KR20060136290A - Method and apparatus for transceiving downlink data to combining receive data in ofdm system - Google Patents

Abstract

The present invention relates to a method and apparatus for downlink data transmission and reception for receiving signal combining of a terminal in an OFDM-based cellular system. In the proposed method, the base station informs the terminal of the combining information, and the cells that can be combined can use the same radio resource and the same scrambling sequence when transmitting data, so that the combining can be performed naturally without any additional operation from the terminal reception side. . In addition, the terminal can compensate for the received data signal by combining the channel estimation value calculated from the pilot signal of each cell to compensate for the received signal. Through the transmission and reception operation as described above, the reception performance of the UE located in the cell overlapping region can be improved.

OFDM, combining, diversity, channel estimation

Description

TECHNICAL FIELD AND METHOD AND APPARATUS FOR TRANSMITTING RECEIVED DATA FOR COMBINATION OF RECEIVED DATA IN ORthogonal Frequency Division Multiplexing System.

1A and 1B show a typical OFDM transceiver

2 is a diagram illustrating an example of a combining concept and radio resource allocation according to a preferred embodiment of the present invention.

3 is a flowchart illustrating a base station transmission operation according to a preferred embodiment of the present invention.

4 is a flowchart illustrating a terminal receiving operation according to a preferred embodiment of the present invention.

5 is a view showing an operation example according to the first embodiment of the present invention.

6 is a diagram illustrating a configuration of a base station transmitting apparatus according to the first embodiment of the present invention.

7 is a diagram showing the configuration of a terminal receiving apparatus according to the first embodiment of the present invention.

8 is a diagram showing an example of operation according to the second embodiment of the present invention;

9 is a view showing an operation example according to the third embodiment of the present invention.

The present invention relates to an Orthogonal Frequency Division Multiplexing (OFDM) system, and more particularly, to a method and apparatus for transmitting and receiving downlink data for enabling a terminal to combine received data.

Recently, orthogonal frequency division multiplexing (OFDM) transmission technology has been widely applied as a technology for broadcasting and mobile communication systems. OFDM technology eliminates interference between multipath signal components commonly found in wireless communication channels, guarantees orthogonality among multiple access users, and enables efficient use of frequency resources, thereby enabling existing code division multiple access (Code Division). Compared to the Multiple Access (hereinafter referred to as CDMA) technology, this technology is useful for high speed data transmission and wideband systems. The OFDM technology is a method of transmitting data using a multi-carrier, and a plurality of sub-carriers having mutually orthogonality by converting symbol strings serially input in parallel. That is, it is a type of Multi Carrier Modulation (MCM) scheme carried on a plurality of subcarrier channels.

1A and 1B illustrate a transceiver structure of a typical OFDM system.

Referring to the OFDM transmitter illustrated in FIG. 1A, a channel coding block 102 is an encoder that receives a predetermined information bit string as an input and performs channel coding. In general, a convolutional encoder, a turbo encoder, or a low density parity check (LDPC) encoder is used as the channel coding block 102. The modulation block 104 performs modulation such as Quadrature Phase Shift Keying (QPSK), 8-ary PSK (8PSK), 16-ary Quadrature Amplitude Modulation (16QAM), and 64-QAM (64-ary QAM). Although omitted in FIG. 1A, a rate matching block may be additionally included between the channel coding block 102 and the modulation block 104 to perform repetition and puncturing. It is self-evident.

The serial / parallel block 106 receives the output of the modulation block 104 as an input and converts the input signal into a parallel signal. An Inverse Fast Fourier Transform (IFFT) block 108 receives the parallel signal as an input and performs an IFFT operation. The output of the IFFT block 108 is converted to a serial signal in parallel / serial block 110. Cyclic Prefix (CP) adder 112 adds a predetermined CP to the serial signal, and frequency-converts the output of CP Adder 112 in RF (Radio Frequency) transmission (TX) block 114. After RF processing, filtering and amplification are performed.

The OFDM receiver shown in FIG. 1B is implemented as the reverse operation of the transmitter. When an OFDM signal is received by an OFDM receiver, the RF receive block 116 amplifies and frequency downconverts the OFDM signal, and the CP remover 118 removes the CP from the output of the RF receive block 116. The output signal of the CP remover 118 is converted into a parallel signal by the serial / parallel block 120 and subjected to FFT operation in the FFT block 122 and then by the parallel / serial block 124 into a serial signal. .

After the channel correction block 126 performs channel estimation and channel compensation on the serial signal, the demodulation block 128 outputs the output signal of the channel correction block 126 to the modulation block 104 of the OFDM transmitter. Corresponds to demodulation to QPSK, 8PSK, 16 QAM, 64QAM and the like. The channel decoding block 130 performs decoding on the demodulated signal to finally obtain information bits. Although omitted in FIG. 1B, it is obvious that a rate de-matching block may be additionally inserted between the demodulation block 128 and the channel decoding block 130 to perform the reverse operation of the rate matching block of the transmitter. .

In order to apply the OFDM-based system to a broadcast or mobile communication system, not only data transmission but also transmission of pilot and control information for demodulating and decoding the data in a receiver is required. Since the pilot is data of a pattern promised between the transmitter and the receiver, when a distortion occurs in the received signal by the radio fading channel, the receiver may estimate and remove the distortion generated in the received signal based on the pilot. The control information includes information related to a hybrid automatic repeat request (HARQ) such as a modulation scheme applied to transmission data, a channel coding scheme, a data block size, a subpacket identifier (ID), and the like. The receiver detects the information applied to the transmission data by receiving the control information and performs an operation such as demodulation and decoding of the reception data.

In the OFDM-based cellular communication system, a technique for improving reception performance of a terminal located in an intercell boundary region is required. To this end, as a possible solution, the reception SINR (Signal to Interference and Noise Ratio) of the UE is improved by reducing the amount of interference between adjacent cells. In order to reduce the amount of interference between adjacent cells, data is transmitted by applying a randomizer determined for each cell. The randomizer may be implemented as a scrambling sequence. That is, the transmitter can reduce the amount of interference between adjacent cells by multiplying a signal to be transmitted by a scrambling sequence determined for each cell.

In addition to the technique of reducing the amount of interference between adjacent cells in order to improve the reception performance of the terminal located in the inter-cell boundary region, a technique for enabling the terminal to combine signals received from multiple cells may be considered. Therefore, there is a need to develop a general technology that enables the terminal to combine and decode the received signal in the above situation.

