each of the extracted pilot signals for each transmitting device that transmits a signal to the terminal, The channel between each transmitting apparatus and the terminal is estimated using the propagation delay weight estimated by the weight estimating unit 740 for each transmitting apparatus (S950).

The decoder 760 decodes a signal received by the terminal based on a channel between each transmitting apparatus and the terminal estimated by the channel estimator 750 (S960).

FIG. 7B is a diagram illustrating an embodiment of a propagation delay estimator 730 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention.

FIG. 8B is a diagram illustrating an embodiment of propagation delay estimators 831 and 832 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention.

9B is a flowchart illustrating an embodiment of a propagation delay estimating step S930 among steps of configuring a channel estimation method between each transmitting apparatus and a terminal according to the present invention.

Referring to FIG. 7B, the propagation delay estimator 730 includes a complex multiplier 731, a first accumulator 732, an absolute value calculator 733, a second accumulator 734, and a maximum value searcher 735. ), An exponential function generation unit 736, and a conjugate complex number conversion unit 737.

Referring to FIG. 8B, the propagation delay estimator 830 includes a complex multiplier 831, a first accumulator 832, an absolute value calculator 833, a second accumulator 834, and a maximum value searcher 835. , An exponential function generation unit 836, and a conjugate complex number conversion unit 837.

The complex multipliers 731 and 831 are pilot symbols for each of the symbols transmitted by the corresponding transmission apparatus for each transmitting apparatus that transmits the signal to the terminal, that is, the first and second symbols in FIG. 8. The pilot signal extracted by (710, 811 and 812) and the reference pilot signal corresponding to the extracted pilot signal by conjugate conjugate complex conversion unit (737, 837) and the corresponding pilot position. Generates first complex values proportional to the exponential function generated by the exponential function generator 736, 836 based on the step S931.

The first accumulation processing units 732 and 832 accumulate the first complex values for each symbol of the predetermined section to generate a second complex value.

The absolute value calculators 733 and 833 generate the absolute value of the second complex value (S933).

The second accumulation processing units 734 and 834 accumulate the absolute value of the second complex value for each transmission device to generate an accumulation value for each transmission device (S934).

The maximum value searching units 735 and 835 search for time domain samples that maximize the accumulated value of each transmitting apparatus, and estimate the propagation delay between the corresponding transmitting apparatus and the terminal (S935).

7C is a diagram illustrating an embodiment of a weight estimator 740 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention.

8C is a diagram illustrating an embodiment of weight estimators 841 and 842 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention.

9C is a flowchart illustrating an embodiment of a weight estimating step S940 among steps of configuring a channel estimating method between each transmitting apparatus and a terminal according to the present invention.

Referring to FIG. 7C, the weight estimator 740 includes a delta function generator 741 and a delay unit 742.

Referring to FIG. 8C, the first weight estimator 841 and the second weight estimator 842 respectively include a first delta function generator 841a, a first delay unit 841b, and a second delta function generator ( 842a and a second delay unit 842b.

를 생성하고, 각 송신 장치별로 생성된 시간 영역의 델타함수에 전파지연 추정부(730, 830)에서 추정된 해당 송신 장치와 단말 간의 전파지연만큼 지연부(742, 841b 및 842b)에 의하여 시간지연시켜서 각 송신 장치별로 시간지연된 델타함수를 생성한다.(S941) 그리고 가중 치 추정부(740, 841 및 842)는 이 각 송신장치별로 시간지연된 델타함수에 대한 고속푸리에변환을 고속푸리에변환부(806)에 요청하고, 이 고속푸리에변환이 이루어진 값을 해당 송신 장치의 전파지연 가중치로 추정하게 된다.(S942) The weight estimators 740, 841, and 842 use the delta function generators 741, 841a, and 842a to determine the delta function of the time domain for each transmitter.

Is generated, and the time delay is delayed by the delay units 742, 841b, and 842b by the propagation delay between the corresponding transmitter and the terminal estimated by the propagation delay estimator 730, 830 in the delta function of the time domain generated for each transmitter. The time delayed delta function is generated for each transmitting apparatus (S941). The weight estimator 740, 841, and 842 perform a fast Fourier transform for the time delayed delta function for each transmitting apparatus. In step S942, the fast Fourier transform value is estimated as the propagation delay weight of the corresponding transmission apparatus.

Here, the fast Fourier transform is a basic technique in the OFDM technique. The weight estimator 740, 841, and 842 does not necessarily request the fast Fourier transform unit 806 to obtain the fast Fourier transform value. A fast Fourier transform may be obtained from the transform or another component.

FIG. 7D is a diagram illustrating an embodiment of a channel estimator 750 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention.

8D is a diagram illustrating an embodiment of a channel estimating unit 851, 852 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention.

9D is a flowchart illustrating an embodiment of a channel estimating step S950 among steps of configuring a channel estimating method between each transmitting apparatus and a terminal according to the present invention.

Referring to FIG. 7D, the channel estimator 750 includes a phase distortion remover 851, an interpolator 852, an average calculator 753, and a channel estimation determiner 754.

Referring to FIG. 8D, the first channel estimator 851 and the second channel estimator 852 may include a first phase distortion remover 881, a first interpolator 882, and a first average calculator 883, respectively. The first channel estimation determiner 884 includes a second phase distortion remover 885, a second interpolator 886, a second average calculator 887, and a second channel estimate determiner 888, respectively.

The first and second phase distortion cancellers 881 and 885 both include conjugate complex conversion elements, complex multiplication units, and complex division elements.

The first and second interpolators 882 and 886 both include interpolation elements.

The phase distortion remover 751 of FIG. 7D obtains, from the pilot extractor 710, an extracted pilot signal at a predetermined pilot position for each symbol of a predetermined period symbol of each transmitter. Also, the phase distortion remover 751 obtains the propagation delay weight at the pilot position of the extracted pilot signal using the propagation delay weight estimated by the weight estimator 740. The propagation delay weight is multiplied by the signal value on which the conjugate complex transformation is performed and the extracted pilot signal by the pilot extractor 710. Thereafter, the reference pilot signal at the pilot position stored in the pilot storage unit 720 is obtained, and the result of the multiplication is divided by the reference pilot signal value. Through this, the phase distortion elimination unit 751 obtains a phase distortion elimination channel from which phase distortion due to propagation delay between the corresponding transmission apparatus and the terminal is removed at a predetermined pilot position for each symbol of a predetermined period symbol of each transmission apparatus (S951).

The interpolator 752 performs interpolation on the frequency domain of the frequency domain signal based on the phase distortion elimination channel to obtain an interpolated channel. (S952) Interpolation may use linear interpolation.

Since each channel is interpolated by the number of symbols included in the predetermined interval, the average calculating unit 753 averages the number of interpolated channels by the number of symbols for each transmitter (S953).

The channel estimation determiner 754 estimates a channel between the transmission apparatus and the terminal based on the average channel and the propagation delay weight between the transmission apparatus and the terminal (S954). The estimated channel information is decoded by the decoder 760. Is passed on.