Accordingly, the present invention, which was devised to solve the problems of the prior art operating as described above, provides a method for allowing a terminal to combine signals from multiple cells in order to improve reception performance of a terminal located at an intercell boundary region; Provide the device.

Hereinafter, with reference to the accompanying drawings will be described in detail the operating principle of the preferred embodiment of the present invention. In the following description of the present invention, detailed descriptions of well-known functions or configurations will be omitted if it is determined that the detailed description of the present invention may unnecessarily obscure the subject matter of the present invention. Terms to be described later are terms defined in consideration of functions in the present invention, and may be changed according to intentions or customs of users or operators. Therefore, the definition should be made based on the contents throughout the specification.

The present invention to be described below will be described in detail the transmission and reception operations of the base station and the terminal for the terminal located in the inter-cell boundary region in the OFDM-based cellular communication system.

In the OFDM system, by designing a CP (Cyclic Prefix) in consideration of the delay characteristics of the multipath signal components, the multipath signal components commonly present in a wireless communication system can be received within the CP length and can be recovered without interference with each other. Therefore, it is necessary to take advantage of the OFDM system as described above in a multi-cell environment.

Hereinafter, the principle of operation of the present invention will be described with reference to FIGS. 2A and 2B.

As shown in FIG. 2A, the terminal 206 exists in an overlapping area of cell # 1 202 and cell # 2 204, and radio resource management for the terminal 206 is performed in cell # 1 202. This is in charge. The cell # 1 202 as described above is called a serving cell of the terminal 206, and the cell # 2 204 that is not is referred to as a non-serving cell. There are no special constraints for the cells # 1 202 and # 2 204 that overlap each other. Preferably, the operation of the transceiver of the cell # 1 202 and the transceiver of the cell # 2 204 are simultaneously performed. There is a managing entity, for example Node B (hereinafter, it will be used interchangeably with 'Base Station'), so that the transceiver and the cell # of the cell # 1 202 are present. Assume that cooperation or information exchange between the transceivers of 2 (204) is smooth.

FIG. 2B illustrates an example of radio resource allocation of cells # 1 202 and # 2 204 shown in FIG. 2A.

Referring to FIG. 2B, in transmitting the data 226 from the cell # 1 202 to the terminal 206, the data 226 is transmitted to the cell # 1 202 in order to reduce the amount of interference between adjacent cells. The multiplied scrambling sequence # 1 230 is multiplied and transmitted using the time-frequency resource # 1 222 allocated to the terminal 206 (208). The radio resource allocated to the terminal 206 is determined by a scheduler of the cell # 1 202 serving as a serving cell or a scheduler of the node ratio. The radio resource # 1 222 allocated by the scheduler may be arranged continuously or discontinuously in the time-frequency domain as shown in FIG. 2B.

The radio resource 222 may be represented as a two-dimensional time-frequency resource by dividing the radio resource into a time and frequency domain. The basic unit of the radio resource in the frequency domain is the OFDM sub-carrier (216), and the basic unit of the radio resource in the time domain is the OFDM symbol 218. The transmission time interval (TTI) 220 representing the OFDM subcarrier, the OFDM symbol, and the base unit to be channel coded is determined according to the OFDM system design. The scrambling sequence # 1 230 is a predefined sequence for the cell # 1 202. In FIG. 2B, the scrambling sequence # 1 230 is multiplied by OFDM subcarriers per OFDM symbol.

The pilot signal 228 is also multiplied by the scrambling sequence # 1 230 in order to estimate a channel experienced by the transmission signal of the cell # 1 202 (210), and the radio resource # 2 (224) used at this time. Is not duplicated with the radio resource # 1 222. The radio resource # 2 224 for the pilot signal transmission allocated to the terminal 206 is determined by a scheduler of the cell # 1 202 or a node ratio scheduler which is a predefined or serving cell in system design. The arrangement in the time-frequency domain of the pilot signal 228 shown in FIG. 2B is one example, and may be appropriately arranged to increase channel estimation performance in system design.

The cell # 2 204 may also transmit the same data as the cell # 1 202 to the terminal 206 so that the received signal combining of the terminal may be performed, in this case, from the cell # 2 204. It is assumed that the radio resource # 1 222 is available, similarly to the cell # 1 202, for data transmission. In this case, when a scheduler exists for each cell, the serving cell Cell # 1 202 signals the cell # 2 204 that it uses the radio resource # 1 222 for data transmission. Inform. If the scheduler is present in a higher entity that manages both Cell # 1 202 and Cell # 2 204, e.g., Node Ratio, then the Node Ratio is used by Cell # 1 202. Resource information is reported to the cell # 2.

The cell # 2 204 is a scrambling sequence # 2 232 allocated to the cell # 2 204 for the same data as the cell # 1 202 to be transmitted by the cell # 2 204. Instead of the scrambling sequence # 1 230 used to scramble the data of the cell # 1 202, a multiplication sequence 234 corresponding to the radio resource # 1 222 is multiplied and transmitted (212). Through this operation, the cells # 1 202 and the cells # 2 204 multiply the same data by the same scrambling sequence 234 and allocate the same data to the same radio resource 222 to transmit the same (208, 212). The terminal 206 combines the received signals naturally without having to distinguish from which cell each received signal is received.

The cell # 2 204 multiplies the scrambling sequence # 2 232 of the cell # 2 204 by a pilot signal for estimating a channel experienced by the transmission signal of the cell # 2 204 (214). The radio resource used at this time is preferably equal to the radio resource # 2 224 for pilot transmission of the cell # 1 202. That is, the radio resource allocated to the pilot for channel estimation uses the same radio resource without distinguishing between cells, so that the UE can know that the pilot signal is allocated to the predefined radio resource in all cells.

However, the scrambling sequence # 2 232 multiplied by the pilot of the cell # 2 204 is distinguished from the scrambling sequence # 1 230 multiplied by the pilot of the cell # 1 202. Since the pilot is for estimating the channel state of the cell to which the UE belongs to each cell, the cell can be distinguished by the scrambling sequences 230 and 232. In addition, even though the cell # 1 202 and the cell # 2 204 allocate pilots to the same radio resources, interference between adjacent cells is caused by the scrambling sequence # 1 230 and the scrambling sequence # 2 232. This randomized effect can be obtained.