More specifically, in FIG. 8, it is assumed that the terminal receives signals through two transmitting devices, such as when receiving a cooperative STBC signal from a base station and a relay 1 or a relay 1 and a relay 2.

The STBC scheme is a transmission antenna diversity scheme proposed by SMAlamouti (SMAlamouti, 'A simple transmitter diversity scheme for wireless communications', IEEE Journal on Selected Area in Communications, Vol. 16, pp. 1451-1458, Oct. 1998). From the STBC scheme to Vahid Tarokh et al. (Vahid Tarokh, 'Space time block coding from orthogonal designs', IEEE Trans.on Info., Theory, Vol. 45, pp. 1456-1467, July 1999) It was developed in various forms. Since it is assumed that the terminal receives signals from two transmitting apparatuses, the Alamouti STBC scheme, ie, the Tx.ANT diversity scheme proposed by SMAlamouti (SMAlamouti, 'A simple transmitter diversity scheme for wireless communications') , IEEE Journal on Selected Area in Communications, Vol. 16, pp. 1451-1458, Oct. 1998) will be described first, and then the specific embodiment of FIG. 8 will be described.

First, the Alamouti transmit antenna diversity scheme is a transmit antenna diversity scheme applied when two transmit antennas are used in a transmitter of a multiple input multiple output (MIMO) mobile communication system. Assume that the modulation symbols are xixj. Then, the serial modulation symbols xixj are space-time block coded as shown in Equation 11 by the Alamouti transmit antenna diversity scheme.

A matrix of the form Xij shown in Equation 11 is an encoding matrix according to the Alamouti transmit antenna diversity scheme, and * denotes a complex conjugate operation.

An Alamouti matrix as shown in Equation 11 is an encoding matrix of modulation symbols transmitted through the two transmit antennas, and elements of each row in the Alamouti matrix correspond to each of the two transmit antennas. The element of each column in the Alamouti matrix corresponds to each of the two transmit antennas in the corresponding time period.

That is, in the first time period t ₁ , xi is transmitted through the first transmit antenna (Tx.ANT 1), xj is transmitted through the second transmit antenna (Tx.ANT 2), and the second time interval is transmitted. At t ₁ +1, -x _j ^* is transmitted through the first transmit antenna, and x _i ^* is transmitted through the second transmit antenna Tx.ANT 2.

In the OFDM / OFDMA type cooperative relay system including the base station and at least one cooperative relay according to the above Alamouti transmit antenna diversity scheme, there is one base station and one relay. -Time Coding: STC). Here, an example of using STBC will be described.

In the cooperative relay system, when the number of transmitting antennas of the base station and the relay is 1, the signals of the first and second STBC coded OFDM symbols transmitted from the transmitting end are expressed as follows.

Here, x _{BS , 1} (n), x _{BS , 2} (n) are the transmission signals of the n th time domain samples of the first and second OFDM symbols transmitted from the base station, respectively, x _{RS , 1} (n), x _{RS , 2} (n) is the transmission signal of the n-th time-domain sample of the 1st, 2nd OFDM symbol transmitted by the relay, respectively, X ₁ (k), X ₂ (k) is transmitted by the k-th subcarrier in the frequency domain, respectively Indicates a signal. Under the assumption that the number of receiving antennas of the terminal is 1, the OFDM symbol transmitted by the transmitting antenna passes through the channel between the transmitting apparatus and the terminal of the transmitting antenna and there is a carrier frequency offset, symbol timing offset, and propagation delay. The received signal is expressed as follows.

Here, y ₁ (n) and y ₂ (n) are received signals of the n th sample of the first and second OFDM symbols, H _{BM , 1} (k) and H _{BM , 2} (k), respectively. The frequency response of the channel between the base station and the terminal, H _{RM , 1} (k), H _{RM , 2} (k) _, in the k-th subcarrier of the first and second OFDM symbols between the first and second channels, respectively The frequency response of the channel between the relay and the terminal in the kth subcarrier of the OFDM symbol, ε is the normalized carrier frequency offset, δ is the normalized symbol timing offset, δ _BM , δ _RM is the normalized between the base station and the terminal, the relay and the terminal, respectively Indicates propagation delay. The received signal obtained by synchronizing the carrier frequency and the symbol timing using the synchronization unit 804 shown in FIG. 8A is represented by the following equation.

Equation 14 is expressed as a frequency domain signal by performing a fast Fourier transform.

In Equation 15, if the channel is averaged for two consecutive OFDM symbols for STBC decoding, it can be expressed as follows.

Equation 15 may be expressed as a matrix in the same manner as in the conventional STBC decoding process using Equation 16 as follows.

After taking the conjugate complex transform to Y ₂ (k) in Equation 17, the decoding process can be expressed as follows.

As represented by Equation 18, even if the received frequency domain signal having the propagation delay is synchronized with the estimated carrier frequency offset and the estimated symbol timing offset, the influence on the propagation delay remains. Propagation delay is estimated using the following equation.

는 각각 기지국과 단말 사이의 기지국에서 전송하는 1번째, 2번째 OFDM 심볼에서의 기설정된 파일럿 위치, 릴레이와 단말 사이의 1번째, 2번째 OFDM 심볼에서의 기설정된 파일럿 위치,

는 각각 해당 파일럿 위치에서의 기지국이 단말에 전송하는 1번째, 2번째 OFDM 심볼의 파일럿 신호, 해당 파일럿 위치에서의 릴레이가 단말에 전송하는 1번째, 2번째 OFDM 심볼의 파일럿 신호, 즉 기준 파일럿 신호들이고,

는 각각 기지국과 단말, 릴레이와 단말 사이의 추정된 전파 지연을 나타낸다.The propagation delay between each transmitting apparatus and the terminal is estimated by Equation 19, in this case

Respectively denotes predetermined pilot positions in the first and second OFDM symbols transmitted by the base station between the base station and the terminal, and predetermined pilot positions in the first and second OFDM symbols between the relay and the terminal,

Are pilot signals of the first and second OFDM symbols transmitted from the base station at the corresponding pilot position to the terminal, and pilot signals of the first and second OFDM symbols transmitted from the relay at the corresponding pilot position to the terminal, that is, the reference pilot signals. Entering,

Denotes estimated propagation delays between the base station and the terminal, and the relay and the terminal, respectively.

,

가 같은 신호이면 도 8b의 절대값 연산부(833)의 4개의 출력값인

,

,

,

중 앞의 2개와 뒤의 2개는 각각 기지국과 단말 간의 전파지연, 릴레이와 단말 간의 전파지연에 해당하는 위치에서 시작하는 채널 임펄스 응답의 형태를 가진다. 채널 채널 임펄스 응답이 지수함수적으로 감소하는 형태라 가정할 때 각 송신 장치와 단말 간의 전파지연은 상기 수학식 19과 같이 해당 송신 장치에 대하여 해당 송신 장치에 대한 절대값 연산부들의 출력의 합을 최대로 하는 시간 영역 샘플 위치를 구함으로써 추정할 수 있다. 이 때 정확한 전파지연을 추정하기 위해서는 정수배 반송파 주파수 옵셋이 발생하지 않아야 하기 때문에 동기화부(804)를 통과한 신호를 이용하여 추정한다.In the case of taking the calculation as shown in Equation 19

,

Is the same signal, four output values of the absolute value calculating unit 833 of FIG.