In the system operating as described above, the signal received by the terminal is naturally combined without having to distinguish the data received from the cell # 1 202 and the data received from the cell # 2 204. That is, the cell # 1 202 and the cell # 2 204 transmit data by applying the same radio resource and the same scrambling sequence to the same data, so that a terminal receives a kind of multipath signal from each cell. The same effect as that is obtained, and in an OFDM system, the multipath signals are naturally combined without interference with each other. Channel estimation and compensation should be performed by using a pilot on the received data signal as described above.

The terminal 206 extracts a signal of the radio resource # 2 224 to which a pilot is allocated to a received signal and descrambles the scrambling sequence # 1 230 of the cell # 1 202 to decode the cell. A pilot signal of # 1 202 is obtained and a channel estimate of the cell # 1 202 is calculated from the pilot signal. In addition, the terminal 206 extracts a signal of the radio resource # 2 224 to which the pilot is assigned and descrambles the scrambling sequence # 2 232 of the cell # 2 204 to decode the cell # 2 ( A pilot signal of 204 is obtained, and a channel estimate of the cell # 2 204 is calculated through this. By combining the channel estimates of the cell # 1 202 and the channel estimates of the cell # 2 204 calculated as described above, the final channel estimate of the data signal received by the terminal can be determined. Accordingly, the terminal demodulates and decodes the channel signal after performing channel compensation or channel equalization using the final channel estimate. Zero forcing, Maximum Ratio Combining (MRC), Minimum Mean Square Error (MMSE), and the like are widely used as the channel compensation method.

In the operation of combining the channel estimates, the system must inform the terminal of the cell from which cell the channel estimates are combined. The signaling may be both physical layer (L1) signaling or higher layer (L2) (layer2, L3; layer3) signaling, and each cell may inform the UE of the signaling. Preferably, the serving cell causes the terminal to signal.

3 is a flowchart illustrating a base station transmission procedure according to a preferred embodiment of the present invention.

In step 302, if the terminal is located in an inter-cell overlapping region and can receive data from multiple cells, and the multiple cells can allocate the same radio resource for the same data transmission, the base station receives a signal from the multiple cells from the terminal's point of view It is determined that can be combined. The radio resource is a radio resource allocated by a serving cell or a radio resource commonly allocated by a base station to the overlapping multiple cells. In step 302, the mobile station branches to step 304 for the cells determined to be able to combine the received signals at the terminal. In step 304, the base station determines whether the cell to which the data is to be transmitted is a serving cell.

If it is a serving cell, in step 306, a combining indicator is set and transmitted to the terminal. The combining indicator includes information on all cells that can be combined by the terminal. The combining indicator may be transmitted through physical layer (L1) signaling or higher layer (L2) layer2, L3; layer3 signaling. Accordingly, the UE can know whether combining is possible for the remaining cells by receiving signaling from the serving cell without having to receive the combining indicator from all cells. On the other hand, if it is determined in step 304 that the cell to which the data is to be transmitted is not a serving cell, step 306 is skipped and step 308 is performed.

In step 308, the base station allocates the same data to the same radio resources for all cells that can be combined with the terminal. The radio resource is a radio resource allocated by a serving cell for data transmission or a radio resource that can be commonly allocated to all combineable cells. The information on the same radio resource may be informed through signaling between all the cells that can be combined or the base station may inform all the cells that can be combined.

In step 310 the base station scrambles the data in the same sequence for all combineable cells. The sequence is a sequence used by a serving cell to scramble the data or a sequence commonly assigned to the multiple cells for the purpose of scrambling the combineable data by the base station. The information on the same scrambling sequence may be notified through signaling between all combineable cells or the base station may inform all combineable cells.

In step 312, the scrambled data allocated to the radio resource is transmitted to the terminal. In this case, in order for the terminal to demodulate and decode the data, control information such as a modulation method, a data block size, a channel coding method, and a radio resource is used. The control information transmits only the serving cell. Accordingly, the terminal receives control information from the serving cell and utilizes the data for demodulation and decoding without having to receive the control information from all cells. If necessary, the control information is transmitted from all the cells that can be combined to increase the reception reliability of the control information. The radio resource for transmitting the control information is predefined or can be known by the terminal as system information in a call setup or reconfiguration step between the terminal and the base station. The control information is also transmitted by multiplying with the scrambling sequence of the serving cell.

In addition, in step 310, the base station multiplies and transmits a pilot signal previously transmitted for channel estimation of each cell with a scrambling sequence set for each cell, regardless of whether the terminal can be combined. The pilot signal of each cell is transmitted through radio resources for each cell allocated for the pilot signal. In this case, the radio resource allocated for the pilot signal may be predefined or may be known by the terminal as system information in a call setup or reconfiguration step between the terminal and the base station.

In step 302, for the cells determined to be impossible to combine the received signal from the terminal, the process branches to step 314. In the step 314, cells that cannot be combined cannot perform data transmission.

4 shows a terminal receiving procedure according to a preferred embodiment of the present invention.

In step 402, the terminal receives a combining indicator from the serving cell, and confirms which cells of the data signal can be combined. The n-combinable cells transmit data by applying the same radio resource and the same scrambling sequence to all of the same data, thereby obtaining the same effect as receiving a kind of multipath signal from each cell at the terminal entrance. The multipath signals are naturally combined without interfering with each other.

In step 404, the UE performs channel estimation using the pilot signals of the identified combineable cells. The pilot from the combineable cells is assigned to a radio resource and multiplied by a scrambling sequence to be transmitted in advance, or the UE may know by system information in a call setup or reconfiguration step between the UE and the base station. . The channel estimation is widely known by interpolating and calculating a time domain or a frequency domain of a signal to be compensated using pilot symbols arranged at a specific position in the time-frequency domain.

 In step 406, the UE combines respective channel estimates Ch_Est (1), ... CH_Est (n) for the combineable n cells. As one possible method of combining, the UE may combine each channel estimate by a simple sum of symbols. In step 408, the terminal compensates for the channel distortion of the data signal received by the terminal using the combined channel estimate. As the channel compensation (or channel equalization) method, zero forcing, MRC, and MMSE methods are widely used. In step 410, the terminal demodulates the channel compensated data signal, and finally decodes the demodulated data signal to obtain an information bit.

The main operation principle, the base station transmission procedure and the terminal reception procedure of the present invention have been described so far. Embodiments to be described below will be described with respect to the specific system operation and the transmission and reception apparatus based on the main operation principle.

<< first embodiment >>

The first embodiment uses a common pilot for channel estimation for each cell.

FIG. 5 illustrates an operation example according to the first embodiment of the present invention, in which a terminal 508 exists in an overlapping area of cells # 1 502, cells # 2 504, and cells # 3 506. The cell # 1 502 is a serving cell for the terminal 508, so the cell # 2 504 and the cell # 3 506 become non-serving cells. In order to reduce the amount of interference between adjacent cells, different types of randomizers are required for each cell, and the randomizers are implemented by multiplying and transmitting a different type of scrambling sequence for each cell.

In FIG. 5, the scrambling sequence # 1 is assigned to cell # 1 502, the scrambling sequence # 2 is assigned to cell # 2 504, and the scrambling sequence # 3 is assigned to cell # 3 506. Each scrambling sequence may be given to the terminal as system information in a call setup or reconfiguration step between the terminal and the base station as a predefined sequence. The specific system operation of the first embodiment is almost similar to that described above, in addition to this, a common pilot is used for each cell for channel estimation of each cell, and a specific transmission / reception apparatus will be described.

In transmitting data from the cell # 1 502 to the terminal 508, the cell # 1 502 multiplies the data by the scrambling sequence # 1 to multiply the radio resource # 1 allocated to the terminal 508. To transmit (512). The radio resource allocated to the terminal 508 is a scheduler of the cell # 1 502 serving cell, or a base station that integrates and manages the cell # 1 502, the cell # 2 504, and the cell # 3 506. It is determined by the scheduler. The radio resource # 1 allocated by the scheduler may be arranged continuously or discontinuously in the time-frequency domain.

A common pilot signal for estimating a channel experienced by the transmission signal of the cell # 1 502 is also multiplied by the scrambling sequence # 1 and transmitted (514). The radio resource # 2 used at this time overlaps with the radio resource # 1. It doesn't work. Radio resource # 2 allocated to the terminal 508 for transmission of the common pilot signal is determined by a scheduler of the cell # 1 802 or a scheduler of the base station, which is a predefined or serving cell in system design.

In order for the terminal 508 to demodulate and decode the data transmitted by the cell # 1 502, control information such as a modulation method, a data block size, a channel coding method, and a radio resource is used. The control information is transmitted only to the serving cell (510) so that the terminal 508 can receive control information from the serving cell 502 and use it for data decoding without having to receive the control information from all cells. Radio resource # 3 for transmitting the control information is predefined or can be known by the terminal 508 as system information in the call setup or reconfiguration step between the terminal 508 and the base station. The control information is transmitted by using the radio resource # 3 by multiplying the scrambling sequence # 1 of the serving cell 502.

The serving cell 502 sets a combining indicator 516 for the terminal 508 belonging to the overlapping area and transmits the combined indicator 516 to the terminal. The combining indicator 516 includes information on all cells that can be combined by the terminal 508. The combining indicator 516 may be transmitted through physical layer (L1) signaling or higher layer (L2; layer2, L3; layer3) signaling. The terminal may receive the combining indicator 516 from the serving cell without having to receive signaling from all cells to know whether combining is possible for the remaining cells (ie, non-serving cells). The combining indicator 516 illustrates that data signals of cells # 1 and # 2 can be combined, and data signals of cell # 3 cannot be combined.

The cell # 2 504 may also transmit the same data as the cell # 1 502 to the terminal 508 so that the received signal combining of the terminal may be performed, in this case from the cell # 2 504. An example in which the radio resource # 1 is available similarly to the cell # 1 502 for data transmission is shown. In this case, when a scheduler exists for each cell, the serving cell Cell # 1 502 informs the Cell # 2 504 that the radio resource # 1 is used for data transmission through signaling. If the scheduler is present in the base station, the base station informs the cell # 2 504 that the cell # 1 502 is using radio resource # 1. The cell # 2 804 is not the scrambling sequence # 2 allocated to the cell # 2 504 for the same data as the cell # 1 502 to be transmitted by the cell # 2 504, The data corresponding to the radio resource # 1 is multiplied and transmitted in the scrambling sequence # 1 used to scramble the data of the cell # 1 502 (518). Through this operation, the cell # 1 502 and the cell # 2 504 multiply the same data by the same scrambling sequence and allocate the same data to the same radio resource (512, 518), thereby receiving the received signal from the terminal 508. Combine naturally without having to distinguish which cell is received from.

The cell # 2 504 multiplies the scrambling sequence # 2 of the cell # 2 504 by using a common pilot signal for estimating a channel experienced by the transmission signal of the cell # 2 504 (520). The radio resource is preferably equal to the radio resource # 2 for common pilot transmission of the cell # 1 502. That is, the radio resources allocated to the common pilot for channel estimation use the same radio resources without distinguishing between cells, so that the UE can know that the common pilot signal is allocated to the predefined radio resources regardless of the cell. Can be. However, the scrambling sequence # 2 multiplied by the common pilot of the cell # 2 504 is distinguished from the scrambling sequence # 1 multiplied by the common pilot of the cell # 1 502. Since the common pilot is for estimating the channel state of the cell to which the UE belonging to each cell belongs, the cell can be distinguished by the scrambling sequence. In addition, even when the cell # 1 502 and the cell # 2 504 allocate common pilots to the same radio resources, the interference between adjacent cells is randomized by the scrambling sequence # 1 and the scrambling sequence # 2. Can be.

The cell # 3 506 indicates a case in which the radio resource # 1 allocated by the serving cell to the terminal for data transmission cannot be used. That is, since the terminal cannot combine the signal from the cell # 3 506 as if the multipath signal is received, the cell # 3 506 does not transmit data.

In the system operating as described above, the signal received by the terminal is naturally combined without having to distinguish the data received from the cell # 1 502 and the data received from the cell # 2 504. That is, the cell # 1 502 and the cell # 2 504 transmit data by applying the same radio resource and the same scrambling sequence to the same data, so that a terminal receives a kind of multipath signal from each cell. The same effect as that is obtained, and in an OFDM system, the multipath signals are naturally combined without interference with each other. Channel estimation and compensation should be performed by using a pilot on the received data signal as described above.

The terminal 508 extracts the signal of the radio resource # 2 to which the common pilot is assigned to the received signal and descrambles the scrambling sequence # 1 of the cell # 1 502 to decode the cell # 1 502. A pilot signal of is obtained to calculate the channel estimate of the cell # 1 (502). The channel estimation is widely known by interpolating and calculating a time domain or a frequency domain of a signal to be compensated using pilot symbols arranged at a specific position in the time-frequency domain.