,

,

,

The first two and the latter two have a form of channel impulse response starting from a position corresponding to a propagation delay between a base station and a terminal and a propagation delay between a relay and a terminal, respectively. Assuming that the channel impulse response is exponentially reduced, the propagation delay between each transmitting apparatus and the terminal maximizes the sum of the outputs of the absolute value calculating units for the transmitting apparatus with respect to the transmitting apparatus as shown in Equation 19 above. This can be estimated by obtaining a time-domain sample position. In this case, since the integer carrier frequency offset should not occur in order to estimate the accurate propagation delay, it estimates using the signal passed through the synchronization unit 804.

Propagation delays between the base station and the terminal or the relay and the terminal estimated from Equation 19 are input to the first weight estimator 841 and the second weight estimator 842, respectively, The process for estimating the propagation delay weight of each transmitting apparatus using the propagation delay is as follows.

In Equation 19, δ (n) is a delta function, W _BM (k), and W _RM (k) are frequency positions, that is, a first weight estimation unit at a position k on a frequency domain of a subcarrier transmitting a received signal. A propagation delay weight estimated by 841 and the second weight estimating unit 842 is shown. These propagation delay weights are values for channel estimation between the corresponding transmission apparatus and the terminal. Equation 20 is the same as that of the fast Fourier transform in which the delta function is delayed by the propagation delay between the transmitter and the terminal for each transmitter.

The channel estimators 851 and 852 of FIG. 8A remove the phase distortion due to the propagation delay for each transmitting apparatus from the received frequency domain signal, estimate the channel, and then perform interpolation to perform the interpolation on all subcarriers for each transmitting apparatus. Estimate the channel value. The equation for compensating for the phase distortion due to the propagation delay for each transmitting apparatus in the received frequency domain signal is as follows.

,

는 각각 기지국으로부터 단말이 수신하는 1번째, 2번째 OFDM 심볼에서의 해당 파일럿 위치에서 전파지연에 의한 위상 왜곡을 제거한 후의 추정된 채널인 위상 왜곡 제거 채널,

,

는 각각 기지국으로부터 단말이 수신하는 1번째, 2번째 OFDM 심볼에서의 해당 파일럿 위치에서 단말이 수신한 주파수 영역 신호,

,

는 각각 기지국으로부터 단말이 수신하는 1번째, 2번째 OFDM 심볼에서의 해당 파일럿 위치에서 제1 가중치 추정부(841) 에 의해 추정된 전파지연 가중치의 공액복소수 변환 성분을 나타낸다. 또한

,

는 각각 릴레이로부터 단말이 수신하는 1번째, 2번째 OFDM 심볼에서의 해당 파일럿 위치에서 전파지연에 의한 위상 왜곡을 제거한 후의 추정된 채널인 위상 왜곡 제거 채 널,

,

는 각각 릴레이로부터 단말이 수신하는 1번째, 2번째 OFDM 심볼에서의 해당 파일럿 위치에서 단말이 수신한 주파수 영역 신호,

,

는 각각 릴레이로부터 단말이 수신하는 1번째, 2번째 OFDM 심볼에서의 해당 파일럿 위치에서 제2 가중치 추정부(842)에 의해 추정된 전파지연 가중치의 공액복소수 변환 성분을 나타낸다. From here,

,

Is a phase distortion elimination channel, which is an estimated channel after removing the phase distortion due to propagation delay at the corresponding pilot position in the first and second OFDM symbols received from the base station, respectively.

,

Is a frequency domain signal received by the terminal at the corresponding pilot position in the first and second OFDM symbols respectively received from the base station,

,

Denotes a conjugate complex transform component of the propagation delay weights estimated by the first weight estimator 841 at corresponding pilot positions in the first and second OFDM symbols received by the terminal from the base station, respectively. Also

,

Is a phase distortion removing channel, which is an estimated channel after removing the phase distortion due to propagation delay at the corresponding pilot position in the first and second OFDM symbols respectively received from the relay,

,

Is a frequency domain signal received by the terminal at the corresponding pilot position in the first and second OFDM symbols respectively received from the relay,

,

Denotes a conjugate complex transform component of the propagation delay weights estimated by the second weight estimator 842 at corresponding pilot positions in the first and second OFDM symbols received by the terminal from the relay, respectively.

The process of estimating channel values for all subcarriers from Equation 21 is as follows.

는 각각 기지국로부터 단말이 수신하는 1번째, 2번째 OFDM 심볼의 전 부반송파에 대한 추정된 채널, 릴레이로부터 단말이 수신하는 1번째, 2번째 OFDM 심볼의 전 부반송파에 대한 추정된 채널을 나타낸다.here,

Denotes an estimated channel for all subcarriers of the first and second OFDM symbols received by the terminal from the base station, and an estimated channel for all subcarriers of the first and second OFDM symbols received by the terminal from the relay.

를 사용하여 각 송신 장치별 채 널의 평균을 구하고, 각 송신 장치별 채널 평균에 해당 송신 장치의 전파지연에 의한 위상 왜곡을 보상한다. 그 보상 결과는 STBC 복조를 위하여 사용된다. 이를 표현하는 식은 하기 수학식 23과 같다.Finally, to estimate the channel experienced by the actual received frequency domain signal,

The average of the channels for each transmitting apparatus is calculated using the method, and the phase distortion due to the propagation delay of the corresponding transmitting apparatus is compensated for the channel average of each transmitting apparatus. The compensation result is used for STBC demodulation. The expression representing this is as shown in Equation 23 below.

는 각각 기지국과 단말, 릴레이와 단말 사이의 실제 수신 신호가 경험한 채널의 추정치를 나타낸다. here,

Denote an estimate of the channel experienced by the actual received signal between the base station and the terminal, and the relay and the terminal, respectively.

Substituting the channel estimated in Equation 23 into Equation 18 is as follows.

를 이용하여 단말이 송신 장치들로부터 수신한 주파수 영역 신호인 Y₁(k), Y₂(k)의 소스(source) 신호인 X₁(k), X₂(k)를 추정할 수 있다.In Equation 24, the decoder 860 is a channel estimated by the first and second channel estimators 851 and 852.

The UE may estimate X ₁ (k) and X ₂ (k), which are source signals of the frequency domain signals Y ₁ (k) and Y ₂ (k), which are received by the terminal from the transmitting apparatuses.

Meanwhile, in the above-described specific embodiment of FIG. 8, a channel estimation method and apparatus in a case where one base station and one relay are received in a mutual cooperation relay system and a terminal receives a signal from them are illustrated. However, those skilled in the art, the configuration of the channel estimation method and apparatus according to a preferred embodiment of the present invention even if the sum of the number of base stations and relays in the cooperative relay system increases from 2 to 4 It will be appreciated that this may apply. It will also be appreciated that it is applicable to SFBC as well as STBC in cooperative relay systems.