 In addition, the terminal 508 extracts the signal of the radio resource # 2 to which the pilot is assigned and descrambles the scrambling sequence # 2 of the cell # 2 504 to decode the pilot signal of the cell # 2 504. It calculates the channel estimate of the cell # 2 (504) through this. The terminal 508 combines the channel estimates of the cell # 1 502 and the channel estimates of the cell # 2 504, respectively, calculated as described above, to determine the final channel estimates of the data signal received by the terminal. Can be found. As one possible method of combining, each channel estimate may be calculated as a simple sum of symbol units. The terminal demodulates and decodes the channel signal (or channel equalization) using the final channel estimate for the data signal. Zero forcing, MRC, MMSE method and the like are widely used in the channel compensation method.

6 shows an apparatus for transmitting a base station according to the first embodiment of the present invention. Here, a transmission path of one cell controlled by the base station is shown.

Referring to FIG. 6, in order to transmit traffic data 602, 626 to k terminals User # 1,..., And User #k located in a cell overlap region, channel coding blocks 604 and 628 include the data. Channel code (602, 626). In general, a convolutional encoder, a turbo encoder, or an LDPC encoder is used as the channel coding scheme. The modulation blocks 606 and 630 perform modulation on QPSK, 8PSK, 16 QAM, 64QAM, etc. on the channel coded signal. Although omitted in FIG. 6, it is apparent that a rate matching block may exist between the channel coding blocks 604 and 628 and the modulation blocks 606 and 630 to perform repetition and puncturing.

The serial / parallel blocks 608 and 632 receive the outputs of the modulation blocks 606 and 630 as inputs and make the input signals into parallel signals. Resource mappers 610 and 634 map the parallel signals to radio resources allocated by the scheduler 654. The scheduler 654 performs radio resource allocation in consideration of the scheduling request information and the channel state of the terminal. The data multiplexer 612 multiplexes data signals to be sent to terminals belonging to the serving cell.

The control information and scheduling information 636 necessary for the terminal to demodulate and decode the data signals pass through a channel coding block 638, a modulation block 640, and a serial / parallel block 642, and then a resource mapper 644. ) Is mapped to a radio resource allocated by the scheduler 654 or a predefined radio resource. There may be a plurality of channels for transmitting the control information 636 for each property of the control information.

The pilot 646 for channel estimation passes through the modulation block 648 and the serial / parallel block 650 and then, by the resource mapper 652, a radio resource allocated by the scheduler 654 or a predefined radio resource. Is mapped to. When the control information or pilot is allocated to a predefined radio resource, the information on the allocated radio resource may be known by the terminal as system information in a call setup or reconfiguration step between the terminal and the base station.

The multiplexer 614 scrambles and multiplexes the data signal, control information, and pilot signal. In this case, the serving cell multiplies the multiplexed signal by the scrambling sequence assigned by the serving cell. In the case of a non-serving cell that can be combined, the signal in the time-frequency domain where the combineable data is located is multiplied by the same scrambling sequence as the serving cell, and the signal in the remaining region is multiplied by the scrambling sequence of the non-serving cell. After the transmission.

IFFT block 616 receives the multiplexed signal as an input and performs an IFFT operation. The output of the IFFT block 616 is converted into a serial signal by the parallel / serial block 618. The CP adder 620 adds a predetermined CP to the serial signal, and the RF transmission block 622 transmits the output of the CP adder 620 through RF processing such as frequency rising conversion, filtering, and amplification.

Meanwhile, the serving cell sets a combining indicator for the overlapping cell and transmits the combined indicator to the terminal. The combining indicator includes information on all cells that can be combined by the terminal, and may be transmitted through physical layer signaling or higher layer signaling. The UE may know whether to combine the remaining cells by receiving the signaling from the serving cell without having to receive the combining indicator from all the cells. When the combining indicator is transmitted through physical layer signaling, the combining indicator is set and transmitted in a separate control channel as the control information 636, and is included in the data 602 when transmitted through higher layer signaling. Is sent.

7 shows a receiving device of a terminal according to the first embodiment of the present invention.

Referring to FIG. 7, the signal received via the RF receive block 116 is input to the CP remover 702. CP remover 702 removes the CP for the received signal, and the output signal of CP remover 702 is converted to a parallel signal via serial / parallel block 704 and then FFT operation at FFT block 706. Is converted into a serial signal by parallel / serial block 708. The combining indicator receiver 710 identifies the cells that can be combined through the combining indicator received from the serving cell through physical layer signaling or higher layer signaling, and notifies the channel estimation block 716.

The channel estimation block 716 consists of a channel estimator 712 and a channel estimation combiner 714. The channel estimator 712 extracts a pilot signal from the serial signal provided from the parallel / serial block 708 and descrambles the scrambling sequences of the combineable cells one by one, and then performs the combineable cell through a channel estimation operation. Get the channel estimates, respectively. Channel estimation combiner 714 combines the channel estimates to calculate the final channel estimate.

The channel equalizer 718 performs channel compensation on the serial signal provided from the parallel / serial block 708 by using the obtained channel estimate value, and the channel compensated signal is obtained by separate control information received by the terminal. By using the demodulator 720 and the channel decoder 722, the terminal finally obtains the information bits.

<< 2nd Example >>

The second embodiment uses a common pilot for channel estimation for each cell and uses a dedicated pilot for channel estimation for combining.

8 illustrates an operation example according to the second embodiment of the present invention, in which a terminal 808 exists in an overlapping area of cells # 1 802, cells # 2 804, and cells # 3 806. The cell # 1 802 is a serving cell for the terminal 808, so the cell # 2 804 and the cell # 3 806 become non-serving cells. In order to reduce the amount of interference between neighboring cells, different types of randomizers are required for each cell, and the randomizers are implemented by multiplying and transmitting signals of different types of scrambling sequences for each cell.

In FIG. 8, the scrambling sequence # 1 is assigned to cell # 1 802, the scrambling sequence # 2 is assigned to cell # 2 804, and the scrambling sequence # 3 is assigned to cell # 3 806. Each scrambling sequence may be given to the terminal as system information in a call setup or reconfiguration step between the terminal and the base station as a predefined sequence. The specific system operation of the second embodiment is similar to that of the first embodiment described above. However, a common pilot is used for each cell to help channel estimation of terminals not located in the overlapping region of each cell, and a separate dedicated pilot is used to facilitate data combining and channel estimation of terminals located in the overlapping cell region. do.