Next, a synchronization apparatus and method thereof in an OFDM / OFDMA transparent relay system according to the present invention will be described.

FIG. 10A illustrates an OFDM / OFDMA transparent relay system for analyzing an influence of a carrier frequency offset.

FIG. 10B is a diagram illustrating a Doppler transition according to movement of a terminal in the OFDM / OFDMA scheme of FIG. 10A.

ε_R0M1 로 가정할 수 있다.Referring to FIG. 10A, the effect of the carrier frequency offset is shown, particularly when the relay is a transparent relay for improving data yield. The path determined by path selection among the received signals is indicated by a solid line. BS of FIG. 10A assumes that the base station, RS0 and RS1 are all data yield enhancement relays, and MS0 and MS1 assume mobile terminals. In this figure, the carrier frequency offset between the base station and the relay link, the carrier frequency offset between the link between the base station and the terminal, and the carrier frequency offset between the link between the relay and the terminal are represented by ε _BR , ε _BM , ε _RR , respectively. Depending on the terminal, an appropriate subscript has been added. MS1 estimates the carrier frequency offset with ε _{BM1, which} is the carrier frequency offset between the base station and the terminal link, and receives data from RS0. Since the received signal is received with the carrier frequency offset ε _R0M1 between the relay and the terminal, the actual carrier frequency offset experienced by the terminal is ε _{BM1 -ε R0M1} . In a transparent relay system including a transparent relay for improving data yield, since the terminal and the transparent relay are both synchronized with the base station, the carrier frequency offset between the base station and the terminal link and the carrier frequency offset between the relay and the terminal link Silver ε _BM1

ε _R0M1 can be assumed.

In the above description, the Doppler transition is not considered and the difference between the oscillators of the transmitting and receiving stages in the stationary state is assumed. As described above, since both the terminal and the relay estimate the carrier frequency based on the base station, ε _BM1 The carrier frequency offsets of and ε _R0M1 can be considered that the integer frequency offset is the same and an error occurs only in the minority frequency offset. In other words, the carrier frequency estimation error portion of the oscillator causes the main performance deterioration in the station stop state.

Referring to Figure 10b, the terminal is moving toward the base station at a speed of Vkm / h.

로 주어진다. 여기서 K는 단말의 이동방향에 의해 결정되는 상수이며 -2 ~ +2의 범위를 갖는다. 도 10b의 예는 K의 절대값이 가장 크 게 발생하는 예이다. K 값은 단말이 릴레이와 기지국의 일직선 상에서 기지국을 향해 이동할 때 -2이며, 릴레이를 향해 이동할 때 2이다.Doppler transition is proportional to the speed and carrier frequency of the terminal, so it must be considered in the next generation mobile communication system that supports high-speed mobile environment and has high carrier frequency. When the terminal moves in the direction where the base station is located, the carrier frequency offset between the base station and the terminal link increases due to the Doppler transition, and when the terminal moves in the opposite direction of the base station, the carrier frequency offset between the base station and the terminal link decreases. I.e., carrier frequency offset between the base station and the terminal link is given by ε ε _{+ BM1 Doppler,} carrier frequency offset between the relay and the terminal link is _R0M1 ε _- ε given by the _Doppler. Where ε _Doppler represents the carrier frequency offset due to the Doppler transition. Since a terminal in a region of a transparent relay system including a transparent relay for improving data yield performs a synchronization process with a base station, a frequency offset between a base station and a mobile terminal link is estimated when a carrier frequency offset is estimated. However, because the relay is fixed, the carrier frequency offset between the base station and the relay is not affected by the Doppler transition. Therefore, when the terminal moves, the carrier frequency offset between the base station and the terminal link and the frequency offset between the relay and the terminal link are different. That is, when the terminal receives data from the relay, interference between adjacent subcarriers occurs because the terminal does not synchronize with the carrier frequency between the relay and the terminal link. In a mobile environment, when the terminal receives data from a transparent relay for improving data yield, the carrier frequency offset is

Is given by Here, K is a constant determined by the moving direction of the terminal and has a range of -2 to +2. 10B is an example in which the absolute value of K occurs the most. The value of K is -2 when the terminal moves toward the base station in a straight line between the relay and the base station, and is 2 when moving toward the relay.

As described above, in the transparent relay system, since the terminal does not perform synchronization with the relay, a carrier frequency offset is generated to generate interference between adjacent subcarriers after the fast Fourier transform.

FIG. 11 illustrates an uplink / downlink frame block for carrier frequency offset analysis in an OFDM / OFDMA transparent relay system.

Referring to FIG. 11, in a transparent relay system as shown in FIG. 10, when a terminal compensates a signal received from a relay by estimating a carrier frequency with a signal of a front part of a frame transmitted from a base station when a mobile station moves to a wrong carrier frequency offset It shows the interval 1100 where performance is degraded by. In order that the signal received from the relay does not cause interference between adjacent subcarriers due to the carrier frequency offset, the terminal must separately acquire a carrier frequency offset between the relay and the terminal link.

As described above, the carrier frequency offset between the base station and the terminal link and the carrier frequency offset between the relay and the terminal link are generally the same at the integer carrier frequency offset, but the Kε _Doppler error occurs at the carrier frequency frequency offset. We propose a synchronization method and apparatus for estimating and compensating for this.

The carrier frequency and timing offset tracking unit of the existing mobile communication system tracks the carrier frequency and timing offset using a downlink symbol after the preamble after initial synchronization. In a system including a transparent relay for improving data yield, a terminal receives a preamble and a MAP from a base station and receives data from a relay. In this case, if the carrier frequency and the timing offset tracking unit of the existing mobile communication system are applied as it is, only the timing and the carrier frequency of the signal received from the base station are tracked. Therefore, when the terminal receives a signal from the relay, performance degradation due to the carrier frequency offset occurs. In order to overcome this, the UE should track the carrier frequency offset between the relay and the UE link using the signal received from the relay.For this purpose, the UE estimates the carrier frequency offset in the signal interval received from the relay among the downlink symbols and compensates for it. shall.

을 추정한 이후 기지국으로부터 MAP 등의 제어신호를 전송받는 시점에는 수신신호를

로 보상한 후 신호를 읽어

을 추정하게된다. 즉, 단말이 릴레이로부터 혹은 기지국으로부터 전송받는 시점에서 잘못된 반송파 주파수 오프셋으로 보상하기 때문에 인접 부반송 파간의 간섭이 발생하게 된다. 따라서 본 발명에서는 기지국으로부터 수신되는 신호의 반송파 주파수 오프셋과 릴레이로부터 수신되는 신호의 반송파 주파수 오프셋을 개별적으로 보상, 추정하는 동기화 방법 및 장치를 제공한다.However, simply acquiring the carrier frequency offset between the relay and the terminal link separately may not completely eliminate the interference between adjacent subcarriers due to the incorrectly estimated carrier frequency offset. This is because the received signal must be compensated in advance with the value estimated in the previous step while tracking the carrier frequency and timing offset. That is, the terminal receives data from the relay

After estimating the, the received signal is received when the control signal such as MAP is transmitted from the base station.