In transmitting data from the cell # 1 802 to the terminal 808 (814), the cell # 1 802 multiplies the data by the scrambling sequence # 1 and allocates the radio resource allocated to the terminal 808. Transmit using # 1 (814). The radio resource allocated to the terminal 808 is a scheduler of the cell # 1 802 serving cell or the base station that integrates and manages the cell # 1 802, cell # 2 804, and cell # 3 806. It is determined by the scheduler. The radio resource # 1 allocated by the scheduler may be arranged continuously or discontinuously in the time-frequency domain.

In order to estimate a channel experienced by the transmission signal of the cell # 1 802, a common pilot signal is also transmitted by multiplying the scrambling sequence # 1 (816). The radio resource # 2 used at this time overlaps with the radio resource # 1. It doesn't work. Radio resource # 2 for common pilot signal transmission allocated to the terminal 808 is determined by a scheduler of the cell # 1 802 or a scheduler of the base station that is a predefined or serving cell in system design.

Unlike the first embodiment, the common pilot is used for channel estimation of only terminals not located in the overlap region of each cell. In order for the UE located in the overlapping region to combine the received signals and estimate the channel, a separate dedicated pilot is multiplied by the scrambling sequence # 1 of the serving cell and transmitted using radio resource # 5 (810). The radio resource # 5 does not overlap with radio resources allocated for other data or control information. The radio resource # 5 is determined by a scheduler of the cell # 1 802 serving cell, or a base station scheduler that integrates and manages the cell # 1 802, cell # 2 804, and cell # 3 806. Or predefined. In addition, the serving cell or the base station informs the cell # 2 804 and the cell # 3 806 that the dedicated pilot is used and the radio resource # 5 has been allocated to transmit the dedicated pilot.

In order for the terminal to demodulate and decode the data transmitted by the cell # 1 802, control information such as a modulation method, a data block size, a channel coding method, and a radio resource is used. By transmitting only the serving cell to the control information (812), the terminal can receive control information from the serving cell and use it for data demodulation and decoding without having to receive the control information from all cells. Radio resource # 3 for transmitting the control information is predefined or can be known by the terminal as system information in the call setup or reconfiguration step between the terminal and the base station. The control information is also multiplied and transmitted by the scrambling sequence # 1 of the serving cell.

The serving cell sets a combining indicator 820 for the terminal belonging to the overlapping area and transmits the combined indicator 820 to the terminal. The combining indicator 820 includes information on all cells that can be combined by the terminal and information indicating that channel estimation for a combining operation can be performed by a dedicated pilot. The combining indicator 820 may be transmitted through physical layer signaling or higher layer signaling. The UE may know whether to combine the remaining cells by receiving the combining indicator 820 from the serving cell without having to receive signaling from all cells. The combining indicator 820 illustrates that data signals of cells # 1 and # 2 can be combined, and data signals of cell # 3 cannot be combined.

The cell # 2 804 may also transmit the same data as the cell # 1 802 to the terminal 508 in order to enable the reception signal combining of the terminal, in which case the cell # 2 804 An example in which the radio resource # 1 is available similarly to the cell # 1 802 for data transmission is shown. In this case, when a scheduler exists for each cell, cell # 1 802 serving as the serving cell informs the cell # 2 804 that the radio resource # 1 is used for data transmission through signaling. If the scheduler is present in the base station, the base station informs the cell # 2 804 that the cell # 1 802 is using radio resource # 1. The cell # 2 804 is not the scrambling sequence # 2 allocated to the cell # 2 804 for the same data as the cell # 1 802 to be transmitted by the cell # 2 804, A scrambling sequence # 1 corresponding to the radio resource # 1 is multiplied and transmitted from the scrambling sequence used for scrambling the data of the cell # 1 802 (822). As described above, both the cell # 1 802 and the cell # 2 804 multiply the same data by the same scrambling sequence # 1, allocate the same data to the same radio resource # 1, and transmit (814, 822) the terminal 808. ) Combines naturally without having to distinguish from which cell the received signal is received.

The cell # 2 804 multiplies the scrambling sequence # 2 of the cell # 2 804 by multiplying the common pilot signal for estimating a channel experienced by the transmission signal of the cell # 2 804 (824). The radio resource used is preferably the same as the radio resource # 2 for common pilot transmission of the cell # 1 802. That is, the radio resources allocated to the common pilot for channel estimation use the same radio resources without distinguishing between cells, so that the UE can know that the common pilot signal is allocated to the predefined radio resources regardless of the cell. Can be.

However, the scrambling sequence # 2 multiplied by the common pilot of the cell # 2 804 is distinguished from the scrambling sequence # 1 multiplied by the common pilot of the cell # 1 802. Since the common pilot is for estimating the channel state of the cell to which the UE belonging to each cell belongs, the cell can be distinguished by the scrambling sequences. In addition, even though the cell # 1 802 and the cell # 2 804 allocate common pilots to the same radio resources, the inter-cell interference is randomized by the scrambling sequence # 1 and the scrambling sequence # 2. You can get it.

Unlike the first embodiment, the common pilot is used only for channel estimation by terminals not located in the overlap region of each cell. In order to assist the terminal located in the overlapping region to combine the received signals and estimate the channel, in cell # 2 802, the scrambling sequence # 1 and radio resource # 5 using a dedicated pilot in cell # 1 802 are used. And transmit (826). The cell # 2 804 knows from the serving cell or the base station that the serving cell uses a dedicated pilot and uses radio resource # 5 for transmission of the dedicated pilot.

The cell # 3 806 indicates a case in which the radio resource # 1 allocated by the serving cell to the terminal for data transmission cannot be used. That is, since the terminal cannot combine the signal from the cell # 3 806 as if it receives the multipath signal, the cell # 3 806 does not transmit data.

In the system operating as described above, the signal received by the terminal is naturally combined without the need to distinguish the data received from the cell # 1 802 and the data received from the cell # 2 804. That is, the cell # 1 802 and the cell # 2 804 transmit data by applying the same radio resource and the same scrambling sequence to the same data, so that a terminal receives a kind of multipath signal from each cell. The same effect as that is obtained, and in an OFDM system, the multipath signals are naturally combined without interference with each other.

In addition, both the cell # 1 and the cell # 2 are naturally combined with the data signal by transmitting a dedicated pilot for channel estimation for the combining signal using the same scrambling sequence and the same radio resource. . That is, as in the first embodiment, the process of obtaining the channel estimates and then combining them is not necessary.