Read the signal after compensation

Will be estimated. That is, since the terminal compensates with the wrong carrier frequency offset at the time when the terminal is transmitted from the relay or from the base station, interference between adjacent subcarriers occurs. Accordingly, the present invention provides a synchronization method and apparatus for individually compensating and estimating a carrier frequency offset of a signal received from a base station and a carrier frequency offset of a signal received from a relay.

12A is a diagram illustrating a first embodiment of a synchronization device in an OFDM / OFDMA transparent relay system according to the present invention.

FIG. 13 is a diagram illustrating an embodiment of a synchronization method in an OFDM / OFDMA transparent relay system according to the present invention.

Since each configuration step of the synchronization method of FIG. 13 may be performed by each component of the synchronization device of FIG. 12A, FIG. 12A and FIG. 13 will be described together below.

12A and 13, an initialization process of an OFDM / OFDMA transparent relay system in which embodiments of the present invention can be utilized is as follows.

 When the terminal is powered on, the terminal performs an initial synchronization process using the downlink signal received. In the initial synchronization process, frame search, minority carrier frequency offset, symbol timing offset estimation, and cell search are performed. In the cell search process, the segment to which the terminal belongs and the cell ID is obtained, and the integer carrier frequency offset is estimated.

After performing the downlink initial synchronization, the UE performs the uplink initial ranging process in the uplink period and determines the path using the power of the uplink signal. The base station designates a path (base station or relay) to transmit data to the terminal using uplink reception power.

The UE estimates a carrier frequency and a timing offset with the base station through an initial synchronization process. In addition, the carrier frequency and timing offset of the signal received from the relay are estimated in the receiving section from the relay, and the estimated carrier frequency offset is added to the integer carrier frequency offset made in the initial synchronization to complete the estimation of the carrier frequency offset between the relay and the terminal link. . The offset storage unit 1210 described below is a carrier frequency offset and timing offset for the base station and the carrier frequency offset and timing for the relay obtained through the initialization process after the estimation of the carrier frequency offset between the relay and the terminal link is completed. Save the offset.

12A, a synchronization device according to the present invention includes an offset storage unit 1210, a transmitter identification unit 1220, a compensator 1230, an estimator 1240, and an updater 1250.

The offset storage unit 1210 relates to an offset storage unit 1211 for a base station storing a carrier frequency offset and a timing offset for a base station estimated in advance, and a carrier frequency carrier and a timing offset for a relay estimated in advance. An offset storage unit 1212 is included. (S1310)

In general, the transmitting apparatus identification unit 1220 confirms whether the signal is received by the base station or the relay by the preamble included in the frame of the received signal. If it is determined that the base station transmits a signal, that is, if the received signal is determined to be a MAP signal received from the base station and data (BM signal) received from the base station, the received signal is input to the compensator 1231 for the base station. . If it is determined that the received signal is data (RM signal) received from the relay, the received signal is input to the compensator 1232 for the relay (S1320).

The compensator 1230 includes a compensator 1231 for the base station and a compensator 1232 for the relay, which are divided according to the subject that transmitted the received signal.

을 획득하여 이 오프셋들으로 수신 신호에 대하여 보상을 수행한다.In the case of the compensator 1231 for the base station, the carrier frequency offset and the timing offset for the base station are offset from the offset storage unit 1211 for the base station.

And compensate for the received signal with these offsets.

을 획득하여 이 오프셋들로 수신 신호에 대하여 보상을 수행한다.In the case of the compensator 1232 for the relay, the carrier frequency offset and the timing offset for the relay from the offset storage unit 1212 for the relay are

And compensate for the received signal with these offsets.

In this way, the compensator 1230 compensates the received signal at the offset of the corresponding transmitting device for each transmitting device that has transmitted the received signal (S1330).

The estimator 1240 includes an estimator 1241 for the base station divided by the subject that transmitted the received signal, and an estimator 1242 for the relay.

If the received signal is transmitted by the base station and compensated in the compensator 1231 for the base station, the compensated signal becomes the input b1 of the estimator 1241 for the base station.

If the received signal is transmitted by the relay and the compensation is performed in the compensator 1232 for the relay, the compensated signal becomes the input b2 of the estimator 1242 for the relay.

The estimator 1241 for the base station estimates a carrier frequency offset and a timing offset between the base station and the terminal with respect to the compensation signal of the received signal.

The estimator 1242 for the relay estimates a carrier frequency offset and a timing offset between the relay and the terminal with respect to the compensation signal of the received signal.

In this way, the estimator 1240 newly estimates the carrier frequency offset and the timing offset between the apparatus and the terminal that transmitted the signal to update the previously estimated carrier frequency offset and the timing offset (S1340).

The updater 1250 includes an updater 1251 for the base station divided by the subject that transmitted the received signal, and an updater 1252 for the relay.

 If the received signal is transmitted by the base station, and the estimation unit 1241 for the base station estimates the carrier frequency offset and the timing offset for the base station, the estimated carrier frequency offset and the timing offset are updated for the base station 1251. ) Is input c1.

If the received signal was transmitted by the relay and the estimation of the carrier frequency offset and the timing offset for the relay was made in the estimator 1242 for the relay, the estimated carrier frequency offset and the timing offset are updated for the relay 1125. ) Is input c2.

The updater 1251 for the base station transmits the carrier frequency offset and the timing offset estimated for the base station to the offset storage unit 1211 for the base station, and transmits to the existing base station stored in the offset storage unit 1211 for the base station. The related carrier frequency offset and timing offset are updated to the estimated values.

The update unit 1252 for the relay transmits the carrier frequency offset and the timing offset estimated for the relay to the offset storage unit 1212 for the relay to the existing relay stored in the offset storage unit 1212 for the relay. The related carrier frequency offset and timing offset are updated to the estimated values.

In this way, the updater 1250 updates the carrier frequency offset and the timing offset between the device transmitting the signal and the terminal so that the updated carrier frequency offset and the timing offset can be compensated for the next transmitted signal (S1350).

The first embodiment of the synchronization device according to the present invention in FIG. 12A may be modified like the second embodiment of FIG. 12B in order to minimize hardware required in implementation.

12B is a diagram illustrating a second embodiment of a synchronization device in an OFDM / OFDMA transparent relay system according to the present invention.

Referring to FIG. 12B, identifying a device that has transmitted a received signal by a control signal of the controller 1261 corresponds to a role of the transmitting device identification unit 1220 of FIG. 12A. In addition, since each component corresponds to each component of the synchronization device of FIG. 12A, a description thereof will be made with reference to FIG. 12A.

는 기지국으로부터 수신된 신호의 반 송파 주파수 및 타이밍 오프셋 추정값,

은 릴레이로부터 수신된 신호의 반송파 주파수 및 타이밍 오프셋 추정값을 나타낸다.12C is a diagram illustrating an embodiment of the estimator 1240 among the components of the synchronization device according to the present invention. here

Is a carrier frequency and timing offset estimate of the signal received from the base station,

Denotes a carrier frequency and timing offset estimate of the signal received from the relay.

Referring to FIG. 12C, the estimator 1240 includes an estimator 1241 for the base station and an estimator 1242 for the relay.

The estimator 1241 for the base station includes a first conjugate complex transform unit 1241a, a first complex multiplier 1241b, a first accumulator 1242c, a first maximum value search unit 1241d, and a first phase tracking. Section 1241e.

The estimator 1242 for the relay includes a second conjugate complex converter 1242a, a second complex multiplier 1242b, a second accumulator 1242c, a second maximum value search unit 1242d, and a second phase weight. Includes government 1242e.

Functions of the components of the estimator 1240 may be understood through the following equation. The data signal received from the relay or the data signal received from the base station after compensating by the compensation unit 1230 of FIG. 12A the carrier frequency and the timing offset relating to the transmitting device that has transmitted the received signal with respect to the received signal. Read to estimate timing and carrier frequency offset.

Where i is a delimiter of the data communication path determined according to which transmitting device from the base station and the relay, N _{s , i} is the starting point of the received signal according to the data communication path identified by _i in the frame, M _i is the number of symbols used in connection with the channel estimation of the data communication path identified by i, L is the length of the repetitive signal,-mainly CP size-n is the time-domain sample, and N _D is the CP The length of the symbol, N, represents the size of the fast Fourier transform.

12D is a diagram illustrating a third embodiment of a synchronization device in an OFDM / OFDMA transparent relay system according to the present invention.

Referring to FIG. 12D, the synchronizer 1203 including the controller 1203a and the frequency offset and timing offset synchronizer 1203b is the first embodiment of the synchronization device according to the present invention illustrated in FIGS. 12A and 12B. It can be implemented by the second embodiment. That is, the control unit 1203a may correspond to the transmission device identification unit 1220 of FIG. 12A, and the frequency offset and timing offset synchronization unit 1203b may have other components except for the transmission device identification unit 1220 of FIG. 12A. This is the part that can correspond to them.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. For example, i) a channel estimating and compensating device when two relays perform STBC or SFBC transmissions in a cooperative relay system, and ii) a STBC or 3 when the sum of the number of base stations and relays in the cooperative relay system is three or four. There may be various modifications such as a channel estimation and compensation device in case of SFBC transmission. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

1 is a diagram illustrating each relay according to an application in an orthogonal frequency division multiplexing system or an orthogonal frequency division multiple access (OFDM / OFDMA) relay system;

2 is a diagram illustrating the locations of a base station, a relay, and a terminal in an OFDM / OFDMA relay system;

FIG. 3a illustrates a downlink frame block in an OFDM / OFDMA transparent relay system; FIG.

FIG. 3B is a diagram illustrating the effect of propagation delay caused by a transparent relay on channel estimation in an OFDM / OFDMA transparent relay system; FIG.

3c is a block diagram illustrating uplink and downlink frame for symbol timing analysis in an OFDM / OFDMA transparent relay system;

4A illustrates a first embodiment of a channel estimating apparatus between a transparent relay and a terminal in an OFDM / OFDMA transparent relay system according to the present invention;

4b is a view showing a second embodiment of a channel estimating device between a transparent relay and a terminal in an OFDM / OFDMA transparent relay system according to the present invention;

4C is a diagram illustrating an embodiment of a propagation delay estimator 430 among components of a channel estimating apparatus between a transparent relay and a terminal according to the present invention.

4d is a diagram illustrating an embodiment of a weight estimator 440 among components of a channel estimating apparatus between a transparent relay and a terminal according to the present invention;

4E is a diagram illustrating an embodiment of a channel estimator 450 among components of a channel estimating apparatus between a transparent relay and a terminal according to the present invention;

5A is a flowchart illustrating an embodiment of a channel estimation method between a transparent relay and a terminal in an OFDM / OFDMA transparent relay system according to the present invention;

5B is a flowchart illustrating an embodiment of a propagation delay estimating step (S530) of a configuration step of a channel estimation method between a transparent relay and a terminal according to the present invention;

5C is a flowchart illustrating an embodiment of a weight estimating step S540 among steps of configuring a channel estimation method between a transparent relay and a terminal according to the present invention;

5d is a flowchart illustrating an embodiment of a channel estimating step S550 among steps of configuring a channel estimation method between a transparent relay and a terminal according to the present invention;

FIG. 6A illustrates an uplink / downlink frame block for symbol timing analysis according to a position of a terminal in an OFDM / OFDMA type cooperative relay system; FIG.

FIG. 6B is a view illustrating generation of a symbol timing offset according to propagation delay in an OFDM / OFDMA type cooperative relay system; FIG.

7A is a diagram illustrating a first embodiment of a channel estimating apparatus between each transmitting apparatus and a terminal in an OFDM / OFDMA scheme cooperative relay system according to the present invention;

7B is a diagram illustrating an embodiment of a propagation delay estimator 730 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention;

7C is a diagram illustrating an embodiment of a weight estimator 740 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention;

FIG. 7D is a diagram illustrating an embodiment of a channel estimating unit 750 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention.

 FIG. 8A illustrates a second embodiment of a channel estimating device between a transmitting device and a terminal in an OFDM / OFDMA system for cooperative relay according to the present invention; FIG.

8B is a diagram illustrating an embodiment of propagation delay estimators 831 and 832 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention;

8C is a diagram illustrating an embodiment of weight estimators 841 and 842 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention;

8D is a diagram illustrating an embodiment of channel estimators 851 and 852 among components of a channel estimating apparatus between each transmitting apparatus and a terminal according to the present invention;

9A is a flowchart illustrating an embodiment of a channel estimating method between each transmitting apparatus and a terminal in an OFDM / OFDMA cooperative relay system according to the present invention;

9B is a flowchart illustrating an embodiment of a propagation delay estimating step S930 among steps of configuring a channel estimation method between each transmitting apparatus and a terminal according to the present invention;

9C is a flowchart illustrating an embodiment of a weight estimating step S940 among steps of configuring a channel estimating method between each transmitting apparatus and a terminal according to the present invention;

9D is a flowchart illustrating an embodiment of a channel estimating step S950 among steps of configuring a channel estimating method between each transmitting apparatus and a terminal according to the present invention;

FIG. 10A illustrates an OFDM / OFDMA transparent relay system for analyzing an influence of a carrier frequency offset. FIG.

FIG. 10B is a diagram illustrating a Doppler transition according to movement of a terminal in the OFDM / OFDMA scheme of FIG. 10A.