The terminal extracts the signal of the radio resource # 5 to which the dedicated pilot is allocated and descrambles the scrambling sequence # 1 of the serving cell 802 to thereby decode the cell # 1 802 and the cell # 2 804. A dedicated pilot signal of is obtained as a combined result, and a channel estimate value for the data signal is calculated through the dedicated pilot signal. The terminal demodulates and decodes the channel signal by performing channel compensation (or channel equalization) on the data signal.

The base station transmitting apparatus and the terminal receiving apparatus for implementing the second embodiment are the same as those of FIGS. 6 and 7 mentioned in the first embodiment. However, the pilot resource mapper 652 of FIG. 6 maps the input pilot signal to radio resources for the common pilot and radio resources for the dedicated pilot. When the channel estimation block 716 of FIG. 7 is located in the overlapped region, the channel estimation block 716 obtains the combined dedicated pilot signal of each cell indicated as being able to be combined by the combining indicator, and obtains the combined dedicated pilot signal. To obtain a channel estimate for the combined data signal.

<< third embodiment >>

The third embodiment performs additional data combining while using a common pilot for channel estimation for each cell as in the first embodiment.

9 illustrates an operation example according to a third embodiment of the present invention, in which a terminal 908 exists in an overlapping area of cell # 1 902, cell # 2 904, and cell # 3 906. The cell # 1 902 is a serving cell for the terminal 908, and thus the cell # 2 904 and the cell # 3 906 become non-serving cells. In order to reduce the amount of interference between adjacent cells, different types of randomizers are required for each cell, and the randomizers are implemented by multiplying and transmitting a different type of scrambling sequence for each cell.

In FIG. 9, the scrambling sequence # 1 is assigned to cell # 1 902, the scrambling sequence # 2 is assigned to cell # 2 904, and the scrambling sequence # 3 is assigned to cell # 3 906. Each scrambling sequence may be given to the terminal as system information in a call setup or reconfiguration step between the terminal and the base station as a predefined sequence. The specific system operation of the third embodiment is almost similar to that of the first embodiment. However, in addition to the data combining method in the first embodiment, an additional data combining method is used together.

In transmitting data from the cell # 1 902 to the terminal 908, the cell # 1 902 multiplies the data by the scrambling sequence # 1 to multiply the radio resource # 1 allocated to the terminal 908. And transmit (912). The common pilot signal for estimating the channel experienced by the transmission signal of the cell # 1 902 is also multiplied by the scrambling sequence # 1 and transmitted (914). The radio resource # 2 used at this time overlaps with the radio resource # 1. It doesn't work. Control information such as a modulation method, a data block size, a channel coding method, a radio resource, etc. used to transmit the data transmitted by the cell # 1 502 is multiplied by the scrambling sequence # 1 of the serving cell 902 to be wireless. It is transmitted using resource # 3. (910)

In FIG. 9, the data signal of cell # 2 904 can be combined with the data signal of serving cell 902 in a first combining mode, and the data signal of cell # 3 906 is a serving cell. It is illustrated that the data signal of 902 can be combined with the second combining scheme. Here, the first combining method means that data transmitted using the same scrambling sequence is naturally combined, and the second combining method distinguishes and combines data transmitted using different scrambling sequences by the terminal. Means that.

The method of transmitting the data 918 and the common pilot 920 to the terminal 908 in the cell # 2 904 is the same as that of the first embodiment, and thus a detailed description thereof will be omitted. Since the cell # 2 904 can allocate the same radio resource for data transmission as the radio resource used to transmit the data signal of the serving cell 902, the data signal of the cell # 2 904 is a serving cell ( It is possible to combine the data signal of 902 with the first combining method. That is, both the cell # 1 902 and the cell # 2 904 multiply the same data by the same scrambling sequence and allocate the same data to the same radio resource (912, 918). Combine naturally without having to know which cell it is from.

The cell # 3 906 indicates a case in which the serving cell 902 cannot use the radio resource # 1 allocated to the terminal 908 for data transmission. Accordingly, the cell # 3 906 performs the data transmission using the radio resource # 4 available to the cell # 3 906 and the scrambling sequence # 3 allocated to the cell # 3 906 (924). The pilot signal for estimating the channel experienced by the transmission signal of the cell # 3 906 is also transmitted using the scrambling sequence # 3 (926). The pilot signal of the cell # 3 906 is mapped to the radio resource # 2 and transmitted. In addition, the cell # 3 906 transmits control information for informing that the terminal 908 is using the radio resource # 4 so that the terminal 908 can demodulate and decode the data signal (922). The control information is transmitted using a separate radio resource # 5 and a scrambling sequence # 3 assigned to the cell # 3 906. Radio resource # 5 for transmitting the control information may be predefined or may be given to the terminal as system information in a call setup or reconfiguration step between the terminal and the base station. The terminal 908 combines the data signal from the cell # 3 906 with the data signal of another cell in a second combining method.

The terminal 908 performs channel compensation and data combining on the data signals received from the respective cells 902, 904, and 906 as follows.

The terminal 908 receives the combining indicator 916 from the serving cell 902. The combining indicator 916 may combine the data signal of the cell # 2 904 with the data signal of the serving cell 902 in a first combining manner, and the data signal of the cell # 3 906 may be combined. It is possible to combine the data signal of the serving cell 902 with the second combining method. Since the data signals from the cell # 1 902 and the cell # 2 904 are transmitted using the same radio resource and the same scrambling sequence, they are naturally combined and received from the terminal reception point (first combining method). The terminal 908 combines the channel estimates calculated from the pilot signals of the cell # 1 902 and the cell # 2 904, respectively, and then uses the combined channel estimate to perform the first combining method. Compensate for the received signal.

Specifically, the terminal 908 extracts a signal of radio resource # 2 to which a common pilot is assigned to a received signal and descrambles the scrambling sequence # 1 of the cell # 1 902 to thereby decode the cell # 1 902. ), A pilot signal is calculated, and a channel estimate value of the cell # 1 902 is calculated using the pilot signal of the cell # 1 902. In addition, the terminal 908 extracts a signal of radio resource # 2 to which the pilot is allocated and descrambles the scrambling sequence # 2 of the cell # 2 904 to obtain a pilot signal of the cell # 2 904. The channel estimation value of the cell # 2 904 is calculated using the pilot signal of the cell # 2 904. The terminal may find a final channel estimate for the data signal by combining the channel estimates of the cell # 1 902 and the channel estimates of the cell # 2 904, respectively. Therefore, the signal received by the first combining method is channel compensated using the final channel estimate. The channel compensated signal is referred to as a first channel compensation signal for convenience of description below.