11 is a block diagram illustrating a downlink frame block for carrier frequency offset analysis in an OFDM / OFDMA transparent relay system;

12A illustrates a first embodiment of a synchronization device in an OFDM / OFDMA transparent relay system according to the present invention;

12B illustrates a second embodiment of a synchronization device in an OFDM / OFDMA transparent relay system according to the present invention;

12C illustrates an embodiment of the estimator 1240 among the components of the synchronization device according to the present invention;

FIG. 12D illustrates a third embodiment of a synchronization device in an OFDM / OFDMA transparent relay system according to the present invention; FIG.

FIG. 13 is a diagram illustrating an embodiment of a synchronization method in an OFDN / OFDMA transparent relay system according to the present invention.

Claims (42)

An apparatus for estimating a channel between a transparent relay and a terminal in a quadrature frequency division multiplexing system or a quadrature frequency division multiple access system transparent relay system, A pilot extractor configured to extract pilot signals based on a fast Fourier transformed frequency domain signal after the signal received by the terminal from the transparent relay is synchronized based on the signal received by the terminal from a base station; A propagation delay estimator estimating a propagation delay between the transparent relay and the terminal based on each of the extracted pilot signals and a reference pilot signal which is a predetermined signal value corresponding to each of the extracted pilot signals; And And a weight estimator for estimating a propagation delay weight for estimating a channel between the transparent relay and the terminal on the basis of the estimated propagation delay. The method of claim 1, And a pilot storage unit for storing the set of reference pilot signals. The propagation delay estimator And estimating a propagation delay between the transparent relay and the terminal using a reference pilot signal corresponding to each extracted pilot signal stored in the pilot storage. The apparatus of claim 1, wherein the propagation delay estimator Generating first complex values proportional to each of the extracted pilot signals and a conjugate complex transform value of a reference pilot signal corresponding to each of the extracted pilot signals and an exponential function based on a pilot position of each of the extracted pilot signals; Complex multiplication; An accumulating processor for accumulating the first complex values to generate a second complex value; An absolute value calculator for generating an absolute value of the second complex value; And And a maximum value searcher for searching for a time-domain sample for maximizing an absolute value of the second complex value and estimating a propagation delay between the transparent relay and the terminal. The method of claim 1, wherein the weight estimator Time delaying the delta function in the time domain by the estimated propagation delay, and obtaining a result of the fast Fourier transform on the delta function in the time delayed time domain to estimate the propagation delay weight. The method of claim 1, And a channel estimator configured to estimate a channel between the transparent relay and the terminal based on each of the extracted pilot signals, a reference pilot signal corresponding to each of the extracted pilot signals, and the propagation delay weight. Channel estimation apparatus, characterized in that. The method of claim 5, wherein the channel estimator A pilot of each of the extracted pilot signals based on each of the extracted pilot signals, a reference pilot signal corresponding to each of the extracted pilot signals, and the propagation delay weight at a pilot position of each of the extracted pilot signals; A phase distortion removing unit for obtaining a phase distortion removing channel from which phase distortion due to propagation delay between the transparent relay and the terminal at the position is removed; An interpolator configured to interpolate the frequency domain of the frequency domain signal based on the phase distortion elimination channel to obtain an interpolated channel; And And a channel estimation determiner estimating a channel between the transparent relay and the terminal based on the interpolated channel and the propagation delay weight. 7. The apparatus of claim 6, wherein the interpolation is linear interpolation. The method of claim 5, And a channel compensator for performing channel compensation on a signal received by the terminal based on a channel between the transparent relay estimated by the channel estimator and the terminal. The apparatus of claim 1, wherein the transparent relay is a transparent relay for improving data yield. In the orthogonal frequency division multiplexing system orthogonal frequency division multiple access system comprising a base station and at least one cooperative relay transmitting device and a terminal for receiving a signal transmitted by the transmitting devices in the cooperative relay system An apparatus for estimating a channel between each terminal and the terminal,  A pilot for extracting pilot signals transmitted by a corresponding transmission apparatus for each transmitting apparatus based on a fast Fourier transformed frequency domain signal after the signal received by the terminal is synchronized based on the signal received by the terminal from the base station Extraction unit; A propagation delay estimator estimating a propagation delay between each of the extracted pilot signals and a reference pilot signal that is a predetermined signal value corresponding to each of the extracted pilot signals; And And a weight estimator for estimating a propagation delay weight for estimating a channel between the transmitting apparatus and the terminal for each transmitting apparatus based on the estimated propagation delay between the respective transmitting apparatus and the terminal. Channel estimation apparatus. The method of claim 10, And a pilot storage unit configured to store the set of reference pilot signals for each transmission apparatus. The propagation delay estimator And estimating a propagation delay between each transmitting apparatus and the terminal using a reference pilot signal corresponding to each extracted pilot signal stored in the pilot storage unit. The apparatus of claim 10, wherein the propagation delay estimator Conjugation of each of the extracted pilot signals and a reference pilot signal corresponding to each of the extracted pilot signals for each symbol of a predetermined interval among the symbols transmitted by the transmitting apparatus included in the signal received by the terminal A complex multiplier for generating first complex values proportional to a complex conversion value and an exponential function based on the pilot position of each extracted pilot signal; A first accumulation processor configured to accumulate the first complex values for each symbol of the predetermined section to generate a second complex value; An absolute value calculator configured to generate an absolute value of the second complex value for each symbol of the predetermined section; A second accumulation processor configured to accumulate an absolute value of the second complex value for each transmission device to generate an accumulation value for each transmission device; And And a maximum value searcher for searching for a time-domain sample for maximizing an accumulated value for each transmitting apparatus, and estimating a propagation delay between the transmitting apparatus and the terminal. The method of claim 10, wherein the weight estimator A time delay for time-delaying the delta function of the time domain for each transmission apparatus by the propagation delay between the estimated corresponding transmitter and the terminal, and obtaining a fast Fourier transform with respect to the delta function of the time-delayed time domain. And estimating a propagation delay weight of each transmitting apparatus. The method of claim 10, A channel for estimating a channel between the transmitter and the terminal based on each of the extracted pilot signals for each transmitter, a reference pilot signal corresponding to each of the extracted pilot signals, and a propagation delay weight of the transmitter; And a estimating unit. 15. The apparatus of claim 14, wherein the channel estimator Each of the extracted pilot signals in a channel between the transmitting device and the terminal transmitting the extracted pilot signals for each symbol of a predetermined interval among the symbols transmitted by the transmitting apparatus included in the signal received by the terminal A phase distortion removing unit for obtaining a phase distortion removing channel from which phase distortion due to propagation delay is removed at each pilot position of the pilot position; An interpolator configured to interpolate the frequency domain of the frequency domain signal based on the phase distortion elimination channel to obtain an interpolated channel; An average calculating unit which averages the interpolated channels for each of the transmitting devices; And And a channel estimation determiner for estimating a channel between each transmitting apparatus and the terminal based on the averaged channel and a propagation delay weight between the transmitting apparatus and the terminal. 16. The apparatus of claim 15, wherein the interpolation is linear interpolation. The method of claim 14, Each transmitting device transmits a signal constituting a signal received by the terminal using a predetermined encoding scheme for multiple-input multiple-output (MIMO), And a decoder which decodes a signal received by the terminal based on a channel between each of the transmitter and the terminal estimated by the channel estimator. 18. The apparatus of claim 17, wherein the predetermined coding scheme for MIMO is a space-time coding (STC) scheme. delete delete delete In the method of estimating a channel between a transparent relay and a terminal in a orthogonal frequency division multiplexing method or an orthogonal frequency division multiple access type transmission relay system, A pilot extraction step of extracting pilot signals based on a fast Fourier transformed frequency domain signal after the signal received by the terminal from the transparent relay is synchronized with respect to the signal received by the terminal from a base station; A propagation delay estimating step of estimating a propagation delay between the transparent relay and the terminal based on each of the extracted pilot signals and a reference pilot signal which is a predetermined signal value corresponding to each of the extracted pilot signals; And And a weight estimating step of estimating a propagation delay weight for estimating a channel between the transparent relay and the terminal based on the estimated propagation delay. The method of claim 22, And a pilot storage step of storing the set of reference pilot signals before the pilot extraction step. The propagation delay estimating step And estimating a propagation delay between the transparent relay and the terminal using a reference pilot signal corresponding to each of the stored pilot signals. The method of claim 22, wherein the propagation delay estimating step Generating first complex values proportional to each of the extracted pilot signals and a conjugate complex transform value of a reference pilot signal corresponding to each of the extracted pilot signals and an exponential function based on a pilot position of each of the extracted pilot signals; Complex multiplication step; An accumulation processing step of accumulating the first complex values to generate a second complex value; An absolute value calculating step of generating an absolute value of the second complex value; And And searching for a time-domain sample for maximizing an absolute value of the second complex value to estimate a propagation delay between the transparent relay and the terminal. 23. The method of claim 22, wherein the weight estimating step Delaying a delta function in a time domain by the estimated propagation delay; And Estimating the propagation delay weight by obtaining a fast Fourier transform result of the delta function in the time delayed time domain. The method of claim 22, And a channel estimating step of estimating a channel between the transparent relay and the terminal based on each of the extracted pilot signals, a reference pilot signal corresponding to each of the extracted pilot signals, and the propagation delay weight. Channel estimation method characterized in that. 27. The method of claim 26, wherein the channel estimating step A pilot of each of the extracted pilot signals based on each of the extracted pilot signals, a reference pilot signal corresponding to each of the extracted pilot signals, and the propagation delay weight at a pilot position of each of the extracted pilot signals; A phase distortion removing step of obtaining a phase distortion removing channel from which phase distortion due to propagation delay between the transparent relay and the terminal at the position is removed; An interpolation step of interpolating the frequency domain of the frequency domain signal based on the phase distortion elimination channel to obtain an interpolated channel; And And a channel estimation determining step of estimating a channel between the transparent relay and the terminal based on the interpolated channel and the propagation delay weight. 28. The method of claim 27, wherein the interpolation is linear interpolation. The method of claim 26, And a channel compensation step of performing channel compensation on the signal received by the terminal based on the channel between the transparent relay and the terminal estimated in the channel estimation step. 23. The method of claim 22, wherein the transparent relay is a transparent relay for improving data yield. In the orthogonal frequency division multiplexing system orthogonal frequency division multiple access system comprising a base station and at least one cooperative relay transmitting device and a terminal for receiving a signal transmitted by the transmitting devices in the cooperative relay system In the method for estimating the channel between each and the terminal,  A pilot for extracting pilot signals transmitted by a corresponding transmission apparatus for each transmitting apparatus based on a fast Fourier transformed frequency domain signal after the signal received by the terminal is synchronized based on the signal received by the terminal from the base station Extraction step; A propagation delay estimating step of estimating a propagation delay between each of the extracted pilot signals and a reference pilot signal which is a predetermined signal value corresponding to each of the extracted pilot signals; And And a weight estimating step of estimating a propagation delay weight for estimating a channel between the transmitting apparatus and the terminal for each transmitting apparatus based on the estimated propagation delay between the respective transmitting apparatus and the terminal. A channel estimation method. The method of claim 31, wherein And a pilot storing step of storing the set of reference pilot signals for each transmitting apparatus before the pilot extracting step. The propagation delay estimating step And estimating a propagation delay between the respective transmitting apparatus and the terminal by using a reference pilot signal corresponding to each of the stored pilot signals. 32. The method of claim 31, wherein the propagation delay estimating step Conjugation of each of the extracted pilot signals and a reference pilot signal corresponding to each of the extracted pilot signals for each symbol of a predetermined interval among the symbols transmitted by the respective transmitting apparatuses included in the signal received by the terminal A complex multiplication step of generating first complex values proportional to a complex transform value and an exponential function based on the pilot position of each extracted pilot signal; A first accumulation processing step of generating a second complex value by accumulating the first complex values for each symbol of the predetermined section; An absolute value calculating step of generating an absolute value of the second complex value for each symbol of the predetermined section; A second accumulation processing step of accumulating an absolute value of the second complex value for each transmission device to generate an accumulation value for each transmission device; And And a maximum value searching step of searching for a time-domain sample maximizing an accumulated value for each transmitting apparatus and estimating a propagation delay between the corresponding transmitting apparatus and the terminal. 32. The method of claim 31, wherein the weight estimating step Delaying a delta function in a time domain for each transmission device by the propagation delay between the estimated corresponding transmission device and the terminal; And And estimating a propagation delay weight of each transmitting apparatus by obtaining a fast Fourier transform result of the delta function in the time delayed time domain. The method of claim 31, wherein A channel for estimating a channel between the transmitter and the terminal based on each of the extracted pilot signals for each transmitter, a reference pilot signal corresponding to each of the extracted pilot signals, and a propagation delay weight of the transmitter; And estimating step. 36. The method of claim 35, wherein the channel estimating step Each of the extracted pilot signals in a channel between the transmitting device and the terminal transmitting the extracted pilot signals for each symbol of a predetermined interval among the symbols transmitted by the transmitting apparatus included in the signal received by the terminal A phase distortion removing step of obtaining a phase distortion removing channel from which phase distortion due to propagation delay is removed for each pilot position of the pilot position; An interpolation step of interpolating the frequency domain of the frequency domain signal based on the phase distortion elimination channel to obtain an interpolated channel; An average calculating step of averaging the interpolated channels for each of the transmitting devices; And And a channel estimation determining step of estimating a channel between each transmitting apparatus and the terminal based on the averaged channel and a propagation delay weight between the transmitting apparatus and the terminal. 37. The method of claim 36, wherein the interpolation is linear interpolation. 36. The method of claim 35 wherein Each transmitting device transmits a signal constituting a signal received by the terminal using a predetermined encoding scheme for multi-input multiple-output (MIMO), And a decoding step of decoding a signal received by the terminal on the basis of a channel between the respective transmitting apparatus and the terminal estimated in the channel estimating step. 39. The method of claim 38, wherein the predetermined coding scheme for MIMO is space-time coding (STC). delete delete delete

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