The terminal 908 combines the data signal received from the cell # 3 906 with the data signals of the cell # 1 902 and the cell # 2 904 in a second combining method. That is, the terminal 908 confirms that the data signal of the cell # 3 906 uses the radio resource # 4 from the control information of the cell # 3 906. Accordingly, the terminal 908 acquires the data signal of the cell # 3 906 using the radio resource # 4 and the scrambling sequence # 3 with respect to the received signal. The terminal 908 extracts a signal of radio resource # 2 to which a common pilot is allocated to a received signal, and descrambles the scrambling sequence # 3 of the cell # 3 906 by parsing the cell # 3 906. The pilot signal of the cell # 3 906 is calculated, and the channel estimate value of the cell # 3 906 is calculated. The obtained data signal of cell # 3 906 is compensated using the channel estimate value of cell # 3 906. The channel compensated signal is referred to as a second channel compensation signal for convenience of description below.

The terminal 908 finally combines the first channel compensation signal and the second channel compensation signal (that is, the second combining method), so that the cell # 1 902, the cell # 2 904, Completion of the received signal from cell # 3 906 is completed. The terminal demodulates and decodes the combining signal to finally obtain an information bit.

The base station transmitting apparatus and the terminal receiving apparatus for implementing the third embodiment are the same as those of FIGS. 6 and 7 mentioned in the first embodiment. However, the terminal includes a reception path for generating a first channel compensation signal and a reception path for generating a second channel compensation signal. Each receive path generates a first channel compensation signal and a second channel compensation signal, respectively, and combines the channel compensation signals of each receive path by a separate combiner to obtain a combined data signal.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined not only by the scope of the following claims, but also by those equivalent to the scope of the claims.

In the present invention operating as described in detail above, the effects obtained by the representative ones of the disclosed inventions will be briefly described as follows.

The present invention relates to a method and apparatus for downlink data transmission and reception for receiving signal combining of a terminal located in a cell overlap region in an OFDM-based cellular system. The present invention can improve the reception performance of the terminal located in the overlap region by obtaining the same diversity effect as the terminal receives the multipath signal from each cell.

Claims (9)

A method for transmitting and receiving downlink data for combining received data in an orthogonal frequency division multiplexing system, Transmitting, by a serving cell, a first data signal using a first radio resource and a first scrambling sequence, and transmitting a first pilot signal for identifying the serving cell using a second radio resource and a first scrambling sequence and, At least one non-serving cell adjacent to the serving cell transmits a second data signal identical to the first data signal using the first radio resource and the first scrambling sequence, and the non-serving cell Transmitting a second pilot signal for identification using the second radio resource and a second scrambling sequence; A terminal located in an overlapping region of the serving cell and the at least one non-serving cell receives the first pilot signal to calculate a first channel estimate, and receives the second pilot signal to obtain a second channel estimate. Calculating a final channel estimate by combining the first channel estimate and the second estimate; And receiving, by the terminal, the combined data signal of the first data signal and the second data signal, and channel compensating the combined data signal using the final channel estimate. . The method of claim 1, Transmitting, at the serving cell, a combining indicator indicating whether the second data signal from the at least one non-serving cell is capable of combining with the first data signal. The method of claim 2, wherein the combining indicator, The method characterized in that the transmission through the physical layer signaling or higher layer signaling. A method for transmitting and receiving downlink data for combining received data in an orthogonal frequency division multiplexing system, In the serving cell, a first data signal is transmitted using a first radio resource and a first scrambling sequence, and a first dedicated pilot signal for identifying the serving cell is transmitted using a second radio resource and the first scrambling sequence. Process, In at least one non-serving cell adjacent to the serving cell, transmitting a second data signal equal to the first data signal using the first radio resource and the first scrambling sequence, and the non-serving cell Transmitting a second dedicated pilot signal for identifying a signal using the second radio resource and the first scrambling sequence; A terminal located in an overlapping region of the serving cell and the at least one non-serving cell is a combination of the first dedicated pilot signal and the second dedicated pilot signal using the second radio resource and the first scrambling sequence. Receiving an inning dedicated pilot signal and calculating a channel estimate using the combined dedicated pilot signal; The terminal receives the combined data signal of the first data signal and the second data signal by using the first radio resource and the first scrambling sequence, and the combined data signal by using the channel estimate. And performing channel compensation. The method of claim 4, wherein Sending, at the serving cell, a combining indicator indicating whether the second data signal from the at least one non-serving cell is capable of combining with the first data signal and whether a dedicated pilot is used; Characterized in that the method. The method of claim 5, wherein the combining indicator, The method characterized in that the transmission through the physical layer signaling or higher layer signaling. A method for transmitting and receiving downlink data for combining received data in an orthogonal frequency division multiplexing system, Transmitting, by a serving cell, a first data signal using a first radio resource and a first scrambling sequence, and transmitting a first pilot signal for identifying the serving cell using a second radio resource and a first scrambling sequence and, At least one first non-serving cell adjacent to the serving cell transmits a second data signal identical to the first data signal using the first radio resource and the first scrambling sequence, and the first ratio Transmitting a second pilot signal for identifying a serving cell using the second radio resource and a second scrambling sequence; In at least one second non-serving cell adjacent to the serving cell, a third data signal identical to the first data signal is transmitted using a third radio resource and a third scrambling sequence, and the second non- Transmitting a third pilot signal for identifying a serving cell by using the second radio resource and the third scrambling sequence; A terminal located in an overlapping region of the serving cell and the first non-serving cell receives the first pilot signal to calculate a first channel estimate, and receives the second pilot signal to calculate a second channel estimate. Calculating a final channel estimate by combining the first channel estimate and the second estimate; Receiving, by the terminal, a combined data signal of the first data signal and the second data signal, and generating a first channel compensation signal by channel compensating the combined data signal using the final channel estimate value; Receiving, by the terminal, a third pilot signal to calculate a third channel estimate value, receiving the third data signal, and channel compensating with the third channel estimate value to generate a second channel compensation signal; And combining, by the terminal, the first channel compensation signal and the second channel compensation signal. The method of claim 7, wherein Transmitting, at the serving cell, a combining indicator indicating a combining scheme of the second and third data signals from the first and second non-serving cells. The method of claim 8, wherein the combining indicator, The method characterized in that the transmission through the physical layer signaling or higher layer signaling.

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